Training Module

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SANJEEV KADIANPresents

TRAINING MODULE

INDEX

Particulars Pages

1. Understanding Transformers

2. Core

3. Conductor

4. Bushings

5. Buchholz Relay

6. Hermatically Sealed T/fs

7. Magnetic Oil Level gauge

8. Silicagel Breather

9. Sub-Assemblies

10. Tap Changer

11. Temperature Indicator

12. Transformer Oil

13. Repairing Distribution Transformers

14. Sales & Marketing

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UNDERSTANDING TRANSFORMERS

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TRANSFORMER BASICS

INTRODUCTION

A transformer is basically an electromagnetic static equipment based on the principal of Faraday’s law of electromagnetic induction. A transformer essentially consists of magnetic core, build-up of insulated silicon steel laminations, upon which are wound sets of coils suitably located with respect to each other and termed as primary and secondary windings. Such a combination may be used to derive a voltage higher or lower than what is immediately available. In the former case, the transformer is termed as step-uptransformer, while in the later case, it is known as step-down transformer. The primary winding is that winding to which the supply voltage is applied, irrespective of whether it is higher or lower voltage winding, the other winding to which the load is connected is termed as secondary winding.

THE WORKING PRINCIPLE

If an alternating voltage is applied to the terminals of the primary winding of a transformer, with the secondary winding open-circuited, a very small current will flow in the primary circuit only, which serves to magnetise the core and to supply the iron loss of the transformer. Thus, an alternating magnetic flux is established in the core which induces an e.m.f. in both primary and secondary windings. As primary and secondary windings are wound on the same core and as the magnetic flux is common to both windings, obviously, the voltage induced in the primary and secondary windings are, therefore, in direct proportion to the number of turns in these windings.

LAMINATED CORE

Diagram showing magnetic circuit and windings of a transformer

TRANSFORMER LOSSES

Transformer loss mainly has two components: no-load loss & load loss.

No load loss results from steel materials, used for magnetizing core laminations. It includes hysteresis and eddy current loss, dielectric loss and copper loss due to no-load current.

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Load loss arises from the resistive components, used for building the primary and secondary windings. It comprises I2R loss of windings, loss due to eddy current and stray loss in the tank and core clamp.

Diagram showing various components of losses

EFFICIENCYNo-load loss of the transformer is constant and does not change with variation of load. However, load loss changes in respect of the loading pattern. The transformer will yield maximum efficiency at a load when no-load loss and load loss are equal.

REGULATIONThe regulation of a transformer refers to the change of secondary terminal voltage between no load and load conditions; it is usually quoted as a per cent or per unit value for full load at given power factor.

GENERAL CONSTRUCTION

Constructional Parts

The transformer is comparatively simple structure since there are no rotating parts, or bearings. The chief elements of the construction are –(1) Magnetic circuits, comprising limbs, yokes and clamping structures.(2) Electric circuits, the primary and secondary windings, formers, insulation and bracing devices.(3) Terminals, tappings and tapping switches, terminal insulators and leads.(4) Tank, oil, cooling devices, conservators, dryers and ancillary apparatus.

1. Magnetic CircuitThe magnetic core is built up of laminations of high grade silicon sheet steel, which are insulated from each other by a special coating of varnish. The usual thickness of laminations are 0.18 mm, 0.23 mm, 0.30 mm and 0.35 mm. The two losses, due to varying flux, occur in the core: the eddy current and the

Hysteresis & eddy current

loss

Di-electric loss as a

function of primary & secondary

voltage

Copper loss due to

no-load current

Stray loss in tank &

core clamp

Loss due to eddy current

set-up in the

conductor

I2R lossfor both

primary & secondary windings

No-Load Load

Total

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hysteresis losses. The silicon content of the iron and the nature of annealing are very important in determining the hysteresis loss. Silicon makes the material brittle, thus making it difficult to process.

Core ConstructionThe core built up with high-grade non-aging cold rolled grain oriented silicon steel lamination having high permeability and low hysteresis loss. A three legged, mitered and interleaved type core construction is adopted. Main limbs are bound fiberglass types and clamp plates to ensure adequate mechanical strength, and to prevent vibration during operation rigidly bolt yokes. The clamping structure and core sheet are specially connected not to make one turn circuit & connected to top of tank at one point.

Core construction of modern core type power Transformers Cold rolled grain oriented steel laminations are used for cores of all modern power Transformers. This is because it permits the use of flux densities between 1.6 to 1.8 wb/m2 as compared with 1.3 wb/m2 for hot rolled steel & consequently the weight of both core and windings is reduced.

Cooling of coresIn transformers of medium and high capacity with diameter of circumscribing circle D>=0.35m the cores have the relatively small surface / volume ratio so that the temperature gradient in the core is excessive. In such cases the cooling must be augmented by dividing the core in to different stacks with longitudinal oil ducts (usually 6mm wide) running parallel to the lamination.

Core-ClampingAll core-clamping bolts shall be effectively insulated with enamel or preferably varnish impregnated but not insulated with paper. The joints must be of inter leaved type. Liberal axial ducts must be provided so as to ensure free circulation of oil and efficient cooling of the core, so that the maximum temperature at any point will be within permissible limits.

EarthingPositive earthing of the cabinet shall be ensured for providing two separate earthing pads. The earth wire shall be terminated on to the earthing pad and secured by the use of star of self-etching washer. Using a separate earth wire shall do earthing of hinged door.

Core EarthingWith the exception of individual laminations and core bolts, all internal metal parts of the transformer require earthing.

2. Electric CircuitsThe windings of a transformer are made of copper or aluminium wire and / or strip. Heavy current capacity requires conductors of larger cross-section. To reduce eddy current losses within the conductors, several small wires or parallel strips are preferable than to use one large strip. This gives rise to unequal reactance components of the conductor, which can be reduced by transposing the conductors.

Two types of coil constructions are commonly used – Concentric or Pancake / interleaved. Between coils segments, spacers are provided to permit dissipation of heat from the windings either by ventilation or by a liquid cooling medium.

Double cotton, single cotton with an under layer of enamel or synthetics enamel, or double paper covering are most commonly being used for winding wires. Strips are generally covered with layers of papers known as DPC, TPC, QPC, MPC etc.

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Winding Constructions

The windings are arranged to ensure free circulation of oil and to reduce hot spots in the windings. All materials used in the assembly of windings are insoluble, non-catalytic and chemically inactive in the hot transformer oil. The windings are supported securely in axially as well as radially using radials spacers, axial spacers, press board cylinders and clamp rings, so that they will not be displaced or deformed during short circuits. The coils are clamped by adjustable pressures bolts at are top end and the face is uniformly distributed to the windings using sturdy and to rings.

A transformer generally consists of LT & HT windings. The L.T. windings shall be circular and concentric with HT windings on the outer side the electrical and magnetic balance under all conditions of operation. The arrangement shall permit free circulation of the oil to ensure the absence of hot spots. It is essential that the windings shall be subjected to through sinking occurring at site.

The general design and construction of the transformers and bracing’s of the windings shall be such that no mechanical movements of the coils will be possible with dead short on either side of the transformer. The short circuit ratings of the transformers shall be as per IS 2026 of latest issue. All clearance of windings and other live parts shall be adequate for the maximum voltage operation plus 10 percent. There should be sufficient clearance between H.V. and L.V. windings yoke and the coils and between coil in HT windings to have free oil circulation. Current density in the high voltage and low voltage windings together with the section of wire that will be used therein shall be clearly stated in the tender.

High Voltage ConductorFor distribution transformers of medium capacity, the conductors being chosen for primary winding are mostly round in shape.

low Voltage ConductorIn case of low voltage conductors, since the current is generally high, a rectangular conductor is commonly used. Multiple strips in parallel are also selected for a higher rating transformer.

InsulationThe insulation material to be used for the windings shall be suitable for satisfactory service in tropical climates in this country and full load operation as per ISS. DFC insulation shall be provided for high voltage as well as low voltage windings.

The insulation between the H.V. and L.V. windings and core, comprises Bakelite – paper cylinder or elephantine wrap that is typical. The insulation of conductors may be of paper, cotton or glass tape, glass tape being used for air – insulated transformers.

Paper insulation usually necessitates the use of round coils, while the cross – over of the several strands in a conductor must be properly shaped, and not merely twisted. The high voltage winding is separated from the low – voltage winding by a series of ducts and Bakelite cylinders or barrels.

3 . Lead and Terminals

The connections to the windings are copper rods or bars, insulated wholly or in part, and taken to the bus – bars directly in the case of air – cooled transformers, or to the insulator bushings on the tank top in the case of oil – cooled transformers.

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Terminal Arrangement

a) Bushing terminals shall be provided with suitable terminal connectors of approved type & size for cable/overhead conductors’ termination of HV side & cable termination on LT side.

b) The neutral terminals of 433V winding shall be brought out on a bushing along with the 433V volt phase terminals to form 4 wires system for the 433V. Additional neutral bushing shall be provided for earthing.

4. Transformer Tank

All the tanks are of double welded construction and are reinforced by stiffener of structural steel. All bottled connection to the tank is filled with the compressible oil tight gasket. The tank is provided with two earthing terminals for the purpose of the grounding. The tank and accessories of the transformer can be withstanding full vacuum of 0.1 Tore. And a maximum positive pressure of 1kg / sq.cm. In order to relive the excessive gaseous pressure which may build up by a fault or an arcing inside the tank, it is equipped with a pressure relief device / explosion vent which is designed to operate when the maximum gaseous pressure in the tank exceeds 0.5 kg / 5q. cm.

Tank bodies for most of the transformer are made from rolled steel plates, which are fabricated to from the container. While designing tanks for transformer, a large number of factors include keeping the weight, stray load losses and cost a minimum.

The tanks should be strong enough to withstand stresses produced by jacking and lifting. The size of the tank must be large enough to accommodate cores, windings, internal connections and also must give the require clearance between the windings and the walls.

The fittings include thermometer pockets, drain cock, rollers or wheels for moving the transformer in to position, eye – bolts, for lifting, conservators and breaths. Cooling tubes are welded in, but separate radiators are individually welded and afterwards bolted on.

Radiators

During service, the tank body can dissipate a total loss equivalent to 500 W/Sq m (maximum) of the tank surface area. In case the total loss, i.e. (no-load + load loss) is more than the loss dissipated by tank surface, the loss in excess is required to be dissipated with the help of additional cooling surface which is commonly called radiator.

Classification of radiators

Radiators commonly being used are of three different types:

1. Elliptical tube radiator2. Pressed steel radiator3. Corrugated wall panel

Elliptical tube radiators and pressed steel radiators operate on then convection process of cooling, whereas a corrugated wall panel performs cooling by radiation only.

