Assessment of the 6.6 kV class on-line partial discharge measuring ceramic coupling sensor for winding machines

In order to improve the reliability of the insulation system in the high voltage winding machines, it is necessary to understand the insulation condition and life assessment of the high voltage windings part. Partial discharge (PD) measurement is one of the most effective techniques in the evaluation of insulation condition for the high voltage winding machines. Especially as the on-line PD test provides the ability to monitor effects without interrupting the electrical machines, this method has been proven the major testing technology. Nowadays, EMC (epoxy mica coupler) type capacitive couplers have been the most widely used sensors for on-line PD detection in rotating machines. This paper deals with the electrical characteristics and long-term reliability test results of the 6.6 kV class on-line PD measuring ceramic coupler (CC), which can be easily mounted into high voltage input terminal part, has been developed and tested to continuously measure PD activity during operating condition for winding machines.