Welcome > Press and publications > Fundamental studies on the potential of traditional and active lightning rods
Prof. Dr.Sc.Techn. Eng. Stefan Iliev, ROSTI Ltd. Bulgaria
Eng. Peter Respondek, Dehn+Söhne GmbH+Co.KG, Germany
LABORATORY WORK STUDIES
1. Corona-emission current
Extensive comparative measurements of corona-emission current have been carried out at various types of lightning rods (LR): an ordinary copper rod, aluminum or steel rod (the so called Franklin LR); a simple V-shaped lightning ball-rod, with a diameter of respectively 75 cm and 18 cm; together with an active elliptical LR tip 350 mm.
It was established, that emission current grows with the increase of electrical power of the field E kV/m, but is hardly affected by various types of tips including those of the active LR. All corona electrodes and tips do not emit an increased corona current and are hardly effective as discharge devices, even a V-shaped curved conductor is surpassed in the discharge current.
It has also been noted that at all emission processes, we should take into account the impact of wind as well, which at a given speed may turn away the emission-current.
2. Active lightning rods
For over fifteen years attempts have been made to prove the advantages of the active LR compared with the traditional LR. Numerous publications exist describing the theory and principles as well as hypotheses of the functioning of the active LR. Advertising on a wide scale by producers of the active LR has created the condition of their being mounted in many countries. Probably about 100,000 have been mounted recently in various countries in Europe, America and Asia.
Laboratory studies in France and Australia shows a break-down with the active LR with a time of T = 10 ÷ 60 µs. On this ground we draw the conclusions: the active LRs are much better than the traditional LRs, the protected volume here is considerably larger, the number of LR can be substantially reduced.
The expected 'improvements' in the protective action of the active LR is based on hypotheses, which are not proven scientifically so far and have not seen confirmation in practice.
3. The Institute for Science and Techology at the University of Manchester
Comparative studies, with a examination of a range and stimulation of various possible factors of the process of a lightning stroke and break-down have been conducted. Subject of the study were purchased standard and patented active LR and traditional LR: Dynasphera 3000, GLT, Australia; Pulsar 60 HELITA, France; Prevectron S6, INDELEC, France and a traditional LR - a 1 m. long bar, of massive copper 15 mm thick.
The storm cloud is stimulated by an aluminum board 3x3 with 250 mm thick pipe periphery, placed at a height of 2.5 m. The height of all LR is 1 m. The two LR (active and traditional) at the experiments are placed at an identical distance from the medium point of the highvoltage board. The LRs were subjected to 35 'strokes' or discharges of the impulse generator. After that the places of the LRs were exchanged, excluding any advantage of the positions, and the experiments were conducted once again. Thus the described procedure was done with all active LR cited above.
As a result of 12 test series and 420 discharges were performed, 200 meet the traditional LR (47.6%), 165 meet the active LR (39.3%), at 55 (13.1%) there is no rupture.
The experiments shows that the lightning rupture process has a chance character. In spite of the relatively short air-rupture distance, no greater frequency of rupture through the active LR is established.
These studies represent the full natural spectre of strokes on traditional and active LR at identical electrical geometric conditions. The results do not give any advantage of LR compared to another one.
4. Technical University Darmstadt, Germany
In this research are used impulse waves 1.2/50 µs and 250/2500 µs at a rupture distance of 0.1-4 m. The rupture in the traditional LR appears at a quicker rate (in some cases differences of 122 µs) than at the active LR. The conclusions of this research shows that the active LR and not only ineffective, but also the conception they are based on is erroneous.
COMPARATIVE TESTING IN REAL CONDITIONS
Exceptionally interesting testing has been done at Kuala Lumpur, the capital of Malaysia. Numerous active LR have been mounted there from the 90s, with various forms. This area is characterized with exceptionally high atmospheric activity, with over 200 stormy days a year and this presupposes very good conditions for the study of the action of LR devices in natural conditions.
The initial position on over 25 buildings with mounted active LR is photographed, in order to have documentary proof of damage after strokes of lightning. The sites are observed in the course of several months to several years. There are buildings struck and damaged several times over several months. About 80% of the structures over 60 m. high are struck at least once in the course of 2.5-3 years after the installing of active LR.
The documentation of the damages clearly shows, that they can not protect buildings from direct strokes. There are strokes not only at corners and rims of the structures, but also on the ridge of the roof and the rounded structures, some close to the LR receiver and the areas protected by it.
The conclusion is that there is no ground to consider there is any stronger protective action of active LR.
Reports of direct strokes of lightning in the protectives areas of active LR have been published on many occasions: stroking of a block of flats in Poland, in the Vatican, the rope-bridge Rio-Antirio, near the town of Patra, Greece on the 27.01.2005, the Alcobendas sports hall, around Madrid on 09.10.2005, Judicial Call for Compensation (USA) and elsewhere.
There is also ground for the objection that the lightning strokes could be pointed out in protected areas of traditional LR. There is such a possibility, however here we are speaking of the disputed protective area of the active LR and facilities which are not protected and have been struck in this area. In fact the active LR functions, only as a traditional LR.