To safeguard human life as well as outdoor equipment from excessive voltages and lightning strikes, and to limit the transferred potential to a minimum, an earthing system is required.
To minimize the surge voltage and impact by providing low resistance in the earth grid or path. The goal of earthing design is to offer a path for lighting disconnection while also keeping the highest voltage gradient throughout the surface within safe limits during a fault or surge.
The earthing system comprises mostly of an earthing grid buried near protective equipment in the surface area. A collector network will run from the earthing network to every piece of equipment that has to be earthed. Vertical risers/earthing stips/suitable size cable connect the entire collector network to the earthing grid at various elevations.
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What is lightning?
As we all know, lightning is a common occurrence, and everyone must have witnessed it during a rainy session. There are two charges in any voltage circuit. One is a positive charge, while the other is a negative charge.
We all know that opposite charges attract each other. This phenomenon completes the circuit with the help of a conductor such as a wire, conductor, or even air.
As a result of dielectric breakdown in the air, negative electric charges build up in a thunderstorm and discharge to the ground (positive/ no charge) area.
Why Is Earthing Necessary?
Earthing is utilized for safety and surge prevention against lightning and other types of surges. As a result of the voltage discharge, a large amount of current (about 20-150kA) flows during lightning. If a structure, light tower, human, or other outdoor equipment is struck by surge or direct lightning, a high voltage impulse is transferred to the ground, affecting the body and equipment.
What Are The Advantages of Earthing?
Earthing is necessary for safety reasons, and the government recommends that earthing be used for any system protection. It is required for industrial purposes and is also suggested for domestic uses. The following are some of the key advantages of using an earthing system:
- To protect solar PV module/plates mounted outside from lightning.
- To avoid any human casualties as a result of the surge.
- For the protection and safety of expensive equipment, as well as to avoid any big losses.
- To comply with government regulations in order to obtain clearance for both industrial and domestic applications (above 50kW Solar plant system).
What Is The Process of Earthing?
Due to a surge or lightning strike, a high voltage impulse is sent into the earth through the air and any other equipment connected to the earth, such as buildings, people, tower poles, and so on.
We know that every material has some resistance, therefore we can divert the lightning course or minimize any hazards by creating a low-resistive surge channel to mitigate the lightning impact. For energy distich, charges always follow the least resistive path or the closest point.
As a result, a lightning arrester is installed on top of any protective equipment and is connected to a separate earthing strip/cable that leads to the earthing pit, resulting in a low resistance strike path.
Materials For The Earthing Kit
| Components | Details | Quantity |
|---|---|---|
| Lighting Arrester | Made of Copper Rod, Height – 1.2 – 1.5 meter long, Resistance – 3-5 Ohm | 1 or more as per project requirement |
| Wire | Thickness – 16 sq.mm (DC/AC) | Depending on the project |
| Earthing Pit | 4.5 ft. to 10 ft. | 1 pit for each earthing rod |
| Earthing Rods | Length – 3 Meter. | 3 Rods |
| Chemical Compounds | To reduce the soil resistivity | 1 bag for each pit |
- Galvanized steel – Galvanized iron or tinned copper type flat or rods as available for connection up to LA & subterranean risers are utilised for surface or air contact earthing. To prevent corrosion and extend the life of the material, galvanising steel and tinned copper are employed.
- Copper rod – We can use non-galvanized or untinned copper rod for underground pit earthing.
- Lightning Arrestors – Generally, a 2-3 metre long LA is placed on the surface top to protect the equipment from lightning strikes, depending on the design requirements.
- Flexible single core type Copper cable – Single flexible core FRLS (Fire redundancy low smoke) XLEP/PVC single core flexible copper cable with 1.1kV/0.6kV voltage grade 4,6,10,16, or 25 square millimetres Depending on the design requirements, different cable sizes can be employed. Each PV/ solar module connection, ACDB, and inverter connectivity is 4 sq.mm.
- Bentonite Powder – Bentonite clay is used to reduce earth resistance by providing ground enhancement, which effectively reduces resistance between the soil and the earth electrode (such as copper earth rods or earth mats) by retaining moisture.
- Chemical compounds – This is a sort of earthing substance that is placed to the earth pit to help improve the soil’s condition and reduce soil resistivity. It’s a mixture of sodium and potassium chloride that serves as an ionic chemical to help conduct electricity.
- Insulators are used to isolate the earthing material from the surface area or wall in order to prevent the spread of high voltage impulses into the surface following a lightning strike.
- Installation Accessories – Bolts, clamps, and other installation accessories are utilised to secure the lightning material.
Earthing Installation For Beginners
There are numerous publications and IEC/IEEE/IS standards on earthing calculation and installation accessible. However, we can select an earthing material and kind based on the intended use and material availability on site.
Mat/grid-based underground earthing with GS/Copper material is required for obtaining ground resistance less than 1-ohm meter in high voltage areas, such as any form of a power station, switchyard station, multi-story apartment, and any other facility, as per IEEE 80 standard.
Step 1: Check if Lighting Arrestor is Required
If there are any maximum height structures within a 30 foot (10 meters) radius of the solar panel installation area, there is no requirement for a lightning arrester on that location. If your solar panel installation is at its highest point, a lighting arrester must be installed.
Step 2: Calculate the distance and height.
If step 1 was completed successfully, you should now measure the distance between the solar panels and the lighting arrester installation. The conventional rule is that solar panels and lighting arresters should be 3-4 feet apart.
The second step is to place the lighting arrester 12 to 15 feet away from the solar panel installation. It is subject to change. If solar panels are installed on high-rise panel stands, the height should be between 12 and 15 feet. The golden rule is that solar panels should be no closer than 4 to 5 feet away.
- Distance from solar panel installation: 5-10 feet
- Height of solar panel installation: 6 to 7 ft.
Step 3: Apply Insulators
To avoid touching earthing flat material with the surface, use a porcelain insulator (rated for 1.1kV).
Step 4: Earthing Pit & Chemical Compound
According to government guidelines, three (3) earthing pits are recommended. The first is for the Panel Stand, the second for the Inverter, and the third for the Lighting Arrester. Some soil-enhancement chemical compounds (charcoal & bentonite mixed clay).
Step 5: Wiring
Flexible 16 sq. mm cable for LA earthing hookup. All incoming wires can be contained in a single PVC pipe.
Earthing Kit Price in India
The cost of an earthing kit varies depending on the material chosen and the solar plant’s rating, however for a solar system with a capacity of up to 25 kW and a GI flat/riser rod earthing kit, the cost would be around Rs. 8000 per earthing kit. That means that if you install three earthing kits, the total cost of all rooftop solar plants will be around Rs. 25,000. All components, as well as installation, are included in this price.