A new approach for off-grid Rural Electric Distribution Networks

Technical and Socio-economical analysis of the introduction of

modern control options in off-grid applications

Master Thesis/ C-level

Johan LarssonInstitutionen för Datavetenskap och Elektronik

Abstract

Over 1.5 billion people worldwide lives today without any access to modern energy like electricity.

This thesis analyze the possibilities of using industrial control systems for monitoring, control and surveillance of small rural off grid networks. In a traditional electrical network, the operator only monitors his equipment and the power usage to make sure that the system is working correctly. However in traditional rural off-grid cases the grids are typically small and have their own power source. A small system is required, that will monitor both the net and the small factories within the distribution area. There is also a demand to control the power usage in order to optimize the energy supply, reduce the investment cost and avoid large power fluctuations, that may damage the grid.

Today there are several control systems for electrical distribution networks, such as ABB’s Microscada. This system, however, is normally designed for up to 100,000 or more consumers, which makes it too large, inflexible and expensive for application in rural off grid networks. This thesis elaborate an idea to implement an industrial automation system to analyze if it is possible to use it to control the grid and specific connections such as the temperature in transformers, motors etc. Specifically the industrial control system 800xA from ABB have been explored for the control the grid, with all its components and customers.

In order to implement industrial automation system we need to see the network as an industrial process, where the consumers and equipment is a part of the process that is being controlled and monitored. Many devices are already predefined in the system (e.g. valves, motors etc.) but energy meters and transformers are not. These devices will instead be defined as new objects in the system program.

Johan LarssonInstitutionen för Datavetenskap och Elektronik

Handledare:Sten Bergman StonePower AB

Examinator:Lennart Harnefors Mälardalens Högskola

Table of contents

1 BACKGROUND..................................................................................................................................................4

1.1 EXAMPLES OF SMALL ELECTRICAL GRIDS......................................................................................................4Democratic Republic of Congo the Kaziba project.........................................................................................4Uganda Kisiizi Hospital..................................................................................................................................6The Songea Rural Electrification Project.......................................................................................................8

1.2 CONCLUSION...................................................................................................................................................91.3 RURAL ELECTRIFICATION.............................................................................................................................101.4 RURAL ELECTRIFICATION – BASED ON OLD AND OUTDATED STANDARDS...................................................111.5 EXPERIENCES FROM RURAL ELECTRIFICATION.............................................................................................121.6 OBJECTIVE AND OUTLINE OF THE THESIS....................................................................................................12

2 NETWORK CONTROL/MONTORING AND AUTOMATION SYSTEMS.............................................14

2.1 INTRODUCTION.............................................................................................................................................142.2 SCADA SYSTEMS.........................................................................................................................................142.3 INDUSTRIAL AUTOMATION SYSTEMS...........................................................................................................152.4 COMPARISON OF SCADA AND INDUSTRIAL AUTOMATION SYSTEMS..........................................................152.5 THE NEED OF COMMUNICATION TECHNOLOGY.............................................................................................16

3.0 EMERGING NEW IDEAS APPLICABLE TO RURAL ELECTRIFICATION....................................17

3.1 WHAT NEW STANDARDS COULD POSSIBLE?..................................................................................................17

4. APPLICABILITY OF INDUSTRIAL CONTROL SYSTEMS FOR RURAL ELECTRIFICATION....19

4.1 INTRODUCTION.............................................................................................................................................194.2 DISTRIBUTED AUTOMATION.........................................................................................................................194.3 DISTRIBUTED POWER GENERATION / ENERGY STORAGE.............................................................................204.4 LOAD MANAGEMENT / DEMAND SIDE MANAGEMENT.................................................................................204.5 SURVEILLANCE AND SAFETY MONITORING..................................................................................................20

5 A “HYPOTETICAL” OFF-GRID NETWORK IN KASULU......................................................................21

6 TECHNICAL AND SOCIO-ECONOMICAL IMPLICATIONS OF USING CONTROL TECHNOLOGY IN OFF-GRID NETWORKS.................................................................................................23

7. SUMMARY AND CONCLUSIONS...............................................................................................................25

8. REFERENCES..................................................................................................................................................26

9. ACKNOWLEDGMENT..................................................................................................................................27

APPENDICES.......................................................................................................................................................28

A1: STUDY OF DISTRIBUTION SCADA NETWORKS BASED ON ABB’S MICROSCADA.......................................28A2: CASE STUDY OF INDUSTRIAL AUTOMATION SYSTEMS ABB 800XA...........................................................30

Fortum’s district heating system in Stockholm.............................................................................................30

1 Background

More than 1.5 billion people worldwide are currently living without access to electricity [ABB ref]. A big portion of them, more than 500 million lives I Sub Sahara Africa. Over 80% of the population is located to rural and remote areas.

Many efforts are being made to increase the electricity access and there are many examples of small off grids in the world. Some of them are using renewable energy sources; other is using diesel generators and other fossil fuel sources. This is however not a suitable solution in a long time perspective since price on fossil fuel will increase and it creates exhaust fumes that are dangerous to the environment. These old diesel generators are very in efficient about 60% of the fuel will generate nothing but hot air.

1.1 Examples of small electrical grids

Democratic Republic of Congo the Kaziba project

Background

Kaziba Village is a four-hour drive from the main town Bukavu in the Kivu province. Missionaries have worked here for 70 years and developed the Kaziba Hospital over a period of 40 years. In the early 1970s, it was clear that the hospital could not survive without a secure power-supply. Beginning in the 1980s, three diesel-units with a total output of 50kVA secured the electricity supply to the hospital during emergencies. Normally they could afford to run one 6 kW diesel-unit three evenings a week. Other evenings they had to relay on solar energy, which only supplied the hospital with enough electricity for basic lighting.

