00 aei low cost electrification workshop arusha...

AEI Workshop on

Low cost on-grid electrification technologies

Snow Crest Hotel - Arusha, 3-4 September, 2013

Workshop Report

Content

DAY 1: 3 September, 2013 ............................................................................................................................ 2

DAY 2: 4 September, 2013 ............................................................................................................................ 7

Annex 1: Workshop Agenda ....................................................................................................................... 12

Annex 2: List of Participants........................................................................................................................ 13

Annex 3: Presentations and case studies .................................................................................................... 16

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DAY 1: 3 September, 2013

9:30hrs. - Opening Session:

George Nchwali – Acting Director General, Director of Finance, Rural Electrification Agency (REA),

Tanzania: Mr. Nchwali gave the opening remarks, thanking participants for attending and introducing

the lineup for the Opening Session and the technical presentation session to follow.

Ambassador Ami Mpungwe – Chairman, Rural Energy Board, Tanzania (former Ambassador for

Tanzania). Mr. Mpungwe commended the workshop, spoke of its timeliness and relevance of rural

electrification in the transformation and economic growth of Tanzania and Sub-Saharan Africa. He

challenged the participants to identify the key cost components in the electrification equation, in order

to enable the governments and REAs to realize 100% of the countries’ rural energy potential without

compromising the security and safety of the beneficiaries.

Jenny Maria Hasselsten – Operations Officer, Africa Energy Practice, World Bank. Ms. Hasselsten

welcomed the participants on behalf of the Africa Electrification Initiative (AEI) of the World Bank. She

noted that only approximately 15% of rural households have access to electrification in the SSA region,

naming the high cost of connections as one of the main causes. One of the ways of tackling it is by

addressing the unsuitably high-cost components – through the use of appropriate low cost technologies,

so Ms. Hasselsten encouraged practitioners to take advantage of the workshop and learn more about

the various technological options.

Niklas Hayek – Junior Project Manager, EUEI PDF. Mr. Hayek welcomed participants to the workshop

and introduced the EUEI PDF and its activities (see Annex 3 for presentation slides).

Chrisantha Ratnayake – Consultant Power Engineer. Mr. Ratnayake defined the principal problems in

rural electrification in the region and outlined the main steps and goals of the workshop (see Annex 3 for

presentation slides).

Prof. Izael da Silva – Deputy Vice Chancellor, Academic Affairs, Strathmore University, Kenya. Professor

da Silva provided the Keynote Speech of the workshop and spoke of the importance of local ownership

and motivation in ensuring rural electrification rates keep up with the projected population growth in

the region (see Annex 3 for presentation slides).

10:30hrs. - Presentations – low-cost technology options:

· Eng. Gissima Nyamo-Hanga, REA Tanzania. Eng. Nyamo-Hanga presented the results of the low-

cost electrification study, carried out by the NRECA Foundation (see Annex 3 for presentation

slides).

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· Mr. Ralph Ake Karhammar, Consultant Engineer. Mr. Karhammar presented the Single Wire

Earth Return (SWER) technology on behalf of Mr. Conrad Holland of SMEC (see Annex 3 for


· Prof. Francesco Iliceto, Professor Emeritus, University of Rome ‘La Sapienza’. Prof. Iliceto

discussed the Shield Wire Systems (SWS) technology and its experiences in SSA (see Annex 3 for


· Mr. Jim VanCoevering, Senior Utility Specialist, NRECA Foundation. Mr. VanCoevering

presented low cost technologies that can be used for HT grid extensions (see Annex 3 for


13:30hrs. – Plenary discussion on presented technology options:

The Afternoon plenary session related to a discussion on the technology options presented earlier. Some

of the key questions and issues discussed are summarized below:

Questions:

1. Mr. Benson Muriithi, Chief Manager, Distribution, KPLC. Question to Mr. VanCoevering: Regarding

cutting down substation costs (one of the points argued in Mr. VanCoevering’s presentation) – how do

the substations get protected without the batteries?

Mr. VanCoevering: The central substation battery is eliminated, and the transformer protection is

powered by the CT’s in the transformer itself, using the CT currents to trigger the CB spring. The CB

spring has to be recharged manually by a maintenance professional who comes in at regular intervals,

but the power itself comes from the CTs. The system applies best for rural areas and would be more

challenging in densely populated regions where outage durations would be more of a concern.

2. Prof. da Silva. Questions to Prof. Iliceto and Mr. VanCouvering: i. To Prof. Iliceto, please provide an

overview on the current critical situation in rural electrification in Africa, and the role of SWS in its

transformation. ii. To Mr. VanCoevering, I didn’t see instrument transformers (CTs and PTs) in the

pictures of substations (in Mr. VC’s ppt presentation) – how is the power measured?

i. Prof. Iliceto: When thinking of the appropriate rural electrification technology choice, one should think

of the level of safety and continuity of supply expected and desired. The same measure should be

applied with regards to safety in rural and urban areas, but with regards to continuity of supply (or

reliability considerations) the standards need not be the same – connection costs increase significantly

in rural areas, so the key in these areas is to provide electricity with lesser levels of reliability (involving

slightly more interruptions) but at substantially lower costs. At the same time cost savings should not

result in higher maintenance costs down the line (SWS requires little maintenance, allowing for

significant maintenance savings over the long term).

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ii. Mr. VanCouvering – PT’s and CT’s are physically on the transformer. In the example demonstrated in

the PPT presentation, there are no separate instrument transformers, they are built in as a cost saving

measure.

3. Mr. Ralph Karhammar. Request to the Botswana Power Corporation (BPC) representatives (in

response to Prof. Iliceto’s remarks on SWER): Please discuss your experience with SWER.

Mr. Isaac Tlou (BPC): BPC tested SWER in a number of villages but were forced to pull back on its plans

as the residents voted against the installment of SWER, feeling it was an inferior technology.

Mr. Steven Peloetletse (BPC): at present the lines are designed within a radius of 500 meters, so that

people can be connected within that area, with a standardized additional cost applied to residents

located outside of the 500m radius.

Mr. Tlou (BPC): A lot of political issues are involved in decision-making for appropriate technology

choices, with politicians affecting popular opinion. On another note, BPC relies on South Africa for

procurement of technical equipment, causing delays and issues with maintenance, as equipment cannot

be found in neighbouring countries.

Mr. Jim VanCouvering (presenting slide titled Installed Cost Per Unit from his PPT presentation): The

order of costs for 3-phase 33kV (MV) lines and 400V (LV) lines are approximately of the same range. The

African practice has a large extent of LV lines a key focus on cost savings should be by reducing the LV

line instalations and extending more single phase MV lines at lower cost. The use of small capacity single

phase transformes also simplifies transformer installations and reduces their costs. As most residential

consumers get single-phase power anyway, (even when a three-phase connection is provided) the single

phase solution is practicable. There needs to be an acceptance that there are multiple ways of providing

the same product through different technologies.

Mr. Chris Ratnayake: Another dimension of the problem is getting the consumer buy-in to the

technology employed -which could be one of the reasons for the failure of community acceptance in

Botswana. Upfront consumer participation, with local government involvement in the selection of

schemes is key to successful implementation of an RE project. With the price breakdown of each

technology and technical capability demonstrated to the community, a specific choice can be made

based on the people’s preference. Ex.: Bangladesh, where cooperatives were set up, with a village

representative elected to work with consumers prior to the establishment of a scheme. This also

ensures that the connections are maximized and made as soon as the line is installed. A similar method

is successfully practiced in Tunisia.

4. Mr. Muganzi Medard (REA, Uganda). Question to Eng. Gissima Nyamo-Hanga: Please elaborate on

the conventional TANESCO cost-saving mechanism mentioned in the presentation.

Eng. Gissima (REA, TZ): The main drivers of the costs mentioned in the presentation are: i. system

design considerations (with use of two phase and single phase MV lines) and ii. contracting mechanism.

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The conventional contracting method that TANESCO uses is through the use of company line crews to

carry out the construction, with TANESCO purchasing large quantities of material. The NRECA study

suggested a turnkey approach instead, (with a possible 20% cost reduction based on past experience).

This turnkey method will be tested in two pilot areas to assess the potential.

5. Prof. da Silva (Strathmore University). Question to Eng. Gissima Nyamo-Hanga: Please elaborate on

the role of SWER in the Tanzanian rural electrification Master Plan. As Uganda and Kenya appear to have

no SWER introduction, Tanzania seems to be in the lead with SWER technology.

Eng. Bengiel Msofe (REA, Tanzania): At present there is no national Master Plan (MP) in operation, only

a national prospectus on rural electrification, with the MP expected to be put together in the near

future. SWER is not planned to be implemented in current projects, as the REA is aware of its limitations

in the Tanzanian scenario.

Mr. Jim VanCouvering (NRECA): while SWER was initially presented as an option to the REA TZ during

the progress of the study, the pushback received in response from the populations resulted in choosing

the two-phase/single-phase approach instead.

6. Mr. Augustus Goanue (RERA, Liberia). Question to Prof. Iliceto: The entire electricity sector in Liberia

has been destroyed and reconstructed. The new state plan is to introduce a large transmission line, 12

substations and joint lines with Cote-d’Ivoire, Sierra Leone, Guinea. How can SWS technology be

developed in an area with no LV transmission line in place?

Prof. F. Iliceto (‘La Sapienza’): If there are no LV lines in place, LV reticulation has to be introduced.

Mr. Goanue (RERA): And what is the best technology choice in providing SWS systems?

Prof. Iliceto (‘La Sapienza’): Reinforced aluminium conductors should be used, at a minimum of 75mm2

and up to 100-150mm2. Two shield wires are necessary for three-phase.

Mr. Jim VC (NRECA) - There are two types of SWS in use, one with medium-voltage (with a separate

source transformer that energizes one or two shield wires, say at 33kV) and the other – induced voltage,

where the SW is insulated from the towers, and simply used as a coupling element to the HV

transmission line. The later system has much lower capacity (a few MW).

7. Mr. Tesfaye Tamirat (EEPCO). Question to Mr. VanCoevering: Regarding low-cost sub-station design,

analysis assumes that it is possible to tap in the middle of the transmission line in order to extend energy

to the MV sub-stations, but how can a main transmission line be tapped if the main line is the backbone

of the system – how can you justify the interruptions that would be caused to the main system?

Mr. Jim VanCouvering (NRECA): The substation and tap line becomes a part of the main line for any line

faults. However the blocking effect of the sub-station transformer impedance prevents any additional

“see through” interruption on the main line.

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14.30hrs. - Breakout sessions:

Prior to the breakout sessions Mr. Chris Ratnayake explained the application of a simplified spreadsheet

methodology which can be used for the computation of the voltage drop and loss evaluation of MV and

LV distributors. Details of the technical formulae used and the development of ‘multiplication factors’ to

convert the voltage drop and line loss of a tail-end load, to that of a distributed load situation was

explained. Thereafter the technical breakout sessions were carried out in three groups. Each group was

presented with a ‘case study’ involving a particular distribution system. They were also provided with

the relevant spreadsheets for computation of voltage drops and losses as well as charts of loads and

distances for typical conductor sizes, configurations, power factors and desired voltage drops. The

participants showed much enthusiasm in the carrying out of the exercises with the spreadsheet based

methodology provided. See Annex 3 for presentation slides.

A fourth breakout group (consisting mainly of non-engineering participants) was established to discuss

policy issues related to rural electrification. This group discussed policy measures that need to be

adopted to secure a successful rural electrification program.

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DAY 2: 4 September, 2013

9:00hrs. – Presentation

· Chris Ratnayake (Consultant Power Engineer): Network Planning Issues, Service Connection

Costs and related considerations (see Annex 3 for presentation slides).

Q&A:

1. Augustus Goanue (RERA, Liberia): What if there’s a forecast showing that the load will grow by 80-

100% in the near future. Does that create issues with using a 6mmsq or 10mmsq cable?

C.Ratnayake (Consultant Power Engineer): 4mmsq cable has a rating of over 20amps and 10 mmsq

cable over 40 amps, which are far more than the load used in a rural household; so 4-6mm cables are in

fact quite adequate for small rural households. If there is any concern, my advice is to check a rural

scheme that has been completed 10-15 years earlier and see the load demand. The situation is naturally

very different in an urban setting – more appliances, etc. gets connected over time, but even then the

conductors used can take much higher loads. Therefore it’s crucial to assess past experiences and per

household loads -through checking with instruments such as load loggers which may be installed on the

lines as well on consumer installations. Thus conducting a proper exercise on clarifying what loads are

actually experienced will be very useful.

2. Augustus Goanue (RERA, Liberia): People in rural areas tend to connect from one house to another,

sometimes against the rules. What are the implications from that practice in terms of the load?

C.Ratnayake (Consultant Power Engineer): That practice should be allowed if properly regulated with

loop meters etc. However, naturally the service cable will not be sufficient if indiscriminate extensions

are allowed. A tailored approach is necessary in such situations depending on what is allowed and what

is not allowed in each situation.

3. Q/Comment: Pre-paid metering vs. post-paid, in terms of revenue collection: Post-paid meters could

cost as low as $10-20, as opposed to the more expensive pre-paid meters. While pre-paid is better in

terms of customer management, post-paid is a lot more affordable and allows for making more

connections possible. Nonetheless, post-paid meters are challenging in terms of theft and problematic

revenue collection.

