High incoming voltage, solar PV installation.

[Click-Sure]

Evening folks,

Dad's had a solar PV array fitted last week and its thrown up something interesting!

2 years ago when I moved/replaced his consumer unit the incoming voltage was around the 243v mark, fair enough I thought, however things have changed, the inverter is showing 250v pretty much all the time during generating hours, sometimes even higher! I have verified the inverter's reading with calibrated test equipment.

It looks like the DNO (EMEB/Central Networks) have been busy, what is even more concerning is that the 11000/415 transformer is a good 350 metres away!

Now, because this is so close to 253v, if this limit is breached the inverter will shut down, and it appears from its logs that this has happened around 16:00 on a couple of occasions this week, I assume the connected local load is at its lightest at this time, pushing the voltage up.

This is pretty serious as its effectively costing Dad money now when this happens! I could do with taking a measurement from some neigbors nearer the TX to put to the DNO as in theory they will be a bit higher and probably over the 253v mark.

Any thoughts ladies and gents?

 

[PrinceofDarkness]

'Click', you seem to have answered your own question there: Yes it makes good sense to measure the voltage in neighbouring properties - and most neighbours, in rural settings, are happy to indulge the electrician by allowing such testing. But be sure that your instrument is truly accurate before taking the supplier to task.......

What make/system of PV is it, by the way? Because most half-decent systems have an automatic voltage regulator fitted to avoid this situation........


Lucia.

 

[westie101]

By all means do your checks but don't mention the results!

Simply complain of high voltage at the property without being too specific. The DNO is obliged to install recorders within 7 days.

We are getting more and more cases of "high" voltages that, in a lot of cases, are actually within UK limits. Investigation often shows that equipment is being purchased that is not designed to operate in the UK. I realise it is not the case here but we are getting wary if the volts quoted are within limits.

As an aside we got told by a customer today that "The British Gas Man" had said that the voltage should not be over 250V

 

[Click-Sure]

I'm using a calibrated megger mft1553 to measure voltage so should be ok there.

The panels are Sharp but Inverter is an SML Sunny Boy, best in the business by all accounts, in terms of voltage regulation it sync's with the grid so has to output at grid voltage, it custs out if the grid voltage exceeds the limits in 'GS??'

Getting the DNO to install a recorder would be usefull, can the customer see the results this recorder chucks out or is it for their eyes only?

 

[westie101]

Getting the DNO to install a recorder would be usefull, can the customer see the results this recorder chucks out or is it for their eyes only

There is no reason why not, we are rarely asked though.

Normally the DNO will leave the recorder in far a few days (ours last for 5 until the memory is full) and will contact you after removal to give the result, after that they have a further period of time to correct the situation

 

[bernardgreen]

Does the recording equipment also take account of whether or not the PV solar system is feeding power into the grid and log that information into its memory ?

Reason for asking is that when the solar system is feeding to the grid the voltage drop along the supply cable will be reversed as then power is flowing from the house towards the network.

Therefor when the solar system is feeding the network the voltage on the incomer to the house will be higher than the voltage would be normally.

 

[westie101]

Does the recording equipment also take account of whether or not the PV solar system is feeding power into the grid and log that information into its memory

No, they (the ones we use) are simple plug in data loggers.

I can see your point, but the 253V limit is "not to be exceeded" in any circumstances even if caused by local generation!

 

[Click-Sure]

UPDATE:

Dad had Central Networks out today to take a few readings, we his 253v again today quite a few times, he has found that things are a bit higher than they should be, getting a logger fitted in the next few days, seems re-tapping the archaic transformer we are on takes a while!

 

[westie101]

we are on takes a while!

The work cannot be done with it live so an outage affecting that (and possibly other) transformer will need arranging

 

[Gavin77]

Does the recording equipment also take account of whether or not the PV solar system is feeding power into the grid and log that information into its memory

No, they (the ones we use) are simple plug in data loggers.

I can see your point, but the 253V limit is "not to be exceeded" in any circumstances even if caused by local generation!

Unless your solar array is enourmous, I would have thought it would have a negligable effect on the line voltage.

...Unless every house on the street has it

 

[Taylortwocities]

I din't realise that you had so much sun in Staffordshire!

I must move oop North!

 

[ban-all-sheds]

This is pretty serious as its effectively costing Dad money now when this happens!

My heart bleeds for him....