High voltage control devices

In an elecrical system having a voltage source and a load connected through a power bus including a first circuit breaker, an improved fault current limiting circuit connected in parallel with said first circuit breaker comprising

• a second circuit breaker in series with a high voltage control device,
• said high voltage control device comprising
• (a) a housing;
• (b) an aprotic liquid contained within said housing, said aprotic liquid
• (1) at low fields, having a specific resistivity which decreases with increasing temperature according to an exponential dependence characteristic of semiconductors, and having a first fixed specific resistivity A at a first predetermined temperature below the viscosity transistion temperature,
• (2) at high fields, below the viscosity transition temperature, having a specific resistivity markedly lower than that at low fields, and having a second fixed specific resistivity 1 at said first predetermined temperature, and
• (3) at high fields, above the viscosity transition temperature, having a specific resistivity substantially higher than that at the same high fields below the viscosity transition temperation, but having such specific resistivity at a value below that at low fields, and having a third fixed specific resistivity C at a second predetermined temperature above the viscosity transition temperature,
• (c) means for effecting heat exchange with said liquid,
• (d) at least two spaced electrodes contained within said liquid and each of said electrodes extending from said housing, and
• (e) means for operating said high voltage control device whereby the specific resistivity of said aprotic liquid changes from one of said first, second, or third fixed specific resistivity to another of said first, second, or third fixed specific resistivity.