Abstract
During geomagnetic storms, the geomagnetically induced currents (GIC) cause bias fluxes in transformers, resulting in half-cycle saturation. Severely distorted exciting currents, which contain significant amounts of harmonics, threaten the safe operation of equipment and even the whole power system. In this paper, we compare GIC data measured in transformer neutrals and magnetic recordings in China, and show that the GIC amplitudes can be quite large even in mid-low latitude areas. The GIC in the Chinese Northwest 750 kV Power Grid are modeled based on the plane wave assumption. The results show that GIC flowing in some transformers exceed 30 A/phase during strong geomagnetic storms. GIC are thus not only a high-latitude problem but networks in middle and low latitudes can be impacted as well, which needs careful attention.
Highlights
During strong space weather storms, which are caused by the activity of the Sun, the Earth’s magnetic field is intensely disturbed by the space current system in the magnetosphere and ionosphere
The results show that geomagnetically induced currents (GIC) flowing in some transformers exceed 30 A/phase during strong geomagnetic storms
The modeling of GIC in a power grid can be divided into two steps (e.g., Pirjola 2000): step 1, calculating the geoelectric field induced by a magnetic storm; step 2, calculating the GIC in the power grid
Summary
During strong space weather storms, which are caused by the activity of the Sun, the Earth’s magnetic field is intensely disturbed by the space current system in the magnetosphere and ionosphere. The electric fields induced by time variations of the geomagnetic field drive geomagnetically induced currents (GIC) in electric power transmission networks. Large currents in transformer neutrals have been monitored in the Chinese high-voltage power system many times during geomagnetic storms China is a midlow-latitude country. Transformers have had abnormal noise and vibration Those events have been shown to be caused by GIC based on analyses of simultaneous magnetic data and GIC recordings (Liu & Xie 2005; Liu et al 2009a). The Chinese Northwest 750 kV power grid has long transmission lines with small resistances making it prone to large GIC during geomagnetic storms. It is important to model GIC in that network
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