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J. C. Das. Arc Flash Hazard Analysis and Mitigation
Table of Contents
List of Tables
List of Illustrations
Guide
Pages
ARC FLASH HAZARD ANALYSIS AND MITIGATION
FOREWORD
PREFACE TO SECOND EDITION
PREFACE TO FIRST EDITION
ACKNOWLEDGEMENT
ABOUT THE AUTHOR
1 ARC FLASH HAZARDS AND THEIR ANALYSES
1.1 ELECTRICAL ARCS
1.1.1 Arc as a Heat Source
1.1.2 Arcing Phenomena in a Cubicle
1.2 ARC FLASH HAZARD AND PERSONAL SAFETY
1.3 TIME MOTION STUDIES
1.4 ARC FLASH HAZARDS
1.5 ARC BLAST
1.6 ELECTRICAL SHOCK HAZARD
1.6.1 Resistance of Human Body
1.7 FIRE HAZARD
1.8 ARC FLASH HAZARD ANALYSIS
1.8.1 Ralph Lee’s and NFPA Equations
1.8.2 IEEE 1584 Guide Equations
1.9 PERSONAL PROTECTIVE EQUIPMENT
1.10 HAZARD BOUNDARIES
1.10.1 Working Distance
1.10.2 Arc Flash Labels
1.11 MAXIMUM DURATION OF AN ARC FLASH EVENT AND ARC FLASH BOUNDARY
1.11.1 Arc Flash Hazard with Equipment Doors Closed
1.12 REASONS FOR INTERNAL ARCING FAULTS
1.13 ARC FLASH HAZARD CALCULATION STEPS
1.13.1 NFPA Table 130.7(C)(15)(a)
1.14 EXAMPLES OF CALCULATIONS. Example 1.1
Example 1.2
Example 1.3
Example 1.4
Example 1.5
1.15 REDUCING ARC FLASH HAZARD
1.15.1 Reduction
1.15.2 Arc Flash Labels
REVIEW QUESTIONS
REFERENCES
2 SAFETY AND PREVENTION THROUGH DESIGN: A NEW FRONTIER
2.1 ELECTRICAL STANDARDS AND CODES
2.2 PREVENTION THROUGH DESIGN
2.3 LIMITATIONS OF EXISTING CODES, REGULATIONS, AND STANDARDS
2.4 ELECTRICAL HAZARDS
2.5 CHANGING THE SAFETY CULTURE
2.6 RISK ANALYSIS FOR CRITICAL OPERATION POWER SYSTEMS
2.6.1 Existing Systems
2.6.2 New Facilities
2.7 RELIABILITY ANALYSIS
2.7.1 Data for Reliability Evaluations
2.7.2 Methods of Evaluation
2.7.3 Reliability and Safety
2.8 MAINTENANCE AND OPERATION
2.8.1 Maintenance Strategies
2.8.2 Reliability-Centered Maintenance (RCM)
2.9 SAFETY INTEGRITY LEVEL AND SAFETY INSTRUMENTED SYSTEM
2.10 ELECTRICAL SAFETY IN THE WORKPLACES. 2.10.1 Risk Assessment
2.10.2 Responsibility
2.10.3 Risk Parameters
2.11 RISK REDUCTION
2.12 RISK EVALUATION
2.13 RISK REDUCTION VERIFICATION
2.14 RISK CONTROL
REVIEW QUESTIONS
REFERENCES
3 CALCULATIONS ACCORDING TO IEEE GUIDE 1584, 2018
3.1 MODEL FOR INCIDENT ENERGY CALCULATIONS
3.2 ELECTRODE CONFIGURATION
3.3 IMPACT OF SYSTEM GROUNDING
3.4 INTERMEDIATE AVERAGE ARCING CURRENT
3.5 ARCING CURRENT VARIATION FACTOR
3.6 CALCULATION OF INTERMEDIATE INCIDENT ENERGY
3.7 INTERMEDIATE ARC FLASH BOUNDARY (AFB)
3.8 ENCLOSURE SIZE CORRECTION FACTOR
3.8.1 Shallow and Typical Enclosures
3.9 DETERMINE EQUIVALENT HEIGHT AND WIDTH
3.10 DETERMINE ENCLOSURE SIZE CORRECTION FACTOR
3.11 DETERMINATION OF IARC, E, AND AFB (600 V <VOC ≤ 15,000 V)
3.11.1 Arcing Current
3.11.2 Incident Energy (E)
