Protective distance relay system for power transmission lines

摘要

1,090,862. Protective systems. ENGLISH ELECTRIC CO. Ltd. Feb. 26, 1965 [March 2, 1964], No. 8628/64. Heading H2K. A protective system comprises a distance relay at each end of a protected section, each relay including a non-directional element 17 initiating the transmission of a control signal to the other relay upon a fault occurring within a distance which embraces all of a number of zones of protection extending from both relays, the zones of each relay being provided by a directional element 10 and together extending over the whole of the protected section. On the receipt of a control signal, electromagnetic switches 21, 14 and 22, 23 extend the initial zone of the relay and prevent the tripping of the circuit breaker at that end. The directional element 10 has contacts 16 for interrupting the transmission of the control signal and contacts 15 for tripping the circuit-breaker when a control signal is not received. If a fault occurs in the protected section within the initial zones, i.e. zone 1, of both relays, both elements 10, 17 in each relay respond, the elements 10 closing contacts 15 to trip the circuit-breakers before the transmission of the control signals can prevent such tripping. If the fault occurs in the protected section in zone 1 of one relay (A) and in zone 2 of the other relay (B), the elements 17 cause the transmission of the control signals, but element 10 in relay (A) responds sufficiently quickly to trip the associated circuit-breaker before the incoming signal can prevent it. The transmission of control signals from relay (A) ceases so that contacts 23 at relay (B) reclose but as the electromagnetic switch 21, 14 has a delayed drop-off, the contacts 14 remain open for a short period extending zone 1 of this relay so that the element 10 operates to trip the associated circuit-breaker. For a fault outside the protected section neither circuit-breaker will trip. The element 17 also controls the operation of a further electromagnetic switch 26, 13 which operates with a time delay to change the operation of the element 10 from zone 1 to zone 2 so that tripping is obtained for a zone 2 fault should the transmission arrangements fail. Semi-conductor switching devices may be used instead of the electromagnetic switches.