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A SUMMER TRAINING REPORT ON “DL-765 KV TRANSFORMER PKG, JATIKALAN PROJECT SITE ” Page | 1

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Page 1: L & t training project

A SUMMER TRAINING REPORT

ON“DL-765 KV TRANSFORMER PKG, JATIKALAN PROJECT SITE ”

By-: kundan giriMIET ,meerut

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ACKNOWLEDGEMENT

I would like extend my gratitude to Mr. Sachinder Prakash Pandey, Cluster HR Manager,

Delhi Region, for giving me the opportunity to do my project at L&T Construction. I

would also like to thank him for providing his support and able guidance during the course of my

project.

I would also like to thank Mr.Snehashish Debnath, Project manager, who guided me

throughout my training and encouraged me to do new things and gave their valuable

inputs as and when they thought necessary. Their constructive feedback and insights have helped

me develop a perspective and has also enabled me to overcome challenges that came

during the entire course of the project. Their calm demeanor and willingness to teach has been a

great help in my successfully completing the project. My learning has been immeasurable and

working under them was a great experience.

My sincere thanks also extend to all the staff members of construction for providing a hospitable

and helpful work environment and making my summer training an exciting and memorable

event.

I would also like to thank Amresh Pratap Yadav, HR trainee at L&T constructions and as my

friend has always motivated me to put my best endeavors and match the expectations of the

organization. In spite of his busy schedules, he ensured that he was always available for

providing feedback and ensuring that the project was done with utmost quality and consistency.

Finally, I thank all my fellow trainees who from time to time have helped me with information,

insights and their support. Their cooperation has helped me immensely and made the

experience of the internship program at L&T construction an enriching one.

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CONTENTS

ON “DL-765 KV TRANSFORMER PKG, JATIKALAN PROJECT SITE ”....................................................................1

ACKNOWLEDGEMENT......................................................................................................................................... 2

ABSTRACT........................................................................................................................................................... 5

ORGANIZATION/COMPANY PROFILE............................................................................................................................ 6

DIRECTORS..................................................................................................................................................................7HISTORY.....................................................................................................................................................................8VISION.......................................................................................................................................................................9STRATEGIC MISSION - LAKSHYA....................................................................................................................................9STRENGTH..................................................................................................................................................................9

TRANSFORMERS............................................................................................................................................... 10

BASIC PRINCIPLE.........................................................................................................................................................11Induction law.....................................................................................................................................................12Ideal power equation........................................................................................................................................13Physics of magnetization and EMF....................................................................................................................13

BASIC TRANSFORMER PARAMETERS AND CONSTRUCTION....................................................................................................13Leakage Flux......................................................................................................................................................13Effect of frequency............................................................................................................................................14

ENERGY LOSSES..........................................................................................................................................................15Winding resistance............................................................................................................................................15Hysteresis losses................................................................................................................................................15Eddy currents....................................................................................................................................................16Magnetostriction...............................................................................................................................................16Mechanical losses..............................................................................................................................................16Stray losses........................................................................................................................................................16

TRANSFORMER OIL........................................................................................................................................... 16

EXPLANATION............................................................................................................................................................17TESTING AND OIL QUALITY...........................................................................................................................................18ON-SITE TESTING........................................................................................................................................................19

ELECTRIC POWER DISTRIBUTION....................................................................................................................... 21

HISTORY...................................................................................................................................................................21INTRODUCTION OF ALTERNATING CURRENT......................................................................................................................21

Modern distribution systems.............................................................................................................................23International differences...................................................................................................................................24Distribution network configurations..................................................................................................................25Distribution industry..........................................................................................................................................26

ELECTRIC POWER TRANSMISSION..................................................................................................................... 27

OVERHEAD TRANSMISSION...........................................................................................................................................27UNDERGROUND TRANSMISSION....................................................................................................................................28

ELECTRICAL GRID.............................................................................................................................................. 29

Term..................................................................................................................................................................29

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History...............................................................................................................................................................29Deregulation.....................................................................................................................................................30Redundancy and defining "grid"........................................................................................................................31Aging Infrastructure..........................................................................................................................................31Modern trends...................................................................................................................................................32Future trends.....................................................................................................................................................33Emerging smart grid..........................................................................................................................................33Networked island-able microgrids....................................................................................................................34

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ABSTRACT

The report includes the various methods used by the project team in installing 13 765/400kv

transformers at the Ghummenera village in an under construction PGCIL Power Grid Project.

Special emphasis has been put to highlight all the peculiarities while the task has been

completed. Also the study provides technical information regarding the Machines and

Equipments being used at the work time and the working of the Power Grid.

Personal face to face interaction was done to collect the primary data, to study and analyze the

factors which are important in completion of the project in a manner such that the utilization of

resources is optimum.

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ORGANIZATION/COMPANY PROFILE

Larsen & Toubro Limited (L&T) is a technology, engineering, construction and manufacturing

company. It is one of the largest and most respected companies in India's private sector.

Seven decades of a strong, customer-focused approach and the continuous quest for world-class

quality have enabled it to attain and sustain leadership in all its major lines of business. L&T has

an international presence, with a global spread of offices. A thrust on international business has

seen overseas earnings grow significantly. It continues to grow its overseas manufacturing

footprint, with facilities in China and the Gulf region. The company's businesses are supported

by a wide marketing and distribution network, and have established a reputation for strong

customer support.

L&T believes that progress must be achieved in harmony with the environment. A commitment

to community welfare and environmental protection are an integral part of the corporate vision.

Operating Divisions:

Engineering & Construction Projects (E&C)

Heavy Engineering (HED)

Engineering Construction & Contracts (ECC)

Electrical & Electronics (EBG)

Machinery & Industrial Products (MIPD)

Information Technology & Engineering Services

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DIRECTORS

A. M. Naik

Chairman & Managing Director

 

 

 

J. P. Nayak

Whole-time Director & President

(Machinery & Industrial Products)

 

 

Y. M. Deosthalee

Whole-time Director &Chief Financial Officer

  

 K. Venkataramanan

Whole-time Director & President

(Engineering & Construction Projects)

R. N. Mukhija

Whole-time Director & President

(Electrical & Electronics)

K. V. Rangaswami

Whole-time Director & President

(Construction)

V. K. Magapu M. V. Kotwal

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Whole-time Director & Senior Executive Vice

President

(IT & Technology)

Whole-time Director & Senior Executive Vice

President

(Heavy Engineering)

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HISTORY

The evolution of L&T into the country's largest engineering and construction organization is

among the most remarkable success stories in Indian industry.L&T was founded in Bombay

(Mumbai) in 1938 by two Danish engineers, Henning Holck-Larsen and Soren Kristian Toubro.

Both of them were strongly committed to developing India's engineering capabilities to meet the

demands of industry.

Henning Holck-Larsen and Soren Kristian Toubro, school-mates in Denmark, would not have

dreamt, as they were learning about India in history classes that they would, one day, create

history in that land. In 1938, the two friends decided to forgo the comforts of working in Europe,

and started their own operation in India. All they had was a dream. And the courage to dare.

Their first office in Mumbai (Bombay) was so small that only one of the partners could use the

office at a time!

In the early years, they represented Danish manufacturers of dairy equipment for a modest

retainer. But with the start of the Second World War in 1939, imports were restricted,

compelling them to start a small work-shop to undertake jobs and provide service facilities.