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Corrugated wall panel radiators are commonly being used for sealed type transformers and also on such places where there are restrictions on overall dimensions. The radiators are widely used for transformers built for export, as corrugated wall panel transformers occupy less space and can accommodate more transformers in one container during transport.

Cooling Methods

A Simple cooling1 AN Natural cooling by atmospheric circulation, without any special devices. The

transformer cores and coils are open all round to the air. This method is confined to very small units of a few KV, at low voltages.

2 AB In this case the cooling is improved by an air blast, directed by suitable trunking and produced by a fan.

3 ON The great majority of transformers are oil – immersed with natural cooling, i.e. the heat developed in the cores and coils is passed to the oil and thence to the tank walls, from which it is dissipated. The advantages over air cooling include freedom from the possibility of dust clogging the cooling ducts, or of moisture affecting the insulation, and the design for higher voltages is greatly improved.

4 OB In this method the cooling of an ON – type transformers is improved by air blast over the outside of the tank.

5 OFN The oil is circulated by pump to natural air – cooler. 6 OFB For large transformer artificial cooling may be used. The refrigerator, where it is

cooled by air – blast.7 OW An oil – immersed transformer of this type is cooled by the circulation of water in

cooling tubes is situated at the top of the tank but below oil – level.8 OFW Similar, to OFB, except that the refrigerator employs water instead of air blast for

cooling the oil, which is circulated by pump from the transformer to the cooler.b. Mixed cooling

ON/OFN, ON/OFB, ON/OFW, ON/OB/OFB, ON/OW/OFW, ONAN, ONAF, OFAF

Cooling ductsIn large transformers, the cooling surface of the cores must be augmented otherwise temperature rise will be excessive owing to small surface/volume ratio of the cores. Cooling ducts provides the additional surface. The cooling may be (I) horizontal or (ii) vertical. The vertical cooling ducts are along the direction of laminations and hence can be easily provided. The horizontal ducts are across the laminations and therefore require special punching of core. The oil following through these ducts takes away the heat.

PaintingsTanks should be sand blasted or cleaned by chemical process before painting. In general a primary coat of suitable anticorrosive paints followed by two coats of standard grey is applied on the tanks and radiators.

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SCHEDULE OF TESTS

ROUTINE TESTS

Following tests are conducted on each and every transformer.

Measurement of Insulation Resistance Measurement of Voltage Ratio Separate Source Voltage Withstand Test Induced Over-voltage Withstand Test Measurement of No Load Loss and Current Measurement of Impedance Voltage/Short Circuit Impedance and Load Loss Measurement of Winding Resistance Unbalance Current

TYPE TESTS

Following tests are conducted on only one transformer of each rating for a particular design, subject to client’s requirement.

Impulse Test -- (Conducted by recognized govt. testing laboratory) Short Circuit -- (Conducted by recognized govt. Testing Laboratory) Check of Voltage Vector Relationship Temperature Rise Test Oil Dielectric Test Air Pressure Test Vacuum Test Oil Leakage Test.

FINAL TEST

Following tests are carried out on the Transformer as per sequence. Measurement of Insulation Resistance Measurement of Voltage Ratio and Check of Voltage Vector Relationship Separate Source Voltage Withstand Test Induced Over-voltage Withstand Test Measurement of No Load Loss and Current Measurement of Impedance Voltage/Short Circuit Impedance and Load Loss Measurement of Winding Resistance Unbalance Current Oil Dielectric Test Temperature Rise Test Air Pressure Test Vacuum Test Oil Leakage Test. Magnetic balance test Measurement of zero sequence impedance Measurement of noise level

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TESTING PROCEDURE

INSULATION RESISTANCE:

The Oil/Air Temperature is measured and recorded immediately prior to the test. The insulation resistance of each windings corresponding to other windings and to earth is measured and recorded. I.R Value between : HV & E : Connect Positive terminal of Insulation Tester to HV Bushing and Negative

Terminal to the Earth. LV & E : Connect Positive terminal of Insulation Tester to LV Bushing and Negative

Terminal to the Earth. HV & LV: Connect Positive terminal of Insulation Tester to HV Bushing and Negative to

LVBushing.

VOLTAGE RATIO & VOLTAGE VECTOR RELATIONSHIP:

(A) Measurement of voltage Ratio –To check the voltage ratio of Transformer Ratio Meter is used;

V1 N1 Voltage Ratio = ------ = -------- where, N1 = Primary Turn

V2 N2 N2 = Secondary Turn

(B) Voltage Vector Relationship(Dyn-11)

Transformer’s A-phase of primary side and A-phase of secondary side are shorted, and in primary side 3-Phase supply (About balance voltage 400 Volts) applied at rated frequency. Voltage is , then, measured on following points :-

IV-2V = IV-2w = 1W-2W and !W-2V In this test IV-2W and IV-2V may be same and 1W-2V may be more than 1W-2W

SEPARATE SOURCE VOLTAGE WITHSTAND TEST:

In this test the full test voltage given below applied for 60 seconds between the winding under test and all terminals of remaining windings, core, frame and tank of the transformer connected together to earth.

TESTS :

(A) High Voltage Test - In this test secondary side of the transformer and tank are earthed and from primary side full test Single Phase voltage applied for 60 seconds at rated (50 Hz) frequency.

(B) Low Voltage Test - In this test primary side of the transformer and tank are earthed and from secondary side full test, Single phase voltage applied for 60 seconds at rated (50 Hz) frequency.

INDUCED OVER VOLTAGE WITHSTAND TEST:

The transformer can be tested on either LV or HV side. Double the rated voltage at double the frequency is applied at the testing side. The other side is open circuited.Duration of Test : 60 seconds

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NO LOAD LOSS AND CURRENT:

The test is conducted by a Three Wattmeter Method. The No Load Loss and the no load current are measured at rated frequency at a rated voltage while the other winding is to be left open circuited. In this way after applying rated 3 Phase voltage at rated frequency from LV side, the current is measured in Ammeter. This current will be no load current or magnetizing current, and the total reading of the watt meters will be the Total No Load Loss of the tested transformer.

To measure the No Load Loss and No Load current of Power Transformer one CT-PT set is connected to an Auto Transformer.

IMPEDANCE VOLTAGE/SHORT CIRCUIT IMPEDANCE & LOAD LOSS:

The Impedance voltage/short circuit impedance and load loss are measured at rated frequency by applying an approximately full load current to one winding with the other winding short circuited. The measurements may be made at any current between 25 percent and 100 percent, but preferably not less than 50 percent of the rated current (principal tapping) or tapping current to the test current.

The measured value of Load Loss may be corrected by the following formula :

2 Rated Current Total Loss = -------------------- Test Current

The measured value of the impedance voltage may be corrected by the following formula :

Rated Current Total Impedance voltage = -------------------- Test Current

MEASUREMENT OF WINDING RESISTANCE:

To measure the resistance of LV and HV Winding , Kelvin and Wheatstone Bridge are respectively used. The resistance and temperature of each winding are recorded.

UNBALANCE CURRENT:

In this test of the Transformer, all three phases of secondary (Star Connected) are shorted and shorted point linked to the neutral point of transformer with an Ammeter.Then, full load current at rated frequency is applied to primary (Delta Connected) of the transformer. The current measured between the shorted secondary and the neutral point is the unbalance current. Circuit diagram is respectively same as load loss test :-

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TEMPERATURE RISE TEST:

In this test LV winding of the transformer is shorted and from HV winding full losses (Load loss at 75 Deg. Cent. + No Load Loss) is fed. One thermometer is placed in oil filled thermometer pocket of transformer for oil temp. and other 3 Nos. thermometers in different directions of the transformer for ambient temp. After feeding the total loss at transformer, the voltage current, top oil temp. and ambient temp. is measured. These all readings are taken one by one after every hour. This process is continued till oil temperature rise of transformer remains constant. Keeping oil temp. rise constant, load is reduced at full rated current for one hour, after one hour supply shut-off. After shutting off the supply hot resistances of winding are immediately measured. Thus, after plotting the graph between time and hot resistance, we can find out the highest actual hot resistance at the zero time. In this way the maximum winding temperature rise can be calculated by the following formula :

(a) Hot Resistance x (225+RT)-225 ........... For Aluminium. Cold Resistance

(b) Hot Resistance x (235+RT)-235 ........... For Copper Cold Resistance where, RT = Ambient Temp. at the time of cold resistance :

OIL DIELECTRIC STRENGTH TEST:

To test the Dielectric strength of oil, a motorised oil testing set is used . Before using this instrument, the oil pot of this instrument washed with the same oil, which to be tested. After washing the pot, the gap between the electrodes is set at 2.5 mm and the oil is filled in it. Wait for about 10 minutes, so that the air bubbles disappear. After this, the instrument is switched ‘ON’ and the flash point (in KV) is noted. This process is repeated for six times and the average of the six values is the Dielectric Strength of the oil.

AIR PRESSURE TEST:

This is a type test which is conducted on the transformer tank. The tank may be fixed with a dummy cover with all fittings including bushings in position and subjected to a pressure of 0.35 Kg/Cm2 (Hg) upto 1000 KVA Transformer Tank 0.80 Kg/Cm2 (Hg) above 1000 KVA Transformer Tank

created inside the tank and maintained for one hour. The permanent deflection of flat plate, after pressure has been released should not exceed the values given below:

Horizontal length of flat plate(in mm)

Permanent Deflection(in mm)

Upto and including 750 5751 - 1250 6.5

1251 - 1750 81751 - 2000 9.52001 - 2250 112251 - 2500 12.52501 - 3000 16Above 3000 19

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VACUUM TEST:

This is a type test , which is conducted on transformer tank. The transformer tank may be completed with all fittings including bushings in position and shall be subjected to full vacuum corresponding to (-) 0.7 Kg/Cm.sq.(Hg) created inside the tank for one hour. The permanent deflection of flat plates after the vacuum has been released shall not exceed the value specified below without affecting the performance of the transformer.

Horizontal length of flat plate(in mm)

Permanent Deflection(in mm)

Upto and including 750 5751 - 1250 6.5

1251 - 1750 81751 - 2000 9.52001 - 2250 112251 - 2500 12.52501 - 3000 16Above 3000 19

OIL LEAKAGE TEST:

This is a type test, which is conducted on fully completed transformer. The transformer shall be oil filled and complete with all fittings. Then following air pressure is applied:1) 0.35 Kg/Cm2 (Hg) pressure – For transformers upto 1000 KVA for one hour2) 0.80 Kg/Cm2 (Hg) pressure – For transformers above 1000 KVA for 12 hours

During this period no leakage should occur.

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RAW MATERIAL & ACCESSORIES

The following is the list of the major raw-material required for the manufacture and repair of transformers.

