Power System Protection: Fundamentals and Applications

Description

An all-in-one resource on power system protection fundamentals, practices, and applications Made up of an assembly of electrical components, power system protections are a critical piece of the electric power system. Despite its central importance to the safe operation of the power grid, the information available on the topic is limited in scope and detail. In Power System Protection: Fundamentals and Applications, a team of renowned engineers delivers an authoritative and robust overview of power system protection ideal for new and early-career engineers and technologists. The book offers device- and manufacturer-agnostic fundamentals using an accessible balance of theory and practical application. It offers a wealth of examples and easy-to-grasp illustrations to aid the reader in understanding and retaining the information provided within. In addition to providing a wealth of information on power system protection applications for generation, transmission, and distribution facilities, the book offers readers: A thorough introduction to power system protection, including why it's required and foundational definitions Comprehensive explorations of basic power system protection components, including instrument transformers, terminations, telecommunications, and more Practical discussions of basic types of protection relays and their operation, including overcurrent, differential, and distance relays In-depth examinations of breaker failure protection and automatic reclosing, including typical breaker failure tripping zones, logic paths, pedestal breakers, and more Perfect for system planning engineers, system operators, and power system equipment specifiers, Power System Protection: Fundamentals and Applications will also earn a place in the libraries of design and field engineers and technologists, as well as students and scholars of power-system protection. Cover Title Page Copyright Contents About the Authors Preface Acknowledgements Chapter 1 What Is Power System Protection, Why Is It Required and Some Basics? 1.1 What Is Power System Protection? 1.2 Why Is Power System Protections Required? 1.2.1 Minimize Primary Equipment Damage 1.2.2 Provide Continuity of Service by Minimizing Outage Time and Service 1.2.3 Promote Safety 1.2.4 Maintaining Power System Integrity 1.3 Some Basic Protection System Terms and Information 1.3.1 Relay 1.3.2 Protective Relays 1.3.3 Protective Relaying 1.3.4 Protection Engineering 1.3.5 Protection System Objectives 1.3.6 Protection System Characteristics 1.3.6.1 Selectivity 1.3.6.2 Sensitivity 1.3.6.3 Speed 1.3.7 Protection System Reliability 1.3.7.1 Dependability 1.3.7.2 Security 1.3.8 Protection System Backup 1.3.8.1 Remote Backup 1.3.8.2 Local Backup 1.3.9 Protection System Redundancy References Chapter 2 Basic Power System Protection Components 2.1 General Description 2.2 Power System Protection Components 2.2.1 Instrument Transformers 2.2.2 Protective Relays 2.2.3 Auxiliary Logic 2.2.3.1 Auxiliary Relays 2.2.3.2 Application of Auxiliary Relays 2.2.4 Panels and Racks 2.2.5 Battery Systems Used for Protections 2.2.6 Telecommunications 2.3 Physical Implementation 2.3.1 Relay and Control Building 2.3.2 Location of Instrument Transformers 2.3.3 Terminations 2.3.4 Protection Isolation Devices 2.3.5 Wiring and Cable (Control Wiring) 2.4 Power System Isolation Devices and