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Electrical Earthing: Definition, Benefits and Techniques

Earthing is simply defined as the flow of excess electrical energy to the ground during a fault or in the abnormal condition by a low resistance path. 

In normal condition, no current flows through earth wire. During abnormal or fault condition it provides a path to the leakage current to flow to the ground. 

How does Earthing protect us?

Without Earthing :

Equipment without Earthing

Looking at the above figure, let’s imagine if we don’t have an earth wire. If the live wire fails and touches the machine’s body then the leakage current starts to flow from the machine. If the human body comes in contact with the equipment, the leakage current passes through the body. And he will get shock.

For example: If human body resistance is 1000 Ohm. And Normal voltage is 230V then current flow through the human body,

From Ohms law, Current (I) =Voltage (V)/Resistance(R) =220/1000=0.2A

The current of 0.2A flows through the human body.

With Earthing:

Equipment without Earthing

 If live wire fails and touches the machine’s body, leakage current starts to flow from the machine. If the human body touches the machine he will not get shock. Because Earthing provides low resistance and current flows through earth wire.

The nature of current is that it always flows through a low resistance. Human body has high resistance and earth wire has low resistance so, current will choose the path of low resistance. And the human will not get shock.

Benefits of Earthing

  • It keeps human safe from electrical shocks.
  • It protects the equipment from being damaged from the leakage current.
  • Protective devices like Earth Leakage Circuit Breaker (ELCB), Residual Current Circuit Breaker (RCCB), etc. needs proper earthing for its functioning.

How Earthing is done?

There are various techniques available for Earthing. Rod, Plate, Pipe, Strip are the popular methods.

This article illustrates the procedure of Rod Earthing.

Rod Earthing Diagram
Earthing Diagram (All units are in mm)

Materials Required:

  1. Rod (Electrode) of length 2 to 3 meter.
  2. Earth Pit Diameter should be more than 50cm.
  3. Salt-50kg, Charcoal- 15 kg
  4. GI Pipe
  5. Copper wire

Personal Protective Equipment:

Helmet. Gloves, Footwear, Glasses, Mask.

Procedure: 

  1. Your Earthing location should be of 1.5-meter distance from house.
  2. Make an earth pit of size as mentioned above. The depth of the earth pit must be in the range of 2-3 meters and at least 20cm more than the length of the rod.
  3. Stand the Electrode on the pit (make it centre). The diameter of earth electrode must be selected in such a way that it should have enough strength to be driven into the particular soil conditions without bending or splitting. 
  4. Put a salt of 8kg and charcoal 2 kg per layer around the rod. 
  5. Repeat step 4 until the material exhaust. 
  6. Rod should be dipped in such a way that its top-end should be 0.2m from the ground. After material exhaust backfill the pit with soil free of stones.
  7. Now, the electrode must be connected to grounding bar through earth lead which shall be buried 60 cm deep inside the soil for its protection. While burying the earth lead use GI pipe to cover it.
  8. Do PCC to prevent dryness and make some arrangement for a pair of water.

In this way, Earthing can be completed.

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