Grounding, Bonding, and Shielding for Electronic Equipments and Facilities

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Grounding, Bonding, and Shielding for Electronic Equipments and Facilities

Grounding, Bonding, and Shielding for Electronic Equipments and Facilities
Grounding, Bonding, and Shielding for Electronic Equipments and Facilities -Cont.
Preface
Table of Contents
Table of Contents -Cont.
Table of Contents -Cont.
Table of Contents -Cont.
Table of Contents -Cont.
Table of Contents -Cont.
Table of Contents -Cont.
Table of Contents -Cont.
Table of Contents -Cont.
List of Figures
List of Figures -Cont.
List of Figures -Cont.
List of Figures -Cont.
List of Figures -Cont.
List of Tables
List of Tables -Cont.
Metric Conversion Factors
Chapter 1 Facility Ground System
Facility Ground System
Grounding and Power Distribution Systems
Electrical Noise in Communications Systems
Grounding Safety Practices
Grounding Safety Practices -Cont.
Chapter 2 Earth Electrode Subsystem
Fault Protection
Figure 2-1. Voltage Differentials Arising From Unequal Earth Electrode Resistances and Unequal Stray Currents
Figure 2-2. Voltage Differentials Between Structures Resulting From Stray Ground Currents
Resistance Requirements
Table 2-1 Facility Ground System: Purposes, Requirements, and Design Factors
Soil Resistivity
Measurement Techniques
Table 2-2 Approximate Soil Resistivity (2-3)
Table 2-3 Resistivity Values of Earthing Medium (2-5), (2-6), (2-7)
Figure 2-4. Current Flow From a Hemisphere in Uniform Earth
One-Electrode Method
Four-Terminal Method
Figure 2-5. Idealized Method of Determining Soil Resistivity
Types of Earth Electrode Subsystems
Metal Frameworks of Buildings
Resistance Properties
Figure 2-7. Effect of Rod Diameter Upon Resistance (2-6)
Driven Rod
Figure 2-8. Earth Resistance Shells Surrounding a Vertical Earth Electrode
Table 2-4 Resistance Distribution for Vertical Electrodes
Table 2-5. Simple Isolated Electrodes
Other Commonly Used Electrodes
Figure 2-9. Resistance of Buried Horizontal Conductors
Figure 2-10. Resistance of Buried Circular Plates
Figure 2-11. Ground Rods in Parallel
Square Array of Vertical Rods
Figure 2-12. Ratio of the Actual Resistance of a Rod Array to the Ideal Resistance of N Rods in Parallel
Horizontal Grid (Mesh)
Vertical Rods Connected by a Grid
Figure 2-13. Transient Impedance of an Earth Electrode Subsystem as a Function of the Number of Radial Wires
Transient Impedance of Electrodes
Vertical Rod
Figure 2-14. Current Distribution in Nonuniform Soil
Measurement of Resistance To Earth of Electrodes
Probe Spacing
Figure 2-15. Fall-of-Potential Method for Measuring the Resistance of Earth Electrodes
Figure 2-16. Effect of Electrode Spacing on Voltage Measurement
Probe Spacing -Cont.
Probe Spacing -Cont.
Figure 2-17. Resistance Variations as Function of Potential Probe Position in Fall-of-Potential Method (2-12)
Extensive Electrode Subsystems (2-13)
Table 2-6 Resistance Accuracy Versus Probe Spacing
Figure 2-18. Earth Resistance Curves for a Large Electrode Subsystem
Figure 2-19. Earth Resistance Curve Applicable to Large Earth Electrode Subsystems
Three-Point (Triangulation) Method
Surface Voltages Above Earth Electrodes
Figure 2-21. Triangulation Method of Measuring the Resistance of an Earth Electrode
Flush Vertical Rod
Table 2-7 Step Voltages for a Buried Vertical Ground Rod
Flush Vertical Rod -Cont.
