TRANSFORMERS

2015

A DETAiLED ANALYSISPAK ELEKTRON LIMITED (PEL)RAO SAIM ZAFAR

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Table of ContentsAbstract 2

Introduction 3

History4

Basics 4Modifications 5Why we need transformer? 6

Transformer Definition 7

Working Principle 7

Construction 8

Core type 9

Shell type 10

Some related terms 11

Losses 14

Types of transformers 16

Type on basis of cooling medium 17

Type on basis of design 21

Application of transformers 22

Tests 23

Specifications 27

Capitalized cost 28

Different terminologies 29Capitalization of losses worldwide 34Payback time 41

New technology 45

Slim transformers 45

Conclusion 49

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ABSTRACT

Transformer is an electrical device used for transference of energy by exploiting

the ferromagnetic properties of a conducting core. Electromagnetic induction

allows transfer of energy, but power remains constant and thus energy remains

conserved. The property is exploited at power stations where voltage is stepped up

resulting in decrease in current, allowing maximum power transfer at minimum

cost with minimum losses. Transformers differ from one another on the basis of

their mode of construction, insulating material, cooling process, core type and

winding. Types of transformers can be broadly classified in to two categories as

design type and size type transformers. Modifications in transformers are

introduced to meet the required specifications of the consumer, incooperating

minimum losses, maximum output and small size. Latest version of transformer

which is in market is known as slim transformer. Total capitalization cost of a

transformer which provides a rough estimate of the total life expectancy of a

transformer, along with the payback period mark two significant parameters taken

in to account in detail in this report.

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INTRODUCTION

Electrical energy is inevitable, the sole existence of mankind depends on it. But

easy accessibility of electricity is our main focus of interest. The question of

paramount importance is not only the generation but also distribution of energy.

The conflict is resolved by transformer which serves as an efficient mode of energy

transference. Depending on the application area and system requirement different

transformers use different technologies, with the same working principle. Dry type

and oil immersed transformers differ in cooling mechanisms and insulating

material, which gives each type some specific characteristics making it suitable for

different application areas. The authentication process and quality control is

ensured by carrying out a number of tests, which run parallel comparison of the

specification and the results. Statistical and economic analysis is a prudent step

towards harvesting maximum benefit with minimum losses and therefore taken in

to account while manufacturing a product. Future refinement critically controls

losses, size and cost.

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HISTORY

Transformer is referred to as

‘’the heart of the alternating current system’’

Originally it was invented by Otto Bláthy, Miksa Déri, Károly Zipernowsky of the Austro-Hungarian Empire First designed and used the transformer in both experimental and commercial systems. Later on Lucien Gaulard, Sebstian Ferranti, and William Stanley perfected the design

The property of induction was discovered in the 1830's but it wasn't until 1886 that William Stanley, working for Westinghouse built the first reliable commercial transformer. His work was built upon some rudimentary designs by the Ganz Company in Hungary (ZBD Transformer 1878), and Lucien Gaulard and John Dixon Gibbs in England. Nikola Tesla did not invent the transformer as some dubious sources have claimed. The Europeans mentioned above did the first work in the field. George Westinghouse, Albert Schmid, Oliver Shallen Berger and Stanley made the transformer cheap to produce, and easy to adjust for final use.

William Stanley's First Transformer built in 1885. Single phase AC power.

The first AC power system that used the modern transformer was in Great Barrington, Massachusetts in 1886. Earlier forms of the transformer were used in

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Austro-Hungary 1878-1880s and 1882 onward in England. Lucien Gaulard (Frenchman) used his AC system for the revolutionary Lanzo to Turin electrical exposition in 1884 (Northern Italy). In 1891 mastermind Mikhail Dobrovsky designed and demonstrated his 3 phase transformers in the Electro-Technical Exposition at Frankfurt, Germany.

MODIFICATIONS

1830s-Joseph Henry and Michael Faraday work with electromagnets and discover the property of induction independently on separate continents.

1836 - Rev. Nicholas Callan of Maynooth College, Ireland invents the induction coil

1876 - Pavel Yablochkov uses induction coils in his lighting system

1878 -1883 - The Ganz Company (Budapest, Hungary) uses induction coils in their lighting systems with AC incandescent systems. This is the first appearance and use of the toroid shaped transformer.

1881 - Charles F. Brush of the Brush Electric Company in Cleveland, Ohio develops his own new design of transformer

1880-1882 - Sebastian Ziani de Ferranti (English born with an Italian parent) designs one of the earliest AC power systems with William Thomson (Lord Kelvin). He creates an early transformer. Gaulard and Gibbs later design a similar transformer and loose the patent suit in English court to Ferranti.

1884 - In Hungary Otto Bláthy had suggested the use of closed-cores, Károly Zipernowsky the use of shunt connections, and Miksa Déri had performed the experiments. They found the major flaw of the Gaulard-Gibbs system were successful in making a high voltage circuit work using transformers in parallel. Their design was a toroid shape which made it expensive to make. Wires could not be easily wrapped around it by machine during the manufacturing process.

1884 - Use of Lucien Gaulard's transformer system (a series system) in the first large exposition of AC power in Turin, Italy. This event caught the eye of William Stanley, working for Westinghouse. Westinghouse bought rights to the Gaulard and Gibbs Transformer design. The 25 mile long transmission line illuminated arc

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lights, incandescent lights, and powered a railway. Gaulard won an award from the Italian government of 10,000 francs.