3.11.3 Arc Flash Boundary (AFB)
3.12 DETERMINATION OF IARC, E, AND AFB (VOC ≤ 600 V) 3.12.1 Arcing Current
3.12.2 Incident Energy
3.12.3 Arc Flash Boundary (AFB)
3.13 A FLOW CHART FOR THE CALCULATIONS
3.14 EXAMPLES OF CALCULATIONS
REFERENCES
4 ARC FLASH HAZARD AND SYSTEM GROUNDING
4.1 SYSTEM AND EQUIPMENT GROUNDING
4.1.1 Solidly Grounded Systems
4.2 LOW RESISTANCE GROUNDING
4.3 HIGH RESISTANCE GROUNDED SYSTEMS
4.3.1 Fault Detection, Alarms, and Isolation
4.4 UNGROUNDED SYSTEMS
4.5 REACTANCE GROUNDING
4.6 RESONANT GROUNDING
4.7 CORNER OF DELTA-GROUNDED SYSTEMS
4.8 SURGE ARRESTERS
4.9 ARTIFICIALLY DERIVED NEUTRALS
4.10 MULTIPLE GROUNDED SYSTEMS
4.10.1 Comparison of Grounding Systems
4.11 ARC FLASH HAZARD IN SOLIDLY GROUNDED SYSTEMS
4.12 PROTECTION AND COORDINATION IN SOLIDLY GROUNDED SYSTEMS
Example 4.1
4.12.1 Self-Extinguishing Ground Faults
4.12.2 Improving Coordination in Solidly Grounded Low Voltage Systems
Example 4.2
4.13 GROUND FAULT COORDINATION IN LOW RESISTANCE GROUNDED MEDIUM VOLTAGE SYSTEMS
Example 4.3
4.13.1 Remote Tripping
4.13.2 Ground Fault Protection of Industrial Bus-Connected Generators
Example 4.4
4.13.3 Directional Ground Fault Relays
4.14 MONITORING OF GROUNDING RESISTORS
4.15 SELECTION OF GROUNDING SYSTEMS
REVIEW QUESTIONS
REFERENCES
5 SHORT-CIRCUIT CALCULATIONS ACCORDING TO ANSI/IEEE STANDARDS FOR ARC FLASH ANALYSIS
5.1 TYPES OF CALCULATIONS
5.1.1 Assumptions: Short-Circuit Calculations
5.1.2 Short-Circuit Currents for Arc Flash Calculations
5.2 RATING STRUCTURE OF HV CIRCUIT BREAKERS
5.3 LOW-VOLTAGE MOTORS
5.4 ROTATING MACHINE MODEL
5.5 CALCULATION METHODS
5.5.1 Simplified Method X/R ≤ 17
5.5.2 Simplified Method X/R> 17
5.5.3 E/Z Method for AC and DC Decrement Adjustments
5.6 NETWORK REDUCTION
5.7 CALCULATION PROCEDURE
5.7.1 Analytical Calculation Procedure
5.8 CAPACITOR AND STATIC CONVERTER CONTRIBUTIONS TO SHORT-CIRCUIT CURRENTS
5.9 TYPICAL COMPUTER-BASED CALCULATION RESULTS
5.9.1 First-Cycle or Momentary Duty Calculations
5.9.2 Interrupting Duty Calculations
5.9.3 Low Voltage Circuit Breaker Duty Calculations
5.10 EXAMPLES OF CALCULATIONS
Example 5.1
Example 5.2
5.10.1 Calculation of Short-Circuit Duties
5.10.2 K-Rated 15 kV Circuit Breakers
5.10.3 4.16-kV Circuit Breakers and Motor Starters
5.10.4 Transformer Primary Switches and Fused Switches
5.10.5 Low Voltage Circuit Breakers
5.11 THIRTY-CYCLE SHORT-CIRCUIT CURRENTS
Example 5.3
5.12 UNSYMMETRICAL SHORT-CIRCUIT CURRENTS
5.12.1 Single Line-to-Ground Fault
5.12.2 Double Line-to-Ground Fault
5.12.3 Line-to-Line Fault
Example 5.4
5.13 COMPUTER METHODS
5.13.1 Line-to-Ground Fault
5.13.2 Line-to-Line Fault
5.13.3 Double Line-to-Ground Fault
Example 5.5
