New Solar PV System - Connection to Consumer Unit

[JohnW2]

I rather think that electrical industry procedures will assume that a system is live until it's been proved dead and earthed - on the assumption that anyone can make up a widowmaker and backfeed the network, or an embedded generator could have faulty protection, or ... I doubt that anyone in their right mind would just switch off and then assume that the circuit is dead and safe to touch !

Exactly - which makes me wonder a bit why 'we' are seemingly getting so excited about the technology for making PV inverters shut down when they should (something they'll almost certainly do fairly quickly, even if not 'immediately').

Kind Regards, John

 

[bernardgreen]

If the section the DNO want isolated has a high load when the DNO fuses / breakers are pulled then the connected solar PVs cannot supply that load and voltage in the section drops and this drop is detected by the solar PV invertors and they shut down.

If the section has a very low loading, loading less than the supply from the solar PVs feeding that section of the grid can supply then there is no voltage drop on the section and solar PVs are left on line. Sometimes the voltage on the section will increase when the DNO fuses are pulled and this increase trips the solar PV invertors to shut down.

 

[JohnW2]

If the section the DNO want isolated has a high load when the DNO fuses / breakers are pulled then the connected solar PVs cannot supply that load and voltage in the section drops and this drop is detected by the solar PV invertors and they shut down.

Indeed, I've said that - and I presume that, in practice, that is going to be by far the most common situation.

If the section has a very low loading, loading less than the supply from the solar PVs feeding that section of the grid can supply then there is no voltage drop on the section and solar PVs are left on line.

I've also discussed that, which is really the main issue we are discussing (since the 'common' situation described above is easily understood). At first sight one might think that what you say would be the case, but it seems that the inverters are probably designed to shut down in the event of loss of grid power even if the PVs are able to supply the load in the local 'islanded' part of the network. Techniques such as discussed in the recently-cited paper can probably achieve that, particularly the rate of change of frequency after loss of the grid supply 'reference'.

I haven't yet had a chance to read that paper properly, but I think that it may well provide a better explanation of some of the possibilities. What I wrote in post #36 may well have a lot to do with it.

Kind Regards, John

 

[ericmark]

For the DNO line worker he/she should know by now one needs to short out supply before working, where the problem arises is where some one doing other works hits a cable, we want the system to fail safe as soon as possible. Be it road works, digging the garden, or something hitting over head lines may be as simple as a tree falling we want that made safe ASAP.

they told me it will use a spare fuseway in the distribution board

My consumer unit has a split bus

So he has stated the consumer unit fitted does not have three neutrals so will not accept a RCBO and the intention is to supply one of the bus bars with the power from the inverter rather than fit a new consumer unit. So it seems what ever should be done, in this case it seems it is not being done.