"Dumb" Voltage optimisers

[farmerspark]

Called out today to fluorescent lights flashing on and off. Only 207v at fittings. after abit of a head scratch. Turns out they have had solar PV recently installed, a voltage optimiser was fitted at same time.

Found the optimiser, it had 3 outputs 10% 8% and 6% reductions, originally installed on 10%, so quick swap to 6% and voltage is at 216/217v just around the lower limit of allowed.

Any one come across these things before, and what's the point if it can't reliably keep the voltage within limits.

My thoughts are have it removed by original installers, for a refund

 

[littlespark]

Maybe when the optimiser was originally fitted, there was a higher than normal voltage. And in the meantime, the DNO have realised and dropped it from their transformer. The optimiser is doing what it’s supposed to and dropping the voltage by the percent.
It could be removed, but I don’t think there will be a refund.

Can you read the actual supply, and not the optimised voltage?

the supply voltage should be stated on any previous test certificates, like when the panels were installed.

 

[James]

in my opinion, voltage optimisers are the new snake oil treatment.

sold by persuasive and misleading salespersons with little understanding of what they do and how they do it.

they will reduce the heat output of a resistive heater, reduce the light output of a filament lamp and in those terms, are saving you energy usage.

however, with most heating devices (water or air) all that will happen is they will be on for longer to make up for the shortfall of energy consumption required.
therefore the electric bill wont go down.

inductive loads become less efficient when running at a reduced voltage and for them the electrical usage will actually go up!!

there may be some rare occasions where they can help but i have not heard of one.

 

[farmerspark]

Optimiser is only a couple of months old. Incoming supply voltage was around 228.

I've not come across one before, but it doesn't seem a particularly intelligent way to go about optimising, given the fluctuations of the supply voltage.

 

[James]

230 volts +10% - 6%

I would consider 228V to be as close to perfect as you will get.
therefore surely the supply was at its optimum before they installed it.

 

[farmerspark]

That's what I thought. A couple of volts off the supply voltage and the "optimised" voltage is outside limits.
It's a rural location so I would expect fluctuations

 

[freddo]

I thought voltage optimisers were a thing of the past. It is not helpful having the setting as a percent drop rather than a fixed voltage! I assume this is just a transformer with it's windings connected to 'buck' the supply voltage and has no control electronics?

 

[farmerspark]

@freddo you're right it's at transformer with 3 tap offs 10, 8 and 6% drop. It's a stupid design

 

[James]

OMG!! that is really sh!t
wow

 

[freddo]

Wow that is a really stupid design. I've used this sort of setup for single appliances though. For example an old radio I had that was designed for a 200V supply (my mains voltage is 245V here) to reduce the strain on the HT components as well as reduce heat from the heater circuit dropper resistor.

 

[AJshep]

I remember reading the literature for one of these about 10 or so years ago (when they were popular) I convinced that optimisers needed a digital bypass to be complaint.
I must have been wrong.

 

[James]

I wonder, is this simple voltage optimiser being used to allow the solar inverter to pump power to the grid when the voltages are out of limits?

it would be a method that allowed the inverter to push a higher than allowed voltage into the grid.

see extract from G83 document.



5.3 Interface Protection

The purpose of the Interface Protection is to ensure that the connection of a SSEG system will not impair the integrity or degrade the safety of the DNO’s Distribution System. The interface protection may be located in a separate unit or integrated into the SSEG (the Inverter in the case of technologies which connect via an Inverter).

The DNO is responsible under the Distribution Code for ensuring, by design, that the voltage and frequency at the Connection Point remains within statutory limits. The G83 Interface Protection settings have been chosen to allow for voltage rise or drop within the Customer’s Installation and to allow the SSEG to continue to operate outside of the statutory frequency range as required in the Distribution Code.

5.3.1 Interface Protection Settings and Test Requirements Interface Protection shall be installed which disconnects the SSEG system from the DNO’s Distribution System when any parameter is outside of the settings shown in Table 1.

Table 1 Protection Settings Protection Function Trip Setting Trip Delay Setting (Time)
U/V stage 1 Vφ-n† -13% = 200.1V 2.5s
U/V stage 2 Vφ-n† - 20% = 184V 0.5s
O/V stage 1 Vφ-n† +14% = 262.2V 1.0s
O/V stage 2 Vφ-n†+ 19% = 273.7V3 0.5s
U/F stage 1 47.5Hz 20s
U/F stage 2 47Hz 0.5s
O/F stage 1 51.5Hz 90s
O/F stage 2 52 Hz 0.5s
Loss of Mains*¶ (RoCoF) 1.0 Hzs-1 0.5s

† A value of 230V phase to neutral * Other forms of Loss of Mains techniques may be utilised but the aggregate of the protection operating time, disconnection device operating time and trip delay setting shall not exceed 1.0 second.

¶The required protection requirement is expressed in Hertz per second (Hzs-1). The time delay should begin when the measured RoCoF exceeds the threshold expressed in Hz/s. The time delay should be reset if measured RoCoF falls below that threshold. The relay must not trip unless the measured rate remains above the threshold expressed in Hzs-1 continuously for 500ms. Setting the number of cycles on the relay used to calculate the RoCoF is not an acceptable implementation of the time delay since the relay would trip in less than 500ms if the system RoCoF was significantly higher than the threshold.

The total disconnection time for voltage and frequency protection including the operating time of the disconnection device shall be the trip delay setting with a tolerance of, -0 s + 0.5s.

For the avoidance of doubt voltage and frequency excursions lasting less than the trip delay setting shall not result in disconnection.

————————— 3 For grid surge voltages greater than 230V +19% which are present for periods of <0.5s the SSEG is permitted to reduce/cease exporting in order to protect the equipment.

 

[DT1991]

One I saw today.

 

[James]

I think the poster is highly misleading