Earthing is the method of transmitting uncontrolled electricity discharge directly to the ground through low resistance wires or electrical cables. It is basically a system designed to protect people (and equipment) from the electrical shock caused by electrical leakage. The earthing delivers the “0” (zero) potential to metal parts such as chassis, constructions etc. In the case of the leakage, the current goes from the metal elements through the hearing to point of the lowest possible potential, namely “earth”. If somebody touches the metal elements, even in case of leakage, the electrical potential of the person and the element are equal to 0, so there is no current flow. Without earthing, in the leakage situation, the metal element has higher potential so the electricity goes from the high potential point (metal), through the human body, to the earth.
Regardless of the system voltage, earthing is required in all solar PV power plants. Its main purpose is to reduce the risk of dangerous electrical shocks to the installer or the user from uninsulated metal parts of a plant. There are two common types of earthing done in solar PV power plants:
- Equipment earthing – The basic objective of equipment earthing is human safety by preventing the surge of current to an unsafe level. In this metallic body of equipment / devices is connected to the grounding grid to prevent electric shocks to any personnel touching that equipment or device.
- System earthing – The system earthing is also referred to as neutral earthing. Under this, neutral point of the electrical system is directly connected to the earth.
Earthing in a solar PV power plant
A rooftop solar power plant earthing is usually divided into two parts based on its electrical construction, AC side and DC side.
- DC Earthing – These parts cover the equipment in the DC side of the electrical circuit, such as PV modules, module mounting structures, DC junction box, DC Monitoring Box (if any), etc.
- AC Earthing – These parts cover the equipment in the AC side of the electrical circuit, such as solar Inverter, LT/HT Panels, LT distribution box, etc.
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