Grounding PV Systems: What You Need to Know

Grounding is a central safety feature of every photovoltaic system. It not only protects against electric shocks, but also protects technology and buildings from damage caused by lightning or electromagnetic interference. Correctly installed grounding reduces the risk of fire and increases the service life of the system. Despite its exposed location, a PV system does not increase the risk of lightning – on the contrary: with proper grounding it even offers protection. For this protection to be effective, clear standards, regulations and technical requirements must be adhered to.

Key facts at a glance

• Grounding prevents electric shocks, system damage and fires by safely dissipating electrical currents.
• PV systems do not increase the risk of lightning strikes – they conduct lightning safely when grounded correctly.
• An effective lightning protection system includes external lightning protection (arresting device) and internal surge protection.
• equipotential bonding compensates for dangerous voltage differences and protects people and devices.
• The grounding must be installed and regularly maintained in accordance with DIN 18014 and VDE 0185-305-3.

What does grounding achieve in a photovoltaic system?

Grounding protects photovoltaic systems from electric shocks, lightning damage and fires by safely diverting electrical currents into the ground. It is essential for effective lightning protection and minimizes electromagnetic interference.

Why grounding is important for PV systems

Grounding serves as a fundamental protective measure for every photovoltaic system. They allow electrical fault currents to be safely diverted into the ground. This protects both people and the system technology. Without grounding, there is an increased risk of electric shock, fire or equipment damage. For PV systems with metal frames and modules, a connection to ground is therefore mandatory.

This can prevent live parts from becoming dangerous, especially if there is a defect in the insulation. Grounding also contributes to electromagnetic compatibility. This is important in order to avoid disruptions in the home network and adjacent devices. It enables a functioning equipotential bonding in which all conductive parts are at the same electrical level. This also ensures the so-called “protective equipotential bonding”.

Without grounding, lightning strikes could generate dangerous voltages that could destroy devices. Surges caused by distant lightning strikes are also defused via the grounding system. Therefore, every PV system must be connected to the main ground bar of the building. This is the only way it can be effectively integrated into the home’s protection concept.

The grounding should be checked and documented by a qualified electrician. Regular system maintenance is essential to ensure long-term security.

Lightning protection: how external and internal protection work together

Complete lightning protection always consists of two components: external and internal lightning protection. The external lightning protection is responsible in the event of a direct strike. It consists of air-termination devices, down conductors and grounding components. Lightning rods on the roof capture the voltage and direct it into the ground. This prevents lightning from penetrating the building in an uncontrolled manner.

Grounding ensures that this enormous energy disappears harmlessly into the ground. In addition, the internal lightning protection protects all electrical devices. This so-called surge protection is installed in the electrical distribution and directly on sensitive devices. It prevents tensions from spreading to the network due to distant impacts.

Such surges can damage inverters, routers or storage. Surge arresters (SPD) provide safety by diverting energy into the ground. Both systems must be combined with each other. This is the only way to ensure that the system is protected from both direct and indirect lightning influences. This dual strategy is particularly important for PV systems because they are installed exposed.

The coordination of both systems is regulated in standards such as DIN VDE 0185-305-3. Anyone who foregoes lightning protection risks damage to technology and buildings. Therefore, each PV system should be individually planned and retrofitted if there is no comprehensive protection.

Equipotential bonding as a key safety measure

equipotential bonding electrically connects all conductive parts of a system with one another. The aim is to create the same electrical voltage on all touchable metal parts. This drastically reduces the risk of electric shock or voltage flashovers.

Even in the event of lightning strikes, the current is distributed evenly. This not only protects people, but also technology. equipotential bonding is not only relevant for the PV system. It also affects the entire electrical system in the house. Cables, frames, modules, the inverter and metal house parts must be connected to each other. This creates a closed protection system.

