Articles

Lightning Protection

email_Icon_24X24Contact us to find out which products and services are right for your needs.

Alltec Protection Pyramid Surveys

A Three Part Series

Part III – Lightning Protection

If you missed Part I – “Grounding & Bonding”, or Part II – “Surge Protection”, you may find them here.

This last installment of a three part series relates to the top tier of the Protection Pyramid- direct strike Lightning Protection, the implementation of this capstone tier is additionally required to:

  • Protect critical facilities, equipment, records, and assets.
  • Provide a safe working environment for personnel.
  • Reduce the risk of downtime and lost revenue.
  • Reduce vulnerability of interdependent critical infrastructures, and build a disaster resilient enterprise
  • Minimize liability and maintain a competitive posture.

Grounding & Bonding, and Surge Protection alone are not sufficient to adequately protect a facility. A Lightning Protection System (LPS), should also be incorporated and fully integrated into the facility’s inspection and maintenance program. Along with correctly staged quality surge protection, appropriate bonding and a low impedance and low resistance connection between earth and the LPS components is essential.

In the United States alone, lightning detection systems monitor an average of 25 million flashes of lightning from cloud to ground every year, and lightning is reported to cause $4 billion – 5 billion in damage annually. This destruction can be greatly mitigated with properly designed, installed and maintained Lightning Protection Systems (LPS), which are over 98% effective in preventing damage associated with a lightning strike.

Wrong Lightning Protection 1
Wrong Lightning Protection 2

While elements of grounding systems and surge protection, as described in previous articles, are definitely part of a Lightning Protection System survey, the LPS survey focus should specifically relate to at least one the following standards in order to have a basis for determining and reporting compliance or noncompliance:

  • UL 96A “Standard for Installation Requirements for Lightning Protection Systems”
  • NFPA 780 “Standard for the Installation of Lightning Protection Systems”
  • LPI-175 “Standard of Practice for the Design-Installation-Inspection of Lightning Protection System”
  • NF C 17-102 “Protection against Lightning” Early Streamer Emission Lightning Protection Systems

As with any survey, the best way to start is with a site evaluation:

  • Collect information on types of damages experienced or anticipated by the facility, and create a prioritized outline of survey requirements.
  • Study existing lightning protection system “as-built” drawings.
  • Review site electrical panel layouts, one-line electrical and riser diagrams for power and data lines entering/exiting the facility

Additionally, before the physical walk-through and inspection, it is useful to obtain, review and retain for possible use in the final report, the following:

  • Lightning Protection Specification/Standard related to the installation
  • Site Plan & “Satellite View” using Geographical Coordinates
  • Individual Building/Structure Architectural & Mechanical Rooftop Plans
  • Individual Building/Structure Elevations
  • Individual Building/Structure Wall Sections

After developing an understanding of the facility and its needs, and creating a site specific inspection plan, typical actions include:

  • Perform inspection of structures identified in site evaluation to note/confirm structural material, roof top units, placement, integrity and size of existing air terminals or lightning masts, down conductors, conductor clamps, and ground electrode connections.
  • Note observable services entering the structure and leaving the structure. Note connections of these services to any existing lightning protection system.
  • Determine the integrity of the Lightning Protection System in relation with Grounding and Surge Suppression.
  • Mark-up of existing Lightning Protection System drawings, showing locations of any observed problems and associated photographs.

Annual Inspection, or thorough examination after lightning discharge, roof repairs, construction or modifications which might effect the Lightning Protection System, should include:

  • Air Terminals
  • Bonding Connections to Metal Objects
  • Conductors
  • Ground Connectors
  • Splicers and Connector Fittings
  • Thru-Roof Connectors
  • Evaluation of new additions or protruding structural elements or equipment which may be unprotected

Surge Protection Devices should be inspected every six months or after a major thunderstorm. Every three years, Ground System resistance should be tested per IEEE 81, and the LPS should be tested for continuity.

An on-site survey and evaluation should yield a Survey Report with supporting documentation, including observations, testing and data analysis, and site photographs as needed to document compliance/noncompliance of structural lightning protection systems and include recommendations for any upgrades required to repair nonconformities.

