Projects - User contributions [en]

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-21T08:12:04Z

A1706601: /* Conclusions & Recommendations */

Sponsored by ElectraNet, this project aimed to analyse the impact of reverse power flow due to rooftop solar systems on power transformers in the transmission network. Inverters (used in rooftop solar systems) produce harmonics due to their non-linearity, which have the potential to cause overheating in transformers if occurring in high enough concentrations.

== Introduction ==
[[File:Duck curve.png|thumb|right|Duck Curve <ref>[1] AEMO observations: operational and market challenges to reliability and security in the NEM, Australian Energy Market Operator, 2018.</ref>]]

Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems.
 
Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated.
 
International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.
 
This project uses data from ElectraNets transmission transformer power quality meters. The study is focused on the Adelaide Hills region and surrounds, with several transmission transformers being investigated.

== Project Team ==
=== Students ===
Iman Atefi 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This project answers the following research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# Would these become an issue? If so, when? 
# Are current regulations enough to mitigate these issues? 
# How could these issues be solved by ElectraNet?

== Research ==
=== Standards ===
Australian Standards and other guiding documents were reviewed to identify feasible gaps in the regulations on inverter emissions and transformer harmonics levels. Methods for evaluation, limits and assumptions are of interest to understand where issues could occur whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) were also reviewed. 
 
Key standards for this project were the 61000, 60076 and 4777 series, which cover harmonics, transformers and inverters respectively. These standards impose the following restrictions on harmonic levels in the network:
* Inverters must produce no more than 5% THD overall, with orders of harmonics to the 33rd restricted to below specific THD's (AS 4777.2:2015 Clause 5.6, Table 2 & 3).
* Transformers must have no more than 5% TDD (AS 60076.1:2014 4.2(d)).
* Equipment harmonic limits outlined in AS 61000 series.
 
=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions in power transformers. The following evaluation metrics were used in this project:
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements. It is a weighting of the harmonic load currents according to their effects on transformer heating. Higher order harmonics hold more weighting to the effect on transformer heating.
 
 
=== Transformers ===
[[File:Transformer-report-fig-2-transformer-w-callouts.jpg|thumb|right|Transformer Diagram <ref>[2] Liquid-filled power transformers. ABB, 2020, p. 6.</ref>]]

Power transformers are affected by harmonic currents through heating of the windings. Harmonic currents cause additional heating within the transformers' windings, which is exacerbated by higher-order harmonics which have a larger heating effect due to higher energy levels. When harmonic levels (TDD) are too high (>5%), or high-order-harmonics are significantly high, overheating will occur. 
Overheating causes the insulation materials within transformers (Kraft paper, oil, bushings) to age faster than planned. This is called 'ageing' and can cost hundreds of thousands of dollars in early maintenance and replacement of the affected power transformer.
 
 

=== Inverters ===
Inverters produce harmonic waveforms due to their non-linearity. Inverters commonly use switching frequencies of 18-20kHz. These high switching frequencies are used to reduce the power usage of inverters, making them more efficient. While limited by standards, it is possible harmonics in the distribution system could be amplified (or cancelled out) when interacting with one another. With enough harmonic sources in the network, it is possible to have total harmonic distortions over the threshold, even if individual inverters are operating within limits.
 
 
== Analysis ==
[[File:Solar Capacity Map.jpg|thumb|left|Proportional Solar Capacity by Postcode]]

Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network was analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB was used for this analysis, with a range of plots developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots generated included average harmonic current levels for summer and winter, and day and night, to compare at times where solar generation will be maximised (summer daytime) and minimised (night time), or reduced (winter daytime). Furthermore, K-Factor levels at these times were plotted.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source was used to evaluate the growth of solar generation capacity versus the growth of harmonic current levels in the system over time.
 

== Conclusions & Recommendations ==
[[File:AvgHIperSeason02.png|thumb|left|Harmonic Distribution Comparison]]
[[File:HIcontrToKf01.png|thumb|right|K Factor Distribution Comparison]]
[[File:KfactorS&W.png|thumb|right|K Factor over Time]]

This study concluded that there is no evidence of a correlation between harmonic magnitudes seen at transmission transformers in the region, and the amount of solar energy being generated by photovoltaic systems. Furthermore, the harmonic levels as seen at these transmission transformers and the consequent k-factors are significantly lower than the 5% threshold, indicating no foreseeable threat to transformers. 
 
The existing harmonic standards applied by Standards Australia and by SAPN are sufficient to mitigate the risks from harmonics due to rooftop solar systems. 
 
It is recommended that other regions of South Australia's power network are investigated and that harmonic orders over the 50th are investigated. This study was limited by these two factors, and as inverters are using increasingly high switching frequencies, higher harmonic orders should be investigated to ensure no effects. 
 
 
 
 

== References ==

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-21T08:09:00Z

A1706601: /* Conclusions & Recommendations */

Sponsored by ElectraNet, this project aimed to analyse the impact of reverse power flow due to rooftop solar systems on power transformers in the transmission network. Inverters (used in rooftop solar systems) produce harmonics due to their non-linearity, which have the potential to cause overheating in transformers if occurring in high enough concentrations.

== Introduction ==
[[File:Duck curve.png|thumb|right|Duck Curve <ref>[1] AEMO observations: operational and market challenges to reliability and security in the NEM, Australian Energy Market Operator, 2018.</ref>]]

Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems.
 
Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated.
 
International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.
 
This project uses data from ElectraNets transmission transformer power quality meters. The study is focused on the Adelaide Hills region and surrounds, with several transmission transformers being investigated.

== Project Team ==
=== Students ===
Iman Atefi 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This project answers the following research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# Would these become an issue? If so, when? 
# Are current regulations enough to mitigate these issues? 
# How could these issues be solved by ElectraNet?

== Research ==
=== Standards ===
Australian Standards and other guiding documents were reviewed to identify feasible gaps in the regulations on inverter emissions and transformer harmonics levels. Methods for evaluation, limits and assumptions are of interest to understand where issues could occur whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) were also reviewed. 
 
Key standards for this project were the 61000, 60076 and 4777 series, which cover harmonics, transformers and inverters respectively. These standards impose the following restrictions on harmonic levels in the network:
* Inverters must produce no more than 5% THD overall, with orders of harmonics to the 33rd restricted to below specific THD's (AS 4777.2:2015 Clause 5.6, Table 2 & 3).
* Transformers must have no more than 5% TDD (AS 60076.1:2014 4.2(d)).
* Equipment harmonic limits outlined in AS 61000 series.
 
=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions in power transformers. The following evaluation metrics were used in this project:
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements. It is a weighting of the harmonic load currents according to their effects on transformer heating. Higher order harmonics hold more weighting to the effect on transformer heating.
 
 
=== Transformers ===
[[File:Transformer-report-fig-2-transformer-w-callouts.jpg|thumb|right|Transformer Diagram <ref>[2] Liquid-filled power transformers. ABB, 2020, p. 6.</ref>]]

Power transformers are affected by harmonic currents through heating of the windings. Harmonic currents cause additional heating within the transformers' windings, which is exacerbated by higher-order harmonics which have a larger heating effect due to higher energy levels. When harmonic levels (TDD) are too high (>5%), or high-order-harmonics are significantly high, overheating will occur. 
Overheating causes the insulation materials within transformers (Kraft paper, oil, bushings) to age faster than planned. This is called 'ageing' and can cost hundreds of thousands of dollars in early maintenance and replacement of the affected power transformer.
 
 

=== Inverters ===
Inverters produce harmonic waveforms due to their non-linearity. Inverters commonly use switching frequencies of 18-20kHz. These high switching frequencies are used to reduce the power usage of inverters, making them more efficient. While limited by standards, it is possible harmonics in the distribution system could be amplified (or cancelled out) when interacting with one another. With enough harmonic sources in the network, it is possible to have total harmonic distortions over the threshold, even if individual inverters are operating within limits.
 
 
== Analysis ==
[[File:Solar Capacity Map.jpg|thumb|left|Proportional Solar Capacity by Postcode]]

Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network was analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB was used for this analysis, with a range of plots developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots generated included average harmonic current levels for summer and winter, and day and night, to compare at times where solar generation will be maximised (summer daytime) and minimised (night time), or reduced (winter daytime). Furthermore, K-Factor levels at these times were plotted.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source was used to evaluate the growth of solar generation capacity versus the growth of harmonic current levels in the system over time.
 

== Conclusions & Recommendations ==
This study concluded that there is no evidence of a correlation between harmonic magnitudes seen at transmission transformers in the region, and the amount of solar energy being generated by photovoltaic systems. Furthermore, the harmonic levels as seen at these transmission transformers and the consequent k-factors are significantly lower than the 5% threshold, indicating no foreseeable threat to transformers. 
 
The existing harmonic standards applied by Standards Australia and by SAPN are sufficient to mitigate the risks from harmonics due to rooftop solar systems. 
 
It is recommended that other regions of South Australia's power network are investigated and that harmonic orders over the 50th are investigated. This study was limited by these two factors, and as inverters are using increasingly high switching frequencies, higher harmonic orders should be investigated to ensure no effects. 

[[File:AvgHIperSeason02.png|thumb|left|Harmonic Distribution Comparison]]
[[File:HIcontrToKf01.png|thumb|center|K Factor Distribution Comparison]]
[[File:KfactorS&W.png|thumn|right|K Factor over Time]]
 
 
 
 
 
 
 
 
 
 
 
 
 
 

== References ==

File:KfactorS&W.png

2020-10-21T08:08:30Z

A1706601: A1706601 uploaded a new version of File:KfactorS&W.png

K-Factor levels in continuous time for summer, winter, day and night.

