Training Report

Industrial Training Report

Preface This Industrial Training Report is prepared after completion of 23 weeks of Industrial training at Hemas Power PLC., Ceylon electricity Board and Lanka Electricity Company (Pvt.) Ltd. Completion of 22 weeks Industrial Training is compulsory for the award of the Degree of the Bachelor of Science in Engineering from the University of Moratuwa, Sri Lanka and it is conducted after the completion of level 3 semesters 1. Industrial Training program was carried out by the National Apprentice and Industrial Training Authority (NAITA) in collaboration with the Training Division of the University of Moratuwa. This report contained with my experiences and knowledge I gathered during my training period from 15/02/2010 to 23/07/2010. Chapter 1 is included with introduction of my three training places. And chapter 2 is included with my experiences which are learned during my training. And finally Chapter 3 is conclusion which gives a summary about the training.

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Acknowledgement I grant my gratitude to all who helped me to get a proper training. I should thank to NAITA and Industrial Training Division for conducting an Industrial Training Program with this success. Furthermore, I should thank to the Department of Electrical Engineering for restructuring the training program for this worth, collaborating with the Industrial Training Division. And also I thank Mr. Kishan Nanayakkara, who is the managing director of Hemas Power Plc. for preparing us the opportunity to have training in Hemas Power, and Mr. Krishantha Wimalasiri for presenting the helping hand when we were in an ocean of unknown. I thank to all the staff members in Hemas Power for helping me on gathering the knowledge of their fields. Special thanks to Dr. Narendra de Silva for offering us the opportunity to have training in LECO. And I grant my gratitude to all the engineers in System Development Division, System Operations, and Nugegoda Branch Office. Furthermore, I thank to the staff in Ekala meter repairing and testing lab and Transformer repairing lab, and Boralasgaamuwa Customer service Center. My special thanks to Mr. Buddhadasa, electrical engineer in internal training for preparing a training opportunity in CEB. And I should give my gratitude to Mrs. Mendis, who is the DGM of Other Hydro Complex, for giving us the chance to be in S’wawa power station and gather knowledge. And also thankful to all the chief engineers in Transmission, Operation and Maintenance, Samanalawewa Power Station, Kalanithissa Power Station and Kalanithissa Combined Cycle Power Plant, Generation Planning Branch and System Control Center. And also I thank to the engineers and other staff members in CEB, who helped us sharing their knowledge.

S. R. M. D. T. S. Wijesekara Department of Electrical Engineer Faculty of Engineering University of Moratuwa. S R M D T S WIJESEKARA | 070549D

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Content Preface.........................................................................................................................................i Acknowledgement.....................................................................................................................ii Content......................................................................................................................................iii List of Figures............................................................................................................................v List of Tables.............................................................................................................................vi Introduction.........................................................................................................................vii 1.1 Hemas power.................................................................................................................viii 1.1.1 Organizational Structure...........................................................................................ix 1.1.2 Strength.....................................................................................................................ix 1.1.3 Weaknesses...............................................................................................................ix 1.1.4 Profitability...............................................................................................................ix 1.1.5 Usefulness to society..................................................................................................x 1.2 Ceylon Electricity Board..................................................................................................x 1.2.1 Vision.........................................................................................................................x 1.2.2 Mission.......................................................................................................................x 1.2.3 Present Performances of CEB....................................................................................x 1.2.4 Strength of the CEB..................................................................................................xi 1.2.5 Weaknesses of CEB..................................................................................................xi 1.2.6 Profitability...............................................................................................................xi 1.2.7 Usefulness to the society...........................................................................................xi 1.3 Lanka Electricity Company............................................................................................xii 1.3.1 Organizational structure.........................................................................................xiii 1.3.2 Present performance...............................................................................................xiii 1.3.3 Profitability.............................................................................................................xiii 1.3.4 Strength of the company.........................................................................................xiii 1.3.5 Weaknesses of the company...................................................................................xiii S R M D T S WIJESEKARA | 070549D

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Training Experience...........................................................................................................xiv 1.4 Hemas power..................................................................................................................xv 1.4.1 Hemas building power system.................................................................................xv 1.4.2 Mini Hydro Plants................................................................................................xviii 1.4.3 Designing a mini hydro plant..................................................................................xxi 1.4.4 Trash rack design..................................................................................................xxvi 1.4.5 Financial Structure of a company and evaluation for acquire a company...........xxvii 1.4.6 Gidddawa mini hydro power plant.....................................................................xxviii 1.4.7 Maintenance schedule..............................................................................................35 1.5 Ceylon Electricity Board................................................................................................36 1.5.1 Hydro Power Generation – Samanalawawa Power Station.....................................36 1.5.2 Kalanithissa Power Station & Kalanithissa Combine Cycle Power Plant...............41 1.5.3 Transmission Operation and Maintenance Branch..................................................44 1.5.4 System Control Centre ............................................................................................47 1.5.5 Generation Planning.................................................................................................50 1.6 LECO..............................................................................................................................55 1.6.1 System Development Division................................................................................56 1.6.2 System Operations ..................................................................................................58 1.6.3 Branch Office...........................................................................................................61 1.6.4 Customer Service Center (Depot)............................................................................63 Conclusion............................................................................................................................65 Annexes ...................................................................................................................................68 Annex 1 – MATLAB Program on flow duration curve......................................................69 Annex 2 – MATLAB Program on turbine selection-1........................................................70 Annex 3 – MATLAB Program on turbine selection-2........................................................71 Annex 4 – Trash rack design...............................................................................................72 Annex 5 – Teamwork workshop certificate.........................................................................73 Annex 6 – Maintenance schedule........................................................................................74


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List of Figures Figure 1.1-1 - staff of the Hemas Power PLC...........................................................................ix Figure 1.3-2- LECO Distribution Areas..................................................................................xii Figure 1.3-3 - LECO Organizational Structure........................................................................xii Figure 2.1-4 - Power system of Hemas building.....................................................................xvi Figure 2.1-5.............................................................................................................................xix Figure 2.2-6 - Annual Hydrograph........................................................................................xxii Figure 2.2-7 - Flow Duration Curve......................................................................................xxii Figure 2.2-8 - Turbine Efficiency Curve...............................................................................xxiv Figure 2.2-9 Turbine Selection Chart....................................................................................xxiv Figure 2.5-10 - Waterway of Giddawa MHP........................................................................xxix Figure 2.5-11 - Electrical System of Giddawa MHP.............................................................xxx


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List of Tables Table 2.1-1 - Hemas Building Electricity Expenditures........................................................xvii Table 2.6-2.1 - CEB training schedule * the LECO period. Not relevant to this section......36 Table 3.5-3.1 - LECO training Schedule..................................................................................55


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Introduction


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1.1 Hemas power Hemas Power PLC is a strategic investment company, which invests in power sector, generation area. The company is a sub company of Hemas Holdings PLC and functions as the holding company of the group’s power sector investments. The company has currently invested in one thermal power plant and three mini hydro power plants. The company was formed in 2003 and public listed some time after Hemas Holdings was public listed. Currently, 75% of the capital of the company is owned by Hemas Holdings and remain 25% are issued as the public shares. The price of the share on Hemas Power is about 23.00 LKR currently. Hemas Power invested in Heladanavi 100MW thermal power plant as the first invested project. In this project, 15% of the capital was invested by Hemas Power and another 15% was by Lakdanavi Ltd. The rest 70% was collected as loans. Te capital cost of the plant was 6.2M LKR. Currently 50% of the voting shares are owned by Hemas Power. The operations and maintenances are conducted by Lakdanave Ltd, who is the operation and maintenance contractor of the plant. The plant was commissioned in 2004. The unit cost of the plant is about 16 to 18LKR. As the second project and as the first renewable energy project of hemas power, Giddawa Hydro Power was established. It was located in Giddawa, Theldeniya in Kandy district. From the feasibility to the operation all the procedures in this plant, was done by the Hemas Power. The plant was registered as Giddawa Hydro Power. More details about this project will be discussed in later chapters. As the third project the Magal Ganga Small Hydropower plant was set up. The prefeasibility and feasibility studies were done by Okanda Power Grid (Pvt.) Ltd. The documents were acquired by Hemas Power in the feasibility stage. The plant is located at S R M D T S WIJESEKARA | 070549D

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Daraniyagala in the Kegalle District and it is fed from the river Magal Ganga. The capacity of the plant is 2.4MW. The power plant is supposed to be commissioned in 2011. The Senok Mark Hydro power plant which is located at Lindula, Thalawakale was acquired by Hemas power in operation level. The capacity of the power plant is 2.6MW. And the power plant is fed from Agra Oya.

1.1.1 Organizational Structure

The company is acted as a sub-company of Hemas holdings as said

above.

The

organizational

structure could be shown as figure 1.1. Currently Electrical Engineer and

Mechanical

Engineer

are

Figure 1.1-1 - staff of the Hemas Power PLC.

working as the project managers. The complete staff is about 60 personals with the project staff who are working in the project sites. 1.1.2 Strength

Hemas power achieved to more than Rs.5 billion as the annual revenue with a minimum number of staff like 60. And also, the staffs in the plants as well as in the managerial level are very much loved to the company and the power plants. Having such a staff is the greatest strength the Hemas Power have. 1.1.3 Weaknesses

Even though the staff is very much love to the company, the employees in the lower levels like labors are leaving the company due to the insufficiency of the salary. This is an improper management practice. Through this the lack of the sufficient staff to the power plants could be occurred. 1.1.4 Profitability

When considering the power generation, the renewable power generation is an extremely profitable field. Because, the electricity is classified as an essential item and the foul cost in renewable plants are very low. Due to that reason the company is in a stable financial state.


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Industrial Training Report 1.1.5 Usefulness to society

In a time, which the country is facing a relatively downcast financial state, and spending a high price to the thermal energy, invest and encourage the renewable power sector could be considered as a great service to the country. And also, the company always tries to help to the people who are living nearby the plant area.

