Development of automatic, continuous partial discharge monitoring systems to detect motor and generator partial discharges

Abstract

Partial discharge testing is widely used to monitor the condition of the electrical insulation in high voltage motor and generator stator windings. In the past, virtually all online partial discharge testing has been performed on a periodic basis, for example every six months. Two different monitoring systems have been developed which enable the continuous measurement and storage of partial discharge data. The first system is a full-featured system which captures all the partial discharge information, including a pulse magnitude and pulse phase analysis. This system duplicates all the features of a portable instrument, and is intended for use on high voltage machines which see many load changes, are equipped with online expert systems, or are in remote locations. The second system which has been developed is intended for medium voltage motors (2.3 to 4.1 kV). For some failure processes on such motors, partial discharges may only yield a few weeks or months of warning of failure. Thus, continuous partial discharge measurement is essential to give the maximum possible warning time. This system has only basic capabilities for data collection, in order to minimize cost. Both systems employ advanced electrical interference separation methods to minimize the risk of false indications and the need for expert intervention.