OFFICIAL USE ONLY:

PASS/FAIL_____________________REVIEWED BY CORDINATOR_______________________ DATE

REVIEWED AND SIGNED _____________________________________________________

Name; JANEGRACE WANJIKU Reg No.; E021-01-0692/2019

DEDAN KIMATHI UNIVERSITY OF

TECHNOLOGY

GANTO ENTERPRISES LIMITED

P.O. BOX 2569-10100,
NYERI.

STUDENTS’ EXTERNAL ATTACHMENT REPORT

DATE: 28/04/2023
S T U D E N T ‘S P A R T I C U L A R S

Name of student: NJIRIRI JANEGRACE WANJIKU…………………. (Surname

first)

Registration No. of the student: E021-01-0692/2019

Department: ELECTRICAL AND ELECTRONICS ENGINEERING

Course of study: BACHELOR OF SCIENCE IN ELECTRICAL AND

ELECTRONICS

ENGINEERING

Year of study: 4th year

Company Attached: GANTO ENTERPRISES LIMITED

Station Attached: NYERI, CLASSIC

Address of Company: P.O. BOX 2569-10100, NYERI

Name of Company Supervisor: ANTHONY GATHOGO

Cell Phone of Company Supervisor:0723494821

Directions to the Attachment: CLASSIC NYERI

Email of the Company Supervisor: gantoenterprises@yahoo.com

Duration: From: … 13/03/2023 to:28/04/2023

No. of weeks: 8 weeks

Official rubber stamp

{ }

{ }
INTRODUCTION
The attachment period lasted for 2 weeks from 7 th February to 30th April 2022 at Ganto
enterprises limited. This is a company established and run by Anthony Gathogo, a Kenya
Power and Lighting Company (KPLC) contractor. The company is located at Nyeri, Classic.
The attachment was a success since I got the chance to actualize the theory studied in class.
With the guidance of various supervisors at Ganto enterprises I was able to engage in various
electricity related exercises as well as learn new things which I believe have equipped me for
the industry. The purpose of the industrial attachment was thus achieved since I was able to
enhance my understanding from what I had been learning theoretically in class by doing
practical and real-life tasks.

The main objectives of this attachment period were:

 To be equipped with the major skills required in my profession.

 To promote invention and innovation skills.
 Encourage better team work and cooperation skills.

I believe I was able to achieve all my objectives. I sincerely thank my family for making the
attachment possible and the Ganto’s Company for giving me this opportunity to learn various
skills from them.

Above all, I would love to thank God for keeping me safe and healthy through the entire ten-
week attachment period.

This report gives breaks down the activities I did in various departments, the challenges I
faced and the skills acquired.
ACTIVITIES OF THE ORGANISATION
Summary of activities done by the organization.

 Trimming of trees near power lines

 Replacement of rotten poles
 Replacement of old fuses in a transformer with new ones
 Fresh wiring of the transformer
 Measuring earth resistance of various transformers
 Bush clearing for the constructions of new lines.
 Building structures for transformers
 Construction of new lines
 Electric meter reading and recording.
 Disconnection of power supply to institutions and homesteads that do not comply.
 Reconnection of power supply through meter box upon customers’ meeting the required
demands.

1.CONSTRUCTION OF NEW CONDUCTION LINES

One of the company’s activity is the construction of overhead transmission line, both low
voltage transmission lines and the high voltage transmission lines. The high voltage
transmission line is the overhead conducting lines that are in the national grid. They are
constructed with poles of 45 meters and 42 meters to raise them very high due to their high
voltages. This overhead transmission lines are used together with pylons to transmit
electricity from the areas of generation to the substation and from the substation to a
stepdown transformer.
The low voltage transmission lines come in either 3 phase 4 lines wire system or a single
phase 2 wire system. The 3 phase four wire system is made up of the three phases of
transmission that is the Red, Yellow, Blue and the neutral while the single-phase wire system
has one of the phases and the neutral.
Consumers running projects with high electricity demand require the 3-phase wire system
while where the demand is not high the single-phase wire system is used.

