Power System Protection 001

(1)

Power System Protection S.A.Soman Overview Electrical Energy Systems Types of Protection Relays Introduction Evolution of Relays Circuit Breaker What is a circuit breaker? Summary

Power System Protection

S.A.Soman

Department of Electrical Engineering IIT Bombay

(2)

Introduction

1 Overview

Electrical Energy Systems Types of Protection

2 _Relays

Introduction

Evolution of Relays

3 _{Circuit Breaker}

What is a circuit breaker?

(3)

Introduction

1 Overview

Electrical Energy Systems

Types of Protection

2 _Relays

Introduction

Evolution of Relays

(4)

Introduction

Electrical Energy is

Generated at few kV and stepped up. Transmitted through AC and HVDC lines. Stepped down and distributed at load centers.

Its natural mode of synchronous operation knits the system together.

(5)

Introduction

(6)

Introduction

Why do we need protection?

Electrical apparatus operates at various voltage levels and may be enclosed or placed in open. Under abnormal operating conditions protection is necessary for

Safety of electrical equipments. Safety of human personnel.

(7)

Introduction

1 Overview

Electrical Energy Systems

Types of Protection

2 _Relays

Introduction

Evolution of Relays

(8)

Introduction

Types of Protection Apparatus Protection

Transmission Line Protection Transformer Protection Generator Protection Motor Protection Busbar Protection System Protection Out-of-Step Protection Under-frequency Relays Islanding Systems

(9)

Introduction

(10)

Introduction

(11)

Introduction

1 Overview

2 _Relays

Introduction

Evolution of Relays

(12)

Introduction

What is a Relay?

A relay is a logical element which process the inputs (mostly voltages and currents) from the system and issues a trip decision if a fault within its jurisdiction is detected. Inputs to a relay are

Current from a current transformer. Voltage from a voltage transformer.

(13)

Introduction

(14)

Introduction

1 Overview

2 _Relays

Introduction

Evolution of Relays

(15)

Introduction

Evolution of Relays

If we zoom into a relay, we can see three different types of realization:

Electromechanical Relays. Solid State Relays.

(16)

Introduction

Electromechanical Relays First generation of relays.

Uses the principle of electromechanical energy conversion. Immune to

electromagnetic

(17)

Introduction

Solid State Relays

These relays were developed with the advent of transistors, operational amplifiers etc. Their functionality is through various operations like comparators etc. Their advantages are

More flexible.

Self checking facility.

Less power consumption and low burden. Improved dynamic perfomance characteristics. High seismic withstand capacity.

(18)

Introduction

Numerical Relays

Operation of a numerical relay involves analog to digital conversion of voltage and currents obtained from VT and CTs. These samples are fed to the microprocessor or DSP where the protection algorithms process these signals and necessary decisions are taken.

(19)

Introduction

Its advantages are Maximum flexibility.

Provides multiple functionality.

Self checking and communication facility. It can be made adaptive.

(20)

Introduction

1 Overview

2 _Relays

Introduction

Evolution of Relays

(21)

Introduction

What is a Circuit Breaker?

A circuit breaker is basically a switch to interrupt the flow of current.

It opens on relay command.

It has to handle large voltages and currents.

The inductive nature of power system results in arcing between the terminals of a CB.

CBs are categorized based on the interrupting medium used.

(22)

Introduction

Summary

Necessity of a protection system. Types of Protection.

Three generations of relays. Role of circuit breakers.