1885 - George Westinghouse orders a Siemens alternator (AC generator) and a Gaulard and Gibbs transformer. Stanley begin experimenting with this system.

1885 - William Stanley makes the transformer more practical due to some design changes: "Stanley's first patented design was for induction coils with single cores of soft iron and adjustable gaps to regulate the EMF present in the secondary winding. This design was first used commercially in the USA in 1886". William Stanley explains to Franklin L. Pope (advisor to Westinghouse and patent lawyer) that is design was salable and a great improvement. Pope disagrees but Westinghouse decides to trust Stanley anyway. George Westinghouse and William Stanley create a transformer that is practical to produce (easy to machine and wind in a square shape, making a core of E shaped plates) and comes in both step up and step down variations. George Westinghouse understood that to make AC power systems successful the Gaulard design had to be changed. The toroid transformer used by the Ganz Company in Hungary and Gibbs in England were very expensive to produce (there was no easy way to wind wire around an iron ring without hand labor).

1886 - William Stanley uses his transformers in the electrification of downtown Great Barrington, MA.This was the first demonstration of a full AC power distribution system using step and step down transformers.

Later 1880s - Later on Albert Schmid improved Stanley's design, extending the E shaped plates to meet a central projection.

1889 - Russian-born engineer Mikhail Dolivo-Dobrovolsky developed the first three-phase transformer in Germany at AEG. He had developed the first three phase generator one year before. Dobrovolsky used his transformer in the first powerful complete AC system (Alternator + Transformer + Transmission + Transformer + Electric Motors and Lamps) in 1891

1880s - Today - Transformers are improved by increasing efficiency, reducing size, and increasing capacity.

Why we need transformer?

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Main use of transformer is voltage manipulation

Due to the high cost of transmitting electricity at low voltage and high current levels, transformers fulfill a most important role in electrical distribution systems. Utilities distribute electricity over large areas using high voltages, commonly called transmission voltages. Transmission voltages are normally in the 35,000 volt to 50,000 volt range. We know that volts times amps equals watts, and that wires are sized based upon their ability to carry amps. High voltage allows the utility to use small sizes of wire to transmit high levels of power, or watts. You can recognize transmission lines because they are supported by very large steel towers that you see around utility power plants and substations. As this electricity gets closer to its point of use it is converted, through the use of transformers, to a lower voltage normally called distribution voltage. Distribution voltages range from 2,400 to 25,000 volts depending upon the utility. Distribution lines are the ones that feed the pole mount and pad mount transformers located closest to your home or place of business. These transformers convert the distribution voltages to what we call utilization voltages. They are normally below 600 volts and are either single-phase or three-phase and are utilized for operating equipment, including light bulbs and vacuum cleaners in our homes, to motors and elevators where we work. This is the point at which the Dry-Type Distribution Transformer comes into play. It is used to convert the voltage provided by the utility to the voltage we need to operate various equipment.

DEFINITIONTransformer is a device that converts alternating current at a certain voltage to a n alternating current at a different voltage keeping frequency constant, by electromagnetic induction.

WORKING PRINCIPLETransformers work on the principle of mutual induction.

Transformer consists of two coils that have no electrical connection but are magnetically coupled. The coil connected with the supply is known as primary coil and the other connected to the load is known as secondary coil. Normally a

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transformer has steel or an iron core; core is insulated from the windings. When primary coil is connected to the AC supply, alternating voltages produces varying magnetic field in the core and this varying magnetic field induces magnetic flux in the secondary coil. The frequency of the induced EMF is the same as the frequency of the applied voltage

CONSTRUCTIONTransformers basically consist of two windings that are usually inductive and a laminated core. The coils are insulated from the core as well from each other. Normally the core is of steel or soft iron. The steel used is having high silicon content and sometimes heat treated, to provide high permeability and low hysteresis loss. Laminated sheets of steel are used to reduce eddy current loss. A container is also required for the assembling of core and windings. Bushing is required for getting terminals out of container. Some insulating medium is also required; it depends on the type of transformer used. If the transformer is oil-based then an oil conservator is also needed.

The sheets are cut in the shape as E, I and L. To avoid high reluctance at joints, laminations are stacked by alternating the sides of joint.

Types:On the basis of construction transformer has two types:

Core type transformer

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Shell type transformer

Core type transformer:

In this transformer windings surround a considerable amount of core. Windings are present at the opposite limbs of the core. These transformers are also known as single window type transformers.

The coils are wound in helical layers with different layers insulated from each other by paper or mica. Both the coils are placed on both the limbs. The low voltage coil is placed inside near the core while high voltage coil surrounds the low voltage coil. Core is made up of large number of thin laminations.

As the windings are uniformly distributed over the two limbs, the natural cooling is more effective. The coils can be easily removed by removing the laminations of the top yoke, for maintenance.

Advantages: Low cost Useful in low voltage applications Easy to repair Non-intricate design

Disadvantages: Inability to avoid high voltage surges Low mechanical strength

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Shell type transformers:

Shell Type Transformers has a double magnetic circuit. The core has 3 limbs. Both the windings are placed on the central limb. The core encircles most part of the windings. The cols used are generally multilayer disc type or sandwich coils. Each high voltage coil is in between two low voltage coils and low voltage coils are nearest to tip and bottom of the yokes.

Advantages:1. Useful in high voltage applications:

These transformers are useful in large capacity and higher medium voltage applications.

