Blunt rod lightning protection advantages over nonconventional approaches

Blunt Rod Lightning Protection Advantages

Over Nonconventional Approaches

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Contents

Introduction

Rod Lightning Protection Ad-vantages Over Nonconventional Approaches

Background of Lightning Protection

ESE and LDA Debunked

Legal Precedence

Summary

Acknowledgements

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WP043/USA/0416 © Copyright 2016 DEHN Inc.

Introduction

This article discusses the advantages of Blunt Rod (BR) Light-ning Protection over Nonconventional early streamer emission (ESE) and lightning dissipation array (LDA) approaches.The objective of this article is to show the reader that the blunt end Franklin rod remains the safest and most effective means of protecting structures from the risk of fire and damage due to lightning.Many standards provide excellent insight into best practices, suggested methods and installation guidelines for lightning protection systems using BR lightning rod deployment over the region to be protected. The NFPA 780 and IEC 62305 both provided fire safety guidance and both adhere to BR practices with no recognition, suggestion or reference to ESE or LDA types.These industry-leading systems always promote a facility-wide approach addressing, air terminations, down conductors, earthing electrodes and surge protective devices.The BR technology developed by Franklin in 1752 remains the only open peer-reviewed and proven means to assure fire safety due to lightning. And the insurance underwriters indus-try only recognizes BR technology. These advantages give en-gineering and design professionals the confidence needed to install best measures for lightning risk mitigation.

Background of Lightning Protection

A lightning protection system functions by intercepting the direct lightning strike energy as it hits near a structure and safely diverting it to the Earth. Much has been published on this topic in great detail by academic experts and industry-leading standards bodies.Lightning phenomena is roughly based on the discharge of huge charge regions high in the atmosphere into the Earth. This discharge initiates high overhead and starts a rapid de-scent “in the general direction” of Earth with no real high resolution target. In fact, the actual final discharge pathway is only established after the charge region is close enough to the ground to create a finer grained resolution electric field based influence for small step leader coronas to initiate from all of the available sources at ground level. Several leaders all “reach out” to the rapidly descending charge region and the “winner” establishes the plasma bolt and subsequent return strokes. In other words, the lightning does not have a real plan when it starts to fall, but only near the end do the step leaders feel enough electric field influence to reach up and connect. This all occurs in 10’s to 100’s of microseconds.The Franklin rod allows a preferred step leader jump off point and establishes the discharge path through the rod and down conductors into the Earth, where the charge is dissipated safe-ly. This is the only proven means of avoiding lightning damage and is prescribed by the NFPA and IEC peer-reviewed lightning standards.

Figure 1 Excerpt from DEHN Lightning Protection Guide (1)

Figure 2 Photo courtesy SCW 2016

leader

Figure 2.1.5

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ESE and LDA Debunked

Nonconventional lightning protection apparatus fall into ei-ther the ESE or LDA types. The effectiveness of these appara-tus over conventional BR systems has been disproved in such comprehensive work as Uman and Rakov with the University of Florida, “A Critical Review of Nonconventional Approaches to Lightning Protection” (2002). This work offers a thorough investigation of the claims of nonconventional approaches and shows no actual advantage of these ESE and LDA systems.This paper from Uman (2) (3) , and many other noted works on this topic point to the best real world studies conducted in New Mexico by Moore (4) who found that BR type LPS were struck 12 times over seven years where as ESE and sharp tip systems were never struck. This paper also pointed to the FAA 1990 report showing Tampa area airports struck by lightning even though they were equipped with LDA apparatus intended to dissipate strikes before they are attracted to a structure.When compared side by side in a laboratory, Noack et al (5), testing has shown that blunt tip rods actually attract the strike with an overwhelming % of strike occurrence. Even when in-stalled side by side with and ESE, the BR franklin device works best. And the LDA still was struck a low % of times, and did not scare away the lightning test discharge.Here is the basic diagram of an ESE product. The rising ambi-ent electric field is said to charge up the internal capacitance to a level that self-initiates an upward bound leader, inducing Figure 3 Excerpt from Noack Testing (5)

Figure 4 ESE Photo courtesy MHD 2016

+ + + +

Result of 420 discharges:¨ 200 to the Franklin lightning rod (47.6 %)¨ 165 to the ESE devices (39.3 %)¨ 55 without puncture (13.1 %)

1 Lightning rod (Franklin)3 Pulsar 60, Helita, France4 Prevectron S6, Indelec, France2 Dynasphere 3000, GLT, Australia

1 m

h =

2.5

m

1 2 3 4

Generator: DC 45 kVSwitching voltage: DC 840 kV

Figure 5 LDA Photo courtesy SCW 2016

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a strike to the ESE and shunting the energy to Earth. No third party testing has produced any sort of leader advantage or tendency of the ESE device to be struck in preference to con-ventional BR protection.Uman and Rakov have shown rigorously that the time advan-tage and extra distance coverage claims of ESE supporters are invalid. The “early streamer” cannot send a step leader up to the cloud any faster than a BR Franklin rod.The basic summary drawn from world-leading experts on non-conventional lightning protection systems does not support the manufactures claims of those ESE and LDA apparatus.There is no experimental evidence that ESE apparatus can pro-tect a larger volume of airspace by virtue of provoking a faster upward leader speed to attract lightning to itself from farther away. An LPS system that is deployed using these ESE param-eters will leave much of the area unprotected when compared to any conventional evaluation.Lightning elimination arrays such as the LDA cannot prevent the initiation of lightning in the thunder cloud and are unprov-en to be able to avert an imminent lightning strike. These LDA systems are in fact struck themselves and offer no more pro-tection than the placement of similar sized BR air terminations.As illustrated in the photo in figure 5 of an LDA installation in Fort Pierce, FL. Notice the conventional lightning rods along building perimeter. It is not clear if these rods were installed before or after the concrete monopole and wire mesh LDA.