Classification of Overhead Transmission Lines

A transmission line has *three constants R, L and C distributed uniformly along the whole
length of the line. The resistance and inductance form the series impedance. The capacitance
existing between
Conductors for 1-phase line or from a conductor to neutral for a 3-phase line forms a shunt
path throughout the length of the line. Therefore, capacitance effects introduce complications
in transmission line calculations. Depending upon the manner in which capacitance is
considered; the overhead transmission lines are classified as:
 Short transmission lines. When the length of an overhead transmission line is up to
about 50
km and the line voltage is comparatively low (< 20 kV), it is usually considered as a short
transmission line. Due to smaller length and lower voltage, the capacitance effects are small
and hence can be neglected. Therefore, while studying the performance of a short
transmission line, only resistance and inductance of the line are considered.
Medium transmission lines. When the length of an overhead transmission line is about
50-
150 km and the line voltage is moderately high (>20 kV < 100 kV), it is considered as a
medium transmission line. Due to sufficient length and voltage of the line, the capacitance
effects are considered. For purposes of calculations, the distributed capacitance of
the line is divided and lumped in the form of condensers shunted across the line at one or
more points.
Long transmission lines. When the length of an overhead transmission line is more
than 150
km and line voltage is very high (> 100 kV), it is considered as a long transmission line. For
the treatment of such a line, the line constants are considered uniformly distributed over the
whole length of the line and rigorous methods are employed for solution.
It may be emphasized here that exact solution of any transmission line must consider the fact
that the constants of the line are not lumped but are distributed uniformly throughout the
length of the line.
However, reasonable accuracy can be obtained by considering these constants as lumped for
short and medium transmission lines.
Materials and equipment required for the construction of new transmission line
There are a wide range of equipment used in this sector, some of the few equipment are
Auger bit: Auger, tool (or bit) used with a carpenter’s brace for drilling holes in wood.
It looks like a corkscrew and has six parts: screw, spurs, cutting edges, twist, shank,
and tang. The screw looks like a tapered wood screw and is short and small in
diameter; it centers the bit and draws it into the work. At the working end of the twist
there are two sharp points called spurs, which score a circle equal in diameter to the
hole, and two radial cutting edges that cut shavings within the scored circle. The twist
is helical and carries the shavings away from the cutters. The tang is square and
tapered and fits in the chuck on the brace. Expansive auger bits have adjustable blades
with cutting edges and spurs that can be extended radially to cut large holes. Metal-
cutting twist drills can drill holes in wood, but they cannot produce as clean a hole as
an auger bit or as large a hole as an expansive auger
Climbing gear: this consists of a particular kind of shoe that is made of steel or iron. It
is wrapped around the normal safety boot and is tightened. There are of two types;
those that are purposed to climb wooden poles an those that are purposed to climb
concrete poles. They are distinctively looking depending on the task they do.
The tools and equipment used in overhead transmission lines are so many to be detailed. I
attained the necessary information in the field and got first-hand experience even in using
some of the tools and equipment.

2.REPLACEMENT OF TRANSMISSION POLES

Replacement of transmission poles is done due to age-related wear and tear or to ensure safe
ground clearances are maintained. The rotten poles are uprooted using the HIAB machine or
manually. New holes are dug and the rotten poles are replaced with new ones, either concrete
poles or new treated wooden ones.
3.BUSH CLEARING

Trimming of trees near power lines was done to avoid the trees from coming into contact
with power lines. In my attachment period at Ganto’s, this was done manually by use of
machete.

The precaution was done to eliminate the following hazards:

 Fire damage to property from branches sparking in dry conditions

 Serious injury from electrocution due to contact with trees touching the power lines.

Auger bit

Concrete pole climbing shoes

Wooden pole climbing shoes

4. TRANSFORMER WIRING AND INSTALLATION OF FUSES

A transformer is a static piece of equipment used for raising or lowering the voltage of an ac
supply with a corresponding decrease or increase in current. Transformers are rated in
KVA.Transformers come in different sizes and different ratings. There are two types of
transformers;
 Step-up transformers
A step-up transformer is a transformer that increases the voltage from the
primary coil to the secondary coil while managing the same power at the rated
frequency in both coils. It converts low voltage & high current from the primary
side to the high voltage & low current on the secondary side of the transformer.

