142010-26-0138_BUF_UA_Observatory_Roof_Replacement_Statement_of_Work_Attachment_2A.pdf

Department of Commerce National Oceanic & Atmospheric Administration National Weather Service

NATIONAL WEATHER SERVICE MANUAL 30-4106

April 25, 2017

Maintenance, Logistics, and Facilities

Facilities Management, NWSPD 30-41

LIGHTNING PROTECTION, GROUNDING, BONDING, SHIELDING, AND SURGE

PROTECTION REQUIREMENTS

NOTICE: This publication is available at: http://www.nws.noaa.gov/directives/.

OPR: W/OF2 (W. Freeman) Certified by: W/OF2 (M. Burkes)

Type of Issuance: Routine

SUMMARY OF REVISIONS: This directive supersedes NWSM 30-4106, “Lightning

Protection, Grounding, Bonding, Shielding, and Surge Protection Requirements”, dated July 16, 2014. Changes made to reflect the NWS Headquarters reorganization effective April 1, 2015. It includes the following major additions:

a. See “record of changes” on the following page.

Signed 4/11/2017

Deirdre Reynolds Jones. Date

Director, Office of Facilities http://www.nws.noaa.gov/directives/

NWSM 30-4106 April 25, 2017

U.S. Department of Commerce

National Oceanic and Atmospheric Administration

National Weather Service

Lightning Protection, Grounding, Bonding, Shielding, and Surge Protection

Requirements

NWSM 30-4106

NWSM 30-4106 April 25, 2017

(This page intentionally left blank.)

NWSM 30-4106 Technical Manual Deficiency Report

INSTRUCTIONS: Use the form provided here to comment on the content of this manual, suggest improvements, or identify deficiencies. Please be as specific as possible in describing deficiencies and recommended solutions. You may complete the form electronically within Adobe Reader and then either submit the form electronically or in hard copy as follows:

Electronic Submission: E-mail the completed form to Will.Freeman@noaa.gov Hard-Copy Submission: Print the completed form and mail to:

National Weather Service

Facilities Management Branch W/OF2 c/o Will Freeman

1325 East-West Highway, SSMC2

Silver Spring, MD 20910-3280

PAGE

PARA/FIG/

TABLE NO.

COMMMENT

RECOMMENDED SOLUTION:

TYPE OF COMMENT: Deficiency Improvement

REMARKS:

Name of Submitter:

Address:

City/State/Zip:

Date Submitted:

NWS USE ONLY

Date Rcvd Control No. Comment Publication Date

Record of Changes

Change

No.

Date

Title or Brief Description

Entered By

1 1.2 Added: IEEE Std. 1692 as a required reference document & Motorola R56B as a required reference document Page 1-1 (page 27 of 184)

LPGI &

Affiliates

2 1.2 Added: definition of a “low resistance as a value = 1.0 ohms”, a value necessary to minimize lightning induced GPR Page 1-1 (page 27 of 184)

LPGI &

Affiliates

3 Added an Appendix A1: Lightning Audit and Safety Checklist as a required audit for the protection of equipment and personnel pages 120 of 184 through page 130 of 184

LPGI &

Affiliates

4 2.5.2.1 C Added: “Arrester response time shall be less than 5 nanoseconds in order to capture the lightning current spike” Page 2-5 (39 of 184)

LPGI &

Affiliates

5 Added a Chapter 3: Radial Grounding, Electrical Protection, Equipment Specifications and Installation Guidelines for NWS Fac Facilities pages 100 of 184 through page 112 of 184

LPGI &

Affiliates

6 2.7.5.4 Added: “Nonmetallic fuel storage tanks shall not be installed.”

Page 2-15 (page 49 of 184)

LPGI &

Affiliates

7 Added: Figures 3-1, 3-2, 3-3, and 3-4 pages 109 of 184 through page 112 of 184

LPGI &

Affiliates

8 2.5.1 Surge Levels Added: less than five (5) nanoseconds is required without malfunction Page 2-3 (page 37 of 184)

LPGI &

Affiliates

9 2.5.2 Added: Silicone Avalanche Diode (SAD) and Metal Oxide Varistor (MOV) Page 2-4 (page 38 of 184)

LPGI &

Affiliates

10 2.5.4.3 C Added: Silicone Avalanche Diode (SAD) with a response time of less than 5 nanoseconds Page 2-8 (page 42 of 184)

LPGI &

Affiliates

11 2.6.3 C Added: Silicone Avalanche Diode (SAD) with a response time of less than 5 nanoseconds Page 2-10 (page 44 of 184)

LPGI &

Affiliates

12 Index expanded to accommodate additions and changes to NSW Manual

LPGI &

Affiliates

NWSM 30-4106 APRIL 25 2017

ii

TABLE OF CONTENTS

Section Title Page

Chapter 1 Introduction........................................................................................................ 1-1

1.1 Purpose and Scope ............................................................................................... 1-1

1.2 Minimum Requirements for Lightning Protection .............................................. 1-1

1.3 Organization of the Manual ................................................................................. 1-1

1.4 Applicable Documents......................................................................................... 1-3

1.5 Acronyms and Abbreviations .............................................................................. 1-5

1.6 Acknowledgments ............................................................................................... 1-6

Chapter 2 Lightning Protection Design, Engineering, Acquisition, Installation, and

