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Powergrid maharanibagh 400/220 KV gis substation

SUMMER TRAINING REPORT

Submitted By:

Lingaya’s institute of Management and Technology

Table of Content

1. Certificate………………………………………………………3

2. Acknowlegment ………………………………………………4

3. About the company…………………………………………..5

4. Introduction to GIS…………………………………………...11

5. Advantages of GIS……………………………………………13

6. Types of substation switchgear [AIS/HIS/GIS]………….14

7. Space Reduction Analysis with AIS/HIS/GIS…………….18

8. Specifications of GIS and AIS……………………………....19

9. 400/220 KV GIS Substation with Automation…………….23

10. Components of GIS

Circuit

Breaker……………………………………………………………………

………28

Current

Transformer……………………………………………………………….

. 33

Voltage

Transformer………………………………………………………………

…35

Disconnector and Earthing

switches………………………………………36

Surge Arrestor – CVT- Wave

Trap…………………………………………39

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SF6

gas……………………………………………………………………………

…………….41

CERTIFICATE

This is to certify that the ROHIT VERMA student of a Batch Electrical

Branch 2nd Year Lingaya’s Institute of management & Technology

Faridabad has successfully completed his industrial training at

Power Grid Maharani Bagh – 400/220 KV GIS S/S at New Delhi for

Six week from 14th JUNE to 31st JULY 2010

He has completed the whole training as per the training report

submitted by him.

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Training Incharge

Power Grid Maharani Bagh

NEW DELHI

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Acknowledgment

I would like to express my gratitude to all those who gave me the possibility to complete

this report. I want to thank the Power Grid Corporation of India for giving me

permission to commence this report, and to do the necessary Training work and to use

departmental data and for their corporation and friendly assistance.

It was a very nice experience for me to have a training course in Power Grid Maharani

Bagh – 400/220 KV GIS S/S and I am sure it will be useful for my future career. I will

not forget to give all my respect to our training head Mr. G.N.D.Elangovan and our

instructor Mr NAVEEN for his help and kind behave.

I would like to express special thanks to Mr. ALOK, Deputy General Manager. I am

really appreciating his infinite support and cooperation for offering me this opportunity to

attend this training course.

I would also like to thank the training in charge of Lingaya’s Institute of management

& Technology Faridabad and all the faculty member of Electrical department for their

effort of constant co-operation. Which have been significant factor in the accomplishment

of my industrial summer training.

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About The Company

POWERGRID, A Navratna Public Sector Enterprise, is one of the largest transmission

utilities in the world. POWERGRID wheels about 45% of the total power generated in the

country on its transmission network. POWERGRID has a pan India presence with around

77,000 Circuit Kms of Transmission network and 124 nos. of EHVAC & HVDC sub-stations

with a total transformation capacity of 89,000 MVA.POWERGRID has also diversified into

Telecom business and established a telecom network of more than 21,000 Kms across the

country. POWERGRID has consistently maintained the transmission system availability

over  99% which is at par with the International Utilities

POWERGRID has in-house expertise at par with global standards in the field of Planning,

Engineering, Load Despatch and Communication, Telecommunication, Contracting,

Financial and Project Management. POWERGRID is offering consultancy not only in India

but also on international level leveraging upon its strong in-house technical expertise

developed over the years. POWERGRID is assisting various State Power utilities in

implementation of their transmission /sub-transmission projects on turnkey basis. In the

international arena, POWERGRID has also secured consultancy assignments in Afghanistan,

Nepal, Bhutan, Nigeria and Dubai against stiff competition from international consultants.

Our prestigious assignment of a 200km long 220kV line in Afghanistan commissioned in

Jan` 2009. Besides, for a proposed under-sea interconnection with Sri Lanka, a pre-

feasibility report has already been submitted. Recently, POWERGRID has been identified as

the implementing agency for 230kV transmission project in Myanmar to be funded by Govt.

of India. POWERGRID has taken lead role and significantly contributing in Government of

India’s nation building schemes of Accelerated Power Development and Reforms Programme

(APDRP) and Rajiv Gandhi Grameen Vidyutikaran Yojana (RGGVY) which are aimed at

bringing qualitative improvement in the distribution sector.

