Calculation of geomagnetically induced currents in mid- to low-latitude power grids based on the plane wave method: A preliminary case study

Geomagnetically induced currents (GIC) with large amplitudes have been found flowing in the Yang-Huai power transmission system, Jiangsu, and at the Ling'ao Nuclear Power Plant, Guangdong, China. In order to assess the effects of GIC, it is necessary to know the level of GIC in the power grids. In this paper, the main purpose of which is to introduce GIC observations and studies in such a mid- to low-latitude country as China, the authors calculate GIC in the power grids on the basis of the simple Plane Wave Method and present a discrete algorithm according to which software has been developed to calculate the Earth surface electric field. The data of two strong magnetic storms at the Zhaoqing Geomagnetic Observatory are used to calculate the electric field and GIC at the Ling'ao Nuclear Power Plant. The measured data and the calculated results agree well, and calculations are thus applicable to assessing GIC in power grids. Additionally, the Heihe 220 kV power grid has been modeled to calculate GIC at three substations. The results show that the power grid topology and parameters are important factors for GIC levels in middle- and low-latitude regions and even larger GIC may occur in these areas.