UHF characteristic of PD in oil-paper insulation under DC Voltage

A test system with UHF and UWB detection technologies developed to measure PD under DC voltage is introduced in this paper. According to the typical defects in oil-paper insulation of converter transformer, six corresponding PD models are designed. The test results of PD UWB detection under DC voltage show that the PD current pulses have a very short rise-time, which are capable of radiating UHF signals at frequencies up to at least 300 MHz, and these electrical magnetic waves can be picked up by the UHF sensor. The DBM spectrum analysis is made for all UHF signals of the models, which shows that they differ with various defects, and the maximum amplitudes of the energy distribution against the UHF are also different. These indicate the on-line monitoring for the UHF PD signal under DC voltage should be realized utilizing the narrowband filter with adaptive center frequency.