An Industrial training report

on

“Study of Design Features Of 220 KV Circuit Breaker”.

at ABB Ltd. Vadodara Gujrat

Submitted by

Neeraj Kumar

B. tech. IV Year (VII Semester)

Electrical Engineering

DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING

GOVIND BALLABH PANT ENGINEERING COLLEGE

PAURI GARHWAL (UTTARAKHAND) - 246194

[1]

PREFACE

The knowledge of any subject is incomplete until it is done practically. Electrical is a field, which

requires thorough knowledge of the subject along with its practical applications. This

establishment has given me the opportunity to have the better understanding of this field.

This report consists of the description of my work “Study of Design Features Of 220 KV Circuit

Breaker” during the period of my summer training at at ABB Ltd. Vadodara Gujrat During this

period I got a chance to learn Electrical Switchgear protection Manufacturing. The basic aim of

this report is to study the Characteristics of manufacturing of LTB E – SF6 circuit breaker

as well as the latest manufacturing techniques employed to produce a quality product.

This training helped me enhance my knowledge at a great level. It has made me understand the

problems in a more logical way and deal with them analytically.

Neeraj Kumar

Electrical Engg.

Final Year

[2]

ACKNOWLEDGEMENTS

First and foremost, I would like to thank Dr. Y.Singh (HOD Electronics and Electrical Dept.,

G.B.P.E.C.) and Mr. Sandeep Kumar (Training and Placement Officer, G.B.P.E.C.), who gave me a

chance to undergo training at ABB Ltd. Vadodara Gujrat . My sincere thanks goes to Mr. Mihir

Sabnish (B&S HR) for his prodigious guidance, persuasion, and painstaking attitude, reformative

and prudential suggestion throughout my summer training schedule.

Special thanks go to Mr.K.Patel (Engineer). Who helped me a lot in giving minute details of

manufacturing techniques of circuit breaker. Department and enlightened me with the

knowledge of Exchange equipments and their working.

Last but not the least, my sincere thanks to all the staff members and friends for instilling in me

a sense of self-confidence.

[3]

CONTENTS

Title…………………………………………………………………………….page no.

Chapter 1 Introduction…………………………………………………………….05

Chapter 2 Circuit breaker………………………………………………………...11

Chapter 3 Live tank circuit breaker D&E…………………………………....….25

Chapter 4 Project -LTB E – SF6 circuit breaker………………………………...27

Chapter 5 Circuit breaker Applications …………………………………..39

Chapter 6 Bibliography…………………………………………………………….44

Chapter 7 Conclusion…………………………………………….………………45

[4]

CHAPTER 1

INTRODUCTION

1.1 ABB - a global leader

ABB (www.abb.com) is a global leader in power and Automation technologies that

enable utility and Industry customers to improve performance while lowering

environmental impact. The ABB Group of companies operates in around 100 countries.

ABB’s Power Technologies division offers electric, gas and water utilities as well as

industrial and commercial customers a wide range of products, system and services for

power generation, transmission and distribution. ABB’s turnkey solution capabilities in

the sector range from bulk power transmission, substations and complete electrification

to utility automation and distribution systems. The product offering covers a wide

spectrum of technologies across the entire voltage range including indoor and outdoor

circuit breakers, air and gas insulated switchgear, disconnectors, capacitor banks and

reactive power compensators,in India has a long-standing presence over several

decades. The company has extensive local manufacturing across 8 centres supported

by a

marketing presence, including 26marketing offices and a network of around

500channel partners. The operation also has 8 service

centres in addition to customer training hubs and

global R & D centres.

The history of ABB goes back to the late nineteenth century ,and is a long illustrious

record of innovation and technological leadership. The ABB group of companies

operates in around 100 countries and employs 110,000 people.ABB operate in india

include 14 manufacturing facilities and over 6500 employees.

[5]

The company was incorporated on 24th December 1949 as Hindustan electric limited. In

1965,the company‘s name was changed to Hindustan Brown Boveri Ltd(HBB).pursuant

to scheme of amalgamation of Asea Limited with HBB with effect from 1st january

1989,the name was further changed to Asea Brown Boveri Ltd(ABB) with effect from

13th october 1989. Flakt India Ltd. Was amalgamated with ABB with effect from 5 th

October 1995.