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-21T08:05:11Z

A1706601: /* Conclusions & Recommendations */

Sponsored by ElectraNet, this project aimed to analyse the impact of reverse power flow due to rooftop solar systems on power transformers in the transmission network. Inverters (used in rooftop solar systems) produce harmonics due to their non-linearity, which have the potential to cause overheating in transformers if occurring in high enough concentrations.

== Introduction ==
[[File:Duck curve.png|thumb|right|Duck Curve <ref>[1] AEMO observations: operational and market challenges to reliability and security in the NEM, Australian Energy Market Operator, 2018.</ref>]]

Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems.
 
Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated.
 
International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.
 
This project uses data from ElectraNets transmission transformer power quality meters. The study is focused on the Adelaide Hills region and surrounds, with several transmission transformers being investigated.

== Project Team ==
=== Students ===
Iman Atefi 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This project answers the following research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# Would these become an issue? If so, when? 
# Are current regulations enough to mitigate these issues? 
# How could these issues be solved by ElectraNet?

== Research ==
=== Standards ===
Australian Standards and other guiding documents were reviewed to identify feasible gaps in the regulations on inverter emissions and transformer harmonics levels. Methods for evaluation, limits and assumptions are of interest to understand where issues could occur whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) were also reviewed. 
 
Key standards for this project were the 61000, 60076 and 4777 series, which cover harmonics, transformers and inverters respectively. These standards impose the following restrictions on harmonic levels in the network:
* Inverters must produce no more than 5% THD overall, with orders of harmonics to the 33rd restricted to below specific THD's (AS 4777.2:2015 Clause 5.6, Table 2 & 3).
* Transformers must have no more than 5% TDD (AS 60076.1:2014 4.2(d)).
* Equipment harmonic limits outlined in AS 61000 series.
 
=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions in power transformers. The following evaluation metrics were used in this project:
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements. It is a weighting of the harmonic load currents according to their effects on transformer heating. Higher order harmonics hold more weighting to the effect on transformer heating.
 
 
=== Transformers ===
[[File:Transformer-report-fig-2-transformer-w-callouts.jpg|thumb|right|Transformer Diagram <ref>[2] Liquid-filled power transformers. ABB, 2020, p. 6.</ref>]]

Power transformers are affected by harmonic currents through heating of the windings. Harmonic currents cause additional heating within the transformers' windings, which is exacerbated by higher-order harmonics which have a larger heating effect due to higher energy levels. When harmonic levels (TDD) are too high (>5%), or high-order-harmonics are significantly high, overheating will occur. 
Overheating causes the insulation materials within transformers (Kraft paper, oil, bushings) to age faster than planned. This is called 'ageing' and can cost hundreds of thousands of dollars in early maintenance and replacement of the affected power transformer.
 
 

=== Inverters ===
Inverters produce harmonic waveforms due to their non-linearity. Inverters commonly use switching frequencies of 18-20kHz. These high switching frequencies are used to reduce the power usage of inverters, making them more efficient. While limited by standards, it is possible harmonics in the distribution system could be amplified (or cancelled out) when interacting with one another. With enough harmonic sources in the network, it is possible to have total harmonic distortions over the threshold, even if individual inverters are operating within limits.
 
 
== Analysis ==
[[File:Solar Capacity Map.jpg|thumb|left|Proportional Solar Capacity by Postcode]]

Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network was analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB was used for this analysis, with a range of plots developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots generated included average harmonic current levels for summer and winter, and day and night, to compare at times where solar generation will be maximised (summer daytime) and minimised (night time), or reduced (winter daytime). Furthermore, K-Factor levels at these times were plotted.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source was used to evaluate the growth of solar generation capacity versus the growth of harmonic current levels in the system over time.
 

== Conclusions & Recommendations ==
This study concluded that there is no evidence of a correlation between harmonic magnitudes seen at transmission transformers in the region, and the amount of solar energy being generated by photovoltaic systems. Furthermore, the harmonic levels as seen at these transmission transformers and the consequent k-factors are significantly lower than the 5% threshold, indicating no foreseeable threat to transformers. 
 
The existing harmonic standards applied by Standards Australia and by SAPN are sufficient to mitigate the risks from harmonics due to rooftop solar systems. 
 
It is recommended that other regions of South Australia's power network are investigated and that harmonic orders over the 50th are investigated. This study was limited by these two factors, and as inverters are using increasingly high switching frequencies, higher harmonic orders should be investigated to ensure no effects. 
 
[[File:AvgHIperSeason02.png|thumb|left|Harmonic Distribution Comparison]]
 
 
 
 
 
 
 
 
 
 
 

== References ==

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-21T08:04:43Z

A1706601: /* Conclusions & Recommendations */

Sponsored by ElectraNet, this project aimed to analyse the impact of reverse power flow due to rooftop solar systems on power transformers in the transmission network. Inverters (used in rooftop solar systems) produce harmonics due to their non-linearity, which have the potential to cause overheating in transformers if occurring in high enough concentrations.

== Introduction ==
[[File:Duck curve.png|thumb|right|Duck Curve <ref>[1] AEMO observations: operational and market challenges to reliability and security in the NEM, Australian Energy Market Operator, 2018.</ref>]]

Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems.
 
Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated.
 
International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.
 
This project uses data from ElectraNets transmission transformer power quality meters. The study is focused on the Adelaide Hills region and surrounds, with several transmission transformers being investigated.

== Project Team ==
=== Students ===
Iman Atefi 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This project answers the following research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# Would these become an issue? If so, when? 
# Are current regulations enough to mitigate these issues? 
# How could these issues be solved by ElectraNet?

== Research ==
=== Standards ===
Australian Standards and other guiding documents were reviewed to identify feasible gaps in the regulations on inverter emissions and transformer harmonics levels. Methods for evaluation, limits and assumptions are of interest to understand where issues could occur whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) were also reviewed. 
 
Key standards for this project were the 61000, 60076 and 4777 series, which cover harmonics, transformers and inverters respectively. These standards impose the following restrictions on harmonic levels in the network:
* Inverters must produce no more than 5% THD overall, with orders of harmonics to the 33rd restricted to below specific THD's (AS 4777.2:2015 Clause 5.6, Table 2 & 3).
* Transformers must have no more than 5% TDD (AS 60076.1:2014 4.2(d)).
* Equipment harmonic limits outlined in AS 61000 series.
 
=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions in power transformers. The following evaluation metrics were used in this project:
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements. It is a weighting of the harmonic load currents according to their effects on transformer heating. Higher order harmonics hold more weighting to the effect on transformer heating.
 
 
=== Transformers ===
[[File:Transformer-report-fig-2-transformer-w-callouts.jpg|thumb|right|Transformer Diagram <ref>[2] Liquid-filled power transformers. ABB, 2020, p. 6.</ref>]]

Power transformers are affected by harmonic currents through heating of the windings. Harmonic currents cause additional heating within the transformers' windings, which is exacerbated by higher-order harmonics which have a larger heating effect due to higher energy levels. When harmonic levels (TDD) are too high (>5%), or high-order-harmonics are significantly high, overheating will occur. 
Overheating causes the insulation materials within transformers (Kraft paper, oil, bushings) to age faster than planned. This is called 'ageing' and can cost hundreds of thousands of dollars in early maintenance and replacement of the affected power transformer.
 
 

=== Inverters ===
Inverters produce harmonic waveforms due to their non-linearity. Inverters commonly use switching frequencies of 18-20kHz. These high switching frequencies are used to reduce the power usage of inverters, making them more efficient. While limited by standards, it is possible harmonics in the distribution system could be amplified (or cancelled out) when interacting with one another. With enough harmonic sources in the network, it is possible to have total harmonic distortions over the threshold, even if individual inverters are operating within limits.
 
 
== Analysis ==
[[File:Solar Capacity Map.jpg|thumb|left|Proportional Solar Capacity by Postcode]]

Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network was analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB was used for this analysis, with a range of plots developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots generated included average harmonic current levels for summer and winter, and day and night, to compare at times where solar generation will be maximised (summer daytime) and minimised (night time), or reduced (winter daytime). Furthermore, K-Factor levels at these times were plotted.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source was used to evaluate the growth of solar generation capacity versus the growth of harmonic current levels in the system over time.
 

== Conclusions & Recommendations ==
This study concluded that there is no evidence of a correlation between harmonic magnitudes seen at transmission transformers in the region, and the amount of solar energy being generated by photovoltaic systems. Furthermore, the harmonic levels as seen at these transmission transformers and the consequent k-factors are significantly lower than the 5% threshold, indicating no foreseeable threat to transformers. 
 
The existing harmonic standards applied by Standards Australia and by SAPN are sufficient to mitigate the risks from harmonics due to rooftop solar systems. 
 
It is recommended that other regions of South Australia's power network are investigated and that harmonic orders over the 50th are investigated. This study was limited by these two factors, and as inverters are using increasingly high switching frequencies, higher harmonic orders should be investigated to ensure no effects. 
 
