UNIVERSITY UNIVERSITY OF MORATUWA Faculty of Engineering Non-GPA Module 3992: Industrial Training Training TRAINING REPORT
Training Establishments: DIMO Power Solutions Pvt. Ltd Lanka Electricity Company (LECO) Pvt. Ltd Ceylon Electricity Board (CEB) Overall Training Period: 14/05/2012 to 02/11/2012 Name: S. B. Nawarathne Registration No: 090594D Field of Study: Electrical Engineering En gineering Date of submission: 16/11/2012 i
Preface This report contains an overall assessment of my 24 week training period from from my perspective. The training period was divided divided into 3 parts: The 12 weeks at DIMO Power Power Solutions Pvt. Ltd, 4 weeks at LECO Pvt. Ltd and 8 weeks at the Ceylon Electricity Board. The report consists of three chapters: Chapter one gives basic introduction to the three training establishments, including their
functions, organizational structures, etc… It also focuses each company‟s strengths, weaknesses, its importance for the t he power sector and my own personal thoughts thoughts on how to improve their functions. Chapter two will focus in detail the entries of my training diary, i.e. details of work I had to carry out, difficulties faced while I was up to those tasks and a detailed det ailed description of plant/equipment/process (and how they are interconnected) that I had the chance to observe during my training period. Chapter three will feature an evaluation e valuation of my whole training experience from my point of view. In which, I will comment on the effectiveness of t he training program, to what extent it has helped me to understand the industry and provide suggestions on how it co uld be further improved.
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Preface This report contains an overall assessment of my 24 week training period from from my perspective. The training period was divided divided into 3 parts: The 12 weeks at DIMO Power Power Solutions Pvt. Ltd, 4 weeks at LECO Pvt. Ltd and 8 weeks at the Ceylon Electricity Board. The report consists of three chapters: Chapter one gives basic introduction to the three training establishments, including their
functions, organizational structures, etc… It also focuses each company‟s strengths, weaknesses, its importance for the t he power sector and my own personal thoughts thoughts on how to improve their functions. Chapter two will focus in detail the entries of my training diary, i.e. details of work I had to carry out, difficulties faced while I was up to those tasks and a detailed det ailed description of plant/equipment/process (and how they are interconnected) that I had the chance to observe during my training period. Chapter three will feature an evaluation e valuation of my whole training experience from my point of view. In which, I will comment on the effectiveness of t he training program, to what extent it has helped me to understand the industry and provide suggestions on how it co uld be further improved.
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Acknowledgement It was a great privilege pr ivilege to complete my 24 months of training as part of my Undergraduate course. Obviously, this experience would not have been poss ible without the help of some so me really collaborative, understanding and experienced people who helped us to get a first person, hands on experience experience of some major parts of the power sector. First and foremost I would like thank the National Apprentice Apprent ice and Industrial Training Authority (NAITA), Director and staff of the industrial training division of the University of Moratuwa for offering such a program to undergraduate students who have not yet seen the light of industry such as I was before this experience. Secondly, I would like to express my great appreciation towards Dr. Satish Namasivayam (lecturer in charge of industrial training tra ining for the Electrical Engineering department) who cooperated as responsively as possible between the st udents and the private sector/CEB in order to realize our preferences. I would like to further extend my gratitude to the following people who I had the pleasure of meeting during my training experience (in chronological order): Mr. Jude Fernando (Deputy General Manager, DIMO Power Solutions Pvt. Ltd.) for interviewing and accepting me as a trainee t rainee and advising me on how to progress in the first 12 weeks. Mr. Pubudu Niroshan (Project Manager, DIMO DI MO Power Solution Pvt. Ltd.) and Mr. Rajiv Nagayodavithana (Electrical Engineer, Engineer, DIMO Power Solutions Pvt. Ltd) for for assessing and advising me on my attitude, conduct and correcting diary entries. Mrs. Manel Nanayakkara (Electrical Engineer, Internal I nternal training, Ceylon Electricity Board) for making the arrangements for eight weeks of valuable training at CEB. Mr. B. Bernard Perera Perer a (Training Consultant, TTC, Lanka Electricity Company Pvt. Ltd) who arranged the 4 weeks of valuable and unique training at LECO Pvt. Ltd. Last but not least I would like like to acknowledge the contribution of all Engineers, Technicians and Other employees who have influenced my training experience for the better good.
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Contents I. Preface ............................................................................................................................... i II. Acknowledgement ............................................................................................................ ii III. Content.......................................................................................................................... iii IV. List of Figures ............................................................................................................... vii IV. List of Tables ............................................................................................................... viii 1. INTRODUCTION TO TRAINING ESTABLISHMENTS ................................................ 1 1.1 DIMO Power Solutions Pvt. Ltd .................................................................................. 1 1.1.1 Organizational Structure ........................................................................................ 2 1.1.2 Strengths ............................................................................................................... 2 1.1.3 Weaknesses ........................................................................................................... 2 1.1.4 Suggestions for improvements ............................................................................... 3 1.1.5 Threats to survivability and Profitability ................................................................ 3 1.1.6 Usefulness to the country ...................................................................................... 3 1.2 Ceylon Electricity Board .............................................................................................. 3 1.2.1 Functions of CEB .................................................................................................. 4 1.2.1.1 Generation ..................................................................................................... 4 1.2.1.2 Transmission .................................................................................................. 4 1.2.1.3 Distribution .................................................................................................... 4 1.2.2 Organizational Structure ........................................................................................ 5 1.2.3 Strengths ............................................................................................................... 5 1.2.4 Weaknesses ........................................................................................................... 5 1.2.5 Suggestions for improvements ............................................................................... 6 1.2.6 Threats to survivability and Profitability ................................................................ 6 1.2.7 Usefulness to the country ...................................................................................... 6 1.3 Lanka Electricity Company Pvt. Ltd ............................................................................ 6 1.3.1 Organizational Structure ........................................................................................ 7 1.3.2 Strengths ............................................................................................................... 7 1.3.3 Weaknesses ........................................................................................................... 7 1.3.4 Suggestions for improvements ............................................................................... 8 1.3.5 Threats to survivability and Profitability ................................................................ 8 1.3.6 Usefulness to the country ...................................................................................... 8 iii
2. TRAINING EXPERIENCE............................................................................................... 9 2.1 Training Experience at DIMO Power Solutions Pvt. Ltd .............................................. 9 2.1.1 TSSGSP Lot A_2 Project ..................................................................................... 9 2.1.2 CEB SCADA/DMS ............................................................................................ 10 2.1.2.1 Introduction ................................................................................................. 10 2.1.2.2 Deficiency Clearing ..................................................................................... 11 2.1.2.3 SCADA system in Ring/Radial Substations.................................................. 13 2.1.2.4 Components used in the RTU panel ............................................................. 14 2.1.2.5 Siemens TM 1703 ACP Automation Unit .................................................... 17 2.1.2.6 Equipment used on the panel side................................................................. 17 2.1.2.7 Communication method ............................................................................... 20 2.1.2.8 SCADA overview ........................................................................................ 20 2.1.3 Details on exposure to other equipment while on deficiency clearing................... 21 2.1.3.1 Satellite Switchgear...................................................................................... 21 2.1.3.2 High Voltage Switchgear in Ring/Radial Substations ................................... 23 2.1.3.3 Low Voltage Switchgear in Ring/Radial and Satellite Subst ations ................ 24 2.1.3.4 Numerical relay - SIPROTEC Compact 7SJ80 ............................................. 25 2.1.3.5 DC power supply system in the Ring/Radial substations .............................. 24 2.1.3.6 Transformer at Primary Substation ............................................................... 26 2.2 Training Experience at the Ceylon Electricity Board .................................................. 26 2.2.1 Samanalawewa Hydro Power Station. ................................................................. 26 2.2.1.1 General/Technical specifications of the plant ............................................... 27 2.2.1.2 The process of generating electricity ............................................................ 28 2.2.1.3 Starting and Synchronising........................................................................... 28 2.2.1.4 Maintenance................................................................................................. 28 2.2.2 Kukuleganga Hydro Power Station. ..................................................................... 29 2.2.2.1 General/Technical specifications of the plant ............................................... 29 2.2.2.2 Synchronising the generator ......................................................................... 30 2.2.2.3 Excitation ..................................................................................................... 30 2.2.2.4 Mechanical Auxiliaries ................................................................................ 31 iv
2.2.3 Kelanitissa Power Station (KPS) ......................................................................... 32 2.2.3.1 Specifications for the 20 MW Gas turbines .................................................. 33 2.2.3.2 Specifications on GT-7................................................................................. 33 2.2.3.3 Starting Sequence of the 20 MW Gas turbine ............................................... 33 2.2.3.4 How it works. .............................................................................................. 34 2.2.3.5 Synchronous condenser mode ...................................................................... 34 2.2.3.6 Excitation ..................................................................................................... 34 2.2.3.7 Ratcheting and Barring................................................................................. 35 2.2.4 KCCPS (Kelanitissa Combined Cycle Power Station) ......................................... 35 2.2.4.1 Specifications of the plant ............................................................................ 35 2.2.4.2 The HSRG (Heat Recovery Steam Generator) ............................................. 36 2.2.4.3 Auxiliaries ................................................................................................... 36 2.2.5 Sapugaskanda Diesel Power Station .................................................................... 37 2.2.5.1 Station A, specifications ............................................................................... 37 2.2.5.2 Station B, specifications ............................................................................... 37 2.2.5.3 Station Switchyard ....................................................................................... 38 2.2.5.4 Starting of the diesel engine/generator .......................................................... 38 2.2.5.5 Excitation system for station B generator ..................................................... 39 2.2.6 Transmission Operations and Maintenance .......................................................... 39 2.2.6.1 Pannipitiya Grid Substation .......................................................................... 39 2.2.6.1.1 Switchyard components.......................................................................... 39 2.2.6.1.2 Protection ............................................................................................... 41 2.2.6.2 Biyagama grid substation ............................................................................. 44 2.2.6.2.1 Line Maintenance ................................................................................... 44 2.2.6.2.2 Transmission equipment ......................................................................... 45 2.3 Training Experience at Lanka Electricity Company Pvt. Ltd. .................................... 46 2.3.1 Branch Office ...................................................................................................... 46 2.3.1.1 Accounts division......................................................................................... 46 2.3.1.2 Customer Service ......................................................................................... 46 2.3.1.3 Administration ............................................................................................. 47 v
2.3.2 Systems Operations ............................................................................................. 47 2.3.2.1 Control centre scheduling ............................................................................. 47 2.3.2.2 Meter testing lab .......................................................................................... 48 2.3.2.3 Transformer repair workshop ....................................................................... 49 2.3.3 Customer Service Centre ..................................................................................... 49 2.3.3.1 Materials used by LECO for distribution purposes ....................................... 49 2.3.3.2 Energy meter replacement ............................................................................ 50 2.3.4 Engineering and Operations ................................................................................ 50 2.3.4.1 Procurement ................................................................................................. 51 2.3.4.2 Load forecasting .......................................................................................... 51 2. CONCLUSION ............................................................................................................... 52 V. Abbreviations .................................................................................................................. ix VI. References ..................................................................................................................... xi VII. Annexes ....................................................................................................................... xii
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List of figures Figure 1.1 DIMO Power Solutions Organizational Structure ................................................. 2 Figure 1.2 CEB Organizational Structure .............................................................................. 5 Figure 1.3 LECO Organizational Structure ............................................................................ 7 Figure 2.1 Front view of RTU panel .................................................................................... 14 Figure 2.2 Basic diagram of interposing relay...................................................................... 18 Figure 2.3 Voltage transducer connection............................................................................ 19 Figure 2.4 Current transducer connection ............................................................................ 20 Figure 2.5 SCADA network ................................................................................................ 21 Figure 2.6 Internal diagram of RMU ................................................................................... 22 Figure 2.7 Single line diagram for a typical LV distribution in Ring/Radial Sub. ................ 24 Figure 2.8 Block diagram of DC supply .............................................................................. 25 Figure 2.9 Turbine bearing locations ................................................................................... 31 Figure 2.10 HVAC system .................................................................................................. 32 Figure 2.11 Method of rotating diode excitation .................................................................. 34 Figure 2.12 Distance Protection........................................................................................... 42 Figure 2.13 Arrangement for differential protection ............................................................ 42 Figure 2.14 Power Transformer arrangement ....................................................................... 43
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List of tables
Table 1.1 Generation Details ................................................................................................. 4 Table 1.2 Substation Details .................................................................................................. 4 Table 2.1 Test Results ......................................................................................................... 10 Table 2.2 Different types of signals ..................................................................................... 13 Table 2.3 Disc error test and results ..................................................................................... 48
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1.
