CHAPTER ONE
INTRODUCTION
1.1 Background of Study
Electrical energy is generated at power stations which are usually located far away from load centres [1]. Thus, a network of conductors between the power stations and the consumers is required in order to harness the power generated. This network of conductors may be divided into two main components, namely, the transmission system and the distribution system [1]. As power flows in the lines, a significant amount is lost. Accurate knowledge of these power losses on transmission lines and their minimization is a critical component for efficient flow of power in an electrical network. Power losses result in lower power availability to final consumers. Hence, adequate measures need to be taken to reduce power losses to the barest minimum.
Power plants' planning in a way to meet the power network load demand is one of the most important and essential issues in power systems. Since transmission lines connect generating plants and substations in power network, the analysis, computation and reduction of transmission losses in these networks are of great concern to scientists and engineers.
Studies have indicated that as much as 9% or more of total power generated is consumed as [1]
losses at the transmission level [2]. The losses can be separated to active and reactive component of branch current, where the losses produced by reactive current can be reduced by the installation of shunt capacitors. Capacitors (capacitor banks) are widely used in transmission systems to reduce energy and peak demand losses, release the MVA capacities of transmission apparatus and to maintain a voltage profile within permissible limits [3]. The objective of optimal capacitor placement problem is to determine the size, type, and location of capacitors to be installed on the transmission network to achieve positive economic response. The economic
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benefits obtained from the loss reduction weighted against capacitors costs while keeping the operational and power quality constraints within required limits. Fuzzy logic provides a remedy for any lack of uncertainty in the data. Fuzzy logic is a subset of conventional (Boolean) logic that has been extended to handle the concepts of partial truth-values, between ‘completely true’ and ‘completely false’.
The ideas of fuzzy logic dates all the way back to Plato who proposed that there is a third region between true and false. Fuzzy logic is a technique of making a choice answer to questions, other than ‘yes’ or ‘no’. It resembles human reasoning in the use of approximate information and uncertainty to generate decision. The fuzzy logic is a designed technique used in providing tools for dealing with imprecision that are intrinsic to many problems. The fuzzy set theory implements clauses of data that are not sharply defined. To that effect, the degree of power loss incurred in transmission lines is evaluated using Fuzzy logic in MATLAB toolbox.
Furthermore fuzzy logic has the advantage of including heuristics and representing engineering judgments into the capacitor allocation optimization process.
1.2 Statement Of The Problem
Presently, many electrical energy companies in a number of countries are experiencing very high losses. Studies show that about 9% of total power generated is wasted in the form of losses at the transmission level in Nigeria [1]. Similarly, voltage drops and/or over-voltages are frequently experienced by TCN in transmitting electricity. To reduce these losses and improve voltage profile, shunt capacitor banks are installed on transmission sub-stations. With active power loss reduction and voltage profile improvement as objectives, the optimal capacitor placement problem aims to determine the optimal capacitor location and capacitor sizes in the transmission systems. Efficient methods are required to determine the best location and sizes.