In this case, normalization with current I
c
will no longer work properly either. The normalization is canceled in
a phase-segregated manner. This means that the non-normalized value is used in place of the normalized
value (see Figure 7-8).
Charging/Energizing the Capacitor Bank or a Phase of the Bank
Charging of the bank takes place when the discharged bank is switched on to the network. Charging of a
phase can occur in case of network faults. If a phase-to-ground voltage drops to 0 V due to a network fault,
the respective phase is discharged and the return of the phase-to-ground (after the fault has been cleared) will
charge the phase.
Charging the bank or a phase of the bank causes inrush currents in the respective phases. To avoid overfunc-
tion in case of sensitive threshold settings, the stages using compensated unbalanced values are blocked in a
phase-selective way by setting
I
unbal.,comp.
to 0 A. These stages are:
•
Counter stage
•
I> stage, if set to operate with compensated unbalanced values
The blocking (
I
unbal.,comp.
set to 0 A) lasts for 250 ms after energizing detection. Afterwards, the calculated
I
unbal.,comp.
is processed again.
Energizing detection takes place in a phase-selective way by monitoring the phase current I
c
flowing into the
bank. If a phase current exceeds the threshold Current Thresh.CB Open, energizing in this phase is
detected.
Logic for Counting Faulty C-Elements
This part of the General functionality is only important if counter stages are used.
Capacitor Bank Protection
7.4 Current-Unbalance Protection for Capacitors, 3-Phase
SIPROTEC 5, Overcurrent Protection, Manual 981
C53000-G5040-C017-8, Edition 07.2017
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