⎯
18
⎯
6 F 2 S 0 8 4 6
2.2.2 Earth
Fault
Figure 2.2.2.1 shows the circuit in the event of a single-phase earth fault. It is not simple to exactly
measure the distance up to the fault point for a single-phase earth fault.
This is because the impedance of the zero-sequence circuit including the earth return is generally
different from the positive-sequence impedance. Therefore, the faulted phase voltage is not simply
proportional to the faulted phase current.
Figure 2.2.2.1 Single-Phase Earth Fault
It is necessary to analyze the impedance seen by the relay in the event of a single-phase earth fault
according to the method of symmetrical components. Figure 2.2.2.2 shows an equivalent circuit
for the single-phase earth fault based on the method of symmetrical components. Assuming the
positive-sequence, negative-sequence and zero-sequence voltages are V1F, V2F and V0F, the
voltage at the relay point of each symmetrical circuit is given by the following equation. However,
suppose that the positive-sequence impedance and negative-sequence impedance are the same and
influences of the fault resistance are ignored.
V1 = Z1
×
I1 + V1F ..................................... (2-7)
V2 = Z1
×
I2 + V2F ..................................... (2-8)
V0 = Z0
×
I0 + Z0m
×
I0m + V0F............... (2-9)
where, V1: Relay point positive-sequence voltage
V2: Relay point negative-sequence voltage
V0: Relay point zero-sequence voltage
V1F: Fault point positive-sequence voltage
V2F: Fault point negative-sequence voltage
V0F: Fault point zero-sequence voltage
I1: Relay point positive-sequence current
I2: Relay point negative-sequence current
I0: Relay point zero-sequence current
I0m: Adjacent line zero-sequence current
Z1: Fault point - relay point positive-sequence impedance
Z0: Fault point - relay point zero-sequence impedance
Z0m: Adjacent line zero-sequence mutual impedance
Taking account of the fact that the faulted phase voltage VaF at the point of fault is,
VaF = V1F + V2F + V0F = 0.........................................(2-10)
phase A voltage Va at the relay is calculated from the following equation:
ia
vaF
va
vb
vc
Summary of Contents for GRZ100 B Series
Page 264: ... 263 6 F 2 S 0 8 4 6 Appendix A Block Diagram ...
Page 271: ... 270 6 F 2 S 0 8 4 6 ...
Page 272: ... 271 6 F 2 S 0 8 4 6 Appendix B Signal List ...
Page 307: ... 306 6 F 2 S 0 8 4 6 ...
Page 308: ... 307 6 F 2 S 0 8 4 6 Appendix C Variable Timer List ...
Page 310: ... 309 6 F 2 S 0 8 4 6 Appendix D Binary Input Output Default Setting List ...
Page 321: ... 320 6 F 2 S 0 8 4 6 ...
Page 322: ... 321 6 F 2 S 0 8 4 6 Appendix E Details of Relay Menu and LCD Button Operation ...
Page 331: ... 330 6 F 2 S 0 8 4 6 ...
Page 340: ... 339 6 F 2 S 0 8 4 6 Appendix G Typical External Connections ...
Page 377: ... 376 6 F 2 S 0 8 4 6 ...
Page 384: ... 383 6 F 2 S 0 8 4 6 Appendix J Return Repair Form ...
Page 388: ... 387 6 F 2 S 0 8 4 6 Customer Name Company Name Address Telephone No Facsimile No Signature ...
Page 389: ... 388 6 F 2 S 0 8 4 6 ...
Page 390: ... 389 6 F 2 S 0 8 4 6 Appendix K Technical Data ...
Page 401: ... 400 6 F 2 S 0 8 4 6 ...
Page 402: ... 401 6 F 2 S 0 8 4 6 Appendix L Symbols Used in Scheme Logic ...
Page 405: ... 404 6 F 2 S 0 8 4 6 ...
Page 406: ... 405 6 F 2 S 0 8 4 6 Appendix M Example of Setting Calculation ...
Page 417: ... 416 6 F 2 S 0 8 4 6 ...
Page 418: ... 417 6 F 2 S 0 8 4 6 Appendix N IEC60870 5 103 Interoperability and Troubleshooting ...
Page 434: ... 433 6 F 2 S 0 8 4 6 Appendix P Inverse Time Characteristics ...
Page 437: ... 436 6 F 2 S 0 8 4 6 ...
Page 438: ... 437 6 F 2 S 0 8 4 6 Appendix Q Failed Module Tracing and Replacement ...
Page 444: ... 443 6 F 2 S 0 8 4 6 Appendix R Ordering ...
Page 447: ......