3
CURRENT TRANSFORMER SUPERVISION
The Current Transformer Supervision function (CTS) is used to detect failure of the AC current inputs to the
protection. This may be caused by internal current transformer faults, overloading, or faults on the wiring. If there
is a failure of the AC current input, the protection could misinterpret this as a failure of the actual phase currents
on the power system, which could result in maloperation. Also, interruption in the AC current circuits can cause
dangerous CT secondary voltages to be generated.
3.1
CTS IMPLEMENTATION
Differential current transformer supervision is based on the measurement of the ratio of negative sequence
current to positive sequence current (I2/I1) for each CT. When this ratio is not zero, one of the following two
conditions may be present:
●
There is an unbalanced fault
●
There is a 1 or 2 phase CT problem
If the I2/I1 ratio is greater than the high set value, CTS I2/I1>2 at all ends, it is almost certainly a genuine fault
condition, thus the CTS will not operate. If this ratio is detected at one end only, one of the following conditions
may be present:
●
A CT problem
●
A single end fed fault condition
The positive sequence current I1 is used to confirm whether it is a CT problem or not. If I1 is greater than the
setting CTS I1 at all terminals, it must be a CT problem and CTS is allowed to operate. If this condition is detected at
only one end, the device assumes it is caused by either an inrush condition or a single-end fed internal fault. In this
case, CTS operation is blocked.
The CTS status setting under the CT SUPERVISION sub-heading can be set to either
indication
or
restraint
. In indication mode, the CTS alarm time delay is automatically set to zero. If a CT failure is present, an
alarm would be issued without delay, but the differential protection would remain unrestricted. In restraint mode,
the differential protection is blocked for 20 ms after CT failure has been detected, after which the restraint region
of the bias characteristic increases according to the setting Is-CTS , which has been defined in the DIFF
PROTECTION column.
K2
K1
Is1/K1
Is2
Ibias/In
Is1
Is-CTS
Idiff/In
Restraint region
Operating region
V01226
Figure 133: CTS restraint region increase
The low impedance REF, earth fault and NPS overcurrent protection functions are internally blocked by CTS when a
CT failure is detected in the relevant CT. However, earth fault protection is immune to CTS blocking if IN> input is
set to measured.
P64x
Chapter 14 - Supervision
P64x-TM-EN-1.3
291
Содержание P642
Страница 2: ......
Страница 18: ...Contents P64x xvi P64x TM EN 1 3 ...
Страница 24: ...Table of Figures P64x xxii P64x TM EN 1 3 ...
Страница 25: ...CHAPTER 1 INTRODUCTION ...
Страница 26: ...Chapter 1 Introduction P64x 2 P64x TM EN 1 3 ...
Страница 36: ...Chapter 1 Introduction P64x 12 P64x TM EN 1 3 ...
Страница 37: ...CHAPTER 2 SAFETY INFORMATION ...
Страница 38: ...Chapter 2 Safety Information P64x 14 P64x TM EN 1 3 ...
Страница 50: ...Chapter 2 Safety Information P64x 26 P64x TM EN 1 3 ...
Страница 51: ...CHAPTER 3 HARDWARE DESIGN ...
Страница 52: ...Chapter 3 Hardware Design P64x 28 P64x TM EN 1 3 ...
Страница 87: ...CHAPTER 4 SOFTWARE DESIGN ...
Страница 88: ...Chapter 4 Software Design P64x 64 P64x TM EN 1 3 ...
Страница 98: ...Chapter 4 Software Design P64x 74 P64x TM EN 1 3 ...
Страница 99: ...CHAPTER 5 CONFIGURATION ...
Страница 100: ...Chapter 5 Configuration P64x 76 P64x TM EN 1 3 ...
Страница 121: ...CHAPTER 6 TRANSFORMER DIFFERENTIAL PROTECTION ...
Страница 122: ...Chapter 6 Transformer Differential Protection P64x 98 P64x TM EN 1 3 ...
Страница 165: ...CHAPTER 7 TRANSFORMER CONDITION MONITORING ...
Страница 166: ...Chapter 7 Transformer Condition Monitoring P64x 142 P64x TM EN 1 3 ...
Страница 189: ...CHAPTER 8 RESTRICTED EARTH FAULT PROTECTION ...
