Electrical Power Systems

Transcription

1 Electrical Power Systems CONCEPT, THEORY AND PRACTICE SECOND EDITION SUBIR RAY Professor MVJ College of Engineering Bangalore PHI Learning Pfcte tofm Delhi

2 Preface xv Preface to the First Edition xvii Chapter 1 Introduction Historical Development of Power Systems Functional Requirements of a Power System Sources of Energy for Generation of Electricity Electric Energy Consumption Power System Structure Electrical Load Interconnection Operational Challenges of Interconnected System Abnormal Situations About this Book 11 Chapter 2 Fundamental Concepts of AC Circuits Sinusoidal AC Quantities Phasor Representation Reactance Power in AC Circuits Three-phase Circuits Transients in Electrical Circuits Per Unit Representations of Electrical Quantities Base Values 25 Review Questions 27 PART I ELECTRIC POWER TRANSMISSION AND DISTRIBUTION Chapter 3 General Considerations of Transmission and Distribution Some Preliminary Issues Choice of Frequency Choice of Voltage Mode of Transmission and Distribution More Complicated Issues Overhead Lines 40 v

3 3.2.2 Underground Cables Substations and Distribution Systems High Voltage DC Transmission Expectation 41 Review Questions 43 Chapter 4 Electrical Characteristics, Modelling and Performance of Aerial Transmission Lines Inductance of Aerial Lines Fundamentals of Steady Magnetic Field Magnetic Field of a Long Straight Conductor Magnetic Field in a Group of Parallel Cylindrical Conductors Inductance of Single-phase and Three-phase Lines Concepts of Geometric Mean Distances Bundled Conductors and Computation of Inductance Computation of Inductance of Double-circuit Three-phase Lines Capacitance of Aerial Lines Fundamentals of Electric Field Potential Difference between Two Points External to a Long Straight Isolated Conductor with Uniformly Distributed Charge Potential Difference between Two Points due to Multiple Conductors Capacitance of Single-phase and Three-phase Systems Computation of Capacitance Using Geometric Mean Distances Influence of Earth on Conductor Capacitance Resistance Shunt Conductance An Exact Mathematical Model Equivalent Circuit Model Some Important Concepts ABCD Constants of 'Electrically Short Lines' Interpretation of the General Circuit Constants ABCD Two Four-Terminal Networks in Cascade Efficiency Regulation Some Important Observations Power Equations and Line Compensation 107 Review Questions 117 Chapter 5 Overhead Line Construction Route Selection Line Supports Sag and Clearance 127

4 5.4 Sag-Tension Relation Effect of Wind and Ice Covering on Sag Calculation Stringing of Transmission Lines Location of Tower Structures Span Tower Spotting Vibration of Conductors Ground Wires Insulators for Overhead Lines Fundamentals of Insulation Breakdown Materials Types Voltage Distribution Across a Suspension Insulator String String Efficiency Arcing Shield and Rings Number of Disc Units in a String Methods of Improving Voltage Distribution Across Insulator Strings Electrical Tests on Line Insulations Terms Used in Standards High Voltage Tests on Line Insulators Corona Mechanism of Corona Power Loss in Air 171 Review Questions 175 Chapter 6 Underground Cables Cable Components Conductor Insulating Material Shields Sheath, Jacket and Armour Types of Power Cables and Constructional Features Electrical Characteristics of Cables Insulation Resistance of a Single-core Cable Conductor Inductance Cable Capacitance Electric Stresses in Single-core Cables Dielectric Losses and Loss Tangent of a Cable Sheath and Armour Losses Computation of Ampacity of Cables Laying of Cables Electrical Breakdown of Cables DC Cables 204 Review Questions 205

