A Guide to Earthing and Lightning Protection Equipment

Every year people lose their lives due to lightning strikes. During thunderstorms, lightning can discharge up to 200,000 amps in a few seconds. The most important aspect of understanding lightning protection is that not only a direct lightning strike can have devastating effects on people, buildings, and the natural environment but also more frequently, electronic equipment is damaged by surges caused by remote lightning discharges (caused because of Lightning Electromagnetic Impulses or LEMPs) or switching operations in larger electrical systems.

In order to fully protect themselves, structures and electronic equipment must use Lightning Protection and Earthing equipment that has been designed and tested according to the best international standards. The international standard for Lightning Protection referred to as IEC 62305 – ‘Protection against Lightning’, (which is also accepted by many countries as a national standard) especially adopted by the Bureau of Indian standard as IS IEC 62305, in one of its parts explains the need for planning, erection, testing and maintenance of lightning protection systems for building structures without any height limit.

A proper lightning protection system (consisting of the air terminal, down conductor, earthing) design is very important to ensure increased protection of a building against lightning and its effects. Systems followed in most of the buildings now are unfortunately not meeting the basic or statutory requirements. Since only a mere vertical air terminal will not solve the purpose for the protection of a building unless the entire building is sufficiently protected either with the Angle of protection method, Mesh conductor method or Calculated as per rolling sphere method.

Effective lightning protection is achieved only if the following points are followed:

• Type of protection
• Level of protection based on risk assessment
• Technically qualified product as per latest and relevant IEC standards
• Sizes and dimensions of components
• Location of air terminal and coverage
• Conductor routing and connections
• Sufficient and required earthing provisions
• Proper utilization of natural components as down conductor if applicable.

Design guidelines: The following design guidelines need to be followed to ensure safer installation of the external LPS.

• A down-conductor should be installed at each exposed corner of the structure where this is possible.
• The down-conductors should form a direct continuation of the air-termination conductors
• Straight and vertical so that they provide the shortest and most direct path to earth
• The formation of loops in the down conductor shall be avoided, but where this is not possible the distance ‘s’ shall be maintained.
• Connection of down conductors to gutters or down-spouts even if they are covered by insulating materials.
• Usage of multiple connections with different materials should not be permitted.
• Insufficient conductor dimensions (non-complying material as mentioned in IEC 62305-3 Table – 5) should be strictly avoided.
• When the distance from down conductors to combustible materials cannot be assured, the cross-section of the down conductor shall not be less than 100 sq. mm.
• The electrical insulation between the air-termination or down-conductors and the structural metal parts, the metal installations, and the internal systems can be achieved by providing a distance ‘d’ between the parts greater than the separation distance ‘s’.

S’ = (Ki) x {Kc/Km} x L

Where:
Ki – depends on the selected class of LPS
Kc – depends on the lightning current flowing on the down conductors
Km – depends on the electrical insulation material
L – length in meters along the air-termination or down-conductor, from the point where the separation distance is to be considered, to the nearest EPB point.

Standards (IEC): The International Electrotechnical Commission prepares and publishes International Standards for all electrical, electronic and related technologies and is the leading international organization in its field.

• IEC 62305 – Protection Against Lightning, is the apex level document that informs the standards for lightning protection around the world. 
• UL & CSA are North American certification bodies that are followed widely in the US, Canada and other parts of the world.
• UL 467: Grounding and Bonding Equipment, 
• UL 96A: Installation requirement and C22 for lightning protection system are few important standards in this field.

Bottom Line: Earthing & Lightning Protection System must be installed for the safety of people and to protect buildings, electronic equipment from the impact of lightning.