Earthing plays a vital role in all electrical systems. The correctly designed and installed earthing system i.e. earthing rods or grounding rods will safeguard both lives & equipment. A Good Earth Connection should have :

• Low electrical resistance to earth.
• Good Corrosion resistance.
• Ability to carry high currents repeatedly.
• A reliable life of at least 30 years.

Soil Conditions
Achieving a good earth will depend on local soil conditions. A low soil resistivity is the main Aim. The factor affecting the resistivity are :

• Moisture content of the soil
• Chemical composition of the soil e.g. Salt content.
• Temperature of the soil.

The moisture content in the soil decreases the resistivity of the soil. Similarly, increase in the salt content reduces the resistivity, while reduction in temperature of the soil increases the resistivity.

Selection of the Correct Earth Electrodes
A soil resistivity survey indicates lower resisitivity at greater depths. Often these levels are some meters below the surface. The most economical way of reaching them is by Deep Driven Earth Rod Electrodes. When deep driving is not possible mainly due to rocks, underneath, parallel driven shorter rods, plates, mates or buried conductors or a combination of three can be used.

Earth Rod Electrodes
Earth rods are commonly made from solid copper or stainless steel with copper bonding. Copper Bonded Earthing Rods or Copper Bonded Grounding Rods are commonly used due to strength, corrosion resistance and comparatively low cost. Earth Rod

Copper Bonded Earth Rod System
This system includes rod along with accessories.

• Driving Stud : These are made from steel & suitable for use with Power Hammers.
• Coupling : These are made from copper alloy & counter bored to enclose threads. Coupling is high strength & also highly corrosion resistant. These are used to connect driving stud to rod or rod to rod.
• Rod : Steel rod with core of low carbon provides tensile strength at least of 600 N/mm2. These rods are molecularly bonded with 99.9 % pure electrolytic copper up to thickness of 0.25mm, Rolled threads at each end gives strength than cut threads.
• Clamp : These are made from high copper content alloy strong resistance to corrosion.

Lightning Protection
BS6651:1992 clearly advices strict adherence to the provision of conventional lighting protection system.

Design Consideration
The principle competence of a conventional lighting system in accordance with BS 6651 are :

• Air Termination Network
• Down Conductors
• Earth Termination Network
• Bonding

Air Termination Network
On high-risk structures such as, explosives factories, nuclear power plants, no part of roof should be more than 2.5m from an air termination conductor. This is generally achieved by applying a 5m x 10m mesh to the roof. 10m x 20m Mesh 60 m

For most structures, a mesh of 10m x 20m is considered sufficient. The zone of protection offered by an air termination network is considered to be 45 for heights up to 20m. Above this height the zone of production is determining by the 'Rolling Sphere Method'. 140 m

Down Conductors
The architectural design affects the location of down conductor. These should be one down conductor for every 20m. These should be evenly spaced & distances not mere that 20m. They should be routed as directly as possible from the air termination network to the earth termination network to length of conductor forcing the loop should not exceed eight times the width of its open side.

Earth Termination Network
Each down conductor must have a separate earth termination. The provision should be made in each down conductor for disconnection from the earth for testing purposes.

Bs6651 states that the resistance to earth of the complete lightning protection system measured at any point should not exceed 10 ohms. BS 6651 also states that the combined earth rod length of system should be no less then 9m, whilst each individual earth rod should be not less than 1.5m in length.

Bonding
When a lightning protection system is struck, its electrical protection with respect to earth is significantly raised and if resistance offered by the down conductor becomes more then the other metalwork on the structure, the discharge seeks alternative path to earth by side flashing.

Hence, it is vital that all the exposed metal work is bonded into the lightning protection installation.

Earthing is the electrical drain path for stray energy in an electrical circuit. Grounding is the most effective method of the earthing. Inserting rods, plates, or strips the ground resistance can be reduced up to 22 %. i.e. if the original ground resistance 300 ohms it can be reduced to 66 ohms. It is essential to have a resistance value of 2 ohms for sensitive electronic and electrical equipments.

In order to achieve the required resistance value of 2 ohms and below it is essential to add minerals, hygroscopic compounds, expansion compounds and diffusion compounds to the soil. 'TEREC ' is a miracle compound comprising of all the needed additives. When 10 kg of TEREC is induced in to the soil the required resistance value of 2 ohms can be easily achieved permanently for 15 years.

'TEREC ' is the only reliable and permanent grounding solution for the safety of human, livestock, equipments and property.