基于传递函数的电力变压器绝缘故障加信诊断方法

INSULATION FAULT DIAGNOSISOF POWER TRANSFORMER BY SIGNAL-EXCITATION METHOD BASED ON TRANSFER FUNCTION

大型电力变压器的绝缘故障点定位是绝缘在线监测的难题之一。针对这一问题 ,文中提出了加信诊断法。首先 ,建立了基于 Bergeron法的变压器等值电路模型 ,该模型考虑了损耗及互感 ;其次 ,以某台 1 1 0 k V/2 0 MVA SF6气体绝缘电力变压器为算例 ,比较并分析了具有不同频谱特性的激励对传递函数数值计算的影响 ,总结得出最优的激励信号应为具有丰富频域分量的激励 ,它能够比较全面和准确地捕获传递函数的特征 ;最后 ,计算了矩形波脉冲激励下 ,饼间短路、饼间放电及饼对地放电 3种故障情况的传递函数 ,对比分析了这 3种不同故障对应的传递函数特征 ,为绝缘故障的诊断和定位提供了依据。

A signal- excitation diagnosis method is proposed to monitor and locate insulation faults of power transformer. A transformer equivalent circuit,which includes power loss and m utual inductance of transformer disks,is developed and then a transient calculational model by Bergeron's method is built to com pute the responses of different positions to certain exciting signal. A transfer function,defined as neutral point current divided by exciting voltage in frequency dom ain,is used to diagnose transformer faults. The influence of exciting signals with differentfrequency bands on transfer function calculation is discussed by sim ulation on a 110 k V/2 0 MVA power transformer with SF6gas insulation. The results show that the characteristics of transfer function can be obtained thoroughly and exactly under the exciting signal with broad frequency band. With the rectangular impulse input,the transfer functions under three types of faultsituation:disc- to- disc short,disc- to- disc discharge and disc- to- ground discharge,are calculated.Two cases are analyzed:the same disc with different fault types;differentdiscs with the same fault type.Characteristic differences of transfer function in these two cases are presented, which offers a basis to the location of fault point.