Figure 2-22. Variation of Surface Potential Produced by a Current Flowing Into an Isolated Ground Rod
Buried Vertical Rod
Figure 2-23. Surface Potential Variation Along a Grid
Buried Horizontal Grid
Minimizing Step Voltage
Beating of Electrodes
Transient Current
Minimum Electrode Size
Water Retention
Figure 2-25. Seasonal Resistance Variations of Treated and Untreated Ground Rods
Electrode Encasement
Salting Methods
Figure 2-27. Alternate Method of Chemical Treatment of Ground Rod
Protection Techniques
Soil Resistivity
Figure 2-28. Relative Depths of Unconsolidated Materials, Subarctic Alaska
Figure 2-29. Typical Sections Through Ground Containing Permafrost
Figure 2-30. Illustration Showing Approximate Variations in Substructure
Improving Electrical Grounding in Frozen Soils
Installation and Measurement Methods
Figure 2-31. Installation of an Electrode During the Process of Backfilling with a Salt-Soil Mixture
Figure 2-32. Apparent Resistivity for Two Soils at Various Moisture and Salt Contents
Figure 2-35. Resistance-to-Ground Curves for an Electrode Surrounded by a Backfill of Saturated Silt
References
Chapter 3. Lighting Protection Subsystem
Figure 3-1. Charge Distribution in a Thundercloud
Development of A Lighting Flash
Strike Likelihood
Figure 3-2. Mean Number of Thunderstorm Days Per Year for the United States
Figure 3-3. Worldwide Isokeraunic Map (Sheet 1 of 4)
Figure 3-3. Worldwide Isokeraunic Map (Sheet 2 of 4)
Figure 3-3. Worldwide Isokeraunic Map (Sheet 3 of 4)
Figure 3-3. Worldwide Isokeraunic Map (Sheet 4 of 4)
Structures Less Than 100 Meters High
Cone of Protection
Figure 3-5. Effective Height of a Structure
Flash Parameters
Figure 3-6. Zones of Protection Established by a Vertical Mast and a Horizontal Wire
Mechanical and Thermal Effects
Table 3-1 Range of Values for Lightning Parameters (3-5)
Conductor Impedance Effects
Induced Voltage Effects
Figure 3-9. Inductive Coupling of Lightning Energy to Nearby Circuits
Figure 3-10. Normalized Voltage Induced in a Single-Turn Loop by Lightning Currents
Capacitively-Coupled Voltage
Figure 3-11. Capacitive Coupling of Lightning Energy
Figure 3-11. Capacitive Coupling of Lightning Energy
Figure 3-13. Step-Voltage Hazards Caused by Lightning-Induced Voltage Gradients in the Earth
Basic Protection Requirements
Strike Likelihood
Criticalness to System Mission
References
Chapter 4. Fault Protection Subsystem
Figure 4-1. Grounding for Fault Protection
Ground-Fault-Circuit-Interrupter (GFCI)
Figure 4-2. Single-Phase 115/230 Volt AC Power Ground Connections
Figure 4-3. Three-Phase 120/208 Volt AC Power System Ground Connections
Figure 4-4. Connections for a Three-Phase "Zig-Zag" Grounding Transformer
Chapter 5. Grounding of Signal Reference Subsystem
Table 5-1 Properties of Annealed Copper Wire
Table 5-2 Parameters of Conductor Materials (5-4)
Figure 5-1. Surface Resistance and Skin Depth for Common Metals
AC Resistance
Figure 5-2. Resistance Ratio of Isolated Round Wires
Reactance
Figure 5-3. Nomograph for the Determination of Skin Effect Correction Factor (5-6)
Figure 5-4. Low Frequency Self-Inductance versus Length for 1/0 AWG Straight Copper Wire (5-7)
Resistance Properties vs Impedance Properties
Table 5-4 Sixty-Hertz Characteristics of Standard Cables
Table 5-6 Impedance Comparisons Between No. 12 AWG and 1/0 AWG
Rectangular Conductors
Figure 5-7. Resistance Versus Length for Various Sizes of Copper Tubing
Structural Steel Members
Figure 5-8. AC Resistance versus Frequency for Copper Tubing (5-7)
