GB426628A - Improvements in and relating to protective devices for electric circuits - Google Patents

Abstract

426,628. Protective cut-out arrangements. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.- (Assignees of Allgemeine Elektricitõts-Ges.; 2, Friedrich Karl-Ufer, Berlin) Aug. 4, 1933, No. 21964. Convention date, Aug. 4, 1932. [Class 38 (v)] In a protective arrangement having a relay 2 energized in accordance with the current and voltage of the circuit to be protected, the current coil 5 of the relay being connected, as described in Specification 349,199, with the secondary winding 6 of a current transformer, upon whose core is placed an additional winding 7 energized in accordance with the voltage, the relay 2 is adapted on operation to open a circuit-breaker 10, the reclosing of which is controlled by a ballast resistance 12 so connected that sufficient current is permitted to flow in the current coil 5 of the relay to prevent reclosure of the circuitbreaker until both sides of the latter are at the same potential. In the single-phase arrangement shown in Fig. 1, the ballast resistance 12 is placed in series with the winding 6 across the contacts of the circuit-breaker 10, and an auxiliary switch 9 opens the circuit of the winding 7 when the circuit-breaker opens. An adjustable resistance 8 is included in the circuit of the winding 7. In a modification, Fig. 2 (not shown), the invention is applied to a threephase network, the current transformer being connected in one of the phases, and the ballast resistance being placed in series with the secondary winding of the current transformer across another phase. In another arrangement, Fig. 4, the coil 7 is not cut out when the circuitbreaker 10 opens, but is connected by the switch 9 in series with the ballast resistance 12 across the contacts of the phase R energizing the current transformer. Another auxiliary switch 15 connects the voltage coil 1 of the relay 2 to the phase R when the circuit-breaker opens, the coil 1 being normally connected to a phase T in advance of the phase R when the circuit-breaker is closed.