"John Rumm" wrote in message
...
dennis@home wrote:

What Peter said, and lower earth fault loop impedance (hence quicker
disconnect times),


Hmm,
An RCD would disconnect an earth fault in 30ms even with a high
impedence earth.

If it is a circuit protected by RCD that is.

Not all socket circuits need to be RCD protected. Some you would not want
to be either (like ones with high leakage, such as IT systems for example)

Why would an IT system have high leakage?
There is no reason for it to have any leakage.

High impedence to earth is probably safer for the individual who
completes the circuit.

Without an RCD, 1 ohm as opposed to say 0.5 will keep him connected for a
fair bit longer.

There would be no difference between such circuits.
The victim would only pass milliamps and there would be no trip without an
RCD.

By high impedance I meant something that would actually limit the current to
safe values.


BTW if you want to design a circuit that is really safer then it would be
possible to add a test box on the end of a radial circuit that measured the
drop from the consumer unit and intentionally applied a trip if there was a
fault. I don't suppose it was practical a few years ago but it is now and
only needs someone to design it and get it approved. It would prevent all
these bad joints from being a problem.