On-line monitoring of multiple insulation parameters of high voltage XLPE cable

The insulation parameter model of XLPE(crosslinked polyethylene) cable exerted by AC voltage is established,and the behavior of insulation parameters of the cable with deteriorated insulation is analyzed.It is suggested to comprehensively evaluate the insulation condition of XLPE cable by its working insulation resistance,equivalent capacitance,dielectric loss factor and their change tendency,which is analyzed in availability and rationality.An on -line monitoring system of high voltage XLPE cable is designed.Nonlinear least square fitting based on LM(Levenberg -Marquardt) algorithm is applied in the fitting of sampled signals.The harmonics obtained by fast Fourier transform analysis is taken as the initial values of LM and the fitting results are used to calculate the monitored parameters.Simulation results show that,the algorithm has fast convergence and high precision,and better restrains the influences of frequency fluctuation,direct current component and harmonic contents.