Electromagnetic time reversal for online partial discharge location in power cables: Influence of interfering reflections from grid components

In online single-sided partial discharge (PD) location, the measured PD reflection patterns are affected by the characteristics of all the components of the associated power network. This paper analyses the performance of a PD location method based on electromagnetic time reversal (EMTR) theory, when interfering reflections contribute to the transient signals emitted by the PD event. The topology analysed is formed from a ring main unit (RMU) in a medium voltage grid with mixed cross-linked polyethylene and paper-insulated lead-covered (PILC) cable sections. The PD reflection patterns, observed at the RMU, are disturbed by the reflections coming from the impedance discontinuities of the circuit and by the reflections coming from the cable ends of the PILC cables connected to the RMU. The simulated configuration is chosen such that classical location techniques tend to fail due to overlapping peaks and other signal distortion. This is because the classic techniques are based on identifying individual reflection peaks from which the PD source can be determined via differences in time of arrival. The numerical investigation shows that the accuracy of the EMTR-based location method is robust against these effects, achieving a PD localisation with an error less than the 0.1%. The results also show that the EMTR-based method can localise PDs using a PD monitoring point located somewhere along the network and not necessarily at the line termination.