Attch 7 - HNDBK 419A.pdf

MIL-HDBK-419A

29 DECEMBER 1987

SUPERSEDING

MIL-HDBK-419

21 JANUARY 1982

MILITARY HANDBOOK

GROUNDING, BONDING, AND SHIELDING

FOR

ELECTRONIC EQUIPMENTS AND FACILITIES

VOLUME I OF 2 VOLUMES

BASIC THEORY

AMSC N/A EMCS/SLHC/TCTS

DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited

DEPARTMENT OF DEFENSE

WASHINGTON DC 20301

MIL-HDBK-419A

GROUNDING, BONDING, AND SHIELDING FOR ELECTRONIC EQUIPMENTS AND FACILITIES

1. This standardization handbook was developed by the Department of Defense in accordance with established procedure.

2. This publication was approved on 29 December 1987 for printing and inclusion in the military standardization handbook series.Vertical lines and asterisks are not used in this revision to identify changes with respect to the previous issue due to the extensiveness of the changes.

3. This document provides basic and application information on grounding, bonding, and shielding practices recommended for electronic equipment. It will provide valuable information and guidance to personnel concerned with the preparation of specifications and the procurement of electrical and electronic equipment for the Defense Communications System.The handbook is not intended to be referenced in purchase specifications except for informational purposes, nor shall it supersede any specification requirements.

4. Every effort has been made to reflect the latest information on the interrelation of considerations of electrochemistry, metallurgy, electromagnetics, and atmospheric physics. It is the intent to review this handbook periodically to insure its completeness and currency. Users of this document are encouraged to report any errors discovered and any recommendations for changes or inclusions to: Commander, 1842 EEG/EEITE, Scott AFB IL 62225-6348.

5. Copies of Federal and Military Standards, Specifications and associated documents (including this handbook) listed in the Department of Defense Index of Specifications and Standards (DODISS) should be obtained from the DOD Single Stock Point: Commanding Officer, Naval Publications and Forms Center, 5801 Tabor Avenue, Philadelphia PA 19120. Single copies may be obtained on an emergency basis by calling (AUTOVON) 442-3321 or Area Code (215)-697-3321. Copies of industry association documents should be obtained from the sponsor. Copies of all other listed documents should be obtained from the contracting activity or as directed by the contracting officer.

PREFACE

This volume is one of a two-volume series which sets forth the grounding, bonding, and shielding theory for communications electronics (C-E) equipments and facilities. Grounding, bonding, and shielding are complex subjects about which in the past there has existed a good deal of misunderstanding. The subjects themselves are interrelated and involve considerations of a wide range of topics from electrochemistry and metallurgy to electromagnetic field theory and atmospheric physics.These two volumes reduce these varied considerations into a usable set of principles and practices which can be used by all concerned with, and responsible for, the safety and effective operation of complex C-E systems. Where possible, the principles are reduced to specific steps. Because of the large number of interrelated factors, specific steps cannot be set forth for every possible situation. However, once the requirements and constraints of a given situation are defined, the appropriate steps for solution of the problem can be formulated utilizing the principles set forth.

Both volumes (Volume I, Basic Theory and Volume II, Applications) implement the Grounding, Bonding, and Shielding requirements of MIL-STD-188-124A which is mandatory for use within the Department of Defense.

The purpose of this standard is to ensure the optimum performance of ground-based telecommunications equipment by reducing noise and providing adequate protection against power system faults and lightning strikes.

This handbook emphasizes the necessity for including considerations of grounding, bonding, and shielding in all phases of design, construction, operation, and maintenance of electronic equipment and facilities. Volume I, Basic Theory, develops the principles of personnel protection, fault protection, lightning protection, interference reduction, and EMP protection for C-E facilities. In addition, the basic theories of earth connections, signal grounding, electromagnetic shielding, and electrical bonding are presented. The subjects are not covered independently, rather they are considered from the standpoint of how they influence the design of the earth electrode subsystem of a facility, the selection of ground reference networks for equipments and structures, shielding requirements, facility and equipment bonding practices, etc. Volume I also provides the basic background of theory and principles that explain the technical basis for the recommended practices and procedures; illustrates the necessity for care and thoroughness in implementation of grounding, bonding, and shielding, and provides supplemental information to assist in the solution of those problems and situations not specifically addressed.

In Volume II, Applications, the principles and theories, including RED/BLACK protection, are reduced to the practical steps and procedures which are to be followed in structural and facility development, electronic engineering, and in equipment development. These applications should assure personnel equipment and structural safety, minimize electromagnetic interference (EMI) problems in the final operating system; and minimize susceptibility to and generation of undesirable emanations.The emphasis in Volume II goes beyond development to assembly and construction, to installation and checkout, and to maintenance for long term use.

Four appendices are provided as common elements in both volumes. Appendix A is a glossary of selected words and terms as they are used herein. If not defined in the glossary, usage is in accordance with Federal Standard 1037, Glossary of Telecommunication Terms. Appendix B is a supplemental bibliography containing selected references intended to supply the user with additional material. Appendix C contains the table of contents for the other volume. Appendix D contains the index for the two-volume set.

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TABLE OF CONTENTS

CHAPTER 1 - FACILITY GROUND SYSTEM

1.1 GENERAL

1.2 APPLICATION

1.3 DEFINITIONS

1.4 REFERENCED DOCUMENTS

1.5 DESCRIPTION

1.5.1 Facility Ground System

1.5.2 Grounding and Power Distribution Systems

1.5.3 Electrical Noise in Communications Systems

1.6 BONDING, SHIELDING, AND GROUNDING RELATIONSHIP

1.7 GROUNDING SAFETY PRACTICES

2.1 2.1.1 2.1.2 2.1.3 2.1.4 2.2 2.2.1 2.2.2 2.2.2.1 2.2.2.2 2.2.3 2.3 2.3.1 2.3.2 2.3.3 2.4 2.4.1 2.4.2 2.4.2.1 2.4.2.2 2.5 2.5.1 2.5.2 2.5.3

CHAPTER 2 - EARTHING AND EARTH ELECTRODE SUBSYSTEM

OBJECTIVES

Lightning Discharge Fault Protection Noise Reduction Summary of Requirements

RESISTANCE REQUIREMENTS

General Resistance to Earth

National Electrical Code Requirements

Department of Defense Communications Electronics Requirements Lightning Requirements