1.2 ABB FEATURES

120 years of technology and innovation

Unparalleled domain competence

Vast global experience

Total solution provider

Large installed base

Environment-friendly technologies

.

[6]

1.3 MAIN PLANTS IN INDIA

NORTH ZONE

NBCC Tower

4th Floor

No. 15, Bhikaji Cama Place

New Delhi 110 066

EAST ZONE

4th Floor

No. 9

Elgin Road

Kolkata 700 020

WEST ZONE

ABB House

Dr. S B Path

Ballard Estate

Mumbai 400 038

SOUTH ZONE

Embassy Star, 1st Floor

No. 8, Palace Road

Vasanth Nagar

Bangalore 560 052

[7]

Century Plaza

No. 3C, 3D, 3F, 3rd Floor

561 / 562, Anna Salai

Teynampet

Chennai 600 018

CENTRAL ZONE

Vandana House

1st Floor

G E Road, Ramkund

Raipur 492 001

[8]

1.4 Breakers & Systems : Landmarks

1965 :25 kV CIRCUIT BREAKER

1966 :245 kV AIRBLAST CIRCUIT BREAKER

1978 :420 kV AIRBLAST CIRCUIT BREAKER

1982 :145kV SF6 CIRCUIT BREAKER WITH PUFFER TECHNOLOGY

1984 :245KV SF6 CIRCUIT BREAKER WITH PUFFER TECHNOLOGY

1988 :36/72.5 kV SF6 CIRCUIT BREAKER WITH SELF BLAST

TECHNOLOGY

1988 :420KV SF6 CIRCUIT BREAKER WITH PUFFER TECHNOLOGY

1994 :145KV SF6 CIRCUIT BREAKER WITH SELF BLAST

TECHNOLOGY

2000 :420KV, 50KA SF6 CIRCUIT BREAKER WITH PUFFER

TECHNOLOGY

2002 :25kV POLE MOUNTED INTERRUPTER

2002 :72.5KV INDOOR CIRCUIT BREAKER WITH FIXED CONTACT &

EARTH SWITCH

2003 :DEVELOPMENT OF SWITCH SYNC TYPE CIRCUIT BREAKER

2006 :245 KV SPRING OPERATED CIRCUIT BREAKER WITH AUTO

PUFFER TECHNOLOGY

2007 :420KV SPRING OPERATED CIRCUIT BREAKER WITH AUTO

PUFFER TECHNOLOGY

[9]

[10]

CHAPTER 2

Circuit breaker  

The circuit breaker is the most important and complicated of all types of power

circuit interruption equipment.

This is due to its highly important capability of interrupting the powerful short

circuit current, over and above its normal role of conducting, isolating and

interrupting nominal load currents.

2.1Main Components of Circuit Breaker

Power circuit

It is where the main current flows or is interrupted; and it includes:

Arcing chamber

The arcing chamber is a closed volume containing a fixed contact, a moving

contact and the interrupting medium. The current is established when the moving

contact touches the fixed contact and interrupted when they part.

An arc is created when the contacts part. The interrupting medium is responsible

for quenching the arc and establishing the nominal level of isolation between the

open contacts.

[11]

Insertion resistor

The sudden modification of circuit characteristics, when circuit breakers operate,

produces peak voltage impulses where the level is determined by the circuit

characteristics. These impulses may reach very high levels and must be

reduced.

Operating mechanism

It is where the needed energy to part the contacts and to extinguish the arc is

developed.

It includes devices, called energy accumulators, to store the needed energy.

Examples of accumulators are:

Springs

Nitrogen-charged cylinders

The most common operating mechanisms in circuit breakers are:

Spring operated

Hydraulically operated

Pneumatically operated

Control

The order to operate the breaker is launched in the control part of the circuit

breaker, as an electric impulse of a fraction of a second duration. The order is

then amplified in the operating mechanism to a complete circuit breaker

operation capable of interrupting short circuit currents.

The control includes:

[12]

Closing and tripping coils

Control relaying system

Pressure switches and gauges

Surveillance and alarm system

Re-inflating system to restore the energy spent on the operation.

2.1Circuit breaker types

The main problem of circuit breakers stems from the nature of their existence.

