LIGHTNING PROTECTION 2: GROUNDING
- rentechsyst
- Oct 8, 2020
- 3 min read
Updated: Jul 20, 2024
As previously mentioned lightning can cause serious damage to your solar equipment. And this lightning strike does not have to be direct; even a few kilometers (NOT just a few meters) away can cause damage!! The primary protection for your PV system should be Grounding; and this is an absolute must!! Grounding is the process of joining/bonding a piece of equipment or metal part electrically to the earth.
Before we even go outside (where the lightning is :) ) grounding is necessary inside the building to protect equipment from becoming energised and damaged in the event of a fault. ALL appliances inside the building must be connected to a mains grounding bar in the Distribution Board. This grounding also; thankfully; prevents electrical shocks that can potentially take place when one gets in touch with the exposed metal part of equipment/appliances.
With proper grounding full fault current flows through the resistance equipment grounding tripping a breaker; shutting down the circuit; and removing the immediate shock potential.[2]. The solar inverter and charge controller; inside the building need to be grounded; as the housing/shell is usually metallic which can conduct electricity in the event of a fault inside.
Ok back to our subject: lightning. When there is a storm that has lightning, the clouds build up a static electric charge which results in accumulation of the opposite charge in objects on the ground. Objects that are that are not connected electrically to the earth tend to accumulate the charge more strongly than the surrounding earth. Connecting metal objects to the earth allows some of the charge to be “drained” to the earth thus making your panels less attractive to the lightning. Also if lightning does strike the grounding connection provides a safe path for discharge directly to the earth rather than through your wiring and appliances/equipment [3].
Grounding your panels provides some protection to the system in the event of a direct or indirect lightning strike by limiting voltage imposed on a system by lightning, line surges (ZESA surges) and unintentional contact with higher-voltage lines. It also limits the voltage-to-ground that can occur on normally non-current-carrying metal components like frames and rails[1]. Grounding of the panel frames also protects people from any possible electric shocks from exposed current carrying metal parts.
How is grounding done? Exposed metal parts (e.g frame of solar panels; frame of inverter; frame of charge controller) are connected to an appropriately sized copper wire then the wire is connected to a grounding rod in the earth (hit into the ground)… with the grounding rod for the panels preferably separate from the internal grounding of-course (though some standards allow connection of panel grounding to the inverter; but we recommend the method of separate grounding). Care must be taken in grounding the solar panel frames. These panel frames are made of Aluminium and connecting directly to the copper wire causes a phenomenon called “galvanic corrosion”.. this is basically accelerated preferential corrosion caused by joining two or more metals of very different corrosive potential . To ground the panels a stainless steel lug (see below) is used to electrically connect the frame and the copper wire.. alternatively you can make use of coating that prevents elements that cause corrosion from entering.
Due to the importance of grounding; it is strongly advised that you use a qualified installer or electrician to ensure that your system has this primary form of protection from lightning. In the next post we look at secondary protection: surge arresters/surge protection devices
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About Author:
Lovewell Chitiyo is a Mechanical Engineer with 15 years experience in the building services Engineering consultancy, renewable energy systems and sustainable design fields. He is currently studying Masters in Renewable Energy at Stellenbosch University in South Africa
Lovewell is an Accredited Professional with the Green Building Council of South Africa for Existing Buildings Performance and New Buildings; Interiors, holding several qualifications and certification in Renewable Energy and Sustainability.
Lovewell also has vast experience in design, supervision, installation and commissioning of several projects locally and regionally in the last 15 years.
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