ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades UK cooker/RCD problem

Only most recently Vienna's distribution is being changed over from TT to TN, so there was no way to do TN-C. To make things even nicer, until the late 1970ies large parts of Vienna ran on a 127/220V grid without neutral (I assume wye connected transformers with grounded star point, but the neutral was not supplied to the customers).
So the most common way of grounding at least kitchen and bathroom outlets was until 01/01/01 running a ground wire to the nearest available water pipe, using it as a grounding electrode (or in better cases just as a grounding conductor up to the equipotential bonding in the basement). Even though such systems have to be replaced I'm pretty sure many of them are still around. I've seen one today... too bad the water mains are all PEx tubing... Think that would affect the ground resistance?
In Austria we're limited to a maximum of 165 ohms.

With new TN-C supplies the PEN has to be grounded locally and is split up at the service entrance point (Hausanschlußkasten). Approved means of grounding are flat iron 3x30mm or round copper, 30mm in diameter and 4.5m long.
Where in Germany Schuko sockets with TN-C jumpers were retrofitted in Vienna (and most parts of Austria) the old ungrounded sockets were just left in place. Today I checked out an apartment that has one single Schuko socket on 100sq. m...

Guten Tag Wolfgang,

Welcome to the forum.

In Britain we have TN-S, TN-C-S, and TT in use, which complicates earthing arrangements considerably.

TN-S was installed in the old urban areas, most of the distribution being by armored underground cables with the armor used as the separate earthing path back to the sub-station.

TT was the norm in rural areas for a long time, and necessitated the use of various earth-leakage devices just as for the TT systems common in France.

In residential applications, the voltage-operated ELCB (Earth-Leakage Circuit Breaker) was the norm for a long time, and many are still in use although now obsolete. These were superseded by the current-operated ELCB, or RCD to use the present-day terminology, which has gradually increased in sensitivity over the years.

As you say, with the high loop impedance which is possible on a TT system, the use of such a device is the only way to ensure that the power is disconnected at all, nevermind that it happens within the 0.4 second specified by the current regs.

TN-C-S was called PME here -- Protective Multiple Earthing. Its use goes back to at least the 1930s, but originally it was only used in specific rural areas in which local conditions made it very difficult to get a good ground connection. In fact the installation of a PME distribution system for an area back in the early days had to be by the explicit approval of the Secretary of State.

Gradually, TN-C-S has become more widely accepted and used, especially over the last 25 years or so. Extra earth connections have been installed on the neutrals of distribution lines, and it's now possible for any installation to be connected as TN-C-S.

Even though PME earthing is available now to all, of course there are still many properties using their own local earth and wired as TT. In my immediate neighborhood (rural Norfolk) I would estimate that at least 90% of domestic systems are still TT.

Where PME/TN-C-S is used here, the bond is at the service block just before the meter. From that point onward, neutral and earth are kept strictly separate.

There are some diagrams showing the various British arrangements here:
https://www.electrical-contractor.net/ubb/Forum15/HTML/000044.html



The 50-volt figure was also the limit set for the voltage-operated ELCB here. In practice, most of them would actually trip at a much lower voltage.



Yes, in English:

R = resistance
X = reactance (capacitive or inductive)
Z = impedance, i.e. SQRT (R^2 + X^2)

Plural: impedances


Your English is far better than our German I'm sure (Texas_Ranger excepted ).

Those long technical terms in German are scary!



[This message has been edited by pauluk (edited 10-01-2005).]

Surprisingly the letters for resistance, reactance, and impedance are the same in English and German. i think voltage (German U) and current (German I) are different. Power is P, apparent power (U*I, given in VA) is S and reactive power (unit var) is Q. Inductive reactance is XL and capacitive reactance is XC (subscript L and C).

Back to earthing arrangements... for some reason the voltage in Austria is 65V AC, not 50.

Voltage operated ELCB - German FU (Fault voltage interruptor)

HELP!!!! This thread has given me a real headache! Wolfgang's revelations about the effectiveness of earthing via a simple rod have led me to realise that my three-phase antique woodworking machines, run off a generator, have inadequate protection against earth faults/shock.
The alternator is wired star, and makes around 400v 50hz. A full description has been been posted, (see Photos for Discussion 5-18-05), and at that time I re-wired centre star to earth on advice from the Forum. There's about 10 metres max. between the alternator and the furthest machine, and I have a 10A 3ph breaker as overload, which see. All machines are earthed using a discrete shop 4 ft copper rod into heavy clay.
Ideas anyone?

Alan
Oh, and thanks Wolfgang!

@ Alan Belson:

Sorry, not regularly online at the moment.

1. Might be better to open a new thread?!
(Started with a leaking cooker, didn't we?)

2. Can you load up a wiring scheme of your existing installation.

3. Is that workshop in UK or F, public or completely private.

CU Wolfgang

[This message has been edited by Wolfgang (edited 10-03-2005).]

The symbol I is used for current in English too. (C is capacitance).

Voltage is normally V or E, but with harmonized standards coming into effect many "official" sources such as the I.E.E. are now using U for voltage as well.

Isn't "Spannung" the German for voltage?

Yep, a good idea. I've opened a new thread here .

Wolfgang -- Alan's workshop is in France where he now lives.

Correct. I don't have the slightest idea where the letter U is derived from.

German Wiki says that U might be derived from Latin urgere = to drive .See English "urgent"

Actually the reason for having an earthing system is a bit more complicated than that. Think about it .. if you have no earthing system then what would happen if you touched an appliance with a live metal case...nothing!