Continuous Remote Online Partial Discharge Monitoring of HV Ex/ATEX Motors in the Oil and Gas Industry

This paper presents results from the continued application of a new technique for the remote online partial discharge (OLPD) testing and monitoring of in-service high-voltage (HV) explosive atmosphere (Ex)/atmosphere-explosive (ATEX) motors operating in hazardous gas zones. The technique employs high-current wideband high-frequency current transformer sensors located remotely from the motor under test, at the switchboard end of the HV feeder cable. Significant cost and operational benefits can be gained from this remote monitoring technique as the stator winding condition of these motors can be monitored without having to enter the hazardous gas (Ex/ATEX) zone. The work described in this paper is a continuation of that carried out by the same authors, as reported at the 2012 IEEE Petroleum and Chemical Industry Technical Conference, and includes the development of proposed condition guidelines for assessing the condition of the stator winding insulation systems of large populations of aged HV motors, based on an OLPD “league-table” database. Two case studies are presented wherein the HV stator insulation condition and reliability of in-service motors, operating in hazardous gas zones, and HV generators were assessed using both online and offline partial discharge (PD) testing and monitoring techniques. The case studies emphasize the importance of carrying out extended continuous OLPD monitoring of in-service rotating HV machines to detect underlying trends in PD activity over time. This paper concludes with how condition monitoring data can support reliability-centered maintenance and condition-based management regimes.