INTRODUCTION TO TRAINING ESTABLISHMENTS
1.1
DIMO Power Solutions Pvt. Ltd.
Vision: To be the team who sets standards while pro viding total solutions for the energy
sector‟s needs Mission: To set the benchmark in the power industry by delivering innovative, re liable and
efficient solutions for the nation‟s energy demands through a team of dedicated and competent staff. DIMO Power Solutions (formerly known as DIMO Power Engineering) falls under of the 5 business sectors of DIMO (Diesel and Motor Engineering) Pvt. Ltd which is the Electromechanical and Biomedical Engineering Sector . „DIMO power solutions‟ is in the business of providing “turn-key” solutions for
power transmission and distribution. DIMO
has been a partner of Siemens (India) for over 50 years, most o f the products offered are from Siemens and they comply with all IEC regulations and ISO requirements. In the fiscal year 2011/2012 profits have risen, with DIMO Power solutions completing a major project; the SCADA/DMS project, they were also able to built t he step up substations for the first ever private sector owned wind turbine plant. DIMO together with Siemens has secured some projects under the TSSGSP that has been put in effect by the CEB, this involves augmentation and construction of some substations.
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1.1.1
Organizational Structure
Chairman/CEO
Managing Director
Director In-Charge
Business Unit Manager
Commercial Executive
Administrative Executive
Design/Commissioning Engineer
Assistant Engineers
Project Manager
Key Account Manager
Project Engineers
Assistant Engineer
Site Supervisor
Sales Engineer
Service Engineer
Electrical Foreman
Figure 1.1 DIMO Power Solutions Organizational Structure
1.1.2
Strengths
Partner of globally recognized power engineering company – Siemens
Run under an experienced and well known company – DIMO Pvt. Ltd.
Run by an adequate and competent amount of staff
Hire labor/man power separately as sub-contractors
1.1.3
Weaknesses
Some products from Siemens India are not up to the standards of S iemens Germany (subjective)
Difficult to monitor labor or progress at all times, due to lack of supervisors
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1.1.4
Suggestions for improvements
To gain success and recognition in the power sector by completing more high end projects
To expand the department as to provide an easier working environment for Engineers (especially during times of projects when there is not enough space for employees, not just trainees).
1.1.4
Threats to survivability and Profitability
Since almost all huge projects that DIMO undertake are contracts from CEB, the
department‟s existence is highly dependent on the performance of CEB.
There are a few serious competitors such as ABB or LTL that can pose a threat to t he Siemens market.
1.1.5
Usefulness to the country
With an increasing growth accompanied by a greater demand for power; the installation, maintenance and repair of electrical equipment from MCBs to switchgear to t ransformers to substations becomes an even greater challenge. With new and affordable technologies coming into the world, we need companies like DIMO and Siemens to introduce them to Sri Lanka in order to maintain the reliability and safety of the power supply for our day to day works. 1.2
Ceylon Electricity Board
Vision: Enrich Life through Power Mission: To develop and maintain an efficient, coordinated and economical system of electricity supply to the whole of Sri Lanka, while adhering to o ur core values – Quality, Service to the nation, Efficiency and effectiveness, Commitment, Safety, Professionalism, Sustainability. The CEB is a government owned corporation involved in generation, transmission and distribution of electricity. It was developed for the sole purpose o f providing electricity to all types of customers of the country. The second main objective is to provide electricity to the vulnerable customers at an affordable price, wherever t hey may be located. Therefore, it is not-profit oriented. 3
1.2.1 Functions of CEB
CEB has most ownership over the country‟s generation and distribution assets, while has full ownership over transmission. 1.2.1.1 Generation
Source of Power
Table 1.1 – Generation Details No. of power stations Installed Capacity (MW)
Hydro
16
1207
Thermal-Oil
6
548
Thermal-Coal
1
300
Wind
1
3
Total
24
2058 Source: CEB Statistical Digest 2011
1.2.1.2 Transmission
Table 1.2 – Substation Details Substation type
No. of substations
Capacity (MVA)
132/33 kV (Grid)
46
3043
220/132/33 kV (Grid)
5
2100/500
220/132 kV (Grid)
2
405
132/11 kV (Grid)
5
369
33/11 kV (Primary)
124
1090
33 kV/LV and 11 kV/LV
22839
5625
(Distribution) Source: CEB Statistical Digest 2011 This gives a total of 23021 substations with a total capacity of 13134 MVA. 1.2.1.3 Distribution
From Table 1.2, it can be seen that there are 22839 distribution substations. The total number of consumers has increased by 5.3% from 2010 to 2011. The distribution area has been divided into 4 regions – Region 1, Region 2, Region 3 and Region 4 with a tot al of 194 Customer Service Centers.
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1.2.1
Organizational structure
AGM Generation AGM Transmission AGM Distribution – Re ion 1 AGM Distribution – Re ion 2
Chairman and
General
members of the
Manager
AGM Distribution – Re ion 3 AGM Distribution – Re ion 4
board AGM Asset Management and Centralized Services AGM Corporate Strategy AGM Projects AGM Finance Mana er
Figure 1.2 CEB Organizational Structure
1.2.3
Strengths
CEB is government owned and therefore pledges to provide reliable and affordable electricity to the community
CEB has the freedom to plan and augment the existing system without external interferences (national and international).
1.2.4
Weaknesses
Since CEB owns almost all of the generating assets o f the country, it has to make comprises to keep up with the demand.
CEB has some outdated equipment; hence there are problems in importing spare part s from manufacturers as some of them do not even exist in the market at this point in time or simply the products have been discontinued.
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1.2.5
Suggestions for Improvements
Move towards sustainable energy sources such as Wind, Solar, Hydro, etc …
Encourage more IPPs (Independent Power Producers)
Invest in newer technologies for communications, materials and co ntrol systems for the sake of both reliability and safety.
1.2.6
Threats to Survivability and Profitability
Currently there is no huge threat to the survivability. However, CEB is always incurring losses. The only good thing to say is that the magnitude of loss has decreased from the year 2010 to 2011. CEB is a government-owned corporation;
any threat to the government‟s
financial status is also a threat to its survivability as long as CEB still depends on imported
Oil (Naphtha, Auto Diesel, Heavy Fuel, etc…). 1.2.7
Usefulness to the country
Since CEB owns most part of the power sector, it is important to note that it plays a huge role
in the country‟s development. The availability of electricity is a catalyst to any sector of the country; be it education, business, agriculture, etc… Therefore it is vital to reach out to each and every individual as well as to protect the vulnerable consumers. Since CEB stands for these claims, it is a very useful asset to the country. 1.3
Lanka Electricity Company (LECO) Pvt. Ltd.
Vision: Enjoy being the light for lives of people through innovative eco-friendly business Mission: To provide the best energy solutions to the society through continuous innovations LECO was a company first established in 1983 for the purpose of electr icity distribution. The main reason for this was that before there were large inefficiencies in the net work; high
losses, incorrect billing, theft of electricity, etc… Today LECO has 7 branches in Galle, Kaluthara, Kotte, Kelaniya, Moratuwa, Negombo and Nugegoda. LECO is by majority owned by the CEB and the Treasury and the rest by the UDA and local authorities. The main function of LECO is to purchase electricity from CEB 33/11 kV substations and sell to the 230/400 V consumer end. LECO also needs to make sure inefficiencies in the system are kept to a minimum (like those discussed above).
