SUMMER TRAINING PRESENTATION

“CROMPTON GREAVES,MANDIDEEP”

“Smart Solutions , Strong Relationships”

INTRODUCTION

Crompton Greaves established in1878, by R.E.B. Crompton. The company merged with F.A Parkinson in the year 1927 to form

Crompton Parkinson Ltd., (CPL). It collaborate with GCC. In the year 1947. Today, Crompton Greaves (CG) is part of the Avantha Group. The new identity, Avantha, was launched worldwide on 15

November 2007. It Awarded for 2000-2001, by the Indian Institution of

Industrial Engineering, for successfully implementing his vision of

making Crompton Greaves a world-class manufacturing company.

Power Transformer

Transformers with ratings above 5000KVA are used in generating stations and sub- stations for stepping up or stepping down the voltage are called power transformers .These transformers are manipulated to operate almost always at or near the rated capacity.

Purpose of Power Transformer

The purpose of a power transformer is to transfer efficiently and instantaneously from an external electrical source to an external load.In doing so, the transformer also provide important additional capabilities such as

The primary to secondary turns ratio can be established to efficiently accommodate widely different input/output voltage levels.

Multiple secondary with different numbers of turns can be used to achieve multiple outputs at different voltage levels

Classification of Power Transformer

Generator transformers for thermal, nuclear, hydro and gas generating stations.

Up to 450-900MVA. Auto transformer for step up and step down. Reactors, series and shunt up to 80MVA. Multi winding auto and generator transformers

Generator transformers for thermal, nuclear, hydro and gas generating stations.

Upto 450MVA,500kV class, three phase. 900MVA, 500kV in a bank

Crompton Greaves Consist mainly four divisions:-

Quality Production Testing Dispatch

Quality Check

Two major functions are performed

1) 103 Movement The 103 Movement is performed when the stock is received at the company gates, the material is checked against the list of the materials ordered however no entry accounting is done at this moment, the acknowledgment of the reception of the materials is done but its validity is not communicated.

2) 105 Movement

The materials are then unloaded from the truck into the stores and the quality assurance department checks whether the materials received are of appropriate quality. During the 105 movement, the materials department safely stores the materials received in the Stores with appropriate utilization of the space available

Quality check Quality is checked by two processes:-

1.Physically

In this , components are checked physically Ex :-there should be no cracks, no impression , no damage of the component .

2)Dimensionally

In this, components are checked by precise instrument. Ex:-vernier caliper, meter gauge etc. In this inspection we also control the temperature and moisture .Before releasing an order, it ensures that the components are physically and dimensionally correct, so periodic checking of actual inventory status and the one available in the system is necessary.

In any discrepancy, the few people can be deployed in checking inventory from time to time. Any correction may be entered in the system and the process continues till the discrepancy disappears.

Design of Transformer

There are mainly three branches involved in design of transformer. All the three worked in a co-ordinated manner thus complimenting each other in order to accomplish the task . The three branches are:-

i) Electrical

ii) Mechanical

iii) Control

i)Electrical

Electrical section takes care of the design and the windings and arrangements of insulations. The design procedure consists of preparing an electrical specification sheet and an insulation arrangement drawing, along with a bill of materials(BOM).The task of core cutting is also based on data from the above specifications .The most important job of cooling is also taken care of by electrical section. Finally the testing of the transformer for various faults conditions is done by the electrical division.

ii) Mechanical

The mechanical section comes into picture after the designing part . The design of the tank, support structures are looked after by mechanical section . In short the core coil assembly is handled by them.

iii)Control

The control of transformer is of prime importance. It provides control of the taps , oil and winding temperature etc . Remote tap changer controller (RTCC) provides remote tap changing ability. Oil temperature indicator(OTI) and winding temperature indicator(WTI) Keep a check on oil and winding temperature respectively . Magnetic oil gauge (MOG) shows the level of oil present in the transformer.

