Tbea vocatinal training

Project Report
On
“Manufacturing of Transformer”
In partial fulfillments of the requirements for the degree of
Bachelor of Electrical Engineering
2014-2015
Submitted by
Deepkumar G. Shah
Enroll. No. 110050109029
BITS edu campus
Varnama, Vadodara
Affiliated to,
Gujarat Technological University
Chandkheda, Gandhinagar

ACKNOWLEDGEMENT
An individual cannot do project of this scale. I take this opportunity to express my
acknowledgement and deep sense of gratitude to the individuals for rendering valuable
assistance and gratitude to me. Their input have played a vital role in success of this report
and formal piece of acknowledgement may not be sufficient to express the filings of gratitude
towards the people who had help me to successfully completion of my training. I got my
vocational training as a analytics in Quality Department
I would like to wish my sincere thanks to my project guide Mr. Vinaypratap Singh
(Department ofInprocess Quality) for his keen interest and giving valuable guidance at
every stage of this project. Later on I would like to confer the flower of acknowledgement to
the company guide Mr. Santanu Mitra (Head ofQuality Department),who is also my
external guide.
I take this opportunity to thank all respondents who spared their precious time to provide with
me valuable input for project without which it would have not been possible.
I firmly believe that there is always a scope of improvement. I welcome any suggestions for
further enriching the quality of this report.

INTRODUCTION
Tebian Electric Apparatus (TBEA) is a Chinese manufacturer of power transformers and
other electrical equipment, and a developer of transmission projects. Along with
competitors Tianwei Baobian Electric (TWBB) and the XD Group, it is one of the major
Chinese manufacturers of transformers.
The company builds transformers and also develops transmission lines as an EPC
contractor. In Ethiopia, TBEA was in 2009 awarded the contract to develop the
transmission line to Addis Ababaa for the Gilgel Gibe III Dam. In September 2010 in
Zambia, the state power company ZESCO signed an EPC contract with TBEA to build
334 million USD 330 kV high voltage transmission lines, which would supply power to
Eastern, Luapula, Northern and Muchinga Provinces. The project held a groundbreaking
on July 2012. The project is to include two transmissions lines: one from Pensulo
substation in Serenje to Kasama via Mpika, another transmission line from Pensulo
substation to Chipata via Msoro and extension of the existing Pensulo substation to
accommodate the two transmission line bays.
Outside of China, TBEA is also coming up with a manufacturing base for transformers,
solar equipments & cables in Gujarat, India. The Indian division is registered under the
name TBEA Energy (India) Pvt. Ltd. and will cater to India, African, Middle East and
other markets.
IN INDIA THE TBEA HAS FOLLOWING TYPES OF PRODUCTS
MANUFACTURING.
 Power Transformer
 Reactor
 Bushing
 C.T.
And also Power Transmission and transformer testing is also done in TBEA in India.

INFORMATION FLOW DIAGRAM IN GENERAL TRANSFORMER
MANUFACTERING COMPANY:-

MAIN COMPONENTS & ACCESSORIES OF
TRANSFORMER
PRINCIPLE OF CONSTRUCTION & MAIN COMPONENTS
Principally the magnetic circuit i.e. core should remain at earth potential and coils are charged
to their respective voltages.
Apart from core and coils, a transformer needs the followings:
• Core insulating materials
• Coil insulating materials
• Insulating cylinder between primary and secondary coils
• Steel frame to hold the core
• Core clamping screws to apply mechanical rigidity to core assembly
• Connection materials
• Tap changing switch, if provided
• Steel container (M.S. Tank) to house the core-coil assembly
• Suitable insulating terminals
• Insulating and cooling material (Transformer Oil)
• Radiators to enhance cooling surface
Whether it is a step-up or step-down transformer, the
low voltage winding is generally placed nearer to the
core. High voltage winding remains away from the
core and is placed over LT coil in co-axial fashion.
Right kind of insulation is needed to insulate the core
from the secondary coil. Similarly insulating cylinder
and oil ducts are used in between coils. Vertical
supports of coils are done through insulating rings and
blocks.
Windings are made either from aluminum or copper,
in the shape of wires (for small current) or rectangular
strip (for high current). For oil cooled transformer,
winding wires are either enamel coated or paper
covered. Strips are usually paper covered. Electrical
Grade Insulating Paper (EGIP) of very thin thickness
(in the order of 1.5 to 2 mil) are used for covering the
wires and strips. Paper cylinders, rings and blocks are
made from insulating pressboard.
Steel frame either in the shape of rolled angle or

channel or formed channel from mild steel sheet are used to hold the core assembly. To apply
rigidity, the core assembly is further tightened with horizontal and vertical screws.
Use of Insulating Oil as Cooling Medium
While in operation, the transformer i.e., core and winding emits heat which is detrimental to
the insulating materials being used for transformer construction. It is customary to keep the
temper nature under control. Mineral oil, available from fractional distillation of crude
petroleum liquid has a unique property to cool the transformer as well as acts as an insulating
material. The oil is used in medium and high voltage transformers. The active part of the
transformer i.e., core-coil assembly is placed inside a leak proof steel enclosure (no. 10) and
is filled with insulating oil. The oil acts as a media to carry heat from the windings up to the
tank surface. The tank then dissipate the heat to the atmosphere by radiation. In the process of
transferring heat from winding to tank, the winding and oil retain certain amount of heat. If
the rise in temperature of winding and oil exceeds pre-determined values of 50°C rise for
winding and 40°C rise for oil, the electrical properties of both oil and insulating materials
start deteriorating. To limit the rise in temperature of winding and oil, the tank surface area
needs to be increased. It is customary to use radiators in such cases. Radiators are made from
steel pipe, either in the shape of round or elliptical tubes or in the form of fins (discussed
separately in section-II). It has an inlet, an outlet and is fixed in the tank wall. Hot oil
circulates through such radiators and gets cooled by convection process. This aspect has been
discussed at length in the later part of the book.
All openings and joints like tank cover, terminal holes, inspection pocket, tap switch handle,
air release plug etc. are sealed with respective components and sealing gaskets. Connection to
the bushing terminals are made. Oil is added to the required level. Now the transformer is
complete and is ready for floor testing. High voltage test is recommended to carry out at least
24 hours after the oil being filled, as the paper insulation used inside the transformer needs
time to absorb oil and to offer higher electrical strength to the windings.

CONSTRUCTION OF CORE
The basic core material is electrical steeland is available in the form of thin laminated sheet,
commercially know as Cold Rolled Grain Oriented (CRGO) Silicon Steel. It is an alloy
steel which contain certain percentage of silicon. This material has excellent magnetic
property of high permeability and low hysteresis loss at reasonable operating flux density,
which is 1.6 Tesla. When a coil is placed in a closed magnetic circuit and is energized with an
alternating voltage, a magnetic loss occurs in the core material which is commercially known
as ‘Core Loss’. Core loss has two components: HYSTERESIS LOSS AND EDDY
CURRENT LOSS. Hysteresis Loss depends upon the quality of magnetic material at the
operating flux density, frequency of the system and weight of core material. Eddy current loss
is inversely proportional to the thickness of the laminated
sheet and that is why we have seen a mark improvement of
the availability of thinner sheet, in the range of 0.18 mm,
0.23 mm, 0.27 mm, 0.30 mm, 0.35 mm. Each laminated
sheet is insulated on either side by a thin oxide film,
commonly known as ‘Carlite film’. The laminations
available from mills are in the form of roles. After the steel
is produced in the mill, it is annealed at a temperature of
800 to 900°C. This is done to get the magnetic grain
uniform towards the rolling direction. The rolled
laminations are sheared to various shape and designed
dimensions as indicated in Fig.
Fig. represents a view of assembled core of a 3-phase, 3
limb transformer. Two side limbs are identified as ‘A’ and
are identical in shape. The ends are sheared at 45°. The
center limb is identified as ‘B’ and the ends are cut at 90°.
The top and bottom limbs are identified as ‘C’ and are identical in shape. The ends of ‘C’
laminations are cut at 45°C and have a ‘V’ notch at the center to match ‘A’ and ‘B’. All these
laminations are sheared in such a configuration so as to enable them match the assembly
without leaving air gap between them. To minimize the eddy current loss, the core
laminations are made thin. In order to build a stack core,it is assembled layer by layer in
staggered way. During the process of assembly one has to take utmost care towards joints and
ensure that the joints between lamination are free from air gap. Further the laminations need a
few millimeter overlap to build a firm assembly. Usually for small transformers up to 100
kVA, an overlap of 5 mm is kept in each joint. Overlap and assembly of alternate layers have
been shown in Fig.

