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CHAPTER ONE

1.0 INTRODUCTION

The project is about the reinforcement of Electricity Power Supply and

Installation of 1 NO. 300KVA, 11KV/415V Transformer at Onicha-Ugbo in

Aniocha North Local Government Area of Delta State at the cost of five

million nine hundred and forty-nine thousand twenty naira seventy kobo

(N5,949,020.70k). My work as an Electrical Engineer attached to Onicha-

Ugbo in Aniocha North Local Government Area is to go for survey on areas

that have made request for reinforcement of electricity power supply or

those areas that do not have electricity power supply. I visited the Onicha-

Ugbo community on request for reinforcement of Electricity power supply

by the indigenes.

On getting to the areas concerned, feasibility studies which covers where

the transformer can be installed suitably is put into consideration. The

distance from the existing High Tension Overhead (OH) line is also

considered. The case of installing a 300KVA, 11/.415KV transformer at

Onicha-Ugbo covers a distance of five hundred (500) meters for the High

Tension Overhead (OH) lines.

1.1 SCOPE OF WORK

The scope of work for the project includes (i) construction of 11kv High

Tension Overhead lines and low tension lines (ii) Installation of

300KVA,11KV/415V transformer substation (iii) Inspection and testing.

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1.2 DELIMITATION OF THE REPORT

This report is restricted to Delta North Senatorial District of Delta State.

While in some areas that are waterlogged, details cannot be given as Delta

North Senatorial District is not known to be waterlogged. Onicha_Ugbo

town is taken into consideration and the scope is limited to only a small

part of Delta State.

1.3 OBJECTIVE OF THE TECHNICAL REPORT

At the end of the exercise the technical report exposed the reader to the

operation of various components used in the reinforcement of electricity

power supply and installation of transformers. The technical report will also

serve as a teaching aid on the basic principles of installation of

transformers.

The need for the report became necessary since one of the criteria for

Chartership in the engineering profession is to give a small technical report

on one’s experience within few years of practical application of engineering

teachings, therefore, my work experience.

DESIGN CRITERIA/METHODOLOGY APPLIED ON THE PROJECTS

In carrying out the design for reinforcement of electricity power supply in

Onicha-Ugbo, the following considerations, criteria and methods were put

into use.

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2.0 Survey / Drawing/Design

2.1 Survey

Survey of the area is done by taking note of existing High tension/low

tension lines. There may be need to extend the high tension only or with

low tension lines running across it. Then I will find out the best option in

taking electricity to that point that is in need. The mapping out of the area

for the transformer substation is also covered in the survey. The distance of

the high tension line is measured locally by taking each step as one metre

and in every forty-five steps a span of low tension line is concluded while by

taking a step of seventy a span of high tension line is concluded. Metre tape

can be used if available and naming of street is made in the survey for

better accuracy and if the distance is much, the car speedometer can be

initialized while the distance is recorded at the point where the distance

covers.

2.2 DRAWING / DESIGN

In drawing, we represent the low tension lines, high tension lines,

transformer, streets, roads and necessary guide that can lead one to install

as designed. The representation covers both existing and proposed lines as

shown in the design figure I. The legend will surely show how/where the

poles are to be placed and where the transformers are to be installed. The

span for low tension line is forty-five metres while for high tension lines

outside the town is seventy metres. At every ten spans, there exists an

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interpole or H-pole with four stay-wires with each pole having three pin

insulators and four shackle insulators and steel galvanized cross arm.

The conductor for high tension and low tension is 100mm2 AAC/ACSR

Aluminium conductor wire. The height of the High tension pole is 10.4 m

while … will be buried. The height of the low tension is 8.5m while will be

buried. Concrete poles as support were used in the installation.

2.3 CONNECTIONS (SUBSTATION)

The following connections were done at the substation. The H-pole must be

mounted at the substation. The H-pole will bear the two or more channel

iron, the lightening arrestor and J&P fuses. The 35mm2 x 3HT dropper cable

runs from the 11KV over head (OH) High Tension line to the primary or high

voltage side of the 300KVA, 11KV/415V transformer.