1.2 Ceylon Electricity Board Ceylon Electricity Board, which is commonly known as the CEB was established by the Ceylon Electricity Board act in 1969 under the Ministry of Irrigation and Power. Later on, the CEB was transferred to the Ministry of energy and power. Currently this institute is governed by the Ceylon Electricity Board act 1969 and Sri Lanka Electricity act 2009. The CEB has divided into three divisions; Generation, transmission and Distribution. Currently, the license for generation and distribution are issued for IPPs as well as the CEB and CEB is the only one who is having the license for transmission. 1.2.1 Vision

“Be an internationally recognized efficient utility providing high quality service to all its stakeholders.” 1.2.2 Mission

“To provide reliable quality electricity to the entire nation at internationally competitive prices effectively and efficiently through a meaningful partnership with skilled and motivated employees using appropriate state-of-the-art technology for the socio economic development of the country in an economically sustainable manner while meeting acceptable environment standards”. 1.2.3 Present Performances of CEB

CEB is the largest organization related to the power sector in Sri Lanka and the main controller of the power sector. 74% of the installed capacity in Sri Lanka is owned by CEB. And the current total capacity which is owned by CEB is about 1902.1MW. And also, it serves more than 90% of area in Sri Lanka through the transmission and distribution lines owned by CEB. Due to the large size and the complexity of the organization, even though the organizational structure is well structured, the management had become a problem. There are S R M D T S WIJESEKARA | 070549D

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many inefficiency in CEB and it was categorized as an institute, run in a loss state. To overcome this problem and to generate reliable operation out of CEB, a restructuring for CEB was proposed. According to that, the CEB is supposed to divide into three individual sectors and privatize them was proposed. But, due to the criticisms of the trade unions, the proposal was failed from the parliament. 1.2.4 Strength of the CEB

The assets, which is owned by CEB is about billions of rupees. Due to that asserts it keeps the control over the power sector in Sri Lanka. And also, it is having the all three license for Generation, Transmission and Distribution. Furthermore, the only licensee of transmission is CEB. This makes CEB, the most powerful institute in power sector. 1.2.5 Weaknesses of CEB

CEB is an organization which is operated under the Sri Lanka Government. So the rights of the employees are significantly strong. So the employees, who are not taking a part of the critical decision makings and the critical issues, are acted in an unproductive manner. This makes CEB a loss counting organization. And also, because of CEB is operated under the government, some important decisions like building plants are taken through the government. So the control of the CEB is gone out of its hand, sometimes to the people who are not having the proper understanding of the field’s important areas. This makes the operation difficult to CEB. 1.2.6 Profitability

As said above, the CEB is conducted under huge losses. This had made the organization unprofitable. Proposals to improve the profitability had come out time to time. But due to some reasons, these attempts have been restrained. 1.2.7 Usefulness to the society

The electricity, as said above, is an essential service. Manipulating such a sector in a reliable manner is a great social service to the country. Even though the distribution ends are having come problems, as a macro scale picture, CEB provides a quality vice very good service through the generation, transmission and satisfactory service through distribution. The staff in key positions of the institute are always try to conduct a safe and reliable service to the country. As an example, the number of blackouts is minimum and the voltages in the transmission ends are usually kept within the range.


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1.3 Lanka Electricity Company. Lanka Electricity Company, commonly known as LECO is an electricity distribution company. This company is the only company which is having the power distribution license instead of CEB. The LECO distribution areas are extended from Negombo to Galle, in the west coastal area of the island. LECO was established in 1983, as a solution for the inefficient electricity supply in above mentioned areas. Before 1983, the electricity distribution of these areas was controlled by the local authorities. By considering the inefficiencies, the government decided to establish a private company for the electricity distribution. Then LECO established, but the full ownership of the company is belonged to the Government authorities. 15% of the electricity distribution is owned by LECO. For the administration simplicity, the LECO distribution network is divided into seven branches. They are Negambo, Kelaniya, Kotte, Nugegoda, Moratuwa, Kaluthara and Galle respectively. There is a LECO training school is established in Ekala. Each branch is consists several depots. And the staff is about 1500 personals. Currently LECO is operating is 39 local Government areas and over 500,000 consumers are having the service of Figure 1.3-2- LECO Distribution Areas

LECO.

LECO purchases the electricity from the primary substations as 11kV power. Then it distributes as 11kV high voltage for bulk consumers and 400V low voltage power.


Figure 1.3-3 - LECO Organizational Structure

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Industrial Training Report 1.3.1 Organizational structure

The LECO organizational structure could be shown as figure 1.2

1.3.2 Present performance

LECO maintains the distribution network in a good state. The distribution losses are kept below 6% while the distribution loss in CEB is having higher value like 14%. Furthermore, LECO maintains a GPS based geographical information system, which helps LECO in asset management in a highly accurate manner. LECO always tries to gather the new technology to the Sri Lankan power distribution area. Currently, LECO has invested in a meter production factory in Bandaragama. The projects like net-metering and broadband service via power lines could be taken as the future steps, willing to be taken by LECO. 1.3.3 Profitability

As said above, LECO maintains the network in a loss-minimum manner. This makes the company loss reduced profitable one. Furthermore, the components used in the LECO distribution network, prevents stalling the electricity in a higher degree. The distribution business is operated under a tariff system. So the profits should be gained mainly by reducing the losses and maintaining the network in a good condition. 1.3.4 Strength of the company

The company is having a well structured, technological system to maintain the network. So supplying a quality vice good service has become simple. Furthermore LECO areas are having a high density of consumers. This has become an extra profit to LECO. 1.3.5 Weaknesses of the company

The interconnection between the employee levels of the company has become minimum. So the disagreement between the managerial level and the other employee levels are occurred. This might caused to the reduction of the satisfactory of the employees.


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Training Experience


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1.4 Hemas power 1.4.1 Hemas building power system.

As our first assignment, we were assigned to analyze the power system of the Hemas building, Colombo. The building was locates adjacent to the Bristol street and York street itself, and the workplaces are located facing the both streets and the corridors inside the building in upper floors. Eusifully Trust, the owner of the company, conducts all the maintenances of the building including provide the requirements like electricity, water, maintain the buildings systems etc. It charges for the services from the residents. Hemas holdings and Eusifully trust are shareholders of each other. The building was constructed about 50 years ago and since then Hemas has resident it. In understanding the electrical system of the Hemas building, as our first step, we went to meet Mr. Jeffry Mohomad, who was the manager of Eusifully trust. He and Mr. Piyasiri, a maintainer of the electrical system, helped us on understanding the electrical system. The power system of the Hemas building could be divided into two, the main power system and the alternative system. The main power system is containing a 1000kVA transformer, a bus bar, metering gauge units and main switches. The power is taken from CEB as 11kV to the transformer. Then the electricity is transformed to 400v and taken to a bus bar. The residents in Hemas building could have the postal address belong to either Bristol Street or York Street. Due to these two kinds of addresses, the power distribution system in the building is too divided into two sections; Bristol street side and York street side. Through the above bus bar, the power is divided to above sections. Those section lines are then connected to another two bus bars, through metering units and main switches. As the alternative power system, a 640kVA diesel generator is placed. The generator is connected to a different bus bar through switching units.


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Then the main and alternative systems are joined together to supply the power to consumers. Each feeder in the main lines busses are joined with a feeder from generator bus bar through changeover switches and connected to the consumer through metering units. The system could have optimized if the alternative system joined with the main lines before the distribution bus bars. This will reduce the cost for individual changeover switches and reduces the respond time. It improves the performance of the system. We observed the main control room. The bus bars were double bus bars and the meters were digital meters, which

were

measuring

capable

the

of

maximum

demand. In addition, there are two

measuring

instruments,

which are capable of measuring the power factors, Voltages, Currents active

and

powers

reactive for

and

separate

phases. In order to improve the power quality those parameters were measured. We

observed

the

generator too. It is a diesel generator, which an engine runs as the prime mover. It had the following characteristics.

Figure 2.1-4 - Power system of Hemas building

Prime mover speed –

1500rpm

Rated Power -

512kW

565kW (stand by)

640kVA

706kVA (stand by)

924A

1019A (stand by)

Rated Current


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The generator is maintained by Trade Promoters Ltd. Sri Lanka. The CEB prepares two separate bills to the two sides of the building. The billing details relevant to December 2009 are given below. Table 2.1-1 - Hemas Building Electricity Expenditures

For Bristol street kWh 57900 kVA 242 Total

Cost – Rs 700902 181500 882402

For York Street kWh 35371 kVA 202 Total Total

Cost – Rs 488119.80 151500 639619.80 1522021.80

This amount is divided among the consumers according to their usage. Eusifully Trust staff does this billing. Energy meters belong to each consumer is placed in the control room. According to the above data, Eusifully Trust pays about 333,000 LKR for the reactive power. And also the power factor of the building is about 0.2 due to the usage of the air conditions and florescent lamps. We took the readings of the power factor. To save that expenditure and improve the system performance, it is willing to install a capacitor bank in the building. We met Mr. Lalith Athugoda, who has a contract about the improvements of the building electrical system on this matter. According to his calculations about 1 million LKR will be spent to install the capacitor bank. Through this the power factor could be improved up to 0.85. The cost for the installation of the capacitor bank could be recovered within 2 years and the profits could be gained from the third year. The capacitor bank is scheduled to install in 2011. On the third day of the training we were attend to a trip switch testing of the building, which is conducted to improve the safety of the building. The testing is scheduled for once three months. We attend to the tests with Mr. Vajira. There are three tests were done in the testing procedure; No-trip, rated trip and fast trip. It uses an instrument called RCCB digital tester to conduct the tests, which facilitates to all above tests. As the first step of the testing procedure, the power is cut off from the main switch. Then the tester is attached to the bus bars. Then, for the given currents, the respond time of the trip switch is checked. In no-trip the trip switch should not operate and in the fast trip test the trip switch should operate immediately.


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In the beginning of the 2nd week, we presented a presentation about the electrical system of hemas building.

1.4.2 Mini Hydro Plants

We learnt about the mini hydro plants in the first week onward. The hydro plants, which the power generation is below 10MW and above 1MW, are roughly categorized into the category, Mini Hydro Plants. This kind of power plants is generally considered as a most cost effective and reliable power producing power plants. Because, • Mini hydro power plant uses the kinetic energy of the flowing water to produce the power. Therefore, the fuel cost for this kind of plant is nil. And also the source is renewable. Therefore, the risk of lacking the fuel is minimum. • This kind of pants are not releases the green house gasses or any kind of hazarders gas. This will improve the environmental friendliness. • In hydro power plants, the efficiency is high (about 70%-90%) relative to the other power producing technologies. • The power of the power plant varies with the water flow of the river. The water flow varies with the annual rainfall. Therefore, the predictability of this kind of power plants is high relative to the other renewable power producing technologies. • The water flow of a river varies slowly in most cases. So, the power output

varies slowly. Therefore, the power output is said to be stable in this kid of power plants. So, the reliability is relatively above to the other renewable power producing technologies. And also, the plant could be designed to meet a higher plant factor. In hydro power plants, the power is generated using the kinetic energy of a water flow. This energy could be mentioned using the head and flow terms P=ρgQH By including the efficiency, the power output could be presented. P=ηρgQH S R M D T S WIJESEKARA | 070549D

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Therefore, the parameters of the hydropower generation are head (H), Flow (Q) and Efficiency (η). By matching those parameters in an appropriate power generating technology, the mini hydro plants are designed. The structure of a mini hydro scheme is slightly different from the other hydro plants. In most cases, these power plants are run-off-river type. That means the water storage of this kind of scheme is minimum. A mini hydro plant could be designed to either divert the water flow and run the plant or construct the plant in the river. Canal and penstock type could be taken as an example for the diversion type and Barrage type and Syppen type could be taken for the non-Diversion type. When there is a sufficient head, the diversion type is used. Construction in this type is relatively easier than the non-Diversion type. In Sri Lanka, because of the commonness of the sites, diversion type mini hydro plants are common. All the mini hydro plants belong to Hemas Power are Diversion type. The components of the mini hydro plant A sketch of a waterway of a mini hydro plant is shown in fig 2.1. •

Weir – The water flowing in the river is collected to a small reservoir

•

Inlet – the water collected in the reservoir is diverted to the channel. In most of the times, there is a gate to control the inlet.

