If this is the first time for you then I will suggest you have a look at my previous post about the electrical earthing system. You will get a lot of ideas for a perfect earthing system. In this post, I am going to discuss some of the major technical consideration during earthing system and the factors affect of the earth resistance. So let’s go.
Some Major Technical Consideration During Earthing System:
- First of all current carrying capacity. The current carrying path must have enough capacity to deal with the maximum fault current during fault time. The magnitude of the earth fault current can influence by the total impedance of the neutral point to ground circuit.
- Between the earth and the neutral point, the resistance of the earth and the current path must be low enough to prevent the rise of voltage.
- The main earthing system must be separate from the lightning protection system.
- Soil condition and resistivity always depend upon the local area. A systematic survey can be run and the resistivity of the soil should be carried out.
Earth Resistance Factors Affecting:
Earth electrode always depends on the electrical resistance of the soil in which types of electrode are installed and its turn determined by the following factors.
- Extent of the Moisture: The resistivity of the soil always varies with the moisture content in the soil. You can get a little advantage if the moisture content exceeding 20% in soil. But if the moisture is below 20% then the resistance increases sharply. When approximately 90% of the resistance between the electrode and the earth lies with the radius of 2m. For this situation, the best method is chemical treatment. You need to dig a shallow trench about 30cm deep around the electrode.
- Soil Nature: The sites of the earthing system can be chosen by the following order of preference.
Wet Sand Pit and Damp
Wet Marshy Ground
- Presence of the Suitable Salt Dissolved in Soil Moisture: In absence of the natural salt, water alone cannot provide the adequate conductivity. You need to use Sodium Chloride, Calcium Chloride, Copper Sulphate, and Sodium Carbonate for a better result when addition water fails to give the desired result. If you want you can use Charcoal and common salt for the same purpose.
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