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|I
bias
|= 0.5 (|I
LOCAL
| + |I
REMOTE1
| + |I
REMOTE2
|)
Assume a load current of I
L
flowing from end LOCAL to REMOTE1 and REMOTE2. Assume also a high resistance
single-end fault of current I
F
, being fed from end LOCAL. In the worst case, we can also assume I
F
to be in phase
with I
L
:
I
LOCAL
= I
L
+ I
F
I
REMOTE1
= -y*I
L
where 0<y<1
I
REMOTE2
= - (1-y) I
L
|I
diff
|= |I
F
|
|I
bias
| = |I
L
| + 0.5 |I
F
|
Phase current differential protection sensitivity when |I
bias
| < Phase Is2:
The phase current differential protection would operate if |I
diff
| > Phase k1 |I
bias
| + Phase Is1
therefore:
|I
F
| > (Phase k1 |I
L
| + Phase Is1) / (1 - 0.5 Phase k1)
For Phase Is1 = 0.2 pu, Phase k1 = 30% and Phase Is2 =2.0 pu, then
●
for |I
L
| = 1.0 pu, the phase current differential protection would operate if |I
F
| > 0.59 pu
●
for |I
L
| = 1.59 pu, the phase current differential protection would operate if |I
F
| > 0.80 pu
If |I
F
| = 0.80 pu and |I| = 1.59 pu, then |I
bias
| = 1.99 pu, which reaches the limit of the low percentage bias curve.
Phase current differential protection sensitivity when |
bias
| > Phase Is2:
The phase current differential protection would operate if |I
diff
| > Phase k2 |I
bias
| - (Phase k2 - Phase k1) Phase Is2 +
Phase Is1
therefore:
|I
F
| > (Phase k2 |I
L
| - (Phase k2 - Phase k1) Phase Is2 + Phase Is1) / (1 - 0.5 Phase k2)
For Phase Is1= 0.2 pu, Phase k1 = 30%, Phase Is2 = 2.0 pu and Phase k2 = 100%, then,
●
for |I
L
| = 2.0 pu, the phase current differential protection would operate if |I
F
| > 1.6 pu
●
for |I
L
| = 2.5 pu, the phase current differential protection would operate if |I
F
| > 2.6 pu
Fault resistance coverage
Assuming the fault resistance R
F
is much higher than the line impedance and source impedance, then for a 33 kV
system and 400/1 CT:
|I
F
| = (Vph-n /R
F
)(1/CT ratio) pu = 47.63/R
F
pu
Based on the analysis above, the phase current differential protection detects a fault current in excess of 0.59 pu
with a load current of 1 pu flowing. The fault resistance is less than 47.63/0.59 = 81 ohms in this case.
With a short time overload current of 2.0 pu, the phase current differential protection can detect a fault resistance
of 47.63/1.6 = 30 ohms or lower.
Chapter 6 - Current Differential Protection
P54A/B/C/E
120
P54xMED-TM-EN-1
Summary of Contents for P4A
Page 2: ......
Page 20: ...Contents P54A B C E xviii P54xMED TM EN 1 ...
Page 27: ...CHAPTER 1 INTRODUCTION ...
Page 28: ...Chapter 1 Introduction P54A B C E 2 P54xMED TM EN 1 ...
Page 38: ...Chapter 1 Introduction P54A B C E 12 P54xMED TM EN 1 ...
Page 39: ...CHAPTER 2 SAFETY INFORMATION ...
Page 40: ...Chapter 2 Safety Information P54A B C E 14 P54xMED TM EN 1 ...
Page 52: ...Chapter 2 Safety Information P54A B C E 26 P54xMED TM EN 1 ...
Page 53: ...CHAPTER 3 HARDWARE DESIGN ...
Page 54: ...Chapter 3 Hardware Design P54A B C E 28 P54xMED TM EN 1 ...
Page 86: ...Chapter 3 Hardware Design P54A B C E 60 P54xMED TM EN 1 ...
Page 87: ...CHAPTER 4 SOFTWARE DESIGN ...
Page 88: ...Chapter 4 Software Design P54A B C E 62 P54xMED TM EN 1 ...
Page 99: ...CHAPTER 5 CONFIGURATION ...
Page 100: ...Chapter 5 Configuration P54A B C E 74 P54xMED TM EN 1 ...
Page 120: ...Chapter 5 Configuration P54A B C E 94 P54xMED TM EN 1 ...
Page 121: ...CHAPTER 6 CURRENT DIFFERENTIAL PROTECTION ...
Page 122: ...Chapter 6 Current Differential Protection P54A B C E 96 P54xMED TM EN 1 ...
Page 149: ...CHAPTER 7 AUTORECLOSE ...
Page 150: ...Chapter 7 Autoreclose P54A B C E 124 P54xMED TM EN 1 ...
