Experimental investigation of typical partial discharge signals in medium-voltage switchgear

Partial discharges (PDs) phenomena in medium-voltage switchgears usually exist and are worth being paid more attention. In this paper, a kind of special switchgear cabinet and two kinds of typical PD sources is designed for the PD measurements. Based on the two typical PD models, measurement sensitivity and influence factors of above four kinds of detection methods are researched and analyzed. The experimental results show that Pulsed current (PC) method is the most sensitive to PD signals but it is also more sensitive to the electromagnetic disturbance. Holes on the switchgear cabinet are important for Acoustic Emission (AE) method. The cabinet materials and sensor positions have no significant influence on Transient earth voltage (TEV) signal. Impermeability magnetic material has more significant influence on preventing Ultra-high-frequency (UHF) signals transmission than the permeability magnetic material, which is unfavorable for detection of UHF signal. Larger holes on switchgear cabinet are beneficial to the measurement of UHF method. For the needle-plane model, the phase-resolved partial discharge (PRPD) graph changes from “ball” shape to the “M” shape as the voltage increases. Different from needle-plane model, PRPD graph of suspended-metal model exists significant stratification phenomena.