LECO‟s tariff structure is
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prepared by the PUCSL (Public utilities commission of Sri Lanka) in a way that the
company‟s survivability is assured. 1.3.1
Organisational Structure
Chairman & Board of directors
General Manager
Head of Operations
System Operations Manager
Chief Financial Officer
Branch Manager
Head of Engineering
Training Manager
Branch Enginee Control Centre System Operations
Customer Services
Electrical Engineer
Human Resources & Administration
Systems Development Manager
Design Engineers
IT Section
Procurement/ Supply Manager
Test Engineer
Administrative Officer
Branch Accountant
Communications
Figure 1.3 LECO Organizational Structure 1.3.2
Strengths
Breakdowns are immediately addressed, overall state o f customer service is satisfactory
1.3.3
There is adequate staff and the organization is well structured Weaknesses
There are no plans for future expansion, the growth of customers will one day saturat e 7
Old technology in most places
Street lamp consumption is considered as a loss
1.3.4
Suggestions for improvements
Replace old analog energy meters by new digital meters (although this is being carried out it is still not 100% in effect)
Introduce remote switching as well (for LBS and Auto reclosers)
The control centre mimic is very much out of date and replacement by a digital system would make handling interruptions more efficient
1.3.5
Threats to survivability and Profitability
Maintaining profit is the key to its survival therefore it should cut down on losses and prevent theft of electricity as much as possible. Mismanagement can be a key factor in incurring losses as we see that some branches are making profits while others are making losses. 1.3.6
Usefulness to the country
LECO has set the benchmark for Electricity distribution. Its custo mer service centers and branch offices are responsive and apt. It has also helped to take the load off CEB in an area where it is difficult to maintain a good quality of supply due to the large concentration of consumers.
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2.
TRAINING EXPERIENCES
2.1
Training Experience at DIMO Power Solutions Pvt. Ltd
Our first 12 weeks of training was held here, we repo rted to Mr. Jude Fernando who was the DGM (who had previously interviewed us). He introduced us to Mr. Pubudu Niroshan (Project manager) who in turn acquainted us with all the other Engineers in the depar tment. When we first arrived there were currently no projects of great importance, DIMO had recently won a bid for the Transmission System Strength Grid Substation Project (TSSGSP) LOT A_2. This project involved 2 main components: i. ii.
Construction of new grid substations at Naula, Maho and Pallekele Augmentation of existing grid 132/33kV Grid Substations at Galle, Habarana, Matara, Panadura and Puttlam.
The other major project that was available at that time was the CEB SCADA/DMS (Supervisory Control and Data Acquisition/Distribution Management System) project. This project had already been commissioned and was now in a later post-commissioning stage. 2.1.1
TSSGSP Lot A_2 Project
This project was still in its blooming stages, drawings were still being approved and foundations were still being laid out (substation/transformer). I had the least exposure to this project during my 12 weeks at DIMO. The first 2 weeks I spent at the office were highly focused on tender documents regarding this project, where I learnt a lot about the structure of the tender documents and some highly technical terms used in power engineering. Regarding the project I only had the chance of studying an approved document for the transformer foundations. This involved some calculat ions that were highly Civil Engineering related although it was important to our department as we ll. Since building a grid substation is a very long process, I had the chance to read a preliminary report: Report on quarry dust fill material for use under the main transformer at CEB grid substation at Matara – This report is basically about of the assessment o f the suitability of
quarry dust as a fill material for the transformer foundation at the Matara 132 /33 kV GSS.
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The report features 3 types of tests that were carried out in the laboratory:
Atterberg limits
Sieve Analysis test
Proctor Compaction test
The specifications for a good fill material are:
The minimum dry density when compacted to 95% proctor density shall be 1800 kg/m3
The soil is well graded (That is the grading curve is within the acceptable limits defined by BS 882: 1992)
The following results were obtained from the samples supplied: Table 2.1 – Test Results Proctor dry density (kg/m )
2064
Optimum moisture content (%)
9.9
Soil Plasticity
Non-Plastic
Based on the above information, quarry dust material can be recommended as a suitable fill material for the transformer foundation. 2.1.2
CEB SCADA/DMS (Supervisory Control and Data Acquisition/Distribution Management System) project.
2.1.2.1 Introduction
This also known as Package D under CCEDD project, Package D involves the implementation of a SCADA system, including construction of the Distribution Control Centre (situated at Primary A). The system will gather data from over 200 substations (i.e. real time values pertaining to any substation) to monitor and control the 11 kV supply within the Colombo region.
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The scope of the work consisted of the design, supply, installation and commissioning of the following:
The SCADA and DMS itself and full functionality from a central control centre (DCC) and data communication system (optic-fiber, leased lines, wireless
communication, etc…)
Remote Terminal Units (RTUs) at Primary Substations (132/33 kV)
Remote Terminal Units (RTUs) at Ring/Radial Substations (11/0.4 kV)
Remote Terminal Units (RTUs) at Satellite substations (11/0.4 kV)
This project was by now a lready commissioned and in proper working condition for the most part. However, there was still a post-commissioning process going on, known as deficiency clearing. So for the next 10 weeks I had the opportunity to go to these various substations and take part in them, which will be explained in the next sub section. 2.1.2.2 Deficiency Clearing
This is where a list of deficiencies is prepared by a CEB Engineer after visiting some of the substations involved in the project. The Engineer in charge of the project at DIMO t hen creates a template deficiency clearance list, which has to be checked at each and every substation. So during deficiency clearing each and every possible deficiency has to be checked so that it is compliant with the checklist. For Primary and Ring/Radial Substations, a folder is maintained which contains details o f; the type of deficiency, action performed in order to correct, and signatures from both an employee of DIMO and an Electrical Superintendent from CEB (which has been assigned to the project). This document is usually signed whenever a deficiency is cleared, sometim es if it cannot be cleared a comment has to be made (this will be later on inspected by an Engineer) and later on an action will be taken to r esolve it. Satellite stations are much simpler as they are smaller in size and the number of defects is less. They too have a checklist which is used to correct defects. Each day an agreement is made between the DIMO assistant engineer and the ES from CEB on the substation locations to which they are to visit during that day. Deficiency clearing is usually a laborious job and is carried out by technicians; these are sub-contractors hired by DIMO (as they do not provide man power). The technicians are usually d ivided into teams of 11
two along with a supervisor; they are then dropped off at several substations. Once all possible deficiencies are cleared the Supervisor and the ES will sign the checklist ensuring that both parties are satisfied. During my upcoming 10 weeks of training, I was placed as such a supervisor. I started off with Ring/Radial substations under the guidance of the assistant engineer; together we covered over 70 Ring/Radial substations (a 100% of defects were not rectified due to lack of time/material). By 02/07/2012, deficiency clearing of satellite stations began and so I was assigned sole responsibility of a group of technicians. I was to supervise t he work, give any directions necessary, complete the checklist and finally coordinate with ES to see if everything was up to their expectations. I was given the task of keeping track of labor allocation during that day. During the period of 02/07/2012 to 02/08/1012 my training partner and I managed to cover all the satellite stations (over a 100). A copy of the deficiency clearing forms a nd labor allocation forms are provided in the annex. There were a number of difficulties I had while on de ficiency clearing. The main one was labor management, laborers are sometimes dodgy and they like to do things their own way. This is sometimes a problem when following a deadline. It was in fact very challenging as there was also a notable age gap between some of the laborers and me. However, my duties were only to keep their minds on the job and remind them if they missed anything. Another problem was that most workers do not like to adhere to safet y regulations such as
wearing overalls, safety shoes, etc… I did not directly intervene with any technicians, but I simply relayed this information to my superior – Assistant Engineer. Another challenge was adapting to the conditions of the substations such as heat, noise, pollution, etc… Since we had the job of supervising work and visiting many different substations, we had exposure to a lot of different equipment, especially the ones used in the SCADA project. We also had the chance to observe different kinds of transformer s, circuit breaker panels, diesel
generators, etc… The next chapter will feature technical details regarding the overall nature of the SCADA system.
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2.1.2.3 SCADA system in Ring/Radial Substations
There are over a 100 Ring/Radial Substations, each one contains a number of panels (Feeder panels, Metering panels, Bus couplers). The purpose of SCADA is to supervise and control (from the DCC), for this it must be capable of obtaining signals and sending signals to and from the panels respectively. There are 4 types of signals involved: i.
Single Information Signals
ii.
Double Information Signals
iii.
Double Command Signals
iv.
Analog Values Table 2.1 – The different types of signals
Single Information Signals
Double Information
Double Command
Analog
Signals
Signals
Values
Circuit breaker open
Circuit breaker open
Current +
Circuit breaker closed
Circuit breaker closed
Current –
Communication Alarm
Earth switch open
Dummy Relay ON
Over Current Alarm
Earth switch closed
Dummy Relay OFF (1)
Earth Fault Alarm
Local Indication
Circuit Breaker Faulty
Remote Indication
Busbar 1 Voltage status
Dummy Relay ON (1)
alarm(2)
Dummy Relay OFF(1)
Aux. Power Supply fault (1)
RTU Alarm
(1)
(1)
(3)
Voltage +
Voltage – (3)
Busbar 2 Voltage status alarm(2) (1) – These signals are only used for components within the RTU panel itself (2) – These signals are used only for the Bus Section (3) – These signals are only used for the Metering panels Note: All other signals are common to every feeder panel
The RTU panel needs to send and receive signals to and from the panels using some sort of equipment (which is held inside the RTU). This will be discussed in the next chapter.
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2.1.2.4 Components used in the RTU panel
As discussed above there are three t hree types of signals involved, involved, these signals are handled by different modules inside the RTU panel known as modules, they are:
DO (Digital Output) modules
DI (Digital Input) modules
AI (Analog Input) modules
PS (Power Supply) modules
PE (Peripheral Interface) modules
Communication and Processing module
Cubicle Lamp 60 W Master Control Element
6
6
6
I-
D
6
I-
D
6
I-
D 2
2
2
2
I-
-6
1
6
1
4 0 0
0
0
P
D
D
AD
A
6
-6 1
31
3
P E S
O
OI-
-6 0
1
0
0
2
1
0
2
6
Inverter
D E
S
ACIN, DCIN, AC MCB, DC MCB, DCDI, DCDO (These are all MCBs)
Thermostat
P P
0
0
4
I-66
2
1
2
I6
2
12
20
Door limit switch
6 02
0
0 0
Heater switch and plug point
Heater
Terminal blocks
Figure 2.1 Front view of RTU panel
All modules used in this project are from fro m Siemens AG, they are made to communicate with the TM 1703 ACP Automation Unit. I will now elaborate on the ratings of modules one by one;
14
1. DO module – DO DO 6212 No. of Outputs
8 Binary Outputs
Nominal Voltage
24 VDC (As used in the the project)
Maximum continuous current
2 A, 5 A for 1 minute
Power Supply Operating Voltage
4.7…5.1 VDC, 800 mW
2.
DI module – DI DI 6102
No. of Inputs
16 Binary Inputs
Nominal Voltage
24 VDC
Operating points
< 12 V (logic 0) >16 V (logic 1)
Rated Current
1…1.5 mA
Power Supply Operating voltage
4.7…5.1 VDC, 170 mW
3.