SOIL RESISTIVITY

General Typical Resistivity Ranges

Environmental Effects

MEASUREMENT OF SOIL RESISTIVITY

General Measurement Techniques

One-Electrode Method Four-Terminal Method

TYPES OF EARTH ELECTRODE SUBSYSTEMS

General Ground Rods Buried Horizontal Conductors

Page

1-1 l - l l - l l - l l-2 l-2 l-3 l-4 l-5 l-5

2 - l 2 - l 2-2 2-2 2-2 2-5 2-5 2-5 2-5 2-5 2-5 2-7 2-7 2-7 2-7 2-8 2-8 2-8 2-8

2-13 2-15 2-15 2-15 2-15 i

TABLE OF CONTENTS (Continued)

Paragraph P a g e

2.5.4 Grids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15

2.5.5 Plates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15

2.5.6 Metal Frameworks of Buildings. . . . . . . . . . . . . . . . . . . . . . . . . . 2-16

2.5.7 Water Pipes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16

2.5.8 Incidental Metals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16

2.5.9 Well Casings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16

2.6 RESISTANCE PROPERTIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17

2.6.1 Simple Isolated Electrodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17

2.6.1.1 Driven Rod. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17

2.6.1.2 Other Commonly Used Electrodes . . . . . . . . . . . . . . . . . . . . . . . . 2-23

2.6.2 Resistance of Multiple Electrodes . . . . . . . . . . . . . . . . . . . . . . . . . 2-23

2.6.2.1 Two Vertical Rods in Parallel. . . . . . . . . . . . . . . . . . . . . . . . . . 2-23

2.6.2.2 Square Array of Vertical Rods . . . . . . . . . . . . . . . . . . . . . . . . . 2-27

2.6.2.3 Horizontal Grid (Mesh). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-29

2.6.2.4 Vertical Rods Connected by a Grid . . . . . . . . . . . . . . . . . . . . . . . 2-30

2.6.3 Transient Impedance of Electrodes . . . . . . . . . . . . . . . . . . . . . . . . 2-32

2.6.4 Effects of Nonhomogeneous (Layered) Earth. . . . . . . . . . . . . . . . . . . . 2-32

2.6.4.1 Hemispherical Electrode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-32

2.6.4.2 Vertical Rod . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-33

2.6.4.3 G r i d s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-33

2 . 7 MEASUREMENT OF RESISTANCE-TO-EARTH OF ELECTRODES. . . . . . . 2-35

2.7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-35

2.7.2 Fall-of-Potential Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-35

2.7.2.1 Probe Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-36

2.7.2.2 Extensive Electrode Subsystems.. . . . . . . . . . . . . . . . . . . . . . . . 2-42

2.7.2.3 Test Equipments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-45

2.7.3 Three-Point (Triangulation) Method. . . . . . . . . . . . . . . . . . . . . . . . 2-46

2.8 OTHER CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-47

2.8.1 Surface Voltages Above Earth Electrodes. . . . . . . . . . . . . . . . . . . . . 2-47

2.8.1.1 Step Voltage Safety Limit. . . . . . . . . . . . . . . . . . . . . . . . . . . 2-47

2.8.1.2 Step Voltages for Practical Electrodes. . . . . . . . . . . . . . . . . . . . . . 2-49

2.8.1.2.1 Flush Vertical Rod. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-49

2.8.1.2.2 Buried Vertical Rod . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-53

2.8.1.2.3 Buried Horizontal Grid. . . . . . . . . . . . . . . . . . . . . . . . . . . 2-55

2.8.1.3 Minimizing Step Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-56

2.8.2 Heating of Electrodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-57

2.8.2.1 Steady State Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-57

2.8.2.2 Transient Current. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-57

2.8.2.3 Minimum Electrode Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-59 ii

Paragraph

2.9 ELECTRODE ENHANCEMENT

2.9.1 Introduction

2.9.2 Water Retention

2.9.3 Chemical Salting

2.9.4 Electrode Encasement

2.9.5 Salting Methods

2.10 CATHODIC PROTECTION

2.10.1 Introduction

2.10.2 Protection Techniques

2.10.3 Sacrifical Anodes

2.10.4 Corrosive Atmospheres

2 .11 GROUNDING IN ARCTIC REGIONS

2.11.1 Soil Resistivity

2.11.2 Improving Electrical Grounding in Frozen Soils

2.11.2.1 Electrode Resistance

2.11.2.2 Installation and Measurement Methods

2.11.2.2.1 Electrode Installation

2.11.2.2.2 Backfill

2.12 REFERENCES

2-59 2-59 2-60 2-60 2-62 2-63 2-63 2-63 2-65 2-65 2-66 2-66 2-66 2-70 2-71 2-71 2-71 2-71 2-75

CHAPTER 3 - LIGHTNING PROTECTION SUBSYSTEM

3.1 THE PHENOMENON OF LIGHTNING. . . . . . . . . . . . . . . . . . . . . . . . 3 - l

3.2 DEVELOPMENT OF A LIGHTNING FLASH. . . . . . . . . . . . . . . . . . . . . 3-3

3.3 INFLUENCE OF STRUCTURE HEIGHT. . . . . . . . . . . . . . . . . . . . . . . . 3-3

3.4 STRIKE LIKELIHOOD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

3.5 ATTRACTIVE AREA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10

3.5.1 Structures Less Than 100 Meters High . . . . . . . . . . . . . . . . . . . . . . . 3-10

3.5.2 Cone of Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11

3.6 LIGHTNING EFFECTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13

3.6.1 Flash Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13

3.6.2 Mechanical and Thermal Effects . . . . . . . . . . . . . . . . . . . . . . . . . 3-15

3.6.3 Electrical Effects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-17

3.6.3.1 Conductor Impedance Effects. . . . . . . . . . . . . . . . . . . . . . . . . . 3-17

3.6.3.2 Induced Voltage Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18

3.6.3.3 Capacitively-Coupled Voltage . . . . . . . . . . . . . . . . . . . . . . . . . 3-21

3.6.3.4 Earth Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-21

3.7 BASIC PROTECTION REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . 3-25

3.8 DETERMINING THE NEED FOR PROTECTION . . . . . . . . . . . . . . . . . . . . 3-26

3.8.1 Strike Likelihood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-26

Page iii

Paragraph

3.8.2 3.8.3 3.9 3.10

Type of Construction Criticalness to System Mission

APPLICABLE CODES

REFERENCES

CHAPTER 4 -FAULT PROTECTION SUBSYSTEM

3-26 3-27 3-27 3-28

4 .1 4.1.1 4.1.2 4.2 4.3 4.4 4.5

FAULT PROTECTION

Power System Faults Ground-Fault-Circuit-Interrupter (GFCI)

