变压器直流电阻试验后剩磁影响及对策

The Remanence Influence of Transformer DC Resistance Test and Its Countermeasures

阐述了大型变压器在直流电阻试验中,会在铁芯中产生剩磁,当发变组进行零起升压或变压器空载合闸时,可能会造成差动保护误动作。结合实例分析了变压器剩磁产生的原因及现象,并提出了可以利用减小直流电阻试验电流值及试验时间、控制电压合闸相位角、差动保护设置二次谐波交叉闭锁三种方法来减少变压器剩磁,避免差动保护误动。

In the DC resistance test of large transformer,remanence will be generated in the core of transformer.When the generator-transformer unit raises voltage from zero or experience no-load switch-on,the differential protection may cause malfunction.Based on the reasons and phenomena about remanence generating,this article puts forward three ways to reduce the remanence and prevent differential protection malfunctioning,including reducing the current and testing time during the DC resistance test,controlling phase angles of voltage closing,and setting the second harmonic blocking differential protection.