A Ufer Earth is a type of local earth with very low impedance, which can improve the safety of TT earthing systems. It is even low enough impedance to use as a lightning conductor earth.
A Ufer Earth consists of a connection to steel mesh reinforcement in a building's concrete ground slab, with the sheets of mesh being tied with wire before the slab is poured. It can therefore only be fitted at new build time, it is rarely practical to retrofit.
A Ufer Earth is not used alone, a conventional earth rod is still needed as usual.
Ufer Earthing explained. Note that the site also discusses standard US grounding practices, which are not identical to ours.
Using Ufer Earthing in conjunction with the standard earth rod brings 3 main advantages:
- Much lower TT earth resistance makes the house earthing system safer and more effective.
- Ufer earthing equipotentially bonds a house's concrete slab floor to the electrical earthing system, eliminating the risk of shock from the CPC or equipotential bonding to floor. This risk exists with TT systems, and to a lesser extent with PME supplies.
- Lastly a Ufer earth means the house has 2 earths, and loss of a connection to either one does not leave the building with no working earth, which can happen with standard TT systems, and which is a dangerous fault.