Switching of no-load cable is one of the operating duties required by H.V. circuit breaker. During this switching

it would produce the higher switching overvoltage which is harmful to the safety of electrical system operation. Therefore it is necessary to make the switching test for the circuit breaker of 110kV class（including 66kV） and the above. The field tests of 110kV no-load cable were carried out in Shanghai electric system. The auther preliminarily proposes his viewpoint on the testing conditions and the criteria for references.