GE Multilin
L90 Line Current Differential System
10-5
10 APPLICATION OF SETTINGS
10.2 CURRENT DIFFERENTIAL (87L) SETTINGS
10
•
For relay 3, channel 1 communicates to relay 1 and channel 2 communicates to relay 2
Consequently, to achieve the maximum sensitivity of 0.2 pu at the terminal with a CT ratio of 2000/5 (400 amps line primary
differential current), the following pickup values are chosen:
(EQ 10.17)
Choosing relay as a reference with a breakpoint value of 5.0 pu, breakpoints for relays 2 and 3 are calculated as follows:
(EQ 10.18)
(EQ 10.19)
To verify the calculated values, we have:
(EQ 10.20)
This satisfies the equality condition indicated earlier.
During on-load tests, the differential current at all terminals should be the same and generally equal to the charging current
if the tap and CT ratio settings are chosen correctly.
Pickup relay 1
0.4
Pickup relay 2
0.2
Pickup relay 3
0.8
Breakpoint relay 2
Breakpoint relay 1
CT
ratio
relay 1
CT
ratio
relay 2
----------------------------------------
5.0
1000 5
2000 5
--------------------
2.5
Breakpoint relay 3
Breakpoint relay 1
CT
ratio
relay 1
CT
ratio
relay 3
----------------------------------------
5.0
1000 5
500 5
--------------------
10.0
Breakpoint relay 1
CT
ratio
relay 1
5.0 1000 5
1000
Breakpoint relay 2
CT
ratio
relay 2
2.5 2000 5
1000
Breakpoint relay 3
CT
ratio
relay 3
10.0 5000 5
1000
Summary of Contents for UR Series L90
Page 652: ...A 16 L90 Line Current Differential System GE Multilin A 1 PARAMETER LISTS APPENDIX A A ...
Page 772: ...B 120 L90 Line Current Differential System GE Multilin B 4 MEMORY MAPPING APPENDIX B B ...
Page 802: ...C 30 L90 Line Current Differential System GE Multilin C 7 LOGICAL NODES APPENDIX C C ...
Page 812: ...D 10 L90 Line Current Differential System GE Multilin D 1 IEC 60870 5 104 APPENDIX D D ...
Page 824: ...E 12 L90 Line Current Differential System GE Multilin E 2 DNP POINT LISTS APPENDIX E E ...
Page 834: ...F 10 L90 Line Current Differential System GE Multilin F 3 WARRANTY APPENDIX F F ...
Page 846: ...xii L90 Line Current Differential System GE Multilin INDEX ...