GB1076773A - Improvements relating to fault protection for electric power distribution systems - Google Patents

Abstract

1,076,773. Protective arrangements; automatic circuit-breakers. A. REYROLLE & CO. Ltd. July 28, 1964 [April 29, 1963], No. 16809/63. Headings H2B and H2K. A power distribution system has an auto-reclosing circuit-breaker R4A controlling the supply to a cable or line 10 having a plurality of sectionalizers 1S3, 2S2, 3S1 spaced apart in series along the cable or line, each sectionalizer having a counting mechanism arranged to open the sectionalizer during a " dead-time " of the circuit breaker after a predetermined number of fault current passages less than the number of operations of the circuit-breaker required to cause it to lock open. The mechanism of each succeeding sectionalizer beyond the first is set to open the sectionalizer after fewer passages of fault current than the one before it, and the circuit-breaker is provided with an indicator to indicate the number of times the circuit-breaker has opened so as to show which sectionalizer has opened. Fig. 1 shows a system fed from both ends through circuit-breakers R4A, R4B arranged to look out after four successive opening and closing cycles within a short period. The sectionalizers 1S3, 4S3 open after three passages of fault current, the sectionalizers 2S2, 5S2 open after two passages of fault current and the sectionalizers 3S1, 6S1 after a single passage of fault current. With this arrangement the sectionalizer 3S1 would normally be open, but in a further arrangement in which the loop is normally closed, each sectionalizer is provided with two counting mechanisms respectively responsive to supplies from opposite ends of the cable or line. Each sectionalizer has a solenoid 20 energized in the event of overload or unbalance currents to operate a pawl 26 so as to raise a rack 37 one step, Fig. 3A. The return of the rack is delayed by a dash pot 40, the positioning of which determines the number of steps the rack has to be raised before a flange 60 lifts a stirrup 56 so that it engages behind a claw 61 on the solenoid plunger 25. Then as the circuit-breaker opens causing the solenoid to be de-energized, a spring (not shown) returns the plunger 25 and through the stirrup 56 turns a latch 54 to release the tripping lever 50 of the sectionalizer.