Smart meters

It could be several things such as the Uo, energy used in maintaining communications. Unlikely, AFAIK, to be pf.

Could well be power factor in my view. I very much doubt that the electricity meter consumes that much.

A capacitive power factor can result from loads that derive an extra low voltage internal supply from the mains by a capacitive dropper.

An inductive power factor can result from discharge lighting, lightly loaded copper/iron transformers and electric motors. Errors in measurement can result from the actual supply voltage being less than 240 volts. 100 watts at 220 volts will be a greater current than 100 watts at 240 volts. Or you clamp meter may be inaccurate at low currents.

Smart meters do measure true KWH and not KVARH

Joules 

www.utilitybidder.co.uk/.../

Thanks for the replies  I think it could be partly what the meter itself used  but mostly the slightly lagging PF of my fridge and freezer I'm not too sure how accurate  my clamp meter is but it reads within 10 to 15 mA of a different meter a plug in watt miser device   as has been said before all meters are going to be a little bit different unless I spend shedloads to buy a really good meter. But I havnt got that sort of cash going begging

I've just measured the current in the phase tail to the meter and it works out as about 200mA more

How does it compare with the same reading taken from the outgoing tail? That should tell you how much is down to the meter's self-consumption and how much is due to your installation.

I would have thought that self consumption would have been a handfull of Watts at most.

I'd agree that a poor PF is the likely cause of a high current reading - I've got an open enegy monitor that attempts to measure PF amoungst everything else and when my demand is low the PF is pretty awful. I guess it's down to all the small items having electronic PSUs these days. Switch on a large resitive load (e.g. kettle or oven) and it's back up to almost 1.0.

   - Andy.

They would change the electric meter to change the gas meter, because the gas meter reports to the electric meter which submits both readings.

If the meter were really consuming 230V*0.2A = 46 Watts continuously it'd be getting pretty hot given its small size. We might expect that if it were the surface temperature of the case would be tens of degrees above ambient and presumably it isn't. A Watt or two is more realistic for the power consumption of the meter.

Hi  I've just rechecked my readings but first I cleaned my clamp meters jaws and checked its battery's and all well there the readings I got this time are that the smart meter draws around 30mA  or 7.2 watts  30mA times 240 volts this seems a reasonable figure the meter is only slightly warm to the touch I won't do it again don't like disturbing the tails too much. I took the suggestion made on here of measuring first the tail from the DNO fuse to the meter then from the meter to my DB. My original measurement was with the freezer running so I think it may have a less than unity PF anyhow think I've done it properly now!!

DUoS Charging for LV and
HV Metered Connections
A guide to understanding WPDs charges for using our distribution system

https://www.westernpower.co.uk/downloads/6787

There is the guide, now tell me if domestic customers pay an additional charge for a poor power factor?

Well for the time being WPs domestic users are not half hourly metered, so they do not get charged for poor power factors. Yet.

But even though that is true, some digital power meters that are the basis of the new smart meters are not as good at correcting for power factor due to funny wave-forms, compared to the traditional poor power factor where both the current and voltages are nice sinewaves, just offset in time.

A slightly dated study by some chaps at the University of Twente  highlighted some problems with electronic loads, and digital sampling meters, reporting quite bad over reading compared to the reference spinning disc metering (over  500% in some conditions !).

(Measurements were repeated with more meters and supplied from standard, low internal impedance, mains supply in the laboratory. Deviations of +475%, +566%, +569%, +581%, +582% and -31% and -32% were registered, with again the positive deviation for Rogowski coil current sensors and negative deviations for the Hall sensors.)

The meters used were the 3 phase smart meter kind used in Holland, but there is no reason to assume that UK specific single phase models by the same makers would be so much different internally- they are all tested to the same Euronorms after all.

Mike.

PS Selling power factor correction caps to domestic users is a bit of snake oil, but some low pass filtering on any really spiky loads may be worth while.