Grounding terminals in photovoltaic mounting systems
Grounding terminals are safety-critical components in photovoltaic systems and are used to create electrical potential equalization between all metal parts of the system. They ensure the connection between the module frame, the mounting system and the building's earthing system, thereby making an important contribution to lightning and personal protection.
Grounding terminals, more than just a screw terminal
The design of grounding terminals is based on high-quality, corrosion-resistant material, typically stainless steel or refined aluminum. The contact elements are designed in such a way that when the terminal is tightened, they penetrate the oxide layer of the metal surfaces to be connected and ensure a permanently low contact resistance. Special toothed discs or contact teeth dig into the metal surfaces and create a gas-tight, long-term stable electrical connection.
Modern grounding terminals often have multifunctional properties. For example, they can be integrated into module terminals and then simultaneously take over the mechanical fastening and electrical contacting of the modules. This integration significantly reduces the installation effort and ensures a continuous grounding connection across the entire module surface.
The dimensioning of the grounding terminals depends on the expected fault and lightning currents. The cross-section of the contact surfaces must be large enough to be able to carry these currents without excessive heating. The mechanical stability of the connection is ensured by defined tightening torques, which are typically between 8 and 12 Nm.
The long-term stability of the grounding connections is particularly important. The terminals must withstand extreme weather conditions, UV radiation and thermal stress caused by day-night cycles. The materials used are therefore carefully matched to avoid electrochemical corrosion. When combining different metals, the electrochemical voltage series must be observed.
The installation of earthing terminals requires particular care and may only be carried out by qualified specialists. The contact surfaces must be clean and free of oxidation. After installation, the contact resistance must be measured and documented. Typical limit values are a maximum of 0.1 ohms per connection point.
The standard-compliant installation of earthing terminals is regulated by various regulations, in particular by VDE 0100-712 and the lightning protection standard DIN EN 62305. The terminals must have appropriate test certificates and be approved for use in photovoltaic systems. Regular maintenance and inspections of the earthing connections are mandatory and must be documented.
Innovative developments in the field of earthing technology aim to further simplify installation and at the same time increase reliability. Self-tapping contact elements and tool-free assembly systems are becoming increasingly important. The integration of monitoring functions that enable continuous monitoring of the earthing connections is also increasingly in demand.
The correct selection and installation of earthing terminals is an essential factor for the operational safety of a photovoltaic system. A well-thought-out earthing concept not only protects people and the system, but is also a prerequisite for trouble-free operation over the entire service life of the system of 20-30 years.