GB434952A - Improvements in protective arrangements for electric distribution systems - Google Patents

Abstract

434,952. Protective cut-out systems. AUTOMATIC ELECTRIC CO., Ltd., Strowger Works, and BURNS, G. A., 32, Score Lane, Broadgreen, both in Liverpool, and RAYNER, T. R., 2, Stretton Avenue, Wallasey, Cheshire. March 7, 1934, No. 7292. [Class 38 (v)] In a protective arrangement for a distribution system, potentials obtained respectively from current andpotential transformers connected to a power line are each arranged to operate two devices respectively after a delay which varies dependent on the value of the potential concerned, the operation of the device associated with the potential transformer PX serving to re-start the delay period for the device associated with the current transformer CX, while the operation of the latter device initiates the tripping of the breaker. Preferably, the potentials are rectified at BR1, BR2, and the apparatus shown is duplicated at the far end of the protected section. Neon lamps or similar gas discharge tubes N1, N2 are connected across condensers C1, C2 adapted to be charged through resistances R1, R2, of such value that for normal conditions N1 flashes and energizes the relay G, which, at g<1> shorts the condenser C2 before the lamp N2 flashes. With a short-circuit at the far end of the feeder, lamp N2 is arranged to have a less flashing interval than N1, so that it operates the trip relay T. To give protection against arc-overs, which have a relatively high impedance, a further trip circuit is provided, but is arranged to operate with a sufficient time delay to allow a short-circuit on an adjacent section to be cleared by the breakers of that section.