Switchgear and Protection

Week 1: Unit– I Basics of Protection

• Necessity, functions of protective system.

• Normal and abnormal conditions.

• Types of faults and their causes.

Week 2: Unit– I Basics of Protection

• Protection zones and backup protection

• Short circuit fault calculations in lines fed by generators through transformers

• Need of current limiting reactors and their arrangements.

Week 3: Unit– II Circuit Interruption Devices

• HRC fuses – Construction, working, characteristics and applications.

• Arc formation process, methods of arc extinction (High resistance and Low resistance),

Arc voltage, Recovery voltage, Re-striking voltage, RRRV.

Week 4: Unit– II Circuit Interruption Devices

• Isolators- Vertical break, Horizontal break and Pantograph type.

• L.T. circuit breaker (Air circuit breakers (ACB), Miniature circuit breakers (MCB), Moulded case circuit breakers (MCCB) and Earth leakage circuit breaker (ELCB)) - Working and applications. HT circuit breakers (Sulphur-hexa Fluoride (SF6), Vacuum circuit breaker) - Working, construction, specifications and applications.

Week 5: Unit– II Circuit Interruption Devices

• Selection of LT and HT circuit breakers (ratings)

• Selection of MCCB for motors.

• Gas insulated switchgear.

Week 6: Unit– III Protective Relays

• Fundamental quality requirements: Selectivity, Speed, Sensitivity, Reliability, Simplicity, Economy.
• Protective relays: Classification, principle of working, construction and operation of – Electromagnetic (Attracted armature type, Solenoid type, Watt-hour meter type) relay.

Week 7: Unit– III Protective Relays

• Overcurrent relay-Time current characteristics.

• Basic relay terminology- Protective relay, Relay time, Pick up, Reset current, current setting, Plug setting multiplier, Time setting multiplier.

• Microprocessor based over current relays: Block diagram, working.

• Thermal relay. Block diagram and working of Static relay.

Week 8: Unit– III Protective Relays

• Distance relaying- Principle, operation of Definite distance relays.

• Directional relay: Need and operation.

• Operation of current and voltage differential relay.

Week 9: Unit– IV Protection of Alternator and Transformer

• Alternator Protection

o Faults, Differential protection Over current, earth fault, overheating and field failure, protection.

o Reverse power protection.

Week 10: Unit– IV Protection of Alternator and Transformer

• Transformer Protection

o Faults, Differential, over current, earth fault, over heating protection, Limitations of differential protection.

o Buchholz relay: Construction, operation, merits and demerits.

Week 11: Unit– V Protection of Motors, Bus-bar and Transmission Line

• Motor Faults. Short circuit protection, Overload protection, Single phase preventer.

• Bus bar and Transmission line, Faults on Bus bar and Transmission Lines.

• Bus bar protection: Differential and Fault bus protection.

Week 12: Unit– V Protection of Motors, Bus-bar and Transmission Line

• Transmission line: Over current, Distance and Pilot wire protection.