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.