AI module – AI AI 6300
No. of Analog inputs inputs
4 inputs (2 groups of 2 each)
Measuring ranges
Current measurement -20…0…+20 mA Voltage measurement -10…0…+10 V
Resolution
0.013% at ±20 mA 0.025% at ±10 V
Power Supply Operating voltage
4.
4.7…5.1 VDC, max. 480 mW
PS module – PS PS 6620
Operating Voltage
24 VDC
Output voltage (TM Bus)
5.1 VDC ± 1% (as used in the project)
Max. Output Power
8W
15
PE module – PE PE 6400
5.
Processor
80C251SQ-16, 16 MHz
Program Memory
PE-ROM 256 Kbytes Kbytes
Main Memory
RAM 64 Kbytes
Power Supply Operating Voltage
4.7…5.1 VDC, max. 720 mW
A PE-6400 module can communicate communicate with up to 8 I/O modules (AI, DI or DO) with the TM 1703 ACP via the Ax 1703 Peripheral Per ipheral bus at a transmission t ransmission rate of 16 Mbps. Each PE module is equipped with a power supply. Master Control Element – CP CP 6014
6.
This is the module responsible for acquisition, processing and output of processed dat a. This Unit is capable of communicating with the above modules (except PS module) t hrough the Peripheral Element. Furthermore it is responsible for communicating data between that substation and the DCC using some form of communication. This module can interface up to 16 PE modules. The master control element contains severa l communication interfaces; -
Serial Interface for point to point or simply running running diagnostics or tests on site
-
LAN/WAN Ethernet for communication of data from substation to DCC
-
Profibus DP for communication between Master Control and Numerical Relays within the 11 kV panels.
This module contains a small flashcard; this card co ntains the firmware that runs the whole SCADA system. Furthermore, it holds the parameters for each and every DO, DI and AI module. E.g.
D00 of DI-6102 will hold the Circuit breaker OFF indication D01 of DI-6102 will hold the Circuit breaker ON indication
The flash card may be programmed pro grammed on site or using a computer, to the t he user‟s wishes. Note: The number of modules used in the RTU, i.e. AI, DI, DO or PE depend on the number
of signals used, which in turn depends on the number of panels at the substation, E.g. Satellite Satellite stations only one DO, DI and CP module (instead of Master Control Element) because there
16
is need to control only the PCB actuator. Another thing is that there are extra modules in some substation for spare signals. 2.1.2.5 Siemens TM 1703 ACP Automation Unit
TM 1703 ACP is the name given to the whole system inside the RTU (when all the above are connected). There are several advantages of this system:
If a module fails, it can easily be replaced
There is room for more expansion (up to 16 peripheral elements)
Allows setting of parameters or diagnostics or test ing both locally and remotely using a software called TOOLBOX II
Can be compatible with other SAS from Siemens
2.1.2.6 Equipment used on the panel side
There are several components within the panel side which are used t o transmit and receive data to and from the panels. These are: i.
Terminal blocks
A terminal block consists of a set of knife type gate terminals. These are found inside the 11 kV panels. The terminal blocks are like an inter mediate point between the RTU and the 11 kV panel. The use of the knife gate terminal is to easily isolate any necessary connection from the RTU panel for maintenance or repairing. ii.
Local/Remote Switches
When the switch is on Local, the supply to all DO modules are cut off, meaning that remote operation of that breaker panel is not possible, also supply will be given dir ectly to the circuit breaker tripping/closing circuit and not through the interposing relays (will be discussed next) so that the breaker can be tripped on site. When switch is set to Remote, supply to all modules are available, the circuit breaker tripping/closing circuit is supplied through the interposing relays, meaning that only Remote operation of breakers is possible.
17
iii.
Interposing relays
Since the PLC contacts of the DO modules are not rat ed for operating the tripping circuit directly, interposing relays need to be used. In t his case, the interposing relay coil is connected across the PLC circuit, but the relay contacts are rated for the tripping circuit. There are two kinds of interposing relays used: Interposing relay open which is used for the circuit breaker trip circuit; this is controlled by one DO module relay output. Interposing relay output which is used for the circuit breaker close circuit; t his too is controlled by one DO module relay output.
24 VDC
0 VDC
DO Module
Interposing relay OPEN or CLOSE
Circuit breaker trip/close circuit
Figure 2.2 Basic diagram of interposing relay iv.
Transducers
Voltage transducers are used to convert the value of r.m.s voltage into a dc current. The VTs are directly connected to the exist ing metering Potential transformer (11/0.11 kV) within the metering panel. The VT can be easily programmed using the software via a USB/Serial port. The ratings of the VT are given below: Power supply
24 VDC (< 4 VA)
Accuracy class
0.5%
Voltage measuring range
0 to 110 V
Frequency
50 Hz
DC output current
4 to 20 mA (as programmed)
18
3 phase, 50 Hz, 11 kV Busbar Withdrawable VCB
Metering Voltmeter
Fuse
Voltage transducer Earth Switch Fuse
Metering Potential Transformer
24 VDC
0 VDC
To AI module
Figure 2.3 Voltage transducer connection
Current transducers are used to convert the value of r.m.s current into a dc current. The CTs are directly connected to the existing metering Current t ransformer (400/1 or 200/1 in most cases). The CT can be easily programmed using the software via a USB/Serial port. The ratings of the CT are given below: Power supply
24 VDC (< 4 VA)
Accuracy class
0.5%
Current measuring range
0 to 1 A and 0 to 5 A (depending on current transformer)
Frequency
50 Hz
DC output current
4 to 20 mA (as programmed)
19
3 phase, 50 Hz, 11 kV Busbar
Withdrawable VCB
Current Transformer
Metering ammeter
C/T Shortlinks
Current Transducer
0VDC
24 VDC
Earth Switch
To AI module
Figure 2.4 Current transducer connection
2.1.2.7 Communication method
The TM 1703 ACP unit needs to communicate with the DCC using some form of communication; this is done through fibre-optic cables or leased lines from SLT (Sri Lanka Telecomm) network. An Ethernet Media Converter is used to convert the output from the TM 1703 (Ethernet) to fibre-optic cables. An SLT modem is used where fibre-optic cables are unavailable; this is a leased line from SLT. The standard use is IEC 60870-5 which sets standards for communication between any two systems in the SCADA network. 2.1.2.8 SCADA Overview
Each RTU panel has an IP address in the network that it‟s connected in which allows to specifically identify it. Below is the overview d iagram of SCADA: Note: Not only Ring/Radial Sub. Are involved in SCADA, there are Primary and Satellite
stations but they are not explained here as the concept is the same. Drawings for Ring/Radial subs are too cumbersome, a wiring diagram for Satellite st ation is provided in Annex 4. 20
IEC 60870-5-104
Figure 2.5 SCADA network 2.1.3
Details on exposure to other equipment while on deficiency clearing.
2.1.3.1 Satellite Switchgear
The Trident Fused Oil Ring Main Unit (RMU) is the main feature of a sat ellite station. RMUs are usually connected to another RMU (in a different sat ellite station) or they are connected to at least one Ring/Radial Substation. The RMU has 3 connections, two o f which are Ring Switches and the other is a TEE OFF for the transfo rmer feeder (the feeder is protected by an internal fused switch). One ring switch is always connected to a motorized act uator therefore only one feeder can be controlled using SCADA. By controlling I mean t urning the switch on and off. Only one DO module is used here and there are two interposing relays located inside the PCB Control actuator. The interposing relays operate the motorized circuit t hat drives the actuator back and forth in order to turn the switch ON and OFF. A wiring diagram of t he SCADA in satellite stations is given in Annex 4.
21
To RMU/Sub
To RMU/Sub
Internal diagram of RMU
11/0.4 kV Transformer
Figure 2.6 Internal diagram of RMU
The ratings of a typical RMU are given below: Ring Switch
Rated Current
630 A
Making Capacity
50 kA (peak)
Breaking Capacity
630 A
Short time withstand
20 kA/3 s
Basic impulse level
95/110 kV
Fuse switch
Rated Current
200 A
Making Capacity
50 kA
Breaking capacity
20 kA
Short time withstand
3.15 kA/3s
Basic impulse level
95/110 kV
22
2.1.3.2 High Voltage Switchgear in Ring/Radial Substations
The main switchgear I observed were Air Insulat ed, Vacuum Circuit Breaker Switchgear. The Switchgear has 4 main compartments:
Low Voltage chamber; which houses metering equipment, SCADA equipment
(discussed above) and Numerical relays, etc…
Circuit breaker chamber; which houses the vacuum circuit breaker itself (The VCB is on a withdrawable truck)
Busbar compartment; contains the busbar which runs throughout the whole set of panels
Cable compartment; which houses the incoming/outgoing feeder, also has current and voltage transformers for measurement (discussed in the previous section)
The ratings are: Rated Voltage
12 kV
Rated feeder current
Up to 1450 A
Rated busbar current
2000 A
Vacuum Circuit Breaker
Rated current
Up to 1600 A
Rated power frequency withstand voltage 1 min.(r.m.s)
28 kV
Rated lightning impulse withstand voltage
75 kV
Rated short circuit breaking current(r.m.s)
26.3 kA
Rated short time current (r.m.s) withstand (3 sec.)
