GB237016A - Improvements in protective arrangements for electrical systems - Google Patents

Abstract

237,016. Brown, W. J., and Metropolitan-Vickers Electrical Co., Ltd. April 17, 1924. Cut - out arrangements.-Relates to a protective system of the kind in which frequencies each of which is high in relation to the line frequency are superimposed respectively on the sections of the line and tuned relays responsive only to the superimposed frequency of a section are employed to isolate the section on fault. The circuits through which the protective frequency is fed into the desired section are provided with condensers and reactances whereby they offer a low impedance to such high frequencies, and the ends of the protected section are provided also with condensers and reactances so proportioned as to constitute tuned resonant circuits to the high frequency and, consequently, to confine it to its particular section. In the arrangement shown in Fig. 1, the high-frequency generator 5 which may be a. dynamo-electric machine or a thermionic oscillation generator supplies the superimposed frequency to the singlephase circuit 1, 2 through acceptor circuits 6, 7. Tuned rejector circuits 8, 9 and 10, 11 are provided at the end of the line to confine the frequency to its particular section. In Fig. 4, the high-frequency is led into the system through the transformer 17, 18. Compound rejector circuits as applied to a three-phase system are shown in Fig. 6 and the corresponding acceptor circuits in Fig. 7. By means of a star-connected balanced resistance connected in parallel with the conductors, the effect of heavy line capacity currents may be overcome. Two or more protective currents of different frequencies may be superimposed on the line system and separate relays provided for each protective current.