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6
HIGH IMPEDANCE REF
The device provides a high impedance restricted earth fault protection function. An external resistor is required to
provide stability in the presence of saturated line current transformers. Current transformer supervision signals do
not block the high impedance REF protection. The appropriate logic must be configured in PSL to block the high
impedance REF when any of the above signals is asserted.
6.1
HIGH IMPEDANCE REF PRINCIPLE
This scheme is very sensitive and can protect against low levels of fault current, typical of winding faults.
High Impedance REF protection is based on the differential principle. It works on the circulating current principle as
shown in the following diagram.
V00671
R
Z
m1
R
CT1
R
L1
Z
m2
V
s
R
CT2
R
L3
I
F
I
S
R
L4
R
L2
Healthy CT
Saturated CT
A-G
Protected
circuit
I
R
ST
I = I
s
+ I
F
Figure 107: High Impedance REF principle
When subjected to heavy through faults the line current transformer may enter saturation unevenly, resulting in
imbalance. To ensure stability under these conditions a series connected external resistor is required, so that most
of the unbalanced current will flow through the saturated CT. As a result, the current flowing through the device
will be less than the setting, therefore maintaining stability during external faults.
Voltage across REF element V
s
= I
F
(R
CT2
+ R
L3
+ R
L4
)
Stabilising resistor R
ST
= V
s
/I
s
–R
R
where:
●
I
F
= maximum secondary through fault current
●
R
R
= device burden
●
R
CT
= CT secondary winding resistance
●
R
L2
and R
L3
= Resistances of leads from the device to the current transformer
●
R
ST
= Stabilising resistor
High Impedance REF can be used for either delta windings or star windings in both solidly grounded and
resistance grounded systems. The connection to a modern IED are as follows:
Chapter 9 - Current Protection Functions
P54A/B/C/E
212
P54xMED-TM-EN-1
Содержание P4A
Страница 2: ......
Страница 20: ...Contents P54A B C E xviii P54xMED TM EN 1 ...
Страница 27: ...CHAPTER 1 INTRODUCTION ...
Страница 28: ...Chapter 1 Introduction P54A B C E 2 P54xMED TM EN 1 ...
Страница 38: ...Chapter 1 Introduction P54A B C E 12 P54xMED TM EN 1 ...
Страница 39: ...CHAPTER 2 SAFETY INFORMATION ...
Страница 40: ...Chapter 2 Safety Information P54A B C E 14 P54xMED TM EN 1 ...
Страница 52: ...Chapter 2 Safety Information P54A B C E 26 P54xMED TM EN 1 ...
Страница 53: ...CHAPTER 3 HARDWARE DESIGN ...
Страница 54: ...Chapter 3 Hardware Design P54A B C E 28 P54xMED TM EN 1 ...
Страница 86: ...Chapter 3 Hardware Design P54A B C E 60 P54xMED TM EN 1 ...
Страница 87: ...CHAPTER 4 SOFTWARE DESIGN ...
Страница 88: ...Chapter 4 Software Design P54A B C E 62 P54xMED TM EN 1 ...
Страница 99: ...CHAPTER 5 CONFIGURATION ...
Страница 100: ...Chapter 5 Configuration P54A B C E 74 P54xMED TM EN 1 ...
Страница 120: ...Chapter 5 Configuration P54A B C E 94 P54xMED TM EN 1 ...
Страница 121: ...CHAPTER 6 CURRENT DIFFERENTIAL PROTECTION ...
Страница 122: ...Chapter 6 Current Differential Protection P54A B C E 96 P54xMED TM EN 1 ...
Страница 149: ...CHAPTER 7 AUTORECLOSE ...
Страница 150: ...Chapter 7 Autoreclose P54A B C E 124 P54xMED TM EN 1 ...
Страница 207: ...CHAPTER 8 CB FAIL PROTECTION ...
Страница 208: ...Chapter 8 CB Fail Protection P54A B C E 182 P54xMED TM EN 1 ...
Страница 219: ...CHAPTER 9 CURRENT PROTECTION FUNCTIONS ...
Страница 220: ...Chapter 9 Current Protection Functions P54A B C E 194 P54xMED TM EN 1 ...
Страница 244: ...Chapter 9 Current Protection Functions P54A B C E 218 P54xMED TM EN 1 ...
Страница 247: ...CHAPTER 10 VOLTAGE PROTECTION FUNCTIONS ...
