Development of compact gas-filled bushings with new inner-grounded electrode

In Europe and the USA, the use of gas-filled bushings with hollow composite insulators has increased. Hollow composite insulators are superior in that they are light, explosion proof, and pollution resistant, and their economic efficiency is advantageous at larger classes especially. However, developing compact gas-filled bushings by improving electric field distribution is important. The main issue for making design more compact is finding a way to reduce electric field strength on the outside hollow composite insulator around the inside grounded electrode tip. A new-type inner grounded electrode structure which consists of ring-shaped electrode and cylindrical electrode is proposed. This paper describes the effect of reduction of maximum value of electric field strength on the outside hollow insulator by the new-type one. Finally, the insulation performance of the prototype of 800-kV gas-filled bushing is described with a discussion of the results of testing fundamental insulation and overvoltage.