•

Channel – The water, which is diverted from the weir, is carried to the forebay tank. The channel could be an open

channel,

a

closed

Figure 2.1-5

channel and a combination of both. In most cases, the filtering methods like trash rack and desilting tank are placed in the channel. By the trash racks the heavy floating parts like plant parts, which is coming with the water, is collected and by desilting tank the heavy particles like sand are collected. S R M D T S WIJESEKARA | 070549D

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•

Forebay Tank – The water carried through the channel is collected to the forebay tank. The water flow relative to the water storage in the channel is relatively high. So, in a sudden stop, the water is collected in the forebay tanks and channel. The excess water is spilled from the banks. To create a safe way to exit the excess water the spillways are constructed. The spillways are placed in the forebay tank and in the channel.

•

Penstock – The water, which is coming through the forebay tank, is carried to the turbine creating a high head difference and high kinetic energy. Duo to the sudden variations of the flow in stopping and starting, heavy pressure currents could be generated through the penstock. To survive those currents, the penstock is usually made by steel.

•

Turbine – The turbine is the most important part of the waterway of the mini hydro plant. It converts the kinetic energy of the water flow to kinetic energy of the coupled shaft.

•

Tailrace – The water, which is used by the turbine, is released to the river through the tailrace.

The electrical system is consists the following components. •

Generator – The kinetic energy of the rotating shaft is converted to the electrical energy by the generator. Typically, the output voltage of a generator varies from 400V to 15kV. The synchronous type generators are generally used in mini hydro plants.

•

Breaker s and bus bars – The breakers and bus bars too installed in the system to provide the protection and reliability.

•

Transformer – The transformers are used to convert the power from generator output voltage to transmission voltage (33kV in Sri Lanka). Generally, the number of transformers is equal to the number of generators units.

•

Measuring instruments - to measure the power output from the plant, an Energy meter is installed.


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1.4.3 Designing a mini hydro plant

We learned the procedure of designing a mini hydro plant. The first step of designing a mini hydro plant is selecting the site. In this, the flow of the river and the head could be gain is considered. As the primary need, a place, which could gain a head as high as possible, is selected. The place should have the higher head with a maximum slope, because, when the slop is high, the length of the penstock becomes low. Therefore, the loss in the penstock reduces. Furthermore, the ability to carry water to the selected area is checked too. This means, there should be a point to tap the river, which is above in height, to the highest point of the selected area. Then a place to build the weir should be select. In this, the ability to carry a sufficient amount of water to the plant is considered. If the tapping point is lower in height to the selected designed penstocks highest point, the ability to bring the water to the penstock becomes impossible. If the tapping point is very high, the flow is become low and due to the slope, the channel will washout. So the tapping point is selected slightly above the penstock start. In this tapping point, a weir is build and diverted to the plant site. As the second step, the flow of the river in the tapping point is measured. In measuring the flow of the river, two criteria could be used. First criteria is measure the cross section and the speed of the river at the tapping point. In this method, the instant accurate flow could be measured. However, gathering hydrology data about a long period like a year is difficult. In this case, an approximate method is used. In this method, the catchment area of the river for the tapping point is calculated. The area, which the rainfall collects to the given point of a river, is simply referred as the catchment area. The area is selected using maps of the area. The hydrology data about the rainfall is collected then. Through this rainfall data, a fair rainfall model along the year could be developed. Then the catchment area is divided to the areas according to the manner of the environment like forest cover and the appearance of the soil. Then the rainfall is multiplied by the sub areas of the catchment area weighted by the factor, which represents the amount of S R M D T S WIJESEKARA | 070549D

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water collected to the river per unit rainfall and get the sum of the flows. From this method, an annual hydrograph is created. In annual hydrograph (Figure 3.1), the day-by-day flow variation Vs the day of the year is plotted. However, in designing process, to calculate the energy and other facts, the annual hydrograph is not sufficient. Therefore, the Flow Duration Curve (Figure 3.2) is plotted. In this graph, the flow Vs the number of days which the floe is available is plotted. This curve is more useful in Figure 2.2-6 - Annual Hydrograph

choosing the design flow. We were given an assignment to study the flow duration curve and create a program to calculate the critical parameters for various design flows.

Figure 2.2-7 - Flow Duration Curve

1.4.3.1Criteria

In diverting the water flow, an amount of water is released to go through the natural river for environmental and ecological reasons. This flow is called the compensation flow or by-pass flow. In energy calculation, this flow is subtracted from the flow duration curve. Then, for few design flows, the following calculations were done. 1. Plant factor- the term ‘plant factor’ is referred to the portion of the annual energy output to the produced energy output.


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Plant factor =

Energy generated per year Maximum output * 8760

This could be converted to the terms related to the flow duration curve as follows. Plant factor =

Area under the FDC and resign flow Area under the design flow

2. Excedance – The term ‘excedance’ is referred to the portion of the number of

days, which the plant could be operated in full load, to the number of days the plant operated. Excedance =

full load operated days Plant operated days

This could simply extracted by taking the point, which the FDC and design flow is intersected. 3. Annual energy output- the annual energy output could be calculated using the area under the FDC and design flow. Annual energy output = η ρ g H × Area under curve × 86400

By optimizing the above values with the cost for the equipments and project, the design flow is selected. We modeled the above criteria in a MATLAB Program. In it, for different design flows, the plant factor, excedance and the annual energy is calculated. The efficiencies of different turbines are different. To make the calculation fairer, the turbine type is too taken as an input. The MATLAB program has been attached as the annex 1


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Then using the above flow and head, the turbine is selected. We were given an assignment to understand the turbine selection criteria and create a program to select the turbine according to the flow and head. Turbines In hydropower generation, there are two types of turbines are used; impulse type and reaction type. In impulse type, high-speed water jets are used to run the turbines. In reaction type, the pressure difference of the input and output is used to run the turbine. In mini hydropower schemes, the following turbines are used. •

Pelton – Pelton wheel is an impulse type turbine. In this turbine, water-jets are directly focused to the buckets of the turbine. This turbine is suitable for the high head low flow applications.

•

Turgo – Turgo turbine is too an impulse type turbine. In this turbine, waterjets are placed slightly angled from the wheels plane. This turbine is used in high and medium head applications.

•

Francis – This is a reaction type turbine. This is used in medium head applications. In Sri Lanka the sites with medium head is common. So these kinds of turbines are widely used in Sri Lanka.

•

Crossflow – This is an impulse type turbine; but used in low head high flow applications. When the plant is constructed as non-diversion plant, this turbine is used.

•

Propeller – These turbines are used in low head turbines. This is a reaction type turbine and like a propeller in the boats in shape. The water flow is moving in the shafts axis direction in this turbine.

•

Kaplan – This turbine is too a reaction type turbine. It is used in low head applications.


Figure 2.2-8 - Turbine Efficiency Curve

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Figure 2.2-9 Turbine Selection Chart


The efficiency variation of the turbines with the flow percentage is plotted in the fig To fulfill the assignment, we created a MATLAB program (m file) based on an algebraic method. The relevant m file is attached as the annex 2-a. But in evaluation the program, it malfunctioned. So, our training engineer gave us a graphical method, which Hemas power uses as a source, and the relevant chart. Therefore, we modeled the chart to a MATLAB m file. The relevant MATLAB files are attached as the annex-2 and annex-3

While after those selections, the projects feasibilities were evaluated. In this, the following facts are considered. •

Summery – in this section a quick representation of the following chapters are given. Furthermore, all the key data and the comparisons with the other energy options are described.

•

Environmental impact analysis – in this chapter, the environmental impacts could be occurred is discussed. Generally, the information about the living creatures of the site area, the methodology used in the survey relevant to environment and other environmental factors are considered. Furthermore, the bypass release is too decided in this chapter.

•

Socio-economic viability – in this chapter the social and economical states of the people who are living in relevant site area is discussed. Furthermore, the impact of the living style of the relevant people is too described.

•

Hydrology analysis – In this, the hydrological analysis is included. The flow analysis method, flow analysis data and the energy calculation results are represented in this chapter.

•

Cost/profit analysis – in this chapter, the economical analysis about the costs and profits are described.

•

Component details – in this chapter, the equipment provider details, all the equipment details and the cost analysis is included. Furthermore, the details about the quotations considered and the reasons for the selection are too described. S R M D T S WIJESEKARA | 070549D

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•

Annexes – relevant materials like the rainfall data, the Flow Duration Curve, the site maps and the reports taken from the relevant authorities and analyzers are attached to the

During the training period, we had the chance to refer the feasibility report of Giddawa project.

1.4.4 Trash rack design

In the 7th week, I was given an assignment to design a trash rack for the Thalawakale power plant (Senok Mark Hydro) The filter, which is used to filter the large floating parts in the water, is called the trash rack. As a practice, the trash racks are designed fitting bars vertically to a frame. So then the trashes remain could remove using the rakes. The trash rack whish was to design, was supposed to be placed in the desilting tank. The following data was given, •

The dimension of the channel – to calculate the cross section of the flow.

•

The dimension of the desilting tank.

•

The width of the bars of the trash rack.

•

The width should be kept in the holes of the trash rack

•

20% extra space from the cross section of the channel for make the flow continues and 150 angles.

•

The medium height of the water flow. S R M D T S WIJESEKARA | 070549D

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As the first step, I modeled the site area in AutoCAD, and measured the effective cross section area of the channel (A). Then the effective cross section of the trash rack will be 120% into (A) Effective cross section of the trash rack (Atr) = A × 1.2 Thos is the cross section of the holes. Therefore, the effective cross section of the trash rack would be the Atr into width of a hole and a bar over width of a hole. In here the effect of the angled edges are neglected. Under water cross section of the trash rack (AUw) = A × 1.2 × (Wh+ Wb)/ Wh Then, a plane of an angle 150 to the z direction is drawn in the AutoCAD file and the intersection cross section area was taken for few places in the trash rack. Then the place which gives the AUw was found and decided it as the proper place to place the trash rack. The drawing of the assignment is attached as the annex 4

1.4.5 Financial Structure of a company and evaluation for acquire a company.

We met Mr. Ravi, who is the economist of Hemas Power, to learn about the financial structure of a company. He learnt us about the power business, capital structures of a company and the economic evaluation for an acquirement of a company. There are two kinds of capital collection methods; Lendership and ownership. The lendership is referred to the investments with an interest. In this relationship, the investor is not having any ownership to the capital and company and the invested money should be paid with a fixed interest. The ownership is referred to the investment, which makes the investor own a part of the profit and a risk. In calculating the profits, the share of the landership is S R M D T S WIJESEKARA | 070549D

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taken as a liability and subtracted from the gross profit. Then a share for the future usage is saved and the rest is divided among the owners. These decisions are taken by the board of directors. In acquiring a company, an economic evaluation is done. While after getting known that a company is about to sell, the financial state and the future revenues are evaluated and the revenues are projected to the present value. Then the cost of equity is evaluated. The cost of equity reflects the opportunity cost of the purchase. The cost of equity could be evaluated by the following equation. Cost of equity = riskless rate + premium factor × risk factor If the cost of equity is lower than the forecasted present value of the company, the purchasing is viable. In power purchasing by CEB, they create an account for the power plan, not the owner. This will simplify the accountings of the CEB side. Se the power plants should be registered as individual companies by law. Then the payments for the power purchasing are paid for the individual power plant. And also, the changes of the managements are not affected to the CEB procedure. Because of the power plants are considered as companies, acquiring a company is relevant to the field.

