500kV自耦变压器中性点串接小电抗对继电保护装置的影响

Impact of Joining-up between Small Reactance and Neutral Point of 500kV Autotransformer on Protective Relay Device

以500 kV电网单台主变压器中性点串接小电抗接地的系统模型为基础,从不同故障位置、小电抗阻值线路长度及系统运行方式等方面分析500 kV变电站220 kV侧母线发生接地故障时线路零序过流保护、零序方向保护、主变压器中性点零序过流保护以及变压器差动保护受到的影响,说明500 kV自耦变压器中性点串接小电抗是抑制500 kV变电站220 kV侧母线单相短路电流的有效措施。

On the basis of the earthing system model of joining-up between single main transformer of 500 kV grid and small reactance, the paper analyzes impact on zero-sequence overflow protection of lines, zero-sequence directional protection, zero-sequence overflow protection of neutral point of main transformer as well as differential protection of transformer un- der circumstance of earthing faults at 220 kV side bus of 500 kV substation in respects of various fault locations, line length of numerical value of small reactance and operation mode of the system. It is demonstrated that joining-up between small reactance and neutral point of 500 kV autotransformer is an effective measure for suppressing single-phase short-circuit current of 220 kV side bus of 500 kV substation.