ABB Relion 670 Series Applications Manual page 256

Section 10
Unbalance protection
grounded and ungrounded capacitor bank configurations. For double WYE configuration, two
instances of the function can be used.
For a grounded capacitor bank configuration, the differential voltage is calculated using the
bus voltage and tap voltage from the bank with the corresponding voltage ratio for each
phase. For an ungrounded capacitor bank configuration, the differential voltage calculation
also includes the capacitor bank neutral voltage, which is measured from the neutral to system
ground. If the neutral VT is not available, the SCPDPTOV function uses the zero sequence
component of the bus voltage as the neutral voltage.
Figure 119
capacitor bank, respectively. For double WYE configuration, the phase voltage differential
protection function can be applied by considering two instances of the function for the left
and right WYE sections, separately. The complete double WYE capacitor bank protection can
be established by OR operation of the signals from both instances of the function.
U
IEC19000652 V1 EN-US
Figure 119: Grounded double WYE connected SCB
Where,
U , U
L1 L2
U
TapL1_L
the left WYE section of the SCB.
U
TapL1_R
the right WYE section of the SCB.
250
and Figure 120 shows the grounded and ungrounded configurations of double WYE
L1
L2
L3
C
C
C
Tap C
L1
C
C
C
C
U
TapL1_L
, and U are the bus voltages of phases L1, L2, and L3 respectively.
L3
, U , and U are the tap voltages of phases L1, L2, and L3 respectively from
TapL2_L TapL3_L
, U , and U are the tap voltages of phases L1, L2, and L3 respectively from
TapL2_R TapL3_R
© Copyright 2017 Hitachi Power Grids. All rights reserved
C
C
C
C
C C
C C C
C
C
C
N
1MRK 511 401-UEN Rev. K
C
C
Tap
C
U
TapL1_R
C
IEC19000652-1-en.vsdx
Bay control REC670
Application manual