Control Interfaces 2.4.1 Isolation Devices 2.4.2 Control Interfaces 2.5 Redundancy Arrangements 2.5.1 Instrument Transformers 2.5.2 Dual Breaker Trip Coils Chapter 3 AC Signal Sources 3.1 Introduction 3.2 Current Transformers 3.2.1 Current Transformer Secondary Burden 3.2.2 Current Transformer Types 3.2.2.1 Bar‐Type CT 3.2.2.2 Bushing‐Type CT 3.2.2.3 Window‐Type CT 3.2.2.4 Wound‐Type CT 3.2.3 Current Transformer Polarity 3.2.4 Current Transformer Ratios 3.2.5 Auxiliary Transformers 3.2.6 Current Transformer Accuracy Classifications 3.2.7 General Characteristics of CTs 3.2.8 Response of CTs Under Transient Power System Conditions 3.2.8.1 The Effect of CT Saturation on Protections 3.2.8.2 Causes of CT Saturation 3.2.8.3 Flux Remanence in the CT Core 3.2.8.4 Use of Air Gaps to Reduce Remanence 3.2.8.5 Methods to Ensure Correct CT Performance 3.2.9 General Requirements for CT Sizing 3.2.9.1 Maximum Expected Load Current 3.2.9.2 Maximum Symmetrical Fault Current 3.2.9.3 Maximum CT Burden 3.2.9.4 Calculate the Steady‐state CT Secondary Voltage (VS) 3.2.9.5 CT Application Example 3.3 Voltage Sources 3.3.1 Magnetic Voltage Transformers 3.3.1.1 Magnetic Voltage Transformers Equivalent Circuit 3.3.1.2 Protection of VTs 3.3.2 Capacitive Voltage Transformer (CVT) 3.3.3 Bushing Potential Devices References Chapter 4 Basic Types of Protection Relays and Their Operation 4.1 General 4.2 Fundamental Principles and Characteristics 4.2.1 Non‐directional Induction Disk Overcurrent 4.2.2 Induction Principle of Operation 4.3 Overcurrent 4.3.1 Induction Disc Time‐Overcurrent 4.3.2 Inverse Time‐Overcurrent Relay 4.3.2.1 Inverse Time‐Overcurrent Characteristics 4.3.2.2 Basic Pickup Current Setting 4.3.2.3 Time Dial Adjustment 4.3.2.4 Setting Adjustments for an Inverse Time‐Overcurrent Relay 4.3.3 Time Coordination with Overcurrent Relays 4.3.3.1 Coordination Time for Electromechanical Relays 4.3.3.2 Coordination Time for Digital Relays 4.3.4 Directional Overcurrent Relays 4.3.4.1 Method of Directioning 4.3.4.2 The Watt‐Hour Structure 4.3.4.3 The Induction Cup Structure 4.3.4.4 Relay Phase Relationship of Voltage and Current in a Directional Relay 4.3.4.5 Typical Application of Directional Phase Overcurrent Relays 4.3.4.6 Typical Application of Ground Directional Overcurrent Relays 4.4 Differential 4.4.1 General 4.4.2 Differential Principle Used in Bus Protection 4.4.2.1 Fundamental Principle of Operation 4.4.2.2 Security for Out‐of‐Zone Faults 4.4.2.3 Low Impedance Differential Protection 4.4.2.4 High Impedance Differential Protection 4.4.3 Differential Principle Used in Transformer Protection 4.4.3.1 Percent Differential Relay 4.5 Distance 4.5.1 General 4.5.2 Need for Distance Protection 4.5.3 Impedance Relay Principle of Operation 4.5.4 MHO Relay Principle of Operation 4.5.4.1 Offset‐MHO Relay Principle of Operation 4.5.4.2 Reactance – Type Distance Relay 4.5.4.3 Blinder‐Type Distance Relay Reference Chapter 5 Protection Information Representation, Nomenclature, and Jargon 5.1 General 5.2 Protection Drawing Types 5.2.1 Single‐line Diagram 5.2.2 Three‐Phase Diagram (AC EWD) 5.2.2.1 Transcription of Information from AC EWD to Single‐Line Diagrams 5.2.3 DC Elementary Wiring Diagrams – Also Known as DC Control Diagrams 5.2.4 Electrical Arrangement (EA) 5.2.5 Connection Wiring Diagrams (CWD) 5.2.6 Protection Logic Diagrams 5.2.7 Protection Settings Records and Support Information 5.2.8 Protection