Frequency Components of Geomagnetically Induced Currents for Power System Modelling

TL;DR

This paper investigates the frequency spectrum of geomagnetically induced currents in power systems, emphasizing the importance of low-frequency components below 50 mHz for accurate dynamic response modelling.

Contribution

It provides an analysis of measured GIC spectra, identifying dominant frequencies and quantifying errors from simplified models, enhancing GIC modelling accuracy.

Findings

GIC spectra depend on geomagnetic disturbance and earth conductivity

Dominant frequencies for GIC modelling are below 50 mHz

Using these frequencies introduces quantifiable modeling errors

Abstract

Geomagnetically induced currents (GICs) in power systems are conventionally modelled as direct currents, based on their commonly described quasi-DC nature. For more representative power system dynamic response modelling, it is necessary to model GICs using low-frequency AC. After analysing spectra of geomagnetic field measurements and GICs in several power systems, preliminary results indicate that the GIC spectra depend on the magnitude and frequency spectrum of the geomagnetic disturbance, the earth conductivity and the electrical characteristics of the network. In this paper, analysis based on measured GIC power spectra suggests that the dominant frequencies to use in GIC modelling and simulation are typically below 50 mHz. The associated error introduced by only using these frequencies is also quantified. The results have implications for modelling the geoelectric fields inducing GICs, dynamic models of power system response and the need for GICs and their associated driving fields to be measured at intervals not exceeding 10 s.