POWERGRID continues to give major thrust to Research & Development activities, which

are mainly for optimization of cost of power transmission and also for conservation of Right-

of-Way. Towards this, various new technologies have been adopted suiting Indian power

system such as up gradation of transmission lines, use of Thyristor Controlled Series

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Compensation, high temperature endurance conductors, development of pole type tower

structure for 400KV transmission lines, GPS/GIS based survey techniques etc. POWERGRID

has taken initiative for development of major transmission highways using higher

transmission voltage levels, i.e. 765 kV EHV AC and ±500 kV HVDC as a viable alternatives

to achieve efficient utilization of existing Row and increased power transfer capability for

transfer of bulk power over long distances. Development of high capacity ±800kV, 6000MW

HVDC transmission system and 1200kV Ultra High Voltage (UHVAC) super grid, has been

taken up to address the above issues.

Performance of the company

POWERGRID, the Central Transmission Utility (CTU) of the country, is responsible for

providing matching transmission network for generation capacity programme under Central

Sector, implementation of various system strengthening schemes, load dispatch &

communication schemes and inter-regional links. During X five year Plan, POWERGRID

made an investment of about Rs. 18,920 Crore against the approved outlay of Rs. 21,370

Crore.

The key financial parameters have witnessed a quantum jump during the X five year Plan

period as indicated below:

On the physical performance

front, POWERGRID added

about 19,170 Ckt. Kms of Extra

High Voltage transmission lines,

36 no. of EHV sub-stations and

Power transformation capacity

of about 25,130 MVA during X

Plan, thereby enhancing its

overall transmission network to

59,461 Ckt. Kms, 104 sub-

stations and 59,417 MVA of

transformation capacity by end of X Plan

Green Grid |

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ENVIRONMENT AND SOCIAL MANAGEMENT IN POWERGRID

Power Grid Corporation of India Ltd. (POWERGRID), an ISO

14001 certified company and the Central Transmission Utility

of the country is one of the largest power transmission utilities

in the world.

Its developmental activities have had minimal environmental

and social impact owing to very nature of activities that does

not involve disposal of any pollutant in land, air or water or any large scale excavation

resulting in soil erosion. POWERGRID is committed to achieve the goal of Sustainable

Development, realizing that, given the scale of its operations, it is inevitable that there is

some impact upon both natural environment and communities. To address these issues,

POWERGRID has adopted a pro-active approach and developed a comprehensive

“Environmental Social Policy & Procedures” (ESPP) in 1998 through extensive national

consultations.

The ESPP outlines POWERGRID`s approach and commitment

to deal with environmental and social issues, relating to its

transmission projects, and lays out management procedures and

protocols to mitigate the same. It provides a framework for

identification, assessment, and management of environmental

and social concerns at both organizational and project levels, within the adopted principles

of avoidance, minimization and mitigation.

Environment & Social Policy Statement

“POWERGRID is committed to the goal of sustainable development and conservation of

nature and natural resources, through continually improving its management system,

accessing specialist knowledge for management of significant environmental and social

issues and introducing state of the art and internationally proven technologies, while

strictly following the basic principles of Avoidance, Minimization and Mitigation.”

The basic principle of the ESPP is Avoidance, Minimization and Mitigation. The existing

provisions of ESPP have been upgraded and modified recently (March’05) in line with the

changed rules and guidelines of Govt. of India, including that of multilateral funding agency

like World Bank, ADB, JBIC etc and suggestion/best practices and feedback received from

different sites. During the revisions of ESPP, the consultative process was further enlarged

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to engage all stakeholders, including Project Affected Persons (PAPs) and the local

communities.

ESPP has also been reviewed by an independent committee constituted by POWERGRID,

comprising eminent environmentalists / Social scientists of international repute, and

representatives nominated by multilateral funding agencies. The committee has completed

review of updated ESPP keeping in view international best practices and shall be overseeing

the compliance of ESPP by POWERGRID.

The ESPP spells out POWERGRID’s environment and social policy, and its

commitment to:

• Ensure total transparency in dealing with all the stakeholders i.e. concerned government

agencies, local communities, individual landowners and employees through a well-defined

public consultation process as well as dissemination of relevant information about the

project at every stage of implementation.

• Maintain the highest standards of corporate responsibility not only towards its employees

but also to the consumers and the civil society, social responsibility through various

community development activities for promoting socio-economic development and

enriching the quality of life of the community in areas around its establishments, most

importantly through people’s participation.

• To minimise adverse impacts on the natural environment by consciously economising on

the requirement of land for civil structures, reducing the width of the Right of Way ( ROW)

etc.

INITIATIVES ADOPTED TOWARDS CONSERVATION OF ENVIRONMENT:

• Tremendous reduction in forest involvement in

implementation of transmission lines. For example, forest

involvement which was about 6% in 27,000 Circuit Km. of

lines till 1998 has come down to 2% with proactive and

systematic conservatory approach adopted in construction of

20,500 Circuit Km. line during last 6 years.