CLASSIFICATION OF CONSTRUCTION
Construction of core is classified by the placement of its primary and secondary coils in the
core and how the core is being constructed.
Two type of core constructions are familiar.
They are:
(a) Core Type and
(b) Shell Type.
Fig. represents a schematic view of core-type and shell type transformers. In core type
transformer, the windings are placed on either limb of the core,whereas in shell type
transformer, the windings are placed in the center limb only. The side limbs are left open. In
other words we can simply say that in core type transformer the windings surround a
considerable part of the core,whereas in shell type transformer the core surrounds a
considerable part of the windings. Electrically shell type transformer performs better than
core type transformer as the flux generated in the magnetic circuit remain concealed in the
core and the loss of flux in air is minimized. However in core type transformer, a good
amount of flux is lost in the air. This loss of flux is called leakage flux. Generally core type
transformer is cheaper and hence is widely used in industries.
To simplify the view and to make the construction easily understandable, the primary and
secondary coils have been shown separately wound on either side of the core (a) or placed
one above the other (Fig. b). Practically this is not correct. The coils are usually wound co-
axially as shown in Fig. earlier. Co-axial coils have better linkage of flux in the windings and
also it reduces the leakage flux.

ACCESSORIES:-
Even though the transformer is basically a static device, many changes in pressure and
temperature are constantly occurring. The temperature and pressure changes must be
monitored and their changes compensated. Also, because of the transformer’s high voltage
and power capabilities, there are areas of extremely high voltage stress,and many
opportunities for large surges and fault conditions. The following auxiliary equipment is used
to monitor and compensate for many of these factors,and can be found on most power
transformers.
BUSHINGS:-
o The leads from the primary
and secondary windings most
be safely brought through the
tank to form a terminal
connection point for the lie and
load connections. The bushing
insulator is constructed to
minimize the stresses at these
points, and to provide a
convenient connection point.
The bushing is designed to
insulate a conductor from a
barrier, such as a trans. former
lid, and to safely conduct
current from one side of the
barrier to the other. Not only
must the bushing insulate the
live lead from the tank
surfaces,but it must also
preserve the integrity of the
tank’s sealand not allow any
water,air, or other outside
contaminants to enter the tank.
o There are severaltypes of
bushing construction; they are
usually distinguished by their
voltage ratings, although the
classifications do overlap:
Solid (high alumina) ceramic-
(up to w5kv) Porcelain-oil
filled (25 to 69kV) Porcelain-
compound (epoxy) filled (25 to
69kV) Porcelain--synthetic
resin bonded paper-filled (34.5 to 115kV) Porcelain-oil-impregnated paper-filled
(above 69kV, but especially above 275kv)
o For outdoor applications, the distance over the outside surface of the bushing is
increased by adding “petticoats” or “watersheds” to increase the creepage distance
between the line terminal and the tank. Contaminants will collect on the surfaces of
the bushing and form a conductive path. When this creepage distance is bridged by
contaminants, the voltage will flashover between the tank and the conductor. This is
the reason why bushings must be kept clean and free of contaminants.

PRESSURE RELIEF DEVICES:-
o When the transformer is overloaded for extended periods, or when an internal
fault occurs,high pressures will occur in the tank. There are a number of
devices used to accommodate this pressure change.
o Pressure relief valves. Pressure relief valves are usually installed behind the
pressure gauge on sealed tank units. They are used incoduction with
pressurized nitrogen systems and can be mounted in the gas bottle cabinet or
on the tank wall. The bleeder valve is set to bleed-off any pressures that
exceed a,pre-set level (usually around 8-10 psi). This valve is an integral part
of the pressurized gas system, and its failure can result in a rupture of the
tank.
 TEMPERATURE GAUGES:-
o Temperature gauges are either of the “hot spot” or “average tank
temperature” type. There are many designs in use. Most average tank
temperature gauges consist of a spiral wound bi-metallic element that is
directly coupled to a dial-type indicator.
o Both average reading and hot spot temperature gauges can use a bulk-type
detecting unit that is immersed in the oil either near the top of the oil level
(see figure 84), or near the windings at the spot that is expected to be the hot
test. A capillary tube is connected to the bulb and brought out of the tank.

The temperature indication is provided either by a, linew marking on the tube
itself, or by a dial-type indicator.
Dial-type gauges can have up to three sets of contacts that will actuate any of the
following devices:
(1) The lowest setting usually actuates eternalcooling fans that will come on
at a preset temperature level. The fans will shut off once the temperature has
been reduced to the prescribed level.
(2) The contacts can also be set to actuate remote alarms that will alert
maintenance personnel of the condition of the transformer. These devices
must be reset even though the temperature has returned to normal.
(3) The highest and most critical contact setting on the temperature gauge is
connecting to an r&y or a circuit breaker that will trip out and de-energize the
transformer.
 TAP CHANGERS:-
o Transformers are often required to operate under changing primary voltages,
or to provide a number of different secondary voltages. Most transformers
are equipped with a tap changer (see fig- W), and any number of taps can be
brought off of either of the windings to accomplish this voltage change. Tap
changers can be conveniently divided into two categories: no-load tap
changers and load tap changers.
o No-load tap changers. No-load tap changing is usually accomplished on the
primary side of a step- down power transformer. The taps are usually
provided 2-l/2 percent intervals above and below the rated voltage & the
transformer must be de-energized before the tap position can be changed. The
taps are changed either by turning a hand wheel, moving a selector switch, or
lowering the oil level, opening the manhole, and actually reconnecting the
winding leads to various positions on a terminal board. No-load tap changers

are usually used to accommodate long-term variations in the primary voltage
feed.
o Load tap changers: Load tap changers are usually located on the secondary
side of the transformer. They are used to control the current and voltage as
the load is varied. Load tap changing transformers are used especially for
furnace applications, and to regulate the changing voltages found in large
substations.
o Because load tap changers are required to open and close the circuit while it
is hot, they incorporate a number of devices to minimize the switching time
and the amount of (the arc) released. Some tap changers use vacuum bottle
type breakers to interrupt the current flow, while others use a conventional
main/arcing contact mechanism, much like that found in a circuit breaker.
Other tap changers use resistor or reactor circuitry in the mechanism to limit
the current flow at the time the switching occurs. Load tap changers can be
either automatic or manual, and can be used to vary the voltage and current
by as much as 2 or 3 percent, depending on application.
o Most load tap changers are immersed in oil and are contained in a separate
compartment from the primary and secondary windings. Because of the large
amounts of energy (switching arcs) produced, the oil in the tap changing
compartment deteriorates at a much faster rate than the oil in the main
compartment
 LIGHTENING ARRESTERS:-
o Lightning (surge) arresters most transformer installations are subject to surge
voltages originating from lightning disturbances, switching operations, or
circuit faults. Some of these transient conditions may create abnormally high
voltages from turn to turn, winding to winding, and from winding to ground.
The lightning arrester is designed and positioned so as to intercept and reduce

the surge voltage before it reaches the electrical system. a. Construction.
Lightning arresters are similar to big voltage bushings in both appearance and
construction. They use a porcelain exterior shell to provide insulation and
mechanical strength, and they use a dielectric filler material (oil, epoxy, or
other materials) to increase the dielectric strength (see Figure 8-7). Lightning
arresters,however,are called on to insulate normal operating voltages, and to
conduct high level surges to ground. In its simplest form, a lightning arrester
is nothing more than a controlled gap across which normal operating voltages
cannot jump. When the voltages exceeds a predetermined level, it will be
directed to ground, away from the various components (including the
transformer) of the circuit. There are many variations to this construction.
Some arresters use a series of capacitances to achieve a controlled resistance
value, while other types use a dielectric element to act as a valve material that
will throttle the surge current and divert it to ground.

LAYOUT OF QUALITY DEPARTMENT
INCOMING MATERIALS FOR QUALITY ASSURANCE
INTRODUCTION
Quality of the finished products depends a great deal on the quality of the basic inputs. As
such we must ensure the availability of quality materials at the right time. It is strongly
recommended that the incoming materials be inspected for quality assurance before they are
regulated for production.
The design department should prepare the technical specifications for all basic input materials
with working tolerances as recommended by ISS and/or customer specifications and also
based on experience. Standard formats for material inspection reports of all major raw
materials should be prepared in advance. On receipt of materials at stores, they should be
inspected in accordance with the requirements and recorded. The quality assurance engineer
should review the outcome of such inspections before the materials are released for
production.
PURCHASE CONTROL
As said earlier, the quality of the finished product depends on the quality of input materials
and components purchased from various sources. This chapter highlights the procedures to be
adopted to ensure the quality of purchased raw materials and components.
The following are fewof the activities the purchaser should do:
(a) Selection of suppliers
(b) Incorporation of all quality requirements in the purchase order
(c) Analysis of quotations with quality in perspective
(d) Surveillance quality audit at the supplier’s works
Quality Department
Incoming Quality
Department
In process Quality
Department
ISO Department