5.14 SHORT-CIRCUIT CURRENTS FOR ARC FLASH CALCULATIONS
REVIEW QUESTIONS
REFERENCES
6 ACCOUNTING FOR DECAYING SHORT-CIRCUIT CURRENTS IN ARC FLASH CALCULATIONS
6.1 SHORT CIRCUIT OF A PASSIVE ELEMENT
6.2 SYSTEMS WITH NO AC DECAY
6.3 REACTANCES OF A SYNCHRONOUS MACHINE
6.3.1 Leakage Reactance
6.3.2 Subtransient Reactance
6.3.3 Transient Reactance
6.3.4 Synchronous Reactance
6.3.5 Quadrature-Axis Reactances
6.3.6 Negative Sequence Reactance
6.3.7 Zero Sequence Reactance
6.4 SATURATION OF REACTANCES
6.5 TIME CONSTANTS OF SYNCHRONOUS MACHINES. 6.5.1 Open-Circuit Time Constant
6.5.2 Subtransient Short-Circuit Time Constant
6.5.3 Transient Short-Circuit Time Constant
6.5.4 Armature Time Constant
6.6 SYNCHRONOUS MACHINE BEHAVIOR ON TERMINAL SHORT CIRCUIT
6.6.1 Equivalent Circuits during Fault
6.6.2 Fault Decrement Curve
Example 6.1
Example 6.2
6.7 SHORT CIRCUIT OF SYNCHRONOUS MOTORS AND CONDENSERS
6.8 SHORT CIRCUIT OF INDUCTION MOTORS
Example 6.3
6.9 A NEW ALGORITHM FOR ARC FLASH CALCULATIONS WITH DECAYING SHORT-CIRCUIT CURRENTS
6.9.1 Available Computer-Based Calculations
6.9.2 Accumulation of Energy from Multiple Sources
6.9.3 Comparative Calculations
6.10 CROWBAR METHODS
REVIEW QUESTIONS
REFERENCES
7 PROTECTIVE RELAYING
7.1 PROTECTION AND COORDINATION FROM ARC FLASH CONSIDERATIONS
7.2 CLASSIFICATION OF RELAY TYPES
7.3 DESIGN CRITERIA OF PROTECTIVE SYSTEMS
7.3.1 Selectivity
7.3.2 Speed
7.3.3 Reliability
7.3.4 Backup Protection
7.4 OVERCURRENT PROTECTION
7.4.1 Overcurrent Relays
7.4.2 Multifunction Overcurrent Relays
7.4.3 IEC Curves
Example 7.1
Example 7.2
7.5 LOW VOLTAGE CIRCUIT BREAKERS
7.5.1 Molded Case Circuit Breakers (MCCBs)
7.5.2 Current-Limiting MCCBs
7.5.3 Insulated Case Circuit Breakers (ICCBs)
7.5.4 Low Voltage Power Circuit Breakers (LVPCBs)
7.5.5 Short-Time Bands of LVPCBs Trip Programmers
Example 7.3
7.6 SHORT-CIRCUIT RATINGS OF LOW VOLTAGE CIRCUIT BREAKERS
7.6.1 Single-Pole Interrupting Capability
7.6.2 Short-Time Ratings
7.7 SERIES-CONNECTED RATINGS
7.8 FUSES
7.8.1 Current-Limiting Fuses
7.8.2 Low Voltage Fuses
7.8.3 High Voltage Fuses
7.8.4 Electronic Fuses
7.8.5 Interrupting Ratings
7.9 APPLICATION OF FUSES FOR ARC FLASH REDUCTION. 7.9.1 Low Voltage Motor Starters
7.9.2 Medium Voltage Motor Starters
7.9.3 Low Voltage Switchgear
7.10 CONDUCTOR PROTECTION
7.10.1 Load Current Carrying Capabilities of Conductors
7.10.2 Conductor Terminations
7.10.3 Considerations of Voltage Drops
7.10.4 Short-Circuit Considerations
7.10.5 Overcurrent Protection of Conductors
7.11 MOTOR PROTECTION
7.11.1 Coordination with Motor Thermal Damage Curve
Example 7.4
7.12 GENERATOR 51-V PROTECTION
7.12.1 Arc Flash Considerations
Example 7.5
REVIEW QUESTIONS
REFERENCES
