GE Multilin
T60 Transformer Protection System
9-7
9 COMMISSIONING
9.2 DIFFERENTIAL CHARACTERISTIC TEST EXAMPLES
9
e) INTERMEDIATE CURVE BETWEEN BREAKPOINT 1 AND BREAKPOINT 2
This procedure tests the intermediate section of the differential characteristic curve that lies between the Breakpoint 1 and
Breakpoint 2 points (points
B
1
and
B
2
on the Differential Restraint Characteristic diagram).
1.
Inject currents so that the magnitude of
I
r
is between the restraint magnitudes defined by Breakpoint 1 and Breakpoint
2; that is:
(EQ 9.10)
For this example,
. Remember that the maximum current is the restraint current
.
2.
The following differential and restraint current should be read from the T60 actual values menu:
The
ratio is 36.77% and the Differential element does not operate because the actual
is still too
low at
.
Due to the mathematical complexity involved in shaping the curve between Breakpoint 1 and Breakpoint 2, an
Excel-based simulation tool is available from the GE Multilin website (look in the support documents for the
product). With this tool, the user can see the preset
curve point ratios and the actual
ratio as per
the entered test currents. The tool graphically indicates differential and restraint current magnitudes and indi-
cates whether the relay should operate.
3.
In this example, a ratio of
causes the element to trip. Decreasing
I
1
as shown in the table below increases
the differential current
I
d
, causing the element to operate.
4.
The following differential and restraint current should be read from the T60 actual values menu:
WINDING 1
WINDING 2
PHASE SINGLE CURRENT (I
1
)
PHASE SINGLE CURRENT (I
2
)
A
0 A
∠
0°
A
0 A
∠
0°
B
1.2 A
∠
0°
B
3.5 A
∠
–180°
C
1.2 A
∠
–180°
C
3.5 A
∠
0°
PHASE DIFFERENTIAL CURRENT (I
d
)
PHASE RESTRAINT CURRENT (I
r
)
A
0
∠
0°
A
0
∠
0°
B
1.287 pu
∠
–180°
B
3.5 pu
∠
–180°
C
1.287 pu
∠
0°
C
3.5 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
1.1 A
∠
0°
B
3.5 A
∠
–180°
C
1.1 A
∠
–180°
C
3.5 A
∠
0°
PHASE DIFFERENTIAL CURRENT (I
d
)
PHASE RESTRAINT CURRENT (I
r
)
A
0
∠
0°
A
0
∠
0°
B
1.471 pu
∠
–180°
B
3.5 pu
∠
–180°
C
1.471 pu
∠
0°
C
3.5 pu
∠
0°
I
r
at Breakpoint 1
(
)
I
r
I
r
at Breakpoint 2
(
)
< <
2 pu
I
r
8 pu
< <
I
r
3.5 pu
=
I
d
I
r
⁄
I
d
1.287 pu
=
I
r
3.5 pu
=
NOTE
I
d
I
r
⁄
I
d
I
r
⁄
I
d
I
r
⁄
38%
>
Summary of Contents for T60
Page 6: ...vi T60 Transformer Protection System GE Multilin TABLE OF CONTENTS ...
Page 14: ...xiv T60 Transformer Protection System GE Multilin TABLE OF CONTENTS ...
Page 34: ...1 20 T60 Transformer Protection System GE Multilin 1 5 USING THE RELAY 1 GETTING STARTED 1 ...
Page 490: ...5 344 T60 Transformer Protection System GE Multilin 5 10 TESTING 5 SETTINGS 5 ...
Page 522: ...6 32 T60 Transformer Protection System GE Multilin 6 5 PRODUCT INFORMATION 6 ACTUAL VALUES 6 ...
Page 536: ...7 14 T60 Transformer Protection System GE Multilin 7 1 COMMANDS 7 COMMANDS AND TARGETS 7 ...
Page 568: ...10 12 T60 Transformer Protection System GE Multilin 10 6 DISPOSAL 10 MAINTENANCE 10 ...
Page 596: ...A 28 T60 Transformer Protection System GE Multilin A 1 PARAMETER LISTS APPENDIX A A ...
Page 716: ...B 120 T60 Transformer Protection System GE Multilin B 4 MEMORY MAPPING APPENDIX B B ...
Page 762: ...E 10 T60 Transformer Protection System GE Multilin E 1 IEC 60870 5 104 PROTOCOL APPENDIX E E ...
Page 774: ...F 12 T60 Transformer Protection System GE Multilin F 2 DNP POINT LISTS APPENDIX F F ...