Earthing system is required to protect human life as well as protection of outdoor equipment against ex-cessive touch voltages & lightning strcoks and to keep transferred potential to a minimum. To provide the low resistance of the earth grid or path for nurtalize the surge voltage and impact. The objective of earthing design is to provide path for distich of lighting and keep the maximum voltage gradient along the surface within safe limits during fault/surge.
The earthing system mainly consists of earthing grid buried in the surface arae near to protective equipments. From the earthing network, collector network will run to all equipments which are to be earthed. The complete collector network at different elevations is connected to the earthing grid by vertical risers/earthing stips/suitable size of cable.
What is lightning?
As all we knows about Lightning & everyone must have been seen in the rainy session. In any of the voltage circuit there is two charge One is Positive and another one is negative. Now Negative charge travel in to the direction of positive charge to make circuit complete with the help of some path like wire, conductor & air also. Now the Lightning is same phenomenon of in which negative electric charges are built up in a thunderstorm to discharge to the ground (positive/ no charge) area as a result of dielectric breakdown in the air.
Why Earthing is required?
Earthing is used for safety and protection purpose from lightning & any kind of surge. During the lightning, A huge amount of current (around 20-150kA) flow as resultant of voltage discharge. If surge or direct lightning strike in building, light towers, human or any other outdoor equipment, a high voltage impulse is transmitted in to the ground and it will affect the body and equipments.
What are the benefits of Earthing?
Earthing is required for safety purpose and it will also recommended by government to use earthing for any of system protection. For industrial application it is mandatory to use and also recommended for domestic applications. There are major following benefits on earthing system,
- To protect outdoor installed solar PV module/plates from lightning.
- To avoid any human causality due to surge.
- For protection & safety of cost equipment & avoid any major loss.
- To campily government norms to get approval in case of Industrial as well as Domestic application (above 50kW Solar plant system).
How does Earthing work?
Due to Surge or Lightning strike high voltage impulse transmitted into earth through air & any of the other equipment connected to earth like building , human, tower poles etc. We know every material has some resistive quality so we any divert the lightning route or avoid the any hazard case with providing the low resistive path to surge for neutralize the lightning impact. Charge always follow low resistive path or nearest point for distich of energy. Hence Lightning arrester used at the top of any protective equipment and same will connect with separated earthing strip/cable upto earthing pit to achieve low resistance path for strike.
Earthing Kit Materials
Made of Copper Rod
Height - 1.2 - 1.5 meter long
Resistance - 3 Ohm - 5 Ohm.
Quantity - 1 (Compulsory), 1+ (As per project requirement)
|Wire||Thickness - 16 sq.mm (DC / AC anyone)|
Plain Area - 4.5 ft. to 10 ft.
Hilly Area - (Will update soon)
Quantity - 3
Length - 8 feet.
1. Galvanized steel - For surface or air contact earthing material used Galvanized Iron or tinned copper type flat or rods as per availability for connection upto LA & undergrounds risers. Galvanizing steel and tinned copper are specifically used to avoid corrosion on the material and to prolong the life.
2. Copper rod – For undergrounds pit earthing we can used non- galvanized or untinned copper material.
3. Lightning arrestors –Generally 2-3 meter long LA used based on the design requirement used on the surface top o protect the equipment from lightning spickes.
4. Flexible single core type Copper cable – Single core flexible copper with 1.1kV/0.6kV voltage grade, FRLS (Fire redundant low smoke) XLEP/PVC 4,6,10,16 or 25 sq. mm. cable size can be used based on the design requirement. 4 sq.mm for each PV/ solar module connection, ACDB & inverter interconnection.
5. Bentonite Powder – Bentonite clay used to lower the resistance to earth by providing ground enhancement effectively reducing the resistance between the soil and earth electrode (such as copper earth rod or earth mats) by retaining moisture.
6. Chemical compounds –This is special type of earthing material added to earth pit that helps in improving the condition of the soil and reducing the soil resistivity. It is mixture of sodium & potassium chloride & the compound acts as ionic chemical, which assists in conducting electricity.
7. Insulators - They are used for isolating the earthing material from surface area or wall to avoid spreed of high voltage impulse into surface during lightning strike.
8. Installation accessories – Bolt, clamps & other accessories are used to fix the lightning material.
Beginner Guide for Earthing Installation
So many articles and IEC/IEEE/IS standard available on earthing calculation and regarding to installation. However we can choose earthing material and type based on the required purpose and availability of material at site. Earthing for High voltage area, like any type of Power station, Switchyard station, multi floor apartment & any other plant etc. mat/grid based underground earthing with GS/Copper material need to provide for achieving ground resistance less than 1 ohm meter as per IEEE 80 standard.
a. Earthing Kit Installation in Plain Areas
b. Earthing Kit Installation in Hilly Areas
For normal area as like house, ground area, pole etc. we can provide standard earthing with buried of copper/GI material 3 meter rod in to the ground with some soil enhancing compound material to achieve low resistive path for earthing and lightning.
Step 1: Check Requirement of LA
Survey Solar Panel Installation Area, if you find any maximum height buildings in 30 feet (10 meters) radius areas, there is no need of lighting arrester on that site. If your solar panel installation is on maximum height there, it must be install Lighting arrester.
Step 2: Measure Distance & Height of Installation
If you check step 1, then you should measure the distance from solar panels and lighting arrester installation. The standard guideline is distance should be 3-4 ft. from solar panels and lighting arrester. And the second step is height of lighting arrester should be 12 to 15 ft. from solar panel installation. It can be vary. If anyone installs solar panels on high rise panel stands, then it should be approx. 12 to 15 ft. The golden rule is 4 to 5 ft. maximum from solar panels.
Distance: 5-10 ft. distance from solar panel installation
Height: 6 to 7 ft. height of solar panel installation
Step 3: Use Insulator
Porceline insulator (suitable for 1.1kV) to avoid touching of earthing flat material with surface.
Step 4: Earthing Pit & Chemical Compound
Three (3) nos. Earthing pit recommended as per Govt. Guideline. One is for Panel Stand, Second is for Inverter & third is for Lighting Arrester. Some Soil enhancing chemical compound material (charcole & bentonite mixed clay)
Step 5: Wiring
16 sq. mm. flexible Cable for for LA earthing connection. You can put all incoming wires in single pvc pipe.
Cost of Earthing kit
Cost of earthing kit also depend up on the selected type of material & rating of solar plant, however for upto 25kW solar system with GI flat/riser rod earthing kit cost would be approx. Rs. 8000 per per earthing kit. That means, if you install 3 earthing kit, you have to pay approx. Rs. 25,000 for all rooftop solar plants. In this cost, you will get all components, and installation too.
So many vendors available in market with earthing solution. However in Loom Solar, earthing solution & kits are available with wide range of earthing material options. Please visit Loom solar or contact with solar expert team.