User:Sudip nair

Lightning Energy

Lightning is a capricious, random and unpredictable event. Its physical characteristics include current levels sometimes in excess of 200 kA and speeds approaching one-third the speed of light. Globally, some 2000 on-going thunderstorms cause about 100 lightning strikes to earth each second.

Because of its heavy investment in equipment (towers, electronic equipment, and satellite dishes), lightning is a major concern for the industry. A broadcast tower, typically the tallest structure in its area, is a prime target of lightning. If your tower or other facilities are a target of lightning strikes, the lightning will destroy your tower as well as the electronic system inside the tower. To avoid these unwanted effects, you should evaluate your lightning protection system.

Lightning is a product of electrically charged storm clouds. The charged clouds induce an opposite charge (ground charge) on the surface of the earth beneath it as they travel through the atmosphere. When the ground charge reaches a structure, the cloud charge pulls it up onto the structure, concentrating the ground charge on and around it. I the ground charge build to a level exceeding the dielectric (insulation resistance) of the intervening air, an arc or lightning strike will occur. The process begins with stepped leaders branching down from the clouds. When they come within close proximity to the ground, approximately 500 feet, the electric field intensity at ground level becomes so strong that objects and structures begin to break down electronically, shooting steamers up toward the stepped leaders. When a streamer and a stepped leader connect, a path is created for a lightning strike.

The phenomenology of lightning strikes to earth, as presently understood, follows an approximate behavior:

1. The downward Leaders from a thundercloud pulse towards earth seeking out active electrical ground targets.

2. Ground-based objects (fences, trees, blades of grass, corners of buildings, Towers, lightning rods, etc., etc.,) emit varying degrees of electric activity during this event. Upward Streamers are launched from some of these objects. A few tens of meters off the ground, a “collection Zone” is established according to the intensified local electrical field.

3. Some Leader(s) likely will connect with some Structure(s). Then the “switch” is closed and the current flows, we see lightning.

Lightning effects can be direct and/or indirect. Direct effects are from resistive (ohmic) heating, arcing and burning. Indirect effects are more probable. They include capacitive, inductive and magnetic behavior. To protect the structures or Telecommunication towers against lightning a lightning protection system is needed which collects the lightning energy and discharge the lightning currents to the earth through down conductors.

Early Streamer Emission Lightning Arrester

Early Streamer Emitting air terminals are designed to emit a streamer early in the streamer- formation phase of a lightning strike, thereby becoming the preferred lightning attachment point.

As the ground charge builds immediately before the lightning strike, the ESE air terminal accumulates ground charge. ln the instant before the strike, when the stepped leaders are branching down from the cloud, the ESE terminal emits a series of pulses of ground charge, forming a streamer from itself before streamers emit from other structures. lts streamer reaches the stepped leaders before competing streamers, thereby winning the competition.

FOUDRETECH Early Streamer Emission Air Terminal - STAR

Foudretech offers a high end ESE air terminals “STAR”. Foudretech ESE Air Terminal STAR contains a central part and covered by the capturing petals electrically isolated with an earthed central zone. The insulation material used to electrically isolate the panels are comprised of a base polymer which provides high ozone and UV resistance with high di-electric strength. The capturing petals are designed in such a way that it emits a flow of ions directed at the cloud, channeling the lightning discharge to a determined point. This way the system achieves to attract the lightning flash and raise the strike point to an altitude higher than the structure to be protected. The effect is that a larger protection area is created.

Advantage

• 100% discharge efficiency. • Level of protection classified as very high. • Guarantees electrical continuity and continued function after repetitive lightning discharges. • Non-electronic: Guarantees long duration. • External power supply not necessary. • Insulation guarantee. • No wear.

Lightning Counter

Detect and register lightning impacts with occur over an external lightning protection system.

Grounding

The grounding systems must address low earth impedance as well as low resistance. A spectral study of lightning’s typical impulse reveals both a high and low frequency content. The high frequency component resides in the long, high energy “tail” in the impulse.