5 Chapter 7 Substation and Distribution System Substation Types of Substations Location of a Substation Substation Equipments and Accessories Layout of Substation Bus Arrangements Earthing Distribution Systems Primary Distribution System Arrangements Primary Feeder Conductor Size Secondary Distribution System Arrangements Distributor Design Transmission and Distribution Losses Reasons for High Technical Losses Application of Capacitors to Distribution System 242 Review Questions 250 PART II POWER SYSTEM OPERATION Chapter 8 Elements of Electric Power Generation Basic Methods of Production of Electrical Energy Conventional Methods of Electric Power Generation Steam Power Stations Main Components of a Steam Power Station Hydro-electric Stations Water Storage Schematic Layout of a Hydro-electric Station Pumped-Storage Plants Nuclear Power Station Principles of Atomic Physics Revisited Components of a Nuclear Reactor Some Common Reactor Types Disposal of Nuclear Waste Indian Nuclear Power Plants Gas Turbine Plants Salient Characteristics of Various Types of Power Plants Cogeneration Distribution Power Generation Synchronous Generator Revisited Basic Principles Circuit Model for a Cylindrical Rotor Synchronous Generator Concept of an Infinite Bus Power Control of a Finite Machine Connected to an Infinite Bus 287

6 8.8.5 Salient Pole Synchronous Generator Operational Constraints of a Synchronous Generator Connected to a Large Network 296 Review Questions 298 Chapter 9 Load Flow Studies An Illustrative Two-bus System Load Flow Problem Power Flow Equations System Variables Classification of Buses Gauss-Seidel Iterative Technique Applied to Solution of Power Flow Equations Computational Strategy Newton-Raphson Algorithm for Solution of PFE Elements of the Jacobian Matrix Computational Steps for Solving PFEs by N-R Method Sparsity Features Fast Decoupled Technique Representation of Tap Changing Transformer 331 Review Questions 333 Chapter 10 Power System Economics Characteristics and Classification of Consumers Diversity and Its Impact Tariff Structure Cost of Electrical Energy Two-part Tariff Operational Strategy to Meet Load Demand Optimum Scheduling of Generators Economics of Steam Plants Optimum Scheduling for a Lossless System Optimal Scheduling Considering Transmission Losses Unit Commitment Hydro-thermal Co-ordination Short-term Load Forecasting (STLF) 369 Review Questions 370 PART III POWER SYSTEM TRANSIENTS AND PROTECTION Chapter 11 Introduction to Power System Transients Basic Concepts of Transients Classification of Power System Transients Concepts of Protection 378

7 D Chapter 12 Over-Voltage Transients in Power Systems and Protection What is Lightning? Charge Formation in Cloud Mechanism of a Lightning Stroke Return Stroke Current Lightning Over-Voltage Interaction between Lightning and the Power System Propagation of Lightning Current and Voltage along Transmission Lines Shape of Lightning Voltage Waves Reflection and Refraction of Rectangular Traveling Waves Successive Reflections Ground Wires Switching Over-Voltages Transient Initiated when a Fault is Cleared Switching Over-Voltages due to Disconnection of an Unloaded Transformer Over-Voltage due to Capacitance Switching Over-Voltages due to Ferro-Resonance Power Frequency Over-Voltages Control of Over-Voltages Due to Switching Protection of System Insulation against Transient Over-Voltages Insulation Co-ordination 420 Review Questions 427 Chapter 13 Short-Circuit Phenomena Symmetrical Faults Sudden Three-Phase Short-Circuit of an Unloaded Generator Explanation of Short-Circuit Currents Mathematical Model Its Complexities Simplified Models of Synchronous Machines for Fault Studies Representation of Transmission Lines, Transformers and Loads Short-Circuit Current Computation Asymmetrical Faults Symmetrical Components Resolution of Three-Phasors into Their Symmetrical Components Some Important Interpretations Sequence Impedances in Symmetrical Systems Power in Terms of Symmetrical Components Sequence Impedances of Components Phase Shift in Star-Delta Transformations Assembling of System Sequence Networks Computation of Asymmetrical Fault Current Series Faults A Systematic Approach to Fault Calculation 489

