Effect of the Presence of Metal Box on Partial Discharge Waveform and Pattern Detected by High Frequency Current Transformer

Power apparatus is usually enclosed by metal box or metal shield. The partial discharge (PD) detection system needs to be designed for this power apparatus. This paper discusses the effect of the presence of the metal box on partial discharge (PD) waveform and partial discharge pattern detected by using high frequency current transformer (HFCT). The PD source is needle plane electrode in air. The measurement was done in two conditions: PD source was placed inside metal box and PD source was placed anywhere without metal box. The effect of the presence of the metal box is observed by measurement of peak to peak voltage of PD waveform and PD number of PD pattern. The experimental results show that Vpp and PD number is higher when the PD source is covered by the metal box. It is considered that the metal box shields the PD source from the external noise.