22
6
F
2
S
0
7
8
9
2.4 Restricted Earth Fault Protection
Restricted earth fault protection (REF) is a zero-phase current differential scheme and applied for
a star-connected winding whose neutral is earthed directly or through a low impedance. It gives
highly sensitive protection for internal earth faults.
REF employs a low impedance current differential scheme which detects the differential current
between the residual current derived from the three-phase line currents and the neutral current in
the neutral conductor as shown in Figure 2.4.1
Figure 2.4.1 Restricted Earth Fault Protection
REF and the overall differential protection
DIFT use the three-phase line currents in common.
GRT100 has two or three REF elements depending on the models to provide separate protection
for all star-connected and neutral-earthed windings. The elements have the same percentage
restraining characteristics and are stable for all faults outside the protected zone.
Figure 2.4.2 shows the scheme logic of restricted earth fault protection when three REF elements
are applied. Each REF element can perform instantaneous or time-delayed tripping of up to five
breakers. Any of the five breaker tripping signals 1REF-1 to 3REF-5 are enabled or disabled by
the scheme switch [1REF1] to [3REF5] settings.
REF
Содержание GRT100 Series
Страница 55: ... 54 6 F 2 S 0 7 8 9 TRANSFORMER PROTECTION GRT100 Operation keys 101B 21 11 Figure 3 1 9 Front Panel ...
Страница 142: ... 141 6 F 2 S 0 7 8 9 Appendix A Block Diagram ...
Страница 144: ... 143 6 F 2 S 0 7 8 9 Appendix B Signal List ...
Страница 159: ... 158 6 F 2 S 0 7 8 9 ...
Страница 160: ... 159 6 F 2 S 0 7 8 9 Appendix C Variable Timer List ...
Страница 162: ... 161 6 F 2 S 0 7 8 9 Appendix D Binary Output Default Setting List ...
Страница 165: ... 164 6 F 2 S 0 7 8 9 ...
Страница 166: ... 165 6 F 2 S 0 7 8 9 Appendix E Details of Relay Menu and LCD and Button Operation ...
Страница 174: ... 173 6 F 2 S 0 7 8 9 Appendix F Case Outline Flush Mount Type Rack Mount Type ...
Страница 179: ... 178 6 F 2 S 0 7 8 9 ...
Страница 180: ... 179 6 F 2 S 0 7 8 9 Appendix G External Connections ...
Страница 185: ... 184 6 F 2 S 0 7 8 9 ...
Страница 200: ... 199 6 F 2 S 0 7 8 9 ...
Страница 201: ... 200 6 F 2 S 0 7 8 9 Appendix J Return Repair Form ...
Страница 205: ... 204 6 F 2 S 0 7 8 9 Customer Name Company Name Address Telephone No Facsimile No Signature ...
Страница 206: ... 205 6 F 2 S 0 7 8 9 ...
Страница 207: ... 206 6 F 2 S 0 7 8 9 Appendix K Technical Data ...
Страница 220: ... 219 6 F 2 S 0 7 8 9 ...
Страница 221: ... 220 6 F 2 S 0 7 8 9 Appendix M Symbols Used in Scheme Logic ...
Страница 224: ... 223 6 F 2 S 0 7 8 9 ...
Страница 225: ... 224 6 F 2 S 0 7 8 9 Appendix N Implementation of Thermal Model to IEC60255 8 ...
Страница 228: ... 227 6 F 2 S 0 7 8 9 ...
Страница 229: ... 228 6 F 2 S 0 7 8 9 Appendix O IEC60870 5 103 Interoperability and Troubleshooting ...
Страница 241: ... 240 6 F 2 S 0 7 8 9 Appendix P Modbus Interoperability ...
Страница 255: ... 254 6 F 2 S 0 7 8 9 ...
Страница 256: ... 255 6 F 2 S 0 7 8 9 Appendix Q Inverse Time Characteristics ...
Страница 259: ... 258 6 F 2 S 0 7 8 9 ...
Страница 260: ... 259 6 F 2 S 0 7 8 9 Appendix R Failed Module Tracing and Replacement ...
Страница 266: ... 265 6 F 2 S 0 7 8 9 Appendix S Ordering ...
Страница 269: ... 268 6 F 2 S 0 7 8 9 3 1 Oct 2 2017 Republished under spin off company ...
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