Germany's invasion of Denmark in 1940 stopped supplies of Danish products. This crisis forced

the partners to stand on their own feet and innovate. They started manufacturing dairy equipment

indigenously. These products proved to be a success, and L&T came to be recognised as a

reliable fabricator with high standards. The war-time need to repair and refit ships offered L&T

an opportunity, and led to the formation of a new company, Hilda Ltd., to handle these

operations. L&T also started two repair and fabrication shops - the Company had begun to

expand. Again, the sudden internment of German engineers (because of the War) who were to

put up a soda ash plant for the Tatas, gave L&T a chance to enter the field of installation - an

area where their capability became well respected.

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VISION

The L&T vision reflects the collective goal of the company. It was drafted through a large scale

interactive process which engaged employees at every level, worldwide.

L&T shall be a professionally-managed Indian Multinational, committed to total

customer satisfaction and enhancing shareholder value.

L&T-ites shall be an innovative, entrepreneurial and empowered team constantly

creating value and attaining global benchmark.

L&T shall foster a culture of caring, trust and continuous learning while meeting

expectations of employees, stakeholders and society.

STRATEGIC MISSION - LAKSHYA

To compete and grow in a globalised business environment, L&T is implementing a strategic

plan (LAKSHYA) for 2005-10. The plan has been drawn up in consultation with a leading

international strategy consultant. It has set ambitious growth targets for each business. Also

included are opportunities for diversification of L&T's business portfolio.

STRENGTH

Larsen and Toubro is a leading technology, engineering, construction and manufacturing

company. The company’s other key activities include manufacturing of electrical and electronic

equipment, services and information technology. The company operates primarily in India. It is

headquartered in Mumbai, India. The company recorded revenues of INR297, 129.9 million

(approximately $7,380.7 million) during the financial year ended March 2008 (FY2008), an

increase of 42.3% over 2007. The operating profit of the company was INR36, 237.6 million

(approximately $900.1 million) during FY2008, an increase of 14.5% over 2007. The net profit

was INR22, 312.5 million (approximately $554.2 million) in FY2008, a decrease of 4% over

2007.

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TRANSFORMERS

A transformer is a power converter that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF), or "voltage", in the secondary winding. This effect is called inductive coupling. If a load is connected to the secondary winding, current will flow in this winding, and electrical energy will be transferred from the primary circuit through the

transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (Vs) is in proportion to the primary voltage (Vp) and is given by the ratio of the number of turns in the secondary (Ns) to the number of turns in the primary (Np) as follows:

By appropriate selection of the ratio of turns, a transformer thus enables an alternating current (AC) voltage to be "stepped up" by making Ns greater than Np, or "stepped down" by making Ns less than Np. The windings are coils wound around a ferromagnetic core, air-core transformers being a notable exception. Transformers range in size from a thumbnail-sized

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coupling transformer hidden inside a stage microphone to huge units weighing hundreds of tons used in power stations, or to interconnect portions of power grids. All operate on the same basic principles, although the range of designs is wide.

While new technologies have eliminated the need for transformers in some electronic circuits, transformers are still found in nearly all electronic devices designed for household ("mains") voltage. Transformers are essential for high-voltage electric power transmission, which makes long-distance transmission economically practical.

BASIC PRINCIPLE

The transformer is based on two principles: first, that an electric current can produce a magnetic field (electromagnetism) and second that a changing magnetic field within a coil of wire induces a voltage across the ends of the coil (electromagnetic induction). Changing the current in the primary coil changes the magnetic flux that is developed. The changing magnetic flux induces a voltage in the secondary coil. An ideal transformer is shown in the adjacent figure. Current

passing through the primary coil creates a magnetic field. The primary and secondary coils are wrapped around a core of very high magnetic permeability, such as iron, so that most of the magnetic flux passes through both the primary and secondary coils. If a load is connected to the

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secondary winding, the load current and voltage will be in the directions indicated, given the primary current and voltage in the directions indicated (each will be alternating current in practice).

INDUCTION LAW

The voltage induced across the secondary coil may be calculated from Faraday's law of induction, which states that: where Vs is the instantaneous voltage, Ns is the number of turns in the secondary coil and Φ is the magnetic flux through one turn of the coil. If the turns of the coil are oriented perpendicularly to the magnetic field lines, the flux is the product of the magnetic flux density B and the area A through which it cuts. The area is constant, being equal to the cross-sectional area of the transformer core, whereas the magnetic field varies with time according to the excitation of the primary. Since the same magnetic flux passes through both the primary and secondary coils in an ideal transformer, the instantaneous voltage across the primary winding equals. Taking the ratio of the two equations for Vs and Vp gives the basic equation for stepping up or stepping down the voltage.

Np/Ns is known as the turns ratio, and is the primary functional characteristic of any transformer. In the case of step-up transformers, this may sometimes be stated as the reciprocal,

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Ns/Np. Turns ratio is commonly expressed as an irreducible fraction or ratio: for example, a transformer with primary and secondary windings of, respectively, 100 and 150 turns is said to have a turn’s ratio of 2:3 rather than 0.667 or 100:150.

IDEAL POWER EQUATION

The ideal transformer as a circuit element, If the secondary coil is attached to a load that allows current to flow, electrical power is transmitted from the primary circuit to the secondary circuit. Ideally, the transformer is perfectly efficient. All the incoming energy is transformed from the primary circuit to the magnetic field and into the secondary circuit. If this condition is met, the input electric power must equal the output power: giving the ideal transformer equation This formula is a reasonable approximation for most commercial built transformers today.

If the voltage is increased, then the current is decreased by the same factor. The impedance in one circuit is transformed by the square of the turns ratio. For example, if an impedance Zs is attached across the terminals of the secondary coil, it appears to the primary circuit to have an impedance of (Np/Ns)2Zs. This relationship is reciprocal, so that the impedance Zp of the primary circuit appears to the secondary to be (Ns/Np)2Zp.

PHYSICS OF MAGNETIZATION AND EMF

The ideal model not only neglects basic physics factors in terms of primary current required to establish a magnetic field in the core and the contribution to the field due to current in the secondary circuit but also assumes a core of negligible reluctance with two windings of zero resistance. When a voltage is applied to the primary winding, a small current flows, driving flux around the magnetic circuit of the core. The current required to create the flux is termed the magnetizing current. Since the ideal core has been assumed to have near-zero reluctance, the magnetizing current is negligible, although still required, to create the magnetic field. The changing magnetic field induces an electromotive force (EMF) across each winding. Since the ideal windings have no impedance, they have no associated voltage drop, and so the voltages VP and VS measured at the terminals of the transformer, are equal to the corresponding EMFs. The primary EMF, acting as it does in opposition to the primary voltage, is sometimes termed the "back EMF". This is in accordance with Lenz's law, which states that induction of EMF always opposes development of any such change in magnetic field.

BASIC TRANSFORMER PARAMETERS AND CONSTRUCTION

LEAKAGE FLUX

The ideal transformer model assumes that all flux generated by the primary winding links all the turns of every winding, including itself. In practice, some flux traverses paths that take it outside the windings. Such flux is termed leakage flux, and results in leakage inductance in series with the mutually coupled transformer windings. Leakage results in energy being alternately stored in and discharged from the magnetic fields with each cycle of the power supply. It is not directly a

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power loss (see "Stray losses" below), but results in inferior voltage regulation, causing the secondary voltage to not be directly proportional to the primary voltage, particularly under heavy load. Transformers are therefore normally designed to have very low leakage inductance. Nevertheless, it is impossible to eliminate all leakage flux because it plays an essential part in the operation of the transformer. The combined effect of the leakage flux and the electric field around the windings is what transfers energy from the primary to the secondary.

