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L & t training project

  1. 1. A SUMMER TRAINING REPORT ON “DL-765 KV TRANSFORMER PKG, JATIKALAN PROJECT SITE ” Page | 1
  2. 2. By-: kundan giri MIET ,meerut ACKNOWLEDGEMENTI would like extend my gratitude to Mr. Sachinder Prakash Pandey, Cluster HRManager, Delhi Region, for giving me the opportunity to do my project at L&TConstruction. I would also like to thank him for providing his support and able guidanceduring the course of my project.I would also like to thank Mr.Snehashish Debnath, Project manager, who guided methroughout my training and encouraged me to do new things and gave their valuableinputs as and when they thought necessary. Their constructive feedback and insights havehelped me develop a perspective and has also enabled me to overcome challengesthat came during the entire course of the project. Their calm demeanor and willingness toteach has been a great help in my successfully completing the project. My learning has beenimmeasurable and working under them was a great experience.My sincere thanks also extend to all the staff members of construction for providing ahospitable and helpful work environment and making my summer training an exciting andmemorable event.I would also like to thank Amresh Pratap Yadav, HR trainee at L&T constructions and asmy friend has always motivated me to put my best endeavors and match the expectations ofthe organization. In spite of his busy schedules, he ensured that he was always available forproviding feedback and ensuring that the project was done with utmost quality andconsistency.Finally, I thank all my fellow trainees who from time to time have helped me withinformation, insights and their support. Their cooperation has helped me immenselyand made the experience of the internship program at L&T construction an enrichingone. Page | 2
  3. 3. Page | 3
  4. 4. CONTENTSON“DL-765 KV TRANSFORMER PKG, JATIKALAN PROJECT SITE ”......................................................................1ACKNOWLEDGEMENT................................................................................................................................ 2CONTENTS................................................................................................................................................. 4ABSTRACT.................................................................................................................................................. 6ORGANIZATION/COMPANY PROFILE.......................................................................................................... 7 DIRECTORS........................................................................................................................................................ 8 HISTORY..........................................................................................................................................................10 VISION............................................................................................................................................................11 STRATEGIC MISSION - LAKSHYA ......................................................................................................................11 STRENGTH ...................................................................................................................................................... 11TRANSFORMERS...................................................................................................................................... 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.................................................................................................................................................20TRANSFORMER OIL.................................................................................................................................. 20 EXPLANATION...................................................................................................................................................20 TESTING AND OIL QUALITY..................................................................................................................................22 ON-SITE TESTING.............................................................................................................................................. 23ELECTRIC POWER DISTRIBUTION.............................................................................................................. 24 HISTORY..........................................................................................................................................................24 INTRODUCTION OF ALTERNATING CURRENT............................................................................................................24 Modern distribution systems.....................................................................................................................29 International differences............................................................................................................................30 Distribution network configurations..........................................................................................................31 Distribution industry...................................................................................................................................33ELECTRIC POWER TRANSMISSION............................................................................................................. 33 Page | 4
  5. 5. OVERHEAD TRANSMISSION..................................................................................................................................34 UNDERGROUND TRANSMISSION...........................................................................................................................34ELECTRICAL 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.............................................................................................................41JACK (DEVICE FOR LIFTING TRANSFORMERS)............................................................................................ 43 JACKSCREW......................................................................................................................................................44 Vehicle........................................................................................................................................................44 House jack..................................................................................................................................................44 Hydraulic jack.............................................................................................................................................44 Pneumatic jack...........................................................................................................................................45 Strand jack..................................................................................................................................................45REFERENCES............................................................................................................................................. 46 Page | 5
  6. 6. ABSTRACTThe report includes the various methods used by the project team in installing 13 765/400kvtransformers at the Ghummenera village in an under construction PGCIL Power GridProject. Special emphasis has been put to highlight all the peculiarities while the task hasbeen completed. Also the study provides technical information regarding the Machines andEquipments 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 analyzethe factors which are important in completion of the project in a manner such that theutilization of resources is optimum. Page | 6
  7. 7. O RGANIZATION /C OMPANY P ROFILELarsen & Toubro Limited (L&T) is a technology, engineering, construction andmanufacturing company. It is one of the largest and most respected companies in Indiasprivate 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 ofbusiness. L&T has an international presence, with a global spread of offices. A thrust oninternational business has seen overseas earnings grow significantly. It continues to grow itsoverseas manufacturing footprint, with facilities in China and the Gulf region. Thecompanys businesses are supported by a wide marketing and distribution network, andhave established a reputation for strong customer support.L&T believes that progress must be achieved in harmony with the environment. Acommitment to community welfare and environmental protection are an integral part of thecorporate 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 Page | 7
