A Long Term Study on the Performance of Early Streamer Emission Air Terminals in a High Keraunic Region

PGS FORUM

A Long Term Study on the Performance of Early Streamer Emission Air Terminals in a High Keraunic Region

Z.A.Hartono and O. Roniah
Lightning Research Pre. Ltd.
Mail: 457 Jalan B11, Taman Melati
53100 Kuala Lumpur, Malaysia
E-mail: zahartono@ieee.org, robiah@ieee.org

Abstract - The very high keraunic level in Malaysia makes it an ideal location for the field testing of lightning air terminals. The widespread use of the early streamer emission (ESE) air terminals enabled their performance to be studied under real lightning conditions. Lightning strike damage data that would have taken decades to collect in low keraunic regions can be done in a few years only. Using a lighning interception prediction method that was developed by the authors, it was possible to obtain pre-strike and post-strike photographs of the affected buildings. The failure of the ESE air terminals to intercept nearby lightning strikes posed in unacceptable risk to public safety. An earlier version of this study had been submitted to the National Fire Protection Association (USA) in 1999 as part of a review on the efficacy of the ESE air terminals.

Keywords: Air termanals, early streamer emission (ESE), Franklin rods, lightning interception.

1. Introduction

The high keraunic level in Malasia made it an ideal environment for the study of the actual performance of the ESE air terminals under real lightning conditions. The ESE air termanals are the successors to the radioactive air terminals that had been banned in many countries since the late 1980s. The ESE air termanals are claimed to be able to Provide a protective range of up to 100m radius around the structures on which they are installed.

This study was initiated in the late 1980s after it was noted that most buildings equipped with the ESE devices had been struck by lightning. The use of date stamped photography to capture the pre-strike and post-strike images of ESE installed buildings began in the early 1990s after earlier phothographs of lightning damaged buildings were doubted by some Malaysian academics and engineering professionals.
These photographs provided the direct evidece for the performance of the ESE air termanals under real lightning conditions. The first successful post-strike photograph was taken in August 1993, just nine months after the pre-strike photograph was taken. On average, the duration between the pre-strike and post-strike photographs is about 2 years.

The studyas conducted on numerous high-rise and low-rise buildings that had been installed with the low-rise buildings that had been installed with the conventional and unconventional(ESE) air terminals. Most of the study was done on buildings located in the vicnity of KualaLumpur and Shah Alam, two cites where the average annual thunderstorm day is about 250.

The case studies submitted to the NFPA provided indisputable evidence that lightning do strike the buildings after they were installed with the ESE air terminals. They show that the presence of several ESE air termanals, either on the same building or in adjacent buildings, still resulted in lightning strikes on one or more of those buildings.

In the last few years, the number of cases where the lightning damage location (or stricken point)occurred very close to the ESE air termanal has grown significantly. The very close proximuty of the stricken points to the air terminals suggests that their effectiveness is below that of the correctly positoned conbentional air termanal(i.e.Franklin rod).

Studies conducted on buildings equipped with the Franklin rods also exhibited similar stricken points when these rods are not positioned on the high risk locations. Based on this comparison, we conclude that no advantage can be obtained by using the ESE air terminals in protecting the building against direct lightning strikes.

2. Studied on the Efficacy of ESE Air Terminals.

Many studies have been conducted to verify the claims made by the manufacturers test study on radioactive and corona rods conducted by Bouquegneau. [1] explicitly show that there was absolutely no influence on the strike probability.

In a study conducted by Mavkerras et al[2]onthe field performance of radioactive rods, several cases of  failures were reported with the strike points falling within the claimed zone of protection of the ESE devices.

In another study by the same authors, Mackerraset al[3], on ESE air terminals, simple analysis show that the edges of a building will not be protected by an ESE air terminal. The study was presented to the CIGRE Task Force 33.01.03 "Lightning Interception" for the technical meeting held in Milan, Italy, in May 1995.

In a study by Hartono et al[4],[5] using actual field data collected on the distribution of lightning strike damages on buildings, several buildings equipped with the ESE devices were not spared from direct lightning strikes. Some of these data was also Presented to the same CIGRE Rask Force as mentioned above.

