Ethiopia electric utility

1. ETHIOPIAN ELECTRIC UTILITY
BENISHANGUL GUMUZ REGION
UNIVERSAL ELECTRIC ACCESS PROGRAM
PRESENTATION FOR ENTERSHIP STUDENTS
MEGABIT 14, 2013 e.c

2. Table of Content
1. Feasibility Study
2. Site Handover
3. Distribution line route survey
4.Electro-Mechanical design document for MV and LV network
5. MV and LV line Constructions
6. Transformer
7. Pole Support, Protection and Cable Connector
8. Foundation
9. Site Supervision
10. Payment Certificate Preparation
11. Job Completion
12. Material Reconciliation

3. The main product of the company
The main product of Ethiopian Electric Utility-Ueap
are as to its product mixes at the time of installation
it was envisaged/thought to transport different
voltage levels
• Address of 33Kv/0.4kv
• Phase to phase:-380V/50Hz
• Phase to neutral:-220v/50Hz

4. Technical Works Flow of the Company
up to Thechnical Products

5. 1. Feasibility Study(የአዋጭነት ጥናት)
የአ/አ/ኤ/አ/ፕ የአሰራር ሂደት
 የተመረጡ ከተሞች/ቀበሌዎች ከውኃ፤ መስኖና ኢነርጂ ሚኒስቴር በክልል በኩል መቀበል
 ለከተሞች መረጣ ከታች የተዘረዘሩ መስፈርቶች መሟላት አለባቸው
 ቢያንስ የበጋ መንገድ ለነረው ይገባል
 ለህ/ቡ ሰፊ አገልግሎት የሚሰጡ የመንግስትና የመንግስት ያልሆኑ የአገልግሎት ተቋማት
(School,FTC,HC,…) የሚገኙበት ጎጥ ቅድሚያ ትኩረት ሊሰጠው ይገባል
 ለአከባቢው ህ/ብ የመጠጥ ዉኃ አቅርቦት ያለበት ቦታዎች

6. 2. Site Handover
o The Supervisor or the Engineer from UEAP side, who is
participating at the site hand over, should take the following
precautions;
Required documents for site handover
 This manual(reference purpose)
 List of towns to be handed over to the contractor
 Site handover format and data table

7. 1.1 Selection of Voltage Level
 The voltage level of the outgoing feeder from which the tapping is to be made
should be known
 Whenever there is an alternative to tap from either 33 Kv, 20 Kv or 15 Kv, top
most priority should be for tapping from 33 kv.
 If the substation is to be upgraded from 15kv to 33kv line then the tapping voltage
level should be taken as 33kv to be constructed with 33kv accessories (should be
clearly mentioned on the site handover format), if the upgrade of substation is
delayed then the town could be energized by 15kv using 15kv transformer and
after the substation upgrading is complete the town will be energized by 33kv.

8. …Continued…
1.2 Selection of Load center
 The load center is chosen to be the center of the town where the following
different facilities are located
 Health center , FTC, Schools, Government offices, Service center, etc
 The woreda or kebele head should decide the load center for the town when
there is confusion between different villages under the same town name.
 The woreda & kebele should put stamps on the site handover document after
sketched or completed.

9.  The LV line should not be extended to more than the following distance for
the following range of customer with in the 750 m radius
 80 m for 1-4 households
 160 m for 4-6 households
 320 m for 7-10 households
NB:- All the information on the site handover has to be certified (signed and
sealed) by the parties who took part in the site handover, i.e.:
 The Kebele administrator,
 The woreda administrator,
 The Contractor,
 The Supervisor and The Engineer

10. 1.4 Selection of Pole type
Since there are four tyes of pole (concrete pole,
steel Pole, African Wooden pole & Normal wooden
pole we select confertable, durable, based on
topograhpy

11. 3. Distribution Line Survey
Distribution Line Route Survey
 A route survey is a survey made along a line or a narrow width for the location and
construction of linear projects such as transmission and distribution lines, pipe lines, high
ways and rail ways.
 Bush Clearing and Survey
 The bush clearing is mainly made for the medium voltage lines.
 For surveying trees, weeding of the grass and bushes must cut and the trees are
removed from the line area.
 Clearance from the center of the road should be kept 15mt.In some areas it
could be useful to aware the people to prevent high growing bushes/trees to
survive.

