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Littelfuse told us that UK mains goes up to 285VAC once every 20 years

treez

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Hi
A littelfuse Apps guy told us that UK mains goes up to 285VAC once every 20 years. ("..and this year might be that year"). He did not say for how long it stays at that voltage.
I wonder if anyone can confirm this?
(BTW, Thanks very much to Klaus for the Weekend figures from Bavaria for Mains voltage.......they were very stable at 220VAC with little deviations)
But is this 285VAC thing for real?
..And can we proove it yes or no?
 

dick_freebird

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That would be a historical anecdote. Its power
to predict the next excursion's maximum and
time is roughly zero.

You'll be able to prove or disprove it the next
time it either happens, or 20 years since the
last has gone by.

I would not "design to an anecdote". Either it's
a written and validated requirement from
a source who's got the authority to levy it
as such, or it's not (in which case, screw it).
 

KlausST

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Hi,

Single phase loss or (partial) earth ground current may cause the voltages to become unsymmetric.
In worst case the L-N voltage may get as high as the usual L-L voltage. Theoretically. In real world it will be somewhere inbetween.

Klaus
 

BradtheRad

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My real-life experience with unusually high mains voltage... I was ready to charge my backup power system (8 golf-cart batteries) as power resumed after a blackout lasting a few hours. (We lived in the Phila. area at the time where storms often break overhead wires on utility poles.)

My meter read the mains at 135 V. My deluxe power inverter (with battery charging capability) refused to turn on at the raised volt level. I theorized that the electric company spun up extra generators in order to handle a greater load across the region as blackouts ended. But it was equally likely that blackouts caused reduced load which resulted in soaring mains voltage.

135 V mains in US is equivalent to twice that in UK.
 

KlausST

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Hi,

I don't know what's the nominal voltage, here in Germany we have 230V L-N, thus 135V doesn't sound "high". ;-)

For Europe speaking: a huge grid.
When there is "more power available" in the grid than being consumed, then the frequency will rise. The frequency is a better indicator than the voltage. The voltage depends on many parameters, and usually even if huge generators are used to support the grid, they will be voltage limited. The voltage at the source (generator) may be a bit higher than the nominal voltage, because one expects voltage loss on the way to the load (houses).

Thus the (Europe) inverters are sensitive to frequency. Nominal frequency is 50Hz. Inverters usually stop to supply energy when mains frequency is 50.20Hz. In a usual year the frequency does not often go above 50.05Hz. (I hope I remember those values correctly, it was many years ago)
The frequency behavior changed in the past. Older inverters stopped to work when the mains frequency went down below 49.8Hz.
But then one found out that this leads to a domino effect:
Low available power --> drop in mains frequency --> switching OFF inverters --> even less energy available --> frequency drops more --> blackout...
I think modern inverters gradually reduce power (not switching ON/OFF) on high mains frequency, and try to deliver down to a lower frequency limit (below 49.8 Hz).

No guarantee for the values ...

Klaus
--- Updated ---

But is this 285VAC thing for real?
..And can we proove it yes or no?
This high voltage is caused by errors. This won't be a whole grid problem, it's more a local problem.
Can we prove errors? I mean future errors. I don't think. Not in timing and not in magnitude.

Klaus
 

Easy peasy

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Depending on your weather region you can expect a 1kV transient P-N to earth several times a year too - if you are fed from a large nuclear power station the chances of the mains going over 265Vac are slim,
If you are fed from wind farms then 285Vac might well happen - although dips are more the norm with wind farms ...
 

schmitt trigger

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If you would like to visualize a fascinating real time Worldwide frequency deviation map, please go to the following webpage;
Fnetpublic.etk.edu

This site is hosted by the Power information technology laboratory, at the University of Tennessee.
I am proud to be involved in this project as I have been hosting a FDR acquisition unit at home for a few years now.
 

treez

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If you are fed from wind farms then 285Vac might well happen - although dips are more the norm with wind farms ...
Thanks, Quarter of elecricity in UK is now supplied by windfarms..

I am wondering where we can find the power grid company's confession that it really does go up to 285VAC?
 

Easy peasy

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If you live close to a large distribution transformer ( 1 MVA ) with on load tap changing - you will see a lot of interesting things on the mains ...
 

treez

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Thanks yes i am sure there would be lots of short spikes on the mains then....we are interested in fairly long term (eg more than 5 mins) at 285VAC or higher?
 

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