Computation And Analysis Of Geomagnetically Induced Current In Guangdong Power Grid

Geomagnetically induced currents(GIC),caused by geomagnetic storms at the Earth's surface,can result the potential safety hazard and large area blackout in electrical power grid.GIC can propagate in electric power transmission grids,causing transformer DC bias magnetic effect,further producing the misoperation of protection of equipment in electric power system.In recent years,some accidents of geomagnetic storms have occurred in Jiangsu,Guangdong and Zhejiang power grids.AsGuangdong power grid is located in area of low latitude and economic development,it is worth studing the safety hazard and braking measures of GIC in Guangdong power grid.Using the data monitored from Zhaoqin geomagnetic station in Gongdong durning three period of 14-15 December 2006,5-6 August 2011 and 17 March 2015,this paper analyzes the relations of GIC,magnetic storm type,electrical structure of the earth and topology of power grids inGuangdong power grid.In theory,the calculation model of earth surface potential(ESP)is deduced based on Maxwell Equations according to magnetotelluric sounding method,and is applied to the GIC calculations of above three geomagnetic storms.The resultsof calculation show that the sensitivity of electrical field in east and west direction to the variations of geomagnetic storm is more than that of electrical field in north-south direction.Furthermore,referring to Lehtinen and Pirjola,we deduce the calculation model of GIC in electrical power grids based on the structure of electrical power grids of Guangdong.And using 500 kVGuangdong power grid as a calculation case,we investigate the level of total GIC for each station of 54 transforming stations in 500 kV Guangdong power grid during the periods of three geomagnetic storms.The results show that the level of total GIC for each station of 54 transforming stations is associated with the index of DST which indicating the intense of geomagnetic storm,with the effect of line length,and with directions and corners of topology of power grids.Also,in order to reduce the impacts of magnetic storms on the Guangdong power grid,the method of reducing GIC is analized,with the GIC optimization model for grounding resistance of 500 kV Guangdong power grid structure and two methods of optimization calculations established,which providing the direction of further investigations.