Figure 5-9. Resistance Ratio of Nonmagnetic Tubular Conductors (5-3)
Figure 5-10. Inductance Versus Frequency for Various Sizes of Copper Tubing (5-7)
Single-Point Ground
Figure 5-12. Single-Point Signal Ground (For Lower Frequencies)
Figure 5-13. Single-Point Ground Bus System Using Separate Risers (Lower Frequency)
Figure 5-14. Single Point Ground Bus System Using A Common Bus
Figure 5-15. Use of Single-Point Ground Configuration to Minimize Effect of Facility Ground Currents
Multipoint Ground
Figure 5-17. Use of Structural Steel in Multiple-Point Grounding
Equipotential Plane
Types of Equipotential Planes
Floating System
Figure 5-18. Recommended Signal Coupling Practice for Lower Frequency Equipment
Higher Frequency Network (>300 kHz, and in some cases down to 30 kHz)
Frequency Limits
References
Chapter 6 Interference Coupling and Reduction
Figure 6-1. Idealized Energy Transfer Loop
Figure 6-3. Equivalent Circuit of Non-Ideal Energy Transfer Loop
Figure 6-4. Practical Combinations of Source-Load Pairs
Conductive Coupling
Free-Space Coupling
Figure 6-6. Conductive Coupling of Extraneous Noise into Equipment Interconnecting Cables
Figure 6-7. Magnetic Field Surrounding a Current-Carrying Conductor
Figure 6-8. Illustration of Inductive Coupling
Near-Field Coupling
Figure 6-9. Illustration of Capacitive Coupling
Capacitive Coupling
Figure 6-10. Equivalent Circuit of Network in Figure 6-9
Far-Field Coupling
Figure 6-11. Characteristic Voltage Transfer Curve for Capacitive Coupling
Figure 6-12. Electric Field Patterns in the Vicinity of a Radiating Dipole
Common Mode Noise
Figure 6-13. Illustration of Conductively-Coupled Common-Mode Noise
Basic Theory of Common-Mode Coupling
Figure 6-14. Common-Mode Noise in Unbalanced Systems
Basic Theory of Common-Mode Coupling
Figure 6-15. Common-Mode Noise in Balanced Systems
Differential Amplifier
Reduction of Circuit Loop Area
Facility and Equipment Requipments
Purpose of Bonding
Figure 7-1. Effects of Poor Bonding on the Performance of a Power Line Filter
Resistance Criteria
Direct Bond
Figure 7-2. Current Flow Through Direct Bonds
Contact Resistance
Surface Hardness
Bond Area
Figure 7-4. Resistance of a Test Bond as a Function of Fastener Torque
Direct Bonding Techniques
Brazing
Figure 7-5. Typical Exothermic Connections
Figure 7-6. Typical Bond Configurations Which Can Be Implemented With The Exothermic Process
Bolts
Figure 7-7. Nomograph for Torque on Bolts (7-6)
Conductive Adhesive
Figure 7-9. An Improperly Riveted Seam
Table 7-2 Ratings of Selected Bonding Techniques
Frequency Effects
Table 7-3 Calculated Inductance of a 6 inch (15.2 cm) Rectangular Strap
Table 7-5 Calculated Inductance of Standard Size Cable
Figure 7-10. Induvtive Reactance of Wire and Strap Bond Jumpers
Figure 7-11. Relative Inductive Reactance versus Length-to-Width Ratio of Flat Straps (7-10)
Figure 7-14. True Equivalent Circuit of a Bonded System
Surface Preparation
Organic Compounds
Figure 7-15. Measured Bonding Effectiveness of a 9-1/2 Inch Bonding Strap (7-5)
Figure 7-16. Measured Bonding Effectiveness of a 2-3/8 Inch Bonding Strap (7-5)
Platings and Inorganic Finishes
Figure 7-17. Basic Diagram of the Corrosion Process
Electrochemical Series
Table 7-6 Standard Electromotive Series (7-12)
Table 7-7 Galvanic Series of Common Metals and Alloys in Seawater (7-13)
Relative Area of Anodic Member
Figure 7-19. Techniques for Protecting Bonds Between Dissimilar Metals
Summary of Guidelines
References
Chapter 8 Shielding
Oppositely Induced Fields
