Geomagnetically Induced Currents and Harmonic Distortion: High Time Resolution Case Studies
Abstract High time resolution (1–5 s) magnetometer, geomagnetically induced current (GIC), and mains harmonic distortion data from the Halfway Bush substation in Dunedin, New Zealand, are analyzed. A recently developed technique using very low frequency (VLF) radio wave data provides high‐resolution...
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| Format: | Article |
| Language: | English |
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Wiley
2020-10-01
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| Series: | Space Weather |
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| Online Access: | https://doi.org/10.1029/2020SW002594 |
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| author | Mark A. Clilverd Craig J. Rodger James B. Brundell Michael Dalzell Ian Martin Daniel H. Mac Manus Neil R. Thomson |
| author_facet | Mark A. Clilverd Craig J. Rodger James B. Brundell Michael Dalzell Ian Martin Daniel H. Mac Manus Neil R. Thomson |
| author_sort | Mark A. Clilverd |
| collection | DOAJ |
| description | Abstract High time resolution (1–5 s) magnetometer, geomagnetically induced current (GIC), and mains harmonic distortion data from the Halfway Bush substation in Dunedin, New Zealand, are analyzed. A recently developed technique using very low frequency (VLF) radio wave data provides high‐resolution measurements of mains harmonic distortion levels. Three case studies are investigated, each involving high rates of change of local geomagnetic field, but with different timescales of magnetospheric driver mechanisms, and different substation transformer configurations. Two cases of enhanced GIC during substorm events are analyzed, and one case of a storm sudden commencement. Time delays between magnetic field fluctuations and induced transformer currents are found to be ~100 s for substorm events, but only ~20 s for the storm sudden commencement containing higher‐frequency variations. Boxcar averaging of the magnetic field fluctuations using running windows of ±2 min leads to spectral power profiles similar to those of GIC profiles, with reduced power at frequencies >0.003 Hz (periods <5 min). Substantially lower mains harmonic distortion levels were observed after the removal of the single phase bank transformer, HWB T4, from the high‐voltage configuration at Halfway Bush. No systematic time delay was found between GIC variations and mains harmonic distortion levels. The power spectra of magnetic field fluctuations and GIC variations during the sudden storm commencement with no harmonic distortion showed low levels of low‐frequency power (<0.003 Hz, periods >5 min). This low‐frequency component of the magnetic field power spectrum appears necessary for mains harmonic distortion to occur. |
| format | Article |
| id | doaj-art-33ada6e45cef47c5b7a43a13d6728947 |
| institution | Kabale University |
| issn | 1542-7390 |
| language | English |
| publishDate | 2020-10-01 |
| publisher | Wiley |
| record_format | Article |
| series | Space Weather |
| spelling | doaj-art-33ada6e45cef47c5b7a43a13d67289472025-01-14T16:35:28ZengWileySpace Weather1542-73902020-10-011810n/an/a10.1029/2020SW002594Geomagnetically Induced Currents and Harmonic Distortion: High Time Resolution Case StudiesMark A. Clilverd0Craig J. Rodger1James B. Brundell2Michael Dalzell3Ian Martin4Daniel H. Mac Manus5Neil R. Thomson6British Antarctic Survey (UKRI‐NERC) Cambridge UKDepartment of Physics University of Otago Dunedin New ZealandDepartment of Physics University of Otago Dunedin New ZealandTranspower New Zealand Limited Wellington New ZealandTranspower New Zealand Limited Wellington New ZealandDepartment of Physics University of Otago Dunedin New ZealandDepartment of Physics University of Otago Dunedin New ZealandAbstract High time resolution (1–5 s) magnetometer, geomagnetically induced current (GIC), and mains harmonic distortion data from the Halfway Bush substation in Dunedin, New Zealand, are analyzed. A recently developed technique using very low frequency (VLF) radio wave data provides high‐resolution measurements of mains harmonic distortion levels. Three case studies are investigated, each involving high rates of change of local geomagnetic field, but with different timescales of magnetospheric driver mechanisms, and different substation transformer configurations. Two cases of enhanced GIC during substorm events are analyzed, and one case of a storm sudden commencement. Time delays between magnetic field fluctuations and induced transformer currents are found to be ~100 s for substorm events, but only ~20 s for the storm sudden commencement containing higher‐frequency variations. Boxcar averaging of the magnetic field fluctuations using running windows of ±2 min leads to spectral power profiles similar to those of GIC profiles, with reduced power at frequencies >0.003 Hz (periods <5 min). Substantially lower mains harmonic distortion levels were observed after the removal of the single phase bank transformer, HWB T4, from the high‐voltage configuration at Halfway Bush. No systematic time delay was found between GIC variations and mains harmonic distortion levels. The power spectra of magnetic field fluctuations and GIC variations during the sudden storm commencement with no harmonic distortion showed low levels of low‐frequency power (<0.003 Hz, periods >5 min). This low‐frequency component of the magnetic field power spectrum appears necessary for mains harmonic distortion to occur.https://doi.org/10.1029/2020SW002594geomagnetically induced currentsharmonic distortiongeomagnetic fieldVLFHalfway Bush substationsubstorm |
| spellingShingle | Mark A. Clilverd Craig J. Rodger James B. Brundell Michael Dalzell Ian Martin Daniel H. Mac Manus Neil R. Thomson Geomagnetically Induced Currents and Harmonic Distortion: High Time Resolution Case Studies Space Weather geomagnetically induced currents harmonic distortion geomagnetic field VLF Halfway Bush substation substorm |
| title | Geomagnetically Induced Currents and Harmonic Distortion: High Time Resolution Case Studies |
| title_full | Geomagnetically Induced Currents and Harmonic Distortion: High Time Resolution Case Studies |
| title_fullStr | Geomagnetically Induced Currents and Harmonic Distortion: High Time Resolution Case Studies |
| title_full_unstemmed | Geomagnetically Induced Currents and Harmonic Distortion: High Time Resolution Case Studies |
| title_short | Geomagnetically Induced Currents and Harmonic Distortion: High Time Resolution Case Studies |
| title_sort | geomagnetically induced currents and harmonic distortion high time resolution case studies |
| topic | geomagnetically induced currents harmonic distortion geomagnetic field VLF Halfway Bush substation substorm |
| url | https://doi.org/10.1029/2020SW002594 |
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