Operation of superconducting fault current limiters in electrical networks

The discovery of ceramic superconducting materials that conduct electric current with practically no losses at temperatures around 77 K (the temperature of liquid nitrogen), known as high-temperature superconductors, opens up a range of innovative application possibilities for electric power systems. For example, the change in resistance of the material during transition from the superconducting to the normal-conducting state can be used to limit the short-circuit current, even before its first peak value is reached. The transition to the normal-conducting state of the superconductor takes place when its critical temperature is exceeded, e.g, as the short-circuit current increases. After clearance of the fault and a short cool-down period, the current limiter automatically returns to its superconducting state. Compared with conventional means of short-circuit current limitation, there is no need for a fault detection device, and the process reverses automatically without components having to be exchanged after a fault occurrence. The further advantages offered by the use of a superconducting fault current limiter in electric power systems are also discussed