The transient nature of lightning with its associated fast rise times and large magnitude currents mean that special consideration needs to be given to earthing, for lightning protection to be effective.
Many factors such as soil resistivity variations, installation accessibility, layout and existing physical features are all site specific and tend to affect decisions on grounding methods employed. The primary aim of a direct strike earthing system is to:
– Efficiently dissipate lightning surge energy into the ground
– Help ensure safety of equipment and personnel
Effective Earthing and Lightning Protection Systems
A good earthing systems will feature the following 7 characteristics:
- Good electrical conductivity
- Conductors capable of withstanding high fault currents
- Long life – at least 40 years
- Low ground resistance and impedance
The basic philosophy of any grounding installation should be an attempt to maximise the surface area of electrodes of conductors with the surrounding soil. Not only does this help to lower the earth resistance of the grounding system, but it also greatly improves the impedance of the grounding system under lightning surge conditions.
- Equipotential bonding
Equipotential bonding helps ensure that hazardous potential differences do not occur between different incoming conductors such as metallic water services, power systems, telecommunication systems and the local ground, and also minuses step and touch potentials.
- Good corrosion resistance
The ground electrode system should be corrosion resistant, and compatible with other conductors that are buried and bonded to the ground system. Copper is by far the most common material used for grounding conductors. In general, some form of maintenance or inspection procedure should be adopted to ensure the long-term effectiveness of a grounding system.
- Electrically and mechanically robust and reliable
Mechanical coupling can be used to join ground conductors, but suffers from corrosion effects when dissimilar metals are involved. As well as mechanical strength, CADWELD connections provide excellent low impedance, long life electrical connections with excellent corrosion resistance. More information on the benefits of exothermically bonded connections can be found here.
A Typical Earthing System
For more information on our range of lightning protection products, visit the earthing section of our website.
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