Transformer Repair Workshop Report [EEE] students

1. AMRITSAR COLLEGE OF ENGINEERING & TECHNOLOGY
TRAINING REPORT
Submitted in partial fulfillment of the requirement for the award of
Degree in
ELECTRICAL AND ELECTRONICS ENGINEERING
BY
Punjab Technical University
Jallandhar
Submitted to:- Submitted by:-
Er. Ajaypal Singh Atinder Pal Singh Virk
Om Prakash
Narinder Sharma
Neeraj

2. A
SUMMER TRAINING
REPORT ON
PUNJAB STATE POWER CORPORATION LTD.
TRANSFORMER REPAIR WORKSHOP
AMRITSAR
A
Summer training Report Submitted
In Partial Fulfillment of the Requirements
for the award of Degree of
Bachelor of Technology
In
Electrical & Electronics Engineering
By
Atinder Pal Singh Virk
Om Prakash
Narinder Sharma
Neeraj

3.  Punjab State Power Corporation Limited
 Workshop Organization Headed by Chief Engg. Of
Workshop = Iqbal Singh
 Aim – To repair damaged Transformer at cheap rates
instead of paying high amounts to privates
sectors
 2 major circles = Amritsar [4] , Patiala [8]
 Working = Monthly target to repair 120 units
 25 KVA = 1 unit
 63 KVA = 1.5 unit
 100 KVA = 2 unit
 200 KVA = 4 unit
Introduction to Organisation

4. Additional
Superintending
Engineer
Junior Engineer Fore Man
FitterHelper

5. TRW Yard
Washing
Section
TRW Store
Tank
Repaiing
Section
Core Ovening
Section
Box-Up
Section
Dehyration
Filling
Section
Pre Testing
Painting
Final
Testing
TRW Store

6.  A transformer is a Static
device, which transfers
electric power from one
circuit to another.
 Does so without change
of frequency.
 Has voltage at the recei-
-ving end lower or higher
from the supply circuit.

8. Working Principle:- The main principle of operation of
a transformer Faraday’s law of
electromagnetic induction
According to Faraday’s law,
“Rate of change of flux linkage with respect to time is
directly proportional to the induced EMF in a conductor
or coil".

9.  A transformer consists of a rectangular core
of soft iron in the form of sheets (.35mm to
.5mm for 50Hz to 25Hz frequency).
 Two separate coils of insulated wires, a
primary coil and a secondary coil are wound
on the core. These coils are well insulated
from one another.

10. Core Type
In this type of
T/F the winding
surround the major
part of core.
Shell Type
In this the core
surround the
major part of the
winding

12.  There are generally two types of
transformer
 Step up transformer
 Step down transformer
 Some important types are given as:
 Auto-transformer
 Poly-phase transformer
 Leakage transformer
 Resonant transformer
 Instrument transformers

13.  A step up transformer
is a device that
converts low
alternatic voltage to
high alternating
voltage.
 In another word, a
transformer in which
Ns>Np that is called
step up transformer.

14.  A step down
transformer is a
device that
converts high
alternatic voltage
to low alternatic
voltage.
 In another word, a
transformer in
which Np>Ns that
is called step down
transformer.

15.  An autotransformer
with a sliding brush
contact
 An autotransformer
has only a single
winding with two
end terminals, plus
a third at an
intermediate tap
point.

16. For three-phase
supplies,
 A bank of three
individual single-
phase
transformers can
be used,
 OR all three
phases can be
made as a single
three-phase
transformer.

17.  Current transformers,
designed to be looped
around conductor.
 A current transformer
is a measurement
device
 provide a current in its
secondary coil
proportional to the
current flowing in its
primary.

19.  BUCHHOLZ RELAY: It is a very
sensitive gas and oil operated
instrument which safely detect
the formation of gas or sudden
pressure inside the oil transformer.
 CONSERVATOR:- It is used
to provide adequate space
for the expansion of oil when
transformer is loaded or when
ambient temperature changes

20.  TANK:- Basically this is a container
used to keep windings and insulation
oil. The tank is Made up of Mild
Steel.
 SILICA GEL BREATHER:It absorb
the moisture from the air. it is a
chemical material these are the
only one main component inside
the breather basically silica gel is
a brown colored one after the
absorption silica gel become pink

21.  OIL LEVEL INDICATOR: It is used
to show the oil level in the transfor-
-mer. this is a ordinary part situated
on the side of the conservator for
proper oil checking oil tank wants a
specific amount of oil.
 RADIATORS:- These are used for
the purpose for the cooling of the
transformer oil. The oil circulates
all the time from these radiator
parts

22.  Winding temprature indicator: used to
show the temperature of transformer
winding.
 TEMPERATURE METER (O.T/W.T):
These are used for taking the readings of
O.T.I - Oil Temperature Indicator and W.T.I
- Winding Temperature Indicator
 Tap-changer: This is used for the tapping
of the Transformer at different levels.