In some applications increased leakage is desired, and long magnetic paths, air gaps, or magnetic bypass shunts may deliberately be introduced in a transformer design to limit the short-circuit current it will supply. Leaky transformers may be used to supply loads that exhibit negative resistance, such as electric arcs, mercury vapor lamps, and neon signs or for safely handling loads that become periodically short-circuited such as electric arc welders. Air gaps are also used to keep a transformer from saturating, especially audio-frequency transformers in circuits that have a direct current component flowing through the windings. Leakage inductance is also helpful when transformers are operated in parallel. It can be shown that if the "per-unit" inductance of two transformers is the same (a typical value is 5%), they will automatically split power "correctly" (e.g. 500 kVA unit in parallel with 1,000 kVA unit, the larger one will carry twice the current).

EFFECT OF FREQUENCY

Transformer universal EMF equation

If the flux in the core is purely sinusoidal, the relationship for either winding between its rms voltage Erms of the winding, and the supply frequency f, number of turns N, core cross-sectional area a and peak magnetic flux density B is given by the universal EMF equation:

If the flux does not contain even harmonics the following equation can be used for half-cycle average voltage Eavg of any wave shape:

The time-derivative term in Faraday's Law shows that the flux in the core is the integral with respect to time of the applied voltage. Hypothetically an ideal transformer would work with direct-current excitation, with the core flux increasing linearly with time. In practice, the flux rises to the point where magnetic saturation of the core occurs, causing a large increase in the magnetizing current and overheating the transformer. All practical transformers must therefore operate with alternating (or pulsed direct) current.

The EMF of a transformer at a given flux density increases with frequency.[36] By operating at higher frequencies, transformers can be physically more compact because a given core is able to transfer more power without reaching saturation and fewer turns are needed to achieve the same impedance. However, properties such as core loss and conductor skin effect also increase with frequency. Aircraft and military equipment employ 400 Hz power supplies which reduce core and winding weight. Conversely, frequencies used for some railway electrification systems were much lower (e.g. 16.7 Hz and 25 Hz) than normal utility frequencies (50 – 60 Hz) for historical reasons concerned mainly with the limitations of early electric traction motors. As such, the transformers used to step down the high over-head line voltages (e.g. 15 kV) were much heavier

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for the same power rating than those designed only for the higher frequencies. Operation of a transformer at its designed voltage but at a higher frequency than intended will lead to reduced magnetizing current. At a lower frequency, the magnetizing current will increase. Operation of a transformer at other than its design frequency may require assessment of voltages, losses, and cooling to establish if safe operation is practical. For example, transformers may need to be equipped with "volts per hertz" over-excitation relays to protect the transformer from overvoltage at higher than rated frequency.

One example of state-of-the-art design is transformers used for electric multiple unit high speed trains, particularly those required to operate across the borders of countries using different electrical standards. The position of such transformers is restricted to being hung below the passenger compartment. They have to function at different frequencies (down to 16.7 Hz) and voltages (up to 25 kV) whilst handling the enhanced power requirements neededfor operating the trains at high speed. Knowledge of natural frequencies of transformer windings is necessary for the determination of winding transient response and switching surge voltages.

ENERGY LOSSES

An ideal transformer would have no energy losses, and would be 100% efficient. In practical transformers, energy is dissipated in the windings, core, and surrounding structures. Larger transformers are generally more efficient, and those rated for electricity distribution usually perform better than 98%.

Experimental transformers using superconducting windings achieve efficiencies of 99.85%.[47] The increase in efficiency can save considerable energy, and hence money, in a large heavily loaded transformer; the trade-off is in the additional initial and running cost of the superconducting design.

Losses in transformers (excluding associated circuitry) vary with load current, and may be expressed as "no-load" or "full-load" loss. Winding resistance dominates load losses, whereas hysteresis and eddy current losses contribute to over 99% of the no-load loss. The no-load loss can be significant, so that even an idle transformer constitutes a drain on the electrical supply and a running cost. Designing transformers for lower loss requires a larger core, good-quality silicon steel, or even amorphous steel for the core and thicker wire, increasing initial cost so that there is a trade-off between initial cost and running cost (also see energy efficient transformer).

Transformer losses are divided into losses in the windings, termed copper loss, and those in the magnetic circuit, termed iron loss. Losses in the transformer arise from:

WINDING RESISTANCE

Current flowing through the windings causes resistive heating of the conductors. At higher frequencies, skin effect and proximity effect create additional winding resistance and losses.

HYSTERESIS LOSSES

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Each time the magnetic field is reversed, a small amount of energy is lost due to hysteresis within the core. For a given core material, the loss is proportional to the frequency, and is a function of the peak flux density to which it is subjected.

EDDY CURRENTS

Ferromagnetic materials are also good conductors and a core made from such a material also constitutes a single short-circuited turn throughout its entire length. Eddy currents therefore circulate within the core in a plane normal to the flux, and are responsible for resistive heating of the core material. The eddy current loss is a complex function of the square of supply frequency and Inverse Square of the material thickness. Eddy current losses can be reduced by making the core of a stack of plates electrically insulated from each other, rather than a solid block; all transformers operating at low frequencies use laminated or similar cores.

MAGNETOSTRICTION

Magnetic flux in a ferromagnetic material, such as the core, causes it to physically expand and contract slightly with each cycle of the magnetic field, an effect known as magnetostriction. This produces the buzzing sound commonly associated with transformers that can cause losses due to frictional heating. This buzzing is particularly familiar from low-frequency (50 Hz or 60 Hz) mains hum, and high-frequency (15,734 Hz (NTSC) or 15,625 Hz (PAL)) CRT noise.

MECHANICAL LOSSES

In addition to magnetostriction, the alternating magnetic field causes fluctuating forces between the primary and secondary windings. These incite vibrations within nearby metalwork, adding to the buzzing noise and consuming a small amount of power.

STRAY LOSSES

Leakage inductance is by itself largely lossless, since energy supplied to its magnetic fields is returned to the supply with the next half-cycle. However, any leakage flux that intercepts nearby conductive materials such as the transformer's support structure will give rise to eddy currents and be converted to heat. There are also radiative losses due to the oscillating magnetic field but these are usually small.

TRANSFORMER OIL

Transformer oil or insulating oil is usually a highly-refined mineral oil that is stable at high temperatures and has excellent electrical insulating properties. It is used in oil-filled transformers, some types of high voltage capacitors, fluorescent lamp ballasts, and some types of

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high voltage switches and circuit breakers. Its functions are to insulate, suppress corona and arcing, and to serve as a coolant.

EXPLANATION

The oil helps cool the transformer. Because it also provides part of the electrical insulation between internal live parts, transformer oil must remain stable at high temperatures for an extended period. To improve cooling of large power transformers, the oil-filled tank may have external radiators through which the oil circulates by natural convection. Very large or high-power transformers (with capacities of thousands of kVA) may also have cooling fans, oil pumps, and even oil-to-water heat exchangers. Large, high voltage transformers undergo prolonged drying processes, using electrical self-heating, the application of a vacuum, or both to ensure that the transformer is completely free of water vapor before the cooling oil is introduced. This helps prevent corona formation and subsequent electrical breakdown under load.

Oil filled transformers with a conservator (an oil tank above the transformer) may have a gas detector relay (Buchholz relay). These safety devices detect the build up of gas inside the transformer due to corona discharge, overheating, or an internal electric arc. On a slow accumulation of gas, or rapid pressure rise, these devices can trip a protective circuit breaker to remove power from the transformer. Transformers without conservators are usually equipped with sudden pressure relays, which perform a similar function as the Buchholz relay. The flash point (min) and pour point (max) are 140 °C and −6 °C respectively. The dielectric strength of new untreated oil is 12 MV/m (RMS) and after treatment it should be >24 MV/m (RMS).Large transformers for indoor use must either be of the dry type, that is, containing no liquid, or use a less-flammable liquid.

