THE APPLICATION OF VOLT/VAr OPTIMISATION ON SOUTH AFRICAN DISTRIBUTION POWER NETWORKS by Dayahalan Thangavelloo Chetty Student Number: 971164226 In fulfilment of Master of Science in Engineering, College of Agriculture, Engineering and Science, University of KwaZulu-Natal October 2016 Supervisor: Prof. Innocent Ewean Davidson Industrial Supervisor: Mr. Mobolaji Bello Declaration - Plagiarism I, Dayahalan Thangavelloo Chetty, declare that 1. The research reported in this thesis, except where otherwise indicated, is my original research. 2. This thesis has not been submitted for any degree or examination at any other university. 3. This thesis does not contain other persons’ data, pictures, graphs or other information, unless specifically acknowledged as being sourced from other persons. 4. This thesis does not contain other persons' writing, unless specifically acknowledged as being sourced from other researchers. Where other written sources have been quoted, then: a. Their words have been re-written but the general information attributed to them has been referenced. b. Where their exact words have been used, then their writing has been placed in italics and inside quotation marks, and referenced. 5. This thesis does not contain text, graphics or tables copied and pasted from the Internet, unless specifically acknowledged, and the source being detailed in the thesis and in the References sections. Signed Dayahalan Chetty …………………… As the candidate’s Supervisor I agree/do not agree to the submission of this thesis Signed Prof. Innocent Ewean Davidson …………………… i Acknowledgements I would like to thank: My supervisor Prof. I.E Davidson for his guidance and support during my research. My industrial supervisor Mr. M.M Bello for persuading me to initiate this research. His technical guidance, motivation, and selflessness in ensuring that I completed this work, is invaluable. My colleague, Mr. A. Ambaram for assisting me with illustrations and critiquing the work. My wife Preshnee and my kids Nikaylan, Myuran and Kalai whom I’m forever indebted to for their love, encouragement and tolerance during my research. My parents, for being my greatest teachers. ii Abstract Electric power utilities can achieve cost savings by maximizing energy delivery efficiency and optimizing peak demand. Technical losses are influenced by both network impedances and currents. Power flow through distribution components are composed of active and reactive components. The reactive power does no real work, but contributes to the overall technical losses. By the appropriate placement and operation of reactive power compensation devices, reactive power flows could either be eliminated or significantly minimized, thus, inherently reducing technical losses. This research investigation presents a method for reactive power compensation of medium voltage radial networks as a cost-effective approach to achieve loss minimization and voltage regulation improvement. The study addresses the optimal placement of distributed shunt capacitors along distribution feeders. A mathematical formulation is developed to show that there is a specific location for a given size of capacitor bank that produces the maximum power loss reduction for a given load distribution on a network. In the Eskom distribution system, for those networks that are voltage constrained, the application of capacitors will also consider raising voltages to statutory requirements, however at the expense of the power loss reduction capability. The method developed maximizes both voltage and power loss reduction. Switching and control strategies are developed to meet these objectives throughout a day cycle. The methodology was tested on an Eskom distribution medium voltage network by power system simulation. Results obtained of improvements in voltage regulation and feeder losses are presented and discussed. The application of shunt compensation and the associated feeder voltage regulation improvement is an enabler for Conservation Voltage Reduction (CVR) that can be applied for demand reduction during peak times. Control strategies for CVR are presented, to cater for an integrated Volt/VAr solution for distribution networks. Furthermore, an assessment of CVR potential within Eskom Distribution networks is presented. This research forms the inception for a series of studies aimed at incorporating Volt/VAr optimization within Eskom Distribution networks. iii Table of Contents 1 Introduction ................................................................................................................................ 1 1.1 Background ......................................................................................................................... 1 1.2 Objectives ............................................................................................................................ 3 1.3 Structure ............................................................................................................................. 3 1.4 List of Publications .............................................................................................................. 5 2 Literature review and the electric power system ....................................................................... 6 2.1 Losses on a power system ................................................................................................... 6 2.1.1 Installation of shunt capacitor banks .......................................................................... 7 2.1.2 Distribution network reconfiguration ......................................................................... 8 2.1.3 Re-conductoring .......................................................................................................... 9 2.1.4 Circulating current minimization ................................................................................ 9 2.1.5 Distribution generation [31] ....................................................................................... 9 2.2 General structure of the modern day power system ....................................................... 10 2.3 Line model ......................................................................................................................... 12 2.3.1 Resistance ................................................................................................................. 14 2.3.2 Inductance ................................................................................................................. 15 2.3.3 Capacitance ............................................................................................................... 16 2.3.4 Voltage regulation of distribution lines .................................................................... 18 2.4 Transformer model ........................................................................................................... 21 2.4.1 Equivalent circuit of transformers ............................................................................ 21 2.4.2 Voltage Regulation of a transformer......................................................................... 24 2.4.3 Transformer Losses ................................................................................................... 25 2.4.4 Transformer on load tap changers (OLTC) ................................................................ 26 2.5 Medium voltage regulator model ..................................................................................... 27 iv 2.5.1 Regulator Losses ........................................................................................................ 30 2.6 Conclusion ......................................................................................................................... 31 3 Assessment of the operating voltage regulation requirements in South Africa....................... 33 3.1 South African quality of supply standards ........................................................................ 33 3.1.1 Voltage compatibility levels and limits ..................................................................... 34 3.1.2 Guidelines for operating voltage ranges in South Africa .......................................... 35 3.2 South African Distribution grid code pertaining to voltage management ........................ 37 3.2.1 Assessments and procedures for Grid Code compliance .......................................... 38 3.3 Voltage apportionment and associated limits used within Eskom Distribution ............... 40 3.4 Voltage operating points for Eskom’s Sub-transmission and Distribution System .......... 42 3.5 Conclusion ......................................................................................................................... 45 4 Current Volt/VAr optimization techniques and approaches .................................................... 46 4.1 The objectives of Volt/VAr optimization ........................................................................... 46 4.2 A review of the levels of implementation and minimum hardware requirements for Volt/VAr management .................................................................................................................. 49 4.2.1 The Standalone traditional approach ....................................................................... 49 4.2.2 The Centralized SCADA approach ............................................................................. 51 4.2.3 The integrated approach involving Distribution Management System (DMS) with