B.Msofe (REA, Tanzania): Most meters in Tanzania are pre-paid, with TANESCO establishing contracts

with Vodafone and other mobile service providers. This is beneficial for both parties in rural areas as the

mobile companies need to expand their networks into rural areas, and the REA TZ is currently

attempting to reach agreements with mobile companies on contributing to the extension of the

electricity network into the regions.

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4. Prof. I. da Silva (Strathmore University, Kenya): KPLC is currently increasing the cost of connections

from approx. $400 to nearly $800, facing a strong backlash from the population. Can the KPLC

representatives comment?

Eng. Benson Muriithi (KPLC): KPLC is a for-profit company that has shareholders, which puts it in a

dilemma in the context of political agendas of various politicians aiming to electrify the entire country.

KPLC’s perspective is that revenue still needs to be generated to maintain shareholder’s interest. Capital

investment into connections, pushed by the government imposes a high burden, with low returns: a 3-

4% increase in the number of connections requires on average an increase in capital investments by

18%. Therefore government subsidies are crucial in ensuring that the capital cost burden is somewhat

relieved.

C.Ratnayake (Consultant Power Engineer): It’s important to identify what you’re charging the customer

for. Some companies ask the customer to contribute 100%, some 30% upfront for the distribution

network extensions, apart from the service connection costs. With respect to the service connections, it

has to be appropriate for the load – if you use 25mmsq for small rural connections, it is inappropriate

and 4, 6, or 10mmsq needs to be used instead. Once investment of building lines is carried out, the aim

of the utility should be to maximize the connection, as then revenue is also improved. The principal

obstacle to connections is high initial cost. Therefore, if KPLC can afford to provide the investment

upfront and receive the money back from consumers over time, the situation should improve.

Eng. Benson Muriithi (KPLC): KPLC operates a revolving loan, requiring that people only put down 20%

of the whole sum for the connection cost, but there is still need for subsidies for overall capital

investments.

10.30hrs. Breakout Sessions

The breakout sessions as commenced on the previous day were continued by the four groups.

13:15hrs. – Presentation of results by Case Study Groups:

1. Group 1: Lifecycle calculations and expenses should also be taken to account along with the

initial capital costs (see Annex 3 for presentation slides).

2. Group 2: (see Annex 3 for case study): The group attempted the selection of SWER, single-phase

and two-phase options, with the parameters being that the voltage drop could not exceed 7%.

The group’s final conclusion, with economic considerations kept in mind, was to build the first

four sections of the line at 33kV using three phase 50mmsq, and then use a SWER line with the

same 50mmsq conductor for the balance portion, which produced the overall voltage drop of

3%.

3. Group 3 (see Annex 3 for case study): The group was tasked with a similar challenge to the

other two (with voltage drop not allowed to exceed 7%). Upon applying various three-phase,

two-phase, single-phase and SWER scenarios on different sections of the line, the conclusion

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was to select the backbone of the line at 50mmsq three-phase and its branches at 50mmsq

SWER.

Comments:

Prof. F. Iliceto: The entire line (in the Ugandan study) can also be planned with SWER, at 33kV, with an

interposing transformer, instead of just the added SWER section at 19kV used by the team – the

increased voltage will thus help reduce the voltage drop by almost 70%.

C. Ratnayake: While the case studies were designed for a target year load to simplify the exercise,

please keep in mind that schemes should be projected and planned with considerations for potential

future load growth. Thus, carrying out the exercise for future years and using the discounted costs and

benefits methodologies described in the technical literature provided and also using operations and

maintenance costs (including losses) is key to developing least cost network development plans. Thus in

the Ugandan case study building the main line on a three phase system with the spur line on low cost

technologies could well be justified due to factors such as the presence of 11 kV lines in the

neighborhood which may be profitably converted to 33 kV and the fact that the line is along a major

road connecting important towns (all of which require further planning analysis).

4. 4. Group 4 (Policy discussion, presented by Benon Bena, REA Uganda): the group represented a

vast diversity of backgrounds – finance, academia, engineering. The principal conclusions were

as follows:

· Each country and sector requires a policy, setting with specific tangible targets that should be

worked out as relevant for each country.

· The roles of the government, academia and the private sector in enhancing rural electrification: It is

thought that there is insufficient successful examples of fully private sector-led investment in rural

electrification (as risks are high in rural areas with low returns), the recommended policy is for

governments to remain in charge of transmission and involve community-based groups that are

private but motivated by service, rather than profit for the distribution component (eg. Argentina,

US (Tennessee in particular), and recent examples in Uganda).

· Training needs to be put in place to enable utilities to run efficiently, particularly if/when new

technologies and practices are introduced, with academia also actively involved, so that capacity is

developed for new technologies, and specialists are trained to fill the positions.

· Planning: densification vs. coverage – which is the priority? If the rural electrification rates are still

low, the emphasis will likely not be put on densification but rather on ensuring major cities and

towns are covered. However, this emphasis should be on major grid lines. Later on, network

densification could be introduced to target additional households. The consensus was also to target

economic actors in order to grow economic centers of activity.

· Both grid and off-grid should be provided, but when the areas targeted are more dispersed and

connection rates are low the target should be on off-grid, with grid extensions coming in once

coverage becomes higher and densification becomes the priority.

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Comment:

C. Ratnayake (Consultant Power Engineer): Grid and off-grid should never be put against each other,

but rather used together in a complementary manner to ensure that appropriate levels of service is

provided at appropriate costs. The concept of the ‘Energy Ladder’ where communities with low levels of

consumption are first supplied with dispersed solutions such as solar home systems which is thereafter

improved to mini grid supply systems and finally to full grid connection is a worthwhile concept to be

followed.

14:15hrs. – Plenary session covering overall issues discussed at the workshop:

Question: How are different countries addressing transaction obstacles for service connections?

C. Ratnayake: Service connection issues are compounded in rural areas, where consumer awareness is

low. In order to facilitate the process a mobilization effort of engaging a local community representative

could be an option. The representative could bear the responsibility of collecting all the service

connection applications and having these processed by the utility. This will reduce the space for

malpractices and processing delays; licensed wiremen can also be introduced to the new consumers to

undertake the work on a collective basis to reduce time and costs of carrying out the services.

Jim VC (NRECA): Village electrification committees have been used to take responsibility for securing

connection commitments from locals. As an example, in Bolivia a 25% commitment was required from

consumers before a line could be put in.

Mr. Muganzi Medard (REA, Uganda): What is the correct definition of access? Is it national coverage of

70%, or 25%, is it about the communities that have access, or about the overall numbers, where some

regions remain entirely un-electrified?

Mr. George Nchwali (REA, Tanzania): While the issue of the definition is still formally unresolved in

Tanzania, REA Tanzania’s definition is to differentiate access from number of connections: connections

relate to counting the number of meters installed, whereas access relates to the number of people who

have access to hospitals, schools, mobile phone charging, electrified water pumps and other services

where they are able to have access to electricity and through which they benefit.

Mr. Peter Kinuthia (Senior Energy Officer, EAC): The EAC congregated in August for discussions on this

matter, with ministry, utility and regulator representatives coming together and agreeing on separating

the notions of connectivity and access. Connectivity is defined per household with an actual connection

extended to it, whereas access was defined as to relate to those who have access to grid and mini-grid

electricity –i.e. a given distance from the LV transformer or line to which a person can connect, even if

not yet connected (the distance itself is still being harmonized and agreed on).

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Question: In Kenya the cost of connection within 600 meters is $800 – which translates into $8 million to

connect 1 million people. As it is said by government that these connections should not be subsidized,

how long will it take a utility to recover such an investment?

Samuel Adjidjonu (Electricity Company of Ghana): In Ghana, the government considers rural

electrification to be a social service and bears the cost fully: the transformer and the LV line. Planning is

done for an entire village, and when the network comes to the door the customer only has to pay $2

upfront. Their contribution is to wire their house, with a six-month grace period given to them to enjoy

the facility, after which the full cost of connection cost has to be paid.

Comment (Kenya): KPLC is working with the World Bank to develop longer, 20-year loans to cover the

long-term funding for electrifying villages, with minimal connection costs charged to the customer.

Same cannot be carried out with short-term loans.

Geoffrey Bakkabulindi (PhD Student, Uganda): How does one calculate demand on the ground

(question related to one of the case studies)?

Jim VC (NRECA): GIS is the most useful tool for planning electrification projects, allowing mapping of the

existing systems, with the base map providing housing clusters and other buildings providing likely

customers. GIS allows for the writing of macros that can estimate the demand from the maps. Generally,

the tendency among utilities is to not take sufficient time to carry out proper planning, instead putting

some extra investment in the network to be on the safe side. However, the more thought that is put

into designing the line, the better will be the results in terms of costs and return on investment.

15:15hrs. – Closing Remarks:

· Mr. Niklas Hayek – provided general closing remarks, thanking participants for two interesting

days of discussions.

· Mr. Chrisantha Ratnayake – provided detailed conclusions and takeaways from the workshop

(presentation to be included in the annex).

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Annex 1: Workshop Agenda

DAY 1 – Tuesday, 3 September 2013

08:15 Registration

09:00

Welcome session

· Opening Speech

· Welcome by Organizers

· Definition of the Problem

· Keynote Speech

Ami Mpungwe, Chairman of the Rural Energy Board Ambassador

Jenny Hasselsten, World Bank

Niklas Hayek, EUEI PDF

Chrisantha Ratnayake, Consultant power engineer

Prof. Izael da Silva, Strathmore University

10:00 Tea break

10:15

Presentations - low cost technology options:

· Single Phase Reticulation: Results of NRECA Low Cost

Electrification Study in Tanzania

· Single Wire Earth Return (SWER)

· Shield Wire Systems

· Low Cost HT Grid Extensions

Eng. Gissima Nyamo-Hanga, REA Tanzania

Ralph Karhammar, Consultant

Prof. Francesco Iliceto, University of Rome

Jim VanCouvering, NRECA Foundation

12:15 Lunch

13:15 Plenary discussion on technology options

Moderation:

Chrisantha Ratnayake, Ralph Karhammar

14:15 Breakout sessions:

Analysis of Selected Case Studies

Group 1

Case Study: Ethiopia

Group 2

Case Study: Uganda

Group 3

Case Study: Single/Three phase alternatives

16:15 Wrap-up Day 1

DAY 2 – Wednesday, 4 September 2013

09:00

Presentation – electrification planning:

· Network Planning Issues, Service Connection Costs and

related considerations

Chrisantha Ratnayake

10:15

Breakout sessions:

Continuation of Case Study Analyses: Phase II: Finding Solutions

Group 1

Case Study: Ethiopia

Group 2

Case Study: Uganda

Group 3

Case Study: Single/Three

phase alternatives

Group 4

Case Study: Policy and

Planning aspects

12:15 Lunch

13:15 Presentation of results of case studies Head of each Breakout Group

14:15 General discussion:

· Low Cost Electrification Technologies

· Service Connection Costs

· Comparison of factors affecting participating countries

Moderation:

Chrisantha Ratnayake, Ralph Karhammar

15:15 Closing Session

· Conclusion

· Closing Remarks

Chrisantha Ratnayake

Eng. Bengiel Msofe, REA Tanzania

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Annex 2: List of Participants

Country Name Title Organization

Botswana Mr.Isaac Tlou Rural Electrification Coordinator Botswana Power Corporation (BPC)

Botswana Mr. Steven Peloetletse Project Management Officer,

Rural Electrification

Botswana Power Corporation (BPC)

Ethiopia Ato Frealem Kure Acting Executive Officer,

Universal Electricity Access

Program (UAEP)

Ethiopia Electric Power Corporation

(EEPCO)

Ethiopia Ato Tesfaye Tamirat A.A. Region Sales & Management

Chief of Staff

Ethiopia Electric Power Corporation

(EEPCO)

Gambia Mr. Aziz Jawara Regional Manager, Upper River

Region

National Water and Electricity

Company (NAWEC)

Ghana Mr. Samuel Adjidjonu Divisional Manager/ Rural

Projects

Electricity Company of Ghana

Kenya Eng. Benson Muriithi Chief Manager, Distribution Kenya Power and Lighting Company

(KPLC)

Kenya Mr. Harun Mwangi Manager & Coordinator, Slum

and Rural Electrification Projects

Kenya Power and Lighting Company

(KPLC)

Liberia Mr. Augustus Goanue Executive Director Rural Renewable Energy Agency

(RERA)

Mozambique Mr. Tirso Nhaguilunguana Electrical Engineer Electricidade de Mocambique (EDM)

Mozambique Mr. Oscar Mauai Electrical Engineer Electricidade de Mocambique (EDM)

Nigeria Eng. Joseph Ciroma General Manager, Project

Management Unit

Power Holding Company of Nigeria

PLC

Rwanda Eng. Dieudonne Ngizwenayo Director of Planning and Design,

Electricity Access Roll-Out

Program (EARP)

Energy, Water and Sanitation

Authority (EWSA)

South Africa Mr. Bruce McLaren Senior Technologist Eskom

Tanzania Mr. George Nchwali Director, Finance and

Administration

Rural Electrification Agency (REA)