Polychlorinated biphenyls (PCBs)

Well into the 1970s, polychlorinated biphenyls (PCB)s were often used as a dielectric fluid since they are not flammable. PCBs do not break down when released into the environment and accumulate in the tissues of plants and animals, where they can have hormone-like effects. When burned, PCBs can form highly toxic products, such as chlorinated dioxins and chlorinated dibenzofurans. Starting in the early 1970s, production and

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new uses of PCBs have been banned due to concerns about the accumulation of PCBs and toxicity of their byproducts. In many countries significant programs are in place to reclaim and safely destroy PCB contaminated equipment. Polychlorinated biphenyls were banned in 1979 in the US. Since PCB and transformer oil are miscible in all proportions, and since sometimes the same equipment (drums, pumps, hoses, and so on) was used for either type of liquid, contamination of oil-filled transformers is possible. Under present regulations, concentrations of PCBs exceeding 5 parts per million can cause an oil to be classified as hazardous waste in California (California Code of Regulations, Title 22, section 66261). Throughout the US, PCBs are regulated under the Toxic Substances Control Act. As a consequence, field and laboratory testing for PCB contamination is a common practice. Common brand names for PCB liquids include "Askarel", "Inerteen", "Aroclor" and many others.

Today, non-toxic, stable silicon-based or fluorinated hydrocarbons are used, where the added expense of a fire-resistant liquid offsets additional building cost for a transformer vault. Combustion-resistant vegetable oil-based dielectric coolants and synthetic pentaerythritol tetra fatty acid (C7, C8) esters are also becoming increasingly common as alternatives to naphthenic mineral oil. Esters are non-toxic to aquatic life, readily biodegradable, and have a lower volatility and a higher flash points than mineral oil.

TESTING AND OIL QUALITY

Transformer oils are subject to electrical and mechanical stresses while a transformer is in operation. In addition there is contamination caused by chemical interactions with windings and other solid insulation, catalyzed by high operating temperature. As a result the original chemical properties of transformer oil changes gradually, rendering it ineffective for its intended purpose after many years. Hence this oil has to be periodically tested to ascertain its basic electrical properties, make sure it is suitable for further use, and ascertain the need for maintenance activities like filtration/regeneration. These tests can be divided into:

1. Dissolved gas analysis

2. Furan analysis

3. PCB analysis

4. General electrical & physical tests:

Color & Appearance

Breakdown Voltage

Water Content

Acidity (Neutralization Value)

Dielectric Dissipation Factor

Resistivity

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Sediments & Sludge

Interfacial Tension

Flash Point

Pour Point

Density

Kinematic Viscosity

The details of conducting these tests are available in standards released by IEC, ASTM, IS, BS, and testing can be done by any of the methods. The Furan and DGA tests are specifically not for determining the quality of transformer oil, but for determining any abnormalities in the internal windings of the transformer or the paper insulation of the transformer, which cannot be otherwise detected without a complete overhaul of the transformer. Suggested intervals for this test are:

• General and physical tests - bi-yearly

• Dissolved gas analysis - yearly

• Furan testing - once every 2 years, subject to the transformer being in operation for min 5 years.

ON-SITE TESTING

Some transformer oil tests can be carried out in the field, using portable test apparatus. Other tests, such as dissolved gas, normally require a sample to be sent to a laboratory. Electronic on-line dissolved gas detectors can be connected to important or distressed transformers to continually monitor gas generation trends. To determine the insulating property of the dielectric oil, an oil sample is taken from the device under test, and its breakdown voltage is measured on-site according the following test sequence:

• In the vessel, two standard-compliant test electrodes with a typical clearance of 2.5 mm are surrounded by the insulating oil.

• During the test, a test voltage is applied to the electrodes. The test voltage is continuously increased up to the breakdown voltage with a constant slew rate of e.g. 2 kV/s.

• Breakdown occurs in an electric arc, leading to a collapse of the test voltage.

• Immediately after ignition of the arc, the test voltage is switched off automatically.

• Ultra fast switch off is crucial, as the energy that is brought into the oil and is burning it during the breakdown, must be limited to keep the additional pollution by carbonisation as low as possible.

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• The root mean square value of the test voltage is measured at the very instant of the breakdown and is reported as the breakdown voltage.

• After the test is completed, the insulating oil is stirred automatically and the test sequence is performed repeatedly.

• The resulting breakdown voltage is calculated as mean value of the individual measurements.

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ELECTRIC POWER DISTRIBUTION

Electricity distribution is the final stage in the delivery of electricity to end users. A distribution system's network carries electricity from the transmission system and delivers it to consumers. Typically, the network would include medium-voltage (less than 50 kV) power lines, substations and pole-mounted transformers, low-voltage (less than 1 kV) distribution wiring and Sometimes meters.

HISTORY

In the early days of electricity distribution, direct current (DC) generators were connected to loads at the same voltage. The generation, transmission and loads had to be of the same voltage because there was no way of changing DC voltage levels, other than inefficient motor-generator sets. Low DC voltages were used (on the order of 100 volts) since that was a practical voltage for incandescent lamps, which were the primary electrical load. Low voltage also required less insulation for safe distribution within buildings. The losses in a cable are proportional to the square of the current, the length of the cable, and the resistivity of the material, and are inversely proportional to cross-sectional area. Early transmission networks used copper cable, which is one of the best economically feasible conductors for this application. To reduce the current and copper required for a given quantity of power transmitted would require a higher transmission voltage, but no efficient method existed to change the voltage of DC power circuits. To keep losses to an economically practical level the Edison DC system needed thick cables and local generators. Early DC generating plants needed to be within about 1.5 miles (2.4 km) of the farthest customer to avoid excessively large and expensive conductors.

INTRODUCTION OF ALTERNATING CURRENT

The competition between the direct current (DC) of Thomas Edison and the alternating current (AC) of Nikola Tesla and George Westinghouse was known as the War of Currents. At the conclusion of their campaigning, AC became the dominant form of transmission of power. Power transformers, installed at power stations, could be used to raise the voltage from the