A circuit breaker has to interrupt weak capacitive or inductive currents, up to high

short circuit currents, and as a result, to extinguish powerful electric arcs. The

problem is then, essentially, an arcing problem.

Another problem is overvoltage impulses; this is related to the nature of the

circuit where it is installed.

One of the major factors influencing the capacity of circuit breakers is the

interrupting medium. It affects circuit breakers' concept and design.

By this principle, circuit breakers are classified in families according to the type of

interrupting medium used.

Three of them are widely preferred by circuit breaker designers around the world. This

is due to their excellent breaking and insulating properties that lead to high performance

and economic designs. They are:

Mineral oil

Compressed air

Sulfur hexafluoride, or SF6

[13]

 

2.1.1Mineral oil

Mineral oil was, until recently, the interrupting medium of choice.

It has excellent breaking and insulating quality especially when it is very pure, as

is the case when it is used in certain devices such as capacitors or transformers,

which are airtight devices.

However, circuit breakers have breathing holes and the oil is in contact with the

arc. Thus, one finds in the breaker's oil a certain amount of impurities, in the form

of moisture and miscellaneous dust, including carbon particles. This decreases

its isolation properties significantly.

It is imperative to monitor the state of the oil inside breakers in service, and to

replace it periodically in function of the number of breaks performed by the

device.

The criteria for oil replacement depend on the structure of the breakers and are

indicated by the manufacturer.

   

[14]

2.1.2 Compressed air

Air at atmospheric pressure has the following advantages:

Good insulation quality

-Always available

Costs nothing

The insulating quality of air rises rapidly with its pressure.

Compressed air was mainly used for interruption in the earlier pneumatic circuit

breaker designs. Later on it was used for insulation between the contacts after they

opened, the latter being placed inside an insulating chamber designed to resist the

air pressure. This reduced significantly the distance between the open contacts.

Air quality for pneumatic circuit breakers:

It should be noted that the excellent quality of air is greatly affected by the humidity.

Indeed, it is important that any condensation in the insulators and air conduits be

avoided, or internal tripping may occur. Installing the costly drying compression

stations greatly raises the cost of operating air blast circuit breakers.

   

[15]

2.1.3 Sulfur hexafluoride, SF6

A certain number of gases, called electronegative, have better insulating qualities

than air. Among them is sulfur hexafluoride, SF6, has seen a great deal of success

in electrical apparatus design because of its excellent insulating properties and

remarkable arc quenching abilities.

It is five times heavier than air, odorless, colorless, nonflammable and non-toxic

when new. Its dielectric strength is 3 times the air's dielectric.

When subjected to an electric arc, it partially decomposes. In the presence of

moisture and impurities it produces acid by-products that attack metal and the

insulating envelopes. An efficient way to reduce by-products is to use activated

alumina inside the chambers containing the gas.

SF6 being a gas at normal temperatures, and at atmospheric pressure it liquefies at

-60 °C, and at 20 bars it liquefies at 20 °C, which is detrimental to its insulating

qualities. For applications at very cold temperatures, it must be heated or mixed with

other gases like Nitrogen or CF4.

   

[16]

Oil circuit breaker

The first high voltage breakers were the bulk oil circuit breakers, followed by the

minimum oil circuit breakers.

In an oil circuit breaker, the arc decomposes part of the oil into gases composed of

70% Hydrogen and 20% Acetylene, and also produces carbon particles.

Bulk oil circuit breaker

It consists of a steel tank partly filled with oil, through the cover of which are mounted

porcelain or composite insulating bushings.

Contacts at the bottom of the bushings are bridged by a conducting cross head

carried by a wooden or composite lift rod, which in common designs drops by gravity

following contact separation by spring action, thus opening the breaker.

An air cushion above the oil level serves as an expansion volume to prevent

pressure from building up inside the chamber after the interruption of the short circuit

current.

Regardless of improvements, the bulk oil circuit breaker presents many

disadvantages:

Great weight and bulk

Risk of fire

Strong reaction to ground

Frequent bushing failure, etc.

   

[17]

Minimum oil circuit breaker

These breakers were developed for 170 and 245 kV systems, the highest voltages

at the time, where the inherent problems of bulk oil breakers were the most severe,

also to eliminate oil as insulating medium and thus reduce the quantity of oil in

switchgear installations to an amount that would not cause any hazard. The

excellent arc-quenching properties of oil, however, were used later in specially

developed oil- and pressure-tight arc-interrupting chambers.

