| Title | The Lehtinen-Pirjola method modified for efficient modelling of geomagnetically induced currents in multiple voltage levels of a power network |
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| Author | Pirjola, R J ;
Boteler, D H; Tuck, L; Marsal, S |
| Source | Annales Geophysicae vol. 40, issue 2, 2022 p. 205-215, https://doi.org/10.5194/angeo-40-205-2022  Open Access |
| Image |  |
| Year | 2022 |
| Alt Series | Natural Resources Canada, Contribution Series 20210276 |
| Publisher | European Geosciences Union |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Subjects | mathematical and computational geology; modelling; geomagnetism; currents; magnetospheric currents; geoelectric variations |
| Illustrations | schematic diagrams; flow charts; tables |
| Program | Public Safety Geoscience Assessing space weather hazards |
| Program | Canadian Hazard Information Service Geomagnetism
and space weather |
| Released | 2022 04 20 |
| Abstract | The need for accurate assessment of the geomagnetic hazard to power systems is driving a requirement to model geomagnetically induced currents (GIC) in multiple voltage levels of a power network. The
Lehtinen-Pirjola method for modelling GIC is widely used but was developed when the main aim was to model GIC in only the highest voltage level of a power network. Here we present a modification to the Lehtinen-Pirjola (LP) method designed to provide
an efficient method for modelling GIC in multiple voltage levels. The LP method calculates the GIC flow to ground from each node. However, with a network involving multiple voltage levels many of the nodes are ungrounded, i.e. have infinite
resistance to ground which is numerically inconvenient. The new modified Lehtinen-Pirjola (LPm) method replaces the earthing impedance matrix [Ze] with the corresponding earthing admittance matrix [Ye] in which the ungrounded nodes have zero
admittance to ground. This is combined with the network admittance matrix [Yn] to give a combined matrix ([Yn]+[Ye]), which is a sparse symmetric positive definite matrix allowing efficient techniques, such as Cholesky decomposition, to be used to
provide the nodal voltages. The nodal voltages are then used to calculate the GIC in the transformer windings and the transmission lines of the power network. The LPm method with Cholesky decomposition also provides an efficient method for
calculating GIC at multiple time steps. Finally, the paper shows how software for the LP method can be easily converted to the LPm method and provides examples of calculations using the LPm method. |
| 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 describes a modification of an established method for modelling geomagnetically induced currents (GIC) in power systems to make it more efficient for modelling GIC in multiple voltage levels of a
power system. It also shows how the existing method can easily be converted to the new modified method. The new method involves inversion of a sparse symmetric matrix that allows for the use of more efficient computational methods. |
| GEOSCAN ID | 328930 |
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