Equipotential bonding can be easily integrated, particularly in buildings with foundation earth electrodes in accordance with DIN 18014. A common source of error is the lack of connection to the main ground bar. This must therefore be checked and recorded during commissioning. The connection is usually made via copper conductors with a defined cross section.

Maintenance is also important – connections can be damaged by corrosion. National standards such as VDE 0100-410 and VDE 0185 apply to equipotential bonding. Correctly installed equalization is a prerequisite for lightning and surge protection. Without it, the protection mechanism does not work reliably. In PV systems, equipotential bonding also ensures EMC protection (electromagnetic compatibility), which reduces network disruptions.

Standards and regulations for grounding PV systems

In Germany, several standards regulate the grounding requirement. For new buildings, the foundation earth electrode according to DIN 18014 is mandatory. This forms the basis for later grounding of the PV system. The grounding itself is carried out according to IEC 60364 and VDE 0185-305-3. For buildings with an external lightning protection system, there is also a requirement that the grounding resistance must be less than 10 ohms. This specification serves to ensure the safe discharge of lightning currents. Compliance is proven through measurement.

Documentation of the installation is also mandatory. The VDE FNN provides practical information on this. Deviations from the standards can lead to liability risk in the event of damage. In addition, many network operators require grounding according to their technical connection conditions (TAB). Additional requirements apply to systems with storage. In particular, inverters, storage and communication systems must be included in the protection concept.

It is also important whether the system is designed as a TN or TT system. This significantly affects the grounding strategy. That’s why planning by a specialist electrical company is essential. Violations of the regulations not only endanger safety, but also the feed-in tariff. If you want to be on the safe side, you should have all applicable regulations checked in advance.

Grounding in practice: design and connections

Grounding is usually connected directly to the main grounding bar (HES). This is usually located in the house connection room. From there the connection to the PV components is established. Copper or tin-plated cables are usually used. These must be weatherproof. The module frames are connected to each other via equipotential bonding conductors.

The connection is made via screw or press terminals. The modules themselves are conductive and connected to the frame. The DC side is also included in the protection. Grounding the inverter is particularly important. This is often the interface between the DC and AC networks. Incorrect grounding at this point can cause dangerous voltages. Surge arresters are also connected directly to ground. They immediately dissipate dangerous overvoltages into the ground.

Grounding must be checked at regular intervals. Corrosion, mechanical damage or loose connections can affect protection. A maintenance interval of 2 to 5 years is recommended. Experts also carry out measurements of the ground resistance. This is the only way the system will remain safe and compliant with standards in the long term.

Does a PV system increase the risk of a lightning strike?

Photovoltaic systems are often considered lightning magnets. But that is a mistake. Studies show: The risk does not increase significantly with a PV system. Rather, the exposed location enables controlled discharge. A correctly installed lightning protection system is a prerequisite. PV modules and substructures are usually made of conductive aluminum or steel.

These materials can absorb and safely dissipate lightning currents. Grounding then ensures safe discharge into the ground. It’s not just the choice of material that matters. What is crucial is the connection of all components to the grounding system. Internal lightning protection also plays a role. Surge arresters prevent damage from nearby impacts. It is also important to implement the building regulations. These require suitable measures as early as planning.

This is particularly crucial in regions with high lightning density. Insurance companies also often require lightning protection measures. Without protection, lightning can cause five-figure damage. Therefore, when implemented correctly, a PV system does not offer any disadvantages, but rather additional protection.

Conclusion

Proper grounding is the backbone of every safe photovoltaic system. It protects human lives, prevents fires and extends the service life of technology. Anyone who pays attention to professional implementation according to standards during planning and installation reduces risks and meets all legal requirements. An individual grounding concept should be created, documented and regularly checked for each PV system.

Sources for NA grounding of PV systems:

• AceFlex – PV system grounding where to connect? We know it!
• DEHN – Grounding and equipotential bonding for PV systems in residential buildings
• VDE – Lightning protection of photovoltaic systems (includes grounding aspects)