2. Better short circuit strength:

The short-circuit strength of the transformer is increased through the use of alternating high and low voltage windings, but the size of the coils does not increase with the transformer's capacity increase.

3. Better mechanical and dielectric strength:

Shell type transformers bear more mechanical and dielectric strength.

4. Efficient cooling system:

Efficient cooling system is a distinguished trait of shell type transformers.

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5. Protection against leakage flux:

Shell-form transformers are also protected against leakage magnetic flux in case of local heating. Their iron core absorbs the leakage flux from the coils. Compared to core-form transformers, there is flexibility in the selection of the wire size, which further helps prevent local heating.

Disadvantages:

Complex construction:These transformers have a complex design.

Hard to repair:Repair is not an easy task in case of shell transformers because manufacture time is equal to the repair time.

Some related terms Tapping:A tap is a connection point along a transformer winding that allows a certain number of turns to be selected. This means, a transformer with a variable turns ratio is produced, enabling voltage regulation of the output. Tapping allows adding or subtracting the number of turns for the fine tuning of the transformer. Tap turns may be present at the end or in the middle of the coil. The tap selection is made with a tap changer mechanism.

Changing taps:

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Following things should be kept in mind while changing taps:

The first step is to de-energize the transformer and be sure that safety measures are applied to all the terminals of the transformer.

When you adjust the bolted connection, make sure that no material enters the transformer oil otherwise it may be dangerous.

Make sure that the connections are free of insulations, resins and oxidations.

When grinding metal make sure that metal particles do not go into the coils or links with any insulation if it happens it will cause the failure of the transformer.

Insulating materials:

Transformer oil:Transformer normally makes use of hydrocarbon mineral oil. It performs the following functions:

It acts as a cooling agent. It provides insulations in combination with the insulating material used

in coils and the conductors.

It has some disadvantages also:

Working of oil-based transformers is temperature dependent i-e cold environment may cause the oil to freeze and high temperature may cause it to boil hence affecting the working of the transformer.

Leakage of oil may create significant problems. The oil may catch fire thus causing a lot of damage.

Insulating paper:

Insulating paper is made of vegetable fiber these fibers are made of cellulose. It can withstand 150◦c.

Air cooling:

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In this type insulation takes through the natural air. A blast of air is blown through fans and blowers. This type of cooling is limited for the transformers not exceeding 25 kV.Diamond dotted paper:These are the insulating paper with diamond shaped epoxy resins. It can withstand 300◦c of temperature. Excellent in insulation property:This is useful for interlayer insulation of transformer winding; provides excellent insulation against heat, moisture and oil. Excellent in adhesive property:

It can be kept adhesive even at 140◦c.

Press boards:Press board is also made up of vegetable fibers and contains cellulose. Solid press board unto 6 mm to 8mm thick is ordinarily made.

The most difficult insulation problem in HT transformer occur at the ends of the windings and lead outs from the windings hence molded pressboards are widely used in these parts for insulation. Synthetic resin bonded paper based laminates are used in voltage stressed zones.

Nomex paper:It has following properties: Inherent Dielectric StrengthIt normally withstand short-term electrical stresses of 18 kV/mm to 34 kV/mm (460 V/mil to 870 V/mil), depending on product type and thickness.

Mechanical ToughnessDensified Nomex products are strong, resilient and (in the thinner grades) flexible, with good resistance to tearing and abrasion.

Thermal StabilityTemperatures up to 200°C have little or no effect on the electrical and mechanical properties of Nomex products.  These properties are retained at

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considerably higher temperatures.  These properties are maintained for at least 10 years of continuous exposure at temperatures up to 220°C.

Chemical CompatibilityNomex products are essentially unaffected by most solvents and are unusually resistant to attacks by acids and alkalis.  They are compatible with all classes of varnishes and adhesives, transformer fluids, lubricating oils and refrigerants.  Because Nomex products are not digestible, they are not attacked by insects, fungi or mold.

Radiation ResistanceNomex paper is essentially unaffected by 800 megarads (8 Mgy) of ionizing radiation and still retains useful mechanical and electrical properties after eight times this exposure.

Flame ResistanceNomex products do not produce known toxic reactions in humans or animals.  Nomex products do not melt and, with a limiting oxygen index (LOI) at 220°C above 20.8—the critical value for combustion in air—they do not support combustion. 

Moisture InsensitivityIn equilibrium at 95% relative humidity, densified Nomex papers and pressboards maintain 90% of their bone-dry dielectric strength, while many of their mechanical properties are actually improved.

Cryogenic CapabilitiesNomex products have found acceptance in a variety of cryogenic applications due to their unique polymer structure

Losses in transformers

In an ideal transformer efficiency is 100% i-e no losses occur; this can only happen when power supplied at input terminal is equal to the power delivered at output

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terminal. Obviously this cannot happen in real transformers. Real transformers suffer losses. Since it is a static device so no mechanical losses occur. The electrical losses faced are: Iron losses Copper losses

Copper loss:These losses occur when heat is dissipated due to the passage of current. They also depend upon the internal resistance of the windings. They are generally given by the formula I2 R.These losses are dependent at the load; since current increases with increase in load these are the variable losses.

