Generators and National Terms of Connection

[SimonH2]

Being that sort of person - ie a pedantic one that actually reads stuff, in this case because I am switching tariff and there's a bit where you have to tick that to say you've read them - I was looking at the National Terms of Connection. Now there's an interesting bit about generators where it says :
If you install, or arrange for the installation of, small-scale generating equipment at the premises – which means one or more sources of electrical energy that have an aggregate rating of no greater than 16 amps per phase connected at low voltage – then you must inform us of your intention to use the source of energy in parallel with our network no later than 28 days after the equipment is commissioned. So long as you do this, you do not need our consent.

Fair enough - that's the rule that allows you to connect up to a 4kW PV array etc ...

But then it goes on to say :
However, if you intend to install or operate any other kind of generating equipment at the premises, you must contact us in advance and obtain our consent.

Now, I am certain that what they are meaning here is if you want to connect a larger generator in parallel with the mains then you need their consent, but ... that's not what it actually says.

Being pedantic, it seems to me that it says you can parallel up to 16A just by notifying. But if you install a changeover switch so you can run on the mains OR independently on a generator, then to my mind a literal interpretation of the terms means you need their consent regardless of size
Rather sloppy wording ?

 

[JohnD]

I am not familiar with the Terms of Connection, but the Electricity Act (which has the force of law) describes how private generators (not for FITS) must be connected using change-overs to prevent them feeding into the grid. It may mention consent, I don't recall.

 

[ban-all-sheds]

Are you planning to install a generator?

 

[JohnW2]

I am not familiar with the Terms of Connection, but the Electricity Act (which has the force of law) describes how private generators (not for FITS) must be connected using change-overs to prevent them feeding into the grid. It may mention consent, I don't recall.

I have no idea, but ....

I imagine that the only point in requiring consent to be obtained would be so that they could verify (presumably by inspection) that the change-over arrangement was satisfactory/safe - but I can't imagine that such 'verification' would, in practice, actually happen!

There wouldn't be much point in requiring consent/authorisation just to make sure that people were aware of the need for a satisfactory change-over arrangement, since those who weren't aware of that probably would also be unaware of the need to apply for consent!

Kind Regards, John

 

[SimonH2]

Are you planning to install a generator?

Well when I come to be doing any work on that part of the installation, it's my intention to make provision. I have a small genny, the oulook is for a return to the 70s, I'd prefer not to use a widowmaker

I imagine that the only point in requiring consent to be obtained would be so that they could verify (presumably by inspection) that the change-over arrangement was satisfactory/safe - but I can't imagine that such 'verification' would, in practice, actually happen!

Logic would say that if they wanted to be able to check that there was suitable provision, then they'd also want to inspect (eg) solar PV installations. It does go on to say that "You must ensure that any generating equipment at the premises complies with the applicable requirements of the distribution code that applies under our licence. Copies of the distribution code are available from the network operator on request." I assume this covers stuff like G59 and G83, but as I don't have that document I can't see.
I've dropped an email to my DNO to ask if this is just sloppy writing, and suggested that if it is then they should pass the comments up so it can be corrected.

There wouldn't be much point in requiring consent/authorisation just to make sure that people were aware of the need for a satisfactory change-over arrangement, since those who weren't aware of that probably would also be unaware of the need to apply for consent!

Indeed

 

[JohnW2]

Logic would say that if they wanted to be able to check that there was suitable provision, then they'd also want to inspect (eg) solar PV installations.

They could be relying on the fact that, as far as I am aware, PV installations have to used approved kit and be installed by approved personnel - which is a bit different from 'anyone' installing whatever provision for generator changeover that they see fit.

However, as I said, in neither case (PV or gennies) do I think that they would have the resources, and probably not the inclination, to 'check the provisions' in each installation.

I assume that the concern is that generation (be it solar or petrol/whatever) which found itself in parallel with the network when the network was 'down' could represent a hazard to DNO personnel working on that network. However, I would have thought that (as I think is standard practice when working on overhead HV cables, or electrified railway tracks/overheads etc.) they would probably take the precaution of earthing the downstream conductors whilst doing their work - but maybe I'm wrong.

Kind Regards, John

 

[JohnD]

PV inverters must close down if grid supply is lost, so they can't backfeed the grid. It appears to be instant.

The installations used on off-grid sites are different.

 

[ban-all-sheds]

Well when I come to be doing any work on that part of the installation, it's my intention to make provision. I have a small genny, the oulook is for a return to the 70s, I'd prefer not to use a widowmaker

"Provision" can take the form of a small CU with the critical circuits, plugged into one of two 60309 outlets - no form of connection between the generator and the network at all.

 

[JohnW2]

PV inverters must close down if grid supply is lost, so they can't backfeed the grid. It appears to be instant.

