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POWER QUALITY – MONITORING, ANALYSIS AND ENHANCEMENT

Edited by Ahmed Faheem Zobaa, Mario Mañana Canteli and Ramesh Bansal

Power Quality – Monitoring, Analysis and Enhancement

Edited by Ahmed Faheem Zobaa, Mario Mañana Canteli and Ramesh Bansal

Published by InTech

Janeza Trdine 9, 51000 Rijeka, Croatia

Copyright © 2011 InTech

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Technical Editor Teodora Smiljanic

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Image Copyright Sergej Razvodovskij, 2010. Used under license from Shutterstock.com

First published August, 2011

Printed in Croatia

A free online edition of this book is available at www.intechopen.com Additional hard copies can be obtained from orders@intechweb.org

Power Quality – Monitoring, Analysis and Enhancement,

Edited by Ahmed Faheem Zobaa, Mario Mañana Canteli and Ramesh Bansal p. cm.

ISBN 978-953-307-330-9

Contents

VI Contents

S. Prabhakar Karthikeyan, K. Sathish Kumar,

I. Jacob Raglend and D.P. Kothari

Preface

Power quality has become an important issue in recent times when many utilities around the world find very difficult to meet energy demands which leads to load shedding and power quality problems. This book on power quality written by experts in their fields will be of great benefit to professionals, engineers and researchers. This book comprises of 16 chapters which are arranged in two sections. Section one covers power quality monitoring, classification, and analysis aspects. Power quality enhancement, reactive power compensation and voltage sag mitigation of disturbances in transmission and distribution system are presented in the second section. Brief discussion of each chapter is as follows.

Chapter 1 presents the monitoring of voltage sags to find its origin and detect types of sags. The calculations of various types of faults which may cause voltage sags have been discussed. Optimal placement of voltage sag monitors has also been discussed in the chapter.

Chapter 2 proposes the applications of discrete wavelet transform (DWT), principal component analysis (PCA) and artificial neural networks (ANN) in order to classify power quality disturbances. The method proposes to analyse seven classes of signals, namely Sinusoidal Waveform, Capacitor Switching Transient, Flicker, Harmonics, Interruption, Notching and Sag, which is composed of four main stages: (1) signal analysis using the DWT; (2) feature extraction; (3) data reduction using PCA; (4) classification using a radial basis function network (RBF). The MRA (Multiresolution Analysis) technique of DWT is employed to extract the discriminating features of distorted signals at different resolution levels. Subsequently, the PCA is used to condense information of a correlated set of variables into a few variables, and a RBF network is employed to classify the disturbance types.

Chapter 3 presents a critical review of apparent power, reactive power and power factor definitions. These definitions are reviewed for single phase and three phase systems and are evaluated under different conditions such as sinusoidal, non sinusoidal, one phase, and balanced and unbalanced three phase systems. Then, a methodology to measure power and power quality indexes based on the instant power theory under non sinusoidal conditions is presented.

XPreface

Chapter 4 deals with the application of power quality monitoring in power system network comprising of distributed energy sources (DER). The importance to integrate power quality analysis functions into protection relay has been described. The voltage and current transducers for measurement of line voltage and current signals have been discussed.

Chapter 5 discusses the applications of signal processing techniques for power quality monitoring. This chapter also presents various classification techniques which are very useful for power system disturbances, e.g. ANN, support vector machines (SVM), pattern recognition, etc. Filter and Wrapper based methods used for removal of irreverent and redundant data and feature selection are discussed.

Chapter 6 presents different methods for the power quality analysis. A comparative analysis of Discrete Fourier Transform (DFT), Short-Time Fourier Transform (STFT), Discrete Wavelet Transform (DWT) and Discrete Stockwell Transform (DST) is presented for power quality analysis.

Chapter 7 presents a review of various preprocessing (DWT, Shannon entropy, signal energy, and fractal dimension) and intelligent techniques (ANN, adaptive NeuralFuzzy Interface Systems (ANFIS), and Neural-Genetic) used for power quality analysis. This chapter also demonstrates the application of ATP (alternative transients program) software preprocessing and disturbance analysis of real distribution system.

Chapter 8 presents the selection of the voltage referential (reference point) which can influence the total harmonic distortion, unbalance factors, voltage sags and swells in three-phase system. The definition of apparent power is reviewed using voltage referential. A methodology based on Blakesley’s theorem is presented in order to allow the association of the most common voltage measurement approaches in such a way that the power quality and power components definitions are not be improperly influenced.

Chapter 9 deals with problems of location of the disturbance source based on the measurements made at a single point of a network (PCC). Methodologies are presented for high harmonics, voltage fluctuations, voltage dips and unbalance that allow the determination of location of the disturbance source at the supplier side (upstream) or at the customer side (downstream) viewed from PCC.

Chapter 10 discusses the theoretical background on STFT, wave transform (WT) and S- transform. The indices which are most frequently used in international standards and four new power quality indices for transient disturbances based on S-transform are defined. The performance of the new power quality indices is evaluated using mathematical and PSCAD/EMTDC simulated disturbance signals.

Chapter 11 presents detailed analysis of active load balancing in a three phase system using reactive power compensation. This chapter develops a mathematical model associated to the circuit proposed by Steinmetz which is commonly used in major