Страница 190: ...Chapter 8 Restricted Earth Fault Protection P64x 166 P64x TM EN 1 3 ...
Страница 215: ...CHAPTER 9 CURRENT PROTECTION FUNCTIONS ...
Страница 216: ...Chapter 9 Current Protection Functions P64x 192 P64x TM EN 1 3 ...
Страница 249: ...CHAPTER 10 CB FAIL PROTECTION ...
Страница 250: ...Chapter 10 CB Fail Protection P64x 226 P64x TM EN 1 3 ...
Страница 259: ...CHAPTER 11 VOLTAGE PROTECTION FUNCTIONS ...
Страница 260: ...Chapter 11 Voltage Protection Functions P64x 236 P64x TM EN 1 3 ...
Страница 274: ...Chapter 11 Voltage Protection Functions P64x 250 P64x TM EN 1 3 ...
Страница 275: ...CHAPTER 12 FREQUENCY PROTECTION FUNCTIONS ...
Страница 276: ...Chapter 12 Frequency Protection Functions P64x 252 P64x TM EN 1 3 ...
Страница 286: ...Chapter 12 Frequency Protection Functions P64x 262 P64x TM EN 1 3 ...
Страница 287: ...CHAPTER 13 MONITORING AND CONTROL ...
Страница 288: ...Chapter 13 Monitoring and Control P64x 264 P64x TM EN 1 3 ...
Страница 306: ...Chapter 13 Monitoring and Control P64x 282 P64x TM EN 1 3 ...
Страница 307: ...CHAPTER 14 SUPERVISION ...
Страница 308: ...Chapter 14 Supervision P64x 284 P64x TM EN 1 3 ...
Страница 322: ...Chapter 14 Supervision P64x 298 P64x TM EN 1 3 ...
Страница 323: ...CHAPTER 15 DIGITAL I O AND PSL CONFIGURATION ...
Страница 324: ...Chapter 15 Digital I O and PSL Configuration P64x 300 P64x TM EN 1 3 ...
Страница 336: ...Chapter 15 Digital I O and PSL Configuration P64x 312 P64x TM EN 1 3 ...
Страница 337: ...CHAPTER 16 COMMUNICATIONS ...
Страница 338: ...Chapter 16 Communications P64x 314 P64x TM EN 1 3 ...
Страница 397: ...CHAPTER 17 CYBER SECURITY ...
Страница 398: ...Chapter 17 Cyber Security P64x 374 P64x TM EN 1 3 ...
Страница 415: ...CHAPTER 18 INSTALLATION ...
Страница 416: ...Chapter 18 Installation P64x 392 P64x TM EN 1 3 ...
Страница 429: ...5 2 CASE DIMENSIONS 60TE E01409 Figure 167 60TE case dimensions P64x Chapter 18 Installation P64x TM EN 1 3 405 ...
Страница 431: ...CHAPTER 19 COMMISSIONING INSTRUCTIONS ...
Страница 432: ...Chapter 19 Commissioning Instructions P64x 408 P64x TM EN 1 3 ...
Страница 454: ...V01505 Figure 173 Harmonic Restraint Test Plane Chapter 19 Commissioning Instructions P64x 430 P64x TM EN 1 3 ...
Страница 460: ...Chapter 19 Commissioning Instructions P64x 436 P64x TM EN 1 3 ...
Страница 461: ...CHAPTER 20 MAINTENANCE AND TROUBLESHOOTING ...
Страница 462: ...Chapter 20 Maintenance and Troubleshooting P64x 438 P64x TM EN 1 3 ...
Страница 477: ...CHAPTER 21 TECHNICAL SPECIFICATIONS ...
Страница 478: ...Chapter 21 Technical Specifications P64x 454 P64x TM EN 1 3 ...
Страница 507: ...APPENDIX A ORDERING OPTIONS ...
Страница 508: ...Appendix A Ordering Options P64x P64x TM EN 1 3 ...
Страница 512: ...Appendix A Ordering Options P64x A4 P64x TM EN 1 3 ...
Страница 513: ...APPENDIX B SETTINGS AND SIGNALS ...
Страница 515: ...APPENDIX C WIRING DIAGRAMS ...
Страница 516: ...Appendix C Wiring Diagrams P64x P64x TM EN 1 3 ...
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