Dielectric spectrum testing is an effective means of finding cable defects. But traditional dielectric spectrum testing requires cable slice sampling, which is very expensive for high voltage power cables. Therefore, this paper explores the method of whole cable testing of high voltage power cables. Due to the large capacitance of the whole cable test, and the current research shows that the low frequency band has a higher sensitivity to reflect cable defects, the test frequency band of the dielectric spectrum is set to 0.01Hz-0.1Hz. Three 110kV power cables with defects were prepared, and the dielectric spectrum measurements of the whole cables were carried out. Restricted by the output voltage of the device, the maximum test voltage is 1/3U₀. The dielectric loss from 0.1Hz-0.05Hz-0.02Hz-0.01Hz under four output voltages of 1/10 U₀-1/5 U₀-1/4U₀-1/3 U₀ was obtained. The research results show that it is feasible to diagnose high-voltage cables by measuring the dielectric spectrum of the whole cable. Although the highest voltage is only 1/3U₀, the dielectric spectra of different defect types have significant differences, which can be diagnosed and identified.
 

high voltage power cable,defect diagnosis,whole cable,dielectric spectrum