SEGREGATION AND ANALYSIS OFDISTRIBUTION LOSSES AND MITIGATING TECHNIQUES Master of Electrical Engineering Thesis J.P.R. JAYASINGHE Department of Electrical Engineering University of Moratuwa, Sri Lanka 2005 84120 Abstract The operational efficiencies of a utility depend on the losses in the electrical distribution network. High losses contribute to inefficient electrical network resulting large tariff to utility consumers. Hence more attention should be paid to minimize and maintain system losses to an economical level. The situation reveals that the distribution losses of the CEB are higher than that of developed countries. Detailed energy audit should be carried out to identify the areas where the loss level is high. The study will help to localize the area suffering from high energy losses. Thus the measurement should be carried by installing energy meters for the said areas. This thesis presents a study about the electrical losses in low voltage distribution system of CEB. The nature of the distribution losses in low voltage power distribution system, their sources, measurement of technical and non-technical losses and their impact on the system are presented. The steps that can be taken to have an assessment of the distribution losses and steps to be taken to reduce technical losses and corrective actions to plug non-technical losses by proper administrative actions are detailed. A methodology to segregate distribution losses is also presented. Variation of low voltage distribution losses and voltage drop with consumer density per km were calculated. According to that results low voltage distribution line length in semi urban areas have to be limited in order to maintain the required voltage regulation and also to bring down LV losses. Unbalance voltages can results in adverse effects on equipment and the electric distribution system. Under unbalanced condition the distribution system will incur more losses as heating effects (I2R losses). More over, inaccuracy of metering power in three phase circuits due to unbalance current or voltage is discussed . Method for the selection of a distribution transformer of optimum capacity for given loading conditions is presented. In this regard economic evaluation is done based on initial transformer cost and operation and maintenance cost of transformer over its life. Contents Declaration Abstract Acknowledgement List of figures List of tables Chapters 1. Introduction. 1.1 Background 1.2 Motivation 1.3 Objectives 1.4 Scope 1.5 Methodology 2. Distribution loss management 2.0 Distribution losses 2.1 Technical losses ... 2.2 Reasons for high technical losses 2.3 Reasons for non-technical losses 2.4 Measures for reducing technical losses 2.4. I Short term measures 2.4.2 Long term measures 2.5 Measures for reducing non technical losses 2.6 Initiative required 3. Calculation of the losses 3.0 Theoretical analysis / ._. Page IT III IV v 3 4 5 5 7 7 7 8 8 9 9 9 10 10 12 12 3.1 Uniformly distributed loads 14 3.1.1 Calculation of voltage drop 14 3.2 Power losses in distribution network 17 3.2.1 Calculation of power losses 17 3.2.2 Improved lumped load model 19 3.3 Theoretical analysis of voltage drop and power/energy loss 21 3.3.1 Calculation of voltage drop 21 3.3.2 Power losses 23 3.3.2.1 Energy losses (kWh) 4. Sample study (segregation of losses) 4.0 Substation selection 4.1 Calculation of distribution system losses 4.1.1 Calculation period 4.2 Total distribution losses 4.3 Methodology 4.3.1 Model data base 4.3.2 Equipment data base 4.3.4 Protection data base 4.4 Net\vork analysis for technical loss reductions 4.5 Segregation of losses 4.5.1 Measuring of total losses 4.5.2 Evaluation of losses 4.6 Identifying of high loss areas 4.7 Advantage of energy audit 5. Impact of voltage imbalance 5.0 Introduction / ~ 23 25 25 26 26 26 28 28 28 28 29 29 29 31 32 32 33 33 5.1 Definitions of voltage unbalance 34 5.2 Losses in imbalance distribution net\vork 37 5.2.1 12R loss in distribution lines due to unbalance 37 5.2.2 Effects of unbalance for the distribution losses 38 5.3 Effect of unbalance voltage at metering power in 3-phase circuit 39 5.3.1 Two and half-element meters 5.3.1.1 Derivation of formulas 5.3.2 Three clement meters 5.3.2.1 Derivation ofbasic formulas for 3-clcmcnt meters 5.4 Mitigation of voltage unbalance and its effects. 6. Sample study (distribution tra nsformer losses) 6.1 Distribution transformers 6.1.1 Analysis of transformer loading 6.1.2 Building of load curve . 1 39 40 42 43 43 45 45 45 46 6.1.3 Load duration curve 47 6.2 Preliminary calculation for selection of transformer 48 6.2.1 Calculation of loss component of 400kYA transformer 48 6.3 Selection of optimum capacity transformer 52 6.3.1 Loss oftransformer life 6.3.2 Comparison of distribution transformers based on economic evaluation 6.3.2.1 Calculation criteria 7. Conclusions, remarks and discussion References Appendices Appendix A -- 52 53 53 56 58 60 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. ~~'-1 J.P.R. Jayasinghe Date. ocr I 0 '1/'>-w s We endorse the declaration by the candidate. Pro~. Perera Date. I (,~- Dr. H.M. Wijekoon Date. ,_. Acknowledgement 1 wish to express my profound gratitude and sincere appreciation to my project supervisors, Professor H.Y.R. Perera and Dr. H.M. Wijekoon for their constant guidance and constructive suggestions. J sincerely thank and highl} value the support in the system planning branch of western province I and Kaldemulla consumer service centre for data collection, load reading, and practical issues in the all phase of this work. Your supports made this work a success. Last but not least 1 would like to express my deepest gratitude !td love to my wife Shiromi and my three sons Binith , Lathika, and Nidula. Your love, invaluable response and patience helped me to reach this target under tiring circumstances . .__ iii List of Figures Figure 3.1 Line to neutral equivalent circuit 3.2 Phasor diagram 3.3 Generalized line with uniformly distributed loads. 3.4 Load lumped at the mid point 3.5 One half load lumped at the end 3.6 Power loss model 3.7 Exact lumped load model 3.8 Exact lumped load model 3.9 Voltage drop in a three phase semi urban scheme. 3.10 Variation of energy loss with consumer density. 4.1 Measuring of total losses 4.2 Steps of Evaluation of losses 5.1 Symmetrical components of an unbalance system voltages. 5.2 Simple three phase network. 5.3 Simple three phase network with impedance in the neutral line. 5.4 Three phase 3 wire delta connected 2-1 /2 element connections. Page 12 13 14 16 16 l 18 19 21 22 24 29 31 35 37 38 40 5.5 Phasor diagram of three phase 4-wirc 2-element meter with delta connected CT 41 5.6 Three phase four wire three element connection 42 5.7 Phasor diagram of3-phase, 4-wirc, 3-elcment meter. 43 6.1 Load curve of Kalapura substation 400kV A. 46 6.2 Load duration curve for Kalapura substation 400kVA. 47 6.3 Transformer loss profile Kalapura 400kVA sub B- 028 50 6.4 Transformer loss profile 200kVA Sub. 51 6.5 Comparison of losses between lower end and higher end transformers. ~ 51 IV List of tables Table Page J_J Past system losses- CEB distribution planning branch report- 2004. 4 3.2 Voltage drop in a three phase semi urban scheme with consumer density. 22 3.3 Percentage power and energy loss with consumer density. 23 6.1 Recommended copper and iron losses for transformers conforming I.S. 2026- 1962. 46 6.2 400kVA Transformer loss profile. 6.3 200kVA Transformer loss profile 6.4 No load and load loss component at 128 kV A average demand. ~ยท v f ...._ 49 50 54