Grid supply voltage too high!?

[cholwill]

We have a 29.76kw system of REC 240w panels. Feeding 2 x SMA 1500TRL Inverters.
Supply is 3 Phase. Input voltage is around 250v constantly, peaking higher at times (we are positioned close to a new sub station).
Our electricians/installers have had permission, from DNO and SMA, to raise peramiters on invertors from 253v to stop them tripping out.
Which would maximise production? - grid at 250+v with higher peramiters on invertors or request DNO to 'turn down' voltage to 230v(ish)?

 

[SolarCity]

The DNO won't turn the voltage down to 230v but they will reduce it if it goes beyond 253v - they are duty bound to do so.

 

[JD6400]

Biggs my guess is that they would turn it down , but at a cost of around £8000 give or take !!!!

Cholwill , i would say that you are very lucky to have been offered the solution that you have been , ukpn now put a little get out clause in when we get back conformation of a G59/2 connection acceptance , that states it should be ok to connect but if the parameters of supply change due to or after connection then we as the install company WILL be liable for the costs to rectify it !

 

[cholwill]

Thanks for those answers. The main question was the second part of the thread. Would the PV push through more kilowatts per hour if the power was turned down grid side to 230v? )
Original question - 'Which would maximise production? - grid at 250+v with higher peramiters on invertors or request DNO to 'turn down' voltage to 230v(ish)?')

 

[Worcester]

Shouldn't make a significant difference, its 'POWER' (aka Watts) that you are pumping out, less Volts more Amps (remember W=V*A), more Volts less Amps. Only danger is it is pushing up the voltage which some local pieces of equipment might not like

 

[SolarCity]

I agree with Worcester. I don't think it will make a difference to the power from the inverter.

However, if the voltage is already high before the PV array is connected then this is a matter for the DNO and they have no right to charge you extra. High voltages will reduce the life of your electronic equipment and lamps and I'd definitely look at getting that sorted.

 

[JD6400]

Hi Biggs

I agree they should not , but i do unfortunately speak from experience ! :frown2:

 

[SolarCity]

Hi Biggs

I agree they should not , but i do unfortunately speak from experience ! :frown2:

I don't see how they have a leg to stand on to be honest. What happened with your case?

 

[JD6400]

Thats as far as i will go on a open forum , will pm you details latter if i remember to , it may be of help to you someday ?

 

[SolarCity]

Thanks fella, that would be appreciated.

 

[Markc]

This has been our issue on the Diehl 3800S system. The average voltage is 245. peaked at 252.5V

UKPN said they could turn the voltage down but then the question would be to keep it over 216V.

 

[besafe]

Hi
I have a pv customer who lives in the sticks .... old farmhouse spilt into two separate properties. The voltage is at the top end of 230 (10% +-) The DNO says that the customer will have to pay for reinforcement as the voltage generated by the inverter will take it over 253V.
I would appreciate any help or advice
Thanks
Chris

 

[JD6400]

How big is the system ?
I will probably be away from the net now until late Thursday night so don't think me rude for not replying ( Got to go back to work for this week !:sad.

 

[besafe]

Hi
Thanks for getting back to me ... whereabouts understood.

Its a 10kW using two SMA 4000

Chris

 

[moggy1968]

looks like you would benefit from some sort of voltage optimiser, could dramatically cut your leccie bills.
From memorey V phase isn't suitable for 3 phase, anyone know of a three phase one out there?

 

[besafe]

Hi ,,, it's on a single phase. Last time I looked VPhase could only manage 16A.
The key issue is that the generated energy fed back to the grid may exceed 253V, thereby causing neighbouring supplies to be too high. If my customers supply was <245V the increase in voltage would not exceed 253, but when you are starting at 251V is always an issue.
Meeting with DNO on site this afternoon, not too optimistic.

 

[danesol]

The DNO won't turn the voltage down to 230v but they will reduce it if it goes beyond 253v - they are duty bound to do so.

With regards to the OP's original question, I was subject unfortunately recently to the complete opposite and I was able to prove that my whole road was subject to voltage of between 209 & 216vAC on each phase on one particular day although we had on the estate been subject for numerous issues over many years. They initially sent out 2 engineers for investigation checking all difference phases in different parts of the road after seeing how low we were, and within 2hrs they were satisfied that nothing was wrong or could be done at street level, and contacted the network controller who then turned up the voltage to 240vAC 30mins later REMOTELY.

I later contacted the DNO to ask what they are able to do at substation level with regards to the fluctuation & control of voltage especially due to when multiple PV installations on the estate could & will kick in at full capacity in the coming months - this is their reply !!!

""Voltage fluctuations outside of prescribed limits are an extremely rare occurrence and as in your case almost always as a result of a Network Incident. Our Network complies with ESQCR (Electricity Safety, Quality and Continuity Regulations) which are in place to ensure so far as is reasonably practicable DNO (Distribution Network Operators) take steps to eliminate risks of interference, danger or interruption of supply.

In addition DNO are targeted and measured against their reliability of supply performance via the Energy Networks Association, Engineering Recommendation P2/6, and OFGEM (Office of Gas and Electricity Markets), I can tell you that Western Power’s record are consistently one of the best. I do appreciate that this is of little consolation as you have recently experienced an Incident but I hope you can appreciate that overall our supplies are reliable.

Western Power along with all other DNO’s do not have voltage regulation equipment within their distribution substations however this is carried out on the Primary network.
The statutory voltage limits set by the ENA allows for plus 10% -6% around the 230 volt norm, this regulation allows for volt drop and load fluctuations on the network.

With regard to your query on technology, we have Overcurrent and Earth Fault protection however damaging voltage fluctuations are usually associated with a fault on an underground cable or overhead line away from the sub station, unfortunately it is not practical to cover this eventuality. ""

 

[edexlab]

We install in WPD's area and regularly have them out to check voltages which are consistently over 253v and on several occasions its been 270v admittedly rural locations ,so their record is not as good as the above letter claims ,but credit to them they've always been onsite in less than 2 hours and sorted it very quickly.

 

[besafe]

Thanks for feedback everyone.
We had the region's DNO out to site this week. The voltage is out in the sticks as with edexlab message, The voltages are 250v plus, as the majority have a transformer on site. The DNO's main concern is that if the generating system takes the voltage over 253v, this could cause problems on neighbouring customers. I am sure we all appreciate that. What was interesting, was that asking them to turn down down the tap, to say 230-240 was met with, that will cost you. But if it was 254v they would do it for nothing. However, in this case, because the neighbours property was separately fed from the same transformer (not teed off) they would allow it.

Historical, as all transformers supplies start off high in urban areas the same starting point was used in rural areas. This high voltage issue has to be considered when working in rural areas as it not always straightforward ... and as the installer, you don't want to be faced with any subsequent upgrade costs.

 

[TedM]

Checking voltage on site should be a standard part of an initial survey, IMO.