Discuss Generator. in the Electrical Forum area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

Reaction score
643
Simple specification: A machine inside a small factory is to be supplied from a generator set. This will not be linked to the main supply. The generator is to supply the machine only.


Im looking for regulations and advice on this. Ive looked through 515 and in particular 515.7.1, a generator set running in parallel with a mains supply. Is this the case here? As it is a separate supply and not connected to the main supply.

Next train of thought is related to the 2 supplies entering the building, Im looking for regulations related to this, Ive found isolation and understand that. I can see 551.7.3 makes note of synchronisation etc. It says care shall be taken and that IF synchronisation is required. My thinking is that it is still required here even though the supplies are not linked, am I correct?. I think if so, this will make them abandon the current generator idea due to costs and take a re think.

The suitability of the generator set and earthing are not in question, only the points above.

Discussions below.
 
The earthing should be in question as that is the only thing you need to give serious consideration to with respect of interconnection of the two supplies as it could be quite dangerous if you get it wrong.

A simple search of the forum should have revealed to you what parallel operation or synchronisation are, I know I have certainly talked about it in the past.

Parallel operation and synchronisation are both concerned with electrically connecting two or more sources of supply so that they share the total load current proportionally.


Sent from my iPad using Tapatalk
 
Last edited:
The earthing should be in question as that is the only thing you need to give serious consideration to with respect of interconnection of the two supplies as it could be quite dangerous if you get it wrong.

A simple search of the forum should have revealed to you what parallel operation or synchronisation are, I know I have certainly talked about it in the past.

Parallel operation and synchronisation are both concerned with electrically connecting two or more sources of supply so that they share the total load current proportionally.


Sent from my iPad using Tapatalk


Thank you for the reply,

The generator earthing would be independent of the main earthing as per the British Standard. I mean the generator suitability and earthing are not in question within this thread.

Yes I understand what synchronisation is, I usually have experience with it on sites with multiple generators where the generators supplies are synchronised before switching in on standby power. I did not know if this would require such a system as the supplies are not being interconnected, just that there would be 2 supplies entering the building.

From your reply I assume you do not think this would be necessary as the 2 supplies are not electrically connected?

From your point of view, the simple specification I have give and with regards to the points I have raised can you see any issues with the proposed plan?.
 
Last edited:
Thank you for the reply,

The generator earthing would be independent of the main earthing as per the British Standard. I mean the generator suitability and earthing are not in question within this thread.

Yes I understand what synchronisation is, I usually have experience with it on sites with multiple generators where the generators supplies are synchronised before switching in on standby power. I did not know if this would require such a system as the supplies are not being interconnected, just that there would be 2 supplies entering the building.

From your reply I assume you do not think this would be necessary as the 2 supplies are not electrically connected?

From your point of view, the simple specification I have give and with regards to the points I have raised can you see any issues with the proposed plan?.

How would you synchronise the supplies without electrically connecting them? And more to the point, what would be the point?

I'm afraid I don't have a copy of the British standard for earthing to which you refer, but I do have a copy of bs7671 and I'm doubtful that not making a reliable and deliberate interconnection of the earthing systems would comply.
The main bonding for the DNO supply and the main bonding for the generator TNS will both be connected to the exact same extraneous parts won't they? And the cpcs of the generator supplied circuits will in themselves be extraneous parts with respect of the DNO fed installation and vice versa?
 
How would you synchronise the supplies without electrically connecting them? And more to the point, what would be the point?

I'm afraid I don't have a copy of the British standard for earthing to which you refer, but I do have a copy of bs7671 and I'm doubtful that not making a reliable and deliberate interconnection of the earthing systems would comply.
The main bonding for the DNO supply and the main bonding for the generator TNS will both be connected to the exact same extraneous parts won't they? And the cpcs of the generator supplied circuits will in themselves be extraneous parts with respect of the DNO fed installation and vice versa?

We are digressing a bit here, I didn't really want to go into earthing as that isnt in question. But the earthing systems would be interconnected, they would be connected as you say through the extraneous parts, cpcs etc but they would also be interconnected at the MET, where the generator and DNO would both be connected. The British standard asks for the generator to have an independent earthing system (if that's the right term, it is late, but you do know what I mean) from the incoming supply. IE you can not rely or use the DNO earthing for the generator earthing and it is that that I was referring to with an independent earth.