A single point grounding systems is achieved when all equipment within the structure(s) are connected to a master bus bar which in turn is bonded to the external grounding system at one point only. Earth loops and differential rise times must be avoided. The grounding system should be designed to reduce a.c. impedance and d.c. resistance. The shape and dimension of the earth termination system is more important than a specific value of the earth electrode. Ground rings around structures are useful.

Man-made earth additives and backfills are useful in difficult soils circumstances: they should be considered on a case-by-case basis where lowering grounding impedances are difficult an/or expensive by traditional means. Regular physical inspections and testing should be a part of an established preventive maintenance program.

Advance Chemical Gel Earthing

By utilizing the metal alloys and natural compounds, is able to provide a multifaceted proactive highly conductive and corrosion free earthing. The electrode is manufactured from custom-made G.I. Tube with adequate galvanization (i.e., more than 80-100 microns) to ensure maximum conductivity and prolonged service life. The earth electrode contains a highly conductive metallic compound that protects the main earth electrode from corrosion in the soil.

Chemical earth electrode is the innovative method of Dual Pipe system having a compartment of outer shell, inner shell with the terminal on the top, fabricated in high quality MS material and subsequent hot dip galvanization to maximum of 80-100 microns in outer shell and 250-300 microns in the inner shell to strengthen the flow/ dissipation of fault/ static current to its maximum safetyness.

Along with an earth electrode, an illustrious compound called as “Reslow grounding minerals” which will be used around the earth electrodes at the time of installation. Reslow grounding minerals is a combination of graphite, natural earth minerals, etc which is of hygroscopic property to retain the moisture for a long time. During installation with proper water pouring, the Reslow grounding minerals will convert into the gel formation and its quality to retain the moisture upto twenty times its dry volume as well as it create a gel layer surrounding of our electrode. Reslow grounding minerals is a combination of totally corrosion free and highly conductive & non-corrosive minerals.

Reslow grounding minerals maintains the moisture surrounding the CHEMRODE, which helps to create the balance & consistence ohmic value within the safe limit without any fluctuation of results, as a safeguard of equipment. As well as its layer works as a highly conductive path to pass the fault current, noise filtrations, resolve the problem of earth to neutral voltage difference and supported to active/ passive lightning protection device too. It also helps to give the life to our earth electrode through its layer between electrode & direct soil, so minimize the chances of corrosion.

INSTALLATION GUIDE

1. Capturing Head: the peak has to be located minimum 2m above the highest part of the area to be protected.

2. Adapter Element: it has to provide the electrical contact between the capturing point and the down going conductor. It is put on the mast, on light poles, pillars, etc…

3. Mast: the mast provides the appropriate height corresponding to the area to be protected by the lightning rod and is usually mounted with 2 or 3 fixings depending on its length.

4. Down-Conductor: it leads the current of the lightning stroke from the capturing head to the earth electrode. The conductors can be of flat or round cable of copper / GI and the minimum area has to be 50 mm². Each lightning rod has to have at least one down- conductor, expect in the following cases, where two down-conductors are needed:

i. ii.

–structures higher than 28m –the horizontal projection is larger than the vertical projection

The path has to be the most rectilinear possible with the shortest distance, avoiding curves. The covering radius should not be less than 20 cm. The down conductor should avoid crossing or the proximity of electrical or telecommunication networks. When the crossing cannot be avoided, then the line has to be inside of a metallic shield, which needs to be extended 1m on each side of the crossing.

5. Conductor Holding Fixtures: Independent of the fixture type, one fixtures per meter is used for the down-conductor.

6. Lightning Counter: This counter is installed above the control joint, and in all cases 2mtr. above the ground. It is mounted on the top of the down conductor.

7. Test Joint: Each down-conductor has to incorporate a test joint, which allows disconnecting the earth electrode and thus allows measuring the resistivity. The test joint is mounted two meters above the ground.

8. Protection Pipe: It is put between the ground and the control joint in order to protect the down conductor against mechanical forces. The pipe is of metallic material and has a length of 2m.