The idea of utilising rapids in the nearby river to generate electricity was first introduced when the hospital was initially developed, but limited know-how and limited avaible resources put constraints on any development until the mid-1980s. The alternatives were connection to the main grid 40 km from Kaziba, or continued use of diesel units at a cost of US$ 0.5 kWh if diesel was available. Both these alternatives were considered much more expensive. Studies in 1988 concluded that the output could amount to 125 kW.

Electrical generation

The turbine is second-hand from a power station in Norway, where it had been in operation for more than 40 years. It has been fully refurbished by Kvaerner Energy, and can produce 125 kW at a head of 6.8m and water flow of 2.4m3/s and 300 rpm. It consists of double Francis turbines, which means that two runners are fitted into the turbine house. This solution makes the turbine very flexible in accommodating variations in water flow, and it can operate successfully at between 10 and 100% of full capacity.

The maximum hydro-power station is 125kW, at a head of 6.8 m and a flow rate of 2.4 m3/s. Average output is estimated to be approximately 750.000 kWh per year, provided the station has an average break of four weeks a year for maintenance of intake, channels, machinery and electrical equipment. It is also unlikely that all the electricity that can be produced will be used in the near future.

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Organisation

CELPA, the local organisation that owns and operates the hospital, has the overall responsibility for the project. Extensive know-how on how to run the power station and the electricity installations was developed in the course of the project’s implementation and test operation. The following responsibilities were necessary:

Management Technical operation of the turbine and generator Technical control of the system at the hospital and connections to local villages Operation of the channels and gates Maintenance of the riverbed, which affects the constructions Tariffs and electricity billing.

This resulted in five permanent employees with responsibility for daily operation of the system. Two with a bachelor degree in electrical engineering but no training during the construction period, two with no education beyond primary school, but had been trained, and one an old school teacher who worked as the foreman. Because of his performance during the construction period and his age, the schoolteacher was chosen as manager, reporting to CELPA. The others were given different responsibilities according to their know-how and experience.

In principle, the organisational structure was created as:

CELPA: Responsible for setting tariffs and budgeting, making decisions regarding the sale of electricity to local villages, paying employees.

The Manager: Electricity billing, making emergency plans (in case of flood, electricity shortfalls, or load shedding). He participates in any meeting regarding the operation of the plant, relevant meetings with CELPA, and follows up work carried out by the other employees. As he had acquired special competence during the work on the channels and riverbeds, he was responsible for maintaining and operating the channel structures, gates and the river training works.

Technical groups 1&2: Trouble shooting groups of two persons each responsible for daily operation and technical maintenance. The two technicians head the groups that alternate to be on standby during nights and weekends.

Basic training

The basic training on how to operate the turbines has passed on sufficient know-how for local employees to follow up daily maintenance. The focus has been on erosion and silting problems in the channel.

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Future use of electricity

If the hospital increased their use of electricity during the night, this would increase water flow in the channel and thus reduce sedimentation. This would enable more electricity to be sold to other costumers and create an extra income for the hospital.

Besides the hospital, the local administration and 50 households in three villages have access to electricity from the power station. It also delivers power to streetlights in a near-by marketplace that are connected. Another 150 households are eager to be connected to the grid. A total of 10 kW is available to other customers besides the hospital, but this could increase if the hospital planned for extensive night-time use.

As the owner, the hospital is not responsible for electrifying houses in the local villages, however the project is seen as a means to start development in the area. The three villages that have access to the grid have each developed an organisation to negotiate with CELPA, in order to put up distribution lines from the hospital and to do the necessary wiring in houses where the families can afford electricity. There is no surveillance system in the grid other than the system that monitors the turbines today.

Uganda Kisiizi Hospital

Background

The village of Kisiizi is located deep in the mountains of north Kigezi in the Rukungiri district in southwest Uganda. It lies about 5400 feet above sea level and the area is one of Uganda’s most densely populated. The hospital was founded in 1958 by Dr John Sharp on the site of an old flax factory which had been built close to a waterfall, facilitating the generation of hydro-electricity. It has a patient catchment area stretching hundreds of miles.

The steady growth of the hospital has, however, outstripped the presently installed 60 kW turbine. As a result, difficulties have arisen in maintaining an uninterrupted supply for the hospital and staff residences. They have therefore installed Distributed Intelligent Load Controllers and Power providers to secure electricity to the hospital. There were issues prior to Load Control such as:

Increased growth System capacity outstripped Poor quality of life for staff, no electric cooking, erratic supply of hot water. Difficulties attracting good staff Frequent blackouts Wasteful dumping of excess generation

The acquired benefits since the installation of Load Control include:

Maximized use of capacity Areas of the hospital have been prioritized to prevent blackouts. Non-essential loads

are shed when demand is approaching blackout levels to prevent power being lost from high priority areas, such as operating theatres.

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Quality of life for the staff has been improved. The load controllers have been fitted in staff residences. When there is very low demand, such as during the night, the excess supply is used to heat water. Prior to this work, hot water to wash with was considered a luxury.

Electric cooking is now possible. There have been no blackouts

Today Kisiizi residents are successfully using luxury domestic appliances, such as food mixers, through their DILC controlled power supply, and there is significantly more hot water.

