PEL Report

Pak Elektron Limited (PEL)
Summer Internship Report 2014
Inspection and Quality Control of Distribution
Transformers
Submitted To : HR Manager PEL
Submitted By : Numan Ameer Nizami
Internship Duration : 9th
June, 2014 to 9th
July, 2014
Department of Electrical Engineering, FAST-NUCES Lahore

Internship Report on Distribution Transformer PEL
Summer 2014 Page 2
TABLE OF CONTENTS
Dedication 2
Acknowledgement 2
Executive Summary 3
Introduction 4
Transformer 5
Distribution Transformer 5
Winding Section 6
Core Section 8
Assembly Section 9
Maintenance Department 10
TR Design Department 11
I & QC Department 14

Summer 2014 Page 3
Dedication
To all those who have supported, encouraged, challenged, and inspired me. And
specially to my Beloved Parents, honorable teachers and friends for all their
guidance, love & attention which has made it possible for me to make it up to this
point and as well as the Internship Supervisors who bestowed me with the
courage, the commitment and the awareness to follow the best possible route, by
their unmatchable style and by best possible training.
Acknowledgement
All the praises are for the almighty, Allah who bestowed me with the ability and
potential to complete this Internship. I also pay my gratitude to the Almighty for
enabling me to complete this Internship Report within due course of time.
Words are very few to express enormous humble obligations to my affectionate
Parents for their prayers and strong determination to enabling me to achieve this
job.
I appreciate the cordial co-operation from all my Internship Supervisors in the
different departments of PEL and also of HR management for providing me
requisite information and knowledge for compilation of my complete Internship.
All the employers of PEL helped me a lot in performing all the activities and in
gaining the practical knowledge of industry. They gave me best environment and
knowledge to enhance my skills.

Summer 2014 Page 4
Executive Summary
Pak Elektron Limited (PEL) is the pioneer manufacturer of electrical goods in
Pakistan. The company has always been contributing towards the advancement
and development of the engineering sector in Pakistan by introducing a range of
quality electrical equipments, home appliances and by producing hundreds of
engineers, skilled workers and technicians through its apprenticeship schemes
and training programs.
I recently have done my internship in PEL, in which I got training from its
Distribution Transformer unit. The internship basically revolved around the
transformer design, manufacturing, I&QC and maintenance. The system, the style
of working & the commitment of the employees in PEL is really exemplary.
The difference between the success & failure is doing things right and doing
things nearly right, & PEL has always tried for success & that is why it is known to
be one of the leading companies in Pakistan.
In this report I have given a very brief review of what I have seen and learnt
during my internship. I have mentioned all these as I have made an internship as
according to the schedule. This report will give its reader knowledge about the
PEL and power division especially about transformer unit.
I have made it possible to write each and every thing that I have learnt here. I
have all my practical efforts in the form of this manuscript that’s the asset for my
future career.

Summer 2014 Page 5
Introduction
It was established in 1956 in technical collaboration with M/s AEG of Germany. In October
1978, the company was taken over by Saigol Group of Companies. At that juncture, the company
was only manufacturing transformers and switchgears. With the Saigols in management, PEL
started expanding its product range by entering into Air Conditioner manufacturing.
PEL has two divisions of its business.
1. Appliances Division
2. Power Division
Appliances Division
PEL’s Appliances Division is the flag carrier of the Saigol Group. Appliances Division includes
the products; Air Conditioner, Refrigerator, Washing Machine, Water Dispenser and Microwave
Oven. Today, PEL has become a household name. Its products are not only in great demand in
the local market but the Company has also started exporting its appliances to foreign markets.
Power Division
PEL Power Division is one of the major electrical equipment suppliers to WAPDA & KESC.
Since 1956 the company manufactures transformers, energy meters, switchgears, kiosks,
compact stations and shunt capacitor banks. PEL also has had the privilege of getting its
equipment approved and certified from well-reputed international consultants.
ISO 9001 CERTIFICATION:
PEL was 16th
Company in Pakistan that got ISO 9001 Certification in 1997, since then PEL
Management is applying this International Standard Practices for Effectively Managing
Quality of Products and Services that Company Offers.