Figure 8-1. Electromagnetic Transmission Through a Slot
Figure 8-2. Transmission Line Model of Shielding
Absorption Loss
Reflection Loss
Table 8-1 Electrical Properties of Shielding Materials at 150 kHz (8-3)
Table 8-2 Absorption Loss, A, of 1 mm Metal Sheet (8-2)
Figure 8-3. Absorption Loss for One Millimeter Shields
Figure 8-4. Wave Impedance versus Distance from Source
Table 8-3 Coefficients for Magnetic Field Reflection Loss
Figure 8-5.Reflection Loss for Iron,Copper, and Aluminum with a Low Impedance Source
Plane Wave Field
Figure 8-7. Plane Wave Reflection Loss for Iron, Copper ,and Aluminum
High Impedance Field
Figure 8-9. Universal Reflection Loss Curve for High Impedance Fields (8-3)
Figure 8-10. Reflection Losses for Iron, Copper, and Aluminum with a High Impedance Source
Table 8-4 Calculated Reflection Loss in dB of Metal Sheet, Both Faces (8-2), (8-3)
Re-Reflection Correction Factor
Table 8-5. Coefficient for Evaluation of Re-Reflection Correction Term,C
Table 8-6 Correction Term C in dB for Single Metal Sheet (8-2)
Figure 8-12. Absorption Loss and Multiple Reflection Correction Term
Table 8-7 Calculated Values of Shielding Effectiveness (8-2)
Table 8-7 Calculated Values of Shielding Effectiveness (8-2) -Cont.
Table 8-7 Calculated Values of Shielding Effectiveness (8-2) -Cont.
Figure 8-14. Theoretical Attenuation of Thin Iron Sheet (8-5)
Measured Data
Table 8-8 Measured Shielding Effectiveness in dB for Solid-Sheet Materials (8-3)
Figure 8-16. Measured Shielding Effectiveness of High Permeability Material as a Function of Measurement Loop Spacing (8-6)
Table 8-9 Summary of Formulas for Shielding Effectiveness
Multiple Solid Shields
Coatings and Thin-Film Shields
Screens and Perforated Metal Shields
Screens and Perforated Metal Shields -Cont.
Screens and Perforated Metal Shields -Cont.
Screens and Perforated Metal Shields -Cont.
Figure 8-18. Measured and Calculated Shielding Effectiveness of Copper Screens to Low Impedance Fields (8-8)
Table 8-12 Effectiveness of Non-Solid Shielding Materials Against Low Impedance and Plane Waves (8-7)
Table 8-13 Effectiveness of Non-Solid Shielding Materials Against High Impedance Waves (8-3)
Figure 8-19. Shielding Effectiveness Of a Perforated Metal Sheet as a Function of Hole Sizes
Table 8-14 Comparison of Measured and Calculated Values of Shielding Effectiveness for No. 22, 15 Mil Copper Screens (8-8)
Seams Without Gaskets
Figure 8-21. Slot Radiation (Leakage) (8-9)
Figure 8-22. Shielding Effectiveness Degradation Caused by Surface Finishes on Aluminum (8-4)
Seams With Gaskets
Figure 8-23. Influence of Screw Spacing on Sheilding Effectiveness
Figure 8-25. Shielding Effectiveness of an AMPB-65 Joint as a Function of Overlap (8-6)
Table 8-15 Characteristics of Conductive Gasketing Materials
Figure 8-26. Typical Mounting Techniques for RF Gaskets
Waveguide-Below-Cutoff
Table 8-16hielding Effectiveness of Hexagonal Honeycomb Made of Steel with 1/8-inch Openings 1/2-Inch Long (8-10)
Screen and Conducting Glass
Selection of Shielding Materials
Figure 8-28. Shielding Effectiveness of Conductive Glass to High Impedance Waves (8-11)
Figure 8-30. Light Transmission Versus Surface Resistance for Conductive Glass (8-7)
Use of Conventional Building Materials
Figure 8-31. Shielding Effectiveness of Some Building Materials (8-12)
Figure 8-32. Center Area Attenuation of Induced Voltage by 15 Foot High Single-Course Reinforcing Steel Room (8-13)
Cable Shields
Table 8-17 Comparison of Cable Shields
Cable Shields -Cont.