Functions for Distributed Intelligent Load Controllers (DILC) and Power providers

Power providers are designed to give the customer a maximum amount of current, for example 2 A. If the user exceeds the limit, the power will be turned off and restored when the load is below the limit. DILC monitors the frequency at a given value; if the frequency drops below this value the system begins to disconnect loads in order to maintain stability within the grid.

The controllers have been fitted with an additional safety feature, which allows the user to manually switch devices, such as irons and electric cookers, back on when the power again is available. This will prevent any accidents from arising, should the user leave the device unattended, while the power has been shed temporarily.

Future

It is proposed that the turbine be upgraded due to the increasing demand for electricity (currently approximately 125 kW). The hospital has investigated the possibility to expand the hydro-plant to a maximum of 250 kW. Given excess capacity, the hospital could be a private distributor to nearby trading centres, towns and markets for a number of years, until the main grid reaches Kisiizi. However, they will still be using load control to secure the hospital’s electrical demands. The 60 kW turbine will be used as backup for the hospital after some refurbishing.

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The Songea Rural Electrification Project

Background

The Songea Rural Electrification Project is based on the development of a micro hydro-power generation source in Ndolela, Mahanje Ward. A transmission system will connect the source with four villages in Wino ward (Maweso, Matetereka, Wino and Lilondo), and three villages in Mahanje (Mahanje, Madaba, Mkongotema). The total population in the area exceeds 26,000, and the number of households is about 5,000. In total there is an estimated 400 other institutions (domestic, commercial and social). During the coming 10 years the numbers of households is estimated to grow to more than 6,000, and the number of institutions to more than 500. Besides network-connected customers, some of the more remote households, and also the poorer ones, are given the option to be electrified through battery charged system.

Many schools, clinics, and rural community centres lack basic infrastructure such as telecommunications, refrigeration for essential vaccines, and drinking water due to non-existent or poorly functioning electricity supplies.

Power today

Currently, the most dominant energy source in the area is wood fuel. Milling and processing of crops is done using diesel-powered engines, while cooking typically is done with firewood and charcoal. Lighting typically consists of kerosene lamps.

Today the only exploited site in the district is Welela, where catholic missionaries have installed 100 kW mini hydro-power sources, for their own use as well as to a minor extent for serving the public street lights and supply power to a community owned grain mill.

The stone quarry is powered by diesel engines with a total power of 300 kW. Close to Madaba on the Ruhuhu River at Ndolela, the African Plantations

Corporations Ltd owns and operates a 80 kW mini-hydro for coffee irrigation. There are at least 50 milling machines currently run by diesel engines in sizes up to 15

kW. Approximately 60 institutions/private homes in the area have already installed solar

PV systems and rely on battery power.

Future power

The power generation will be located in Ruhuhu River at the Ndolela site. The generation will start at 500 kW and expand to 1000 kW, in this project with a potential to expand to 3000 kW over a long-time perspective.

The number of users is predicted to increase to 1200 after 5 years. In this time the villages of Lutukira, Igawisenga and possibly Ifinga will be considered electrified.

Even if much effort are concentrated around reforming the power sector in many developing countries, strengtening the national utilities and expand access a fundamental fact is that a big portion of the population lives far from the national grids in remote and rural areas.

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In acountry, like e.g. Ethiopia the National Electricity Company (EEPCO) operate a national interconnected system and over 26 Self Contained Systems (SCS). The self contained systems are concentrated around larger centers in the country and these off-grid networks are mainly powered by diesel generators.

In a country like Tanzania, the National utility, TANESCO, in a similar way operates an National Grid and a number of district centers are locally powered by diesel generators. In the town of Kigoma at Lake Tanganyika in the north west corner of Tanzania at the border , 9 diesel engines of approximatel 0.5 MW supply the township of Kigoma and ist approximately 5,000 customers with electricity. The energy supply amounts to 25,000 l diesel per day

An observation from these off-grid applications are that they are based on the same technology as the interconnected system, the comply with national applicable standards and are typically limited by financing means.

1.2 Conclusion

As the examples show there is possible to create small off grid electrical networks, the problem is to find a renewable energy source that can provide the area with electricity, but it also shows the need of load control in order to secure power to hospitals, factories etc. One of the key factors is the number and type of users, and the possibility to use some renewable energy source.

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1.3 Rural Electrification

The main problems with rural electrification are typically described as:

the long distance between the loadcenter and the National electrical grid the low number of consumers/users who (sustainably) can afford electricity the low number of productive (daytime) loads the high cost per connection the lack of financing

One solution to the problem of long distances is to use locally available renewable energy sources, such hydro-plants, solar cells, biomass or wind power generators, and thereby create a local distribution network for the area, which may connect a number of villages.

Characteristics of off-grid networks

In this thesis there are two real rural electric networks described, Kisiizi in Uganda and Kaziba in Congo. Both networks were built to provide hospitals with electricity, but has later expanded to also provide electricity to nearby households, for street lighting and productive users, markets etc. Kaziba has a 125 kW hydro turbine and Kisiizi has one of 60 kW.

Stability, surveillance, service, security, education, backup systems, load control, soft starters?

Today in a contry like e.g. Tanzania, in Sub Sahara Africa, only 1% of the rural population, which constitutes 85% of the total population, has access to electricity. Often the power source at local factories consists of a diesel engine, which is an effective power source but has a negative impact on the environment and is uneconomical in the long run, since prices on fossil fuels such as diesel, petrol, etc. is expensive and will increase with time. The factories that use this type of energy supply can keep these for a power backup if the grid should fail. The power source of a typical household is often a battery that is charged with a diesel engine.

