GE T60, Instruction Manual

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9-10 T60 Transformer Protection System GE Multilin
9.2 DIFFERENTIAL CHARACTERISTIC TEST EXAMPLES 9 COMMISSIONING
9
9.2.4 TEST EXAMPLE 3
Yg/D30° TRANSFORMER WITH PHASE B TO C FAULT ON THE DELTA SIDE.
Transformer: Y/D30°, 20 MVA, 115/12.47 kv, CT1 (200:1), CT2 (1000:1)
Figure 9–4: CURRENT DISTRIBUTION ON A YG/D30° TRANSFORMER WITH AN a TO b FAULT ON THE LV SIDE
Three adjustable currents are required in this case. The Phase A and C Wye-side line currents, identical in magnitude but
displaced by 180°, can be simulated with one current source passed through these relay terminals in series. The second
current source simulates the Phase B primary current. The third source simulates the delta “b” and “c” phase currents, also
equal in magnitude but displaced by 180°.
TEST PHASE INJECTED CURRENT DISPLAYED CURRENT STATUS
W1 CURRENT W2 CURRENT DIFFERENTIAL RESTRAINT
Balanced
Condition
A 0.25
∠
0° 0
∠
0° 0
∠
0° 0
∠
0° Not Applicable
B 0.5 ∠ –180° 0.8 ∠ 0° 0 ∠ 0° 0.8 ∠ 0°
C 0.25
∠
0° 0.8
∠
–180° 0
∠
0° 0.8
∠
–180°
Min Pickup
change the
Min PKP to
0.2 pu
A 0.25 ∠ 0° 0 ∠ 0° 0 ∠ 0° 0 ∠ 0° Block
I
d
= 0.051 < Min PKP
B 0.5
∠
–180° 0.95
∠
0° 0.154
∠
0° 0.948
∠
0°
C 0.25 ∠ 0° 0.95 ∠ –180° 0.155 ∠ 0° 0.950 ∠ –180°
Minimum
Pickup
A 0.25
∠
0° 0
∠
0° 0
∠
0° 0
∠
0° Operate
I
d
= 0.102 > Min PKP
B 0.5 ∠ –180° 1.05 ∠ 0° 0.253 ∠ 0° 1.049 ∠ 0°
C 0.25
∠
0° 1.05
∠
–180° 0.255
∠
0° 1.050
∠
–180°
Slope 1
return the
Min PKP to
0.1 pu
A 0.25 ∠ 0° 0 ∠ 0° 0 ∠ 0° 0 ∠ 0° Block
I
d
/
I
r
= 13.2%
B 0.5
∠
–180° 0.92
∠
0° 0.123
∠
0° 0.919
∠
0°
C 0.25 ∠ 0° 0.92 ∠ –180° 0.123 ∠ 0° 0.919 ∠ –180°
Slope 1 A 0.25
∠
0° 0
∠
0° 0
∠
0° 0
∠
0° Operate
I
d
/
I
r
= 15.9%
B 0.5 ∠ –180° 0.95 ∠ 0° 0.153 ∠ 0° 0.948 ∠ 0°
C 0.25
∠
0° 0.95
∠
–180° 0.153
∠
0° 0.948
∠
–180°
Intermediate
Slope 1 & 2
A 2 ∠ 0° 0 ∠ 0° 0 ∠ 0° 0 ∠ 0° Block
I
d
/
I
r
= 84.3%
< 86.6% computed
B 4
∠
–180° 1
∠
0° 5.37
∠
–180° 6.37
∠
0°
C 2 ∠ 0° 1 ∠ –180° 5.37 ∠ 0° 6.37 ∠ –180°
Intermediate
Slope 1 & 2
A 2
∠
0° 0
∠
0° 0
∠
0° 0
∠
0° Operate
I
d
/
I
r
= 87.5%
> 86.6% computed
B 4 ∠ –180° 0.8 ∠ 0° 5.57 ∠ –180° 6.37 ∠ 0°
C 2
∠
0° 0.8
∠
–180° 5.57
∠
0° 6.37
∠
–180°
Slope 2 A 4 ∠ 0° 0 ∠ 0° 0 ∠ 0° 0 ∠ 0° Block
I
d
/
I
r
= 93.7%
< Slope 2 = 95%
B 8
∠
–180° 0.8
∠
0° 11.93
∠
–180° 12.73
∠
0°
C 4 ∠ 0° 0.8 ∠ –180° 11.93 ∠ 0° 12.73 ∠ –180°
828738A1.CDR
Y /d 30 ° Transformer
F
I (f) = 0.5 pu –270°
A
∠
I (f) = 0.866 pu –90°
b
∠
I (f) = 0
a
I (f) = 0.866 pu –270°
c
∠
I (f) = 1 pu –90°
B
∠
I (f) = 0.5 pu –270°
C
∠
A
B
C
A
B
C