Tanzania Eng. Bengiel Msofe Director, Technical Services Rural Electrification Agency (REA)

Tanzania Mr. Musa Muze Legal Affairs Manager Rural Electrification Agency (REA)

Tanzania Ms. Grace Mathew Training and Capacity Building

Manager


Tanzania Mr. Seleman Byarugaba Finance Manager Rural Electrification Agency (REA)

Tanzania Ms. Justina Uisso Project Appraisal and Supervision

Manager


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Tanzania Ms. Jaina Msuya Information, Education and

Communication Officer


Tanzania Ms. Theresia Nsanzugwanko Ag. Head of Procurement

Management Unit


Tanzania Mr. Clement Kisinga Procurement Officer Rural Electrification Agency (REA)

Tanzania Mr. Gissima Nyamo-hanga Ag. Technical Assistance Manager Rural Electrification Agency (REA)

Tanzania Ms. Salome Lelly Internal Auditor Rural Electrification Agency (REA)

Tanzania Ms. Ester Mponda Administration Officer Rural Electrification Agency (REA)

Tanzania Ms. Vestina Rwelengera Ag. Monitoring and Evaluation

Manager


Tanzania Ms. Innocensia Makinge Accounts Officer Rural Electrification Agency (REA)

Tanzania Mr. Geoffrey Mwakijungu ICT Officer Rural Electrification Agency (REA)

Tanzania Daniel Mungure Senior Accountant Rural Electrification Agency (REA)

Tanzania Mr. Nicolaus Moshi Ag. Planning and Database

Management Manager


Tanzania Mr. Willa Haonga Legal Affairs Officer Rural Electrification Agency (REA)

Tanzania Mr. Theophil Bwakea Project Identification and

Promotion Officer


Tanzania Mr. Emmanuel Yesaya Project Identification and

Promotion Officer


Tanzania Mr. Advera Mwijage Technical Assistance Officer Rural Electrification Agency (REA)

Tanzania Peter Shayo Planning Engineer TANESCO

Tanzania Mr. Ephraim Cheyo District Manager, Mbozi TANESCO

Tanzania Mr. Seleman Mgwira Engineer TANESCO

Tanzania Mr. Elsam Byempaka

Turyahabwe

Project Development Officer East African Community

Tanzania Mr. Peter Kinuthia Senior Energy Officer East African Community

Tanzania Mr. Fredrik Werring ROYAL NORWEGIAN EMBASSY

Tanzania Mr. Elsam Byempaka

Turyahabwe

Project Development Officer East African Community

Tanzania Mr. Peter Kinuthia Senior Energy Officer East African Community

Tanzania Mr. Happy Ndunguru Rural Electrification Agency (REA)

Tanzania Mr. Emilian Nyanda Ministry of Energy and Minerals

Tanzania Mr. Bernd Multhaup Programme Manager GIZ Tanzania

Tanzania Ms. Lydia Mugarula TPCC

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Uganda Mr. Godfrey Werikhe Manager, Project Development &

Management


Uganda Mr. Muganzi Medard Manager, ERT Programme Rural Electrification Agency (REA)

Uganda Mr. John Turyagenda Senior Projects Engineer

(Construction)


Uganda Ms. Flavia Uwayezu Senior Projects Engineer

(Planning)


Uganda Mr. Joseph Nyanzi Kubo Engineer Power Networks Ltd.

Uganda Mr. Geoffrey Bakkabulindi PhD Candidate, Department of

Electrical and Computer

Engineering

Makerere University

Uganda Mr. Benon Bena Investment Planning and

Promotion


Zambia Mr. Nason Musonda Power Distribution Development

Officer

Rural Electrification Authority

Zambia Mr. Suzyo Silavwe Provincial Rural Electrification

Officer

Rural Electrification Authority

Speakers

Tanzania Hon. Ami Mpungwe Chairman Rural Energy Board Ambassador

Tanzania Mr. George Nchwali Acting Director General Rural Electrification Agency (REA)

Tanzania Eng. Gissima Nyamo-Hanga Ag. Technical Assistance Manager Rural Electrification Agency (REA)

Tanzania

Kenya Prof. Izael da Silva Deputy Vice-Chancellor Strathmore University

Sri Lanka Mr. Chrisantha Ratnayake Consultant Power Engineer

Australia Mr. Ralph Karhammar Consultant Power Engineer

USA Mr. James VanCoevering Senior Utility Specialist National Rural Electric Cooperative

Association (NRECA)

Italy Prof. Francesco Iliceto Emeritus Professor Rome University La Sapienza

Tanzania Eng. Bengiel Msofe Director, Technical Services Rural Electrification Agency (REA)

Team

Jenny Hasselsten Operations Officer World Bank

Tatia Lemondzhava Consultant Energy Analyst World Bank

Niklas Hayek Junior Project Manager EUEI PDF

Blaga Zlateva Intern GIZ Tanzania

Gidibo Tindwa Events and PR Coordinator GIZ Tanzania

16

Annex 3: Presentations and case studies

Niklas Hayek – EUEI PDF

Chrisantha Ratnayake - Definition of the Problem

Prof. Izael da Silva - Keynote Speech

Eng. Gissima Nyamo-Hanga – Results of NRECA Low Cost Electrification Study in Tanzania

Ralph Karhammar / Conrad Holland - Single Wire Earth Return (SWER)

Prof. Francesco Iliceto - Shield Wire Systems

Jim VanCoevering - Low Cost Distribution Technologies

Jim VanCoevering – Low Cost Transmission Approaches

Chrisantha Ratnayake - Volt drop and loss

Chrisantha Ratnayake – Rural Electrification Planning

Bruce McLaren – Group 1 Assessment

Case Study - Distribution System Study of MV networks

Chrisantha Ratnanyke - Volt drop calculations & Distribution Factors

AEI - Workshop conclusions

EU Energy Initiative Partnership Dialogue Facility

1

What we do

� Policy, Strategy and Regulation

development

� Institutional Building and

Strengthening

� Capacity Building

� Knowledge Sharing: Dialogue

events and thematic studies

How we work

� We coordinate with

governments and regional

organizations

� We cooperate with ESMAP,

the AEI, REN21, IRENA, etc.

� We procure international and

local technical expertise

Who we are

� An instrument developed and funded by six EU member states and the

European Commission in the context of the EU Energy Initiative (EUEI).

� We aim to develop policies and strategies that contribute to improved

access to affordable and sustainable energy services.

2

Country Projects

Tanzania:

Biomass Energy

Strategy (BEST)

Country Projects

Tanzania:

Biomass Energy

Strategy (BEST)

Regional Projects

SADC/RERA:

Mini-Grids Regulation

Regional Projects

SADC/RERA:

Mini-Grids Regulation

Dialogue Events

Uganda:

Energy Stakeholder

Dialogue

Dialogue Events

Uganda:

Energy Stakeholder

Dialogue

Thematic Studies

PRODUSE:

Productive Use of

Energy Manual

Thematic Studies

PRODUSE:

Productive Use of

Energy Manual

Project Examples

log

AEI Workshop on


Agenda for 3 September

09:00 Welcome Session

Tea break

10:15 Presentations - low cost technology options

12:15 Lunch

13:30 Plenary discussion on technology options

Tea break

14:15 Breakout session: Analysis of selected case studies

16:30 End of day 1


Workshop

Arusha, 3-4 September, 2013

Definition of the Problem

Chris Ratnayake

Consultant Power Engineer

Electricity Access

� World: 1.3 billion people without access

� Rural SSA: 465 million people

� 85% unserved (urban + rural)

� lowest electrification rates in the world

Source: �World Energy Outlook 2011�

International Energy Agency

SSA - Sub Saharan Africa

Expenditure and Impact

� $275 billion expected expenditures from 2010

to 2030 in all countries (�New Policies

Scenario�)

� Unserved in SSA will increase: to 538 million

� Population growth outpaces electrification

� Other regions: unserved population is greatly

diminished

Issues

� Sparse populations

� Remoteness from existing power facilities

� High cost solutions (developed for urban

areas)

� Explore all available avenues of reducing

high investment costs

An issue of the highest priority

� UN declaration: 2012 �International year

of Sustainable Energy for all�

� SSA governments keen: rural

electrification has highest priority

� Substantial funds allocated by National

Budgets and International Financing

Organizations

Our Responsibilities

� As practitioners and financiers

� As persons entrusted with providing rural

access

� High cost and inappropriate solutions not

acceptable

Reasons for current status

� Replication of standards developed for urban

systems

� Load densities vastly different

� Poor availability of planning tools

� Transmission planning well established

� Distribution planning given scant respect

� Poor data availability and documentation

The way forward

� Understand all available technologies

� Develop good planning capabilities

� Improve data base

� Characteristics of existing rural loads

� Data on unserved areas

� Load growth rates

� GIS based information

Our Goal

� Ensure each Dollar on RE is spent as efficiently

as possible

� Ensure long term sustainability and long term

cost reductions

� Systems built for existing loads

� With allowance for later improvements

� Search for �Appropriate Solutions�

Objectives of the Workshop

� Greater awareness of available techniques

� Provide planning tools, guidelines

� Facilitate practical applications

� Create a forum of exchange of views

� Today

� In the future; forum under Africa Electrification

initiative�

Scope of Workshop

� Provide a greater understanding of solutions

to MV and LV rural distribution

� Service connection costs

� Resolving problems related to poor

connectivity of completed schemes

� Addressing low cost solutions for HT

development

� Scope: entire range from HT to households

Workshop agenda

� Presentations from experts

� Case studies

� You will find solutions to the problems

� Understand application of simple techniques

� Interaction among participants

� South-South interaction

� Learn from success stories and avoid failures

� We hope that we will all leave Arusha a little more wiser than when we came in!

Thank You

and

Good luck with the discussions!

�Africa is indeed coming into fashion.�

Horace Walpole, 1774

Africa Electrification Initiative Practitioner Workshop � Arusha 3-4 September 2013

Keynote Address

The True Size of Africa Fertility rate per woman

Nigeria 2011 Fertility rate = 5.7

Population 2011 = 166 million

Projected 2050 = 402 million Source: US Census Bureau 2011

Nigeria2011 Fertility rate = 5.7


Projected 2050 = 402 millionSource: US Census Bureau 2011

Ethiopia 2011 Fertility rate = 6.0



Ethiopia2011 Fertility rate = 6.0



DRC 2005 Fertility rate = 6.1



DRC2005 Fertility rate = 6.1



2010

Growth

Rates

Growth

Rates

Who

is

helping

Africa?

The West focus since the 1950s

� Humanitarian disaster relief

� Occasional self-interested military intervention

� Help Africa to grow enough food for its needs

� Slash population growth

� Seek medical solutions for communicable diseases � Seek medical solutions for communicable diseases

China focus since the 2000s � Promote economic growth

� Act as peace broker

� Make massive investments in infrastructure

� Provide large-scale technical training

� Promote expansion of trade pa

Required investment for SE4All

Ole Sangale Road, Madaraka Estate. PO Box 59857-00200, Nairobi, Kenya

Tel: (+254) (0)703 034000/200/300 Fax : +254 (0)20 607498

Email: [email protected] Website: www.strathmore.edu

Africa Electrification Initiative (AEI) � Low Cost

Workshop

3rd � 4th September, 2013

SnowCrest Hotel � Arusha TANZANIA

Presenter:

Eng. Gissima Nyamo-Hanga

Technical Assistance Manager

Rural Energy Agency

P.O. BOX 7990 Dar es Salaam TANZANIA

Tel: +255 22 241 2001 -3

Fax: +255 22 241 2007

E-mail: [email protected]

Website: www.rea.go.tz

Topic: Results of the NRECA Low Cost Electrification

Study in Tanzania

Presentation Outline

� Objectives

� Project Components

� Rationale

� Cost Comparisons

� Features of TANESCO Standard Designs

� Features of Alternative Designs and Results

� Contracting Mechanisms

� Low Cost Consideration for Industrial Consumers

� Financing and Affordability Analysis

Project Components

� Task 1: New Standards and Design

� Task 2: Effective Procurement

� Task 3: Financing Schemes

Objectives of the Low Cost Project

� Design of a low cost electrification model

� Design, standards, construction

� Procurement mechanisms to reduce cost

� Financing schemes to increase connection rates

� Demonstration of Low Cost Model through

preparation of Pilot Projects

� Specific project design- originally 15 projects in 12

regions with about 12,000 total consumers

� Preparation of bid documents for materials and

construction

� Sustainability � capacity building

� Participation by PIU: MEM, REA, TANESCO and EWURA.

Rationale

� Drive: � Cost of construction of distribution facilities were

perceived to be high;

� Methodology: � Comparison with costs of similar facilities in Kenya,

Uganda, South Africa and Bolivia;

� Evaluation of construction designs and material

selection.