(e) Inspection and verification of incoming materials and components
(f) Reporting defects and settlement of disputes with the suppliers
(g) Assistance to subcontractors or vendors by way of training, technical advice etc.
(h) Review and rating of suppliers from the point of view of product quality and adherence to
delivery schedule.
ASSESSMENT OF THE SUBCONTRACTOR OR VENDOR
This is one of the crucial controls on the purchase activities, as the quality of the purchased
products depends mainly on the suppliers. An institutionalized procedure for assessing the
strength of the suppliers is essential. They should be evaluated on the basis of the following:
(a) their ability to meet the quality requirements of the products or services.
(b) Availability of machinery, tools and manpower at the required technical levels.
(c) Their commercial and financial viability.
(d) Their production capacity and ability to maintain specified delivery schedule.
(e) The effectiveness of their quality assurance system.
There are a number of ways to assess prospective suppliers. Previous performance in
supplying the same or similar kind of products is a useful indicator. For this it is essential that
a detailed record of incoming supplies and their quality status is maintained. The records in
question should contain details of quantity supplied, quantity rejected, and adherence to
delivery schedules and share in total supplies to the company over the period being reviewed.
For one-time purchase or when the quantity involved is very small, the buyer should carry out
detailed inspection and testing of the product before granting approval for its use.
METHODOLOGY OF CAPACITY VERIFICATION
Since the capacity verification is a purchase function, overall responsibility of this activity is
that of the purchase department. Normally, it involves visits by company’s experts to the
subcontractor’s or vendor’s works. Before organizing such a visit, the subcontractors or
vendors should be asked to furnish data on its production facilities, organization, personnel
and finance along with data on its ability to supply the product at the requisite quality level.
Since the assessment of a supplier requires expertise in different areas,such as process
engineering, quality control and finance, some of which may not be available in the purchase
department, a committee is usually appointed for this task. The committee comprises experts
from different functional groups. However,overall co-ordination is provided by the
purchasing department. The committee examines data submitted by the prospective suppliers.
A team of experts should visit the workplaces of suppliers who look promising to carry out a
physical verification of their facilities, infrastructure and quality assurance system. While it is

necessary for the assessment team to obtain the data it needs, it should not assume the role of
inspectors. No criticism of the supplier and its facilities should be made. The assessment team
should confine itself to areas directly affecting the supplier’s ability to execute the order in
question. Generally, the use of standard questionnaire is advisable. Important aspects to be
covered during assessment are listed below:
(a) Can the subcontractors or vendor’s plant and machinery produce at the required rate?
(b) Are all the machines capable of maintaining quality parameters within acceptable limits?
(c) Does the firm have a well-staffed quality organization and a functional quality control
programmer?
(d) Does the firm use a considerable number of components obtained from the trade or from
subcontractors? If so, how does it control the quality of these components?
(e) What are the firm’s sources of raw materials? Does it maintain adequate reserve stocks to
safeguard itself from interruptions in the supply of materials? How is the supply of raw
materials ensured?
(f) Does the firm have complete testing facilities for the product in question?
(g) Has the firm executed an order for a product similar to the one being considered? If so,
details of the order should be obtained.
(h) What is the financial standing of the firm?
(i) What is the general attitude of the firm’s management towards quality assurance?
The purchase department takesone or the other ofthe following actions on the basis of
the findings ofthe assessment committee:
(a) If the firm in question is found to have a sound quality assurance system,its name is
included in the list of registered suppliers.
(b) If the firm has minor deficiencies, it is advised to take remedial actions and it is registered
after further verification.
(c) If the company has any significant defect,it is informed that it cannot for the moment be
registered as a supplier.
Subcontractors or vendors should be registered for specific products and for limited period,
e.g. two years. In addition to monitoring the products they supply, the company should
periodically check that the subcontractors or vendors in its register maintain performance
standards as laid down by the company. A group should be formed in the purchase
department for this periodic monitoring of subcontractors or vendors.
All findings should be properly recorded and the data is used for updating the register of
approved subcontractors or vendors. Suitable guidelines and criteria should also be laid down
for the addition or deletion of registered names.

PURCHASING DATA
Successfulprocurement begins with a clear definition of requirements. Usually requirements
are contained in the contract specifications, drawings and purchase orders provided to the
subcontractors or vendors.
Appropriate methods should be developed to ensure that the requirements are clearly defined,
communicated and most importantly understood clearly by the subcontractors or vendors.
These methods may include written procedures for the preparation of specifications, drawings
and purchase orders, meetings between the suppliers and the company prior to release of
purchase orders.
Purchase documents should contain data clearly describing the product or service
ordered. Important elements are listed below:
(a) Precise identification of product and grade
(b) Inspection instructions
(c) Quality standard to be applied etc.
All inspection/test methods and technical requirements should refer to the appropriate
national and international standards. The status of all documents mentioned in the purchase
order should be clearly indicated. When technical requirements, drawings and inspection
procedures are cited, it is essential that they are identified by their document numbers in order
to remove any source of confusion. Detailed quality requirements should be stated in the
purchase order; any intermediate inspection requirements should be shown as ‘hold point’ in
the purchase order. ‘Hold point’ is a point in the manufacturing process beyond which the
subcontractors or vendors will not proceed without the buyer’s explicit permission/clearance.
CONTROL OF ADEQUACY AND CORRECTNESS OF PURCHASE
DATA
A company should have specific procedures for verifying a purchase order before it is
released. Possible methods are listed below:
(a) All specifications (e.g. technical, metallurgical, mechanical and other quality
requirements) are clearly stated in the drawings so that these can be reproduced in the
purchase order.
(b) A reference number is given to the drawing and the subcontractors or vendors are asked to
refer to the drawing for all specifications.
(c) The quality assurance department is required to verify the purchase order for completeness
and accuracy of all specifications.
(d) The requirements are discussed with the design and quality assurance departments before
being reproduced in the purchase order.
The other procedures to be followed should also be made clear in the purchase order. For
example, the buyer may expect the approval of a proto-type sample before undertaking batch

production. The subcontractors or vendors may not have this in mind at all. Such procedural
details should carefully be spelt out in the purchase order.
CHECKS ON INCOMING MATERIALS
So far we have discussed some of the procedures for the purchase of raw materials and
components conforming to required quality. On receipt of materials at stores, they should be
subjected to various checks as per pre-determined quality guidelines. The Quality Assurance
Engineer (QAE) should review the outcome of such inspections before the materials are
released for production.
Formats for such quality checks of some of the major raw materials and components are
shown in the following pages. In case,the complete tank body is fabricated outside through
sub-vendors, then it is considered to be a component and should be subjected to quality
checks. Reports gives details of such checks.
CONCLUSIONS
This Topic mainly dealt with the purchase procedures and quality checks on some of the basic
raw materials and components. Once the requirement of quality is understood, it is very easy
for the working engineers to maintain it. The main responsibility lies with the design
department where the specifications of raw materials and the components are prepared. Once
the specifications are available, they should be circulated to the respective vendors to enable
them to check the materials for compliance before dispatch. With the process of quality
checks at the incoming stages,it is possible to reduce the rejection/failure of the finished
products. Moreover with such activities, overall quality of the equipment including longer
operational life may also be expected.
The power utilities, while carrying out the inspection of the finished products at the
manufacturer’s premises, may desire to review the inspection reports on the raw materials and
components. The utilities should demand these reports to encourage the manufacturers to
maintain them for verification and review. The improvement on the quality of the finished
transformer is achievable only when the buyer and the manufacturer join hands for the
common cause,i.e. quality assurance.

INPROCESS QUALITY ASSURANCE
INTRODUCTION
The easiest way to keep a check on the quality of the finished products is by carrying out in
process inspection on the components produced by various departments. This is necessary to
ascertain the quality of the components as well as to ensure that the components are made in
line with the requirements of customer specifications. In case,any of the components is found
defective or beyond acceptable quality norms, it is very easy to take corrective measures at
the manufacturing stages. This will help to reduce the probability of failure of a complete
product at the finished stage. Cost of rejection and/or rework is reduced by way of inprocess
checking. Some of the performance figures like ratio, resistance etc. can very well be
monitored during inprocess inspection.
DESIGN VALIDATION
Transformer & Reactor Manufacturing General Process Diagram:-
Winding
Construction
Core
Assembly
Connection
Process
Tapping
Device
Assembly
Tanking &
Erection
Process
Drying Process
Tank
Fabrication
Final Fittings
With All
Assembly
HT & LT
Winding
Termination
Painting
Oil Filling &
Termination Testing Dispatch

MANUFACTERING OF TRANSFORMER
THE TRANSFORMER IS MANUFACTURING IN THE BASIS OF ABOVE
DIAGRAM. IN INDUSTRY THE TRANSFORMER IS MANUFACTURE FROM THE
ABOVE BASIS, AND THE DETAIL ABOUT THE MANUFACTURING PROCESS IS
EXPLAINED BELOW:-
 DESIGN OF TRANSFORMER:-
Our designers are familiar with all international and national standards such as ANSI,IEC
since we supply our transformers throughout the world.
Every transformer is individually designed to its specific requirements and applications.
The following specially-developed computer programs are used to further ensure the
reliability of the product:
 Greater optimization of design in relation to labor and material costs, loss evaluation
and sound level,
 Greater distribution of voltage stresses during lightning impulse and switching surge
conditions,
 Greater behavior during short-circuit conditions,
 Greater analysis of those areas where high electrical stresses can occur,and,
 Greater calculations of stray losses and thermal effects.
Should seismic withstand be required, TBEA Power Systems can provide either a
static or a dynamic design analysis to prove that the transformer can withstand the sp.