Relay Threshold/Pickup Settings 5.2.9 Relay Configuration and Settings File 5.3 Nomenclature and Device Numbers 5.3.1 Commonly Used Protection Device Numbers 5.3.2 Prefix and Suffix Meaning 5.3.3 Interlocks 5.4 Classification of Relays 5.4.1 Methods of Operation 5.4.2 Response Characteristics 5.5 Protection Jargon 5.5.1 Relay Operation and Performance 5.5.2 Protection System Operation and Performance Reference Chapter 6 Per‐Unit System and Fault Calculations 6.1 General 6.2 Per‐Unit 6.2.1 Base Quantity Equations 6.2.1.1 Establish the Base Voltage (kV) and Power (MVA) 6.2.1.2 From Base Voltage and Power, Calculate the Base Current and Impedance 6.2.2 Per‐Unit General 6.2.3 Per‐Unit Impedance 6.2.4 Conversion of PU Values To Different Bases 6.2.5 A Summary for Solving a Problem Using Per Unit 6.2.6 Example 6.3 Fundamental Need for Fault Information 6.3.1 Types of Faults 6.3.1.1 Balanced vs. Unbalanced 6.4 Symmetrical Components 6.4.1 Theory of Symmetrical Components 6.4.1.1 Positive Sequence Phasors 6.4.1.2 Negative Sequence Phasors 6.4.1.3 Zero‐Sequence Phasors 6.4.2 Phase Quantities In Terms of Sequence Components 6.5 Sequence Impedances of Power Apparatus 6.5.1 Synchronous Machinery 6.5.2 Transmission Lines 6.5.3 Transformers 6.5.3.1 Equivalent Circuit: Positive and Negative Sequence Impedances 6.5.3.2 Zero‐Sequence Circuit and Impedance 6.5.3.3 Zero‐sequence Impedance with Neutral Grounding Impedance 6.5.3.4 Banks of Three, Single‐Phase Transformers 6.5.3.5 Typically Used Transformers and Models 6.6 Balanced Fault Analysis 6.6.1 Balanced Fault Calculations 6.6.2 Simplifying Assumptions 6.7 Sequence Networks 6.7.1 Sequence Network Interconnections 6.7.1.1 Principle of Interconnections 6.8 Summary of Unbalance Fault Calculations 6.8.1 Positive Sequence Diagram 6.8.2 Negative Sequence Diagram: 6.8.3 Zero‐Sequence Diagram 6.8.4 Conduct the Fault Study 6.9 High‐Level Summary of the Fault Calculation Process 6.9.1 Develop a Single‐Line Diagram of the Studied Area 6.9.2 Determine the Studied Power System Element Impedances 6.9.3 Develop Sequence Impedance Models 6.9.4 Determine the Fault Types and System Conditions 6.9.5 Conduct the Fault Studies and Determine Relay Quantities 6.10 Useful Fault Calculation Formulas/Methods 6.10.1 Conversion from Short Circuit Values to System Impedances 6.11 Fault Calculation Examples 6.11.1 Three‐Phase Fault Example 6.11.2 Line‐to‐Ground Fault Example 6.11.2.1 Positive Sequence 6.11.2.2 Negative Sequence Network 6.11.2.3 Zero‐Sequence Network 6.11.2.4 Reduction in the Positive Sequence Network 6.11.2.5 Reduction in the Zero‐Sequence Network 6.11.2.6 Calculate the L‐G Fault References Chapter 7 Protection Zones 7.1 Protection Zones General 7.2 Zones Defined 7.3 Zone Overlap Around Breakers 7.4 Protection Zoning at Stations 7.4.1 HV Switching Stations 7.4.2 LV Distribution Stations 7.4.2.1 The Transformer Zone 7.4.2.2 The Bus Zone 7.4.2.3 The Distribution Feeder Zone 7.5 Protection Zones in General 7.5.1 Lines 7.5.2 Transformers 7.5.3 Generators 7.5.4 Protection Zones Overlapping Between Stations 7.6 Backup Protection 7.6.1 Remote Backup 7.6.2 Local Backup 7.7 CT Configuration and Protection Trip Zones 7.7.1 CTs Connected in Wye 7.7.2 CTs Connected in Delta 7.8 Where Protections Zones do not Overlap Around Breakers 7.8.1 Blind Spot Created by Non‐Overlap of Protections Zones around Breakers 7.9 Lines Terminating Directly on Buses at a HV