[[File:AvgHIperSeason02.png|Left|Thumb|Harmonic Distribution Comparison]]
 
 
 
 
 
 
 
 
 
 
 

== References ==

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-21T08:02:38Z

A1706601: /* Conclusions & Recommendations */

Sponsored by ElectraNet, this project aimed to analyse the impact of reverse power flow due to rooftop solar systems on power transformers in the transmission network. Inverters (used in rooftop solar systems) produce harmonics due to their non-linearity, which have the potential to cause overheating in transformers if occurring in high enough concentrations.

== Introduction ==
[[File:Duck curve.png|thumb|right|Duck Curve <ref>[1] AEMO observations: operational and market challenges to reliability and security in the NEM, Australian Energy Market Operator, 2018.</ref>]]

Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems.
 
Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated.
 
International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.
 
This project uses data from ElectraNets transmission transformer power quality meters. The study is focused on the Adelaide Hills region and surrounds, with several transmission transformers being investigated.

== Project Team ==
=== Students ===
Iman Atefi 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This project answers the following research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# Would these become an issue? If so, when? 
# Are current regulations enough to mitigate these issues? 
# How could these issues be solved by ElectraNet?

== Research ==
=== Standards ===
Australian Standards and other guiding documents were reviewed to identify feasible gaps in the regulations on inverter emissions and transformer harmonics levels. Methods for evaluation, limits and assumptions are of interest to understand where issues could occur whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) were also reviewed. 
 
Key standards for this project were the 61000, 60076 and 4777 series, which cover harmonics, transformers and inverters respectively. These standards impose the following restrictions on harmonic levels in the network:
* Inverters must produce no more than 5% THD overall, with orders of harmonics to the 33rd restricted to below specific THD's (AS 4777.2:2015 Clause 5.6, Table 2 & 3).
* Transformers must have no more than 5% TDD (AS 60076.1:2014 4.2(d)).
* Equipment harmonic limits outlined in AS 61000 series.
 
=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions in power transformers. The following evaluation metrics were used in this project:
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements. It is a weighting of the harmonic load currents according to their effects on transformer heating. Higher order harmonics hold more weighting to the effect on transformer heating.
 
 
=== Transformers ===
[[File:Transformer-report-fig-2-transformer-w-callouts.jpg|thumb|right|Transformer Diagram <ref>[2] Liquid-filled power transformers. ABB, 2020, p. 6.</ref>]]

Power transformers are affected by harmonic currents through heating of the windings. Harmonic currents cause additional heating within the transformers' windings, which is exacerbated by higher-order harmonics which have a larger heating effect due to higher energy levels. When harmonic levels (TDD) are too high (>5%), or high-order-harmonics are significantly high, overheating will occur. 
Overheating causes the insulation materials within transformers (Kraft paper, oil, bushings) to age faster than planned. This is called 'ageing' and can cost hundreds of thousands of dollars in early maintenance and replacement of the affected power transformer.
 
 

=== Inverters ===
Inverters produce harmonic waveforms due to their non-linearity. Inverters commonly use switching frequencies of 18-20kHz. These high switching frequencies are used to reduce the power usage of inverters, making them more efficient. While limited by standards, it is possible harmonics in the distribution system could be amplified (or cancelled out) when interacting with one another. With enough harmonic sources in the network, it is possible to have total harmonic distortions over the threshold, even if individual inverters are operating within limits.
 
 
== Analysis ==
[[File:Solar Capacity Map.jpg|thumb|left|Proportional Solar Capacity by Postcode]]

Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network was analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB was used for this analysis, with a range of plots developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots generated included average harmonic current levels for summer and winter, and day and night, to compare at times where solar generation will be maximised (summer daytime) and minimised (night time), or reduced (winter daytime). Furthermore, K-Factor levels at these times were plotted.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source was used to evaluate the growth of solar generation capacity versus the growth of harmonic current levels in the system over time.
 

== Conclusions & Recommendations ==
This study concluded that there is no evidence of a correlation between harmonic magnitudes seen at transmission transformers in the region, and the amount of solar energy being generated by photovoltaic systems. Furthermore, the harmonic levels as seen at these transmission transformers and the consequent k-factors are significantly lower than the 5% threshold, indicating no foreseeable threat to transformers. 
 
The existing harmonic standards applied by Standards Australia and by SAPN are sufficient to mitigate the risks from harmonics due to rooftop solar systems. 
 
It is recommended that other regions of South Australia's power network are investigated and that harmonic orders over the 50th are investigated. This study was limited by these two factors, and as inverters are using increasingly high switching frequencies, higher harmonic orders should be investigated to ensure no effects. 
 
 
 
 
 
 
 
 
 
 
 
 

== References ==

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-20T01:44:36Z

A1706601: /* Analysis */

Sponsored by ElectraNet, this project aimed to analyse the impact of reverse power flow due to rooftop solar systems on power transformers in the transmission network. Inverters (used in rooftop solar systems) produce harmonics due to their non-linearity, which have the potential to cause overheating in transformers if occurring in high enough concentrations.

== Introduction ==
[[File:Duck curve.png|thumb|right|Duck Curve <ref>[1] AEMO observations: operational and market challenges to reliability and security in the NEM, Australian Energy Market Operator, 2018.</ref>]]

Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems.
 
Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated.
 
International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.
 
This project uses data from ElectraNets transmission transformer power quality meters. The study is focused on the Adelaide Hills region and surrounds, with several transmission transformers being investigated.

== Project Team ==
=== Students ===
Iman Atefi 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This project answers the following research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# Would these become an issue? If so, when? 
# Are current regulations enough to mitigate these issues? 
# How could these issues be solved by ElectraNet?

== Research ==
=== Standards ===
Australian Standards and other guiding documents were reviewed to identify feasible gaps in the regulations on inverter emissions and transformer harmonics levels. Methods for evaluation, limits and assumptions are of interest to understand where issues could occur whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) were also reviewed. 
 
Key standards for this project were the 61000, 60076 and 4777 series, which cover harmonics, transformers and inverters respectively. These standards impose the following restrictions on harmonic levels in the network:
* Inverters must produce no more than 5% THD overall, with orders of harmonics to the 33rd restricted to below specific THD's (AS 4777.2:2015 Clause 5.6, Table 2 & 3).
* Transformers must have no more than 5% TDD (AS 60076.1:2014 4.2(d)).
* Equipment harmonic limits outlined in AS 61000 series.
 
=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions in power transformers. The following evaluation metrics were used in this project:
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements. It is a weighting of the harmonic load currents according to their effects on transformer heating. Higher order harmonics hold more weighting to the effect on transformer heating.
 
 
=== Transformers ===
[[File:Transformer-report-fig-2-transformer-w-callouts.jpg|thumb|right|Transformer Diagram <ref>[2] Liquid-filled power transformers. ABB, 2020, p. 6.</ref>]]

Power transformers are affected by harmonic currents through heating of the windings. Harmonic currents cause additional heating within the transformers' windings, which is exacerbated by higher-order harmonics which have a larger heating effect due to higher energy levels. When harmonic levels (TDD) are too high (>5%), or high-order-harmonics are significantly high, overheating will occur. 
Overheating causes the insulation materials within transformers (Kraft paper, oil, bushings) to age faster than planned. This is called 'ageing' and can cost hundreds of thousands of dollars in early maintenance and replacement of the affected power transformer.
 
 

=== Inverters ===
Inverters produce harmonic waveforms due to their non-linearity. Inverters commonly use switching frequencies of 18-20kHz. These high switching frequencies are used to reduce the power usage of inverters, making them more efficient. While limited by standards, it is possible harmonics in the distribution system could be amplified (or cancelled out) when interacting with one another. With enough harmonic sources in the network, it is possible to have total harmonic distortions over the threshold, even if individual inverters are operating within limits.
 
 
== Analysis ==
[[File:Solar Capacity Map.jpg|thumb|left|Proportional Solar Capacity by Postcode]]

Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network was analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB was used for this analysis, with a range of plots developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots generated included average harmonic current levels for summer and winter, and day and night, to compare at times where solar generation will be maximised (summer daytime) and minimised (night time), or reduced (winter daytime). Furthermore, K-Factor levels at these times were plotted.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source was used to evaluate the growth of solar generation capacity versus the growth of harmonic current levels in the system over time.
 

== Conclusions & Recommendations ==
This study concluded that there is no evidence of a correlation between harmonic magnitudes seen at transmission transformers in the region, and the amount of solar energy being generated by photovoltaic systems. Furthermore, the harmonic levels as seen at these transmission transformers and the consequent k-factors are significantly lower than the 5% threshold, indicating no foreseeable threat to transformers. 
 
The existing harmonic standards applied by Standards Australia and by SAPN are sufficient to mitigate the risks from harmonics due to rooftop solar systems. 
 
It is recommended that other regions of South Australia's power network are investigated and that harmonic orders over the 50th are investigated. This study was limited by these two factors, and as inverters are using increasingly high switching frequencies, higher harmonic orders should be investigated to ensure no effects.

== References ==

File:HIcontrToKf01.png

2020-10-20T01:43:02Z

A1706601: A1706601 uploaded a new version of File:HIcontrToKf01.png

Average monthly K-Factor by harmonic order over winter, summer, day and night.

File:AvgHIperSeason02.png

2020-10-20T01:29:53Z

A1706601: A1706601 uploaded a new version of File:AvgHIperSeason02.png

Plot of average harmonic TDD seen at the transmission transformer per month for winter, summer, day and night.