Maintenance for NWS Facilities and Equipment ........................................... 2-1

2.1 Surge and Transient Protection Requirements .................................................... 2-1

2.1.1 Existing Electronic Equipment Designs ................................................ 2-1

2.1.2 Installation by Others ............................................................................. 2-1

2.2 External Lines and Cables ................................................................................... 2-1

2.2.1 Fiber-optic Lines .................................................................................... 2-1

2.2.2 Balanced Pair Lines ............................................................................... 2-1

2.2.3 Ferrous Conduit ..................................................................................... 2-2

2.2.4 Ferrous Conduit Penetration of Facility ................................................ 2-2

2.2.5 Existing Unused Metallic Conduit, Conductors, and Cables ................. 2-2

2.3 Interior Lines and Cables ..................................................................................... 2-2

2.4 Electronic Equipment Transient Susceptibility Levels ........................................ 2-2

2.5 Power Line Surges ............................................................................................... 2-3

2.5.1 Surge Levels .......................................................................................... 2-3

2.5.2 Facility AC Surge Protection Device .................................................... 2-4

2.5.2.1 Characteristics ...................................................................... 2-4

2.5.2.2 Packaging ............................................................................. 2-5

2.5.2.3 Installation ............................................................................ 2-6

2.5.3 Surge Protection Devices for Distribution and Branch Panels .............. 2-7

2.5.4 Electronic Equipment Power Entrance .................................................. 2-7

2.5.4.1 Characteristics ...................................................................... 2-7

2.5.4.2 Packaging ............................................................................. 2-8

2.5.4.3 DC Power Supply Transient Suppression ............................ 2-8

2.6 Conducted Signal, Data, and Control Line Transients ........................................ 2-8

2.6.1 Transient Levels ..................................................................................... 2-9

2.6.1.1 Surge Protective Device Testing Compliance ..................... 2-9

2.6.2 Protection Design................................................................................... 2-9

2.6.3 Characteristics...................................................................................... 2-10

2.6.4 Location of Landline Transient Protection .......................................... 2-10

2.6.5 Installation of Suppression Components at Electronic Equipment ...... 2-11

2.6.6 Externally Mounted Electronic Equipment ......................................... 2-11

2.6.7 Axial Landlines .................................................................................... 2-11 i

TABLE OF CONTENTS (Continued)

2.6.7.1 Protection Design ............................................................... 2-11

2.6.7.2 Metal Bulkhead Connector Plates ...................................... 2-12

2.6.7.3 Installation of Suppression Components

at Facility Entrances ........................................................... 2-12

2.6.7.4 Installation of Suppression Components

at Electronic Equipment Entrances ..................................... 2-13

2.6.8 Location of Transient Protection .......................................................... 2-13

2.6.9 Fiber-optic Cable .................................................................................. 2-13

2.7 Lightning Protection System Requirements ....................................................... 2-13

2.7.1 Materials ............................................................................................... 2-14

2.7.2 Main Conductors .................................................................................. 2-14

2.7.2.1 Structural Steel Used as Main Conductors ......................... 2-14

2.7.3 Hardware .............................................................................................. 2-14

2.7.3.1 Fasteners ............................................................................. 2-14

2.7.3.2 Fittings ................................................................................ 2-14

2.7.4 Guards .................................................................................................. 2-14

2.7.5 Bonds.................................................................................................... 2-14

2.7.5.1 Metallic Bodies Subject to Direct Lightning Discharge ... 2-15

2.7.5.2 Metallic Bodies Subject to Induced Charges ...................... 2-15

2.7.5.3 Exhaust Stack Grounding ................................................... 2-15

2.7.5.4 Above-Ground Fuel and Oil Storage Tanks ....................... 2-15

2.7.6 Conductor Routing ............................................................................... 2-15

2.7.6.1 Down Conductors on Fiberglass Mounting Poles .............. 2-16

2.7.7 Down Conductor Terminations ............................................................ 2-16

2.7.8 Buildings .............................................................................................. 2-16

2.7.8.1 Air Terminals...................................................................... 2-16

2.7.8.2 Number of Down Conductors ............................................ 2-16

2.7.8.3 Metal Parts of Buildings ..................................................... 2-16

2.7.8.4 Roof-Mounted Antennas .................................................... 2-17

2.7.8.5 Radomes Not Mounted on Towers ..................................... 2-17

2.7.8.6 Upper Air Buildings ........................................................... 2-17

2.7.9 Antenna Towers ................................................................................... 2-18

2.7.9.1 Number of Down Conductors ............................................ 2-18

2.7.9.2 Towers Without Radomes .................................................. 2-18

2.7.9.3 Radomes ............................................................................. 2-18

2.7.9.4 Towers With Radomes ....................................................... 2-18

2.7.9.5 Antenna Protection ............................................................. 2-19

2.7.9.6 Tower Guying ..................................................................... 2-19

2.7.9.7 Waveguide, Coaxial Line, and Conduit Protection ............ 2-20

2.7.9.8 Staircase/Ladder Protection ................................................ 2-21

2.7.10 Fences ................................................................................................... 2-21 vi

