GE unveils 420 kV, 63 kA g³ GIS circuit-breaker prototype March 30, 2022 | Europe Company News GE Renewable Energy’s Grid Solutions unveiled its 420 kV, 63 kA g³ (pronounced 'g'-cubed) gas-insulated substation (GIS) circuit-breaker prototype. This content is available to only paying subscribers. Username or E-mail Password Remember Me Forgot Password