1. Protection & Switchgear
For the Protection of Power System and its Components

2. Faults in power system:
Definition : ?
Over voltage/Under voltage
Over current
Over load, short circuit,
Over frequency/Under frequency
Phase imbalance/ Single phasing/ Sometimes opens in the circuit
Mechanical faults

3. Protection zones:

4. Protection zones:

5. Types of protection Human Equipment Earthing
Different Protection schemes
Unit protection and Non-unit protection

6. Classification of protection schemes:
In unit type
Differential Protection
Carrier aided protection,
Non-unit type
Over current, over/under voltage, over/under frequency, distance protection

7. Working Principle of pSP:

8. The protection team: Relays Circuit Breaker (CB)
Electrical
Electromagnetic
Static
Numerical
Mechanical
Pressure (Buchholz)
Flow
Thermal
Circuit Breaker (CB)
Air break CB, MCB
( kV, 500 MVA)
Bulk oil CB
(Upto 36 kV)
Minimum Oil CB
(3.6 – 245 kV)
Air blast CB
(145 – 1100 kV, 60 GVA)
SF6 CB
(3.6 – 800 kV, 50 GVA
Vacuum CB
(3.6 – 36 kV, 2 GVA)
Solid state CB
Instrument Transformer
DC batteries

9. Electrical Relays: Over-Voltage, Over-Current, Over-Frequency
According to characteristic quantities and application can be classified as:
Over-Voltage, Over-Current, Over-Frequency
Under-Voltage, Under-Frequency
Directional Power Relay
Differential Relay,
Distance Relay
Reactance Relay, Impedance Relay, Mho Relay, offset Mho relay, Quadrilateral Relay

10. unit Protection schemes:
Generator protection
Motor protection
Transformer protection

11. Generator protection Generator Faults Stator winding faults
(phase to earth, phase to phase, inter-turn)
Rotor circuit faults
Conductor to earth, inter-turn fault, rotor open circuit, loss of excitation, unbalance stator current
Abnormal operating condition
Failure of prime mover, field failure, unbalance loading, over voltage at generator terminal, over loading, over speed, ventilation failure

12. Generator protection Differential protection (Merz-Price protection)
Stator protection
Rotor fault protection
Differential protection
(Merz-Price protection)
(Biased differential protection)
Stator Inter-turn prot.
Balanced earth fault prot
Stator over heating prot.
Negative sequence prot.
Protection against motoring
Rotor earth fault prot.
Loss of Excitation prot.
Auto. Field suppression
Rotor overheating
Rotor temp. alarm
Vibration Protection
Bearing overheating
Over speed protection
Generator protection

13. A.C. Motor protection Phase to phase Phase to earth Inter-turn
Faults :
Protection:
Phase to phase
Phase to earth
Inter-turn
Prolonged overloading
Stalling
Unbalanced supply voltage
Single phasing
Under voltage
Reverse phase
Loss of synchronism
Stator Over current
Stator over heating
Rotor over heating
Under voltage
Unbalanced and single phasing
Reverse phase
Ammortisseur over heating
Loss of excitation
Loss of synchronism
Field winding over heating
A.C. Motor protection

14. Transformer protection:
Buchholz protection
Core balance leakage protection
Combined leakage and overload protection
Differential protection (Biased)
Harmonic restraint relay
Magnetic balance protection
Restricted earth fault
Frame leakage protection
Generator transformer unit protection

15. Line & Feeder protection
Over current and earth fault protection
Time graded protection for
Radial, parallel and ring main feeder using directional power relay
Current graded protection
Differential pilot wire protection
Carrier current protection
Distance protection
Impedance relay, reactance relay, Mho relay, offset Mho relay, quadrilateral relay,

16. Definite time over current (50) & Inverse time over current (51)
Basic protection principle

17. Over voltage (59) & under voltage (27)
Voltage balance (Differential)
Basic protection principle
Basic protection principle

18. Uses both current and voltage to determine the zone of the fault
Based on KVL
Three phase system loops, RY,YB,BR, RG, YG, BG
Phase comparator principle
Phase and ground faults
Distance relaying
Basic protection principle

19. S1 = IR ZR – VR
S2 = VR
Distance relaying

20. Distance relaying

21. Differential protection
Based on KCL
Used for protection of Generator, Motor, Transformer, Busbar, Transmission line, Reactor
Differential protection
Basic protection principle

22. Busbar & transformer differential protection

23. Line differential protection

24. Device number identification
21 Z1 – Z4 : phase distance relay for zone 1 to 4
21N z1 – Z4 : ground distance relays for zone 1 to 4
50H : high set instantaneous over current relay
50 : instantaneous over current relay
62 : time delay for tripping
67N : directional relay in neutral
SER/DFR : sequence of event recorder/ digital fault recorder
Device number identification
List box method and fill box method

25. Others: Bus bar protection
Protection against over voltage due to lightning using LA
Insulation coordination
Earthing
Travelling wave ralays

26. Thank you