26.3 kA
Rated short circuit making current(peak)
66 kA
23
2.1.3.3 Low Voltage Switchgear in Ring/Radial and Satellite Substations
From transformer feeder
MCCB
HRC Fuse
Figure 2.7 Single line diagram for a typical LV distribution in Ring/Radial Sub. Usually MCCBs (Moulded Case Circuit Breakers) are directly connected to the LV side of the transformer. They are usually rated for 690 VAC, 1600 A (depends on requirement). Settings can be made on the MCCB itself and even a short t ime delay can be set when grading two MCCBs in series. HRC fuses are normally connected to the supply from MCCB. The most common type of fuse used is: Rated voltage(AC)
690 VAC
Rated voltage(DC)
440 VAC
Rated short circuit breaking capacity
120 kA (AC) and 25 kA (DC)
Rating
400 A (depending on need)
HRC fuses need to be placed on fuse links, 3 per each phase. The fuse links need have the same voltage ratings as the HRC fuse. 2.1.3.4 Numerical relay - SIPROTEC Compact 7SJ80
This is a commonly used numerical protection relay for 11 kV circuit breaker panel. It s features are: 24
Instantaneous and definite-time overcurrent protection(1)
Inverse time overcurrent protection
High impedance restricted ground fault protection(2)
Overvoltage/Undervoltage
Over-frequency/Under-frequency
(1)
(1) – Used for feeder protection (2) – used for transformer protection Although there are many protection features, only overcurrent and earth fault protection has been implemented for the breakers. One of the advantages of this unit is that it is capable of communicating with the master control element in the RTU panel using the Profibus-DP protocol. 2.1.3.5 DC power supply system in the Ring/Radial substations
There are a number of reasons to supply DC voltage inside the substation:
To supply PS modules in the RTU panel
To supply the tripping/closing circuit in the circuit breaker panels
To supply transducers and interposing relays as described in sect ion 2.1.2.4
To supply power to the Numerical relays
To supply power for motor operated spring charging
To supply the emergency 24 VDC battery bank
Below is an illustration of the DC supply distribution within the substation:
AC Supply
AC
Battery
DC
Breaker
Charger
Breaker
RTU Panel
11 kV panels
24 VDC Battery Bank
Figure 2.8 Block diagram of DC supply
25
The Battery charger consists of 3 phase rectifiers that convert 400 VAC to 24 VDC to maintain a continuous DC supply. It also supplies the emergency battery bank. In the event that the converter fails, the DC supply is provided through the battery bank. 2.1.3.6 Transformer at Primary Substation
The typical rating of a Transformer at a Primary Substation is: Rated voltage
132/11 kV
Type of cooling
ONAN/ONAF
Rated power
15000/30000 kVA
Rated primary current
65.6/131.2 A
Rated secondary current
787.5/1575 A
Connection symbol
Y Nyn0
Year of manufacture
1984
Manufacturer
BBC (Brown Boveri & Cie)
2.2
Training Experience at the Ceylon Electricity Board
Our training experience at CEB happened during the period of 8 weeks from 27/08/2012 to 19/10/2012. The first 4 weeks comprised of Generation, 2 weeks at Hydro Power Stations; Samanalawewa and Kukuleganga (1 week each) and the next 2 weeks at Thermal Power Stations; Kelanitissa Power Station, Kelanitissa Combined Cycle Power Station and Sapugaskanda Power Station. The next 4 weeks of training was under the Transmission Operation and Maintenance, which comprised of 2 weeks at the Pannipitiya Grid Substation (of which 3 days was at t he communication branch) and 2 weeks at the Biyagama Grid Substation (of which 3 days was Hotline maintenance). 2.2.1 Samanalawewa Hydro Power Station
The project started in 1986, with the financial aid fro m Japan and the British government, it was commissioned in 1992. The plant is capable of generating a maximum of 120 MW to the national grid.
26
2.2.1.1 General/Technical specifications of the plant Generator ratings
Turbine ratings
Type
Vertical shaft salient pole
Type
Vertical shaft Francis
Output (MVA)
70.6
Rated output
70.2 MW (320 m head)
Output (MW)
60
Max. output
73.3 MW (345 m head)
Power factor
0.85
Discharge
21 m /s
Output voltage
10.5 kV
Speed
500 Rev/min.
Amperes
3882 A
Poles
12
Generator Transformer Ratings
Speed
500 Rev/min
Capacity
71 MVA
Max. Over Speed
884 Rev/min
Power factor
0.85
Excitation
153 V/ 1543 A
Voltage
138/10.5 kV
Manufacturer
GEC ALSTHOM (Made in
Current
297/3904 A
Vector symbol
Y Nd11
Cooling method
ONAN/ONAF
UK)
Reservoir Details
Catchment area
Power Tunnel
341.7 km
Type
Concrete Steel-lined horseshoe type
Gross capacity
274 x 10 m
Length
5.15 km
Live storage capacity
215 x 10 m
Diameter
4.5 m
Gradient
1:100
Dam
Surge Chamber
Type
Clay core rock-fill
Diameter
18 m
Embankment length
480 m
Depth
95 m
Height
100 m
Spill limit
460 m AMSL
Spillway gates
3 - Radial Crest type
27
2.2.1.2 The process of generating electricity
Water enters through the main intake point through the control gate; t his water comes down through the power tunnel. Then it transitions into the penstock (at the portal valve house). The penstock leads directly to the MIV (Main Intake Va lve); this is a spherical type valve. The main objective of the MIV is to allow/disallow water t hrough to the turbine side. Before opening the MIV, pressure must be equalized on both sides of t he MIV (prevent exposure of turbine blades to sudden high pressure). This is done using a by-pass valve. The water then enters the turbine blades through a spiral casing which decreases in diameter. This makes sure that the pressure on the turbine blades are equalized everywhere as to maintain a constant torque (otherwise the turbine blades will be damaged). The rate of water flow into the turbine wheel is controlled by the guide vanes (there are 20 guide vanes). The extent of opening of the guide vanes controls the rat e of water flow into the turbine; this in turn is controlled by the governor. The governor is of electro -mechanical type, the droop setting is normally set to 4.5% and a dead-band of 0.5% of 50 Hz is maintained. 2.2.1.3 Starting and Synchronising
There are 3 generator controlling modes:
Supervisory: This is a sequence of automated steps that can be monitored from the TOSHIBA control system
ULCP (Unit Local Control Panel): All steps of t he Supervisory mode can be done manually from this panel
LCP (Local Control Panel)
2.2.1.4 Maintenance
In the event of any kind of maintenance (preventive or correct ive likewise), there are several safety procedures that must be followed. First all generat ing equipment from the generator to the switchyard must be isolated and earthed from the live bus. A series of steps must be followed by the ES or Engineer, this involves following a sequence of steps and interlocks.
28
The main steps are given below:
Trip Air Circuit breaker which is connected to the 10.5/0.4 kV auxiliary busbar
Earth the auxiliary transformer
Confirm that the Synchronizing breaker has been turned OFF
Make sure the Synchronizing breaker is isolated from both ends and earthed properly
Note: Before maintenance a work permit must be issued by the OE and then cancelled after
the work has been completed. 2.2.2
Kukuleganga Hydro Power Station
This is the first run-off river type hydro project in Sri Lanka. The specialty of this plant is that it can run as a base load power plant as long as there is a continuous flow of water up to a certain level. The main advantage is t hat upstream populations do not need to be resettled as there is no need for a catchment area. The main disadvantage is that there is no way of storing the energy and therefore no power over matching demand with generation in times of need. 2.2.2.1 General/Technical specifications of the plant Generator ratings
Turbine ratings
Type
Vertical shaft salient pole
Type
Vertical shaft Francis
Output (MVA)
42
Rated output
35.3 MW (183 m head)
Output (MW)
35
Max. output
40 MW (177 m head)
Power factor
0.85
Discharge
21.30 m /s
Output voltage
13.8 kV
Speed
500 Rev/min.
Amperes
1758 A
Poles
12
Generator Transformer Ratings
Speed
500 Rev/min
Capacity
46 MVA
Max. Over Speed
865 Rev/min
Power factor
0.85
Excitation
94.8 V/ 1120 A
Voltage
132/13.8 kV
Manufacturer
Toshiba Corporation
Current
209.2/1925 A
Vector symbol
Y Nd5
Cooling method
OFWF
29
2.2.2.2 Synchronising the generator
The generator starting and synchronizing is fully automated. The system has to follow a certain number of steps before this happens: i.
Standstill
ii.
Turbine Operation
iii.
Line Operation (used only when synchronizing to a live bus)
iv.
Line Charging (used only when synchronizing to a dead bus)
The above steps can occur under 3 different modes:
Auto mode: Each step is carried out automatically within a predefined time period, if this is exceeded all the steps are rolled back to the initial position.
BP (Break Point) mode: Similar to Auto mode, but if the t ime period is exceeded then the system waits for someone to take corrective action (this is usually used after maintenance).
Step mode: Here each step needs to be carried out/confirmed one by one either locally or remotely.
2.2.2.3 Excitation
Static excitation is used here, it is provided to the rotor through the slip ring compartment. Initial excitation is carried out by the field flashing unit, this occurs for a few milliseconds until the voltage of the generator builds up to a certain level. Flashing is done using a dc supply from the battery bank (38 VDC). Afterwards the field breaker is closed. The field current is then set t hrough the AVR; which adjusts the firing angle to the Thyristor Bridge to acquire the desired value of excitat ion. The power for excitation is derived from a 13.8 kV/155 V, 340 kVA transformer.
30
2.2.2.4 Mechanical Auxiliaries
i.
Bearings There are four different types:
Thrust bearings: Used to support the turbine shaft while it is in operat ion
Turbine Guide bearings: Since the turbine wheel is subjected to instability and vibrations, these are used to keep from swaying along the horizontal plane
Upper guide bearings and Lower guide: Keep the top part of the shaft horizontal and the centre of the shaft from buckling. They are named respective to the generator position.
High pressure pumps are used to maintain a thin layer of oil between the bearings and the shaft collar (approx. 140 bar). Low pressure pumps are used to circulate t his oil in and out of the sump as to remove the heat from the oil. So oil is used as both a lubricant and a coolant.
Thrust bearings Upper guide bearings Generator Lower guide bearings Shaft coupling Turbine guide bearings
Figure 2.9 Turbine bearing locations
31
ii.
Braking Braking is usually applied at 165 rpm while stopping the generator. During emergencies, it is applied at around 250 rpm. A separate dust collection system is available to remove any dust that can be formed from the wearing off of brake pads.
iii.
Chiller System (HVAC) Since this is an underground power cavern, air supply and quality is of great importance, as well as maintaining the temperatures for personnel, relays, breakers and other electrical equipment. Below is a block diagram of the HVAC in the underground power cavern: o
Chilled water supply (at 6 C)
Refrigerant
Air Handling Unit
Water from
Chiller/ Evaporator
(AHU)
draft tube Chilled water o
(at 9 C)
Condenser Intake Air
Refrigerant Supply Air Water to draft tube
Figure 2.10 HVAC system
2.2.3
Kelanitissa Power Station (KPS)
KPS is one of the 3 plants under the Thermal Complex of CEB. Here are some facts about it:
First commissioned in 1964 with 2 x 25 MW steam turbines
In 1980, 3 gas turbines were added (20 MW each) named GT1 ,GT2, GT3
3 more gas turbines installed in 1981 (20 MW each) named GT4, GT5, GT6
FIAT GT7 installed in 1997 with a capacity of 115 MW
32
2.2.3.1 Specifications for the 20 MW Gas turbines
Turbine rated speed
5100 rpm
Generator rated speed 3000 rpm Generating voltage
11 kV
Fuel Type
Auto Diesel
GT1-3 are connected to the 11/132 kV GIS, whereas GT4-6 are connected the 11/33 kV AIS. The rotor coupled to the turbine is meant to rotate at 3000 rpm using a gear reduction unit.
