Over voltage

[cully]

Quick question re over voltage
In my street there are some houses with solar panels and one in particular had to remove a “ GivEnergy” ev charger as it continually faulted due to over voltage (250 volts) which National grid stated was the top end of their spec.
My neighbour has had a dishwasher on one occasion and a wine chiller on another occasion that faulted when the power had been restored after an outage.
He checked with Nat power after the recent one this week and the fault was a blown fuse.
The tranny for the street is 20mtrs from his house, but the fuse wasn't at the tranny it was at the sub station.
Considering the solar panels Is it possible there could be an over voltage spike thats damaged equipment or is it coincidence?
I’m a mechanical engineer so if I’m way out with my thoughts I understand!
Thanks

 

[SithLordHood]

The standard mains voltage in the UK is 230 volts, with a typical tolerance range of 216.2–253 volts. This is a range of -6% to +10%.

Applying ohms law to voltage and current states that the higher the voltage the lower the current.

All sounds a load of b0**0**$ to me.

 

[ericmark]

My solar panels display the voltage on the app,

it does not seem to have ever fallen to 230 volt, but neither has it ever tripped out the panels on over voltage. It does list when some thing has gone wrong.

In the main the dates con-inside with when I had work done, I would say AC Voltage out of range is a brown out, not over voltage, But since all recorded best ask the local with solar panels how often they trip out.

 

[JohnD]

230V is the nominal voltage

But the supply is deliberately aimed at about 240V

 

[JohnW2]

230V is the nominal voltage ... But the supply is deliberately aimed at about 240V

I'm not sure about "aimed at". I would be more inclined to suggest that supply voltage was commonly around 240 V when the 'nominal voltage' was 240 V, and they have not bothered to change anything/much since the 'nominal' voltage fell by 10 V

 

[ebee]

If you consider that 240V single phase always was and always is the common UK voltage and it always will be then you would not be far wrong.
Only the nominal voltages changed not the actual voltages, they are 240v single phase and 415 three phase but simply declared as 230 and 400.
It was an agreement in mostly European countries in a smoke filled room after committee meetings lasting yonks. It is called harmonisation.

It was not a totally daft idea really. It was a fudge of sorts to tidy up the UK (and it`s historical dependencies) having 240V and a lot of Europe having mostly 220V as one of its voltages and encouraged manufacturers to produce appliances that performed fairly similarly in any of those countries and further afield.

Of course it would be a ludicrous step to go one further and declare that the world voltage should become 1000v plus or minus 100% and therefore include almost everything almost everywhere but you start to see the point of what might be sensible and what is not.

 

[EFLImpudence]

Not sure of the point you were making, but -

Applying ohms law to voltage and current states that the higher the voltage the lower the current.

If you apply Ohm's law to the Voltage and current you will get the resistance of the item(s) being used.

The current is calculated by dividing the Voltage by that resistance[Ohms] (which usually does not alter(much)) therefore with an increase in Voltage there will be an increase in current.

In the same manner the power[Watts] also varies up and down with the Voltage.

All sounds a load of b0**0**$ to me.

 

[ericmark]

The standard mains voltage in the UK is 230 volts, with a typical tolerance range of 216.2–253 volts. This is a range of -6% to +10%.

Agreed but in real terms nothing changed until solar panels arrived, at which point at last house the voltage dropped. This was due to panels locking out on over voltage, the result was my kitchen fluorescent lamp stopped working, it was a 65 watt fat tube, which became unavailable, but with the high volts the 58 watt would work, once it dropped to 230 volt, I had to revert to LED tubes.

Applying ohms law to voltage and current states that the higher the voltage the lower the current.

This does not actually work, the fluorescent lamp with a wire wound ballast if the volts went up by 20 volt would double in current draw, we at one point could get a consumer unit with an auto stepping auto transformer to combat this problem. However when we moved to electronic HF ballasts then yes lowing the volts increased the amps, this is also the case for most switch mode power supplies.

However pure resistive load, say a 3 kW heater at 240 volt, will draw 3000/240=12.5 amp, that means it will be 240/12.5=19.2Ω and it is the ohms which are fixed, so at 230 volt/19.2Ω = 11.97917 amp or 2755 watts.

Yes still using ohms laws, but the maths depends on what is fixed, and if the load in linear to the volts. Motors and fluorescent tubes the load is not linear to volts.

