ABB RET670 - Page 677

Load
T1
I
L
T2
I
cc....T2
I
cc....T1
V
B
V
L
I
T1
I
T2
I
C
I
T
2
-
I
C
Load
T1
I
L
T2
I
cc....T2
I
cc....T1
V
B
V
L
I
T1
I
T2
I
T2
I
T1
I
T1
I
C
en06000512_ansi.vsd
ANSI06000512 V1 EN
Figure 284: Capacitor bank on the LV-side
From figure 284 it is obvious that the two different connections of the capacitor banks
are completely the same regarding the currents in the primary network. However the
CT measured currents for the transformers would be different. The capacitor bank
current may flow entirely to the load on the LV side, or it may be divided between the
LV and the HV side. In the latter case, the part of I
C
that goes to the HV side will
divide between the two transformers and it will be measured with opposite direction
for T2 and T1. This in turn would be misinterpreted as a circulating current, and would
upset a correct calculation of I
cc
. Thus, if the actual connection is as in the left figure
the capacitive current I
C
needs to be compensated for regardless of the operating
conditions and in ATCC this is made numerically. The reactive power of the capacitor
bank is given as a setting Q1, which makes it possible to calculate the reactive capacitance:
1MRK504116-UUS C Section 3
IED application
671
Application manual