Further Reading on Protective Relaying
8 UNIT PROTECTION SYSTEMS
8.1 OVERLAPPING THE ZONES OF PROTECTION
8.2 IMPORTANCE OF DIFFERENTIAL SYSTEMS FOR ARC FLASH REDUCTION
8.3 BUS DIFFERENTIAL SCHEMES
8.3.1 Overcurrent Differential Protection
8.3.2 Partial Differential Schemes
8.3.3 Percent Differential Relays
8.4 HIGH IMPEDANCE DIFFERENTIAL RELAYS
8.4.1 Sensitivity for Internal Faults
8.4.2 High Impedance Microprocessor-Based Multifunction Relays
8.5 LOW IMPEDANCE CURRENT DIFFERENTIAL RELAYS
Example 8.1
8.5.1 CT Saturation
8.5.2 Comparison with High Impedance Relays
8.6 ELECTROMECHANICAL TRANSFORMER DIFFERENTIAL RELAYS
8.6.1 Harmonic Restraint
8.7 MICROPROCESSOR-BASED TRANSFORMER DIFFERENTIAL RELAYS
8.7.1 CT Connections and Phase Angle Compensation
Example 8.2
Example 8.3
8.7.2 Dynamic CT Ratio Corrections
8.7.3 Security under Transformer Magnetizing Currents
8.8 PILOT WIRE PROTECTION
8.9 MODERN LINE CURRENT DIFFERENTIAL PROTECTION
8.9.1 The Alpha Plane
8.9.2 Enhanced Current Differential Characteristics
8.10 EXAMPLES OF ARC FLASH REDUCTION WITH DIFFERENTIAL RELAYS
REVIEW QUESTIONS
REFERENCES
9 ARC FAULT DETECTION RELAYS
9.1 PRINCIPLE OF OPERATION
9.2 LIGHT INTENSITY
9.3 LIGHT SENSOR TYPES
9.4 OTHER HARDWARE
9.5 SELECTIVE TRIPPING
9.6 SUPERVISION WITH CURRENT ELEMENTS
9.7 APPLICATIONS. 9.7.1 Medium Voltage Systems
9.7.2 Low Voltage Circuit Breakers
9.7.3 Self-Testing of Sensors
9.8 EXAMPLES OF CALCULATION
9.9 ARC VAULT™ PROTECTION FOR LOW VOLTAGE SYSTEMS
9.9.1 Detection System
REVIEW QUESTIONS
REFERENCES
10 OVERCURRENT COORDINATION
10.1 STANDARDS AND REQUIREMENTS
10.2 DATA FOR THE COORDINATION STUDY
10.3 COMPUTER-BASED COORDINATION
10.4 INITIAL ANALYSIS
10.5 COORDINATING TIME INTERVAL
10.5.1 Relay Overtravel
10.6 FUNDAMENTAL CONSIDERATIONS FOR COORDINATION
Example 10.1
10.6.1 Settings on Bends of Time–Current Coordination Curves
10.7 COORDINATION ON INSTANTANEOUS BASIS
10.7.1 Selectivity between Two Series-Connected Current-Limiting Fuses
10.7.2 Selectivity of a Current-Limiting Fuse Downstream of Noncurrent-Limiting Circuit Breaker
Example 10.2
10.7.3 Selectivity of Current-Limiting Devices in Series
10.8 NEC REQUIREMENTS OF SELECTIVITY
10.8.1 Fully Selective Systems
10.8.2 Selection of Equipment Ratings and Trip Devices
Example 10.3
10.9 THE ART OF COMPROMISE
REVIEW QUESTIONS
REFERENCES
11 TRANSFORMER PROTECTION
11.1 NEC REQUIREMENTS
11.2 ARC FLASH CONSIDERATIONS
11.3 SYSTEM CONFIGURATIONS OF TRANSFORMER CONNECTIONS
11.3.1 Auto-Transfer of Bus Loads
11.4 THROUGH FAULT CURRENT WITHSTAND CAPABILITY
11.4.1 Category I
11.4.2 Category II
11.4.3 Category III and IV
11.4.4 Observation on Faults during Life Expectancy of a Transformer
11.4.5 Dry-Type Transformers