 

[fixitflav]

Applying ohms law to voltage and current states that the higher the voltage the lower the current.

That's true if the power stays constant as the voltage varies, eg an electric motor.
If the load is a resistor the current varies directly with volts, and power as volts^2.

This was discussed at some length in thread below

What amp fuse for a fridge freezer

Does it matter what we call it, as long we use the right formula? A rose by any other name would smell as sweet! Good grief! Well I can't stop you. Crack on.

www.diynot.com

 

[JohnW2]

Applying ohms law to voltage and current states that the higher the voltage the lower the current.

For a start, in terms of Ohm's Law,you have that back-to-front. Per that Law,with any 'fixed' load, increasing voltage will increase current proportionately.

You were probably thinking of the fact that, to achieve the same power, if voltage increases then less current is needed - but that will only happen if something is done (manually or 'automatically')to reduce the current. Otherwise, as above, increasing voltage will increase current, and hence also increase power. The most common things that do make that automatic adjustment are those with 'switth mode' power supplies (e.g. many/most electronic things) or 'inverters'.

Even if there is, say, thermostatic control of the load (e.g. electric heater, immersion heater, kettle etc.) increasing voltage will still increase current (hence also power) but the thermostatic control will reduce the amount of time for which that current flows, thereby preventing an increase in in energy supply due to the increase in voltage.

Kind Regards, John

 

[FrodoOne]

The standard mains voltage in the UK is 230 volts, with a typical tolerance range of 216.2–253 volts. This is a range of -6% to +10%.

The -6% to +10% was a "fudge" - so that Countries using a nominal 240 V could go on doing so when the IEC/EU "decreed" a "standard" voltage of 230 V.

"Household" Solar Panels (EXPORTING energy) tend to push-up the voltage in the "local area".
This must be so, since the only way that such panels can "feed" into the (local) part of the "Grid" is to produce a higher voltage - to drive the current in - thus taking part of the "load" from the local "Grid" transformer.

In this part of Australia there are now limits as to the number of premises in any Supply "Block" which are allowed to export Solar energy into their (local) part of the "Grid" - to prevent the "local" voltage being higher than the "Standard", during Daylight hours.

 

[ebee]

The -6% to +10% was a "fudge" - so that Countries using a nominal 240 V could go on doing so when the IEC/EU "decreed" a "standard" voltage of 230 V.

"Household" Solar Panels (EXPORTING energy) tend to push-up the voltage in the "local area".
This must be so, since the only way that such panels can "feed" into the (local) part of the "Grid" is to produce a higher voltage - to drive the current in - thus taking part of the "load" from the local "Grid" transformer.

In this part of Australia there are now limits as to the number of premises in any Supply "Block" which are allowed to export Solar energy into their (local) part of the "Grid" - to prevent the "local" voltage being higher than the "Standard", during Daylight hours.

Yes that would make sense.

 

[JohnD]

Don't their inverters cut out when voltage is outside limits?

In my area, I have seen "sunny day" voltage reach 244V

 

[ericmark]

If my supply was curtailed if the voltage went out of limits, then it would remove worries like loss of PEN, but that would not be very practical, so I have two devices to help limit the problems, one is an earth rod, the other is surge protection devices, it does not guarantee, no over voltage, but it does reduce the chance of it doing damage to items in the home.

Comparing notes with my son, he has no SPD and I do, I have replaced far fewer LED bulbs to him. as to if the SPD has any bearing on this, not a clue.

 

[JohnW2]

If my supply was curtailed if the voltage went out of limits, then it would remove worries like loss of PEN, but that would not be very practical ...

John was talking about solar inverters switching off when grid supply voltage 'went out of limits', wasn't he, and that's something I understand soes happen?

, so I have two devices to help limit the problems, one is an earth rod, the other is surge protection devices, it does not guarantee, no over voltage, but it does reduce the chance of it doing damage to items in the home.

The earth rod could not sink very much current and I'm not at all sure that SPDs would help much

Comparing notes with my son, he has no SPD and I do, I have replaced far fewer LED bulbs to him. as to if the SPD has any bearing on this, not a clue.

Hmmm. I thinki t's probably "horeswes forcourses". As I've said many times, I have something like 70 LED lamps/bulbs in my house,but no SPDs, and very rarely have to replace any of them.