  8. 8. 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. RangaswamiWhole-time Director & Whole-time Director & Whole-time Director & President President President (Engineering & (Electrical & (Construction)Construction Projects) Electronics) Page | 8
  9. 9. V. K. Magapu M. V. KotwalWhole-time Director & Whole-time Director &Senior Executive Vice Senior Executive Vice President President (IT & Technology) (Heavy Engineering) Page | 9
  10. 10. HISTORYThe evolution of L&T into the countrys largest engineering and construction organizationis among the most remarkable success stories in Indian industry.L&T was founded inBombay (Mumbai) in 1938 by two Danish engineers, Henning Holck-Larsen and SorenKristian Toubro. Both of them were strongly committed to developing Indias engineeringcapabilities to meet the demands of industry.Henning Holck-Larsen and Soren Kristian Toubro, school-mates in Denmark, would nothave 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 ofworking in Europe, and started their own operation in India. All they had was a dream. Andthe courage to dare. Their first office in Mumbai (Bombay) was so small that only one ofthe partners could use the office at a time!In the early years, they represented Danish manufacturers of dairy equipment for a modestretainer. 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.Germanys invasion of Denmark in 1940 stopped supplies of Danish products. This crisisforced the partners to stand on their own feet and innovate. They started manufacturingdairy equipment indigenously. These products proved to be a success, and L&T came to berecognised as a reliable fabricator with high standards. The war-time need to repair and refitships 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 - theCompany 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 chanceto enter the field of installation - an area where their capability became well respected. Page | 10
  11. 11. VISIONThe L&T vision reflects the collective goal of the company. It was drafted through a largescale 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 - LAKSHYATo compete and grow in a globalised business environment, L&T is implementing astrategic plan (LAKSHYA) for 2005-10. The plan has been drawn up in consultation with aleading international strategy consultant. It has set ambitious growth targets for eachbusiness. Also included are opportunities for diversification of L&Ts business portfolio. STRENGTHLarsen and Toubro is a leading technology, engineering, construction and manufacturingcompany. The company’s other key activities include manufacturing of electrical andelectronic equipment, services and information technology. The company operatesprimarily in India. It is headquartered in Mumbai, India. The company recorded revenues ofINR297, 129.9 million (approximately $7,380.7 million) during the financial year endedMarch 2008 (FY2008), an increase of 42.3% over 2007. The operating profit of thecompany was INR36, 237.6 million (approximately $900.1 million) during FY2008, an Page | 11
  12. 12. 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. Page | 12
  13. 13. TRANSFORMERSA transformer is a power converter that transfers electrical energy from one circuit toanother through inductively coupled conductors—the transformers coils. A varying currentin the first or primary winding creates a varying magnetic flux in the transformers core andthus a varying magnetic field through the secondary winding. This varying magnetic fieldinduces a varying electromotive force (EMF), or "voltage", in the secondary winding. Thiseffect is called inductive coupling. If a load is connected to the secondary winding, currentwill flow in this winding, and electrical energy will be transferred from the primary circuitthrough the transformer to the load. In an ideal transformer, the induced voltage in thesecondary winding (Vs) is in proportion to the primary voltage (Vp) and is given by theratio 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 alternatingcurrent (AC) voltage to be "stepped up" by making Ns greater than Np, or "stepped down" Page | 13
  14. 14. 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 weighinghundreds of tons used in power stations, or to interconnect portions of power grids. Alloperate on the same basic principles, although the range of designs is wide.While new technologies have eliminated the need for transformers in some electroniccircuits, 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 PRINCIPLEThe transformer is based on two principles: first, that an electric current can produce amagnetic field (electromagnetism) and second that a changing magnetic field within a coilof wire induces a voltage across the ends of the coil (electromagnetic induction). Changingthe current in the primary coil changes the magnetic flux that is developed. The changingmagnetic flux induces a voltage in the secondary coil. An ideal transformer is shown in the Page | 14
  15. 15. adjacent figure. Current passing through the primary coil creates a magnetic field. Theprimary 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 andsecondary coils. If a load is connected to the secondary winding, the load current andvoltage will be in the directions indicated, given the primary current and voltage in thedirections indicated (each will be alternating current in practice). INDUCTION LAWThe voltage induced across the secondary coil may be calculated from Faradays law ofinduction, which states that: where Vs is the instantaneous voltage, Ns is the number ofturns in the secondary coil and Φ is the magnetic flux through one turn of the coil. If theturns of the coil are oriented perpendicularly to the magnetic field lines, the flux is theproduct of the magnetic flux density B and the area A through which it cuts. The area isconstant, being equal to the cross-sectional area of the transformer core, whereas themagnetic field varies with time according to the excitation of the primary. Since the samemagnetic 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 Page | 15
  16. 16. equations for Vs and Vp gives the basic equation for stepping up or stepping down thevoltage.Np/Ns is known as the turns ratio, and is the primary functional characteristic of anytransformer. In the case of step-up transformers, this may sometimes be stated as thereciprocal, Ns/Np. Turns ratio is commonly expressed as an irreducible fraction or ratio: forexample, a transformer with primary and secondary windings of, respectively, 100 and 150turns is said to have a turn’s ratio of 2:3 rather than 0.667 or 100:150. IDEAL POWER EQUATIONThe ideal transformer as a circuit element, If the secondary coil is attached to a load thatallows current to flow, electrical power is transmitted from the primary circuit to thesecondary circuit. Ideally, the transformer is perfectly efficient. All the incoming energy istransformed from the primary circuit to the magnetic field and into the secondary circuit. Ifthis condition is met, the input electric power must equal the output power: giving the idealtransformer equation This formula is a reasonable approximation for most commercial builttransformers today.If the voltage is increased, then the current is decreased by the same factor. The impedancein one circuit is transformed by the square of the turns ratio. For example, if an impedanceZs is attached across the terminals of the secondary coil, it appears to the primary circuit tohave an impedance of (Np/Ns)2Zs. This relationship is reciprocal, so that the impedance Zpof the primary circuit appears to the secondary to be (Ns/Np)2Zp. PHYSICS OF MAGNETIZATION AND EMFThe ideal model not only neglects basic physics factors in terms of primary current requiredto establish a magnetic field in the core and the contribution to the field due to current in thesecondary circuit but also assumes a core of negligible reluctance with two windings of zeroresistance. When a voltage is applied to the primary winding, a small current flows, drivingflux around the magnetic circuit of the core. The current required to create the flux istermed the magnetizing current. Since the ideal core has been assumed to have near-zeroreluctance, the magnetizing current is negligible, although still required, to create themagnetic field. The changing magnetic field induces an electromotive force (EMF) acrosseach winding. Since the ideal windings have no impedance, they have no associated voltagedrop, and so the voltages VP and VS measured at the terminals of the transformer, are equalto the corresponding EMFs. The primary EMF, acting as it does in opposition to theprimary voltage, is sometimes termed the "back EMF". This is in accordance with Lenzslaw, which states that induction of EMF always opposes development of any such change inmagnetic field. BASIC TRANSFORMER PARAMETERS AND CONSTRUCTION Page | 16