1.4.6 Gidddawa mini hydro power plant

Giddawa mini hydro plant is the first renewable power plant, which started by Hemas Power. The site is located at the village called Giddawa in Theldeniya, Kandy. This is the fourth cascade placed power mini hydro plant in the river. Followings are the details relevant to the power plant. S R M D T S WIJESEKARA | 070549D

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Gramasewaka division – Ambalagala & Giddawa Divisional secretarial division – Theldeniya Pradeshiya Sabha – Mada Dumbada Provincial council – Central Province (Kandy) The gross head of the power plant is 27m and the net head is 26.3m. The rated discharge is 4.3m3/s. In the 10th week I was given a chance to get training in this plant for a week in plant training. I was given an assignment to prepare a maintenance schedule for the plant. About that assignment will be described in a later chapter. The plant is constructed crossing the river ‘Hulu Ganga’. A weir is constructed crossing the river about 800m above the plant area. It is 15m in long and 2m in height. The weir is constructed using rocks and concrete. There is a bypass to keep the river live. The channel is constructed in the left bank of the weir. The intake is constructed in a left most position of the weir. The channel is constructed through the left bank. It is 2m high and 3m wide. The length of the channel is about 800m. The inlet gate is constructed about 20m after the intake.

And

a

desilting

tank

is

Figure 2.5-10 - Waterway of Giddawa MHP

constructed in the middle of the channel. Its dimensions are 3m × 4m × 6m. There is a spill way in the desilting tank and a gate to remove the sands is placed in the bottom. A trash rack is too placed in the end of the tank. In the end of the channel, the forebay tank is placed. It is 6m wide, 8m high and 9m long. There are two spillways placed in the forebay tank. The spillway in the tank is the first designed spillway. But it couldn’t be able to provide enough space for the whole spill in a S R M D T S WIJESEKARA | 070549D

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sudden stop. So a spillway outside the forebay was constructed. There is a sand gate similar to the desilting tank is placed in the end of the forebay tank. There is a trash rack too. In the end of the forebay tank, two penstocks were placed. The penstocks are 70m long. They are 1.5m in diameter and 12mm in thickness, steel. From the penstock the water is transferred to the two horizontal spiral Francis turbines. Through this two synchronous generators were driven. The rates speed of the turbine is 500 rpm and manufactured by Gugler Hydro Energy, Australia. The rated output of the turbine is 1012kVA.A hydraulic system, which is coupled with a weight, is used as the auto-closing method of the guide vanes. Then the used water is released to the river through the tailrace. The generator is a 12 pole salient pole rotor synchronous generator. The technical

Figure 2.5-11 - Electrical System of Giddawa MHP

details of the generator are given below. •

Rated power – 1150kVA

•

Output voltage – 400V

•

Power factor – 0.85

•

Excitation – 90V 3.6A brushless

•

Rated current – 1160A

excitation.


xxx

Figure 2.5-3 GHP Weir

Figure 2.5-4 - GHP channel

Figure 2.5-5 - GHP Forebay Tank

Figure 2.5-6 - GHP Electrical Equipments

Figure 2.5-7 - GHP tail race

Figure 2.5-8 - GHP Penstock

The power output of the generators is then transferred to the transformer through breakers. There are two 1250kVA transformers are placed in the plant. Through this the power is transformed to 33kV. Then the transformer outputs are connected to a bus bar through breakers. These breakers are the ones, which were closed in synchronization. Then the bus bar output is sent to the national grid through a 33kV transmission line. An energy meter is coupled with the line through a Current Transformer. From this the power output and the reactive power usage is measured. The transmission line is proposed to connect the Theldeniya gantry. But currently the line is connected to a feeder of the Karandeniya gantry. 1.4.6.1Experience in plant

I reported to the power plant about 12.30pm on Monday. I started to refer the manuals of the power plants components in the evening. On Tuesday and Wednesday, I studied about the waterway system and the other systems of the power plant, the hierarchy of the staff and the works done by those staff members. And also I gathered the information for the assignment of preparing a maintenance schedule. The staff of the power plant is consisting one plant supervisor, four plant operators and eight labors. All of the staff is lived nearby the plant area except supervisor. The supervisor; Mr. Pramathilaka, controls and supervises the plant. The administration part is completely done by the supervisor. The plant operators are worked in an 8-hour shift manner. The shifts are changed at 6am, 2pm and 10pm. The operations of the power plant machinery are completely done by the plant operators. The maintenance of the power plant is done by the labors under the supervision of the supervisor or operator. And also, the cleaning of the plant is done by the labors. They also worked in a shift schedule, two personals in a one shift. Dering my training in Giddawa; I attended to the works done by operators. I synchronized a generator once tripped due to the phase shift failure. I got the readings of the power output, reactive power input and power factors. I got the opportunity to attend few night shifts with the power plant operators. Moreover, I studied the works done by labors. I attended to clean the trash racks twice.

1.4.6.2Teamwork – leadership development program.

In Thursday, there was a teamwork and leadership development program in the plant. The program was organized by Hemas Power, to develop the leadership and mutual understanding of the staff of Giddawa hydro power plant. The program was conducted by corporate training division, Academy of Adventure, Belihul Oya. I was too had the chance to attend to this function. The function was conducted as a one-day course. The whole staff was divided into two groups as about six personalities per group. Both the groups had to go through the activities and complete them. There were eight challenges and are focused on the abilities like self confidence, commitment, leadership. The tasks had named as team building, trust challenge, lava crossing, magical turtle, key punch, human knot and blind walk. Those activities were focused on developing different attitudes and abilities on the staff of the power plant. The concentration, mutual understanding and the strategy were became the essential abilities in this tasks. That experience was a real fun. The certificate, I was given for the participation is attached as the annex 5 In the last day of the Giddawa, Mr. Premathilaka thought me about the power distribution system around the Theldeniya area. And the power flow of the power plant. I was given the chance to travel around the Theldeniya area and see the Karandeniya gantry and Rajawaka Air Break Switch. A single line diagram of the area is shown in the figure 4

1.4.6.3Review

Figure 2.5-9 Single line diagram of Theldeniya Distribution Area

The plant is facing a large difficulty in the incoming water flow. The forest cover in a part of the catchment area has been removed few years back. So the water flow is not regular throughout the day and sudden water flows are generated at the rains in the upper part of the

river. So the controlling has become difficult and due to the large spill out in the sudden flows, the energy is wasted. Due to that, the plant factor has been reduced to the designed value. Furthermore, the plant output is connected to a feeder. So the voltage fluctuations and phase shifting are generated. This has made the increase of the number of tripping in the plant. The plant is a run-off-river type one and for each tripping the water is spilled from the forebay tank. This makes a huge energy waste. Throughout the week, I was given the chance to stay in the plant in the night as well as the day. Through this I had the chance to learn about their duties in the plant, their lifestyle, and there relationship with the power plant. The villagers are deeply bounded with the power plant in the re lifestyle. And the power plant administration and Hemas itself too became more helpful for the villagers, and tries to improve the living condition of the villagers through the social servicing activities like improve the conditions of the village school. And also, because of the plant, the sudden floods generated have been limited. Furthermore, I observed that the staff working hard to do their duties as best as possible. They extremely cared about the power plant. And also, became more helpful for the visitors too. I should be more thankful for the plant staff for helping me out in letting me get experiences and helping me out in various ways throughout the week.

1.4.7 Maintenance schedule

I was given an assignment to create a maintenance schedule for Giddawa power plant in the 9th week of the training. As the first step of the assignment, I gathered the information about the mini hydro plants, the components using in the plants and the maintenance of the components. Then I organized the information found. End of the week, I gave a presentation on the assignment progress – the gathered information about the maintenance of the mini hydro plants. In the week, which I was in Giddawa, the maintenances which are conducted by the staff were gathered. The information gathered before the Giddawa week was mainly based on the electrical and mechanical equipments. The information about the civil constructions like the weir and channel, are gathered during the in plant training. Then I combined the maintenance in a schedule such that, not to be clash with each other. And matched them with the appropriate period, for example cleaning the tanks are not scheduled in the wet period. And also I gathered the information about the safety of the personals who is doing the maintenance. As the final presented item, I had to prepare a booklet for the maintenance and the maintenance schedule. The booklet is attached as annex 6

1.5 Ceylon Electricity Board During the CEB Training period, we had to gather knowledge about power generation and transmission. The Distribution is supposed to be covered in the Lanka Electricity Company period. We had the chance to attend five training places during eight weeks period covering two regions; Generation and Transmission. We got the training schedule for the CEB training period as follows Period 03/05/2010 – 14/05/2010 17/05/2010 – 11/06/2010 14/06/2010 – 25/06/2010

Training area Transmission

Place Pannipitiya,

Kotuoda,

Operation & Maintenance Veyangode & Kolonnawa GSS *LECO Hydro Power Samanalawewa Power

Generation 28/06/2010 – 09/07/2010 Thermal

Station Power

Kalanithissa Power Station,

Generation

Kalanithissa Combine Cycle Plant.

12/07/2010 – 16/07/2010

Generation Planning

and

Generation Planning Branch, design CEB Head Office, Colombo.

branch 19/07/2010 – 23/07/2010

System Center

Table 2.6-2.1 - CEB training schedule section

Control

CEB,

Kent

road,

Dematagoda. * the LECO period. Not relevant to this

From this, Hydro Power Generation and Thermal Power Generation are belonging to Generation section and Transmission, Operation & Maintenance, System Control Center and Generation Planning & design branch are belonging to Transmission section. To make it clear, the chapters about the CEB Training is organized as in section relevant manner, instead of the order of attend.

1.5.1 Hydro Power Generation – Samanalawawa Power Station.

Samanalawewa Power Station is a most important power plant in Sri Lankan power generation. It generates and releases a 120MW maximum power generation to the national grid. And it is the largest power producer in the southern part of the power grid. The plant is placed in

Walawe basin and operated using the water which is collected at Samanalawewa, in Balangoda area. The construction of the power plant was started in 1989 and it was commissioned in 1994. The plant is operated under the Deputy General Manager (DGM) of other hydro complex. The plant is located at Hapugala, Balangoda. We had the opportunity to attend and learn about the power station and the systems and operations through these two weeks. 1.5.1.1The waterway

The Samanalawewa reservoir is built by building a dam crossing the Walawe River at Pambahinna. The reservoir is fed from Diyawini oya and Katupath oya, which are the branches of the Walawe River. The dam is 107m in height and 500m in length. And it is clay core rock filled type dam. It is having three spillways with radial gates placed on it .The gross storage of the reservoir is about 274× 106 m3. The reservoir is designed to spill at 460 m above MSL. But due to the leak in the right bank, now a decision to spill the reservoir at 455 m above MSL has been taken. The intake, which is used to take the water to the powerhouse, is located about 5.5kms away from the dam site. The intake structure includes a screen to filter the water and two hydraulic controlled gates; the control gate and the emergency gate. The minimum intake water level of the reservoir is 424 m above MSL. And the live storage capacity is 215 × 106 m3 Through the intake the water is entered to the power tunnel. The power tunnel is a horseshoe type 5.35km long tunnel and it is having a slope about 1:100. The diameter of the tunnel is 4.5m. The power tunnel is ended with the surge chamber. It is about 12m high from the ground level and about 18m in diameter. The surge chamber is connected with the portal valve house through a steel tunnel. Due to this steel structure, the damage to the tunnel in a sudden trip becomes minimum. The waterway is divided into two from the portal valve house. There are two Butterfly valves placed in this valve house, for the two outlets of the water. One outlet of the portal valve house is currently blocked and kept for the future expansion of the plant and the other outlet is connected to a penstock.

