Lightning & Surge Protection
What is lightning?
Lightning is a giant spark of electricity in the atmosphere between clouds, the air, or the ground. In the early stages of development, air acts as an insulator between the positive and negative charges in the cloud and between the cloud and the ground. When the opposite charges builds up enough, this insulating capacity of the air breaks down and there is a rapid discharge of electricity that we know as lightning. The flash of lightning temporarily equalizes the charged regions in the atmosphere until the opposite charges build up again. Lightning can occur between opposite charges within the thunderstorm cloud (intra-cloud lightning) or between opposite charges in the cloud and on the ground (cloud-to-ground lightning).
Historically, the study of lightning can be tracked since Benjamin Franklin (1706 – 1790) era. Franklin concluded that clouds are electrically charged. In the experiment where he standing on an electrical stand, holding an iron rod to gain an electrical discharge between the other hand and a ground, concluded that if the clouds were electrically charged, then sparks would jump between the iron rod and a grounded wire. This experiment was furthered performed by Thomas Francois Dalibard (1709 – 1799) in May 1752 where sparks were observed to jump from the iron rod during a thunderstorm. G.W. Richmann (1711 – 1753) was killed by lightning when he proved that thunderclouds have electrical charge. According to Lukasz Staszewski from University of Technology, Poland, Benjamin Franklin endeavoured to test the theory of sparks shared some similarity with lightning using a spire which was being erected in Philadelphia. While waiting for completion of the spire, he got the idea by using a flying object like a kite. In June 1752, it was reported that he raised a kite. Key was attached on his end of the string, and he tied it to a post with a silk thread. As time passed, loose fibers on the string stretching out, he then brought his hand close to the key and a spark jumped the gap. The rain had soaked the line and made it conductive. Although this experiment showed that lightning was a discharge of static electricity, there was little improvement in theoretical understanding for more than 150 years.
Lightning can be formed in four types of processes which are charge separation, leader formation, discharge and re-strike. The process of charge separation is still the subject of research with one hypothesis, the polarization mechanism, which has two components. Firstly, falling droplets of rain become electrically polarized as they fall through the charge separation is trigger by the ionization of an air molecule by an incoming cosmic ray.
A video showing that different lightning discharges at different locations
What causes thunder?
Lightning causes thunder! Energy from a lightning channel heats the air to around 18,000 degrees Fahrenheit. This causes the air to rapidly expand, creating a sound wave known as thunder. The stepped leader causes the initial tearing sound, and the ground streamer causes the sharp click or crack heard at a very close range, just before the main crash of thunder
How a lightning protection system works?
Lightning protection systems have been in use in one fashion or another for over two hundred and fifty years, well before electricity was harnessed as a usable form of power. In the past one hundred years, progressive scientific study has contributed to the body of knowledge concerning lightning and its behavior. Engineering and construction standards for lightning protection have been published in the United States for over one hundred years. During the past century, various governmental and private organizations keeping statistics on the performance of lightning protection systems have found that they are highly effective. Underwriter’s Laboratories statistics showed that these systems prevented damage due to lightning approximately 99% of the time, when installed in accordance with accepted engineering standards.
Why we need lightning protection system?
- Protection of human and livestock against injury / death.
- Prevention of structural damage.
- Reduction of secondary effects
Lightning protection methods
A. Conventional type lightning protection system
BS EN/IEC 62305 is the international standard
B. ESE (Early Streamer Emission ) type lightning protection system
French standard NF C 17-102
Main component of a lightning protection system
I. Air terminal / Air termination network
The role of the air terminal/ air termination is to capture the lightning discharge current and dissipate it harmlessly to earth via down conductor and earthing system.
The Air terminal can take many forms specified by the various engineering standards available. In general, it is a metal device that is connected in an electrically and mechanically robust fashion to the down conductor system. Air termination network is a combination of vertical & horizontal (or at an angle to horizontal) metallic elements of specified properties.
II. Down conductor system
Effective path to the ground that carries a huge lightning current. Copper strips and Copper cables are mostly used But other metals are also allowed by standards)
III. Earth electrode
Earth electrode is the path to discharge lightning current safely to the ground. There are many methods and components are used as earth termination. Diameters of each electrode (for cylindrical type), number of interconnected electrodes, depth, Resistivity of soil are the factors that affect effectiveness of an earth electrode.
Why phoenix contact?
Phoenix Contact is a pioneer in the development of surge protective devices. Decades of experience together with intensive fundamental research in cooperation with universities and technical colleges lay the foundations for the technical expertise required during the development of surge protective devices.
Thier in-house, accredited pulse and high-current laboratory allows them to develop thier products safely and in line with standards from the initial idea right through to series production.
An innovation example: Development of the spark gap
Spark gaps are the powerful components inside surge protective devices. They are able to safely discharge very high currents. Development ranged from open, free-blowing to encapsulated spark gaps. But there was still one problem. The high line follow current.
In 2015, Phoenix Contact brought the first spark gap onto the market that works so perfectly that no more line follow currents occur. This new spark gap is extremely powerful and, due to the fact that there is no line follow current, is also very durable.
The spark gap as the power pack for the new lightning current arresters
The unique spark gap enables the development of compact and high-performance protective devices.Advantages:
- Long service life of the protective devices and the electric installation thanks to a spark gap free line-follow current.
- Space-saving installation with the compact design.
- Easy replacement in the event of servicing with protective devices which all feature a pluggable design.
- Operators are kept informed of the status of the protective device at all times with the optical, mechanical status indicator.
- No mismatching of connectors with mechanical coding.