  17. 17. LEAKAGE FLUXThe ideal transformer model assumes that all flux generated by the primary winding linksall the turns of every winding, including itself. In practice, some flux traverses paths thattake it outside the windings. Such flux is termed leakage flux, and results in leakageinductance in series with the mutually coupled transformer windings. Leakage results inenergy being alternately stored in and discharged from the magnetic fields with each cycleof the power supply. It is not directly a power loss (see "Stray losses" below), but results ininferior voltage regulation, causing the secondary voltage to not be directly proportional tothe primary voltage, particularly under heavy load. Transformers are therefore normallydesigned to have very low leakage inductance. Nevertheless, it is impossible to eliminate allleakage flux because it plays an essential part in the operation of the transformer. Thecombined effect of the leakage flux and the electric field around the windings is whattransfers energy from the primary to the secondary.In some applications increased leakage is desired, and long magnetic paths, air gaps, ormagnetic bypass shunts may deliberately be introduced in a transformer design to limit theshort-circuit current it will supply. Leaky transformers may be used to supply loads thatexhibit negative resistance, such as electric arcs, mercury vapor lamps, and neon signs orfor safely handling loads that become periodically short-circuited such as electric arcwelders. 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 thewindings. Leakage inductance is also helpful when transformers are operated in parallel. Itcan be shown that if the "per-unit" inductance of two transformers is the same (a typicalvalue is 5%), they will automatically split power "correctly" (e.g. 500 kVA unit in parallelwith 1,000 kVA unit, the larger one will carry twice the current). EFFECT OF FREQUENCYTransformer universal EMF equationIf the flux in the core is purely sinusoidal, the relationship for either winding between itsrms voltage Erms of the winding, and the supply frequency f, number of turns N, corecross-sectional area a and peak magnetic flux density B is given by the universal EMFequation: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 Faradays Law shows that the flux in the core is the integralwith respect to time of the applied voltage. Hypothetically an ideal transformer would workwith 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 Page | 17
  18. 18. increase in the magnetizing current and overheating the transformer. All practicaltransformers must therefore operate with alternating (or pulsed direct) current.The EMF of a transformer at a given flux density increases with frequency.[36] Byoperating at higher frequencies, transformers can be physically more compact because agiven core is able to transfer more power without reaching saturation and fewer turns areneeded to achieve the same impedance. However, properties such as core loss andconductor skin effect also increase with frequency. Aircraft and military equipment employ400 Hz power supplies which reduce core and winding weight. Conversely, frequenciesused 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 withthe limitations of early electric traction motors. As such, the transformers used to step downthe high over-head line voltages (e.g. 15 kV) were much heavier for the same power ratingthan those designed only for the higher frequencies. Operation of a transformer at itsdesigned voltage but at a higher frequency than intended will lead to reduced magnetizingcurrent. At a lower frequency, the magnetizing current will increase. Operation of atransformer 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 needto be equipped with "volts per hertz" over-excitation relays to protect the transformer fromovervoltage at higher than rated frequency.One example of state-of-the-art design is transformers used for electric multiple unit highspeed trains, particularly those required to operate across the borders of countries usingdifferent electrical standards. The position of such transformers is restricted to being hungbelow the passenger compartment. They have to function at different frequencies (down to16.7 Hz) and voltages (up to 25 kV) whilst handling the enhanced power requirementsneededfor operating the trains at high speed. Knowledge of natural frequencies oftransformer windings is necessary for the determination of winding transient response andswitching surge voltages. ENERGY LOSSESAn ideal transformer would have no energy losses, and would be 100% efficient. Inpractical transformers, energy is dissipated in the windings, core, and surroundingstructures. Larger transformers are generally more efficient, and those rated for electricitydistribution 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 largeheavily loaded transformer; the trade-off is in the additional initial and running cost of thesuperconducting design.Losses in transformers (excluding associated circuitry) vary with load current, and may beexpressed as "no-load" or "full-load" loss. Winding resistance dominates load losses, Page | 18
  19. 19. whereas hysteresis and eddy current losses contribute to over 99% of the no-load loss. Theno-load loss can be significant, so that even an idle transformer constitutes a drain on theelectrical supply and a running cost. Designing transformers for lower loss requires a largercore, 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 (alsosee energy efficient transformer).Transformer losses are divided into losses in the windings, termed copper loss, and those inthe magnetic circuit, termed iron loss. Losses in the transformer arise from: WINDING RESISTANCECurrent flowing through the windings causes resistive heating of the conductors. At higherfrequencies, skin effect and proximity effect create additional winding resistance and losses. HYSTERESIS LOSSESEach time the magnetic field is reversed, a small amount of energy is lost due to hysteresiswithin the core. For a given core material, the loss is proportional to the frequency, and is afunction of the peak flux density to which it is subjected. EDDY CURRENTSFerromagnetic materials are also good conductors and a core made from such a materialalso constitutes a single short-circuited turn throughout its entire length. Eddy currentstherefore circulate within the core in a plane normal to the flux, and are responsible forresistive heating of the core material. The eddy current loss is a complex function of thesquare of supply frequency and Inverse Square of the material thickness. Eddy currentlosses can be reduced by making the core of a stack of plates electrically insulated fromeach other, rather than a solid block; all transformers operating at low frequencies uselaminated or similar cores. MAGNETOSTRICTIONMagnetic flux in a ferromagnetic material, such as the core, causes it to physically expandand contract slightly with each cycle of the magnetic field, an effect known asmagnetostriction. This produces the buzzing sound commonly associated with transformersthat can cause losses due to frictional heating. This buzzing is particularly familiar fromlow-frequency (50 Hz or 60 Hz) mains hum, and high-frequency (15,734 Hz (NTSC) or15,625 Hz (PAL)) CRT noise. Page | 19
  20. 20. MECHANICAL LOSSESIn addition to magnetostriction, the alternating magnetic field causes fluctuating forcesbetween the primary and secondary windings. These incite vibrations within nearbymetalwork, adding to the buzzing noise and consuming a small amount of power. STRAY LOSSESLeakage inductance is by itself largely lossless, since energy supplied to its magnetic fieldsis returned to the supply with the next half-cycle. However, any leakage flux that interceptsnearby conductive materials such as the transformers support structure will give rise toeddy currents and be converted to heat. There are also radiative losses due to the oscillatingmagnetic field but these are usually small. TRANSFORMER OILTransformer oil or insulating oil is usually a highly-refined mineral oil that is stable athigh temperatures and has excellent electrical insulating properties. It is used in oil-filledtransformers, some types of high voltage capacitors, fluorescent lamp ballasts, and sometypes of high voltage switches and circuit breakers. Its functions are to insulate, suppresscorona and arcing, and to serve as a coolant. EXPLANATIONThe oil helps cool the transformer. Because it also provides part of the electrical insulationbetween internal live parts, transformer oil must remain stable at high temperatures for anextended period. To improve cooling of large power transformers, the oil-filled tank mayhave external radiators through which the oil circulates by natural convection. Very large orhigh-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 undergoprolonged drying processes, using electrical self-heating, the application of a vacuum, orboth to ensure that the transformer is completely free of water vapor before the cooling oilis introduced. This helps prevent corona formation and subsequent electrical breakdownunder load.Oil filled transformers with a conservator (an oil tank above the transformer) may have agas detector relay (Buchholz relay). These safety devices detect the build up of gas insidethe transformer due to corona discharge, overheating, or an internal electric arc. On a slowaccumulation of gas, or rapid pressure rise, these devices can trip a protective circuitbreaker to remove power from the transformer. Transformers without conservators areusually equipped with sudden pressure relays, which perform a similar function as the Page | 20
