Contents

• Introduction• Components• Protective Devices• Types of Protection• Coordination• Performance Measures

Introduction

• Power-system protection is a branch of electrical power engineering that deals with the protection of electrical power systems from faults through the isolation of faulted parts from the rest of the electrical network.

Components

Protection systems usually comprise five components:• Current and voltage transformers• Protective relays• Circuit breakers• Batteries• Fuses

Continue……• Current & Voltage Transformer: Current &

Voltage Transformer to step down the high voltages and currents of the electrical power system to convenient levels for the relay.

Current Transformer Voltage Transformer

Continue…..

• Protective Relays to sense the fault and initiate a trip, or disconnection.• Circuit Breakers to open/close the system based on

relay and auto reclose commands.

Digital Relay Circuit Breakers

Continue….

• Batteries to provide power in case of power disconnection in the system.

• Fuses for parts of a distribution system, fuses are capable of both sensing and disconnecting faults

Batteries Fuses

Protective Devices

Functionality:• Automatic operation, such as auto-re-closing or

system restart• Monitoring equipment which collects data on the

system for post event analysis.

Parts of Protective Devices

There are three parts of protective devices:• Instrument transformer• Relay• Circuit Breaker

Circuit Breaker Relay Inst Transformer

Advantages (Protective Devices)

Major advantages of protective devices are:

• Safety• Economy• Accuracy

Types of Protection

There are several types of protection:• Over Load• High Voltage Transmission• Earth Fault• Back-Up

Continue……

• Overload: Overload protection requires a current transformer which simply measures the current in a circuit.

• High Voltage Transmission: (Protection on the transmission and distribution serves two functions)At a basic level, protection looks to disconnect equipment which experience an overload or a short to earth.

Continue….

• Earth Fault: Earth fault protection requires current transformers and senses an imbalance in a three-phase circuit

• Back-Up: The objective of protection is to remove only the affected portion of plant and nothing else

Coordination

• Protective device coordination is the process of determining the "best fit" timing of current interruption when abnormal electrical conditions occur. The goal is to minimize an outage to the greatest extent possible.

Performance Measures

We can measure a protection systems performance with following:• Reliability• Selectivity• Speed• Economy• Simplicity

Questions ?

THANK YOU !!!