Light Sensors as Detectors of Tracking Deterioration

This paper describes the result of light-pulse measurement with light sensors for detecting the tracking deterioration on the surface of organic insulating materials by means of the IEC 587 tracking test method. Three kinds of light sensors were used for detection of the discharges generated on the insulator surface. Each of the sensors can respond to ultraviolet (Su), visible light (Sv) and infrared (Sr), respectively. An Su sensor continuously counted the light pulses from the start of the test until it came to final tracking breakdown, in which case an almost constant rising rate of total number TN of the light pulses was observed. On the other hand, the rising rate of TN curves with Sv and Sr sensors during the tracking deterioration were classified into three regions according to a transition from one discharge state to another with tracking deterioration. Therefore, it was found that the measurement of the rising rate of the TN curves with Sv and Sr sensors was a suitable means for detecting the transition of the tracking deterioration. The time required and the occupied rate for respective regions were measured using the light sensors. The time required and the occupied rate for respective regions depended on both the sample and the applied voltage. It also was clarified that the test conditions have a significant influence on the main process which determines the time of the final tracking breakdown.