 Step down transformers

A step-down transformer is a type of transformer that converts the high voltage (HV)
and low current from the primary side of the transformer to the low voltage (LV) and
high current value on the secondary side of the transformer.c
Fuses are installed to the primary and secondary sides of the transformer and are used to
prevent the transformer from blowing due to short circuits. Replacement of fuses is done to
connect back the customers with power and also for maintenance. The two types of fuses are
link fuses and low voltage fuses.

LINK FUSES

dropout expansion fuse 11kv

LOW VOLTAGE FUSE

Fuses are always connected in primary overhead feeder lines and taps to protect distribution
transformer from current surges and overloads.
THE MAIN PARTS OF A TRANSFORMER ARE:

Core
The core of the transformer is used to support the windings. It is made of soft iron to reduce
eddy current loss and Hysteresis loss, and provides low reluctance path to the flow of
magnetic flux. The diameter of a transformer’s core is directly proportional to copper loss
and inversely proportional to iron loss.

Windings
Windings consist of several copper coil turns bundled together, each bundle connected to
form a complete winding. Windings can be based either on the input-output supply or on the
voltage range. Windings that are based on supply are classified into primary and secondary
windings, meaning the windings to which the input and output voltage is applied
respectively. On the other hand, windings based on voltage range can be classified into high
voltage and low voltage windings.
Transformer oil
The transformer oil insulates as well as cools the core and coil assembly. The core and
windings of the transformer must be completely immersed in the oil that normally contains
hydrocarbon mineral oils.

Conservator
The conservator is an airtight metallic cylindrical drum fitted above the transformer that
conserves the transformer oil. It is vented at the top and is filled only half with the oil to
allow expansion and contraction during temperature variations. However the main tank of the
transformer with which the conservator is connected is completely filled with the oil through
a pipeline.

Breather
The breather is a cylindrical container filled with silica gel, which is used to keep the air that
enters the tank moisture-free. This is because the insulating oil when reacts with moisture can
affect the insulation and cause internal faults, which is why it is a must to keep the air free
from moisture. In the breather, when the air passes through the silica gel, the moisture
contents are absorbed by the silica crystals.

Tap changer
To balance voltage variations within the transformer, tap changers are used. There are two
types of tap changers – on load and off load. In on load tap changers, tapping can be changed
without isolating transformer from the supply, while in off load, the transformer needs to be
disconnected from the supply.

Breather
The breather is a cylindrical container filled with silica gel, which is used to keep the air that
enters the tank moisture-free. This is because the insulating oil when reacts with moisture can
affect the insulation and cause internal faults, which is why it is a must to keep the air free
from moisture. In the breather, when the air passes through the silica gel, the moisture
contents are absorbed by the silica crystals.

Tap changer
To balance voltage variations within the transformer, tap changers are used. There are two
types of tap changers – on load and off load. In on load tap changers, tapping can be changed
without isolating transformer from the supply, while in off load, the transformer needs to be
disconnected from the supply.

Cooling tubes
As the name suggests, cooling tubes are used to cool the transformer oil. The circulation of
oil within the transformer may be natural or forced. In the case of natural circulation, when
the oil temperature rises, the hot oil naturally moves to the top and cold oil moves down,
while in case of forced circulation, an eternal pump is used.

Buchholz Relay
Placed over the connecting pipe that runs from the main tank to conservator tank the
Buchholz Relay senses the faults occurring within the transformer. It operates by the gases
emitted due to decomposition of transformer oil during internal faults. Thus, this device is
used to sense and in turn protect the transformer from internal faults.
Thermometer:
Thermometer is also used in above 50KVA transformers. It is used to measure temperature of
oil. In high power transformers, thermometer is also used inside windings which measure
temperature of windings. Whenever temperature increase up to dangerous level, it activates
alarum signal.
Dial type thermometers are usually used for activation of alarms in abnormal conditions. It
gives reading directly through a sensor. Whenever oil temperature increases to specific level,
it provides signal to alarm circuit. Thermometer usually placed close to transformer name
plate.
Bushings
Bushings are used to bring windings terminals out of tank and also use for insulation. For
example, porcelain, oil filled and capacitor type bushings. Arching horns are also connected
to bushings to provide protection from lightning. In above 34 KV transformer, completely
sealed condenser type bushings are used. In less than 25KV transformer plain bushings are
used.