 QUALITY ASSURANCE:-
Main goal is to build products which perform safely and reliably, meeting the requirements
specified by its customers and providing excellent life cycle value. The establishment of
measurement standards and inspection procedures is only one step towards this goal. The
major step is the complete commitment of all employees towards the entire concept of
quality.
All TBEA Power Systems plants are ISO 9001 certified. Certification was achieved through
recognized institutes such as AIB Vinçotte, Kema and the Canadian General Standards Board.
ISO 9001 includes the greatest number and scope of quality system elements available in the
9000 series, including elements such as delivery and service. The ISO standards describe
elements of quality systems which are designed to ensure that products and services meet all
requirements before they are delivered to the customer. In order to achieve registration,
facilities have to document every process they follow, and successfully undergo an audit by
an independent third party.
Qualified employees inspect, check and sign the progressive control record book system at
their particular stage of manufacture. The quality inspectors audit the system by checking
various aspects of the work to ensure that the system is working correctly. They direct any
corrective action that may be required. In addition, inspectors perform incoming and final
inspections to ensure that materials meet the required quality level.
The progressive control record system ensures that a complete, permanent record is kept of
each stage of the manufacturing process. The method of using qualified employees to perform
inspections in their own area requires that they are well- trained in the procedures and purpose
of the work they carry out. All employees continue to receive in-depth training in all aspects
of their jobs.
 WINDINGS:-
Windings are of circular design, with concentric coil placement. This arrangement provides
the highest short-circuit strength while providing good cooling of conductor surfaces. Both
copper and aluminum conductor can be supplied depending upon customer requirements.
Generally, only copper conductor is used in medium and large MVA designs.
Conductors are either paper- or Nomex® covered magnet wire or continuously transposed
cable. High tensile-strength conductor is supplied if required to meet anticipated short-circuit
forces. Conductors cross sections are chosen to be as large as possible to minimize short-
circuit stress,while ensuring that eddy losses in the conductors are kept under control.
Continuously transposed cable can be supplied with epoxy bonding; greatly increasing its
short-circuiting strength. Modern winding machines utilize fully adjustable steelmandrels to
ensure tight tolerances and more efficient winding operations. The winding machines are
equipped with hydraulic braking devices which ensure that the proper tension is maintained
on the winding.
Winding types are selected by the design engineer, depending upon the specific application.
Strip, barrel, layer, helical, disc, shielded and interleaved disc types are all available to the
designer, depending on the voltage and current requirements of the design. Control of
electrical stress is achieved by placement of custom- designed stress rings on the ends of high

voltage windings and anywhere else they are required. Dovetailed key spacers are employed
to give the windings extra strength.
Oil flow through the windings is directed in a zigzag pattern to ensure cooling of all
conductor surfaces and to limit the hot spot temperature. Carefulattention is paid to ensure an
even distribution of oil to all sections of all windings.
On request,fiber optic temperature sensors can be inserted in the winding to measure actual
hotspot temperatures during testing and in service.
Following completion ofthe windings:-
 All coils are dried in a hot air oven and hydraulically pressed to size to obtain the
design height and to guarantee full short- circuit resistance.
 This allows an accurate determination to be made of their final size and provides
a dimensionally-stable assembly
 The windings are then ready to be mated with the core, lead work and other
internal accessories.
TYPES OF WINDINGS:-
CONSTRUCTION OF WINDING IN POWER TRANSFORMER:-
The windings consist of the current-carrying conductors wound around the sections of
the core, and these must be properly insulated, supported and cooled to withstand
operational and test conditions.
The terms winding and coil are used interchangeably in this discussion. Copper and
aluminum are the primary materials used as conductors in power-transformer
windings.
Winding
Disc Type
Winding
Interleaved
Winding
Strip Type
Winding
Barrel Type
Winding
Shield Type
Winding
Helical Winding

While aluminum is lighter and generally
less expensive than copper, a larger cross
section of aluminum conductor must be
used to carry a current with similar
performance as copper. Copper has
higher mechanical strength and is used
almost exclusively in all but the smaller
size ranges, where aluminum conductors
may be perfectly acceptable.
The conductors used in power
transformers are typically stranded with a
rectangular cross section, although some
transformers at the lowest ratings may
use sheet or foil conductors. Multiple strands can be wound in parallel and joined together at
the ends of the winding, in which case it is necessary to transpose the strands at various points
throughout the winding to prevent circulating currents around the loop(s) created by joining
the strands at the ends.
Individual strands may be subjected to differences in the flux field due to their respective
positions within the winding, which create differences in voltages between the strands and
drive circulating currents through the conductor loops.
Proper transposition of the strands cancels out these voltage differences and eliminates or
greatly reduces the circulating currents. A variation of this technique, involving
many rectangular conductor strands combined into a cable, is called continuously transposed
cable (CTC),as shown in Figure.
In core-form transformers, the windings are usually arranged concentrically around the core
leg, as illustrated in Figure,which shows a winding being lowered over another winding
already on the core leg of a three-phase transformer.
FIGURE 2: CONCENTRIC ARRANGEMENT, OUTER
COIL BEING LOWERED ONTO CORE LEG OVER TOP OF INNER COIL
FIGURE 1: CTC

 INTERLEAVED WINDING:-
With an interleaved arrangement,
individual coils are stacked,separated by
insulating barriers and cooling ducts. The
coils are typically connected with the
inside of one coil connected to the inside
of an adjacent coil and, similarly, the
outside of one coil connected to the outside
of an adjacent coil. Sets of coils
are assembled into groups, which then
form the primary or secondary winding.
When considering concentric windings, it
is generally understood that circular
windings have inherently higher
mechanical strength than rectangular
windings, whereas rectangular coils can have lower associated material and labor
costs.
Rectangular windings permit a more efficient
use of space,but their use is limited to small
power transformers and the lower range of
medium-power transformers, where the internal forces are not extremely high. As the
rating increases,the forces significantly increase, and there is need for added strength
in the windings, so circular coils, or shell-form construction are used.
Concentric coils are typically wound over cylinders with spacers attached so as
to form a duct between the conductors and the cylinder. The flowofliquid
through the windings can be based solely on natural convection, or the flowcan
be somewhat controlled through the use of strategically placed barriers within
the winding.
 PANCAKE WINDINGS:-
Several types of windings are commonly referred to as “pancake” windings due to
the arrangement of conductors into discs. However,the term most often refers to a
coil type that is used almost exclusively in shell-form transformers.
FIGURE 3: EXAMPLE OF
INTERLEAVED WINDING IN SHELL
CONSTRUCTION
FIGURE 3: PANCAKE WINDING DURING
PROCESS

The conductors are
wound around a
rectangular form, with
the widest face of the
conductor oriented
either horizontally or
vertically. Figure
illustrates how these
coils are typically
wound.
 LAYER (BARREL) WINDINGS:-
Layer Windings are among the simplest of windings in that the insulated conductors
are wound directly next to each other around the cylinder and spacers.
Several layers can be wound on top of one another, with the layers separated by solid
insulation, ducts, or a combination. Several strands can be wound in parallel if the
current magnitude so dictates.
Variations of this winding are often used for applications such as tap windings
used in load-tap-changing (LTC) transformers and for tertiary windings used for,
among other things, third-harmonic suppression.
 HELICAL WINDINGS:-
Helical windings are also referred to as
screw or spiral windings, with each term
accurately characterizing the coil’s
construction. A helical winding consists
of a few to more than 100 insulated
strands wound in parallel continuously
along the length of the cylinder, with
spacers inserted between adjacent turns
or discs and suitable transpositions
included to minimize circulating
currents between parallel strands.
The manner of construction is such that the
coil resembles a corkscrew. Figure shows a
helical winding during the winding process.
Helical windings are used for the higher-
current applications frequently encountered
in the lower-voltage classes.
FIGURE 4: STACKED PANCAKE WINDINGS
FIGURE 5: LAYER WINDINGS

 DISC WINDING:-
A disc winding can involve a single strand or several strands of insulated conductors
wound in a series of parallel discs of horizontal orientation, with the discs connected
at either the inside or outside as a crossover point. Each disc comprises multiple turns
wound over other turns, with the crossovers alternating between inside and outside.
FIGURE OUTLINES THE BASIC
CONCEPT, SHOWS TYPICAL
CROSSOVERS DURING THE
WINDING PROCESS.
Most windings of25-kVclass and
above used in core-form
transformers are disc type. Given the
high voltages involved in test and
operation,
Particular attention is required to avoid
high stresses between discs and turns
near the end of the winding
when subjected to transient voltage
surges.
Numerous techniques have been
developed to ensure an
acceptable voltage distribution along
the winding under these conditions.
FIGURE 7: DIS C WINDING INNER & OUTER
CROSSOVERS
FIGURE 6: DISC WINDING LAYOUT