EARTH CONNECTION

AC POWER LINE GROUND

TEST EQUIPMENT

REFERENCES

CHAPTER 5 - GROUNDING OF SIGNAL REFERENCE SUBSYSTEM

4 - l 4 - l 4-3 4-3 4-3 4-5 4-6

5.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 1

5.2 CONDUCTOR CONSIDERATIONS. . . . . . . . . . . . . . . . . . . . . . . . . . 5 - l

5.2.1 Direct Current Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - l

5.2.2 Alternating Current Impedance . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - l

5.2.2.1 Skin Effect. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

5.2.2.2 AC Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

5.2.2.3 Reac t ance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7

5.2.2.4 Proximity Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10

5.2.3 Resistance Properties vs Impedance Properties . . . . . . . . . . . . . . . . . . . 5-10

5.2.4 Effects of Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12

5.2.4.1 Stranded Cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-13

5.2.4.2 Rectangular Conductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-13

5.2.4.3 Tubular Conductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-13

5.2.4.4 Structural Steel Members . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15

5.3 SIGNAL REFERENCE SUBSYSTEM NETWORK CONFIGURATIONS . . . . . . . 5-15

5.3.1 Floating Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15

5.3.2 Single-Point Ground (for Lower Frequencies) . . . . . . . . . . . . . . . . . . . . 5-18

5.3.3 Multipoint Ground (for Higher Frequencies).. . . . . . . . . . . . . . . . . . . . 5-24

5.3.3.1 Equipotential Plane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26

5.3.3.2 Types of Equipotential Planes. . . . . . . . . . . . . . . . . . . . . . . . . . 5-27

5.3.4 Floating System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-28 iv

Paragraph

5.4 SITE APPLICATIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-28

5.4.1 Lower Frequency Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-29

5.4.2 Higher Frequency Network. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-30

5.4.3 Frequency Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-31

5.5 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-32

CHAPTER 6 - INTERFERENCE COUPLING AND REDUCTION

6.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-l

6.2 COUPLING MECHANISMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

6.2.1 Conductive Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

6.2.2 Free-Space Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

6.2.2.1 Near-Field Coupling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

6.2.2.2 Inductive Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8

6.2.2.3 Capacitive Coupling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-11

6.2.2.4 Far-Field Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-14

6 .3 COMMON-MODE NOISE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-17

6.3.1 Basic Theory of Common-Mode Coupling. . . . . . . . . . . . . . . . . . . . . . 6-19

6.3.2 Differential Amplifier. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-23

6.4 MINIMIZATION TECHNIQUES. . . . . . . . . . . . . . . . . . . . . . . . . . . 6-23

6.4.1 Reduction of Coupling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-23

6.4.1.1 Reference Plane Impedance Minimization . . . . . . . . . . . . . . . . . . . . 6-23

6.4.1.2 Spatial Separation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-24

6.4.1.3 Reduction of Circuit Loop Area. . . . . . . . . . . . . . . . . . . . . . . . . 6-24

6.4.1.4 Shielding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-24

6.4.1.5 Balanced Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-24

6.4.2 Alternate Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-24

6.5 FACILITY AND EQUIPMENT REQUIREMENTS. . . . . . . . . . . . . . . . 6-25

6.6 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-25

CHAPTER 7 - BONDING

7.1 DEFINITION OF BONDING.. . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - l

7.2 PURPOSES OF BONDING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - l

7.3 RESISTANCE CRITERIA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3

7.4 DIRECT BONDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4

7.4.1 Contact Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6

7.4.1.1 Surface Contaminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7

7.4.1.2 Surface Hardness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7

7.4.1.3 Contact Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7

7.4.1.4 Bond Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 8

7.4.2 Direct Bonding Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-10

7.4.2.1 Welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-10

7.4.2.2 Brazing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-11

7.4.2.3 Soft Solder. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-14

7.4.2.4 Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-14

7.4.2.5 Rivets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-15

7.4.2.6 Conductive Adhesive. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16

7.4.2.7 Comparison of Techniques. . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16

7.5 INDIRECT BONDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16

7.5.1 Resistance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-19

7.5.2 Frequency Effects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-19

7.5.2.1 Skin Effect.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-19

7.5.2.2 Bond Reactance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-19

7.5.2.3 Stray Capacitance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-23

7.6 SURFACE PREPARATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-25

7.6.1 Solid Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-26

7.6.2 Organic Compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-26

7.6.3 Platings and Inorganic Finishes . . . . . . . . . . . . . . . . . . . . . . . . . . 7-29

7.6.4 Corrosion By-Products. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-29

7.7 COMPLETION OF THE BOND. . . . . . . . . . . . . . . . . . . . . . . . . . . 7-29

7.8 BOND CORROSION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-30

7.8.1 Chemical Basis of Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-30

7.8.1.1 Electrochemical Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-31

7.8.1.2 Galvanic Series. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-31

7.8.2 Relative Area of Anodic Member . . . . . . . . . . . . . . . . . . . . . . . . . 7-34

7.8.3 Protective Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-34

7.9 WORKMANSHIP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-34

7.10 SUMMARY OF GUIDELINES. . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-36

7.11 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-37

CHAPTER 8 - SHIELDING

8.1 FUNCTION OF AN ELECTROMAGNETIC SHIELD. . . . . . . . . . . . . . . 8 - l

8.2 BASIC SHIELDING THEORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 -2

8.2.1 Oppositely Induced Fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 -2

8.2.2 Transmission Line Analogy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 -2

8.2.3 Nonuniform Shielding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4

MIL-HDBK-419A

TABLE OF CONTENTS (Continued)

Paragraph Page vi

Paragraph

8.3 8.3.1 8.3.2 8.3.2.1 8.3.2.2 8.3.2.3 8.3.3 8.3.4 8.3.4.1 8.3.4.2 8.4 8.4.1 8.4.2 8.4.3 8.5 8.5.1 8.5.2 8.5.3 8.5.3.1 8.5.3.2 8.6 8.7 8.7.1 8.7.2 8.8 8.8.1 8.8.2 8.9 8.9.1 8.9.2 8.9.3 8.10 8.10.1 8.10.2 8.11 8.12 8.12.1 8.12.2 8.12.3

SHIELDING EFFECTIVENESS OF CONTINUOUS SINGLE-THICKNESS SHIELDS.