  21. 21. Buchholz relay. The flash point (min) and pour point (max) are 140 °C and −6 °Crespectively. The dielectric strength of new untreated oil is 12 MV/m (RMS) and aftertreatment it should be >24 MV/m (RMS).Large transformers for indoor use must either beof the dry type, that is, containing no liquid, or use a less-flammable liquid.Polychlorinatedbiphenyls (PCBs)Well into the 1970s,polychlorinated biphenyls(PCB)s were often used asa dielectric fluid sincethey are not flammable.PCBs do not break downwhen released into theenvironment andaccumulate in the tissuesof plants and animals,where they can havehormone-like effects.When burned, PCBs canform highly toxicproducts, such aschlorinated dioxins and chlorinated dibenzofurans. Starting in the early 1970s, productionand new uses of PCBs have been banned due to concerns about the accumulation of PCBsand toxicity of their byproducts. In many countries significant programs are in place toreclaim and safely destroy PCB contaminated equipment. Polychlorinated biphenyls werebanned 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 foreither type of liquid, contamination of oil-filled transformers is possible. Under presentregulations, concentrations of PCBs exceeding 5 parts per million can cause an oil to beclassified as hazardous waste in California (California Code of Regulations, Title 22,section 66261). Throughout the US, PCBs are regulated under the Toxic Substances ControlAct. As a consequence, field and laboratory testing for PCB contamination is a commonpractice. 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 theadded expense of a fire-resistant liquid offsets additional building cost for a transformervault. Combustion-resistant vegetable oil-based dielectric coolants and syntheticpentaerythritol tetra fatty acid (C7, C8) esters are also becoming increasingly common asalternatives to naphthenic mineral oil. Esters are non-toxic to aquatic life, readilybiodegradable, and have a lower volatility and a higher flash points than mineral oil. Page | 21
  22. 22. TESTING AND OIL QUALITYTransformer oils are subject to electrical and mechanical stresses while a transformer is inoperation. In addition there is contamination caused by chemical interactions with windingsand other solid insulation, catalyzed by high operating temperature. As a result the originalchemical properties of transformer oil changes gradually, rendering it ineffective for itsintended purpose after many years. Hence this oil has to be periodically tested to ascertainits basic electrical properties, make sure it is suitable for further use, and ascertain the needfor maintenance activities like filtration/regeneration. These tests can be divided into:1. Dissolved gas analysis2. Furan analysis3. PCB analysis4. 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 ViscosityThe 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 arespecifically not for determining the quality of transformer oil, but for determining anyabnormalities in the internal windings of the transformer or the paper insulation of the Page | 22
  23. 23. transformer, which cannot be otherwise detected without a complete overhaul of thetransformer. 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 5years. ON-SITE TESTINGSome 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 distressedtransformers to continually monitor gas generation trends. To determine the insulatingproperty of the dielectric oil, an oil sample is taken from the device under test, and itsbreakdown 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 mmare surrounded by the insulating oil.• During the test, a test voltage is applied to the electrodes. The test voltage is continuouslyincreased 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 itduring the breakdown, must be limited to keep the additional pollution by carbonisation aslow as possible.• The root mean square value of the test voltage is measured at the very instant of thebreakdown and is reported as the breakdown voltage.• After the test is completed, the insulating oil is stirred automatically and the test sequenceis performed repeatedly.• The resulting breakdown voltage is calculated as mean value of the individualmeasurements. Page | 23
  24. 24. ELECTRIC POWER DISTRIBUTIONElectricity distribution is the final stage in the delivery of electricity to end users. Adistribution systems network carries electricity from the transmission system and delivers itto 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. HISTORYIn the early days of electricity distribution, direct current (DC) generators were connected toloads at the same voltage. The generation, transmission and loads had to be of the samevoltage because there was no way of changing DC voltage levels, other than inefficientmotor-generator sets. Low DC voltages were used (on the order of 100 volts) since that wasa practical voltage for incandescent lamps, which were the primary electrical load. Lowvoltage also required less insulation for safe distribution within buildings. The losses in acable are proportional to the square of the current, the length of the cable, and the resistivityof the material, and are inversely proportional to cross-sectional area. Early transmissionnetworks used copper cable, which is one of the best economically feasible conductors forthis application. To reduce the current and copper required for a given quantity of powertransmitted would require a higher transmission voltage, but no efficient method existed tochange the voltage of DC power circuits. To keep losses to an economically practical levelthe Edison DC system needed thick cables and local generators. Early DC generating plantsneeded to be within about 1.5 miles (2.4 km) of the farthest customer to avoid excessivelylarge and expensive conductors. INTRODUCTION OF ALTERNATING CURRENT Page | 24
  25. 25. The competition between the direct current (DC) of Thomas Edison and the alternatingcurrent (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 ofpower. Power transformers, installed at power stations, could be used to raise the voltagefrom the generators, and transformers at local substations could reduce voltage to supplyloads. Increasing the voltage reduced the current in the transmission and distribution linesand hence the size of conductors and distribution losses. This made it more economical todistribute power over long distances. Generators (such as hydroelectric sites) could belocated far from the loads. In North America, early distribution systems used a voltage of2.2 kV corner-grounded delta. Over time, this was gradually increased to2.4 kV. As citiesgrew, most 2.4 kV systems were upgraded to 2.4/4.16 kV, three-phase systems. In threephase networks that permit connections between phase and neutral, both the phase-to-phasevoltage (4160, in this example) and the phase-to-neutral voltage are given; if only one valueis shown, the network does not serve single-phase loads connected phase-to-neutral. Somecity and suburban distribution systems continue to use this range of voltages, but most havebeen 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 systemsused 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 Europeanpower distribution systems also differ in that North American systems tend to have a greaternumber of low-voltage step-down transformers located close to customers premises. Forexample, in the US a pole-mounted transformer in a suburban setting may supply 7-8houses, whereas in the UK a typical urban or suburban low-voltage substation wouldnormally be rated between 315 kVA and 1 MVA and supply a whole neighbourhood. Thisis because the higher voltage used in Europe (415 V vs 230 V) may be carried over agreater distance with acceptable power loss. An advantage of the North American setup isthat 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 moreefficient, and due to diversity there need be less spare capacity in the transformers, reducingpower wastage. In North American city areas with many customers per unit area, networkdistribution will be used, with multiple transformers and low-voltage buses interconnectedover several city blocks. Rural electrification systems, in contrast to urban systems, tend touse higher voltages because of the longer distances covered by those distribution lines (seeRural Electrification Administration). 7.2, 12.47, 25, and 34.5 Kv distribution is common inthe United States; 11 kV and 33 kV are common in the UK, New Zealand and Australia; 11kV and 22 kV are common in South Africa. Other voltages are occasionally used. In NewZealand, Australia, Saskatchewan, Canada, and South Africa, single wire earth returnsystems (SWER) are used to electrify remote rural areas. While power electronics nowallow for conversion between DC voltage levels, AC is preferred in distribution due to theeconomy, efficiency and reliability of transformers. High-voltage DC is used fortransmission of large blocks of power over long distances, or for interconnecting adjacentAC networks, but not for distribution to customers. Electric power is normally generated at11-25kV in a power station. To transmit over long distances, it is then stepped-up to 400kV, Page | 25