� Cost drivers: � Contracting mechanism employed

� Design and configuration of facilities

Cost Comparisons: TANESCO and Turnkey

Phase 1 of REA

Installed Cost per Unit

Construction Type Unit TANESCO Turnkey

33 kV 3 Phase Line (100 mmsq ACSR) Km. $26,104 $20,680

50 kVA Transformer Ea. $10,791 $8,879



400 LV Line (100mmsq Al) Km. $21,536 $21,261

Service Drop Single Phase-30m Ea. $515 $369

Service Drop Three Phase-30m Ea. $983 $621

Cost Comparisons: TANESCO with Uganda and Kenya

Cost Comparison Tanzania, Uganda, and Kenya

Construction Type Unit TANESCO Uganda Kenya

33 kV 3 Ph (100 mmsq ACSR) Km. $26,104 $13,085 $18,941

50 kVA Transformer Ea. $10,791 $5,439 $9,518



400 LV Line (100mmsq Al) Km. $21,536 $11,165 $16,802


Service Drop Three Phase-30m Ea. $983

Cost Comparisons: Other Southern African

Countries Comparison Costs for Southern Africa

Construction Type Unit South

Africa Zambia Mozambique

33 kV 3 Ph (100 mmsq ACSR) Km. 32,500 29,102 30,000

50 kVA Transformer Ea. 10,489

100 kVA Transformer Ea. 18,000 14,519


SWER Line Km. 13,929

400 LV Line (100mmsq Al) Km. 25,000 19,552

Service Drop Single Phase-30m Ea.

Service Drop Three Phase-30m Ea. 800

Cost Comparisons: Other Developing Countries

Installed Costs of Distribution Lines in Other Developing Countries

Construction Type Unit Dominican

Republic Bolivia Bangladesh

33kV 3 ph (100mmsq) km. $18,912 $16,200

33kV 3 ph (50mmsq) km. $14,998 $9,600

10kVA Transformer Ea. $929 $670 $665



400 LV Line 3 phase Km. $5,800 $7,800

230 LV Line 1 phase Km. $5,100 $4,700

Service Drop Single Phase-30m Ea. $123 $148 $60


Observations Regarding Cost Comparisons

� TANESCO internal costs are higher than neighboring countries, especially Uganda

� Introduction of turnkey contracting has reduced cost difference but more fundamental changes are required

� TANESCO costs are lower than those of Southern African countries

� Comparison with countries outside the region highlights opportunities for cost reduction

� Configuration

� LT line and transformer cost

� Service drop cost

TANESCO Standard Design and Configurations

� 33 KV construction costs: � Basic design;

� Selection of materials: poles, conductors, transformers, etc.;

� Major cost contributor compared with contracting

mechanisms.

� Transformer and LV Systems Cost: � Basic configuration of transformers;

� Use of H � frame platforms;

� Small single phase transformers not used (10/15/22/37.5

KVA);

� Use of large oversize conductors for LV systems, sometimes

up to 100 mm2;

� Use of three phase four line in areas where majority of

customers are single phase.

TANESCO Standard Design and Configurations contd�

� Service Drop Cost and Method of Collection:

� Conductor size is large, sometimes up to 50 mm²;

� Configuration of the service drop is complex with

many hardware items;

� Full pay for service drop is constructed;

� Suppresses willingness of consumers to purchase..

Alternative Configurations

� Evaluated on the density or population basis;

� service areas on which to test configurations:

� Semi-urban, moderate density large villages organized

into streets.

� Villages organized along identifiable streets

� Low Density Villages with non-organized and scattered

consumers.

� Construction tests evaluated using load flow

models:

� Determining voltage and loss performance

Alternative Case Study Configurations

� Case A: Base Case - TANESCO standard:

� Both 33KV main lines and laterals use 100mm² conductors;

� 100 and 200KVA Transformers on main or lateral lines;

� LV lines: open wire constructions with 100mm² conductors

� Case B: Modified TANESCO standard:

� Three phase three wire 33KV using cross-arm structures on

and 100mm² conductors on main lines;

� Three phase laterals with 50mm² conductors;

� 25KVA Transformers on laterals and main lines;

� Limit length of LV lines/circuits to consumers to 300 metres

from the Transformer

Alternative Case Study Configurations contd�

� Case C: 33KV 2-phase laterals and 1-phase transformers:

� 3 phase 3 wire multi-grounded 33KV lines

� 100mm² conductors on main lines and 25mm2 on laterals;

� 15/25/37.5KVA transformers, 25mm² covered triplex

conductors, customers up to 200 metres away .

� Case D: 19KV Phase to neutral laterals and single phase

transformers:

� 3 phase 4 wire multi-grounded 33KV lines and cross-arms;

� 100mm² conductors on main lines;

� Neutral conductor extended to the sub-station;

� 19KV single phase laterals and neutral lines of 25mm²;

� Use of 10/15KVA single phase transformers.

Alternative Case Study Configurations contd�

� Case E: 19KV Single Wire Earth Return (SWER) Laterals:

� 3 phase 3 wire multi-grounded 33KV lines and cross-arms;

� 100mm² conductors on main lines;

� Neutral conductor extended to the sub-station;

� 19KV single phase SWER laterals of 25mm²;

� Fed from 33/19KV 50/100KVA isolating transformers

connected phase to phase on the 33KV side;

� Use of 10/15KVA single phase transformers.

Summary of Performance Results of Alternative

Cost Studies

Cost %Cost

$/ConsumerCost %

Cost

$/Consumer

TANESCO Standard Design 100% $532 100% $2,727

Case B Modified TANESCO 86% $461 72% $1,976

Case C: 33kV Two Phase HT 74% $396 37% $1,022

Case D: 19kV Single Phase HT 72% $382 44% $1,196

Case E: 19kV SWER

w/isolation transformers79% $421 31% $844

Case E2: 19kV SWER w/o

isolation transformers68% $361 28% $773

Summary of Results of Configuration Comparisons

Moderate Density Sytstem

Alternative Approaches

Low Density System

Rationale for Selection of Two Phase HT as a Low

Cost Technology

� NRECA recommended two- phase HT as the preferred low cost option for Tanzania for the following reasons:

� While SWER is cheaper than the TANESCO standard HT construction for low density projects, two phase service achieves most of the cost benefits over SWER.

� For moderate density applications there is almost no difference in cost between two phase and SWER, and SWER presents some challenges in execution.

� For a given voltage drop criteria, two phase has 50% more capacity than SWER

� Two phase service can supply three phase service to consumers using standard equipment.

Contracting Mechanisms

� TANESCO implementation mechanism: � Conventional method

� Turnkey project implementation mechanism: � Adopted by REA in Turnkey Phases 1 & 2

� Reduces cost by 20% compared to conventional

mechanism;

� Bulk procurement implementation mechanism: � Bulky purchase of line materials (economies of scale);

� Contracting labour component;

� To be tested by REA in Kilombero and Mbozi pilot areas;

� Challenge is warehousing and material control.

3. Bulk Procurement Implementation Mechanism

� REA large scale procurement with supply of

materials to contractor ;

� Procurement through bonded agents who

maintain warehouses:

� Receive and issue materials.

� Procurement through suppliers who are

responsible for holding materials and issuing

them to REA projects;

� Example of Bulky Purchase: � Turnkey projects which are of the tune of US$2.2 million to

US$8.8 million and are designed on regional basis(one

location).

Consideration of Technical Approach for Industrial

Consumers

� For Low Cost electrification approach:

§ Supply of three phase power to small industries is a big challenge here in Tanzania;

§ This has apparently been an obstacle to the use of single phase lines in the past.

§ The market in Tanzania is for 3 phase 400 volt motors:

vRural electrification is not going to change this fact;

§ Consumers resist single phase motors due to shortage in the market and concerns about their reliability;

§ Some efforts to construct single phase projects in the past have been converted back to three phase.

Technical Approach for Industrial Consumers

� Proposed solutions to power small industries from a single phase source.

� For motors of 5HP or less: Cost difference between single and three phase service drop means that 5HP single phase motors are reasonable

� Phase converters: to convert single phase power to quasi-three phase service to power a standard 400 volt three phase motor

� Open wye-Open delta Transformer Connection: The single phase laterals proposed for the Kilombero and Mbozi projects consist of two phase wires of the 33kV system. It is therefore possible to create a three phase connection using the earth return for a neutral and an open wye-open delta transformer connection.

Phase Converter

Schematic of Phase Converter Features

� Requires 400 volt input, so

different transformer

� Pilot motor capacity 125% of mill

motor

� Active switches and capacitors to

control voltage

� Requires 400 volt single phase

meter

� Lights via 400/230 volt lighting

transformer

Open Wye-Open Delta Transformer

Features

� Two transformers

19kV/400 volts

� Earth return neutral

� Produces 400 volt three

phase service

� Standard meter (though

w/o neutral)

� Also requires 400/230 volt

lighting transformer

LV Multiplex Low Cost Service Drop

� Low Cost High Security Service � 10mm2 Airdac

conductor

� Prepayment meter with measuring unit on pole

� Customer interface unit in residence

� 50Amp service capacity

� $US200 est. cost w prepayment meter

� Service is earthed for safety

Affordability Analysis & Options for Making

Rural HH Connections More Affordable

Analysis address @ How much can rural households afford to pay for electricity service and

the current cost of connection to the grid?

@ What are the options for a program to finance the costs of household

connections to make them more affordable?

Method for Analysis @ Household income survey in Kilombero area

@ Random sample of households identified in GIS survey

@ Analysis of ability to pay for electricity and associated costs based on

current expenditure for energy

Affordability of Electric Connection

Income

Quintile

Energy

ExpenitureCorrection WTP

Electric

Consumption

kWH

Total

Electric

Bill USD

Monthly

Savings

Q1 $6.13 80% $4.90 25 $1.17 $3.73

Q2 $6.59 80% $5.27 25 $1.17 $4.10

Q3 $8.15 80% $6.52 30 $1.41 $5.11

Q4 $11.10 120% $13.32 60 $9.12 $4.20

Q5 $16.66 135% $22.49 120 $16.47 $6.02

Affordability Analysis and Strategies

The primary obstacles to connection in rural

areas served by the national grid are: @ The high cost of connection, relative to disposable income

@ Cost of internal house wiring

@ The requirement by TANESCO, that potential customers pay the full cost of

the service connection up front

Recommended Strategies for increasing

connections @ Use of ready boards for lowest income consumers

@ Cost reduction of service drops to 50% of current level or less

@ Deferred payment scheme for recovery of connection costs and long term

loans for house wiring.

Thank You for Your Attention!

SWER for Remote Rural Distribution

Examining Costs and Fault Protection

Conrad W. Holland, SMEC New Zealand Ltd.

September 2013

Abstract

� Single Wire Earth Return (SWER) has been used in New Zealand since the 1930s and is still actively used in rural New Zealand, Australia, South Africa and parts of South East Asia.

� We update the cost structure for SWER and look at modern innovations that can be applied to:

� Drive down costs and

� Improve reliability

SWER � What is it ?

� SWER is Single Wire Earth Return power distribution. Instead of using 2 or 3 wires to distribute electricity SWER uses one wire with the return path through the ground. This is cheaper and easier to build and maintain, but has capacity and other limitations.

SWER in New Zealand

� The early work on SWER in New Zealand was carried out by Loyd Mandeno, who for a time held the SWER patent in Australia and New Zealand.

� Mandeno�s paper �Rural Power Supply, Especially in Back Country Areas� is the classic reference for the technology and established New Zealand as a SWER pioneer.

� Since the publication of Mandeno�s paper in 1947 things have moved on and we will examine the relevance of SWER today and explore the enhancements carried out in the intervening years

The Decline of SWER in New Zealand

� In New Zealand SWER is not as prevalent as it once was; the reasons for this include:

� Limitation of the maximum earth current to 8 Amps by NZECP 41:1993

� Better access to power in rural areas

� Higher household after-diversity maximum demands (2-5kW per house)

� Higher load densities which mean that two-wire-single phase or three-wire three-phase distribution is more suitable

� Higher quality of supply expectations

� Demand for three-phase supply for large motors

� The technology is still however valuable in remote areas where population density is low or where the demand per household is low and is less expensive than two-wire or three-wire reticulation.

The Rise of SWER in Australia

STATE Conventional 22 kV

single and three

phase

Conventional 11 kV

and below single

and three phase

SWER, at 19.1 kV

or 12.7 kV

circuit kilometres circuit kilometres circuit kilometres

NEW SOUTH

WALES & ACT

30,596 108,794 30,075

VICTORIA 59,304 1,597 28,274

QUEENSLAND 0 61,610 64,375

SOUTH

AUSTRALIA

0 15,720 31,382

WESTERN

AUSTRALIA[1]

14,555 1,750 41,253

TASMANIA 11,253 2,999 614

NORTHERN

TERRITORY

Under 11 kV 2,989 12

TOTAL 115,708 195,459 195,985[2]

[2] This compares with a total system length for conventional distribution at all voltages in New Zealand of 111,841 overhead circuit kilometres, www.comcom.govt.nz.

SWER World Wide � South Africa

� South African Initiatives

� Micro SWER

� The South African concept of micro SWER allows SWER extensions without isolating transformers for loads under 5 kVA. This type of supply is principally aimed at supplying remote mobile phone repeater sites

� Formalising The Design Process

� The design and installation of SWER has been formalised through the ESKOM distribution standard for MV reticulation by 19 kV single-wire earth return.

