Hi Paul,
when reading 0 Ohms, I'd ask: How far and is the transformer and estimate the R of the loop.
So is it realistic? In Germany you will always hear people say (literally): Who measures a lot, will measure a lot of crap.
I am in the situation that we have our own transformer (360kVA) in the building and nevertheless I have never read such values.
So this (low Ze) should rather be an industrial problem, where you will have to calculate short currents being unable to measure them correctly because of big or paralleled transformers and very short distances on strong copper busbars.
In Germany btw you usually never determine Ze , but only Zs for any circuit that is not protected by an RCD. Maximum short circuit current is defined to be 6kA for MCBs and 25KA for mains fuses at the entrance. To guarantee this is the job of the Poco, we don't care about it in domestic installations.
