GB313208A - Improvements in or relating to electrical indicating and/or recording apparatus - Google Patents

Abstract

313,208. Phillips, W., and Elliott Bros. (London), Ltd. March 9, 1928. Pressure and current at distant places, measuring; power meters. -In order to minimize the effect of the resistance of long connecting leads between an instrument transformer and an instrument, the secondary winding of the instrument transformer supplies the primary winding of a second or separating transformer the secondary winding of which consists of a large number of turns of fine wire. As shown applied to an ammeter indicating at a central station the current flowing in a circuit k at a substation, a measuring transformer a has its primary winding h connected in the circuit k and its secondary winding i connected to the primary winding of a separating transformer b, the secondary winding d of which is connected through leads f to the ammeter g at the central station. The secondary winding d of the transformer b consists of a large number of turns of fine wire so that the full-load current therein is of the order of 0.1 or 0.05 ampere, thereby reducing the load on the measuring transformer. Connected across the winding d is a shunt resistance c, or an inductance, or both, of such a value as to limit the voltage across the winding d to say 200 volts if the instrument circuit is opened. A gas discharge lamp e which becomes illuminated at a pressure of 200 volts may be connected across the winding d to serve as a visual signal of undue rise of pressure. The lamp e may be replaced by a spark gap, relay, bell, &c.