CORE CORK SHEET COPPER GASKET WASHER OIL BUSHING CLAMP STEEL (TANKS) CLAMPING MEMBER RADIATORS / WALL PANELS ARCING HORNS TAP CHANGER OFF LOAD, ON LOAD BIMETALLIC CONNECTOR BUSHINGS & FITTINGS EARTHING LUGS COPPER SHEET & FLAT SRBP TUBE OIL CONSERVATOR COTTON TAPE BREATHER EMPIRE SLEEVING DIAL TYPE THERMOMETER PRESS BOARD OIL LEVEL GAUGE INSULATING KRAFT PAPER PRESSURE RELIEF DEVICE INLINE CONNECTOR BUCHHOLZ RELAY BAKELITE SHEET OIL & WINDING TEMP. INDICATOR CI PLUG RATING & DIAGRAM PLATE BRIGHT ROD BI-DIRECTIONAL ROLLERS BOLTS, NUTS, WASHER CABLE BOX PRIMER & FINISH PAINT LIFTING LUGS INSLULATING VARNISH TERMINAL MARKING PLATE SOLDER WIRE AIR RELEASE PLUG LUGS VALVES GROUNDING TERMINALS

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CORE

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CORE

The need for electrical steel sheets of highest quality has increased in recent years due to rapid development of electrical machinery industry in many countries. Grain Oriented steel sheets namely ORIENTCORE, ORIENTCORE H1-B & ORIENTCORE HI-B.LS are some of the finest quality of core.

ORENTCORE.HI-B is a breakthrough in that it offers higher magnetic flux density, lower core loss and lower magnetostriction than any conventional grain-oriented electrical steel sheet.

ORIENT.HI-B.LS is a novel type with marked lower core losses, produced by laser irradiation of the surface of ORIENTCORE.HI-B sheets.

Quality

Stable product quality Core loss are extremely low in rolling direction Permeability is extremely high in rolling direction Lamination factor is higher Excellent Insulation coatings

Standard Sizes

ORIENT.HI-B ORIENT.HI-B.LSCoils Thickness 0.23mm & 0.27mm

0.30mm & 0.35mm0.23mm,0.27mm

Standard Width 914 mm & 950 mmAvailable Width From 50mm to 1000 mm From 50mm to 950 mm

Cut length Thichness Same as for coilsLength Lengths upto 3100 mm are available in 840 mm and

914 mm widthsCore cut in customer specified sizes can also be provided

Annealing of stacked electrical sheets

Though ORIENTCORE and ORIENTCORE.HI-B are grain orient steel sheets with excellent magnetic properties, mechanical stress during such operations as cutting, punching and bending affect their magnetic properties adversely. When these stress are excessive, stress relief annealing is necessary.

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Following method is observed for stress relief annealing

1. Stacked electrical steel sheets are heated thoroughly in the edge-to-edge direction rather than in the face-to-face direction, because heat transfer is far faster in side heating.

2. A cover is put over sheets stacked on a flat plate. Because ORIENTCORE and ORIENTCORE.HI-B have extremely low carbon content and very easily decarburized at annealing temperatures, the base, cover and other accessories used are of very low carbon content .

3. To prevent oxidation so as to protect the coating on the sheets, a nonoxidizing atmosphere free from carbon sources is used having less than 2%hydrogen or high-purity nitrogen gas. Due point of the atmosphere is maintained at 0ºC or less.

4. Care is taken to the flatness of annealing base, because an uneven base distorts cores, leading to possible distortion during assembly.

5. Annealing temperature ranging from 780ºC to 820ºC is maintained for more than 2 hours or more. Cooling is done upto 350ºC in about 15 hours or more.

Available Grades

ORIENTCOREo M1, M2, M3, M4, M5 & M6

ORIENTCORE.HI-Bo 23ZH90, 23ZH95, 27ZH95,27ZH100,30ZH100o M-0H,M-1H,M-2H,M-3H

ORIENTCORE.HI-B.LSo 23ZDKH90,27ZDKH95

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Conductor

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CONDUCTOR

Conductors are one of the principal materials used in manufacturing of transformers. Best quality of copper rods are procured from indigenous as well as foreign sources. Normally 8 mm & 11 mm rods are procured. For each supply of input, test certificate from suppliers is obtained and at times, such input is got tested from reputed test labs.

Various sizes as specified by customers can be drawn. At each stage of drawing of copper wires & strips, the dimension is measured all around and in case found oversize particular die is replaced forthwith. During final stage of drawing smoothness and brightness is strictly observed. Elongation, Springiness & Tensil strength are thoroughly tested. While drawing, care is taken that the physical properties of the conductors are maintained.

After the wires & strips are drawn as per clients requirements they are moved on to paper covering process. To prevent the inclusion of copper dust or other extraneous matter under paper covering the conductor is fully cleaned by felt pads or other suitable means before entering the paper covering machine. As per the customers requirements DPC, TPC & MPC conductors are produced. It is ensured that each layer of paper is continuous, firmly applied and substantially free from creases. No bonding or adhesive material is used except to anchor the ends of paper. Any such bonding materials used to anchor the ends do not have deleterious effect on transformer oil, insulating paper or the electric strength of the covering. It is ensured that the overlapping percentage is not less than 25% of the paper width.

Arrangement of layersAccording to the number of layers used the paper is applied as follows.

Two layers:-Where there are two layers both of them are wound in opposite directions.

More than two layersWhere there are more than two layers all the layers are applied in the same direction, all, except the outermost layer is butt wound, and the outermost layer is overlap wound. Within each group of papers the position of the butt joints of any layer relative to the layer below is progressively displaced by approximately 30 percent of the paper width.

Note: Overlapping can also be done as per customer requirements.

Grade of paperThe paper, before application, is ensured to be free from metallic and other injurious inclusions and have no deleterious effect on insulating oil. The thickness of paper used is between 0.025 mm to 0.075 mm.

Enameled ConductorApart from paper covered conductors, we have all the facilities of producing enameled conductors as per customer specified requirements.

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BUSHINGS

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BUSHINGS

Insulators and Bushings are built with the best quality Porcelain shells manufactured by wet process. The materials that go into the manufacture of these insulators offer best quality mechanical and electrical characteristics. The standard colour of the glaze is brown, but white glazed insulators can also be made available on request.

Manufacturing process

For manufacture of electro porcelain, high quality indigenous raw materials viz, China Clay, Ball Clay, Quartz and Feldspar is used. The raw materials in lots undergo thorough test in quality control laboratory before being user for manufacture.

Quartz and feldspar are ground to required finesses and then intimately mixed with ball and china clay in high speed blungers. They are then passed through electromagnetic separators, which remove iron and other magnetic impurities. The slip produced is passed to a filter press where extra water is removed under pressure and the resulting clay cakes are aged over a period. The aged cakes are extruded to required form viz., cylinders, on high vacuum de-airing pug mill. The extruded blanks or cylinders are given shapes of Insulators / Bushings which are conditioned and are shaped on copying lathes as the case may be.

These shaped insulators / bushings are then dried under controlled conditioned and then they are glazed, Trade mark, month, year and country of manufacture are marked before firing. The glazed shells are fired in fuel efficient kilns having temperature controls to ensure uniformity of firing high strength in porcelain shells. Metal parts used in the assembly of Insulators, are of blackheart and malleable cast iron and are hot dip galvanized to conform to international standards.

Testing, Assembly & packing

All insulators & bushings undergo routine electrical and mechanical tests. The tests before and after assembly are carried out according to IS Specifications, to ensure their suitability for actual conditions of use. Porosity tests are also carried out regularly on samples from every batch, to ensure that the insulators are completely vitrified. These insulators are then visually checked and sorted, before they are packed in sea worthy packing, to withstand transit conditions.

Types of Insulators & Bushings

Bushing Insulatorso Hollow Porcelain Bushings upto 33 KV o Application : Transformers, Capacitors, Circuit Breakers etc.

Pin Insulatorso Pin Insulators conforming to ISS, B.S., IEC and other international

standards upto 33 KV

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Post type Insulatorso Post type insulators, complete with metal fittings, generally IS

Specifications and other International Standards upto 33 KV Solid Core Insulators

o Line Posto Long Rodo Support

Special Type Insulatorso C.T. upto 66 KVo P.T. toto 33 KVo Weather Casing

L.T. Insulatorso Shackel Typeo Spool Typeo Pin Typeo Guy strain

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Product Specification

1. H.V. Bushings (IS:3347) 1. 12-17.5 KV / 250 amps2. 12-17.5 KV / 630 amps3. 12-17.5 KV / 1000 amps4. 12-17.5 KV / 2000-3150 amps5. 24 KV / 250 amps6. 24 KV / 630 amps7. 24 KV / 1000 amps8. 24 KV / 2000 – 3150 amps9. 36 KV / 250 amps10. 36 KV / 630 amps11. 36 KV / 1000 amps12. 36 KV / 2000-3150 amps

2. L.V. Bushings (IS:3347) 1. 1 KV / 250 amps2. 1 KV / 630 amps3. 1 KV / 1000 amps4. 1 KV / 2000 amps5. 1 KV / 3150 amps

3. H.V. Bushings (IS:8603) 1. 12 KV / 250 amps2. 12 KV / 630 amps3. 12 KV / 1000 amps4. 12 KV / 2000-3150 amps5. 36 KV / 250 amps6. 36 KV / 630 amps7. 36 KV / 1000 amps8. 36 KV / 2000-3150 amps

4. C.T. Bushings (IS:5612) 1. 12 KV2. 24 KV3. 36 KV

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EPOXY BUSHINGS

All Epoxy Resin Cast Components are made from hot setting reins cured with anhydrides; hence these provide class-F Insulation to the system. In an oxidizing atmosphere, certain amine cured Epoxy Resins can start to degrade at 150ºC whereas the anhydride cured systems are stable at 200ºC therefore our epoxy components are cured with anhydrides which gives them a longer life.

Electrical & Mechanical Properties

Compressive Strength 1500-2000 Kg/cm2

Tensil Strength 650-850 Kg/cm2

Di-electric Strength 18-22 KV/mm

Range of products available in the market

1. All designs of bushings for sealed type distribution transformers2. All designs of Spouts, Trolley bushings etc for 1.1 KV oil circuit breakers3. Resin cast CT’s & PT’s for 1.1 KV Instrument panels4. Any design of Bus Bar supports for control panels

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Buchholz Relay

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BUCHHOLZ RELAY

Power transformers are considered to be highly reliable type equipment, yet, in order to ensure the continuity of service that modern conditions demand, protective devices are required. The purpose of such devices is to disconnect faulty apparatus before large scale damage caused by a fault to the apparatus or to other connected apparatus. Such devices generally respond to a change in the current or pressure arising from the faults and are used for either signaling or tripping the circuits.