For a better understanding  of this subject, Rakov and Unam[6] provide a comprehensive and critical review of the ESE air terminals.

3. Case Studies of Lightning Strikes to Buildings equipped with ESE Air Terminals.

The study was done by taking the pre-strike photographs of the ESE installed buildings from all sides. These buildings were then visually inspected every few months to determine whether any recent lightning strike damage had taken place. Photographs of any new stricken points were taken whenever they were detected and these photographs were then archived for the purpose of this study.

A comparison of the stricken points shows that their shape and size are similar but not identical.

They seemed to be dependent on the number of strokes received, the strength of the lightning stroke current, the shape of the structure and the material composition of the stricken part. Damages to parapet walls made of bricks were found to be more severe than that made of reinforced concrete.

The following case studies show some examples of the pre-strike and post-strike photographs of lightning damaged buildings that were taken recently.

The case studies highlight the very close proximity of some lightning strikes to the ESE air terminals, showing that they are unable to protect the buildings as claimed by their manufacturers.

Case Study #1: Royal Selangor Club (RSC) Annexe Building in Kiara Hill, Kuala Lumpur

This building was installed with an Australian made ESE air terminal mounted on a 5m pole in 1998 (Figure 1). The main roof is approximately 40m long with the air terminal installed in the middle according to the Collection Volume Method (CVM) design.

Although the air terminal is claimed to have a protective range exceeding 50m, lightning reportedly struck and damaged the facade which was about 20m away (Figure 2).

Case Study #2: Wisma Tanah Building, Kuala Lumpur

This government administrative building was installed with a French made ESE air terminal mounted on a 5m guyed pole in 1999. The building was also installed with the Franklin rods but they were located about 0.5m away from the corners of the building (Figure 3).

In 2003, the building was observed to have been struck by lightning on the corner of the building that was about 10m away and about 8m below the air terminal (Figure 4).

The air terminal was claimed to comply with the French standard NFC 17-102 that was developed by the ESE manufacturers. The standard had been domestically criticized by a French scientific agency, INERIS [7], which found that the basis of the standard was unsound and that the manufacturers of the ESE air terminals had not tested their product against the standard. The INERIS report also included the NFPA report on the ESE that was published in 1999.

Case Study #3: Setapak Ria Apartment Buildings

These buildings had been installed with the French made ESE air terminals when they were photographed in 1997. The buildings consist of multi-tiered roofs and the air terminals were centrally located on the highest roof per apartment building.

A recent survey shows that the buildings had been struck several times by lightning. A close inspection shows that some of the stricken points had occurred on the same roof where the air terminals were located (Figures 5 and 6).

In these cases, the stricken points had come to within 10m of the air terminals that were installed at the center of the roof.

Case Study #4: Villa Putri Apartment Buildings, Kuala Lumpur

These 170m high split-level conjoined buildings were installed with the Australian made ESE air terminals mounted on 5m poles. One air terminal was installed per apartment building and they were centrally located on the roof (Figure 7).

The taller apartment block has a square-shaped concrete upper roof structure with rounded corners while the lower apartment block has a semi-circular middle and lower roof structures. According to the ESE manufacturer, these roof structures have much lower field intensification by virtue of their shapes and hence a lower risk of lightning interception.

On the other hand, the air terminal has been designed to provide an enhanced field intensification that could result in a successful capture of lightning strikes.

However, within a five year period, it was observed that seven stricken points had occurred on the rounded edges of the upper, middle and lower roofs. These stricken points clearly show that the enhanced protection claimed by the manufacturer was non-existent (Figure 8).

4. Case Studies of Lightning Strikes to Buildings equipped with Franklin Rods.

The studies show that in nearly all cases of lightning damages to buildings installed with the Franklin rods, the rods were found to have been installed some distance away from the stricken points i.e. the high risk locations.

Where the Franklin rods had been located at the predicted interception point and where the down conductors were position and installed correctly, no lightning damage was observed.

The positions of the air terminal play a crucial role in the design of an effective conventional lightning protection system. This had been highlighted by Darveniza [8] and had been proposed in the draft Australian/New Zealand lightning protection standards [9].

