ABB SPAU 140 C-AA RS 488 001-AA PROTECTION RELAY

Product Description

ABB SPAU 140 C-AA RS 488 001-AA PROTECTION RELAY

The relay incorporates two identical stageswhich operate as independent units. Both stagesof the synchro-check relay has two parallel functions: a synchro-check function and a voltagecheck function.The synchro-check relay can be used for twodifferent operating conditions, the most typicalof which is where both sides of the circuitbreaker to be closed are live. Then synchronismis always checked before the circuit breaker isgiven the permission to close. The other situation is where one or both sides of the circuitbreaker to be closed are dead and, consequently,frequency and phase difference cannot be measured. In this case the relay checks the energizing direction. The user is able to define the voltage range within which the measured voltage isdetermined to be "live" and "dead".The purpose of the synchro-check function isto find the instant when the voltages on bothsides of the circuit breaker are in synchronism.The conditions for synchronism are met whenthe voltages on both sides of the circuit breakerhave the same frequency, are in phase and are ofsuch a magnitude that the concerned busbarsor lines can be regarded as live.When the frequency, phase angle and voltageconditions are fulfilled, the duration of the synchronizing conditions is checked so as to ensure that they will still be met when the contacts of the circuit breaker close. This durationis determined on the basis of the frequency andphase difference measured. Depending on thecircuit breaker and the closing system, the delay from the moment the closing signal is givenuntil the circuit breaker finally closes is about50 - 250 ms. The CB operate time selected tellsthe relay for how long, at least, the conditionshave to persist.The voltage-check function checks the energizing direction. Energizing is defined as the situation where a dead network part is connectedto an energized section of the network. The conditions of the network sections to be controlledby the circuit breaker, i.e. which side has to belive and which side dead, are determined by setting. A situation where both sides are dead ispossible as well.When the energizing direction corresponds tothe settings, the situation has to be constant fora certain time before the close signal is permitted. The purpose of this operate time (dead time)is to make sure that the dead side remainsdeenergized and that the situation is not due toa temporary interference. Should the conditionsnot persist for the specified operate time, theoperate time is reset and the procedure is startedagain when allowed by the conditions. Not until the required energizing situation has beenconstant throughout the set operate time, circuit-breaker closing is permitted.