Spectrum Analysis of the Partial Discharge Pulses in XLPE Cable and Frequency Band Selection of Sensors

The exponential attenuation function,trapezoidal function,Gaussian function and circular function are used to describe the partial discharge(PD) pulses in XLPE cables,and the upper frequency limit of the PD pulses is analyzed quantitatively,which matches well with that of the detected PD pulses after FFT.The least squares techniques are used to fit the attenuation characteristics of different frequency component in XLPE cables and the best expression is given.Considering ratio of the output signals magnitude and the input signals magnitude from 0.7 to 1 as the focus energy range of the PD pulses,the bandwidth of sensors is advised in this paper when detecting the partial discharge of XLPE cable with different length.For a 5-meter-long cable joint,the upper frequency limit of sensors should be not less than 168.9 MHz and the bandwidth is several tens MHz when PD is measured in longer cables.