2.7.10.1 Fences and Gates ................................................................ 2-21

2.7.10.2 Overhead Power Line Considerations................................ 2-21

2.7.11 Radar Towers ....................................................................................... 2-22

2.7.11.1 Main Ground Plate and Power Distribution ....................... 2-23

2.7.11.2 Roof, Structural Steel, Reinforcing, and Other

Metal Element Bonding ..................................................... 2-23

2.7.11.3 Signal, Communications, Coaxial Cables, and

Control Line Protection ...................................................... 2-23

2.7.11.4 Signal Grounding ............................................................... 2-23

2.7.11.5 Multipoint Grounding ........................................................ 2-23

2.7.11.6 Single-Point Grounding ..................................................... 2-24

2.8 Earth Electrode System Requirements .............................................................. 2-24

2.8.1 Site Survey ........................................................................................... 2-24

2.8.2 Design .................................................................................................. 2-24

2.8.2.1 Chemical Enhancements .................................................... 2-25

2.8.2.2 Chemical Rods ................................................................... 2-25

2.8.2.3 Engineered Soils ................................................................ 2-26

2.8.2.4 Coke Breeze ....................................................................... 2-26

2.8.2.5 Ground Dissipation Plates (Noncorrosive Soils) ............... 2-27

2.8.2.6 Installation in Corrosive Soils ............................................ 2-28

2.8.3 Configuration ....................................................................................... 2-28

2.8.4 Ground Rods ........................................................................................ 2-28

2.8.4.1 Material and Size ............................................................... 2-28

2.8.4.2 Spacing ............................................................................... 2-28

2.8.4.3 Depth of Rods .................................................................... 2-28

2.8.4.4 Location ............................................................................. 2-28

2.8.4.5 Chemical Enhancement ..................................................... 2-29

2.8.5 Interconnections ................................................................................... 2-30

2.8.6 Access Well ......................................................................................... 2-30

2.9 Electronic Multipoint Ground System Requirements ........................................ 2-30

2.9.1 Facilities Requiring a Signal Reference Structure ............................... 2-31

2.9.1.1 Equipotential Planes in New Facilities .............................. 2-31

2.9.1.2 SRS Methods in Existing Facilities ................................... 2-32

2.9.1.3 Bonding Electronic Equipment to the SRS ........................ 2-32

2.9.1.4 Facilities Without SRS ....................................................... 2-33

2.9.2 Ground Plates, Cables, and Protection ................................................ 2-33

2.9.2.1 Ground Plates and Busses .................................................. 2-33

2.9.2.2 Ground Conductors ............................................................ 2-34

2.9.2.3 Protection ........................................................................... 2-34

2.9.3 Building Structural Steel ...................................................................... 2-35

2.9.3.1 Metal Building Elements ................................................... 2-35 iv

2.9.4 Interior Metallic Piping Systems .......................................................... 2-35

2.9.4.1 Ground Connections ........................................................... 2-35

2.9.5 Electronic Supporting Structures ......................................................... 2-35

2.9.5.1 Conduit ............................................................................... 2-36

2.9.5.2 Cable Trays and Wireways ................................................. 2-36

2.9.6 Multipoint Grounding of Electronic Equipment .................................. 2-36

2.9.6.1 Electronic Signal Return Path ............................................ 2-37

2.9.6.2 Shield Terminations of Coaxial and Other Cables ............. 2-37

2.9.7 Electronic Equipment Containing Both Low- and High-

Frequency Circuits ............................................................................... 2-37

