VAMP 135
Over-, under-, residual voltage and
frequency relay
Technical description
VAMP Ltd
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VM135.EN008
3.4.
Trip circuit supervision
Trip circuit supervision is used to ensure that the wiring from
protective relay to the circuit breaker is in order. This circuit is
most of the time unused but when the protection relay detects a
fault in the network it is too late to notice that the circuit
breaker cannot be tripped because of a broken trip circuitry.
A digital input of the relay can be used for trip circuit
monitoring.
•
The digital input is connected parallel with the trip contacts
(Figure 3.4-1).
•
A resistor module VR10CB enables supervision also when
the circuit breaker is open. The module consist resistor for
110 Vdc and 220 Vdc and is connected according the
auxiliary voltage.
•
The digital input is configured as Normal Closed (NC).
•
The digital input delay is configured longer than maximum
fault time to inhibit any superfluous trip circuit fault alarm
when the trip contact is closed.
•
The trip relay should be configured as non-latched.
Otherwise a superfluous trip circuit fault alarm will follow
after the trip contact operates and remains closed because
of latching.
Figure 3.4-1 shows the situation when the circuit breaker is
closed. If the digital input is not in active state it indicates that
there is something wrong in the trip circuitry.
Figure 3.4-2 shows the situation when the circuit breaker is
open. The resistor module VR10CB ensures that the digital
input is in active state also in this situation. If the digital
input is not in active state it indicates that there is something
wrong in the trip circuitry.
If a communication protocol is in use the digital input event
will tell the control system that there is a circuit breaker
failure.
If serial communication is not in use, any of the unused output
relays can be configured to follow the state of the inverted and
delayed digital input. This relay will then give a "trip circuit
failure" alarm to the control system if there is a failure.
The user may also configure a dedicated digital input event
text, e.g. "TRIP CIRCUIT FAILURE", to be displayed on the
local display of the protective relay whenever there is a trip
circuit failure.