Process Chart

Winding Coil clamping Coil Assembly Core Building

Core Coil Assembly

[ Auto Clave]

Connection

Vapour Phase Drying

Servicing

Dispatch Painting Testing Tanking

Coil clamping

Winding

Winding is of two types:-1.High Voltage Coils: A solid cylindrical former of predetermined diameter and length is being used as has

over which is made. Generally round insulated wire of either copper (Cu) or Aluminium (Al) is used as

basic raw material. The coils are made in number of layer. These leads are properly sleeved and locked at number of points.

2.Low Voltage Coils: L.V. Coils are also one of the components of transformer. The procedure of making

low voltage coil is generally same as above. The shape of the basic raw-material (Al or Cu) is rectangular

Diagram of Winding

Coil Assembly

The basic raw-material is COLD ROLLED GRAIN ORIENTED

(CRGO) Silicon Steel It 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. These laminations are assembled in such a manner that there is

no air gap between the joints of two consecutive sheets. The entire assembly is done on a frame commonly known as core

channel. These frames being used as a clamping support of the core assembly

Diagram of Coil Assembly

Core Building an Insulation

It provides the permanent support for insulation and coil assembly.

Insulation

Insulation materials are used to provide an electrical insulation between parts at different potentials.It reduces short circuit.Mostly used insulators are:-

plywood,rubber,plastic,wraps,spacers,blocks,pcb(precompressed board) etc.

Types of insulation:-

i)Main insulation

ii)End insulation

Properties of Ideal Insulating Material

High insulation resistance High dielectric strength Low dielectric Losse and low dielectric loss angle No attraction for moisture Good heat conductivity High mechanical strength to withstand vibration and

winding

Diagram of Insulation

Auto Clave

A strong, pressurized, steam-heated vessel, as for laboratory experiments or sterilization.

Autoclaves use to increase the efficiency and performance of any plant.This equipment comprises a vacuum in which a cylinder containing a piston is situated at one end and can be closed at the end by a hollow piston containing a condenser casing. The cylinder is evacuated through a port and the piston is lowered to close the port immediately an injection valve is opened to fill the cylinder with an impregnating substance.

Core Coil Assembly

The components produced in the coil winding and core assembly stage are then taken into core-coil assembly stage.

The core assembly is vertically placed with the foot plate touching the ground. the top yoke of the core is removed. The limbs of the core are tightly wrapped with cotton tape and then varnished.

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. Insulating block of specified thickness and number are placed both

at the top and bottom of the L.V.Coil. Cylinder made out of corrugated paper or plain cylinder with oil

ducts are provided over L.V.Coil.

H.V. Coils are placed over the cylinder. Gap between each section of H.V. Coils including top & bottom

clearances is maintained with the help of oil ducts, as per the design/drawings.

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

Primary and secondary windings are connected as per the requirements. Phase barrier between H.V. phases are placed as per requirement.

Connections to the tapping switch (if required) are made. Finally, the component is placed in the oven.

Diagram of Core Coil Assembly

Vapour Phase Drying

Drying of a utilized power transformer is an object that has been worked on for many years.

The main problem is to achieve an optimal drying of an aged power transformer without the displacement to a

workshop, as this operation is very cost intensive and sometimes no longer possible.

Over 40 power transformers with a power of up to 400 MVA were dried successfully on site.

Tanking

All tanks are made of high quality steel and can withstand vacuum as specified by the international standards and the customer. All welds are tested, ensuring 100% leak proof of seems and mechanical strength. Transformer with Corrugated Fin-Type radiators can also be supplied. The fins are manufactured of Gold-rolled steel. The fin height and length are according to customer's specifications and fins can be plain or embossed. All transformer tanks are given a smooth finishing by using the "SHOT BLASTING

Fittings like drain valves, HV& LV Bushings, conservator, oil level indicator and explosion vent are fitted in the tanks.

The Core-coil assembly is then placed into the tank and properly locked up.

Pure filtered transformer oil is filled in the tank to immerse the assembly only.

Connections of primary and secondary to the terminal bushings are made. Operating handle for ratio switch is fitted, wherever required.

