Tim
Shouldn't really trip as earth and neutral are the same connection at the sub-station. Or even at you own consumer unit if you are on PME ( Protective Multiple Earth) as I am.
Will try to post a c-o-c.
Beware of ELCB and RCD. Not same. ELCB's are (IIRC) voltage operated whereas RCD's are current. Most in UK are RCD's .. Lot of stuff in earth faults and various means of knocking off the power under fault conditions.
Dave BC
c-o-c herewith ..
This should be read with some caution, it may NOT apply to every distribution system
It'a a damn long time since I did any of this for real, but ...
The (IIRC) High Voltage distribution is 3-wire Delta ( AKA Mesh ) and goes into the local Sub Station transformer and gets stepped down in voltage and also connected Star ( AKA Wye ), as per LH diag. Which is where the Neutral and Earth appear.
RCD's
On the RH diag, we have a magnetic core, attached to which is some means of mechanically opening the breaker. Like a solenoid. So, assuming we have no fault, all the current goes from line thro' the top coil, load, lower coil, thence down the neutral return. The two coils are contra wound, and, as the currents are identical the magnetic pull generated by one coil is negated by the other. One is pushing the same amount as the other is pulling. Nothing happens. If we close the test switch, we get If (fault current) to ground. Both the load and fault current go thro the top coil, but only the load current thro lower coil. Not equal and opposite any more. Device will trip. Lights go out. Telly packs up. Women folk squawk piteously 'cos no Eastenders etc.
There are all sorts of ways of doing this, just one of many. Lots are 'transistor aided' or whatever.
Suggest you Google stuff like Star/Delta RCD PME etc.
That 220v on Trion's Mill should not trip any RCD if earthed. BUT, it may be the machine has been modified, with greater or lesser competence, at some time, and thus may not be to the cct. It' s not possible to tell, I think he needs an Electrician ON SITE ...
Remote theorizing is fun, but has it's limits ..
Dave BC