Poor grounding contributes to downtime but an excess of good grounding is also dangerous and increases the risk of equipment failure.
The purpose of earthing is to ensure human safety as well as instrument safety. Higher earth resistance can cause fault currents to flow through human body causing serious injury or death. The ideal value of earth resistance should be around 5 Ohms.
We often add water & add salts at regular intervals into the earth pits in order to maintain the value of earth resistance. This keeps the earth pit moist and damp. Over a period of time, the corrosive soils with high amount of moisture, salt content and high temperatures can degrade the earthing electrodes and their connections. The earth resistance when the earthing electrodes are installed is lower but over a longer period, the earthing rods starts eroding ultimately increasing the resistance of the ground. This may result in bad earthing adding to the risk of loss of safety.
With increase in value of earth resistance, if exceeds 20 per cent, the technician should investigate the source of problem and make the correction to lower the resistance by replacing or adding ground rods to the system. Therefore, we can state that water and salts added in order to improve earth resistance over a period of time are also responsible for eroding the earth electrode ultimately increasing the earth resistance. Hence, it is necessary to check annually the condition of the electrodes so as to add or replace electrodes in order to reduce risk.
Pranav Bhargav, Product Manager –
TMI, Rishabh Instrument