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Improvements in or relating to protective systems for locking the protection relays of electrical lines in unstable conditions
Improvements in or relating to protective systems for locking the protection relays of electrical lines in unstable conditions
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机译：改进或涉及用于在不稳定条件下锁定电线保护继电器的保护系统
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573,748. Protective cut-out systems. COMPANIA PARA LA FABRICACION DE CONTADORES Y MATERIAL INDUSTRIAL SOC. ANON., and VITEAU, P. March 31, 1944, No. 6015. [Class 38 (v)] A system for distance-protection against faults is prevented from responding to asynchronous fluctuations by blocking relays remaining continuously locked whilst the frequency of the fluctuations exceeds a given value. The tripping of a circuit-breaker 3 controlling a line 2 by the closure of contact 41 of a relay 4 of a protective device 1, is controlled by a blocking device comprising two impedance relays 5, 6 associated respectively with auxiliary relays 7, 8 energised by a voltage source 9. A fault causes simultaneous closure of contacts 51, 61 of relays 5, 6, but as relay 7 operates faster than relay 8 the former operates to open contacts 711 and prevent operation of relay 8, and to close contact 71 giving control of the circuit breaker to relay 4. With asynchronous line fluctuations of less than criticial frequency, when impedance decreases below Z1, relay 6 operates first to close contact 61 thereby energising a condenser 10, and, througb contacts 711, the relay 8, the contacts 81 closing and contacts 811 opening to break the circuit-breaker trip circuit. When the impedance Z2 Z1 relay 5 operates to energize relay 7 and open contacts 711 but relay 8 remains energised through closed contact 81. As impedance rises above Z2SP1 Z2 contacts 51 open to de-energize relay 7, and as it rises above Z1SP1 Z1 contacts 61 open but relay S remains energized during a time td by discharge through it of the condenser 10. If the frequency of fluctuation is greater than the critical value the relay 8 is still in the energized position when relay 6 again closes so that the protection remains locked when time between the opening and closing of contacts 61 is less than td. A modification is described in which the auxiliary relay associated with relay 6 short-circuits the coil of the auxiliary relay associated with relay 5 to afford the locking, and the delay in unlocking is provided by the former auxiliary relay having a short-circuited ring, Fig. 2, (not shown).
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