Abstract
The investigations on dc tracking resistance should be enhanced due to the increasing of organic insulating materials being used with do power. This paper describes the do tracking failure of organic insulating materials by use of the IEC Publ. 112 method. Although the use of direct voltage is spreading in our society currently, there have been few studies on the mechanism of the tracking resistance with direct voltage. This paper presents a study on tracking resistance of paper base phenolic laminates (PL) and glass cloth base epoxy resin laminates with and without flame-retardant (EX1, EX2) with direct voltage application. The test with alternating voltage is also made in order to compare the influence of discharge wave forms on tracking failure for that with direct voltage application. The test results show that the apparent CTI values with direct voltage are bigger than those with alternating voltages. It can be considered that this difference is caused by the discharging characteristics which depend on the types of voltage wave forms.
