This course provides an exhaustive coverage on switchgears, Operation of circuit breakers, types of relays, lightning arrestors and protection of various equipment like alternators, transformers, transmission lines and feeders.
Introduction to power electronics devices - Necessity and function of protective system, Normal and abnormal conditions. Types of faults and their effects - Faults in a power system - Types of fault - Representation of symmetrical faults. Current limiting reactors and its necessity - Current limiting reactors - Types of current limiting reactors - Types of reactor schemes - Bus-bar reactors. Short circuit kVA and calculations - Percentage reactance - Percentage reactance and base kVA - Methods of short-circuit kVA calculations - Problems.
Switchgear and its classifications- Switchgear - Features of switchgear - Classification of switchgear - Different types of switchgear - Fuses. Basic fuse terminology - Introduction - Types of fuse - Definition - Typical cut-off characteristics for a cartridge fuse - Fuse element material - Time - Current characteristic of fuse - Problem - Advantages and Disadvantages of fuse - Selection of fuse. HRC fuse -Characteristics of HRC fuse - Advantages and disadvantages of a HRC fuse - Selection of HRC Fuse. Isolating Switches - Types of isolator - Pantograph isolator. Phenomenon of an arc formation - Factors responsible for maintenance of arc - Arc interruption theories - Methods of arc extinction - Low resistance or current zero method. Classification of circuit breakers - Circuit breakers - Classification of circuit breakers based on medium of arc quenching. Minimum oil circuit breakers - Operation of MOCB. Principle of air blast circuit breakers - Air blast circuit breaker (A.B.C.B) - Types of air blast circuit breaker (A.B.C.B) - Axial Blast Circuit Breakers - Vacuum Circuit Breakers (VCB) - Sulphur hexa fluoride circuit breaker - Properties of sulphur hexafluoride (SF6) Gas - Construction and working of SF6 circuit breaker - Advantages of SF6 circuit breaker. ACB, MCB, MCCB, ELCB and comparison of fuse and MCB - Circuit breaker - Magnetic hydraulic MCB - Assisted bimetal tripping MCB - Design and rating of MCBs - ELCB + MCB combination circuit breaker - Categories of MCBs - Advantages of MCB - Moulded case circuit breakers (MCCB) - Application of (RC + MCB) combination circuit breakers - Earth leakage circuit breakers - Voltage operated ELCB - Current operated ELCB - Technical specifications. Selection and rating of circuit breakers - Selection of circuit breakers - Problem - Circuit breaker ratings.
Probable faults in alternator stator and rotor - Introduction to protection of alternators Alternator faults. Causes of excessive heating and its scheme of protection - Stator over heating protection or thermal protection - Causes of excessive heating. Differential protection for alternators - Stator protection - Differential protection for generators. Earth fault protection for stator and rotor, inter turn protection (or) split phase protection - Balanced earth-fault protection or stator earth-fault protection - Rotor fault protection - Stator inter-turn protection. Need and working of field suppression protection - Loss of excitation (or field failure) protection - Protection against rotor overheating because of over excitation - Automatic field suppression and use of neutral circuit breaker. Protection of motor - Induction motor protection - Protection circuit for induction motor - Single phasing preventer - Ground fault protection - Phase fault protection. Transformer protection - Introduction to transformer protection - Open circuits - Percentage differential protection for transformers - Merz-Price protection for star-delta transformer - Problem - Problems encountered in differential protection - Harmonic restraint and harmonic blocking. Buchholz relay - Applications of Buchholz relay.
Protective relaying - Protective zones - Primary and backup protection - Methods of backup protection - Speed and time. Classification of protective relays - Distance type relays - Terminologies used in protective relaying - Time/P.S.M. curve. Instrument transformers - Problem - Construction of current transformers - Why secondary of C.T. should not be open ? - Potential transformer (P.T.) - Comparison of C.T. and P.T. - Advantages and disadvantages of instrument transformer - Coupling capacitor voltage transformer (CCVTs). Electromagnetic relay - Solenoid and plunger type relay - Advantages, disadvantages and applications of electromagnetic relays - Thermal relays - Static relay - Basic elements of a static relay - Definite or Fixed time function - Comparison of static and electromagnetic relays - Semiconductor devices used in static relays - Static time current relay - Static instantaneous over current relay. Microprocessor based relays and auxiliary switch flags - Microprocessor based relay. Over current relays - Introduction to over current relays - Nondirectional induction type over current relay - Time-current characteristics - Problems. Directional relay - Directional power relay - Directional induction type over current relay - Operation - Directional characteristics. Distance relays - Torque equation - Operating characteristics on R-X diagram - Disadvantages of plain impedance relay - Use of impedance relay for transmission - Reactance relay - Operating characteristics - Mho relay or Admittance relay - Problem - Offset Mho relay - Classification of distance relays - Distance time impedance relay - Setting of distance relays. Differential relay - Introduction to differential relays - Biased beam relay or Percentage differential relay - Voltage balance differential relay. Staic and microprocessor based over current relays - Directional static over current relay, Microprocessor based over current relay. Over voltages - Introduction - Voltage surge, Causes of over voltages, Internal causes of over voltages, Lightning, Mechanism of lightning. Protection of G.S., S.S. and transmission lines against direct stroke - Protection against lightning - Protection of transmission lines against direct strokes, Requirements of ground wire, Counterpoises, Advantages and disadvantages of ground wire. Lightning arresters - Types of lightning arresters - Horn gap arrester - Multigap arrester - Expulsion type arrester - Valve type arrester - Thyrite type lightning arrester. Surge diverter - Requirement of surge diverter - Operation of a typical surge diverter (Lightning arrester) - Classification of surge arresters. Protection against travelling waves and insulation co-ordination - Protection of electrical apparatus against travelling waves (Indirect strokes) - Insulation Coordination - Nominal System Voltage.
Protection of Bus-Bar - Types of schemes for Bus-bar protection, Frame leakage protection, Bus-Bar arrangements. Protection of transmission line - Pilot wire protection - Pilot wire protection using circulating current differential relaying scheme - Protection of transmission lines using distance and impedance relays - Definite distance relay - Combined protection by using definite distance and time distance relays. Protection of feeder - Protection of radial feeders using time graded fuses - Protection of parallel feeders - Protection of ring main system - Differential protection for parallel feeders of transmission lines.