Summer 2014 Page 6
Transformer
A transformer makes use of Faraday's law and the ferromagnetic properties of an iron core to
efficiently raise or lower AC voltages. It of course cannot increase power so that if the voltage is
raised, the current is proportionally lowered and vice versa.
Distribution Transformer
PEL made distribution transformer’s range includes oil immersed core type transformers, Dry
type (VP impregnated) transformers and autotransformers. These transformers are tailor made
for various ratings. IEC or national standards are followed. PEL offer distribution transformers
voltage up to 33 kVA and ratings up to 30 MVA.
PEL offers transformer tanks with corrugated walls, detachable radiators and tubular
arrangement. The corrugated tanks have a better cooling efficiency, since the fins are
expandable. Tanks are hermetically sealed where possible. In order to meet sophisticated
requirements of customers PEL has also started manufacturing transformers with foil winding.
Foil winding efficiently uses space which results in size reduction. It has better heat dissipation
and also increases potential to withstand short circuit current.
PEL transformers are available for various applications:
• Distribution Transformers (Pole /Pad Mounted)
• Auto Transformers
• Furnace Transformers
• Welding Transformers
• Chokes for furnace Transformers
• Any other special requirement
Start of Internship at PEL UNIT-2
On my first day at PEL, unit 2, we were first briefed by the Mr. ARSHAD Human Resource
Manager. We were informed that we will be following a specific plan during our internship. We
were provided a schedule according to which we have to do work .schedule routine is given
below;

Summer 2014 Page 7
• 9 to 13 June
Winding Section
• 14 to 18 June
Core Section
• 19 to 23 June
Assembly Section
• 24 to 28 July
Maintenance Department
• 29 to 03 July
TR Design Department
 04 To 09 July
I&QC Department
Now I will explain every section.
Winding Section
In the winding section L.V and H.V windings of the coil are made.
Raw Material
1. For L.V winding
• Paper insulated flat copper wire (For 10KVA to 50KVA)
• Copper foil (For 100KVA and above)
2. For H.V winding
• Enamel copper wire (For 10KVA to 200KVA)

Summer 2014 Page 8
• Paper insulated flat copper wire (400KVA and above)
Type of Insulation Material
• Diamond dotted paper (For insulation between layers of windings)
• Press pan sheet (For end collars)
• Creep paper pipe (For insulation of terminal of tap changer)
• Craft paper (Used for insulation in disc winding)
• Thermo ducts
Types of Windings
• Disc winding
• Packet winding
• Layer winding
• Foil winding
Machines Used
• Slitting machine is used for the cutting of bundles of insulation material.
• L.V Foil winding machines are used for foil winding on L.V side for
transformers of the rating 100KVA and above.
• L.V paper insulated copper winders are used for winding of P.I copper
wire for transformers of the rating 10KVA to 50KVA.
• H.V P.I copper winders are used for the winding of P.I copper wire for
transformers of the rating 400KVA and above.
• H.V enamel copper winders are used for the winding of enamel copper
wire for the transformer of the rating 10KVA to 400KVA.

Summer 2014 Page 9
Core Section
In the core section upper, side and yoke limbs of the core are made.
Raw Material
Raw material used for the making of core is M4 grade silicone steel sheet which is an alloy
of iron and silicon. Silicon is used to increase the permeability of iron.
Machines
• Slitting machine is used to cut the big roll of silicon steel sheet in required
sizes (widths) according to the rating of transformer.
• Power press machines are used to make limbs. They are operated manually.
• After cutting of limbs V punching is done on the yoke limb which is called
yoke notching.
• PLC cutting machines are also used to make limbs. There are two PLC
machines. SDRI machine has a capacity of 40,000 limbs per day. L.A.E machine
has a capacity of 60,000 limbs per day. In CNC machines length, width and angle
are given as input.
• L.A.E measuring table is used to check errors in angle, width and length.
Iron Losses
Iron losses are the flux losses in core. Major factors in iron losses are;
• Quality of material.
• Bur.
• Air gap.
To reduce iron losses
• Material should be of good quality.
• Limbs should be bur free.
• Limbs should be rust free.
• Weight of core should be according to Tr. Design