Figure 8-34. Shielding Effectiveness of Various Types of RF Cables as a Function of Frequency (8-15)
Terminations and Connectors
Table 8-18 Connector Application Summary
Figure 8-36. RF-Shielded Connector
Demountable (Modular) Enclosures
Table 8-19 Characteristics of Commercially Available Shielded Enclosures (8-13)
Table 8-19 Characteristics of Commercially Available Shielded Enclosures (8-13) -Cont.
Figure 8-38. Use of Finger Stock for Door Bonding
Custom Built Rooms
Foil Room Liners
Testing of Shields
Low Impedance Magnetic Field Testing Using Small Loops
Additional Test Methods
Figure 8-40. Coplanar Loop Arrangement for Measuring Shield Effectiveness
Equipment Disturbances
Equipment EMI Properties
Signal Properties
References
References -Cont.
Chapter 9 Personnel Protection
Table 9-1 Summary of the Effects of Shock (9-1) (9-2)
Shock Prevention
Static Electricity
Laser Hazards
X-Ray Radiation
Chapter 10 Nuclear EMP Effects
Figure 10-1. EMP from High Altitude Bursts
Surface-Burst EMP
Other EMP Phenomena
Comparison with Lightning
Long Overhead Lines
Long Buried Lines
Figure 10-5. The Normalized Current Waveform for Various Values of the Depth Parameter p (Exponential Pulse)
Vertical Structures
Penetrating Conductors
Figure 10-7. Shield to Exclude Electromagnetic Fields
Figure 10-8. Electromagnetic Penetration Through Small Apertures
Penetrating Conductors
Figure 10-9. Shielding Integrity Near Interference-carrying External Conductors
Amount of Protection Needed
Figure 10-10. Magnetic Field Penetration of Apertures
Where Protection is Applied
Metal-Oxide Varistors
Waveguide Penetration of Facility Shield
Figure 10-12. Waveguide Feedthroughs
Sleeve and Bellows Attachment
Figure 10-13. Bellows with Slitted Sleeve Waveguide Attachment
Braided Wire Sleeve
Figure 10-15. Stuffing Tube for Waveguide
References
Chapter 11 Notes
Appendix A Glossary
Appendix A Glossary -Cont.
Appendix A Glossary -Cont.
Appendix A Glossary -Cont.
Appendix A Glossary -Cont.
Appendix A Glossary -Cont.
Appendix B Supplement Bibliography
Appendix B Supplement Bibliography -Cont.
Appendix B Supplement Bibliography -Cont.
Appendix B Supplement Bibliography -Cont.
Appendix B Supplement Bibliography -Cont.
Appendix B Supplement Bibliography -Cont.
Appendix B Supplement Bibliography -Cont.
Appendix B Supplement Bibliography -Cont.
Appendix B Supplement Bibliography -Cont.
Appendix B Supplement Bibliography -Cont.
Appendix B Supplement Bibliography -Cont.
Appendix B Supplement Bibliography -Cont.
Appendix B Supplement Bibliography -Cont.
Appendix B Supplement Bibliography -Cont.
Appendix B Supplement Bibliography -Cont.
Appendix B Supplement Bibliography -Cont.
Appendix C Table of Contents for Volume II
Appendix C Table of Contents for Volume II -Cont.
Appendix C Table of Contents for Volume II -Cont.
Appendix C Table of Contents for Volume II -Cont.
Appendix C Table of Contents for Volume II -Cont.
Appendix C Table of Contents for Volume II -Cont.
Appendix C Table of Contents for Volume II -Cont.
Appendix C Table of Contents for Volume II -Cont.
Appendix C Table of Contents for Volume II -Cont.
Appendix D Index
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
Appendix D Index -Cont.
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Grounding, Bonding, and Shielding for Electronic Equipments and Facilities