Absorption Loss Reflection Loss

Low Impedance Field Plane Wave Field High Impedance Field

Re-Reflection Correction Factor Total Shielding Effectiveness

Measured Data S u m m a r y

SHIELDING EFFECTIVENESS OF OTHER SHIELDS

Multiple Solid Shields Coatings and Thin-Film Shields Screens and Perforated Metal Shields

SHIELD DISCONTINUITY EFFECTS (APERTURES)

Seams Without Gaskets Seams With Gaskets Penetration Holes

Waveguide-Below-Cutoff Screen and Conducting Glass

SELECTION OF SHIELDING MATERIALS

USE OF CONVENTIONAL BUILDING MATERIALS

Concrete Reinforcing Steel (Rebar)

CABLE AND CONNECTOR SHIELDING

Cable Shields Terminations and Connectors

SHIELDED ENCLOSURES (SCREEN ROOMS)

Demountable (Modular) Enclosures Custom Built Rooms Foil Room Liners

TESTING OF SHIELDS

Low Impedance Magnetic Field Testing Using Small Loops Additional Test Methods

PERSONNEL PROTECTION SHIELDS

DETERMINATION OF SHIELDING REQUIREMENTS

Equipment Disturbances Electromagnetic Environmental Survey Equipment EMI Properties

8-4 8-5 8-6

8-10 8-13 8-15 8-19 8-19 8-27 8-27 8-31 8-31 8-32 8-33 8-41 8-42 8-45 8-45 8-50 8-52 8-53 8-56 8-56 8-56 8-59 8-59 8-63 8-63 8-66 8-70 8-71 8-72 8-73 8-74 8-74 8-74 8-76 8-76 8-77 vii

Paragraph

8.13 8.13.1 8.13.2 8.13.3 8.13.4 8.14

SYSTEM DESIGN CONSIDERATIONS

S i z e Layout Signal Properties Cost

REFERENCES

CHAPTER 9 - PERSONNEL PROTECTION

8-77 8-78 8-78 8-78 8-78 8-79

9.1 9.1.1 9.1.2 9.2 9.3 9.4 9.5 9.6

ELECTRIC SHOCK

Levels of Electric Shock

Shock Prevention

STATIC ELECTRICITY

RADIO FREQUENCY (RF) RADIATION HAZARDS

LASER HAZARDS

X-RAY RADIATION

REFERENCES

CHAPTER 10 - NUCLEAR EMP EFFECTS

9 - l 9 - l 9-3 9-3 9-5 9-5 9-6 9-6

10.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 - l

10.2 EMP GENERATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 - l

10.2.1 High-Altitude EMP (HEMP).. . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 - l

10.2.1.1 Early-Time HEMP.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 - l

10.2.1.2 Late-Time HEMP (MHDEMP). . . . . . . . . . . . . . . . . . . . . . . . . . 10-3

10.2.1.3 Intermediate-Time HEMP. . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3

10.2.2 Surface-Burst EMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3

10.2.3 Other EMP Phenomena . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-4

10.2.4 Comparison With Lightning. . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-5

10.3 HEMP INTERACTION WITH SYSTEMS.. . . . . . . . . . . . . . . . . . . . . . . 10-5

10.3.1 Current in Long Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-6

10.3.1.1 Long Overhead Lines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-6

10.3.1.2 Long Buried Lines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-7

10.3.1.3 Vertical Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-9

10.3.2 HEMP Interaction With Local Structure. . . . . . . . . . . . . . . . . . . . . . 10-9

10.3.2.1 Shields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-9

10.3.2.2 Penetrating Conductors. . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-10

10.3.2.3 Apertures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-11

P a g e viii

Paragraph

TABLE OF CONTENTS (Continued)

10.4 PROTECTION AGAINST HEMP

10.4.1 HEMP Barrier

10.4.1.1 Shield

10.4.1.2 Penetrating Conductors

10.4.1.3 Apertures

10.4.2 Allocation of Protection

10.4.2.1 Amount of Protection Needed

10.4.2.2 Where Protection is Applied

10.4.2.3 Terminal Protection Devices

10.4.2.3.1 Spark Gaps and Gas Tubes

10.4.2.3.2 Metal-Oxide Varistors

10.4.2.3.3 Semiconductors

10.4.2.3.4 Filters

10.4.2.4 Waveguide Penetration of Facility Shield

10.4.2.4.1 Introduction

10.4.2.4.2 In-Line Waveguide Attachment

10.4.2.4.2.1 Sleeve and Bellows Attachment

10.4.2.4.2.2 Braided Wire Sleeve

10.4.2.4.2.3 Stuffing Tube for Waveguide

10.5 REFERENCES

CHAPTER 11 - NOTES

11.1 SUBJECT TERM (KEY WORD) LISTING

APPENDICES

A GLOSSARY

B SUPPLEMENTAL BIBLIOGRAPHY

BI SUBJECT CROSS REFERENCE

BII LISTINGS

C TABLE OF CONTENTS FOR VOLUME II

D INDEX

10-13 10-13 10-13 10-13 10-15 10-15 10-15 10-17 10-17 10-17 10-18 10-18 10-18 10-19 10-19 10-21 10-21 10-23 10-24 10-25