There is today a non-existing service schedule for the equipment that is used; the general idea is to run until it fails and there is no surveillance system that can monitor and alarm the owner. This causes unnecessary downtime in the grid and high service costs. Today in the case of a network failure the whole grid is shut down, resulting in a total power loss. This is costly for factories due to production loss and in many cases disposal of material that cannot be used for its purpose. If there is a grid control system, it is possible to redirect the current, avoiding a lengthy whole-system shutdown while repairs are done, which will minimize the number of disconnected users.

1.4 Rural electrification – based on old and outdated standards

The national utility in Tanzania, TANESCO, normally apply a technical standard for 33 kV and 11 kV medium voltage distribution networks that is similar to the typical European 3-wire design standard (BS 1320). This implies high connection costs for the line extension and many times unnecessary high power transfer capability. Often a network of this type can transfer more than 15 MVA over shorter distances despite tha fact that rural villages seldom require more than 100 kVA.

Cost efficiency requires an optimized network. This will reduce costs for transformers, cables, controlling equipment etc. As spare parts will be available with short notice from manufactures, service will be more efficient.

An advantage with one single standard is that manufactures do not have to produce special items, in worst case a producer may have to get special machines in order to produce the special item. It is also easier to maintain the equipment with standard components because the manufactures knows what parts to keep in stock, if the part is not in stock they can produce it on short notice.

1.5 Experiences from rural electrification

There is rather limited information available of rural electrification and especially of off-grid applications. However, a background can be found in “Rural Electrification”, by Adriaan Zoomers [1]. Other, and more technical information can be found in the ESMAP publication “Mini-grid Design Manual” from the World Bank [2]. More recent information about rural electrification and barriers can be found in another more recent ESMAP study. Xxxxx [3], which include ae country survey, made in Mocambique, Uganda, Tanzania and Zambia

Distribution networks are often built around European standards, like e.g. BS 1320 and comprise of 11, 22 or 33 kV distribution voltage pole and wire systems. Designs are often made with respect to 20-25 year load increase.

Among the many problems reported distribution systems are not only expensive to build but olso expensive to operate and maintain. For planning purpose many National utilites apply a rule of thumb that O&M costs are approximately 2.5% of the invesment cost/km line. In practise it can be much higher due to theft and vandalism.

Many Mini-grid (off-grid) distribution network systems are operated only at low voltage (400V) and control of the system frequency is maintained trough the hydro or diesel generators themselves. Systems in many villages are operated only a few hours daily, essentially due to the costly fuel (petrol, diesel oil etc.). Typically there ar no meters and the consumers pay an equal amoumt to cover the operating costs (the fuel). When generators fail or transformer breaks there is typically no maintenance fund to revert to.

There are ways to implement service schedules in the system to prevent a system crashes and increase the lifespan of the equipment. The diesel that is used can work as UPS and can be controlled and started by remote access so that the factories can operate even during a power down. If a power overload should occur in the network, the systems operator can disconnect a specific load, preventing a total power loss in the grid and perform repair service without shutting down the whole grid.

1.6 Objective and outline of the thesis

Still over 1.5 billion people lives without access to electricity. Despite many initiatives from governments, development institutions, bilateral donors and private entrepreneurs electric connections is not keeping up with population growth in many countries,

The need for information and control of electrical networks in order to gain better reliability, greater efficiency and cost effectiveness is increasing. The systems on the market today are large and able to handle up to 100.000 connections. However, in most applications there are typically less than a few thousand connections. If an industrial system is used it can provide surveillance and control for other applications aside from the grid, such as irrigation pumps, mills, levels in water-tanks, service and maintenance schedules etc.

The thesis will briefly analyze rural off-grid electrification and concentrate on applicability of control technology. The key questions in the thesis are:

What can be done to improve the performance of off-grid rural electrification networks?

How can it be achieved? What implications are like to be expected from control technology?

This thesis is outline as follows: Chapter 2 contain a description of SCADA and Autiomation systems. Chapter 3 discuss what functions can be automated in off-grid networks. Chapter 4 discusses implications of modern control into network control and a hypotetical case is described with its socio-economical analysis. Chapter 5 is summarizing the thesis and outlines the main findings. Chapter 6 contains references. There are two Appendix regarding Automation systems and description of a number of off-grid networks.

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2 Network Control/Montoring and Automation systems2.1 Introduction

Today the increasing demands for profitability set high demands on production units. These demands include increased capacity, operation efficiency, and reduced expenses. In order to meet these demands, the direction of technology is to integrate control systems of several facilities to one operation central. This chapter will describe two different systems: Industrial Automation systems (IA), and SCADA network system. There are similarities and differences between the two, and each system has its advantages and disadvantages. However, both systems demand extensive education of the personnel that will operate and maintain it.

2.2 SCADA systems

The SCADA network system consists of one or several Master Terminal Units (MTU), which controls and monitors a large number of Remote Terminal Units (RTU), designed for large systems such as a national grid. The MTU is generally a PC that operates SCADA management software like Microscada1. RTUs are generally small devices for industrial and outdoor environments, communicating over common protocols such as TC/IP, fieldbus, profibus, etc.

The SCADA network system is not designed to disconnect loads or for energy storage systems like flywheels etc; the general purpose is to monitor substations, circuit breakers and notify if there is a failure. If there is a frequency fluctuation in the grid they compensate it with increasing or decreasing the power, creating stability in the network. They can however disconnect substations if there is a failure or if there is scheduled service that requires disconnection.

