GE UR T60, Instruction Manual

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9-6 T60 Transformer Protection System GE Multilin
9.2 DIFFERENTIAL CHARACTERISTIC TEST EXAMPLES 9 COMMISSIONING
9
d) SLOPE 1 TEST
Inject current in such a manner that the magnitude of I
r
is larger than the restraint current of 0.67 pu, corresponding to the
intersection of the minimum PKP and Slope 1 and smaller than the Breakpoint 1 setting; that is,
(EQ 9.9)
1. Change the current magnitudes as follows:
2. The following differential and restraint current should be read from the T60 actual values menu:
The Percent Differential element will not operate even though I
d
is larger than the Minimum Pickup, because I
d
is not large enough to make the ratio larger than the Slope 1 setting of 15%. The actual ratio is 11.3%.
3. Adjust the I
1
current as shown below (thereby increasing I
d
) and verify that the element operates.
4. The following differential and restraint current should appear in the T60 actual values menu:
5. The actual ratio is now 17%. Verify that the element operates correctly.
WINDING 1 WINDING 2
PHASE SINGLE CURRENT (I
1
) PHASE SINGLE CURRENT (I
2
)
A 0 A
∠
0° A 0 A
∠
0°
B 0.48 A ∠ 0° B 1 A ∠ –180°
C 0.48 A
∠
–180° C 1 A
∠
0°
PHASE DIFFERENTIAL CURRENT (I
d
) PHASE RESTRAINT CURRENT (I
r
)
A 0 ∠ 0° A 0 ∠ 0°
B 0.113 pu
∠
0° B 1 pu
∠
–180°
C 0.113 pu ∠ 0° C 1 pu ∠ 0°
WINDING 1 WINDING 2
PHASE SINGLE CURRENT (I
1
) PHASE SINGLE CURRENT (I
2
)
A 0 A ∠ 0° A 0 A ∠ 0°
B 0.45 A
∠
0° B 1 A
∠
–180°
C 0.45 A ∠ –180° C 1 A ∠ 0°
PHASE DIFFERENTIAL CURRENT (I
d
) PHASE RESTRAINT CURRENT (I
r
)
A 0
∠
0° A 0
∠
0°
B 0.170 pu ∠ 0° B 1 pu ∠ –180°
C 0.170 pu
∠
0° C 1 pu
∠
0°
I
r
intersection of Min PKP and Slope 1
( )
I
r
actual
( )
I
r
Break 1
( ) < <
NOTE
I
d
I
r
⁄
I
d
I
r
⁄