Case Study #5: Damansara Secondary School Buildings, Kuala Lumpur.

These buildings have been installed with the conventional system but the Franklin air terminals and conductors were not positioned at the known high risk locations i.e. at the ridge ends and edges of the gable roof.

As expected, the stricken points occurred at the predicted locations (Figures 9 and 10). The failure of the Franklin rods to intercept the lightning stroke has more to do with erroneous positions of the rods rather than the rods themselves.

Case Study #6: Hicom Apartments, Shah Alam.

Similar to the school buildings mentioned above, the Franklin rods were not positioned at the known high risk locations. Since these buildings have been built more than a decade ago, many of the apartment blocks had been struck by lightning at almost the exact same location i.e. at the ridge ends of the gable roof. In some cases, adjacent blocks of apartment display similar stricken points (Figures 11 and 12).

These damages could have been prevented if the Franklin rods had been installed right on top of the ridge ends. In this way, the recommendations mentioned in the draft Australian/New Zealand standard represent a significant step towards a more effective application of the conventional air terminal and should be seriously considered.

5. Conclusions.

This study provides the direct evidence required to show that the ESE air terminals do not provide the enhanced protection as claimed by their proprietors.

The study has highlighted the following facts:
(a) That the ESE lightning protection technology is scientifically and technically unsound by virtue that some of the buildings equipped with one or more of the devices had been struck by lightning repeatedly over a period of time.
(b) That the enhanced protection claimed by the manufacturers of the ESE air terminals are unfounded by virtue that some of the lightning damaged locations had been found to be very close to and, in many instances, at a lower height than the position of the ESE air terminal.

This study also shows that for the conventional air terminal to be effective in protecting the building from damage by lightning, they must be positioned correctly on the buildings. Since the vulnerable parts of the building are already known, installing an air terminal at these locations will ensure a successful interception of the lightning stroke.

6. References

[1] Bouquegneau, C., “Laboratory tests on some radioactive and corona lightning rods”, 18th International Conference on Lightning Protection, Munich 1985.

[2] Mackerras, D., Darveniza, M. and Liew Ah Choy, “Standard and non-standard lightning protection methods”, Journal of Electrical and Electronic Engineering, Australia, 7, 133-140, 1987.

[3] Mackerras, D., Darveniza, M. and Liew Ah Choy, “Critical review of claimed enhanced lightning protection properties of ESE air terminals for lightning protection of buildings”, report submitted to the CIGRE Task Force 33.01.03, May 1995.

[4] Hartono, Z. A. and Robiah, I., “A method of identifying the lightning strike location on a structure”, International Conference on Electromagnetic Compatibility, Kuala Lumpur 1995.
http://www.elek-kor.com.pl/pdf/narozniki.pdf

[5] Hartono, Z. A., and Robiah, I., “The Collection Surface Concept as a Reliable Method for Predicting the Lightning Strike Location”, 25th International Conference on Lightning Protection, Rhodes - Greece, September 2000
http://www.hvlab.ee.upatras.gr/iclp2000/proceedings/328_333.pdf

[6] Uman, M. A. and Rakov, V. A., “A Critical Review of Non-conventional Approaches to Lightning Protection”, Bulletin of the American Meteorological Society, December 2002
http://plaza.ufl.edu/rakov/Uman&Rakov%20(2000).pdf

[7] Gruet, P, “Etude des Paratonnerres a Dispositif d’Amorcage: Ministere de l’Amenagement du Territoire et de l’Environment”, Institut National de l’Environnement Industriel et des Risques, October 2001
http://www.ineris.fr/recherches/download/PDA.pdf

[8] Darveniza, M.,"The Placement of Air Terminals to Intercept Lightning in Accordance with Standards - Revisited", 26th International Conference on Lightning Protection, Krakow - Poland, September 2002.
http://www.power.nstu.ru/conference/ICLP%202002/proceedings/10a03.pdf

[9] Draft for Public Comment, Australian/New Zealand Standard, Lightning Protection, (Revision of AS/NZS 1768 - 1991), pp. 33
https://committees.standards.com.au/COMMITTEES/EL-024/C0044/DR02359-PDR.pdf