4
RESIDUAL OVERVOLTAGE PROTECTION
On a healthy three-phase power system, the sum of the three-phase to earth voltages is nominally zero, as it is the
vector sum of three balanced vectors displaced from each other by 120°. However, when an earth fault occurs on
the primary system, this balance is upset and a residual voltage is produced. This condition causes a rise in the
neutral voltage with respect to earth. Consequently this type of protection is also commonly referred to as 'Neutral
Voltage Displacement' or NVD for short.
This residual voltage may be derived (from the phase voltages) or measured (from a measurement class open
delta VT). Derived values will normally only be used where the model does not support measured functionality (a
dedicated measurement class VT). If a measurement class VT is used to produce a measured Residual Voltage, it
cannot be used for other features such as Check Synchronisation.
This offers an alternative means of earth fault detection, which does not require any measurement of current. This
may be particularly advantageous in high impedance earthed or insulated systems, where the provision of core
balanced current transformers on each feeder may be either impractical, or uneconomic, or for providing earth
fault protection for devices with no current transformers.
4.1
RESIDUAL OVERVOLTAGE PROTECTION IMPLEMENTATION
Residual Overvoltage Protection is implemented in the RESIDUAL O/V NVD column of the relevant settings group.
Some applications require more than one stage. For example an insulated system may require an alarm stage and
a trip stage. It is common in such a case for the system to be designed to withstand the associated healthy phase
overvoltages for a number of hours following an earth fault. In such applications, an alarm is generated soon after
the condition is detected, which serves to indicate the presence of an earth fault on the system. This gives time for
system operators to locate and isolate the fault. The second stage of the protection can issue a trip signal if the
fault condition persists.
The product provides two stages of Residual Overvoltage protection with independent time delay characteristics.
Stage 1 provides a choice of operate characteristics, where you can select between:
●
An IDMT characteristic
●
DT (Definite Time)
The IDMT characteristic is defined by the following formula:
t = K/( M - 1)
where:
●
K= Time multiplier setting
●
t = Operating time in seconds
●
M = Derived residual voltage setting voltage (VN> Voltage Set)
You set this using the VN>1 Function setting.
Stage 1 also provides a Timer Hold facility.
Stage 2 can have definite time characteristics only. This is set in the VN>2 status cell
The device derives the residual voltage internally from the three-phase voltage inputs supplied from either a 5-limb
VT or three single-phase VTs. These types of VT design provide a path for the residual flux and consequently permit
the device to derive the required residual voltage. In addition, the primary star point of the VT must be earthed.
Three-limb VTs have no path for residual flux and are therefore unsuitable for this type of protection.
Chapter 11 - Voltage Protection Functions
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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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