• Massive plantations in sub-stations where about 2 to 4 acre of land is being afforested with

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suitable species of plants in consultation with local forest department in almost each of its

85 sub-stations. A separate fund is also earmarked for this, although not being mandatory.

• Measures like Compensatory Afforestation involving plantation over twice the area,

affected by the project. This not only helped in compensating loss of vegetation, but has

also increased forest cover. POWERGRID have contributed about US $ 25 million (Rs. 110

Crore) to different State forest authorities towards Afforestation on more than 10,000 ha of

land over the last decade.

• POWERGRID is developing compact substations to have barest minimum land

requirement and tries to locate sub-station on Govt. land to minimize social impact.

• Provision for Rain Water Harvesting and collection of even used/waste water for its

conservation and recharging of ground water.

• Adoption of innovative tower design like multi-circuit and very tall towers to protect

wildlife, trees in ecologically sensitive areas (In Tehri transmission line tree felling was

reduced to 14739 against earlier estimate of 90000 trees in Rajaji National Park due to

installation of 85 m high towers)

• Providing financial assistance to State Government/ Institutions for conservation of flora

and fauna.

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IntroductionToGIS

Gas Insulated Substation

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GIS - Gas Insulated Substation

The increasing demand of electrical power in cities and industrial centres necessitates the installation of a compact and efficient distribution and transmission network. High voltage gas insulated switchgear (GIS) is ideal for such applications.

The range of application of SF₆ Gas Insulated Switchgear extends from voltage Ratings of 72.5 kV up to 800 kV with breaking currents of up to 63 kA, and in special cases up to 80 kA. Both small transformer substations and large load- centre substations can be designed with GIS technology.

The distinctive advantages of SF₆ Gas Insulated Switchgear are: compact, low Weight, high reliability, safety against touch contact, low maintenance and long life. Extensive in-plant preassembly and testing of large units and complete bays reduces assembly and commissioning time on the construction site.

GIS equipment is usually of modular construction. All components such as busbars, disconnectors, circuit-breakers, instrument transformers, cable terminations and joints are contained in earthed enclosures filled with sulphur Hexafluoride gas (SF₆).

Gas Insulated Substations (GIS) is a compact, multicomponent assembly enclosed in a ground metallic housing in which the primary insulating medium is compressed.

Sulphur hexafluoride (SF6) gas. SF6acts as an insulation between live parts & the earthed metal closure.

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ADVANTAGES OF GIS

Gas Insulated Switchgear (GIS) that uses compresses sulphur hexafluoride (SF6) gas overcomes many of the limitations of the conventional open type AIS, as it offers the following advantages:

The space occupied by the switchgear is greatly reduced.

It is totally unaffected by atmospherically conditions such as polluted or

Saline air in industrial and coastal areas, or desert climates.

It possesses a high degree of operational reliability and safety to personal.

It is easier to install in difficult site conditions ( e.g. on unstable ground or

in seismically active areas)

In addition to having a dielectric strength much greater than that of air,

SF6 has the advantages of being nontoxic and non flammable.

Gas insulated Substations have easy maintenance ( nearly zero

Maintenance )

For underground powerhouse of Hydro electric power project where

space constraint is a major issue.

Less field erection time & less erection cost.

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Surge Arrestor Bus port insulator Current transformer

Capacitor Voltage Transformer

Live Tank Circuit Breaker

Disconnector

Dead Tank Circuit Breaker

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Surge ArrestorBus Port Insulator

Capacitor Voltage Transformer

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Specifications

Of

GIS

Gas Insulated Substation

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The weight and size of the GIS equipment do not change appreciably with the voltage class as the bulk of the current – carrying components and enclosures have identical dimensions for similar thermal and short time current.

The additional insulation required for the next voltage class is achieved by increasing gas density.

Owing to these flexibilities, a few manufacturers offer the same equipment for two voltage classes (like 170/145 kV).

Even when the GIS equipment is designed for an individual voltage class, the

dimensions and weights of the equipment differ marginally

Table shows the dimensions, weight and floor loading for three voltage classes of GIS.

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Earth Clearance: This is the clearance between live parts and earthed structures, walls, screens and ground.

Phase Clearance: This is the clearance between live parts of different phases.

Section Clearance: This is the clearance between live parts and the terminals of a work section. The limits of this work section, or maintenance zone, may be the ground or a platform from which the man works.

