G99 knocked back by DNO - trying understand proposed "reinforcemen"

Qyburn

JC_Derby said:

generally Transformers have 5 tap settings in 2.5% stages.
Please bear in mind QYburn they are basing their (likely software based analysis) on a system voltage - do you know what your actual voltage is at your property.

It's just under 240V.

mgiht also be worth at some point if you are getting nowhere asking what there losses strategy is on undersized transformers? I'm presuming you are the only customer connected to your transformer as its 16kva...

Yes it's just us on the transformer. From what SSEN say the limit is the service cable from transformer to house rather than the transformer itself.

Qyburn

Reed_Richards said:

I don't rate my chances of persuading my wife not to boil the electric kettle if she could, she regards that as an essential

My colleague is the same, when he was sorting out his generator that was one of the requirements. However we have a gas hob and a proper kettle from the days when we had a Rayburn. Not quite as convenient as electric kettle but almost as fast.

But going back to what you said earlier, does that mean your kitchen power points are on your emergency backup?

Reed_Richards

Qyburn said:

But going back to what you said earlier, does that mean your kitchen power points are on your emergency backup?

The ones for the fridge and the freezer are, and they're both double sockets with one socket spare.  But I don't think my wife has twigged that these might be used to boil a kettle.  You do need to be careful, because if you empty the battery to the point where the inverter loses power then it won't start up again when the sun shines.

JC_Derby

Reed_Richards said:

JC_Derby said:

Regarding the DC coupled battery - that would change the way that your generation is analysed - likely not cumulatively as it is (when AC coupled).

My generation meter measures the AC output from the inverter as export, import and the default reading is the difference between the two.  This difference is what I have actually generated, except for any losses that result from charging and discharging the battery.  So my generation is possibly measured as being slightly less than if I didn't have a DC-coupled battery, but it's not something I worry about.  

What i meant was how the DNO analysed The set up. i understand AC coupled inverter and batteries are cumulated,  but DC coupled, analysed differently. consequently they can allow more ( i believe) if the battery is Dc connected.

Qyburn

JC_Derby said:

What i meant was how the DNO analysed The set up. i understand AC coupled inverter and batteries are cumulated,  but DC coupled, analysed differently. consequently they can allow more ( i believe) if the battery is Dc connected.

Yes that's my understanding. The DNO accounts for the AC coupled battery's rated output in addition to the inverter when they consider total system size.

Qyburn

Reed_Richards said:

Yes, I guess that's true.  In which case you want a manual switchover so you can turn off all the non-essentials first to ensure you don't demand a greater power output than your battery is capable of, if it's dark at the time so you have no solar power.  Of course you'll have to do that with the aid or a torch or a candle.  Or maybe you light you way to the consumer unit, switch off all circuits except the lights, throw the manual switchover to give yourself light, wander round and disconnect anything that might draw high power when it comes back on, then re-enable the power circuits. 

I won't need to do anything as dramatic as that. Background load is around 100-200W depending I guess on cycling of fridge and freezer, so absolutely no problem powering up and then switching off non essentials afterwards. There's nothing that's going to draw high power of it's own accord, rather than by deliberately being switched on.

Reed_Richards

I'm not thinking of devices that would draw a high power of their own accord, I'm thinking of things that would draw high power because they were switched on when there was a power outage. 

I just did an little experiment, switched on my vacuum cleaner, switched it off at the socket, on at the socket again and it sprang back into life.  Perhaps I'm old fashioned, still having a mains-powered vacuum cleaner?  Or I strongly suspect my electric hob would come back on when power is restored after a cut.  The oven would do that too, probably.       

Qyburn

Yes you're correct. My power tools wouldn't but that's because they are specifically fitted with NVR switches that release when mains power is disconnected. But it's as good as certain that our oven would come back on, possibly not the microwave, and who knows about washing machine, tumble dryer or dishwasher.

So it would depend on what we were in the midst of doing at the time.

Qyburn

Final update from SSEN, they've now confirmed that they can't retap the transformer (thankfully I didn't have to pay £2K to find out). They cane up with an alternative which was described as "overlaying the service cable".

In detail they would install a pole in the middle of our yard, with 28m of overhead LV cable (described as 95mm Wavecon 4 core) from the transformer pole. This will then join onto the existing service cable at the foot of the pole. Unfortunately that's not workable for us, having a pole in the middle of the yard and cable overhead, so that really knocks the reinforcement option on the head. Out of interest I looked up the cable specification, and all this work would only reduce voltage drop/rise by around 20%.

JC_Derby

Wow
some seriously bad planning there.
95Wavecon is an underground cable....i think they probably meant 95 ABC.

Just out of interest Qyburn - why cant you go DC coupled... How often do you suffer lengthy power cuts that would require you to go into Islanded mode to self run?