12. 4. Electro-Mechanical design document for MV and LV network
 The following basic points must fulfill not only those for approval
A. Single line drawing
 Medium voltage level (15/33kv) must be indicated.
 Road map, pole spot and bench marks, should be shown clearly on the drawings
 In Towns, MV and LV poles must be indicated using different colours & symbols.
 The quantity & Type of angle supports to be used must be clearly described on
drawing
 LV cannot be extended more than 750mt from the transformer
 In special cases upto 900m distance may be approved after detailed analyses of the
voltage drops, short-circuit currents and functionality of fuse protection.

13. Cont…
B.GPS data
 All GPS formats including LV/MV should be filled & submitted with the single line
diagram
 Distance between poles must be as per contract agreement.
 Hand written GPS data is not accepted.
 Official seal of the contractor & signature and status Title of the company manager must
be put on every copy
C. Profile drawing
 Span between poles must be shown clearly
 Elevation of pole must be shown clearly
 Bench mark indications must be shown clearly
 Voltage level of feeder 15/33kvmust be shown clearly

14. Cont…
 Control of the voltage drop
 The voltage drop is checked at the end of the same branch as the
short circuit protection (longest branch).
 The voltage drop at the transformer has only negligible effect on
the total voltage drop at the end of LV-line, and is therefore not
considered here.
POLE PIT DIGGING
Before starting the pole pit digging, one must verify if there are any
water pipes, underground cables or similar obstacles in the concerned
area.
Pole pit: is a ground ditch prepared to erect poles
vertically. Hence, it will enable to construct overhead distribution
lines with their necessary supporting materials.

15. CONDUCTORS
The type and sizes of the conductors for MV -lines are:
 All aluminium alloy conductor AAAC 95 mm2 for main lines, and
 All aluminium alloy conductor AAAC 50 mm2 for branch lines.
TOOLS
 The Installation working tools are in two parts, (i) common tools for the whole
group, and (ii) personal tools:
• Climbing shoes for concrete pole
• Climbing shoes for steel pole
• Universal Pliers
• Safety Belt
• Wire strainer
• Pulley
• Cable phase separator
• Conductors cutter

16. Cont…
• Cable phase separator
• Ladder for climbing poles
• Aluminum gin poles for lifting and erection of poles and steel towers
• Hoisting blocks for wire ropes
• Fork wrench
• Wire brush
• Torque wrench
• Operating road
• Insulation tester
• Clamp on meter
• Dynamometer
• Pulling ropes
• Wire cutter
• Ladders

17. Finalizing and producing of all Design Documents
for Construction
Final plan-profile
The complete plan-profile should include:
 Distance from taping point
 Pole number and GPS point
 Size of angle in degree
 Types of ground (soil type)
 Pole type
 Size and type of conductor
 Length of span
 Height and plan location of telephone, transmission and other power lines.
 Obstacles such as rivers, streams, railways, or other obstacles or ground over
which the erection cannot be carried out in the normal manner.
 The general guideline for span of medium voltage and low voltage line is
attached below

18. MV WITH CONCRETE POLE CONSTRUCTION:
While surveying the following angles and assembly type should be put into consideration.
Type of
Assembly
Angle Option 1 Option 2 Option 3
Pole
Type
Support
type
span Pole Type Suppo
rt type
Span Pole Type Support
type
span
Suspension 0o-2o 1x300
dan
with guy
wire
100mt 1x300 dan - 100mt SA Wooden
pole
with Guy
wire or
wooden pole
90mt
Light angle 1 2o-15o 1x300
dan
with guy
wire
100mt 1x300 dan with
guy
wire
90mt 2x SA
Wooden pole
with Guy
wire or
wooden pole
80mt
Light angle 2 15-30o 1x500da
n
with guy
wire
90mt 650dan no
support
90mt SA Wooden
pole
with Guy
wire or
wooden pole
70mt
Heavy angle 30o-60o 1x800da
n
with guy
wire
80mt 2x650/500da
n
with
Guy
wire
80mt SA Wooden
pole
with Guy
wire or
wooden pole
70mt
T-off 90o 1x800da
n
70mt 1*650dan with
Guy
wire
SA Wooden
pole
with Guy
wire or
wooden pole
40mt for
tapping
Dead end 0o 1x800da
n
70mt 1x650dan with
Guy
wire
2x SA
Wooden pole
with Guy
wire or
wooden pole
70mt
Tension tower 0o 2*300da
n
100mt 2x SA
Wooden pole
with Guy
wire or
wooden pole
Transformer 0o 2x300da
n
SA –South African wooden pole
N.B: According to the situation, the above options might vary as per the notification from the engineering
office.

