Figure. 7.3. - 165. Trip circuit supervision by using one DI and non-latched trip output. With this connection, the current keeps
flowing to circuit breaker opening coil via the closing auxiliary contacts (52b) of the circuit breaker even after the circuit breaker
is opened. This leads to a need for resistor R which will reduce the current so that the coil is not energized, and the relay output
does not need to cut off the coils inductive current.
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 con rm 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 circuit breaker would be long
enough. When CB failure protection is used it might be good to add the CBFP operation time to the
digital input activation time (t
DI
= t
CB
+ t
IEDrelease
+ t
CBFP
). See attached picture below.
Figure. 7.3. - 166. The digital input used for TCS needs to have normally closed polarity and 1.0 second activation delay to avoid
nuisance alarms while circuit breaker is controlled open.
Non-latched outputs are seen in the output matrix as hollow circles. Latched contacts are painted. See
below presented gure.
AQ-T216
Instruction manual
Version: 2.00
245
© Arcteq Relays Ltd