Page 207: ...CHAPTER 8 CB FAIL PROTECTION ...
Page 208: ...Chapter 8 CB Fail Protection P54A B C E 182 P54xMED TM EN 1 ...
Page 219: ...CHAPTER 9 CURRENT PROTECTION FUNCTIONS ...
Page 220: ...Chapter 9 Current Protection Functions P54A B C E 194 P54xMED TM EN 1 ...
Page 244: ...Chapter 9 Current Protection Functions P54A B C E 218 P54xMED TM EN 1 ...
Page 247: ...CHAPTER 10 VOLTAGE PROTECTION FUNCTIONS ...
Page 248: ...Chapter 10 Voltage Protection Functions P54A B C E 222 P54xMED TM EN 1 ...
Page 261: ...CHAPTER 11 FREQUENCY PROTECTION FUNCTIONS ...
Page 262: ...Chapter 11 Frequency Protection Functions P54A B C E 236 P54xMED TM EN 1 ...
Page 268: ...Chapter 11 Frequency Protection Functions P54A B C E 242 P54xMED TM EN 1 ...
Page 269: ...CHAPTER 12 MONITORING AND CONTROL ...
Page 270: ...Chapter 12 Monitoring and Control P54A B C E 244 P54xMED TM EN 1 ...
Page 300: ...Chapter 12 Monitoring and Control P54A B C E 274 P54xMED TM EN 1 ...
Page 301: ...CHAPTER 13 SUPERVISION ...
Page 302: ...Chapter 13 Supervision P54A B C E 276 P54xMED TM EN 1 ...
Page 312: ...Chapter 13 Supervision P54A B C E 286 P54xMED TM EN 1 ...
Page 323: ...CHAPTER 14 DIGITAL I O AND PSL CONFIGURATION ...
Page 324: ...Chapter 14 Digital I O and PSL Configuration P54A B C E 298 P54xMED TM EN 1 ...
Page 336: ...Chapter 14 Digital I O and PSL Configuration P54A B C E 310 P54xMED TM EN 1 ...
Page 337: ...CHAPTER 15 FIBRE TELEPROTECTION ...
Page 338: ...Chapter 15 Fibre Teleprotection P54A B C E 312 P54xMED TM EN 1 ...
Page 354: ...Chapter 15 Fibre Teleprotection P54A B C E 328 P54xMED TM EN 1 ...
Page 355: ...CHAPTER 16 ELECTRICAL TELEPROTECTION ...
Page 356: ...Chapter 16 Electrical Teleprotection P54A B C E 330 P54xMED TM EN 1 ...
Page 366: ...Chapter 16 Electrical Teleprotection P54A B C E 340 P54xMED TM EN 1 ...
Page 367: ...CHAPTER 17 COMMUNICATIONS ...
Page 368: ...Chapter 17 Communications P54A B C E 342 P54xMED TM EN 1 ...
Page 439: ...CHAPTER 18 CYBER SECURITY ...
Page 440: ...Chapter 18 Cyber Security P54A B C E 414 P54xMED TM EN 1 ...
Page 457: ...CHAPTER 19 INSTALLATION ...
Page 458: ...Chapter 19 Installation P54A B C E 432 P54xMED TM EN 1 ...
Page 471: ...CHAPTER 20 COMMISSIONING INSTRUCTIONS ...
Page 472: ...Chapter 20 Commissioning Instructions P54A B C E 446 P54xMED TM EN 1 ...
Page 513: ...CHAPTER 21 MAINTENANCE AND TROUBLESHOOTING ...
Page 514: ...Chapter 21 Maintenance and Troubleshooting P54A B C E 488 P54xMED TM EN 1 ...
Page 530: ...Chapter 21 Maintenance and Troubleshooting P54A B C E 504 P54xMED TM EN 1 ...
Page 531: ...CHAPTER 22 TECHNICAL SPECIFICATIONS ...
Page 532: ...Chapter 22 Technical Specifications P54A B C E 506 P54xMED TM EN 1 ...
Page 558: ...Chapter 22 Technical Specifications P54A B C E 532 P54xMED TM EN 1 ...
Page 559: ...APPENDIX A ORDERING OPTIONS ...
Page 560: ...Appendix A Ordering Options P54A B C E P54xMED TM EN 1 ...
Page 565: ...APPENDIX B SETTINGS AND SIGNALS ...
Page 566: ...Appendix B Settings and Signals P54A B C E P54xMED TM EN 1 ...
Page 790: ...Appendix B Settings and Signals P54A B C E B224 P54xMED TM EN 1 ...
Page 835: ...APPENDIX C WIRING DIAGRAMS ...
Page 836: ...Appendix C Wiring Diagrams P54A B C E P54xMED TM EN 1 ...
Page 849: ......