Looking at ABB’s Microscada as an example, the RTU would be a COM500 communication server located in the substation from which it communicates with the MTU that operates the SYS500 system server on a PC, called the SYS500 computer. This means that every substation must have a COM500 that communicates with the surveillance equipment mounted in the station, monitoring temperature, in- and outgoing power and circuit breakers.

1 See appendix A1

2.3 Industrial Automation Systems

There are several industrial automation systems on the market today. They are powerful systems for automation and control. Many of them are based on the notion that everything is an object: motors, circuit breakers, transformers, etc, but they can also see a substation as an object, and transformers and breakers as objects within the object. They communicate over standard protocols such as profibus and fieldbus, and may be operated by remote and send alarms through the mobile telephone system by SMS or e-mail directly to a cellular phone.

The industrial automation system used in Fortums district heating plants, ABB’s 800Xa, is described in appendix A2. The programming language used in this system is mainly object-oriented with a variety of user-interface options such as ladder diagrams, sequence list, block diagrams and text lists. This is familiar to PLC programming. It is possible to retrieve information from every object within the system in order to see that everything is running as it should, and also see service schedules, running info etc.

As there will only be a few people with access to the system configuration, this provides the system with security from unwanted tampering.

2.4 Comparison of SCADA and Industrial Automation systems A SCADA system is generally designed to monitor the grid with its components (circuit breakers, substations) and in some cases remote control of substations if they are automated. The power generation often has its own surveillance system. In an Industrial Automation system it is possible to control specific loads and the use of energy storage systems2, and control the power generation all in order to gain an integrated control system.

Since there are no RTUs in an IA system, that are because the signals are being processed by I/O cards, CPU and the software that are located in the operation centre.? In both systems there are service schedules in order to keep the equipment functional and in good shape to prevent breakdown of the grid. Both systems can communicate over common protocols.

The SCADA network system does not require the same real time analysis as the IA system, since the SCADA system main objective is to monitor and control the grid, and the IA system’s main goal is to control an industrial process. There is a difference in the way that the problem is viewed, the SCADA system views it as a network and the IA system views it as a process.

2 These will be considered more specifically in chapter 4

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2.5 The need of communication technology

In order to use these systems, communication is required. The systems can communicate with each other in two ways: over modem or local Area Networks (LAN). The latter is preferable in order to secure the communication between the different stations that are being monitored in real time. This requires that a LAN is integrated in the electrical network when it is planned, otherwise there has to be a telephone line or a possibility to use a wireless system in the stations monitored. There are not large amounts of data sent, but with LAN the problem with a modem that can be disconnected is being less.

There is a need for a server in order to make the different stations communicate with the operators. This does not require the operators to be stationed at every station as it only needs one station of operations, but it will be possible to connect a laptop to every station in order to search for errors and to conduct diagnostics test of the equipment or upgrade the system. Fortum is using a fibre optic LAN for communication between the different stations.

2.6 An Ethernet Network

Prylar…..uppbyggnad

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3.0 Emerging new ideas applicable to Rural Electrification

3.1 What new standards/solutions could possible?

Three stage solution

In Finland they are using a 20/1/0.4 kV system (hänvisning) with a very good result. The boundaries of the 1kV system are defined in the first article of the EU low voltage directive. The basic idea with this system is to provide areas there the population are spread over a large area with smaller losses in the grid. The economical conclusion is that the nr of users and the length of the cables are the key factors. The author’s means that more research are needed within certain fields of 1kV distribution

Figure XX Feeding the residential customers with a) traditional and b) three-stage solution

This figure describes where the system is designed to be used it shows the advantage with it. It is possible to reduce the number of branches and the length of the MV grid. What is the disadvantage? In many cases it is not economical to use this system as an actual part of the low voltage network, and there has to be research done in some areas. But it is a option in sparsely populated areas.

Discuss ABC and XLPE cable solutions (ECA)

Introduce Transfix ideas (from Staffanstorp)

Introduce Voltage Controllers (TSI)

AC/DC system

Ekonomi utrustning……

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4. Applicability of Industrial Control systems for Rural Electrification

4.1 Introduction

Today many rural electric networks are planned and built according to their maximum peak load, (typically predicted 25 year ahead) which may be many times higher than the average and initial load demand. Often the only surveillance equipment is mounted on the generation side (turbines etc), if any control system exists at all except manual control. This causes unnecessary high investment cost.

In an Industrial Automation system, the loads may be precisely controlled in order optimize the distribution network. This control can prevent higher than allowed peak power to be transmitted. To meet a fluctuating power demand, some kind of energy storage devices may instead be installed on the costumer side, and these may be controlled by an automation system.

4.2 Distributed Automation

The main benefit of distributed automation is a reduction of the outage time and the non-delivered energy in case of faults in the network. Creating a service and maintenance schedule would minimize the system’s downtime and the use of diesel engines. This also reduces the cost for repairs on turbines and transformers due to improper maintenance.

Power Flow control

In order to keep the grid stable, the requirement for the system is that it controls the frequency, voltage, current, active and reactive power in both ends in order to measure the power loss in the system and detect short-circuits.

Switching/ fault control

The general idea of automated substations is remote operated switchgear, remote monitored fault indicators and remote monitored short-circuit indicators. The system can communicate with Ethernet, SMS or E-mail through the mobile phone net. Communication will be over Ethernet with the TCP/IP protocol, securing a fast and reliable communication with the systems sensors, CPUs and I/O cards.

System Protection

In order to protect the substation and the transformer inside there will be a surveillance system that monitors the temperature and prevents overheated transformers, which could lead to transformer breakdown and costly replacements and/or repairs. There is a possibility to install web cameras and other surveillance equipment (door sensors) to secure the station from break-ins.