The 300mm2 x 1PVC/SWA/PVC (U/G) cable will run from the secondary or

low voltage side of the transformer and linking up to the feeder pillar. The

provision for the feeder pillar is 800A 4-way and the up-riser cable of

150mm2 x 4LT will now distribute to the 4-wire Low Tension (LT) lines. The

schematic representation of this section is as shown in fig.ii, fig.iii and

fig.iv,

The high tension overhead is made up of 10.4m concrete pole, steel

galvanized cross arms, channel iron, tie straps, pin insulators, disc insulator

and j-hooks, clamps, clevis. The high tension overhead pole has three pin

insulators and for every ten (10) poles of HT line, two poles are mounted

(H-pole) which will bear the steel galvanized channel iron. The tie straps

support the steel galvanized cross arms. Eighteen number disc insulators

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are used for 33KV line where there is only one section while six number disc

insulator will be adequate where there is only one section for 11KV line.

Danger plates are mounted on every high tension overhead pole. Anti-

climbers of 3 meter per pole is also placed around the pole. Every high

tension pole should be earthed. The j-hooks, clamps, clevis should be the

anchor for the disc insulator.

2.5 TRANSFORMER PROTECTION

The setting up of a high tension line that goes with a transformer involves

huge amount of money. Therefore, there is need to protect the

transformer network. The provision made by the use of J&P fuses,

lightening arrestors and aerial line isolator (especially for 33KV overhead

line) go a long way in protecting the transformer network.

EARTHING

Earthing is done to limit the potential (with respect to the general mass of

the earth) of current-carrying conductors forming part of the system, and

non-current carrying metal work associated with equipment, apparatus and

appliances connected to the system.

The sizes of earthing and bonding connections should be based on the

following; High Voltage steel work earth lead or bonding – to be suitable for

each fault currents of the H.V. system typical conductor requirements for

11KV are as follows:

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Since the project in question is ground mounted substations – earth leads

32mm2 (3/3.75mm2) copper conductor, bonding connections 25mm x 3mm

copper strip or 25mm x 6mm aluminium strip. The MV neutral shall be

connected to earth electrodes at or near the substation and to any metallic

sheath and armouring of the MV distributors. The combined value for these

electrodes should not exceed 10 ohms. The HV steel work earth electrodes

provided for this purpose should be capable of passing a fault current of at

least twice the value required to operate the line protection equipment.

The maximum resistance of these electrodes should not exceed 70 ohms.

In general, earthing is done on the transformer, feeder pillar and the

conductors. The trenches dug in order to bring the earth pole are of four /

three holes measuring 5ft x 5ft for the transformer, 4ft x 4ft for the feeder

pillar, conductors and lightening arrestors.

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CHAPTER THREE

DESCRIPTION OF MATERIALS AND RATING

3.0 LINE CONDUCTORS – Material Sizes and Stranding

The line conductors for new distribution systems shall preferably be

aluminium or ACSR (Aluminium Copper Steel Reinforced) of appropriate

size as recommended below. Copper line conductors shall be used for

maintenance purposes only where copper lines already exist. Copper

conductors will, however, continue to be required for special purposes such

as drop leads to equipment, earthing etc. The recommended conductors

for the project are shown in the following table:

Copper or copper

equivalent to B.S.

125 1970

To B.S. 215 part 1

1970

ACSR

Metric Metric Current

rating

Area

metric

Stranding

AL (mm) Steel (mm)

35mm2

70mm2

50mm2

100mm2

150mm2

181A

271A

346A

-

50mm2

100mm2

-

6/3.35

6/4.72

-

1/3.35

7/1.57

The neutral conductor shall be of the same size as the phase conductor.

