Siemens 7UT51 Instruction Manual page 51

7UT51 v3
Io-Correction - Refer to Figure 4.6. And Section 4.3.5
on page 49
I* = Normalized Current
Wye-Winding: I0-Correction
*
I
A , Corr
*
I
B , Corr
*
I
C , Corr
Delta-Winding:
Phase-Shift Correction and I0-Elimination
− + =
* * *
I I I 0
a 1 3
− + =
* * *
I I I 0
2 1
b
− + =
* * *
I I I
0
c 3 2
− = −
* * * *
I I I I
a b 1 3
− = −
* * *
I I 3 I I
a b 1
1
− = −
* * *
( I I ) I
1
a b
3
⎡
*
I
Delta-Winding
, 1
⎢
Currents after
⎢ *
I
, 2
Transformation
⎢
*
to primary side
⎢
I
⎣
, 3
Differential
Currents
calculated
by the relay
PRIM-2330C
1
= +
* *
I I
A N
3
1
= +
* *
I I
B N
3
1
= +
* *
I I
C N
3
[ ]
1
= + +
* * * * *
I I I I
0 1 2 3
3
− +
* *
I I
2 1
− −
* * *
I I
1 3 2
=
* * *
I I
0 , 1 lim
E
⎤
⎡ ⎤
... 1 .... 1 .... 0
E lim
⎥
⎢ ⎥
1
=
⎥
... 0 .... 1 .... 1
⎢ ⎥
E lim
3
⎥
⎢ ⎥
−
⎣ 1 .... 0 .... 1 ⎦
⎥
⎦
E lim
= +
* * *
I I I
D , A A , Corr , 1 E lim
= +
* * *
I I I
D , B B , Corr , 2 E lim
= +
* * *
I I I
, , , 3 lim
D C C Corr E
Transformer Differential Protection (87T and 87HS)
External Single Phase to Ground Fault,
Io-Elimination
Refer to Figure 4.7
Wye-Winding
Currents:
= ∠
*
I 1
A
=
*
I 0
B
=
*
I
0
C
= 1
*
I
0
= ∠
*
I 1
N
.
I
I
I
Delta-Winding Currents after I0-Elimination
and Phase-Shift Correction:
⎡ ⎤
⎡
*
*
I
I
a
⎢ ⎥ , 1 E lim
⎢
*
⎢ ⎥
I *
⎢
I
b
, 2 E lim
⎢ ⎥
⎢
*
I
*
⎣ ⎦
⎢
I
⎣
c
, 3 E lim
Differential
Current:
Delta-Winding
Currents:
=
*
I 1
0
180
1
=
*
I 0
2
=
*
I 0
3
=
*
I I
∠
0
180
a
3
=
*
I I
0
b
0
=
*
I I
c
Wye-Winding Currents after
I0-Elimination:
2
= − = ∠
* * *
I I
3
A , E lim A 0
= − = 1 ∠
* * *
I I
B , E lim B 0 3
= − = 1 ∠
* * *
I I
3
C , E lim C 0
⎤
⎡ ⎤
*
⎡ ⎤ I
... 1 .... 1 ... 0
⎥ a
⎢ ⎥
⎢ ⎥
1
=
*
⎥
... 0 .... 1 ... 1 ⎢ I ⎥
⎢ ⎥
b
3
⎥
⎢ ⎥
⎢ ⎥
−
*
⎣ 1 .... 0 ... 1 ⎦
I
⎥
⎣ ⎦
⎦
c
= +
* * *
I I I
, , lim , 1 lim
D A A E E
= +
* * *
I I I
D , B B , E lim , 2 E lim
= +
* * *
I I I
D , C C , E lim , 3 E lim
4
∠
0
0
− = ∠
* * 0
I 1 0
1 3
− = ∠
* * 0
I
1 180
2 1
− =
* *
I 0
3 2
0
180
0
0
0
0
⎡ ⎤
2 ∠
0
0
⎢ 3 ⎥
⎢ ⎥
= 1 ∠
0
180
⎢ ⎥
3
⎢ ⎥
1 ∠
0
180
⎢ ⎥
⎣ ⎦
3
=
0
=
0
No Trip !
=
0
51