Minimum oil circuit breakers for high voltage are single-interrupter up to 170 kV and

multiple-interrupter breakers for 230 kV and higher.

Contacts are placed in a cylindrical, insulating envelope, with connection terminals at

either end, and placed on an insulating support.

Compared to a bulk oil breaker, ground isolation is considerably improved by the

elimination of the vulnerable isolating bushings and of the metal tank in proximity of

the arc. The oil no longer insulates to ground, and oil volume is reduced by a factor

of 10 to 20.

They use an arc-control device in the arcing chamber which physically shortens the

arc and the arcing time, thereby reducing the arc energy.

When the breaker interrupts small currents, the arc is extinguished by a forced axial

flow of oil. In short-circuit range the arc is quenched as a function of current. The arc

is blown by a jet of oil at right angles to its axis, and extinguished.

.

   

[18]

Air blast circuit breaker

Until recently, the air blast circuit breakers have dominated the high and very high

voltage applications. From 170 kV to 800 kV and breaking capacity from 20 kA to

100 kA.

Over 100 kV the breaker has multiple chambers connected in series. Each element

is optimized to around 80 kV. At first, 800 kV breakers had 12 chambers in series

per phase, now they have only 8 chambers per phase.

Although increasing the air pressure increases the speed of dielectric regeneration,

it is still relatively slow. Insertion resistors are often used to reduce voltage surges.

For example, adding insertion resistors, single or double step, to reduce closing

voltage surges, is easily done. Also, it is capable of achieving very fast breaking

times, 2 cycles and even less, improving the network's stability.

In general, air blast circuit breakers are high tech and robust equipment, with great

electrical and mechanical endurance. Contact wear is low due to the short arc

duration and low arc voltages.

The compressed air circuit breaker has two major disadvantages:

Installation of expensive compression stations

High noise levels on operation

   

[19]

SF6 Circuit breaker

Sulfur hexafluoride (SF6) gas has proved to be an excellent arc-quenching and

insulation medium for circuit breakers.

SF6 breakers are available for all voltages ranging from 14.4 kV to 800 kV,

continuous current up to 4000 A and symmetric interrupting ratings up to 63 kA.

SF6 circuit breakers are either the dead tank design, or the live tank design and the

GIS design.

During recent years SF6 circuit breakers have reached high phenomena.

Their completely closed gas system eliminates any exhaust during switching

operations and thus adapts to environmental requirements. They may be installed

horizontally or vertically, according to the structural requirements of the substation.

The quick dielectric regeneration of the arc plasma in SF6 makes insertion resistors

unnecessary, simplifying the apparatus.

Their compact design considerably reduces space requirements and building and

installation costs. In addition, SF6 circuit breakers require very little maintenance.

   

[20]

SF6 Circuit Breakers

SF6 circuit breakers operate to switch electric circuits and equipment in and out of the

system. These circuit breakers are filled with compressed sulfur-hexafluoride gas which

acts to open and close the switch contacts. The gas also interrupts the current flow

when the contacts are open.

Figure 1. SF6 gas power circuit

breaker Figure 2. SF6 gas power circuit

breaker

In SF6 circuit breakers, the same principle is employed, with SF6 as the medium

instead of air. In the "puffer" SF6 breaker, the motion of the contacts compresses the

gas and forces it to flow through an orifice into the neighborhood of the arc. Both types

of SF6 breakers have been developed for EHV (extra high voltage) transmission

systems

[21]

2.2 MAKE/BREAK CONTACTS

The breaker's heart is the switching element. It is where the arc quenching takes

place. It mainly contains the make/break contacts and the interrupting medium. The

make/break contacts functions can be reduced to:

Conduct the electric current when the breaker is closed.

Withstand the arc's destructive effect while interrupting.

Generally, the make/break contacts have a stationary part and a moving part. By

bringing the moving part to touch the stationary one, electric current flows and the

breaker is closed.

By driving the moving contact away from the stationary contact the electric arc

develops and by quenching it the current stops flowing and the breaker is open.

