Safety Concerns with Voltage Optimisers

A recent FB thread suggested that fitting a voltage optimiser is an acceptable way to overcome the G98-required grid overvoltage feature in inverters where the incoming supply voltage is at or near the upper limit. At least one distributor repeats this claim.
Defeating this safety feature and tricking the inverter to continuing working with a real grid supply voltage of over 270V is in breach of the supply agreement and creates a potentially dangerous situation for other nearby properties.

Thoughts from GE?

If you fancy... have a look at the 'energy networks association' Engineering Recommendation G99
Issue 1 – Amendment 8 - 1 September 2021 ((section 7)
It recognises the problem by the look of it, placing the responsibility for compliance on the Optimiser equipment/setup. Therefore I guess only optimisers with a G98/99 certification are legal.

It's out of control and anti-social. If I could, I would issue the installers and DNOs involved with ASBOs!

GE inverters are manufactured to spec and type-approved, it's not GE's fault if customers misuse them.

The last few weeks, since the weather improved DNO's have been inundated with enquiries from customers with solar panels who cannot export due to high voltages. Standard response is to refer the customer to their solar installer. Installers have been fitting voltage optimisers. Everyone is happy:

1. Customer is happy because they can export and get paid again.
2. Installer is happy because it's money for an easy job.
3. DNO is happy because they don't have to do anything.
4. Optimiser manufacturers (including GE) are happy with increased sales.

Unfortunately there is a domino effect. When one installation increases export using an optimiser, the increased voltage means other installations export less. They then fit optimisers and the voltage rises again.

The poor elderly couple, who have no solar, don't realise their kettle and toaster just failed because their supply voltage is up at 280Volts! Guess they just have to buy new ones and sigh "They don't make things like they used to".

It's not fair, but I don't know how to fix it.

Rubikcube It's not fair, but I don't know how to fix it.

I spoke to our DNO and they put a voltage recorder on our supply. They agree it's high but don't want to adjust the local distribution transformer as it's a generic problem and spreading. Instead they're looking at making a tap change at the 33/11kV transformer so that the whole distribution network reduces by about 5%. They trialled this solution elsewhere on their network and complaints in that network area have stopped. They're moving slowly because they're not sure if there are any unforeseen consequences; but they are aware and are doing something.

From the National Grid website:-

"LV voltages must be kept within the statutory limits of 230V + 10% or - 6% (253.3V-216.2V). With minimal active voltage control beyond 33/11kV transformers and designs based on demand dominated networks, LV voltages are generally set as high as possible to allow for voltage drop along the network and ensure that voltages never drop below the limits. "

At 270-280V there is absolutely no argument. The DNO Must do a tap change to bring the Voltage back within statutory limits.

Depends on what is fitted but most will be quite thick and bi directional in their application. (I've no idea what's in the GE one) however it's fairly clear ENA's stance:

Voltage Management Units in Generator’s Installation
7.7.1 Voltage Management Units are becoming more popular and use various methods, in most cases, to reduce the voltage supplied from the DNO’s Distribution Network before it is used by the Generator. In some cases where the DNO’s Distribution Network voltage is low they may increase the voltage supplied to the Generator. Some technologies are only designed to reduce voltage and cannot increase the voltage.

7.7.2 The use of such equipment has the advantage to the Generator of running appliances at a lower voltage and in some cases this can reduce the energy consumption of the appliance. Some appliances when running at a lower voltage will result in higher current consumption as the device needs to take the same amount of energy from the system to carry out its task.

7.7.3 If a Voltage Management Unit is installed between the Connection Point and the Power Generating Module in a Generator’s Installation, it may result in the voltage at the Generator side of the Voltage Management Unit remaining within the limits of the protection settings defined in Table 10.1 while the voltage at the Connection Point side of the unit might be outside the limits of the protection settings. This would negate the effect of the protection settings. Therefore, this connection arrangement is not acceptable and all Power Generating Modules connected to the DNO’s LV Distribution Network under this Engineering Recommendation shall be made on the Connection Point side of any Voltage Management Unit installed in a Generator’s Installation.

