@ Alan D:

The very West of Germany is just the western border to Belgium and the Netherlands around Aachen.

German power grids have a long history of many little power companies (here used to be 3 of them in one city).

Nevertheless the probably most typical grid is TN-C-S. This means that you got four wires entering your house. One of them is ground and neutral at the same time (in Europe called PEN). The other have 230V against ground and 400 against each other at 120°.

In older installation until 1971 the combined PEN usually continued 'til wall outlet or lamp. So you got just two wires, but one is the earthed Neutral, usually bridged in the outlet between one pole and earth brackets of Schuko! In pre-computer times this worked quite well, if only skilled persons worked on it. Main danger is a breaking PEN leading to full phase voltage on the (metal) bodies of faulty devices. Now it is obsolete as the difference in potentials by high currents using the PEN is a problem for electronic equipment.

Unearthed circuits are usually pre-WW2 or GDR.

Now in an actual installation you separate N and PE at the entrance in a house and bond it to a ground electrode in the foundations (mandatory for new houses). A PEN is today formally only allowed for more than 10mm2 but uncommon. In older houses it is very typical, however.

Actual minimum for a new meter is a 3 phase-63 A mains or 43,5 kW. This is usually enough for 6 of them ,but ...
Fuses become rare and more and more replaced by selective breakers. The N is normally never switched nor protected.

Protection by RCD is for TN-C-S in residences only mandatory for bathrooms and similar and outlets used also from the outside of a house (30 mA).

But in certain regions you also will find TT-grids with different designs.
For TT it is more or less necessary as the principal rule is the above mentioned 0.4 seconds. After that period of time fault voltage must be below 50 VAC. Without RCD it would need a very very good ground electrode system.

That might be enough for the moment. Feel free to correct my technical terms in English, as this is not simple in German already.


[This message has been edited by Wolfgang (edited 09-29-2005).]