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TitleTransformer-level modeling of geomagnetically induced currents in New Zealand's South Island
AuthorDivett, T; Richardson, G S; Beggan, C D; Rodger, C J; Boteler, D HORCID logo; Ingham, M; MacManus, D H; Thomson, A W P; Dalzell, M
SourceSpace Weather vol. 16, issue 6, 2018 p. 718-735, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20180375
PublisherAmerican Geophysical Union (AGU)
Mediapaper; on-line; digital
File formatpdf (Adobe® Reader®); html
SubjectsHealth and Safety
ProgramPublic Safety Geoscience Northern Canada Geohazards Project
Released2018 05 20
AbstractDuring space weather events, geomagnetically induced currents (GICs) can be induced in high-voltage transmission networks, damaging individual transformers within substations. A common approach to modeling a transmission network has been to assume that every substation can be represented by a single resistance to Earth. We have extended that model by building a transformer-level network representation of New Zealand's South Island transmission network. We represent every transformer winding at each earthed substation in the network by its known direct current resistance. Using this network representation significantly changes the GIC hazard assessment, compared to assessments based on the earlier assumption. Further, we have calculated the GIC flowing through a single phase of every individual transformer winding in the network. These transformer-level GIC calculations show variation in GICs between transformers within a substation due to transformer characteristics and connections. The transformer-level GIC calculations alter the hazard assessment by up to an order of magnitude in some places. In most cases the calculated GIC variations match measured variations in GIC flowing through the same transformers. This comparison with an extensive set of observations demonstrates the importance of transformer-level GIC calculations in models used for hazard assessment.
Summary(Plain Language Summary, not published)
Space weather refers to the dynamic conditions on the Sun and in the space environment, in particular, in the near-Earth environment, that can affect critical infrastructure. NRCan operates the Canadian Space Weather Forecast Centre and conducts research into space weather effects on power systems, pipelines, radio communications and GNSS positioning to help Canadian industry understand and mitigate the effects of space weather. This paper deals with geomagnetically induced currents (GICs) in New Zealand's South Island power transmission network. This work improved on previous studies by examining the GIC in individual transformer windings and compared them to observations. This comparison demonstrated the importance of transformer-level GIC calculations in models used for hazard assessment.

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