Oil gauge
Oil gauge is used for the measurement of oil in transformer. It displays oil level. Oil gauge is
usually of dial type. Pointer on dial type gauge used to measure oil level. It is used with
medium level to high voltage transformers.
Radiator
In 50KVA above transformers, radiators are used with main tank of transformer for cooling
purpose. It is like a pipes or tubes. It increases the surface area of transformer. Radiator
makes cooling in transformer more effective. This method of cooling is called ONAN (oil
natural air natural).
Cooling fans
In 26MVA and above transformers, cooling fans are also used on radiator. Oil temperature
gauge provide on or off signal for cooling fans. When temperature becomes greater than 75º,
temperature oil gauge turns on cooling fans. This method of cooling is called ONAF (oil
natural and air forced).
Oil pumps
 In 26 MVA above transformers oil pumps are also used along with cooling fans and radiator
oil pumps used to rotate oil in transformer. This method of cooling is called OFAF (oil
forced and air forced).

4.REPLACEMENT OF A FAULTY TRANSFORMER

Transformers may become faulty due to the following reasons:
 misapplication
 Vibration
 High Operating Temperature
 Lightning or Line Surges
 Overloading
 Care of Control Equipment
 Lack of Cleanliness
 Care of Idle or Spare Equipment
 Improper Lubrication
 Careless or Negligent Operation

The organization has a responsibility of identifying faulty transformers and replacing them.
 The following measures are taken by the organization to prolong the life of the
transformers;
 Installing transformers and keeping electrical loading within the design range.
 Protecting units from surges and other external hazards.
 Performing Gas-in-oil analysis annually to measure the dissolved gases in the oil that
are created by developing faults in the transformer.
 Keeping the porcelain bushings and insulators clean.
 On liquid-cooled units, checking the radiators for leaks, rust, accumulation of dirt, and
any mechanical damage that would restrict the oil flow.
 Keeping electrical connections tight.
 Inspecting tap changes on a regular basis.
 The transformer windings, bushings, and arresters have a Power Factor test on a
three-year basis.
 Checking the ground connection on the surge arrester annually.

4.5TRANSFORMER PROTECTION USING SURGE DIVERTERS

Surge diverters are used to protect transformers from electrical surges. The following include
considerations in substation protection;
 Separation distance. This is the distance between arrestor and protected equipment. If
too large, voltage at the protected equipment could exceed its required insulation level
due to reflection and travelling waves.
 Altitude. Surge performance of insulation at a substation is highly dependent on
elevation. Longer insulations are required at higher elevation.
5. MEASURING EARTH RESISTANCE
The earth resistance of various transformers is measured using the earth tester. Measuring of
earth resistance is done to help in maintenance of the transformer. The earth resistance should
always be less than 10 ohms.
Should there be an increase in resistance overtime, the problem is investigated and correction
is done to lower the resistance by replacing or adding ground rods to the ground systems.
The ground resistance is lowered using below methods:
 By driving the ground electrodes deeper
 By increasing the diameter of the ground electrode
 By using multiple ground electrodes

Earth tester

HOW AN EARTH TESTER WORKS

6.METERING
. An electric meter, or energy meter, is a device that measures the amount of electric
energy consumed by a building, tenant space, or electrically powered equipment. This
makes it possible for the supplier to bill the consumer.
There are two types of power meters; The prepaid and Postpaid power meters.
A prepaid power meter is a type of meter with a customer interface unit that has a screen
resembling that of a mobile phone, which allows customers to manage their power
consumption the same way they manage credit units for their mobile phones.
A postpaid meter The Post-paid meters are “Analogue” electrical reading meter. The meter
connection first starts by dropping the phase and neutral from the network into the meter.
From the meter, it is connected into a circuit breaker before being connected to various
electrical devices used for lighting.
7.WIRING OF A DISTRIBUTION BOX
This board acts as the main electrical supply system for any commercial or residential entity.
There are three types of Distribution Boards
Main Distribution Board (MDB)
It receives the incoming electric supply usually 240V from the secondary transformer through
the electric pole and energy meter.
Sub Distribution Board (SDB)
It is used to distribute electricity within a selected area or building. It is connected and
supplied from the MDB through different wires and cables as per requirement.
Final Distribution Board (FDB)
It provides electricity to the final circuits and switches are used to control it.
The phase and neutral supply lines are feed to the board and connected to the energy meter
through a fuse
It is then connected to an isolator that acts as a switch as it opens and closes the line manually
It is then connected to the RCCB that protects the system from current leakage
From the RCCB the neutral line is connected to the neutral link and live through the mini
circuit breaker.
8.POWER SYSTEMS
An electric power system consists of generation stations, power stations, transmission lines,
distribution lines and loads.

