MIL-HDBK-419A Grounding, Bonding, And Shielding For .

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MIL-HDBK-419A29 DECEMBER 1987SUPERSEDINGMIL-HDBK-41921 JANUARY 1982MILITARY HANDBOOKGROUNDING, BONDING, AND SHIELDINGFORELECTRONIC EQUIPMENTS AND FACILITIESVOLUME I OF 2 VOLUMESBASIC THEORYAMSC N/AEMCS/SLHC/TCTSDISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited

DEPARTMENT OF DEFENSEWASHINGTON DC 20301MIL-HDBK-419AGROUNDING, BONDING, AND SHIELDING FOR ELECTRONIC EQUIPMENTS AND FACILITIES1.This standardization handbook was developed by the Department of Defense in accordance withestablished procedure.2.This publication was approved on 29 December 1987 for printing and inclusion in the militarystandardization handbook series.Vertical lines and asterisks are not used in this revision to identify changeswith respect to the previous issue due to the extensiveness of the changes.3.This document provides basic and application information on grounding, bonding, and shieldingpractices recommended for electronic equipment. It will provide valuable information and guidance topersonnel concerned with the preparation of specifications and the procurement of electrical and electronicequipment for the Defense Communications System.The handbook is not intended to be referenced in purchasespecifications 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 considerationsof electrochemistry, metallurgy, electromagnetics, and atmospheric physics. It is the intent to review thishandbook periodically to insure its completeness and currency. Users of this document are encouraged to reportany 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 thishandbook) listed in the Department of Defense Index of Specifications and Standards (DODISS) should beobtained from the DOD Single Stock Point: Commanding Officer, Naval Publications and Forms Center, 5801Tabor 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 beobtained from the sponsor. Copies of all other listed documents should be obtained from the contractingactivity or as directed by the contracting officer.

MIL-HDBK-419APREFACEThis volume is one of a two-volume series which sets forth the grounding, bonding, and shielding theory forcommunications electronics (C-E) equipments and facilities. Grounding, bonding, and shielding are complexsubjects about which in the past there has existed a good deal of misunderstanding. The subjects themselves areinterrelated and involve considerations of a wide range of topics from electrochemistry and metallurgy toelectromagnetic field theory and atmospheric physics.These two volumes reduce these varied considerationsinto a usable set of principles and practices which can be used by all concerned with, and responsible for, thesafety and effective operation of complex C-E systems. Where possible, the principles are reduced to specificsteps. Because of the large number of interrelated factors, specific steps cannot be set forth for every possiblesituation. However, once the requirements and constraints of a given situation are defined, the appropriatesteps 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, andShielding 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 telecommunicationsequipment by reducing noise and providing adequate protection against power system faults and lightningstrikes.This handbook emphasizes the necessity for including considerations of grounding, bonding, and shielding in allphases 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 earthconnections, signal grounding, electromagnetic shielding, and electrical bonding are presented. The subjects arenot covered independently, rather they are considered from the standpoint of how they influence the design ofthe earth electrode subsystem of a facility, the selection of ground reference networks for equipments andstructures, shielding requirements, facility and equipment bonding practices, etc. Volume I also provides thebasic background of theory and principles that explain the technical basis for the recommended practices andprocedures; illustrates the necessity for care and thoroughness in implementation of grounding, bonding, andshielding, and provides supplemental information to assist in the solution of those problems and situations notspecifically addressed.In Volume II, Applications, the principles and theories, including RED/BLACK protection, are reduced to thepractical steps and procedures which are to be followed in structural and facility development, electronicengineering, and in equipment development. These applications should assure personnel equipment andstructural safety, minimize electromagnetic interference (EMI) problems in the final operating system; andminimize susceptibility to and generation of undesirable emanations.The emphasis in Volume II goes beyonddevelopment 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 wordsand terms as they are used herein. If not defined in the glossary, usage is in accordance with Federal Standard1037, Glossary of Telecommunication Terms. Appendix B is a supplemental bibliography containing selectedreferences intended to supply the user with additional material. Appendix C contains the table of contents forthe other volume. Appendix D contains the index for the two-volume set.

