Surge Arresters construction and working

SURGE/ LIGHTENING ARRESTERS DELIVERED TO

SIR WAQAS JAVAID

GROUP INTRODUCTION

• ATEEQ-UR-REHMAN (2013-EE-528)• MUHAMMAD FAISAL IKRAM (2013-EE-516)• FAISAL SATTAR (2013-EE-501)• AYESHA KHAN (2013-EE-539)

CONTENTS • Introduction of Surge Arresters• Introduction of lightening • Lightening protection• Construction of Surge Arresters• How does Surge Arresters works?• Uses of Surge Arresters• Types of Surge Arresters

INTRODUCTION OF SURGE ARRESTERS

• What is SUGRE ?• A surge is basically a very High voltage which suddenly acts

on a transmission line just like lightening which fall on a transmission line or any where else.• And these surge arresters are not actually the policeman to

catch the surge or lightening.It is basically a device

When a voltage surge is created, it wants to equalize itself .

The method of providing maximum protection for equipment is quite simple. Create a pathway for the voltage surge (electricity) to get to and into the ground outside your house as quickly as possible.

The first step is simple. Create an excellent grounding system for your household electrical system. Many homes have a single grounding rod and /or a metallic underground water pipe which are part of the electrical grounding system.

The second step in household surge protection is to install a lightning arrester inside of your electric service panel. These devices can be extremely effective in intercepting large voltage surges which travel in the electric power lines. If for some reason you do not have a large enough grounding wire, or enough ground rods.

Similarly in electrical transmission line ,when surge comes to occur or lighting phenomenon the different devices are use to diverge the surge.one most commely used arresters.

OTHER DEVICES SIMILAR TO LIGHTENING ARRESTERS

• Surge Suppressor: This is also a surge diverter, but generally for voltages

well below 1000 volts.• TVSS (Transient Voltage Surge Suppressor):

Again this is also a surge diverter, but generally for voltages well below 1000 volts.

How do Lightning

Arresters Protect Power Systems?

LIGHTENING

Definition of Lightening Significance of Lightening Mechanism of lightening discharge Keraunic Level Types of Lightening Effect of Lightening Protection against Lightening.

INTRODUCTION OF LIGHTENING • What is Lightening?• An electric discharge between

cloud and earth, between clouds or between the charge centers of the same cloud is known as lightning. • Lightening is a huge spark that take place

when cloud is charged to such a high potential that dielectric strength of air is destroyed.

INTRODUCTION OF LIGHTENING 132KV TRANSMISSION LINE WITHOUT SURGE ARRESTERS

132KV TRANSMISSION LINE WITH SURGE ARRESTERS

OVER TO

Faisal Sattar

MECHANISM OF LIGHTENING DISCHARGE• Lightening discharge is initiated by a

streamer from the cloud which progress towards the earth in series of steps called Stepped Leader.• Streamer moves from earth towards cloud is

called Return Streamer.• Leader streamer and return streamer has

opposite charge.• When Leader streamer and return streamer

meets one another then a short circuit is established between earth and cloud give rise to a large current flow and Lightening phenomenon produced .

KEY POINTS ABOUT LIGHTENING DISCHARGE

• A lightning discharge usually made up of a number of separate strokes.• 87% of all lightening strokes results from negatively charged

clouds.• 13% of all lightening strokes results from positively charged

clouds.• Through out the world nearly 100 lightening strokes occur per

second• Lightening discharge current range from 10kA to 90kA.

KERAUNIC LEVEL• It is defined as the average number of days per year when

thunder can be heard in a given area.• The keraunic number has been used to set standards for safe

design of electrical systems in structures connected to the local power grid.• The annual number of lightning flashes hitting one square km

of ground, Ng, can be calculated from the following formula

• Td is the keraunic number.

TYPES OF LIGHTENING STROKESA lightning stroke is defined as a

direct stroke if it hits either the tower or the shield wire or the phase conductor.

Cloud will induce a charge of opposite polarity on lines when potential b/w cloud and line exceeds the breakdown value of air discharge occurs.

