Lightning Protection Report

JP TECHNOSOFT AHMEDABAD

REPORT ON LIGHTNING PROTECTION www.jptechnosoft.com of 7

PROJECT:

DOCUMENT: A REPORT ON LIGHTNING PROTECTION

1. PREAMBLE

a) About Lightning and it’s Protection:

- Lightning is the visible discharge of static electricity within a cloud, between clouds, or between

tile earth and a cloud. A lightning protection system is a system designed to protect a structure

from damage due to lightning strikes by intercepting such strikes and safely passing their

extremely high voltage currents to ground. Most lightning protection systems include a network

of lightning rods, metal conductors, and ground electrodes designed to provide a low resistance

path to ground for potential strikes.

b) Requirement of Lightning Protection:

- Lightning can strike anywhere on earth. If struck, structures in these areas will generally sustain

more damage when there is no lightning protection system present.

- To prevent homes and other properties against damage or complete destroy and subsequent fire

hazard.

- Most important is to save life of human being and other living objects in proximity of striking of

lightning.

- To prevent damage of electronics equipments in close proximity of striking of lightning due to

induced voltage.

c) Role of Lightning Protection System

- A lightning protection system does not prevent lightning from striking; it provides a means for

controlling it and preventing damage by providing a path for the discharge of lightning energy.

- A lightning protection system provides a means by which discharge of lightning may enter or

leave earth without passing through and damaging non-conducting parts of a structure.

d) Relevant Standards:

For installations in INDIA, lightning protection systems can be designed in accordance with

a) Indian Standard: IS: 2309(2005): “Protection of Buildings and Allied Structures against Lightning

– Code of Practice”.

b) International Electro-technical Commission: IEC: 62305 –Part III (2005): Protection against

lightning –Physical damage to structures and life hazard.

c) British Standard: BS: CP-326



2 COMPONENTS OF EXTERNAL LIGHTNING PROTECTION SYSTEM

- The principal components of a lightning protective system are

a) Air Terminations

b) Down conductors

c) Earth termination

Fig.1 General Arrangement Lightning Protection System

2.1 Air Termination

Air termination systems can be composed of any combination of the following elements

a) Rods (Vertical Air Terminals) – Rolling sphere method (used for tall buildings with narrow base)

b) Meshed conductors / Catenary wires (Horizontal Air Terminals) – For flat roofs

If building height is less than 30 meters, 45 degree cone of protection can be used. For building height

more than 30 Meters, 30 degree cone of protection shall be considered.

2.2 Down Conductor

It’s a vertical conductor which provides connection between air termination and ground and which shall

have following features in order to reduce the probability of damage.

a) Several parallel paths

b) Minimum length of the current paths

c) Equipotential bonding to conducting parts of the structure if required.

2.3 Earth Termination

When dealing with the dispersion of the lightning current into the ground, to minimize any potentially

dangerous over voltages, the shape and dimensions of the earth termination system are the important

criteria. There are two basic types of earth electrode arrangements available.

2.3.1 Type-A arrangement (Non-mesh Arrangement)



This type of arrangement comprises horizontal or vertical earth electrodes installed outside the structure

and connected to down conductors.

2.3.2 Type-B arrangement (Mesh Arrangement)

This type of arrangement comprises a ring conductor external to the structure to be installed either in

contact with the soil for atleast 80% of its total length, or a foundation earth electrode. Such earth

electrodes may also be meshed.

2.4 Material and size Recommendations

Indian standard recommended values are shown below:

The values given in above table are minimum required parameters. However, due to installation

parameters like humidity, soil resistivity, ambient temperature, ground temperature, corrosion allowances,

safety factor shall be considered to have longer life with prolonged functioning.

Component Min. Dimensions

required in mm

Min. Area Required in

mm2 Air terminations

Aluminium, copper and galvanized steel strip 20 × 3 60.00 Aluminium, aluminium alloy or, phosphor bronze and galvanized steel rods

10.0 dia 78.54

Vertical Down conductors Aluminium, copper or galvanized steel strip 20 × 3 60.00 Aluminium, aluminium alloy galvanized steel rods 10.0 dia 78.54

Earthing terminations

Hard-drawn copper rods for direct laying into soft ground 12.0 dia 113.00

Hard-drawn or annealed copper rods for indirect laying underground

10.0 dia 78.54

Phosphor bronze for hard ground 12.0 dia 113.00 Copper-clad or galvanized steel rods 10.0 dia 78.54

Fixed connection(s) in aluminium, aluminium alloy, copper, galvanized steel

External

Strip 20 × 3 60.00 Rods 10.0 dia 78.54

Internal

Strip 20 × 1.5 30.00 Rods 6.5 dia 33.00

Stranded flexible connection (bonds)

External, aluminium 560/0.5 70.00 External, annealed copper 990/0.3 70.00 Internal, aluminium 276/0.4 35.00 Internal, annealed copper 1 107/0.2 35.00



3. EARLY STREAMER EMISSION (ESE):

3.1 There are several manufacturers provide installations claiming following consequences:

The Early Streamer Emission air terminal uses the naturally occurring electrical field to complete the timely

release of an upward streamer. As a thunder storm gathers overhead the ambient electrical field surrounding

the ESE begins to rise in voltage, which initiates triggering of an upward streamer fro ESE terminal. With

release of upward streamer from the final tip earlier than other competing structural points, the rod captures

lightning discharge. Upon the approach of a down leader towards the protected area there is a rapid increase in

the electric field. The energy is conveyed to ground via down conductors. When the energy enters the

dedicated lightning earth, it is safely dissipated without risk to personnel and equipment. The concept allows

for a larger or enhanced area of protection to be provided by the ESE in comparison to a conventional system.

