Grounding System Design of 1 000 kV Ultra-high Voltage Substation

The 1 000 kV ultra-high voltage system has the properties of high voltage grade,huge transmission capacity,and huge short-circuit current,in order to guarantee its safe and reliable operation,the requirements for the grounding system of its substation are very strict.The method to decide the grounding resistance value according to the curve of the current division factor of short-circuit fault current is put forward in this paper.Based on the electromagnetic filed numerical analysis method,the electrical parameters of the grounding system in multi-layer soil for Jindongnan substation in China were analyzed.The analysis results show that horizontal grounding grid can ensure the ground potential rise smaller than 5 000 V,but the touch voltage exceeds the permitted value.Then the effect of vertical grounding electrodes to reduce the touch voltage is discussed,and the influences of the optimal design of the horizontal grounding grid on the grounding resistance,step and touch voltages were analyzed.The design scheme of the grounding systems for Jindongnan substation is proposed.At last,the sheath ground model of secondary cable is suggested.