File:AvgHIperSeason02.png

2020-10-20T01:29:19Z

A1706601: A1706601 uploaded a new version of File:AvgHIperSeason02.png

Plot of average harmonic TDD seen at the transmission transformer per month for winter, summer, day and night.

File:AvgHIperSeason02.png

2020-10-20T01:28:54Z

A1706601: A1706601 uploaded a new version of File:AvgHIperSeason02.png

Plot of average harmonic TDD seen at the transmission transformer per month for winter, summer, day and night.

File:AvgHIperSeason02.png

2020-10-20T01:23:22Z

A1706601: A1706601 uploaded a new version of File:AvgHIperSeason02.png

Plot of average harmonic TDD seen at the transmission transformer per month for winter, summer, day and night.

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-20T01:17:02Z

A1706601: /* Analysis */

Sponsored by ElectraNet, this project aimed to analyse the impact of reverse power flow due to rooftop solar systems on power transformers in the transmission network. Inverters (used in rooftop solar systems) produce harmonics due to their non-linearity, which have the potential to cause overheating in transformers if occurring in high enough concentrations.

== Introduction ==
[[File:Duck curve.png|thumb|right|Duck Curve <ref>[1] AEMO observations: operational and market challenges to reliability and security in the NEM, Australian Energy Market Operator, 2018.</ref>]]

Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems.
 
Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated.
 
International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.
 
This project uses data from ElectraNets transmission transformer power quality meters. The study is focused on the Adelaide Hills region and surrounds, with several transmission transformers being investigated.

== Project Team ==
=== Students ===
Iman Atefi 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This project answers the following research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# Would these become an issue? If so, when? 
# Are current regulations enough to mitigate these issues? 
# How could these issues be solved by ElectraNet?

== Research ==
=== Standards ===
Australian Standards and other guiding documents were reviewed to identify feasible gaps in the regulations on inverter emissions and transformer harmonics levels. Methods for evaluation, limits and assumptions are of interest to understand where issues could occur whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) were also reviewed. 
 
Key standards for this project were the 61000, 60076 and 4777 series, which cover harmonics, transformers and inverters respectively. These standards impose the following restrictions on harmonic levels in the network:
* Inverters must produce no more than 5% THD overall, with orders of harmonics to the 33rd restricted to below specific THD's (AS 4777.2:2015 Clause 5.6, Table 2 & 3).
* Transformers must have no more than 5% TDD (AS 60076.1:2014 4.2(d)).
* Equipment harmonic limits outlined in AS 61000 series.
 
=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions in power transformers. The following evaluation metrics were used in this project:
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements. It is a weighting of the harmonic load currents according to their effects on transformer heating. Higher order harmonics hold more weighting to the effect on transformer heating.
 
 
=== Transformers ===
[[File:Transformer-report-fig-2-transformer-w-callouts.jpg|thumb|right|Transformer Diagram <ref>[2] Liquid-filled power transformers. ABB, 2020, p. 6.</ref>]]

Power transformers are affected by harmonic currents through heating of the windings. Harmonic currents cause additional heating within the transformers' windings, which is exacerbated by higher-order harmonics which have a larger heating effect due to higher energy levels. When harmonic levels (TDD) are too high (>5%), or high-order-harmonics are significantly high, overheating will occur. 
Overheating causes the insulation materials within transformers (Kraft paper, oil, bushings) to age faster than planned. This is called 'ageing' and can cost hundreds of thousands of dollars in early maintenance and replacement of the affected power transformer.
 
 

=== Inverters ===
Inverters produce harmonic waveforms due to their non-linearity. Inverters commonly use switching frequencies of 18-20kHz. These high switching frequencies are used to reduce the power usage of inverters, making them more efficient. While limited by standards, it is possible harmonics in the distribution system could be amplified (or cancelled out) when interacting with one another. With enough harmonic sources in the network, it is possible to have total harmonic distortions over the threshold, even if individual inverters are operating within limits.
 
 
== Analysis ==
[[File:AvgHIperSeason02.png|thumb|left|Harmonic Distribution Comparison]]
[[File:HIcontrToKf01.png|thumb|left|K-Factor Distribution Comparison]]
[[File:KfactorS&W.png|thumb|left|K-Factor Comparison over Summer and Winter]]
[[File:Solar Capacity Map.jpg|thumb|left|Proportional Solar Capacity by Postcode]]

Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network was analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB was used for this analysis, with a range of plots developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots generated included average harmonic current levels for summer and winter, and day and night, to compare at times where solar generation will be maximised (summer daytime) and minimised (night time), or reduced (winter daytime). Furthermore, K-Factor levels at these times were plotted.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source was used to evaluate the growth of solar generation capacity versus the growth of harmonic current levels in the system over time.
 

== Conclusions & Recommendations ==
This study concluded that there is no evidence of a correlation between harmonic magnitudes seen at transmission transformers in the region, and the amount of solar energy being generated by photovoltaic systems. Furthermore, the harmonic levels as seen at these transmission transformers and the consequent k-factors are significantly lower than the 5% threshold, indicating no foreseeable threat to transformers. 
 
The existing harmonic standards applied by Standards Australia and by SAPN are sufficient to mitigate the risks from harmonics due to rooftop solar systems. 
 
It is recommended that other regions of South Australia's power network are investigated and that harmonic orders over the 50th are investigated. This study was limited by these two factors, and as inverters are using increasingly high switching frequencies, higher harmonic orders should be investigated to ensure no effects.

== References ==

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-20T01:16:09Z

A1706601:

Sponsored by ElectraNet, this project aimed to analyse the impact of reverse power flow due to rooftop solar systems on power transformers in the transmission network. Inverters (used in rooftop solar systems) produce harmonics due to their non-linearity, which have the potential to cause overheating in transformers if occurring in high enough concentrations.

== Introduction ==
[[File:Duck curve.png|thumb|right|Duck Curve <ref>[1] AEMO observations: operational and market challenges to reliability and security in the NEM, Australian Energy Market Operator, 2018.</ref>]]

Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems.
 
Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated.
 
International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.
 
This project uses data from ElectraNets transmission transformer power quality meters. The study is focused on the Adelaide Hills region and surrounds, with several transmission transformers being investigated.

== Project Team ==
=== Students ===
Iman Atefi 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This project answers the following research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# Would these become an issue? If so, when? 
# Are current regulations enough to mitigate these issues? 
# How could these issues be solved by ElectraNet?

== Research ==
=== Standards ===
Australian Standards and other guiding documents were reviewed to identify feasible gaps in the regulations on inverter emissions and transformer harmonics levels. Methods for evaluation, limits and assumptions are of interest to understand where issues could occur whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) were also reviewed. 
 
Key standards for this project were the 61000, 60076 and 4777 series, which cover harmonics, transformers and inverters respectively. These standards impose the following restrictions on harmonic levels in the network:
* Inverters must produce no more than 5% THD overall, with orders of harmonics to the 33rd restricted to below specific THD's (AS 4777.2:2015 Clause 5.6, Table 2 & 3).
* Transformers must have no more than 5% TDD (AS 60076.1:2014 4.2(d)).
* Equipment harmonic limits outlined in AS 61000 series.
 
=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions in power transformers. The following evaluation metrics were used in this project:
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements. It is a weighting of the harmonic load currents according to their effects on transformer heating. Higher order harmonics hold more weighting to the effect on transformer heating.
 
 
=== Transformers ===
[[File:Transformer-report-fig-2-transformer-w-callouts.jpg|thumb|right|Transformer Diagram <ref>[2] Liquid-filled power transformers. ABB, 2020, p. 6.</ref>]]

Power transformers are affected by harmonic currents through heating of the windings. Harmonic currents cause additional heating within the transformers' windings, which is exacerbated by higher-order harmonics which have a larger heating effect due to higher energy levels. When harmonic levels (TDD) are too high (>5%), or high-order-harmonics are significantly high, overheating will occur. 
Overheating causes the insulation materials within transformers (Kraft paper, oil, bushings) to age faster than planned. This is called 'ageing' and can cost hundreds of thousands of dollars in early maintenance and replacement of the affected power transformer.
 
 

=== Inverters ===
Inverters produce harmonic waveforms due to their non-linearity. Inverters commonly use switching frequencies of 18-20kHz. These high switching frequencies are used to reduce the power usage of inverters, making them more efficient. While limited by standards, it is possible harmonics in the distribution system could be amplified (or cancelled out) when interacting with one another. With enough harmonic sources in the network, it is possible to have total harmonic distortions over the threshold, even if individual inverters are operating within limits.
 
 
== Analysis ==
[[File:AvgHIperSeason02.png|thumb|left|Harmonic Distribution Comparison]]
[[File:HIcontrToKf01.png|thumb|left|K-Factor Distribution Comparison]]
[[File:KfactorS&W.png|thumb|left|K-Factor Comparison over Summer and Winter]]
[[File:Solar Capacity Map.jpg|thumb|left|Proportional Solar Capacity by Postcode]]

Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network was analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB was used for this analysis, with a range of plots developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots generated included average harmonic current levels for summer and winter, and day and night, to compare at times where solar generation will be maximised (summer daytime) and minimised (night time), or reduced (winter daytime). Furthermore, K-Factor levels at these times were plotted.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source was used to evaluate the growth of solar generation capacity versus the growth of harmonic current levels in the system over time.
 