The penstock is about 670m in length and made with steel. The elevation of the penstock is about 364m. The internal diameter varies from 3.85m to 2.85m on the bottom. The penstock is divided to two in the end and supplied the water to the two turbines through spherical type valves. The valves are operated by high pressure oil servo motor with weigh assisted closure. The diameter of the inlet valve is 1500mm and the designed pressure is about 440m. There is a by-pass valve with the diameter of 200m to equalize the pressures of the both sides of the valve before open the valve. The turbines are spiral case vertical Francis type. The rated output of the turbine is 70200kW when operating at the net head of 320m. The speed of the motor is 500rpm. The guide vanes are operated by a ring which is coupled with two servo mechanisms governed by hydroelectric governor system. The water used by the turbines is then released to the Walawe river trough the tailrace. 1.5.1.2The electrical system

There are two vertical shafted salient pole 3 phase generators which are driven by the two Francis turbines. The rated output is 60MW and the output voltage is 10.5kV. The power factor of the turbine is 0.85 and the rated speed is 500rpm. The output of the generator is carried to the transformer through isolated phase busbars (IBPS) filled with dry air. It was tapped to take the power to the excitation system and the auxiliary system. Then the power generated by the generators is transformed to transmission voltage (132kV) through two three phase 10.5/138 kV transformers. They are rated at 71MVA. The tapings of the transformer are manually operated. The windings are oil cooled and the cooling is classifies as ONAN/ONAF. The power transformed to 132kV is then send to the switchyard. There is a UI bus bar system is placed in Samanalawewa Power Station switchyard. To save the space and create a reliable system the bus system is constructed in that manner. The two double circuit transmission lines from Balangode & Embilipitiya and the two generator outputs are connected to the switchyard. The bus bars are coupled using a bus coupler.

The auxiliary of the power plant is provided in three ways. As the primary method two unit transformers are used. The power output of the generators are tapped and converted to 400V. In the power plant not operated situations, the power is taken through a 33kV feeder from Balangode GSS. If it’s also not possible, the diesel generator placed in the plant is used. The all auxiliary supplies are gathered to a busbar with interlocking to each other. The excitations of the generators are done using excitation transformers and thyristor banks. There is a battery bank placed as the back-up method of excitation. The S’wawa is become more famous because of the leak in its right bank. Due to the composition of the soil in the reservoir area, an amount of water collected to the reservoir is leaked through the right bank of the dam. The leaking rate is about 2.5m3/s. The water is leaked through the mountain and collected inside the mountain. Then this water leaves the mountain from a single place in the right bank. The leak is used as an irrigation outlet to the Kalthota area. We reported to S’wawa power station in 14th June about 2.00pm. We met Mr. Sepala Karunasena, who was the chief engineer of the S’wawa plant. He gave us a presentation about the S’wawa power station and gave us a schedule to be followed in next two weeks. In the second day we visited to the sections of the power plant and learned about the important components of the power plant. In the third day we visited to the switchyard and learnt about the electrical system in S’wawa. The following is a brief description about S’wawa power scheme. In Friday we had the chance to attend a routine maintenance of the unit two. These kinds of maintenances are conducted once a month for a unit. In this, the following inspections and maintenances are done. 1. A visual inspection is done for the inlet valves, the turbine outside, the cooling water pumps, hydraulic systems and all the pumping systems in the power plant, for cracks, leaks or any other troublesome situations. 2. The outside of the components are cleaned for dust. 3. The cover of the generators are removed and the parts inside are cleaned for the dust.

4. A visual inspection for the components like breaking pads and the excitation brushes are done. During the maintenance, we had the chance to inspect the components of the hydraulic and waterway systems. And also we had the chance to go inside the generator and identify the parts of the generator. 1.5.1.3Fire Protection

In Monday of the next week we learned about the safety procedures and the fire protection schemes. As the fire protection of the generator there is a CO2 bank placed in the power plant. When a fire is occurred in the generator the bank is actuated by the heat detector sensors which are placed in the generator inside. Then, the generator is filled with the CO 2. In maintenances the bank is deactivated through a manual interlocking system. As the fire protection in the transformer, a high pressure water injection system is placed. When a fire is occurred the sensors are actuated and a high pressure water jets are injected to the transformer. 1.5.1.4Emergency

In an emergency, all the staff is trained to leave the building through the front door. There were many path marks to identify the way t o leave the building. And also there are fire fighter materials placed in the most suitable places around the power house. And also there are emergency tripping switches are placed around the generator. An emergency drill is take place in the plant every year. 1.5.1.5Dam site

In Wednesday we had a chance to visit the S’wewa dam site and Intake. In this visit, we observed the intake, the Dam and the Barges – the boats used in wet blanketing. We also had the chance to visit the tunnels used to take the readings of the pressures inside the right bank, and to see the leak.

1.5.2 Kalanithissa Power Station & Kalanithissa Combine Cycle Power Plant.

As the 9th and 10th weeks of the training second half, we had the chance to attend and learn about Kalanithissa power plants. The first week is for the Kalanithissa Power Station and the second week for Kalanithissa Combined Cycle Power Plant. Kalanithissa Power Plant, which is commonly known as KPS, is located in Paliyagoda, Colombo. This is a major thermal power plant belong to CEB. The installed capacity of the power plant is 215MW. This power plant is considered to be a key power station in blackout situations. In blackouts, the KPS are taken to the system and the Colombo area is powered as an individual unit. 1.5.2.1Gas turbines

KPS is having six frame-5 gas turbines and one Feat gas turbine, which is similar to frame 9 in size and capacity. The frame 5 GTs commonly known as small GTs are having the rated capacity of 20MW, a small GT has been out of operation for a long time, and dissembled. We had the chance to observe the parts of this GT. A special feature of this GTs is that, it can operate in the synchronous compensator mode. 1.5.2.2Synchronous compensator mode

The synchronous compensator is a component, which consumes the reactive power and releases reactive power. In GT’s case, this term refers to the no-load running of the generator. To bring the generator to the sync. comp. mode the following procedure is followed; first the generator is started and brought to the full speed. Then the generator is synchronized to the system. Then the power input of the generator is reduced by decreasing the fuel input. At this time, the generator is started to run using the power in the system. Due to the special gear system, which is used in the GT, between the turbine and the Generator, the turbine is disengaged from the generator and the generator started to run as a synchronous motor. In this state, by varying the excitation current, the reactive power could be generated. The Feat GT is a gas turbine which is having a rated capacity of 115MW. The unit cost of this GT is about 26 LKR/kWh while the small GTs are having a unit cost about 40 LKR/kWh. There were two 25MW steam turbines in KPS and they were out of operation since 2003.

1.5.2.3Switchyard

The switchyard in KPS is having the both 132kV and 33kV. The small GTs except GT1, are connected to the 33kV busbar through 10.5/33kV transformers. The 33kV busbar is a bus section type. The GT1 and the GT7 are connected to the 132 busbar through 10.5/132kV transformers. This busbar is a UI type busbar system. The 633kV busbar is connected to the 132kV busbar through 33/132 kV inter bus transformer. The power generated in KPS is transferred to the Kolonnawa through 132kV double circuit transmission line and to Biyagama through 220kV double circuit transmission line. The Biyagama lines are connected to the switchyard through 220/132kV step-down transformers and a gas insulated substation. As the second week in the thermal generation we had the opportunity to visit and learn about the Kalanithissa combined Cycle power station. The full capacity of the power plant is 165MW; 110MW from Gas turbine and 55MW from steam turbine. The gas turbine of the KCCP can use diesel or naphtha as the fuel. But in the starting, only diesel is used as the fuel. The energy in the exhaust is used as the source to the steam turbine. The exhaust is dent through the Heat Recovery Steam Generator (HRSG). The energy in the exhaust is then transferred to the steam carried through the HRSG, in two stages. Low pressure and high pressure steam. This steam will be sent through the turbines. The high pressure steam is sent through the high pressure turbine and the low pressure steam and used high pressure steam is sent through the low pressure turbine. The high pressure turbine runs at 9000rpm and the low pressure turbine runs at 3000rpm. The low pressure turbine is directly coupled to the generator shaft and the high pressure turbine is coupled using a gear system. Then the generator shaft speed becomes 3000rpm. The used steam is condensed in the condenser and reused to generate the steam. The output of the high pressure turbine is 25MW and the low pressure turbine is 30MW. Because of the combined cycle uses the exhaust energy, energy to be wasted is saved. So, the efficiency increases. The unit cost of the power plant with the steam turbine is about 16 to 18 LKR. But, when the plant runs without the steam turbine, the unit cost increases to 26 to 28LKR.

1.5.2.4Water Treatment

KCCP uses the water from the Kalani River for the usages like generate stream and cooling water. The water pumped from the Kalani River are treated and made up before use. Following steps are used in this process. As the first step Cl is applied to the water. This chlorine is generated using the sea water. NaCl + H2O

Electrolysis

NaOCl + H2

Then Al2(SO4)3 and NaOH is applied to the water. Al2(SO4)3 is generated by reacting a conjugant aid and an amid. through this the Al(OH)3 is generated. Al2(SO4)3 + 6NaOH

3Na2SO4 + 2Al(OH)3

With this Al(OH)3 precipitate an amount of suspended particles are removed from the water. Through this the water is purifies to meet 5NTU. This water is then filtered using pressure filters (3NTU) and multimedia filters (2NTU). Then to remove the excess chlorine NahSO4 is applied. To remove the ions, the water is send through Reverse Osmosis Membranes. From this the conductivity of the water is meet 100µSs-1. Then the water is sent through an ion exchange bed. From this, the anions and the cations are replaced with H+ and OH-. After all of this procedure, to keep the ph amount to 9, NH4OH is added.

