GE Multilin T60 Transformer Protection System 8-11
8 COMMISSIONING 8.2 DIFFERENTIAL CHARACTERISTIC TEST EXAMPLES
8
8.2.5 TEST EXAMPLE 4
D/D0° TRANSFORMER WITH PHASE B TO C FAULT ON THE SECONDARY DELTA WINDING.
Transformer: D/D0°, 20 MVA, 115/12.47 kv, CT1 (200:1), CT2 (1000:1)
Figure 8–5: CURRENT DISTRIBUTION OF D/D TRANSFORMER WITH AN a TO b FAULT ON THE LV SIDE
Slope 2 A 4 0° 0 0° 0 0° 0 0° Operate
I
d
/I
r
= 95.7%
> Slope 2 = 95%
B8 –180° 0.6 0° 12.13 –180° 12.73 0°
C4 0° 0.6 –180° 12.13 0° 12.73 –180°
TEST PHASE INJECTED CURRENT DISPLAYED CURRENT STATUS
W1 CURRENT W2 CURRENT DIFFERENTIAL RESTRAINT
Balanced
Condition
A0 0° 0 0° 0 0° 0 0° Not Applicable
B 0.435 –90° 0.8 –270° 0 0° 0.8 –270°
C 0.435 –270° 0.8 –90° 0 0° 0.8 –90°
Min Pickup A 0 0° 0 0° 0 0° 0 0° Block
I
d
= 0.065 < Min PKP
B 0.09 –90° 0.23 –270° 0.065 0° 0.230 –270°
C 0.09 –270° 0.23 –90° 0.065 0° 0.230 –90°
Min Pickup A 0 0° 0 0° 0 0° 0 0° Operate
I
d
= 0.101 > Min PKP
B 0.21 –90° 0.486 –270° 0.102 0° 0.486 –270°
C 0.21 –270° 0.486 –90° 0.101 0° 0.486 –90°
Slope 1 A 0 0° 0 0° 0 0° 0 0° Block
I
d
/I
r
= 14% < 15%
B 0.651 –90° 1.39 –270° 0.195 0° 1.39 –270°
C 0.651 –270° 1.39 –90° 0.195 0° 1.39 –90°
Slope 1 A 0 0° 0 0° 0 0° 0 0° Operate
I
d
/I
r
= 16.8% > 15%
B 0.63 –90° 1.39 –270° 0.233 0° 1.39 –270°
C 0.63 –270° 1.39 –90° 0.233 0° 1.39 –90°
Intermediate
Slope 1 & 2
A0 0° 0 0° 0 0° 0 0° Block
I
d
/I
r
= 52.6%
< 60% computed
B1.2 –90° 4.63 –270° 2.44 –270° 4.63 –270°
C1.2 –270° 4.63 –90° 2.44 –90° 4.63 –90°
Intermediate
Slope 1 & 2
A0 0° 0 0° 0 0° 0 0° Operate
I
d
/I
r
= 68.8%
> 60%
computed
B0.8 –90° 4.63 –270° 3.18 –270° 4.63 –270°
C0.8 –270° 4.63 –90° 3.18 –90° 4.63 –90°
TEST PHASE INJECTED CURRENT DISPLAYED CURRENT STATUS
W1 CURRENT W2 CURRENT DIFFERENTIAL RESTRAINT
828739A1.CDR
D/d0° Transformer
F
I (f) = 0
A
I (f) = 0.866 pu –90°
b
∠
I (f) = 0
a
I (f) = 0.866 pu –270°
c
∠
I (f) = 0.866 pu –90°
B
∠
I (f) = 0.866 pu –270°.
C
∠
A
B
C
A
B
C
H winding X winding
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