This document provides an overview of the power system protection course including the modules, objectives, and key topics. Module 1 covers the introduction to power system protection including the need for protective schemes, types of faults, zones of protection, essential qualities of protection, and classification of protective relays. It also discusses relay construction and operating principles, focusing on electromechanical, static, and numerical relays. Overcurrent protection is introduced as one of the key protective schemes.

1. COURSE CODE :18EE72
POWER SYSTEM PROTECTION
(Core Subject)
Faculty : SRIDHAR N H
Assistant professor

2. Module-1
 Introduction to Power System Protection:
 Need for protective schemes
 Nature and Cause of Faults
 Types of Faults, Effects of Faults
 Fault Statistics, Zones of Protection
 Primary and Backup Protection
 Essential Qualities of Protection
 Performance of Protective Relaying
 Classification of Protective Relays
 Automatic Reclosing
 CTs-VTs for protection

3. Cont…..,
 Relay Construction and Operating Principles:
 Electromechanical Relays,
 Static Relays – Merits and Demerits of Static Relays,
 Numerical Relays,
 Comparison between Electromechanical Relays and Numerical
Relays.
 Overcurrent Protection:
 Introduction,
 Time – current Characteristics,
 Current Setting,

4. Objective of power system protection
 To isolate a fault section of electrical power system
from the rest of the live system so that rest portion
can function satisfactorily without any severer
damage due to fault current.

5.  What Components (Equipment) Do We Protect?
•Generators
•Transformers
•Lines
•Buses
•Capacitors

6. Protective system elements
 Fuses
 Circuit breakers
 Relays
 CTs &PTs

7. An electrical power system consists of generators,
transformers, transmission and distribution lines, etc.
Short circuits and other abnormal conditions often
occur on a power system. The heavy current associated
with short circuits is likely to cause damage to
equipment if suitable protective relays and circuit
breakers are not provided for the protection of each
section of the power system. Short circuits are usually
called faults by power engineers. Strictly speaking, the
term fault simply means a defect. Some defects, other
than short circuits, are also termed as faults. For
example, the failure of conducting path due to a break in
a conductor is a type of fault.
NEED FOR PROTECTIVE SCHEMES

10. Effects of faults
 Heavy short circuit current may damage to equipment or
any other element due to over heating and high
mechanical force set up due to heavy current.
 Area associated with short circuit may cause fire hazards.
 There may be reduction in the supply voltage of the
healthy feeders, resulting in the loss of industrial loads.
 Short circuit may cause the unbalancing of supply
voltages and currents ,thereby heating rotating
machines.
 There may be loss of system stability.
 Loss of revenue.

14. Primary &back-up protection

15. There are three types of back-up protection
Remote backup
Relay backup
Breaker backup

17. Performance of protective relay
 Correct operation
 Incorrect operation
 No conclusion

19. BASED ON SPEED OF OPERATION
Instantaneous Relay
Time Delay Relay
High Speed Relay
Ultra High Speed Relay

20. Over Current Protection
Distance Protection
Carrier Current Protection
Differential Protection
classification of protective
schemes

24. Relay Construction and Operating
Principles

25. Electromechanical Relays
 A relay is an electromechanical device having
electrical, magnetic and mechanical components.
The relays control the electric circuit by opening or
closing the contacts of that circuit. An
electromechanical relay consists of three terminals
namely common (COM), normally closed (NC) and
normally opened (NO) contacts. These can either get
opened or closed when the relay is in operation.
These relays can work on both AC and DC supply
sources.

27. 1. HINGED ARMATURE TYPE
2. PLUNGER TYPE
3. BALANCED BEAM TYPE
4.MOVING COIL TYPE
5. POLARISED MOVING IRON
TYPE
6.REED TYPE
ATTRACTED ARMATURE
RELAYS

28. HINGED ARMATURE TYPE

29. PLUNGER TYPE

30. BALANCED BEAM TYPE

31. MOVING COIL TYPE

32. POLARISED MOVING IRON TYPE

33. REED TYPE