The grounding of overvoltage protection to a quality ground is a requirement for their correct functioning. The ground is presented by protection conductor PE.
The conductor PE isseparately laid down in 5-conductor TNS system, which is enacted by standard. It is enacted for households, offices and industry. Energetics should secure this system type at the secondary side of a transformer already. All the installed overvoltage protection devices are connected to the equipotential busbar PAS by means of PE conductors. This PAS busbar has the closest potential to the ground potential.
In TNC systems overvoltage protection devices are grounded onto PEN conductor, where differential balancing currents are flowing. That is why it doesn´t ensure as quality conditions for overvoltage protection functioning as the PE conductor.
The values of the whole grounding resistance and the resistance of grounding conductors PE, PEN in the conductor routing at the ends, are stipulate by standard CSN 33 2000-4-41. It is necessary to avoid loop connection of switchboards during the realization of the building grounding which make conditions for flow of faulty currents and a potential difference between conductors PE and PEN in their route towards ground potential. Star configuration drawing of the grounding conductors acc. to EN 62 305 is the optimal way how to eliminate these unfavourable effects.