Is my grid voltage too high?

[Imhotep]

I think my inverter is tripping out because of high mains voltage. It happened once before and I was advised to change it's country to Australia which worked. But I am now having the same problem. Has anyone successfully had their voltage reduced? And if so, how do I go about it?

Cheers

 

[f0ster]

yes it is too high but you might not get much help from the dno, it is quite common now with pv installations and turbines pushing up the voltage, the dno will want to monitor it for a week and if it does not go above 253VAC to often he will not want to do anything. what I have done is to change the country code on some of my customers installations to Germany. one of the makes of inverters we have used in the past gave country codes and also the voltage range for each country so changing to Germany gave it an upper voltage higher than ours of 253VAC. I think your inverter is a samil solar lake do you have the access password for these I have been trying to contact samil.

 

[milkloss]

Bit of a newbie to this sort of stuff but doesn’t it imply the dno doesn’t want your power if they’re running the voltage high? If you up your output voltage what’s happens if the rest do the same?

 

[f0ster]

the dno is legally bound to do something if the voltage exceeds 253VAC but of late they have been taking it to the limit before they will do anything, they normally inspect the transformer and wind it down but if it has been in situ for a number of years they cannot wind it down and have to replace it at a cost of 10s of thousands of pounds, so you see why they are reluctant to do anything unless they really have to. with all of the renewables the grid voltage keeps being pushed up further. in Germany the upper limit is up past 260VAC. one of my customers has a 5kw pv array that produces very little due to the inverter keeps restarting due to the grid voltage is just above 250VAC, it is up at this voltage due to a solar farm up the road that is now on stream. the DNO has not kept up with developments in renewables and they have let the network fall in to disrepair by waiting until it is too late to do anything instead of forward planning.

 

[storming]

Your transformer can be tapped now by your DNO.

S

 

[Wombat]

We were over the 253 limit but it took them over 6 months to tap our transformer

 

[jcb360]

How many kW of inverter(s) do you have connected to the grid?

If your DNO won't tap down the grid transformer, reduce the voltage yourself with your own transformer?

Something like this:
https://uk.rs-online.com/web/p/products/4368877/

N.B. You would need to check the specification of transformer required with an electrical engineer/competent electrician - above just an example!

 

[f0ster]

if it has been there for quite a few years you might find it cannot be altered.

 

[Imhotep]

F0ster: thanks for the info. Try 000111.

 

[Imhotep]

Interesting thought milkloss. Are they using voltage to control supply from renewables? And if so, is that fair play? Perhaps I should have read the small print more carefully.

 

[TechWise]

Interesting thought milkloss. Are they using voltage to control supply from renewables? And if so, is that fair play? Perhaps I should have read the small print more carefully.

Automatic Voltage Regulation is typically performed in the primary substation where 33kV is stepped down to 11kV. Therefore changing a transformer tap there affects a very wide area.

As has been said, the DNO is duty bound to act where the voltage at your property is out with 6% of nominal. If you have a new(ish) transformer supplying your property, it will most likely have an off-line tap changer meaning they simply switch out the line and change the tap. If it doesn't have a tap changer, it's a new transformer job.

It is highly unlikely that this is a deliberate act to constrain renewable generation as most large generators are connected at the transmission level. If they were deliberately pushing your voltage up, it would push up everyone coming off of that Primary which is likely to garner complaints!

 

[TechWise]

Apologies, for a Low Voltage connection, the tolerance is +10% and minus 6%. This is to give DNOs some wiggle room in case of a legacy transformer operating at the old nominal voltage of 240V.

 

[Imhotep]

Thanks techwise. Does that mean the voltage can get to 264 before the DNO is obligated to do something? Just a bit worried that might paralyse my inverter.

 

[Imhotep]

Sorry 253V

 

[TechWise]

That is my understanding anyway. The legislation is contained in the "The Electricity Safety, Quality and Continuity Regulations 2002" which you can access here: http://www.legislation.gov.uk/uksi/2002/2665/regulation/27/made

Section 27, Clause 3 states:
"
(3) For the purposes of this regulation, unless otherwise agreed in writing by those persons specified in paragraph (2), the permitted variations are—
(a)a variation not exceeding 1 per cent above or below the declared frequency;
(b)in the case of a low voltage supply, a variation not exceeding 10 per cent above or 6 per cent below the declared voltage at the declared frequency;
(c)in the case of a high voltage supply operating at a voltage below 132,000 volts, a variation not exceeding 6 per cent above or below the declared voltage at the declared frequency; and
(d)in the case of a high voltage supply operating at a voltage of 132,000 volts or above, a variation not exceeding 10 per cent above or below the declared voltage at the declared frequency.
"

I would stress that I no longer work in this field so I am unable to advise you on whether any amendments have been made to the legislation since 2002. To the best of my knowledge though, this is still the relevant legislation. In short, it would appear that you are snookered unless the voltage exceeds 253V.

That being said, this legislation has been in force for some time and it is perfectly within their rights for a DNO to allow the voltage to fluctuate between these limits. Indeed, it is virtually impossible to avoid voltage swings depending on loading, generation and network layout. I would be asking the question as to why an inverter installed on the UK distribution network cannot operate over the range of voltages that the UK distribution network is expected to operate over! In my humble opinion anyway

 

[Exfarmer]

I have had a thread recently on this problem.
It is an increasing problem and the DNO ‘s seem to be having serious problems across the country with this.
They are not allowed to have the voltage above 253 volts per phase but lookiing at yours there is nothing to auggest yours has gone over.
If the input supply goes over 253 while your system is turned off , you hsve a real issue and needs chasing.
If it goes over 253 while your generator is running the DNO should do something about it , but they will be less inclined.
However , by giving you a connection they are duty bound to carry your power away at less than 253 volts per phase, you need to fight your corner I am afraid

 

[f0ster]

we have installed a lot of renewables and we are finding that the dno is reluctant to do anything unless it actually goes over the 253VAC for a prolonged period of time. he installs a monitor for a week and for just the odd peak of over 253VAC he will not do anything. the customer has his inverter tripping out on a regular basis especially if there are other renewables in the area. what we are now finding is the dno is charging us £1100 for inspecting the local transformer before we can get a grid connection.

 

[Imhotep]

Just a quick update. Western power has been a joy. I feared I would get caught in the usual circle of passing the buck, but a knowledgeable engineer came out, and it looks like the problem will be sorted.

 

[HAM135]

Had the same problem here,ours was hitting 261v at times,engineer was a total dick that SSE sent out,tried to make out it was our 30kw solar that was causing the problem,eventually they put on monitors and admitted it was high and tapped it down,was very tempted to put in a claim against sse as we have went through a lot of household appliances in the last few yrs and have been told that running voltage to high can cause premature failure,never did though as trying to prove it would be difficult.