Protective devices in the ideal case must be sensitive to all faults, simple in operation, robust for services and economically feasible. Considering liquid immersed transformer, a near ideal protective device is available in the form of gas and oil operated relay described here. The relay operates on the well known fact that almost every type of electric fault in a liquid immersed transformer gives rise to a gas. This gas is collected in the body of the relay and is used in some way or the other to cause the alarm or the tripping circuit to operate.

The principle of the gas and oil relay was first successfully demonstrated and utilized by “Buchholz” many years back.

Applications

Double element relays can be used in detecting minor and major faults in a transformer. The alarm element will operate, after a specified volume of gas has collected to give an alarm indication. Examples of incipient faults are.

1) Broken down core bolt insulation2) Shorted lamination3) Bad contacts4) Overheating of parts of windings

The alarm element will also operate in the event of oil leakage, or if air gets into the oil system. The trip element will be operated by an oil surge in the event of more serious faults such as

1) Earth faults2) Winding short circuit3) Puncture of bushings4) Short circuit between phases

The trip element will also be operated if a rapid loss of oil occurs.

Available range

Relays for users outside India

Type SRIE GORIE GOR2E GOR3ENo. of Switching System

1 2 2 2

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Pipe bore in mm 25 25 50 80Transformer ratingIn MVA

≤ 1.6 ≤ 5.0 > 5.0≤ 10.0

> 10.0

Relays for users in India

Type GOR1 GOR2 GOR3 SRI SRI/VNo. of Switching System

2 2 2 1 1

Pipe bore in mm 25 50 80 25 25Transformer ratingIn MVA

< 1.0 > 1.0≤ 10.0

> 10.0 For OLTC

< 1.0

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Hermatically Sealed T/fs

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HERMETICALLY SEALED TRANSFORMERS

Sealed from environment by

a) Welded Lidb) Bolted Lid

For fin type radiators For corrugated tanks

Nitrogen gas cushion Transformer is located above the totally filled with fluidliquid level and level being

indicated on the liquid level indicatorpositioned at thehighest point on the lid

A pressure relief device may be fitted to regulate the inernal pressure

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Magnetic Oil Level Gauge

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MAGNETIC OIL LEVEL INDICATOR

Magnetic oil level indicators are used for varied purposes. In Transformer they are mounted on the conservator to read oil level and to set off an alarm when the oil level falls below a predetermined level.

It consists of following parts.

a. Gear assemblyb. Magnetic couplec. Float with armd. Cam assembly with mercury switche. Dial and pointer.

The float is hinged and swings up or down when oil level rises or falls. This rise or fall rotates the bevel gear and thus the pinion of the gear assembly. The pinion on turn rotates the driving magnet inside the conservator. The follower magnet positioned outside carries a pointer and a cam. The pointer reads oil level and the cam is set to operate the mercury switch at a predetermined low level.

One normally open mercury switch is provided to actuate low level alarm. The switch is adjustable to compensate error in orientation of pad. Leads of this switch are connected to the terminals.

Specifications

1. Operating Liquids Transformer oil to IS:335 & other oils2. Working temperatures 0 to 100ºC of oil3. Working pressure 0 to 4 Kg/Sq.cm.4. Environment Suitable for indoor & outdoor use5. Electric Switch One SPST Mercury Switch6. Contact rating 5 Amps 240 V A.C. 0.5 Amp 240 V.D.C.7. Switch Operation Normally open, closes when oil level drops

to near empty condition, recovers automatically on rising of oil level.

Model SO-4 SO-6Dial Size 100 150Weight 2.2 2.9

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Silica gel Breather

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SILICAGEL BREATHERS

Breathing Process

Breathing is the process wherein Transformer sucks the air inside or pushes the air outside its body. When Transformer is loaded or unloaded, the oil temperature inside the transformer tank rises or falls. Accordingly, the air volume inside the tank changes by either sucking in or pushing out the air. This phenomenon is called “Breathing” of the transformer.

Now, the air which is being sucked in contains either foreign impurities and / or humidity which changes dielectric strength of oil. For proper working of Transformer, it is absolutely necessary that dielectric strength of transformer oil remains unimpaired. Hence, it is necessary that air entering into the transformer is free from moisture & foreign impurities.

Window Type Silicagel Breathers

The breather is made out from Aluminium (Gravity) die cast in two parts i.e. Top shell & bottom shell and a gel compartment is made out from Tin plate which is known as removable inner container. The inner gel container can be withdrawn by unscrewing the wing-nuts removing the top shell or bottom shell portion of the breather in case of two piece model.

A sight windows have been provided to observe / inspect the condition of Slicagel & Oil level.

An oil seal made out of aluminium sheet is fitted in the base of the breather to prevent diffusion of moisture into silicagel when no breathing is taking place.

Clear view type Silicagel Breather

Is based on DIN standard 42567. Visibility is excellent, because the entire compartment is transparent. The change in colour of gel in any part of the mass is clearly visible, even from a distance as against very poor visibility in window type design.

The entire oil cup is also transparent. Hence, change in the level of oil as well as any sedimentation in oil is clearly visible as against invisibility in window type

Available range

From 0.125 Kg to 15 Kg capacitySn Silicagel Content Transformer rating Suitable for transformer

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(in Kgs) (in KVA) holding oil(in litres)

1 0.125 200 3002 0.250 300 4503 0.500 500 7504 1.000 2000 14005 1.500 5000 30006 3.000 7000 75007 4.000 10000 150008 6.000 15000 210009 8.000 20000 2700010 10.000 25000 3200011 15.000 30000 47000

Above table is just a guide line. The gel content or the size of the breather is determined by the volume of air passing through the breather, the oil contents of the transformer and the atmospheric conditions at the place of installation. Hence the ultimate user should decide the size and gel content of the breather that would suit to him.

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Sub-Assemblies

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SUB ASSEMBLIES

Sub Assemblies are categorized as under:-

HV & LV Coils Core Assembly Core-Coil Assembly Pressed Steel Radiators & Panels MS Tanks Corrugated & Radiator type

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COILS

Coils are of two typea) High Voltage Coils b) Low Voltage Coils.

1. HIGH VOLTAGE COILS. H.V. Coils are one of the components of finished transformers. High voltage

coils are made on automatic layer setting winding machines. A solid cylindrical former of predetermined diameter and length is being used as base over which the coil is made. Generally round insulated wire of either copper or aluminium is used as basic raw-material. The coils are made in no. of layers. The starting and finishing leads of each coils are terminated on either side of the coil. These leads are properly sleeved and locked at no.of points.

2 LOW VOLTAGE COILS: L.V. Coils are also one the components of transformer. The procedure of

making low voltage coil is generally same as described above, except that the shape of the basic raw-material is rectangular.

Disc Winding in process Finished Disc winded coil

CORE ASSEMBLY

1. Core is one of the components of finished transformer. Core assembly is done manually.

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2. The basic raw-material is Cold Rolled Grain Oriented Silicon Steel and is in the form of thin sheets, cut to size as per design. Generally three different shapes of core laminations are used in one assembly. Notching is performed to increase the magnetic path. The laminations are put through annealing process.

3. These laminations are assembled in such a manner that there is no air gap between the joints of two consecutive sheets.

4. The entire assembly is done on a frame commonly known as core channel These frames are used as a clamping support of the core assembly. Hooks are provided on the core frame for easy movement of core assembly. The entire assembly is tightened by corebolt.

Core Assembly of Distribution Transformer

Core Assembly in process ofPower Transformer

CORE - COIL ASSEMBLY:The components produced in the coil winding and core assembly stage are taken into Core-Coil assembly Stage.

1. The Core assembly is vertically placed with the foot plate touching the ground. The top yoke of the core is removed and is kept in a safe place. The limbs of the core are tightly wrapped with cotton tape and then varnished.

2. Cylinder made out of insulating press board / pressphan paper is wrapped on all the three limbs. Low voltage coil is placed on the insulated core limbs.

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Insulating block of specified thickness and number are placed both at the top and bottom of L.V. Coil.

3. Cylinder made out of corrugated paper or plain cylinder with oil ducts are provided over LV Coil. HV Coils are placed over the cylinder. Gap between each section of HV coils including top and bottom clearances is maintained with the help of oil ducts; as per the design/drawings.

4. The Top Yoke is refilled. Top core frame including core bolts and tie rods are fixed in position.

5. Primary and secondary windings are connected as per the requirements. Phase barrier between HV Phases are placed as per requirement. Connections to the tapping Switch (if required) are made. Finally, the entire component is placed in the Oven for removal of moisture content. After drying the component is ready for tanking.

Distribution TransformerCore Coil Assembly

Power TransformerCore Coil Assembly

TANKS

Best quality MS Sheets, Press Steel Radiators and Corrugated Panels are procured from indigenous and foreign sources. These radiators and panels are welded with the tanks fabricated in-house. In case of Power Transformers Radiators provided are of detachable form due to large in size and ease of shipment.

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Tank Fabrication in process Corrugated Tank

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Tap Changer

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OLTC

On Load tapchangers marketed by us are tested as per IS 8468-1977 Amendment 1-1980. On Load Tapchanger (OLTC) are also suitable for off circuit furnace duty application. It comprising of driving mechanism and high speed selector switch. Optional equipments include Remote Tapchanger Control Cubicle (RTCC) with indicating apparatus, fitted with devices to prevent malfunctioning. Designed for unidirectional power flow but can be used for bidirectional power flow under certain combinations of current rating and step voltage.

The tap changer is designed for operation at current upto 300 amperes. The Selector Switch which is capable of making and breaking load current in addition to selecting tapping, is housed in an oil filled container and separated from the transformer oil by an oil-tight cast epoxy resin Terminal Board.

At one end of the container a separate chamber houses the motor and driving mechanism. A weather proof door provides access to the operating mechanism and a suitably positioned window allows easy reading of the tap position indicator.

Available Range

Sn Rated Voltage

Max. Steps

Max. Step Voltage

Max. Rated Current

Oil Content

Tappings Flange Dimension

SC withstand

KV Nos. Volts Amps Ltrs mm K Amps for 2 Sec.

1 11 8 600 300 440 Linear 840 x 832 3.5 2 11 4 220 100 300 Linear 1035x990 2.03 33 8 1200/750 125/300 440 Linear 840 x 832 3.54 33 16 1200/750 100/300 780 Linear 1043x1035 3.55 33 20 1200/750 125/300 780 Linear 1043x1035 3.56 33 16 1200/850 100/300 380 Coarse/

fine plus-minus

1066x830 3.5

7 33 9 1200/850 100/300 380 Linear 1066x830 3.58 33 16 1000/750 300/500 1200 Linear 1499x1207 5.09 66 16 1200/750 125/300 1200 Linear 1499x1207 3.510 66 16 1200/750 125/300 850 Linear 1072x1110 3.511 66 20 1200/750 125/300 850 Linear 1072x1110 3.5

OFF CIRCUIT TAP CHANGER

Off Circuit Tap changers are used for adjusting the voltage of oil immersed transformers under de-energised condition by adding or cutting out turns of primary or secondary windings.