Contact design and choice of materials are greatly affected by the arc's energy, duration

and the chemical reactions that may occur with the ambient medium under the arc's

effect.

[22]

2.3 ELECTRIC ARC

The electric arc is a natural phenomenon. Despite its destructive nature it is of

great use to current switching in circuit breakers. It acts as variable impedance

from zero value when the breaker is closed to infinity when the breaker is open.

Fig-4 Electric Arc Chamber

[23]

2.4 HIGH-PRESSUREARC

Found in blast type circuit breakers (air-blast, SF6 and oil circuit breakers). Great

heat generation and relative long durations characterize them. They also

generate deposition of solid by-products that may affect the conductivity of the

contacts.

2.4 VACUUM ARC

Found in vacuum circuit breakers. They are limited and of short duration. They

cause no deposition of by-products.

[24]

CHAPTER 3

Live tank circuit breaker D&E

3.1 Live tank circuit breaker-D(LTB D-Breaker)

With Auto-Puffer for outdoor installation

LTB D is operated by a motor-charged spring operating mechanism type BLK or

FSA, or by the digital servomotor-system, Motor Drive. The energy required for

interrupting short-circuit current is partly taken from the arc itself, thereby reducing

the energy required from the operating mechanism to less than 50 percent

compared to a conventional SF6 puffer-type circuit breaker. The low energy

requirements result in reduced stresses, which in turn lead to increased reliability.

Options:

Can be equipped with Switch sync Controller for elimination of transients

Equipment for safer handling of SF6 gas

Composite insulators

Grey insulators

With draw able design

Extended creepage distance across insulators

Bracket for installation of current transformer type IMB

Bursting discs

Technical data :-

Rated voltages 72.5 - 170 kV

Rated current 3150 A

[25]

Rated breaking current 40 kA

Ambient temperatures -50°C to +50°C

3.2Live tank breaker- E(LTB-E)

With Auto-Puffer for outdoor installation

LTB E is operated by a motor-charged spring operating mechanism type BLK or

type BLG. The energy required for interrupting short-circuit current is partly taken

from the arc itself, thereby reducing the energy required from the operating

mechanism to less than 50 percent compared to a conventional SF6 puffer-type

circuit breaker. The low energy requirements result in reduced stresses, which in

turn lead to increased reliability.

Options:

Can be equipped with Switch sync Controller for elimination of transients

Equipment for safer handling of SF6 gas

Composite insulators

Grey insulators

With draw able design

Extended creepage distance across insulators

Bursting discs

Technical data

Rated voltages 72.5 - 550 kV

Rated current 4000 A

[26]

Rated breaking current 50 kA

Standards Complies with international standards IEC and

other major standards like ANSI, DIN, GOST, etc.

Ambient temperatures -40°C to +50°C

CHAPTER 4

LTB E – SF6 circuit breaker

LTB E is an outdoor SF6 circuit breaker designed for System voltages in the range of

245 to 550 kV and rated short-circuit currents up to 50 kA. The design incorporates an

advanced Auto-Puffer interrupter based on the latest developments in arc technology

and dielectrics. The energy required for interrupting short circuit Currents is partly drawn

from the arc itself, thereby

reducing the energy required for the operating mechanism by more than 50 percent as

compared with a conventional SF6 puffer type circuit breaker.The low energy

requirements result in a design optimized for low operating forces which in turn results

in higher reliability .All single pole operated circuit breakers are equipped with one

operating mechanism per pole .Circuit breakers with one breaking unit per pole can be

operated with one operating mechanism per breaker .The LTB E circuit breaker

complies with the international standards IEC and ANSI.

restrike-free interruption of capacitive currents due to optimized ‘contact’ design and

movement Optimum quenching at zero current ensures low over-voltages during

switching of inductive currents Protection from gas leakage by double X-rings in

dynamic seals and double O-rings in static seals, tested in varying climatic conditions

over 30 years of field operations. (SF6 gas loss lower than 1 percent / year.)

[27]

4.1Key features and advantages

Optimized contact gap ensures high dielectric

Strength even when the SF6 gas in the pole is

at atmospheric pressure

Low noise level due to low mechanical energy

required for operation

Pre-tested, pre-assembled units for easy

installation

Optimized pole and structure for high seismic

‘withstand’ capability

Synchronised switching with Switch sync.

relay (optional)

Supervisory control with condition monitoring

equipment Switch guard / Switch control

[28]

4.2 Design.

Circuit-breaker type-LTB 72.5-170D1/B.