2.10 Electronic Single-Point Ground System Requirements ..................................... 2-37

2.10.1 Ground Plates ....................................................................................... 2-37

2.10.2 Isolation ................................................................................................ 2-37

2.10.3 Resistance ............................................................................................. 2-38

2.10.4 Ground Conductor Size ........................................................................ 2-38

2.10.4.1 Main Ground Conductor..................................................... 2-39

2.10.4.2 Trunk and Branch Ground Conductors .............................. 2-39

2.10.4.3 Electronic Equipment Ground Conductors ........................ 2-39

2.10.4.4 Interconnections ................................................................. 2-39

2.10.5 Labeling ................................................................................................ 2-39

2.10.6 Equipment Requiring Electronic SPGs ................................................ 2-39

2.10.6.1 Electronic SPGs .................................................................. 2-39

2.10.6.2 Electronic SPG Terminals .................................................. 2-39

2.10.6.3 Isolation .............................................................................. 2-39

2.10.6.4 Electronic Signal Lines and Cables .................................... 2-40

2.10.6.5 Termination of Individual Shields ...................................... 2-40

2.10.6.6 Termination of Overall Shields .......................................... 2-40

2.10.6.7 Single-Point Grounding of Electronic Equipment .............. 2-40

2.11 National Electrical Code Grounding Compliance .............................................. 2-43

2.11.1 Grounding Electrode Conductors ......................................................... 2-43

2.11.2 Equipment Grounding Conductors ...................................................... 2-45

2.11.3 Color-Coding of Conductors ................................................................ 2-45

2.11.3.1 Ungrounded Conductors ..................................................... 2-45

2.11.3.2 Grounded Conductors ......................................................... 2-45

2.11.3.3 Equipment Grounding Conductors ..................................... 2-46

2.11.3.4 Conductor Routing ............................................................. 2-46

2.11.3.5 Non-Current-Carrying Metal Equipment Enclosures ......... 2-46

2.12 Other Grounding Requirements ......................................................................... 2-47

2.12.1 Electronic Cabinet, Rack, and Case Grounding ................................... 2-47

2.12.1.1 Mounting Surfaces ............................................................. 2-47

2.12.2 Receptacles ........................................................................................... 2-47 vi

2.12.3 Equipment Power Isolation Requirements .......................................... 2-48

2.12.4 Portable Operational Equipment.......................................................... 2-49

2.12.5 Fault Protection .................................................................................... 2-49

2.12.5.1 Metal Control Shafts .......................................................... 2-49

2.12.5.2 Shielded Compartments ..................................................... 2-49

2.12.6 AC Power Filters ................................................................................. 2-49

2.12.7 Grounding of RF Transmission Lines and Antennas ........................... 2-49

2.12.7.1 Satellite Ground Station Antenna Grounding

(Directly to Building EES) ................................................. 2-49

2.12.7.2 Satellite Ground Station Antenna Grounding

(Connecting to the Ground Test Well) ............................... 2-50

2.12.7.3 Rooftop Antennas With an Existing LPS .......................... 2-50

2.12.7.4 Rooftop Antennas Without an Existing LPS ..................... 2-50

2.13 Bonding Requirements ...................................................................................... 2-50

2.13.1 Resistance ............................................................................................ 2-50

2.13.2 Methods ............................................................................................... 2-51

2.13.2.1 Exothermic Welds .............................................................. 2-51

2.13.2.2 Welds ................................................................................. 2-51

2.13.2.3 Dissimilar Metals ............................................................... 2-51

2.13.2.4 Mechanical Connections .................................................... 2-52

2.13.3 Bonding Straps and Jumpers ............................................................... 2-54

2.13.4 Fasteners .............................................................................................. 2-55

2.13.5 Metal Elements Requiring Bonding .................................................... 2-55

2.13.5.1 Earth Electrode Risers ........................................................ 2-55

2.13.5.2 Counterpoise Cables .......................................................... 2-55

2.13.5.3 Underground Metallic Pipes and Tanks ............................. 2-55

2.13.5.4 Steel Frame Buildings ........................................................ 2-56

2.13.5.5 Interior Metallic Pipes ........................................................ 2-56

2.13.5.6 Electrical Supporting Structures ........................................ 2-56

2.13.5.7 Flat Bars ............................................................................. 2-56

2.13.6 Temporary Bonds ................................................................................ 2-56

2.13.7 Inaccessible Locations ......................................................................... 2-56

2.13.8 Coupling of Dissimilar Metals ............................................................. 2-56

2.13.9 Surface Preparation .............................................................................. 2-56

2.13.9.1 Paint Removal .................................................................... 2-56

2.13.9.2 Inorganic Film Removal .................................................... 2-56

2.13.9.3 Area To Be Cleaned ........................................................... 2-57

2.13.9.4 Final Cleaning .................................................................... 2-57

2.13.9.5 Completion of the Bond ..................................................... 2-57

2.13.9.6 Refinishing of the Bond ..................................................... 2-57

2.13.9.7 Machined Surfaces ............................................................. 2-57 ix

2.13.9.8 Surface Platings or Treatments .......................................... 2-57

2.13.10 Bond Protection ................................................................................... 2-58

2.13.10.1 Paint ................................................................................... 2-58

2.13.10.2 Inaccessible Locations ....................................................... 2-58

2.13.10.3 Compression Bonds in Protected Areas ............................. 2-58

2.13.10.4 Corrosion Protection .......................................................... 2-58

2.13.10.5 Vibration ............................................................................ 2-58

2.13.11 Bonding Across Shock Mounts ........................................................... 2-58

2.13.12 Enclosure Bonding ............................................................................... 2-58

2.13.12.1 Subassemblies .................................................................... 2-59

2.13.12.2 Equipment .......................................................................... 2-59

2.13.13 Connector Mounting ............................................................................ 2-59

2.13.14 Shield Terminations ............................................................................. 2-59

2.13.15 RF Gaskets ........................................................................................... 2-59

2.14 Shielding Requirements ..................................................................................... 2-60

2.14.1 Conductor and Cable Shielding ........................................................... 2-60

2.14.1.1 Signal Lines and Cables ..................................................... 2-60

2.14.1.2 Termination of Individual Shields ..................................... 2-60

2.14.1.3 Termination of Overall Shields .......................................... 2-60

2.14.1.4 Wire and Cable Routing ..................................................... 2-63

2.15 Electrostatic Discharge Minimization, Control, and Prevention ....................... 2-63

2.15.1 Hard and Soft Grounds ........................................................................ 2-64

2.15.1.1 Hard Grounds ..................................................................... 2-64

2.15.1.2 Soft Grounds ...................................................................... 2-64

2.15.1.3 Panel-to-Understructure Resistance ................................... 2-65

2.16 Additional Guidelines ........................................................................................ 2-65

Chapter 3 Radial Grounding, Electrical Protection Equipment Specifications and

Installation Guidelines for NWS Facilities…………………………………...……………..3-1

3.1 Purpose ................................................................................................................ 3-1

