. Electric railway journal . action provides an instantaneous reset whichprevents the time relay from having a cumulative char-acteristic. Safeguarding the Substation Apparatus An automatic substation must necessarily be betterprotected than an ordinary manually-operated stationbecause the automatic control is required to take care ofall operating contingencies that may arise. The protec-tive features which have been provided in the controlequipment under discussion are described below. Protection against Lotv Voltage at Starting.—RelayNo. 2, an induction type relay operating on single-phasepo
. Electric railway journal . action provides an instantaneous reset whichprevents the time relay from having a cumulative char-acteristic. Safeguarding the Substation Apparatus An automatic substation must necessarily be betterprotected than an ordinary manually-operated stationbecause the automatic control is required to take care ofall operating contingencies that may arise. The protec-tive features which have been provided in the controlequipment under discussion are described below. Protection against Lotv Voltage at Starting.—RelayNo. 2, an induction type relay operating on single-phasepotential, is calibrated to open its contact at 80 percent of normal line potential. In case there is insuffi-cient potential to start the converter this relay will notopen. Protection against Reversed Phase and Phase Failure.—Relay No. 18, a standard type CP induction relayhaving polyphase potential coils, is operated directlyfrom the power transformer secondaries, so that if for May 17, 1919 Electric Railway Journal 951. THE UNDERLOAD DELAY RELAY any reason polyphase potential of adequate amount foroperation of the converter is not present this relaywill not close its contact. Thus the starting switch cir-cuit relay will be opened and the station will be dis-connected from the line. Protection against Alternating-Current Overload.—The overload protection is normally set for 200 per centof normal full-load current and with a sufficient time in-terval to allow the direct-current overload relay to oper-ate in advance of the alternating-current relay. Onequipment with primary voltage of 17,000 or less,current transformers and type CO relays are used,these being standard induction overload relays. Forpotentials above 17,000 volts a series high-tension in-duction relay is used which obviates the necessity for using curre n ttransformers in-sulated for thefull line voltage. Direct - Cur-rent Reversed -Current Protec-tion.—Pro tec-tion against re-versal of energyflow in direct-
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