1.5.3 Transmission Operation and Maintenance Branch

In the first two weeks of the training second half, we were assigned to Colombo region in Transmission operation and maintenance branch for the training. During the period we had the chance to visit the Pannipitiya, Kotugoda, Veyangoda and Kolonnawa grid substations. In the third day of training, we went to the Pannipitiya GSS. Pannipitiya GSS is a GSS which is having 220kV system, 132kV system 33kV system and a capacitor bank. This GSS is one of the most important Grid Sub Stations. The substation is connected to Biyagama GSS through a 220kV double circuit transmission line. The incoming power through the 220kV line are taken to 220kV busbar and transformed to 132kV through six singe phase auto transformers. The capacity of an autotransformer is 83.3MVA and 500MVA is build together. Then it is fed to the 132kV busbar. There are seven feeders connected to the 132kV busbar. Two double circuit transmission lines from Kolonnawa and Ratmalana, two single circuit transmission lines from Horana and Mathugama and an underground cable transmission line from Dehiwala. The 132kV power is then transformed into 33kV through three 3-phase transformers. The rating of the transformers is 90MVA. The transformed power is then carried to the 33kV GIS (Gas Insulated Substation). From this GIS 12 feeders are taken out and two of them are considered as the special feeders (Feeder 11 and 12). Then the power is taken to the outdoor busbar. This is a special type of busbar. Any feeder could be connected to this busbar and also have the ability to transfer the power without connecting to the busbar. If a failure is occurred in the 33kV system, the outside busbar is used to feed the faulty feeder. The autotransformers are coupled to create two 3-phase transformers. The 33kcv outputs of the transformers are connected in delta configuration. The terminals of the delta are connected to the capacitor bank. The capacitor bank is now out of operation. In the next two weeks, we visited to the Kolonnawa GIS, Kotugoda GSS and Veyangoda GSS. Throughout the week, we identified and observed the components of a grid substation.

1.5.3.1Circuit Breaker

To connect or disconnect power lines in either no-load or on-load conditions without developing arcs, the breakers are used. In earlier systems, the Oil circuit Breakers are used. But later they were replaced by the SF6 filled Circuit Breakers. The special reason to use this type of breakers is, the high arc quenching property and insulation property of SF 6 gas under high pressure. The breakers which are placed in 220kV switchyard at Pannipitiya are rated as 245kV. The normal allowable current is 4000A and the breaking current is 50kA. The maximum wording pressure of SF6 is 0.8 Pa. 1.5.3.2Isolators

Isolator is a mechanical switch which is operated in no load condition. This is an open type switch and, it could be seen whether the isolator is open or closed physically. If an isolator is operated in on-load condition, the arks could be generated. So, as a practice the isolators are operated after the breaker. Most of the isolators are provided with an earthling switch in it. So, in maintenance, the earthling could be too done through the isolator. 1.5.3.3Current transformers

The current transformers are generally used as a measuring instrument in the areas like protection and measurement. In here the power line is used as the primary winding and a secondary winding is created around the power line. The current generated in the secondary winding is proportional to the current carrying through the power line. There might be multiple cores used in different purposes, in a single CT. The secondary windings of a CT should always in a closed circuit during the operation. Otherwise, the CT could be destroyed with huge blasts. 1.5.3.4Voltage Transformer

The voltage transformers, commonly known as VTs are generally used in protection and instrumentation purposes, as a measuring instrument for voltage. One end of the primary winding of VT is connected to the power line and the other end is connected to the ground. The secondary winding is placed such that, the voltage is lower than the primary winding’s. One terminal of the secondary winding too connected to the ground.

1.5.3.5Surge arrestors

Surge arrestors, which are commonly known as lightning arrestors are used in protection from the higher voltage surges. As a practice this equipment is applied to protect the high reliable and high cost equipments. As a practice, SAs are used in connection point of every power line connected to the GSS and the both primary and secondary sides of the power transformers. 1.5.3.6Bus bar

In power systems, the bus bars are acted as the modes or vertices of the network. There are various kinds of busbars used in Grid substations. Single bus, double bus and main & transfer bus could be taken as the examples. In double bus bar systems, bus couplers are used to connect the busses. But in single bus systems, most of the time, bus sections are used. 1.5.3.7Carrier equipments

In the SCADA system, which is used by the CEB in communication, in PLC technology, the Y phase is used as the communication line. This is called as Power Line Carrier system and in this purpose the carrier equipments like wave trap and CVT are used. Most of the switchgears of substations are built as outdoor open switchgears. But in the situations where, there is no room for bulky switchgears, as a more reliable option, Gas Insulated Substations are used. GIS is an indoor compacted model of switchgear, which is in a SF6 filled environment. GIS are more reliable because, the maintenance of the switchgear is minimum and the operation of this kind of switchgear is relatively easier than the outdoor switchgears. But, the cost of this kind of assembly is relatively higher than the outdoor type.

1.5.4 System Control Centre

In controlling and keeping the Sri Lankan power system live, The System Control Center ants a key role. It is established to conduct a safe and reliable service in power generation and transmission. Through this the above areas are monitored and controlled. Mainly the following tasks are performed by SCC. In the 12th training week of the second half, we had the chance to attend and learn about the SCC and its main functions. •

Decide the power plants should be dispatched.

•

Decide the amount of power should be supplied to the system by those power plants individually.

•

Monitor the parameters like voltage in the transmission lines and maintain them in the acceptable limits.

•

Schedule and monitor the maintenance of the system Etc.

1.5.4.1The operation policies

In order to conduct a safe and reliable service, the operation policies for SCC are declared. It includes the priority order, thermal and hydro dispatch guidelines, the voltage ranges should be maintained in transmission lines and spinning reserve and maximum generation unit guidelines. 1.5.4.2The load curve

The plot of the active and reactive power usage Vs time is considered as the load curve. In CEB the load curve is plotted using the values, which are measured from the major power stations. The special places like the night peak, the day peak, the morning peak and the off peak could be easily identified in this curve. And also the \lifestyle of the Sri Lankan population is too described using this plot. Using this plot, the power generation during the day could be forecasted and planed.

1.5.4.3Voltage drop

If the voltage of a transmission end lies out of the acceptable range, it is said to be a voltage outrange in the system. There are two kind of voltage outranges. Voltage drop and voltage rise. Generally, when the load centers are located far away from the power stations voltage outranges are occurred. When the inductive loads are connected to the system in a bulky manner, with the power stations are far away, the voltage drops could be occurred. In this situations, add reactive power to the system from power stations, improve the power factor using the components like capacitor banks and static Var compensators and change the tap setting of the transformers are the actions could be taken in this situations. When the transmission line is too long and the delivering power is low, due to the capacitance of the transmission lines, the voltage rises could be occurred. This effect is called the Ferranti effect. In these situations, the reactive power injection to the transmission line is limited as much as possible. Furthermore, the tap settings are changed to limit the consumer voltage to the acceptable limits. In our training period in SCC, we had the chance to see a voltage drop in western area substations. In this period, the hydropower generation is maximized. Therefore, a situation, which the load centers with reactive power and far away from the power stations, is occurred. The result was a huge voltage drop in Biyagama Grid Substation. Therefore, a thermal plant, which is located around the Colombo area had to be taken to the system. 1.5.4.4Power generation

Power generation in Sri Lanka could be categorized into two as thermal and hydro. The hydropower generation too could be categorized into three complexes. Mahaweli complex is a cascade complex which is mainly operated in accordance with the irrigation requirements. The irrigation department makes the decisions of the energy production by these power plants. Rantambe, Bovatenna powerhouse outlet and Bowatenna reservoir is the main irrigation outlets of this complex. Laxapana complex is mainly operated to meet the power requirements. This is too cascade system and there are three reservoirs and two ponds in this complex. The complex is designed in a manner such that, when all the power plants are operated in full load, the lover ponds are filled. In order to get the maximum output, a concept called pond regulating is

performed. According to this concept, when the full load is not requires to the system, the upper power plants are stopped and the pond levels are let reduced. When the full load is required, the full complex is operated in full load. So then, the decreased water levels are increases without spilling the reservoirs. The complex is operated too to supply the water to Ambathale water treatment plant in dry seasons. The major hydro plants which are not belong to those complexes and the IPPs are gathered to the Other Hydro Complex. There is one irrigation outlets in S’wewa to Kaltota area. The thermal generation could be divided into two categories, CEB owned and IPPs, the IPPs supply the power under the power purchasing agreement. A weekly meeting to plan the power availability for a typical day is held in every week. The irrigation department and CEB are participated to this meeting. The power availability of every plant and the operating instructions are decided to the next week in this meeting. In decision making to dispatch the power plants the following facts are considered, •

The reactive power requirement to the system and the maintenance requirements.

•

The opportunity cost and the capacity charge if the plant is thermal IPP.

•

The drinking water, environment and irrigation requirement priorities if the plant is hydro.

•

The availability of the water (position of the reservoir and the water level) if the plant is a hydro.

1.5.5 Generation Planning

The electricity demand of the country is increasing with the time because of the growth of the users as well as the growth of usage of the electricity. So to conduct a reliable service the planning becomes a necessary item. We were supposed to be in the System Control Center in our last two weeks. However, our schedules were changed and we got the chance to learn the generation planning in Generation Planning Branch. This branch is operating under the transmission division of CEB. Its main responsibility is to prepare and implement the plans to meet the future demand. The tasks of this branch could be listed as below, •

Forecast the future demand.

•

Prepare the long term generation expansion plan

•

Conduct the Pre-feasibility, feasibility and site surveying studies.

•

Financing

1.5.5.1Demand forecasting.

To create a trustworthy plan, the accurately forecasted date becomes a vital source, so the demand forecasting in an accurate manner, becomes an important section in the planning procedure. There are three demand forecasts, which are conducted by the CEB. 1. System Demand Forecast. – By System Control Center. 2. Forecast in Distribution Planning – By all four distribution regions. 3. Long Term National Demand Forecast – By Generation Planning Branch. From these forecasts, first two forecasts use the trend analysis method. These forecasts are not discussed in here. Meanwhile, the forecast which is used in Generation Expansion Plan uses an econometric model.

In this, the forecast is conducted for 20 years and it is updated per one year. The demand is divided into three categories to increase the accuracy of the forecast; Domestic, Commercial and religious & Street lighting. In the domestic demand forecasting, a linear regression formula is created. In this the following variables are used, •

Previous year demand

•

Gross Domestic Product per capita

•

Population

•

Avg. electricity price

•

Leading demand

•

Domestic consumer accounts

•

Leading domestic consumer accounts

•

Leasing GDP per capita. Etc.

The variables used could be changed according to the demand pattern. From these variables, the independent variables are determined. After that, the regression formula is prepared. The linear regression formula for the domestic demand for 2008 as follows. Ddom (t)i = b1 + b2× GDPPCi + b3× Ddom(t-1) + ei Where, Ddom(t)i – Domestic demand for ith year. GDPPCi - Gross Domestic Product Per Capita for ith year b1, b2, b3 - constants ei – error for ith year

The Industrial and General Purpose tariff categories are gathered to the Commercial category. This also uses the same procedure as the Domestic category, but the variables are changed. •

Previous year demand

•

Gross Domestic Product

•

Average Electricity Price

•

Leading demand

•

Leading GDP

•

Population

•

Industrial Consumer Accounts

•

Leading industrial Consumer Accounts

The leaner regression formula for commercial category for 2008 as follows, Di&gp(t)i = b1 + b2× GDPi + ei Where, Di&gp(t)i – Industrial & General Purpose demand for ith year. GDPi - Gross Domestic Product for ith year b1, b2 - constants ei – error for ith year

In the Religious and Street Lighting category, because of the share of this for national demand is relatively small and only one variable is identified, a trend analysis is done. The formula for this category is as follows. St = b1× (1+g)t

ln(St) = B1 + t× ln(1+g) After building the formulas, they are tested and verify for the accuracy. Then they are used to forecast the future demands. The sum of these three for a year is taken as the forecasted demand for the year. Final Energy Demand Forecast = Ddom(i)i + Di&gp(t)i + St Then the final energy generation is forecasted adding the total losses to the energy demand forecast. Final Energy Generation Forecast = Final Energy Demand Forecast + Total energy Losses Then the peak is forecasted by dividing the energy demand by the load factor. Peak Forecasted =

Final Generation Forecast Load Factor × 8760

1.5.5.2Generation planning

After the demand is forecasted, the plan for next 15 years is prepared. In planning the future generation, the following parameters are considered. 1.5.5.2.1 Capacity required for ith year.