Construction

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Tap changing is done by rotating an insulating driving shaft. Bridgings are made between two terminal stud contacts either by snap action of self centering spring loaded ring or by sliding palm fixed with centre drive shaft. The centre shaft is operated by means of an externally mounted hand wheel on a double sealed stuffing box having spring loaded positioner with tap position indicator. Indicator mechanically shows the tap number of which the tap changer is operating. Provision is made for pad locking in any tap position. Between first and last position stoppers are provided to avoid bridiging across range.

Material of construction

Sn. Parts Material Specification1. Centre driving shaft FRP pultruded rod Epoxy based2. Phase Board Phenolic laminated paper

base sheetGr. P3 of IS:2036

3. Terminal Stud High conductivity Hard Copper OR Free machining Brass

IS:613IS:319

4. Bridiging Ring Hard Copper (Medium) Oxygen free OR Free machining Brass Tube

Conductivity to BS 1977C 103 IS:319

5. Tie rod insulating tube & spacers

Phenolic laminated paper tube & FRP tube

Gr. P3 Epoxy Based

6. Spring Spring Steel IS:4454 Part I Gr. II7. Stuffing Box CI or CS8. Handle CS or Aluminium9. Supporting Structure CS Gr. Fe 540 W-HT

IS:961

Available RangeKV AMPS POSITION TYPE HANDLE11 30 5 SB T

30 7 SB T30 9 TR T30 11 TR W60 5 SB T60 7 SB T60 9 SB T60 5 TR W60 7 TR W60 9 TR W60 11 TR W

100 5 SB W100 7 SB W100 5 TR W

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KV AMPS POSITION TYPE HANDLE100 7 TR W100 9 TR W100 11 TR W150 5 TR W150 9 TR W250 5 TR W250 7 TR W250 9 TR W500 5 TR W500 9 TR W

22 30 5 SB T30 7 SB T30 5 TR T30 7 TR T30 9 TR T60 5 SB T60 7 SB T60 5 TR W60 7 TR W60 9 TR W

100 5 TR W100 7 TR W100 9 TR W150 5 TR W150 7 TR W150 9 TR W250 5 TR W250 7 TR W250 9 TR W

22/11 30 5 SB T30 7 SB T30 5 TR W30 7 TR W30 9 TR W60 5 SB T60 7 SB T60 7 TR W60 7 TR W60 9 TR W

100 5 TR W100 7 TR W

33/11 30 7 TR W

33 30 5 TR T30 7 TR T30 9 TR T60 5 TR W60 7 TR W60 9 TR W60 11 TR W

100 5 TR W

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KV AMPS POSITION TYPE HANDLE100 7 TR W100 9 TR W150 5 TR W150 7 TR W150 9 TR W400 5 TR W

SB : Side Base Construction T : ‘T’ handleTR : Tie Rod Construction W : Wheel Handle

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Temperature Indicator

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TEMPERATURE INDICATOR (Dial Type)

Measuring SystemWhen heated, volumetric expansion of liquid will be proportional to the rise in temperature. A sensing bulb, a measuring bellows and a small bore capillary tubeconnecting the two from the measuring system which is filled with liquid. When the bulb is exposed to a rise in temperature, the liquid inside the measuring system expand proportionately causing corresponding volumetric changes in the bellows. Since one end of the bellows is anchored it will move linearly in proportion to the measured temperature.

World Class Product Ergonomically designed 270º part circular scale Complete temperature and head compensation for bellows & capillary line No periodic site adjustment Upto four electrically isolated heavy duty control switches Winding temperature indication by thermal image device Remote transmission for electrical repeater Switch & circuit testing facility from outside the case. All circuits to ground tested at 2500 volts A.C. 50 Hz for 60s Maximum temperature indicating pointer Ventilated weather proof case (Protective class IP 55 of IEC 529)

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SPECIFICATIONS

1. Dial 140 mm diameter with 270º part circular scale marked boldly for rapid reading.

2. Standard Ranges 0-120ºC, 20-240ºC, 30-150ºC, 0-150ºC3. Accuracy of indication ±1.0% f.s.d4. Control Switches Upto 4 numbers, electrically isolated normally

open S.P.S.T. dry electrode mercury and glass switches.

5. Switch Rating 5 Amps continuous at 250 Volts A.C. or D.C. overload rating of 10 Amps in A.C. circuit only for short duration such as motor starting. Switches are independently adjustable for making and breaking contacts at pre-set temperatures.

6. Capillary Standard Lengths 5m, 6m, 10m and 12m stainless steel armour sheathed

7. Bulb Type F or Type M 8. Case Finish Stove enameled hammerstone deep blue

outside and all white inside.9. Case Mounting Projection mounting with back straps. Weather

proof case (protective class IP 55 of IEC 529) is suitable for outdoor service. However a canopy type weather shield will improve visibility under tropical conditions.

10. Capillary Entry Bottom or Top of case – vertical11. Electrical Entry Bottom of case – vertical through 2 holes (19

mm or 26 mm)12. Maximum Pointer Resettable from outside by means of a

screwdriver is fitted to the instrument window. A special damping device ensures accuracy of readings even under vibration conditions.

13. Switch Testing A switch testing knob is fitted on the instrument lid to facilitate checking of the switch settings from outside, without removing the instrument lid.

14. Electrical Connection Are made to the terminal blocks inside the instrument case. Approved insulating materials are used and all circuits to ground tested at 2500 Volts A.C. 50 Hz for 60 seconds. A wiring diagram is fixed inside the instrument case.

Temperature Indicators with dials of 60º segmental scale & 240º part circular scale is also available.

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Transformer Oil

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TRANSFORMER OIL

Transformer oil is a petroleum base mineral oil used extensively in power and distribution electrical equipments such as transformers, switchgears, capacitors and allied equipments. It provides insulation between windings, winding to core, winding to tank and acts as a coolant to take away the heat generated by power losses and also acts as an arc quenching medium.

QualityQuality of transformer oil marketed by us has to undergo tests and checks conforming to IS-335 of BIS (Bureau of Indian Standards) and also international standards: Oxidation stability, gas absorption, chemical deterioration, break down voltage, resistivity, dielectric dissipation factor etc. Physical characteristics tests are also conducted in a routine manner. We offer following distinct advantages:-

1. High Volume Resistivity at 27ºC & 90ºCHigh insulation resistance between transformer windings or higher megger value.

2. Very low dielectric dissipation factorReduces temperature rise during service, because of lower electrical losses.

3. Highly refined oilReduces aromatic content and sulphur content.

4. Low ViscosityImproves cooling

5. Higher initial interfacial tensionSmoother functioning of oil with lesser maintenance due to low deterioration.

6. Low S.K. valueOptimum Refining

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Technical Characteristics

1 Appearance : Clear, transparent and free from suspended matter or sediment.

2. Density at 29.5ºC (Max) : 0.89 g/cm3

3. Kinematic Viscosity at 27ºC (Max) : 27 cst4. Interfacial tension at (Closed) (Min) : 0.04 N/m5. Flash point Pensky-Marten (Closed) (Min) : 140ºC6. Pour Point (Max) : -6ºC7. Neutralisation Value (Total Acidity) (Max) : 0.03 mg KOH/gm8. Corrosive Suplhus

(in terms of Classification of copper strip): Non-Corrosive

9. Electric Strength (Min)a) New untreated oil : 30 KVb) After treatment : 60 KV

10. Dielectric Dissipation factor (tan delta) at 90ºC (Max) : 0.00211. Specific Resistance (Resistivity)

a) at 90ºC (Min) : 35 x 1012 ohm cmb) at 27ºC (Min) : 1500 x 1012 ohm cm

12. Oxidation Stabilitya) Neutralisation value after Oxidation (Max) : 0.40 mg KOH/gmb) Total Sludge after oxidation (Max) : 0.10 by weight

13. Presence of Oxidation inhibitor : Absent14. Water Content (Max) : 50 PPM15. Tests on Sample aged for 96 hours as per ASTM

Open Beaker method with Copper catalystA) Dielectric dissipation factor at 90ºC (Max) : 0.2B) Specific Resistance (Resistivity) Ohm-cm (Min)

a. at 90ºC : 0.20 x 1012

a. at 27ºC : 2.5 x 1012

C) Neutralisation Value mg KOH/gm (Max) : 0.05D) Sludge by n-heptane (Max) : 0.05

16. S.K. Value % (Typical) : 8

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Repairing Distribution Transformers

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PROCEDURE FOR REPAIRING DISTRIBUTION TRANSFORMERS

The procedure for repairing transformers is divided into three main stages. These are (1) pre-repair stage (2) repair stage & (3) post repair stage. All

these stages are detailed below:

I. Pre-repair StageThe pre-repair stage is further broken down into sub stages, each sub stage being enumerated as follows:

1. Preliminary Inspection (Site / Depot)

If required by the client then the damaged transformer is examined at the installation site or at the client's depot by the firm's representative in presence of the client's representative (normally the substation in-charge or the Depot manager).

All observations are recorded on a pre-formatted table in the preliminary inspection report (format enclosed). Photographs of the transformer in a) installed i.e., undisturbed state, b) opened state i.e., after de-tanking the transformer must be snapped. Care should be taken to snap all necessary views of the transformer in both the states.

The transformer is checked for the following:i) State of the main tank ii) State of the conservator vesseliii) State of the Radiatorsiv) State of Bushings and Fittings (viz. Arcing Horn etc.)v) State of the Dehydrating Breathervi) State of Windingsvii) State of the Coreviii) State of the Transformer Oilix) State of the Valves (viz. PRV, Drain Valves etc.)x) Missing parts, if any.

A site / preliminary inspection report is prepared and signed by the firm's representative and counter signed by the client's representative.

If undertaking the repair of the transformer is expected by both the concerned parties to be economical then suitable transportation of the same to the repair works is arranged.

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Note : At the time of receiving the damaged transformer the repair firm's representative must ensure that the state of transformer is clearly indicated on the receipt slip i.e., all the missing and damaged items must be clearly mentioned.

2. Lifting:

The damaged transformers are lifted from the client's depot and brought to

our works.

3. Unloading: The transformer are unloaded at the unloading bay by the loading / unloading personnel.

- 2 -

4. Offer for Joint Inspection: The client is intimated of the transformer arrival. Date and time of joint inspection is finalised.