Diagram of Tanking

Temperature Rise Limit

In consumer or industrial applications a Transformer temp. rise of 40०C-50०C may be acceptable, reassuring in a maximum internal temperature 100०C. However, it may be wiser to use the next size large core to obtain reduce temperature rise and reduced losses for better power supply efficiency.

Testing of Transformers

The structure of the circuit equivalent of a practical transformer is developed earlier.

The performance parameters of interest can be obtained by solving that circuit for any load conditions. The equivalent circuit parameters are available to the designer of the transformers from the various expressions that he uses for designing the transformers. But for a user these are not available most of the times. Also when a transformer is rewound with different primary and secondary windings the equivalent circuit also changes. In order to get the equivalent circuit parameters test methods are heavily depended upon. From the analysis of the equivalent circuit one can determine the electrical parameters. But if the temperature are several tests that can be done on the transformer.

Method of Testing

This is nothing but the resistance measurement of the windings by applying a small

d.c voltage to the winding and measuring the current through the same. The ratio gives

the winding resistance, more commonly feasible with high voltage rise of the transformer is required, then test method is the most dependable one. There windings. For low voltage

windings a resistance-bridge method can be used. From the d.c resistance one can get the

a.c. resistance by applying skin effect corrections.

Painting

The entire procedure of painting is done under two stages:

Cleaning of tanks The cleaning of tank is done normally by chipping/grinding. The outside surface of the tank is short blasted to achieve a very

fine and smooth finish

Painting of tanks After cleaning the tanks, a coat of hot oil resistance paint is applied

on the internal surface of the tank. The outside surface is painted with a coat of Red Oxide primer and

subsequently with one coat of enamel paint as per customer's requirement.

Separate primary and secondary winding facilitate high voltage input/output isolation , especially important for safety in off-line applications.

Losses

Transformer loss is some times limited directly by the need to achieve required over all power supply efficiency . More often, transformer losses are limited by a maximum ” Hot Spot”. Temperature at the core surface in side the centre of the windings.

1)Worst case losses

2)Winding losses

1.Worst case losses

Transformer losses should be examined under worse case conditions that the power supply expected to operate over long periods of time , not under transient conditions Transformer losses can be put into three major categories:-

i)Core hysteresis losses

ii)Core eddy current losses

i)Core hysteresis losses:-It is a function of flux swing and frequency . In all buck –derived applications under steady state conditions. Hysteresis is constant, regardless of changes in voltage(Vin) or load current.

ii)Core eddy current losses:-It is really I²R loss in the core material. If Vin doubles , peak I²R loss quadruples , core eddy current loss is proportional to Vin. Worst case is at high Vin.

2.Winding loss

Peak secondary current equals load current and peak primary current equals load current divided by the turns ratio . Peak currents are independent of Vin . But a constant peak currents (constant load),r.m.s current squared(and I²R loss) is proportional to duty cycle D and inversely proportional to Vin.

Finishing

Fittings and accessories as per customer's specification and drawing are checked.

Air Pressure test is subjected to avoid any leakage and seepage on all transformer.

Transformers are filled with oil upto the minimum level marking, wherever necessary.

Loose accessories like, earthing terminals, bimetallic connectors, dial type thermometers are also checked for proper fittings.

Conclusion

I was given the opportunity to do my summer internship project in the CG which is the largest transformer manufacturing enterprise . To conclude this project report I can say that the company holds a good , market share and is managing well even when there is a big competition . market in front of CG study proves that the company has entered into the technical collaboration with many international firms through acquisitions Where , the competition is increasing day by day like this Crompton Greaves is hanging its working style in performance and providing after sales . services to the customer.

Suggestion

Insulation arrangements for the 132 kV class power transformer was standardized with 220 kV class as reference. The accomplishment of the project has enabled the design engineers to reduce the time preparation of bill of materials(BOM)from 4 to 6 hrs.

 

 

 

THANK YOU

REPRESENTED BY:- KANHAIYA KUMAR &

RANVIJAY KUMAR SINGH

(JAI NARAIN COLLEGE OF TECHNOLOGY,BHOPAL)