With highly sensitive electrical and electronic components in solar installations, the need for protection of these costly equipment against fault and lightning current is very much necessary. Electrostatic discharge can damage sensitive electronic equipment and disturb the solar power supply. Any voltage difference between individual electronic units can destroy valuable equipment. In addition, noise can cause data distortion and errors. Thus, the requirement for earthing arises. We, at EcoSoch, take earthing seriously and use quality components to safeguard sensitive equipment.
Lightning Arrester (LA)
For conventional LA, we use Cu bonded rods of 1m length and diameter ranging from 16-20mm and these are installed on the topmost part of the rooftop to protect the solar system from lightning strikes. It is installed on a nylon-66 insulated base of good mechanical and di-electric strength with a thickness of 20mm having a capacity to withstand lightning strikes of Extra High Voltage (150kV). The coverage of the LA would be based on the Protective Angle method.
On sheet roof, the LA is installed with the help of a short rail as below:
We also provide Early Streamer Emission (ESE) type LA for larger buildings with a coverage of 107m as shown below:
Earthing Strip / Down Conductor
As per clause 5.6.2 of IEC/IS 62305 – Part 3/2010, lightning down conductors require a minimum configuration of 50 sq.mm cross sectional area and can be of Cu, Al, Cu bonded steel, GI, etc. The conductor can be of round or flat form.
Though BESCOM mentions that earthing down conductors can have a minimum size of 6 sq.mm copper wire or 10 sq.mm aluminium wire or 70 sq.mm hot dip galvanized steel flat, we use insulated round aluminium down conductor of 8mm dia with OBO clamps for residences as shown below. Note that 8mm dia translates to a 50 sq.mm cross sectional area.
Insulated conductors are used in the field of external lightning protection to reduce or avoid the separation distance according to IEC 62305-3. Due to insulated down conductors, a sufficient dielectric strength of the insulation in case of lightning voltage impulses and a targeted manipulation of the electrical field strength at both ends of the cable is possible. This prevents the creeping discharges that would otherwise occur.
For larger projects, we use 25x3mm Insulated GI strip and earth insulators usually made of Red DMC (Dough Moulding Compound) as shown below. These can be installed on the terrace roof, wall or sheet roof.
The earth strip joints should be continuous arc welded or riveted together (where welding is not possible). Zn paint will be applied at the place of the welded joint to prevent corrosion.
We do not use a bare down conductor connected to the LA because if there is a direct lightning strike on the LA, then the current would flow down this bare conductor to the earth. However, during the current flow, arcing could take place onto metal constructions or into electrical installations within the building as shown in the below image.
Thus, there is direct coupling into the electrical installation in the building. If you want to learn more, check out page 86-87 of the OBO Lightning protection guide. This direct coupling can be prevented if we use insulated down conductors as shown in the image on the right.
Earth rods (Cu bonded)
Earth rods provided by us have 99.9% pure electrolytic Cu which is molecularly bonded with steel rod which is nickel sealed and is again coated with tin to give an extra layer of coating of 12 microns (as per IEC 62439) over the 100/250 microns copper bonding (as required under UL 467 and IEEE spec), which ensures total protection from galvanic corrosion. The same is ideal for seashore areas and in areas with low soil resistivity. At its core, these earth rods are made up of superior quality low carbon high tensile strength steel rods of 1.2m length and 14.2mm or 17.2mm dia.
The earth rods are manufactured as per IS 3043/1987 (Code of practice for earthing) and tested under the criteria mentioned in UL 467 (Adherence of Coating test, Bend test). They are CPRI tested and certified with a high tensile strength of at least 600N/sq.mm. This ensures performance and double protection as required under UL 467 and IEEE spec which makes sure that our copper bonded rods are excellent in corrosive soil.
There are also additional benefits of our earth rods as illustrated below:
Test report can be accessed here.
The Backfill compound or Earth enhancing compound is poured around the earth rod to increase the earth’s conductivity. The compound does this by enhancing the earth’s moisture absorption & retention property and by enriching the charge carrying ions in the soil, hence improving the overall efficiency of the earthing system.
These are high quality products with a lifespan of 25-30 years and follows IEEE 14.5(d) standard. These are permanent installations with no/least fluctuation in ohmic value. Test report can be accessed here.
The earth pit cross section is shown below for a 1.2m earth rod used for smaller projects and a 3m Cu bonded rod which is typically used in large projects.
Note that connection of earth strip to earth rod shall be with SS304 nut, bolt and washers. In case of more than 1 earth rod (for large projects), separation between two earth rods shall be more than the length of the earth rod and ideally double the earth rod length. Earth rod shall not be located closer than 1.5m from the building for large projects.
Earth pit chambers made of high-density poly polypropylene are used in the final stage of Electrical Earthing in order to give an external covering from direct contact of any kind. It has excellent resistance to acids & alkali and High dielectric property. They are stabilized against degradation by non-brittle and by sunlight to prevent cold weather damage. We also use cement based earthing chambers.