All earthing systems require specific key components in order for them to be beneficial, with lightning protection the designer planning the earthing system must decide on the conductor type to be used of which there are three commonly used types of conductor:
- Flat tape
- Solid Circular
- Stranded Cable
Above ground there is a choice of conductor materials that can be used, albeit the choice is often between copper or aluminum, however below ground the most appropriate conductor material is copper, this is mainly because copper possesses greater anti corrosion properties.
Earth rods and earth plates are commonly used as Earth installations, the primary function of earth rods is to take advantage of lower resistivity soils at greater depths than standard excavation will allow. Earth plates are used to attain an effective earth in shallow soil where ground conditions are not conductive for installing earth rods.
All effective earthing systems also rely on connections and joints that provide good electrical conductivity with high mechanical strength. Joints and connections that are poorly chosen and incorrectly installed will potentially damage and compromise the performance of the earthing system.
A high quality electrical connection is required, exothermic welding is a straight forward method that uses no external power or heat source. Connections are created using the high temperature reaction between powdered copper oxide and aluminium. Correct connections will never loosen and are highly conductive and have exceptional corrosion resistance.
Compression connections may be used in circumstances where exothermic welding is not suitable for creating long-lasting connections. Very sturdy joints can be provided by compression connectors, they can be buried in the ground or in concrete.
When permanent connections are not appropriate, the ideal method is mechanical clamps. Mechanical clamps are more often used on smaller scale installations where periodic disconnection for testing is required. Top quality mechanical clamps are manufactured from high copper content alloy and will as a minimum posses mechanical strength, outstanding corrosion resistance and conductivity.
It's crucial that all earthing systems receive frequent inspection and testing, installation inspection pits enable easy access to earth electrodes and conductors. A reliable and convenient way of providing a common earth point is via the use of earth bars, integral disconnection links mean the earth bars can be isolated for testing purposes.
In areas where necessary resistance levels are difficult to obtain, Earth electrode backfills can be used, these products such as Marconite or Bentonite effectively enhance the electrodes surface area thus reducing its resistance to earth.
