Effects of Dispersion and Multi-Path Propagation in Partial Discharges Location

Dispersion and multi-path propagation distort partial discharge (PD) pulses that travel along power cables. This article proposes a theoretical framework that models the PD source location error owing to these effects. Regarding dispersion, a closed-form expression is proposed to estimate the PD bandwidth reduction at the cable ends, as well as the expected location error due to propagation velocity variation. A new expression is proposed for the difference of times of arrival (TOAs), which exhibits dependence with frequency. Multi-path propagation also introduces a non-linear dependence with frequency in the TOAs, which leads to location errors when the echo is very close to the main PD signal. Three location algorithms (based on cross-correlation, phase increment, and energy criterion) are investigated under noise, dispersion, and multi-path conditions. Simulation results show that the energy criterion algorithm is very sensitive to dispersion, but it is robust to multi-path propagation. The algorithm based on phase increments is the most sensitive to noise. Finally, the best location method for noisy, highly dispersive, multi-path propagation is the one based on cross-correlation.