SWER World Wide � South Africa II

� South African Initiatives

� Eskom Distribution Guide 34-618: Part 1, Network Planning Guideline for Voltage Technology and Phasing, January 2011

� Eskom Distribution Guide 34-453 Part 4: Section 4: Particular requirements for 19kV Single Wire Earth Return (SWER) overhead reticulation, December 2007

� Eskom SWER drawing standards D-DT-0400 Series and associated assembly, earthing and transformer drawings, noting that these are predominately wood pole construction

SWER Technology Development

� When looked at in isolation, SWER as a technology has barely moved since Mandeno published his first paper in 1947.

� If we look more closely, we can see the technology has improved significantly and is well suited to modern grid connected distribution for remote customers with low loads.

� Insulators

� Vibration Damage

� Conductors

� Voltage Regulation

� System Modelling

� Remote Control and Scada

� Protection and Switchgear


� Insulators - Pin insulators were once widely used throughout the industry. There are now other options such as a) post insulators or pin post insulators for in-line and small angle structures; and b) polymer insulators for strain structures.

� Vibration Damage - To get the maximum reduction in costs, SWER construction uses long spans. These spans can be up to 300 metres on 12 metre poles over level ground. To achieve these long spans, the conductor is strung with everyday tension of greater than 18%, which can accelerate vibration damage to the conductor.


� Conductors - Where previously Nº 8 galvanised fence wire was a common choice for SWER conductor, there are now families of conductor that are more suitable, e.g. stranded galvanised steel conductor to AS1222.1 and aluminium-clad steel conductor to AS1222.2

� Voltage Regulation - SWER systems have inherently poor regulation due to the Ferranti effect coupled with long line lengths. Poor regulation for SWER systems has been further aggravated by increase in load over time. Intelligent voltage regulators are available which also offer an improved load drop compensation setting range


� System Modelling � At the design stage, accurate computer based load flow studies can be carried out :

� shunt reactors and voltage regulators

� Increasing the SWER voltage

� Reconductoring

� Load balancing

� Converting the initial section of the feeder to two-wire single-phase or three-phase configurations

� Splitting feeders

� Calculating peak losses and energy losses

� Calculating theoretical reliability of supply

� Motor starting studies


� System Remote Control and SCADA - In general SWER systems are very robust as there is no possibility of clashing, there are fewer poles and less line hardware than for two-wire reticulation. When faults occur, line patrols have to traverse large lengths to isolate sections and then identify and repair faults. This method of fault restoration can take many hours depending on the location of the fault. System remote control and SCADA can be conveniently located at auto-reclosers and regulators to minimise the fault outage duration, and remotely collect demand data for system planning purposes.


� Protection and Switchgear - With SWER, there is always a residual current flowing through the earth, between the distribution transformer and the isolating transformer. Sensitive earth fault protection is therefore difficult to apply down-stream of the isolating transformer There are presently three systems that can be used or are under development to detect faults that do not produce enough fault current to be detectable by conventional over current relays or fuses:

� High impedance fault analysis

� Open conductor detection

� Signature based detection

Directly Earthed SWER

� One of the principle issues for direct SWER is earth (ground) fault protection or high impedance earth fault protection. How do you differentiate between an earth (ground) fault and the normal SWER earth (ground) return current?

� CIGRE WG B5.94 High Impedance Faults, 2009 definition �A high impedance ground fault results when a primary conductor makes unwanted electrical contact with a road surface, sidewalk, sod, tree limb, or with other surface, or object which restricts the flow of fault current to a level below that reliably detectable by conventional overcurrent devices�

� In parts of the world such as the USA and Australia, owing to the particular characteristics of the distribution system with single phase loads, the tripping level of the conventional ground over-current relays has to be adjusted to values that are above the neutral imbalance on the grid. Consequently, a significant percentage of ground faults cannot be detected.

.

Directly Earthed SWER II

� Paraphrasing ESKOM DST 34-453, page 85

� The 33kV networks to which SWER can be directly connected must be sourced from a substation with an NEC (delta secondary) or a star secondary with a directly connected earth

� The earth electrode carries continuous current and should be specifically designed for the application.

� There should not be Sensitive Earth Fault (SEF) protection. The protection should be overcurrent earth fault protection on isolation transformer feeders and overcurrent and arc detection on direct connected SWER feeders.

� The LV supply is the same as that for conventional MV supplies. Three-phase LV supplies are only available by using the conversion technology which is commercially available at present.

� Single-phase and dual-phase motors have been developed as will and can be used.

� The SWER load current on a specific network must not exceed 25A because of the effect which this load current has on nearby telecommunications networks


� Motor Starting - Voltage depression during motor starting is an issue for SWER and conventional distribution systems. In Maunsell�s work on rural electrification in developing countries, inability to run large motors is the major objection to installing SWER in preference to three-phase networks.

� Small motors � conventional 230 volt induction motors can be used in ratings of up to 5 horsepower on SWER Systems

� 10 to 15 horsepower motors � specialty single phase motors and electronic starters, connected 460 V for use with 230-0-230 V distribution transformers

SWER Cost Structure

� The following table updates the cost structure for SWER so that indicative costs may be derived when carrying out economic and financial analysis of proposed SWER installations.

� The costs were based on 2003 costs for SWER materials and equipment purchased in Lao P.D.R using the international competitive bidding procedures of the World Bank.

� A breakdown of these costs is as follows, a spreadsheet is also available. The cost of distribution materials e.g. poles, insulators, conductor and distribution transformers will be greater in most African countries

SWER Cost Structure � Budget Costs

Construction Unit Unit Price Unit Price

USD NZD[1]

12.7 kV, 1-phase SWER

Overhead Line

Circuit

kilometre 3,067 5,590

12.7/0.46/0.23 kV, SWER

Distribution Transformer, 16 kVA

Each 1,925 3,509

12.7/0.46/0.23 kV, SWER

Distribution Transformer, 25 kVA

Each 2,184 3,981

22/12.7/0.23 kV, SWER, 2 Pole,

Isolating Transformer, 160 kVA

Each 4,314 7,864

[1] Converted from United States Dollars at the exchange rate on 17 March 2003, USD/NZD, 0.5486

Conclusions

� SWER has developed considerably since its inception. Modern materials, equipment and planning methods can be used to enhance new installations, and extend the life of existing installations.

� In the context of rural electrification for developing countries, SWER is still an ideal technology to employ in the initial stages of electrification. The important issue is to plan the network with an upgrade path from SWER to two-wire and then three-wire three-phase distribution.

� Direct SWER or SWER without the use of isolating transformers is possible in certain situations. The Brazilian experience may be worth further study in this regard

SWER Examples

ESKOM DST 34-453

One example worthy of mention is regarding the supplies to rural clinics. The customer applied for standard 50 kVA, three- phase supplies. ESKOM approached the customer to establish whether a three- phase supply was required at the clinics. The only possible use was for the pumping requirements. It was established through consultation with the pump suppliers that the pumping requirements could be satisfied using single-phase pump motors. This opened the way for Eskom to quote for the clinic supplies using single-phase technologies such as MV two- phase and SWER. The bottom line was that because of the savings a further 25 clinics could be connected with the budget available to the customer.

SWER Examples

a 10 km supply line to supply a 22 kW pump motor and a 25 kVA 3 phase

requirement the options could look like this:

It is clear that Single phase MV and SWER are worthwhile for the customer. Besides the customer benefit the benefit to the Utility is in the reduction in the number of poles and hardware. It can be noted that a supply line of at least 2 Km is needed for the cost of a 50kVA isolation transformer with fuse protection to be discounted by the savings in line costs. Therefore a rule of thumb could be to only use SWER if the ultimate line length is greater than 2 km.

Three Phase Two Phase SWER

(ZAR) (ZAR) (ZAR)

MV line cost 530,000 357,750 223,359

Isolation transformer + recloser cost 0 0 42,000

Customer transformer cost 12,000 12,000 25,000

Extra cost for 1 phase motors 0 8,000 8,000

Total 542,000 377,750 298,359

Savings compared to 3 phase 0 164,250 243,641

Cost as a percent of the 3 phase cost 100% 70% 55%

SWER Bibliography

� www.ruralpower.org frequently asked questions on SWER (faq)

� Eskom Distribution Guide 34-618: Part 1, Network Planning Guideline for Voltage Technology and Phasing, January 2011

� Eskom Distribution Guide 34-453 Part 4: Section 4: Particular requirements for 19kV Single Wire Earth Return (SWER) overhead reticulation, December 2007

� Eskom SWER drawing standards D-DT-0400 Series and associated assembly, earthing and transformer drawings, noting that these are predominately wood pole construction

� http://www.powerwater.com.au/networks_and_infrastructure/standard_drawings Power and Water, steel pole SWER standard drawings

� http://www.ergon.com.au/__data/assets/pdf_file/0019/61282/OH_Manual_SWER_CONSTRUCTION.pdf Ergon Energy SWER standard drawings

� http://www.redenergia.com/media/209172/ntd-16.pdf Brazilian SWER standards in Portuguese

Questions

[email protected]

RURAL ELECTRIFICATION WITH

THE SHIELD WIRE SCHEME

APPLICATIONS IN DEVELOPING

COUNTRIES

by F. ILICETO Emeritus Professor

University of Rome �La Sapienza� Rome, Italy

[email protected]

AEI � AFRICA ELECTRIFICATION INITIATIVE

WORKSHOP IN ARUSHA (TANZANIA), SEPTEMBER 2013

1

� Low cost power supply from the interconnected grid to villages, small towns, farms, factories, water pumping stations located near or at some distance from the route of the HV lines (110-330kV)

� The SWS is applicable for rural electrification along the route of the HV lines, which is not economically justifiable with the conventional solutions (MV lines routed along the HV lines and supplied by HV/MV transformers stations).

1. AIM OF SHIELD WIRE SCHEME (SWS)

AEI � AFRICA ELECTRIFICATION INITIATIVE WORKSHOP IN ARUSHA (TANZANIA), SEPTEMBER 2013

2


� The SWSs consist of:

- Insulating for MV operation (20-34.5kV) the shield wire(s)

from the towers of the HV line

- Energising the shield wire(s) at MV from the HV/MV

transformer station at one end of the HV line

- Using the earth return of current

- Supplying loads by means of distribution transformers

branched between the shield wire(s) and the ground.

� The most used SWSs are shown in Figs. 1/A - 1/B.

� If the HV line is protected by one shield wire, only the Single-Phase Earth-Return SWS can be realised (Fig. 1/A).

3

2. CONCEPT OF SWSs � If the HV/MV transformer station of origin of the SWL has a

MV winding with the neutral solidly grounded as shown in Fig. 1/A, the SWL can be directly supplied from one terminal of the MV winding. This scheme is also applicable if the neutral is grounded via a grounding transformer of low homopolar reactance of via a reactor of low impedance, If neutral is high-impedance grounded or has a rated voltage unsuitable for the long SWLs (too low), the SWL is supplied via an interposing transformer.

� If the HV line is protected by 2 shield wires, by using the earth return as the 3rd phase conductor, a 3-phase MV line is realised (Fig. 1/B)


4

Fig.1/A - �Single-phase Earth-return� SWS applicable to HV

lines provided with one shield wire 5

Fig.1/B - �3-Phase� SWS applicable to HV lines provided with

two shield wires 6


� Scheme of Fig. 1/B shows how the 3-Phase SWS is balanced in the simplest manner, with a grounding resistor-reactor (R-L circuit) and with unsymmetrical power factor correction capacitors.

The voltage drop in the R-L circuit adds to the low resistive voltage drop of the earth return circuit (ohmic resistance of earth path is a function of frequency and is only 0.05 ohm/km at 50Hz). The total voltage drop is made about equal to the drop in the shield wires.

The unsymmetrical capacitors (Cw1-0, Cw2-0, Cw1-w2) cancel out the voltage dyssimmetries along the SWL, which are caused by the unsymmetrical induced voltages and leakage capacitive currents from the HV circuit. Capacitors also eliminate the risk of ferroresonance overvolages.

7


� The 3-Phase SWL can be supplied by a dedicated tertiary winding of the HV/MV transformer, as shown in Fig. 1/B. If a dedicated tertiary winding is not available, a MV/MV interposing transformer is used.

� In Sub-Saharan Africa most of power distribution utilities give preference to the 3-Phase SWS. The main objection to the 1-Phase SWS is the difficulty of procurement of single-phase motors that are required with rated power up to ~ 25kW.

� Fig. 2 shows the typical circuit schematic of a �3 Phase� SWS in the villages and the independent multiple earthing system applied for achieving the low ground resistance required for the earth return of current and for safety of people.

� In the HV/MV substations supplying the SWS, the station ground mat is used for earth return of current. 8

Fig. 2 � Circuit schematic of �3-Phase� SWS distribution in the villages,

showing independent earthing of MV and LV networks 9

� The insulation of shield wires with suspension insulators provided with arcing horns, does not change the lightning performance (flashover rate) of the HV line, as shown by the analysis and confirmed by many years of operation experience.

Fig. 3 shows the toughened glass rigid insulator strings usually applied for insulation of the shield wires.

� The voltage imbalance at the supply points of all the consumers of �3-Phase� SWSs (Fig.1-B) and at the busbars supplying the Single-Phase Earth-Return SWSs (Fig. 1/A) is limited to a very small value (negative-sequence voltage £1%).

