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Partial Discharge Detection of On-Line Cables Based on Hilbert Huang Transform

Hilbert-Huang transforms calculation method was used in the study on signal of partial discharge from on-line cable. The partial discharge signal was made to be intrinsic mode function (IMF) by empirical mode decomposition (EMD).The cubic spline interpolation was selected as the interpolation function and ideal envelope curve was achieved to eliminates defects such as overshoot and undershoot effectively. Appropriate lock-in amplifier was choosed and pre-amplifier and phase sensitive detection circuit was designed to determine the calculation programs. The results showed that the test system can effectively capture the weak PD signals in cable under complex environmental conditions and the PD signal waveform obtained was improved through Hilbert-Huang transforms.The state of insulation and the remaining life of the cable can be judged effectively,which has practical significance for improving the grid security.