Power system structure

 Generation system- these are the systems that generate the electricity. It can either be
conventional (not replenished by natural processes i.e. gas) and non- conventional
(replenished by natural process i.e. hydro and solar energy)
 Transmission system- transmits bulk electrical energy from generation station to the
main load station. It is made up of transformers and transmission lines
 Distribution system- it gives out energy from medium voltage stations to consumer
locations
 Load / energy sink- this is the end equipment where the transmitted electric energy is
converted to other useful energy

The electric supply system can be done through

1. AC system- it has a frequency of 50/60Hz and carries both reactive and active power
and changes direction within a given period. This system is preferred as it allow the
voltage to be stepped up and has easy maintenance
2. DC system- it carries only active power and flows in only one direction. It is cheap as
if requires only two conductors. Has no skin effect as the entire cross section is
utilized and it is free from dielectric losses
PROJECTS INVOLVED IN
I took part in the installation of a ground mounted step-down transformer at the newly
constructed Nyeri town main transport termini. We performed the whole wiring of the
transformer, mounted the fuse carriers and run underground cables to power the whole stage.
I also got the chance to take part in the construction of low voltage transmission lines. I
acquired the knowledge on the all the tools and materials used in construction of such a line
and how to power consumer houses using dropper cables from the pole to their meter box.
Aside from that, I took part in the changing of the step-down transformer in the new Sunrise
hostel at bomas where we replaced the existing transformer with a bigger transformer with a
higher kVA rating due to the construction of the Maisha hostel. The existing transformer
could not power the area since the demand was higher hence need for update.
Other projects I got the chance to involve in include the installation and powering of street
lights and flood lights around Nyeri, installation and activation of the new modern meters for
the residents of karogoto, construction of a high-tension line at karatina and the upgrading of
a single phase two wire system to a 3 phase four wire system at karatina.

WEAK AND STRONG POINTS OF THE ATTACHMENT

The whole attachment period was a learning experience and I am happy to say I achieved all
my objectives. I was able to put into practice what I had learned theoretically in the
institution and this enabled me to acquire various skills. The attachment exercise has also
helped to appreciate various aspects of electrical engineering.
From the activities that I was involved I achieved the following objectives;
 Learned how to do meter reading and recording. I also learned how to recognize a
meter using serial numbers
 Learned how to connect and disconnect power from main supply
 Learned how distribution wiring is done in households.
 Learned how to do fresh wiring of a transformer and hoe to replace fuses
 Acquired the skill of repairing fault transformers and fault lines
 Learned how to measure earth resistance and methods of lowering the resistance

In conclusion, the attachment period was a learning experience since it helps one to acquire
extra knowledge in the field other than what is learnt in class. It also enhances students
understanding of what was taught theoretically because of interactions with various
equipment not available in school. The period has enabled me gain integrity, honesty and
other ethical skills beneficial to the job market.
POINT OF IMPROVEMENT AND RECOMMENDATIONS
The attachment period was well planned and it was a success. The attachment period should
be taken seriously by the students since it helps one gain more understanding on various
aspects of engineering. Despite this, the following consideration should be put into place;

 The institution should consider engaging the students in more practical work than
theory since it is easy to understand
 The school should help students in finding attachment places. This is to enable
students get attached early so that they can complete the attachment on time.

PROBLEMS ENCOUNTERED
 Harsh weather conditions making working quite difficult.
 Risk of attack by wild animals.
 Poor roads making some place inaccessible.
 Unwanted vegetation hindering movement.
 Language barrier
 Lack of protective gear
 Not securing a place for attachment soon
 Gender based discrimination