ABB RELION 620 Series Technical Manual page 797

1MRS757644 F
620 series
Technical Manual
GUID-D7B7D142-7CF4-4DFB-B8E5-876F6C3579C7 V1 EN
Figure 404: Example of double-Y-connected shunt capacitor bank unbalance
protection
Connect the phase current analog input I_A and unbalance current
I_UNB to the IED for the CUBPTOC function to start working.
Steps to measure natural unbalance current
1. The setting Natural Comp Enable must be set to "TRUE".
2. The capacitor bank must be energized.
3. The capacitor bank compensated unbalance current I_COM_AMPL is observed
from Monitored data.
4. The command Record unbalance must be activated by selecting the value
"Record" which stores the unbalance reference for future unbalance calculations.
5. The compensated unbalance current (I_COM_AMPL) is re-checked to be
approximately zero.
Section 4
Protection functions
791