Insulation characteristics of XLPE cables for high frequency voltage with a PWM inverter

The development of feeder cables is being advanced for use in supplying power to propulsion coils to realize the Yamanashi experimental lines of a superconducting magnetic levitation railway (Maglev). A step voltage waveform is applied to the XLPE insulation of feeder cables by an inverter in which high frequencies are superimposed on the basic commercial frequency. The authors devised electrical testing equipment that can output such specific waveforms, and they investigated the effect of such waveforms on the insulation properties of XLPE cable, the breakdown characteristics of the model cables, and their long-term characteristics. As a result, it was learned that the insulation breakdown depends on the voltage waveform peak value and that the long-term characteristics are determined by the basic frequency. This knowledge will be useful for the insulation design of the feeder cable system of the Yamanashi experimental line.