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generators, and transformers at local substations could reduce voltage to supply loads. Increasing the voltage reduced the current in the transmission and distribution lines and hence the size of conductors and distribution losses. This made it more economical to distribute power over long distances. Generators (such as hydroelectric sites) could be located far from the loads. In North America, early distribution systems used a voltage of 2.2 kV corner-grounded delta. Over time, this was gradually increased to2.4 kV. As cities grew, most 2.4 kV systems were upgraded to 2.4/4.16 kV, three-phase systems. In three phase networks that permit connections between phase and neutral, both the phase-to-phase voltage (4160, in this example) and the phase-to-neutral voltage are given; if only one value is shown, the network does not serve single-phase loads connected phase-to-neutral. Some city and suburban distribution systems continue to use this range of voltages, but most have been converted to 7200/12470Y, 7620/13200Y, 14400/24940Y, and 19920/34500Y. European systems used 3.3 kV to ground, in support of the 220/380Y volt power systems used in those countries. In the UK, urban systems progressed to 6.6 kV and then 11 kV (phase to phase), the most common distribution voltage. North American and European power distribution systems also differ in that North American systems tend to have a greater number of low-voltage step-down transformers located close to customers' premises. For example, in the US a pole-mounted transformer in a suburban setting may supply 7-8 houses, whereas in the UK a typical urban or suburban low-voltage substation would normally be rated between 315 kVA and 1 MVA and supply a whole neighbourhood. This is because the higher voltage used in Europe (415 V vs 230 V) may be carried over a greater distance with acceptable power loss. An advantage of the North American setup is that failure or maintenance on a single transformer will only affect a few customers. Advantages of the UK setup are that the transformers may be fewer, larger and more efficient, and due to diversity there need be less spare capacity in the transformers, reducing power wastage. In North American city areas with many customers per unit area, network distribution will be used, with multiple transformers and low-voltage buses interconnected over several city blocks. Rural electrification systems, in contrast to urban systems, tend to use higher voltages because of the longer distances covered by those distribution lines (see Rural Electrification Administration). 7.2, 12.47, 25, and 34.5 Kv distribution is common in the United States; 11 kV and 33 kV are common in the UK, New Zealand and Australia; 11 kV and 22 kV are common in South Africa. Other voltages are occasionally used. In New Zealand, Australia, Saskatchewan, Canada, and South Africa, single wire earth return systems (SWER) are used to electrify remote rural areas. While power electronics now allow for conversion between DC voltage levels, AC is preferred in distribution due to the economy, efficiency and reliability of transformers. High-voltage DC is used for transmission of large blocks of power over long distances, or for interconnecting adjacent AC networks, but not for distribution to customers. Electric power is normally generated at 11-25kV in a power station. To transmit over long distances, it is then stepped-up to 400kV, 220kV or 132kV as necessary. Power is carried through a transmission network of high voltage lines. Usually, these lines run into hundreds of kilometers and deliver the power into a common power pool called the grid. The grid is connected to load centers (cities) through a sub-transmission network of normally 33kV (or sometimes 66kV) lines. These lines terminate into a 33kV (or 66kV) substation, where the voltage is stepped-down to 11kV for power distribution to load points through a distribution network of lines at 11kV and lower.

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MODERN DISTRIBUTION SYSTEMS

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Electric distribution substations transform power from transmission voltage to the lower voltage used for local distribution to homes and businesses. The modern distribution system begins as the primary circuit leaves the sub-station and ends as the secondary service enters the customer's meter socket. Distribution circuits serve many customers. The voltage used is appropriate for the shorter distance and varies from 2,300 to about 35,000 volts depending on utility standard practice, distance, and load to be served. Distribution circuits are fed from a transformer located in an electrical substation, where the voltage is reduced from the high values used for power transmission. Conductors for distribution may be carried on overhead pole lines, or in densely-populated areas where they are buried underground. Urban and suburban distribution is done with three-phase systems to serve residential, commercial, and industrial loads. Distribution in rural areas may be only single-phase if it is not economical to install three-phase power for relatively few and small customers. Only large consumers are fed directly from distribution voltages; most utility customers are connected to a transformer, which reduces the distribution voltage to the relatively low voltage used by lighting and interior wiring systems. The transformer may be pole-mounted or set on the ground in a protective enclosure. In rural areas a pole-mount transformer may serve only one customer, but in more built-up areas multiple customers may be connected. In very dense city areas, a secondary network may be formed with many transformers feeding into a common bus at the utilization voltage. Each customer has an "electrical service" or "service drop" connection and a meter for billing. (Some very small loads, such as yard lights, may be too small to meter and so are charged only a monthly rate.) A ground connection to local earth is normally provided for the customer's system as well as for the equipment owned by the utility. The purpose of connecting the customer's system to ground is to limit the voltage that may develop if high voltage conductors fall on the lower-voltage conductors, or if a failure occurs within a distribution transformer. If all conductive objects are bonded to the same earth grounding system, the risk of electric shock is minimized. However, multiple connections between the utility ground and customer ground can lead to stray voltage problems; customer piping, swimming pools or other equipment may develop objectionable voltages. These problems may be difficult to resolve since they often originate from places other than the customer's premises.

INTERNATIONAL DIFFERENCES

In many areas, "delta" three phase service is common. Delta service has no distributed neutral wire and is therefore less expensive. In North America and Latin America, three phase service is often a Y (wye) in which the neutral is directly connected to the center of the generator rotor. The neutral provides a low-resistance metallic return to the distribution transformer. Wye service is recognizable when a line has four conductors, one of which is lightly insulated. Three-phase wye service is excellent for motors and heavy power use. Many areas in the world use single-phase 220 V or 230 V residential and light industrial service. In this system, the high voltage distribution network supplies a few substations per area, and the 230 V power from each substation is directly distributed. A live (hot) wire and neutral are connected to the building from one phase of three phase service. Single-phase distribution is used where motor loads are small.

North America

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In the U.S. and parts of Canada and other countries, split phase service is the most common. Split phase provides both 120 V and 240 V service with only three wires. The house voltages are provided by local transformers. The neutral is directly connected to the three-phase neutral. Socket voltages are only 120 V, but 240 V is available for heavy appliances because the two halves of a phase oppose each other.

Europe

In Europe, electricity is normally distributed for industry and domestic use by the three-phase, four wire system. This gives a three-phase voltage of 400 volts and a single-phase voltage of 230 volts. For industrial customers, 3-phase 690 / 400 volt is also available.

Japan

Japan has a large number of small industrial manufacturers, and therefore supplies standard low-voltage three phase-services in many suburbs. Also, Japan normally supplies residential service as two phases of a three phase service, with a neutral. These work well for both lighting and motors.

Rural services

Rural services normally try to minimize the number of poles and wires. Single-wire earth return (SWER) is the least expensive, with one wire. It uses high voltages, which in turn permit use of galvanized steel wire. The strong steel wire permits inexpensive wide pole spacings. Other areas use high voltage split-phase or three phase service at higher cost.

Metering

Electricity meters use different metering equations depending on the form of electrical service. Since the math differs from service to service, the number of conductors and sensors in the meters also vary.

Terms

Besides referring to the physical wiring, the term electrical service also refers in an abstract sense to the provision of electricity to a building.

DISTRIBUTION NETWORK CONFIGURATIONS

Distribution networks are typically of two types, radial or interconnected (see spot network). A radial network leaves the station and passes through the network area with no normal connection to any other supply. This is typical of long rural lines with isolated load areas. An interconnected network is generally found in more urban areas and will have multiple connections to other points of supply. These points of connection are normally open but allow various configurations by the operating utility by closing and opening switches. Operation of these switches may be by remote control from a control center or by a lineman. The benefit of the interconnected model is that in the event of a fault or required maintenance a small area of network can be isolated and

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the remainder kept on supply. Within these networks there may be a mix of overhead line construction utilizing traditional utility poles and wires and, increasingly, underground construction with cables and indoor or cabinet substations. However, underground distribution is significantly more expensive than overhead construction. In part to reduce this cost, underground power lines are sometimes co-located with other utility lines in what are called common utility ducts. Distribution feeders emanating from a substation are generally controlled by a circuit breaker which will open when a fault is detected. Automatic circuit reclosers may be installed to further segregate the feeder thus minimizing the impact of faults.

Long feeders experience voltage drop requiring capacitors or voltage regulators to be installed. Characteristics of the supply given to customers are generally mandated by contract between the supplier and customer. Variables of the supply include:

• AC or DC - Virtually all public electricity supplies are AC today. Users of large amounts of DC power such as some electric railways, telephone exchanges and industrial processes such as aluminum smelting usually either operate their own or have adjacent dedicated generating equipment, or use rectifiers to derive DC from the public AC supply

• Nominal voltage and tolerance (for example, +/- 5 per cent)

• Frequency, commonly 50 or 60 Hz, 16.6 Hz and 25 Hz for some railways and, in a few older industrial and mining locations, 25 Hz.

• Phase configuration (single-phase, polyphase including two-phase and three-phase)

• Maximum demand (usually measured as the largest amount of power delivered within a 15 or 30 minute period during a billing period)

• Load factor, expressed as a ratio of average load to peak load over a period of time. Load factor indicates the degree of effective utilization of equipment (and capital investment) of distribution line or system.