Direct stroke

TYPES OF LIGHTENING STROKES• Indirect stroke results from the

electrostatically induced charge on the conductor due to presence of charged clouds • Induced charge leaks slowly to earth

via insulators.• Induced charge moves in both direction

in the form of travelling waves.• Most of the surge in transmission line

is caused by indirect stroke.

• Indirect stroke

EFFECTS OF LIGHTENING• Traveling waves • Insulator damage• Transformer damage• Lightening discharge constitute the main cause of non-

programmed outages of electrical system.• 65% line outages originate from Lightening strokes • Surges produced by Lightening are not felt by most of the

industrial equipment e.g. computers, Aluminum and steel mills .

EFFECTS OF LIGHTENING

PROTECTION AGAINST LIGHTENING• Earthing screen.• Overhead ground wires• Lightening Arresters

EARTHING SCREEN• Earthing screen provides protection to power stations and

sub-stations against direct stroke.• It consist of a network of copper conductor mounted all over

the electrical equipment in the substation and power station.• Shield is properly ground through low resistance path.• Limitation: • It does not provide protection against travelling

waves.

OVER HEAD GROUND WIRES• Protect transmission line against direct stroke.• Ground wires are placed above line conductors in such a way

that all lightening strokes are intercepted by them.• Tower rises potential is given by Vt= I.R• Vt less than insulator flashover then no trouble occur• Tower footing resistance must be very low.

OVER HEAD GROUND WIRES

OVER HEAD GROUND WIRES

• An effective shielding requires a strategic positioning of earth wires so that lightning stroke reach to earth wires or ground.• Most favorable position is

obtained when circle around earth wire and conductor meat at same point on horizontal line.

OVER HEAD GROUND WIRES

LIGHTNING ARRESTERS

• Provide protection against direct as well as indirect stroke• Protect power station and Transmission line

EARTHING IN VIEW OF LIGHTENING PROTECTION• Tower Earthing resistance and surge impedance is an

important parameter in determination of lightening flashover.• Earthing resistance is a variable quantity.• Depend upon soil and non linear conduction of earth • Even if constant stroke current pass it changes with time.

EARTHING IN VIEW OF LIGHTENING PROTECTION

OVER TO

Muhammad Faisal Ikram

CONTENTS• Lightening Rod• Classes of Surge Arresters• Working of lightening Arresters• Surge arrester in Transformer• Surge arrester in Transmission line.• Short circuit test• What is MOV?• How does dose current flows in Arresters

LIGHTENING ROD• A lightning rod or lightning

conductor is a metal rod or metallic object mounted on top of an elevated structure, such as a building, a ship, or even a tree, electrically bonded using a wire or electrical conductor to interface with ground or "earth" through an electrode, engineered to protect the structure in the event of lightning strike

LIGHTENING ROD

• Surge arresters is not a lightening Rod although it does the same operation that the lightening do.• But its construction and

working principle is very different from the lightening Rod.

CLASSES OF SURGE ARRESTERS

• Station Class• Intermediate Class•Distribution Class• Secondary Class

WORKING OF SURGE ARRESTERS

•Normal Operation•Occurrence of High

Voltage• Function as a non linear

resistor

SURGE ARRESTERS IN TRANSFORMER

• Surge Arresters are used in transformer both at transmission level and at distribution level.• The rating of arresters used

at these are different because of voltage levels.

SURGE ARRESTERS IN TRANSFORMER

SURGE ARRESTERS IN TRANSMISSION LINE

• Surge Arrester is also used in Transmission system just for the same and basic purpose which is the safety of our equipment's and also the transmission line

SHORT CIRCUIT TEST OF ARESSTER

• Before the installation of surge arrester many test are applied on this to mark it as verified.• One of them is short circuit

test• In this surge arrester is

introduced to very high voltage surge and check weather It can bear it or not.

SURGE ARRESTERS (BASIC CONSTRUCTION)

• Surge arresters is consist of MOV discs.• What is MOV?• MOV is Metal Oxide Varistor.• The most common type

of Varistor is the Metal-Oxide Varistor (MOV). This type contains a ceramic mass of zinc oxide grains, in a matrix of other metal oxides (such as small amounts of bismuth, cobalt, manganese) sandwiched between two metal plates (the electrodes)

SURGE ARRESTERS (BASIC CONSTRUCTION)• The basic structure of surge

arresters is consist of MOV discs which basically acts as a semiconductor for normal voltages but when a surge appears or comes it becomes a conductor and provides a short path to the ground to a very high voltage surge.

