CBFP function can be triggered from overcurrent (phases and residual), digital output monitor, digital
signal or combination of these mentioned triggers.
In current dependent mode CBFP function constantly measures phase current magnitudes and
selected residual current. In signal dependent mode any of the IED binary signal can be used for
triggering the CBFP. In binary output dependent mode CBFP monitors selected output relay control
signal status. Blocking signal and setting group selection controls the operating characteristics of the
function during normal operation.
Outputs of the function are CBFP START, RETRIP, CBFP ACT and BLOCKED signals. Setting
parameters are static inputs for the function which are changed only by user input in the setup phase
of the function. CBFP function utilizes total of eight separate setting groups which can be selected from
one common source. Also the operating mode of the CBFP can be changed by setting group
selection.
The operational logic consists of input magnitude processing, threshold comparator, block signal
check, time delay characteristics and output processing.
Inputs for the function are setting parameters and measured and pre-processed current magnitudes
and binary input and output signals. Function output signals can be used for direct IO controlling and
also for user logic programming. The function registers its operation into 12 last time-stamped registers
and also generates general time stamped ON/OFF events to the common event buffer from each of the
two output signal. Time stamp resolution is 1ms. Function provides also cumulative counters for
RETRIP, CBFP, CBFP START and BLOCKED events.
In the following gure is presented the simpli ed function block diagram of the CBFP function.
Figure. 5.4.7. - 29. Simpli ed function block diagram of the CBFP function
Measured input values
Function block uses analog current measurement values. Function uses always the fundamental
frequency magnitude of the current measurement input. For residual current measurement I01, I02 or
calculated I0 can be selected. -20ms averaged value of the selected magnitude is used for pre-fault
data registering.
Table. 5.4.7. - 86. Analogic magnitudes used by the CBFP function.
Signal
Description
Time base
IL1RMS
Fundamental RMS measurement of phase L1/A current
5 ms
IL2RMS
Fundamental RMS measurement of phase L2/B current
5 ms
AQ-T257
Instruction manual
Version: 2.00
© Arcteq Relays Ltd
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