Energy Metering

To prevent theft of power, energy meters will be mounted inside the substation. There will be electrical energy meters that can be monitored by remote access and current limiters. The

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usage will estimated, though there is maximum limit due to the fact that the current limiter has a specific maximum current (1, 2, 5A). It will thus be possible to calculate the power loss in the system as the metering is taking place at both ends.

4.3 Distributed Power Generation / Energy Storage

Energy storage systems can be used to follow load, stabilize voltage and frequency, manage peak loads and improve power quality. There are many ways to store energy in order to meet peak demands on a daily or weekly basis: either on the generation side in the form of extra ponds, or on the user end with fuel cells, flywheels, and different types of batteries or diesel engines, each with its advantages and disadvantages. It is clear that for long storage requirements like for weeks or months, the pond is the best choice. However, for daily load levelling it might be cheaper to use other means that do not require as heavy duty constructions and that have a shorter response time. A hydro-jet has some response time due to the fall of the water in the penstock and the start of the turbine.

If energy storage on the user side is implemented, the MV grid design can be optimized, since the cable on the MV net does not need to be oversized in order to meet the load peaks but may be dimensioned for an average load demand. Coupled with advanced power electronics, storage systems can reduce harmonic distortions and eliminate voltage sags and surges.

4.4 Load Management / Demand Side Management

In order to maintain grid optimization there is a need for load control to keep the network stable. This can be done with Distributed Intelligent Load Controllers (DILC), power providers (see appendix A3.2 for example) and/or distributed automation systems. With these devices it is possible to prioritize certain connections, such as hospitals, radio stations, police posts etc., and create load scheduling systems for grain mills and battery chargers in order to prevent sudden power surges, making the network instable due to frequency and voltage drops which is a result of too many loads starting at once.

To prevent power surges in the grid when large loads start up their motors (for example see appendix A 3.3), control equipment is required. One way to prevent large power drops is to install soft starters, which minimizes voltage drop during start up at the cost of a later achievement of maximum torque than with a conventional starter.

The mills that are connected to the grid could have a system that prevents all mills from starting at the same time. The queue will have the form of a signal system that indicates when the mill can start. In order to do this, the system will be defined to only start a specific number of mills based on a load calculation that defines a maximum load schedule.

4.5 Surveillance and Safety Monitoring

There is a possibility to offer security surveillance of industrial areas, mobile phone stations, shops, offices etc., as well as monitoring water tanks, environment parameters like

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temperature and moisture in order to optimize e.g. irrigation, thus avoiding most of the water that is being used for irrigation evaporating.

4.6 Auxiliary Process Control functions

Intelligent functions integrated in components in the station.

Adaptation to two-way communication in order to exchange information and control between the control centres and the stations. Remote surveillance of the consumers’ electrical meters.Real-time control of the grid using fibre-optic LAN.Optimized grid construction resulting in a cost-efficient networkPossibilities to offer automation and control of factories, engines and manufacturing processes in real time.Security surveillance of crucial places and transformers, temperature and circuit breakers where the local energy company can control the grid by remote access through the Internet.Disconnecting loads at a frequency change in order to maintain network stability.Control of turbine RPMs to avoid drastic increases in speed which may damage the ball bearings, etc., leading to high repair costs.Control of start sequences in factories by starting motors in sequences instead of all motors at the same time, and using soft starters in order to minimize the power spikes that occur during start-up.

5 A “hypotetical” off-grid network in Kasulu

Background

Kasulu is the main “village”, but the idea of the project is to electrify the near-by villages of Tulieni, Herujuu, Kabanga and Kihabwa in order to be cost-efficient. In this case there are no large loads like in Wino with its stone quarry and livestock institute, but there are several mills, a hospital, about 170 stores, hotels and bars as well as 445,000 inhabitants in the area. The power source is a hydro plant located in the Mwoga River. The main objective is to control the hydro plant in order to secure power to the hospital and diocese of Kasulu, preventing vaccines and medication from being destroyed due to lack of refrigeration for a long period of time. If there is a diesel power source in the hospital, it will be used as UPS and should be controlled by remote from the control centre and directly from the hospital in order to secure the electric power.

Power Generation today

Today the village of Kasulu does not have a continuous power supply. The installations that are known are:

Diesel generators at the Teachers Training College (TTC) provide power for about four hours a day to the College and a few other consumers.

A pilot plant for the collection of methane from a digester alongside a dairy at the TTC. The methane plant forms part of an integrated operation. Dung from the dairy is fed into the digester. Methane is collected from the digester, while digested dung is

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removed, dried and used to fertilise vegetable gardens. Methane from the digester is mixed with diesel and used to generate electricity.

A diesel generator at St Augustines Spiritual and Pastoral centre is run for three hours a day to provide lightning.

A run of river hydro-power installation has been installed in order to provide power to the Mission Station and Hospital at Kabanga, about 10km from the Mwoga site. This is however unable to provide power to other consumers when the flow in the river is too low.

Future source of power generation

The river has the following potential for power generation:

150 kW during the dry season, when the river flow is estimated to be about 0.1 m3/s. Peak generation of 300 kW when the flow in the river is about 0.2m3/s, or when

sufficient storage is available in the waterways.