5. Joint inspection: All observations made must be recorded on a pre-formatted table in the inspection report.(format enclosed)

i) On the arrival of the Inspector/s deputed by the client the transformer /s is / are brought inside the shed to the ear marked inspection area.

ii) If sealed, the seals are broken in the presence of the inspector.

Transformer Tank & Conservator Vesseliii) If present, drain oil from the transformer tank and conservator vessel into a

separate marked drum. Visually inspect the conservator vessel for cracks / damages. Remove the vessel.

iv) Check transformer tank for leakages / damages, especially the radiator fins / tubes. Check if there are any parts missing. Also check the pressure relief valve.

v) Transformer OilCheck the dielectric strength of the oil drained from the transformer tank. Make note of its colour and any adour arising from it. Also check for any foreign material.

Bushing & Accessories

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vi) Check the condition of bushings i.e., whether cracked or broken. Remove them. Note their specification.

vii) Check the condition of terminal rods whether it is "pitted" or damaged. Remove them. Note down their specifications.

viii) Dehydrating Breather

Check the silica gel in breather assembly. Note its colour and

quantity. Also check oil in the oil cup. Note its colour and quantity.

ix) Opening the transformer Open the transformer lid and raise the transformer core-coil assembly. Wait for some time to allow excess oil to drip into the tank. Now place the assembly on to a oil tray.

x) Metallic PiecesCheck if there are any metallic pieces on the yoke or else where.

- 3 -

xi) Tap ChangerCheck the condition of the tap changer contacts and connections. Check whether its functioning is proper or not. In most cases the tap changer is found damaged beyond salvage and has to be replaced.

The connections & windignsxii) Check whether the terminal leads and lugs are broken or burnt.

xiii) Check if the inter coil connections, delta connections and its neutral connections are loose, broken or burnt. Check whether the windings appear burnt.

Subsequent to visual examination of the core-coil assembly continuity and ratio tests should be performed on all windings to locate the fault and its nature. (if necessary the inter coil connection may be cut)

xiv) Remove the yoke. Take out the windings and if necessary re-perform the continuity test to positively identify the fault. (If in the windings)

xv) The Core

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Check the condition of the core whether it is pitted, scratched, melted, has any hot spots, and has any foreign material deposits. The diameter, cross-sectional Area, window height and limb size of the core must be recorded.

xvi) Conductor size and current density

The conductor size of both LV and HV windings must be measured and recorded. The current density as per

observed sizes be also calculated and recorded. It should be checked whether this current density is in conformity with the magnitude

stipulated. In case of irregularity it must be recorded and the inspector

appraised of the same. xvii)Weighing

The terminal rods and the windings must be weighed and their weights recorded. These must also be tagged and authenticated by the inspector.

Note : In case any warranty / guarantee on the repaired transformer is required by the client and if any of the winding is found damaged during the joint / preliminary inspection then all the windings have to be replaced.

xviii)Joint Inspection ReportThe inspection report presenting all the observations must be counter signed by both the inspector and the repair firm's representative.

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6. Preparation for repair i) List of works : For each damaged transformer under consideration, a list of

works to be carried out for its repair is prepared.

ii) Estimate for repair work

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In consonance with the list of works, an estimate of repair cost be made.

(format enclosed)

iii) Economic viability

In context to economic limitations, if any, imposed by the client and in

reference to the guide lines, if any, laid down by the client the economic viability in taking up the repair of

the transformer be worked out.

iv) Submission of EstimateThe estimate is sent to the client for approval.

v) Approval of EstimateThe next phase is to be taken up only upon receipt of approved estimate / work order placed by the client for repair of specific damaged transformers. If, for any reason, the client disapproves the estimate then the cost of to and fro transport of the transformer must be realised from the client.

vi) DesignIf the repair work is found cost effective and the repair work entails major overhauling then electrical design is made by the design engineers keeping in mind the required C.D, core diameters, core cross-sectional area, window height, limb size, total copper weight, maximum flux density, rating, vector group, voltage class, no load losses and the load losses.

vii) Material procurement The design department submits the bill of materials along with the electrical design to the WM (Works Manager). The WM informs the store officer of the material requirements if the material is unavailable or short the store officer accordingly advises the WM. If necessary, the WM then indents the purchase of the requisite material.

The purchase manager procures the material and places it with the store.

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The store on receipt of the material invites the QC manager to inspect the same. Only subsequent to the QC manager's approval can the store accept and issue the material.

viii) Work OrdersMeanwhile in reference to each list of works and corresponding design the WM prepares and issues the work orders to various departmental heads.

- 5 -ix) Requisition of material

On the basis of work orders issued to them, the departmental heads requisition the necessary materials from the store.

II. The Repair StageThe scope of repair works essentially depends on the technical condition of the transformer and the nature of its failure. The transformer repair may be sub divided into two types. (a) minor : This entails tightening of

connections or replacement of one or more individual components excluding the windings and the core.

(b) major : This involves the replacement of winding and

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insulation, re-insulation of core laminations etc.

All minor repairs are carried out without necessitating redesign or major material procurement.

The repair stage (major) or the actual / physical repair process is comprised of a number of steps, each entailing the contribution of one or more departments. These steps along with the pivotal department and its role are enumerated as follows:

1) Preparation of winding formersThis is done by the maintenance department. The maintenance department is also responsible for the upkeep of all machines, sub-station, and various other equipment.

2) Preparation of the windings

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i) The LV Winding Deptt.: This department prepares the LV winding as per the work order issued to them. It should be noted that the work orders are specific i.e., they relate to a particular design. This work is carried out adhering to certain work instructions, which are general in nature, but pertain to the department.

ii) The HV winding departmentThis department prepares the HV winding as per the work order issued to them. They also have their own work instructions.

3) Insulation The insulation cutting department is responsible for cutting and providing the insulation material required by various departments. This is done as per work orders issued to them.

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Note : Stage inspection Quite often the client requires to inspect the prepared windings. Thus it becomes necessary to invite the client for stage inspection of the prepared windings. The clients representative visits the works and inspects the windings for conductor size, CD and weight. These are recorded on the stage inspection report, which is counter signed by both the inspector and the firm's representative. On the written approval of the inspector, and if not already done the estimate of cost of repair is filed with the clients for approval. Only after the receipt of the clients concurrence or in strong anticipation of the same, the next step is taken up.

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4) Preparation of the core The core assembly department cleans, varnishes and reassembles the core laminations as per the work orders issued to them.

5) Core-Coil AssemblyThe coil assembly department with inputs from the winding, insulation cuttings and the core assembly department assembles the windings on the core, placing the requisite insulation material at the specified places. It also makes the necessary delta, neutral and inter coil connections. It brings out terminal leads and solders / brazes the connection lugs on them. It also assembles and connects the tap changers. This all is done as per the work orders issued to them.

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On completion of the core coil assembly the departmental head invites the testing engineer to perform the ratio and the resistance tests on the completed assemblies. If the tests are in conformity with specifications the assemblies are put in the drying ovens.

6) Drying of TransformerThe core-coil assembly in the drying oven are periodically checked for insulation resistance values with a suitable megger by personnel of the tank-up department. Only when the stipulated megger values (about 1500 Mohms) have been attained do the tank up people take these assemblies out for tanking up.

7) Tank cleaning & Leakage testing

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The tank cleaning department thoroughly cleans and checks the transformer tanks & the conservator vessel for any leakages. If any lekages are found they are plugged with welding by the maintenance people.

8) Painting of transformer tank & Conservator Vessel

The painting department paints the transformer tank and the conservator vessel as per the work order issued to them.

9) Tank-upThe tank-up department mounts the transformers into the cleaned and painted tanks as per work orders issued to them. The transformer tank is topped up with oil of dielectric strength of breakdown value 60 KV at 2.5 mm electrode gap. The

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transformer oil should also be free of any contaminants.

Note : In all cases of transformer repair the old transformer oil is to be replaced with new transformer oil.

10) Transformer Oil TreatmentThe oil treatment Plant Operator should ensure that high quality transformer oil (Clear and BDO 60 KV at 2.5 mm gap) is available at all times for topping up the transformers.

11) Quality Control in the repair stageThe QC department is responsible for maintaining a strict vigil on all in process, regularly sampling and inspecting at each inprocess stage the quality of work and material. Thus, ensuring snag free end product.

12) Testing of transformers

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After tank up the repaired transformers are lined up in the testing area. The testing engineer carries out on them all routine and any other tests specified by the client. Any anomalies found are referred to the responsible department for correction. After error correction, the transformers are re-tested. Only after the testing engineer, QC manager & the works manager are satisfied with the results the transformers are to be moved out by the loading / unloading personnel to the ear marked storage bay.

III.Post Repair Stage

1. Intimation to the clientOn completion of the repairs the client is intimated and invited to carry out

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the final inspection of the transformers.

2. Final InspectionThe client's representative shall examine and conduct tests on the transformers to satisfy himself of their worthiness. If any minor anomalies are noticed, they are put right. The final inspection report is prepared and counter signed by both the client's representative and the firm's representative. (normally the testing engineer)

3. Pre-despatch inspection & DespatchOn receipt of the schedule of despatch from the client for the repaired transformers they are subjected to a pre-despatch check by the QC department. Any irregularity is corrected and only thereafter the

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transformers are loaded on to the carrier.

4. InvoicingAs per the approved estimate the invoice for repairs carried out is duly prepared including applicable taxes and duties and presented to the client for realisation.

Note : In case of doubt or difficulty of any nature the WM / Testing Engineer / QC Manager / Finance Manager / Purchase Manager / Sales Manager shall approach the Manager (Engineering) / Chief Engineer and seek his directions.

