L & t training project

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

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By-: kundan giri
MIET ,meerut

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
CONTENTS................................................................................................................................................. 4
ABSTRACT.................................................................................................................................................. 6
ORGANIZATION/COMPANY PROFILE.......................................................................................................... 7
DIRECTORS........................................................................................................................................................ 8
HISTORY..........................................................................................................................................................10
VISION............................................................................................................................................................11
STRATEGIC MISSION - LAKSHYA ......................................................................................................................11
STRENGTH ...................................................................................................................................................... 11
TRANSFORMERS...................................................................................................................................... 13
BASIC PRINCIPLE................................................................................................................................................14
Induction law..............................................................................................................................................15
Ideal power equation.................................................................................................................................16
Physics of magnetization and EMF............................................................................................................16
BASIC TRANSFORMER PARAMETERS AND CONSTRUCTION..........................................................................................16
Leakage Flux...............................................................................................................................................17
Effect of frequency.....................................................................................................................................17
ENERGY LOSSES................................................................................................................................................ 18
Winding resistance.....................................................................................................................................19
Hysteresis losses.........................................................................................................................................19
Eddy currents..............................................................................................................................................19
Magnetostriction........................................................................................................................................19
Mechanical losses......................................................................................................................................20
Stray losses.................................................................................................................................................20
TRANSFORMER OIL.................................................................................................................................. 20
EXPLANATION...................................................................................................................................................20
TESTING AND OIL QUALITY..................................................................................................................................22
ON-SITE TESTING.............................................................................................................................................. 23
ELECTRIC POWER DISTRIBUTION.............................................................................................................. 24
HISTORY..........................................................................................................................................................24
INTRODUCTION OF ALTERNATING CURRENT............................................................................................................24
Modern distribution systems.....................................................................................................................29
International differences............................................................................................................................30
Distribution network configurations..........................................................................................................31
Distribution industry...................................................................................................................................33
ELECTRIC POWER TRANSMISSION............................................................................................................. 33

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OVERHEAD TRANSMISSION..................................................................................................................................34
UNDERGROUND TRANSMISSION...........................................................................................................................34
ELECTRICAL GRID...................................................................................................................................... 36
Term...........................................................................................................................................................36
History........................................................................................................................................................36
Deregulation...............................................................................................................................................37
Redundancy and defining "grid"................................................................................................................38
Aging Infrastructure...................................................................................................................................39
Modern trends ...........................................................................................................................................39
Future trends..............................................................................................................................................40
Emerging smart grid..................................................................................................................................40
Networked island-able microgrids.............................................................................................................41
JACK (DEVICE FOR LIFTING TRANSFORMERS)............................................................................................ 43
JACKSCREW......................................................................................................................................................44
Vehicle........................................................................................................................................................44
House jack..................................................................................................................................................44
Hydraulic jack.............................................................................................................................................44
Pneumatic jack...........................................................................................................................................45
Strand jack..................................................................................................................................................45
REFERENCES............................................................................................................................................. 46

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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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O RGANIZATION /C OMPANY P ROFILE

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 Y. M. Deosthalee

Whole-time Director & Whole-time Director &
President Chief Financial Officer
(Machinery & Industrial
Products)

K. Venkataramanan R. N. Mukhija K. V. Rangaswami

Whole-time Director & Whole-time Director & Whole-time Director &
President President President

(Engineering & (Electrical & (Construction)
Construction Projects) Electronics)

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V. K. Magapu M. V. Kotwal

Whole-time Director & Whole-time Director &
Senior Executive Vice Senior Executive Vice
President President

(IT & Technology) (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

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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"

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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 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

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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 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

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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, 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

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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 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

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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 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,

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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

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.

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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 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

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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 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.

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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

 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

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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.

• 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

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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 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,

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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

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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

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

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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 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

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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).

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

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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

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

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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

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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. 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

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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.

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

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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.

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

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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.

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

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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 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

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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.

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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 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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