If you have an RCD installed after the MP and your earthing relay is working, that will work.
You should route the generator supply cable so that it is protected against earth faults and short circuits (double insulation, cable in steel conduit, and suitable labels in junction or connection boxes noting that it is a generator system). That way, anyone qualified to work on the system will be aware of this special feature.
Wow — I wasn’t expecting such a quick response to my question about this topic — I’m impressed!!
No, I haven’t tried it yet! However, before committing to an experiment costing around €450, I wanted to check with the community here first. But now I’ll give this experiment some more serious consideration.
When the MP switches to “mains”, it opens the earthing relay first. The control timings may need to be changed.
In one of my use cases, a generator (3P~) with insulation monitoring is connected via a 3P RCD at the input of the setup to the MPII, whose two outputs are each protected by a 30 mA RCD. That works without any problems too.
Thanks for pointing that out! I had understood the function of the grounding relay to be that, if the AC-In fails, it connects AC-Out1 to earth, and when voltage is present at AC-In, it takes the PE from the generator — in this case, that would be the generator casing earth / earth rod. In the generator’s Euro plug, the PE is connected to the casing, but not to the star point. Please let me know if I’m wrong about this or if there’s anything else I haven’t quite thought through!
Yes, that depends on the generator manufacturer. The TT also has “two PEs”: the primary-side PE (e.g. the transformer core or casing), with the secondary-side PE arranged the other way round. This is all designed so that an insulation fault doesn’t have serious consequences.
In a generator, the frame may be wired separately from the generator star point.
I’ve got an ex-military generator here: 1x 3Ph (380V, 12A), 3x 2Ph, each (230V, 32/16/10A)
So it’s a real jack of all trades. I intend to use the 2Ph 230V 16A connection with a Europlug, and in that case I’d have no problem adding two extra RCDs at the input for protection.
P.S. My use case is an ex-military 5-tonne truck with a container body, to which supply cables are connected. The condition of the upstream fuses is sometimes unknown. So the 3P input RCD is intended to provide basic protection, while the MP with its two outputs protects the container’s electrical installation. Various other features (load management, automatic generator start) are unused.
That fruitful discussion this morning has encouraged me to take another look at the circuit diagram for my Kirsch generator, to find out exactly how the earth connection is implemented and works with the voltage regulation for this all-singing, all-dancing setup (IT system), and with the casing and the earthing rod.
Load management / auto-start should also remain disabled on my system — it’s an emergency power system, and no machine starts here unless I’m standing right next to it.
Yes, those are the old regulators (you probably have some kind of test probe to check the insulation resistance manually). If you can, get yourself a spare regulator as well.
