Earthing systems are a vital aspect that find application in many industries such as telecommunication, oil and gas, petrochemicals, power, civil and computer sciences. Earthing is essential for all computer networks, power distribution panels, substations, telecommunication towers, microwaves, precision tool making, industrials machines and even electrical home appliances. The importance assigned to earthing can be determined from the fact that service providers do not enable supplies unless this important parameter has been adhered to.
In case the earthing systems are not sound, installers and manufacturers hesitate to provide warranties. The key objectives of an earthing system are as follows:
. Lightning and overvoltage protection
. Reassuring human safety in fault and normal conditions with restricting step and touch voltage
. Assuring proper functioning of electrical and electronic equipments
. Avoiding malfunctioning or total break-down of electrical and electronic equipments
A reliable, permanent earthing system is a great aid to ensure proper functioning of electronic and electrical equipment. This avoids break-downs caused by static build up, surge voltage, switching and electromagnetic fields created by lightning discharge.
What is Shock?
There are few reliable figures for shock current effects, because they differ from person to person, and for a particular person, with time. However, over one milliampere of current in the body produces the sensation of shock, and that one hundred milliamperes is likely quickly to prove fatal, particularly if it passes through the heart.
If a shock persists, its effects are likely to prove to be more dangerous. For example, a shock current of 500 mA may have no lasting ill effects if its duration is less than 20 ms, but 50 mA for 10 s could well prove to be fatal. The effects of the shock will vary, but the most dangerous results are ventricular fibrillation (where the heart beat sequence is
disrupted) and compression of the chest, resulting in a failure to breathe.
Another important factor to limit the severity of electric shock is the limitation of earth fault loop impedance. Whilst this impedance adds to that of the body to reduce shock current, the real purpose