Strike Pad

The role of an air termination system is to capture the lightning discharge current and dissipate it harmlessly to earth via the down conductor and earth termination system. Therefore it is important to use a correctly designed air termination system.

IEC/BS EN 62305-3 advocates the following, in any combination, for the design of the air termination:

• Air rods (or finials) whether they are free standing masts or linked with conductors to form a mesh on the roof
• Catenary (or suspended) conductors, whether they are supported by free standing masts or linked with conductors to form a mesh on the roof
• Meshed conductor network that may lie in direct contact with the roof or be suspended above it (in the event that it is of paramount importance that the roof is not exposed to a direct lightning discharge) The standard makes it quite clear that all types of air termination systems that are used shall meet the positioning requirements laid down in the body of the standard. It highlights that the air termination components should be installed on corners, exposed points and edges of the structure.

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