Summer 2014 Page 10
Assembly Section
In the assembly section there are 17 processes in which all the components of the transformer
are put together to form a transformer. Important processes in the assembly section are;
Core Coil Assembly
In the core coil assembly coil is fitted in the core and upper yoke limb is inserted to complete the
core, then core is tightened using upper and lower pressing beams. For coil to coil insulation and
core to coil insulation press pan sheet is used. For insulation between bottoms pressing beam and
coil wooden base is used.
• Before Connection Test (BCT)
In the BCT area turns ratio of the coil is checked using TTR meter.
• H.T, L.T Connections
In this section Y-Delta connections are made. Tap changer is connected with the coil.
Connections are made according to work order specifications given by the design department.
Taping is done on these connections to avoid any short circuit.
• After Connection Test (ACT)
In the ACT area turns ratio of the transformer is checked using TTR meter.
• Furnace
After ACT transformer is kept in the furnace for 48 to 72 hours according to its rating. It is done
to evaporate all the moisture from core or coil. Temperature of the furnace is 120o
to 130o
.
• Cover Plate Assembly
In this section H.T, L.T bushings, through bolts, eye bolts connectors, arcing horns and other
parts are inserted in cover plate.

Summer 2014 Page 11
• Pre Tanking Section
When transformer is unloaded from the furnace it is inserted in the tank as quickly as possible to
avoid the getting of moisture in the live part. Live part of the transformer should be inserted in
the tank in 50mins to 1 ½ hours.
• Oil Filling Section
In oil filling section oil is filled in the tank under vacuum. Amount of oil to be filled can be
found from bill of quantity (BOQ). For 10kv to 200kv oil filling chambers are used and for
transformers above 200kv oil is filled manually.
• Settling Area
After oil filling every transformer is kept for 12 hours in the settling area to check for oil leakage
and oil level.
Maintenance Department
Maintenance Department is the mother of all departments as it look to every department, and is
being called by every department in case of need. Maintenance department has to maintain every
thing of the factory with and without the call of the department.
Department in which the problem arises send a request for their problem to maintenance
department. Maintenance department generates a work order towards for the solution of their
problem. After the matter is solved (repair) maintenance department send a feedback report to
the concerned department to inquire their satisfactory. If the department is satisfied then the
work order is closed. This all communication is done electronically by software developed by
PEL known as MMS.
Maintenance Monitoring System (MMS)
• Receives the maintenance request.
• Generates the work order.
• Updates the status.
• Feedback.

Summer 2014 Page 12
There are two types of Maintenances:
Preventive Maintenance is a precautionary maintenance to avoid certain breakdowns. This may
include service, tuning, oil checking etc of the machines frequently.
Breakdown Maintenance is special maintenance or repair in case any machine certainly stops
working and is on request.
Maintenance department classify the system in to two parts:
• Common
It includes AUTO, ELECTRICAL and MECHANICAL.
• TR unit 2
It includes all the machines used in the factory.
TR Design Department
The Design department is the most important department of the Transformer division. Because
the basis of any transformer is laid here. It is the starting step in the production of any type of
transformer. This department can be subdivided into two main categories:
• Electrical Design
• Mechanical Design
Working Procedure of the Design Department
Whenever any client wants to purchase any transformer, it sends its required specifications to the
Marketing department of PEL. This is called Enquiry. The marketing department then sends this
enquiry to the design department. The design department performs three main tasks:
• Estimation of the Cost
• Dimensional Sketch
• Datasheet

Summer 2014 Page 13
These three things are then sent to the marketing department, which is the feedback to the
client’s enquiry. If the client feels satisfied with these things, then it gives the order to the
marketing department. The marketing department then sends the Sales Advice to the design
section, which mainly defines the number of transformers to be produced and the duration of the
supply.
Once the ordered is confirmed, then the design department starts its working in full swing. The
work is then divided into two subsections; electrical team performs the electrical design, whereas
the mechanical team is mainly concerned with mechanical design.
The electrical design team is mainly involved in the designing of the Core, LT and HT windings.
The mechanical design team works on the layout, body of the transformer. The design is made
on Pro-E and AutoCAD software.
The electrical design generally works with a faster pace, because it has to inform the Material
Planning Control section that this much material is required for the production. Same is the case
with the mechanical team, but since core and winding are to produce first, so there production
starts a bit earlier.
Most of us were doing electrical engineering and but there was a mechanical engineering student
as a internee with us , so we were told about the electrical part and little about mechanical as
well. The design and its calculations are mainly done via software. Once a design is finalized and
is according to the requirements of the client, a TR document is prepared that defines each and
everything regarding the design.
TR File:
TR file describes the production department that what is actually being required by the customer
and how it us to be achieved. The production is then done keeping in view the TR file. Following
are the few important things:
TR no, Fb no, KVA rating, connection type(vector group), cooling mechanism, design no, taps,
losses quoted and calculated, temperature rise, the cross sections of HV and LV windings, the
dimensions (cross section area, height, width, steps etc) of core, type of HV and LV winding,
total no. of layers in HV and LV, turns in each winding, the inner and outer diameter of HV and
LV, the nature of conductor used in winding, the level and layers of insulation, the number of
thermo ducts, the clearance distances, the end collar dimension, the total weight of HV and LV
windings, tapping details, HV and LV winding layout, the description regarding the material
required in winding and core.