  26. 26. 220kV or 132kV as necessary. Power is carried through a transmission network of highvoltage lines. Usually, these lines run into hundreds of kilometers and deliver the powerinto 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. Theselines terminate into a 33kV (or 66kV) substation, where the voltage is stepped-down to11kV for power distribution to load points through a distribution network of lines at 11kVand lower. Page | 26
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  29. 29. MODERN DISTRIBUTION SYSTEMS Page | 29
  30. 30. Electric distribution substations transform power from transmission voltage to the lowervoltage used for local distribution to homes and businesses. The modern distribution systembegins as the primary circuit leaves the sub-station and ends as the secondary service entersthe customers meter socket. Distribution circuits serve many customers. The voltage used isappropriate for the shorter distance and varies from 2,300 to about 35,000 volts dependingon utility standard practice, distance, and load to be served. Distribution circuits are fedfrom a transformer located in an electrical substation, where the voltage is reduced from thehigh values used for power transmission. Conductors for distribution may be carried onoverhead 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 isnot economical to install three-phase power for relatively few and small customers. Onlylarge consumers are fed directly from distribution voltages; most utility customers areconnected to a transformer, which reduces the distribution voltage to the relatively lowvoltage used by lighting and interior wiring systems. The transformer may be pole-mountedor set on the ground in a protective enclosure. In rural areas a pole-mount transformer mayserve 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 transformersfeeding into a common bus at the utilization voltage. Each customer has an "electricalservice" or "service drop" connection and a meter for billing. (Some very small loads, suchas yard lights, may be too small to meter and so are charged only a monthly rate.) A groundconnection to local earth is normally provided for the customers system as well as for theequipment owned by the utility. The purpose of connecting the customers system to groundis to limit the voltage that may develop if high voltage conductors fall on the lower-voltageconductors, or if a failure occurs within a distribution transformer. If all conductive objectsare 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 tostray voltage problems; customer piping, swimming pools or other equipment may developobjectionable voltages. These problems may be difficult to resolve since they oftenoriginate from places other than the customers premises. INTERNATIONAL DIFFERENCESIn many areas, "delta" three phase service is common. Delta service has no distributedneutral wire and is therefore less expensive. In North America and Latin America, threephase service is often a Y (wye) in which the neutral is directly connected to the center ofthe generator rotor. The neutral provides a low-resistance metallic return to the distributiontransformer. Wye service is recognizable when a line has four conductors, one of which islightly 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 industrialservice. In this system, the high voltage distribution network supplies a few substations perarea, and the 230 V power from each substation is directly distributed. A live (hot) wire and Page | 30
  31. 31. neutral are connected to the building from one phase of three phase service. Single-phasedistribution is used where motor loads are small.North AmericaIn 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 housevoltages 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 appliancesbecause the two halves of a phase oppose each other.EuropeIn 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-phasevoltage of 230 volts. For industrial customers, 3-phase 690 / 400 volt is also available.JapanJapan has a large number of small industrial manufacturers, and therefore supplies standardlow-voltage three phase-services in many suburbs. Also, Japan normally supplies residentialservice as two phases of a three phase service, with a neutral. These work well for bothlighting and motors.Rural servicesRural services normally try to minimize the number of poles and wires. Single-wire earthreturn (SWER) is the least expensive, with one wire. It uses high voltages, which in turnpermit use of galvanized steel wire. The strong steel wire permits inexpensive wide polespacings. Other areas use high voltage split-phase or three phase service at higher cost.MeteringElectricity meters use different metering equations depending on the form of electricalservice. Since the math differs from service to service, the number of conductors andsensors in the meters also vary.TermsBesides referring to the physical wiring, the term electrical service also refers in an abstractsense to the provision of electricity to a building. DISTRIBUTION NETWORK CONFIGURATIONSDistribution networks are typically of two types, radial or interconnected (see spotnetwork). A radial network leaves the station and passes through the network area with no Page | 31
  32. 32. normal connection to any other supply. This is typical of long rural lines with isolated loadareas. An interconnected network is generally found in more urban areas and will havemultiple connections to other points of supply. These points of connection are normallyopen but allow various configurations by the operating utility by closing and openingswitches. Operation of these switches may be by remote control from a control center or bya lineman. The benefit of the interconnected model is that in the event of a fault or requiredmaintenance 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 traditionalutility poles and wires and, increasingly, underground construction with cables and indooror cabinet substations. However, underground distribution is significantly more expensivethan overhead construction. In part to reduce this cost, underground power lines aresometimes co-located with other utility lines in what are called common utility ducts.Distribution feeders emanating from a substation are generally controlled by a circuitbreaker which will open when a fault is detected. Automatic circuit reclosers may beinstalled to further segregate the feeder thus minimizing the impact of faults.Long feeders experience voltage drop requiring capacitors or voltage regulators to beinstalled. Characteristics of the supply given to customers are generally mandated bycontract between the supplier and customer. Variables of the supply include:• AC or DC - Virtually all public electricity supplies are AC today. Users of large amountsof DC power such as some electric railways, telephone exchanges and industrial processessuch as aluminum smelting usually either operate their own or have adjacent dedicatedgenerating 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 fewolder 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 a15 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. Loadfactor indicates the degree of effective utilization of equipment (and capital investment) ofdistribution 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 Page | 32
