Live earths in a TT system

[South Spark]

Went to put in a new circuit (for a solar inverter) on a property with a TT system (the first time I've encountered one). The existing system is a dog's breakfast with three splits at the after the meter at a Henley block. There's some kind of 60 amp breaker labelled BS 842 in the mix. This may be an early earth leakage device but I don't know.

So I split off from the Henley block again and connected a mini DB with a 30ma/40 amp RCBO. All tests were fine - including a very low ZE of 0.35, until the RCD test - the thing just wouldn't trip.

Taking the cover off to investigate I brushed my hand on the earth bar - which was live!

After investigation all the earths were live - testing with my MFT and a straight voltage tester between live and earth showed 240v.

I disconnected my entire new circuit and tested again - same result.

My question is : Have the fuses not blown because there is in fact no path to earth (a long lead test to the earth rod gave a reading of 55 ohms) or am I doing something really dumb?

Chances are it's been like this for a while - the system works merrily along but presumably is very dangerous.

[ian1]

testing live to earth will read 240v it is the live giving you the reading try neutral to earth and see what you get

[spinlondon]

With a Ze of 0.35Ω, the earth and neutral must be connected somewhere as per TN-C-S.
There is no way that you you could get as low as 0.35Ω with a TT system.

[johno123]

With a Ze of 0.35Ω, the earth and neutral must be connected somewhere as per TN-C-S.
There is no way that you you could get as low as 0.35Ω with a TT system.

yep. looks like a neutral to earth fault somewhere before the RCD, never come across a Ze that low on a TT system before.

[aadambell]

This seems to be the first time I have heard about a TT system showing that low a Ze. Like others, I too get a feeling there must be a neutral-earth connection somewhere you are missing out on.