11-1

A - l B - l B - l B-2 C - l D - l ix

LIST OF FIGURES

Figure Page

2-l

2-2 2-3

Voltage Differentials Arising from Unequal Earth Electrode Resistances and Unequal Stray Currents Voltage Differentials Between Structures Resulting from Stray Ground Currents Typical Variations in Soil Resistivity as a Function of Moisture, Temperature, and Salt Content Current Flow From a Hemisphere in Uniform Earth Idealized Method for Determining Soil Resistivity Effect of Rod Length Upon Resistance Effect of Rod Diameter Upon Resistance Earth Resistance to Shell Surrounding a Vertical Earth Electrode Resistance of Buried Horizontal Conductors Resistance of Buried Circular Plates Ground Rods in Parallel Ratio of the Actual Resistance of a Rod Array to the Ideal Resistance of N Rods in Parallel Transient Impedance of an Earth Electrode Subsystem as a Function of the Number of Radial Wires Current Distribution in Nonuniform Soil Fall-of-Potential Method for Measuring the Resistance of Earth Electrodes Effect of Electrode Spacing on Voltage Measurement Resistance Variations as Function of Potential Probe Position in Fall-of-Potential Method Earth Resistance Curves for a Large Electrode Subsystem Earth Resistance Curve Applicable to Large Earth Electrode Subsystems Intersection Curves for Figure 2-18 Triangulation Method of Measuring the Resistance of an Earth Electrode Variation of Surface Potential Produced by a Current Flowing Into an Isolated Ground Rod Surface Potential Variation Along a Grid Effect of Chemical Treatment on Resistance of Ground Rods Seasonal Resistance Variations of Treated and Untreated Ground Rods Trench Method of Soil Treatment Alternate Method of Chemical Treatment of Ground Rod Relative Depths of Unconsolidated Materials, Subarctic Alaska Typical Sections Through Ground Containing Permafrost Illustration Showing Approximate Variations in Substructure Installation of an Electrode During the Process of Backfilling Apparent Resistivity for Two Soils at Various Moisture and Soil Contents Configuration of Nearly Horizontal Electrodes Placed in the Thawed Active Layer . .

2-3 2-4

2-4 2-5 2-6 2-7 2-8 2-9 2-10 2-11 2-12

2-9 2-11 2-14 2-18 2-18 2-20 2-24 2-25 2-26

2-28 2-13

2-14 2-15 2-16 2-17

2-31 2-34 2-37 2-38

2-18 2-19 2-20 2-21 2-22

2-41 2-44 2-45 2-47 2-48

2-23 2-24 2-25 2-26 2-27 2-28 2-29 2-30 2-31 2-32 2-33

2-52 2-54 2-61 2-61 2-64 2-64 2-67 2-68 2-69 2-72 2-73 2-73

X

LIST OF FIGURES (Continued)

2-34 2-35 2-36

2-37

2-38

Resistance-to-Ground Curves for an Electrode Driven Into Ice-Rich Silt Resistance-to-Ground Curves for an Electrode Surrounded by Backfill of Saturated Silt.

Resistance-to-Ground Curves for an Electrode Surrounded by Water Saturated Salt-Soil Backfill Resistance-to-Ground Curves for an Electrode Surrounded by Water Saturated Salt-Soil Backfill Resistance-to-Ground Curves for Electrodes Placed in Holes Modified by Spring Changes

2-73 2-74

2-74

2-74

2-74

3-l Charge Distribution in a Thundercloud . . . . . . . . . . . . . . . . . . . . . . . . 3 -2 3-2 Mean Number of Thunderstorm Days Per Year for the United States . . . . . . . . 3 -5 3-3 Worldwide Isokeraunic Map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6 3-4 Attractive Area of a Rectangular Structure . . . . . . . . . . . . . . . . . . . . . 3-12 3-5 Effective Height of a Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12 3-6 Zones of Protection Established by a Vertical Mast and a Horizontal Wire.. . . . . . . . 3-14 3-7 Some Commonly Used Lightning Shielding Angles. . . . . . . . . . . . . . . . . . . 3-14 3-8 Illustration of Processes and Currents Which Occur During a Lightning Flash to Ground . 3-15 3-9 Inductive Coupling of Lightning Energy to Nearby Circuits . . . . . . . . . . . . . . . 3-19 3-10 Normalized Voltage Induced in a Single-Turn Loop by Lightning Currents . . . . . . 3-20 3-11 Capacitive Coupling of Lightning Energy. . . . . . . . . . . . . . . . . . . . . . . 3-22 3-12 Coupling of Lightning Energy Through an Interconnected Facility . . . . . . . . 3-23 3-13 Step-Voltage Hazards Caused by Lightning-Induced Voltage Gradients in the Earth. . . . . 3-24

4-1 Grounding for Fault Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2 4-2 Single-Phase 115/230 Volt AC Power Ground Connections . . . . . . . . . . . . . . . 4-4 4-3 Three-Phase 120/208 Volt AC Power System Ground Connections . . . . . . . . . 4-5 4-4 Connections for a Three-Phase “Zig-Zag” Grounding Transformer . . . . . . . . 4-6

5-1 Surface Resistance and Skin Depth for Common Metals . . . . . . . . . . . . . 5-4 5-2 Resistance Ratio of Isolated Round Wires . . . . . . . . . . . . . . . . . . . . . . 5-6 5-3 Nomograph for the Determination of Skin Effect Correction Factor . . . . . . . 5-8 5-4 Low Frequency Self Inductance Versus Length for 1/0 AWG Straight Copper Wire . . . 5-9 5-5 Self Inductance of Straight Round Wire at High Frequencies. . . . . . . . . . . . . . 5-9 5-6 Resistance Ratio of Rectangular Conductors . . . . . . . . . . . . . . . . . . . . . 5-14 5-7 Resistance Versus Length for Various Sizes of Copper Tubing . . . . . . . . . . . . . . 5-14 5-8 AC Resistance Versus Frequency for Copper Tubing. . . . . . . . . . . . . . . . . . 5-16 5-9 Resistance Ratio of Nonmagnetic Tubular Conductors . . . . . . . . . . . . . . . . . 5-17 5-10 Inductance Versus Frequency for Various Sizes of Copper Tubing. . . . . . . . . . . . 5-18 5-11 Floating Signal Ground.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-19 xi

