Monitoring system for stator winding insulation in high voltage electrical machines with novel sensor

On line Partial Discharge (PD) detection is a common method for insulation monitoring in high voltage electrical machines. The paper presents a new type of PD detection sensor which is a micro strip line device embedded in the stator slot (referred to as MSLS) and an insulation monitoring system using the new sensor. The MSLS characteristics are described in detail. The experimental results in the lab and in a plant show that the monitoring system with the new sensor has better noise rejection performance than other methods. Based on the test results, the paper discusses the calibration problem of PD in the stator windings of high voltage electrical machines. The output of the monitoring system signal is affected by the frequency characteristics of the detection circuit, the frequency spectrum characteristics of PD, and the transfer performance from the PD site to the sensor. The calibration of the apparent charge in the stator windings of electrical machines is relative to the location of PD site.