The capacity of the country in a particular moment should be higher than the instant demand of the country. So, as the worst case, the full capacity of the country should be higher than the maximum demand. The difference between the maximum demand and the full capacity is referred as the reserve margin. Hence, the full capacity is built by adding the maximum demand to the reserve margin. After forecasting the maximum demand, the reserve margin for the year is too decided. By adding those two, the capacity requirement is calculated. 1.5.5.2.2 Existing Generation

The current generation of the country is taken as the existing generation. This is expressed in the capacity terms.

1.5.5.2.3 Retirement schedule

Due to the reasons like the technology developments and the fuel price changes, the power plants are considered as aging elements. So a date for the retirement of the plant is decided. Then a schedule for the retirements is prepared and used for the generation planning. 1.5.5.2.4 Committed plants

The plants, which are fixed to develop, are called the committed plants. The dates of the commissioning of these plants are fixed and the capacities of these plants will be added to the system in the given period in a certain manner. So the flexibility to adjust these plants is minimum. 1.5.5.2.5 Candidate plants

The plants which are having the capability to build and not yet decided to build is called ad the candidate plants. In planning, the only type of plants, which are having the capability to adjust, is candidate plants. The above parameters are interconnected to each other in the following manner. Capacity required for ith year

Existing

Retirement

= capacity - for ith year +

Committed Candidate plants + plants

In the planning process simply, the candidate plants are adjusted to meet the capacity requirement. To make this planning reasonable, the generation is planned in the most technically feasible, economically feasible and least cont manner. This is practically done using the software called WASP. In this planning the following options are considered as the candidate plant options. •

Candidate hydro projects.

•

Nuclear

•

Hydro capacity extends

•

Dendro

•

Candidate thermal projects

•

Mini hydro

•

Pump storage – Demand

•

Wind

•

HVDC – Hi-Voltage Direct

shifting method •

LNG – liquid natural gas

Current transmission lines.

1.6 LECO

As the second part of the training second session we had the chance to attend and learn the distribution division from Lanka Electricity Company Ltd. for 4 weeks period. Within this training we had the chance to learn the distribution functions and distribution planning and we had the exposure to the experience in distribution sector. In this training period the following schedule had to be followed.

Period 17/05/2010 – 21/05/2010

Training area Training place System Development SDD in LECO Head Office

24/05/2010 – 28/05/2010

Division System Operations

System Operations division in Head

Customer Service Center Branch Office

Office, Training center in Ekala Boralasgamuwa CSC Nugegoda Branch Office

31/05/2010 – 04/06/2010 07/06/2010 – 11/06/2010

Table 3.5-3.1 - LECO training Schedule

1.6.1 System Development Division

As the first week in LECO, we had to train in the System Development Division. This division is responsible for the High voltage planning (in LECO the term high-voltage is referred to 11kV), procurement and network data controlling. Throughout the week we learnt about those areas. 1.6.1.1High Voltage Planning

With the time, the demand for the electricity is increased. With that increment, the performance of the electricity distribution network is decreased. To overcome this matter, the distribution network is planned for next few years. The planning process for the LECO distribution network is done for 5 years and the plan is updated in 3 years. In this following process is followed. 1.6.1.2Load forecasting

The demand is increasing continuously. So, forecast the load for the next few years is an essential step in planning process. There are two kinds of load forecasts conducted in LECO; general load forecast and special load forecast. In spacial load forecast, the future trends for load changes relevant to the space, is considered. The future trends of establishing an industry in an open space could be taken as an example. In general demand forecast only the past data are used. In forecasting the demand, a time trend for the demand is constructed using the past data. Using this formula, the future demands for next five years are forecasted iteratively. 1.6.1.3Load flow analysis

In load flow analysis, the loads are categorized into three categories. 1. Constant impedance loads 2. Constant power loads 3. Constant current

Using this legend, the high voltage network is modeled. Then the current flows and voltages are calculated for the maximum demand. In planning the forecasted values are used and the modeled network is simulated for the voltages and feeder loadings. Is there are problems with the voltages and feeder loadings, following solutions are applied. 1. Load transfer – the load transfer is the first option the situations like voltage drops and feeder and transformer loadings. Because, the cost for this kind of option is minimum 2. New feeder construction – when the voltage is dropped, but the PSS loading is in the acceptable limits, this option is used. In this, a new feeder is connected to the problematic loads. 3. New substations construction and upgrades– when the PSS is overloaded this option is considered. In this either the existing PSS upgrade or construct a new PSS and transfer troublesome load is done. The network is simulated using PSS/ADEPT software. In this, with and without the solutions given for the last year is simulated. After the simulations the proposals are gathered to the plan. 1.6.1.4GIS – Geographic Information system

LECO manages a geographic information system and a database in asset management in the network. In this all the properties and the geographical position about each component placed in the network is gathered to a database. Using this, a geographical map for the network is constructed. The system updates in the following manner. A draftsman from each branch collects the data about the changes in the network according to the system alternation form. This form is filled when a change to the system is done. The draftsman reaches to the location and records the geographical location and the relevant information about the component in a GPS recorder. Then those data is transferred to the computer and corrects the GPS data using base files. After that the network is plotted in a map. Then the data is sent to the head office in every month. After every three months, a booklet containing the maps is prepared and sent to the branches.

1.6.2 System Operations

As the second week in LECO we had the chance to learn in System Operations. The system operations section is responsible for maintaining the current situation of the network. In this the following tasks are done. 1.6.2.1Scheduling the interruptions in the network

In this the following procedure is followed. First, the information about the planned interruptions of the Branches for maintenance and new constructions, and the interruptions for the CEB maintenance are gathered. Then they are scheduled in a practically feasible manner. In this, the facts like giving priority for necessary feeders, demand variations and the human resource availability are considered. Then, after the approval for the schedule, the necessary details about the interruptions are publicized through the printed media and LECO web site. 1.6.2.2Issuing work permits and monitoring the maintenances

The safety of the personals is considered as the most prior necessity of the electricity sector. So when the maintenances are occurred, they are monitored in personally by the system Control. In this first all the switching instructions for the interruption is given by SO. These switching should be personally observed by the relevant officer. Then, after verifying that all the given instructions are followed the permit to work is issued. After that, the maintenance is started. After the relevant maintenance is finished and all the personals are reported to the safe place, the officer requests for cancel the permit. In this, the permit is cancelled and the switching instructions for retrieve the network is given by the SO. In Tuesday and Wednesday we had the opportunity to visit the training center in Ekala. In this, we learned about the meter testing and meter repairing, transformer testing and repairing and observed the components used in LECO network. 1.6.2.3The energy meter testing and repairing

When the accuracy of meter readings is kept out of the appropriate region of ±2.5%, the relevant meter is said to be malfunctioned. The energy meters could be malfunctioned due to following reasons

•

Binding the dirt in the disks and air gaps.

•

Burnouts and short circuits of the windings

•

Decrease of the magnetism of the damping magnets

•

Malfunctions in the bearings ( Gummy oils and dirt, decrease the magnetism in magnetic bearings, improper adjustments)

•

Disk rubbing and Creeping.

•

Vibration of the mounting In meter repairing, if the malfunction is occurred due to an outage of a component, the

relevant component is replaced with the proper component. If the malfunction could be recovered b adjusting the parameters of the meter, then the meter is tested and calibrated to meet the proper functioning. In meter testing following procedure is used. •

The cover is removed and the meter is connected to the testing bench. There are two testing benches places in LECO meter testing lab, which are capable of testing 10 and 20 parallel meters respectively.

•

Then the meter is left to preheat by applying the power to the meter

•

Then the following tests are conducted. o Error test – this is conducted to test the error in disk rotation. The meter is tested in following conditions. 1. 5% of Ib and 1 pf 2. 100% of Ib and 1 pf 3. Imax and 1 pf 4. 100% of Ib and 0.5 pf

Then the error is calculated and if the error is not in acceptable limits, the meter is calibrated using the Full load adjustment (Adjust the position of permanent magnet), the Low load adjustment (Adjust the position of potential coil) and the Inductive load adjustment (Adjust the resistor connected in series with the shading coil) o

Dial test – check whether the counter is functioning properly

o Creep test – check whether the meter is not running in no-load condition After gaining the meter to the satisfactory limits, the meter is sent to re-use. We had the chance to dissemble an energy meter and observe the components of the meter.

1.6.3 Branch Office

As the forth week in LECO training, we had the chance to attend and learn about the Branch functions and the structure of a branch. The branch, which we had the chance to visit, was Nugegoda Branch. Boralasgamuwa, Nugegoda and Maharagama CSCs are operated under this Branch. Billing, job costing and constructions could be taken as some of functions of the Branch office. 1.6.3.1Billing

The billing procedure is conducted as follows, The electricity bills for all the customers are prepares and printed in branch office. And it keeps the records of all the consumers as different accounts in PRONTO system. These accounts are completely managed by the Branch office. Then the printed bills are sent to the Depots or in other words CSCs. The revenue officers in the Depots issue the electricity bills for the consumers keeping the branch office copy-1 with them. The bundles of these copies are returned to the branch office after issuing the bills. The consumer accounts could be referenced through the PRONTO system. The payments could be done to the CSCs, branch office itself, and authorized agents and through the banks. The payments done through the banks are updated through the Head Office. The customer copy is returned to the customer and the branch office copy-2 and agent/Bank copy is kept with the agent. Then the branch office copy-2 is too sent to the branch office. From this the payment is registered and deposited to the customer account. 1.6.3.2New connections

When a new connection is establishing the following procedure is followed. First the customer applies a new connection through an application. The details including the name, address, connection type, map and the equipments in use are forwarded with the application. The Gramasewaka certificate is an essential document out of the above documents. Then a technical officer, who is responsible of estimation preparation, goes to the site and gathers the relevant information like the service wire length, transformer no, etc. The nearest

customer number is too noted down in case of the easiness of the identification. Then the estimate is prepared. The customer has to pay the estimated amount to CSC and sign a contract. After that, the LECO employees in CSC provide the connection and issue a meter seal docket. Then the file of the new connection is sent to the branch office and updates the PRONTO system. 1.6.3.3Constructions

While the high voltage constructions are being done by SDD, the low voltage constructions are done by the branch office. There are two kinds of constructions; LECO initiated and Customer initiated. In here the LECO initiated constructions are considered. LECO initiated constructions are mainly focused on upgrading the network performances. In this, following quality vice parameters are considered. •

The voltage of the consumer end should be within the range 230±6%V.(216.2V–243.8V)

•

The Frequency should be within the range 50±1%Hz (49.5Hz – 50.5Hz)

•

The power should be available 24hours. From this, in Branch office constructions, the voltage is used. Furthermore, the feeder

loadings and transformer loadings are taken into account as the performance vice parameters. Using the consumer data the transformers are modeled as individual networks and simulated using the “LV design” software, for the voltages and feeder loading for the next 5 years. Through this, the matters of the network are identified. Then the most feasible and cost effective solutions out of the followings are identified. •

Load transfer

•

Tap position change

•

New feeders

•

New transformer

•

Feeder rearrangement

1.6.4 Customer Service Center (Depot)

As the third week of the LECO training, we had the chance to learn about the CSC and the functions of it. And also we had the chance to attend the tangible works done by CSC, like maintenances and reconnections. The CSC which we had the chance to attend is Boralasgamuwa CSC. 1.6.4.1The tariff categories

Some of the tariff categories have been mentioned in the earlier chapters. But the exposure to the tariff categories is mainly gained during the LECO CSC period. The electricity is categorized as an essential item. So the electricity is sold to the customer in a tariff format instead of a price deciding method. In tariff format, the consumers are divided into few categories. They are, •

Domestic – this category is the one which is having the largest category in consumer count. The consumers who are using the electricity for domestic usage are belonging to this category. The cost of a unit in this category is relatively high, because, the consumers in this category are not contributing to the GDP.

