Presented by:Md. Shabuddin Shaikh

ID:5551310102nd Batch 6st Semester

Course InstructorDr. Mohammad R. Alam (RA)Department of EEE

Hamdard University Bangladesh

Protection Equipment in a Power Plant

CONTENTS

• Introduction

• Protective Relay

• Circuit-breaker

• Fuse

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

• 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.

How relay look

Electromagnetic Attraction type Relay

Circuit-breaker

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

Classification of Circuit Breakers:

The circuit breakers may be classified as follows:

a. Oil circuit breakers.

b. Air-blast circuit breakers.

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

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.

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

Thanks to All