Propagation Characteristics of Partial Discharge Current Pulse for Branched Line

Abstract

At joint and terminal sections of electric power cables, there is possibility to occur partial discharges (PDs) in defects of insulating materials. Therefore, PD measurement is useful from a viewpoint of assessing insulation deterioration of electric power cables. There are some measurement systems to locate PDs, however, it is quite difficult and complicated in the case where cable lines include branched lines because the PD current pulse separately flows at the branch line. To establish a PD location system, the investigation of propagation characteristics of PD current pulse for branched lines is necessary. Based on EMTP simulations and experiments, we evaluated how a PD current pulse propagates at a Y-branch. The results showed that the separation of a PD current pulse is dependent on frequency component of the PD current pulse and the cable impedance after branching. The frequency components of a PD current pulse, which are higher than the resonant frequency of lines, tend to flow into the longer cable side.