Grounding effect on transient earth voltage signal induced by partial discharge in metal box model

This paper deals with advancement of insulation diagnosis technology for high voltage equipment by partial discharge (PD) detection using transient earth voltage (TEV) detection method. Our previous study showed that detected TEV signal contains both high-frequency and low-frequency components around 500 MHz and 30 MHz, respectively. To further investigate the principle of detecting the low frequency components, this paper presents experiment and finite difference time domain analysis of TEV signal propagation. Results revealed that the signal intensity detected by TEV sensor with grounding is about five to six times as much as that without the grounding. Furthermore, when grounded, the low frequency components tend to be strongly detected. In other words, it is suggested that PD current including the low frequency component is induced on the surface of the metal box via the ground line, and this component greatly influences the TEV detection intensity.