== Conclusions & Recommendations ==
This study concluded that there is no evidence of a correlation between harmonic magnitudes seen at transmission transformers in the region, and the amount of solar energy being generated by photovoltaic systems. Furthermore, the harmonic levels as seen at these transmission transformers and the consequent k-factors are significantly lower than the 5% threshold, indicating no foreseeable threat to transformers. 
 
The existing harmonic standards applied by Standards Australia and by SAPN are sufficient to mitigate the risks from harmonics due to rooftop solar systems. 
 
It is recommended that other regions of South Australia's power network are investigated and that harmonic orders over the 50th are investigated. This study was limited by these two factors, and as inverters are using increasingly high switching frequencies, higher harmonic orders should be investigated to ensure no effects.

== References ==

File:Solar Capacity Map.jpg

2020-10-20T01:15:38Z

A1706601:

Proportional map of solar system capacities for systems of 5MW or less, in each postcode of the Adelaide Hills and surrounds.

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-13T08:41:15Z

A1706601:

Sponsored by ElectraNet, this project aims to analyse the impact of reverse power flow due to rooftop solar systems on power transformers in the transmission network. Inverters (used in rooftop solar systems) produce harmonics due to their non-linearity, which have the potential to cause overheating in transformers if occurring in high enough concentrations.

== Introduction ==
[[File:Duck curve.png|thumb|right|Duck Curve <ref>[1] AEMO observations: operational and market challenges to reliability and security in the NEM, Australian Energy Market Operator, 2018.</ref>]]

Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems.
 
Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated.
 
International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.

== Project Team ==
=== Students ===
Iman Atefi 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This project answers the following research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# Would these become an issue? If so, when? 
# Are current regulations enough to mitigate these issues? 
# How could these issues be solved by ElectraNet?

== Research ==
=== Standards ===
Australian Standards and other guiding documents were reviewed to identify feasible gaps in the regulations on inverter emissions and transformer harmonics levels. Methods for evaluation, limits and assumptions are of interest to understand where issues could occur whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) were also reviewed. 
 
Key standards for this project were the 61000, 60076 and 4777 series, which cover harmonics, transformers and inverters respectively. These standards impose the following restrictions on harmonic levels in the network:
* Inverters must produce no more than 5% THD overall, with orders of harmonics to the 33rd restricted to below specific THD's (AS 4777.2:2015 Clause 5.6, Table 2 & 3).
* Transformers must have no more than 5% TDD (AS 60076.1:2014 4.2(d)).
* Equipment harmonic limits outlined in AS 61000 series.
 
=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions in power transformers. The following evaluation metrics were used in this project:
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements. It is a weighting of the harmonic load currents according to their effects on transformer heating.
 
 
=== Transformers ===
[[File:Transformer-report-fig-2-transformer-w-callouts.jpg|thumb|right|Transformer Diagram <ref>[2] Liquid-filled power transformers. ABB, 2020, p. 6.</ref>]]

Power transformers are affected by harmonic currents through heating of the windings. Harmonic currents cause additional heating within the transformers' windings, which is exacerbated by higher-order harmonics which have a larger heating effect due to higher energy levels. When harmonic levels (TDD) are too high (>5%), or high-order-harmonics are significantly high, overheating will occur. 
Overheating causes the insulation materials within transformers (Kraft paper, oil, bushings) to age faster than planned. This is called 'ageing' and can cost hundreds of thousands of dollars in early maintenance and replacement of the affected power transformer.
 
 

=== Inverters ===
 
 
== Analysis ==
[[File:AvgHIperSeason02.png|thumb|left|Harmonic Distribution Comparison]]
[[File:HIcontrToKf01.png|thumb|left|K-Factor Distribution Comparison]]
[[File:KfactorS&W.png|thumb|left|K-Factor Comparison over Summer and Winter]]

Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network was analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB was used for this analysis, with a range of plots developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots to be generated include harmonic current levels versus power, THD over time, with average and standard deviation measurements, day vs night harmonic levels, harmonic levels versus solar generation size, and many more.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source will also be used for analysis.
 
More to be added.

== Conclusions & Recommendations ==
To be added.

== References ==

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-13T08:35:12Z

A1706601:

Sponsored by ElectraNet, this project aims to analyse the impact of reverse power flow due to rooftop solar systems on power transformers in the transmission network. Inverters (used in rooftop solar systems) produce harmonics due to their non-linearity, which have the potential to cause overheating in transformers if occurring in high enough concentrations.

== Introduction ==
[[File:Duck curve.png|thumb|right|Duck Curve <ref>[1] AEMO observations: operational and market challenges to reliability and security in the NEM, Australian Energy Market Operator, 2018.</ref>]]

Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems.
 
Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated.
 
International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.

== Project Team ==
=== Students ===
Iman Atefi 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This project answers the following research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# Would these become an issue? If so, when? 
# Are current regulations enough to mitigate these issues? 
# How could these issues be solved by ElectraNet?

== Research ==
=== Standards ===
Australian Standards and other guiding documents were reviewed to identify feasible gaps in the regulations on inverter emissions and transformer harmonics levels. Methods for evaluation, limits and assumptions are of interest to understand where issues could occur whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) were also reviewed. 
 
Key standards for this project were the 61000, 60076 and 4777 series, which cover harmonics, transformers and inverters respectively. These standards impose the following restrictions on harmonic levels in the network:
* Inverters must produce no more than 5% THD overall, with orders of harmonics to the 33rd restricted to below specific THD's (AS 4777.2:2015 Clause 5.6, Table 2 & 3).
* Transformers must have no more than 5% TDD (AS 60076.1:2014 4.2(d)).
* Equipment harmonic limits outlined in AS 61000 series.
 
=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions in power transformers. The following evaluation metrics were used in this project:
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements. It is a weighting of the harmonic load currents according to their effects on transformer heating.
 
 
=== Transformers ===
[[File:Transformer-report-fig-2-transformer-w-callouts.jpg|thumb|right|Transformer Diagram <ref>[2] Liquid-filled power transformers. ABB, 2020, p. 6.</ref>]]

Power transformers are affected by harmonic currents through heating of the windings. Harmonic currents cause additional heating within the transformers' windings, which is exacerbated by higher-order harmonics which have a larger heating effect due to higher energy levels. When harmonic levels (TDD) are too high (>5%), or high-order-harmonics are significantly high, overheating will occur. 
Overheating causes the insulation materials within transformers (Kraft paper, oil, bushings) to age faster than planned. This is called 'ageing' and can cost hundreds of thousands of dollars in early maintenance and replacement of the affected power transformer.
 
 

=== Inverters ===
 
 
== Analysis ==
[[File:AvgHIperSeason02.png|thumb|left|Harmonic Distribution Comparison]]
[[File:HIcontrToKf01.png|thumb|left|K-Factor Distribution Comparison]]
[[File:KfactorS&W.png|thumb|left|K-Factor Comparison over Summer and Winter]]

Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network was analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB was used for this analysis, with a range of plots developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots to be generated include harmonic current levels versus power, THD over time, with average and standard deviation measurements, day vs night harmonic levels, harmonic levels versus solar generation size, and many more.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source will also be used for analysis.

== Conclusions & Recommendations ==

== References ==

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-13T08:32:32Z

A1706601: /* References */

Sponsored by ElectraNet, this project aims to analyse the impact of reverse power flow due to rooftop solar systems on power transformers in the transmission network. Inverters (used in rooftop solar systems) produce harmonics due to their non-linearity, which have the potential to cause overheating in transformers if occurring in high enough concentrations.

== Introduction ==
[[File:Duck curve.png|thumb|right|Duck Curve [1]]]

Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems.
 
Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated.
 
International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.

== Project Team ==
=== Students ===
Iman Atefi 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This project answers the following research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# Would these become an issue? If so, when? 
# Are current regulations enough to mitigate these issues? 
# How could these issues be solved by ElectraNet?

== Research ==
=== Standards ===
Australian Standards and other guiding documents were reviewed to identify feasible gaps in the regulations on inverter emissions and transformer harmonics levels. Methods for evaluation, limits and assumptions are of interest to understand where issues could occur whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) were also reviewed. 
 
Key standards for this project were the 61000, 60076 and 4777 series, which cover harmonics, transformers and inverters respectively. These standards impose the following restrictions on harmonic levels in the network:
* Inverters must produce no more than 5% THD overall, with orders of harmonics to the 33rd restricted to below specific THD's (AS 4777.2:2015 Clause 5.6, Table 2 & 3).
* Transformers must have no more than 5% TDD (AS 60076.1:2014 4.2(d)).
* Equipment harmonic limits outlined in AS 61000 series.
 
=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions in power transformers. The following evaluation metrics were used in this project:
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements. It is a weighting of the harmonic load currents according to their effects on transformer heating.
 
 
=== Transformers ===
[[File:Transformer-report-fig-2-transformer-w-callouts.jpg|thumb|right|Transformer Diagram [2]]]

Power transformers are affected by harmonic currents through heating of the windings. Harmonic currents cause additional heating within the transformers' windings, which is exacerbated by higher-order harmonics which have a larger heating effect due to higher energy levels. When harmonic levels (TDD) are too high (>5%), or high-order-harmonics are significantly high, overheating will occur. 
Overheating causes the insulation materials within transformers (Kraft paper, oil, bushings) to age faster than planned. This is called 'ageing' and can cost hundreds of thousands of dollars in early maintenance and replacement of the affected power transformer.
 
