39
6
F
2
S
0
7
8
9
CT saturation during through faults.
2.11.2 High-set Overcurrent Element HOC
High-set overcurrent element HOC is an instantaneous overcurrent characteristic, and is applied
in the differential circuit. The characteristic is expressed by the following equation:
Id
kh
Id is defined as follows for three-winding transformer.
I
d
= |kct1
I
1
+ kct2
I
2
+ kct3
I
3
|
where,
kct1, kct2, kct3: CT ratio matching settings of primary, secondary and tertiary winding
HOC is an un-restrained current differential element which can protect a transformer against
damage due to a heavy internal fault, because it has a simple operation principle and high-speed
operation. Note that HOC is not immune to transformer inrush currents and therefore cnnot be
applied with a sensitive setting.
2.11.3 Restricted Earth Fault Element REF
The restricted earth fault element REF has dual percentage restraining characteristics. Figure
2.11.2 shows the characteristics on the differential current (Id) and restraining current (Ir) plane.
Id is a differential current between the residual current of each winding and the neutral current
and Ir is a restraining current which is the larger of the residual current and the neutral current.
I
d
I
d =
I
r (one-end infeed)
DF2
DF1
kct
ik
kp
I
r
Figure 2.11.2 Restricted Earth Fault Element
Characteristic DF1 is expressed by the following equation:
I
d
p1
I
r
+ (1-p1)
ik
kct
where,
p1: slope of DF1 (fixed to 10%)
ik: minimum operating current
kct: CT ratio matching of line CT to neutral CT (when plural line CTs are applied, maximum
kct is employed.)
For the 1REF element, I
d
and I
r
are calculated by the following equations when applied to a
circuit with one neutral CT and three line CTs. (For the REF element application, see Appendix
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 ...
Страница 270: ......