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Minimum Clearance for Different Voltage Level [AIS]

Minimum clearance for Different voltage levels [GIS]

Specifications for 400 KV GIS (ELK-3)

Specifications for 220 KV GIS (ELK-14)

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400/220 KV GIS Substation with Automation

400 kV/ 220 kV Substation with 5 bays at 400 kV and 7 bays at 220 kV

2 nos. 315 MVA, 400/220/33 kV Three phase Auto Transformers

Gas Insulated Switchgear type ELK -3 at 400 kV and ELK-10 at 220 KV from ABB Switzerland

Substation commissioned in 2007.

Power received from BALLABGARH & DADRI at 400 KV.

Power supplied to Delhi Transco at 220 KV.

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To ICT-1 To ICT-2

FROM BALLABGARH FROM DADRI

Single Line Diagram26

1. Barrier insulator2. Busbar Gas Compartment3. Feeder Gas Compartment4. CB Gas compartment5. Voltage transformer

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Components of GIS:

1. Circuit Breaker 5. Maintenance Earthing Switch

2. Operating Mechanism 6. Fast Acting Earthing Switch

3. Current Transformer 7. Voltage Transformer4. Disconnecter 8. SF6 Bushing

CIRCUIT BREAKER

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Bus Bars Circuit Breaker Disconnecting Switches Earthing Switches Current Transformer Voltage Transformer Cable and Boxes Gas Supply and Gas monitoring Equipment

A circuit breaker is an automatically-operated electrical switch designed

to protect an electrical from damage caused by overload or short circuit.

Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow.

Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation

Current interruption in a high-voltage circuit-breaker is obtained by separating two contacts in a medium, such as SF6, having excellent dielectric and arc quenching properties.

After contact separation, current is carried through an arc and the arc is interrupted & cooled by a gas blast of sufficient intensity.

Design of Circuit Breaker

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Each CB comprises three single-phase metal enclosed breaker poles.

Each Pole consists of operating mechanism, the interrupter column with 2 interrupting chambers in series & the enclosure with the basic support structure.

Assembly of metal enclosed Breaking poles

To guarantee simultaneous interruption, the chambers are mechanically connected in series.

One grading capacitor guarantees an equalized voltage distribution.

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Advancement in circuit breaker technology

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SELF BLAST TECHNIQUE

Making use of arc energy to produce the pressure necessary to quench the arc and obtain current interruption. Low current interruption, up to about 30% of rated short-circuit current, is obtained by a puffer blast.

A Valve between the expansion and compression volumes.

When interrupting low currents the valve opens under the effect of the over pressure generated in the compression volume. The blow-out of the arc is made as in a puffer circuit breaker by compression of the gas obtained by the piston action.

In the case of high currents interruption, the arc energy produces a high overpressure in the expansion volume, which leads to the closure of the valve and thus isolating the expansion volume from the compression volume.

The overpressure necessary for breaking is obtained by the optimal use of the thermal effect.

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Spring Operating Mechanism

Each Pole of the CB is equipped with the Hydraulic spring operating mechanism.

It combines the advantages of both Hydraulic operating mechanism & spring energy storage type.

A Hydraulic pump moves oil from low pressure reservoir to high pressure reservoir side of the energy piston.

Opening & Closing of CB is initiated by trip coil actuation.

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CURRENT & VOLTAGE TRANSFORMER

Current transformer (CT) is used for measurement of electric currents. Current transformers are also known as instrument transformers.

Current transformers are commonly used in metering and protective

relays in the electrical power industry.

When current in a circuit is too high to directly apply to measuring instruments, a current transformer produces a reduced current accurately proportional to the current in the circuit, which can be conveniently connected to measuring and recording instruments.

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VOLTAGE TRANSFORMERS

Voltage transformers (VTs), also referred to as “Potential transformers" (PTs), are used in high-voltage circuits.

They are designed to present a negligible load to the supply being measured, to allow protective relay equipment to be operated at lower voltages, and to have a precise winding ratio for accurate metering.

The advantages of the voltage Transformer as follow:

Variable location on feeder and busbars.

Integrated disconnecting facility for GIS and power cable testing without

dismantling and gas handling.

Flexible gas compartment allocation for optimal service oriented gas

supervision.

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VOLTAGE TRANSFORMERS

The single pole inductive voltage transformer is connected to switchgear with the connecting flanges with a barrier insulator.

The primary winding is insulated with SF6 gas & connected to high voltage terminal.

The primary winding is wounded on the top of the core & secondarywindings.

The secondary winding is connected the secondary winding is connected to the terminals in the external terminal box through a gas tight multiple bushing.

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DISCONNECTORAND

EARTHING SWITCHES

Disconnectors and Earthing switches are safety devices used to open or to close a circuit when there is no current through them.

