Test methods and results for recent outdoor insulation in Japan

This paper describes new test methods and some typical test results for a recently developed external insulation in Japan. The paper starts with the introduction of the results of the tests that were conducted specially on the external insulation for 1100 kV/10 GW ac transmission line and +/-500 kV/2.8 GW dc overhead line section, recently constructed in Japan using heavy duty insulators, giant bushings, etc. Various special tests were made on the external insulation in order to investigate the performance at such high service voltages since those had never been used before, and secondly because of the high reliability required and the importance of the lines. Introduced next are test methods and some related results on long term performance for the new type of insulators, such as semiconducting glaze and polymer insulators. Also included in the paper are the development of some special test methods and results on line arresters for transmission and distribution lines, which have been accepted widely in Japan.