Such Installations uses following devices:

a) 2” dia. GI Pipe or equivalent CU/AL pipe

b) Stainless Steel ESE terminals

c) Lightning Strike Recorder

Fig.2 ESE Air Terminal

3.2 Our observations in comparison with Conventional system are as follows:

Feature Conventional System (Faraday cage) ESE (Early Streamer Emission)

Complying Standard Complying to IEC 62305‐3 & IS 2309/IS 3043

Not approved by scientists/IEC/IS. Comply NFC only. NFC‐ National French Code not applicable in India.

Insurance cover Yes. As it is approved by IS & CEIG No. Not approved by IS & CEIG

Current sharing Many parallel paths provided. LEMP has minimal effects.

Max. 2 parallel paths. High LEMP can damage Electronic equipments.

Experience Used for many decades without any failure.

Just 10 years old. Malaysia many buildings with ESE damage has been reported.

Grounding Type B as per IEC 62305‐1 (recommended for industries)

Recommended only for small residences (not even apartments)

Down Conductor As per standard. More than one down conductor to dissipate the Lightning current to the ground.

One down conductor is recommended, this is also not as per NFC 17102.

Installation Time consuming but effective Less time consuming but ineffective

LEMP : Lightning Electro Magnetic Pulse caused by high current flow due to direct lightning strike. Recommendations: Since ESE doesn’t comply to any accepted standard, method is not recommended.



4. DESIGN AND INSTALLATION OPTIONS:

4.1 HORIZONTAL LIGHTNING PROTECTION AIR TERMINATION (OPTION 1)

a) Selected size of Conductor Strip for Air Termination and Down Conductor considering corrosion

allowance and safety factor as 2: 25x6 mm GI Strip

b) Mesh spacing selected as horizontal Air terminations considering kalzip roof profile so as to any point

on roof shall not be beyond 9 Mtr reach of horizontal air termination: 9 Mtr x 18 Mtr

c) Down conductor spacing: At every 30 Mtr on periphery

Fig. 3 Air Termination Network Guideline as per IS

d) Separate earthing to be provided for every down conductor spaced at 30 Mtr. Earthing mesh conductor

will attract huge network hence can be avoided as area is large.

e) Horizontal air termination network and down conductor network shall be installed in electrical isolation

with the base as roof itself is conductive material.

4.2 VERTICAL LIGHTNING PROTECTION AIR TERMINATION (OPTION 2)

Vertical air termination network helps protecting buildings having more heights and lesser span. The

option can not be worked out in our case because of following reasons.

a) With more span in case of exhibition hall area, no. of such vertical air termination required is

more as coverage of each terminal is very less.

b) Every such terminations need two down conductors for redundancy, results in more no. of down

conductors makes system costly.

c) Exhibition hall has slopping profile of roof hence vertical terminal required at intermittent slops

which will spoil look.

4.3 KALZIP USED AS LIGHTNING PROTECTION AIR TERMINATION (OPTION 3)

4.3.1 In place of GI strip, if Kalzip structure (Aluminium sheet) can be used as an air termination with

following conditions:

a) Structure sheet shall be conductive

b) If Structure sheet shall have thickness minimum 7 mm, no horizontal or vertical air termination

network is required, structure sheet it self can be used as air termination network.

c) if Structure sheet shall have thickness less than 7 mm and more than 0.7 mm, structure sheet can

be used as an air termination network provided flash is anticipated, which will damage the roof

sheet due to lightning striking with heavy arc formation. [Refer: Table 5 “Minimum Thicknesses of

Sheet Metal Used for Roofing” (Clause 11.1) Page No. 17 of IS:2309]



Fig. 4 Reference Table IS:2309

d) Sheets of structure shall be fully zipped to ensure contact between each other.

e) Structure shall be effectively earthed.

f) At the interface between roof and walls, each and every profiled sheet must be connected using short

aluminium strips.

g) Window openings shall not be exceeding 1.5m x 1.5m. Larger openings must be avoided or bypassed

using aluminium strips.

4.2.2 With Kalzip structure to be used as air termination following are the benefits:

a) Economic and efficient protection against lightning strikes.

b) No need for dedicated or additional lightning protection devices such as horizontal or vertical air

termination network which spoils aesthetic of structure.

4.3.3 With Kalzip structure to be used as air termination following are the drawbacks:

a) Whenever lightning strikes even if once in years, such a strike hitting a Kalzip, will result into hole

formation in one of the sheet seems facing striking. Damage of this nature would lie above the line of

weathering and may cause damage to sub-structure if strike persists.

b) Electronic equipment such as communication and security systems work on extra low voltage,

computer data networks, control systems etc need protection against the electromagnetic effects caused

due to flashing of lightning.



5. CONCLUSION:

Recommendations:

- Most effective solution appears to be option no. 1 and hence recommended.

- In case of exhibition hall, roof sheet (Kalzip) is proposed with AL material with 0.9 mm thickness.

This is throughout conductive sheet and will have no openings hence Option no. 3 can be worked out

if client can take a call on repairing of punctured sheets after stroke and ensure that gathering of

people below the roof will not get affected by it. All the operations below roof after incident of

lightning must be guaranteed safer by providing secondary protection measures, which looking to

usage of area and safety of people, seems difficult to achieve, hence not recommended.

Lightning Protection Report

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