  33. 33. DISTRIBUTION INDUSTRYTraditionally the electricity industry has been a publicly owned institution but starting in the1970s nations began the process of deregulation and privatization, leading to electricitymarkets. A major focus of these was the elimination of the former so called naturalmonopoly of generation, transmission, and distribution. As a consequence, electricity hasbecome more of a commodity. The separation has also led to the development of newterminology to describe the business units (e.g., line company, wires business and networkcompany). ELECTRIC POWER TRANSMISSIONElectric-power transmission is the bulk transfer of electrical energy, from generating powerplants to electrical substations located near demand centers. This is distinct from the localwiring between high-voltage substations and customers, which is typically referred to aselectric power distribution. Transmission lines, when interconnected with each other,become transmission networks. In the US, these are typically referred to as "power grids" orjust "the grid." In the UK, the network is known as the "National Grid." North America hasthree major grids, the Western Interconnection, the Eastern Interconnection and the ElectricReliability Council of Texas (ERCOT) grid, often referred to as the Western System, theEastern System and the Texas System. Historically, transmission and distribution lines wereowned by the same company, but starting in the 1990s, many countries have liberalized theregulation of the electricity market in ways that have led to the separation of the electricitytransmission business from the distribution business.Most transmission lines use high-voltage three-phase alternating current (AC), althoughsingle phase AC is sometimes used in railway electrification systems. High-voltage direct-current (HVDC) technology is used for greater efficiency in very long distances (typicallyhundreds of miles (kilometres), or in submarine power cables (typically longer than 30miles (50 km). HVDC links are also used to stabilize against control problems in largepower distribution networks where sudden new loads or blackouts in one part of a networkcan otherwise result in synchronization problems and cascading failures. Diagram of anelectric power system; transmission system is in blue Electricity is transmitted at highvoltages (110 kV or above) to reduce the energy lost in long-distance transmission. Poweris usually transmitted through overhead power lines. Underground power transmission has asignificantly higher cost and greater operational limitations but is sometimes used in urbanareas 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. Asophisticated control system is required to ensure electric generation very closely matchesthe demand. If the demand for power exceeds the supply, generation plants andtransmission equipment can shut down which, in the worst cases, can lead to a major Page | 33
  34. 34. regional blackout, such as occurred in the US Northeast blackouts of 1965, 1977, 2003, andin 1996 and 2011. To reduce the risk of such failures, electric transmission networks areinterconnected into regional, national or continental wide networks thereby providingmultiple redundant alternative routes for power to flow should (weather or equipment)failures occur. Much analysis is done by transmission companies to determine themaximum reliable capacity of each line (ordinarily less than its physical or thermal limit) toensure spare capacity is available should there be any such failure in another part of thenetwork. OVERHEAD TRANSMISSIONThe contiguous United States power transmission grid consists of 300,000 km of linesoperated by 500 companies’ 3-phase high voltage lines in Washington State High-voltageoverheadConductors are not covered by insulation. The conductor material is nearly always analuminium alloy, made into several strands and possibly reinforced with steel strands.Copper was sometimes used for overhead transmission but aluminium is lighter, yields onlymarginally reduced performance, and costs much less. Overhead conductors are acommodity supplied by several companies worldwide. Improved conductor material andshapes are regularly used to allow increased capacity and modernize transmission circuits.Conductor sizes range with varying resistance and current-carrying capacity. Thicker wireswould lead to a relatively small increase in capacity due to the skin effect that causes mostof 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 coronadischarge.Today, transmission-level voltages are usually considered to be 110 kV and above. Lowervoltages such as 66 kV and 33 kV are usually considered subtransmission voltages but areoccasionally used on long lines with aluminum light loads. Voltages less than 33 kV areusually used for distribution. Voltages above 230 kV are considered extra high voltage andrequire different designs compared to equipment used at lower voltages. Since overheadtransmission wires depend on air for insulation, design of these lines requires minimumclearances to be observed to maintain safety. Adverse weather conditions of high wind andlow temperatures can lead to power outages. Wind speeds as low as 23 knots (43 km/h) canpermit conductors to encroach operating clearances, resulting in a flashover and loss ofsupply. Oscillatory motion of the physical line can be termed gallop or flutter depending onthe frequency and amplitude of oscillation. UNDERGROUND TRANSMISSION Page | 34
  35. 35. Electric power can also be transmitted by underground power cables instead of overheadpower lines. Underground cables take up less right-of-way than overhead lines, have lowervisibility, and are less affected by bad weather. However, costs of insulated cable andexcavation are much higher than overhead construction. Faults in buried transmission linestake longer to locate and repair. Underground lines are strictly limited by their thermalcapacity, which permits fewer overloads or re-rating than overhead lines. Longunderground cables have significant capacitance, which may reduce their ability to provideuseful power to loads. Page | 35
  36. 36. ELECTRICAL GRIDVoltages and depictions of electrical lines are typical for Germany and other Europeansystems. An electrical grid is an interconnected network for delivering electricity fromsuppliers 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; and3) 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 whichincludes the following three distinct operations:1. Electricity generation - Generating plants are usually located near a source of water, andaway from heavily populated areas. They are usually quite large to take advantage of theeconomies 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 powerlong distances–often across state lines, and sometimes across international boundaries, untilit reaches its wholesale customer (usually the company that owns the local distributionnetwork).3. Electric power distribution - Upon arrival at the substation, the power will be steppeddown in voltage—from a transmission level voltage to a distribution level voltage. As itexits the substation, it enters the distribution wiring. Finally, upon arrival at the servicelocation, the power is stepped down again from the distribution voltage to the requiredservice voltage(s). TERMThe term grid usually refers to a network, and should not be taken to imply a particularphysical layout or breadth. Grid may also be used to refer to an entire continents electricalnetwork, a regional transmission network or may be used to describe a subnetwork such asa local utilitys transmission grid or distribution grid. HISTORYSince its inception in the Industrial Age, the electrical grid has evolved from an insularsystem that serviced a particular geographic area to a wider, expansive network that Page | 36
