Study on the UHF technique applied in PD detection

Partial discharge can cause a high risk for the dielectric stability of high voltage equipment. In order to detect PD activity while equipment is operating, the ultra high frequency (UHF) detection technique is introduced. On-site PD measurements are made at cable connectors by means of log periodic dipole antenna housed outside the equipment. Thus a sensitive PD measurement even in noisy environment is possible. On-site measurements during operation showed the great potential for condition assessment [1]. This paper tries to explore the spectral distribution characteristic of electrical discharge in electric transmission and transformation equipment by using UHF technique. These researches include simulate PD sources and then use the contact-less way to discover the characteristic frequency of each type within and without the faraday cage, thereby establish the correspondence between certain characteristic frequency components of electromagnetic radiation and specific equipment deficiency. All these results showed that either radiation signal in time domain waveform or amplitude frequency diagram transformed by FFT has certain distinction and provided a basis for fault pattern recognition applied on PD detection of electrical equipment.