Figure Page

1-72 1-73 1-74 1-75 1-76 1-77 1-78 1-79 1-80 1-81

1-82

1-83 1-84

1-85 1-86 1-87 1-88 1-89 1-90 1-91 1-92 1-93 1-94 1-95 1-96 1-97 1-98 1-99 1-100 1-101

2-1 Transmitter Building. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 2-2 Communication Center/Receiver Building Expansion. . . . . . . . . . . . . . . . . . 2-3 2-3 Earth Resistance Measurement at a Typical Facility. . . . . . . . . . . . . . . . . . 2-7 2-4 Resistance Measurement Work Sheet. . . . . . . . . . . . . . . . . . . . . . . . 2-8 2-5 Sample of a Completed Resistance Measurement Work Sheet . . . . . . . . . . . . . . 2-9

Bonding of Equipment Cabinets to Cable Tray Bonding to Flexible Cable and Conduit Bonding to Rigid Conduit Connection of Bonding Jumpers to Flat Surface Bolted Bond Between Flat Bars Bracket Installation (Rivet or Weld) Use of Bonding Straps for Structural Steel Interconnections Direct Bonding of Structural Elements Connection of Earth Electrode Riser to Structural Column Measured Electromagnetic Shielding Effectiveness of a Typical Building at 6 Feet Inside Outer Wall Measured Electromagnetic Shielding Effectiveness of a Typical Building at 45 Feet

. . . . 1-148

. . . . 1-149

. . . . 1-149

. . . . 1-150

. . . . 1-151

. . . . 1-151

. . . . 1-152

. . . . 1-153

. . . . 1-153

Inside Outer Wall Shielding Effectiveness of Rebars Shielding Effectiveness of a Grid as a Function of Wire Diameter, Wire Spacing, and Wavelength Shield Absorption Loss Nomograph Nomograph for Determining Magnetic Field Reflection Loss Nomograph for Determining Electric Field Reflection Loss Nomograph for Determining Plane Wave Reflection Loss Shielding Effectiveness of Aluminum Foil Shielded Room Shielding Effectiveness of Copper Foil Shielded Room Formation of Permanent Overlap Seam Good Corner Seam Design Pressure Drop Through Various Materials Used to Shield Ventilation Openings Typical Single-Point Entry for Exterior Penetrations (Top View) Entry Plate Showing Rigid Cable, Conduit, and Pipe Penetrations Effect of Rod Length on Ground Resistance Grounding of 120/208V 3-Phase, 4-Wire Wye Power Distribution System Grounding of Single-Phase, 3-Wire 110/220V Power System Grounding of 28 VDC 2-Wire DC Power System Connecting Ground Subsystems for Collocated Shelters Greater than 20 Feet Apart . .

Method of Grounding a Fence

1-155

1-155 1-156

1-158 1-161 1-165 1-166 1-167 1-168 1-168 1-169 1-169 1-170 1-174 1-175 1-180 1-181 1-183 1-184 1-189 1-192 xii

F igu re Page

7-14 True Equivalent Circuit of a Bonded System . . . . . . . . . . . . . . . . . . . . . 7-24 7-15 Measured Bonding Effectiveness of a 9-1/2 Inch Bonding Strap . . . . . . . . . . . . . 7-27 7-16 Measured Bonding Effectiveness of 2-3/8 Inch Bonding Strap . . . . . . . . . . . . . . 7-28 7-17 Basic Diagram of the Corrosion Process . . . . . . . . . . . . . . . . . . . . . . . 7-30 7-18 Anode-to-Cathode Size at Dissimilar Junctions . . . . . . . . . . . . . . . . . . . . 7-35 7-19 Techniques for Protecting Bonds Between Dissimilar Metals. . . . . . . . . . . . . . 7-35

8-1 8-2 8-3 8-4 8-5 8-6 8-7 8-8 8-9 8-10 8-11 8-12 8-13 8-14 8-15 8-16

8-17 8-18

8-19 8-20 8-21 8-22 8-23 8-24

8-25 8-26 8-27 8-28 8-29

Electromagnetic Transmission Through a Slot

Transmission Line Model of Shielding

Absorption Loss for One Millimeter Shields Wave Impedance Versus Distance from Source Reflection Loss for Iron, Copper, and Aluminum With a Low Impedance Source. . .

Universal Reflection Loss Curve for a Low Impedance Source Plane Wave Reflection Loss for Iron, Copper, and Aluminum Universal Reflection Loss Curve for Plane Waves Universal Reflection Loss Curve for High Impedance Field

Reflection Losses for Iron, Copper, and Aluminum With a High Impedance Source . .

Graph of Correction Term (C) for Copper in a Magnetic Field Absorption Loss and Multiple Reflection Correction Term When I’ = 1 Theoretical Attenuation of Thin Copper Foil Theoretical Attenuation of Thin Iron Sheet Measured Shielding Effectiveness of High Permeability Metals Measured Shielding Effectiveness of High Permeability Material as a Function of Measurement Loop Spacing Measured Shielding Effectiveness of Two Sheets of High Permeability Metal Measured and Calculated Shielding Effectiveness of Copper Screens to Low Impedance Fields Shielding Effectiveness of a Perforated Metal Sheet as a Function of Hole Size Shielding Effectiveness of a Perforated Metal Sheet as a Function of Hole Spacing Slot Radiation (Leakage) Shielding Effectiveness Degradation Caused by Surface Finishes on Aluminum Influence of Screw Spacing on Shielding Effectiveness

Shielding Effectiveness of AMPB-65 Overlap as a Function of Screw Spacing Along Two Rows, 1.5 Inches Apart Shielding Effectiveness of an AMPB-65 Joint as a Function of Overlap Typical Mounting Techniques for RF Gaskets Enlarged View of Knitted Wire Mesh Shielding Effectiveness of Conductive Glass to High Impedance Waves Shielding Effectiveness of Conductive Glass to Plane Waves

8 - 3 8-4 8-9

8-10 8-12 8-13 8-14 8-15 8-16 8-17 8-22 8-22 8-26 8-26 8-29

8-29 8-32

8-37 8-40 8-40 8-43 8-44 8-46

8-46 8-47 8-49 8-50 8-54 8-55 xiii

Figure P a g e

8-30 8-31 8-32

8-33 8-34 8-35 8-36 8-37

8-38 8-39 8-40

10-1 10-2 10-3 10-4

10-5

10-6

10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14 10-15

Light Transmission Versus Surface Resistance for Conductive Glass Shielding Effectiveness of Some Building Materials Center Area Attenuation of Induced Voltage by 15 Foot High Single-Course Reinforcing Steel Room Surface Transfer Impedance Shielding Effectiveness of Various Types of RF Cables as a Function of Frequency . . .

