GB240157A - - Google Patents

Abstract

240,157. International General Electric Co., Inc., (Assignees of Allgemeine Elektricitõts Ges.). Sept. 20, 1924, [Convention date]. Cut-out arrangements. - In the protection of more than two parallel connected lines 1, 2, 3 by means of wattmeter type relays b<1>, b<2>, b<3> one for each line, one winding of each relay carries a current proportional to the difference between the current flowing in its own line and that flowing in another line, while the other winding carries a current proportional to the difference between the current flowing in its own line and that flowing in a third line. If J1, J2, J5 are the (normally equal) currents flowing in the three lines, the relay windings are so interconnected with one another and with the current transformers a1, a2, a3, as shown, that the distribution of currents in the windings is that indicated in Fig. 1. Normally there is no torque on any of the relays but, in the event of fault on any one of the parallel lines, its corresponding relay, and that only, is operated to trip the corresponding circuit-breaker. In order to obtain discriminating protection for the finally remaining pair of parallel feeders, the circuit-breakers are arranged to cut out their relay windings and current transformer windings when they trip and to cut in a differential or other known protective connection k by opening the switch h, as shown in Fig. 3.