Test Example 3 - GE T35 Instruction Manual

9.2 DIFFERENTIAL CHARACTERISTIC TEST EXAMPLES
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
Balanced
Condition
Min Pickup
change the
Min PKP to
0.2 pu
Minimum
Pickup
Slope 1
return the
Min PKP to
0.1 pu
Slope 1
Intermediate
Slope 1 & 2
Intermediate
Slope 1 & 2
9
Slope 2
Slope 2
9-10
∠
I (f) = 0.5 pu –270°
A
A
∠
I (f) = 1 pu –90°
B
B
C
∠
I (f) = 0.5 pu –270°
C
INJECTED CURRENT
W1 CURRENT W2 CURRENT
0.25 0°
A
0.5 –180° 0.8 0°
B
0.25 0° 0.8 –180°
C
0.25 0°
A
0.5 –180° 0.95 0°
B
0.25 0° 0.95 –180°
C
0.25 0°
A
0.5 –180° 1.05 0°
B
0.25 0° 1.05 –180°
C
0.25 0°
A
0.5 –180° 0.92 0°
B
0.25 0° 0.92 –180°
C
0.25 0°
A
0.5 –180° 0.95 0°
B
0.25 0° 0.95 –180°
C
2 0°
A
4 –180°
B
2 0° 1 –180°
C
2 0°
A
4 –180° 0.8 0°
B
2 0° 0.8 –180°
C
4 0°
A
8 –180° 0.8 0°
B
4 0° 0.8 –180°
C
4 0°
A
8 –180° 0.6 0°
B
4 0° 0.6 –180°
C
T35 Transformer Protection System
Y/d30° Transformer
DISPLAYED CURRENT
DIFFERENTIAL
0 0° 0 0°
0 0°
0 0°
0 0° 0 0°
0.154 0°
0.155 0°
0 0° 0 0°
0.253 0°
0.255 0°
0 0° 0 0°
0.123 0°
0.123 0°
0 0° 0 0°
0.153 0°
0.153 0°
0 0° 0 0°
1 0° 5.37 –180°
5.37 0°
0 0° 0 0°
5.57 –180°
5.57 0°
0 0° 0 0°
11.93 –180°
11.93 0°
0 0° 0 0°
12.13 –180°
12.13 0°
9 COMMISSIONING

9.2.4 TEST EXAMPLE 3

I (f) = 0
a
A
∠
I (f) = 0.866 pu –90°
b
B
F
C
∠
I (f) = 0.866 pu –270°
c
828738A1.CDR
STATUS
RESTRAINT
0 0°
Not Applicable
0.8 0°
0.8 –180°
0 0°
Block
I
= 0.051 < Min PKP
d
0.948 0°
0.950 –180°
0 0°
Operate
I
= 0.102 > Min PKP
d
1.049 0°
1.050 –180°
0 0°
Block
I I
/ = 13.2%
d r
0.919 0°
0.919 –180°
0 0°
Operate
I I
/ = 15.9%
d r
0.948 0°
0.948 –180°
0 0°
Block
I I
/ = 84.3%
d r
6.37 0°
< 86.6%
computed
6.37 –180°
0 0°
Operate
I I
/ = 87.5%
d r
6.37 0°
> 86.6% computed
6.37 –180°
0 0°
Block
I I
/ = 93.7%
d r
12.73 0°
< Slope 2 = 95%
12.73 –180°
0 0°
Operate
I I
/ = 95.7%
d r
12.73 0°
> Slope 2 = 95%
12.73 –180°
GE Multilin