19. Pole top accessories
 Over head accessories Installation:- Cross arm, Tie strap, Bolt and nut M10, Long Bolt, Big
Collar, Pin type Insulators/Composite Post Insulator, Disk insulators/Composite chain
Insulator.
 Conductor types and Cross-sections: The factors governing the selection of conductor
materials are low resistivity, high tensile strength, low cost and easy availability.
 The following cross-sections and type of conductor are recommended for 15/33KV
distribution network:-AAAC 50mm2, AAAC 95mm2
 Transportation of Conductor Drum and drum Strands:
 Conductor drums shall be handled in such a manner as to prevent from damaging
especially when loading, transporting, and unloading from trucks.
 The drum should never be dropped. They may be rolled as indicated by the arrow on the
drum.

20. 6. Transformer
 It is the basic/static electrical device (equipment) in generation as well as for
distribution systems which step up and step down alternating voltage
 Transformers would transform alternating currents and voltages
 Basic elements of transformers
 Core of transformers (iron core & air gap)
 Primary winding (connected to the source)
 Secondary winding (connected to the load side)
 Function of transformers is as flow
 Impedance matching
 Isolations
 Step up & step down

21. Cont..
TRANSFORMER FAULT
Transformer faults at rural substation according to Finnish failure statistics report in 1995 and
1996 are caused by:-
• Lightning stroke 70%
• Other Weather conditions 5%
• Animals 5%
• Overload 5%
• Other or unknown reasons 15%
TRANSFORMER CHECKING
 Visual Inspection
• Is the outer body damaged or not?
• Is there oil leakage or not?
• Oil level checking

22. Cont..
Horn-Gaps checking
 Is the silica gel dry (blue in color)?
 Continuity Test (using Megger Insulation Tester)
 Test the insulation between Primary side or High Voltage Side (b/n R&S,R&T and
S&T)
 If the ohmmeter reads some value it is fine
 If the ohmmeter reads Infinite or very high value it is open therefore there is
problem
 Test the insulation between Secondary Side or Low Voltage Side (b/n R&S,R&T
and S&T)
 If the ohmeter reads some Low value it is fine
 If the ohmeter reads Infinite or very high value it is open therefore there is
problem
Insulation Test
 Test the insulation between Primary Side and Secondary Side (b/n R&T,R&s, S&T
and S&r,r&t, S&t and T&n, s&n, r&n )
 If the ohmeter reads Infinite or High value it is fine.
 If the ohmeter reads some low value it is open therefore there is problem.

23. TRANSFORMER WINDING
Check all the accessories are available
Cross arms
Lightening - Arresters
Insulators
Drop out or Cut out Fuse (with proper Fuse Links)
Earthling rods & copper conductors

24. Cont..
 Check all the accessories are in appropriate size and rate
 The rating of Lighting arrester, drop out fuse and HRC (High
Rupturing capacity) fuse has to match to the transformer
rate.
 Installation of drop-out fuses
 It shall be erected at least a height of 7.2m from ground.
 It shall be checked for proper alignment and matching

25. Cont…
 The standard transformer sizes for rural distribution are 50 kVA, 100 kVA and 200 kVA.
 The transformer installation starts by the installation of the transformer crossarms.
 The cross-arms are fixed to the pole by bolts and nuts or collars.
 Then the transformer is lifted in place, preferably by using a crane on a truck or
alternatively using a winch and tackle.
 The transformer is fixed to the cross-arms by using bolts and rigid iron bars (preferably
L -shaped irons or iron tubes).
 The iron bar comes under the cross-arms, and the bolts are going through the
transformer legs and are fixed to the iron bars.
 It is advisable to carry out the installation works above the transformer (MV-fuses) before
the actual transformer installation.
 This will prevent possible damages to the transformer bushings during the installation
works.