Connector for Shield Within a Shield RF-Shielded Connector Effectiveness of Circumferential Spring Fingers for Improving the Shielding of a Connector Use of Finger Stock for Door Bonding Coaxial Loop Arrangement for Measuring Shield Effectiveness Coplanar Loop Arrangement for Measuring Shield Effectiveness

EMP From High Altitude Bursts

Schematic Representation of High-Altitude EMP Generation Surface-Burst Geometry Showing Compton Electrons and Net Current Density, Short-Circuit Current Induced at the End of a Semi-Infinite Above-Ground Wire By an Expodential Pulse The Normalized Current Waveform for Various Valves of the Depth Parameter (Expodential Pulse) Short Circuit Current Induced at the Base of a Vertical Riser by a Vertically Polarized Incident Wave Shield to Exclude Electromagnetic Fields Electromagnetic Penetration Through Small Apertures Shielding Integrity Near Interference - Carrying External Conductors Magnetic Field Penetration of Apertures Exclusion of Waveguide Current From Interior of Facility Waveguide Feedthroughs Bellows With Slitted Sleeve Waveguide Attachment Braided Wire Sleeve Clamped to Waveguide Stuffing Tube for Waveguide

8-55 8-57

8-58 8-62 8-62 8-65 8-65

8-66 8-69 8-75 8-75

10-2 10-2 10-4

10-7

10-8

10-9 10-11 10-12 10-14 10-16 10-19 10-20 10-22 10-23 10-24 xiv

LIST OF TABLES

Table

2-1 Facility Ground System: Purposes, Requirements, and Design Factors. . . . . . . . 2-6

2-2 Approximate Soil Resistivity. . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9 2-3 Resistivity Values of Earthing Medium. . . . . . . . . . . . . . . . . . . . . . . . 2-10

2-4 Resistance Distribution for Vertical Electrodes. . . . . . . . . . . . . . . . . . . . 2-21 2-5 Simple Isolated Electrodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-22 2-6 Resistance Accuracy Versus Probe Spacing . . . . . . . . . . . . . . . . . . . . 2-43 2-7 Step Voltages for a Buried Vertical Ground Rod. . . . . . . . . . . . . . . . . . . . 2-50 2-8 Methods of Reducing Step Voltage Hazards. . . . . . . . . . . . . . . . . . . . . . 2-56 2-9 Effect of Moisture Content on Earth Resistivity. . . . . . . . . . . . . . . . . . . . 2-66

2-10 Effect of Temperature on Earth Resistivity.. . . . . . . . . . . . . . . . . . . . . 2-66

3-1 Range of Values for Lightning Parameters . . . . . . . . . . . . . . . . . . . . . . 3-16

5-1 Properties of Annealed Copper Wire. . . . . . . . . . . . . . . . . . . . . . . . . 5-2 5-2 Parameters of Conductor Materials . . . . . . . . . . . . . . . . . . . . . . . . . 5-3 5-3 DC Parameters of Some Standard Cables.. . . . . . . . . . . . . . . . . . . . . . 5-11 5-4 Sixty-Hertz Characteristics of Standard Cables. . . . . . . . . . . . . . . . . . . . 5-11 5-5 One-Megahertz Characteristics of Standard Cables. . . . . . . . . . . . . . . . . . 5-12

5-6 Impedance Comparisons Between #12 AWG and 1/0 AWG.. . . . . . . . . . . . . . . 5-12

7-1 DC Resistance of Direct Bonds Between Selected Metals . . . . . . . . . . . . . . . . 7-8 7-2 Ratings of Selected Bonding Techniques. . . . . . . . . . . . . . . . . . . . . . . 7-18 7-3 Calculated Inductance of a 6 Inch (15.2 cm) Rectangular Strap . . . . . . . . . . . . . 7-20 7-4 Calculated Inductance of 0.05 Inch (1.27 mm) Thick Straps. . . . . . . . . . . . . 7-20

7-5 Calculated Inductance of Standard Size Cable . . . . . . . . . . . . . . . . . . . 7-21 7-6 Standard Electromotive Series. . . . . . . . . . . . . . . . . . . . . . . . . . . 7-32 7-7 Galvanic Series of Common Metals and Alloys in Seawater. . . . . . . . . . . . . . . 7-33

8-1 Electrical Properties of Shielding Materials at 150 kHz. . . . . . . . . . . . . . . . . 8-7 8-2 Absorption Loss, A, of 1 mm Metal Sheet. . . . . . . . . . . . . . . . . . . . . . . 8-8

8-3 Coefficients for Magnetic Field Reflection Loss.. . . . . . . . . . . . . . . . . . . 8-11

8-4 Calculated Reflection Loss in dB of Metal Sheet, Both Faces . . . . . . . . . . . . . . 8-18 8-5 Coefficients for Evaluation of Re-Reflection Correction Term, C. . . . . . . . . . 8-20 8-6 Correction Term C in dB for Single Metal Sheet.. . . . . . . . . . . . . . . . . . . 8-21 8-7 Calculated Values of Shielding Effectiveness. . . . . . . . . . . . . . . . . . . . . 8-23 8-8 Measured Shielding Effectiveness in dB for Solid-Sheet Materials . . . . . . . . . . . . 8-28

8-9 Summary of Formulas for Shielding Effectiveness. . . . . . . . . . . . . . . . . . . 8-30 8-10 Magnetic Material Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 8-31 xv

LIST OF TABLES (Continued)