2.2.3.2 Specifications on GT-7
Turbine rated speed:
3000 rpm
Generator rated speed:
3000 rpm
Generating voltage:
11.5 kV
Fuel Type:
Auto Diesel
2.2.3.3 Starting Sequence of the 20 MW Gas turbine
1. Once all the auxiliaries are in working condition, the Check/Ready indicator lights up 2. The master control switch is then set to start position, there are 3 different modes of operation:
Crank mode: The diesel engine rotates up to 1000 rpm without firing up the combustion chamber.
Fire mode: Occurs at crank speed, the combustion chambers are fired up us ing the spark plugs
Auto mode: The turbine is accelerated to 3000 rpm, then the diesel engine disengages and the hot, high pressure gasses drive the turbine up to the rat ed speed of 5100 rpm.
Remote mode: The starting operations can be controlled from the export control centre.
3.
After reaching 5100 rpm, the “Complete Sequence” indicator lights up
4. Synchronise to system either automatically or manually 5. Select peak or base, depending on requirement (Base runs on maximum possible load depending on the ambient temp.)
33
2.2.3.4 How it works.
Air is drawn through an inlet filter to remove any harmful solid part icles
Air is compressed through a multistage axial compressor
Atomizing air is prepared by further compressing using a pressure pump
Atomizing air and fuel are directed into the combustion chamber, spark plugs are used to ignite the chamber
The hot, high pressure gasses from the chambers are used to drive the turbine. The turbine produces enough power to drive the au xiliaries, compressor plus 20 MW of useful energy.
2.2.3.5 Synchronous condenser mode
In this mode, the machine acts as a synchronous motor. It absorbs active power (a small amount) and supplies or absorbs reactive power based on the requirement. This method is very useful for voltage regulation or power factor correct ion in the grid. This is one of the main features of the plant. 2.2.3.6 Excitation
GT1-6 uses rotating diode excitation method, whereas GT7 uses static shunt type excitation.
Figure 2.11 Method of rotating diode excitation The permanent magnet induces an AC current in the stato r winding; the AVR adjusts the firing angle according to the required excitation current, this produces a DC current, which then induces an AC voltage in the exciter rotor winding. This AC voltage is rectified through a set of rotating diodes to produce a dc voltage to the generator rotor winding. 34
2.2.3.7 Ratcheting and Barring
Gas turbines operate at high temperatures, if it was left idle the shaft would sag (this is an 0
undesirable effect). To prevent this ratcheting is do ne where the turbine is rotated 120 every 3 minutes (for 20 MW turbines only). For the GT7, barring is done where the shaft is rot ated continuously at 3 rpm. 2.2.4
KCCPS (Kelanitissa Combined Cycle Power Station)
KCCPS consists of a Gas turbine rated 110 MW and a st eam turbine (High pressure and Low Pressure) rated at 55 MW. Therefore the total output of the plant is 165 MW with a gross efficiency of 46%. 2.2.4.1 Specifications of the plant Gas Turbine Ratings
Power output
110 MW
Fuel
Naphtha/Auto Diesel
Speed
3000 rpm
Exhaust temperature
560 C
Steam Turbine Ratings
HP turbine pressure
72 bar
LP turbine pressure
6.8 bar
HP turbine / LP turbine Speed 9000/3000 rpm ST Generator Ratings
Output
76 MVA
Power factor
0.80
Voltage
11.5 kV
Excitation method
Rotating Diodes
GT transformer rating
Capacity
147 MVA
Voltage
15/220 kV
ST transformer rating
Capacity
83 MVA
Voltage
11.5/220 kV
35
2.2.4.2 The HSRG (Heat Recovery Steam Generator)
As the name implies, the main objective of the HSRG is to recover the heat from the flue gasses that result from the GT and provide ideal temperatures and pressure for the steam before entering the steam turbines. There are two main objectives of the HSRG: To provide superheated, high pressure steam to the HP turbine at around 510 oC, 70
i.
bar. ii.
o
To provide superheated, low pressure steam to the LP turbine at around 215 C, 6.8 bar.
A diverter damper is located before the HSRG, to act as a by-pass valve if any maintenance is to be done on the steam turbine side. The water required for steam is held in the feedwater tank, a de-aerator is present before this to remove any oxygen from the water that may later cause eros ion in the turbine blades. 2.2.4.3 Auxiliaries
There are several mechanical auxiliar y systems in place to make sure that the machines run in good condition and up to maximum efficiency:
Feedwater pumps; one for the LP steam and the other for t he HP steam
Circulating water pumps which remove heat from the final stage of the process to convert steam back to water.
Cooling tower which cools the water in the circulating water pumps
Water treatment plant
AC lube oil pumps
There are several electr ical auxiliaries; these are derived from the 6.6 kV busbar. The busbar supplies power to the AC circulating water pumps, Feedwater pumps and starting motor for GT. The 6.6 kV supply is then stepped down to the 415 V busbar. This busbar supplies power to the 415 VAC/ 128 VDC converter, plus it charges the 128 VDC battery bank. A 128 VDC supply is necessary for the DC lube oil pump. In the event that t he AC lube oil pump fails this is critical. A 48 VDC system is also there to supply relays and other control systems. 36
2.2.5
Sapugaskanda Diesel Power Station
This power station consists of two stations, A and B. Station A has an insta lled capacity of 80 MW (4 x 20 MW machines), it was commissioned in 1984. Station B has been divided into two; Station B1 has an installed capacity of 40 MW and was commissioned in 1998 and Station B2 also has a capacity of 40 MW and was co mmissioned in 1999. So altogether, Station B has 10 x 8 MW diesel generators. 2.2.5.1 Station A, specifications
Station A, comprises of 4 PIELSTICK Engines, the pistons of V-18 type. They run on diesel (for start/stop) and heavy fuel (while running). Generator Ratings
Output
26.5 MVA
Power factor
0.85
Voltage
11 kV
Speed
428 rpm
No. of poles
14
Excitation
100 V/1156 A
Manufacturer
ALSTHOM
2.2.5.2 Station B, specifications
Station B, comprises of 10 MAN, B&W engines, the 8 pistons are of Inline type. Generator Ratings
Output
12.9 MVA
Power factor
0.80
Voltage
11 kV
Current
677 A
Speed
428 rpm
No. of poles
14
Excitation
77 V/415 A
Manufacturer
SIEMENS
37
2.2.5.3 Station Switchyard
Station A and B are both connected to the 11 kV busbar. Station A is connected to two transformers, whereas Station B is connected to two transformers, t here is another transformer although it is for spare use only. The difference in this power station is that the generator output is not directly connected to the transformer, instead a ll generators are connected to a common busbar and then a connection between the transformer and the busbar is made.
Station A and B are connected to earth through 2, 6.5 Ω resistors each. The st ation A 400 V busbar is supplied by 2, 3150 kVA transformers whereas Station B 400 V busbar is supplied by 3, 2000 kVA transformers. The 400 V busbar is used to supply station auxiliaries such as the Lube oil pumps, cooling water pumps, compressed air system. 2.2.5.4 Starting of the diesel engine/generator
Below is the sequence of steps to be followed while loading and de-loading the engine.
Before starting the auxiliaries must be working condition
A process called barring is done where the engine is rotated twice to see if the pistons are stuck.
A process called blowing is done using compressed air to r emove any water or any other remaining
The engine is then rotated to around 100 rpm using compressed air
The airing valve is then closed, and diesel is used a s the fuel.
When generator speed reaches 428 rpm, synchronizing is done.
The generator is then loaded (1 MW/3 min. for Station A and 1 MW/1.5 min. for Station B).
Once the generator reaches 30% of its full load and the temp. of cooling water leaving the cylinders is greater than 70oC, auto changeover to heavy fuel will occur. This means that the engine temp. is high enough to maintain the viscosity of the fuel
During de-loading, a rate of 1 MW/min. is maintained
Switchover from heavy fuel to diesel is done at 70% of full load; this is done to flush out any heavy oil that may remain in the cylinders (which may lat er solidify and cause problems). The machine must run on diesel for at least 45 min. before disconnecting form the system. 38
2.2.5.5 Excitation system for station B generator
The excitation for the generator is provided by the SIDUR 2000 excitation unit (AVR) from Siemens. The power for this unit is derived from a separate 5 phase winding connected to the generator. The exciter on the other hand takes the form of an external-pole generator, which has a separate rotor and stator winding but it coupled to the same shaft as the main rotor. The AVR consists of two main parts, a power controller t hat produces an exciter current into the exciter stator winding and a digital PI controller that keeps the voltage at a given set point. Therefore the PI controller has to communicate with the power controller to set the correct value of excitation. The PI controller has input from the generator output voltage and current. Once the stator exciter current has been set, a voltage will be induced in the exciter rotor winding, since this is an AC voltage, it is rectified via a set of rotating diodes and a DC voltage is fed to the generator rotor winding. Therefore by changing the exciter stator current
we can change the main generator‟s rotor current. Here excitation current for exciter stator is 9 A at rated load which means about 415 A in the main rotor winding. 2.2.6
Transmission Operations and Maintenance
2.2.6.1 Pannipitiya Grid Substation
The substation consists of: i.
220 kV AIS double busbars fed from Biyagama lines 1 and 2. The double busbars are in turn connected to 6 single phase Auto Transformers (220/132/33 kV)
ii.
132 kV AIS double busbars fed from the Auto Transformers plus from lines: KOLONNAWA 1, KOLONNAWA 2, RATHMALANA 1, RATHMALANA 2, DEHIWALA, HORANA, MATHUGAMA.
iii.
33 kV Indoor GIS which is fed from the three 132/33 kV transformers
2.2.6.1.1 Switchyard components
There are various equipment for each incoming and outgoing line. Some of them will be explained next;
39
i.
Surge arrestors These are normally used at the entry point to a GSS and on either side of power transformers. They protect the other switchgear from high voltage surges, especially due to lightning.
ii.
Wave trap These are only seen on the Y phase of each incoming line, t hey prevent high frequency components from passing through. It is usually used to extract the signal for PLC communication.
iii.
CVT (Capacitive Voltage Transformer) These are used to step down line voltages for energy, voltage metering and protective relays. The usually they have two windings that have rated voltage of 11 kV and 110 V.
iv.
