Grid voltage - what voltage are you finding?

[whlphil]

Not getting too much of an issue on the few domestics we do but the commercial ones are nearly always at 245 -252v which kind of makes it a bit close for voltage rise on export.

Any dropoff in local demand and in general we will be looking at the G59 booting us off the network!

What's everybody else finding?

Are you finding where voltage is high that the DNO's are reluctant to tap the transformers?

 

[lamb]

Last week did a 4kWp install, Uoc at utility meter 251V. Line-neutral loop impedance of supply 0.37 Ohms, which at full generation of 15.7A gives a voltage rise of 5.81V (ohms law).

This is causing a supply terminal voltage of 257.53V (0.72V of this rise is due to the conductor resistance in my final circuit) which causes the inverter to trip out on over-voltage.

The Diehl Ako Platinum 3800S actual trip value is 253V, even though the prescribed limit is 264V. Unfortunately this is a set relay value and not a redefinable parameter, so I am forced to liaise with the DNO to have the 11kV/400V transformer tap change lowered.

 

[JD6400]

Last week did a 4kWp install, Uoc at utility meter 251V. Line-neutral loop impedance of supply 0.37 Ohms, which at full generation of 15.7A gives a voltage rise of 5.81V (ohms law).

This is causing a supply terminal voltage of 257.53V (0.72V of this rise is due to the conductor resistance in my final circuit) which causes the inverter to trip out on over-voltage.

The Diehl Ako Platinum 3800S actual trip value is 253V, even though the prescribed limit is 264V. Unfortunately this is a set relay value and not a redefinable parameter, so I am forced to liaise with the DNO to have the 11kV/400V transformer tap change lowered.

One of our clients has just forked out around 5-6 grand for said tap change !

 

[lamb]

According to the DNO (SSEPD) when I spoke to them on friday that is the going rate (due to HV power down). However I am not satisfied with that response, because as far as I am concerned the network operators are obliged to facilitate up to 16 amps per phase of generation on each of their customers supplies.
I shall carry on pushing, and if they do not oblige within a reasonable time frame I will be forced to take up the matter with the ENA, then OFGEM, then the energy ombudsman, and if neccessary the DECC and my customers local newspaper and MP.

 

[whlphil]

Talking to a friend of mine on his last job where he had a problem he got a few people in the local area to phone up and complain about overvoltage after three or four attempts they came out and tapped the tranny.

Unfortunately for me tho we've been having a long discussion to get one turned down recently and thay have flat out refused. Ive been trying to find out what their legal responsibility for providing a generation connection is as they at the moment are not being very helpful, anyone know?

 

[BruceB]

Legal responsibility is ESQC Regulations 27(2) and 27(3)
230V -6% / +10%, ie 216V to 253V.
The Electricity Safety, Quality and Continuity Regulations 2002
Regards
Bruce

 

[malcolmsanford]

Unfortunately if the DNO voltage falls within the -6%/+10% range there is not a lot that can be done. The voltage in most industrial situations is set above a domestic value simply becasue of the demand that this enviroment calls for, the last thing the DNO want is equipment shutting down for under voltage, so they tend to tap at the higher range.

What can be done on the post with 257 volts is, fit a moniter on the supply for a week period. You may find if it is an older network that the original customers requirements have changed over the years and there is no need for a higher tap. Once you prove to the DNO that they are breaking their regulations, they will have to do something about it FOC

 

[whlphil]

Had a logger on the three separate supplies that are fed from the same transformer over Consecutive weeks, proved that current range is 246-252.3v yet they are saying that it's not their policy to tap as someone else may come along and want to connect into that tranny hence then they may have to tap back up!Now to me surely we as a current connection must trump a possible connection in the future but they are not keen to do anything.Is there Legislation that covers this that they have to abide by?

 

[BruceB]

Yes, the legislation is a couple of posts above the one you just made.
The voltage is within the allowed range (unless it goes over that when you start generating).
Regards
Bruce

 

[whlphil]

Yeah thats the problem its within range but we are straight into the busbar on the transformer with the main incoming supply to our site, we reckon we are looking at 3v rise in worst case situation where there's no demand from building (unlikely as they have a 24/7 load) but as the DNO has asked for secondary voltage regulation I'm worried that we may get kicked off when we get the 252v spikes.