FIGURE 8: FINISHED WINDING & WAIT FOR ASSEMBLY

CORE CONSTRUCTION:-
TBEA Power Systems transformers are of the “Core Form” design. All cores are stacked,
using high-quality grain-oriented silicon steel laminations, purchased slit-to-width and coated
with carlite to increase the interlamination resistance and to reduce eddy current losses.
Where loss evaluations justify its use, laser or mechanically scribed or plasma treated silicon
steel will be used.
All cores utilize the step lap principle in the corner joints to reduce losses, magnetizing
current and sound level. The cores are fully-mitered on all joints in order to improve the flux
distribution.
Ultra modern computerized core shears supply fully-mitered, high-efficiency cores. These
machines are able to shear the maximum width of core steel currently available.
Some machines automatically stack the legs and yokes to minimize steel handling and
mechanical stresses,helping to guarantee the designed loss level.
The laminations are stacked in steps, resulting in a circular core shape which gives the
windings optimum radial support, especially during short-circuit conditions.
The exposed edges of all finished cores are bonded with low viscosity, high- strength epoxy
resin on the legs and bottom yoke to help lower the sound level. The temperature rise of the
core is designed to be low and is controlled, if necessary,by carefulplacement of vertical oil
ducts within the core packets.
The core is clamped using structural steelclamps which provide high strength under both
static (lifting and clamping) and dynamic (short-circuit) mechanical loads. The clamps are
very lightweight for their strength and provide a smooth surface facing the winding ends,
eliminating regions of high local electrical stress.
CONSTRUCTION OF CORE IN POWER TRANSFORMER:-
The core, which provides the magnetic path to channel the flux, consists of thin strips of high-
grade steel, called laminations, which are electrically separated by a thin coating of
insulating material.
The strips can be stacked or wound, with the windings either built integrally around the core
or built separately and assembled around the core sections.
Core steel can be hot or cold-rolled, grain-oriented or non-grain oriented, and even
laser-scribed for additional performance.
Thickness ranges from 0.23 mm to upwards of 0.36 mm. The core cross section can be
circular or rectangular, with circular cores commonly referred to as cruciform construction.
Rectangular cores are used for smaller ratings and as auxiliary transformers used within a
power transformer. Rectangular cores use a single width of strip steel, while circular cores use
a combination of different strip widths to approximate a circular cross-section.
The type of steel and arrangement depends on the transformer rating as related to cost factors
such as labor and performance.

Just like other components in the transformer, the
heat generated by the core must be adequately
dissipated.
While the steel and coating may be capable of
withstanding higher temperatures,it will come in
contact with insulating materials with limited
temperature capabilities. In larger units, cooling
ducts are used inside the core for additional
convective surface area,and sections of laminations
may be split to reduce localized losses.
The core is held together by, but insulated from,
mechanical structures and is grounded to a single
point in order to dissipate electrostatic buildup. The
core ground location is usually some readily
accessible point inside the tank, but it can also be
brought through a bushing on the tank wall or top for external access.
This grounding point should be removable for testing purposes, such as checking for
unintentional core grounds. Multiple core grounds, such as a case whereby the core is
inadvertently making contact with otherwise grounded internal metallic mechanical
structures,can provide a path for circulating currents induced by the main flux as well as a
leakage flux, thus creating concentrations of losses that can result in localized heating.
The maximum flux density of the core steelis normally designed as close to the knee of the
saturation curve as practical, accounting for required over excitations and tolerances that exist
due to materials and manufacturing processes.
For power transformers the flux density is typically between 1.3 T and 1.8 T, with the
saturation point for magnetic steelbeing around 2.03 T to 2.05 T.
There are two basic types ofcore construction used in power transformers: core form
and shell form.
In core-form construction, there is a single path for the magnetic circuit. Figure shows a
schematic of a single-phase core, with the arrows
showing the magnetic path.
Single phase applications, the windings are typically
divided on both core legs as shown. In three-phase
applications, the windings of a particular phase are
typically on the same core leg, as illustrated in
Figure.
Windings are constructed separate of the core and
placed on their respective core legs during core
assembly. Figure shows what is referred to as the
“E” – assembly of a three-phase core-form core
during assembly.
FIGURE 9: SCHEMATIC OF SINGLE-
PHASE CORE-FORM CONSTRUCTION.

In shell-form construction, the core provides multiple
paths for the magnetic circuit. Figure is a schematic
of a single-phase shell-form core,with the two
magnetic paths illustrated.
The core is typically stacked directly around the
windings, which are usually “pancake” – type
windings, although some applications are such that
the core and windings are assembled similar to core
form.
Due to advantages in short-circuit and transient-
voltage performance,shell forms tend to be used
more frequently in the largest transformers, where
conditions can be more severe. Variations of three-
phase shell-form construction include five- and
seven-legged cores,depending on size and
application.

 INSULATION:-
All major insulation is manufactured from the
highest quality transformer board or Nomex®
insulation material, fully oil impregnable to
eliminate internal partial discharges from voids.
Winding keyspacers are manufactured from
pre-compressed transformer board to provide
high mechanical and short-circuit strength.
Care is taken in the manufacturing of the
insulation components to ensure that all critical
surfaces have an adequate supply of oil during
impregnation and service in order to limit
partial discharges.
MANUFACTERING PROCESS OF
INSULATING PRESSBOARD:
Pure virgin sulfate cellulose sheet (wood pulp)
is the basic raw material for insulating
pressboards and presently it is being imported.
In addition to 40 to 60 per cent fibre, wood pulp contains other substances including
pentosans
And lignin. These substances and other impurities must be separated from the individual
fibres and washed by means of different chemical processes. However,all of these processes
must be carried out in such a manner that the cellulose itself is not attacked.
The cellulose is then dispersed in fresh water and temporarily stored in pulp chest. The
individual fibres are crushed in order to expose additional surface area. Paper or pressboard
strength is primarily determined by the bonding forces between the fibres, whereas the fibres
themselves are stressed far below the breaking point. The bonding forces are influenced
primarily by the type and degree of refining.
Fibres separated in this manner are mixed with water in mixing chest and are again subjected
to intensive cleaning. In this process even pure sulphate cellulose fibres, which do not comply
with high quality standards for single fibres, are extracted since they get intertwined and form
small knots rather than float in the water as individual fibres. The cellulose-water mixture is
routed through a wide rotating cylindrical screen. While the water flows through the
cylindrical screen,the cellulose fibres are filtered out on the screen surface and form a paper
cylinder.
The higher the paper grade, the thinner the paper web and greater the number of layers. There
Are approximately 35 layers (each having a thickness of 30 microns) per millimetre thickness
of insulating pressboards. The wet lamination of many thin layers without bonding agent will
form the required thickness of board. This is done on the board making machine by
continuous winding of the paper layer onto the forming roll.
Manufacturing of the wet sheet is done as described above. Then dehydration, compression
and drying are performed in special hot process. This pressboard is designated as pre-
compressed transformer board. The density of such material is approximately 1.25 g/cm3.
The wet sheets which contain approximately 70 per cent water are dried and compressed in
one operation between two heated plates. They are exposed temporarily to alternating

temperature and pressure. They are completely dry when they leave the press and are ready for
further processing.
The hot moist fibres assume a plastic behaviour and become cross-linked and much stronger
Than in the case of conventional, elementary pressure application. This yields a material resistant
to bending with rigid tensile and pressure behaviour. The sheets leave the hot press in a
completely stress free status and remain flat and dry. The sheets retain their shape in hot oil even
after decades of operation.
We have discussed the manufacturing process of electricalgrade pressboards from soft wood
Sulfate pulp. There are various forms of raw materials used for manufacturing pressboards.
Some of them are mentioned below:
 Unbleached soft wood sulfate pulp for electrical grade (discussed above)
 Unbleached soft wood sulfate pulp combined with used cotton fibres
 Virgin or used cotton fibres
 Pressboards made of used cellulose fibres (waste paper)
 Pressboards produced from chemically thermo-stabilized cellulose
 Pressboards manufactured from synthetic fibres (applicable for air cooled transformers)
ELECTRICAL & MECHANICAL PROPERTIES
A comparative chart representing the electrical and mechanical properties of various grades of
Pressboards, commonly used by the transformer industry is shown in Table.
A summary of the discussions on the insulating pressboards is given below:
 In case, the transformer manufacturers want to use indigenous material, it should be
sourced

 From M/s Sen Apathy Whiteley or M/s Raman Boards, since their products are
guaranteed for quality and as on today, there are no other manufacturers who can match
their quality.
 Since the pressboard is highly hygroscopic in nature, right kind of storage increases the
reliability of the material.
 Hygienic environment in the shop floor also has a great bearing on quality, since dust,
metal fillings etc. can cause havoc on electric strength.
 Selection of grade and thickness is one of the major criteria which affect the quality of the
Ultimate product.
 To counter the hygroscopic property of insulating pressboard, we must ensure proper
drying before impregnating with dry insulating oil.
 The materials should be accepted on the basis of mills test certificates and must be
reviewed by the quality assurance engineer.
The right choice of material along with environmental checks offer a longer life to the transformer
While improper selection or incorrect processing of materials may adversely affect its
performance.
CORE & COIL ASSEMBLY:-
First, the individual windings are assembled one over the other to form the entire phase
assembly.
The radial gaps between the windings are subdivided by means of solid transformer board
barriers.
Stress rings and angle rings are placed on top and bottom of the windings to achieve a
contoured end insulation design for optimal control of the oil gaps and creepage stresses.
The complete phase assemblies are then carefully lowered over the separate core legs and
solidly packed towards the core to assure optimal short circuit capability.
The top core yoke is then repacked and the complete core and coil assembly is clamped.
The lead exits (if applicable) and the lead supports and beams are installed. All winding
connections and tap lead connections to the tap changer(s) are made before drying the
complete core and coil assembly in the vapor phase oven.

