A method for denoising of DC test signal

In low voltage electrical apparatus inspection direct current test, the test signal has an abrupt changing structure because of operation of opening or closing of switchgear. Affected by strong electromagnetic field, experiment signal carries noise on testing spot. For accurate measurement test signal must be processed before analyzing its parameter. In this paper, a filter technique, wavelet shrinkage or soft threshold method that was based on wavelet transform, was introduced. Experiment results show that signal de-noising is carried out without smoothing out the over voltage, over current sharp structures.