Short Answer:

To ensure safety and proper functioning of an electrical system, the earthing resistance must be kept low. When resistance is high, fault current cannot flow easily into the earth, which may cause electric shocks or equipment failure. There are several effective methods to reduce earthing resistance, such as increasing the number of electrodes, using chemical treatment, deepening the electrodes, and improving soil moisture.

These techniques help create a better connection between the earth and the grounding system, allowing current to flow safely during faults or surges. Reducing earthing resistance is especially important in dry or rocky soil conditions.

Detailed Explanation:

Methods Used to Reduce Earthing Resistance

Earthing resistance is the opposition offered by the ground (soil) to the flow of electrical current from an earthing electrode into the earth. A low resistance is desirable because it ensures that any fault current or leakage current safely dissipates into the ground without causing harm to equipment or people.

If earthing resistance is too high, it can fail to trip protective devices or may cause dangerous voltage rise on metal surfaces. Therefore, engineers take special steps to reduce earthing resistance and maintain it within safe limits.

Common Methods to Reduce Earthing Resistance

Increasing the Depth of the Earth Electrode

The deeper the electrode is placed, the lower the resistance.
Deeper layers of soil tend to have more moisture and conductivity, which help reduce resistance.
Rods or pipes are driven vertically into the ground up to several meters, depending on the soil condition.

Advantage: Simple and effective in many locations.

Using Multiple Electrodes (Parallel Grounding)

Installing multiple electrodes and connecting them in parallel helps distribute the fault current.
Each electrode shares the current path, which lowers the overall resistance.

Advantage: Useful in large installations or poor soil areas.

Increasing the Diameter or Surface Area of the Electrode

A larger surface area in contact with the soil helps reduce resistance.
This can be done by using wider rods, flat copper strips, or metal plates.

Advantage: Increases contact with soil, improving current dissipation.

Improving Soil Conductivity

Mixing salt and charcoal around the electrode helps keep the soil moist and increases conductivity.
These materials retain moisture and create a good ionic path for current.

Note: Regular maintenance is required because these materials may leach or degrade over time.

Using Chemical Earthing Systems

In areas with high-resistance soil (like rocky or sandy ground), chemical earthing is used.
Chemical electrodes are filled with compounds that attract moisture and improve soil conductivity.
They are maintenance-free and provide consistent resistance over time.

Advantage: Very effective in dry or difficult soil types.

Maintaining Proper Soil Moisture

Resistance increases in dry soil, so keeping the soil moist around the electrode is important.
Sprinkling water or using a permanent water source helps retain low resistance.

Note: This is especially useful during summer or in arid regions.

Using Bentonite Clay or Conductive Backfill

Bentonite is a type of clay that swells when wet and surrounds the electrode to enhance contact with soil.
Conductive backfill materials (like carbon-based compounds) are also used to improve performance.

Advantage: Forms a stable and long-lasting low-resistance environment.

Avoiding Corrosion and Ensuring Tight Connections

Loose or corroded connections between earthing components increase resistance.
Proper joints, clamps, and anti-corrosion treatment ensure that the system remains effective over time.

Advantage: Maintains low resistance and long-term reliability.

Conclusion

Maintaining low earthing resistance is essential for the safety and stability of electrical systems. There are various methods to reduce earthing resistance, such as increasing electrode depth, using multiple or larger electrodes, adding salt or chemicals, and maintaining soil moisture. These techniques help provide a safe path for fault current and protect both equipment and people from electrical hazards. Choosing the right method depends on the soil condition, system requirements, and environmental factors.