MIL-HDBK-419ATABLE OF CONTENTSCHAPTER 1 - FACILITY GROUND 7PageGENERAL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .APPLICATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .DEFINITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .REFERENCED DOCUMENTS. . . . . . . . . . . . . . . . . . . . . . . . . .DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Facility Ground System. . . . . . . . . . . . . . . . . . . . . . . . . . . . .Grounding and Power Distribution Systems . . . . . . . . . . . . . . . . . . . . .Electrical Noise in Communications Systems. . . . . . . . . . . . . . . . . . . .BONDING, SHIELDING, AND GROUNDING RELATIONSHIP . . . . . . . . .GROUNDING SAFETY PRACTICES. . . . . . . . . . . . . . . . . . . . . .1-1l-ll-ll-ll-2l-2l-3l-4l-5l-5CHAPTER 2 - EARTHING AND EARTH ELECTRODE SUBSYSTEM2.1OBJECTIVES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.1.1Lightning Discharge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.1.2Fault Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.1.3Noise Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.1.4Summary of Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.2RESISTANCE REQUIREMENTS. . . . . . . . . . . . . . . . . . . . . . . . . . .2.2.1General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.2.2Resistance to Earth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.2.2.1National Electrical Code Requirements . . . . . . . . . . . . . . . . . . . . .2.2.2.2Department of Defense Communications Electronics Requirements . . . . . . . . .2.2.3Lightning Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.3SOIL RESISTIVITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.3.1General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.3.2Typical Resistivity Ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.3.3Environmental Effects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.4MEASUREMENT OF SOIL RESISTIVITY. . . . . . . . . . . . . . . . . . . . . . .2.4.1General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.4.2Measurement Techniques. . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.4.2.1One-Electrode Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.4.2.2Four-Terminal Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.5TYPES OF EARTH ELECTRODE SUBSYSTEMS. . . . . . . . . . . . . . . . . . . .2.5.1General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.5.2Ground Rods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.5.3Buried Horizontal Conductors. . . . . . . . . . . . . . . . . . . . . . . . . . 2-82-82-82-132-152-152-152-15

TABLE OF CONTENTS (Continued)ParagraphPageGrids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.5.4Plates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.5.5Metal Frameworks of Buildings. . . . . . . . . . . . . . . . . . . . . . . . . .2.5.6Water Pipes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.5.7Incidental Metals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.5.8Well Casings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.5.9RESISTANCE PROPERTIES . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.6Simple Isolated Electrodes . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.6.1Driven Rod. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.6.1.1Other Commonly Used Electrodes . . . . . . . . . . . . . . . . . . . . . . . .2.6.1.2Resistance of Multiple Electrodes . . . . . . . . . . . . . . . . . . . . . . . . .2.6.2Two Vertical Rods in Parallel. . . . . . . . . . . . . . . . . . . . . . . . . .2.6.2.1Square Array of Vertical Rods . . . . . . . . . . . . . . . . . . . . . . . . .2.6.2.22.6.2.3Horizontal Grid (Mesh). . . . . . . . . . . . . . . . . . . . . . . . . . . . .Vertical Rods Connected by a Grid . . . . . . . . . . . . . . . . . . . . . . .2.6.2.4Transient Impedance of Electrodes . . . . . . . . . . . . . . . . . . . . . . . .2.6.3Effects of Nonhomogeneous (Layered) Earth. . . . . . . . . . . . . . . . . . . .2.6.4Hemispherical Electrode . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.6.4.1Vertical Rod . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.6.4.2Grids. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.6.4.3MEASUREMENT OF RESISTANCE-TO-EARTH OF ELECTRODES. . . . . . .2.7Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.7.1Fall-of-Potential Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.7.2Probe Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.7.2.1Extensive Electrode Subsystems. . . . . . . . . . . . . . . . . . . . . . . .2.7.2.22.7.2.3Test Equipments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Three-Point (Triangulation) Method. . . . . . . . . . . . . . . . . . . . . . . .2.7.32.8OTHER CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.8.1Surface Voltages Above Earth Electrodes. . . . . . . . . . . . . . . . . . . . .Step Voltage Safety Limit. . . . . . . . . . . . . . . . . . . . . . . . . . .2.8.1.1Step Voltages for Practical Electrodes. . . . . . . . . . . . . . . . . . . . . .2.8.1.2Flush Vertical Rod. . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.8.1.2.1Buried Vertical Rod . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.8.1.2.2Buried Horizontal Grid. . . . . . . . . . . . . . . . . . . . . . . . . . .2.8.1.2.3Minimizing Step Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.8.1.3Heating of Electrodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.8.2Steady State Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.8.2.1Transient Current. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.8.2.2Minimum Electrode Size . . . . . . . . . . . . . . . . . . . . . . . . . . . 572-572-572-59ii

MIL-HDBK-419ATABLE OF CONTENTS (Continued)ParagraphPage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -662-702-712-712-712-712-75THE PHENOMENON OF LIGHTNING. . . . . . . . . . . . . . . . . . . . . . . .DEVELOPMENT OF A LIGHTNING FLASH. . . . . . . . . . . . . . . . . . . . .INFLUENCE OF STRUCTURE HEIGHT. . . . . . . . . . . . . . . . . . . . . . . .STRIKE LIKELIHOOD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ATTRACTIVE AREA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Structures Less Than 100 Meters High . . . . . . . . . . . . . . . . . . . . . . .Cone of Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .LIGHTNING EFFECTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Flash Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Mechanical and Thermal Effects . . . . . . . . . . . . . . . . . . . . . . . . .Electrical Effects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Conductor

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