Supply installation

Lightning Protection Installation

A brief explanation of a BSEN 62305 system we are able to install:

Air Termination System
The three basic methods recommended for determining the position of the air termination systems are:

  • The rolling sphere method
  • The protective angle method
  • The mesh method

Down Conductor System
Down conductors should within the bounds of practical constraints take the most direct route from the air termination system to the earth termination system. The lightning current is shared between the down conductors. The greater the number of down conductors, the lesser the current that flows down each. This is enhanced further by equipotential bonding to the conductive parts of the structure.

Lateral connections either by fortuitous metalwork or external conductors made to the down conductors at regular intervals is also encourage.

The down conductor spacing corresponds with the relevant Class of LPS

Class of LPS Mesh Size (m) Down Conductor Spacing (m)
I 5×5 10
II 10×10 10
III 15×15 15
IV 20×20 20

Earth Termination System
The earth termination system is vital for the dispersion of the lightning current to safely and effective get to the ground. Although lightning current discharges are a high frequency event, at present most measurements taken of the earthing system are carried out using low frequency proprietary instruments. The standard advocates a low earthing resistance requirement and points out that can be achieved with an overall earth termination system of 10 ohms or less.

In line with BS 6651, the standard recommends a single integrated earth termination system for a structure, combining lightning protection, power and telecommunication systems. The agreement of the operating authority or owner of the relevant systems should be obtained prior to any bonding taking place.

Three basic earth electrode arrangements are used:

  • Type A arrangement
  • Type B arrangement
  • Foundation earth electrodes