Grounding is an important part of the safety and performance of photovoltaic systems. Grounding means connecting to earth at a point with zero reference potential. Two methods are used for equipment grounding and system grounding. Equipment grounding means the bonding together of metal frames, enclosures, or conductive materials that normally do not transmit electricity and connecting them to earth. This keeps these materials at a potential of 0 volts to earth.
System grounding is the connection of one of the current-carrying conductors in the system (DC or AC) to ground at a single point, which means that the conductor will be referenced to ground and thus will remain at a potential of 0 V to ground. Since potentials on exposed surfaces must be prevented, therefore equipment grounding is required on all systems, while system grounding is not necessary [1]. All power grids in houses or apartments are grounded, which means that both the equipment and the system are grounded. System grounding is the connections made for DC to the negative wire and for AC to the neutral wire, these wires become the ground wires.
A ground fault is an unintentional, electrically conductive connection between the current conductor of an electrical circuit and normally non-current conductors, such as metal enclosures, metal raceways, metal equipment, or grounding ( Fig. 1 ).

A properly grounded PV panel is shown in Fig. 2. The metal enclosure is connected to the ground rod via the equipment grounding conductor. This grounding connection provides a zero potential to earth, making it safe for a person to touch the box and the electronics used in the PV system.

The Fig. 2 shows lightning protection with an additional grounding conductor directly connecting the photovoltaic panel to the ground rod. This connection provides a direct, low-ohm path. The electronics have their own connection to ground. With this grounding, the risk of lightning effects is greatly reduced. All electrical systems are subject to transient surges. Voltage spikes can be caused by direct lightning strikes, nearby lightning that induces current and voltage on system conductors, or power line surges that are often caused by large industrial motors or other large inductive loads that are turned off and on. While lightning is always a problem, the most common probability of a surge comes from the utility grid, so entire houses and their appliances need surge protection. Long wire runs between the board and the inverter also increase this risk. Typical surge protection locations are at the entrance to the AC grid and the system monitoring equipment that is part of the photovoltaic system. The best surge protection is a well-grounded system.
Equipment grounding is absolutely necessary in all photovoltaic systems [2]. A grounding conductor is used to connect all supporting components and exposed metal parts that may come in contact with current-carrying conductors, such as PV panel frames, system mounting components, metal bases of equipment such as inverters, disconnects, and meters, metal junction boxes, metal brackets that support conductors, and any exposed metal part that may come in contact with conductors. Under normal conditions, current does not flow in the grounding conductor. The only time it conducts current is during a fault, when current flows through a low resistance path to ground. The grounding element is a galvanized steel tape (called cooper) buried in the ground or a rod driven into the ground ( Fig. 3 ). There may also be other methods that give direct contact between the grounding conductor and the ground in a hole, trench, or foundation.

A ground wire is usually a bare copper wire used to connect to a grounding element. The differences between the materials that make up the connector must be considered here. The wrong ones will cause corrosion, followed by increased resistance and loss of connection to earth.
An example grounding scheme for a complete photovoltaic system mounted on the roof or façade of a building is shown on Fig. 4. Structural components and boxes with electronic and switching equipment are grounded. The negative wire of the photovoltaic panels (DC) is grounded to earth before the inverter. This protects the inverter from malfunction. This creates a system ground on the DC side. The AC side equipment ground wire runs from the inverter to the main service system, connecting all wires and grounding them.
An ungrounded PV system must meet all equipment grounding requirements, that is, all boxes and structural components must be grounded. No negative or positive conductor is grounded on the DC side, that is, there is no grounding on the DC side. None of the current-carrying conductors on the DC side are connected to ground. The lack of system grounding does not affect the functionality of the system, but it does provide an opportunity to more easily detect faults, either between the current-carrying conductors or the ground. In this case, special inverters for use in ungrounded systems must be used. PV panel circuits must be protected, and insulated multi-conductor cables should be installed in special raceways. The cables for PV panels must have insulation that is more durable than other single-wire cables. Both must be protected by overcurrent protective devices and must be disconnectable.

Grounding on the AC side is accomplished by connecting the AC neutral wire to ground at one point. The AC grounding is made in the main service box, which is connected to the boxes and components. The neutral wire, which becomes the grounded conductor, is connected to the wire that connects the rails and metal housing bodies.