核电站低压厂用变压器零序保护的分析与改进

Analysis and improvement on zero sequence protection of low voltage auxiliary power transformer in nuclear power station

核电站低压厂用变压器中性点零序保护采用"定时限"设计,多次出现因低压负荷回路发生单相接地故障引起的低压厂用变压器零序保护越级动作事件。梳理低压厂用变压器零序保护整定原则和分析上下级差保护配合要求,提出低压厂用变压器零序保护采用"定时限+反时限"两段式保护改进方案,经过保护校验和现场验证,改进方案可在核电站应用和推广。

The zero sequence protection for neutral point of low voltage transformer is the definite time characteristic in nuclear power station.Low voltage electrical feeder fault resulted in zero sequence protection of low voltage transformer leapfrog trip. According to the setting principle of zero sequence of low voltage transformer and analysis of protection coordination,the zero sequence protection scheme was improved with definite time and inverse time characteristic.The improved two section protection scheme can be used in the low voltage transformer of nuclear power station after protection checking and onside testing.