Table

8-11

8-12 8-13 8-14

8-15 8-16

8-17 8-18 8-19

Calculated Values of Copper Thin-Film Shielding Effectiveness in dB Against Plane-Wave Energy Effectiveness of Non-Solid Materials Against Low Impedance and Plane-Waves Effectiveness of Non-Solid Shielding Materials Against High Impedance Waves Comparison of Measured and Calculated Values of Shielding Effectiveness for No. 22, 15 mil Copper Screens Characteristics of Conductive Gasketing Materials Shielding Effectiveness of Hexagonal Honeycomb Made of Steel With 1/8-Inch Openings l/P-Inch Long Comparison of Cable Shields Connector Application Summary Characteristics of Commercially Available Shielded Enclosures

8-33 8-38 8-39

8-41 8-48

8-51 8-60 8-64 8-67

9-1 Summary of the Effects of Shock . . . . . . . . . . . . . . . . . . . . . . . . . . 9-2

10-1 Shielding by Diffusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-10 xvi

1.1 GENERAL.

CHAPTER 1

FACILITY GROUND SYSTEM

1.1.1 This handbook addresses the practical considerations for engineering of grounding systems, subsystems, and other components of ground networks. Electrical noise reduction is discussed as it relates to the proper installation of ground systems. Power distribution systems are covered to the degree necessary to understand the interrelationships between grounding, power distribution, and electrical noise reduction.

1.1.2 The information provided in this handbook primarily concerns grounding, bonding, and shielding of fixed plant telecommunications-electronics facilities; however, it also provides basic guidance in the grounding of deployed transportable communications/electronics equipment.

1.1.3 Grounding, bonding, and shielding are approached from a total system concept, which comprises four basic subsystems in accordance with current Department of Defense (DOD) guidance. These subsystems are as follows:

a . An earth electrode subsystem.

b . A lightning protection subsystem.

c . A fault protection subsystem.

d . A signal reference subsystem.

1.2 APPLICATION. This handbook provides technical information for the engineering and installation of military communications systems related to the background and practical aspects of installation practices applicable to grounding, bonding, and shielding. It also provides the latest concepts on communications systems grounding, bonding, and shielding installation practices as a reference for military communications installation personnel.

1.3 DEFINITIONS. A glossary of unique terms used in this handbook is provided in Appendix A. All other terms and definitions used in this handbook conform to those contained in Joint Chiefs of Staff Publication No.

1. (JCS Pub 1), FED-STD-1037, MIL-STD-463, and the Institute of Electrical and Electronics Engineers (IEEE) dictionary.

1.4 REFERENCED DOCUMENTS. Publications related to the subject material covered in the text of this handbook are listed in Appendix B. The list includes publications referenced in the text and those documents that generally pertain to subjects contained in the handbook but are not necessarily addressed specifically.

l - l

1.5 DESCRIPTION. The ground system serves three primary functions which are listed below. A good ground system must receive periodic inspection and maintenance to retain its effectiveness. Continued or periodic maintenance is aided through adequate design, choice of materials, and proper installation techniques to ensure that ground subsystems resist deterioration or inadvertent destruction and thus require minimal repair to retain their effectiveness throughout the life of the facility.

a . Personnel safety. Personnel safety is provided by low-impedance grounding and bonding between equipment, metallic objects, piping, and other conductive objects, so that currents due to faults or lightning do not result in voltages sufficient to cause a shock hazard.

b . Equipment and facility protection.Equipment and facility protection is provided by low-impedance grounding and bonding between electrical services, protective devices, equipment, and other conductive objects, so that faults or lightning currents do not result in hazardous voltages within the facility. Also, the proper operation of overcurrent protective devices is frequently dependent upon low-impedance fault current paths.

c . Electrical noise reduction. Electrical noise reduction is accomplished on communication circuits by ensuring that (1) minimum voltage potentials exist between communications-electronics equipments, (2) the impedance between signal ground points throughout the facility to earth is minimal, and (3) that interference from noise sources is minimized.

1.5.1 Facility Ground System. All telecommunications and electronic facilities are inherently related to earth by capacitive coupling, accidental contact, and intentional connection. Therefore, ground must be looked at from a total system viewpoint, with various subsystems comprising the total facility ground system. The facility ground system forms a direct path of known low impedance between earth and the various power, communications, and other equipments that effectively extends in approximation of ground reference throughout the facility. The facility ground system is composed of an earth electrode subsystem, lightning protection subsystem, fault protection subsystem, and signal reference subsystem.

a . Earth electrode subsystem. The earth electrode subsystem consists of a network of earth electrode rods, plates, mats, or grids and their interconnecting conductors. The extensions into the building are used as the principal ground point for connection to equipment ground subsystems serving the facility. Ground reference is established by electrodes in the earth at the site or installation. The earth electrode subsystem includes the following: (1) a system of buried, driven rods interconnected with bare wire that normally form a ring around the building; or (2) metallic pipe systems, i.e., water, gas, fuel, etc., that have no insulation joints;

or (3) a ground plane of horizontal buried wires. Metallic pipe systems shall not be used as the sole earth electrode subsystem. Resistance to ground should be obtained from the appropriate authority if available or determined by testing. For EMP considerations, see Chapter 10.

b . Lightning protection subsystem. The lightning protection subsystem provides a nondestructive path to ground for lightning energy contacting or induced in facility structures. To effectively protect a building, mast, tower, or similar self-supporting objects from lightning damage, an air terminal (lightning rod) of adequate mechanical strength and electrical conductivity to withstand the stroke impingement must be provided. An air terminal will intercept the discharge to keep it from penetrating the nonconductive outer coverings of the structure, and prevent it from passing through devices likely to be damaged or destroyed. A

1-2 low-impedance path from the air terminal to earth must also be provided. These requirements are met by either (1) an integral system of air terminals, roof conductors, and down conductors securely interconnected to provide the shortest practicable path to earth; or (2) a separately mounted shielding system, such as a metal mast or wires (which act as air terminals) and down conductors to the earth electrode subsystem.

c . Fault protection subsystem. The fault protection subsystem ensures that personnel are protected from shock hazard and equipment is protected from damage or destruction resulting from faults that may develop in the electrical system. It includes deliberately engineered grounding conductors (green wires) which are provided throughout the power distribution system to afford electrical paths of sufficient capacity, so that protective devices such as fuses and circuit breakers installed in the phase or hot leads can operate promptly.

If at all possible the equipment fault protection conductors should be physically separate…