V/f
V/Hz>1 Trip Set
3ph V /Hz>1 Trip
V00867
Freq Not found
Blk 3ph V/Hz>1
&
IDMT
3ph V /Hz>1 Start
V/f
V/Hz>1 Trip Set
3ph V /Hz>1 Trip
Freq Not found
&
DT
3ph V /Hz>1 Start
Note: The diagram is for a 3-phase VT. The logic for a 1-phase VT is the same .
This diagram does not show all stages . Other stages follow similar principles.
V/f
V/Hz Alarm Set
3Ph V/Hz> Alarm
Freq Not found
&
DT
V/Hz>1 Trip
TMS
V/Hz>1
Delay
V/Hz>1 Delay
V/Hz Alarm
Delay
Figure 119: Overfluxing protection logic
2.2
APPLICATION NOTES
2.2.1
OVERFLUXING PROTECTION SETTING GUIDELINES
The pick up value for the overfluxing elements depends on the nominal core flux density levels. Unit transformers
generally run at higher flux densities than transmission and distribution transformers, so they require a higher pick
up setting and shorter tripping times which reflect this. Transmission transformers can also be at risk from
overfluxing conditions, and you should take withstand levels into consideration when deciding on the required
settings.
The IEEE C37.91-2000 standard states that overexcitation of a transformer can occur whenever the ratio of the per
unit voltage to per unit frequency (V/Hz) at the secondary terminals of a transformer exceeds its rating of 1.05 per
unit (PU) on transformer base at full load, 0.8 power factor, or 1.1 PU at no load.
Please refer to clause 4.1.6 in IEEE C57.12.00-2006 for further clarification on the capability of a transformer to
operate above rated voltage and below rated frequency.
The element is set in terms of the actual ratio of voltage to frequency. You can therefore calculate the overfluxing
threshold setting V/Hz>(n) Trip Set, as follows:
A setting of 1.05 p.u. would equate to 110/50 x 1.05 = 2.31
where:
●
The VT secondary voltage at rated primary volts is 110 V
●
The rated frequency is 50 Hz
You should set the overfluxing alarm stage threshold V/Hz Alarm Set, lower than the trip stage setting, to provide
an indication that abnormal conditions are present and to alert an operator to adjust system parameters
accordingly.
You should choose the time delay settings to match the withstand characteristics of the protected transformer. For
an inverse time characteristic, set the time multiplier setting, V/Hz>1 Trip TMS such that the operating
characteristic closely matches the withstand characteristic of transformer. For definite time trip stages, set the
time delay V/Hz>(n) Trip Delay cells. The alarm stage time delay is set in the V/Hz Alarm Delay cell.
P64x
Chapter 12 - Frequency Protection Functions
P64x-TM-EN-1.3
257
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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