For example a back up generator. I have attached relavant info.
Reads to me like it only gives options to connect to an MEN switchboard.
But the exception
"Exception: When connected to a distribution switchboard and operating on
the alternative supply, the submain neutral and protective earthing
conductors may be operated in parallel through a remote MEN connection"
Not 100% sure what it's trying to say. Any ideas?
Alternative supply connected to db?
Re: Alternative supply connected to db?
I read it as, if you the alternative power supply is connected to a Dist Board without an MEN link the conductors need to meet the requirements of the Exceptions, the MEN connection is upstream
Re: Alternative supply connected to db?
this clause (7.3)applies only to generation system;
subclause 7.8.3 is headed "connection to installation; and
part 1 of it is headed alternative supplies.
which tells us which conductors are being referred to:
the N & the PEC of the wiring connecting the alternative supply to the installation.
There's no restriction on making this connection at a DB; which is clearly allowed for in 2.3.3.1.
We have a general requirement that earths and neutrals within an installation don't operate in parallel.
This used to be common, in days when every DB had a N-E link as well as most having a PEC in the submain.
This parallel connection means that load current flows in the PEC - which is something we do not want.
And that's why we no longer install "linked-busbar switchboards".
This clause simply re-states this requirement; and then relaxes it - provided certain conditions are met.
That means the relaxation can't be applied to any set of N&E conductors other than conductors connecting an alternative supply to an installation at a DB.
So the rule applies regardless of whether or not the DB has a N-E link; and while the presence / absence of a N-E connection at the particular DB may affect how the requirement applies in a particular case, it's not the basis of it. (If that's what it meant, that's what it would say).
In every case, there will be an NE link - at least one, often several - within the installation; simply because it's an MEN installation.
The incoming (MEN supply) N to an installation must never be switched.
The incoming submain N to a DB may or may not be switched by the switching device for the alternative supply.
If not switched, there will remain an "remote" N-E connection via the MEN (and any other N-E connections.
In some cases, the generating system will have an N-E link also; which would mean the N&E of the alternative supply would be operating in parallel.
In most cases, the answer is to remove the N-E connection within the generating system.
But that's not always practicable, especially when adding to legacy systems with multiple gensets;.
Another way is to ensure that the source selection switching device disconnects the N of the circuits being supplied by alternative power from the normal supply. B
Again, not always practicable.
So the Exception allows for parallel operation - but only if the conditions are met.
If you're dealing with a mechanically driven genset, you can get more detail from "3010".
But if you're using some other form of generating system; you may only have these high-level requirements in 7.3 of "3000".
For special applications, see the relevant "companion" Standard; eg "3001" for connectable installations.
For example; "4777" series doesn't cover using an inverter as an alternative supply; it only covers supplementary supply.
subclause 7.8.3 is headed "connection to installation; and
part 1 of it is headed alternative supplies.
which tells us which conductors are being referred to:
the N & the PEC of the wiring connecting the alternative supply to the installation.
There's no restriction on making this connection at a DB; which is clearly allowed for in 2.3.3.1.
We have a general requirement that earths and neutrals within an installation don't operate in parallel.
This used to be common, in days when every DB had a N-E link as well as most having a PEC in the submain.
This parallel connection means that load current flows in the PEC - which is something we do not want.
And that's why we no longer install "linked-busbar switchboards".
This clause simply re-states this requirement; and then relaxes it - provided certain conditions are met.
That means the relaxation can't be applied to any set of N&E conductors other than conductors connecting an alternative supply to an installation at a DB.
So the rule applies regardless of whether or not the DB has a N-E link; and while the presence / absence of a N-E connection at the particular DB may affect how the requirement applies in a particular case, it's not the basis of it. (If that's what it meant, that's what it would say).
In every case, there will be an NE link - at least one, often several - within the installation; simply because it's an MEN installation.
The incoming (MEN supply) N to an installation must never be switched.
The incoming submain N to a DB may or may not be switched by the switching device for the alternative supply.
If not switched, there will remain an "remote" N-E connection via the MEN (and any other N-E connections.
In some cases, the generating system will have an N-E link also; which would mean the N&E of the alternative supply would be operating in parallel.
In most cases, the answer is to remove the N-E connection within the generating system.
But that's not always practicable, especially when adding to legacy systems with multiple gensets;.
Another way is to ensure that the source selection switching device disconnects the N of the circuits being supplied by alternative power from the normal supply. B
Again, not always practicable.
So the Exception allows for parallel operation - but only if the conditions are met.
If you're dealing with a mechanically driven genset, you can get more detail from "3010".
But if you're using some other form of generating system; you may only have these high-level requirements in 7.3 of "3000".
For special applications, see the relevant "companion" Standard; eg "3001" for connectable installations.
For example; "4777" series doesn't cover using an inverter as an alternative supply; it only covers supplementary supply.