一种鉴别变压器励磁涌流和内部故障的新原理

提出一种利用电流波形特征识别变压器励磁涌流和内部故障的方法,该方法综合利用变压器差电流波形在空投涌流时会呈现出尖顶波特性和间断特征,而故障时差电流波形基本为基频正弦波的差异,先计算差电流与其中所包含基频正弦波的相关度J,再进一步利用励磁涌流尖顶的凹弧特征构造一个系数k,根据J和k进一步构造一个函数J1区分变压器的励磁涌流和内部故障。动模试验结果表明该方法能够正确区分励磁涌流和故障电流,在空投变压器时能够可靠地闭锁励磁涌流;在变压器各种内部故障时能够可靠地开放保护,动作时间一般在20 m s左右,具有较高的灵敏度和可靠性能够满足现代变压器对保护动作可靠性的要求。而且该方法实现方便,计算量小,具有良好的在实际工程中应用的价值。

Novel scheme to discriminate inrush current from internal fault of power transformer

A new algorithm based on the waveform characteristics is presented.The method synthesizes the characteristic of peak curve and dead angle,while the fault current nearly keeps sinusoid when inrush current seriously distorts.First,this paper calculates the correlation coefficient J of fundamental component of difference current,then according to inrush current characteristic of the peak and concave curve,constructs coefficient k,finally in reference to coefficient of J and k,the discriminate between inrush current and fault current of power transformers can be made.Amount of simulations show this algorithm is effective when internal fault.Moreover,the method is easy to realize and calculating quantity is small.This new identification method has good application value in engineering. This project is supported by National Natural Science Foundation of China(No.50277012).