Chemical Earthing and Its Impact: A Critical Analysis Based on IEC 62305-3

by Ohm Engineering Works | Oct 08, 2024 | Electric Company

Introduction

When it comes to effective earthing practices, a critical consideration is the soil's resistivity. As electrical installations depend heavily on proper earthing for safety and performance, understanding when and how to use earthing compounds becomes vital. The IEC 62305-3 standard offers valuable guidance on the use of "Earth Enhancing Compounds" in various soil conditions, providing insights that should shape installation decisions.

What Does IEC 62305-3 Say About Earthing Compounds?

According to Clause 5.4.2.2 of IEC 62305-3, the use of earthing electrodes and compounds is determined by soil resistivity:

In soils with resistivity greater than 3000 Ωm, the use of Type B earthing arrangements or earthing enhancing compounds is recommended to ensure proper grounding.
In soils with resistivity below 200 Ωm, the effectiveness of earthing compounds is significantly reduced, making their application unnecessary.
In low-resistivity soils (e.g., below 100 Ωm), there is a high risk of corrosion of the earth electrode, especially if chemical earthing is used.

Decoding the Guidelines

These points lead to key conclusions:

In soils with resistivity below 3000 Ωm, natural soil conditions may be sufficient for proper earthing without the need for additional compounds.
In soils with resistivity under 200 Ωm, earthing enhancing compounds lose effectiveness. In such cases, natural grounding should suffice.
In low-resistivity soils (below 100 Ωm), the use of chemical earthing compounds can accelerate electrode corrosion, threatening the long-term safety and efficiency of electrical systems.

The Case Against Chemical Earthing in India

In India, the soil resistivity in many regions is typically below 100 Ωm, making the use of chemical earthing or earth-enhancing compounds largely unnecessary. In fact, using these compounds in low-resistivity soils can have negative consequences. The salts and chemicals present in these compounds can cause rapid corrosion of the earth electrodes, leading to:

Increased failure risk in grounding systems
Higher maintenance costs due to frequent electrode replacements
Safety hazards, especially in critical industrial and commercial installations

The Hidden Risks of Chemical Earthing

Chemical earthing compounds often contain salts and other corrosive substances to reduce soil resistivity, but they can severely damage the metal components of the earth electrodes. Over time, the corrosion weakens the connection between the electrode and the earth, leading to:

Compromised performance of the grounding system
Increased likelihood of failure, especially during high-load situations
Additional costs for frequent maintenance and replacements

Alternatives to Chemical Earthing

For soils with naturally low resistivity, several alternatives ensure effective and safe earthing without the risks associated with chemical compounds:

Galvanized or Copper-bonded Earth Electrodes: These materials are naturally resistant to corrosion and provide long-term grounding stability in various soil conditions.
Deep Earthing: In areas with low-resistivity surface soil, driving electrodes deeper into the ground can achieve the desired earthing effect.
Comprehensive Soil Analysis: A thorough analysis of soil resistivity before installation will help determine whether earthing enhancing compounds are truly necessary or if they could be counterproductive.

Conclusion: Think Twice Before Using Chemical Earthing

Based on the IEC 62305-3 standard, it’s clear that chemical earthing compounds are often unnecessary and can even be harmful in Indian soil conditions where resistivity frequently falls below 100 Ωm. The risks of accelerated corrosion, increased maintenance, and potential safety hazards should engineers and contractors to carefully consider alternatives before using chemical earthing compounds.

By adhering to international standards and understanding the specific soil conditions at each site, electrical installations can be made safer, more reliable, and more cost-effective in the long term.

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