3.2 Applicability ...................................................................................................... 3-63

3.3 Tower and Equipment Building Installation Recommendations ....................... 3-63

3.3.1 Grounding System Design and Grounding System Eval. Method ...... 3-64

3.3.2 Design of Ideal Tower and Equipment Building Earth Grounding ..... 3-64

3.3.3 Placing Ground Rods and Bonding to Metallic Objects ...................... 3-64

3.3.4 Grounding Conductor Requirements Inside Equipment Bldg ............. 3-65

3.3.5 AC Power Grounding Electrode and DC Rectifier.............................. 3-64

3.3.6 Transient Voltage Surge Suppression (TVSS) .................................... 3-64 viii

3.3.7 Coaxial Cable, Waveguide and Bulkhead Panel ................................. 3-65

3.3.8 Communication Facility Isolation from a Lightning Induced Ground

Potential Rise (GPR)............................................................................ 3-65

3.3.9 Equipment Building Lightning Protection System ............................. 3-65

3.4 Personnel Safety .............................................................................................. 3-63 ix

Appendix A Lightning Safety Checklist for NWS Sites ...................................................... A-1

Appendix A1 Lightning Audit and Safety Checklist for NWS Sites………………………A1-1

Appendix B Lightning Protection Checklist ........................................................................ B-1

Appendix C Lightning Protection Rationale........................................................................ C-1

Appendix D Grounding Requirements for Nonstructural Metal Elements...................... D-1

Appendix E Electrical Ground Loops .................................................................................. E-1

Appendix F Typical ESD Event and EMI Meter .................................................................F-1

Appendix G “Fall of Potential” Method for Resistance Measurements............................ G-1

Appendix H Types of Lightning Protection Systems............................................................ H-1

Appendix I Alternative Lightning Protection System for Upper Air Building

(Catenary Type) ..................................................................................................... I-1

GLOSSARY................................................................................................................... Glossary-1

INDEX................................................................................................................................. Index-1 x

LIST OF FIGURES

Figure Title Page

Figure 2-1 Bonding of Grounding Conductor to Its Enclosed Conduit for Used Conductors ............................................................................................ 2-3

Figure 2-2 Waveguide, Coaxial Line, and Conduit Penetration (for NWS Facility Only) . 2-12

Figure 2-3 Lightning Protection for Upper Air Buildings (Franklin Rod Design) .............. 2-17

Figure 2-4 Lightning Protection for Radomes and Radar Antenna

Platforms (Crown of Thorns) ............................................................................. 2-19

Figure 2-5 Multiple Guy Wire and Anchor Grounding ....................................................... 2-20

Figure 2-6 Grounding a Fence ............................................................................................. 2-22

Figure 2-7 Fall of Potential Method for Measuring Ground Resistance ............................. 2-25

Figure 2-8 Ground Rod and Chemical Enhancement Material Installation ........................ 2-26

Figure 2-9 Grounding Trench Detail ................................................................................... 2-27

Figure 2-10 Ground Plate Detail ............................................................................................ 2-29

Figure 2-11 Concrete Grounding Access Well ...................................................................... 2-31

Figure 2-12 Facility Grounding System ................................................................................ 2-32

Figure 2-13 Grounding Ring Used for a Signal Reference Grid ........................................... 2-33

Figure 2-14 Electronic Single-Point Ground System Installation ......................................... 2-38

Figure 2-15 Single-Point Grounding for an Individual Unit or Piece of

Electronic Equipment ......................................................................................... 2-41

Figure 2-16 Single-Point Electronic Ground Bus Bar Installation in Rack or Cabinet ......... 2-42

Figure 2-17 Separately Derived System ................................................................................ 2-44

Figure 2-18 Order of Assembly for Bolted Connections ....................................................... 2-47

Figure 2-19 Bonding of Connectors to Mounting Surface .................................................... 2-48

Figure 2-20 Grounding of Overall Cable Shields to Connectors and Penetrating Walls ....... 2-61

Figure 2-21 Grounding of Overall Cable Shield to Terminal Strip ....................................... 2-63

Figure 3-1 Ideal Lightning-Dissipating Single-Point Grounding System………………….

Figure 3-2 Master Ground Bar (MGB) bonding sequence using PANI methodology……..

Figure 3-3 Current flow from a lightning induced GPR without any isolation protection

Figure 3-4 No Current flow from a lightning induced GPR using isolation protection xi

LIST OF TABLES

Table Title Page

Table 2-1 Line-to-Ground Surge Levels for 120/240, 120/208 Y and 277/480 Y Service Line ................................................................................ 2-4

Table 2-2 NEMA Enclosure Types ...................................................................................... 2-6

Table 2-3 Conducted Landline Transient Levels ................................................................. 2-9

Table 2-4 Size of Electronic Multipoint Ground Conductors ............................................ 2-34

Table 2-5 Minimum Number of Twists for Power Conductors ......................................... 2-46

Table 2-6 Acceptable Couplings Between Dissimilar Metals ........................................... 2-52

Table 2-7 Torque Requirements for Bolted Bonds ............................................................ 2-53