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LIST OF RAW MATERIALS

1. Winding & Connection Wiresa) LV Winding Wire (DPC Copper)b) HV Winding Wire (SE Copper)c) Terminal Lead Wire (MPC

Copper)d) Copper Flate) Copper Foil

2. Insulationa) Kraft Paperb) Pressboardc) Pre-compressed Pressboardd) Cotton Tapee) Empire Sleevef) Glass Sleeveg) Bakelite Flath) SRBP Tubei) Permali Wood

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j) Haldi Woodk) Press Paperl) Crepe Paperm) Webbing Tape

3. Transformer Oil

4. Tapping Switch ( Of relevant tap nos. & specifications )

5. Adhesives a) Synthetic Gumb) PVA Emulsion

6. Connection Lugs

7. Solder Wirea) Sn:Pb=70:30b) Sn:Pb=60:40

8. Brazing Rod

9. Welding Electrode

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10. Bolt, Nuts and Washers

11. Porcelain Bushings, Accessories and Fittings

12. Rubberised Cork Sheet

13. Shellac Gasket Sealing Compound

14. Talc Powder

15. Borax

16. Soldering Flux

17. Dehydrating Breather

18. Pressure Relief Valve

19. Silica Gel

20. Oil Temperature Indicator

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21. Winding Temperature Indicator

22. Valvesa) Wheel Valveb) Flange Valve

23. Radiatorsa) Elliptical Tubeb) Pressed Steel c) Corrugated Panel

24. Oil Level Gauge

25. Air Release Plug and Socket

26. Cable Glands

27. Paints and Varnishesa) Insulating Varnishb) Red Oxide Primerc) Paints of various coloursd) Thinner

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e) EC Thinner

28. Asbestos Sheet (Red Jointing Sheet)

29. Lock

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LIST OF ESSENTIAL EQUIPMENT & MACHINERY

WINDING DEPARTMENT:

HT Winding Machine Motorised 3 H.P. 3 Phase “V” Belt Drive with Automatic Layer Setter, Mechanical Clutches & Turn counter, Spool Stand with brakes. Foot speed control.

LT Winding MachineMotorised 3 H.P. 3 Phase “V” Belt Drive with Mechanical Clutches & Turn counter, Spool Stand & Foot speed control.

TURN COUNTERDirect digital display of number of turns, complete with detachable “Yoke Assembly” and sunmica working table. Range: 0-2200 TurnsAccuracy: ±0.1%, ±1 TurnPower : 230 V. AC + 10%, 50 Hz.COIL ASSEMBLY DEPARTMENT :Gas Welding Set

PAPER COVERING DEPTT.:Vertical Strip Covering MachineMotorised Vertical type Single head TPC Strip Covering Machine with Reduction Gear and Friction Clutch. Complete with electrical and standard accessories.

Vertical Wire Covering Machine Motorised 2 HP Vertical type Tripple head DPC Wire Covering Machine. Complete with electrical and standard accessories.

Vertical Wire Covering Machine Motorised Vertical type Double head TPC Wire Covering Machine. Complete with electrical and standard accessories.

Paper Slitting Machine20 inch. Capacity. Complete with electrical and standard accessories.

Butt Welding Machine for Strips 25 KVA

for Wire 8 KVAfor thin wire 1.5 KVA

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INSULATION DEPARTMENT :4' Power Sharing Machine

3' Triddle Sharing Machine

10 Tonne Power PressGeared, Heavy Duty fitted with Gear Guard. 3 Phase Electric motor with Prestige push button type starter “V” Belt set & fitting with automatic lubrication system.

Portable Jigsaw Motorised, single phase power input 580 W.

Hand Operated Small Circle Cutting Machine

Spacer Deburring MachineMotorised with complete electrical and standard accessories.

MAINTENANCE DEPARTMENTLathe Machine 6'

Motorised fitted with quick change Norton type Gear Box, having Hardened

& ground Bed slideways, spindle, Tail Stock Quill, Ground spliced shaft in Gear

box complete with steady guide. Traveling guide face plate and driving guide with reversing switch with Dog Chuck and Single slot, self centering

chuck, 3 H.P. 3 phase Electric motor "V" Belts & Fittings.

Shaper 2'Two feet stroke length. With electrical motor and standard accessories.

Bench Grinder (8”)With electrical motor and standard accessories.

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Radial Drill Machine 1"Motorised 1 H.P. 3 Phase ‘V’ Belt Drive with Starter.Capacity 40 mm

Pillar Drill Machine (3/4”)With Gears and motorised.

Arc Welding Set

3 Phase, 440 Volts oil filled with welding holder and welding cable. Machine

having Tapping for 75 Amp. 100 Amp. 150 Amp. 200, 250, 300 & 350 Amp.

Gas Welding Set

For Brazing and Soldering. Complete with Torch, nozzles, trolley and hose.

Threading Machine(Capacity: 25 mm diameter)Motorised 1 H.P. 3 Phase motor with Reversing switch, Mechanical clutch, “V” Belt and multi speed pulley and die head chaser in mm size/inch size.

Circular Saw MotorisedFor steel cutting.

Vices - Size 3 Size 2 M.S. Forged Body, Slid Hand Operated.

Portable Hand DrillCapacity 12.5 mm.

Portable Hand DrillCapacity 6mm.

Portable Hand GrinderCapacity 4”.

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Portable Angle GrinderCapacity 100 mm 180 mm

PAINTING AND TANK TESTING DEPARTMENT :Air Compressor with 2 nos. Spray GunCapacity 3 H.P 1 H.P.

Air Pressure Gauge 0 - 30Size 75 mm Dia

MATERIAL HANDLING :

5 Tonne Electric Hoist with Gantry and End Carriage

Hydraulic Pallet Truck (2.5 T)

TANK UP DEPARTMENT :

Portable Air Blower

Portable Hot Air Blower

Hydraulic Lugs Crimping Machine with set of dies

Manual Lugs Crimping Machine

TRANSFORMER OIL DEPARTMENT :

Oil Storage Tank Capacity 5000 KL

Oil Filtering Machine(Capacity - 250 litres/hour Output)With a pair of Hoses 10 mtrs. And vacuum pump. Electrically heated with thermostat controls.Heater consumption 21.6 Kw and 1 H.P., 3 phase motor for circulating transformer oil

Suction Pump 1 H.P 2 H.P.

Complete with motor, hose and clamps.

Vacuum Pump1 HP, 3 Phase, 415 Volt. Capacity 650 mm of Hg.

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OTHERS :

Heating Chamber with Elements and Control PanelDimensions : 8’ x 8’ x 8’

Weighing Scale (Electronic)1 Tonne300 Kg.50 Kg.

GENERATORS :

Capacity 125 KVA

Capacity 30 KVA

Capacity 10 KVA

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LIST OF ESSENTIAL HAND TOOLS FOR REPAIR OF DISTRIBUTION TRANSFORMERS

Sl.No Item Size Quantity1. 'D' SPANNERS 1/4” x 5/16” 4 Nos.

5/16” x 3/8” 4 Nos.3/8” x 1/2” 3 Nos.5/8” x 3/4” 6 Nos.3/4” x 1” 4 Nos.1” x 1 1/4” 4 Nos.1/2” x 5/8” 4 Nos.1 1/2" x 1 1/4" 4 Nos.18 x 19 mm 3 Nos.10 x 11 mm 4 Nos.16 x 17 mm 4 Nos.19 x 22 mm 4 Nos.30 x 32 mm 4 Nos.27 x 24 mm 4 Nos.

2. RING SPANNERS 1/4” x 5/16” 2 Nos.5/16” x 3/8” 2 Nos.3/8” x 1/2” 2 Nos.1/2” x 5/8” 2 Nos.5/8” x 3/4” 2 Nos.3/4” x 1” 2 Nos.10 x 11 mm 4 Nos.16 x 17 mm 4 Nos.19 x 22 mm 4 Nos.30 x 32 mm 4 Nos.27 x 24 mm 4 Nos.

3. BOX SPANNERS 1/4” x 5/16” 4 Nos.5/16” x 3/8” 6 Nos.3/8” x 1/2” 6 Nos.1/2” x 5/8” 6 Nos.5/8” x 3/4” 12 Nos.3/4” x 1” 8 Nos.10 x 11 mm 4 Nos.16 x 17 mm 4 Nos.19 x 22 mm 4 Nos.30 x 32 mm 4 Nos.27 x 24 mm 4 Nos.

4. SLIDE WRENCH Small size 4 Nos.Medium size 4 Nos.Big size 4 Nos.

5. PIPE WRENCH 14” 2 Nos.18” 2 Nos.24” 2 Nos.

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Sl.No Item Size Quantity6. HAMMER 250 Gms. 6 Nos.

Boll Type 500 Gms. 6 Nos.1 Kg. 4 Nos.

7. PLIER 8” 6 Nos.

8. NOSE PLIER 6” 12 Nos.

9. CUTTER PLIER 6” 6 Nos.

10 MICRO METER SCREW GAUGE(Manual Reading)

0 to 25 mm 2 Nos.

11 (a) VERNIER CALLIPER 0 to 300 mm 4 Nos.

11 (b) VERNIER CALLIPER 0 to 200 mm 4 Nos.

12. I.D. CALLIPERS 10" 6 Nos.12" 6 Nos.18" 4 Nos.

13. O.D. CALLIPERS 10" 6 Nos.12" 6 Nos.18" 4 Nos.

14. KNIFE 12” 12 Nos.

15.RIGHT ANGLE (Tri square)

4”6"

2 Nos.2 Nos.

12” 2 Nos.

16. TAPE SCALE 3 Mtr. 6 Nos.

17. STEEL SCALE 1 Ft. 6 Nos.2 Ft. 6 Nos.3 Ft. 4 Nos.

18. SCREW DRIVER 4” 6 Nos.6” 6 Nos.12” 6 Nos.

19. HAND HACKSAW 12” 4 Nos.HAND HACKSAW BLADE 1/2"x12" 4 Nos.

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Sl.No Item Size Quantity(HIGH SPEED)

20 (a) SLING ROPE 3/8” Thick 2 Nos.1/2” Thick 3 Nos.5/8” Thick 3 Nos.3/4” Thick 3 Nos.

20 (b) JUTE ROPE 1 1/2" Thick 20 Mtrs.

21. SLING HOOK & U CLAMP 3/8” 6 Nos.1/2” 6 Nos.5/8” 6 Nos. 3/4” 6 Nos.1” 4 Nos.1 1/4” 4 Nos.

22. SCISSORS 12” (10 No.) 12 Nos.

23. LEATHER MALLET 50 mm 6 Nos.75 mm 4 Nos.

24. STRIP BENDER & TWISTER

According to the Strip size

6 Nos.

25. FIBRE SETTER 6 Nos.

26. CENTRE PUNCH 2 Nos.

27. CUTTING TOOLSV Tool Left ToolRight ToolCobalt Tool

2 Sets each

28. CHISEL 6 Nos.

29. OIL CAN 200 Ml. 10 Nos.

30. DIVIDER Small size 3 Nos.Big size 3 Nos.

31. LATHE MACHINE MARKING BLOCK

2 Nos.

32. “C” CLAMP 18” 2 Nos.10” 2 Nos.15” 2 Nos.4” 6 Nos.

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Sl.No Item Size Quantity

33. DRILL STRAIGHT SHANK 3/16” 6 Nos.1/4” 12 Nos.5/16” 12 Nos.3/8” 6 Nos.

34. DRILL TAPER SHANK 7/16” 12 Nos.1/2” 12 Nos.9/16” 12 Nos.11/16” 12 Nos.5/8” 12 Nos.3/4” 12 Nos.1” 6 Nos.11/4” 6 Nos.1 1/2” 6 Nos.2” 4 Nos.