 

=== Inverters ===
 
 
== Analysis ==
[[File:AvgHIperSeason02.png|thumb|left|Harmonic Distribution Comparison]]
[[File:HIcontrToKf01.png|thumb|left|K-Factor Distribution Comparison]]
[[File:KfactorS&W.png|thumb|left|K-Factor Comparison over Summer and Winter]]

Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network was analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB was used for this analysis, with a range of plots developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots to be generated include harmonic current levels versus power, THD over time, with average and standard deviation measurements, day vs night harmonic levels, harmonic levels versus solar generation size, and many more.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source will also be used for analysis.

== Conclusions & Recommendations ==

== References ==
<ref>[1] AEMO observations: operational and market challenges to reliability and security in the NEM, Australian Energy Market Operator, 2018.</ref>
<ref>[2] Liquid-filled power transformers. ABB, 2020, p. 6.</ref>

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-13T08:31:48Z

A1706601: /* Transformers */

Sponsored by ElectraNet, this project aims to analyse the impact of reverse power flow due to rooftop solar systems on power transformers in the transmission network. Inverters (used in rooftop solar systems) produce harmonics due to their non-linearity, which have the potential to cause overheating in transformers if occurring in high enough concentrations.

== Introduction ==
[[File:Duck curve.png|thumb|right|Duck Curve [1]]]

Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems.
 
Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated.
 
International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.

== Project Team ==
=== Students ===
Iman Atefi 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This project answers the following research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# Would these become an issue? If so, when? 
# Are current regulations enough to mitigate these issues? 
# How could these issues be solved by ElectraNet?

== Research ==
=== Standards ===
Australian Standards and other guiding documents were reviewed to identify feasible gaps in the regulations on inverter emissions and transformer harmonics levels. Methods for evaluation, limits and assumptions are of interest to understand where issues could occur whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) were also reviewed. 
 
Key standards for this project were the 61000, 60076 and 4777 series, which cover harmonics, transformers and inverters respectively. These standards impose the following restrictions on harmonic levels in the network:
* Inverters must produce no more than 5% THD overall, with orders of harmonics to the 33rd restricted to below specific THD's (AS 4777.2:2015 Clause 5.6, Table 2 & 3).
* Transformers must have no more than 5% TDD (AS 60076.1:2014 4.2(d)).
* Equipment harmonic limits outlined in AS 61000 series.
 
=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions in power transformers. The following evaluation metrics were used in this project:
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements. It is a weighting of the harmonic load currents according to their effects on transformer heating.
 
 
=== Transformers ===
[[File:Transformer-report-fig-2-transformer-w-callouts.jpg|thumb|right|Transformer Diagram [2]]]

Power transformers are affected by harmonic currents through heating of the windings. Harmonic currents cause additional heating within the transformers' windings, which is exacerbated by higher-order harmonics which have a larger heating effect due to higher energy levels. When harmonic levels (TDD) are too high (>5%), or high-order-harmonics are significantly high, overheating will occur. 
Overheating causes the insulation materials within transformers (Kraft paper, oil, bushings) to age faster than planned. This is called 'ageing' and can cost hundreds of thousands of dollars in early maintenance and replacement of the affected power transformer.
 
 

=== Inverters ===
 
 
== Analysis ==
[[File:AvgHIperSeason02.png|thumb|left|Harmonic Distribution Comparison]]
[[File:HIcontrToKf01.png|thumb|left|K-Factor Distribution Comparison]]
[[File:KfactorS&W.png|thumb|left|K-Factor Comparison over Summer and Winter]]

Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network was analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB was used for this analysis, with a range of plots developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots to be generated include harmonic current levels versus power, THD over time, with average and standard deviation measurements, day vs night harmonic levels, harmonic levels versus solar generation size, and many more.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source will also be used for analysis.

== Conclusions & Recommendations ==

== References ==
<ref>"[1] AEMO observations: operational and market challenges to reliability and security in the NEM," Australian Energy Market Operator, 2018.</ref>

File:Transformer-report-fig-2-transformer-w-callouts.jpg

2020-10-13T08:30:27Z

A1706601: A1706601 uploaded a new version of File:Transformer-report-fig-2-transformer-w-callouts.jpg

== Summary ==
Transformer parts diagram.

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-12T23:50:53Z

A1706601:

Sponsored by ElectraNet, this project aims to analyse the impact of reverse power flow due to rooftop solar systems on power transformers in the transmission network. Inverters (used in rooftop solar systems) produce harmonics due to their non-linearity, which have the potential to cause overheating in transformers if occurring in high enough concentrations.

== Introduction ==
[[File:Duck curve.png|thumb|right|Duck Curve [1]]]

Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems.
 
Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated.
 
International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.

== Project Team ==
=== Students ===
Iman Atefi 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This project answers the following research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# Would these become an issue? If so, when? 
# Are current regulations enough to mitigate these issues? 
# How could these issues be solved by ElectraNet?

== Research ==
=== Standards ===
Australian Standards and other guiding documents were reviewed to identify feasible gaps in the regulations on inverter emissions and transformer harmonics levels. Methods for evaluation, limits and assumptions are of interest to understand where issues could occur whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) were also reviewed. 
 
Key standards for this project were the 61000, 60076 and 4777 series, which cover harmonics, transformers and inverters respectively. These standards impose the following restrictions on harmonic levels in the network:
* Inverters must produce no more than 5% THD overall, with orders of harmonics to the 33rd restricted to below specific THD's (AS 4777.2:2015 Clause 5.6, Table 2 & 3).
* Transformers must have no more than 5% TDD (AS 60076.1:2014 4.2(d)).
* Equipment harmonic limits outlined in AS 61000 series.
 
=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions in power transformers. The following evaluation metrics were used in this project:
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements. It is a weighting of the harmonic load currents according to their effects on transformer heating.
 
 
=== Transformers ===
[[File:Transformer-report-fig-2-transformer-w-callouts.jpg|thumb|right|Transformer Diagram]]

Power transformers are affected by harmonic currents through heating of the windings. Harmonic currents cause additional heating within the transformers' windings, which is exacerbated by higher-order harmonics which have a larger heating effect due to higher energy levels. When harmonic levels (TDD) are too high (>5%), or high-order-harmonics are significantly high, overheating will occur. 
Overheating causes the insulation materials within transformers (Kraft paper, oil, bushings) to age faster than planned. This is called 'ageing' and can cost hundreds of thousands of dollars in early maintenance and replacement of the affected power transformer.
 
 
=== Inverters ===
 
 
== Analysis ==
[[File:AvgHIperSeason02.png|thumb|left|Harmonic Distribution Comparison]]
[[File:HIcontrToKf01.png|thumb|left|K-Factor Distribution Comparison]]
[[File:KfactorS&W.png|thumb|left|K-Factor Comparison over Summer and Winter]]

Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network was analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB was used for this analysis, with a range of plots developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots to be generated include harmonic current levels versus power, THD over time, with average and standard deviation measurements, day vs night harmonic levels, harmonic levels versus solar generation size, and many more.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source will also be used for analysis.

== Conclusions & Recommendations ==

== References ==
<ref>"[1] AEMO observations: operational and market challenges to reliability and security in the NEM," Australian Energy Market Operator, 2018.</ref>

File:Duck curve.png

2020-10-12T23:49:23Z

A1706601:

Average operational demand in SA over 24hrs, for consecutive years. AEMO.

File:Transformer-report-fig-2-transformer-w-callouts.jpg

2020-10-12T06:06:21Z

A1706601: Transformer parts diagram.

== Summary ==
Transformer parts diagram.

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-12T06:03:16Z

A1706601:

Sponsored by ElectraNet, this project aims to analyse the impact of reverse power flow due to home solar systems on power transformers in the transmission network. Inverters (used in home solar systems) produce harmonics due to their non-linearity, which may cause overheating of transformers. This project expects to provide ElectraNet with insight into any effects on their transformers; allowing ElectraNet to evaluate the need to implement any protective measures or derating of transformers well before any issues arise.

== Introduction ==
Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems.
 
Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated.
 
International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.

== Project Team ==
=== Students ===
Iman Atefi Nezhad 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This project answers the following research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# Would these become an issue? If so, when? 
# Are current regulations enough to mitigate these issues? 
# How could these issues be solved by ElectraNet?

== Research ==
=== Standards ===
Australian Standards and other guiding documents were reviewed to identify feasible gaps in the regulations on inverter emissions and transformer harmonics levels. Methods for evaluation, limits and assumptions are of interest to understand where issues could occur whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) were also reviewed. 
 
Key standards for this project were the 61000, 60076 and 4777 series, which cover harmonics, transformers and inverters respectively. These standards impose the following restrictions on harmonic levels in the network:
* Inverters must produce no more than 5% THD overall, with orders of harmonics to the 33rd restricted to below specific THD's (AS 4777.2:2015 Clause 5.6, Table 2 & 3).
* Transformers must have no more than 5% TDD (AS 60076.1:2014 4.2(d)).
* Equipment harmonic limits outlined in AS 61000 series.
 
=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions in power transformers. The following evaluation metrics were used in this project:
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements. It is a weighting of the harmonic load currents according to their effects on transformer heating.
 