What would be the point, im not quite sure, thats why I asked for confirmation. When trying to cover all angles with a proposed plan like this it's good to put ideas and thoughts out for advice, see if points have been missed but also to see if things are being over thought, as quite often happens.


"Knowledge has to be improved, challenged, and increased constantly, or it vanishes."


Sent from my E5823 using Tapatalk
 
Last edited:
I get what you are talking about on the earthing front now.

Maybe point was the wrong word, maybe 'what would it achieve' would be the better question.
What I mean is the way to answer the question, in my opinion, is to establish what the effect (positive or negative) of synchronisation would be.

As far as I can see there would be nothing achieved and it would neither present not remove a danger.
As far as I know the only reason for synchronising two supplies is to connect them together, in this case syncing the genset in to the grid.

But the only reason I have ever synchronised generators is to create a running backup/redundant supply for events.
I've also done it the old fashioned way as a practical demonstration of the theory, basically syncing 2x ~2kVA sets to boil a 3kW kettle
 
If the generator is just to run a single machine, then there is no need to treat the installation as having two supplies or to synchronise anything.
your biggest bugbear will be to keep any earthing separate.
Simplest method is not to earth either the generator or the machine it supplies, though it may not be possible.
 
Simple specification: A machine inside a small factory is to be supplied from a generator set. This will not be linked to the main supply. The generator is to supply the machine only.


Im looking for regulations and advice on this. Ive looked through 515 and in particular 515.7.1, a generator set running in parallel with a mains supply. Is this the case here? As it is a separate supply and not connected to the main supply.

Next train of thought is related to the 2 supplies entering the building, Im looking for regulations related to this, Ive found isolation and understand that. I can see 551.7.3 makes note of synchronisation etc. It says care shall be taken and that IF synchronisation is required. My thinking is that it is still required here even though the supplies are not linked, am I correct?. I think if so, this will make them abandon the current generator idea due to costs and take a re think.

The suitability of the generator set and earthing are not in question, only the points above.

Discussions below.
Just to get my head straight: the genset will supply only this 1 machine, will the machine be linked to the Mains? seems an odd set up.
 
Just to get my head straight: the genset will supply only this 1 machine, will the machine be linked to the Mains? seems an odd set up.
The machine will not be linked to the mains Pete as it does not have the capacity for it, so they are looking to supply this from a generator. It will run a couple of times a week. The previous owners used the set up and there looking to do the same. A main supply upgrade is not possible for them at the present time.

Sent from my E5823 using Tapatalk
 
If the generator is just to run a single machine, then there is no need to treat the installation as having two supplies or to synchronise anything.
your biggest bugbear will be to keep any earthing separate.
Simplest method is not to earth either the generator or the machine it supplies, though it may not be possible.

Is it necessary to keep the earthing within the building separate for the machine from the main supply earth?. As I understood, an independent earthing system for the generator was required but not throughout the installation.

As Dave mentioned that wouldn't be possible anyway due to extraneous parts etc. It will all be connected together.



Sent from my E5823 using Tapatalk
 
If the generator is just to run a single machine, then there is no need to treat the installation as having two supplies or to synchronise anything.
your biggest bugbear will be to keep any earthing separate.
Simplest method is not to earth either the generator or the machine it supplies, though it may not be possible.

My involvement with generators is pretty much only within the bounds of BS7909, where any generator above 6kVA is required to be referenced to earth. So my immediate thought is always to earth them.

But you do raise an interesting and potentially workable point. A generator can be set up as an isolated supply (IT system), but there are a few cons with such a solution, one being the need for insulation monitoring and another being the potential hassle when tracing faults.

I think it could still be a worthwhile option to explore, but a lot will depend on the physical size and nature of the machine.
 

Reply to Generator. in the Electrical Forum area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

Electrical Forum

Welcome to the Electrical Forum at ElectriciansForums.net. The friendliest electrical forum online. General electrical questions and answers can be found in the electrical forum.
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock