一种防止变压器纵差保护区外故障误动的新方法

在对电流互感器饱和进行理论分析的基础上,基于对差动电流采样值波形特征的识别,提出了一种防止变压器纵差保护区外故障误动作的新方法。该方法通过面积比较法和相位比较法两个判据,不仅能有效地区分内、外部故障,从而在区外短路且电流互感器严重饱和情况下对纵差保护实现实时闭锁,而且在闭锁时间段内能利用相位比较法有效地对系统进行监测,当发生区外转区内故障时适时解除闭锁信号,开放保护。判据利用了故障后第1周期的数据,不会影响比率制动特性的动作时间,计算简单,易于实现。大量仿真结果证明了该方法的有效性和正确性。

A New Method for Preventing External Fault Malfunction of Transformer Differential Protection

Based on an analysis of current transformer saturation and the waveform identification of sampling values of the differential current, a new method is proposed to prevent the external fault malfunction of transformer differential protection. By making use of the two criteria for area comparison and phase comparison, this method can not only effectively differentiate internal faults and external faults to perform real time locking of the differential protection under the condition of external fault with current transformer seriously saturated, but also effectively monitor the system during the lock-up interval with the phase comparison. When the external fault turns into an internal one, the protection can be released. As the data of the first period after the fault is used, the criteria will not affect the acting time of the ratio coefficient. The calculation is simple and the implementation is easy. The simulation results show that the method is efficient and correct.