Electric Distribution Systems E-Book

Abdelhay A. Sallam

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Serie: IEEE Press Series on Power Engineering
• Sprache: Englisch

Seitenzahl: 661

Veröffentlichungsjahr: 2011

Beschreibung

This book provides a comprehensive treatment of electricdistribution systems. Few books cover specific topics in more depthand there is hardly any book that deals with the key topics ofinterest to distribution system engineers. The book introducesthese topics from two points of view: 1) The practical point of view by providing practical examplesand the problems which can be solved. 2) The academic point of view where the analysis and varioustechniques used for distribution system planning are explained. The most outstanding feature of this book is a combination ofpractical and academic explanation of its contents. Anotheroutstanding feature is a collection of the traditional and currenttopics of distribution systems condensed into one book. The reader will gain an understanding of distribution systemsfrom both practical and academic aspects, will be able to outlineand design a distribution system for specific loads, cities, zones,etc.. Readers will also be able to recognize the problems which mayoccur during the operation of distribution systems and be able topropose solutions for these problems.

Leseprobe

Table of Contents

Cover

Series page

Title page

Copyright page

PREFACE

ACKNOWLEDGMENTS

Part I: FUNDAMENTAL CONCEPTS

CHAPTER 1 MAIN CONCEPTS OF ELECTRIC DISTRIBUTION SYSTEMS

1.1 INTRODUCTION AND BACKGROUND

1.2 DUTIES OF DISTRIBUTION SYSTEM PLANNERS

1.3 FACTORS AFFECTING THE PLANNING PROCESS

1.4 PLANNING OBJECTIVES

1.5 SOLUTIONS FOR MEETING DEMAND FORECASTS

1.6 STRUCTURE OF DISTRIBUTION NETWORKS

CHAPTER 2 LOAD DEMAND FORECASTING

2.1 INTRODUCTION

2.2 IMPORTANT FACTORS FOR FORECASTS

2.3 FORECASTING METHODOLOGY

2.4 SPATIAL LOAD FORECASTING (SLF)

2.5 END-USE MODELING

2.6 SPATIAL LOAD FORECAST METHODS

Part II: PROTECTION AND DISTRIBUTION SWITCHGEAR

CHAPTER 3 EARTHING OF ELECTRIC DISTRIBUTION SYSTEMS

3.1 BASIC OBJECTIVES

3.2 EARTHING ELECTRIC EQUIPMENT

3.3 SYSTEM EARTHING

3.4 MV EARTHING SYSTEMS

3.5 EARTHING SYSTEMS IN LV DISTRIBUTION NETWORKS

CHAPTER 4 SHORT-CIRCUIT STUDIES

4.1 INTRODUCTION

4.2 SHORT-CIRCUIT ANALYSIS

CHAPTER 5 PROTECTION OF ELECTRIC DISTRIBUTION SYSTEMS

5.1 INTRODUCTION

5.2 TYPES OF RELAY CONSTRUCTION

5.3 OVERCURRENT PROTECTION

5.4 RECLOSERS, SECTIONALIZERS, AND FUSES

5.5 DIRECTIONAL PROTECTION

5.6 DIFFERENTIAL PROTECTION

5.7 THERMAL PROTECTION

5.8 OVERVOLTAGE PROTECTION

CHAPTER 6 DISTRIBUTION SWITCHGEAR

6.1 NEED FOR SWITCHGEAR

6.2 SWITCHGEAR LAYOUT

6.3 DIMENSIONING OF SWITCHGEAR INSTALLATIONS

6.4 CIVIL CONSTRUCTION REQUIREMENTS

6.5 MV SWITCHGEAR DEVICES

6.6 LV SWITCHGEAR DEVICES

6.7 PROTECTION CLASSES

6.8 SPECIFICATIONS AND IMPLEMENTATION OF EARTHING

6.9 SAFETY AND SECURITY OF INSTALLATIONS

6.10 ASSESSMENT OF SWITCHGEAR

6.11 STEPS FOR INSTALLING SWITCHGEAR

6.12 ARC FLASH HAZARDS

Part III: POWER QUALITY

CHAPTER 7 ELECTRIC POWER QUALITY

7.1 OVERVIEW

7.2 POWER QUALITY PROBLEMS

7.3 COST OF POWER QUALITY

7.4 SOLUTIONS OF POWER QUALITY PROBLEMS

7.5 SOLUTION CYCLE FOR POWER QUALITY PROBLEMS

CHAPTER 8 VOLTAGE VARIATIONS

8.1 VOLTAGE QUALITY

8.2 METHODS OF VOLTAGE DROP REDUCTION

8.3 VOLTAGE SAG CALCULATIONS

8.4 ESTIMATION OF DISTRIBUTION LOSSES

CHAPTER 9 POWER FACTOR IMPROVEMENT

9.1 BACKGROUND

9.2 SHUNT COMPENSATION

9.3 NEED FOR SHUNT COMPENSATION

9.4 AN EXAMPLE