3. MAIN FEATURES OF SWSs


10

Fig. 3 � Typical rigid toughened glass insulator string for 34.5 kV

�3-Phase� and �Single-Phase Earth-Return� SWLs 11

Dimensions are in mm

� Wet 50 Hz � 60 s withstand voltage 130kV rms +)

� Dry 1.2/50 ms impulse withstand voltage 270kV peak +)

� Creepage distance 1200 mm

� Electromechanical failing load ³50 kN

+) without arcing horns

� In the new HV lines, the SWSs use aluminium conductor steel reinforced (ACSR) shield wires, with cross section of 70¸125 sqmm. A suitable cable has 19 wires of same diameter (7 galvanized steel wires and 12 aluminium wires) with 63% of aluminium in the cross-section.

Some SWSs have been implemented in existing HV lines, by insulating their already installed steel or alumoweld shield wire(s).

� The reach of SWSs with rated voltage of 34,5kV is up to and also over 100 km.

� The �3-Phase� SWSs have about the same loading capability of a normal MV overhead line of same length, with the same phase-to-phase rated MV and conductors of same ohmic resistance. Loading capability is some MW at 34,5kV. Typical loading capabilities are shown in Fig. 4.


12

+) load p.f. on LV side of MV/LV transformers; �� Distributed load; � � � Concentrated load

Fig. 4 � Loading capability versus length of �3-Phase� SWLs operated at 34.5kV: a.1�a.2: ACSR, S=125.1 sqmm shield wires on a 230kV-60Hz line b.1�b.2: ACSR, S=76.9 sqmm shield wires on a 161kV-50Hz line 13

0

2

4

6

8

10

12

14

16

0 25 50 75 100 125 150d [km]


b) Failure of a single-phase 15/34.5kV � 3 MVA interposing transformer manufactured with windings arrangement and tap-changer location not in conformity with the technical specification.

� In Togo, a small single-phase distribution transformer has failed because it had a 20kV primary winding and had been supplied from the shield wires at 34.5kV. A surge arrester with guaranteed maximum continuous operation voltage (MCOV) of 27kV has failed because it was energized at 34.5kV. The specified MCOV was 38kV. Two capacitor units have failed due to erroneous connection to the SWL.

19


� The SWLs are subject to transient faults (i.e. without equipment damage), caused generally by lightning in the stormy weather seasons. Statistical operation recording of transient faults in Ghana have shown that the rate of transient faults of the 3-phase 30-34.5kV SWLs is not higher than the rate of transient faults of the 3-phase 34.5kV distribution lines in same regions, of same length supported by lattice steel towers. These 34.5kV conventional lines have been reported to undergo in Ghana also ~ 7% of permanent faults.

20


� The spur MV lines (usually on wooden poles) connecting the villages to the SWL of HV line, behave similarly to the conventional equivalent MV lines and may undergo permanent faults (broken conductors; bush fires; damage of poles; contacts with trees; short circuits between wires caused by large birds or wind; etc.). Faults on spur lines are cleared by fuses installed at take-off from the SWL (at HV tower). An effective protection coordination between these fuses and the circuit breaker at sending end of the SWL is necessary, for limiting the number of outages of the SWL and for easy fault location, in particular when the number of spur lines (villages) supplied by a SWL is large. 21

� The large majority of transient faults of the SWLs are cleared by the automatic high-speed reclosure of the circuit breaker at the sending end, or are cleared in any case by the follow-up manual reclosure by the operators of the HV/MV substation, as usual for the transient faults of conventional MV lines.

� Rural electrification planning should consider that the use of very long SWLs (say, 100km) without reclosers in intermediate points, in areas with high keraunic level, aimed with priority to minimal cost, brings along the acceptance of a rate of transient faults and possible short interruptions to consumers that is proportional to the SWL length. This occurs also for the MV conventional lines of same length. An example is a 34.5kV 3-Phase SWL of Laos with length of 129km which supplies over 30 villages (see Fig.7). In Ghana the 30kV 3-Phase SWL Tamale-Buipe (initially 104km; see Fig.5) has been extended to 176km for supply at Kintampo of a repeater station of the Ghana Broadcasting Corporation.


22

5. COST ESTIMATES

� Planning of alternative solutions have been made for

some rural electrification projects with long distance (125 to 250km) between the HV/MV transformer stations and with villages located along the whole route of the HV lines. Cost analysis has shown that the investment for making electricity available at MV with the SWS to all the communities is only 10-15% of the cost of the conventional solution using independent MV long lines of same rated voltage.

� The cost of MV/LV pole mounted distribution transformers supplied by the SWL and of the LV reticulation in the villages is practically the same as for the conventional MV/LV distribution.


23


� A 161kV�200km line had been contracted in Sierra Leone, with 2 60 sqmm galvanized steel shield wires grounded at each tower. A variation order was issued to Contractor for the installation of 2 108 sqmm ACSR shield wires insulated for operation at 34.5kV with the insulator strings of Fig.3. The total turn-key price increase (supplies, transports, erection, etc.) has been 1700 U.S.$ per km of line.

� Price of a rigid insulator string as per Fig.3 is ~ 65 U.S.$.

Price of an unsymmetrical 3-Phase capacitor bank for a 34.5kV SWS rated at 1000 kVAR (2 units in series per phase) is ~ 7000 U.S.$.

Price of a grounding resistor-reactor depends on the ohmic and current ratings (7000 to 14000 U.S.$.).

24


� In some cases, after several years of operation of the two SWLs of a long HV line, the construction of a new HV/MV transformer station in an intermediate point of the HV line may be justified, to serve a largely increased load of a town initially supplied by a SWL. Then the two long initial SWLs are split each in two shorter SWLs, with larger loading capability and lower rate of faults, being supplied also by the new HV/MV station. In the town served by the new station, the MV/LV transformers and the LV reticulation will continue to be operated with only minor changes on the MV supply equipment (MV/LV transformers remain the same).

25

6. SUPPEMENTARY COMMENTS � If an optical ground wire (OPGW) is applied in the HV line

for telecommunications, the SWS can be realised by insulating for MV a standard OPGW. The required accessories and fittings are available in the market. 34.5kV SWLs with OPGW are in operation in Togo and Burkina Faso.

Part of the cross section of an OPGW must be of aluminium or aluminium alloy, in order to ensure a low ohmic resistance for limiting the overheating by the short circuit currents that is dangerous for the fibre optics. An OPGW is thus, by its concept, suitable for use as a conductor of a SWL. Protection of SWLs using an OPGW must warrant fast fault clearing.


26


� The SWLs do not increase the impact on the environment of the HV line. An independent MV line routed along the HV line requires the widening of the right-of-way and has therefore an impact on forestry and agriculture.

� SWLs are a deterrent to vandalism and theft of HV lines, because the communities along the line must protect the line to ensure power supply to themselves from the SWL.

� A detailed Technical Specification of all the components of the SWSs is available on request to the writer of this presentation (free of charge, in english language, electronic form).

27


� A question is if the 3-Phase SWS is feasible without use of the earth return of current and of the special equipment for supply of the 3-Phase SWLs (R-L circuit; unsymmetrical capacitors; dedicated tertiary winding or interposing transformer). For this purpose, the HV line should be provided with 3 �shield wires�, the 3rd being either on tower top in flat configuration or may be crossing the tower body in a window of lattice structure, at an height above soil somewhat lower than height of the lower HV conductors(s). This solution, never applied so far, is technically feasible, however it would require the design of special towers and higher cost of the HV line.

28

� Ghana: About 1000km of 161kV�50Hz lines have been equipped with SWLs. The 30-34.5kV SWSs shown in Fig.5 have been in operation since 1989.

� Brazil: �3-Phase� 34.5kV SWSs have been in operation since 1995 in a 230kV-60Hz line (Fig.6).

� Laos: �Single-Phase Earth-Return� 25kV SWSs are in operation since 1996 in 190 km of 115kV-50Hz lines. �3-Phase� 34.5kV SWSs are in operation since 2002-2003 in 335km of 115 kV lines (Fig. 7).

6. SWSs IN OPERATION


29

Fig. 5 - Single-line diagram of some insulated SWSs in Ghana (year 1989) 30

6

31

Fig. 7 - Single-line diagrams of 34.5 kV �3-Phase� SWSs in Laos (year 2002)

Total length of 34.5kV lateral lines:4.7km

Length of SWL: 25.6km

Forecast load of SWL in year 2018: 790kW

Total length of 34.5kV lateral lines:3.3km


[kW]Loads

23

67.1

51

13

Xiang Ngeun SS

Muang Cha

(Initial stage)

+1x452kVAR

2x333kVAR

22kV ( Initial stage )

( Initial stage )

[kW]

Distance

Loads

[Km]

N° of node

2x60kVAR

2

4.2

71

20

18

8

Length of SWL: 74.6km; total length of 34.5kV lateral lines: 21.6km

E

34.5kV

0+j0

0

01

50

1

115kV

Ban Don SS

Non Hai SS

115kV

D

0

34.5kV

22kV

0.0

01

.58

0

22kV

0.0

40.6

12

66

Future 34.5kV lateral line

Houay Deua

2x125kVAR


32

.39

30

.39

28

.81

22

.29

17

.73

20

.25

12

.57

[Km]

[kW]

5

12

01

20

3 4

75

6

15

0

7

18

8

12

0

8 9 10

75

N° of node

Loads

12

0

11

75

12

23.2

120

32 41

+1x115kVAR

9.5

87

.82

5.1

2

33

76

48

76

End of SWL

10.3

17.6

16.5

20.5

8 106

80

40

Distance

48 22

38

34

31.1

32.1

25.6

5

28.6

7

34.1

9

37.6

11

Length of SWL: 32.4km

(Initial stage)+1x145kVAR

13 14

62

56

Na Am

44.6

47.1

Length of SWL: 76km; total length of 34.5kV lateral lines:19.6km

Length of SWL: 104.4km; total length of 34.5kV lateral lines: 54.2km

4.0

075

+1x225kVAR

N° of node

[Km]

[kW]

0.0

0

115kV

Xaignabouli SS

C

B

22kV

34.5kV

13.5

0

00

.00

34.5kV

19

0

0

115kV

Xieng Khuang SS

115kV

Nam Leuk SS

A

0

2x170kVAR

22kV

13.6

22kV

34.5kV

0.0

0

0

[Km]Distance

2x170kVAR

2x200kVAR

Loads

N° of node

[kW]



Muang Cha SS

28.7

48.9

28.1

25.0

45.1

22.0

20.9

19.7

1

[kW]

75

3x333 kVAR

350

11.3

31

88

42 31

120

120

75

7.2

7

9.7

09

.26

65

120

17.5

7

Loads

65

75

1 2

80

3 4

Distance

N° of node7

Loads

300

1200

[Km]

98

75

28.7

4

32.1

6

(Final stage)

5

75

6

75

7

( Initial stage )

27.1

6

11

128

80

80

80

40

119

160

40

80

40

80

Distance

15.2

71

6.9

8

10.0

4

6.9

3

12.6

7

21 3 54

24.2

9

19.3

9

21.6

92

0.5

1

876 9 10

128

240

80

40

80

80

128

37.9

1

17

31.7

4

29.1

5

28.1

2

141213 1615

39.9

2

18

64.1

76.0

60.4

62.1

22kV

11

+1x334kVAR

12

41.6

0

1110

120

75

75

38.4

7

40.4

0

151413

38

75

75

46.5

74

5.3

0

48.4

3

150

10

150

35

8 9

3950

19

59.6

738

1716

75

75

53.9

1

51.2

8

2120 22

75

38

120

61.3

56

0.9

3

64.8

7

14+j4

( Final stage )

80

256

80

40

40

+1x225kVAR

61.1

1

20

55.9

3

19

68.3

9

63.3

4

66.4

1

2221 23

80

280

80

208

80

40

128

83.2

9

25

77.3

9

24

89.1

29

1.0

8

26 27

3x200kVAR( Final stage )

28

73.8

675

26272524

38

76

38

75

70.4

36

9.1

1

73.7

17

2.1

2

29

38

74.6

0

N°

of

nod

e

121.3529

[K

m]

129.28

123.28

31

30

Dis

tan

ce

104

.40

28

32

� Sierra Leone: A �3-Phase� 34.5kV SWS is in operation since 2010 in the 1st 161kV-50Hz line built in the country (Fig. 8).

� Ethiopia: �Single-Phase Earth-Return� 34.5kV SWSs have been built in the late 1990s in 200 km of 132kV-50Hz lines (Fig. 9). Reportedly, conventional MV line now serve most of the villages in 3-phase.

� Togo: �3-Phase� 34.5kV SWSs are in operation in 265km of 161kV-50Hz lines. One of the shield wires is an insulated OPGW (Fig.10).

� Burkina Faso: �3-Phase� 34.5 kV SWSs are in operation in 330 km of 225kV-50Hz lines. One insulated shield wire is an OPGW (Fig.11).


33

Fig. 8 - Single-line diagram of 34.5 kV �3-Phase� SWSs in Sierra Leone

34

Fig. 9- Single-line diagrams of 34.5 kV �Single-Phase Earth-Return� SWSs in Ethiopia (year 2000). Operation has been discontinued.