The normal arrangement of conductors for a three phase, 4-wire from

top to bottom shall be as follows:

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Red phase no. 1

Yellow phase no. 2

Blue phase no. 3

Neutral no. 4

3.1 MINIMUM HEIGHT OF CONDUCTORS

The lowest conductor (neutral) on the pole shall not be less height above

ground level at any point, after adjusting for the increased sag at 150oF (65

C), than

Over roads and streets - 5.5m

Along roads or over other places accessible to vehicular traffic -4.91m

Over places normally accessible to pedestrian traffic only -4.30m

3.2 LENGTH OF SPAN

The standard span of 45 metres shall be regarded as normal for spans over

45 meters, the high tension overhead line span may be considered up to

70m outside town.

3.3 SUPPORTS

The approved poles are pre-stressed, reinforced concrete poles of 10.4m

(34ft) for high tension pole and 8.6m (28ft) for low tension pole.

3.4 INSULATORS

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Insulators shall be of brown porcelain or of toughened glass

3.5 STAYS

Stay wire shall be of 4/8 S.W.G and 7/8 S.W.G galvanized steel strand of 45

ton quality and shall comply with B.S 183 as applicable. Please see fig v.

3.6 RODS

Stay rods shall be galvanized steel and comply with the requirement shown

in fig.vi.

3.7 GROUND MOUNTED TRANSFORMER

The substation shall be fenced using block and cement. The substation

compound shall be surfaced with crushed stone, graded 1 ½ “ down and

finished with a ¾ ” nominal size stone chippings. The transformer plinth and

foundation of the feeder pillar shall be taken through the topsoil with a

minimum (150mm) depth of mix concrete. This may be increased when

necessary to good load bearing ground.

3.8 SUBSTATION EQUIPMENT – TRANSFORMER

The transformer is oil-immersed, naturally cooled (typed On) suitable in all

respects for outdoor operations, three phase 11000/415 volts, 300KVA. The

schematic representation of this section is as shown in fig. vii, fig. viii and

fig. ix.

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Transformer is a static electromagnetic apparatus which transforms one

alternating current system into another with different voltage and current

levels, but of the same frequency. Transformers are designed in various

forms for different applications, some of these are:

a. Power transformers used for the transmission and distribution of

electric power.

b. Instrument transformers – used for connecting instruments for the

measurement of current and voltage.

c. Radio transformers – used in radio and electronic circuit.

INSULATOR: A device that opposes the flow of current and does introduce

resistance into the circuit e.g, sand, paper etc.

CONDUCTOR: A device that allows the flow of current and does not

introduce any resistance to it. E.g, copper, aluminium, steel etc.

SPAN: The span is the horizontal distance between two adjacent supports.

INTERMEDIATE POLE: AN intermediate pole is a pole on which the

conductors are supported on pin insulators.

SECTION POLE: A section pole for the purpose of this specification is an ‘H’

pole inserted into the line where additional strengthening is required,

stayed both ways in the direction of the line of route and with the

conductors made off on tension insulation on each side.

BONDING WIRE: The bonding wire is a conductor connecting together

metal components.

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EARTHING WIRE: A conductor connecting components or a bonding wire to

an earth electrode.

CHAPTER FOUR

THE BILL OF ENGINEERING MEASUREMENT AND EVALUATION / TESTING OF

FINISHED PROJECT

4.0 THE BILL OF ENGINEERING MEASUREMENT AND EVALUATION

Herein referred to as BEME is a document showing the materials and

quantity of materials with their local costing in one’s currency or

international currency and at the back cover, the total cost for the

execution of the Engineering job. Please see fig.x,xi,xii,xiii and fig.xiv for the

enclosure of BEME for the reinforcement of electricity power supply at

Onicha-Ugbo in Aniocha North of Delta State.

In the case of my area of work, the costing for survey, high tension line

materials, high tension overheads labour, substation materials, substation

labour, transportation of materials, contingency, amount allowed for

Ministry of Mines, Power and steel and PHCN pre-commissioning testing

fees and connection to PHCN National Grid and value added tax of 5%. This

BEME is only restricted as a presentation from the Department of Electricity

Power supply, Ministry of Energy, Asaba.