  37. 37. incorporated multiple areas. At one point, all energy was produced near the device orservice requiring that energy. In the early 19th century, electricity was a novel inventionthat competed with steam, hydraulics, direct heating and cooling, light, and most notablygas. During this period, gas production and delivery had become the first centralizedelement in the modern energy industry. It was first produced on customer’s premises butlater evolved into large gasifiers that enjoyed economies of scale. Virtually every city in theU.S. and Europe had town gas piped through their municipalities as it was a dominant formof household energy use. By the mid-19th century, electric arc lighting soon becameadvantageous compared to volatile gas lamps since gas lamps produced poor light,tremendous wasted heat which made rooms hot and smoky, and noxious elements in theform of hydrogen and carbon monoxide. Modeling after the gas lighting industry, ThomasEdison invented the first electric utility system which supplied energy through virtual mainsto light filtration as opposed to gas burners. With this, electric utilities also took advantageof economies of scale and moved to centralized power generation, distribution, and systemmanagement.During the 20th century, institutional arrangement of electric utilities changed. At thebeginning, electric utilities were isolated systems without connection to other utilities andserviced a specific service territory. In the 1920s, utilities joined together establishing awider utility grid as joint-operations saw the benefits of sharing peak load coverage andbackup power. Also, electric utilities were easily financed by Wall Street private investorswho backed many of their ventures. In 1934, with the passage of the Public Utility HoldingCompany Act (USA), electric utilities were recognized as public goods of importance alongwith gas, water, and telephone companies and thereby were given outlined restrictions andregulatory oversight of their operations. This ushered in the Golden Age of Regulation formore than 60 years. However, with the successful deregulation of airlines andtelecommunication industries in late 1970s, the Energy Policy Act (EPAct) of 1992advocated deregulation of electric utilities by creating wholesale electric markets. Itrequired transmission line owners to allow electric generation companies open access totheir network. DEREGULATIONWith deregulation, a more complex environment occurred as opposed to the traditionalvertically-integrated monopoly that oversees the entire grid’s operations. Newer participantsentered the market including Independent Power Providers (IPPs) who decided andconstructed the new facility; Transmission Companies (TRANSCOs) who constructed andowned the transmission equipment; retailers who signed up end-use customers, procuredtheir electric service, and billed them; integrated energy companies (combined IPPs andretailers); and Independent System Operation (ISO) who managed the grid being indifferentto market outcomes. Also, day-to-day to long term operations altered. Infrastructureadditions which were long-term planning now became an investment analysis with IPPs thatdecided construction of a new power plant under economic considerations (taxes, labor and Page | 37
  38. 38. material costs) and ability to obtain financing. Load and supply management that fell undermid-term planning became risk management as private utilities had to manage a portfolio ofend customers and assets with the company’s risk preference. Day-ahead scheduling andreal time grid management in the short-term planning which involves forecasting demandand dispatch schedule became asset management as power plants and grid equipment wasassets to be scheduled and dispatched. Here, the ISO sets dispatch schedule at the marketclearing price where the supply bids of generating units equilibrated with demand bids ofretailers.Many engineers argue the unfortunate disadvantages that stem from deregulation. Whereunder regulated monopolies, long distance energy lines were used for emergencies asbackup in case of generation outages, now, particularly in North America, the majority ofdomestic generation is sold over ever-increasing distances on the wholesale market beforedelivery to customers. Consequently, the power grid witnesses fluctuating power flows thatimpact system stability and reliability. To reduce system failure, the power flow of atransmission line must operate below the transmission line’s capacity. Yet now, companiesare continually operating near capacity.Additionally, as utilities exchange power to other utilities, power flows along all paths ofconnection. Therefore, any change in one point of generation and transmission affects theload on all other points. Oftentimes, this is unanticipated and uncontrolled. Usually, alonger line’s capacity is less than a shorter line’s capacity. If not, power-supply instabilityoccurs resulting in transmission lines that break or sag. Such phase and voltage fluctuationscause system interruptions as witnessed in the Northeast Blackout of 1965 (which involveda circuit breaker to trip) and 2003 (which involved a sagging line on a tree that rippled inmagnitude). Furthermore, IPPs add new generating units at random locations determined byeconomics that extend the distance to main consuming areas adversely affecting powersupply. Also, utilities, because of competitive information needs, do not publicize neededdata 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 thegrid. Experts advocate for fundamental changes to avoid serious consequences in the nearfuture. REDUNDANCY AND DEFINING "GRID"A town is only said to have achieved grid connection when it is connected to severalredundant sources, generally involving long-distance transmission. This redundancy islimited. Existing national or regional grids simply provide the interconnection of facilitiesto utilize whatever redundancy is available. The exact stage of development at which thesupply structure becomes a grid is arbitrary. Similarly, the term national grid is somethingof an anachronism in many parts of the world, as transmission cables now frequently crossnational boundaries. The terms distribution grid for local connections and transmission grid Page | 38
  39. 39. for long-distance transmissions are therefore preferred, but national grid is often still usedfor the overall structure. AGING INFRASTRUCTUREDespite the novel institutional arrangements and network designs of the electrical grid, itspower delivery infrastructures suffer aging across the developed world. Four contributingfactors to the current state of the electric grid and its consequences include:1. Aging power equipment – older equipment have higher failure rates, leading to customerinterruption rates affecting the economy and society; also, older assets and facilities lead tohigher inspection maintenance costs and further repair/restoration costs.2. Obsolete system layout – older areas require serious additional substation sites andrights-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 areineffective in addressing current problems of aged equipment, obsolete system layouts, andmodern deregulated loading levels4. Old cultural value – planning, engineering, operating of system using concepts andprocedures that worked in vertically integrated industry exacerbate the problem under aderegulated industry MODERN TRENDSAs the 21st century progresses, the electric utility industry seeks to take advantage of novelapproaches to meet growing energy demand. Utilities are under pressure to evolve theirclassic topologies to accommodate distributed generation. As generation becomes morecommon from rooftop solar and wind generators, the differences between distribution andtransmission grids will continue to blur. Also, demand response is a grid managementtechnique where retail or wholesale customers are requested either electronically ormanually to reduce their load. Currently, transmission grid operators use demand responseto 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). Smallergenerators, usually not owned by the utility, can be brought on-line to help supply the needfor power. The smaller generation facility might be a home-owner with excess power fromtheir solar panel or wind turbine. It might be a small office with a diesel generator. Theseresources can be brought on-line either at the utilitys behest or by owner of the generationin an effort to sell electricity. Many small generators are allowed to sell electricity back tothe grid for the same price they would pay to buy it. Furthermore, numerous efforts are Page | 39
  40. 40. underway to develop a "smart grid". In the U.S., the Energy Policy Act of 2005 and TitleXIII of the Energy Independence and Security Act of 2007 are providing funding toencourage smart grid development. The hope is to enable utilities to better predict theirneeds, 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 andreliability of this system. Currently the system is reliant upon relatively few generationstations. This makes current systems susceptible to impact from failures not within saidarea. Micro grids would have local power generation, and allow smaller grid areas to beseparated from the rest of the grid if a failure were to occur. Furthermore, micro gridsystems could help power each other if needed. Generation within a micro grid could be adownsized industrial generator or several smaller systems such as photo-voltaic systems, orwind generation. When combined with Smart Grid technology, electricity could be bettercontrolled and distributed, and more efficient. Conversely, various planned and proposedsystems to dramatically increase transmission capacity are known as super, or mega grids.The promised benefits include enabling the renewable energy industry to sell electricity todistant markets, the ability to increase usage of intermittent energy sources by balancingthem across vast geological regions, and the removal of congestion that prevents electricitymarkets from flourishing. Local opposition to siting new lines and the significant cost ofthese projects are major obstacles to super grids. FUTURE TRENDSAs deregulation continues further, utilities are driven to sell their assets as the energymarket follows in line with the gas market in use of the futures and spot markets and otherfinancial 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’selectric 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 andgas firms begin to merge operations as they see advantage of joint affiliation especially withthe reduced cost of joint-metering. Technological advances will take place in thecompetitive wholesale electric markets such examples already being utilized include fuelcells used in space flight, aero derivative gas turbines used in jet aircrafts, solar engineeringand photovoltaic systems, off-shore wind farms, and the communication advances spawnedby the digital world particularly with micro processing which aids in monitoring anddispatching.Electricity is expected to see growing demand in the future. The Information Revolution ishighly reliant on electric power. Other growth areas include emerging new electricity-exclusive technologies, developments in space conditioning, industrial process, andtransportation (for example hybrid vehicles, locomotives). EMERGING SMART GRID Page | 40
  41. 41. As mentioned above, the electrical grid is expected to evolve to a new grid paradigm--smartgrid, an enhancement of the 20th century electrical grid. The traditional electrical grids aregenerally used to carry power from a few central generators to a large number of users orcustomers. In contrast, the new emerging smart grid uses two-way flows of electricity andinformation 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 threesystems in smart grid- the infrastructure system, the management system, and the protectionsystem. The infrastructure system is the energy, information, and communicationinfrastructure underlying of the smart grid supports1) advanced electricity generation, delivery, and consumption;2) advanced information metering, monitoring, and management; and3) advanced communication technologies. In the transition from the conventional powergrid to smart grid, we will replace a physical infrastructure with a digital one. The needsand 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 managementand control services. Most of the existing works aim to improve energy efficiency, demandprofile, utility, cost, and emission, based on the infrastructure by using optimization,machine learning, and game theory. Within the advanced infrastructure framework of smartgrid, more and more new management services and applications are expected to emerge andeventually revolutionize consumers daily lives. The protection system is the subsystem insmart grid that provides advanced grid reliability analysis, failure protection, and securityand privacy protection services. We must note that the advanced infrastructure used insmart grid on one hand empowers us to realize more powerful mechanisms to defendagainst 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 toget richer data to and from customer smart meters and other electric devices, is also itsAchilles heel from a privacy viewpoint. The obvious privacy concern is that the energy useinformation stored at the meter acts as an information rich side channel. This informationcan be mined and retrieved by interested parties to reveal personal information such asindividuals habits, behaviors, activities, and even beliefs. NETWORKED ISLAND-ABLE MICROGRIDSAs the electricity grid becomes increasingly vulnerable to faults from equipment failure orwillful attack, the risk of a major national scale grid failure is rising. Physicist AmoryLovins has said that following hundreds of blackouts in 2005, Cuba reorganized itselectricity transmission system into networked micro grids and cut the occurrence ofblackouts to zero within two years, limiting damage even after two hurricanes. Networkedisland-able micro grids describes Lovins’ vision where energy is generated locally fromsolar power, wind power and other resources and used by super-efficient buildings. When Page | 41
  42. 42. each building, or neighborhood, is generating its own power, with links to other "islands" ofpower, the security of the entire network is greatly enhanced. This type of setup isn’timmune to large scale power failures, such as the large scale outage Cuba experienced inSeptember 2012. This raises doubts as to if this setup will make any reliabilityimprovements to the already reliable electrical grids such as those in Australia and theUnited States Page | 42
  43. 43. JACK (DEVICE FOR LIFTING TRANSFORMERS)A jack is a mechanical device used as a lifting device to lift heavy loads or apply greatforces. 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 acar jack, floor jack or garage jack which lifts vehicles so that maintenance can beperformed. More powerful jacks use hydraulic power to provide more lift over greaterdistances. Mechanical jacks are usually rated for a maximum lifting capacity (for example,1.5 tons or 3 tons). Page | 43
  44. 44. JACKSCREW VEHICLEJackscrews 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 bymanual force alone. The jack shown at the right is made for a modern vehicle and the notchfits into a hard point on a unibody. Earlier versions have aplatform to lift on the vehicles frame or axle. HOUSE JACKA house jack, also called a screw jack is a mechanicaldevice primarily used to lift houses from their foundation.A series of jacks are used and then wood cribbingtemporarily supports the structure. This process is repeateduntil the desired height is reached. The house jack can beused for jacking carrying beams that have settled or forinstalling new structural beams. On the top of the jack is acast iron circular pad that the 4" × 4" post is resting on.This pad moves independently of the house jack so that itdoes not turn as the acme-threaded rod is turned up with ametal rod. This piece tilts very slightly but not enough torender the post dangerously out of plumb. HYDRAULIC JACKHydraulic jacks are typically used for shop work, rather than as an emergency jack to becarried with the vehicle. Use of jacks not designed for a specific vehicle requires more thanthe usual care in selecting ground conditions, the 2.5 ton house jack that stands 24 inchesfrom top to bottom fully threaded out. Jacking point on the vehicle, and to ensure stabilitywhen the jack is extended. Hydraulic jacks are often used to lift elevators in low andmedium rise buildings. A hydraulic jack uses a fluid, which is incompressible, that is forcedinto a cylinder by a pump plunger. Oil is used since it is self-lubricating and stable. Whenthe plunger pulls back, it draws oil out of the reservoir through a suction check valve intothe pump chamber. When the plunger moves forward, it pushes the oil through a dischargecheck valve into the cylinder. The suction valve ball is within the chamber and opens witheach draw of the plunger. The discharge valve ball is outside the chamber and opens whenthe oil is pushed into the cylinder. At this point the suction ball within the chamber is forcedshut and oil pressure builds in the cylinder. Page | 44
  45. 45. In a bottle jack the piston is vertical and directly supports a bearing pad that contacts theobject being lifted. With a single action piston the lift is somewhat less than twice thecollapsed height of the jack, making it suitable only for vehicles with a relatively highclearance. For lifting structures such as houses the hydraulic interconnection of multiplevertical jacks through valvesenables the even distribution offorces while enabling closecontrol of the lift.In a floor jack (aka trolleyjack) a horizontal piston pusheson the short end of a bellcrank,with the long arm providing thevertical motion to a lifting pad,kept horizontal with a horizontallinkage. Floor jacks usuallyinclude castors and wheels,allowing compensation for thearc taken by the lifting pad. Thismechanism provides a lowprofile when collapsed, for easymaneuvering underneath thevehicle, while allowingconsiderable extension. PNEUMATIC JACKA pneumatic jack is a hydraulicjack that is actuated bycompressed air - for example, airfrom a compressor - instead ofhuman work. This eliminates theneed for the user to actuate thehydraulic mechanism, saving effort and potentially increasing speed. Sometimes, such jacksare also able to be operated by the normal hydraulic actuation method, thereby retainingfunctionality, even if a source of compressed air is not available. STRAND JACKA 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. Page | 45
  46. 46. REFERENCES1. Larsen & Toubro Engg. And constructions official documents (Delhi)2. Standard Handbook for Electrical Engineers3. 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. Page | 46

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