Iron losses:Iron losses are also known as core losses. These are dependent at the frequency of the supply voltage and on the magnetic properties of the core material. Since these are constant factors so iron losses are the constant losses.Core losses are basically divided into two types: Eddy current Hysteresis loss

Eddy current:

When AC supply is provided to the primary coil; varying current induces magnetic field due to this EMF is induced in the secondary coil. During this process some of the flux is lost in the core which gives rise to the swirls of current perpendicular to the direction of magnetic field. This is known as eddy current. This current is not delivered to the load but it decreases the efficiency of the transformer.Eddy current can be reduced by using laminations in the core and by dividing core in small parts so that less current may pass through it.

Hysteresis loss:When demagnetization curve of the core do not follow the same path as the magnetization curve instead follow a different path; this is known as hysteresis

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loss. This loss occurs due to the non-alignment of the domains which do not find time to rearrange themselves during demagnetization.Hysteresis can be avoided by using core of: high magnetic permeability low coercivity and high resistance using air core

TPES OF TRANSFORMERS

Transformers can be broadly classified in to two categories, which differ in insulating medium, mode of construction and place of application. Types on basis of Cooling medium Types on basis of Design

TYPES ON BASIS OF COOLING MEDIUM:

On the basis of cooling agent, two type of transformers are:

Dry Type Transformer. Oil Immersed Transformer

DRY TYPE TRANSFORMER:In dry type transformer, no oil is used for insulation and cooling purpose. The cooling medium for dry type transformer is natural air.In Dry Type Transformer, cooling is done by air ventilation, providing low heat services for indoor situations where oil leakage could cause a fire or environmental hazard.

METHODS OF COOLING:

There are two cooling methods.

a) Natural Cooling:

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Dry type transformers can be Natural Cooled with Air. The natural convection of the air removes the heat generated by the transformers.

b) Forced Air Cooling:

This involves cooling the windings of the transformers with forced air, usually by means of external fans and blowers.

ADVANTAGES: Dry Type Transformers need less maintenance. Fire Proof vaults and Toxic gas removing system are not required. Dry type transformers are usually located closer to the load, resulting in cost

savings because of shorter cable and reduced electrical losses.

DISADVANTAGES: The efficiency of dry type transformers is lower than that of conventional

transformers. Dry type transformers cannot be designed for very high voltages and are

designed up to the MV range.

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OIL IMMERSED TRANSFORMER:

In oil immersed transformer, oil is used for the purpose of insulation and cooling of core and windings. The core and coils of the transformer are immersed in oil which cools and insulates. Oil circulates through ducts in the coil and around the coil and core assembly, moved by convection. The oil is cooled by the outside of the tank in small ratings, and in larger ratings an air-cooled radiator is used.

METHODS OF COOLING:

Oil Natural Air Natural Oil Natural Air Forced Oil Forced Air Forced Oil Forced Water Forced

OIL NATURAL AIR NATURAL:

In this method, the heat generated in the core and winding is transferred to the oil. The heated oil flows in the upward direction and then in the radiator. The heat from the oil will dissipate in the atmosphere due to the natural air flow around the transformer. In this way, the oil in transformer keeps circulating due to natural convection and dissipating heat in atmosphere due to natural conduction.

OIL NATURAL AIR FORCED:

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Forced air provides faster heat dissipation than natural air flow. In this method, fans are mounted near the radiator and may be provided with an automatic starting arrangement, which turns on when temperature increases beyond certain value.

Oil Forced Air Forced

In this method, oil is circulated with the help of a pump. The oil circulation is forced through the heat exchangers. Then compressed air is forced to flow on the heat exchanger with the help of fans.

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Oil Forced Water Forced:

In this method, forced water flow is used to dissipate heat from the heat exchangers. The oil is forced to flow through the heat exchanger with the help of a pump, where the heat is dissipated in the water which is also forced to flow. The heated water is taken away to cool in separate coolers.

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OILS USED IN OIL IMMERSED TRANSFORMER:

Mineral oil is basically used in Oil Immersed Transformer. Silicone-based or fluorinated hydrocarbons are also being used alternative of mineral oil.

ADVANTAGES:

An oil immersed transformer can operate at high voltages and high power ratings.

They are very reliable and can handle many years of operations without creating faults.

Oil filled transformers are more flexible for outdoors usage. More efficient than dry type transformers.

DISADVANTAGES:

Mineral Oil used is highly flammable.

TYPES ON BASIS OF DESIGNS:On basis of design, focusing on shape and size two main classifications are:

Pad mounted Transformer Pole mounted Transformer

PAD MOUNTED TRANSFORMER:

A pad mount transformer is a ground mounted distribution transformer in a locked steel cabinet mounted on a concrete pad. Since all energized connection points are securely enclosed in a grounded metal housing. Their enclosed construction allows the installation of pad-mount transformers in public areas without the need of protective fencing.

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ADVANTAGES:• Extended security for personnel because of the non-existence of exposed parts under voltage.

• Indoor and outdoor installation.

• Minimum space required for installation.

• They are safe and reliable.

• Quick implementation and low cost.

POLE MOUNTED TRANSFORMER:

Pole mounted transformers are mounted on an electrical service pole, usually at the level of the overhead cables. Pole-mounted transformers often include accessories

such as surge arresters or protective fuse links. Pole mounted transformers are small in size so that it is easy to install them on single pole structures. This makes the transformers inaccessible, reducing the risk of injury to animals and people.

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ADVANTAGES: Small in size and easy to install. Inaccessible by people and animal so reduced risk of injury.

