6 F 2 T 0 1 7 2
T
C
T
C
A
B
C
Operate time
Figure 2.2.1 Conjunction of Inverse and Instantaneous Overcurrent Protection
The current setting is set 1.3 to 1.5 times higher than the probable maximum fault current in the
event of a fault at the remote end. The maximum fault current for elements OC2 to OC4 is obtained
in case of three-phase faults, while the maximum fault current for elements EF2 to EF4 is obtained
in the event of single phase earth faults.
2.2.2 Staged Definite Time Overcurrent Protection
When applying inverse time overcurrent protection for a feeder system as shown in Figure 2.2.2,
well coordinated protection with the fuses in branch circuit faults and high-speed protection for the
feeder faults can be provided by adding staged definite time overcurrent protection with
time-graded OC2 and OC3 or EF2 and EF3 elements.
Fuse
GRE110
Figure 2.2.2 Feeder Protection Coordinated with Fuses
Configuring the inverse time element OC1 (and EF1) and time graded elements OC2 and OC3 (or
EF2 and EF3) as shown in Figure 2.2.3, the characteristic of overcurrent protection can be
improved to coordinate with the fuse characteristic.
17
Summary of Contents for GRE110
Page 183: ...6 F 2 T 0 1 7 2 Appendix B Signal List 184 ...
Page 191: ...6 F 2 T 0 1 7 2 Appendix C Event Record Items 192 ...
Page 196: ...6 F 2 T 0 1 7 2 Appendix D Binary Output Default Setting List 197 ...
Page 199: ...6 F 2 T 0 1 7 2 Appendix E Relay Menu Tree 200 ...
Page 210: ...6 F 2 T 0 1 7 2 Appendix F Case Outline 211 ...
Page 211: ...6 F 2 T 0 1 7 2 Case Outline for model 400 401 420 421 820 and 821 212 ...
Page 212: ...6 F 2 T 0 1 7 2 Case Outline for model 402 and 422 213 ...
Page 213: ...6 F 2 T 0 1 7 2 Appendix G Typical External Connection 214 ...
Page 245: ...6 F 2 T 0 1 7 2 Appendix J Return Repair Form 246 ...
Page 249: ...6 F 2 T 0 1 7 2 Customer Name Company Name Address Telephone No Facsimile No Signature 250 ...
Page 250: ...6 F 2 T 0 1 7 2 Appendix K Technical Data 251 ...
Page 256: ...6 F 2 T 0 1 7 2 Appendix L Symbols Used in Scheme Logic 257 ...
Page 259: ...6 F 2 T 0 1 7 2 Appendix M Modbus Interoperability 260 ...
Page 289: ...6 F 2 T 0 1 7 2 Appendix N IEC60870 5 103 Interoperability 290 ...
Page 296: ...6 F 2 T 0 1 7 2 Appendix O PLC Default setting 297 ...
Page 298: ...6 F 2 T 0 1 7 2 Appendix P Inverse Time Characteristics 299 ...
Page 304: ...6 F 2 T 0 1 7 2 Appendix Q IEC61850 Interoperability 305 ...