I'll have look at the regs

 

[whlphil]

What are the terms around a connection be it generation or load? Is that covered under the 'Supply licence conditions'? or is it under something else?

 

[BruceB]

I am not sure what you mean by, "What are the terms....."
The regulations for the DNO are the ones I have cited.
If they fail to meet those then they are liable to a fine at level 5 (£5000 iirc) on conviction.
That may not be much for them, but they do not want criminal convictions and they take it seriously...normally.

Regret I do not know what you mean by secondary voltage regulation in this context.

Regards
Bruce

 

[whlphil]

I am not sure what you mean by, "What are the terms....."
The regulations for the DNO are the ones I have cited.
If they fail to meet those then they are liable to a fine at level 5 (£5000 iirc) on conviction.
That may not be much for them, but they do not want criminal convictions and they take it seriously...normally.

Regret I do not know what you mean by secondary voltage regulation in this context.

Regards
Bruce

Sorry I'll explain a little clearer, the DNO has stat obligations to provide for people connecting to the network on a load basis what I was wondering is what (or are there any) the stat conditions surrounding a generation connection eg whats the regulations on a legal basis that they must adhere to - I had a read through the document you posted the link to thanks and came to the conclusion that refusal to tap a transformer may contravene 2665 section 25 point 1

Secondary voltage regulation in this case is essentially a second g59 set

 

[BruceB]

Sorry I'll explain a little clearer, the DNO has stat obligations to provide for people connecting to the network on a load basis what I was wondering is what (or are there any) the stat conditions surrounding a generation connection eg whats the regulations on a legal basis that they must adhere to - I had a read through the document you posted the link to thanks and came to the conclusion that refusal to tap a transformer may contravene 2665 section 25 point 1

Secondary voltage regulation in this case is essentially a second g59 set

The ESQC regs apply whether you are connecting to the grid as a 'load' or as a 'generator' or a bit of both. Sect 25(1) does not seem particularly relevant to me; it is the sections I have already cited 27(2) and 27(3). It sounds like the voltage might not be out of specification until after you connect the generation, so perhaps you might have to do it, monitor it, then complain. But you are at the liimit of my direct experience on this so I will bow out now.

Regards
Bruce

 

[whlphil]

Will it be the case then that if we do force the voltage outside limits on a regular basis then they are duty bound to tap the tranny to bring it down within limits? or will they just set the secondary regulation at a level that means we cant force the voltage outside limits and constantly get cutoff.

Thats my main worry that I dont end up in a situation where after we've invested £300k in a system we cant get the payback as we cant generate for constantly being booted off the system by the secondary regulation?

Thanks for your suggestions Bruce I'll read sec 27 again! :teeth_smile:

 

[malcolmsanford]

As you have paid this type of money out, have you thought if the DNO are not playing ball of fitting an industrial transient voltage suppressor. They are designed mainly as surge protection but a lot of the new ones also act on over voltage conditions to bring the voltages back into line, though not sure if there would be any conflict installing this with a PV generator, but can't see why there should be.

 

[JD6400]

The last time we had some independent monitoring equipment fitted the chap from the company pointed out that the dno has a clause in it's supply contract that allows it to go out of parameters for Up to 10 % of the time with out penalty , now i have never checked this claim but if true that is a huge amount of down time on a system !

 

[whlphil]

The last time we had some independent monitoring equipment fitted the chap from the company pointed out that the dno has a clause in it's supply contract that allows it to go out of parameters for Up to 10 % of the time with out penalty , now i have never checked this claim but if true that is a huge amount of down time on a system !

We have a clause within our contract that states we are not responsible for system downtime due to elements beyond our control such as no grid or grid problems (overvoltage) forcing shut down on plant etc etc

Its a good point tho as its another one of those that you need to have covered. This is a good example of why commercial scale is so much harder work than domestic, I really wouldn't advise it if you are not used to end client contracting we also have a construction company and a development company and so are well used to complex contracts (arse covering).