APPLICATIONS OF TRANSFORMER Power transformers are used to minimize energy losses due to voltage drop

in transmitting electricity over long distances. They match loads with internal resistance so that there is maximum power

transfer. Dry Type Transformers are used mostly in indoor applications i.e.

hospitals, schools and commercial buildings where safety and reliability are mandatory.

Each wind turbine is connected to a step-up transformer which boosts the generating output of the turbine generator.

Transformer can increase or decrease the value of capacitor, an inductor or resistance in an AC circuit. It can thus act as an impedance transferring device.

It can be used to prevent DC from passing from one circuit to the other. Transformers with several secondaries are used in television and radio

receivers where several different voltages are required. Oil Immersed Transformers are used in utilities and power plant. Step-down Transformer is used in Distribution System to step down 11KV

voltages to 220-230V.

TESTS

Transformer is subjected to a number of tests to ensure that it is in accordance to the specifications provided. The tests are run to check different parameters of the, and are critically analyzed according to the set standard. The main tests which are normally executed are:

Type Test Routine Test Short- Circuit Test Open – Circuit Test

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High Voltage Impulse Test

Type Test:To prove that the transformer meets client’s specifications and design expectations, the transformer has to go through different testing procedures in manufacturer sites. Some transformer tests are carried out for confirming the basic design expectancy of that transformer. These tests are done mainly in a prototype unit not in all manufactured units in a lot. Type test of transformer confirms main and basic design criteria of a production lot. Different Type test that done on transformer are as follows.

Transformer Winding Resistance measurement Transformer Ratio Test Transformer Vector group test Measurement of impedance voltage/short circuit impedance (principal tap)

and load loss (Short circuit test). Measurement of no load loss and current (Open circuit test). Measurement of insulation resistance. Dielectric tests of transformer. Temperature Test Vacuum Tests Tests on on-load tap change

Routine Test:Routine tests of transformer is mainly for confirming operational performance of individual unit in a production lot. Routine tests are carried out on every unit manufactured.

Transformer winding resistance measurement. Transformer ratio test. Transformer vector group test. Measurement of impedance voltage/short circuit impedance (principal tap)

and Load loss (Short circuit test). Measurement of no load loss and current (Open circuit test) Measurement of insulation resistance. Dielectric tests of transformer.

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Tests on on-load tap-changer. Oil pressure test on transformer to check against leakages past joints and

gaskets.

Open Circuit test:In open circuit test rated voltage is applied to the input side (primary)

but secondary side is left open. A voltmeter, an ammeter and a wattmeter are connected to the input side to measure voltages, current and power respectively. As the normally rated voltage is applied to the primary, so iron losses will occur in the transformer core. As the primary no-load current (Io) which is nearly 2-10% of rated IL measured by the ammeter is very small as Copper losses are negligible in the primary and null to the secondary side so Wattmeter measures the core losses at no-load and they remain the same at all loads.

NowIron losses = Wo (Wattmeter Reading)No-load Current = Io (Ammeter Reading)Applied Voltage = V1 (Voltmeter Reading)In this caseInput = Output + LossesOutput = V2I2cosθAs I2 = 0 (As Secondary is open-circuited)So Output = 0ThereforeInput = Iron Losses

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Short Circuit Test:In this test which is known also as Impedance test, a small fraction usually 2 to 5% of the rated input voltage is applied at the primary which is usually the high voltage (HV) winding. While the secondary side which is usually the low voltage (LV) winding is short circuited by a wire through an ammeter.

Also an Ammeter, Voltmeter and Wattmeter are connected on the primary side. The primary voltage is gradually increased until the full load current I1 flow through the primary. At this point I2 also has full load current. Under these conditions the copper losses are maximum while the iron losses are negligible because of the small primary voltage.Here

Input = Output + LossesWhere Output = V2I2cosθAs V2 = 0 so Output = 0 Input = Copper Losses at Full load

High Voltage Impulse Test:

High voltage impulse test is carried out, to test the transformer capacity to withstand the voltage surges that are caused due to lightening or switching. The ability of a transformer to withstand these voltage surges depends on the insulation

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or dielectric strength of insulting and cooling medium. Artificial generation of lightening impulse is carried out using Impulse Generators.

Impulse Generation:Impulse generation is carried using Impulse Generators which consists of energy banks, which generate high voltage beam used for testing. The energy bank comprises on capacitors connected in parallel along with charging resistors, which are discharged in series to create the impulse voltage. There are approximately twenty capacitors each of 150kV, which produce a high voltage impulse of about three million volts. The impulse test sequence is applies successfully to each line terminal of tested winding. The other line terminals and windings are kept earthed during the process.

SPECIFICATIONS

The Business Unit Distribution Transformers pursues a quality policy aimed at integral quality and development of a working environment receptive to continuous improvement. The whole organization is involved in such a way that all

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delivered products and services satisfy the quality expectations of both external and internal customers.

COUNTRY RATINGS VOLTAGES

USA Up to 10 MVA Up to 72.5 kV

Belgium Up to 7 MVA Up to 72.5 kV

Ireland Up to 5 MVA Up to 72.5 kV

CAPITALIZATION

Capitalization - definition

It is defined as the provision of capital for a company, or conversion of assets or income of a company to capital is called capitalization.

The process of classifying a cost as long term investment, rather than charging it to its current operations is also defined as capitalization.

