\ TIME DEPENDENT TRANSMISSION LOSSES IN NATIONAL NETWORK A Dissertation submitted to the Department of Electrical Engineering, University of Moratuwa in partial fulfillment of the requirements for the Degree of Master of Science by P.A.N.SHANTHA Supervised by: Professor Ranjit Perera LIBRARY . : KSiTY (?, MMATt'i. A. S.H LAM* MORATUWA Department of Electrical Engineering University of Moratuwa, Sri Lanka November 2008 University of Moratuwa 92957 6 Z I T H 9 2 2 5 7 DECLARATION The work submitted in this dissertation is the result of my own investigation, except where otherwise stated. It has not already been accepted for any degree, and is also not being concurrently submitted for any other degree. UlX. S WVA+tvO P.A.N.Shantha 2008/11/24 I endorse the declaration by the candidate. ABSTRACT Ceylon Electricity Board (CEB) has the responsibility of Transmission and most o'f the Generation and Distribution of electric power in Sri Lanka. Today, total technical and non technical losses (Energy losses) are around 15.67%. It is a large loss compared with losses in developed countries. Losses will also affect electricity tariff. At the end, it affects domestic, commercial and industrial consumers as well as Gross Domestic Product (GDP) of the country. Transmission losses are very important to future planning and design of the National Network. Losses should be minimized as much as possible. 'As Ceylon Electricity Board has not yet investigated t ime dependent transmission losses in National Electric Network accurately, this study focused on the following, • Study thirty minutes t ime interval transmission losses in National Network for a day. • Transmission network is modelled and simulated using M A T L A B programme and calculation of power f low and transmission losses. • Analysis of the simulated results. Simulation results show that peak loss is recorded at 19.30 p.m. and amounting to 3.17% of total generation. Day minimum is recorded at 3.30 a.m. and minimum loss is 1.52% of total generation. Any time in between 0.00 a.m. to 24.00 midnight, Transmission losses vary f rom 1.52 % to 3.17 %. n ACKNOWLEDGEMENT Thanks are due first to my supervisor, Professor Ranjit Perera, for his great insights, perspectives and guidance. I also thank Mr. R.J. Gunawardena-Addit ional General Manager (Transmission), Mr. T.D. Hadagama-Deputy General Manager (System Control Branch), Mr. J. Nanthakumar-Chief Engineer (Operation Audit), Mr. L. Weerasinghe-Chief Engineer (System Operat ions) , Mr. T. Senavirathna- Electrical Engineer (System Control), Dr. L.D.L. Perera-Electrical Engineer (Transmission Planning) and Dr. A.M.D.R. Samarakoon-Chief Engineer (Generation Planning) for facilitation me with the necessary data and information Lastly, I should thank many individuals, friends and col leagues who have not been mentioned here personally in making this educational process a success. May be I could not have made it without your support. i i i CONTENTS Declaration Abstract Acknowledgement List of Figures List of Tables 1. Introduction 1.1 Background 1.2 Motivat ion 1.3 Object ive 1.4 Scope of work 2 National Generat ion, Transmission and Distribution System 2.1 Ceylon Electricity Board 2.2 Generat ion 2.3 Transmiss ion 2.4 Distribution 2.5 Transmission losses 2.6 Total system losses 3 Theoretical Development 3.1 Electrical characteristics of transmission lines 3.1.1 Overhead lines 3.1.2 Underground cables 3.2 Per formance equations of the transmission tines 3.2.1 Equivalent circuit of a transmission line 3.2.2 Nomina l ji equivalent circuit 3.3 Transformers 3.3.1 Representation of two-winding t ransformers 3.3.2 Equivalent n circuit representation 3.4 Three winding t ransformers 3.5 Power f low analysis 3.5.1 Nonl inear power f low 3.5.2 Selection of solution method 3.5.3 Newton Raphson (N-R) method 3.6 Line f low equations 3.7 M A T L A B 4 Methodology 4.1 Assumpt ions for load flow calculation 4.2 Model l ing national transmission network 4.3 Simulation Procedure 5 Result and Analysis 5.1 Results of load flow study 5.2 Active power generation, consumption and losses 5.3 Reactive power generation, consumption and losses 5.4 Evaluation of energy loss 6 Conclusion and Recommendation 6.1 Conclusion and discussion References Annexes Annex 1 National Transmission Network 44 Annex 2 Data of Transmission Lines and Under Ground Cables 45 Annex 3 Data of Existing Transformers (Two Winding) 47 Annex 4 Data of Existing Transformers (Three Winding) 49 Annex 5 Data of Generators 50 Annex 6 Location of Existing, Committed and Candidate Power Stations 52 Annex 7 Reservoir Systems in Kelani and Walawe river basins 53 Annex 8 Reservoir Systems in Mahaweli river basins 54 Annex 9 C E B Distribution Regions 55 Annex 10 M A T L A B Programme for Load Flow Analysis 56 Annex 11 Bus Data input file 62 Annex 12 Line Data input file 63 Annex 13 Thirty Minutes P,Q Loads 64 Annex 14 Thirty Minutes Active and Reactive Power Generat ion 84 vi List of Figures Figure 2.1 M a p of national transmission system 7 Figure 2.2 System losses form 1978 to 2007 8 Figure 3.1 Current and voltage relationship of a distributed parameter lines 12 Figure 3.2 Equivalent circuit of a transmission line 14 Figure 3.3 Basic equivalent circuit of a two winding t ransformer 16 Figure 3.4 Per unit equivalent circuit 18 Figure 3.5 Standard equivalent circuit for a t ransformer 18 Figure 3.6 Transformer representation with O N R 20 Figure 3.7 Three winding transformer 21 Figure 3.8 Three winding transformer equivalent circuit 22 Figure 3.9 Equivalent circuit of a transmission link for evaluating line f lows 27 Figure 4.1 Selected bus bars of the transmission network 28 Figure 5.1 Transmiss ion losses as a percentage 35 Figure 5.2 Transmission losses (MW) 35 Figure 5.3 Active power generation, Consumption and losses 36 Figure 5.1 Transmission losses with and without t ransformer resistance 36 Figure 5.4 Reactive power generation, consumption and losses 38 vii List of Tables Table 2.1 C E B transmission Voltage levels and allowable tolerances 5 Table 2.2 Total System Losses from 1978 to 2007 8 Table 2.3 Forecast Energy Losses 9 Table 4.1 Line data 29 Table 4.2 Bus data 29 Table 4.3 M A T L A B functions 30 Table 5.1 Results of thirty minutes Load f low analysis 34 vi i i