The breaker pole constitutes a sealed unit, which

Includes one or two breaking unit(s), support and

Operating insulators, as well as pole linkage housing

With tripping spring attachment. A filter for

Absorbing moisture maintains quality of SF6 gas.

The circuit-breaker is made up of three separate poles. These consist of three

main parts.

At the bottom is a mechanism in alloy housing, above this is hollow post

insulators through which the operating insulator runs and at the top is the

breaking unit.

Each breaking unit consists of one breaking chamber insulator, which together

with an upper and a lower flange make up the enclosure, and upper and lower

current path and a puffer. The puffer, which is designed with integrated lower

operating current contacts, runs outside of the lower current path. The upper

operating current contacts are integrated in the upper current path.

The poles are mounted on a separate hot-dipped galvanized column frame.

The frame consists of two welded formed plate halves, which are interconnected

with bolted cross stays.

[29]

4.3 LTB-E Circuit-breaker gas system

The circuit-breaker poles are as standard design, permanently filled with gas to

the following pressure at +20°C:

for LTB 72.5-145D1/B, 50 Hz:

0.5 MPaabs,SF6 gas for circuit-breakers operating down to -40°C ambient

temperature

0.7MPaabs, SF6 gas mixed with N2 gas or CF4 gas for circuit-breakers

operating down to -50°C ambient temperature.

for LTB 72.5-145D1/B, 60 Hz:

0.7MPaabs,SF6 gas for circuit-breakers operating down to -30°C

ambient temperature

0.7MPaabs,SF6 gas mixed with N2 gas or CF4 gas for circuit-breakers

operating down to -50°C ambient temperature.

for LTB 170D1/B, 50 and 60 Hz:

[30]

0.7MPaabs,SF6 gas for circuit-breakers operating down to -30°C ambient

temperature

0.7MPaabs, SF6 gas mixed with N2 gas or CF4 gas for circuit-breakers

operating down to -40°C ambient temperature.

4.4 Operating mechanism

The circuit breaker is operated by a motor charged

spring operating mechanism, which is installed in

compact splash-proof and corrosion resistant

housing.

Three BLK 222 mechanisms are used for single

pole operation at 245 kV

One BLG 1002A mechanism is used for three

pole operation at 245 kV

Three BLG 1002A mechanisms are used for

single-pole operation at 420 Kv

The LTB circuit-breaker is operated by a motor-charged spring operating

mechanism type BLK 222.

The operating mechanism is connected to the circuit-breaker poles’ mechanisms

via a pull-rod system.

The circuit-breaker is closed by means of the operating mechanism, which

houses the closing springs. On closing, the opening spring is tensioned, which is

permanently fixed to the pole’s link gear. The tripp latch in the operating

[31]

mechanism keeps the circuit-breaker in the closed position. Opening of the

circuit breaker only requires the release off the trip latch.

The normal operating cycle is: O-0.3 s-CO-3 min-CO (according to IEC) or CO-

15 s-CO (according to ANSI)

4.5 Standards

The circuit-breakers comply with the requirements according to IEC Publication

60056 and in most cases also ANSI C37 and are restrike-free when breaking a

capacitive load.

4.5 Testing and Quality Assurance

The circuit breakers are type tested as per

IEC standards for each circuit breaker.

Mechanical endurance tests performed for

10,000 operations.

Routine test reports issued showing actual

test results.

The manufacturing facility is ISO 9001 certified,

covering all aspects of production and testing to

ensure the highest quality standards.

The manufacturing facility is also EHS certified

[32]

for Environment and Occupational Health and

Safety Management Systems (OHSMS).

4.7 Transportation and erection

The LTB E circuit breaker poles are transported as complete units filled with SF6

gas to a slight overpressure. Circuit breaker poles with two breaking units per

phase are supplied as two separate units: breaker-head

and support insulator.

Erection work at site can be done within a day.

SF6 gas should be filled to specified working

pressure by the following equipment:

One special control valve for connection to

the SF6 gas bottle and a gas-filled hose

with connectors.

