A testing research on composite air clearance for live line working on 500 kV DC transmission lines

In this paper, the insulation characteristics of composite air clearances of both tension towers and suspension towers for live line working on 500 kV DC transmission lines are introduced. The tests are carried out in two ways. One is to simulate the man riding on the tension insulator strings moving to the conductor side. The other is to simulate the soft ladder carrying a man slipping to the conductor side along the slideway which is mounted on the crossarm. During the test, different working conditions are considered, such as tests with different switching impulse waveforms, the existence of damaged insulators within the string and so on. As a result, the safety and reliability of live line working on 500 kV DC power transmission lines has been confirmed.