Indeed. That's why I said that, if 'approved' inverters are used, the DNO would probably not feel any need to 'check' that adequate safety provisions were in place - but, as I also said, the situation is different with 'ad hoc' arrangements for changeover to a petrol genny - which people could somehow 'do wrong'. The question of the earth has always been a matter for debate, but is seems from the DPC that the "18th" may be trying to at least partially address that issue.

Kind Regards, John

 

[JohnW2]

"Provision" can take the form of a small CU with the critical circuits, plugged into one of two 60309 outlets - no form of connection between the generator and the network at all.

Indeed. As I have described in the past, that is partially what I do. In addition, I have some circuits ('emergency' lighting throughout the house, and a few scattered sockets) which are only ever fed from the genny supply - so, again, never presenting a risk of connection between genny and network.

Kind Regards, John

 

[SimonH2]

They could be relying on the fact that, as far as I am aware, PV installations have to used approved kit and be installed by approved personnel

I don't think that's the case - at least as far as the installation is concerned. However, in practical terms, they have to be installed by an MCS approved contractor if you want the FITs - and without the FITs (ie other people's money ), they aren't worth installing.

 

[JohnW2]

I don't think that's the case - at least as far as the installation is concerned. However, in practical terms, they have to be installed by an MCS approved contractor if you want the FITs - and without the FITs (ie other people's money ), they aren't worth installing.

Indeed ... but it's primarily the kit that matters, and I presume they have to be of an 'approved' type with all the necessary safety features built in, regardless of who installs it?

Kind Regards, John

 

[SimonH2]

I assume G83 applies here, G59 applies to larger generators.

Oh, some interesting slides here. Note on slide 7 it has the details : "In UK law the 16A requirement is from the Electricity Safety, Quality and Continuity Regulations – Regulation 22 ..."
Yes, if you are installing off the shelf kit for a system up to 16A/ph and just notifying, then the equipment is "configured to disconnect itself electrically from the parallel connection when the distributor’s equipment disconnects the supply of electricity to the person’s installation". It doesn't seem to say anything about approvals, but from a DIY PoV it would be hard to show compliance with that requirement other than by using equipment that the manufacturer has certified as complying - or using an external protection relay (aka G59 relay).

And from the "small world" storybook. A while ago, one of out customers at work put in a turbine (89kW). The manufacturer of the system asked for "an IP address" so we gave them one which wouldn't conflict with the rest fo the network. What they didn't say was that their system used three (controller and two display panels) - and they set one of them to conflict with the customer's PBX Needless to say, we had to sort the mess out for them by changing the address fo the PBX. But I digress.
A couple of weeks later, I was talking to my brother, who mentioned that he'd just been to witness G59 tests for connecting a water turbine in the same location - late on a Friday afternoon. He commented on how the owner was "irritated" that at 4:30 the manufacturers guys knocked off and left it till Monday morning to finalise installation and handover - so he lost a whole weekend of generation. I did have a login so I could look at the graphs from the system - interesting to see how water level and output corresponded (with lags) to local rainfall.


Getting even more off topic, on page 8 I see "RoCoF can not always discriminate between loss of mains and system disturbances. For safety it should be slightly trip happy. This becomes an issue with increasing generation penetration."
I guess this is alluding to (eg) a system event such as the loss of a large generator causing a short term drop in frequency. If that then triggers lots of embedded generation to also trip off the grid, that will further exacerbate the problem, potentially causing a cascade effect where more or less all the embedded generation trips off - which on a sunny and windy day could be a significant additional loss of generation capacity, turning a routine drama into a crisis

"Loss of supply" isn't a simple matter any more - at least for protection considerations. If there's enough embedded generation, then conceivably it could be capable of running a significant chunk of local distribution network as an island should some upstream event happen (eg an 11kV loop get tripped offline from the supplying substation). Thinking of the 89kW turbine above, that would certainly be capable of supplying the local area - but with crap voltage and frequency control - if it didn't trip in a timely fashion. I could imagine a few residential areas where there's enough solar PV to supply an island if it's sunny enough - though the inverters for that would be capable of reasonable voltage and frequency control if they were configured for it.

 

[SimonH2]

Ah, Energy Networks Association information for Engineering Recommendation G83
In it, it has a link to THE DISTRIBUTION CODE and THE GUIDE TO THE DISTRIBUTION CODE
where it says "until 1 March 2014 it is permissible ... fully type tested in accordance with G83/1-1 ... After 1 March 2014 it will only be ... that complies with G83/2"
So a distinct change in wording there from "type tested" to "complies with".

 

[ban-all-sheds]

.... which on a sunny and windy day could be a significant additional loss of generation capacity, turning a routine drama into a crisis ...

A crisis which would not arise if those responsible for providing generating capacity had not decided that a spiffing way to provide it would be millions of tiny generators tied into the grid.