Capitalization Cost

Capitalization Cost is defined as an expense that is added to the cost basis of a fixed asset on a company's balance sheet. Capitalized Costs are incurred when building or financing fixed assets is invested upon. Capitalized Costs are not expenses in the period they were incurred, but recognized over a period of time via depreciation or amortization.

A capitalized cost doesn't appear on the income statement, but instead appears on the long term assets account and a credit side on the cash account of the balance sheet. However, the depreciation expense related to the capitalized cost would

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appear as an expense on the income statement. Since long-term assets is larger due to the effect of capitalization, the depreciation costs are also larger proportionally.

Total Ownership Cost

The concept of the capitalization cost makes the pathway for the introduction of the important concept of Total Ownership Cost (TOC) that is a financial estimate intended to help buyers and owners to determine the direct and indirect cost of a product or system. The TOC is a widely used concept from the management accounting. It is the sum of different cost associated with a product, such as the purchase cost, Installation cost, commissioning cost, operational cost, maintenance cost (over the useful life time period, such as 20 -30 years) and emission costs (as per the regulations).

The Total Ownership Cost is the factor that is brought into consideration during purchase of transformers, when comparing the cost of the losses occurred due to the transformer, this cost can be quite significant when calculated over the total

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useful life. A low loss can appear to be expensive in short term or in means of initial capital investment, but over the long period of time (such as the useful age of the transformer) it would cost lesser when compared to a high loss transformer with smaller initial capital investment.

The Total Ownership Cost introduces the concept of Pay-Back Time Period, which can be defined as the total time required by the investment to pay back the cost incurred on the investment.

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CAPITALIZATION OF LOSSES:

The capitalized cost (CC) of a transformer can be expressed as sum of the purchase price (Ct), the cost of no load losses and the cost of the load losses, or as a formula:

CC=Ct + K1 x P0 + K2 x PK

Where k1 represents the assigned cost of no load per watt P0. The value of no load losses per watt K2. The assigned cost of load losses per watt and Pk the value of the load losses per watt.P0 and Pk are transformer properties. K1 and K2 are properties that depend on the expected loading of the transformer and energy prices. K1 and K2 are calculated as follows:

K1 = (1+ i)n−1i .(i+1)n ×C × 8760

K2 = (1+ i)n−1i .(i+1)n ×C × 8760 ×(

Il

I r)

2

Where:

i = interest rate (% per year)

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n = lifetime (years)

C = kWh price (EUR/kWh)

8760 = numbers of hours in a year

IL = loading current

IR = rated current

EXAMPLE OF TOC CALCULAIONS IN PAKISTAN:

TOC= Purchase Price + K1 x (no load losses) + K2 x (load losses)

Transformer rating: 200 kVA

Where:

K1 = Rs. 195.99 per KW

K2 = Rs. 299.99 per KW

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For Low Loss Transformer:

Purchase price= Rs. 580,165

No load losses = 396 KW

Load losses = 2728 W

TOC1 = Rs. 580,165 + 195,99 x (396) + 299.99 x (2728)

= Rs. 1476149.76

For High Loss Transformer:

Purchase price = Rs 387,000

No load losses = 495 W

Load loses = 3410 W

TOC2 = Rs. 387,000 + 195.99 x (495) + 299.99 x (3410)

= Rs 1,506,980.95

Benefit of using low loss transformer = TOC2 – TOC1

= 1,506,980.95 – 1,476,149.76

= Rs. 30,831.19

INFLUENTIAL FACTORS OF THE “A FACTOR”:

The parameters with highest influence on A are:

1. Energy Price2. Interest rate3. Economic lifetime

The other input parameters have no influence on A. Interest rate and the A factor have a negative correlation.

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INFLUENTIAL FACTORS ON THE “B FACTOR”

The parameters with highest influence on B are:

1. The load2. Energy price3. Interest rate4. Economic lifetime

Most important input parameter of Factor A is the energy price and the most influencing parameter on B factor is load.

CAPITALIZATION OF LOSSES WORLDWIDE

METHODOLOGY OF COMPUTING TOC IN INDIA

TOC = Ic + (A x Wi ) + (B x Wc )

TOC = total owning cost

Ic = initial cost including taxes of transformer as quoted by the manufacturer.

A factor = cost of no load losses in Rs/watt

B factor = cost of load losses in Rs/watt

Wi = no load losses quoted by the manufacturer in watt

Wc = load losses quoted by the manufacturer in watt

A factor = H x Ec/1000 x ((1+r ¿¿n−1¿ /r ¿

B factor = A factor x LLF

H = no of service hours per year of the distribution transformer = 8400 hours

Ec = average energy cost (Rs/kWh) at 11kv/33 kv for the utility

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n = life of transformer in years = 25 years

LLF = loss load factor = 0.3 LF + 0.7 LF2, where LF is load factor

LF for rural areas = 0.5

LF for urban areas = 0.7

METHODOLOGY OF COMPUTING TOC IN KUWAIT

The capitalization will be based on the following assumptions:

Interest on capital: 10%

Capitalization period: 10 years

Charge per unit: 0.026 KD/kWh

Loss load factor: 0.26

Demand factor (D): 0.5

Transformer’s energy iron loss / year (PEE) = 8760 x iron loss

Transformer’s energy winding loss / year (PWDG) = 8760 x LLF x D x D x winding loss

Total energy = A + B

Capitalized operational losses = 6.14 x (A + B) x Charge per unit

METHDOLOGY OF COMPUTING TOC IN SAUDI ARABIA

Transformer vendors / manufacturers shall be evaluated by using the following capitalization formula:

T = P + 11,000 X C + 4000 X W

T = Total capitalized cost in Saudi Riyals

P = initial cost of transformer in Saudi Riyals

C = iron (core) losses in KW (no load losses)

W = copper (winding) losses in kW at rated load (load losses)

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ADVANTAGES:

Life cycle cost analysis is a method that encompasses not only the initial purchase price but also the comparative costs of competing models, equalized to present day dollars. Since the operating cost of a transformer over its life may be many times its initial price the only fair comparison with competing models must take operating costs into account.

Another benefit to owning a transformer with low life cycle cost, results from the fact that it runs cooler. Loss in the form of heat reduces the life of a transformer by causing damage to the insulation over time. It can also cause transformers to fail. Consequently, a transformer with lower life cycle cost would be expected to have a longer life and lower failure rate, as well as lower losses.

A transformer with lower losses reduces the amount of power generation needed to accommodate the losses. This in turn reduces the emission of greenhouse gases, i.e. carbon dioxide produced by fossil fuel generators.

DISADVANTAGES:

The drawback of this process is, as mentioned, the difficulty in predicting the future load profile and electricity costs and tariffs with any confidence. On the other hand, these optimization efforts depend on material prices, particularly active materials, i.e. conductor and core material. Dynamic optimization makes sense when there is the different price volatility of different materials like aluminium and copper or high and low loss magnetic steel.

For large transformers, above a few MVA , the cost of losses are so high that transformers are custom built, tailored to the loss evaluation figures specified in the request for quotation for a specific project.

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For distribution transformers, often bought in large batches, the process is undertaken once every few years. This yields an optimum transformer design, which is then retained for several years less so changed dramatically. In fact the loss levels established in national standards reflect established practice of preferred designs with respect to loss of evaluation values.

The result that can be drawn from this report is that the purchase of higher-cost higher-efficiency unit instead of a lower cost, low efficiency unit will result in significant savings over the life of the transformer. As for the environmental benefits, the high efficiency copper wound transformer will contribute to reducing greenhouse gas emissions by reducing the consumption of fossil fuel necessary to accommodate excessive transformer losses.

Net Present Value

Present Value

If you understand Present Value, you can skip straight to Net Present Value.

 

So $1,000 now is the same as $1,100 next year (at 10% interest).

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We say the Present Value of $1,100 next year is $1,000

Because we could turn $1,000 into $1,100 in one year (if we could earn 10% interest).

And we have in fact just used the formula for Present Value:

PV = FV / (1+r)n

PV is Present Value FV is Future Value r is the interest rate (as a decimal, so 0.10, not 10%) n is the number of years

DEFINITION of 'Net Present Value - NPV'

The difference between the present value of cash inflows and the present value of cash outflows. NPV is used in capital budgeting to analyze the profitability of an investment or project. 

The following is the formula for calculating NPV: 

where:

Ct = net cash inflow during the period

Co= initial investment

r = discount rate, and

t = number of time periods 

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In addition to the formula, net present value can often be calculated using tables, as well as spreadsheets such as Microsoft Excel.

Explanation of Net Present Value

Example: Let us say you can get 10% interest on your money.

So $1,000 now could earn $1,000 x 10% = $100 in a year.

Your $1,000 now would become $1,100 by next year.

So $1,100 next year is the same as $1,000 now.

Determining the value of a project is challenging because there are different ways to measure the value of future cash flows. Because of the time value of money, a dollar earned in the future won’t be worth as much as one earned today. The discount rate in the NPV formula is a way to account for this. Companies have different ways of identifying the discount rate, although a common method is using the expected return of other investment choices with a similar level of risk.

For example, if a retail clothing business wants to purchase an existing store, it would first estimate the future cash flows that store would generate, and then

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discount those cash flows into one lump-sum present value amount of, say $565,000. If the owner of the store was willing to sell his business for less than $565,000, the purchasing company would likely accept the offer as it presents a positive NPV investment. Conversely, if the owner would not sell for less than $565,000, the purchaser would not buy the store, as the investment would present a negative NPV at that time and would, therefore, reduce the overall value of the clothing company.

Use in decision making:

if It means Then

NPV > 0 the investment would add value to the firm

the project may be accepted

NPV < 0 the investment would subtract value from

the firm

the project may be rejected

NPV = 0 the investment would neither gain nor lose

value for the firm

We should be indifferent in the decision whether to accept or reject the project. This project adds no monetary value. Decision should be based on other criteria, e.g., strategic positioning or other factors not explicitly included in the calculation.

The discount rate:

The rate used to discount future cash flows to the present value is a key variable of this process.

A firm's weighted average cost of capital (after tax) is often used, but many people believe that it is appropriate to use higher discount rates to adjust for risk, opportunity cost, or other factors. A variable discount rate with higher rates applied to cash flows occurring further along the time span might be used to reflect the yield curve premium for long-term debt.

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Pay-Back Period

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Payback period in capital budgeting refers to the period of time required to recoup the funds expended in an investment, or to reach the break-even point. For example, a $1000 investment which returned $500 per year would have a two-year payback period. The time value of money is not taken into account.