Switching Station Chapter 8 Transformer Protection 8.1 Introduction 8.2 General Principles 8.3 Differential Protection Power Transformers 8.3.1 Factors Affecting Transformer Differential Protection 8.3.2 Phase Shifting from Primary to Secondary 8.3.3 The Flow of Zero‐Sequence Current 8.3.3.1 Substation Grounding Requirements 8.3.3.2 Artificial Ground Sources 8.3.4 Flow of Zero‐Sequence Currents in Differential Circuits 8.3.4.1 Delta–Wye Transformer 8.3.4.2 Wye–Delta Transformer 8.3.5 Restricted Ground Fault Protection 8.3.5.1 Theory of Operation 8.3.6 Percent Differential Relay Settings 8.3.6.1 Current Transformer Mismatch and Under‐Load Tap Changing 8.3.6.2 Percent Differential Relay Operation 8.3.6.3 Maximum System Unbalance 8.3.6.4 Introduction of Slope Under Fault Conditions 8.3.6.5 Effect of Magnetizing Current Inrush on Differential Relays 8.3.6.6 Third Restraint Winding 8.3.6.7 Transformer Overload Protections for Double Transformer Contingency 8.4 Percent Differential Protection Autotransformers 8.5 Transformer Percent Differential Setting Examples 8.5.1 Power Transformer Percent Differential Protection Setting Example 8.5.2 Autotransformer Percent Differential Protection Setting Example 8.5.3 Power Transformer Restricted Ground Fault Setting Example Reference Chapter 9 Bus Protection 9.1 Introduction 9.2 Typical Bus Arrangements 9.3 Bus Protection Requirements 9.4 Methods of Protecting Buses 9.4.1 Differential Protection 9.4.1.1 Low Impedance Bus Differential Protection 9.4.1.2 High Impedance Bus Differential Protection 9.4.1.3 Differential Protection with Digital Relays 9.4.1.4 Bus Differential Protection Zones 9.4.2 Bus Blocking Protection 9.5 Example High Impedance Differential Protection Setting Reference Chapter 10 Breaker Failure Protection and Automatic Reclosing 10.1 Introduction 10.2 Breaker Failure General Background 10.2.1 Typical Breaker Failure Tripping Zones 10.2.2 Principles of Breaker Failure Protection 10.2.3 Requirements for Breaker Failure Protection 10.2.4 Types of Initiation 10.2.5 Speed of Operation 10.2.6 Determination of Breaker Failure Condition 10.2.6.1 62a Logic Path (Mechanical‐Breaker Failure Detection) 10.2.6.2 62b Logic Path (Electrical Breaker Failure Detection) 10.2.6.3 62c Logic Path (Low Magnitude Fault Breaker Failure Detection) 10.2.7 Additional Generic Features of Breaker Failure Protection 10.2.7.1 Early Trip Function 10.2.7.2 Breaker Test Switch Supervision 10.2.8 Circuit Operation of Breaker Failure 10.2.9 Coordination with Other Protections 10.2.10 Non‐Duplication of Breaker Failure 10.2.10.1 Non‐Duplication of Breaker Failure Example 10.2.10.2 Impact on Protection Separation 10.2.11 Load‐Substation Bus Fault and LV Breaker Failure 10.2.12 Pedestal Breaker and Free‐Standing CT Frame Leakage Protection 10.2.12.1 Protection Blind Spot 10.2.12.2 Frame Leakage Protection 10.3 Breaker Automatic Reclosing General Background 10.3.1 Automatic Reclosing Timing 10.3.2 Reclosing Supervision 10.3.3 Lockout 10.3.4 Long‐Time Cancel 10.3.5 Initiation and Cancellation of Reclosing Chapter 11 Station Protection 11.1 Introduction 11.2 Types of Stations 11.2.1 Switching Stations 11.2.2 Load Substations 11.3 Station and Protection Architecture 11.3.1 Terminal/Switching Station 11.3.1.1 Breaker and Half Arrangement 11.3.1.2 Ring Bus Arrangement 11.3.2 Load‐Substation Typical Arrangement 11.3.2.1 Load Substation with Double Transformer