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TitleComparison of methods for modelling geomagnetically induced currents
AuthorBoteler, D HORCID logo; Pirjola, R JORCID logo
SourceAnnales Geophysicae vol. 32, 2014 p. 1177-1187, Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20140385
PublisherCopernicus GmbH
Mediapaper; on-line; digital
File formatpdf; xml
SubjectsHealth and Safety
ProgramPublic Safety Geoscience Northern Canada Geohazards Project
Released2014 09 19
AbstractAssessing the geomagnetic hazard to power systems requires reliable modelling of the geomagnetically induced currents (GIC) produced in the power network. This paper compares the Nodal Admittance Matrix method with the Lehtinen-Pirjola method and shows them to be mathematically equivalent. GIC calculation using the Nodal Admittance Matrix method involves three steps: (1) using the voltage sources in the lines representing the induced geoelectric field to calculate equivalent current sources and summing these to obtain the nodal current sources, (2) performing the inversion of the admittance matrix and multiplying by the nodal current sources to obtain the nodal voltages, (3) using the nodal voltages to determine the currents in the lines and in the ground connections. In the Lehtinen-Pirjola method, steps 2 and 3 of the Nodal Admittance Matrix calculation are combined into one matrix expression. This involves inversion of a more complicated matrix but yields the currents to ground directly from the nodal current sources. To calculate GIC in multiple voltage levels of a power system, it is necessary to model the connections between voltage levels, not just the transmission lines and ground connections considered in traditional GIC modelling. Where GIC flow to ground through both the high-voltage and low-voltage windings of a transformer, they share a common path through the substation grounding resistance. This has been modelled previously by including non-zero, off-diagonal elements in the earthing impedance matrix of the Lehtinen-Pirjola method. However, this situation is more easily handled in both the Nodal Admittance Matrix method and the Lehtinen-Pirjola method by introducing a node at the neutral point.
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. Assessment of geomagnetic hazard requires accurate modeling of the geomagnetically induced currents (GIC) that are expected to occur during a given geomagnetic disturbance (GMD). This paper compares the two main modeling methods and shows that they are equivalent. The paper also shows how to model GIC in multiple voltage levels of a power system.

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