G. Ziegler. Digital Differential Protection
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G. Ziegler, 10/2005 Seite 120
Differential Protection Symposium
Belo HorizonteNovember 2005
L1
L2
L3
∆IE>
HI earthcurrentdifferential protection
G. Ziegler, 10/2005 Seite 121
Differential Protection Symposium
Belo HorizonteNovember 2005
L1
L2
L3
∆IE>
U0>
Tripping
Earth currentdifferential protectionforgenerators
G. Ziegler, 10/2005 Seite 122
Differential Protection Symposium
Belo HorizonteNovember 2005
050100150200250300
5
0
5
10
15
20
I
Rush
/I
N
T
st
T
Rush
I
st
/I
N
t
st
(ms)
Motor startingcurrent
G. Ziegler, 10/2005 page 123
Differential Protection Symposium
Belo HorizonteNovember 2005
Transformer
Differential Protection
Gerhard Ziegler
G. Ziegler, 10/2005 page 124
Differential Protection Symposium
Belo HorizonteNovember 2005
Transformer: Function principle and equivalent circuits
1
2
2
1
1
w
I
w
I
w
I
⋅
=
⋅
+
⋅
µ
At load and short-circuit:
'2,1
I
I
<<
µ
2
2
1
1
w
I
w
I
⋅
=
⋅
'
21 σσ
X
X
TK
X
+
=
'
2
U
1
U
'
2
1
I
I
=
'
21
R
R
TK
R
+
=
Equivalent electromagnetic circuit
1
R
'
2
R
1
σ
X
'
2
σ
X
µ
X
1
U
µ
I
1
I
'
2
I
'
2
U
Equivalent electric circuit
Φ
w
1
U
1
U
2
I
1
w
2
I
2
σ1
Φ
σ2
Φ
TK
R
TK
X
G. Ziegler, 10/2005 page 125
Differential Protection Symposium
Belo HorizonteNovember 2005
Rated power
MVA
850
600
300
300
40
16
6.3
0.63
Ratio
kV/kV
850/21
400/230
400/120
230/120
110/11
30/10.5
30/10.5
10/0.4
No-load magnetizing
current
% In
0.2
0.25
0.1
0.1
0.1
0.2
0.2
0.15
Short-circuit
voltage
% UN
17
18.5
19
24
17
8.0
7.5
4.0
Typical Transformer data
G. Ziegler, 10/2005 page 126
Differential Protection Symposium
Belo HorizonteNovember 2005
Transformer Inrush current
Source: Sonnemann, et al.: Magnetizing Inrush phenomena in transformer banks, AIEE Trans., 77, P. III, 1958, pp. 884-892
Inrush-current of a single
phase transformer
Flux
φ
φ
I
Rush
U
t
I
m
φ
Rem
G. Ziegler, 10/2005 page 127
Differential Protection Symposium
Belo HorizonteNovember 2005
mC
I
mA
I
A
I
B
I
mCmAA
I
6
1
I
6
5
I ⋅−⋅=
mCmAB
III ⋅−⋅−=
6
1
6
1
mAmCC
I
6
1
I
6
5
I ⋅−⋅=
A
Φ
C
I
Oscillogram:
Inrush currents of a Y-∆-transformer
Neutral of Y-winding earthed
D
I
A
I
B
I
C
I
Source: Sonnemannet al. : Magnetizing Inrush phenomena in transformer banks, AIEE Trans., 77, P. III, 1958, pp. 884-892
B
Φ
C
Φ
A
I
B
I
C
I
G. Ziegler, 10/2005 page 128
Differential Protection Symposium
Belo HorizonteNovember 2005
20
40
60
80
100
90
O
180
O
270
O
360
O
17,5%
)1(
)(
m
m
I
I
ν
)1(
)2(
m
m
I
I
)1(
)3(
m
m
I
I
240
O
B
B
360
O
Width of base B
Inrush current : Content of 2nd und 3rd harmonic
%
G. Ziegler, 10/2005 page 129
Differential Protection Symposium
Belo HorizonteNovember 2005
Inrush currents of a three-phase transformer
recorded with relay 7UT51