Differential Protection 11.3.2.2 Load Substation with Single Transformer Differential Protection 11.3.3 Fault Isolation via HV Isolating Devices 11.3.3.1 Normally Open Bus‐Tie Breaker 11.3.3.2 Normally Closed Bus‐Tie Breaker 11.3.4 Fault Isolation via Tele‐Protection 11.3.5 Station Tele‐protection Subsystems 11.3.5.1 Tele‐Protection Using Frequency Shift Keying 11.3.5.2 Tele‐Protection Using T1 (Digital) 11.4 Station Switchgear Type 11.4.1 Terminal/Switching Station Outdoor Switchgear 11.4.2 Terminal Station Indoor Switchgear 11.4.3 Load‐Substation Outdoor Switchgear 11.4.4 Load‐Substation Indoor Switchgear 11.5 Sub‐Transmission Types and Station Grounding 11.5.1 Exclusive Three‐wire Sub‐transmission 11.5.2 Exclusive Four‐wire Sub‐transmission 11.5.3 Combined Three‐Wire and Four‐Wire Sub‐Transmission 11.5.4 Station Grounding Bar 11.6 Master Ground Chapter 12 Capacitor Bank Protection 12.1 Capacitor Banks 12.2 Purpose for Shunt Capacitors on Power System Networks 12.3 Capacitor Bank Construction 12.3.1 Individual Capacitor Units 12.3.2 Basic Series – Parallel Arrangement 12.3.3 Capacitor Bank Configurations 12.3.4 Shunt Capacitor Grounding 12.3.5 Capacitor Types by Fusing 12.3.5.1 Fused 12.3.5.2 No Fuses 12.3.6 Capacitor Bank Ratings 12.3.6.1 An Example Fused Capacitor Bank Rating 12.3.6.2 An Example Fuseless Capacitor Bank Rating 12.3.7 Information Required Before Protection Settings Calculations 12.3.8 General Shunt Capacitor Bank Protection Principles 12.4 Capacitor Bank Protection 12.4.1 Fused Capacitor Banks 12.4.1.1 Neutral Unbalance Protection 12.4.2 All Capacitor Banks 12.4.2.1 Overcurrent Protection 12.4.2.2 Overvoltage Protection 12.5 Capacitor Bank Breakers 12.6 Capacitor Bank Sample Settings 12.6.1 Double‐Wye Ungrounded Configuration – Externally Fused 12.6.2 Single‐Wye Ungrounded Configuration – Externally Fused 12.6.3 Wye Grounded Configuration – Fuseless 12.6.4 Phase and Ground Overcurrent Protection 12.6.5 Overvoltage Protection Reference Chapter 13 Synchronous Generator Protection 13.1 Introduction 13.2 General 13.2.1 Generator Basics and Functions 13.2.1.1 Prime Mover 13.2.1.2 Rotor 13.2.1.3 Stator 13.2.1.4 Governor Controls 13.2.1.5 Voltage Control (Exciter and AVR) 13.2.1.6 Station Service/UAT (Unit Auxiliary Transformer) 13.3 Generator/Unit Transformer Protections 13.3.1 Generator Differential (87G) 13.3.2 Main Unit Transformer Differential (87T) 13.3.3 Generator‐Transformer Overall Zone Protection (87O) 13.3.4 Split‐Phase Differential (87SP Hydraulic Only) 13.3.5 Stator Ground (59G) 13.3.6 Loss of Excitation (40) 13.3.7 Phase Unbalance (46) 13.3.8 Under‐Frequency (81) 13.3.9 Over‐excitation 24 13.3.10 Out‐of‐Step (21–78) 13.3.11 Reverse Power (32) 13.3.12 Transmission System Backup 13.3.12.1 Phase Backup (21,51V) 13.3.12.2 Ground Backup (51TG) 13.4 Current Transformers 13.5 Generator Protection Sample Settings 13.5.1 Sample Setting 1 – Large Hydraulic Generators 13.5.1.1 Differential (87) 13.5.1.2 Split‐Phase Differential (87SP) 13.5.1.3 Stator Ground (59G) 13.5.1.4 Loss of Excitation (40) 13.5.1.5 Phase Unbalance (46) 13.5.2 Sample Setting 2 – Large Thermal Generators 13.5.2.1 Differential (87) 13.5.2.2 Stator Ground (59G) 13.5.2.3 Loss of Excitation (40) 13.5.2.4 Over‐Excitation (24) 13.5.2.5 Out‐of‐Step (21–78) 13.5.2.6 Phase Unbalance (46) 13.6 Generator Control and Protection Systems Coordination 13.6.1 Synchronous Generator Phasor Diagrams/Capability 