Grid supply voltage too high!?

besafe · Feb 14, 2012

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 · Feb 14, 2012

SolarCity said:
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 · Feb 16, 2012

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 · Feb 16, 2012

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.