Imakoma - NGK INSULATORS, LTD. Nagoya, Mizuho, Japan
Suzuki - NGK INSULATORS, LTD. Nagoya, Mizuho, Japan
Fujii - NGK INSULATORS, LTD. Nagoya, Mizuho, Japan
Nakachi - NGK INSULATORS, LTD. Nagoya, Mizuho, Japan

Reliability of power transmission lines depends on long-term performance of the suspension insulators used on the lines. The importance of such long-term performance of the insulators has been recently noted, and thus various causes of insulator deterioration are verified and laboratory test method for evaluating the long-term performance of insulators are studied. The evaluation methods explained here include thermal-mechanical performance test, steep front impulse flashover test, power arc test, salt fog aging cycle test, autoclave test. From the test results, it can be said that the abovementioned evaluation methods are effective to select high reliability suspension insulators.