Metal Oxide Discs

THE MOV DISK• The MOV disk is a very fast acting

electronic switch• It is an open switch to standard

system AC voltage and a close switch to lightening voltages.• By magnifying the MOV material

5000 times, Metal Oxide Grains and Dopants in the material can be discerned• Each MOV Disk with a 35mm

diameter and a 35mm height contains about 28 Billion MOV Grains

The MOV Grains and their Junctions are the Electronic Switches that turn on and off in unison to divert the lightning around the equipment.

A lightning arrester is essentially a collection of billions of microscopic junctions of Metal Oxide Grains that turn on and off in microseconds to form a current path from the top terminal to the ground terminal of the arrester.

So there you have it. A Lightning Arrester is a device, used on power systems, that contains billions of electronic switches that divert lightning

around sensitive equipment and

saves them from damage.

OVER TO

Ayesha Khan

TYPES OF SURGE ARRESTERS

• Rod Gap Arrester• Horn Gap Arrester• Multigap Arresters• Expulsion Type Arrester• Valve Type Arresters

ROD GAP ARRESTER

• Simple type of diverter.• Consists of two 1·5 cm rods.• The distance between gap and

insulator must not be less than one-third of the gap length.• Due to its limitations, Rod-gap

arresters are used only as ‘Back up’ protection.

ADVANTAGES DISADVANTAGES

• Under normal operating conditions gap remains non-conducting.• On the occurrence of a high

voltage surge on the line, the gap sparks over and the surge current is conducted to earth.

• Rods may melt or get damaged.• The climatic conditions

affect the performance of rod gap arrester.• The polarity of the surge

also affects the performance of this arrester.

HORN GAP ARRESTERS

• Consists of two horn shaped metal.• Horn is connected to the line

through a resistance R and choke coil L.

• Choke does not allow the transients to enter the apparatus to be protected.

ADVANTAGES DISADVANTAGES

• The arc is self-clearing.• Series resistance helps in

limiting the follow current to a small value.

• The bridging of gap can render the device useless.• The setting of horn gap is

likely to change due to corrosion or pitting.• Time of operation is

comparatively long.

MULTIGAP ARRESTER

• It consists of a series of metallic (generally alloy of zinc) cylinders.• Cylinders are separated by

air gap and are connected with series and shunt resistances.• Such arresters are applied

where voltage does not exceed 33kV.

ADVANTAGES DISADVANTAGES

• They have the lowest let-through voltage and the best controlled clamping behavior of the various arrestor types.• It provides safety and

prevents damage to expensive equipment.

• Their current handling capabilities are the smallest of all.• Such arresters can be

employed only where system voltage may not exceed 33kV.

EXPULSION TYPE ARRESTERS

• This type of arrester is also called ‘Protector tube’.• Commonly used on system

operating at voltages up to 33 kV.• It essentially consists of Rod

Gap, Upper Electrode and Lower Electrode.• One expulsion arrester is placed

under each line conductor.

ADVANTAGES DISADVANTAGES

• They are not very expensive.• They are improved form of

rod gap arresters.• They can be easily installed.

• They can perform only limited number of operations.• it is not suitable for the

protection of expensive equipment. • This type of arresters cannot

be mounted in an enclosed equipment.

VALVE TYPE ARRESTERS

• They are extensively used on systems operating at high voltages.• They incorporate non-linear resistors• It consists of two assemblies • Series spark gaps• Non-linear resistor discs.• The non linear elements are connected

in series with the spark gap.

ADVANTAGES DISADVANTAGES

• They provide very effective protection (especially for transformers and cables) against surges.• They operate very rapidly

• They fail to check the surges of every steep Wave.• Their performance is

adversely affected by the entry of moisture into the enclosure.

APPLICATIONS OF VALVE TYPE ARRESTERS

• According to there applications valve type arresters are classified as Two types• Station type: Generally used for protection of equipment in

power stations operating on voltages upto 220kV or higher.• Line type: Are used for station handling voltages upto 66kV.

Thank

You