CHAPTER 1
INTRODUCTION
ET 601 – POWER SYSTEMET 601 – POWER SYSTEM
PROTECTIONPROTECTION
CHAPTER OUTLINES
After completed this chapter, students should be
able to:
1. Understand the constitution of power system
...
POWER SYSTEM PROCESS
EHV Transmission
System (275 kV)
Generator Transformer
Yd1
Syncronous Generator -
275 kV
(Base Load Generator)
Super Grid
...
SINGLE LINE DIAGRAM
PROTECTION SYMBOL
two-winding
transformer
current transformer
two-winding
transformer
generator
bus
voltage transformer
ca...
 Safeguard the entire system to maintain
continuity of supply
 Minimize damage and repair costs where it
senses fault
 ...
1. Normal operation means that there are no failures of
equipment and/or no mistakes committed by personnel.
This also mea...
Objective to achieve philosophies
 These requirements are necessary, firstly for early
detection and localization of faults, and
 Secondly for prompt remo...
• minimum fault duration and
consequent equipment damage and
system instability.
• assurance that the protection will
perf...
 A power system fault may be defined as any
condition or abnormality of the system which
involves the electrical failure ...
 Symmetrical fault
Faults giving rise to equal currents in lines
displaced by
equal phase angles i.e 120o
in three phase
...
SYMMETRICAL FAULT
THREE- PHASE FAULTTHREE- PHASE FAULT
THREE PHASE - EARTHTHREE PHASE - EARTH
FAULTFAULT
UNSYMMETRICAL FAULT
PHASE – PHASE FAULTPHASE – PHASE FAULT
TWO PHASE – EARTHTWO PHASE – EARTH
FAULTFAULT
SINGLE PHASE - EA...
OPEN CIRCUIT FAULT
SINGLE- PHASE OPENSINGLE- PHASE OPEN
CIRCUITCIRCUIT
TWO- PHASE OPENTWO- PHASE OPEN
CIRCUITCIRCUIT
THREE...
BASIC COMPONENT
 Figure shows basic connections of
circuit breaker control for the
opening operation. The protected
circuit X is shown by...
 The power system is divided into protection zones
defined by the equipment and the available circuit
breakers. Six categ...
PROTECTIVE ZONE DIAGRAM
 Although the fundamentals of protection are quite
similar, each of these six categories has protective
relays, specifica...
 Main or primary protection
First in line of defense is main protection which ensures
quick action and selective clearing...
PRIMARY & BACK UP PROTECTION
WHICH ONE PRIMARY AND BACK UP???
UNIT PROTECTION
- Able to detect and respond to fault occurring
only within its own zone protection.
- Have absolute discr...
NON UNIT PROTECTION
- Does not have absolute discrimination(selectivity).
- No defined area of coverage
- Also known as “b...
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Et601 chapter1 ayu

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Et601 chapter1 ayu

  1. 1. CHAPTER 1 INTRODUCTION ET 601 – POWER SYSTEMET 601 – POWER SYSTEM PROTECTIONPROTECTION
  2. 2. CHAPTER OUTLINES After completed this chapter, students should be able to: 1. Understand the constitution of power system 2. Know the need of protection system 3. Understand basic requirement of protection evaluation 4. Understand the type of fault and their effect 5. Know the basic components of protection 6. Understand basic concept of protection system.
  3. 3. POWER SYSTEM PROCESS
  4. 4. EHV Transmission System (275 kV) Generator Transformer Yd1 Syncronous Generator - 275 kV (Base Load Generator) Super Grid Transformer 275/132 kV Yy0d1 Gas Turbine (Pick-up Generation) Transmission Transf. 132/11 kV Yy0d1 Transmission Transf. 132/33 kV Yd1 Distribution Transf. 33/11 kV Dy1 33 kV11 kV 132 kV 11 kV 132 kV 275 kV Hydro Power Plant (Spinning Reserve ) FLOW OF POWER SYSTEM
  5. 5. SINGLE LINE DIAGRAM
  6. 6. PROTECTION SYMBOL two-winding transformer current transformer two-winding transformer generator bus voltage transformer capacitor circuit breaker transmission line delta connection wye connection circuit breaker fuse surge arrestor static load disconnect
  7. 7.  Safeguard the entire system to maintain continuity of supply  Minimize damage and repair costs where it senses fault  Ensure safety of personnel. Why need protection system?
