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CTs may be close to saturation so a high bias current is needed. More differential current is then needed to trip the
circuit breakers, allowing greater security from external faults and less risk of maloperation.
This is achieved by defining an operating current characteristic. Often a triple slope characteristic is used as shown
below.
K1
K2
Restraint region
Operate region
Is2
Is1
Ibias
Idiff
V00664
High Set Threshold
Figure 35: Compensation using biased differential characteristic
Idiff is the differential current, which is the vector sum of all the current inputs. Ibias is a current which is
proportional to the scalar sum of all currents entering and leaving the zone. The bias current is used to calculate
an operating current. If the differential current calculated by the IED is above the operation current, then the
device will trip (providing no blocking signals are asserted).
The characteristic can be defined by setting certain parameters such as the minimum operating current Is1 (Iset
1), Is2 (Iset 2), K1 and K2. Is1 sets the minimum operating current. Is2 sets the level of bias current at which the
steeper slope sets in. Constants K1 and K2 define the slopes. A High Set Threshold is usually defined, which ensures
the device will operate for very high currents, even if blocking signals are present.
The slope parts of the characteristic curve provide stability for external faults that cause CT saturation. The high
bias current region of the characteristic curve has a steeper slope than the low bias current region in order to
improve the stability even further for high-current external faults. The first slope, K1, compensates for CT errors
and tap changer errors. The second slope, K2, compensates for CT saturation. Is1 should be set above transient
overfluxing and Is2 should be considered as the transformer full load current. The CTs are sized according to the
transformer full load current.
2.3
THREE-PHASE TRANSFORMER CONNECTION TYPES
There are two ways of connecting a three-phase transformer winding:
●
Star-connected (sometimes known as Y, or Wye)
●
Delta-connected (sometimes known as
D
or D)
In some transformers, the windings are split at the centre point and terminals are brought out so that they can
also be interconnected. These windings can be zig-zag connected (Z-connected).
The more common connection types are:
●
Y-y
●
Y-d
●
Y-z
●
D-d
●
D-y
●
D-z
To differentiate between the low and high voltage sides of the transformer, a standard convention has been
adopted whereby lower case is used for the low voltage side and upper case is used for the high voltage side.
P64x
Chapter 6 - Transformer Differential Protection
P64x-TM-EN-1.3
101
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 ...
Страница 590: ......
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