Chapter 6. Description of Operation of Protection Subsystem
6-23
M7IRDA2003I
7IRD-A/J/M: Distribution Protection & Control Terminal
© ZIV APLICACIONES Y TECNOLOGÍA, S.L.U. 2020
6.8.1 Trip Coil Circuit
In Figure 6-12 (Breaker Open), input IN-5 is energized through the internal resistor R3. Input IN-
6 is not energized since the voltage at terminal B17 is less than pickup because the resistance
of R1 is larger than that of the trip coil. In this situation Trip Coil Circuit Supervision with 52
Closed (SSP-1) is active and Trip Coil Circuit Supervision with 52 Open (SBAIA) is inactive,
causing Trip Coil Circuit Supervision Failure (FCD) to be inactive.
If the trip coil opens, the input IN-6 is energized and the SBAIA signal is activated, causing
deactivation of the output of the exclusive OR gate and 5 seconds later the activation of the Trip
Coil Circuit Supervision Failure (FCD) signal.
When the circuit breaker is closed, the status of the 52/a and 52/b contacts will change and
consequently (assuming the trip coil is not open circuited) inputs IN-6 and IN-5 will be inverted
as well as the SSP-1 and SBAIA signals. However, the FCD output will remain deactivated
since both inputs at the exclusive OR gate have different logic values.
The purpose of the 5 second time delay is to compensate for the time gap between the closing
of the 52/a and opening of the 52/b contacts. In general, SSP-1 and SBAIA signals will not
change their states simultaneously and a transient logic “0” will appear at the output of the
exclusive OR. When this disagreement lasts less than 5 seconds this “0” will not modify the
state of FCD.
If the trip coil circuit is opened while the breaker is closed, input IN-5 is energized and SSP-1 is
activated initiating the deactivation of the output of the exclusive OR gate and 5 seconds later,
activation of the Trip Coil Circuit Supervision Failure (FCD) signal.
If a trip occurs while the breaker is closed and the breaker opens reversing the status of the
52/a and 52/b contacts, the FCD signal will not be activated regardless of the time duration of
the trip command. If the breaker did not execute the command, the FCD signal is activated in 5
seconds.
If the DC control voltage disappears, the inputs that are energized reverse their state.
Consequently, the inputs of both exclusive OR gates become inactive, initiating activation of
both Trip and Close Coil Circuit Supervision Failure Outputs (
FCD and FCC).
When the supervision function detects an open circuit in the trip circuit and therefore the inability
to initiate a trip, Manual Close breaker operations processed through the terminal unit will not be
permitted.
6.8.2 Close Coil Circuit
The explanation given for the trip coil circuit also applies to the close coil circuit, with the close
coil, the relevant operation circuit, and changing opening orders for closing orders.
It is also necessary to take into account that for the Close Coil Circuit the activation time is
about 20 sec, instead of the 5 sec for the Trip Coil Circuit.
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