Sequential switching of dump resistors and reclosing on a 100-KJ system

A fault in an electric power system may be cleared if the faulty section is isolated and de-energised. If the section is then re-energized quickly by reclosing the circuit breakers, there is a good chance that the system can become fully operative again. Similarly in a superconducting system it is often possible to reclose successfully after a fault. However the system inevitably stores a large amount of magnetic field energy which must first be reduced. The speed at which stored energy may be transferred or dumped is limited by the voltage which the insulation can withstand safely. Sequential switching of dump resistors can keep the voltage within safe design limits and at the same time reduce the stored energy quickly, resulting in less damage and a greater possibility of reclosing successfully. Following successful reclosing tests on a smaller system, a 100 kJ system has now been investigated for sequential switching of dump resistors, followed by reclosing the power supply breakers. The paper describes a microprocessor controlled system in which the micro-processor is used to detect faults, make decisions and initiate appropriate switching action.