Development of a Current Limiter Using Vacuum Arc Current Commutation. Phase 2. Maximizing the Current Rating of a Single 72-KV Device Using a Minimum Amount of Parallel Capacitance. Final Report

摘要

Phase 1 of this study showed the feasibility of developing a current limiter using vacuum arc current commutation. The objective of Phase 2 has been to increase the commutation current of a single 72 kV device while also reducing the value of the parallel capacitance. The program has been largely experimental in nature, although a parallel theoretical effort has provided device and circuit guidelines. A total of 14 prototype vacuum devices were designed, built and evaluated, and the major parameters varied were device geometry, characteristics of the parallel circuit, electrode actuation speed, waveshape of the applied transverse magnetic field, point on wave of electrode separation, and the use of series connected vacuum interrupters. Progress can be determined by comparing the commutation levels with Phase 1. For the earlier 15 kV circuit, the commutation level increased to 14.5 kA for a parallel capacitance of 50 mu F. In particular, commutation levels of 12 kA (50 mu F) were observed in circuits where the transient recovery voltage of 50 kV approximated the transient associated with a 72 kV circuit. Here, the necessary conditions of rapid electrode separation were approximated by actuation to 2 cm in 1.4 ms. Analysis involving assumptions about the actuator and sensor characteristics indicates that the present device could reduce by half the fault currents associated with 72 kV/10 kA and possibly 72 kV/15 kA circuits. A Phase 3 program is recommended aimed at further improving the device performance, and in particular at developing a concept for a 145 kV fault current limiter. (ERA citation 05:015701)