 
=== Transformers ===

Power transformers are affected by harmonic currents through heating of the windings. Harmonic currents cause additional heating within the transformers' windings, which is exacerbated by higher-order harmonics which have a larger heating effect due to higher energy levels. When harmonic levels (TDD) are too high (>5%), or high-order-harmonics are significantly high, overheating will occur. 
Overheating causes the insulation materials within transformers (insulative Kraft paper, oil) to age faster than planned. This is called 'ageing' and can cost $100's of thousands in early maintenance and replacement of the affected power transformer.
 
 

=== Inverters ===
 
 
== Analysis ==
[[File:AvgHIperSeason02.png|thumb|left|Harmonic Distribution Comparison]]
[[File:HIcontrToKf01.png|thumb|left|K-Factor Distribution Comparison]]
[[File:KfactorS&W.png|thumb|left|K-Factor Comparison over Summer and Winter]]

Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network was analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB was used for this analysis, with a range of plots developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots to be generated include harmonic current levels versus power, THD over time, with average and standard deviation measurements, day vs night harmonic levels, harmonic levels versus solar generation size, and many more.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source will also be used for analysis.

== Deliverables ==
* Standards Summary Report
* Evaluation Methods Summary Report
* Code from Data Analysis
* Final Reports

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-12T02:57:32Z

A1706601:

File:KfactorS&W.png

2020-10-12T02:56:06Z

A1706601:

K-Factor levels in continuous time for summer, winter, day and night.

File:HIcontrToKf01.png

2020-10-12T02:54:27Z

A1706601:

Average monthly K-Factor by harmonic order over winter, summer, day and night.

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-12T02:47:25Z

A1706601:

Sponsored by ElectraNet, this project aims to analyse the impact of reverse power flow due to home solar systems on power transformers in the transmission network. Inverters (used in home solar systems) produce harmonics due to their non-linearity, which may cause overheating of transformers. This project expects to provide ElectraNet with insight into any effects on their transformers; allowing ElectraNet to evaluate the need to implement any protective measures or derating of transformers well before any issues arise.

== Introduction ==
Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems.
 
Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated.
 
International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.

== Project Team ==
=== Students ===
Iman Atefi Nezhad 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This project answers the following research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# Would these become an issue? If so, when? 
# Are current regulations enough to mitigate these issues? 
# How could these issues be solved by ElectraNet?

== Research ==
=== Standards ===
Australian Standards and other guiding documents were reviewed to identify feasible gaps in the regulations on inverter emissions and transformer harmonics levels. Methods for evaluation, limits and assumptions are of interest to understand where issues could occur whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) were also reviewed. 
 
Key standards for this project were the 61000, 60076 and 4777 series, which cover harmonics, transformers and inverters respectively. These standards impose the following restrictions on harmonic levels in the network:
* Inverters must produce no more than 5% THD overall, with orders of harmonics to the 33rd restricted to below specific THD's (AS 4777.2:2015 Clause 5.6, Table 2 & 3).
* Transformers must have no more than 5% TDD (AS 60076.1:2014 4.2(d)).
* Equipment harmonic limits outlined in AS 61000 series.
 
=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions in power transformers. The following evaluation metrics were used in this project:
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements. It is a weighting of the harmonic load currents according to their effects on transformer heating.
 
 
=== Transformers ===

Power transformers are affected by harmonic currents through heating of the windings. Harmonic currents cause additional heating within the transformers' windings, which is exacerbated by higher-order harmonics which have a larger heating effect due to higher energy levels. When harmonic levels (TDD) are too high (>5%), or high-order-harmonics are significantly high, overheating will occur. 
Overheating causes the insulation materials within transformers (insulative Kraft paper, oil) to age faster than planned. This is called 'ageing' and can cost $100's of thousands in early maintenance and replacement of the affected power transformer.
 
 

=== Inverters ===
 
 
== Analysis ==
Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network was analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB was used for this analysis, with a range of plots developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots to be generated include harmonic current levels versus power, THD over time, with average and standard deviation measurements, day vs night harmonic levels, harmonic levels versus solar generation size, and many more.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source will also be used for analysis.

[[File:AvgHIperSeason02.png|thumb|left|Harmonic Distribution Comparison]]

== Deliverables ==
* Standards Summary Report
* Evaluation Methods Summary Report
* Code from Data Analysis
* Final Reports

File:AvgHIperSeason02.png

2020-10-12T02:47:13Z

A1706601:

Plot of average harmonic TDD seen at the transmission transformer per month for winter, summer, day and night.

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-12T02:40:10Z

A1706601: /* Transformers */

Sponsored by ElectraNet, this project aims to analyse the impact of reverse power flow due to home solar systems on power transformers in the transmission network. Inverters (used in home solar systems) produce harmonics due to their non-linearity, which may cause overheating of transformers. This project expects to provide ElectraNet with insight into any effects on their transformers; allowing ElectraNet to evaluate the need to implement any protective measures or derating of transformers well before any issues arise.

== Introduction ==
Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems.
 
Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated.
 
International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.

== Project Team ==
=== Students ===
Iman Atefi Nezhad 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This project answers the following research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# Would these become an issue? If so, when? 
# Are current regulations enough to mitigate these issues? 
# How could these issues be solved by ElectraNet?

== Research ==
=== Standards ===
Australian Standards and other guiding documents were reviewed to identify feasible gaps in the regulations on inverter emissions and transformer harmonics levels. Methods for evaluation, limits and assumptions are of interest to understand where issues could occur whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) were also reviewed. 
 
Key standards for this project were the 61000, 60076 and 4777 series, which cover harmonics, transformers and inverters respectively. These standards impose the following restrictions on harmonic levels in the network:
* Inverters must produce no more than 5% THD overall, with orders of harmonics to the 33rd restricted to below specific THD's (AS 4777.2:2015 Clause 5.6, Table 2 & 3).
* Transformers must have no more than 5% TDD (AS 60076.1:2014 4.2(d)).
* Equipment harmonic limits outlined in AS 61000 series.
 
 
=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions in power transformers. The following evaluation metrics were used in this project:
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements. It is a weighting of the harmonic load currents according to their effects on transformer heating.
 
 
=== Transformers ===

Power transformers are affected by harmonic currents through heating of the windings. Harmonic currents cause additional heating within the transformers' windings, which is exacerbated by higher-order harmonics which have a larger heating effect due to higher energy levels. When harmonic levels (TDD) are too high (>5%), or high-order-harmonics are significantly high, overheating will occur. 
Overheating causes the insulation materials within transformers (insulative Kraft paper, oil) to age faster than planned. This is called 'ageing' and can cost $100's of thousands in early maintenance and replacement of the affected power transformer.
 
 

=== Inverters ===
 
 
== Analysis ==
Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network was analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB was used for this analysis, with a range of plots developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots to be generated include harmonic current levels versus power, THD over time, with average and standard deviation measurements, day vs night harmonic levels, harmonic levels versus solar generation size, and many more.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source will also be used for analysis.

== Deliverables ==
* Standards Summary Report
* Evaluation Methods Summary Report
* Code from Data Analysis
* Final Reports

File:Large power transformer.jpg

2020-10-12T02:37:47Z

A1706601: By STM guanajuato - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=15293688

== Summary ==
By STM guanajuato - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=15293688

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-12T02:36:25Z

A1706601:

Sponsored by ElectraNet, this project aims to analyse the impact of reverse power flow due to home solar systems on power transformers in the transmission network. Inverters (used in home solar systems) produce harmonics due to their non-linearity, which may cause overheating of transformers. This project expects to provide ElectraNet with insight into any effects on their transformers; allowing ElectraNet to evaluate the need to implement any protective measures or derating of transformers well before any issues arise.

== Introduction ==
Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems.
 
Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated.
 
International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.

== Project Team ==
=== Students ===
Iman Atefi Nezhad 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This project answers the following research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# Would these become an issue? If so, when? 
# Are current regulations enough to mitigate these issues? 
# How could these issues be solved by ElectraNet?

== Research ==
=== Standards ===
Australian Standards and other guiding documents were reviewed to identify feasible gaps in the regulations on inverter emissions and transformer harmonics levels. Methods for evaluation, limits and assumptions are of interest to understand where issues could occur whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) were also reviewed. 
 
Key standards for this project were the 61000, 60076 and 4777 series, which cover harmonics, transformers and inverters respectively. These standards impose the following restrictions on harmonic levels in the network:
* Inverters must produce no more than 5% THD overall, with orders of harmonics to the 33rd restricted to below specific THD's (AS 4777.2:2015 Clause 5.6, Table 2 & 3).
* Transformers must have no more than 5% TDD (AS 60076.1:2014 4.2(d)).
* Equipment harmonic limits outlined in AS 61000 series.
 
 
=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions in power transformers. The following evaluation metrics were used in this project:
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements. It is a weighting of the harmonic load currents according to their effects on transformer heating.
 
 
=== Transformers ===
[[File:Large power transformer.jpg|400px|thumb|Large power transformer]]

Power transformers are affected by harmonic currents through heating of the windings. Harmonic currents cause additional heating within the transformers' windings, which is exacerbated by higher-order harmonics which have a larger heating effect due to higher energy levels. When harmonic levels (TDD) are too high (>5%), or high-order-harmonics are significantly high, overheating will occur. 
Overheating causes the insulation materials within transformers (insulative Kraft paper, oil) to age faster than planned. This is called 'ageing' and can cost $100's of thousands in early maintenance and replacement of the affected power transformer.
 