The power generation source proposed is two turbines with a diesel as a backup system for load peaks. There is a need for a head pond in order to store water for a four-hour load peak. The period over which peak generation can occur will become shorter as the flow in the river approaches 0.1 m3/s, the design flow for one turbine. At flows of 0.1 m3/s or less, it will be possible to run only one turbine continuously. Should the flow fall below about 0.08 m3/s, it will no longer be possible to generate at full capacity and it will only be possible to supply reduced demand below 150 kW. This will occur during particularly dry periods when the flow in the river is low. The turbines proposed are two Pelton turbines with a total capacity of 334 kW.

The grid design

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6 Technical and Socio-economical Implications of using control technology in off-grid networks

Introducing modern control technology in off-grid networks could imply different benefits to the local utility and the customers. This section will differentiate the benefits and analyze some of the potential technical and socio-economical benefits.

SCADA network systems are currently becoming more integrated and therefore now looks more like Industrial Automation systems, but still with the difference in the type of communication with the monitored devices. SCADA network systems normally use MTUs and RTUs for surveillance. With an Industrial Automation system, the network must be considered a “process”, like a modern manufacturing industry, such as an oil refinery, mining, pharmaceutical or paper industry. These systems can be very complex and places demands on the operator’s expertise. They have to understand a large number of operation situations and how these interact with other systems.

6.1 Benefits to the utility

The level of education for the staff will vary, but everyone needs to understand the basics of the system, both the software and the hardware, in order to maintain the grid stability and avoid unnecessary downtime. They will also need to be able to prioritize the alarms that occur in order to see which failure that caused the alarm. As an example, if the generation goes down, the alarm will go off on both the generation side and in the substation because the power demand will exceed the supply and an overload of the transformer could occur. Here they will need to see which alarm is the most critical and take action at the right place.

One difference between the systems is the way in which the system is configured from the beginning. The Industrial Automations system 800xA is more user friendly with graphical interface and uses more predefined libraries, while a Microscada typically uses a high level language (SCIL) for its setup and control. Another difference is the operating system used in the computers. 800xA uses Windows XP pro or Windows 2000, while Microscada uses Windows NT or NT server. (Windows XP pro is to prefer, since most computers that are sold today have this operative system preinstalled.)

6.2 Benefits to the customers

The IA systems are designed to be cost-efficient for the company in terms of production capacity, minimized unwanted downtime and reduction of the number of bottlenecks in the production line. Where the SCADA Network system’s main design is to monitor an electrical network, this does not require the same real time analysis since the circuit breakers only have two indications: on or off. It is also possible to integrate a security system in the IA system in the form of web cameras and/or breakers in doors or windows and let it monitor the areas that need security surveillance.

In the IA system it is possible to simulate different aspects of the process. This is useful, particularly during training of the staff, testing upgrades and different scenarios that may occur. It is also possible to view maintenance history, available spare-parts etc.

6.3 Technical and Socio-Economical analysis

Xx

EducationOwnership

Profit

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7. Summary and Conclusions

7.1 Summary

Since they do not have access to the national electrical grid, they must rely on the local grid to provide electricity. Since these are small electrical networks with limited power sources, it is crucial that the grid is stable even during power peaks that occur when large machines start up.

In small rural grids a large system is not required, but there is still a need to control and monitor even a small grid. The maintenance is scheduled at suitable times with minimum down time, creating a service that prevents equipment failure due to lack of maintenance. There is also a need for control of large loads such as mills, stone quarries, water pumps etc. In this case the local power company can provide them with that possibility of control system for there motors all in order to optimize the grid.???

There is also a need for security surveillance in substations, factories etc in order to prevent tampering or theft of equipment. It is also possible to offer local industries automation of their manufacturing processes. This can be done with an IA system.

7.2 Conclusions

xx

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8. References

ABB (2002) Introduction to Microscada Technology, Product guide

Arvidson A, Forslund H, Kjellström B, Martinac I, (2005) Renewable Energy Technologies for Decentralised Rural Electricity Services, Stockholm Environment Institute

Bak-Jensen J, Jorgensen H J, (2004) Practical implementation of distribution automation

Bergman S, Davies I, (2005) Mainstreaming low cost innovation in electric distribution networks. Analysis for SIDA

Bergman S, StonePower AB; private communication

Björklund T, Råberg M,(2004) Model based monitor functions for safer and more efficient of remotely operated plants, Värmeforsk service AB Stockholm

Cegrell T, (1986) Power system control technology, Prentice-Hall. Cambridge

Cory B.J, Weedy B.M, (1998), Electric Power Systems, John Wiley & Sons Ltd. Chichester.Dec G, Fortum AB

ESMAP, (1999) Mini-Grid Design Manual, The International Bank for Reconstruction and Development/ The World Bank Washington, D.C

Gaunt C T, (2003) Electrification technology and processes to meet economic and social objectives in Southern Africa, Department of electrical engineering University of Cape Town

Jonsson B.V, ABB Automation Technologies AB.

Jonsson M, ABB Automation Technologies AB.

Kaipia T, Lassila J, Lohjala J, Partanen, (2005) Overview to economical effeiciency of 1000v low voltage distribution systems

Lembke T (2003), Distributed local energy storage options to reduce power generation, transmission and distribution costs in two proposed off grid systems in Tanzania, Uppsala

Malhães da Silva J, (1999) The Challenge of Rural Energy Poverty in Developing Countries, World Energy Council, London

Matthews T, (2002) Kisiizi Hospital: A Distributed Intelligent Load Management Solution

Ninham Shand Consulting services, (2002) Mwoga Hydro Feasibility study

Wino Development Association/ Stonepower AB, (2005) The Songea Rural Electrification Project a proposal

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9. Acknowledgment

I would like to thank the following persons:

Sten Bergman, who gave the background and theme and for giving me the opportunity to do a very interesting bachelor thesis. Ylva Bergman for extensive help in editing my “poor english”. My girlfriend Åsa, for pushing me to do this, since I did not really have a good excuse not to and last but not least to my friend Dag Nyström, who called me a fool for not doing it earlier.