9.5 HOW TO DETERMINE COMPENSATION

CHAPTER 10 HARMONICS IN ELECTRIC DISTRIBUTION SYSTEMS

10.1 WHAT ARE HARMONICS?

10.2 SOURCES OF HARMONICS

10.3 DISTURBANCES CAUSED BY HARMONICS

10.4 PRINCIPLES OF HARMONIC DISTORTION INDICATIONS AND MEASUREMENT

10.5 FREQUENCY SPECTRUM AND HARMONIC CONTENT

10.6 STANDARDS AND RECOMMENDATIONS

CHAPTER 11 HARMONICS EFFECT MITIGATION

11.1 INTRODUCTION

11.2 FIRST CLASS OF SOLUTIONS

11.3 SECOND CLASS OF SOLUTIONS

11.4 THIRD CLASS OF SOLUTIONS

11.5 SELECTION CRITERION

11.6 CASE STUDIES

Part IV: MANAGEMENT AND MONITORING

CHAPTER 12 DEMAND-SIDE MANAGEMENT AND ENERGY EFFICIENCY

12.1 OVERVIEW

12.2 DSM

12.3 NEEDS TO APPLY DSM

12.4 MEANS OF DSM PROGRAMS

12.5 INTERNATIONAL EXPERIENCE WITH DSM

12.6 POTENTIAL FOR DSM APPLICATION

12.7 THE DSM PLANNING PROCESS

12.8 EXPECTED BENEFITS OF MANAGING DEMAND

12.9 ENERGY EFFICIENCY

12.10 SCENARIOS USED FOR ENERGY-EFFICIENCY APPLICATION

12.11 ECONOMIC BENEFITS OF ENERGY EFFICIENCY

12.12 APPLICATION OF EFFICIENT TECHNOLOGY

CHAPTER 13 SCADA SYSTEMS AND SMART GRID VISION

13.1 INTRODUCTION

13.2 DEFINITIONS

13.3 SCADA COMPONENTS

13.4 SCADA SYSTEMS ARCHITECTURES

13.5 SCADA APPLICATIONS

13.6 SMART GRID VISION

Part V: DISTRIBUTED GENERATION

CHAPTER 14 DISTRIBUTED GENERATION

14.1 POWER SYSTEMS AND DISTRIBUTED GENERATION (DG)

14.2 PERFORMANCE OF DISTRIBUTED GENERATORS

14.3 CASE STUDY

REFERENCES

Index

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R. AbariM. El-HawaryS. NahavandiJ. AndersonB. M. HammerliW. ReeveF. CanaveroM. LanzerottiT. SamadT. G. CrodaO. MalikG. Zobrist

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Copyright © 2011 by the Institute of Electrical and Electronics Engineers, Inc.

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Published simultaneously in Canada

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Library of Congress Cataloging-in-Publication Data:

Sallam, A. A. (Abdelhay. A.)

Electric distribution systems / A.A. Sallam.

p. cm.—(Ieee press series on power engineering ; 45)

ISBN 978-0-470-27682-2 (hardback)

 1. Electric power distribution. I. Title.

TK3001.S325 2010

621.319—dc22

2010033573

oBook ISBN: 978-0-470-94389-4

ePDF ISBN: 978-0-470-94384-7

ePub ISBN: 978-1-118-00221-6

PREFACE

The main consideration of distribution systems, as intermediate media between the subtransmission systems and the customer’s premises, is to maximize the utilization of electric energy to supply the end users with energy in a secure and efficient manner. Several circuits feed customers at different locations, in comparison to the transmission and subtransmission systems, which have only a few circuits. Distribution systems have to cater to a large variety of customers with significantly different demand patterns.

In addition, developments in sustainable and renewable generation (commonly referred to as distributed generation) application of a large class of power electronics-based devices demand response programs feasible for use with smart grid technologies, and so on have added new complexities in the planning, design, and operation of distribution systems. This has made the analysis of distribution systems rather complex.

Due to the large variety of customers and demands, electric distribution systems cover a very broad spectrum of topics. The topics covered in this book are relevant from both the academic and practical aspect. They are of interest for electric utilities and industry as well as individuals working with distribution systems.

