9-16
L90 Line Current Differential System
GE Multilin
9.2 OPERATING CONDITION CHARACTERISTICS
9 THEORY OF OPERATION
9
9.2OPERATING CONDITION CHARACTERISTICS
9.2.1 DESCRIPTION
Characteristics of differential elements can be shown in the complex plane. The operating characteristics of the L90 are
fundamentally dependant on the relative ratios of the local and remote current phasor magnitudes and the angles of
/
as shown in the
Restraint Characteristics
figure.
The main factors affecting the trip-restraint decisions are:
1.
Difference in angles (+ real represents pure internal fault when currents are essentially in phase, – real represents
external fault when currents are 180° apart).
2.
The magnitude of remote current.
3.
The magnitude of the local current.
4.
Dynamically estimated errors in calculations.
5.
Settings.
The following figure also shows the relay's capability to handle week-infeed conditions by increasing the restraint ellipse
when the remote current is relatively small (1.5 pu). Therefore, uncertainty is greater when compared with higher remote
currents (3 pu). The characteristic shown is also dependant on settings. The second graph shows how the relay's trip-
restraint calculation is made with respect to the variation in angle difference between local and remote currents. The char-
acteristic for 3 terminal mode is similar where both remote currents are combined together.
I
loc
I
rem
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 ...