PREVECTRON® : On-site testing in real lightning conditions
Camp Blanding results in Florida between 1993 and 1995
Several on-site test sessions carried out at Camp Blanding in Florida, U.S.A. in 1993, 1994 and 1995 gave very useful and interesting results. Three of the typical scenarios encountered are described below.
1. Demonstration of the PREVECTRON®’s abilities : (Fig. 1 & 2).
In these diagrams, the electrical activity of a single rod (Fig. 1 ) can be compared to that of a PREVECTRON® (Fig. 2) as both are subjected at the same moment to an identical electric field. A current greater than 1 amp can clearly be seen at the tip of the PREVECTRON® appearing several dozen microseconds before the initial return stroke. While this is happening, the single rod remains inactive. This is one example of the PREVECTRON®’s onsite abilities.
Figure 1 - Single rod
Figure 2 - PREVECTRON S6.60
2. Demonstration of how the PREVECTRON® works : (Fig. 3).
In this diagram, the PREVECTRON ®’s trigger can be seen in gray operating each time the electric field (in blue) increases. This is the on-site confirmation of how well the PREVECTRON ® works in real conditions.
3. Demonstration of the PREVECTRON®’s resistance to lightning strikes :
After being subjected to 8 lightning discharges, each of more than 10 kA, a standard PREVECTRON® was checked and certified to be in perfect working order. This is the on-site confirmation of the PREVECTRON®’s robust nature.
Figure 3
PREVECTRON® ater
being subjected to 8 lightning discharges, each of more than 10 kA
Cachoeira Paulista results in Brazil between 2000 and 2002
For the first time, video footage allowed scientists to see how the upward leader develops from the PREVECTRON®2 while, in identical field conditions and at the same instant, the simple rod exhibited no discernable activity.
In both cases, the flashes were recorded over at least four frames, or 130ms at 30fps. The two images above were captured during naturally occurring, non-triggered lightning conditions and clearly highlight the truth behind the theory that the PREVECTRON®2’s ionization system provides for the emission of an early streamer.
The data collected also allowed the precursor currents at the top of the PREVECTRON®2 lightning rods to be measured and compared with the activity around the simple rod. The graphs above show the shape and amplitude of the current signals for both types of tip. The initial pulses (low-level corona effects with no propagation) appear simultaneously on the PREVECTRON®2 lightning conductor and the simple rod. However, the shape of the current around the PREVECTRON®2 then shows the triggering of an upward leader, which then propagates until the first return stroke appears (induction saturation). During this time, the similarly sized corona around the simple rod represents its vain attempts to trigger a leader.
A - The PREVECTRON®2’s basic operating principle was verified and shown to comply with the positive results obtained previously at Camp Blanding in Florida and Saint Privat d’Allier in France: the PREVECTRON®2’s ionization system reacts automatically as soon as any sudden build-up in the electrical field - synonymous with a downward leader - is detected.
B - The data collected during the triggered launches highlights the robust construction of the PREVECTRON®2 lightning conductor, capable of withstanding repeated high-intensity lightning strikes: the average current measured in a lightning strike triggered at Cachoeira Paulista is 27kA (compared to just 13.5kA in Florida over the course of the 1993-94 test campaign at Camp Blanding), with an average of 6 return strokes (greater than 3kA).
C - The scientists were able to collect invaluable tropical storm data over the course of each test campaign, while INDELEC’s partners pursued their research projects, involving - among others - the study of electromagnetic interference on overhead telecommunications lines. Video footage taken using high-speed cameras has enabled researchers to collect an unprecedented series of images and other information on the build-up of a lightning strike (see photos of downward stepped leaders taken from video footage).
Single rod
PREVECTRON S6.60
Nadachi results in Japan between 1998 and 2002
This report presents the results of more than 4 years of monitoring from 1st quarter 1998 to 1st quarter of 2002 with dozen of exposures showing cloud/ground flashes.
In 1998, of the 32 impacts - most of which were of the upward type - 29 were caught by the ESE protection system, thereby avoiding considerable damage to the generators and auxiliary equipment. 2 impacted the turbine closest to the protection system and one impacted the turbine farther away.
However, the three probably low intensity impacts that hit the generators only cause traces at the surface of the blades, but no structural damages to the turbines. In December 2001, the Prevectron S6.60 has been changed to a Millenium type, the latest version developed by INDELEC engineers, based on the results of research in real-lightning conditions conducted by the company for the last 10 years. 12 lightning strikes have been recorded on the site from December 14 to December 30 with an impressive 100% success rate for the Prevectron Millenium (the 12 strikes were caught by the ESE air terminal).
Prise de vue en conditions réelles