2.3.3
BASIC ALGORITHM
The multi-ended differential sample based algorithm employs the RMS value, in which the instantaneous
differential current is the sum of instantaneous current of all terminals:
i
n
i
n
diff
Tm
m
M
( )
( )
=
=
∑
1
Where, i
Tm
is the current of mth terminal; M is the number of terminals; i
diff
is instantaneous differential current; n
is present sample number.
The RMS value of the differential current is used for the discriminative criteria:
I
n
N
i
k
diff
diff
k
n
N
n
( )
( )
=
= −
+
∑
1
2
1
Where, I
diff
is the RMS value of i
diff
; N is the window length in samples for RMS calculation, which is selected as a
cycle of fundamental frequency; n is present sample; k is history sample number within the window length N.
Similarly, the I
bias
, which is the sum of the RMS value of currents of all terminals:
I
n
N
i
k
Tm
Tm
k
n
N
n
( )
( )
=
= −
+
∑
1
2
1
I
n
I
n
bias
Tm
m
M
( )
[
( )]
=
=
∑
1
2
1
Where, I
bias
is RMS value of bias current; I
Tm
is RMS value of i
Tm
; M is the number of terminals; N is the window
length in samples for RMS calculation, which is selected as a cycle of fundamental frequency; n is present sample
number; k is the history sample number within the window length N.
2.3.4
FEATURES OF MULTI-ENDED LINE DIFFERENTIAL
To practically implement a Multi-ended differential system, the following technical challenges must be resolved:
Charging current: The capacitive current is caused by the equivalent shunt capacitance of lines. For short line/
cable, the capacitive current is negligible, multi-ended line differential should work without problem. But for line
more than 50km or cable more than 10km, higher pickup setting could be used to prevent fault relay operation,
but this will desensitise the protection. The capacitive current is recommended to be compensated to achieve
sensitive protection. Therefore, with VT input, a new capacitive current compensation algorithm for distributed
parameter line is developed to achieve high sensitivity in multi-ended differential.
Data synchronization: The remote data should be aligned with the local measured data. Due to the
communication time delay from remote end to local end as well as due to the un-synchronized sampling between
the relays at local end and remote ends data is not synchronised. Ping-Pong is employed for data synchronization.
CT Saturation: When the fault is severe, the CTs at different terminals could be unbalanced and saturated, which
results in high unbalanced current in differential current when the external fault occurs. The multi-ended line
differential must include an enhance CT saturation technique to detect internal / external faults and indirectly
reduce the CT requirement.
The above features will be discussed in detail in the following section.
2.3.5
ALGORITHM OVERVIEW
The overall protection scheme is constructed by incorporating many small functions which enables functionality of
multi-end differential to be as accurate as possible.
Chapter 6 - Current Differential Protection
P54A/B/C/E
102
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: ......