Continuous, remote on-line partial discharge (OLPD) 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, on-line partial discharge (OLPD) testing and monitoring of in-service, high voltage (HV) Ex/Atex motors operating in hazardous gas zones. The technique employs high current, wideband, high frequency current transformer (HFCT) 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 IEEE-PCIC 2012 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 on-line partial discharge (OLPD) `league table´ database. Two case studies are presented wherein the HV stator insulation condition and reliability of in-service motors, operating in a hazardous gas zones, and HV generators were assessed using both on-line and off-line partial discharge testing and monitoring techniques. The case studies emphasize the importance of carrying out extended, continuous on-line partial discharge monitoring of in-service rotating HV machines to detect underlying trends in partial discharge activity over time. The paper concludes with how condition monitoring data can support reliability centered maintenance and condition-based management regimes.