Lightning Protection Example 1

Deviation: The surveillance camera, which was installed after the original lightning protection system installation, is unprotected from a lightning strike. An air terminal is required for the camera since the metal arm does not have a metal thickness of greater than 3/16 of an inch. Also the camera arm lacks a bond to the lightning protection system to prevent side flash.

Reference: Per NFPA 780-2014; paragraph 4.6.2.1 The tip of an air terminal shall be not less than 10 in. (254 mm) above the object or area it is to protect. Paragraph 4.6.1.4 . Metal parts, of a structure that are exposed to direct lightning flashes and that have a metal thickness of 3/16 in. (4.8 mm) or greater shall only require connection to the lightning protection system in accordance with Section 4.8.

Recommendation: Installation of a 5/8 x 18” aluminum air terminal with a 2” aluminum horizontal air terminal clamp base. The air terminal and base shall be installed at the outer portion of the camera arm. A “dead-end” single run conductor shall be spliced to the main run conductor located on the parapet coping with a two-bolt parallel cable splicer.

Reference: NFPA 780-2014 paragraph 4.9.2 Dead Ends. A “dead ended” main conductor shall be permitted between a single strike termination device or connector fitting and a main conductor run under the following conditions: (2) At a main protected roof level, where the horizontal portion of the dead-end conductor is not more than 8ft (2.4 m) in total length.

Lightning Protection Example 2

Deviation: Apparently, during a repair, the air terminal was removed from the coping and is being positioned by the stiffness of the aluminum conductor. No adhesive was present to indicate that the base was re-adhered to the coping after the repairs.

Reference: Per NFPA 780-2014 paragraph 4.6.2.2.1 Air terminals shall be secured against overturning or displacement by one of the following methods:
(1) Attachment to the object to be protected
(2) Braces that are permanently and rigidly attached to the structure.

Recommendation: Remove all existing adhesive from the bottom of the air terminal base, or replace the air terminal base, and adhere the base with an approved roofing adhesive. Confirm the distance between the adjacent air terminals does not exceed twenty feet (20’-0”).

Lightning Protection Example 3

Deviation: The lightning protection cable routed to the through roof cable connector is creating a “U” pocket increasing impedance on the flow of a stroke charge.,/p>

Reference: Per NFPA 780-2014; paragraph 4.9.4.1 Conductors shall maintain a horizontal or downward coursing free from “U” or ”V” (down and up) pockets.

Recommendation: The lightning protection conductor shall be routed from the roof surface to the through roof cable connector at a slope not greater than 3” per foot (3/12).

Reference: NFPA 780-2014; paragraph 4.9.6.1 Conductors shall be permitted to he coursed through air without support for a distance of 3 ft (0.9 m) or less. NFPA 780-2014; paragraph 4.9 Conductors. Main conductors shall interconnect all strike termination devices and shall form two or in or paths from each strike termination device downward, horizontally, or rising at no more than 1/4 slope to connections with grounding electrodes.

This three part series on the topic of “Alltec Protection Pyramid Surveys” stresses the importance of understanding the interrelationship and interdependence of the three tiers in protecting any facility. Even when suitably designed and installed, continuous inspection and maintenance is required for all systems to function.

Without proper grounding, neither the surge suppression nor lightning protection will function correctly. Without surge suppression, equipment is exposed to the secondary effects of lightning as well as internally generated transient voltages. Direct strike lightning protection protects the physical structure and its contents. These three subsystems interlock into a very robust and stable whole.

ALLTEC proposes that its engineering team work with your designated representatives to evaluate your facilities and investigate all problems and concerns related to lightning protection, surge suppression and grounding at the selected facilities. ALLTEC personnel have the skills, experience and tools to accomplish the requirements of this project in a timely and professional manner. We look forward to working with you.

If you have an existing or planned facility, be sure to give ALLTEC a call or email. We can make sure your operation is the safest possible facility, backed by our team of dedicated risk-mitigation experts. If you have a current or future project that needs grounding/bonding solutions, surge suppression or lightning protection please contact ALLTEC at either 1-828-646-9290 or online-info@alltecglobal.com

Rev. 20160929

Big Boom design Logo
Powered by : Big Boom Design : Blog

Share this post with your friends!