Table 2-8 Metal Connections for Aluminum and Copper Jumpers ................................... 2-55

Table 2-9 Minimum Separation Distance Between Signal and Power Cables .................. 2-64

CHAPTER 1

Introduction

1-1

CHAPTER 1

Introduction

1.1 Purpose and Scope

This manual provides design, engineering, acquisition, installation, and maintenance direction and guidance for implementation of effective lightning protection for use by technical staff both at the headquarters and regional levels. The design and installation direction and guidance in this document provide a systematic approach to minimizing electrical hazards to personnel, damage to facilities and electronic equipment from lightning, transients, electrostatic discharge (ESD), power faults, and electromagnetic interference. These electrical provisions shall apply to any new construction or major renovation being performed after the date of the adoption of this manual. Existing electrical installations that do not comply with the provisions of this manual shall be permitted to continue in use without any corrections. If major renovations (defined in the

Glossary) are to be made to existing electrical systems, or major renovations to existing buildings are undertaken, or major additions are planned, then compliance with the manual is required.

1.2 Minimum Requirements for Lightning Protection

National Weather Service (NWS) facilities and systems are located in such diverse physical and electrical environments that each may require different design and installation methods. However, all should meet the minimum NWS requirements for safe lightning protection. Users should become familiar with the information contained herein and apply it to specific design and installation requirements for new facilities, as well as for maintaining and retrofitting existing facilities.

The minimum requirements for bonding and grounding are those specified by IEEE Std. 1692:

"IEEE Guide for the Protection of Communication Installations from Lightning Effects", and the

National Fire Protection Association’s NFPA 70, National Electrical Code. The minimum requirements for lightning protection are those specified by IEEE Std. 1692: "IEEE Guide for the

Protection of Communication Installations from Lightning Effects", and the NFPA 780, Standard for Installation of Lightning Protection Systems. These guidelines provide information intended to aid engineers in design and installation methods for lightning protection of NWS facilities. A critical link in the proper operation of electronic equipment is to have an effective low-resistance facility grounding system. An effective low-resistance facility grounding system design required to minimize lightning strike current or lightning induced Ground Potential Rise (GPR) is less than one (1.0) ohm to remote earth.

All contractors performing work at an NWS facility involving installation of a lightning protection system shall meet the requirements of this manual, if it is part of the contract statement of work (SOW).

1.3 Organization of the Manual

Chapter 2 of this manual specifies requirements for surge and transient protection, lightning protection, earth electrode system (EES), electronic multipoint ground system (MPG), electronic single-point ground system (SPG), electrostatic discharge (ESD) minimization, control and prevention requirements for cables, and National Electrical Code (NEC) compliance.

Additional information is provided in eight appendixes:

1-2

Appendixes A, A1 and B include checklists and audit outline for lightning safety and lightning protection.

Appendixes C through I provide information supplementary to the main text.

1-3

A glossary and index are also included at the end of the manual.

Comments and suggestions from users of this manual are welcome and may be submitted in electronically or in hard copy using the Technical Manual Deficiency Report immediately following the title page of this manual.

1.4 Applicable Documents

The following documents are applicable to the subject of this manual. Unless stated otherwise, National Weather Service organizations performing operations shall use the latest available issue or revision of each document listed.

American National Standards Institute (ANSI)/Institute of Electrical and Electronics

Engineers

ANSI/IEEE C62.41 Recommended Practice on Surge Voltages in Low Voltage

AC Power Circuits

ANSI/IEEE C62.45 IEEE Guide on Surge Testing for Equipment Connected to

Low-Voltage AC Power Circuits

ANSI/IEEE 1100

Emerald Handbook

ANSI/IEEE 142

Green Handbook

Recommended Practice for Powering and Grounding

Electronic Equipment

Grounding of Industrial and Commercial Power Systems

Motorola R56B Standards and Guides for Communication Sites

IEEE STD 100 IEEE Standard Dictionary of Electrical and Electronics

Terms

IEEE STD 1692 IEEE Guide for the Protection of Communication

Installations from Lightning Effects

IEEE STD 367 IEEE Recommended Practice for Determining the

Electrical Power Station Ground Potential Rise and

Induced Voltage From a Power Fault

Federal Aviation Administration

FAA-STD-019c Lightning Protection, Grounding, Bonding and Shielding

Requirements for Facilities

FAA-STD-019d Lightning and Surge Protection, Grounding, Bonding and

Shielding Requirements for Facilities and Electronic

Equipment

Military Documents

NOTE: If the guidance in this manual differs from that specified in a referenced document, the guidance in this manual shall govern.

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MIL-HDBK 419A Grounding, Bonding, and Shielding for Electronic

Equipment and Facilities

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National Fire Protection Association (NFPA)

NFPA 70 National Electrical Code

NFPA 780 (2004 Edition) Standard for the Installation of Lightning Protection

Systems

Underwriters Laboratories, Inc.

UL 96 Standard for Lightning Protection Components

UL 96A Standard for Installation Requirements for Lightning

Protection Systems

UL 1449 (2nd Edition) Standard for Safety for Transient Voltage Surge

Suppressors

1.5 Acronyms and Abbreviations

The following list contains all approved acronyms and abbreviations used within the National

Weather Service Facilities Lightning Protection Manual.

