Technology of AC Short-Circuit Current Controlled Fast Vacuum Breaking in a Short Arcing Time

The objective of this paper is to propose a technology of an AC short-circuit current controlled fast vacuum breaking in a short-arcing-time, executed by a fast vacuum circuit breaker (FVCB). The technology comprises of a determination of the minimum opening velocity, a fast prediction of the short-circuit current zero point, and an optimization of the Thomson coil actuator. The minimum opening velocity of 3.2 m/s is determined when a couple of cup-type axial magnetic field contacts are used to break a short-circuit current of 40 kA. The needed duration for the prediction of the short-circuit current zero is 4.0±0.4 ms. The optimization of the actuator aiming at minimizing both the stored energy of the opening & closing capacitors and the moving mass of the transmission parts of the FVCB. Terminal fault test duties of T100s and T100a, were performed on a prototype of 363 kV/5000 A-63 kA FVCB in order to verify the controlled breaking performance. The controlled short-arcing-time of the prototype was 2.5 ms, which was demonstrated by a successful breaking of the short-circuit current of 80.6 kA under an opening velocity of 4.5 m/s.