The operator or utility engineer who is interested in studying or working on distribution systems needs to know the topics addressed in this book and their practical implementation. Different aspects of system planning should be studied to define the system structure that feeds present and future demands. The protection system and switchgear based on short-circuit calculations and earthing systems must be designed. Power quality, system management, and automation as well as distributed generation are essential for the reader’s awareness since they play a prominent role in system operation.

Various major topics are grouped together in this book in five parts.

PART I: FUNDAMENTAL CONCEPTS

The fundamental concepts of distribution systems are the subject of Chapter 1. The duties of distribution engineers including the factors affecting the planning process are introduced here. It is aimed at identifying the key steps in planning. The layout of the distribution system for both small and big cities and examples of structures used in distribution systems at medium and low voltages are presented.

The primary function of the distribution system is to feed electric loads. Therefore, it is necessary to determine during the planning process not only the present load and its makeup but also the expected load growth in the near future. Definitions of load forecast terms and different methods of estimating the demand forecast are explained in Chapter 2 with application examples.

PART II: PROTECTION AND DISTRIBUTION SWITCHGEAR

This part includes earthing, protection systems, and distribution switchgear. Earthing in distribution systems is an important subject that deserves to be studied, especially as the protection system is based on it. Various methods of earthing and a general description of the types of protection used in distribution systems are presented in Chapters 3 and 5, respectively. The design of protection necessitates some explanation of short-circuit calculation methods, and these are presented in Chapter 4.

Automation and measuring equipment for distribution systems is installed in the switchgear (indoor or outdoor). Therefore, details about switchgear devices and the major factors affecting the design of switchboards are included in Chapter 6.

PART III: POWER QUALITY

It is not sufficient to just plan the distribution system to meet the load demand with minimum interruptions (number and duration). It is of crucial importance to emphasize the quality of supply, in particular, when feeding sensitive loads. Therefore, the key elements of power quality (voltage quality, power factor, and harmonics) and means of their improvement are explained in Chapters 7–11.

PART IV: MANAGEMENT AND AUTOMATION

It is desirable to achieve a plan of a distribution system that takes into account the economics, that is, reducing the expenses and investments. How to verify these requirements is explained in Chapter 12 by applying demand-side management and energy-efficiency policies.

In addition, more attention should be given to the enhancement of distribution system performance. Methodologies applied to improve the performance of the distribution systems, such as distribution system automation and monitoring where automation helps to decrease the system interruptions, increase the reliability, and enhance the performance, are also discussed.

Monitoring helps in timely decision making. The difference between the system automation and monitoring, using supervisory control and data acquisition (SCADA) systems, is illustrated with the aid of examples. SCADA definitions and components, architectures of SCADA systems, and the conditions of using various architectures are given in Chapter 13. In addition, the smart grid vision is illustrated as a recent trend for the development of system automation and SCADA applications.

PART V: DISTRIBUTED GENERATION

Electricity produced using local generation including small renewable sources with the goal of feeding local loads or as backup sources to feed critical loads in case of emergency and utility outage is often referred to as “distributed generation” in North American terms and “embedded generation” in European terms. Therefore, distributed generation produces electricity at or near the place where it is used to meet all or a part of the customers’ power needs. It ranges in size from less than 1 kW to tens or, in some cases, hundreds of kilowatts. On the other hand, demand for electric energy continues to grow and a large investment is required to develop both the distribution and transmission systems accordingly. Thus, great attention is being paid to utilizing private and distributed energy sources to be able to meet the load demand. Different types of distributed energy sources and the benefits gained from interconnecting these sources with the distribution system are described in Chapter 14.

Electric power distribution systems cover a broad spectrum of topics that need to be included in such a book. To keep the overall length of the book within a reasonable limit, many of these topics could not be covered in depth. Therefore, all material is supported by an extensive list of references where the interested reader can get more details for an in-depth study.

ABDELHAY A. SALLAM

OM P. MALIK

ACKNOWLEDGMENTS

No work of any significance can be accomplished without the help received from many sources. In that respect, this book is no exception. The authors are grateful for the invaluable help received from many sources. We wish to express our gratitude to the following, in particular, without whose help it would not have been possible to put this book together:

Mr. Hany Shaltoot of Schneider Electric, Egypt, for providing access to a number of relevant articles and company practices relating to the distribution systems. He also helped with obtaining permission from Square D to include in the book information on AccuSine® product.Square D North America for permission to include the AccuSine® product photos.Technical and sales staff members of ABB, Egypt, for making available manuals describing the company practices and a number of illustrations included in the book with permission.Dr. Azza Eldesoky for the information on load forecasting that is included in the book, and Dr. Ahmed Daoud for editing some of the illustrations.Dr. Tamer Melik, Optimal Technologies (Canada) Inc., for making available the report on which a part of the material in Chapter 14 is based.European Commission, Community Research, Smart Grids technology platform for making available the report on which a part of the material in Chapter 13 is based.

