V00633
V
res
= -3V
o
I
R1
= I
H1
I
a1
I
b1
V
res
= -3V
o
I
R3
= I
F
+ I
H3
I
L
-I
H1
-I
H2
I
R3
= I
L
- I
H1
- I
H2
a) Capacitive and inductive currents
C
B
A
3V
0
I
H3
I
H2
I
L
I
H1
I
B1
I
A1
N
b) Unfaulted line
c) Faulted line
Figure 44: Phasors for a phase C earth fault in a Petersen Coil earthed system
It can be seen that:
●
The voltage in the faulty phase reduces to almost 0V
●
The healthy phases raise their phase to earth voltages by a factor of
Ö
3
●
The triangle of voltages remains balanced
●
The charging currents lead the voltages by 90°
Using a core-balance current transformer (CBCT), the current imbalances on the healthy feeders can be measured.
They correspond to simple vector addition of I
A1
and I
B1
, I
A2
and I
B2
, I
A3
and I
B3
, and they lag the residual voltage
by exactly 90º.
The magnitude of the residual current I
R1
is equal to three times the steady-state charging current per phase. On
the faulted feeder, the residual current is equal to I
L
- I
H1
- I
H2
(C). This is shown in the zero sequence network
shown in the following figure:
V00640
I
ROF
= Residual current on faulted feeder
I
ROH
= Residual current on healthy feeder
I
OF
= I
L
– I
H1
– I
H2
– I
H3
I
ROF
= I
H3
+ I
OF
so:
I
ROF
= I
L
– I
H1
– I
H2
3X
L
I
L
-V
0
X
CO
IH
3
IH
2
IH
1
Healthy feeders
Faulty feeder
I
ROF
I
ROH
I
ROH
I
OF
Figure 45: Zero sequence network showing residual currents
In practical cases, however, resistance is present, resulting in the following phasor diagrams:
P24xM
Chapter 6 - Current Protection Functions
P24xM-TM-EN-2.1
117
Summary of Contents for P24DM
Page 2: ......
Page 17: ...Appendix C Wiring Diagrams 467 P24xM Contents P24xM TM EN 2 1 xv...
Page 18: ...Contents P24xM xvi P24xM TM EN 2 1...
Page 24: ...Table of Figures P24xM xxii P24xM TM EN 2 1...
Page 25: ...CHAPTER 1 INTRODUCTION...
Page 26: ...Chapter 1 Introduction P24xM 2 P24xM TM EN 2 1...
Page 37: ...CHAPTER 2 SAFETY INFORMATION...
Page 38: ...Chapter 2 Safety Information P24xM 14 P24xM TM EN 2 1...
Page 51: ...CHAPTER 3 HARDWARE DESIGN...
Page 52: ...Chapter 3 Hardware Design P24xM 28 P24xM TM EN 2 1...
Page 66: ...Chapter 3 Hardware Design P24xM 42 P24xM TM EN 2 1...
Page 67: ...CHAPTER 4 SOFTWARE DESIGN...
Page 68: ...Chapter 4 Software Design P24xM 44 P24xM TM EN 2 1...
Page 77: ...CHAPTER 5 CONFIGURATION...
Page 78: ...Chapter 5 Configuration P24xM 54 P24xM TM EN 2 1...
Page 94: ...Chapter 5 Configuration P24xM 70 P24xM TM EN 2 1...
Page 95: ...CHAPTER 6 CURRENT PROTECTION FUNCTIONS...
Page 96: ...Chapter 6 Current Protection Functions P24xM 72 P24xM TM EN 2 1...
Page 188: ...Chapter 6 Current Protection Functions P24xM 164 P24xM TM EN 2 1...
Page 189: ...CHAPTER 7 RESTRICTED EARTH FAULT PROTECTION...
Page 190: ...Chapter 7 Restricted Earth Fault Protection P24xM 166 P24xM TM EN 2 1...
Page 201: ...CHAPTER 8 CB FAIL PROTECTION...
Page 202: ...Chapter 8 CB Fail Protection P24xM 178 P24xM TM EN 2 1...
Page 215: ...CHAPTER 9 CURRENT TRANSFORMER REQUIREMENTS...
Page 216: ...Chapter 9 Current Transformer Requirements P24xM 192 P24xM TM EN 2 1...
Page 224: ...Chapter 9 Current Transformer Requirements P24xM 200 P24xM TM EN 2 1...
Page 225: ...CHAPTER 10 VOLTAGE PROTECTION FUNCTIONS...
Page 226: ...Chapter 10 Voltage Protection Functions P24xM 202 P24xM TM EN 2 1...
Page 245: ...CHAPTER 11 FREQUENCY PROTECTION FUNCTIONS...
Page 246: ...Chapter 11 Frequency Protection Functions P24xM 222 P24xM TM EN 2 1...
Page 261: ...CHAPTER 12 POWER PROTECTION FUNCTIONS...
Page 262: ...Chapter 12 Power Protection Functions P24xM 238 P24xM TM EN 2 1...
Page 265: ...CHAPTER 13 MONITORING AND CONTROL...
Page 266: ...Chapter 13 Monitoring and Control P24xM 242 P24xM TM EN 2 1...
Page 294: ...Chapter 13 Monitoring and Control P24xM 270 P24xM TM EN 2 1...
Page 295: ...CHAPTER 14 SUPERVISION...
Page 296: ...Chapter 14 Supervision P24xM 272 P24xM TM EN 2 1...
Page 312: ...Chapter 14 Supervision P24xM 288 P24xM TM EN 2 1...
Page 313: ...CHAPTER 15 DIGITAL I O AND PSL CONFIGURATION...
Page 314: ...Chapter 15 Digital I O and PSL Configuration P24xM 290 P24xM TM EN 2 1...
Page 327: ...CHAPTER 16 COMMUNICATIONS...
Page 328: ...Chapter 16 Communications P24xM 304 P24xM TM EN 2 1...
Page 386: ...Chapter 16 Communications P24xM 362 P24xM TM EN 2 1...
Page 387: ...CHAPTER 17 CYBER SECURITY...
Page 388: ...Chapter 17 Cyber Security P24xM 364 P24xM TM EN 2 1...
Page 405: ...CHAPTER 18 INSTALLATION...
Page 406: ...Chapter 18 Installation P24xM 382 P24xM TM EN 2 1...
Page 419: ...CHAPTER 19 COMMISSIONING INSTRUCTIONS...
Page 420: ...Chapter 19 Commissioning Instructions P24xM 396 P24xM TM EN 2 1...
Page 443: ...CHAPTER 20 MAINTENANCE AND TROUBLESHOOTING...
Page 444: ...Chapter 20 Maintenance and Troubleshooting P24xM 420 P24xM TM EN 2 1...
Page 453: ...CHAPTER 21 TECHNICAL SPECIFICATIONS...
Page 454: ...Chapter 21 Technical Specifications P24xM 430 P24xM TM EN 2 1...
Page 486: ...Chapter 21 Technical Specifications P24xM 462 P24xM TM EN 2 1...
Page 487: ...APPENDIX A ORDERING OPTIONS...
Page 488: ...Appendix A Ordering Options P24xM 464 P24xM TM EN 2 1...
Page 491: ...APPENDIX B SETTINGS AND SIGNALS...
Page 493: ...APPENDIX C WIRING DIAGRAMS...
Page 494: ...Appendix C Wiring Diagrams P24xM 468 P24xM TM EN 2 1...
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