UK G99 DNO approval, self install commissioning help

[kevdav100]

Hi,

So I have successfully installed my system, I have DNO approval for 6.4kW export, I have an electrician coming to sign off the part P documents, but has anybody got any experience with the commissioning documents I need to complete and send to the DNO.

Searching I think I need to complete form A3-1, and A2-4, but a little confused as to some of the contents of the forms.

And are those the only forms I need to complete, and do i need to send any other documents such as conformity documents of the inverter.

System is working pretty well, but obviously not exporting just yet, but generating some good energy and storing it in the battery for use in the evening and at night, battery gets down to around 38% over night, been a pretty good day today, so will be interesting to see what a cloudy miserable day generates.

[Daza]

who is your DNO? a lot of that is conformaty of the product from memory that it isolates it self from the grid, that it takes a set amount of time before it reconnects ie syncs with the grid rather than connecting instantly, it should disconnect almost instantly during a power cut though there should be timings, your sparkie should be able to help you with the above stuff but if i where you make sure you know what they are asking you for before the sparkie comes.

Every DNO is different mine never asked for proof but i satisfied them on all the prior points of the application had to duplicate the manufatres test sheet in the commisioning part and the other stuff mentioned but cant remember what else to be honest i hope this helps. PS have you done a Sepeart earth if your going down the island mode route?

[kevdav100]

Its National Grid Electricity Distribution (West Midlands) Plc, I have connected the earths to the incoming earth points of the supply, but was thinking to drive an earth spike into the ground and also connect to that, although I dont think that is required, but may be advisable, but we rarely have power cuts, although they may become more common now Milliband is in charge of power

[Ronski]

I’d let your electrician deal with the earths, he will know what is required. If you have a backup circuit or whole house back then you will need an earth rod, but it needs to be done properly and checked.

Once my system was comissioned I sent in the following to UK Power Networks.

1. Form A3-2 - I got the electrician to sign the form, I just signed as the generator.
2. Site layout plan
3. System Schematic

I had previously sent in the inverter G99 certificate.

You may find the following thread useful, not my thread but I have replied on there.

My experience getting G99 approval in the UK, for grid tied inverter over 3.68kW

[kevdav100]

The whole house is on passthrough, so if the inverter disconnects from the grid, or there is a power cut, we still have full power throughout the house, the earths are connected directly to the incoming Earth of the house so there is no disconnection on the earth circuit at any point, so the whole installation should still be protected, unless of course there is an earth fault prior to the incoming earth point on the DNO side.

I will have a read of the link.

[Daza]

Unless its PME you will need it, as outlined below, but most people still supplimentry bond to the PME with an earth rod, i opeted for a full TT system and disconnected mine from the grid but ive gone down 4.5 meters so my earth reading was 2.15 Ohms after i finished which is really good for a TT system and well with in the requirements, all my supply pipes are plastic other wise i may have just supplmentry bonded to the DNO’s with the rod.

Earthing arrangements for island mode operation

In connected mode, an installation with a TN earthing arrangement (TN-C-S or TN-S) may use the distributor’s means of earthing. In a TT system, the consumer’s earth electrode is used – but care needs to be taken to ensure that this provides an earth of sufficient quality.

However, when the installation moves to island mode, it is important to make special earthing provisions.

Regulation 551.4.3.2.1 of BS 7671 states that, in TN systems, generators operating as a switched alternative to the public supply cannot continue to rely on the distributor’s means of earthing.

In systems where a low voltage supply is provided to the installation, the neutral of the supply is earthed at the distributor’s transformer.

Accordingly, in systems operating in island mode, the distributor’s neutral-earth link cannot and must not be relied upon, as this is switched out when the live conductors are disconnected.

An installation that operates in island mode therefore requires:

• a switching mechanism to disconnect live conductors of the installation that are to be powered in island mode from the grid. The IET Code of Practice for Electrical Energy Storage Systems calls this an island mode isolator
• a switching mechanism to provide a neutral for the island mode The IET Code of Practice for Electrical Energy Storage Systems calls this an N-E bond relay, and
• a consumer earth electrode. In TT systems, this may be the TT system consumer electrode, if it meets specific technical requirements.

The earthing arrangement of most EESS in island mode, where the installation has a low voltage public supply connection, is therefore always TN-S.

Note: If the N-E bond relay were not present, and the EESS inverter has a permanent connection between neutral and earth, RCDs in the installation would operate, as this would effectively be a neutral to earth fault in the installation.

Note: In installations where PME conditions apply in connected mode, PME conditions continue to apply in island mode. This is because the distributor’s means of earthing remains connected, even though it is not used.

Table 1: Connected and island mode earthing arrangements for installations with a low voltage public supply connection

[kevdav100]

Thanks for the info, will look into that tomorrow, we have a TN-C-S arrangement