Criteria for renovating Circuit-Breakers of 500 kV MTS

In the Kansai region of Japan, 500 kV substations first introduced gas-insulated switching equipment in 1973, and currently 230 units are in operation. The first-generation gas circuit breakers (GCBs) installed initially have already been replaced. The second-generation GCBs, which were introduced from the late 1970s, have now been in service for about 40 years; they have not been replaced and are showing advanced ageing.