ABB Relion 670 Series Applications Manual page 261

1MRK 511 401-UEN Rev. K
• The capacitance of a healthy unit can be calculated as follows:
C
u
IECEQUATION19122 V1 EN-US
• If an element fails in the unit, the capacitance of the unit changes to:
C
x
IECEQUATION19123 V1 EN-US
Where,
C is the capacitance of the faulty unit
x
F is the number of elements failed in a unit (F
e
• The capacitance of the faulty section can be calculated as follows:
=
C
1
IECEQUATION19124 V1 EN-US
• The capacitance of the healthy section can be calculated as follows:
C
2
IECEQUATION19125 V1 EN-US
• The capacitance of phase L1 can be calculated as follows:
C
L
IECEQUATION19222 V1 EN-US
• For a grounded capacitor bank configuration, the differential voltage is calculated by
using the bus voltage and tap voltage from the bank with the corresponding voltage ratio
for phase L1 as follows:
U
TapL
IECEQUATION19126 V1 EN-US
UDIFL
IECEQUATION19217 V1 EN-US
Where,
U
L1
U
TapL1
UDIFL1 is the differential voltage of phase L1
• The differential phase voltages are expressed in percentage of base voltage UBase as
follows:
PUDIFLx
IECEQUATION19376 V1 EN-US
Bay control REC670
Application manual
P
= ´ =
e
C 4.6667 C
e e
S
e
æ ö
( ) Pe
- ´
ç P F ÷
e e -
S 1
ç ÷
= ´
e
C
ç ÷
P
( )
- +
e
P F
ç ÷
e e -
è ø
S 1
e
C
x
  
P C 4.6667 C
u u e
æ ö
´
C C
= ç
÷
1 2
+
è ø
1 C C
1 2
æ ö
C
= ´ ç
1
÷
U
1 L 1 +
è ø
C C
1 2
1
 
1 U
L 1
USEDURATL 1
is the measured bus voltage of phase L1
is the measured tap voltage of phase L1
UDIFLx
= ´
100
UBase 3
© Copyright 2017 Hitachi Power Grids. All rights reserved
e
= 0, 1, 2, ...13)
e

U
TapL 1
Section 10
Unbalance protection
(Equation 128)
(Equation 129)
(Equation 130)
(Equation 131)
(Equation 132)
(Equation 133)
(Equation 134)
(Equation 135)
255