26. Required MV/LV transformer capacity
 The total load of the transformer's LV network is calculated taking into account the
diversity factor and growth factor.
 After the load has been calculated, the "next bigger" transformer size is chosen, i.e. 50
kVA, 100 kVA, 200 kVA or 315KVA.
So, transformer will select depend on:
 Number of user
 Availability in the market
 Reliability
 Cost
 Transformer Rate/Capacity
Load Balance
The sum of R, S, and T equals to N. & R, S, and T carry equal current.

27. Cont…
Pole- Mounted Distribution Transformer installation
 In distribution networks transformers having maximum capacity up to 315KVA
can be mounted on two poles.
 The construction types of the pole-mounted transformers are:Online
construction & dead end construction
 Depending on the location of the site, one or the other type of construction can
be used.
Transportation and receipt of transformers
 On receipt of transformer at the site, it has to be visually inspected and
insulation resistance of the winding should also be tested.

28. PROTECTIVE DEVICES
Installation of Arrestors
 Arrestor is installed outside and the effect of lightning
is grounded where as surge arrestor installed inside
panels comprising of resistors which consumes the
energy and nullify the effect of surge.
 It uses to protect the transformer against lightning over-voltage.
 They are three in numbers and connected at the top of the H-
pole structure.
 The earth terminal at the bottom of all the three lightning
arrestors are joined together and connected to the earth wire
provided.

29. Cross arms
HRC fuse
Fuse box
Insulator
rs
Lightening Arrestors

30. Function of Lightning arrester
It doesn't absorbs lighting
It doesn't Stop lightning
It doesn’t limit voltage produce by lighting
It divert lighting to the ground
It protect equipment electrically in parallel with it
The heart of all arrestor is MOV(metal oxide varister ), semi conductor sensitive
to voltage.
At normal condition MOV is insulator, but high voltage its open

31. HRC Fuse (High Rupturing capacity).
 It protects the system from damage.
 In step down transformers this fuse is mostly used to protect the transformer from
damaging by means of self-burning.
 The fuse switch shall be installed at a height of 2500mm/2.5mt from the ground
level.
 The fuse switch consists of three high rupturing capacity fuses (HRC).
 The fuses to protect the feeds lint shall be selected based on transformer Rating

32. DISTRIBUTION LINE CONTROL MECHANISM
Section switch:-used to control distribution power in
distance of 20 km
Load break switch :- used to control distribution power in distance
of 20-40km
Auto recloses :-used to control distribution power in distance of
above 40km where repetitive fault occurred & it is automation plc
control system.

33.  Pole mounted auto recloser transformer is constructed H pole is installed on two
cross-arms.
 The two sets of lightning arresters are installed on separate cross-arm above the
recloser.
 All cross-arms, the lightning arresters and the frame of the auto recloser shall be
earthed.
 The control unit of the auto recloser is installed with brackets on about 2.5m
hight on one pole.

34. Drop Out Fuse
Dropout fuse are also used for protection purpose.
This fuse used to connect transformer to high tension for step
down voltage also for repair the transformer when it got problem.
For example, if the transformer got the problem of bushing loose
the problem is solved after the opening the dropout fuse for safety
to repair transformer.

35. EARTHING AT PMT (Pole Mounted transformer)
 The MV- lightning arresters shall be connected to the earthing rod with continuous earth
wire.
 All cross-arms at the PMT, the transformer body, and the LV neutral terminal must then
be connected to the earth wire.
 When aluminium and copper wires are connected together, special bi-metallic (Al/Cu)
connectors must be used.
 The earth wire must be firmly connected to earth rod with a connector.
 The number of earth rods can be increased to reach the required earthing resistance
value.
 In such case, the distance between the earth rods shall be minimum 4 meters.
 The earth wire is connected to earth rod with earthing clamps.

