A comparison of the pollution performance of long rod and disc type HVDC insulators

Long rod insulators made of porcelain and disc type insulators made of porcelain or glass are the main types of HV insulators used since more than 60 years in overhead transmission and distribution lines and also will be the dominating products in the future. Historically based, there exists much published work on the electrical pollution performance of disc (cap and pin) type HV insulators. Only little knowledge exists about the good service pollution performance of the long rod type insulators. This paper compares the test results obtained from artificial pollution tests according to IEC 61245 with both types of HV insulators under same test conditions. The tests were performed with DC voltage at the FGH (Forschungsgemeinschaft fur Elektrische Anlagen), an independent German high voltage test laboratory. It is well known that the sensitivity of insulator strings to pollution effects is much higher at DC than at AC (50 Hz power frequency) voltage. The test results show an equivalent pollution performance of long rod and disc (cap and pin) type insulators under the same pollution conditions and the same electrical stresses