Instruction manual –AQ F210 Feeder Protection IED
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8.1
T
RIP CIRCUIT SUPERVISION
8.1.1
T
RIP CIRCUIT OPEN COIL SUPERVISION WITH ONE DIGITAL INPUT AND
CONNECTED TRIP OUTPUT
Trip circuit supervision is used to monitor the wiring from auxiliary power supply trough IEDs
binary output and all the way to the open coil of the breaker. It is recommended to know that trip
circuit is on healthy state when the breaker is closed. Application scheme for trip circuit
supervision with one digital input is presented in figure below.
Figure 8.1.1-2 Trip circuit supervision by using one DI and non-latched trip output.
Notice that DI monitoring the circuit is used as normally closed. Same applies with the used alarm
relay (if used). In monitoring purposes and especially in trip circuit supervision it is recommended
to use closed contact in normal condition to confirm the condition of wiring. Active digital input
generates less than 2mA current to the circuit. Normally current this small is not able to make the
breaker open coil operate. While the trip relay is controlled and the circuit breaker is being opened
the digital input is shorted by the trip contact as long as the breaker opens. This normally takes
approximately 100ms if the relay is non-latched. Therefore t = 1.0 second activation delay should
be added to the digital input. Basically activation delay just a bit longer than the operation time of