Formula

The formula to calculate payback period of a project depends on whether the cash flow per period from the project is even or uneven. In case they are even, the formula to calculate payback period is:

Payback Period =

Initial Investment

Cash Inflow per Period

When cash inflows are uneven, we need to calculate the cumulative net cash flow for each period and then use the following formula for payback period:

Payback Period = A B

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+ C

In the above formula

A is the last period with a negative cumulative cash flow;

B is the absolute value of cumulative cash flow at the end of the period A;

C is the total cash flow during the period after A

Both of the above situations are applied in the following examples.

Decision RuleAccept the project only if its payback period is LESS than the target payback period.

Examples

Example 1: Even Cash Flows

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Company C is planning to undertake a project requiring initial investment of $105 million. The project is expected to generate $25 million per year for 7 years. Calculate the payback period of the project.

Solution:

Payback Period = Initial Investment ÷ Annual Cash Flow = $105M ÷ $25M = 4.2 years

Example 2: Uneven Cash Flows

Company C is planning to undertake another project requiring initial investment of $50 million and is expected to generate $10 million in Year 1, $13 million in Year 2, $16 million in year 3, $19 million in Year 4 and $22 million in Year 5. Calculate the payback value of the project.

Solution:

CumulativeCash Flow Year Cash Flow

0 (50) (50)

1 10 (40)

2 13 (27)

3 16 (11)

4 19 8

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5 22 30

Payback Period= 3 + (|-$11M| ÷ $19M)= 3 + ($11M ÷ $19M)≈ 3 + 0.58≈ 3.58 years

Advantages and DisadvantagesAdvantages of payback period are:

1. Payback period is very simple to calculate.2. It can be a measure of risk inherent in a project. Since cash flows that

occur later in a project's life are considered more uncertain, payback period provides an indication of how certain the project cash inflows are.

3. For companies facing liquidity problems, it provides a good ranking of projects that would return money early.

Disadvantages of payback period are:

1. Payback period does not take into account the time value of money which is a serious drawback since it can lead to wrong decisions. A variation of payback method that attempts to remove this drawback is called discounted payback period method.

2. It does not take into account, the cash flows that occur after the payback period.

NEW TECHNOLOGIES

With the advancement of technology, novelty and innovation finds free play. Older

technology is being replaced by compact and efficient designs, which have low

cost and profound technology with improved features and mechanisms.

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For a transformer, three factors need further modification:

Losses

Size

Cost

New designs of transformers are required to meet the specifications of the

consumer keeping in view the place of its installation. Latest technology

introduced in transformer is known as slim transformer.

SLIM TRANSFORMER

Merger of dry type and oil immersed transformer, using silicon oil as an insulation medium

SLIM Transformer uses the combination of the technologies of both dry type and oil immersed transformer, functions same and becomes smaller and compact than other. The SLIM transformer uses proven technologies in an innovative design combining Nomex (insulating paper) thermal insulating technology with a class K dielectric fluid(Silicon oil cooling medium). The result is a transformer that is smaller in size, lighter in weight than dry and oil immersed transformer and capable to handle severe overloads.

HISTORY:The concept of SLIM transformers enabled by the use of Nomex as solid insulation is the result of a tight cooperation between 2 companies, CG Power Systems and DuPont. The success story started in 2000 by an agreement to focus development on high temperature fluid filled transformers primarily Targeted to the wind segment. This cooperation is as much at the technical level to always remain on the front end of innovation and maximizing the benefit brought by Nomex, as in the marketing level to jointly position by association of strong brands, to inform end-users and to convince of the value of this concept vs. more conventional technology. By using a high temperature solid insulation, Nomex and a high temperature fluid, silicone, it was possible to design/develop what will be identified as SLIM. The advantages provided by SLIM transformers are primarily:

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smaller size, lower weight at a given power rating capable of handling severe overloads more reliability, more flexibility

With time and a growing market adoption the following features could be added as proven in the field:

reduced fire hazard requiring less servicing

2001 2002 2003 2004 2005 2006 2007 2008 20090

1000

2000

3000

4000

5000

6000Installed Number Of Units

TIME

NUM

BER

OF

UNIT

S

GLOBALLY INSTALLED WIND POWER PLANTS

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49%

26%

25%

2009 Global Installed Wind Power Capacity by Region (MW)

EMEA APEJ

AMERICANS

FEATURES: Compact

Smaller in size and lighter in weight than other types of transformer but have same function.

Overloads

Slim transformer is capable of handling severe overloads.

Environment friendly

Slim transformer is environment friendly. It has smaller environmental footprint.

Reliable

Slim transformer is safer and reliable than that of others.

Extended life

It requires less servicing with an extended lifetime.

Technology

It is based on tried and testing technology.

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AFTER SALE SERVICES: Repairs Maintenance Installation & Commissioning Supply of spare parts Monitoring & Diagnosis Substation operation

CONCLUSION

Transformer is by far the most efficient electrical device employed for transference

of energy, accounting for minimum power dissipation and heat losses. The material

components of transformers differ from one another, depending upon the

specifications and surroundings which will serve as an application platform for it.

Every transformer has distinguished features depending on the construction and the

insulating material, with different dielectric strength and cooling mechanisms.

Each transformer is subjected to a number of tests and critically analyzed to ensure

that the transformer is in compliance with the given requirements. Cost-effective

solution to energy transference leads to total capitalized cost, which include the

total losses and material cost as two decisive parameters while manufacturing a

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transformer. Total ownership cost includes all the investment modules including

installation and maintenance, which along with payback period helps the consumer

to make a well informed decision and obtain maximum benefit.

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