Solar inverter over voltage reports.

JKenH

I wondered if anyone else had come across this. Today I noticed a lot of alerts from one of my inverters and on digging into the data I see these are over voltage reports. The faults caused my inverter to shut down numerous times. Are these related to the grid voltage being too high or is it something to do with the inverter? From the data it seems that every time the data was sampled over a prolonged period the voltage was over 253v (except for two at 252.8) but not everyone resulted in an alert/shutdown. Below are screenshots of the data and the alert code explanation. Any thoughts?

Edit: On checking I have had no over voltage alerts on my other inverter but have seen a “no grid” error code for both inverters. Both inverters immediately reset themselves after each alert.

Martyn1981

Been a long time since overvoltage came up. I'm lucky, only shut one of my inverters down for about 10mins, about 8yrs ago.

Quick brief. To 'pump' the PV leccy into the house and out onto the grid (when excess) the inverter monitors the grid voltage and pushes the AC out at about 2V higher.

Effectively, PV households will push local voltage up a smidge. So, to avoid a vicious circle, when the grid voltage reaches 253V (UK DNO's have (by law) to maintain a voltage of 230V -6%/+10%) inverters have to shutdown, and monitor the voltage, before switching back on when it's gone down.

I think the requirement (for GTI's) came in around 2011/2012, so to obtain UK certification approval (for the DNO's) this has been a requirement for about 10yrs.

What happened next? Well, folk started to see their inverters shutting off, and started to complain to their DNO's. The DNO's weren't happy, and one guy even complained on this forum many years ago, that overvoltage complaints had gone up about 1,000% due to PV installs.

His rants were not well received, since the PV wasn't causing the problem, it was simply letting homeowners know something they didn't before, that a lot of UK households were getting overvoltage, which can (certainly could going back) damage some appliances, or increase wear.

Mr ranty was not happy when I pointed out that the 230V (-6%/+10%) regulations stated that the DNO's had to provide this service 'even' if there was a SSEG(s) (small-scale embedded generation) on the line.

So in short (too late), you notify your DNO that you have concerns, and PV shutdowns, they try to fob you off, you stand firm, they fit a monitoring device for a few weeks/months, then they admit there's a problem, change the tappings (whatever that means) and fix the problem.

Just as an aside, voltage does vary, and higher voltage is more obvious (sometimes) on a sunny summer Sunday afternoon, when demand is low, that's exactly when mine shutdown.

JKenH

Thanks Mart for that explanation. It was sunny this afternoon. I’m away from tonight for the weekend so I’ll get onto the DNO next week. 

Ectophile

I don't know what would cause a "no grid", other than a power cut.

For overvoltage, it may be necessary to find a qualified electrician to investigate.  Two possibilities spring to mind:

• Voltage drop along the wiring from the mains supply to the inverter, because it is too thin or too long.  The voltage at the incoming mains supply is fine, but at the inverter it keeps creeping up at times when generation raches maximum.
• The grid voltage is too high.  It shouldn't be above about 253V.  Traditionally, suppliers would set their transformers to about 250V when installed, expecting that to drop as customers turn things on.  But it goes wrong if the customers are generating power, rather than using it.

If it's the latter, it is up to your local DNO (District Network Operator) to fix it.  Usally by adjusting a tap* at the transformer to lower the voltage a bit.

*No, that's not like a water tap.  Substation transformers will have a number of outputs, or "taps", on the winding, all at slightly different voltages.  The supplier can switch over to a lower voltage one.

Heedtheadvice

Your two responses have it right.

Ecto explains the two error messages regarding over voltage shutdown you copied and posted.

Just to add more verbosely for completeness (ish)

I had a similar problem after having had a Zappi installed. It was not a Zappi issue but it picked up a high voltage on it's monitoring system that caused it to error. My inverter did not and this was presumably just the slight difference in the overvoltage monitoring setting. It was nothing to do with solar generation as it often took place during dark hours.

However I did some data logging over several days and sure enough grid voltage went too high for short periods. I concluded, as confirmation, the inverter and cabling was not an issue but the DNO was at fault. To do this monitoringrequires a high accuracy data logger and that is what the DNO or a competent electrician would use. (They can be hired). Mine was just using a good DVM logged to a laptop but that gave three systems giving high readings so measurement error was small......or they all read high which is unlikely!!

However the problem resolved itself maybe with DNO action and no involvement from me.

As long as you do not have an inverter fault or a (relatively) high resitance path from inverter to grid (connectors, cables, trips, switches etc. back to the incoming fuse) which would be your problem to sort (explanation two in the above posts).  If the problem persists you should either complain to the DNO  with perhaps also time logged data from an electricians measurements. The latter might be give a faster DNO response but with a bit more cost.

Ohms law V=IR applies. When you are generating say 16amps  it only take just over half an ohm in the cables and connections to require the inverter to generate an adition 10volts to match the grid (plus the nominal 2 to push out power) and if the grid is max voltage at 253 or even near it then that would show as over voltage.

Half an ohm is unlikely in an installation except under a fault condition but lower resistance gives a pro rata voltage 'loss'. You would likely need an electrician to check that all out for you.

 If is is not a frequent and annoying problem with lots of generation loss then a straight complaint to the DNO might well be the best/cheapest route.

gefnew

Hi a bit on it from a Solis  seminar page .
Solis Seminar 【Episode 25】 : Solution for "OV-G-V0X" alarm (ginlong.com)

Sailbad

A bit more background....
Originally UK supply was a nominal 240V but to harmonise with Europe this was changed to a nominal 230V without any actual change to the real Voltage. Consequently we all get a slightly higher Voltage than we really should.

JKenH

Thanks to all for the very detailed responses and suggestions. There is quite a lot to take in there.

Heedtheadvice

Sailbad said:

A bit more background....
....... Consequently we all get a slightly higher Voltage than we really should.

No not the case!

Yes we often get voltage higher than 230v or 240v but it is still (usually) within the defined range. It is not higher than we should be getting and is within the range that equipment is designed to use.

The issue is when the grid falls out of spec or there is a problem within the property. Nothing to do with how the voltsge acceptable range is defined!

Ectophile

The UK used to be on 240V ±6%.  That works out at 225 to 254V.

But with some countries in Europe running on 220V, and others on 240V, it was a bit of a mess for manufacturers of electrical appliances.  So it was agreed to change the voltage to 230V ±10%.  That's 207 to 253V.

In reality, we're still on 240V, and nothing has changed.  At times of low load, it's not unknown for the voltage to creep up nearer 250V.

In practice, suppliers in the UK try to keep the voltage to 230V +10% or -6%.  That way older 240V UK appliances won't ever see anything as low as 207V.

JKenH

Moved from the BEV thread