Switchgear and Protection
Course Objective:
To present fundamental knowledge on protection system and its associated components in power system
- Principle of power system protection(3 hours)
- Protection system components and its terminologies
- Basic requirement of protection scheme
- Need of protection scheme in power system
- Back up protection, coordination , protection zone
- Current and Potential Transformers (3 hours)
- Potential transformer: Operation, standard ratios, errors, application
- Current transformer : Wound and bar types, operation, standard ratios
- Accuracy classification , typical knee point voltage , applications
- Fuses (4 hours)
- Types of fuses: Construction, operating characteristic and application
- Fuse element, rated fuse current , minimum fusing factor, fusing factor, pre arcing and arcing time
- Merits and demerits of various types of fuse
- Isolators and Contactors (4 hours)
- Isolators: Construction, operation and uses
- Contactors: Construction and operation, normally open (NO) and Normally Close (NC), auxiliary contacts of contactors and application of contactors
- System Earthing (6 hours)
- Earthing: Definition, purpose, system earthing and body earthing, methods of earthing, substation earthing, measurement of soil resistivity
- Causes of over voltages: Internal cause and external cause
- Over voltage protection: Overhead earth wire, angle of protection, horn gap and rod gap lightning arrestor, surge absorbers
- Isolated neutral, solid neutral, resistance earthing, reactance earthing, Peterson coil earthing
- Circuit Breaker (12 hours)
- Circuit breaking process: Arc phenomena, arc extinction and its methods, pre-arcing and arcing time, restricting voltage and recovery voltage
- Duties of circuit breaker
- Classification of circuit breaker:
- Miniature circuit breaker: Construction, operating principle and application and various types of MCB such as ELCB
- Moulded Case circuit Breaker: Construction, operating principle and application
- Air circuit breaker: Construction, operating merits and demerits, arc extinction phenomena and application.
- Oil circuit breaker: Construction, operating merits and demerits, arc extinction phenomena and application
- Vacuum circuit breaker: Construction, operating merits and demerits, arc extinction phenomena and application.
- SF6 circuit breaker: Construction, operating merits and demerits, arc extinction phenomena and application
- Circuit breaker rating: Rated voltage , rated current, rated frequency, operating duty, making capacity, short time rating
- HVDC circuit breaker
- Auto reclosure
- Testing of circuit breaker
- Protective relays (14 hours)
- Introduction
- Classification of relays
- Method of earth fault detection
- Restricted and unrestricted earth fault protection
- Electromagnet attraction relays
- Electro magnet induction relays
- Buchholz relay
- Over current relays
- Inverse definite minimum time (IDMT) relay, TDS,PSM
- Application of IDMT relay in sectionalized HV feeder, Time-Graded protection/Current Graded protection
- Directional relay (induction type)
- Over current and earth fault relay
- Unit protection scheme/Differential protection
- Advantage of unit protection scheme over non unit protection
- Application of unit protection/differential protection scheme to HV feeders,
- Transformers and generators
- Biased or percentage relay and its application to transformers and generators
- Voltage balance relay
- Universal relay torque equation
- Distance protection
- Impedance, reactance and mho relay
- Application of distance protection relay in sectionalized feeder
- Carrier current protection
- Bus bar protection
- Static and digital Relays (12 hours)
- Need for static relays
- Essential components of static relays
- Comparison of static and electromagnet relays
- Classification of static relays
- A review of Electronic Circuit Commonly used in static relays: Auxiliary DC Voltage Supply,
- Time Delay Circuit, Level Detectors, Multivibrator, logic circuit, use of operational amplifier in static relay,
- Static Over current relays and over volatge/under voltage realy
- Directional static over current relays
- Static differential relays
- Static differential protection scheme applied to transformer
- Static distance relays such as impedance relay, reactance relay and mho relay
- Static differential protection applied to the generator
- Block diagram and Component of digital relay
- Block diagram of microprocessor based protective scheme for protection of transformer, generator and transmission line
- Block diagram of microprocessor based over voltage /under voltage relay
Practical
- Draw magnetizing curve for a protective CT. Check Knee point voltage
- Test over current device in an Air Circuit Breaker for operation using primary injection
- Test an induction disc relay in over current in over current protection scheme for operating characteristics using secondary injection.
- Test an induction disc relay in residual earth fault protection scheme for operating characteristics and setting using secondary injection.
- Check connections on a biased differential protection scheme of transformer. Test the scheme for operation and setting values on internal faults using primary injection
- Measurement of soil resistivity
References
- Sunil S. Rao “Switchgear and protection” Khanna Publishers
- G. Mason “The art and science of protective realying”
- J.B Gupta “Switchgear and protection” Kataria and Sons
Evaluation Scheme:
The questions will cover all the chapters in syllabus. The evaluation scheme will be as indicated in the table below.
Chapters |
Hours |
Marks Distribution* |
1 |
3 |
4 |
2 |
3 |
4 |
3 |
4 |
6 |
4 |
4 |
6 |
5 |
6 |
8 |
6 |
12 |
16 |
7 |
14 |
20 |
8 |
12 |
16 |
Total |
58 |
80 |
*Note: There may be minor deviation in marks distribution
|