35. TAPER SOCKET 2 Sets

36. FILES 10" Flat file 6 Nos.Round file 6 Nos.Half Round 6 Nos.

37. NAIL FILE Flat 2 Nos.Round 2 Nos.Half Round 2 Nos.

38. BLADE 12 Packet

39. COTTON 2 Kg.

40. FELT PAD 10 Nos.

41. POWER HACKSAW BLADE

50 Nos.

42. HAND HACKSAW BLADE 50 Nos.

43. STRIP CUTTER 2 Nos.

44. CHASER SET 3/8” 2 Set1/2” 2 Set5/8” 2 Set3/4” 2 Set

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Sl.No Item Size Quantity1” 2 Set

45. CRIMPING TOOLS WITH DIE

35 Sqr. mm400 Sqr. mm

2 Set

46. HAND DIE (In Inch) WITH ONE HANDLE AND TAP SET

1/4"5/16"3/8"1/2"5/8"3/4"1 1/4"1 1/2"1 3/4"2"

3 Nos.3 Nos.3 Nos.3 Nos.3 Nos.3 Nos.3 Nos.3 Nos.3 Nos.3 Nos.

47. HAND DIE ( In mm) WITH ONE HANDLE AND TAP SET

6 mm8 mm12 mm16 mm20 mm25 mm30 mm42 mm48 mm

3 Nos.3 Nos.3 Nos.3 Nos.3 Nos.3 Nos.3 Nos.3 Nos.3 Nos.

48. METAL TRAYS 4 Nos.

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LIST OF INSTRUMENTS & EQUIPMENT FOR ELECTRICAL TESTING OF DAMAGED / REPAIRED

TRANSFORMERS

1. MEASUREMENT OF WINDING RESISTANCE

a) KELVIN BRIDEMeasuring Range - 0.2 micro ohm to 11 ohm Accuracy ±0.05% micro or ±1 slide wire divn, which is greater rated current: Upto10 Amp. D.C. with light spot Galvanometer D.C. Power source of 6 V. 10 Amp. OVERALL DIMENSION: Length 430 mm, width 280 mm, height 165 mm, galvanometer Length 280 mm, width 180 mm, Height 140 mm

b) WHEAT STONE BRIDGEMeasuring Range - 1 milli ohm to 11.11 mega ohms. Measuring Accuracy: within ±0.075%. Accuracy of series arm = ±0.05% with null detector Galvanometer conductor clamp and 3 D.C. cell of 1.5V. each OVERALL DIMENSION: Length 370 mm, width 260 mm, height 155 mm.

2. POLARITY CHECK & MEASUREMENT OF VOLTAGE RATIO

TURN RATIO METERMeasuring Range - 100-1000 10-100 1-10Accuracy -0.1% Null balancing TypeMains operated with Polarity checking switch

3. MEASUREMENT OF LOSSES AND IMPEDANCE VOLTAGE

a) VOLTMETERMeasuring Range - 0-150/300/600 V. Accuracy ±0.5% Portable Precision grade Moving Iron Low Powerfactor (0.2) A.C. Voltmeter in wooden case provided with Knife edge pointer antiparallex mirror scale.

b) AMMETERMeasuring Range 0-1/5 Amp. Accuracy ±0.5% Portable Precision Moving Iron Low power factor (0.2) A.C. Ammeter in wooden case provided with knife edge pointer antiparallex mirror scale

c) WATTMETERPortable low power factor low wattage analogue wattmeter (0.2 L.P.F) single phase moving coil built in transducer in wooden case provided with knife edge pointer antiparallex mirror scale.Current coil 2.5/5A Potential Coil - 600 V

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Accuracy ±0.5% Measuring Scale 0-300 Watts

d) CURRENT TRANSFORMERRatio: 10-15-30-50-100/5A Rated Burden 15 VA Accuracy Class 0.2 Frequency 50 C/sVoltage Class 660 V Effectively earthed systemPortable current Transformer in Teak Wood case

e) DIMMERSTAT (VARIAC)Continuously variable voltage auto transformer indoor oil cooled construction, motorised with single phase supply portable type suitable to work on 3 phase 50 C/s A.C. Supply with base channel & four wheels. Input: 415 Volts, 3 Phase, 50 C/s A.COutput: 0-470 Volts, 3 Phase, 50 C/s A.CCapacity: 200 Amp.

f) AUTO TRANSFORMERCapacity: 200 KVA, 3 Phase oil cooled and having 2 Nos. Taps of 800 & 1200 Volts, input voltage 400 Volts with base channel & four wheels

g) POWER CAPACITORSCapacity : 100 KVAR Rated Voltage : 440 V. AC50 C/s, 3 Phase with internal delta connection

h)FREQUENCY METERRange 0-70 Hz.

i)STEP-UP TRANSFORMER Capacity 100 KVA, Ratio 220 / 3000 volts with 2 Nos. tapping (150 & 300) in HV Side

4. MEASUREMENT OF INSULATION RESISTANCE

INSULATION TESTER (MEGGER)Voltage:2500 V. Insulation Range: 0-5000 meg. ohmsHand generator and metal body

5. DIELECTRIC STRENGTH OF TRANSFORMER OIL (BREAK DOWN VOLTAGE TEST OF TRANSFORMER OIL)

OIL TESTING SETMotorised, and switch controlled raise or lower the voltage at rate of 2 KV/second (approx.) Input: 240 V, 50 C/s, Single phase Output: 0-100 KV 96 mm2 moving iron meter marked in KV with memory effect. Corona free acrylic type test cell with electrodes, stirring facility, epoxy Treated oil cooled Transformer housed in fibre glass tank, HV Chamber and Zero start inter locking, A fast acting D.C. relay provided to

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protect the unit 2.4 mm/2.5 mm “GO” “NO GO” gauge for gap adjusting, Table mounting type with fibre glass tank for H.V. Transformer and metallic box for control panel.

6. HEAT RUN TEST

a) Stop Watch

b) Thermometer 0-120oC (Stem Type)

c) All equipment used for measurement of losses shall be reused here.

7. INDUCED OVER VOLTAGE WITHSTAND TEST (DOUBLE FREQUENCY DOUBLE VOLTAGE TEST)

a) SLIPRING INDUCTION MOTOR3 Phase, 25 H.P. Slipring motor as generator and frequency changer

b) Squirrel Cage Induction Motor 3 Phase, 10 H.P Induction motor for primemover, auto Star Delta Starter

c) VOLTMETERMoving Iron A.C. Voltmeter of 1.5 classAccuracy Measuring Range 0 - 1200 V.

d) AMMETERMoving Iron A.C. Ammeter of ±1.5 ClassAccuracy, Measuring Range 0-80 A.

e) FREQUENCY METERAccuracy class: 1.0 Measuring Range: 0-150 Hz.

f) DIMMERSTAT (VARIAC)Capacity 28 A, 3 Phase 50 Hz. 0-470 V, output

g) STEP-UP TRANSFORMER Range : 110V / 1100 V

8. MEASUREMENT OF UNBALANCED CURRENT

a)MILLI AMP. METER Range 0-500 MA

b) TONG TESTERMeasuring Range 600 volts, 500 Amp. 1000 ohms

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9. SEPARATE SOURCE VOLTAGE WITHSTAND TEST (HIGH VOLTAGE TEST)

a) HIGH VOLTAGE TRANSFORMERSingle phase oil cooled transformer: Input Voltage 220 Volts, Output Voltage: 0-40-80 KV, KVA Rating: 15

b) VOLTMETERMoving iron A.C. P.T. operated voltmeter accuracy ±1.5%, Range: 0-40/80 KV, P.T. Ratio: 40-80 KV/220 V.

c) AMMETERMoving Iron A.C. AmmeterAccuracy ±0.5%Measuring Range: 0-20 A.

d) DIMMERSTATContinuously variable voltage auto-transformer, indoor oil cooled, construction motorised with single phase supply portable type suitable to work on single phase 50 C/s A.C. supply with base channel and four wheels Input: 240 Volts, single phase 50 C/s A.C.Capacity: 60 Amp. / 28 A

10. SEPARATE SOURCE VOLTAGE WITHSTAND TEST(LOW VOLTAGE TEST)

HIGH VOLTAGE TRANSFORMERSingle phase oil cooled TransformerInput voltage: 220 Volts, Output Voltage: 0-4 KV

11. DIGITAL POWER METER WITH HARMONIC ANALYSISVoltage rating 600 Volts and Current rating 20 Amps.

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Sales & Marketing

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SALES & MARKETING TRANSFORMERS

TENDER / ENQUIRY IDENTIFICATION

Generally tenders are floated by power utilities all over the world. Feasibility of such tenders are studied and thereafter quoted. Some utilities require prior registration which involves factory inspection. Registration of the Company as Quality Product Manufacturer and Supplier with end users, consultants, Turnkey project executors, service organizations, Government/Private Bodies etc. wherever applicable needs to be done. Information regarding product requirements are collected through personal contacts, Newspapers, Magazine, Professional Journal or by any other means.

The techno-commercial team gets involved and the needs of the various potential customers is assessed for technical requirements. The collected technical data is compared with company's manufacturing range to identify that the requirement falls within company's production range.

TENDER PARTICIPATITION & QUOTATIONS:

All inquiries for supply of product are received directly from end users or from other sources.

Tenders/ Inquiries are scrutinized against the standard Tender Review format. The salient features of the tender enquiries are listed and discussed with the concerned departments.

If any discrepancies are noticed, confirmations and / or clarifications are sought from the customer. The cost-sheet is prepared based on material cost estimated. Commercial terms & Technical Particulars describing product specifications are made. Tenders are then prepared and submitted, clearly highlighting any deviations considered.

All Technical and Commercial terms including prices are negotiated, wherever necessary and acceptable, to get maximum advantage.

Successful Tenders/Purchase Orders(P/O) are once again reviewed against the Tender / Contract Review Form before final acceptance.

After acceptance of clients order, P/Os are converted to order confirmation and released to the Design department for the preparation of drawings and the Bill of Material (B.O.M.)

Amendment desired by the Purchaser:Technical and commercial implications are studied. For technically possible amendments financial/commercial concessions are asked. Proper negotiations are conducted prior to taking decision on acceptance or rejection of amendment. Copy of accepted amendment with necessary comments is issued to the concerned departments for necessary implementation.

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Amendment required by the Company:The details of required amendment with full justification and reasoning is conveyed to the Purchaser. The conditions of Contract affecting due to amendment are re-negotiated. After receipt of amendment, a copy is issued to the concerned Departments for necessary implementation.

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THANKS

SANJEEV KADIAN

Mob. 9812415555