Isolators These are like normal switches, mostly based on either side of a circuit breaker. They are accompanied with earthing switches and are us eful for maintenance of the switchgear on site.
v.
Current Transformers These step down line currents to acceptable values for protection and metering equipment. Usually there are a number of tapings on a C/T for both protection and metering.
vi.
Circuit breakers This is the main protection for switchyard equipment including busbars, transformers and lines. Ratings may vary according to the line capacities and voltages. They are also used for bus coupling/decoupling.
vii.
Busbars This is like an intermediary interconnection point or a node for power flow in the system. They can come in U & I, single and double busbar types. In most substat ions, a single busbar is rated to carry the whole load current in the event that the other fails. 40
2.2.6.1.2 Protection
At Pannipitiya GSS, we were given a rather detailed introduction to the types of protection available. There are various kinds of protection available for differe nt equipment in a substation. They will be explained below. i.
Grid Protection
During earth faults, the flow of current into the earth results in a Ground Potential Rise (GPR). If a person is standing on the grid during a fault t he potential gradient across the person may be sufficient to pass a harmful/fatal current through the
person‟s body. For this several protection schemes are in place:
Earthing mesh: To keep step, touch, mesh voltages within acceptable values
Layer of crushed rock on surface: To act as an insulator between the personnel and the earth.
ii.
Transmission line protection
For 33 kV radial feeders, overcurrent and earth fault protection is used and for larger networks 132 kV or 220 kV, distance protection is used.
Distance protection
This is used for lines interconnecting two grids. Distance protection relays are used on either end of the lines to monitor the line impedance based on the values o f voltage and current at the relaying point. If the impedance calculated by the relay is less than the reach point impedance, the relay determines that there is a fault in that zone. Typical time delays used for protection: 132 kV lines
220 kV lines
Zone 1: 0s
Zone 1: 0s
Zone 2: 0.5s
Zone 2: 0.25s
Zone 3: 1.0s
Zone 3: 0.5s
41
Zone 1
Zone 2
Zone 3
Figure 2.12 Distance Protection
Differential protection
In this method the two relays on either side of t he lines check to see if the current entering one side is the same as t he other. This is a very effective form of protection
OPGW cable Relay
Relay
Figure 2.13 Arrangement for differential protection
If the OPGW fails, then distance protection will be activated by both relays.
Busbar protection
Provides protection for busbar earth faults, here the busbar can be divided into zones and selective tripping of the busbar can be achieved.
Breaker failure protection
In the event that a breaker fails to trip after a set amount of times, breaker failure protection will take over. This scheme will trip any other breakers to clear the fault with minimal impact on the power system.
iii.
Transformer protection
A transformer is a crucial and expensive equipment of the grid substation, therefore its protection must be ensured in the highest manner.
42
Mechanical protection
Figure 2.14 Power Transformer arrangement 1 – Buchholz relay, 2 – Protective relay, 3 – OLTC oil conservator, 4 – Transformer oil conservator, 5 – Transformer body, 6 – OLTC compartment, 7 – Dehydrating breather for conservators
Note: OLTC and Main tank are separated, tap changing causes ar cs which may operate the
buchholz relay or deteriorate the insulation level provided by the oil to the t/f windings.
Buchholz relay
There are 3 functions of the buchholz relay:
An accumulation of gas causes the upper float of the re lay to rise and send a alarm signal
A loss of oil causes the upper float of the relay to drop sending a trip signal, a much greater loss of oil causes the lower float to drop sending a trip signal and so disconnecting the transformer
An arc inside the transformer causes a high pressure wave towards the conservator tank enough to activate a damper which immediately disconnects the transformer. 43
Protective relay
This is only for the OLTC; it consists of a flap valve that operates to a very high flow rat e. This in turn disconnects the transformer from the system.
Pressure relief valve
Springs out when a certain value of pressure inside the t ransformer is exceeded.
Silica GEL
This is used to absorb water vapor inside the transformer tank, which may lead to dielectric failure. 2.2.6.2 Biyagama grid substation
The substation consists of:
220 kV double busbar AIS fed from lines; KOTUGODA 1, KOTUGODA 2, KOTHMALE 1, KOTHMALE 2, KELANITISSA 1, KELANITISSA 2, PANNIPITIYA 1 AND PANNIPTIYA 2. The double busbars are connected to 6 single phase Auto Transformers (220/132/33 kV).
132 kV double busbar fed from the Auto Transformers plus lines; SAPUGUASKANDA 1, SAPUGASKANDA 2, SAPUGASKANDA DIESEL 1, SAPUGASKANDA DIESEL 2. There are also 2 SPARE lines.
33 kV single busbar AIS fed from the output of the tertiary winding of the Auto Transformer.
2.2.6.2.1 Line Maintenance
There are two types of maintenance:
Hot line maintenance: Is done while the line is ener gized, involves changing line
hardware or insulators, etc….
Cold line maintenance: Is done while the line is de -energized, involves conductor
repairing, etc…
44
Advantages of Hot line maintenance:
Reliability of the power supply is improved No power loss during maintenance Increases the lifetime of switchgear
Methods of carrying out hot line maintenance:
Hot stick method: Worker is usually at ground potential and uses an insulating stick to carry out work
Bare hand method: Work is carried out while at the same voltage as the live parts, care is taken to keep clearance from other objects at ground potential.
Safety procedures taken before and while hot line maintenance:
Wearing safety shoes, straps, helmets and overalls before commencing work.
Maintaining the minimum safety clearances with live parts; i.e. 3.5 ft. for 132 kV lines and 5.0 ft. for 220 kV lines.
2.2.6.2.2 Transmission equipment
Transmission tower types:
Single circuit Double earth
Single circuit Single earth
Double circuit Double earth
Double circuit Single earth
Type of cable used for transmission: ACSR (Aluminum core steel reinforced) cables and AAACs (All Alloy Aluminum Conductors) are used for HV transmission. The advantages of ACSR are; low co efficient of linear expansion, light weight and comparatively low cost. Insulator types:
Suspension
Tension
Heavy suspension (for mountainous towers) 45
2.3
Guide sets (used where the angle between two lines are small) Training experience at Lanka Electricity Company (LECO) Pvt. Ltd.
Our training at LECO consisted of 4 weeks; 2 weeks from 13/08/2012 to 24/08/2012 and the rest of the 2 weeks from 22/10/2012 to 02/11/2012. Each week we were placed under a different section, they were in chronological order:
Branch Office (Kotte)
Systems Operation
Customer Service Centre
Engineering and Operation
2.3.1
Branch Office
Here we reported to the Branch Engineer at t he Kotte office. Unfortunately we could not get hold of the Branch Manager during this period of time as he was unavailable. 2.3.1.1 Accounts division
The main functions are:
Customer billing – which is done by the revenue officer (RO). RO takes meter readings during the first 20 days of the month.
Revenue Collection – Customers can make payments to branch offices, banks, selected supermarkets. They may pay in cash or by cheque. Each day the accountant receives a payment journal and a billing journal which must be verified a nd accounted.
Non-payment disconnection – If a customer fails to pay within 30 days, a disconnection notice is present on the next bill. The customer must then pay the arrears within 10 days plus a 2% surcharge to avoid disconnect ion.
2.3.1.2 Customer Service
The main facilities offered here are:
Providing new connections
Meter testing
Customer requested shifting 46
2.3.1.3 Administration
This section is under the Administration Officer, he has a number of duties pertaining to that particular branch:
Providing necessary facilities for the employee
Equipment/Vehicle repair and maintenance
Implementing management decisions made by the head office within the branch
Employee profile management
Employee attendance, leaves and OT management
Employee welfare and taking disciplinary action
Maintaining customer records
2.3.2
Systems Operations
2.3.2.1 Control centre scheduling
This unit is responsible for interrupt and switch operation scheduling. i.
Interruption Scheduling When a repair or maintenance is to take place, the CSS of the depot must request the control engineer. The report contains details of what work to be done, what sections to be isolated and the date and time of the operation. Once the interruption is scheduled, the consumers are informed 30 days prior. Work permit It is compulsory that a work permit be issued by the CSS before beginning any work. The permit ensures that all safet y precautions have been taken, after work is complete and the line is energized, the CSS must cancel the work permit; meaning it is no longer safe to work in that area
47
ii.
Switch operation scheduling When an interruption is to take place, instructions or procedures must be writt en. A diagram of the area to be isolated is prepared. This diagram features line details and
LBS locations, etc… Then switching instructions are prepared, this contains details of the switch to be operated, state of the switch, location of the switch, time of
switching, etc… The control centre has a mimic of the entire LECO distribution system. This contains
details of feeders, primary substations, spurs, LBS status, etc… Whenever an LBS status changes, the mimic is updated accordingly. The mimic helps to visualize the network and minimize the area affected by the interruption by finding alternate ways to supply power to the areas affected. 2.3.2.2 Meter testing lab
There are several tests that are done on new and old meters, these will be explained: i.
Disc error test – meters are fed with rated voltage and current for a predetermined number of turns and at the end, the error for one rotation is calculated. The error is defined as the divisions by which the 0 position on the disc is offset from the centre. Table 1.3 Disc error test and results
ii.
Load current
Power factor
Percentage error
5% of balance current
1
< 3.5%
100% of balance current
1
< 2.5%
Full load current
1
< 2.5%
100% balance current
0.5 lag
< 3.0%
Dial test – This is done to check if the dial should increment by exactly 1 unit when 1 kWh of energy is consumed by the user.
iii.
Creep test – 110% of rated voltage is applied to the meters for about 20 minutes to see if the disc rotates by 1 revolution; if so then the meter is faulty.
48
2.3.2.3 Transformer repair workshop
Here we learnt about the different tests performed on transformers. The good thing here was that we had a first person hands-on view of how the tests were performed. i.
Insulation resistance test (also known as Megger test) This is done to see if the insulation level is up to the standard. This involves applying 2500 VDC between the HV/LV, HV/GROUND and LV/GROUND. The results obtained should be within an acceptable value of resistance.
ii.
Ratio test Here 415 V is applied to the HV windings of the transformer. Then measure the following voltages on the LV side; na, nb, nc, ab, bc, ac. The voltage ratio for all three phases must then be similar and close to the actual value. The actual voltage ratio =
11/(400/√3 ) = 47.63 iii.
Oil test The oil test is done in accordance with IEC 156/ BS 5874. In this a sa mple of oil is used to check the voltage at which the breakdown occurs. If the oil fails, it can be purified using the oil treatment plant.