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Appendices A1: Study of Distribution SCADA networks based on ABB’s Microscada

Introduction

Microscada is a microcomputer-based scada system, meaning that it runs on every commercial computer. The main purposes of the Microscada systems are: substation automation for power transmission and distributed automation, and network control and distribution management systems for power distribution. The system can be seen as a network where the control system can communicate with widely distributed processes through a communication system. Different product families can be used together, some products require other Microscada products and some can be used alone (e.g. COM 500 and SYS 500).

Basic system hardware design

A basic SCADA system based on Microscada will use COM 500 with a PC as a Remote Terminal Unit (RTU). The Master Terminal Unit (MTU) may be a stationary PC or a Laptop used as a remote workstation. The RTU will be located on the substation in order to monitor the automation system and protection relays. There will also be a COM 530 for communication between the systems’ different RTUs.

Programming in Microscada

The language used in Microscada is called SCIL (Supervisory Control Implementation Language). This is a high-level language like C or C++, and the programs are created in the

SCIL editor. Like most other programs, SCIL includes features such as variable assignments, arithmetics, conditions, block structure, case statements, loops etc. The commands consists of:

Commands (e.g. !SHOW, #SET, #ON) Objects (e.g. process objects) Expressions (e.g. TIMES, SECOND, CLOCK) Variables (e.g. @variable, %variable) Names (e.g. picture- and dialog names)

There is also a large number of predefined functions for various types of data processing for example:

Arithmetical functions Time functions Database functions File handling functions

The environment is object-based. An object is a programmable entity that represents something. In Microscada, an object may represent process units, system functions or SCIL programs. Objects are defined by their attributes. System objects are programmable units that define the configuration and communication in a Microscada system. There are two different types of system objects: base system objects and communication system objects. These objects define the system configuration together with the PC-NET unit configuration data, with SCIL, system objects are accessed through their attributes. An attribute describes object values, functions, properties and activities. Normally, an object has many different attributes; of which each may be defined with SCIL.

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A2: Case study of Industrial Automation systems ABB 800xA

Fortum’s district heating system in Stockholm

Background

Fortum’s 10 power stations in Stockholm are using the 800xA with some other older systems in its power plant for the water that is being used for district heating. From their location in Märsta, they may by remote access control the district heating grid in western Stockholm. They can control every power plant that is connected to their system as well as pumps, valves etc. From the system, they receive information from every piece of equipment able to send it.

The system operators may by watching their monitors decide on appropriate actions in the case of failure. Processes that are critical to perform, for example shut down or start up of a turbine which demands that certain procedures are done in the right order to avoid unnecessary failure of the turbine at a high cost for the company, is done by the system.

The remote access provides a very efficient use of the power plants within the system. Depending on the outdoor temperature, they decide on how many plants that will provide hot water to the households. This is very cost efficient, as if there is a very high temperature outside, they are able to let one single plant distribute the hot water in the system. This also reduces the negative effects on the environment. It also minimizes the surveillance staff of the system as they may monitor it from one location. It also provides them with live video footage for certain processes, for example the drive belt for fuel to the boilers. System design

The sites in the system all use AC800M with I/O cards to communicate with the system through a fibre optic network. All sites have their own workstations, however these may be overridden by the main system in Märsta. The operative system is mainly Windows XP, but there are some computers with Windows2000 and one Citrix server.

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The system has personalized workspaces for different users:

Operators: An environment allowing for safe system running. Operations Managers: Gives information about uptime, downtime, production and

maintenance costs. Engineers: Allows for performing changes in the system with minimized downtime. Maintenance Personnel: Information to ensure maximum availability to the network.

Upgrade and system service

In order to maintain the system there are computers for engineering where the operators may simulate the upgrades and/or service packages to the system before using it. In order to do this, the memory in the CPU must be at least twice the size of the program. This is however not a problem, since the programs are generally small and the system is designed for this kind of action.

Simulation within the 800 xA system

Typically, only portions of the running plant are included in a simulator’s scope. The Transformation Tool is used for defining the parts of the plant that will be simulated.Automated transfer of control definitions from plant controllers makes the simulator system easy to maintain. Re-transformation after plant modifications supports reuse of transfer configurations in earlier project phases.

Lifecycle simulator

Industrial IT Training Simulators are an integral part of a cost-effective, comprehensive program for all phases of the plant lifecycle by combining operator and maintenance training, control logic development, testing and validation, operator validation, and plant optimization studies into one system.

Runtime simulator functions

Operation of the simulator is performed via the instructor’s station, where the instructor can initiate specific simulator functions including: freeze and resume of control execution, save and load process conditions, set process speed, and simulate process malfunctions.

Maintenance

System 800xA maintenance management features make information within the CMMS (Computerized Maintenance Management System), for example MRO Maximo® andSAP PM®, transparently accessible to users in both the process control and maintenance system environments. Seamless context-sensitive interaction is provided through standard System 800xA CMMS displays, such as active work orders, work order history, preventive maintenance schedules, and available spare parts. When an equipment maintenance condition is detected, work orders are automatically submitted to the CMMS. Work orders required for calibration procedures are submitted to the CMMS, and then automatically populated in the DMS Action List, thus initiating the calibration activity. With these features, System 800xA

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optimizes the work process and significantly reduces the latent time between problem identification and resolution.

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