Страница 248: ...Chapter 10 Voltage Protection Functions P54A B C E 222 P54xMED TM EN 1 ...
Страница 261: ...CHAPTER 11 FREQUENCY PROTECTION FUNCTIONS ...
Страница 262: ...Chapter 11 Frequency Protection Functions P54A B C E 236 P54xMED TM EN 1 ...
Страница 268: ...Chapter 11 Frequency Protection Functions P54A B C E 242 P54xMED TM EN 1 ...
Страница 269: ...CHAPTER 12 MONITORING AND CONTROL ...
Страница 270: ...Chapter 12 Monitoring and Control P54A B C E 244 P54xMED TM EN 1 ...
Страница 300: ...Chapter 12 Monitoring and Control P54A B C E 274 P54xMED TM EN 1 ...
Страница 301: ...CHAPTER 13 SUPERVISION ...
Страница 302: ...Chapter 13 Supervision P54A B C E 276 P54xMED TM EN 1 ...
Страница 312: ...Chapter 13 Supervision P54A B C E 286 P54xMED TM EN 1 ...
Страница 323: ...CHAPTER 14 DIGITAL I O AND PSL CONFIGURATION ...
Страница 324: ...Chapter 14 Digital I O and PSL Configuration P54A B C E 298 P54xMED TM EN 1 ...
Страница 336: ...Chapter 14 Digital I O and PSL Configuration P54A B C E 310 P54xMED TM EN 1 ...
Страница 337: ...CHAPTER 15 FIBRE TELEPROTECTION ...
Страница 338: ...Chapter 15 Fibre Teleprotection P54A B C E 312 P54xMED TM EN 1 ...
Страница 354: ...Chapter 15 Fibre Teleprotection P54A B C E 328 P54xMED TM EN 1 ...
Страница 355: ...CHAPTER 16 ELECTRICAL TELEPROTECTION ...
Страница 356: ...Chapter 16 Electrical Teleprotection P54A B C E 330 P54xMED TM EN 1 ...
Страница 366: ...Chapter 16 Electrical Teleprotection P54A B C E 340 P54xMED TM EN 1 ...
Страница 367: ...CHAPTER 17 COMMUNICATIONS ...
Страница 368: ...Chapter 17 Communications P54A B C E 342 P54xMED TM EN 1 ...
Страница 439: ...CHAPTER 18 CYBER SECURITY ...
Страница 440: ...Chapter 18 Cyber Security P54A B C E 414 P54xMED TM EN 1 ...
Страница 457: ...CHAPTER 19 INSTALLATION ...
Страница 458: ...Chapter 19 Installation P54A B C E 432 P54xMED TM EN 1 ...
Страница 469: ...5 2 CASE DIMENSIONS 60TE E01409 Figure 197 60TE case dimensions P54A B C E Chapter 19 Installation P54xMED TM EN 1 443 ...
Страница 471: ...CHAPTER 20 COMMISSIONING INSTRUCTIONS ...
Страница 472: ...Chapter 20 Commissioning Instructions P54A B C E 446 P54xMED TM EN 1 ...
Страница 513: ...CHAPTER 21 MAINTENANCE AND TROUBLESHOOTING ...
Страница 514: ...Chapter 21 Maintenance and Troubleshooting P54A B C E 488 P54xMED TM EN 1 ...
Страница 530: ...Chapter 21 Maintenance and Troubleshooting P54A B C E 504 P54xMED TM EN 1 ...
Страница 531: ...CHAPTER 22 TECHNICAL SPECIFICATIONS ...
Страница 532: ...Chapter 22 Technical Specifications P54A B C E 506 P54xMED TM EN 1 ...
Страница 558: ...Chapter 22 Technical Specifications P54A B C E 532 P54xMED TM EN 1 ...
Страница 559: ...APPENDIX A ORDERING OPTIONS ...
Страница 560: ...Appendix A Ordering Options P54A B C E P54xMED TM EN 1 ...
Страница 565: ...APPENDIX B SETTINGS AND SIGNALS ...
Страница 566: ...Appendix B Settings and Signals P54A B C E P54xMED TM EN 1 ...
Страница 790: ...Appendix B Settings and Signals P54A B C E B224 P54xMED TM EN 1 ...
Страница 835: ...APPENDIX C WIRING DIAGRAMS ...
Страница 836: ...Appendix C Wiring Diagrams P54A B C E P54xMED TM EN 1 ...
Страница 849: ......