They are used to isolate a part of a circuit, a machine, a part of an overhead line or an underground line so that maintenance can be safely conducted.

The opening of the line isolator or busbar section isolator is necessary for safety, but not sufficient. Grounding must be conducted at both the upstream and downstream sections of the device under maintenance. This is accomplished by Earthing switches.

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Disconnect switches are designed to continuously carry load currents and Momentarily carry short circuit currents for specified duration.

They are designed for no-load switching opening, or closing circuits where negligible currents are made or interrupted (including capacitive current and resistive or inductive current, or when there is no significant voltage across the open terminals of the switch.

Fast Acting Earthing Switch

Fast earth switch and maintenance earth switch are the two types of earth switches used for gas insulated sub-station systems.

Fast earth switch is used to protect the circuit-connected instrument voltage transformer from core saturation caused by direct current flowing through its primary as a consequence of from core saturation caused by direct current flowing through its primary as a consequence of charge stored online during isolation / switching off the line.

Use of fast earth switch provides a parallel (low resistance) path to drain the residual static charge quickly, thereby protecting the instrument voltage transformer from the damages that may otherwise be caused. The basic construction of these earth switches is identical.

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Surge Arrestor – CVT – Wave Trap

Capacitor Voltage Transformers convert transmission class voltages to standardized low and easily measurable values, used for metering, protection and control of the high voltage system.

Additionally, Capacitor Voltage Transformers serve as a coupling capacitor for coupling high frequency power line carrier signals to the transmission line.

Lightning Arresters or Surge Arresters are always connected in Shunt to the equipment to be protected; they provide a low impedance path for the surge current to the ground.

Line trap also is known as Wave trap. It traps Hi-frequency communication signals sent on the line from the remote substation and diverting them to the telecom/tele protection panel in the substation control room (through coupling capacitor tele protection panel in the substation control room (through coupling capacitor and LMU).

This is relevant in Power Line Carrier Communication (PLCC) systems for communication

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among various substations without dependence on the telecom company network.

GIS Termination Elements SF6 – Air Bushings are used for connecting to open terminal equipment

& Overhead transmission lines.

SF outdoor bushings allow the enclosed switchgear to be connected to overhead lines.

CABLE TERMINATION (Fig - a): High-Voltage cables of various types are Connected to SF6 switchgear via cable connection assembly & also it enables the GIS & Cables to be tested separated.

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Transformer connection (Fig - b): Consists of Oil/SF6 bushing, the enclosure, the main circuit end terminal & removable connection. For Hi-Voltage test on GIS, transformer is isolated from switchgear by dismantling the removable connection.

SF6 – Sulphur hexafluoride

The properties of SF6 gas are many and this is why GIS now being commonly used more than AIS because pure SF6 gas is chemically very stable, inert, almost water insoluble, non-inflammable, non-poisonous, odourless, colourless and heavier than air.

Electrical discharges and arc will decompose SF6 gas. On cooling, a large part of the decomposed gas recombines. Reactions may. However, also occur with design material (e.g. with vaporizing arcing contact material). This result in the formation of gaseous sulphur fluoride and solid metallic fluoride are powder and in the presence of water or moisture also in the development of hydrogen-fluoride and sulphur dioxide. Some of these decomposition products are conspicuous through their unpleasant piercing odour.

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GAS DENSITY MONITOR

The insulating and interrupting capability of the SF6 gas depends on the density of the SF6 gas.

The pressure of the SF6 gas varies with temperature, so a mechanical or electronic temperature compensated pressure switch is used to monitor the equivalent of gas density.

Gas Density Monitor is directly mounted on the enclosure. The gas pressure acts on metal bellows, with a reference volume for compensation of the temperature.

In case of gas leakage a micro-switch is actuated. Thresholds for refilling (first stage) or lock-out alarm (second stage) can be mechanically set. The response character is shown in the Moliere diagram.

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Pressure –Temperature Graph

SF6 Gas

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Inter Connecting Transformer [ICT]

An autotransformer is an electrical transformer with only one winding.

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The winding has at least three electrical connection points called taps. The voltage source and the load are each connected to two taps.

One tap at the end of the winding is a common connection to both circuits (source and load). Each tap corresponds to a different source or load voltage.

An autotransformer for power applications is typically lighter and less costly than a two-winding transformer, up to a voltage ratio of about 3:1 beyond that range a two-winding transformer is usually more economical.

In an autotransformer a portion of the same winding acts as part of both the primary and secondary winding.

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SLD OF 220 KV SIDE OF GIS

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