Foundation earth electrode
A foundation earth electrode is a ring earth electrode that is installed directly above or below the foundation level of a structure. Ideally, it is arranged as a closed ring in the foundations surrounding the building and, if necessary, connected to the reinforcement .
The current DIN VDE 0100 -540: 2012-06 differentiates between "foundation earth electrodes, laid in concrete " and "foundation earth electrodes laid in earth". According to DIN VDE 0100 -540, VDE-AR-N 4100 and TAB 2019, a foundation earth electrode must be installed in all new buildings in Germany in accordance with the national standard DIN 18014, and documentation including a measurement report must be created for the installation of the foundation earth electrode. The foundation earth electrode may only be created and checked by a qualified electrician or lightning protection specialist.
function
The foundation earth electrode is part of the electrical protection system, which consists of the connections between all conductive housings of electrical equipment and an earthed protective conductor for "protection against electric shock" . The aim is to avoid potential differences (voltages) on accessible conductive components by means of equipotential bonding and the interruption of the power supply in the event of a fault. For this purpose, the grounding conductors and the protective conductors of the power supply as well as all protective equipotential bonding conductors in the house connection room of a building are brought together on the main earthing rail. An earthing conductor establishes the connection to the foundation earth.
If a lightning protection system is provided, the foundation earth electrode is usually also used for lightning protection earthing and connected to the system's lightning current conductors.
execution
If the foundation earth electrode is to be enclosed on all sides by concrete to protect it from corrosion , it is laid in reinforced concrete on the lowest reinforcement layer. In unreinforced concrete, installation on spacers prevents contact with the ground.
The void-free embedding of strip steel , laid must the steel strip vertically in concrete or to ensure the fresh concrete must be by means of a vibrator to be carefully compacted.
If the reinforcement of the reinforced concrete is to serve as an earth electrode, the reinforcing steel must be welded to one another all around or connected to one another using suitable clamp connectors. If the connecting lugs are also made of reinforcing steel, they must be marked in order to avoid confusion with purely structural steel.
If a separate earth electrode is inserted into reinforced concrete, it must be connected to the reinforcing steel every 2 m (Germany) or every 10 m (Switzerland).
Hot-dip galvanized steel strips or round steel is usually used. If a covering of about 5 cm is guaranteed throughout, the concrete protects the earth electrode from corrosion . If bare or galvanized steel is brought out of the concrete at points that can be affected by moisture, special protection against corrosion is required, as there is a strong corrosive effect on metals on the concrete surface. Alternatively, special connection sets are available, which are often made of stainless steel. For information on the choice of materials and protection against corrosion, see also the main article: Earth electrodes .
The maximum permissible mesh size is 10 m × 20 m. For larger areas, the foundation earth must therefore have additional cross connections. Joints between individual foundations must be bridged with flexible expansion pieces ( dilation bridging ) in order to avoid tearing off the earth electrode.
The connection flag inside the building should protrude from the wall 30 cm above the basement floor and be at least 1.5 m free.
The foundation earth electrode is part of an electrical system and may only be planned, installed and checked by qualified electricians or lightning protection specialists who are entered in the installation directory of an EVU in accordance with the NAV . Documentation must be kept about this. which must be presented to the energy supplier or the building rights office on request.
Foundation earth electrode in the ground
Is not a foundation of concrete or provided by the foundation is bitumen layers ( Black pan ) or insulation boards isolated from the surrounding soil, it is a (ring) grounding below or laid outside the sealing or insulating layer in the ground to a sufficiently low grounding resistance to to reach. A leveling or cleanliness layer made of concrete is often provided below the sealing or insulating layer, in which the earth electrode can be embedded.
If there is a reinforced foundation within the insulating layer, a further foundation earthing is provided here, which serves as a potential equalization conductor. A connection between the inner and the outer foundation earth electrode should be established every 20 m.
Norms
- DIN 18014: regulates the planning, execution and documentation of the foundation earth electrode
- DIN VDE 0100-410: 2018 Installation of low-voltage systems - Part 4-41: Protective measures - Protection against electric shock
- DIN VDE 0100-540: 2012-06 Erection of low-voltage systems - Part 5-54: Selection and erection of electrical equipment - Earthing systems, protective conductors and protective equipotential bonding conductors.
- DIN EN 62305 (VDE 0185-305) Lightning protection - Part 3: Protection of structures and people
literature
- Dieter Vogt, Herbert Schmolke, Roman Wurm: Electrical installation in residential buildings. 6th edition, VDE Verlag GmbH, Berlin and Offenbach, 2005, ISBN 3-8007-2820-6