13.6.1.1 Capability Curve 13.6.2 Steady‐State Stability Limit (SSSL) 13.6.2.1 On a RX Plot 13.6.3 Over‐excitation V/Hz Protection and Control System Coordination 13.6.4 Loss of Excitation Protection and Control System Coordination 13.7 General Generator Tripping Requirements 13.8 Breaker Failure Initiation Reference Chapter 14 Transmission Line Protection 14.1 General 14.2 Basic Line Protection Requirements 14.3 Impedance Relays and Why Not Just Overcurrent Relays 14.3.1 Source Impedance 14.4 Distance Relay Response to Fault Types 14.4.1 Phase Fault Response 14.4.2 Ground Fault Response 14.5 Apparent Impedance 14.5.1 Example of Apparent Impedance 14.5.2 Derivation of Apparent Impedance 14.5.3 Apparent Impedance Effect on Distance Relay Settings 14.5.4 Maximum Apparent Impedance Calculation Example 14.5.5 Apparent Impedance and Paralleled Conductors 14.5.6 Load substations and Apparent Impedances 14.5.6.1 Presence of Tapped Load substations 14.5.6.2 Line Backup Protection at Load substations 14.5.6.3 Large Zone 2 Reaches Seeing into the Load Substation LV Side 14.5.6.4 Load Substations Supplied by Long Taps 14.6 Redundancy/Backup 14.6.1 Need for Protection Backup 14.6.2 Remote and Local Protection Backup 14.6.2.1 Remote Backup 14.6.2.2 Local Backup 14.7 Tele‐Protection (Also Known as Pilot‐Protection) 14.7.1 Tele‐protection Architecture 14.7.2 Protection Scheme Types for Local Backup 14.7.2.1 Direct Underreaching Transfer Trip (DUTT) 14.7.2.2 Permissive Overreaching Transfer Trip (POTT) 14.7.2.3 Directional Comparison Blocking Transfer Trip (DCBTT) 14.8 General Implications 14.8.1 Apparent Impedance Implications 14.8.2 Line Protection Zone 2 Reach Implications 14.8.3 Communication Implications 14.9 Peripheral Requirements of Distance Protection 14.9.1 Distance Relay Response to Three‐Phase Faults 14.9.2 Memory Action 14.9.3 Stub‐bus and Switch Onto Fault Protection 14.9.4 Overcurrent Supervision 14.9.4.1 Supervising Current Elements 14.9.5 Reclosing Coordination with Line End Open – Permissive Echo Timer 14.9.6 Potential Sources 14.9.6.1 Transient Response 14.9.7 Loss of Voltage to Distance Relays 14.9.8 Self‐Monitoring Relays 14.10 Tele‐Protection (Pilot‐Protection) A Historical Perspective 14.11 Tele‐Protection via Power Line Carrier 14.11.1 Protection Architecture with PLC 14.11.1.1 Applications 14.12 Synchronous Optical Network (SONET) 14.12.1 Fiber Installation 14.12.2 Multiplexer (MUX) Equipment 14.12.3 Definition of T1 14.13 Three‐Terminal Lines 14.13.1 Scheme Type and Setting Considerations 14.13.1.1 Permissive Overreaching Scheme 14.13.1.2 Directional Comparison Blocking Scheme 14.13.1.3 Weak End Infeeds and Current Reversals 14.14 Distributed Generation 14.14.1 Traditional Protection Schemes 14.14.2 Conventional Generation vs. Tapped Generation 14.14.2.1 Conventional Generation 14.14.2.2 Tapped Generation 14.14.3 Impact on the Traditional Protection Schemes 14.14.3.1 Permissive Overreaching Scheme 14.14.3.2 Directional Comparison Blocking Scheme 14.14.3.3 Line Differential Scheme 14.14.3.4 Issues with Either Permissive or Blocking Schemes 14.14.3.5 Preferred Scheme to Cater for Multi‐Tapped Generation 14.14.3.6 Converting from Permissive to Blocking Schemes 14.14.3.7 Ground Distance Protection Settings 14.14.3.8 Load substations 14.15 Distance Relay Response to Resistive Faults 14.15.1 Background to Resistive Faults 14.15.1.1 Resistive Faults 14.15.1.2 