ACTIVE PART (PROCESSING OF COIL & CORE ASSEMBLY):-
The completed core and coil assembly is thoroughly dried to pre-determined power factor
readings by the vapor phase drying process, providing the fastest,most efficient and most
effective drying of the transformer insulation available. The vapor phase process uses the
standard kerosene cycle method. In this system, kerosene is vaporized and drawn by vacuum
into a heated autoclave where the transformer has been placed. Condensation of the vapor on
the core and coil assembly rapidly causes the temperature to rise and allows moisture to be
drawn out of the insulation by the vacuum. High temperature and pressure are used to
accelerate the drying process.
When the power factor measurements and the removal rate of moisture have reached the
required levels, the flow of kerosene vapor is stopped and a high vacuum is used to boil off
the remaining moisture and kerosene. Because so much water is removed in this process, the
FIGURE 10: BRAZING OF A 40 MVA 230 KV WINDING LEAD

insulation physically shrinks in size. Following removal from the autoclave, the transformer is
repacked as required and then undergoes its final hydraulic clamping to ensure maximum
short-circuit strength in the finished product.
TANKING:-
The tank design is fully computerized. The computer determines the optimum size and the
number and location of required tank supports. Occasionally the corners of the tank will be
rounded off to further reduce the transformer weight without sacrificing quality and
reliability. The objective is to reduce the tank size and weight as much as possible, which
facilitates easier handling, transportation, assembly and installation on site.
All tanks are designed to withstand full vacuum and are manufactured from high- quality steel
plate.
Facilities for lifting, jacking and pulling are provided on each transformer tank. Hand holes
and manholes are placed for easy access to interior components such as de-energized tap
switches and bushing connections. Tank bases are either flat or have structural members
which allow skidding of the transformer in two directions, as required by the specification.
The transformer can be designed with a welded or a bolted cover or as a bell type tank. All
metal parts are grit-blast cleaned to remove weld splatter, mill scale and oxides, providing an
excellent surface for the adherence of the primer and paint. The inside of the tank is painted
with a white oil-resistant paint to create good visibility during internal inspection.

All metal parts are extensively tested on oil tightness via penetrate and pressure test at the
tank manufacturer and with an extra 24 hours leakage test after complete assembly.
The factors such as weight, stray load losses and minimum cost are kept in mind while
selecting the material for transformer tank. The material must be capable to withstand stresses
due to jacking and lifting and must have capacity to house cores,windings and internal
connections giving adequate clearance between the windings and the walls. Rolled steel plates
are used for tank bodies of most of the transformers. Small tanks are generally welded from
steel plates. The larger tanks are assembled from boiler plates. Usage of aluminum for
transformer tank reduces the weight and the stray magnetic losses. However,it increases the
cost and also needs special attention for lifting to present stressing. The aluminum tanks are
usually made of cast aluminum tank parts, which are mounted on a shallow mild steel tray
and are arranged to carry the main lifting.

OIL PRESERVATION SYSTEM & FAULT PROTECTION:-
Unless otherwise specified, Use a conservator oil preservation system as a standard. Many
publications have stated the technical advantages of this system over both sealed tank and
automatic positive pressure oil preservation systems,these being:
 High dielectric integrity,
 Positive static pressure on unit at all times,
 Reduced maintenance,
 Possibility to use a buchholz relay & to collect gasses
The conservator oil preservation system uses an expansion tank to and from which the
transformer oil may flow freely as it expands or contracts due to oil temperature changes.
This system always provides a head of oil above the main tank and keeps it completely filled.
An oil level gauge is mounted on the conservator and indicates the change in liquid level.
Due to the heating of the oil in the transformer, oil expands and flows freely towards the
conservator. The oil expansion of the On-Load Tap Changer diverter is completely separate
from the transformer oil. A separate compartment is mounted to the main conservator. Both
conservator compartments are equipped with an oil level gauge with a minimum alarm
contact, pipes for oil draining, air inlet from the breather and connection to the transformer or
OLTC. The oil level gauge is tilted downwards for the ease of reading when standing at the
base of the transformer. The breather is filled with silica gel (Caldigel Orange) that removes
all moisture and dust particles from the air that is inhaled by the conservator. To reduce
maintenance and to save the environment, the standard silica gel breather can be replaced by
an automatic breather with repetitive heating cycle on request.
The main conservator can be fitted with a nitrile membrane to avoid all contact of ambient air
with the transformer oil. This eliminates the possibility of moisture entering the transformer
oil and oxidation of the oil in the conservator. On request, a leakage detector can be mounted
on the conservator to signal a rupture of the membrane. A nitrile membrane in the load tap
changer compartment is not possible due to the gasses produced at each tap change operation.
For the same reason,a buchholz relay cannot be fitted on the load tap changer compartment; a
special protective relay is designed for this purpose with an oil-surge sensitive damper system
that cannot be tested with gas pressure (RS2001 by MR) or a spring operated pressure relay
(Beta by ABB).

COOLING & COOLING
CONTROL:-
TBEA Energy, transformers are
commonly cooled with detachable
panel radiators, providing a reliable
and low maintenance cooling
solution. To boost the efficiency of
the radiators fans can be used (ONAF
cooling). If design recommends or
specifications require, the cooling
efficiency can further be increased by
pumping the oil through the windings
(ODAF cooling).
Power transformers has also a large
experience with other type of coolers,
like compact oil-air cooler or oil-
water coolers and these solutions can
be provided on customers demand.
Cooling control is highly dependable
on the transformer and the cooling
design. All components for the
cooling control are selected for their
high quality and time lasting
properties. For pumped units, oil flow
sensors are used for signaling cooling
malfunctions and, when necessary,
for automatically switching to the
backup pump system. Time relays are
used to sequentially start pumps and fans to lower the starting current. All necessary
signaling contacts are provided as a standard. All cooling control equipment is neatly
housed in an IP54 control box (IP55 possible for small control boxes).
TESTING:-
Prior to shipment, all transformers manufactured by Power Systems are tested in
accordance with the latest applicable standards according to customer specifications. All
industry standard and optional tests with the exception of short-circuit tests; can be
performed in-house by trained personnel using accurate and modern test equipment.
 IMPULSE TESTING
A state-of-the-art digital impulse recording system, the Haefely HIAS system,
provides the most accurate analysis of impulse results available today. Electronic
recording of the impulse current and voltage waveforms allows quick
mathematical comparisons to be made, including the difference between the two
waveforms under scrutiny. Accurate printed and plotted final results are quickly

available. If required, photographic transparencies from the impulse oscilloscope
can be supplied.
The construction of the test area incorporates a complete copper mesh ground
mat system, with extensive grounding points provided. This eliminates high
impedance grounds and provides exceptionally clean test records. The impulse
generator is rated at 200 kV per stage for a total of 2.8 MV, with 210 kJ total
stored energy. For precise triggering, this generator is equipped with a
pressurized polytrigatron gap in each stage. For chopped wave tests,a Haefely
multiple chopping gap is used. The plants should be fully capable of performing
lightning impulse, switching impulse and front-of-wave tests as required.
 INDUCED TESTING
For induced testing, a variable voltage alternator, rated 1500/1000 kVA,3/1-
phase, 170/240 Hz, is used. Voltage control is by solid state automatic voltage
regulator, and solid state speed control of the 1000 kW DC driving motor.
During the induced test, partial discharge measurements both in pC and μV are
taken and equipment is available to locate internal partial discharges by the
triangulation method.
 LOSS MEASUREMENT
Power is provided to the loss measuring system by a 5/10 MVA regulating
transformer feeding three single-phase 10 MVA variable ratio transformers and a
110 MVAR capacitor bank. Losses are measured by an automated system using
CTs for current and gas capacitors for voltage. This system has a fully automated
digital readout and printer.
 AC TESTING
A test supply with an output voltage infinitely adjustable from 3-350 kV is
available for high voltage AC testing. To measure the applied voltage level, a
digital peak- responding RMS calibrated voltmeter capable of measuring up to
1600 kV is used.
 SHORT-CIRCUIT TESTING
TBEA Power Systems’ high profile on the international transformer market is
amply backed up by many years of short-circuit testing at the independent test
laboratories of Kema in The Netherlands and IREQ in Canada.
Note: The above tests are generally kept under the testing procedure. Details about the test
procedure is explained further.
TRANSFORMER TESTING PROCEDURES:-
The test on finished transformer is a part of quality assurance. The performance
parameters are checked and reviewed with respect to the guaranteed values and
available tolerance limit. Before declaring a transformer healthy and ready for service,
the transformer should undergo a series of tests which are categorized as under:

