I am a law abiding person so interested, can you share your sources here - where is the max 1kw load that can be leagally controlled this way defined?
Practically I have never experiences of flickering lights (although mine in house all LED so perhaps the power supply in the bulbs can ride it out). I know all my 7 neighbours in the street, assuming some will be on same phase as me, no one has mentioned it.
About 10 years ago I found a useful article on this using Google but can’t now find it. This one though is useful https://www.newtons4th.com/wp-content/uploads/2014/04/APP026-IEC61000-3-3-2013-Electromagnetic-Compatability.pdf You can see from page 7 that in the worst case of 1000 voltage changes per minute (8 Hz) you are only allowed a 0.3% volt change or 230 x 0.3/100 = 0.7 volts.
R = V/I = 0.7/13 = 0.05 ohm for a 3kW/13A load. Thus if the impedance of your supply is worse than 0.05 ohms you may be breaking the spec. I think what the missing article was saying is that average UK houses are at about 0.15 ohm so a 1kW load is OK but not a 3kW one.
I suspect that you have a below average impedance, which is why you get away with it or no one has incandescent bulbs. Neither house I tried a burst fire 3kW diverter on were satisfactory, with noticeable flicker on the incandescent lights at around 1 Hz. What the actual % was I did not measure. It’s not an easy measurement although an oscilloscope may do it.
The other way to minimise flicker is to move the voltage changes as far from 8Hz as possible. But it not that easy to do across all % of load currents. I don’t know what frequency that Farnell one uses. Robin may say he has managed it with his diverter but I am not sure how. Diverters can’t be too slow as the electricity meters will otherwise register a chargeable import. 10 on cycles and 40 off is 20% power at 1Hz but the meter may register it. You can’t go too high as you are working with an integer number of 50Hz cycles, so the highest limit is say 1 on and 4 off but at 10Hz it is close to the 8Hz worst case.
Also useful are Overview on harmonics and Flicker and related specifications used for the testing of AC and DC equipment. and EMC Testing - Part 7 - Emissions of mains harmonic currents, voltage fluctuations, flicker and inrush currents; and miscellaneous other tests
The former mentions the flaw in all this in that it’s all based around flicker of a 60W incandescent bulbs and we can’t buy these any more. The latter includes this statement
7.1.9 Professional equipment
A significant relaxation, present in the original standard, is that no limits apply (more correctly, limits are “under consideration”) for professional equipment with a power of more than 1kW. Professional equipment is defined as “equipment for use in trades, professions or industries and which is not intended for sale to the general public. The designation shall be specified by the manufacturer”. A14 relaxes this slightly more, by allowing the connection to “certain types of low voltage supplies” of non-compliant professional equipment, if the instruction manual contains a requirement to ask the supply authority for permission to connect.
But that is not saying that below 1kW it’s likely to be AOK.
Microwave ovens may use a form of burst firing as they turn on and off at around 0.1Hz to modulate the power. 2% voltage change is allowed at that low frequency so it is OK…
Yes, a Vango Sizzle 800W induction hob can go down to about 400 watts without pulsing. This is what I use in my EV campervan.
Very comprehensive - thanks!
I have never measured but I can see the DNO’s 11kv transformer at the end of my road so I suspect this is the case.
We are very OT now, but I think Campsite electricity is going to become more interesting in the near future. I have never used it, normally rocking up on a bicycle or foot, but last weekend I was in Perthshire. The campsite had recently upgraded the supply to the “posts” to 10A
There was an EV plugged into one charging, probably not very fast, but as EV ownership grows if more than a few people did this I suspect the campsite supply will not last long! Given ever increasing use per pitch the owner had also installed pre-pay meters per post to manage demand, instead of her old practice of charging a fee per day.
Makes total sense. I’ve done a lot of charging on campsites, never had an issue, but I usually charge my van at 6A which is never going to cause an issue on a 10A hookup. It doest matter if it takes 24hrs to charge since most people stay on campsites for a least a couple of days. Happy to pay for the convenience
Agree. Free charging has largely gone and I don’t mind. I did get it free recently at a hotel and I think they did not mind as the admin of charging probably outweighed the consumed electricity at their one 7kW charger. Especially as it was so boxed in in their crammed car park that few could access it.
I see in the spec that the resistance of the lead from your CU to the appliance is included in the measurement. I don’t know why because, even if that lead was thin and dropped 10 volts, it’s not going to be seen by other outlets from your CU, like lighting circuits, or by our neighbour. Only a bulb directly connected at the appliance will see the 10 volt drop. Strange.
Over 25 years ago I had a problem with lights flickering, normally early morning. Not everyone could see it though! The DNO investigated and then went round our village asking people questions and looking at peoples appliances. They came to no resolution. A year later they came back to me and said they had found the source of the problem. They had had another problem, the same, in a much smaller village than ours and on inspection round that village, they spotted the same appliance as one they had seen in ours. It was an electric ‘aga’ type device and the manufacturer had to rectify the fault / design.
I don’t know if the standards cited in this paper are still current, the paper itself is in excess of 20 years old:
The standard EN61000-3-3 was last revised in 2021 so looks up to date. I don’t know if the actual test limits have changed in the last 20 years but probably not. Unfortunately these standards cost a lot of money to buy (try getting hold of a free copy of the one on cEV charge points!). Contents page only:
https://webstore.iec.ch/preview/info_iec61000-3-3{ed3.2}b.pdf