36.  The primary purpose of any Cut-out Fuse is to provide protection to the lines
of your system and the various apparatus on those lines such as
transformers and capacitor banks.
 Cutout fuse provide reliable protection from low-level overloads that just
melt the fuse link, intermediate faults, and very high faults, through
maximum interrupting capacity

37. Phase Balance
• Balancing phase referred to equally distributed the available electrical power to
customer
• There are four (4) wires (three phase and one neutral) which runs from the
transformers to the customers’ house .
• when the phase (3 phase) tapped to give the electrical power to the customers there
may be maximum load from one phase this results to power decreasing to the
customers.
• As a result, the customers had not got sufficient electric light.
• To avoid this problem the phase balance method is required and reach equal power to
the customers without reduction of power.

38. Recommendation
 In our organization there is a problem of electric light for customers due to
interruption of electric light.
 This problem comes due to many cases. Such as:
-damaging of transformer
-overlapping of phases
-burning of protective devices
- burning of transmission line cable
-pole problem and other
 Transformers can be damaged due to increasing of the number of user more than
its capability (rate).

39. EARTHING
 Neutral of LV Network shall be earthed at interval of about 250m
 The earthing shall also be done by installing earthing conductor to the same pit with the
pole itself.
 Earthing of the LV-network is made in order to:
- limit the increase of the voltage in fault cases,
- prevent transfer of the voltage from one system to another,
- prevent the arising of dangerous currents and/or sparking,
Protective earthing:
 The earthing of metal & the exposed conductive parts in the system (excluding the
live parts) will increase the safety and the reliability in the network.
 The neutral of the LV-network should be earthed at the distribution transformer
substation and on the line at every fifth pole (about 200 ... 250 m intervals).

40. Temporary earthing:
 All the conductors shall be connected together and to the ground.
 High voltage can be induced to the line from parallel or crossing live line and also
aerial over-voltage can move along the line to the worksite.
 Therefore the earthing should be made whenever the line is under construction
or repair work.
Cross section of Earthing Conductors
 The cross sections for protective earthings of distribution system are specified as
follows.
 Protective earth wires of Switch disconnector, surge arresters, transformer body
and LV Network shall have a conductor cross section of ………Cu 25mm2

43. kVAr
KW
kVA
Power Factor = 0.73
Active and Reactive Powers before Power Factor Correction

44. Power Factor = 0.92
Active and Reactive Powers after Power Factor Correction
kW (Active)
kVAr
(Reactive
Compencet)
kVA
kVA

45. 9. SUPERVISION
Supervision means controlling/ checking the overall activities of the
project periodically.
This includes:-
Checking the quality of the construction according to standards
Checking the construction standards
Checking the status of the project relative to time
Checking the proper handling of materials etc…

46. Types of supervision
We can have two types of Supervision:-
1.According to the contractor's requisition.
This is when the contractor requests for supervision for payment.
2.Random test supervision
This is applied when checkup of construction quality is found necessary.

47. Non destructive test:
In this case the ueap supervisors/engineers will check the quality of
back fill foundation and depth of the pole pit externally/without pit
excavation/. This is applied at once in every five poles/spans/
By stamping on four sides of the pole pit externally.
Checking the depth of the pit by measuring the pole length above
ground.

48. Destructive test:
In this case the ueap supervisors/engineers will check the
quality of back fill foundation and depth of the pole pit
internally by excavating/by destructing/ at one side of the
pole until the bottom pole is found. This is applied once in
every twenty poles.
Therefore; if the construction fails the required standard,
the contractor is responsible for any remedial action by the
customer/UEAP OFFICE/.

49. 10. Payment Certificate Preparation
 The Contractor/TVET who made contract agreement with UEAP start line
construction can requist payment progress as per supervision/ commissioning
reports of executed work
 Payment can be made due to Pole Transportation, Accessory Transportation,
Transformer Transportation, Foundation and Construction work of towns as per
the detail attached data
 Required Data during payment Preparation:-
 Supervision/ commissioning reports
 KM of sites from store (where distribution material is taken) for transportation
pay purpose

50. 11. Job Completion
 Job Completion & Capitalization:- is done after all work of the
town/kebele is completed to capitalize & record all materials used for
the distribution line construction by collecting GPS location of each
material of LV & Mv

51. 12. Material Reconciliation
Material Reconcilation is the material balancing between
transported from d/t store or from other sites & used for on the
site construction as per Commissioning report.
It is done after the contractor/TVET completes all towns
included in the contract agreement
If there is material lost or damage it will be deducted from their
retantion