  8. 8. 1. Normal operation means that there are no failures of equipment and/or no mistakes committed by personnel. This also means that there is no effect of any natural calamity on the power system. 2. Prevention of electric failure means the provision of features in the design that are aimed at preventing failures. These features include adequate insulation, insulation co-ordination in accordance with the capabilities of lighting arresters, providing overhead ground wires and low tower footing resistance, and adoption of proper operation and maintenance procedures. 3. Mitigation of the effects of electric failure when it occurs implies that certain ‘protection provisions should be incorporated in the system. These provision include limiting the magnitude of short circuit current, provision for promptly disconnecting the faulted section, and features that investigate and send out an alert in the case of an incipient fault. Philosophies
  9. 9. Objective to achieve philosophies
  10. 10.  These requirements are necessary, firstly for early detection and localization of faults, and  Secondly for prompt removal of faulty equipment from service.  In order to carry out the above duties, protection must have the following characteristics:  Reliability  Selectivity  Sensitivity  Speed  simplicity Basic requirement/characteristics
  11. 11. • minimum fault duration and consequent equipment damage and system instability. • assurance that the protection will perform correctly. • maximum continuity of service with minimum system disconnection. • To detect even the smallest fault, current or system abnormalities and operate correctly at its setting
  12. 12.  A power system fault may be defined as any condition or abnormality of the system which involves the electrical failure of primary equipment such as generators, transformers, busbars, overhead lines and cables and all other items of plant which operate at power system voltage.  Electrical failure generally implies one or the other (or both) of two types of failure, namely insulation failure resulting in a short-circuit condition or conducting path failure resulting in an open-circuit condition, the former being by far the more common type of failure. FAULT IN POWER SYSTEM
  13. 13.  Symmetrical fault Faults giving rise to equal currents in lines displaced by equal phase angles i.e 120o in three phase systems. Example: short circuit of all three phase conductors of a cable at a single location  Unsymmetrical fault Faults in which not all the line currents are equal and not all have the same phase. Example (any one): single phase line to ground fault (L-G), two phase to ground (LL-G) fault and phase to phase (L-L) fault. FAULT IN POWER SYSTEM
  14. 14. SYMMETRICAL FAULT THREE- PHASE FAULTTHREE- PHASE FAULT THREE PHASE - EARTHTHREE PHASE - EARTH FAULTFAULT
  15. 15. UNSYMMETRICAL FAULT PHASE – PHASE FAULTPHASE – PHASE FAULT TWO PHASE – EARTHTWO PHASE – EARTH FAULTFAULT SINGLE PHASE - EARTHSINGLE PHASE - EARTH FAULTFAULT
  16. 16. OPEN CIRCUIT FAULT SINGLE- PHASE OPENSINGLE- PHASE OPEN CIRCUITCIRCUIT TWO- PHASE OPENTWO- PHASE OPEN CIRCUITCIRCUIT THREE- PHASE OPENTHREE- PHASE OPEN CIRCUITCIRCUIT
  17. 17. BASIC COMPONENT
  18. 18.  Figure shows basic connections of circuit breaker control for the opening operation. The protected circuit X is shown by dashed line. When a fault occurs in the protected circuit the relay (2) connected to CT and PT actuates and closes its contacts (6).  Current flows from battery (5) in the trip circuit (4). As the trip coil of circuit breaker (3) is energized, the circuit breaker operating mechanism is actuated and it operates for the opening operation.  Thus the fault is sensed and the trip circuit is actuated by the relay and the faulty part is isolated. BASIC COMPONENT
  19. 19.  The power system is divided into protection zones defined by the equipment and the available circuit breakers. Six categories of protection zones are possible in each power system: 1. Generators and generator-transformer units 2. Transformers 3. Bus bars 4. Lines (transmission and distribution) 5. Utilization equipment (motors, static loads, or other) 6. Capacitor or reactor banks (when separately protected) PROTECTIVE ZONE
  20. 20. PROTECTIVE ZONE DIAGRAM
  21. 21.  Although the fundamentals of protection are quite similar, each of these six categories has protective relays, specifically designed for primary protection, that are based on the characteristics of the equipment being protected. The protection of each zone normally includes relays that can provide backup for the relays protecting the adjacent equipment.  The protection in each zone should overlap that in the adjacent zone; otherwise, a primary protection void would occur between the protection zones. This overlap is accomplished by the location of the CTs the key sources of power system information for the relays.
  22. 22.  Main or primary protection First in line of defense is main protection which ensures quick action and selective clearing of faults within the boundary of the circuit section or the element it protects. Main protection is essentially provided as a rule.  Back-up protection It is the second line of defense in case in failure of primary protection. It is designed to operate with sufficient time delays so that primary relaying will be given enough time to function if it is able to. Back up protection gives back up to the main protection, when the main protection fails to operate or is cut out for repairs etc. PRIMARY & BACK UP PROTECTION
  23. 23. PRIMARY & BACK UP PROTECTION WHICH ONE PRIMARY AND BACK UP???
  24. 24. UNIT PROTECTION - Able to detect and respond to fault occurring only within its own zone protection. - Have absolute discrimination. Its zone of protection is well defined. - It does not respond to the fault occurring beyond its own zone protection. - Also referred to as “main protection” - Fast operating time - Example: differential protection of alternators, transformer or bus bars, frame leakage protection, pilot wire and carrier current protection.
  25. 25. NON UNIT PROTECTION - Does not have absolute discrimination(selectivity). - No defined area of coverage - Also known as “back-up protection” - Slower operating time - Example: distance protection and time graded, current graded or both time and current graded.
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