AC alternating current

AIC amperes interrupting capacity

AWG American wire gauge

DC direct current

EES earth electrode system

EGC equipment grounding conductor

EMI electromagnetic interference

EPP equipotential plane

ESD electrostatic discharge

FAA Federal Aviation Administration

GE grounding electrode

GEC grounding electrode conductor

GFCI ground fault circuit interrupter for personnel protection

GFPE ground fault protection for equipment

GP groundable point

GPS Global Positioning System

HVAC heating, ventilation, and air conditioning kcmil kilocircularmil

LPS lightning protection system m meter mA milliamp

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MCOV maximum continuous operating voltage

MPG (Electronic) Multipoint Ground System

MIC meteorologist in charge mm millimeter

MSDS Material Safety Data Sheet

NEC National Electrical Code

NEMA National Electrical Manufacturers Association

NLSI National Lightning Safety Institute

NFPA National Fire Protection Association nS nanoseconds

NWS National Weather Service

PVC polyvinyl chloride

RF radio frequency

RGS rigid galvanized steel

RMS root mean square

SGS Satellite Ground Station

SPD surge protection device

SPG (Electronic) Single-Point Ground

SRG signal reference grid

SRS signal reference structure

UL Underwriters Laboratories Inc.

V Volt

W Watt

1.6 Acknowledgments

The National Weather Service would like to thank the Grounding and Surge Protection (GASP) workgroup within the Federal Aviation Administration and the National Lightning Safety Institute

(NLSI) for their assistance in developing this manual.

CHAPTER 2

Lightning Protection Design, Engineering, Acquisition, Installation, and Maintenance for NWS Facilities and Equipment

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CHAPTER 2

Lightning Protection Design, Engineering, Acquisition, Installation, and Maintenance for NWS Facilities and Equipment

2.1 Surge and Transient Protection Requirements

Lines, cables, and facilities will be protected against the effects of lightning. Ferrous conduit should be used to shield external lines and cables to minimize inductive coupling of transients from lightning discharges. Guard wires should be used to protect buried cables from direct lightning strikes. This will minimize inductive coupling of transients from nearby lightning strikes. Fiber-optic lines and balanced metallic lines should be used when feasible. Electrical and electronic equipment will be protected against conducted and radiated surges and transients from all power, signal, control and/or status lines. Integrated circuits, transistors, diodes, solid-state voltage regulators, capacitors, miniature relays, miniature switches, and miniature transformers, etc., are susceptible to damage and operational upset caused by transients. Transient suppression will be provided at the entrance to any National Weather Service (NWS) facility and all electronic equipment for protection against conducted electrical transients. A surge protection device (SPD), capable of shunting energy represented by the surge levels in Table 2-1 (see Section 2.5.1), should be installed at the facility’s electric power service entrance. All manufacturer SPDs should be listed and labeled according to the Underwriters Laboratories Inc. (UL) standard UL 1449 (2nd edition), and should be tested according to Institute of Electrical and Electronics Engineers standard IEEE C62.45.

2.1.1 Existing Electronic Equipment Designs

For existing electronic equipment designs, equipment-level transient suppression is required. It may be either internal or external to the equipment it is protecting but must follow the grounding, bonding, and shielding methods indicated herein.

2.1.2 Installation by Others

Electronic equipment not installed by its manufacturer or supplier will have all items of material required for installation of transient protection delivered to the site.

2.2 External Lines and Cables

2.2.1 Fiber-optic Lines

Fiber-optic lines are not susceptible to environmental interference or induction fields produced by lightning. Fiber-optic lines should replace metallic conductors when economically and technically feasible. Ferrous conduit shielding and suppression components are not required for fiber-optic conductors unless these lines use metallic or electrically conductive sheaths or strength members.

2.2.2 Balanced Pair Lines

When possible, signals in metallic conductors routed externally between facility shelters and buildings to externally mounted electronic equipment should be designed as balanced, two-conductor, twisted, shielded circuits.

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2.2.3 Ferrous Conduit

In this manual, ferrous conduit is defined as rigid galvanized steel (RGS) conduit. Buried alternating current (AC) power conductors or cables to a facility should be enclosed in watertight, ferrous conduit. The buried ends of this conduit will be bonded to the earth electrode system

(EES) with a bare copper conductor No. 2 AWG, minimum. Conduit joints and fittings will be electrically continuous with a bonding resistance of less than 5 milliohms between joined parts.

Conduit enclosing AC power service entrance conductors will be terminated using conductive fittings from the distribution transformer case and to the service entrance cabinet as the situation dictates. Conduit enclosing signal, control, status, power, or other conductors to electronic equipment will be terminated using conductive fittings. Any metallic conduit entering the facility must be bonded to the EES to minimize transient conductance.

2.2.4 Ferrous Conduit Penetration of Facility

Direct connections will be made from the conduit to a bulkhead connector plate or ground plate

(installed externally or immediately after entering the building) that is connected directly to the

EES using exothermic welds and a minimum No. 4/0 AWG stranded copper conductor. This will be done at each location where above-ground conduits first penetrate a shelter or a building’s exterior wall.

