1000kV特高压变电站接地系统的设计

Grounding System Design of 1000 kV Ultra-high Voltage Substation

特高压系统的电压等级高、容量大,接地短路电流将相当大,为确保电力系统的安全、可靠运行,对接地系统的要求将更加严格。结合晋东南特高压变电站短路电流分流系数变化曲线,提出了变电站接地电阻的设计取值方法。采用电磁场数值计算方法对分层土壤中接地系统的电气参数进行计算。分析表明,晋东南变电站采用水平地网可以将地电位升控制在5000V以内,但接触电压较大,超过了安全限值,探讨了应用深垂直接地极降低接触电压的效果,以及水平接地网的均压优化布置对接地系统接地电阻、接触电压和跨步电压的影响。最后给出了1000kV晋东南特高压变电站接地系统的设计方案以及二次电缆屏蔽层的接地方式。

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.