•

General purpose – The consumers, who are using the electricity for commercial applications and the temporary connections are considered ad the GP consumers. They are having the highest rate.

•

Industrial – The consumers, who are using the electricity for industrial usage, are taken into this category. They should be registered in Ministry of Industry. The rate in this category is relatively low.

•

Hotel – The consumers, who are registered as hotels in ministry of tourism and having at least three star rating, is gathered to this category. They are having a relatively lower rate to the domestic.

•

Religious – the consumers who are registered as religious or social servicing organization in Social Service Department is gathered to this category. The rate for this category is relatively low.

•

Street lighting – the payable for street lighting is collected in an estimated manner from the relevant provincial council.

1.6.4.2Experiences

During the week we had the chance to attend the reconnection visit. In this, five disconnections ate reconnected. When disconnecting a supply, the phase line is removed from the meter, and seals it. When the approval for reconnection is given, the removed phase line is connected to the meter again. If the disconnection is difficult due to the consumer matters, the line is disconnected from the pole. The maintenance gang uses an identical tool for the gang, to seal the meters. After all the works with the meter sealing, a docked is issued. And also, we had the chance to attend a service maintenance visit. In this, we had the chance to attend two meter shiftings, service wire replacement and a meter box replacement. The MCB which is used instead of the fuse in CEB is used to protect the meter. Therefore, it should be connected before the meter. But, what we observed is, connect the MCB after the meter to prevent stealing the electricity from the MCB position. And also, the service wire should be placed in a clearly visible manner, to the revenue officer. We too had the chance to prepare connections of the meter box. Furthermore, the maintenance personals worked in the on-load. They removed the conductor in the live wire for some length for the safety purposes. They used the electricity in the phase for the drilling purposes of the walls.

Conclusion

In this training session the training is restructured for the Electrical Engineering students by dividing the 6-month training period into two and allowing all the students have two different trainings experiences in the same training session. Furthermore, each and every student had the exposure for the government sector as well as the private sector. Through this, we had the chance to acquire the complete knowledge about the field. The knowledge I gathered is a great. As my first training place I had the chance to training in Hemas Power. This company is a great path to acquire knowledge about power generation as an IPP. Because, the company has invested in thermal as well as the mini-hydro fields. We had the exposure to learn about the IPP role in power sector. In my training period I could be able to visit Giddawa mini-hydro plant and Senok Mark mini-hydro plant. This gave me the exposure to the life-style of yet-suburbanized villagers. It was a great experience to be with such a community. Furthermore, I enjoyed the environment very much. Being in the beneath of Knuckles mountain range is a great pleasure. Opportunity to participate in the programs like Teamwork workshop gave a different experience to me. Hemas Power is a company which does a great job with a lesser staff. So facilitating to three trainees and teaching them is a great deal. But they gave their maximum effort to teach us when we wanted, by managing their time too. Hemas Power is a worth place to have an electrical engineering training in IPP sector. We should thankful to Hemas Power for giving us the chance and proper guidance to have a better training. The second session of the training was CEB and LECO training. I had the opportunity to get the knowledge about various sections, in generation and transmission during CEB period. During the training, we had the chance to visit different places and gather the knowledge about different section. Being with a group of colleagues and gather knowledge by moving around the country was a great experience. What I observed in CEB is, the personals in the above level like Engineer and AGM, tries to keep the service provided by CEB in a quality vise good manner. But in the below levels, in most of times, this attitude is not represented. I strongly suggest looking into the matter of inefficiency through this degree. Furthermore, the developments and the improvements of the Generation and the transmission too, are done through the government

decisions, this makes the improvements delayed. We have the experiences of these delays in earlier 2000s. So, create a criteria to accelerate the decision making process through the government could be a very effective step. The attitude I had about the CEB before the training period was completely changed to a great one during the training period, after having the experiences in CEB. LECO was more helpful in understanding the distribution area. In this period we had the exposure to the new technologies could be used for the power sector. The creative ideas use the other fields too, instead of only the electricity related technologies. The major areas, like planning and administrating too learnt during this period. So the LECO period gives us a great knowledge. Furthermore, we had the opportunity to visit service repairs during the CSC week. In this week we had the exposure to the lifestyle of the employees, employed in heavy works like maintenance, in additional to the practical experience. Understanding these employees and their problems leads to the easiness of creating good relationships in engineering future. Moving on to the training establishment again, due to the training, the application of the theories increased the interest of learning them. So, if it’s possible to create an opportunity for the younger generations, to attend to, at least one month training in the earlier years, it would be a great help for them to get the knowledge well. Theory makes the understanding of the exposed; exposure makes the interest of the theory.

Annexes

Annex 1 – MATLAB Program on flow duration curve function details=analizerainfall(FDC,lowermargine,head,TE) %FDC order is [days,values] FDC(2,:) = FDC(2,:)-lowermargine; FDC_Size = size(FDC); for i=0:FDC_Size(1,2) A_days = [A FDC(1,:)'^(FDC_Size(1,2)-i)]; %#ok A_vals = [A FDC(2,:)'^(FDC_Size(1,2)-i)]; %#ok end coff_days = inv(A_days)*FDC(1,:)'; coff_vals = inv(A_vals)*FDC(1,:)'; disp('1 - Pelton'); disp('2 - Francis'); disp('3 - Kaplan'); disp('4 - Small'); turb = input('enter the turbine type:'); turbdet = [.9 .5 .6 .4]; minFlow = min(FDC(2,:)); maxFlow = min(FDC(2,:))/turbdet(1,turb); details1 = []; for i = cast(minFlow,'int16'):1:cast(maxFlow,'int16') x1 = polyval(coff_vals,i); flow = x1*i + quad(@(x)polyval(coff_days),x1,max(FDC(1,:))); power = TE*9.81*flow*head; max_power = TE*9.81*max(FDC(1,:))*i; plant_factor = power/max_power; excedance = x1/max(FDC(1,:)); annual_energy = power*60*60*24*365; dindet = [i power plant_factor excedance annual_energy]; details1 = [details1 dindet']; %#ok end details = details1;

Annex 2 – MATLAB Program on turbine selection-1 function turbine = selectturbine(head,flow) turbine_headmin = [30 6.6 136 62 4 2 1.3 3 2]; turbine_headmax = [734 72 1230 1150 186 27 23 27 147]; turbine_flowmin = [8 34.5 2.5 .1 .8 2.7 2.5 6 .1]; turbine_flowmax = [781 618 52 27 25 170 530 290 12]; turbine_efficiency_mean = [.92 .92 .89 .87 .85 .87 .89 .89 .81]; selected_turbines = ones(1,9); turbinedetails = []; disp('Turbine Order:') disp('1-Vertical shaft Francis') disp('2-Vertical shaft Kaplan') disp('3-Vertical shaft Pelton') disp('4-Horizontal shaft Pelton') disp('5-Small Scale Francis') disp('6-Small Scale Kaplan') disp('7-Bulb turbine') disp('8-Tubular turbine') disp('9-Cross-flow turbine') disp('') for i=1:9 if headturbine_headmax(1,i)|| flowturbine_flowmax(1,i) selected_turbines(1,i) = 0; turbinedetails = [turbinedetails ones(4,1)] else power = 9.806*head*flow*turbine_efficiency_mean (1,i); diameter = 0.168*(power/head)^.447; speed = 80.387*(head^.5/diameter)^.828; no_of_poles = 120*50/speed; syn_nop = 4*cast(no_of_poles/4,'int8'); rec_speed = 120*50/syn_nop; rec_diameter = head^.5/(rec_speed/80.387)^(1/.828); valuemat = [i power rec_speed rec_diameter]; turbinedetails = [turbinedetails valuemat']; end end disp(turbinedetails) [val,idx] = min(turbinedetails(4,:)); switch idx case 1 turbine = 'Vertical shaft Francis'; case 2 turbine = 'Vertical shaft Kaplan'; case 3 turbine = 'Vertical shaft Pelton'; case 4 turbine = 'Horizontal shaft Pelton'; case 5 turbine = 'Small Scale Francis'; case 6 turbine = 'Small Scale Kaplan'; case 7 turbine = 'Bulb turbine'; case 8 turbine = 'Tubular turbine'; case 9 turbine = 'Cross-flow turbine'; end

Annex 3 – MATLAB Program on turbine selection-2 function turbine = selectturbine(flow, head, speed) ssn = 10*(flow/1000)^.5*head^-.75*speed; turbines = []; if ssn<91.287 d = [1;.75]; turbines = [turbines d]; end if ssn>45.643 & ssn<213.003 d = [2;.75]; turbines = [turbines d]; end if ssn>60.858 & ssn<197.789 d = [3;.75]; turbines = [turbines d]; end if ssn>114.401& ssn<457.604 d = [4;.65]; turbines = [turbines d]; end if ssn>88.388 & ssn<1178.511 d = [5;.8]; turbines = [turbines d]; end if ssn>883.883 d = [6;.8]; turbines = [turbines d]; end lngth = size(turbines); if lngth(1,2)~=1 cost = []; for i=1:lngth(1,2) %select type, calc power, selectdia, evaluate cost/profit turbines(2,i); power = 10*head*(flow/1000)*turbines(2,i); specificspeed = 1.2*(head^-1.25)*speed*(power^.5); diameter = selectdia(head , flow , specificspeed); cost = [cost diameter]; end [val,idx] = min(cost); else

idx = 1; end switch idx case 1 turbine case 2 turbine case 3 turbine case 4 turbine case 5 turbine case 6 turbine end

= 'pelt_s'; = 'pelt_m'; = 'turgo'; = 'crossflow'; = 'franecis'; = 'axial';

Annex 4 – Trash rack design

Annex 5 – Teamwork workshop certificate

Annex 6 – Maintenance schedule

Training Report

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