Earth Pit – Technical Aspects & Construction
An Earthing Pit Chamber provides access to check whether earthing (earthing resistance and related information) is functioning properly.
It's made with a UV-stabilized high-impact pit with an easy-to-lock lid, allowing secure and convenient maintenance of earth rod ground termination. Also, it is lightweight and offers enough resistance against moisture (low porosity), good protective properties, long life, safe and secure in any climate condition.
Requirements of Earth Pits:
An earth pit is required to construct a channel for the additional charge generated during operation. A low-resistance path allows excess current to flow freely while keeping the equipment secure.
Where there is a potential source, earthing is essential at that time. In the maximum sector, earth-pit inspections are mandatory every six months.
Megger is used to test resistance. Megger is a high-resistance checking metre that uses Ohms law to measure resistance. In industrial practice, strip & wire earthing are used.
Thunder Protection and Earth Pits:
Copper rods are in high masts for thunder protection, or any tall structure independently has a copper rod on them.
Earth connection maintenance is done separately for a separate building.
Thunder can create unexpected fire or damage, so adequate and separate earthing is required.
Classification - Light Weight Plastic Earth Pit:
Earth Housing Pit is made of high-grade polypropylene for high strength and stress levels, allowing it to withstand a maximum load of 2000 kg.
The lightweight design makes it simple to handle, store, and move, which improves installation efficiency. Due to the simple locking of two units, the termination area is expanded by 100%, allowing deeper earth electrode connections and lessening the impact of dangerous voltage gradients.
Concrete Earth Pit:
Concrete Earth Pits are heavy duty and with a load rating of up to 4000 kg. The connection of the rod is protected by the Concrete Pit, making it accessible for inspection. Installation of the earth bar can be done diagonally in slots provided for numerous conductor connections in the Concrete Inspection Pit.
Significance of Earth Enhancing Compound:
- It reduces soil resistance.
- It's a treatment that lasts for a long time and doesn't need maintenance.
- It's effective under a variety of soil conditions.
- Seasonal fluctuations in resistance levels are minimal.
- Friendly for the environment and easy to handle and install.
- It has no negative impact on the soil.
- It clings to the surface and refuses to wash away.
Methodology to construct:
a) Earth excavation for regular earth, the pit is 1.5 m x 1.5 m x 3.0 m in size.
b) Use Galvanised Iron Plates with dimensions of 500 mm x 500 mm x 10 mm (or greater) to increase Earth Contact and reduce Earth Resistance.
c) When the tested ground resistance is over 3000-ohm metre, Earth Enhancement Compound for an earthing system is suggested, according to IEC 62305. This level of resistance is in dry or rocky locations, according to Indian Standard 3043.
d) As an earth electrode backfill, it reduces soil resistance. The clay is sodium activated montmorillonite, which expands to being dry volume when mixed with water.
e) It can retain moisture for an extended period to absorb moisture from the soil around it (for example, rain).
f) Watering the earth pits in the summer should be done, but with caution to ensure that the pit soil is moist.
g) Sand creates porosity to circulate water and humidity throughout the mixture.
h) Place a 500 mm x 500 mm x 10 mm GI Plate (EARTH PLATE) in the centre of the mixture.
i) To connect the Plate to the System Earthing, use a 30 mm X 10 mm Double GI Strip.
j) It is preferable to utilise a Pipe with a 2.5′′ diameter and a Flange on the top to cover the strip.
k) Cover the top of the pipe with a T joint to keep it from becoming clogged with dust and mud, and run water through it. Ensure it's done from time to time and goes through the bottom of the earth plate.
Interconnection of Different Earth Pit - With Transformer Neutral
Section 5 Page 53 & 54 Clause No. 22.1.3 and 22.3.1 of IS3043 state that the transformer neutral should connect to the ground grid.
The interlinking of the neutral earth pit with the general body earth has been permitted and supported by the previous norm.
According to the standard, an interconnected system should replace the prior practice of separate/isolated earth, for avoiding unnecessary redundancy and expenditure.
The design methodology, resistance measurement, and acceptance criteria of the earth grid when using such an interconnected earth system is specified in the Clauses of IS3043. An appropriate IS3043 excerpt is enclosed.
With Lightning Arrester:
The lightning protection system earth should be solidly bonded to the general earth grid, according to the standards IEC62305-3 and BS7430.
In case the hazardous potential is developed due to lightning strike, such interconnection provided due to lightning arrester with earth pit can withstand that heavy potential and provide a safe path with earthing connection.
With Electronic Equipment:
IEEE142-2007: In Clause No. 5.5.3 of the Section of Electronic Equipment Grounding, this standard discusses separate/isolated grounds.
As per the guideline for electronic equipment manufacturers for earthing, it is very complex to understand the functions and operations of neutral conductors.
IEC-61000-5-2 does not recommend isolated "ISOLATED" earth electrodes for computer and electronic systems. The electronic earth pit/system must connect to the earth grid beneath the soil.
IEEE-1100-2003 This standard discusses isolated grounding and single point grounding systems. It states that two different earthing systems are advised for electronics apparatus for safety and reliability of the connected system. It is beneficial to use a separate earth pit for the electronic system and connect it with the general earth grid.
Features of Various Light Weight and Concrete Based Earth Pit:
- They are tested and approved by CPRI, are long-lasting and require no upkeep.
- Copper coating thickness is homogeneous thanks to a unique production technique.
- It's simple to set up and unbreakable, corrosion-resistant with the lowest ground resistance.
- The copper has a purity of 99.9%. As a result, the capacity to conduct oneself is excellent. The resistance of earth pits to the elements will be determined by the terrain in which they are installed.
- Accordingly, the number of earth pits is determined based on the location's soil resistivity data, a Grid earth resistance value of fewer than 5 Ohms for electrical grids is maintained.
- In solidly grounded neutral transformers, the resistance between Neutral, Body Earth and Panel Earth shall be zero while incorporating earth pits.
- These earth pits are corrosion resistive, and most important Electrical and thermal conductivity are both excellent.
- With advanced engineering and cutting-edge technologies, Installation becomes simple for earth pits.
Steps for Safety of Earth Pits:
1) Regular inspections of Earth-pit.
2) Take the essential precautions to ensure a high level of resistance.
3) Separate the electrical and instrumentation trenches.
4) Separately maintain neutral earth-pits.
5) Separate earthing is required to maintain a high mast or any structure utilised for thunder protection.
6) In the case of 2 earthings, maintain the thickness of the strip-earthing.
All earth systems in an electrical installation, such as neutral earth, lightning protection system earth, and electronic earth, should have their dedicated earth pits/earth terminations, as shown above. However, the rest of the earth's grid should not cut it off.
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