Long term on-line PD monitoring using power line communication in a distribution substation

The purpose of this study is to establish an on-line insulation diagnosis technique using power line communication(PLC) and ferrite cores(FC). So far, we have established and demonstrated an on-line partial discharge (PD) monitoring system (PLC-PDMS) based on the principle of detecting PD as a disturbance of PLC with decreasing information transmission rate (PHY rate). This paper presents application of PLC-PDMS to monitor PD in a distribution substation in service. High frequency CT sensors and ferrite cores were installed at the ground wires of three-phase cables connecting between a three-phase transformer and circuit breakers. Output signals detected with the sensors were recorded with an oscilloscope and PLC-PDMS for about forty days. An attempt was made to compare conventional phase-resolved PD (PRPD) pattern created from signals detected with CTs with PHY rate distribution obtained for each communication quadrant. As a result, it was found that the PHY rate distribution shifted to the lower rate side in the first and third quadrants. This result is consistent with the conventional PRPD pattern. These results suggest that PLC-PDMS can be used for PD monitoring and detection in practical substations.