7.7.4 Generators should note that the over voltage setting defined in Table 10.1 is 4% above the maximum voltage allowed for the voltage from the DNO’s Distribution Network under the ESQCR and that provided they have designed their installation correctly there should be very little nuisance tripping of the Power Generating Module. Frequent nuisance tripping of a Power Generating Module may be due to a fault in the Generator’s Installation or the operation of the DNO’s Distribution Network at too high a voltage. Generators should satisfy themselves that their installation has been designed correctly and all Power Generating Modules are operating correctly before contacting the DNO if nuisance tripping continues. Under no circumstances should they resort to the use of Voltage Management Units installed between the Connection Point and the Power Generating Module.

hoggy that doesn't leave any room for misinterpretation.

@GeorgeRawding a quick Google will show at least one supplier advertising the GE Voltage Optimiser as being suitable for this exact application, which they need to stop doing. Perhaps you should also be highlighting this issue to all GE approved installers to ensure they install your equipment correctly?

mrand31 At 270-280V there is absolutely no argument. The DNO Must do a tap change to bring the Voltage back within statutory limits.

Agreed that the DNO must take action. Our voltage varies from about 240V to 260+ (Zappi trips daily when voltage exceeds 256V, even for a few seconds). There seems to be a paralysis to reduce voltage below 240V when the standard is 230V (+10%, -6%). In fairness, the distribution network design was probably set in the 1940s or 50s when the standard was 240V (+10%, -6%). Lower voltage would result in higher currents and greater I²R distribution losses.

I can see that the DNO doesn't want to set teams of line engineers to pole transformers to drop each one individually when they can do a wholesale compensation on the HV side. I can also see that the installation of microgeneration and the historic mandate from government that each one must be allowed at least 3.68kW export is a problem the DNO wasn't looking for, expecting or welcomes. In retrospect, the export mandate was fitting for early PV adopters to be rewarded for their investment but maybe once FIT ended, the right to export should have been withdrawn with DNOs deciding where their network could benefit from microgeneration.

If all export agreements were withdrawn overnight, the overvoltage problem would go away, the DNO's life would be simpler and the sparkies wouldn't need to install voltage optimisers any more. Anyone think that removing your right to export is a good idea?

stevelewis The challenge is that grid voltage can be too high, not that some may want to optimise their energy use.
One optimiser installation in itself isn't going to make much of a difference, the odds are that the background grid voltage is already too high, what it shoves out just gets absorbed by the network with no problems.
In some ways existing solar installations help to regulate things. When solar generation in an local area drives the local voltage up to exceed 253V the inverters temporarily 'switch off' thereby dropping the voltage, effectively providing a mass reset.
To be fair to the DNO's I suspect they are still trying to get their systems in place to cope with the significant increase in home solar (as well as solar farms) which are seasonal dependant.

SilverArt that's assuming the cable to the local transformer is in good condition. Standards and safety systems are there for a reason.

At work, we had automatic tap changers on the 11kV transformers. This did keep the 415V three-phase and 240V single phase supplies within reaonable bands as the load changed by up to 4MW from hour to hour. The downside was the effects on a batch of Cisco 3750 network switches that I was responsible for:- The power supplies shut themselves down when they saw the sudden, slight, change in Voltage! That took a lot of blood, sweat and tears to fix...

stevelewis Couldn't agree more, which is why the real problem needs to be fixed... High basic grid voltage. If that didn't happen then optimisers wouldn't be needed in the first place.
That said, I am fully aware that the solution is not easy. If I look at my own grid voltage. Every day it looks as if something(s) hits the grid at around 7 in the morning as the voltage drops to 230-235V, the daily low point. Then everything slowly increases until the top end is reached, peaking when max solar is likely, fortunately not too many 'voltage' faults in my case.. (Local DNO was responsive when I suffered last year and fixed the problem.)