 Routine tests
 Type tests
 Special tests
Routine tests are those which are necessarily to be performed on all transformers.
Type and special tests are carried out on the specific requirement of customers. In
case, these tests have already been carried out in the past on a transformer and the
available test certificates with certified drawings are not older than 5 years, the buyer
may not insist on repetition of such tests.
However the buyer should review the original certificates, for all performance
parameters, including tapping details, impedance, losses etc. of the proposed
transformer before granting waival for further test.
CLASSIFICATION OF TESTS
The details of tests under each category may be classified as under:
Routine Tests: The routine tests may be classified into two groups, viz.
 Di-electric tests (1 to 4) and
 Parametric tests (5 to 8)
Type Tests:
 Temperature rise test (9)
 Impulse test (10)
Special Tests:
 Short-circuit test (11)
 Un-balance current on neutral (12)
 Magnetic balance test (13)
 Measurement of zero sequence impedance (14)
 Measurement of noise level (15)

Schedule of routine, type and special tests with individual details are shown in a block
diagram Fig.
Procedure of each test,as indicated in the schedule of test, is well defined in IS-2026 and the
same is reproduced here in sequential order.
Schedule Of Tests
Routine
Dielectric
Separate Source Power
Frequency Test on HV
Induced Over Voltage
Test
Insulation Resistance Of
HV Winding
Dielectric Value Of Oil
Paramatric
Winding Resistance
No Load Losses & No
Load Current Test
Load Losses &
Impedances
Turns ratio on all taps and
on all phases
Type
TemperatureRise Test
Impulse Test
Special
Short Ckt Test
Unbalanced Current Test
Magnetic Balance Test
Measurement of zero
sequence impedance
Measurementof noiselevel

Any of the test procedures discussed above, may be substituted with the relevant paragraphs
of the recommendation of ISS.
Testing engineers should be well conversant with the test procedures. Care should be taken to
avoid any wrong test procedures so that no failure occurs at the final testing of the
transformer.
Moreover, failure during the final test may be reduced considerably, if inspection and stage
testing are done during the process of manufacturing the transformer. It is more cost effective
to rectify a fault at the manufacturing stage instead of undertaking repair on finished
transformer.
The test records should be made available, if necessary,to the design department. These feed
backs help the designer to make more realistic assumptions in future designs.
Accuracy class and the calibration of testing instruments are vital consideration in transformer
testing. For all commercial use, 0.5 class instruments are found acceptable by all power
utilities. Calibration may be done at least once in a year in a Govt. approved test laboratory.
Instruments with green stickers are always preferred. However,yellow sticker instruments,
may also be used except in cases where the accuracies needed are beyond the class of the
instrument. Instruments like current transformers (CTS), potential transformers (PTS) etc.
may be calibrated once in 5 years. Further, in- house calibration of other meters with respect
to green sticker instruments may be accepted in case of emergency. Calibrated thermometers
should be used for measuring temperature. Micrometer, scale, Vernier etc. should be
calibrated in-house once in a year. Further, condition monitoring, as a part of the quality
assurance should be done at frequent interval to avoid damage of the meters and instruments.

BASIC CONCEPTS OF ISO: 9000 AS A QUALITY
ASSURANCE
INTRODUCTION
Some of the practical aspects of ISO: 9000 quality procedures for the upgradation of quality
of the end products. Here,we shall take up the definition of various elements of ISO: 9000
quality system. People working closely with the manufacturing and the servicing industries
are familiar with the word ISO: 9000. Basics of ISO: 9000 quality management systems,
registration approach and registration benefits etc. are highlighted here to provide guidance to
a company wishing to pursue ISO: 9000 quality system.
International quality management and quality standards, known as ISO: 9000 series of
standards, are produced by the technical committee (TC 176) of the International
Organization for Standardization (ISO). Though the ISO: 9000 series of international quality
standards is relatively young, its root can be traced back to the founding of the International
Organization for Standardization (ISO) in 1946. Geneva, Switzerland, based ISO was
established to develop a common set of manufacturing, trade and communication standards.
The objectives of these standards is to facilitate international exchange of goods and services.
One hundred countries are participating in the International Organization for
Standardization—76 full voting privilege members, 20 (observers) correspondent members
and 4 (documentation) subscribers. The ISO organization has 182 active technical
committees, 630 subcommittees, 1918 working groups and 24 ad-hoc study groups. While
ISO publishes thousands of standards,five documents in ISO: 9000 series (ISO: 9000 to
9004) are having a growing impact on international trade.
ISO: 9000 quality system is the collective plans, responsibilities, procedures and resources
which ensure the interest of the customers with respect to quality and delivery. ISO: 9000
stands for system 44standardization and certification rather than for product standardization
and certification.

ISO: 9000 DOCUMENTS
First published in 1987 and revised in 1994 and 2000, ISO: 9000 consists of five documents,
which are:
ISO: 9000: Describes and clarifies quality concepts and provides guidelines for the selection
and use of a series of International Standards on quality systems.
ISO: 9001: Provides a model for quality assurance in design, development, production,
installation and servicing.
ISO: 9002: Describes quality assurance procedures in production, installation and servicing
(design activities not included).
ISO: 9003: Modelfor quality assurance in final inspection and test.
ISO: 9004: Describes each of the quality system elements of ISO: 9000 helping users to
understand the entire operation in sufficient details to select the appropriate elements in
designing quality system for a particular facility.
ISO: 9000 is written in general terms to accommodate the full range of activities undertaken
by the manufacturers and service providers. Companies that achieve quality system
registration can look forward to improved relations with the customers, better control over
paperwork and processes and increased marketability for products and services. It indicates
the requirements of all major activities, such as:
 responsibilities of top managements,
 setting up documentary evidence,
 Systems to prevent and/or correct non-conformance and specific action needed etc.
Quality manual describes the elements of the quality system. It is the ‘top level’ quality
document and is supplemented by specific procedures and work instructions, which describe
business processes to produce quality products and services.
The twenty elements ofISO: 9001 quality system is divided into three groups under
heading:
(a) System management,
(b) System methodology and
(c) System maintenance.
The twenty elements are:
(a) System management.
 Management responsibility.
 Quality system.
 Corrective and preventive action.
 Internal quality audit.
(b) System methodology.
 Contract review

 Design control
 Document and data control
 Purchasing
 Control on customer-supplied products
 Product identification and traceability
 Process control
 Inspection and testing
 Control of non-conforming products
 Handling, storage, packaging, preservation and delivery
 Training
 Servicing
 Statistical techniques
(c) System maintenance
 Control of inspection, measuring and test equipments
 Inspection and test status
 Control of quality records
APPROCH TO ISO: 9000
ISO: 9000 is the beginning for establishing quality efforts. ISO: 9000 merely stipulates where
the documentation is needed to validate the processes and different approaches towards
implementation of ISO: 9000 system, but never indicates how much is required.
ISO: 9000 is not a product certification standards. Registration in no way measures or
recognizes the quality, good or bad, of a company’s final product, or does not mean that two
companies with ISO: 9000 registrations are equivalent.
ISO: 9000 is simple but not too easy. It requires:
(a) Management to be committed, involved, focused and responsive
(b) People to be organized, responsible, authorized, competent, empowered and
knowledgeable.
(c) Processes to be visible, traceable,consistent, repeatable, measurable and documentable
(d) Documents to be appropriate, relevant, simple, understandable and consistent with the
processes in use.
ISO: 9000 standards have basically three requirements:
1. The company must document the quality system and business processes in detail and
identify and document all the processes that affect quality. This includes everything from
training to customer feedback. In ISO language, it is called ‘Plan what to do.
2. The company must ensure that each employee understands and follows the guidelines put
forth by the documentation and to develop and implement a quality assurance programmer. In
ISO language, it is called ‘Do what you have planned.”