132 kV-115.7 km132/15 kV

132 kV-84.7 km

GHIMBI S/S NEKEMPTE S/S

GHEDO S/S

34.5 kV

Sire

230 kV230/132/15 kV22/22/5.5 MVAtwo units

132/15 kV25 MVA15 kV

25 MVA

IT IT

IT: 15kV/34.5kV+2x3.75%-3 MVA

15 kV

15 kV

IT

84.3

1299

35 32.5 31.4 8 km

487 133 1155 100Loads

kW

km 42.7

2180125250179

15 18 28

936 325

60 50

34.5 kV LoadskW

34.5 kV

300 kVAR 300 kVAR 300 kVAR

0 0 73 km 0

Sum of simultaneous peak loads of SWLs in year 2019 =2734 +1987=4721 kW

Total length of SWLs=42.7+73=115.7km

Sum of simultaneous peak

Total length of SWL=84.3 km

loads of SWL in year 2019 =3174 kW

726

132 kV

35 Fig. 10 � Single-line diagrams of 34.5kV �3-Phase� SWSs in Togo

36

Fig. 11 Single-line diagrams of 34.5kV �3-Phase� SWSs in Burkina Faso

37

Results of Low Cost Distribution Approaches Study in Tanzania

Low Cost On-Grid Electrification Technologies

Workshop

Arusha, Tanzania

3-4 September, 2013

Who is NRECA?

n Trade association providing common services to US electric cooperatives

n 860 Distribution cooperatives serve 70% of the land area of the US

n 40 Power Supply cooperatives with 50,000MW of capacity

n 15,000,000 members (about 11% of all US electric consumers)

n 42% of the distribution line in the US belongs to cooperatives

n International programs in 65 countries over 50 years

Background of Project

n Tanzania electrification rate is low

� Only 2% of rural population has access to electricity

� Uptake of connections in electrified projects is slow

n Costs in Tanzania are Considered High

� Costs of line construction viewed as high in relation to other countries both in the region and in other developing countries

� Connection costs/fees for new consumers are high

n The Rural Energy Agency, with the support of the World Bank has undertaken to resolve these issues

Objectives of the Low Cost Project

n Design of a low cost electrification model

� Design, standards, construction

� Procurement mechanisms to reduce cost

� Financing schemes to increase connection rates

n Demonstration of Low Cost Model through preparation of Pilot Projects

� Specific project design, two projects with about 12,000 total consumers

� Preparation of bid documents for materials and construction

n Sustainability

� Participation by TANESCO and other PIU staff

Methodology and Approach New Technical Standards and Designs n Document standard processes used by TANESCO

and identify cost drivers

� Construction standards

� Contracting methods

n Evaluate unit costs for recent construction

� Project costs as opposed to standard costs

� Compare with results from others (e.g. Kenya, Uganda, Bolivia, Dominican Republic, El Salvador)

n Evaluate alternative approaches for reducing costs of construction

n Develop revised rural electric construction standards

Features of Tanzania Electric System n 33kV is the rural electric system HT voltage

n Power transformers have earthed neutrals on 33kV side (Delta wye connected transformers)

n Residual current trip at 25% of phase trip setting but no sensitive earth fault tripping

n All HT lines are three phase and most have 100mm2 conductor

n Most distribution transformers are 100kVA or 200kVA three phase units connected delta-wye

n LT is 4 wire wye three phase system 230/400 volts, using 100mm2 AAC conductor. Single phase lines are rare.

Installed Costs for TANESCO Facilities

Installed Cost per Unit

Construction Type Unit TANESCO Turnkey

33 kV 3 Phase Line (100 mm2 ACSR) Km. $26,104 $20,680




400 LV Line (100mmsq Al) Km. $21,536 $21,261


Service Drop Three Phase-30m Ea. $983 $621

TANESCO -HT Configurations

n TANESCO 33 kV Line Structure, LV Pole, Transformer

Installed Costs for Uganda and Kenya Facilities

Cost Comparison Tanzania, Uganda, and Kenya

Construction Type Unit TANESCO Uganda Kenya

33 kV 3 Ph (100 mm2 ACSR) Km. $26,104 $13,085 $18,941




400 LV Line (100mmsq Al) Km. $21,536 $11,165 $16,802



Typical Distribution Structure for Uganda and Kenya

Installed Costs for Southern Africa

Comparison Costs for Southern Africa

Construction Type Unit South Africa

Zambia Mozambique

33 kV 3 Ph (100 mmsq ACSR) Km. 32,500 29,102 30,000


100 kVA Transformer Ea. 18,000 14,519


SWER Line Km. 13,929

400 LV Line (100mmsq Al) Km. 25,000 19,552

Service Drop Single Phase-30m Ea.

Service Drop Three Phase-30m Ea. 800

Installed Costs for Other Developing Countries

Installed Costs of Distribution Lines in Other Developing Countries

Construction Type Unit Dominican Republic

Bolivia Bangladesh

33kV 3 ph (100mmsq) km. $18,912 $16,200

33kV 3 ph (50mmsq) km. $14,998 $9,600




400 LV Line 3 phase Km. $5,800 $7,800

230 LV Line 1 phase Km. $5,100 $4,700

Service Drop Single Phase-30m Ea. $123 $148 $60


Conclusions Regarding Cost Comparisons

n TANESCO costs are higher than neighboring countries, especially Uganda

n TANESCO costs are lower than those of Southern African countries

n Comparison with countries outside the region highlights opportunities for cost reduction

� Configuration

� LT line and transformer cost

� Service drop cost

Methodology for Low Cost Technology Evaluation

n Identify service areas on which to test configurations

� Moderate density large village system

� Low density remote village area

n Configure multiple test cases using consistent system strategies

n Carry out power flow modeling on the test cases to determine voltage and loss performance

n Develop standard costs for system facilities and prepare cost estimates for the test cases

n Capitalize losses to develop lifetime cost estimate

System Configurations for Test Cases n Base Case

� TANESCO standard design using current HT structures, very few Laterals, large Transformers located on the man line feeding standard LT Lines.

n Case B

� Modified three phase service using crossarm type structures, three phase laterals and 25kVA transformers feeding LT sectors of 25mm2 quadruplex.

n Case C

� Single Phase service using two phase 33kV HT laterals and 16 and 25 kVA single phase transformers with 240/480 triplex LT of 25mm2.

n Case D

� Single Phase service using 19 kV phase/neutral laterals from four wire multigrounded main line, 10 to 25 kVA single Phase transformers and 240/480 triplex LT of 25mm2.

System Configuration for Test Cases-Cont�d

n Case E

� 19kV SWER line fed by isolation transformer from a phase-phase connection on the three wire main line. Transformers 10-25kVA, LT system 25mm2 triplex

n Case E2

� SWER can also be produced without an isolation transformer, with one phase and earth return. The earth return current flows to the main substation and contributes to earth unbalance current.

n Special Considerations for SWER in Moderate Density Applications

� In moderate density applications, SWER grounding grids may be difficult to install due to lack of space. Standard practice is to isolate SWER HT ground from LT earth. This can be difficult also.

� SWER can use wire neutral in the village, with the neutral earthed in open areas outside.

Standard SWER Earthing Electrode Results of Comparisons

Cost %Cost

$/ConsumerCost %

Cost

$/Consumer

TANESCO Standard Design 100% $532 100% $2,727

Case B Modified TANESCO 86% $461 72% $1,976

Case C: 33kV Two Phase HT 74% $396 37% $1,022

Case D: 19kV Single Phase HT 72% $382 44% $1,196

Case E: 19kV SWER

w/isolation transformers79% $421 31% $844

Case E2: 19kV SWER w/o

isolation transformers68% $361 28% $773

Summary of Results of Configuration Comparisons

Moderate Density Sytstem

Alternative Approaches

Low Density System

Features of Low Cost Approach

n Continued use of three phase three wire main lines

n Single phase two wire 33kV laterals with small, high strength conductors for long spans on low density projects (Shrike 16mm2 with 3/4 stranding)

n Wood pole top assemblies to improve insulation level

n Minimize LT by using small single phase transformers

n LT networks provide only single phase service.

n 240/480 volt split single phase LT w covered conductor

n Three phase service to specific consumers with dedicated transformer banks

n Low cost service drops

Consideration of Technical Approach for Industrial Consumers

§ For Low Cost electrification approach, the supply of three phase power to small industries is a big challenge here in Tanzania. This has apparently been an obstacle to the use of single phase lines in the past.

§ The market in Tanzania is for 3 phase 400 volt motors. Rural electrification is not going to change this fact.

§ Consumers resist single phase motors due to shortage in the market and concerns about their reliability.

§ Some efforts to construct single phase projects in the past have been converted back to three phase.

Technical Approach for Industrial Consumers

n Accordingly, NRECA has considered options for supplying power service to small industries from a single phase source.

� For motors of 5HP or less: Cost difference between single and three phase service drop means that 5HP single phase motors are reasonable

� Phase converters: to convert single phase power to quasi-three phase service to power a standard 400 volt three phase motor

� Open wye-Open delta Transformer Connection: The single phase laterals proposed for the Kilombero and Mbozi projects consist of two phase wires of the 33kV system. It is therefore possible to create a three phase connection using the earth return for a neutral and an open wye-open delta transformer connection.

Phase Converter

Schematic of Phase Converter Features

n Requires 400 volt input, so different transformer

n Pilot motor capacity 125% of mill motor

n Active switches and capacitors to control voltage

n Requires 400 volt single phase meter

n Lights via 400/230 volt lighting transformer

Open Wye-Open Delta Transformer

Features

n Two transformers 19kV/400 volts

n Earth return neutral

n Produces 400 volt three phase service

n Standard meter (though w/o neutral)

n Also requires 400/230 volt lighting transformer

Cost Estimate for 20 HP Mill Application

C PIU agreed to proceed on the basis of using the open wye-open delta transformer configuration to provide three phase service on the Low Cost system

Service Type Equipment Description

Equipment Cost

Service Drop and Meter Cost

Total

Single phase/ Phase converter

25kVA transformer

25HP phase converter

2kVA Lighting transformer

$2,795

$2,500

$200(possibly at consumer cost)

$300 $5,795

Open Wye-Open Delta w Lighting transfomer

2x15kVA Transformer

2kVA lighting transformer

$3,484

$200 $550 $4,234

Rationale for Selection of Two Phase HT as a Low Cost Technology

n NRECA recommended two- phase HT as the preferred low cost option for Tanzania for the following reasons:

� While SWER is cheaper for low density projects, two phase HT achieves most of the cost benefits of SWER.

� For moderate density applications no difference in cost between two phase and SWER, and SWER presents some challenges in execution.

� For a given voltage drop criteria and conductor, two phase has 50% more capacity than SWER

� Utility can supply three phase service from two phase lines using open wye-open delta transformer configuration

LV Multiplex Low Cost Service Drop

n Low Cost High Security Service

� 10mm2 Airdac conductor

� Prepayment meter with measuring unit on pole

� Customer interface unit in residence

� 50Amp service capacity

� $US200 est. cost w prepayment meter

� Service is earthed for safety

Wood Pole top Why Wood Crossarms?

0

10

20

30

40

50

60

70

80

90

150 200 250 300 350 400 450

Ind

uce

d F

las

ho

ve

rs/1

00

mil

es/y

ear

BIL (kV)

Induced Flashovers for various BILs

Data from Short, T.A. 1992

Lightning Resistance

Cost: Wood crossarms cost 60% of steel

Conductors Smaller than 50mm2

n Due to the very light loads, economics favor conductors in the range of 25mm2 for both HT laterals and LT

n Small conductors allow longer spans

n However, many jurisdictions limit use of small conductors for mechanical reasons

n Recommendation: Use high strength conductors, such as Magpie or Shrike. Standard ACSRs will not be adequate

Single Phase Transformer

n Single Phase transformer

� 15kVA minimum size

� 240/480 split single phase LT

� LT reduced to 3x 25mm2

Questions???

Thanks

Design of Low Cost Rural Grid

Substations and 132kV Lines

Low Cost On-Grid Electrification Technologies

Workshop

Arusha, Tanzania

3-4 September, 2013

Statement of the Problem

n The countries in Africa tend to be large

n Rural population is dispersed and average energy

required per consumer is low

n Design philosophy for transmission grid emphasizes

high capacity substations, designed for reliability

n Rural systems served by 33kV distribution feeders

extended from large, high capacity grid substations

� 33kV is already the highest distribution voltage practical

� 33kV feeders are often long and highly stressed

n Needed- a way to extend 132kV for rural system

support at low cost

Typical 33kV Feeder Situation Solution Using Express Feeders

Solution with Substation How to Provide Transmission Support

Economically?

n Permit taps on transmission lines rather than at

terminals only

n Make taps radial to use lightweight conductors

n Minimize high voltage switching in delivery

substations

n Accept reduced levels of redundancy in substation

design

� Single transformers

� Self powered transformer protectors

� Eliminate batteries where possible

Example- Use of Tap Connection Transformer Isolates Transmission

from Tap Substation

Tap Applied to a Transmission System with Step Distance Relay Protection

Transformer Impedance Line Equivalent km

MVA Z% Z ohm Single Cond. Dbl Cond.

