If you lose the neutral in TN-C-S, doesn't that mean you lose the earth as well?
You may be relying on a fault current path:
supply live->greenhouse->soil->substation Earth->supply neutral
whereas when islanded you have:
inverter live->greenhouse->soil
and nothing trips. If you have an additional TT earth, you go:
inverter live->greenhouse->soil->earth rod->Earth-*>inverter neutral
where * is the neutral-earth bond in the inverter.
Theo
From a straight earthing PoV, that would normally be the case - you are just making provision for the situations where you lose the supplier earth during a power cut.
In this particular case (local generation from batteries and an inverter), it appears to be complicated by the required switching arrangements that actively disconnect the suppliers earth when running on local power.
Yes.
Yes many of them... It not just the presence of an earth connection that matters, but also that the supply neutral is bonded to it. (normally the output of a generator would be "floating" wrt to earth - so L & N would have a 240V potential difference between them, but no defined PD between either leg and earth).
TBH, the change in terminology from "phase" to "line" probably did not help...
The switch that was fitted on my installation only switches Live & Neutral. All earthing arrangements stay.
I get the impression that the "standard" way of doing on site power generation connections is evolving, and still quite "new". So a number of versions of "the right way to do it" can be expected!
In the absence of specific standards and guidance, I would expect the traditional way of including local generation using a "break before make" transfer switch[1] would be the way to go. However I can see that might become more complicated for installs that can also export back to the the grid from local power (e.g. on a feed in tariff) or to blend grid power with local power, using grid power to make up the difference between demand and local generating capacity.
Some installs seem to include a relay to switch out the PEN conductor as well as the live before the main cutout. That would also disconnect the PME earth from the install.
[1] Like what I did for my generator:HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.