Analysis of PD Signal for Condition Monitoring of MV Switchboards by the Measurement of Transient Earth Voltage

This paper dealt with the application of transient earth voltage (TEV) sensors for the online measurement and analysis of partial discharge (PD) in medium-voltage switchboards. To simulate the typical insulation defects in the switchboards, four types of artificial electrode systems, including high-voltage protrusion, low-voltage protrusion, particle-on-conductor, and void inside cast-resin potential transformer were fabricated. A TEV sensor with a frequency range of 1–150 MHz and a non-inductive resistor were used to detect the PD-induced TEV signal and the PD voltage pulse, respectively. The frequency spectrums of TEV signals were analyzed, and it was found that they had a mutual frequency range of 5–50 MHz. However, the amplitude of TEV signal was not proportional to the apparent charge specified in IEC 60270, resulting the difficulty of quantification of PD. The phase-resolved partial discharge patterns were acquired using the TEV sensor and the developed measuring algorithm, by which distinguishable patterns were obtained from different defects.