20 10.0% 87.1 220 316

25 10.0% 69.7 176 253

30 10.0% 58.1 147 211

Possible Design Features of Low Cost

Substation

n No 132kV line switching in substation

n Initial development with one transformer

n No load tap changing in transformer (address voltage

fluctuations with line voltage regulators if needed)

n Transformer breaker on 132kV side only

n No 33kV bus breaker

n Use of self contained reclosers for 33kV feeder

protection

n No station battery

n Designed for unmanned operation- no control house

Substation Layout

Substation Section View Cost Estimate

Cost Estimates for Other Capacities South Lebanon Sub- Tennessee

Rural 132kV Substation in Michigan

Low Cost Transmission Lines

H-Frame Structure Span Limits

Maximum Spans for Single Pole 132kV Line w 200km/hr Max Wind

Maximum Spans for Two Pole X-Braced H-Frame 132kV Line w 200km/hr Max Wind

Line Costs Single Pole Line with

150mm2 Conductor

Line Cost for H-Frame Line with

150mm2 Conductor

Project Cost Comparison From Previous Power Flow Example

n Alternate 1: 160km of 33kV express feeders with

200mm2 conductor, plus voltage regulators and

capacitors

n Alternate 2: 60km of 132kV line terminating in

1x25MVA substation


Workshop


Voltage drop and loss

calculations

Vector Diagram

of a single section Load

VS

I L r Cos I L x Sin

VR neglected

Voltage drop and loss formula

� For three phase lines:

� V = 3!.!I!. L . (r Cos" + x Sin")

� P = 3 . I2 r . L

� For single phase lines:

� V = 2 . I . L . (r Cos" + x Sin")

� P = 2. I2 r . L

L/n L/n L/n

Distributor with Equal

Loads at Equal Spacing

Is/n Is/n Is/n Is/n Is/n Is/n Is Is/n

Distributed load formula

� Distributed Load V =

( V tail end load) x

� Distributed Load P =

( P tail end load) x [(12+22+-----+n2)/ n2

Multiplying Factors

No Sec MF for V MF for V

1 1 1

2 0.750 0.625

3 0.667 0.519

��

Infinite 0.500 0.333


Workshop


Rural Electrification Planning

and Related Issues

Chris Ratnayake

Consultant Power Engineer

Planning: Current Situation

� In many countries severe lack of focus on any

planning or alternative analyses before

embarking on projects

� Whatever urban standards used replicated

� May have been applicable in the past with

small scale rural expansion �but not anymore

� Urgent need for developing planning

standards and methodologies

Planning Process

� Data requirements (load data, existing

network configurations)

� Network modeling

� Power flow analysis

� Economic and Financial analysis

Improve data availability & accuracy

� All plans are as good as the reliability of data

�Often av. consumption assumed is far in

excess

�Do the figures used represent ADMD?

�Measure loads on transformers (often

severely underloaded)

Improving data availability (cont)

� Data from completed schemes:

�Consumption patterns kWh/m, kWpeak

� Load density W/meter line, kW/kmsq

�Commercial and small industrial loads

�Growth rates (within electrified area)

�Can we identify patterns

Improve data availability (cont)

� Data on unelectrified areas:

� No of houses, dispersion patterns

� Commercial and small industrial loads

� Existing captive diesel plant

� Good maps of the area (with terrain if applicable)

� System data:

� Details of existing networks

� Future additions possible

Examples of consumption analysis 1

<30U-38%, <60 U -74%, <90U -93%

Examples of consumption analysis 2

<30U-34%, <60 U -71%, <90U -97%

GIS data base

� GIS systems � a powerful data capture

medium

� System planning, Analysis and asset

management

� GIS concept: layering, labeling of map objects

(attributes) graphic display

� Data source: digitized maps, scanned images,

GPS survey, Satellite imagery

GIS (cont.)

� GIS increases access to relevant data

� From many sources

� GPS an accurate positioning system at low cost

� Will increase productivity immensely

� However, planning work should not be

postponed till GIS is established! -Need to be

done in parallel

Load Flow Analysis

� Commercially available software

� CYME �Dist (Canada)

� DigSILENT (Germany)

� ETAP (USA)

� TEKLA (Finland)

� PSS (Sincal) (Germany)

� PSCAD Manitoba Hydro (Canadia)

� SynerGEE (USA)

� Milsoft (USA)

Load Flow Analysis (Cont.)

� Simplified tools �Spreadsheet based

computations using multiplying factors

� Voltage drop; Conductor loadings; losses

� Alternative network developments

� Future year loads �Improvements possible

Economic Analysis

� Important issue is the analysis of alternatives

� Discounted present worth calculations �IRR

� Losses �LRMC or AIC

� Discounting -present value of costs and

benefits

� combination of load growth and discount

factors

� Benefits �Willingness to Pay (WIP)

Discounting PV of energy supply

Discounting cost of losses Loss performance with time

� Investment Investment

� 0 3 6 9 12 15 18 21

Loss

es

in k

W

Years

Financial Analysis

� Compute Financial IRR also

� Subsidy issues

� Financial impact on revenue account and

capital account

� Importance of financial sustainability

Section 2: Improving Connection Rates

� Poor connection rates in completed schemes

� Reduces receivables in spite of capital spent

� Objectives not achieved

� Causes:

�High connection costs

�Absence of installment payments

�Transaction difficulties / Obstacles

Solutions - Examples

� Use appropriate service cables

� 16mmsq often used 6mms or 10 mmsq sufficient

� Term payments through monthly bills

� Senegal: 120 months with 15% interest

� Kenya: �Stima� loans (30% front balance in 3 yrs)

� Ghana �self-help� electrification scheme

� Partial subsidies

� OBA Grants (GEF)

Logistical difficulties

� Need for licensed wiremen

� Application and approval process

� Solutions:

� Bunching of applications

� Reduces costs, time consumed and malpractices

� Consumer mobilization agent (consultant or local

organizer)

Eligible households

� Rejection of non-permanent houses

� Thatched roof, mud walls

� Reasons unjustified

� Fire hazard (much more for alternative K-oil use)

� Roof structure �iron sheet roofs more hazardous

� Redressed with simple solutions

� PVC conduit, ready boards

� RE meaningless unless issue is addressed

To Sumarize

� Our goal is to improve planning

standards

� Enhance connections by

innovative mechanisms

Thank You

Work group 1 study

Assignment 1

SWER /phase phase 35 mm

Assignment 2

Initial assessment

• Backbone – A-D maximum load

• Laterals – E,G,H,F, relatively light load

Initial modelling –

Tapered system approach

Option 1

A-D Wolf, laterals – 35 mm

Option 2

A-B Wolf, B-C Dog, C-D Rabbit

Option 3

A-B Wolf, B-D Rabbit.

Refer schedule for analysis

Assignment 2

Analysis

Voltage drop –

When comparing the three options, the relative voltage drop was marginal

Losses–

When comparing the three options, the relative conductor losses between option

2 and 3 was considered to have an impact on the relative costing.

System robustness and capacity –

The Option 2 provided the best medium to long term capability and the relative

loss values made the additional line cost for this section viable.

Results

Option 2 preferred

A-C Wolf, B-D Dog, however one may consider the section B-C Wolf and C-D Dog, depending on the reliability of the source information.

Notes –

The laterals E, G and H - SWER is and option

The lateral F - phase phase is and option

Summary

Assignment summary

%vd losses losses usd/m differential Capital Scheme cost

option 1 95.4 18.83 542.304 0 $ 309,560.00

option 2 94.1 33.58 967.104 424.8 169920 $ 274,700.00

option3 93.6 40.06 1153.728 186.624 74649.6 $ 270,500.00

Ps. from yesterdays discussion

SWER – medium to long term benefits

• Obvious reduction of conductor and insulators

• Single phasing

• Dead side return

• Survey limits/consideration including , swing, uplift, clashing, mech. loading.

Distribution System Study of MV networks: Study S1

Existing network

Section Distance

in km

Load

In kW

AB 15 0

BC 20 50

CD 25 670

BE 20 350

BG 40 265

CF 20 400

CH 17 265

Denotes load point

Problem:

Determine optimum network development for supply to target area

Possible line routes are provided

The best available supply point is at A off the existing 33 kV three phase network

Voltage drop at A for target year is assumed to be 2%

Loads given are for the target planning year

A

B

A

E

A

F

D

C

G

H

COMPUTATIO OF VOLTAGE DROP AND LINE LOSSES OF POWER DISTRIBUTORS

Vector diagram of a single section power line

VS

I L r CosƟ I L x SinƟ

Ɵ VR neglected

The line end voltage drop phase to neutral is: V = I . L . (r CosƟ + x SinƟ) and power loss along a single conductor is: P = I

2 r . L

We thus have the following representation for voltage drop and losses for three phase and single/two

phase systems respectively:

V =K . I . L . (r CosƟ + x SinƟ)

P = K1 . I2 r . L

Where:

K =√3 for balanced three phase and 2 for single or dual phase

K1= 3 for balanced three phase and 2 for single and dual phase

I = line current

L = line length

r = resistance I Ohms per unit length

x = inductance in Ohms per unit length

Ɵ = power factor angle

Distributors

In practice however, a distribution line consist of a number of sections and branches and is loaded at

various points along its length at irregular intervals. In such instances the power flow characteristics

including line voltages at various points and line losses can only be accurately determined by using

suitable computer programs that can address the solution by using iterative processes. However, a

simplified methodology can be developed to obtain an approximate solution which will yield results well

within acceptable accuracy limits.

The computation is made with the distributor modeled as a simple radial line with a number of equally

spaced sections at the ends of which are applied loads of equal magnitude. The total load of the distributer

will be equal to the total of the section loads and the total direct length of the distributor (omitting any

branch lines) will be equal to the length of the model line. Experience has shown that it is very convenient

to model distribution lines by this method ignoring the voltage levels of the branch lines as only the

lowest voltage of the system is of relevance. Also the line losses of branches are often negligible in

comparison with the losses in the main line which carries the main loads. If any branch line is of

significance it can be modeled separately while for the performance of the main network the total load of

the branch line can be taken as acting at the branch point. The representative model is shown in Fig 3

below:

Fig 3:

L/n L/n L/n

Is(n-1)/n Is(n-2)/n Is(n-3)/n Is/n

Is/n Is/n Is/n Is/n Is/n Is/n

No of sections = n

Load at each node = I/n Amps

The current flowing along the sections, commencing with the start of the distributor will be:

Voltage drop of distributor:

The voltage drop in section (i+1) will be:

= K (r cosƟ + x sinƟ)

Accordingly summing up the voltage drops (ignoring the negligible phase angle shift)

Line end voltage drop is:

= K (r cosƟ + x sinƟ) I ( + + )

= K (r cosƟ + x sinƟ) (1 + 2 + 3 +--------+n)

= K (r cosƟ + x sinƟ) ( )

= K (r cosƟ + x sinƟ) L

= (voltage drop of tail end load) .

Power loss of distributor:

The Power loss along section (i+1) will be:

= K1 r

Accordingly summing up the power losses, total loss of distributor is:

= K1 r I2

= K1 r I2 [(1

2+2

2+3

2+--------+n

2)/ n

2

= (losses of tail end load) [(12+2

2+3

2+--------+n

2)/ n

2

Using the above relationships a set of multiplying factors could be derived to convert the tail end load

situation to that of a distributor with the same length and sending end load. The following table presents

the multiplying factors that could be used to determine the line end voltage drop and line losses of a

distributor

No of line

sections

MF for MF for

Volt drop Losses

1 1 1

2 0.750 0.625

3 0.667 0.519

4 0.625 0.469

5 0.600 0.440

6 0.583 0.421

7 0.571 0.408

8 0.563 0.398

9 0.556 0.391

10 0.550 0.385

11 0.545 0.380

Infinite 0.500 0.333

Workshop Conclusions 1. The need for more focused efforts on network planning

� Use of simplified spreadsheet based analysis when specialized

software is not available

� Upgrade technical planning capabilities: GIS data bases,

specialized software

2. Application of appropriate low cost technologies in the planning process

� Use single phase, two phase combinations with the main three phase backbone

� Use SWER where load density is sufficiently low

� If transmission lines are available and high distance from existing MV network try shield wire applications

� Judicious allocation between MV and LV �use of single phase transformers and more MV network to reduce costs

� Use low cost transmission options (pole lines and simplified substation arrangements) for extensions to HT network

� Carry out cost comparisons between technically acceptable alternatives

3. Use appropriate load data in planning

� Collect data from completed schemes

� Find out load per km of line, load per sq. km

� Used analyzed billing data

4. Analyze/address reasons for failure/drawbacks of some applications

� Shield wire systems have sometimes failed due to use of inappropriately designed equipment, non-compliance with specifications

� Perception of low quality of SWER lines due to lack of appropriate consumer relations/education. Can be addressed by better participatory process.

� Address limitations of single phase and SWER networks by proper education of consumers on single phase motors use of phase converters and �open Y, open delta� transformers (to supply three phase supply)

5. Ensure maximum connections from completed schemes

� Reduce connection costs by using appropriate conductor

sizes

� Enable installment payments (with monthly bills)

� Carry out �mobilization� exercises to address transaction

obstacles

� Provide connections to non-permanent houses (thatched

roofs, mud walls etc)

00 aei low cost electrification workshop arusha...

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