In addition, help has been received from a number of other sources to which we are indebted and wish to express our sincere thanks.

All this work requires the moral support of the families and we wish to recognize with our warm appreciation. We dedicate this book: To our wives, Hanzada Sallam and Margareta Malik.

A. A. S

O. P. M

CHAPTER 2

LOAD DEMAND FORECASTING

2.1 INTRODUCTION

Customer load demand in electric distribution systems is subject to change because human activities follow daily, weekly, and monthly cycles. The load demand is generally higher during the daytime and early evening when industrial loads are high, lights are on, and so forth, and lower from late evening to early morning when most of the population is asleep. Estimating the distribution system load expected at some time in the future is an important task in order to meet exactly any network load at whatever time it occurs [17].

On the other hand, the distribution system planning is a multistep process as described by the flowchart (Fig. 1.5) in Chapter 1. The most important key element, on which all steps are based, is load forecast. This defines the distribution system capabilities that need to be achieved by the future system. If it is done inappropriately, all subsequent steps will be directed at planning for future loads different from the load that will develop, and the entire planning process is at risk.

Therefore, load forecast plays a crucial role in all aspects of planning, operation, and control of an electric power system. It is an essential function for operating a power network reliably and economically [18]. So, the need and relevance of forecasting demand for an electric utility has become a much discussed issue in the recent past. It is not only important for distribution or power system planning but also for evaluating the cost-effectiveness of investing in the new technology and the strategy for its propagation.

According to the time horizon, load forecast can be classified as short term, midterm, and long term [19]. Short-term load forecasting (STLF) over an interval ranging from an hour to a week is important for different functions as unit commitment, economic dispatch, energy transfer scheduling, and real-time control. The midterm load forecast (MTLF), ranging from 1 month to 5 years and sometimes 10 or more years, is used by the utilities to purchase enough fuel and for the calculation of various electricity tariffs. Long-term load forecast (LTLF) covering from 5 to 20 years or more is used by planning engineers and economists to plan for the future expansion of the system, for example, type and size of generating plants and transmission lines, that minimize both fixed and variable costs.

STLF involves the prediction of the electric load demand on an hourly, daily, and weekly basis. It is an area of significant economic value to the utilities. It is also a problem that has to be tackled on a daily basis. Reliable forecasting tools would enable the power companies to plan ahead of time for peak demands and better allocate their resources to avoid any disruptions to their customers. It also helps the system operator to efficiently schedule spinning reserve allocation and provides information that enables the possible energy interchange with other utilities. In addition to these economic reasons, it plays an important role in the real-time control and the security function of an energy management system. The amount of savings in the operating costs and the reliability of the power supply depend on the degree of accuracy of the load prediction.

There is an essential need for accuracy in the demand forecast [20, 21]. This is because the underestimated demand forecast could lead to undercapacity resulting in poor quality of service where blackouts may occur. On the other hand, overestimation could lead to overcapacity, that is, excess capacity not needed for several years ahead. Consequently, the utility has to cover the cost of such overcapacity without revenues, and this is not favorable. In addition to ensuring the accuracy of forecast, the rationalization of pricing structures and design of demand-side management programs must be emphasized as well. Demand-side management is implemented using different methods explained in Chapter 12. These methods are based on an hour-by-hour load forecast and the end-use components with a goal of changing the system load shape.

Most forecasting methods use statistical techniques or artificial intelligence algorithms such as regression, neural networks, fuzzy logic (FL), and expert systems. Two methods, the so-called end-use and econometric approaches, are broadly used for medium- and long-term forecasting. A variety of other methods, which include the so-called similar-day approach, various regression models, time series, neural networks, FL, and expert systems, have been developed for short-term forecasting [22].

There is no single forecasting method that could be considered effective for all situations. The selection of a method of load forecast depends on the nature of the data available, and the desired nature and level of detail of the forecasts. Sometimes, it may be even appropriate to apply more than one method and then compare the forecasts to decide the most plausible one. Hence, every utility must find the most suitable technique for its application.

2.2 IMPORTANT FACTORS FOR FORECASTS

Several factors should be considered for STLF, such as time factors, weather data, and possible customers’ classes. The medium- and long-term forecasts take into account the historical load and weather data, the number of customers in different categories, the appliances in the area and their characteristics including age, the economic and demographic data and their forecasts, the appliance sales data, and other factors.