3. The documented quality system must constantly be monitored through internal and external
audits and changed or updated when necessary. Audit means to verify and monitor the
implementation, review and improve where needed. In ISO language, it is called ‘Verification
of activities with respect to what have been planned.’
Three step process to ISO-9000 registration includes:
(a) Management involvement and organizational commitment along with team spirit
(b) Preparation of process:
• Understand the requirement
• Develop a good assessment of current compliance (gap analysis)
• Establish internal audit system
• Document the process
(c) Audit preparation.
• Stimulation
• Understanding the quality policy by all concerned
• Professional attitude
• Good working relationship with the external auditors.
IS0:9000 audit system includes first party audit and third party audit. The first party audit is
performed by trained persons internally according to the established standards and
documentations. The third party audit involves the concept of independent review and
certification by an external organization. The second party audit which is performed by
customer at the supplier’s location may easily be eliminated, if the supplier is ISO: 9000
registered. ISO: 9000 registration assures that the quality processes are implemented and
followed by everyone in the organization and ensure that they are documented and maintained
to a degree that can be demonstrated to an outside agency.
Inherent in ISO: 9000 standards is the concept of two party contractual relationship. ISO:
9000 offers the most fundamental and basic aspects of quality to demonstrate that the
company is doing what it says, so that the customer needs are satisfied. Governmental
purchasing agencies of more and more countries are insisting on ISO: 9000 compliance for
their suppliers.
ISO 9000: ROAD MAP
ISO: 9000 registration steps include the following:
a) Plan your work first
b) Do your work according to the planning
c) Check the product quality according to the standard

d) Know what you and others are doing
e) Involve management and make them understand the concept and obtain their
commitment
f) Establish a quality steering committee with empowerment
g) Train management and employers
h) Communicate registration plan
i) Develop implementation plan
j) Create self-assessment questions
k) Establish quality manual and procedures
l) Establish an internal auditing system
m) Measure compliance to the procedures
n) Establish a comprehensive corrective action system
o) Review results and act appropriately
p) Call independent assessors to audit.
THE HIDDEN STRUCTURE OF ISO: 9001
The clause on ‘‘your work’’ starts when you receive an order or request for tender and finish
the moment you deliver the product or service.
Two clauses (i.e. Management responsibility and Training) relate to ‘‘your people.’’ These
clauses require the staff to be managed in such a way that everyone knows what is going on.
Four clauses on ‘‘your system’’ (i.e. Quality System,Document Control, Corrective Action
and Internal Quality Audit) make sure that you prepare your quality system documents,
control them and audit their implementation so that your business runs smoothly.
Three clauses concerning ‘‘your information’’ (i.e. Product Identification, Records and
Statistical Techniques) make sure that your decisions are based on soild information. They
ask you to identify your products and to keep records.

ISO 9000:2000 QUALITY MANAGEMENT SYSTEM REQUIREMENT
The ISO standard was first published in the year 1982 and subsequently revised in 1987, 1989
and 1991. The standard further underwent some minor revisions in 1994. Finally fifth
revision, ISO 9000:2000 has been adopted to give users the opportunity to add value to their
activities and to improve their performance continually by focusing on the major processes
within the organization.
Extensive surveys have been performed on a worldwide basis to understand the needs of all
the users of the quality management system standards. The new revisions are based on
previous experience with quality management system standards and emerging insights into
generic management systems. This has resulted in a closer alignment of quality management
system with the needs of the organization and better reflect the way the organization runs its
business activities.
The major reasons for the year 2000 revision of the standards are the need to monitor
customer satisfaction, meeting the need for more user-friendly documents, assuring
consistency in quality management system requirements and guidelines, prompting the use of
generic quality management principles by the organization and enhancement of their
compatibility with ISO:14001 (Environmental Management Systems—Specification).
The current revision of the year 2000 is a major structural and strategic revision of the
standards. It incorporates severalconcepts that will tend to bring the standards into better
alignment and harmony with those that are generally considered ‘‘best practice’’ in
contemporary strategies for successfulquality management systems.
QUALITY MANAGEMENT PRINCIPLES
To lead and operate successfully, it is essential to manage the organization in a systematic and
transparent manner. Success can result from implementing and maintaining a management
system that is designed to continually improve performance by addressing the needs of all
interested parties. Managing an organization encompasses quality management amongst other
management disciplines.
In June 1997, the committee had published a guideline document featuring eight principles of
quality management, to facilitate the achievement of quality objectives.
They are listed below:
 Customer focus: Organizations depend on their customers and therefore should
understand current and future customer needs, should meet customer requirements
and should strive to exceed customer expectations.
 Leadership: Leaders establish unity of purpose, direction and the internal
environment of the organization. They create the environment in which people can
become fully involved in achieving the organization’s objectives.
 Involvement of people: People at all levels are essence of an organization and their
full involvement enables their abilities to be used for the organization’s maximum
benefits.
 Process approach:A desired result is achieved more efficiently when related
resources and activities are managed as a process.

 System approach to management: Identifying, understanding and managing a system
of interrelated processes for a given objective contributes to the effectiveness and
efficiency of the organization.
 Continual improvement: A permanent objective of the organization is continual
improvement of its overall performance.
 Factual approach to decision making: Effective decisions are based on the logical or
intuitive analysis of data and information.
 Mutually beneficial customer-supplier relationships: The ability of the organization
and its suppliers to create value is enhanced by mutually beneficial relationship.
 Model of process based quality management systems: Any activity or operation,
which receives inputs and converts them to outputs, can be considered as a process.
Almost all activities and operations involved in making a product or providing a
service are processes.
For organizations to function, they have to define and manage numerous inter-linked
processes.
Often the output from one process will directly from the input to the next process.
The systematic identification and management of the various processes employed
within an organization, and particularly the interactions between such processes,may
be referred to as the ‘Process approach’ to management.
The revised quality management system standards are based on just a process
approach, in line with the guiding quality management principles.
The model shown in Fig. above is intended to function similar to the Plan-Do-Check-
Act (PDCA) model for the continual improvement process of business management
popularized by W. Edwards Deming in the year 1980.

ISO 9004:2004
Guidelines for Performance Improvement
ISO: 9004:2000 gives guidelines on wider range of quality management objectives than ISO:
2001, particularly for the continual improvement in overall performance efficiency and
effectiveness of the organization. This, being a guidance document, is not intended to be used
for third party certification purposes, and acts as a guide for management of the organizations
who wish to move beyond requirements of ISO: 9001. A key element in the ISO: 9004 will be
the ability to perform self-evaluation.
In addition, a new auditing guidance standard, ISO: 19011, is in early draft stage and will
replace ISO: 10011 (part 1, 2, 3) as well as the environmental auditing guideline standards
ISO: 14010, 14011 and 14012.
Both ISO: 9001:2000 and ISO: 9004:2000 are organized to have the same structure and
sequence. These two documents now form what ISO calls a ‘‘consistent pair’’ of quality
management systems standards.
(a) The ISO: 9001:2000 document defines the minimum requirements and
(b) ISO: 9004:2000 provides guidance for companies to go beyond the minimum
requirements by a process of continual improvement.
Fundamental changes in ISO: 9001:2000 series ofStandards
(i) 2000 series is a process oriented structure and is a more logical sequence of the
contents helping to establish vital connection of quality management systems to
organizational processes.
(ii) The new series requires the organization to define continual improvement process
and establish important means to enhance the equality management system. This
concept of continual improvement is one of the new additions to the old standard’s
requirements. In 1994 standards, customer complaints, self-audit, corrective and
preventive action components are pointed in the direction of continual improvement,
but now it is a fundamental theme.
(iii) The evaluation of customer satisfaction is the key information for improvement.
Another fundamental difference in the new standard’s requirements is the extension
of the customer awareness and concern beyond a customer complaint system to the
requirement for actual evaluation of customer satisfaction. The concept of customer
satisfaction as a measure of quality system performance is a fundamental feature of
most modern quality management systems and Total Quality Management (TQM)
models.
(iv) The new series demand increased attention to an organization’s key resources,such
as communication and work environment. The major new requirement is in the area
of resources management—the need to provide and make available specific types of
resources. These will include elements such as information, communication,
infrastructure and work environment.
(v) The new standard with its simpler and clearer language, which is readily translatable
and easily understandable is more compatible with the environment system standards
(ISO: 14000). There is a high probability that at the next revision of these two
standards, they will become unified into a single management standard.
(vi) The new services require increased emphasis on the role of top management, which
includes its commitment to the development and improvement of the quality

management system, consideration of legal and regulatory requirements, and
establishment of measurable objectives at relevant functions and levels.
Time Limit for the Implementation ofISO: 9000/2000
The validity of certification of the standard ISO: 9000/1994 has been extended up to
31st December,2003. Till then it is open to follow ISO: 9000/1994 standards or ISO:
9000/2000 standards. But beyond December,2003, ISO: 9000/1994 standards will be
permanently withdrawn, leaving behind only one standard, i.e. ISO: 9000/2000. It is,
therefore,necessary to study the requirements of the new standards and see how
quickly it can be implemented in the Quality Management Systems.
CONCLUSIONS
In summary, organizations may be required to cope with a host of challenges at any
given time. Some of the challenge’s can be met with pre-planning. Employee’s
education and training should be given prime importance. Top management
commitment, support and dedication are also essential for success. A systematic
approach to utilize customer surveys and feedbacks on service and processes should
be established. Assessment against ISO: 9000 standard will help to identify the
weaknesses and strengths in coping with challenges.
Emphasis must be placed on the prevention of defects,not on inspection, audit or
rework. Quality implementation should be emphasized at all levels. Quality must be
viewed as not just a program, but a process and not an instant cure. Quality must be
an organization wide activity. Excellence, as a way of life in every activity, must be a
guiding factor. Continuous improvement emphasizes that prevention is the strategy
for improving performance through ongoing training and system changes. Dr.
Deming, one of the quality gurus, once stated that the useful management tool for
success is PDCA (PLAN-DO-CHECK-ACT).
Programmed that are well managed tend to show a high degree of success. Quality is
vital to the successes of a company. Quality should become the religion, logic and
culture of the organization. Lastly ISO: 9000 is not a destination, it is a journey.

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