 
=== Inverters ===
 
 
== Analysis ==
Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network was analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB was used for this analysis, with a range of plots developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots to be generated include harmonic current levels versus power, THD over time, with average and standard deviation measurements, day vs night harmonic levels, harmonic levels versus solar generation size, and many more.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source will also be used for analysis.

== Deliverables ==
* Standards Summary Report
* Evaluation Methods Summary Report
* Code from Data Analysis
* Final Reports

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-10-12T00:48:35Z

A1706601:

Sponsored by ElectraNet, this project aims to analyse the impact of reverse power flow due to home solar systems on power transformers in the transmission network. Inverters (used in home solar systems) produce harmonics due to their non-linearity, which may cause overheating of transformers. This project expects to provide ElectraNet with insight into any effects on their transformers; allowing ElectraNet to evaluate the need to implement any protective measures or derating of transformers well before any issues arise.

== Introduction ==
Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems.
 
Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated.
 
International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.

== Project Team ==
=== Students ===
Iman Atefi Nezhad 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This project answers the following research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# Would these become an issue? If so, when? 
# Are current regulations enough to mitigate these issues? 
# How could these issues be solved by ElectraNet?

== Research ==
=== Standards ===
Australian Standards and other guiding documents were reviewed to identify feasible gaps in the regulations on inverter emissions and transformer harmonics levels. Methods for evaluation, limits and assumptions are of interest to understand where issues could occur whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) were also reviewed. 
 
Key standards for this project were the 61000, 60076 and 4777 series, which cover harmonics, transformers and inverters respectively. These standards impose the following restrictions on harmonic levels in the network:
* Inverters must produce no more than 5% THD overall, with orders of harmonics to the 33rd restricted to below specific THD's (AS 4777.2:2015 Clause 5.6, Table 2 & 3).
* Transformers must have no more than 5% TDD (AS 60076.1:2014 4.2(d)).
* Equipment harmonic limits outlined in AS 61000 series.
 
 
=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions in power transformers. The following evaluation metrics were used in this project:
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements. It is a weighting of the harmonic load currents according to their effects on transformer heating.
 
 
=== Transformers ===
<a href="https://commons.wikimedia.org/wiki/File:Large_power_transformer.jpg#/media/File:Large_power_transformer.jpg"><img src="https://upload.wikimedia.org/wikipedia/commons/2/2c/Large_power_transformer.jpg" alt="Large power transformer.jpg"></a> By <a href="//commons.wikimedia.org/w/index.php?title=User:STM_guanajuato&amp;action=edit&amp;redlink=1" class="new" title="User:STM guanajuato (page does not exist)">STM guanajuato</a> - Own work, <a href="http://creativecommons.org/publicdomain/zero/1.0/deed.en" title="Creative Commons Zero, Public Domain Dedication">CC0</a>, <a href="https://commons.wikimedia.org/w/index.php?curid=15293688">Link</a>

Power transformers are affected by harmonic currents through heating of the windings. Harmonic currents cause additional heating within the transformers' windings, which is exacerbated by higher-order harmonics which have a larger heating effect due to higher energy levels. When harmonic levels (TDD) are too high (>5%), or high-order-harmonics are significantly high, overheating will occur. 
Overheating causes the insulation materials within transformers (insulative Kraft paper, oil) to age faster than planned. This is called 'ageing' and can cost $100's of thousands in early maintenance and replacement of the affected power transformer.
 
 
=== Inverters ===
 
 
== Analysis ==
Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network was analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB was used for this analysis, with a range of plots developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots to be generated include harmonic current levels versus power, THD over time, with average and standard deviation measurements, day vs night harmonic levels, harmonic levels versus solar generation size, and many more.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source will also be used for analysis.

== Deliverables ==
* Standards Summary Report
* Evaluation Methods Summary Report
* Code from Data Analysis
* Final Reports

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-08-18T07:59:08Z

A1706601: /* Analysis */

Sponsored by ElectraNet, this project aims to analyse the impact of reverse power flow due to home solar systems on power transformers in the transmission network. Inverters (used in home solar systems) produce harmonics due to their non-linearity, which may cause overheating of transformers. This project expects to provide ElectraNet with insight into any effects on their transformers; allowing ElectraNet to evaluate the need to implement any protective measures or derating of transformers well before any issues arise.

== Introduction ==
Home solar power systems feed power back into the transmission system when they produce an excess in their distribution network. The power network was never designed to accommodate reverse power flow. It has changed the shape of the daily load profile in the SA network and continues to further change the shape as home photovoltaic (PV) systems grow. Stemming from this situation is concern that issues will occur in the network due to the lesser control over home power systems versus traditional large power generation systems. 

Transformers' life spans decrease when overheated, which is caused by overvoltages including those from harmonics and interharmonics in the input power of the transformer. Power inverters used to convert power to AC for transmission into the grid produce harmonics and interharmonics due to their non-linearity. The potential effect of harmonics emitted from inverters, on transmission transformers, will be investigated. 

International and Australian standards specify the allowed amount of harmonic emission from instruments in the network. These limits will be investigated to find whether there is a realistic potential for complying inverters to cause harmonic levels high enough that they are over the acceptable limits at the transmission transformer. Consideration will be given to the robustness of the limitation methods to see whether they are appropriately limiting harmonics.

== Project Team ==
=== Students ===
Iman Atefi Nezhad 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

== Aims ==
This Project will answer 3 key research questions: 
# What harmful effects could harmonics from rooftop PV have on transmission system transformers? 
# When would these become an issue? 
# How could these issues be solved by ElectraNet?

== Method ==
=== Standards ===
Australian Standards and other guiding documents shall be reviewed to identify feasible gaps in the regulations on inverter emissions.
Methods for evaluation, limits and assumptions are of interest to understand where issues could occur, whilst inverters are still meeting regulations. 
South Australian Power Network (SAPN) technical standards (TS) shall also be reviewed, along with consideration of ElectraNet standards.
 
 

=== Evaluation Methods ===
Different methods of evaluation exist for harmonic emissions. These are being compared and evaluated for their effectiveness in accurately portraying harmonic levels in the system with regard to their potential to affect transformers.
==== Total Harmonic Distortion ====
THD evaluates harmonic distortion as a percentage of the current going through the system at that time. Thus, for small currents, harmonic distortion can appear significantly high, whilst in terms of a constant current value, harmonic distortion is not large.
==== Total Demand Distortion ====
Hence, TDD exists. TDD evaluates harmonic distortion as a percentage of rated current. Thus, regardless of the amount of current running through the system, TDD gives a consistent picture of the levels of distortion.
==== K-Factor ====
K Factor is a method for evaluating transformer rating requirements as a function of power losses and harmonic emissions.
 
 
=== Analysis ===
Historic data measured from Power Quality Monitors (PQM's) at transmission stations across the South Australian power network will be analysed to evaluate the effect of rooftop solar output on power quality coming into the transmission transformers. MATLAB is being used for this analysis, with a range of plots being developed to quantify changes in power quality over time and compare these with changes in rooftop solar generation capacity growth over time.
 
Plots to be generated include harmonic current levels versus power, THD over time, with average and standard deviation measurements, day vs night harmonic levels, harmonic levels versus solar generation size, and many more.
 
The Australian Photovoltaic Institute (APVI) collects data on solar systems across Australia. Data from this source will also be used for analysis.

== Deliverables ==
* Standards Summary Report
* Evaluation Methods Summary Report
* Code from Data Analysis
* Final Reports

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-08-18T07:57:38Z

A1706601: /* Standards */

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-08-18T07:54:17Z

A1706601:

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-05-06T05:11:03Z

A1706601: /* Total Demand Distortion */

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-05-06T05:03:51Z

A1706601: /* Deliverables */

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-05-06T02:42:40Z

A1706601:

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-05-06T02:37:56Z

A1706601: /* Method */

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-05-06T02:37:25Z

A1706601: /* Method */

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-05-06T02:36:34Z

A1706601: /* Evaluation Methods */

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-05-06T02:34:58Z

A1706601: /* Method */

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-05-06T02:32:30Z

A1706601:

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-04-16T09:35:46Z

A1706601:

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-04-16T09:33:20Z

A1706601:

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-04-16T08:42:49Z

A1706601:

Power Quality (PQ) impacts the reliability and stability of the system and includes factors such as voltage and current waveform shape and alignment. The growing number of small-scale solar PV distribution network connected installations is impacting the power quality at ElectraNet’s connection point substations. The non-linear nature of solar PV inverters produces noisy, non-sinusoidal waveforms and harmonics. The distorted waveforms may cause transformers to experience additional heating and it is necessary to investigate the potential limitations to transformer ratings.
== Introduction ==
Increasing rooftop solar arrays are changing the existing transmission system. Reverse flow power and the power quality issues created by solar PV inverter outputs are not something the transmission network was designed to deal with. Transformers' life spans decrease when overheated, which can be caused by harmonics and overvoltages. This project will investigate the impact on transformers and consider mitigation effects.
== Project Team ==
=== Students ===
Iman Atefi Nezhad 
Ellen Chinner
=== Supervisors ===
Mr David Vowles 
Dr Gabriel Haines (ElectraNet)

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-03-11T06:53:00Z

A1706601:

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-03-11T06:29:01Z

A1706601:

Projects:2020s1-1551 The Impact of Power Quality on Transmission Transformers

2020-03-11T06:28:26Z

A1706601: Created page with "Power Quality (PQ) impacts the reliability and stability of the system and includes factors such as voltage and current waveform shape and alignment. The growing number of sma..."