11.5 CONSTRUCTING THE THROUGH FAULT CURVE ANALYTICALLY
Example 11.1
11.5.1 Protection with Respect to Through Fault Curves
11.6 TRANSFORMER PRIMARY FUSE PROTECTION. 11.6.1 Variations in the Fuse Characteristics
11.6.2 Single Phasing and Ferroresonance
11.6.3 Other Considerations of Fuse Protection
11.7 OVERCURRENT RELAYS FOR TRANSFORMER PRIMARY PROTECTION
11.8 LISTING REQUIREMENTS
11.9 EFFECT OF TRANSFORMER WINDING CONNECTIONS
11.10 REQUIREMENTS OF GROUND FAULT PROTECTION
11.11 THROUGH FAULT PROTECTION. 11.11.1 Primary Fuse Protection
11.11.2 Primary Relay Protection
11.12 OVERALL TRANSFORMER PROTECTION
11.13 A PRACTICAL STUDY FOR ARC FLASH REDUCTION. 11.13.1 System Configuration
11.13.2 Coordination Study and Observations
11.13.3 Arc Flash Calculations: High Hazard Risk Category (HRC) Levels
11.13.4 Reducing HRC Levels with Main Secondary Circuit Breakers
11.13.5 Maintenance Mode Switches on Low Voltage Trip Programmers
11.13.6 Addition of Secondary Relay
REVIEW QUESTIONS
REFERENCES
12 CURRENT TRANSFORMERS
12.1 ACCURACY CLASSIFICATION OF CTs. 12.1.1 Metering Accuracies
12.1.2 Relaying Accuracies
12.1.3 Relaying Accuracy Classification X
12.1.4 Accuracy Classification T
12.2 CONSTRUCTIONAL FEATURES OF CTs
12.3 SECONDARY TERMINAL VOLTAGE RATING
12.3.1 Saturation Voltage
12.3.2 Saturation Factor
12.4 CT RATIO AND PHASE ANGLE ERRORS
12.5 INTERRELATION OF CT RATIO AND C CLASS ACCURACY
12.6 POLARITY OF INSTRUMENT TRANSFORMERS
12.7 APPLICATION CONSIDERATIONS
12.7.1 Select CT Ratio
12.7.2 Make a Single-Line Diagram of the CT Connections
12.7.3 CT Burden
12.7.4 Short-Circuit Currents and Asymmetry
12.7.5 Calculate Steady-State Performance
12.7.6 Calculate Steady-State Errors
Example 12.1
Example 12.2
Example 12.3
12.8 SERIES AND PARALLEL CONNECTIONS OF CTs
12.9 TRANSIENT PERFORMANCE OF THE CTs
12.9.1 CT Saturation Calculations
12.9.2 Effect of Remanence
12.10 PRACTICALITY OF APPLICATION
12.11 CTs FOR LOW RESISTANCE-GROUNDED MEDIUM VOLTAGE SYSTEMS
12.12 FUTURE DIRECTIONS
REVIEW QUESTIONS
REFERENCES
13 ARC-RESISTANT EQUIPMENT
13.1 CALCULATIONS OF ARC FLASH HAZARD IN ARC-RESISTANT EQUIPMENT
13.1.1 Probability of Arcing Fault
13.2 QUALIFICATIONS IN IEEE GUIDE
13.3 ACCESSIBILITY TYPES
13.3.1 Type 1
13.3.2 Type 2
13.3.3 Suffix B
13.3.4 Suffix C
13.3.5 Suffix D
13.4 IEC ACCESSIBILITY TYPES
13.5 ARC-RESISTANT RATINGS
13.5.1 Duration Ratings
13.5.2 Device-Limited Ratings
Example 13.1
13.5.3 Effect of Cable Connections
13.6 TESTING ACCORDING TO IEEE GUIDE
13.6.1 Criterion 1
13.6.2 Criterion 2
13.6.3 Criterion 3
13.6.4 Criterion 4
13.6.5 Criterion 5
13.6.6 Maintenance
13.7 PRESSURE RELIEF
13.8 VENTING AND PLENUMS
13.8.1 Venting into Surrounding Area
