In the following gure is presented the simpli ed function block diagram of the CBFP function.
Figure. 5.4.9. - 51. 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. 5.4.9. - 99. 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
IL3RMS
Fundamental RMS measurement of phase L3/C current
5 ms
I01RMS
Fundamental RMS measurement of residual input I01
5 ms
I02RMS
Fundamental RMS measurement of residual input I02
5 ms
I0Calc
Calculated residual current from the phase current inputs
5 ms
DOIN
Monitoring of the digital output relay status
5 ms
DIIN
Monitoring of digital input status
5 ms
Selection of the used AI channel is made with a setting parameter. In all possible input channel
variations pre-fault condition is presented with 20 ms averaged history value from -20 ms of Start or
Trip event.
Pick-up characteristics
Current dependent pick-up and activation of the CBFP function is controlled by
ISet
and
I0set
setting
parameters, which de nes the minimum allowed measured current before action from the function. The
function constantly calculates the ratio in between of the setting values and measured magnitude (Im)
per all three phases and selected residual current input. Reset ratio of 97 % is inbuilt in the function
and is always related to the settingvalue. The setting value is common for all measured phases and
single-, dual- or all phases Im exceed of the Iset value will cause pick-up operation of the function.
AQ-F255
Instruction manual
Version: 2.00
© Arcteq Relays Ltd
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