Embed Size (px)
Citation preview
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
[5]
operates in around 100 countries and employs 110,000 people.ABB operate in india
include 14 manufacturing facilities and over 6500 employees.
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 5th
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
[7]
Bangalore 560 052
• 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.
• Insertion resistor
The sudden modification of circuit characteristics, when circuit breakers operate,
produces peak voltage impulses where the level is determined by the circuit
[11]
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:
➢ 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.
[12]
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
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.
[13]
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.
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
[14]
avoided, or internal tripping may occur. Installing the costly drying compression
stations greatly raises the cost of operating air blast circuit breakers.
2.1.2 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.
[15]
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.
[16]
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.
.
Air blast circuit breaker
[17]
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
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.
[18]
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.
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.
[19]
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
2.1 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.
[20]
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.
2.2 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.
[21]
Fig-4 Electric Arc Chamber
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.
2.3 VACUUM ARC
Found in vacuum circuit breakers. They are limited and of short duration. They
cause no deposition of by-products.
[22]
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.
[23]
• 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 kVRated current 3150 ARated 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
[24]
• 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
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
[25]
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.)
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
[26]
4.1 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
[27]
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.
4.1 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
[28]
• 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:
• 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.
4.1 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.
[29]
➢ 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
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.
4.1 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
[30]
ensure the highest quality standards.
➢ The manufacturing facility is also EHS certified
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.
[31]
4.7 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
[32]
➢ 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.
➢ Grease “P”
[33]
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.
4.7 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.
4.7.1 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.
Assembly should always be carried out as the circuit-breaker has been adjusted
and tested with the circuit-breaker poles in this order
[34]
4.7.2 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.
4.7.3 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.
4.7.4 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).
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
[35]
upper nut, which is tightened to a tightening torque of 300-350 Nm.Foundation
bolts, nuts and spacer washers are not supplied.
4.7.5 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.
[36]
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
[37]
Fi
g5-Switching phenomena of Circuit Breaker
[38]
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
[39]
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 ⇒ greater stress on CB Breaking capacity reduce.
5.1.2 Effect of Power Factor on TRV
[40]
)2/(1 LCfn π=
➢ 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
BIBLIOGRAPHY
[41]
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
CONCLUSION
On the whole my training at ASEA BROWN BOVERY LIMITED,(ABB LTD.)
MANEJA VADODRA GUJRAT was very useful experience which has
[42]
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.
[43]