My job entails designing the high tension (HT) overhead lines, low tension

(LT) overhead lines, township distribution network (TDN) lines, the

installation of transformers (transformer substation).

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4.1 TESTING

All pre-commissioning and commissioning tests in substations are the

responsibility of PHCN and Federal Ministry of Energy. My department

carries out supervision and inspection of electrical projects. The following

write-up describes some of the tests to be performed but the actual test

figures may vary.

Overall Requirements

i. High voltage test shall be conducted in accordance with PHCN safety

rules (distribution).

ii. The insulation level of the equipment under test shall be measured

by means of a constant voltage insulation level set e.g, a “megger”

before and after the application of a high voltage test

iii. The application of a high voltage test to any item of equipment shall

be recorded in a “Record of High Voltage Test” form. Please see fig.

xv-xix for the enclosure of test results.

4.2 MATHEMATICS OF DERIVATION OF VALUE FOR BEME

In below column is a little mathematics that will throw more light on the

derivation for High Tension and Low Tension values for materials used in

the design.

Taking the case of the project into consideration that is the reinforcement

of electricity power supply and installation of 2 no. 300 KVA 11KV/415V

transformer S/S at Illah, we have:

H.T Material

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The distance for high tension is 500 meters for the second transformer

while the first is a direct dropping. The five hundred meter will cover about

eleven (11) poles of high tension. Note that for every ten poles, there is a

section of two poles. This will make a total of twelve (12) poles. In this case

two extra poles are used to tie-off the high tension line for the first

transformer dropping. The twelve poles plus the two poles will make a total

of fourteen (14) poles. To derive for cross arm, use the formula as:

Cross arms = Total No. of poles – (section x 2). The total no. of poles here is

12 poles.

Therefore, cross arm = 12 – (section x 2)

= 12 – 2 = 10

Channel Iron = section x 2

Two section exist in this case, therefore, 2 x 2 = 4

Tie straps = Total no. of poles – no. of section = 12-2 = 10

Pin insulation = 3 x cross arm + 2 x no. of section

= 3 x 10 + 2 x 2 = 34

Disc insulator length = No. of span x 3 x distance of one span

= 10 x 3 x 50 = 1.5km = 1.6 km for sagging.

Danger plate = no. of poles = 14

Anti-climber device (barbed wire) = 3meters x no. of poles

= 3 x 14 = 42 meters.

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Stay assembly (complete) = no. of conductor stringing = 12

Earthing system complete with soil treatment

= total no. of pole – ½ (no. of section) + 1

= 14 – ½ (4) = 12

Aerial line isolator, complete handle pole and H.T. accessories = no. of

substation

This is mostly used for 33KV overhead lines

LT Earthing = No. of Poles (not applicable)

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HT Earthing = No. of Poles – section

= 14 – 2 = 12

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CHAPTER FIVE

CONCLUSION, PROBLEM ENCOUNTERED, RECOMMENDATION AND APPENDICES

5.0 PROBLEM ENCOUNTERED

It must be stated here that a little problem was encountered in the course

of the project. Solution was also proffered hence the installation work was

a success. The problem was due to the earthing. From the test the earth

resistance was very high (above 20 ohms) which was not acceptable

Moreover, the earthing was improved by bringing the high resistance to an

acceptable level with connection of more earth rod and earth mat at

different nearby position properly linked with 70mm copper wire.

Another problem that was experienced in the process of preparing the

certificate for the payment of the project, is the delay in pre-commissioning

test by PHCN and Federal Ministry of Energy.

5.1 RECOMMENDATION

i. Proper earthing network should be put in place especially at

substation in order to protect the entire network

ii. PHCN and Federal Ministry of Energy should respond quickly to pre-

commissioning test

5.2 CONCLUSION

The electrification project of Onicha-Ugbo village was satisfactorily

completed. I ensured the use of standard materials. For the installation,

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with earthing and protective devices put in place to achieve the maximum

performance of the installed transformers. The voltage level at the

consumer end was between 220V – 230V at frequency of 50hz at the time

of completion.