GE T60

8-6 T60 Transformer Protection System GE Multilin
8.2 DIFFERENTIAL CHARACTERISTIC TEST EXAMPLES 8 COMMISSIONING
8
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 8.9)
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
)
A0 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
)
A0 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
)
A0 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
)
A0 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