Legal Precedence

There is also a series of legal precedence found against non-conventional lightning protection vendors related to false advertising and possible product liability as seen in Federal District Court of Arizona 2003. Several manufactures of nonconventional apparatus have em-ployed legal bullying in a failed attempt to force the NFPA to acknowledge their products as reported by Mousa (6). This sort of rubber stamp would have been used as an endorsement in their strategic marketing campaigns. Fortunately for con-sumers, engineers and architects, this campaign to forcibly ac-knowledge the now defunct article 781 was stopped after the manufactures were unable to present any evidence to support their product claims. Further, in 2003 these ESE vendors were convicted of falsely advertising the claimed improvements over conventional BR technology.Additional government action was taken in Malaysia and re-ported by Hartono (7) in 2008 declaring ESE devices must not be employed due to damage suffered upon buildings while within the “protection zone” of the ESE devices.And the worst possible scenario has already come to pass ac-cording to the professional assessment of industry leaders. A report released in 2012 (8) by Z. A. Hartono and I. Robiah, two of the world’s leading experts on lightning safety, raises se-

rious questions about the lightning protection equipment in-stalled at Tampa, FL’s Adventure Island water park.In September 2011, a 21-year-old Adventure Island lifeguard was struck by lightning and killed while helping to evacuate patrons from the Key West Rapids water slide. The outdoor wa-ter slide is located between two lightning protection installa-tions, each of which, according to the manufacturer, provides a zone of protection against lightning strikes extending as much as 109 meters. The systems rely on a French-made de-vice, called the Prevectron air terminal, which is not approved by any U.S. safety code or standard and is not supported by independent scientific experts or field data.In commentary related to the death at the park, Bud VanSickle, executive director for the Lightning Protection Institute (LPI) said, “The fact that these ESE systems don’t comply with any U.S. standards should raise serious questions with every ar-chitect, engineer or facility manager responsible for selecting lightning protection systems.“

Summary

Blunt Rod lightning protection systems utilizing industry ac-cepted air terminals, down conductor designs and earthing systems, along with adequate surge protection on the electri-cal wiring systems remains the most effective means to assure equipment and life safety against lightning effects.Existing U.S. standards that offer guidelines towards the man-ufacture and installation of lightning protection systems are developed and updated by Underwriters Laboratory (UL), the National Fire Protection Association (NFPA) and the Lightning Protection Institute (LPI). These standards do not authorize lightning protection for open spaces in the manner employed at Adventure Island.This remains a controversial topic and the industry standards meetings that address the LDA and ESE issues always offer heated discussions. Engineers and designers are encouraged to read all available information on the design of best prac-tice Lightning Protection Systems, and will find the application of BR technology to be the most scientifically peer-reviewed industry standards and underwriter insurance accepted ap-proach.Only the DEHN high voltage insulated cable and insulated air-termination rod system can provide conventional blunt tip Franklin rod protection with an insulated construction to avoid side flash arcing to the protected structure.DEHN has provided the industry with a wide range of com-plaint and certified BR Franklin rod solutions for over 100 years. DEHN is the only manufacture of these innovative, high volt-age isolated, blunt tip lightning rod and conductor systems. These products allow safe down conductor installation and avoid any touch safety danger of flash over or human shock.The DEHN lightning protection products are all thoroughly tested to show the discharge withstand of direct lightning

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Figure 6 The air-termination products are illustrated here.

Figure 7 HVI touch and clearance safety down conductor products are illustrated here.

strike energy. The products meet all guidelines for IEC and UL96A master label protection systems.

The reader is encouraged to review the relevant standards for their location and requirements and select products that offer best in class safety and operational assurance.

For more information contact DEHN, Inc. at www.DEHN-USA.com

Acknowledgements

The Author Mark Hendricks has been in the power quality

industry for 20 years and is the Technical Director with

DEHN, Inc.

(1) DEHN Lightning Protection Guide(2) Uman, M. A., Rakov, V. A.: A Critical Review of Non-

conventional Approaches to Lightning Protection, American Meteorological Society, PP1809/2002

(3) UmanAdd Uman references from his book(4) Moore, C. B., G. D. Aulich, and W. Rison, 2000a:

Measurement of lightning rod response to nearby strikes. Geophys. Res. Lett., 27, 1487-1490.

(5) Noack, F.: Early Streamer Emission devices – Improved lightning protection? ETZ, Offenbach (2002)3-4., p. 2 ff.

(6) Mousa, A. M., National Lightning Safety Institute, Section 5.4.3

(7) (8) Hartono, Z. A.; Mieee a. Robiah, I.: Journal of the Association of Consulting Engineers Malaysia; PP2623/1/2008.



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Blunt rod lightning protection advantages over nonconventional approaches