ABB RELION 620 Series Technical Manual page 790

Section 4
Protection functions
784
GUID-C448B20B-4253-4F41-BB8A-ADA6A8E59CE3 V1 EN
Figure 401: Functional module diagram
Natural unbalance Compensation
A standard double-Y-connected shunt capacitor bank configuration is shown in
Figure 402. The fundamental frequency component of an unbalance current is
measured on the common neutral connecting the two balanced parts of a shunt
capacitor bank, that is, between star point 1 and star point 2.
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Figure 402: Double-Y-connected capacitor bank
The phase angle of the measured fundamental frequency component of the unbalance
current I_UNB is synchronized by using the phase current I_A as a reference.
_
I I UNB
∠ = ∠ − ∠
unb
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_
I A
1MRS757644 F
(Equation 146)
620 series
Technical Manual