• Power factor of connected load

• Earthing systems - TT, TN-S, TN-C-S or TN-C

• Prospective short circuit current

• Maximum level and frequency of occurrence of transients

DISTRIBUTION INDUSTRY

Traditionally the electricity industry has been a publicly owned institution but starting in the 1970s nations began the process of deregulation and privatization, leading to electricity markets. A major focus of these was the elimination of the former so called natural monopoly of generation, transmission, and distribution. As a consequence, electricity has become more of a commodity. The separation has also led to the development of new terminology to describe the business units (e.g., line company, wires business and network company).

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ELECTRIC POWER TRANSMISSION

Electric-power transmission is the bulk transfer of electrical energy, from generating power plants to electrical substations located near demand centers. This is distinct from the local wiring between high-voltage substations and customers, which is typically referred to as electric power distribution. Transmission lines, when interconnected with each other, become transmission networks. In the US, these are typically referred to as "power grids" or just "the grid." In the UK, the network is known as the "National Grid." North America has three major grids, the Western Interconnection, the Eastern Interconnection and the Electric Reliability Council of Texas (ERCOT) grid, often referred to as the Western System, the Eastern System and the Texas System. Historically, transmission and distribution lines were owned by the same company, but starting in the 1990s, many countries have liberalized the regulation of the electricity market in ways that have led to the separation of the electricity transmission business from the distribution business.

Most transmission lines use high-voltage three-phase alternating current (AC), although single phase AC is sometimes used in railway electrification systems. High-voltage direct-current (HVDC) technology is used for greater efficiency in very long distances (typically hundreds of miles (kilometres), or in submarine power cables (typically longer than 30 miles (50 km). HVDC links are also used to stabilize against control problems in large power distribution networks where sudden new loads or blackouts in one part of a network can otherwise result in synchronization problems and cascading failures. Diagram of an electric power system; transmission system is in blue Electricity is transmitted at high voltages (110 kV or above) to reduce the energy lost in long-distance transmission. Power is usually transmitted through overhead power lines. Underground power transmission has a significantly higher cost and greater operational limitations but is sometimes used in urban areas or sensitive locations.

A key limitation in the distribution of electric power is that, with minor exceptions, electrical energy cannot be stored, and therefore must be generated as needed. A sophisticated control system is required to ensure electric generation very closely matches the demand. If the demand for power exceeds the supply, generation plants and transmission equipment can shut down which, in the worst cases, can lead to a major regional blackout, such as occurred in the US Northeast blackouts of 1965, 1977, 2003, and in 1996 and 2011. To reduce the risk of such failures, electric transmission networks are interconnected into regional, national or continental wide networks thereby providing multiple redundant alternative routes for power to flow should (weather or equipment) failures occur. Much analysis is done by transmission companies to determine the maximum reliable capacity of each line (ordinarily less than its physical or thermal limit) to ensure spare capacity is available should there be any such failure in another part of the network.

OVERHEAD TRANSMISSION

The contiguous United States power transmission grid consists of 300,000 km of lines operated by 500 companies’ 3-phase high voltage lines in Washington State High-voltage overhead

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Conductors are not covered by insulation. The conductor material is nearly always an aluminium alloy, made into several strands and possibly reinforced with steel strands. Copper was sometimes used for overhead transmission but aluminium is lighter, yields only marginally reduced performance, and costs much less. Overhead conductors are a commodity supplied by several companies worldwide. Improved conductor material and shapes are regularly used to allow increased capacity and modernize transmission circuits. Conductor sizes range with varying resistance and current-carrying capacity. Thicker wires would lead to a relatively small increase in capacity due to the skin effect that causes most of the current to flow close to the surface of the wire. Because of this current limitation, multiple parallel cables (called bundle conductors) are used when higher capacity is needed. Bundle conductors are also used at high voltages to reduce energy loss caused by corona discharge.

Today, transmission-level voltages are usually considered to be 110 kV and above. Lower voltages such as 66 kV and 33 kV are usually considered subtransmission voltages but are occasionally used on long lines with aluminum light loads. Voltages less than 33 kV are usually used for distribution. Voltages above 230 kV are considered extra high voltage and require different designs compared to equipment used at lower voltages. Since overhead transmission wires depend on air for insulation, design of these lines requires minimum clearances to be observed to maintain safety. Adverse weather conditions of high wind and low temperatures can lead to power outages. Wind speeds as low as 23 knots (43 km/h) can permit conductors to encroach operating clearances, resulting in a flashover and loss of supply. Oscillatory motion of the physical line can be termed gallop or flutter depending on the frequency and amplitude of oscillation.

UNDERGROUND TRANSMISSION

Electric power can also be transmitted by underground power cables instead of overhead power lines. Underground cables take up less right-of-way than overhead lines, have lower visibility, and are less affected by bad weather. However, costs of insulated cable and excavation are much higher than overhead construction. Faults in buried transmission lines take longer to locate and repair. Underground lines are strictly limited by their thermal capacity, which permits fewer overloads or re-rating than overhead lines. Long underground cables have significant capacitance, which may reduce their ability to provide useful power to loads.

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ELECTRICAL GRID

Voltages and depictions of electrical lines are typical for Germany and other European systems. An electrical grid is an interconnected network for delivering electricity from suppliers to consumers. It consists of three main components:

1) power stations that produce electricity from combustible fuels (coal, natural gas, biomass) or non-combustible fuels (wind, solar, nuclear, hydro power);

2) Transmission lines that carry electricity from power plants to demand centers; and

3) transformers that reduce voltage so distribution lines carry power for final delivery.

In the power industry, electrical grid is a term used for an electricity network which includes the following three distinct operations:

1. Electricity generation - Generating plants are usually located near a source of water, and away from heavily populated areas. They are usually quite large to take advantage of the economies of scale. The electric power which is generated is stepped up to a higher voltage-at which it connects to the transmission network.

2. Electric power transmission – The transmission network will move (wheel) the power long distances–often across state lines, and sometimes across international boundaries, until it reaches its wholesale customer (usually the company that owns the local distribution network).

3. Electric power distribution - Upon arrival at the substation, the power will be stepped down in voltage—from a transmission level voltage to a distribution level voltage. As it exits the substation, it enters the distribution wiring. Finally, upon arrival at the service location, the power is stepped down again from the distribution voltage to the required service voltage(s).

TERM

The term grid usually refers to a network, and should not be taken to imply a particular physical layout or breadth. Grid may also be used to refer to an entire continent's electrical network, a regional transmission network or may be used to describe a subnetwork such as a local utility's transmission grid or distribution grid.

HISTORY

Since its inception in the Industrial Age, the electrical grid has evolved from an insular system that serviced a particular geographic area to a wider, expansive network that incorporated multiple areas. At one point, all energy was produced near the device or service requiring that energy. In the early 19th century, electricity was a novel invention that competed with steam, hydraulics, direct heating and cooling, light, and most notably gas. During this period, gas production and delivery had become the first centralized element in the modern energy industry.

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It was first produced on customer’s premises but later evolved into large gasifiers that enjoyed economies of scale. Virtually every city in the U.S. and Europe had town gas piped through their municipalities as it was a dominant form of household energy use. By the mid-19th century, electric arc lighting soon became advantageous compared to volatile gas lamps since gas lamps produced poor light, tremendous wasted heat which made rooms hot and smoky, and noxious elements in the form of hydrogen and carbon monoxide. Modeling after the gas lighting industry, Thomas Edison invented the first electric utility system which supplied energy through virtual mains to light filtration as opposed to gas burners. With this, electric utilities also took advantage of economies of scale and moved to centralized power generation, distribution, and system management.