23. WINDINGS
 PRIMARY WINDING - In the case of power
transmission primary windings are the
main element external connection from
the power is connected to the winding.
 SECONDARY WINDING - This is a another
winding for reducing power (in the case of
step down purpose) .
M
Primary Wining Secondary Wining

24.  This is a outer unit, this is used to
prevent unwanted leakage of
electricity.

25. TRW Yard
Washing
Section
TRW Store
Tank
Repairing
Section
Core Ovening
Section
Box-Up
Section
Dehydration
Filling
Section
Pre Testing
Painting
Final
Testing
TRW Store

26.  Transformer Workshop Yard (TWY):- The
damage transformers are received here. All types of
transformer of 25KV, 63kv, 100kv and 200kv rating
received in damage condition.
 Transformer Repair Workshop Store (TRWS),
Tank & Washing:- In this section the power oil &
windings taken out from the Tank and blank tank is
send for washing in washing section
 Repairing Section: In this
section damage windings are
repaired if all windings are
burnt then whole windings
were replaced with new
windings.

27.  The core shown in fig. is made of
Silicon steel with thickness 0.35 to
0.5mm. These laminated core legs
are tighten with white tape. So,
that the flux in the coils will linked
properly with the other coil.
 The channel's shown in IInd fig.
are also use tighten the core and
Also fix the whole set of core and
Windings in the tank. The main
difference required between the
channel and windings should at
least 16-20mm which can be
increased or decreased according
to the requirement.

28. It is noted that for 25KV, 63KV, 100KV, 200KV
or any Rating Transformer the turn ratio will
not less than 43780 and not more than
44220.
Connections:- The distribution transformer
connection always in star- delta
connections means the connections of
Primary are in Delta connections and the
connection of Secondary in Star Connections.

29.  Core Ovening Section:- Core ovening
section is the most important part of
repairing transformer.
This is used to remove the moisture from
the core and windings of the transformer. In
this the core is placed inside the oven at 40-
60C temp in Summer season and 100-120C
in Winter season.

30.  BOXUP Section:- This is the section where the core
is placed inside the Tank and core is fixed inside the
core and all outer connections were made the
LT and HT were first fixed with
the Brass made rods and then
that rods were fixed with Porc-
-elain Brushes .
 Dehydration Filling Section:- The oil used in the
transformer are Power oil or Mineral oil. It provides
cooling to the transformer. Before filling the oil in the
transformer it is heated at 60KV/minute means 60KV
is applied to the oil for one minute in oil testing
machine. If the oil is withstand with this voltage then
it is further used for filling.

31.  Pre Testing:- In this everything is tested like IR
value, the oil Temp like after filling the oil in tank it
is again tested with 40KV/min. The requirement is
25KV/min but for overload safety purpose it is
tested at 40KV/min.
 Final Testing :- The final testing is divided into
four parts
(a) HVHP (High Voltage & High Pressure)
(b) DVDF (Double Voltage Double Frequency)
(c) No Load Losses
(d) Full Load Losses

32. Maximum Transformer
Efficiency
The efficiency varies as with respect to 2 independent quantities
namely, current and power factor
 Thus at any particular power factor, the efficiency is maximum if
core loss = Iron loss .This can be obtained by differentiating the
expression of efficiency with respect to I2 assuming power factor, and
all the voltages constant.
 At any particular I2 maximum efficiency happens at unity power factor.
 This can be obtained by differentiating the expression of efficiency
with respect to power factor, and assuming I2 and all the voltages
constant.
 Maximum efficiency happens when both these conditions are satisfied.

33. Losses
 Iron or core losses – caused by alternating flux
in core
 Hysteresis losses – During each A.C. cycle current
flows which magnetize and demagnetize the core. As a
result of which energy is lost in each cycle
 Eddy Current losses – Due to consequent heating of
material it results in loss of power
 Copper losses or ohmic losses - Due to ohmic
resistance in transformer winding
 Small losses which are mostly neglected
 Stray load losses – leakage field induces Eddy
currents in tank walls , bolts etc.
 Dielectric losses - occurs in insulation material
basically in oil and solid insulation

34. Open circuit Test
 It is used to determine Lm1 (Xm1)and Rc1
 Usually performed on the low voltage side
 The test is performed at rated voltage and frequency under
 no load

35. Short circuit Test
 It is used to determine Llp (Xeq) and Rp(Req)
 Usually performed on the high voltage side
 This test is performed at reduced voltage and rated frequency
with the output of the low voltage winding short circuited such
that rated current flows on the high voltage side.

36.  For Voltage Step Up
 For Voltage Step Down
 Amplifying Systems
 Loud Speakers

38. Any Queries