2.3.3
Customer Service Centre
In this week I chose the Pitta-Kotte branch as my training location. During the week I had the opportunity to go out on the field and observe t he functions carried out by the TO (Technical Officer), I also had the chance to observe some energy meter replacements (analog and digital). 2.3.3.1 Materials used by LECO for distribution purposes
For 11 kV:
Cross-arms are used to mount insulators; insulators are post, pin or tension type H type connectors are used for 11 kV tee-offs 2
AAC (All Aluminium Conductors) are used for 11 kV transmission (160 mm and 60 mm2 )
Boundary meters, auto-reclosers and load break switches (LBS) 49
For 400 V:
ABC (Aerial bundled conductors) are used for transmission, there ar e two types:
2
2
2
2
2
2
3 x 70 mm + 1 x 50 mm + 1 x 16 mm
Phase + neutral + street lamp
3 x 50 mm + 1 x 35 mm + 1 x 16 mm
Suspension clamps are used for pulling the ABC through straight paths
Tension clamps are used where the ABC path changes d irection
Service lines are terminated by a dead end clamp
For a 3 phase supply 5 tee-offs are used, 3 for the phases and 2 for neutral (one is used as backup in the case the other fails)
For a single phase supply only 2 tee-offs are used
For transformer and feeder protection
Transformers are protected by surge arrestors and drop down lift operate switches (DDLOs).
ABC feeders are protected by feeder disconnect ion switches; these contain HRC fuses rated at 250 or 100 A.
2.3.3.2 Energy meter replacement
The steps involved are: i.
De-energize the transformer by switching off the DDLO switch
ii.
Disconnect all feeder disconnection switches to that transformer
iii.
Replace old meter with new meter while adhering to t he wiring diagram
iv.
Re-energize transformer by switching on DDLO
v. vi.
Reconnect all feeder disconnection switches Check for correct phase sequence using phase sequence meter (only required for analog meters)
2.3.4
Engineering and Operations
Our last week of industrial training was held at t he LECO Head Office, we were placed under the engineering and operations department. At first we were given a basic intro duction to the functions carried out by the department:
Updating construction manuals 50
Proposing new technologies
Preparing standard cost manuals
Load forecasting
Load flow studies
GPS/GIS (Mapping)
Procurement handling
However, we only got the opportunity to know a few of these in deta il, which will be explained in the next sections. 2.3.4.1 Procurement
Procurement is necessary for new service connect ions, breakdowns and maintenance. It is useful to supply materials, services and consultancies. Regulations for procurement are set by the National Procurement Agency in which LECO fal ls under the direct procurement committee (DPC). There are two committees; DPC minor which handles pro curement less than LKR 10 million and DPC major which handles less than LKR 50 million. There are two main ways to procure; tendering (used by DPC major) and quotations (used by DPC minor). Tendering is classified according to the type of bid (Nat ional/International limited bid or National/International competitive bid) and bidding conditions and procedures may change according to that. Quotations are usually submitted by a list of reg istered suppliers. The TEC (Technical Evaluation Committee) is responsible for selecting the winning bid. The recommendations are sent back to the DPC major/minor. Once the DPC approves award letters are sent to the winning bidder/supplier. When the materials arrive they are kept at an inspection bay, a group of engineers (inspection committee) will then inspect a sample. If the materials are in good condition, the stock level will be updated or else t he TEC or inspection team will be held responsible. 2.3.4.2 Load forecasting
The main purpose of load forecasting is for planning, budgeting and expansion activities. Some of the values forecasted are: Energy sales, No. of customers, kVA sales, Purchases, Losses, Revenue, Specific consumption, Consumer mix, Energy mix. There are 4 basic approaches to load forecasting: 51
Judgmental: An expert panel anticipates future growth; it is subjective fro m panel to panel.
Regression: To develop a statistical correlation between a dependent and independent variable (usually time). The results are limited by the data available.
Econometric: Consider complex parameters, only used on a macro economical scale.
End use approach: Data collected on the smallest level (e.g. consumption of a simple appliance). Depends on the reliability of survey data.
LECO uses the simple linear regression model. The model uses past 10 years of data to model for the next 5 years. The model will always have inaccuracies, e. g. meter reading itself has an error of + or – 2.5%. 3. CONCLUSION
It was a great accomplishment to complete my 24 weeks of industrial training. The experiences I had were unparalleled to any of that which I have had earlier in my life. During the period of time I had hands on first-person experience of what was going on in the outside world related to the power sector. I was able to bridge the gap between theory and practical and the experience also helped me to learn and understand some parts o f theory which I was unable to grasp before. The training program offered by the department of electrical engineer ing is different from other departments. Overall I believe that it is a successful training schedule, however there are minor imperfections. Both CEB and the private sector offer a different kind of experience. I was fortunate to join a well known company. Working in the pr ivate sector is very much different from that of the government. Private firms are a lways profit oriented; there is always a different atmosphere as long as there is some kind of a project. It is very challenging to work together with the other engineers and learn from them. However, when I arrived there were currently no projects of great importance, the only ongoing project was deficiency clearing for the SCADA/DMS. I was assigned as a supervisor to a group of technicians; here the major challenge was labor and material management. Here I had to adapt to some harsh conditions and sometimes late working hours. However, I only looked at these experiences in a positive manner because it helped me to grow as a responsible and dedicated worker. During deficiency clearing I was exposed to a wide range of elect rical equipment in Satellite, Ring/Radial and Primary substations. I would have never had this opportunity if I had stayed 52
in the office and read documents instead. However, the major drawback was that I was always out in the field and with little time to actually study the equipment or even consult with the engineers about it. Therefore, I had to find extra t ime to study wiring diagrams and other catalogues to see what it was that I was actually dealing with. I am glad to say that I was given some responsibility (at this stage in time) although it compromised by training to a certain extent. Another difficulty was that I did not get t ime to receive proper feedback from
the engineer in charge of my diary as we were both busy and our schedules didn‟t match. However, I overcame that problem and he was also happy to provide advice over the phone as well. So during those 3 months I felt that I had exposure to the actual conditions under which engineers have to work, especially in the private sector. To future trainees who do undergo training at a private firm, I advise that they do some background research to see if there are any projects underway at that time. Otherwise, it would be a waste of time just sitting around in an office space with no exposure to any kind of engineering. The CEB was a totally different experience, for me it was like a knowledge hub. I was not given any responsibilities or work therefore I had the freedom to read documents, look around and ask questions from the Engineers, Electrical Superintendents and Technicians. CEB has trained many undergraduates for a long time and furthermore it has many training centers in place for engineers and technicians likewise. Therefore, CEB is the best place to get fundamental knowledge about generation and transmission. I was satisfied and humbled by how some engineers and other employees took time from their own schedules to teach us. A problem with CEB is that it does not provide exposure to the latest t echnologies, trainees are only able to learn about the equipment which is already there and most of t hem are outdated. Regarding the CEB schedule four weeks were assigned for transmission where we had to spend two weeks and two different substations each. We covered the grid substations in less than a week and realized that there was not much to do during the rest of the period. Also grid substations seem very idle and it is not a place where electrical engineering is actually practiced. This is obvious also due to the fact that there are no engineers assigned to a certain Grid substation. However, there are many other sectors of CEB that I thought I could learn from during that time period. For example we only had 3 days of tra ining at KPS and KCCP each while others had a full week. 53
Training at LECO was also an enlightening experience although we did have so me trouble getting in touch with some very busy people. I believe that training schedule was proper ly organized and thought of because we had e xposure to almost all sectors of LECO during the four weeks of training. All employees such as Engineers, Accountants, AO, Stores managers, technicians and other staff were very welcoming and informative. I believe LECO is the best place for training under the distribution sector. Finally I believe that the 24 weeks of training has helped me to grow as a student and prepared me to a certain extent to face the outside environment. Apart from the minor defects I have mentioned above, I believe that my training was a success a nd that it will greatly help me in the future.
54
Abbreviations AAAC
All Aluminium Alloy Conductor
ABC
Aerial Bundled Conductor
AC
Alternating Current
ACSR
Aluminium Conductor Steel Reinforced
AGM
Additional General Manager
AIS
Air Insulated Substation
AVR
Automatic Voltage Regulator
CCEDDP
Colombo City Electricity Distribution Development Project
CEB
Ceylon Electricity Board
CEO
Chief Financial Officer
CSS
Customer Service Superintendent
CT
Current Transducer
C/T
Current Transformer
CVT
Capacitive Voltage Transformer
DC
Direct Current
DCC
Distribution Control Centre
DDLO
Drop Down Lift Operate
DIMO
Diesel and Motor Engineering
DMS
Distribution Management System
DPC
Direct Procurement Committee
GIS
Gas Insulated Substation
GSS
Grid Substation
GT
Gas Turbine
HP
High Pressure
HSRG
Heat recovery Steam Generator
HV
High Voltage
HVAC
Heating, Ventilation and Air Conditioning
IPP
Independent Power Producers
KCCPS
Kelanitissa Combined Cycle Power Station
KPS
Kelanitissa Power Station
LBS
Load Break Switch
ix
LECO
Lanka Electricity Company
LP
Low Pressure
LTL
Lanka Transformers Limited
LV
Low Voltage
MCB
Miniature Circuit Breaker
MCCB
Moulded Case Circuit Breaker
OLTC
On Load Tap Changer
OPGW
Optical Ground Wire
PI
Proportional Integral
PLC
Power Line Carrier
PUCSL
Public Utilities Commission of Sri Lanka
RMU
Ring Main Unit
RO
Revenue Officer
RTU
Remote Terminal Unit
SCADA
Supervisory Control and Data Acquisition
SLT
Sri Lanka Telecomm
ST
Steam Turbine
TEC
Technical Evaluation Committee
TSSGSP
Transmission System Strengthening Grid Substation Project
VCB
Vacuum Circuit Breaker
VT
Voltage Transducer
x
References
DIMO Website – www.dimolanka.com
CEB Website – www.ceb.lk
LECO Website - leco.lk
DIMO Annual Report 2011
CEB Annual Report 2010
CEB Statistical Digest 2011
LECO Annual Report 2011
xi
Annexes
Annex 1: Deficiency Clearing form (Page 1)
xii
Annex 2: Deficiency Clearing form (Page 2)
xiii
Annex 3: Labour allocation form
xiv
Annex 4: SCADA wiring diagram for Satellite stations
xv