During the 20th century, institutional arrangement of electric utilities changed. At the beginning, electric utilities were isolated systems without connection to other utilities and serviced a specific service territory. In the 1920s, utilities joined together establishing a wider utility grid as joint-operations saw the benefits of sharing peak load coverage and backup power. Also, electric utilities were easily financed by Wall Street private investors who backed many of their ventures. In 1934, with the passage of the Public Utility Holding Company Act (USA), electric utilities were recognized as public goods of importance along with gas, water, and telephone companies and thereby were given outlined restrictions and regulatory oversight of their operations. This ushered in the Golden Age of Regulation for more than 60 years. However, with the successful deregulation of airlines and telecommunication industries in late 1970s, the Energy Policy Act (EPAct) of 1992 advocated deregulation of electric utilities by creating wholesale electric markets. It required transmission line owners to allow electric generation companies open access to their network.

DEREGULATION

With deregulation, a more complex environment occurred as opposed to the traditional vertically-integrated monopoly that oversees the entire grid’s operations. Newer participants entered the market including Independent Power Providers (IPPs) who decided and constructed the new facility; Transmission Companies (TRANSCOs) who constructed and owned the transmission equipment; retailers who signed up end-use customers, procured their electric service, and billed them; integrated energy companies (combined IPPs and retailers); and Independent System Operation (ISO) who managed the grid being indifferent to market outcomes. Also, day-to-day to long term operations altered. Infrastructure additions which were long-term planning now became an investment analysis with IPPs that decided construction of a new power plant under economic considerations (taxes, labor and material costs) and ability to obtain financing. Load and supply management that fell under mid-term planning became risk management as private utilities had to manage a portfolio of end customers and assets with the company’s risk preference. Day-ahead scheduling and real time grid management in the short-term planning which involves forecasting demand and dispatch schedule became asset management as power plants and grid equipment was assets to be scheduled and dispatched. Here, the ISO sets dispatch schedule at the market clearing price where the supply bids of generating units equilibrated with demand bids of retailers.

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Many engineers argue the unfortunate disadvantages that stem from deregulation. Where under regulated monopolies, long distance energy lines were used for emergencies as backup in case of generation outages, now, particularly in North America, the majority of domestic generation is sold over ever-increasing distances on the wholesale market before delivery to customers. Consequently, the power grid witnesses fluctuating power flows that impact system stability and reliability. To reduce system failure, the power flow of a transmission line must operate below the transmission line’s capacity. Yet now, companies are continually operating near capacity.

Additionally, as utilities exchange power to other utilities, power flows along all paths of connection. Therefore, any change in one point of generation and transmission affects the load on all other points. Oftentimes, this is unanticipated and uncontrolled. Usually, a longer line’s capacity is less than a shorter line’s capacity. If not, power-supply instability occurs resulting in transmission lines that break or sag. Such phase and voltage fluctuations cause system interruptions as witnessed in the Northeast Blackout of 1965 (which involved a circuit breaker to trip) and 2003 (which involved a sagging line on a tree that rippled in magnitude). Furthermore, IPPs add new generating units at random locations determined by economics that extend the distance to main consuming areas adversely affecting power supply. Also, utilities, because of competitive information needs, do not publicize needed data to predict and react to system stress such as with energy flows and blackout statistics. Overall, the economics of the electrical grid do not align sufficiently with the physics of the grid. Experts advocate for fundamental changes to avoid serious consequences in the near future.

REDUNDANCY AND DEFINING "GRID"

A town is only said to have achieved grid connection when it is connected to several redundant sources, generally involving long-distance transmission. This redundancy is limited. Existing national or regional grids simply provide the interconnection of facilities to utilize whatever redundancy is available. The exact stage of development at which the supply structure becomes a grid is arbitrary. Similarly, the term national grid is something of an anachronism in many parts of the world, as transmission cables now frequently cross national boundaries. The terms distribution grid for local connections and transmission grid for long-distance transmissions are therefore preferred, but national grid is often still used for the overall structure.

AGING INFRASTRUCTURE

Despite the novel institutional arrangements and network designs of the electrical grid, its power delivery infrastructures suffer aging across the developed world. Four contributing factors to the current state of the electric grid and its consequences include:

1. Aging power equipment – older equipment have higher failure rates, leading to customer interruption rates affecting the economy and society; also, older assets and facilities lead to higher inspection maintenance costs and further repair/restoration costs.

2. Obsolete system layout – older areas require serious additional substation sites and rights-of-way that cannot be obtained in current area and are forced to use existing, insufficient facilities.

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3. Outdated engineering – traditional tools for power delivery planning and engineering are ineffective in addressing current problems of aged equipment, obsolete system layouts, and modern deregulated loading levels

4. Old cultural value – planning, engineering, operating of system using concepts and procedures that worked in vertically integrated industry exacerbate the problem under a deregulated industry

MODERN TRENDS

As the 21st century progresses, the electric utility industry seeks to take advantage of novel approaches to meet growing energy demand. Utilities are under pressure to evolve their classic topologies to accommodate distributed generation. As generation becomes more common from rooftop solar and wind generators, the differences between distribution and transmission grids will continue to blur. Also, demand response is a grid management technique where retail or wholesale customers are requested either electronically or manually to reduce their load. Currently, transmission grid operators use demand response to request load reduction from major energy users such as industrial plants.

With everything interconnected, and open competition occurring in a free market economy, it starts to make sense to allow and even encourage distributed generation (DG). Smaller generators, usually not owned by the utility, can be brought on-line to help supply the need for power. The smaller generation facility might be a home-owner with excess power from their solar panel or wind turbine. It might be a small office with a diesel generator. These resources can be brought on-line either at the utility's behest or by owner of the generation in an effort to sell electricity. Many small generators are allowed to sell electricity back to the grid for the same price they would pay to buy it. Furthermore, numerous efforts are underway to develop a "smart grid". In the U.S., the Energy Policy Act of 2005 and Title XIII of the Energy Independence and Security Act of 2007 are providing funding to encourage smart grid development. The hope is to enable utilities to better predict their needs, and in some cases involve consumers in some form of time-of-use based tariff. Funds have also been allocated to develop more robust energy control technologies. Decentralization of the power transmission distribution system is vital to the success and reliability of this system. Currently the system is reliant upon relatively few generation stations. This makes current systems susceptible to impact from failures not within said area. Micro grids would have local power generation, and allow smaller grid areas to be separated from the rest of the grid if a failure were to occur. Furthermore, micro grid systems could help power each other if needed. Generation within a micro grid could be a downsized industrial generator or several smaller systems such as photo-voltaic systems, or wind generation. When combined with Smart Grid technology, electricity could be better controlled and distributed, and more efficient. Conversely, various planned and proposed systems to dramatically increase transmission capacity are known as super, or mega grids. The promised benefits include enabling the renewable energy industry to sell electricity to distant markets, the ability to increase usage of intermittent energy sources by balancing them across vast geological regions, and the removal of congestion that prevents electricity markets from flourishing. Local opposition to siting new lines and the significant cost of these projects are major obstacles to super grids.

