Use the ultrasonic signal received by the sensor from the test device to simulate partial discharge and after detailed analysis found that the ultrasonic signal generated by the partial discharge with multiple mutations, the first mutation point should be the starting time of the partial discharge, which should be marked. But the traditional time delay estimation methods are often seem the peak signal mutation as a marker so the positioning accuracy was affected. Wavelet mutation detection technology can identify the signals for the first time mutation, the article describes the principle of wavelet mutation detection technology, and tests to locate the partial discharge, the results show that the positioning accuracy of the method significantly improved and compared to traditional methods the absolute error can be reduced by 1-2 cm.%利用试验装置模拟电力变压器局部放电并对传感器接收的超声信号细节进行分析，发现局部放电产生的超声信号具有多个突变点，其中首次突变点是局部放电的起始时间，应当进行标记。但是传统的时延估计方法往往将信号突变峰值作为标记，定位的精度受到影响。小波突变性检测技术可以辨识信号的首次突变点，介绍了小波突变性检测技术的原理并利用该技术对试验装置的局部放电进行定位，结果表明该方法的定位精度明显提高，与传统方法相比定位的绝对误差可以减少1～2cm。
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