Gas filling can be done without SF6 gas being

released into the atmosphere. No gas treatment

is necessary before gas filling.

[33]

4.8 Lubricants

As a guide to the selection of oils and greases for circuit-breakers, Combined,

Compact HPL and LTB with operating mechanisms, a description is given below

of the application areas as well as trade names and suppliers.

Safety instructions

Protective gloves, long-sleeved overalls and eye protection must be worn when

handling greases and oils.

All spillage shall be covered with an absorption agent and taken care of as

chemical waste according to applicable local directives.

4.8.1 Oil

Oil “A”

Thin, fully synthetic lubricating oil for precision components in the operating

mechanism and circuit-breaker Also used for post lubrication of bearings that

cannot be lubricated with grease “G” without dismantling, e.g. links and link

gears.

Viscosity at 40°C: 62-65 cSt

Lowest pour temperature: -52°C

[34]

Oil “D”

Breaker oil with a low viscosity ~ 6.0 cSt at 20°C. Also used as oil in dashpots.

Dashpots with the letter “s” punched on the cover shall be filled with oil “S”.

Oil “S”

Silicone oil intended for dashpots in heavy-duty operating mechanisms, type

BLG.

Only dashpots with the letter “s” punched on the cover shall be filled with this oil.

4.8.2 Grease

Grease “G”

Low-temperature grease for all types of bearings, gearing and worm gears and

valves in air-blast circuit-breakers.

Also used for greasing sealing rings and crevice corrosion protection on

breakers type HPL and for moving contacts (opening contacts) for

disconnectors.

Grease “K”

Molykote grease for lubricating pins in link gears and in earthquake dampers

Grease “N”

For lubricating moving contacts and puffer cylinders in SF6 circuit-breakers The

grease shall be applied in a very thin layer on the contact’s sliding surfaces.

Grease “L”

Low-temperature grease especially suitable for lubricating precision

components, for example, latch mechanisms in operating mechanisms that shall

work in severe cold.

Grease “M”

Low-temperature grease for long-term and permanent lubrication of worm gears,

and spur gears and other machine elements. Counteracts wear and corrosion.

Also for lubricating moving contacts (opening contacts) for earthing switches.

[35]

Grease “P”

Vaseline for coating contact surfaces on fixed joints on the inside of the breaking

unit.

Grease “S”

Fluoro-silicone grease for lubricating the EPDM-O-rings and as crevice corrosion

protection on circuit-breakers type ED as well as for lubricating rotating shaft

seals on circuit-breakers types LTB and HPL.

4.9 Assembly

Before starting the assembly, make certain that all requisite tools and documents

are on hand.

Standard tools with torque wrenches (10 - 430 Nm).

Lifting device and lifting slings.

Lubricants, see Lubricants 1HSB445409-1 for suppliers and brand names.

Grease “G”: ABB Art. No. 1171 4014-407

Grease “SV”: ABB Art. No. 1171 4016-610.

Check pin, ABB Art. No. 1HSB539782-1

Crank extension, ABB Art. No. 1HSB532188-F.

Crank, ABB Art. No. 2188 754-G.

Applicable dimension drawing and diagrams for the order.

4.9.1 Assembly markings

On delivery the circuit-breakers are supplied dismantled in transport units. The

component parts are marked to facilitate assembly. The circuit-breaker poles and

operating mechanism have been tested together.

Check that the assembly markings correspond with that the serial number on the

operating mechanism corresponds with the serial number on the circuit-breaker.

[36]

Assembly should always be carried out as the circuit-breaker has been adjusted

and tested with the circuit-breaker poles in this order

4.9.2 Foundation

The circuit-breaker’ foundation must be flat and level deviations in mm for the

position of the foundation bolts and phase clearance.

See the dimension drawing for the dimensions of foundation bolts and nuts.

Adjust any deviations using spacer washers, see .The nominal dimensions are

stated on the dimension drawing

for the order in question.

4.9.3 Frame assembly

The frame is supplied in welded halves with six cross stays and nuts, bolts and

washers. Bolt together the halves as shown in Fit the cross stays according to

the numbering 1-4, using the supplied nuts, bolts and washers. N.B Make sure

the stays are fitted as set out in Tighten the bolted joints to a torque of 190 Nm.

