Siemens 7UT51

7UT51 v3
Transformer Differential Protection (87T and 87HS)
4
PRIM-2330C 51
Io
-
Correction
- Refer to Figure 4.6. And Section 4.3.5
on page 49
I* = Normalized Current
External Single Phase to Ground Fault,
Io
-
Elimination
Refer to Figure 4.7
*
lim,1
**
0
*
1
**
*
2
*
3
*
1
*
1
**
*
1
*
2
*
3
*
1
**
*
2
*
3
*
*
1
*
2
*
*
3
*
1
*
)(
3
1
3
0
0
0
Eba
ba
ba
c
b
a
IIIII
IIIIII
IIIIII
III
III
III
=−=−
−−−=−
+−−=−
=+−
=+−
=+−
[]
.
3
1
*
3
*
2
*
1
**
0
IIII
++=
***
,
***
,
***
,
3
1
3
1
3
1
NCCorrC
NBCorrB
NACorrA
III
III
III
+=
+=
+=
Wye-Winding: I0-Correction
Delta-Winding:
Phase-Shift Correction and I0-Elimination
Delta-Winding
Currents after
Transformation
to primary side
Differential
Currents
calculated
by the relay
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
−
=
⎥
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎢
⎣
⎡
*
*
*
*
lim,3
*
lim,2
*
lim,1
1....0....1
1....1....0...
0....1....1...
3
1
c
b
a
E
E
E
I
I
I
I
I
I
*
lim,3
*
,
*
,
*
lim,2
*
,
*
,
*
lim,1
*
,
*
,
ECorrCCD
ECorrBBD
ECorrAAD
III
III
III
+=
+=
+=
Delta-Winding
Currents:
0*
0*
0
*
*
0*
01
180
3
1
0
0
1801
∠=
∠=
=
=
∠=
N
C
B
A
I
I
I
I
I
Wye-Winding Currents after
I0-Elimination:
Wye-Winding
Currents:
0
0
0
*
lim,3
*
lim,
*
,
*
lim,2
*
lim,
*
,
*
lim,1
*
lim,
*
,
=+=
=+=
=+=
EECCD
EEBBD
EEAAD
III
III
III
No Trip !
Differential
Current:
Delta-Winding Currents after I0-Elimination
and Phase-Shift Correction:
0*
0
**
lim,
0*
0
**
lim,
0*
0
**
lim,
0
3
1
0
3
1
180
3
2
∠=−=
∠=−=
∠=−=
III
III
III
CEC
BEB
AEA
⎥
⎥
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎢
⎢
⎣
⎡
∠
∠
∠
=
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
−
=
⎥
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎢
⎣
⎡
0
0
0
*
*
*
*
lim,3
*
lim,2
*
lim,1
180
3
1
180
3
1
0
3
2
1...0....1
1...1....0...
0...1....1...
3
1
c
b
a
E
E
E
I
I
I
I
I
I
0
1801
01
0
0
01
*
2
*
3
*
0*
1
*
2
*
0*
3
*
1
*
*
3
*
2
0*
1
=−=
∠=−=
∠=−=
=
=
∠=
III
III
III
I
I
I
c
b
a