Lightning Protection System and its Classifications

 

Lightning Protection System

A lightning protection system is a system on a structure and intended to protect the structure from lightning strike. That's why, now a days, lightning protection system (LPS) is an impotant part of any building. The requirements vary from building to building and protection system options are several. For Lightning protection renowned international standards like NFPA 780, BS EN/IEC 62305, NFC 17-102 as well as Bangladesh national standard BNBC has to be followed. 

Classification of Lightning Protection System

Now a days, most commonly two type of Lighting Protection System has been used to protect the structure from the lightning. Those are;

1. Early Streamer Emission (ESE) LPS
2. Conventional LPS

Early Streamer Emission (ESE) LPS

It is a modern technology, intelligent design & digital protection. Early Streamer Emission have a great coverage range and higher accuracy in catching the strikes reducing risk around its coverage. One terminal covers a wide area, that makes it very economical as it only requires only 2 down conductors to complete the loop. Also it is easy for maintenance, thanks to its leading technologies. Standard covers by this ESE-102 system are French national standard NF C 17-102 - 2011, NFPA 780, RTN(Russia), IEC etc.

Conventional LPS

It is an age old system, traditional & trusted enough. The most known system for protection from lightning is the conventional mesh conductor type lightning protection system which codes as NFPA 780. Which complies with IEC, IEEE and other international standards as well as BNBC standards. This is the most traditional and old standard for around a century and most used all across the world because of its efficiency and low maintenance caliber compared to other systems. 

Components of LPS and its working principle

Lightning rods or 'air terminals' are only a small part of a complete lightning protection system. In fact, the rods may play the least important role in a system installation. The conductor cables and ground rods are the most important components of a lightning protection system, accomplishing the main objective of diverting lightning current safely past a structure. A lightning protection system is composed of three main components:

1. Rods or 'Air Terminals' - The small, vertical protrusions designed to act as the 'terminal' for a lightning discharge. Rods can be found in different shapes, sizes and designs. Most are topped with a tall, pointed needle or a smooth, polished sphere.

2. Conductor Cables - Heavy cables (right) that carry lightning current from the rods to the ground. Cables are run along the tops and around the edges of roofs, then down one or more corners of a building to the ground rod(s).

3. Ground Rods - Long, thick, heavy rods buried deep into the earth around a protected structure. The conductor cables are connected to these rods to complete a safe path for a lightning discharge around a structure.

The 'lightning rods' themselves, that is, the pointy vertically-oriented terminals along the edges of roofs, do not play much of a role in the functionality of the system. A full protection setup, given good cable coverage and good grounding, would still work sufficiently without the air terminals.