Consideration of Generation Mechanism of Low Frequency Component of Partial Discharge Signal Detected by Transient Earth Voltage

Transient earth voltage (TEV) detection method is drawing attention for its readiness to be installed just on the outer wall of existing equipment, and is useful for partial discharge (PD) detection. The purpose of this research is to establish reliable insulation diagnosis technique of high voltage equipment based on partial discharge detection using TEV method. Our previous study showed that TEV sensor dominantly detects high (several 100 MHz) and low frequency (several 10 MHz) components attributed to the electromagnetic wave propagating through space and discharge current flowing through the ground line, respectively. To investigate a mechanism of generated low frequency components further, this paper deals with the effect of the length of PD measurement circuit on the low frequency component detected by TEV sensor by experiments and simulation of electromagnetic wave propagation using finite difference time domain (FDTD) method. As a result, it was found that the low frequency component includes two different kinds of dominant resonance frequencies determined by assuming the measurement circuit to act as a lumped constant electric circuit and as an antenna such as dipole antenna and loop antenna.