Protective Relay, Switchgear & Fuse

1. Presented by:
Md. Shabuddin Shaikh
ID:555131010
2nd Batch 6st Semester
Course Instructor
Dr. Mohammad R. Alam (RA)
Department of EEE
Hamdard University Bangladesh

2. Protection Equipment in a Power Plant
CONTENTS
• Introduction
• Protective Relay
• Circuit-breaker
• Fuse

3. Introduction:
 In a Power station the generator and transformer are the most
expensive equipments and hence it is desirable to employ a
protective system to isolate the faulty equipment as quickly as
possible to keep the healthy section in normal operation and to
ensure uninterruptable power supply.
 The basic electrical quantities those are likely to change
during abnormal fault conditions are current, voltage, phase
angle and frequency . Protective relays utilizes one or more of
these quantities to detect abnormal conditions in a power
system.
 Protective system cost is 4-5%of the total cost

4. • Protective Relay
A protective relay is a
device that detects the
fault and initiates the
operation of the circuit
breaker to isolate the
defective element from the
rest of the system.

6. Electromagnetic Attraction type Relay

7. Circuit-breaker
A circuit breaker is a piece
of equipment which can
make or break a circuit either
under normal conditions &
under fault conditions.

8. Classification of Circuit Breakers:
The circuit breakers may be classified as follows:
a. Oil circuit breakers.
b. Air-blast circuit breakers.

9. Oil circuit breakers
i. It has high dielectric strength.
ii. Surrounding oil in close proximity to the arc presents a large
cooling surface.
iii. It acts as an insulator between life part and earth

10. Air-blast circuit breakers.
These circuit-breakers employ a high pressure air-blast
as an arc quenching medium. The contacts are opened
in a flow of air-blast established by the opening of blast
valve. The air-blast cools the arc and sweeps away the
arcing products to the atmosphere.

11. Fuses
A fuse is a short piece of metal, inserted in
the circuit, which melts when excessive
current flows through it and thus breaks the
circuit.

12. Thanks toAll