13.8.2 Plenums
13.9 CABLE ENTRIES
REVIEW QUESTIONS
REFERENCES
14 RECENT TRENDS AND INNOVATIONS
14.1 STATISTICAL DATA OF ARC FLASH HAZARDS
14.2 ZONE-SELECTIVE INTERLOCKING
14.2.1 Low Voltage ZSI Systems
Example 14.1
Example 14.2
14.2.2 Zone Interlocking in Medium Voltage Systems
14.3 MICROPROCESSOR-BASED LOW VOLTAGE SWITCHGEAR
14.3.1 Microprocessor-Based Switchgear Concept
14.3.2 Accounting for Motor Contributions
14.3.3 Faults on the Source Side
14.3.4 Arc Flash Hazard Reduction
14.4 LOW VOLTAGE MOTOR CONTROL CENTERS
14.4.1 Desirable MCC Design Features
14.4.2 Recent Design Improvements
14.4.3 Higher Short-Circuit Withstand MCCs
14.5 MAINTENANCE MODE SWITCH
14.6 INFRARED WINDOWS AND SIGHT GLASSES
14.7 FAULT CURRENT LIMITERS
14.8 PARTIAL DISCHARGE MEASUREMENTS
14.8.1 Online versus Offline Measurements
14.8.2 Test Methods
14.8.3 Current Signature Analysis: Rotating Machines
14.8.4 Dissipation Factor Tip-Up
REVIEW QUESTIONS
REFERENCES
15 ARC FLASH HAZARD CALCULATIONS IN DC SYSTEMS
15.1 CALCULATIONS OF THE SHORT-CIRCUIT CURRENTS IN DC SYSTEMS
15.2 SOURCES OF DC SHORT-CIRCUIT CURRENTS
15.3 IEC CALCULATION PROCEDURES
15.4 SHORT CIRCUIT OF A LEAD ACID BATTERY
Example 15.1
15.5 SHORT CIRCUIT OF DC MOTORS AND GENERATORS
Example 15.2
15.6 SHORT-CIRCUIT CURRENT OF A RECTIFIER
Example 15.3
15.7 SHORT CIRCUIT OF A CHARGED CAPACITOR
Example 15.4
15.8 TOTAL SHORT-CIRCUIT CURRENT
Example 15.5
15.9 DC CIRCUIT BREAKERS AND FUSES. 15.9.1 DC Circuit Breakers
Example 15.6
15.9.2 DC Rated Fuses
15.10 ARCING IN DC SYSTEMS
Example 15.7
Example 15.8
15.11 EQUATIONS FOR CALCULATION OF INCIDENT ENERGY IN DC SYSTEMS
Example 15.9
Example 15.10
15.12 PROTECTION OF THE SEMICONDUCTOR DEVICES
15.12.1 Controlled Converters
Example 15.11
REVIEW QUESTIONS
REFERENCES
16 APPLICATION OF ETHERNET AND IEC 61850 COMMUNICATIONS
16.1 IEC 61850 PROTOCOL
16.2 MODERN IEDs
16.3 SUBSTATION ARCHITECTURE
16.4 IEC 61850 COMMUNICATION STRUCTURE
16.5 LOGICAL NODES
16.6 ETHERNET CONNECTION
16.7 NETWORKING MEDIA
16.7.1 Copper Twisted Shielded and Unshielded
16.7.2 Fiber Optic Cable
16.8 NETWORK TOPOLOGIES
16.8.1 Prioritizing GOOSE Messages
16.8.2 Technoeconomical Justifications
16.9 APPLICATION TO ARC FLASH RELAYING AND COMMUNICATIONS
REVIEW QUESTIONS
REFERENCES
APPENDIX A: STATISTICS AND PROBABILITY APPLIED TO ELECTRICAL ENGINEERING
A.1 MEAN MODE AND MEDIAN
A.2 MEAN AND STANDARD DEVIATION
A.3 SKEWNESS AND KURTOSIS
A.4 NORMAL OR GAUSSIAN DISTRIBUTION
A.5 CURVE FITTING: LEAST SQUARE LINE
Example A.1
REFERENCES
APPENDIX B: TABLES FOR QUICK ESTIMATION OF INCIDENT ENERGY AND PPE IN ELECTRICAL SYSTEMS
INDEX
IEEE Press Series on Power Engineering
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