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FUTURE TRENDS

As deregulation continues further, utilities are driven to sell their assets as the energy market follows in line with the gas market in use of the futures and spot markets and other financial arrangements. Even globalization with foreign purchases is taking place. Recently, U.K’s National Grid, the largest private electric utility in the world, bought New England’s electric system for $3.2 billion. See the SEC filing dated March 15, 2000 Here Also, Scottish Power purchased Pacific Energy for $12.8 billion. Domestically, local electric and gas firms begin to merge operations as they see advantage of joint affiliation especially with the reduced cost of joint-metering. Technological advances will take place in the competitive wholesale electric markets such examples already being utilized include fuel cells used in space flight, aero derivative gas turbines used in jet aircrafts, solar engineering and photovoltaic systems, off-shore wind farms, and the communication advances spawned by the digital world particularly with micro processing which aids in monitoring and dispatching.

Electricity is expected to see growing demand in the future. The Information Revolution is highly reliant on electric power. Other growth areas include emerging new electricity-exclusive technologies, developments in space conditioning, industrial process, and transportation (for example hybrid vehicles, locomotives).

EMERGING SMART GRID

As mentioned above, the electrical grid is expected to evolve to a new grid paradigm--smart grid, an enhancement of the 20th century electrical grid. The traditional electrical grids are generally used to carry power from a few central generators to a large number of users or customers. In contrast, the new emerging smart grid uses two-way flows of electricity and information to create an automated and distributed advanced energy delivery network. Many research projects have been conducted to explore the concept of smart grid. According to a newest survey on smart grid, the research is mainly focused on three systems in smart grid- the infrastructure system, the management system, and the protection system. The infrastructure system is the energy, information, and communication infrastructure underlying of the smart grid supports

1) advanced electricity generation, delivery, and consumption; 2) advanced information metering, monitoring, and management; and 3) advanced communication technologies. In the transition from the conventional power grid to smart grid, we will replace a physical infrastructure with a digital one. The needs and changes present the power industry with one of the biggest challenges it has ever faced.

The management system is the subsystem in smart grid that provides advanced management and control services. Most of the existing works aim to improve energy efficiency, demand profile, utility, cost, and emission, based on the infrastructure by using optimization, machine learning, and game theory. Within the advanced infrastructure framework of smart grid, more and more new management services and applications are expected to emerge and eventually revolutionize consumers' daily lives. The protection system is the subsystem in smart grid that provides advanced grid reliability analysis, failure protection, and security and privacy protection

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services. We must note that the advanced infrastructure used in smart grid on one hand empowers us to realize more powerful mechanisms to defend against attacks and handle failures, but on the other hand, opens up much new vulnerability. For example, NIST pointed out that the major benefit provided by smart grid, the ability to get richer data to and from customer smart meters and other electric devices, is also its Achilles' heel from a privacy viewpoint. The obvious privacy concern is that the energy use information stored at the meter acts as an information rich side channel. This information can be mined and retrieved by interested parties to reveal personal information such as individual's habits, behaviors, activities, and even beliefs.

NETWORKED ISLAND-ABLE MICROGRIDS

As the electricity grid becomes increasingly vulnerable to faults from equipment failure or willful attack, the risk of a major national scale grid failure is rising. Physicist Amory Lovins has said that following hundreds of blackouts in 2005, Cuba reorganized its electricity transmission system into networked micro grids and cut the occurrence of blackouts to zero within two years, limiting damage even after two hurricanes. Networked island-able micro grids describes Lovins’ vision where energy is generated locally from solar power, wind power and other resources and used by super-efficient buildings. When each building, or neighborhood, is generating its own power, with links to other "islands" of power, the security of the entire network is greatly enhanced. This type of setup isn’t immune to large scale power failures, such as the large scale outage Cuba experienced in September 2012. This raises doubts as to if this setup will make any reliability improvements to the already reliable electrical grids such as those in Australia and the United States

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JACK (DEVICE FOR LIFTING TRANSFORMERS)

A jack is a mechanical device used as a lifting device to lift heavy loads or apply great forces. Jacks employ a screw thread or hydraulic cylinder to apply very high linear forces.

A mechanical jack is a device which lifts heavy equipment. The most common form is a car jack, floor jack or garage jack which lifts vehicles so that maintenance can be performed. More powerful jacks use hydraulic power to provide more lift over greater distances. Mechanical jacks are usually rated for a maximum lifting capacity (for example, 1.5 tons or 3 tons).

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JACKSCREW

VEHICLE

Jackscrews are integral to the Scissor Jack, one of the simplest kinds of car jacks still used. Scissor car jacks usually use mechanical advantage to allow a human to lift a vehicle by manual force alone. The jack shown at the right is made for a modern vehicle and the notch fits into a hard point on a unibody. Earlier versions have a platform to lift on the vehicles' frame or axle.

HOUSE JACK

A house jack, also called a screw jack is a mechanical device primarily used to lift houses from their foundation. A series of jacks are used and then wood cribbing temporarily supports the structure. This process is repeated until the desired height is reached. The house jack can be used for jacking carrying beams that have settled or for installing new structural beams. On the top of the jack is a cast iron circular pad that the 4" × 4" post is resting on. This pad moves independently of the house jack so that it does not turn as the acme-threaded rod is turned up with a metal rod. This piece tilts very slightly but not enough to render the post dangerously out of plumb.

HYDRAULIC JACK

Hydraulic jacks are typically used for shop work, rather than as an emergency jack to be carried with the vehicle. Use of jacks not designed for a specific vehicle requires more than the usual care in selecting ground conditions, the 2.5 ton house jack that stands 24 inches from top to bottom fully threaded out. Jacking point on the vehicle, and to ensure stability when the jack is extended. Hydraulic jacks are often used to lift elevators in low and medium rise buildings. A hydraulic jack uses a fluid, which is incompressible, that is forced into a cylinder by a pump plunger. Oil is used since it is self-lubricating and stable. When the plunger pulls back, it draws oil out of the reservoir through a suction check valve into the pump chamber. When the plunger moves forward, it pushes the oil through a discharge check valve into the cylinder. The suction valve ball is within the chamber and opens with each draw of the plunger. The discharge valve ball is outside the chamber and opens when the oil is pushed into the cylinder. At this point the suction ball within the chamber is forced shut and oil pressure builds in the cylinder.

In a bottle jack the piston is vertical and directly supports a bearing pad that contacts the object being lifted. With a single action piston the lift is somewhat less than twice the collapsed height of the jack, making it suitable only for vehicles with a relatively high clearance. For lifting

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structures such as houses the hydraulic interconnection of multiple vertical jacks through valves enables the even distribution of forces while enabling close control of the lift.

In a floor jack (aka 'trolley jack') a horizontal piston pushes on the short end of a bellcrank, with the long arm providing the vertical motion to a lifting pad, kept horizontal with a horizontal linkage. Floor jacks usually include castors and wheels, allowing compensation for the arc taken by the lifting pad. This mechanism provides a low profile when collapsed, for easy maneuvering underneath the vehicle, while allowing considerable extension.

PNEUMATIC JACK

A pneumatic jack is a hydraulic jack that is actuated by compressed air - for example, air from a compressor - instead of human work. This eliminates the need for the user to actuate the hydraulic mechanism, saving effort and potentially increasing speed. Sometimes, such jacks are also able to be operated by the normal hydraulic actuation method, thereby retaining functionality, even if a source of compressed air is not available.

STRAND JACK

A strand jack is a specialized hydraulic jack that grips steel cables; often used in concert, strand jacks can lift hundreds of tons and are used in engineering and construction.

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REFERENCES

1. Larsen & Toubro Engg. And constructions official documents (Delhi)

2. Standard Handbook for Electrical Engineers

3. Kaplan, S. M. (2009). Smart Grid. Electrical Power Transmission: Background and Policy Issues. The Capital.Net, Government Series.

4. Kulkarni, S.V.; Khaparde, S.A. (2004). Transformer Engineering: Design and Practice. CRC Press. ISBN 0-8247-5653-3.

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