8 13.3 Neutral Grounding Arcing Ground Other Disadvantages of Ungrounded Systems Grounded Systems Types of Neutral Grounding Present Grounding Practice 497 Review Questions 497 Chapter 14 Elements of Circuit-Breakers and Relays Introduction Zones of Protection Overlapping of Zones Back-up Protection Scheme Function of Circuit-Breaker Arc Restriking or Recovery Voltage 505, 14.6 Arc Quenching Methods and Theories Circuit-Breaker Rating Fault Clearing Process Types of Circuit-Breakers Air-Break Circuit-Breaker Oil Circuit-Breaker Air-Blast Circuit-Breaker (ABCB) Sulphur Hexaffuoride Circuit-Breakers Vacuum Circuit-Breaker.>: Selection of Circuit-Breakers Auto-Reclosing Trip-free Mechanism Relays Attributes of Protective Relaying How Do Protective Relays Operate? Electromechanical Relays Attracted-Armature Relays Induction Type of Relay Actuating Structures for Induction Rejays Torque Equations in Induction Relay General Torque Equation Over-Current Relay and Its Characteristic Time-Current Characteristics Earth-Fault and Phase-Fault Relays Differential Relays Protection of Transmission and Distribution Lines Protection of Distribution Feeders Time Graded Scheme 541

9 Current Graded Scheme Current and Time Graded System Directional Time and Current Grading Distance Protection ' Protection of Transformers Percentage Differential Protection Earth Fault Protection Overcurrent Protection Gas Actuated Relay Protection of Generators Percentage Differential Protection Negative Sequence Relay Static Relays Microprocessor-Based Relays 560 Review Questions 562 Chapter 15 Power System Stability General Concept of Stability Concept of Stability in Power System Steady State Stability and Transient Stability Stability Indicator Power-angle Curve of a Synchronous Machine Connected to an Infinite Bus The Elementary Mathematical Model Swing Equation Difficulties in Solving Swing Equation Regulated Machines Output Power Synchronous Machine Assumptions Analysis of Steady State Stability of an Uncontrolled System Equal Area Criterion Finite Machine Connected to an Infinite Bus Equal-Area Criterion Applied to a Simple Case Application to Practical Cases A Two-Area System Step-by-Step Solution of Swing Equation Discontinuity Digital Computation Using Runge-Kutta Method Methods for Enhancement of Stability Voltage Stability Definitions Types of Voltage Stability A Practical Example of Voltage Collapse 610

10 15.12 Prediction of Voltage Collapse P-V and Q-V Curves Index and Sensitivity Methods Remedy 616 Review Questions 617 Chapter 16 FACTS and High Voltage DC Transmission Constraints in a Transmission System What are the Remedies? Flexible AC Transmission Systems (FACTS) Key Features of FACTS Technology Power Converters Development of FACTS Devices Technology Underlying FACTS High Voltage DC Transmission (HVDC Transmission) Advantages of HVDC Transmission Applications of DC Transmission Economic Distance for HVDC Transmission Configuration of DC Transmission Links Rectifying and Inverting Components Rectifying and Inverting Systems Circuit Elements Configurations for DC Links Disadvantages Parallel Operation of AC and DC Systems Indian Scenario 637 Chapter 17 Control of Active and Reactive Power Active Power and Frequency Control 639 of Control Area Concept Isolated System Transfer Function (Block Diagram of the Isolated System) Automatic Load Frequency Control Loop and Steady State Response Dynamic Response Proportional Plus Integral Control Automatic Load Frequency Control of Multiarea System Tie Line Modelling Block Diagram of Two Area System Static Response of Two Area System Dynamic Response of Two Area System Reactive Power Control Injection and Absorption of Reactive Power Automatic Voltage Regulator (AVR) 656

11 W77M Shunt Reactors Shunt Capacitors Series Capacitor Synchronous Condensers or Compensators Static Var System 660 Review Questions 660 Appendix 1 Laplace Transforms 661 Appendix 2 Iterative Methods for Solving Algebraic Equations Appendix 3 Formation of Bus Admittance Matrix Using Singular Transformation Appendix 4 Optimisation Technique Bibliography Index