GB381111A - Improvements in and relating to electric distribution systems - Google Patents

Abstract

381,111. Converting ;protective systems. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Stone, C. W.; Box 985, Schenectady, New York, U.S.A.) April 18, 1932, No. 11081. Convention date, April 17, 1931. [Class 38 (ii).] In a power supply system, A.C. from bus-bars 11 energized by one or more generators 10 is supplied through transformers 17, 32 and grid-regulated valve rectifiers 12, 13 to a high voltage D.C. transmission line 20 feeding one or more substations 38, 61 each comprising an inverter, transformer, and rectifier arranged and operating as described in Specification 219,026, [Class 38 (ii), Electric currents, Converting &c.], whereby current at a lower voltage is supplied to a D.C. distribution network 36. Grid potentials for the rectifiers 12, 13 are derived from a transformer 21 fed through a phase-shifting arrangement comprising an inductance 24 variably saturated in accordance with load variations, in such manner that the output current of the rectifiers is limited. On the input side of these rectifiers, overload circuit breakers 28, 35 actuated by current transformers 30 (one only being shown) are provided. On the output side of the voltage converters 38, 61 reverse current circuit breakers 39, 62 operated by reverse current relays 51 (one only being shown) are provided. Between the high voltage transmission line 20 and the voltage converters 38, 61 additional circuit breakers 37, 60 are inserted the trip circuits of which are completed-only when the circuit breakers 28, 35 and the reverse current relays associated with the circuit breakers 39, 62 are operated. Thus in the event of a fault arising in any of the apparatus from the transformers 17, 32 to the transformers 46, 67 of the voltage converters, forward current from the bus-bars 11 to the fault is limited either by opening of the circuit breakers 28, 35 or by the grid control arrangements of the rectifiers 12, 13, whilst reverse current from the network 36 to the fault is limited by the unidirectional conductivity characteristics of one or more of the sets of valves. In the event of a fault arising in one of the rectifier valves 42, 43, 65, 66 of the voltage converters, reverse current from the network 36 is prevented by opening of the corresponding circuit breaker 39 or 62. At the same time, forward current causes opening of the corresponding circuit breaker 28 or 35, thus completing the trip circuit of the corresponding circuit breaker 37 or 60. After the latter has opened thus isolating the faulty voltage converter, the corresponding circuit breaker 28 or 35 may be reclosed to restore supply to the high voltage line 20.