Distance Relays and Fault Resistance Coverage 14.15.2 Distance Relay Response to Resistive Faults 14.15.2.1 Expanding MHO Characteristics 14.16 Power System Considerations 14.16.1 Loadability During Normal System Conditions 14.16.2 Loadability During Extreme System Conditions 14.16.3 New Loadability Criteria in North America 14.16.3.1 Various Methods of Blinding Relays to Load 14.17 Line Current Differential Protection 14.17.1 Introduction 14.17.2 Functional Description 14.17.3 Lines with Tapped Load Substations 14.17.4 Two‐Ended Scheme 14.17.5 Three‐Ended Scheme 14.17.6 Clock Synchronization 14.17.7 Settings 14.17.7.1 Line Current Differential Element Settings 14.17.7.2 Distance Element Settings 14.17.7.3 Phase and Ground Distance Settings 14.17.7.4 Distance Elements Settings – Tapped Load‐substation Stations 14.17.7.5 Three‐Terminal Lines 14.17.8 System Considerations 14.17.8.1 Weak End Infeeds and Current Reversals 14.17.8.2 Line Loading and System Swings 14.17.8.3 Tapped Generation 14.18 Pilot Wire Protection 14.18.1 Introduction 14.18.2 Theory of Operation 14.19 Power System Considerations 14.19.1 Fault Clearing Time Criticality 14.19.2 Fault Clearing Performance Categories 14.19.2.1 Normal Clearing Times 14.19.2.2 Breaker Failure Clearing Times 14.19.3 Protection Planning 14.19.4 Fault Clearing Components 14.20 Line Setting Application Example 14.20.1 Two‐Terminal Line Setting Example 14.20.1.1 Setting Zone 1 14.20.1.2 Setting Zone 2 14.20.1.3 Peripheral Settings 14.20.2 Long‐Tapped Transformer Line Setting Example 14.20.2.1 Setting Zone 1 14.20.2.2 Setting Zone 2 14.20.2.3 Setting Zone 3 14.20.2.4 Setting of Relay Elements References Chapter 15 Subtransmission/Distribution Feeder Protection 15.1 Subtransmission/Distribution Characteristics 15.2 Definitions/Characteristics 15.2.1 Distribution Network Feeder Definitions 15.2.2 Feeder Characteristics 15.3 Distribution Feeder Protection Devices 15.3.1 Protection Devices 15.3.1.1 Overcurrent Relays 15.3.1.2 Distance Relays 15.3.1.3 Fuses 15.3.1.4 Automatic Reclosers (AR) 15.4 Protection Coordination Principles 15.4.1 Functions of Distribution/Overcurrent Protection 15.4.2 Coordination General 15.4.2.1 Fuse – Fuse Coordination 15.4.2.2 Fuse – Automatic Recloser (AR) 15.4.2.3 Primary Fuse – Transformer Damage Curve 15.5 Feeder Energization 15.6 Subtransmission Feeder Protection 15.6.1 General 15.6.2 Subtransmission Feeder Protection Requirements 15.6.3 Subtransmission Protection 15.6.3.1 Protection Functions 15.6.3.2 Circuit Operation and Tripping 15.6.4 Automatic Reclosing 15.6.4.1 General 15.6.4.2 Automatic Reclosing Circuit Operation 15.6.5 Relay Settings 15.6.5.1 Three‐Wire vs. Four Wire Feeders 15.6.5.2 General Information/Data Requirements 15.6.5.3 Phase Protection 15.6.5.4 Ground Protection 15.7 Impact of Distributed Generators (DGs) on Distribution Feeder Protection 15.7.1 Significant Protection Issues Caused by Distributed Generation 15.7.1.1 The Feeder Becomes Non‐Radial 15.7.1.2 Islanding 15.7.1.3 Internal Faults (Faults on the Feeder Connecting the DGs) 15.7.1.4 External Faults (Faults on Feeders Adjacent to One Connected to DG) 15.7.1.5 Automatic Reclosing and Synchronism 15.7.1.6 Inrush Current – Interconnection Transformers 15.7.1.7 Summary of Protection Impacts Due to DGs 15.8 Feeder Protection Application Settings Example References Index Books in the IEEE Press Serieson Power and Energy Systems EULA