ABB Relion 670 Series Applications Manual page 251

1MRK 511 401-UEN Rev. K
=
C
1
IECEQUATION19039 V1 EN-US
Where,
C is the capacitance of the faulty quadrant
1
C is the capacitance of the healthy quadrant = 133 × C
Due to the difference in the quadrant capacitances, the unbalance current flowing through the
neutral is calculated by using Thevenin theorem. Apply Thevenin theorem and calculate:
1. The open-circuit unbalance voltage V
2. The open-circuit impedance (Z
=
V V
th U 1
æ
C
=
ç
V
th
è
C
IECEQUATION19040 V1 EN-US
=
V V
th U 1
æ
C
=
ç
V
th
è
C
IECEQUATION19040 V1 EN-US
æ
=
ç
Z
ç
(
th
è
IECEQUATION19041 V1 EN-US
=
I
UNBL 1
IECEQUATION19042 V1 EN-US
æ
=
ç
I
L 1
è
IECEQUATION19043 V1 EN-US
æ
=
ç
V
ç
unit
è
IECEQUATION19044 V1 EN-US
=
% V
unit
IECEQUATION19045 V1 EN-US
Bay control REC670
Application manual
æ ö
+ ´
C 2 C
´ ´ + ´
ç x u ÷
3 C
+ ´
u
è ø
C 5 C
x u
-
V
U 2
- ö
C V
´
1 ÷ L 1
+
ø
C 2
1
-
V
U 2
- ö
C V
´
1 ÷ L 1
+
ø
C 2
1
ö
+ ´
æ ö
C 3 C 1
´
÷ ç
1 ÷
÷
)
+ ´ ´
è ø
C C 2 C ø w
1
æ ö æ ö
-
V C C
= ´
ç th ÷ ç 1 ÷
V
+ ´
L 1
è Z ø è C 3 C ø
th 1
ö
+
C C
´ ´ ´ ´
1 ÷
V w
+ ´
L 1
ø
C 3 C
1
ö æ
ö
´
3 C
C
´ ´
÷ ç
u ÷
÷
( )
+ ´ +
è ø
C 5 C ø C C
x u 1
æ ö
V
´
ç ÷
unit
100
è ø
V
unit Rated
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2 C
u
e
.
th
) between U and U
th 1
´ ´
w C
2 C
V
L 1
/4
by using the following equations:
2
Section 10
Unbalance protection
(Equation 121)
(Equation 122)
(Equation 122)
(Equation 123)
(Equation 124)
(Equation 125)
(Equation 126)
(Equation 127)
245