ABB RELION REX640 Technical Manual page 1311

1MRS759142 F
6.2.3 Functionality
The current circuit supervision function CCSPVC is used for monitoring current
transformer secondary circuits.
CCSPVC calculates internally the sum of phase currents (I_A, I_B and I_C) and
compares the sum against the measured single reference current (I_REF). The
reference current must originate from other three-phase CT cores than the phase
currents (I_A, I_B and I_C) and it is to be externally summated, that is, outside the
protection relay.
CCSPVC detects a fault in the measurement circuit and issues an alarm or blocks the
protection functions to avoid unwanted tripping.
It must be remembered that the blocking of protection functions at an occurring
open CT circuit means that the situation remains unchanged and extremely high
voltages stress the secondary circuit.
6.2.4 Analog channel configuration
CCSPVC has two analog group inputs which must be properly configured.
Table 1244: Analog inputs
Input
I3P
IRES
There are a few special conditions which must be noted with the configuration.
Table 1245: Special conditions
Condition
IRES measured
Improper analog channel configuration causes a validation error if the analog
channels are not completely configured or they do not match with certain settings.
For troubleshooting, check the contents of this chapter and also the preprocessing
blocks in this document. The configuration can be written to the protection relay
once the mismatch is corrected.
6.2.5 Operation principle
The function can be enabled and disabled with the
corresponding parameter values are "On" and "Off".
The operation of CCSPVC can be described with a module diagram. All the modules
in the diagram are explained in the next sections.
REX640
Technical Manual
Description
Three-phase currents
Residual current (measured)
See the preprocessing function blocks in this document for the possible
signal sources.
Description
In case IRES needs to be derived, the function requires that
all CT cores, except for the one used for phase current meas-
urement, must be used and summed externally.
Supervision functions
Operation setting. The
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