4.9.4 Assembling the frame on the foundation

The three frames are the same. Locate the frames on the foundation as in Check

that the frames are upright and adjust them to the same level using the nuts (2).

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For dimensions of foundation bolts, spacer washers and nuts refer to the

dimension drawing.

Fill the gap between the lower nut and the foundation, which should be as small

as possible, with spacer washers. Final tightening of the frame is done with the

upper nut, which is tightened to a tightening torque of 300-350 Nm.Foundation

bolts, nuts and spacer washers are not supplied.

4.9.5 Assembling the circuit-breaker pole on the frame

Check that the bolts (1), have a tightening torque of 79 Nm.

Check that the circuit-breaker pole is sealed before assembling on the frame.

Unscrew the sealing cap (1).

Press the non-return valve’s disk (2) inwards using the test tool (3). A clear

hissing noise should be heard from the pole. If no hissing sound is heard, the

pole leaks. This must be rectified before assembly.

4.9.6 Final assembly of the operating mechanism

Check that the operating mechanism is assembled correctly in relation to the

mechanism housing and frame.

Tighten the bolts (1), in the joint between the pipe flange and the mechanism

housing with the tightening torque 79 Nm.

Tighten the bolts (3),in the joint between the operating mechanism

and the frame with the tightening torque 200 Nm.

Release the lifting device.

Dismantle the operating mechanism’s lifting rails.

Refit the lifting rail bolts.

[38]

CHAPTER 5

Circuit breaker Applications

Arcing In Circuit Breaker

Transient Recovery Voltage (TRV)

Switching Of

Transformer/ reactor

Capacitor Bank

long Lines/ cable

Short-line Fault Terminal Faults

Phase Opposition Switching

Synchronous Switching

First-pole-to-clear Factor

Circuit breakers at high altitude

Circuit breakers in polluted atmosphere

High and low temperature application

[39]

Fig5-Switching phenomena of Circuit Breaker

[40]

5.1 Terms Related to Circuit Breaker

5.1.1Transient Recovery Voltage (TRV)

Fig-6 Transient recovery voltage

During short circuit the fault current is inductive

Current interrupts at natural zero

Due to circuit `L’ & `C’ high frequency voltage appears across CB contacts

[41]

5.1.2 TRV (Transient Recovery Voltage)

Fig-7 TRV

May be oscillatory or non-oscillatory

Frequency of oscillation

L = equivalent system inductance

C = equivalent system capacitance

ƒn = few Hz to several thousand Hz

Increase in fn rate of rise of TRV increases (see Fig a)

voltage stress on contact gap to continue arc

Higher frequency Þ greater stress on CB Breaking capacity reduce.

[42]

Fig aHigh rate of rise of TRV

Low rate of rise of TRV

f n=1/(2 π √ LC )

5.1.3 Effect of Power Factor on TRV

Unity power factor current: at current zero, voltage across CB contacts

also zero hence no stress on contact insulation

Zero power factor current at current zero, voltage is at peak hence stress

on contact insulation due to transient & high rate of rise of TRV

Conclusion : interrupting low power factor current is difficult

[43]

BIBLIOGRAPHY

The following sources have contributed to an extent for some of the contents of this

project. These sources are:-

Reference sources :-

Product Manual

Electricity Today

Advanced Power system

Sunil S.Rao “Switchgear Protection and Power System”

Wadhwa C.L. “Electrical Power System”

Ashfaq Husain & Harun Ashfaq “Basic of Electrical Power System”

Rajput A.K. “Power System Element”

IEEE Journal

Design Section Department of ABB

Internet links:-

www.abb.co.in

www.wikipedia.com

Google search engine

www.electricitytoday.com

www.electricaltools.com

[44]

CONCLUSION

On the whole my training at ASEA BROWN BOVERY LIMITED,(ABB LTD.) MANEJA

VADODRA GUJRAT was very useful experience which has obiviously made a

tremendous impact on my quest for further knowledge in the field of

Electrical Engineering. It has given me a better understanding and

exposure to some of the operational and practical problems that engineers have

to grapple in the designing of Circuit Breaker. The pleasant working atmosphere

and helpful nature of people made staying there and working a memorable

experience.

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