2.2.5 Existing Unused Metallic Conduit, Conductors, and Cables

Bonding of the grounding conductor to its enclosed conduit should be done as shown in the example in Figure 2-1.

2.3 Interior Lines and Cables

All permanently installed interior cables and conductors exceeding 6 feet in length will be enclosed end-to-end in conduit. (Temporary extension cables used for performing maintenance work are excluded.)

2.4 Electronic Equipment Transient Susceptibility Levels

Commercial off-the-shelf (COTS) electronic equipment supplied as part of the facility should be provided with transient protection. This protection will reduce surges and transients to below the equipment susceptibility level determined by the manufacturer. The equipment susceptibility level is the online transient level that may cause damage, degradation, or upset to the connected electronic equipment. The combined facility and equipment entrance protection will be coordinated to limit transients at the equipment entrance to a level below the equipment susceptibility level. The following characteristics should be evaluated. All manufactured electronic equipment must meet the transient susceptibility levels specified in IEEE C62.41.

a. Component Damage Threshold. The transient level sufficient to render the component nonfunctional or operationally deficient.

b. Component Degradation Level. The transient voltage or energy level sufficient to shorten the useful life of the component.

c. Operational Upset Level. The transient voltage or energy level sufficient to cause an unacceptable change in operating characteristics for a duration in excess of 10 milliseconds for analog equipment or a change of logical state for digital equipment.

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Figure 2-1. Bonding of Grounding Conductor to Its Enclosed Conduit for Used Conductors

2.5 Power Line Surges

A surge protection device (SPD) will be provided at the main service disconnecting means to reduce transients conducted to electronic equipment. SPDs may be installed on the load side or line side at the service entrance. Additional SPDs may need to be provided at power line entrances to electronic equipment. SPDs at the main service disconnecting means, as well as at electronic equipment power line entrances, will be functionally compatible.

2.5.1 Surge Levels

Surge levels and the number of occurrences for selection or design of facility AC arresters are provided in Table 2-1. The table defines line-to-ground surge currents and the number of occurrences for low voltage (less than 600 VAC) services. In the table, the 8/20 microsecond current waveform defines a transient reaching peak value in 8 microseconds and decays to 50 percent of that peak value in 20 microseconds. SPDs should be able to tolerate surges of shorter duration i.e., less than five (5) nanoseconds without malfunction.

Remove Insulation at Contact Point

Split Bolt Conductor

Insulated Circuit Grounding Conductor Ground Conductor to Busing

Ground Bushing

Conduit

Source: FAA-STD-019d LM1

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Table 2-1. Line-to-Ground Surge Levels for 120/240, 120/208 Y and 277/480 Y Service Line

Surge Current Amplitude

8 by 20 Microsecond Waveform

(*4 by 10 Microsecond)

Number of Surges

(Lifetime)

10 kA 1,500

20 kA 700

30 kA 375

40 kA 50

50 kA 8

60 kA 6

70 kA 4

100 kA* 2

180-240 kA* 1

2.5.2 Facility AC Surge Protection Device

A facility AC surge protection device should be installed on the load side of the facility service disconnect. The SPD may be a combination of solid-state circuits i.e., silicone avalanche diode

(SAD), metal oxide varistor (MOV), or other devices that fire faster than 5 nanoseconds. For services with a neutral, SPD elements will be connected to protect all surge modes of coupling:

line to ground (L-G), line to neutral (L-N), and neutral to ground (N-G). For services without a neutral, SPD elements will be installed on the primary side, line to line (L-L) and each line to ground (L-G), of any NWS-owned distribution transformer.

Examples:

a. 3-phase, 4-wire DELTA-WYE neutral grounded system: The SPD will be connected for 7 modes of coupling: (L-N) 3, (L-G) 3, and (N-G) 1.

b. 3-phase, 3-wire DELTA grounded system: The SPD will be connected (L-L) 3, (L-G) 3 for 6 modes of coupling.

Using these examples, all possible entry points of overvoltage and surge currents are secured.

2.5.2.1 Characteristics

Minimum functional and operational characteristics of facility SPDs installed at the service disconnect will be as follows:

a. Maximum Continuous Operating Voltage (MCOV). MCOV is the maximum voltage that can be applied across SPD terminals with the device remaining in an off

(nonconducting) state. The MCOV of the SPD will not be less than 115 percent of nominal root mean square (RMS) line voltage.

b. Leakage Current. Leakage current across the device terminals will not exceed 100 microamps at MCOV.

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c. Turn-on Voltage. Turn-on voltage is the minimum voltage across SPD terminals that will cause the arrester to turn on and conduct. Turn on voltage should not exceed

125 percent of MCOV. The arrester response time shall be less than five (5) nanoseconds in order to capture the entire lightning current spike.

d. Discharge (Clamp) Voltage. Clamp voltage is the maximum voltage appearing across an arrester output terminal while conducting surge currents. Clamp voltage should not exceed 160 percent of MCOV.

e. Overshoot Voltage. Overshoot voltage will not exceed 2 times the SPD clamp voltage for more than 10 ns. Overshoot voltage is the surge voltage level appearing across the SPD terminals before the device turns on and clamps the surge to the specified…