Over-voltage protection arrangements for power supply networks particularly for use in telecommunication systems

摘要

654,052. Supply systems for consumption apparatus. STANDARD TELEPHONES & CABLES, Ltd. Aug. 21, 1947, No. 23185. [Class 38 (iv)] [Also in Group XXXIX] In a system in which unattended repeater stations receive operating power over the communicating line excessive voltage is prevented during periods of abnormal reduction in the equipment loading by switching into circuit suitable dummy loads. Fig. 1 illustrates such a system with " go " and "return paths, the power being transmitted from the controlling station CS over the phantom circuit of the two paths to the intermediate unattended stations RS1 ... 5. At each station the power is diverted by filters X to a mains unit M and the unconsumed power is reapplied to the line after voltage adjustment by an autotransformer T, through a further pair of filters X. A dummy load R3 equivalent to the power taken by the local mains unit for H.T. supply is connected when current relay PC is unoperated, e.g. during the heating of the filaments after the initial switching on or when the H.T. current falls, due to a local fault and a dummy load R4 which is equivalent to the load normally supplied by the output transformer T is under the control of a current relay LC and a sluggish no-volt relay NV, the latter of which prevents the load R4 being inserted while the load through LC is building up.