Maintenance-free chemical earthing installation process
Chemical earthing is an advanced grounding method that utilizes chemical compounds to establish a low-resistance pathway to the Earth. It is designed to provide a long-lasting and hassle-free earthing solution. The chemical mix used in this type of earthing system comprises graphite and other conductive materials that facilitate the flow of electrical current. Due to its low-maintenance nature and durability, chemical earthing is becoming increasingly popular as an alternative to conventional earthing systems.
Location for Earth
- Earth electrodes are best situated in low-lying areas that are in close proximity to the building or equipment.
- It is advisable to place the electrodes near existing water bodies or water points, but not in naturally well-drained areas.
- It is not recommended to install earthing electrodes in dry sand, limestone, granite, or any other stony ground.
- It is important to avoid high banks or man-made soil when installing the earthing electrode.
Components of Earthing & Bonding system
The Earthing & Bonding system comprises several essential components, including the Earth electrode, Earth enhancement material, Earth pit, Equi-potential earth busbar, connecting cable, tape/strip, and various other associated accessories. Each of these components plays a crucial role in ensuring the safe and efficient operation of electrical systems.
Design of Earthing & Bonding system
Earth Electrode
The Earth Electrode is a vital component of the earthing system, which is responsible for creating a low resistance path to the Earth. It is typically made of high tensile low carbon steel circular rods that are molecularly bonded with copper on the outer surface. The copper-bonded steel cored rod is preferred due to its superior strength, corrosion resistance, low resistance path to earth, and cost-effectiveness.
To ensure optimal performance, the Earth Electrode must meet specific requirements. It should be at least 17.0mm in diameter and a minimum of 3.0mtrs long. Additionally, the minimum copper bonding thickness should be 250 microns.
To ensure the quality of the Earth Electrode, it can be visually inspected and checked for dimensions and thickness of copper coating using a micron gauge. This ensures that the electrode is up to standard and can perform its role effectively in the earthing system.
Earth Enhancement material
Earth enhancement material is a substance that enhances the effectiveness of earthing systems, especially in areas where the soil conductivity is poor, such as sandy, rocky or areas with varying moisture levels. It is designed to improve the conductivity of the earth electrode and the ground contact area. The ideal earth enhancement material should possess certain characteristics, such as high electrical conductivity, good water retention capacity, low corrosivity, and compatibility with the soil. It shall have following characteristics-
The ideal earth enhancement material is a mixture of graphite and Portland cement, with minimal bentonite content. It should conform to the standards of IEC 62561-7 and ASTM G57-06. This material should have a high level of conductivity, which enhances the ability of the earth electrode to absorb power and retain humidity. Moreover, it should be non-corrosive, have low water solubility, but highly hygroscopic. It must be suitable for installation in dry form or slurry form and should not require the continuous presence of water to maintain its conductivity. It should not dissolve, decompose, or leach out over time, and should not require periodic charging treatment or maintenance.
This earth enhancement material should be compatible with all types of electrodes and soil of varying resistivity. It should also be environmentally friendly, causing no pollution to the soil or local water table, and it should not be explosive. Additionally, it should not cause burns, irritations to the eye or skin, or any other health hazards. Overall, the earth enhancement material should be effective, safe, and sustainable for long-term use in the earthing and bonding system.
Construction of unit earth pit:
To install an earth electrode, a hole with a diameter of 100mm to 125mm is dug to a depth of approximately 2.8 meters. The electrode is then inserted into the hole and gently driven into the soil. At least 150mm of the electrode should be inserted into the natural soil.
Earth enhancement material, in slurry form and weighing a minimum of approximately 30-35 kg, is then filled into the hole and allowed to set. Once set, the composite structure (earth electrode + earth enhancement material) should have a minimum diameter of 100mm, covering the entire length of the hole. The remaining portion of the hole is then filled with backfill soil.
To connect the electrode to the main equi-potential earth busbar in the equipment room and other earth pits, if any, a copper strip measuring 150mmX25mmX6mm is exothermically welded to the main earth electrode. The main earth pit should be located as close as possible to the main equi-potential earth busbar in the equipment room.
Construction of loop Earth by providing multiple earth pits
In certain areas, it may not be possible to achieve an acceptable level of earth resistance with just one earth pit due to high soil resistivity. In such cases, a loop earth system consisting of multiple earth pits should be constructed. The number of pits required should be determined based on the resistance achieved from the previously installed earth pits.
The same procedure as mentioned for a single earth pit should be followed for each additional earth pit. The distance between two successive earth electrodes should be a minimum of 3 meters and a maximum of twice the length of the earth electrode, which is around 6 meters.
After installation, the earth pits should be interlinked using 25x2mm copper tape, and an exothermic welding technique should be used to make the connection. The interconnecting tape should be buried at a depth of no less than 500mm below the ground level and covered with an earth enhancement compound. This loop system ensures that the electrical potential is equalized across all the earth pits and minimizes the risk of electrical hazards.
Measurement of Earth resistance
The effectiveness of the earthing system is determined by measuring the earth resistance at the Main Equi-potential Earth Busbar (MEEB) using the Fall of Potential method. It is essential to have the installation process of the maintenance-free chemical earthing system carried out by qualified professionals with expertise in earthing system design and installation. This will guarantee that the system is correctly installed, operates securely, and functions consistently throughout its life cycle. As a result, it is recommended to hire certified professionals with the required skills and experience to install the earthing system.