Summer 2014 Page 14
Terms
• Data Sheet
Data sheet includes all specification of a transformer
• BOQ
BOQ (Bills of Quantity) contains the amount of material used for the construction
of a transformer.
• Work order
Work order includes the true and sequences of parts to be manufactured.
• Tank Section
In the tanking section cover plate, tank, and other mechanical components of the
transformer are made. Tank has following parts;
• Frame
• Cover plate
• Bottom
• Side plate
• Fin Walls
• Conservator
Raw Material
Raw material for tank and other components are
• MS sheet (Mild steel sheet)
• MSCR sheet (Mild steel cold rolled sheet)

Summer 2014 Page 15
Inspection and quality Control ( I & QC ) Department
Inspection and quality control department ensures; material purchased by the purchase
department is according to the criteria suggested by IEC in their recommendations(Incoming),
during the manufacturing of transformers all the components of transformer are according to
transformer design(in processing),do all the quality tests so that transformer does not fail in real
conditions(Testing). Inspection and quality control department is further divided into three
sections
• Incoming
• In processing
• Testing
• Incoming Section:
Incoming section is responsible for the checking of all the material which is purchased to ensure
that all the material is according to international standards. When the material is purchased it first
comes in the receiving where it is inward gate pass (IGP) number. Incoming section checks
through the system if material has arrived, then quality inspectors from the incoming go to the
store and check the material if material is according to standards set by IEC than material is
approved otherwise it is rejected and supplier compliant application form(SCAF) is sent to
supplier.
There are eight routine tests done in testing section.
• Transformer Turns Ratio Test (TTR Test)
• Winding Resistance Test
• Insulation Resistance Test (Meager Test)
• Induced Voltage Test
• High Voltage Test (Separate source voltage)
• No Load Losses (Open circuit test)
• On Load Losses (Short circuit test)
• Dielectric Tests

Summer 2014 Page 16
1. Transformer Turn Ratio: (TTR Test)
Transformer turn ratio test is done twice on a transformer. Once before the connection and once
after the connection. Transformer turn ratio meter is used for this test. Turn ratio should be as
defined in Tr. Design to pass the test.
2. Winding Resistance
This test is used to check the phase to phase and phase to neutral resistance of transformer.
Phase to Phase resistance should be in ohms (Ω) and phase to neutral resistance should be in
milliohms (Ω).
3. Insulation Resistance Test: (Meager test)
This test is used to check insulation between
H.V Ground
L.V Ground
H.V L.V
4. Induced Over Voltage Test
This test is used to check the winding insulation. In this test voltage is applied on the L.V side
because it is easy to provide. On the L.V side twice the rated voltage at four times the normal
frequency is applied. Test time should be greater than 15 seconds and can be found using the
formula
Time = Rated frequency * 120
Test frequency
5. High Voltage Test: (Separate source voltage)
This test is used to check whether winding is insulated from other parts of transformer or not.
First, all the L.V terminals and body of transformer are earthed. Than 33kv voltage is applied on
the H.V side. IT is checked whether the transformer will stand this voltage for 1 minute or not.

Summer 2014 Page 17
6. No Load Losses: (Open circuit test)
In this test H.V side is kept open and voltage is applied on the L.V side. Than V, I, PF and other
quantities are measured.
7. Load Losses: (Short circuit test)
In this test L.V side is short and current is passed through the L.V side. Than V, I, PF and other
quantities are measured.
8. Dielectric Test
This test is done in the oil testing laboratory and break down voltage should be less than
mentioned in the IEC-60296.

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