That's a very useful overview, @sparky and welcome to the discussion 🙂 

We should perhaps also note that some in-house appliances can cause spikes and anomalies on the mains being sampled by our Smart Meters.
Heat pumps are renowned for inducing harmonics which get passed back to the grid,
and some solar inverters export electricity which varies from the nice clean sine wave we'd expect to see.

However, our UK Smart Meters have been tested under such conditions, and still provide an accuracy level well within the regulations.

Posted by: @sparky

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electronic electricity meters have a lot of information about the voltage and current, and can also easily calculate RMS voltage, RMS current, kVA and other parameters (power factor, kvar, maximum demand etc) but that's a longer story

That data is of interest to the regional DNOs of course.

But they are not permitted to receive data which identifies a particular property.
Instead they see an amalgamated data-set for an area covering 10+ properties.
That allows them to assess whether there might be local fault, or to check how much headroom a substation transformer has before reaching the specified capacity.

Interestingly, a DNO does not receive adequately granular smart meter data to identify electricity theft or sites where consent to export to the grid has not been sought.
Instead they deploy a separate monitoring device which uses AI-based algorithms to pick up such instances.

@sparky

I'm afraid that I cannot agree with your statement that domestic users only pay for the true power received, i.e. kWh.

As you correctly state kW = kVA in a resistive load when the voltage waveform and the current waveform are totally in phase, but this is not always the case when there is inductance and capacitance in the circuit, since the current waveform can either lag or lead the voltage waveform by several degrees. The power generators measure kVA or even MVA which is the apparent power being supplied to all the consumers. The consumers both domestic and industrial are billed on kVA or MVA.

If the voltage and current are out of phase, the 'true' useful power (kWh) will be lower than the 'apparent' power (kVA), so not all the power supplied is being utilised, or conversely the consumer is paying for energy that may not be fully useful.

Because most domestic users don't use vast amounts of energy, the difference between 'true' power and 'apparent' power is not too large to warrant correction, but high power industrial users would try to employ power factor correction to help reduce their energy costs.

To Derek_M 's point, your domestic bill comprises the standing charge and a charge for the kWh used.  KVAh is not measured or billed, and older electricity meters do not have the capacity to measure KVAh.  See also for example

https://www.ukpower.co.uk/home_energy/guide_to_gas_electricity_meters

which says "Standard meters are the most common type of electricity meter in the UK, and measure electricity usage per kilowatt-hour (kWh), which is the number of units of energy you use in one hour."  Also see the Wikipedia entry on "electricity meters" which has more information.

Larger, commercial users may have to pay additional charges if their kVA is significantly larger than their kW (measured by power factor, the ratio of kVA to kW, so as you say they can use power factor correction equipment.  Decades ago, many industrial loads were electric motors, an inductive load, and the power factor correction equipment automatically switched variable amounts of capacitor banks across the line to "balance up" the inductive motors, varying the corrective capacitance as motors, fluorescent lights and other inductive devices were switched on and off.

Although domestic users do not pay for kVA, we pay a higher price for our kWh than industrial users, partly to allow for the uncorrected power factor that may occur.  The DNO has the option to fit power factor correction equipment at substation level, if they think it worth the cost for domestic supplies, but traditionally, domestic loads were mainly incandescent lamps, resistive heaters for space heating and cooking etc, with maybe just a television, washing machine and a few other small non linear loads.

These days, industrial loads are more likely to be variable speed drives and other electronic controllers, which convert AC to DC and use the DC to feed the motor control circuit.  As Transparent points out, older or poorly designed motor controllers or other electronic loads can inject all sorts of troublesome harmonics into the mains.  These harmonics also result in poor power factor, but cannot be corrected by traditional phase correction switched capacitor bank power factor units.  These harmonics are regulated by IEC standards and enforced in the EU (and UK when we were a member) through the EMC directive.  The usual modern solution for any higher power items (eg a heat pump) is to use a power factor correction circuit which forces the line current to closely follow the voltage waveform, together with a filter to remove higher harmonics produced by the power factor correction circuit.  Clearly this becomes much more important when most houses have a heat pump, rather than the occasional installation we have today.  If, as seems likely in future, significant off peak domestic loads are lots of high power heat pumps, their electrical harmonic performance will be important to avoid adverse effects on the electricity network.

Not only do distorted current waveforms and harmonics have the potential to upset metering, but they can also have other serious effects.  For example, in three phase systems, the 50Hz currents in the phases are expected to balance out, so little current flows in the neutral wire.  But if the current has lots of third harmonic (ie 150Hz) they don't cancel, but add up.  There have been instances where older buildings fitted with more modern equipment has had the unfused neutral cable burn out due to overload, as the electrical designers did not envisage lots of third harmonics.

I recall a new emergency service call centre, many years ago, that was fitted out with hundreds of identical PCs, and not much else apart from lighting and staff appliances.  The company I worked for at the time supplied their older design of electricity meter to monitor where the (fairly high) power bill was being incurred.  The totalled readings on the submeters did not correlate with the revenue meter at all, and one unhappy customer.  Fortunately, the design team had just introduced a new design of meter under my guidance, which was designed to meter distorted loads accurately (and report the amount of distortion).  When the new design replaced the old submeters, the problems went away, instantly.

In the domestic context, as older appliances that were not compliant with modern IEC standards are replaced, so any distorted waveforms and poor power factor will fade away over the years and kWh will remain an appropriate measure for domestic billing.

That's one heck of a second post to this forum @sparky !

From the above explanations I'm assuming that you have first-hand knowledge of how smart meters operate internally, both in domestic and commercial environments.
I understand that you will not wish to divulge certain aspects of their operation

• commercial confidentiality; to protect the IPR of past/current employers
• national security issues; preventing hostile 3rd-parties from gleaning information on the UK smart meter network, and potential weaknesses in grid topology

Bearing those factors in mind, are you in a position to tell us any more of your present role and past experience?

I agree with 90% of what you write.
The other 10% is mainly about what is going to happen in future developments.

So I'd appreciate knowing where you stand before raising such issues!
If you work for or advise the Dept Energy (DESNZ) or Ofgem, then I'd word things differently, for example.

Thanks for the kind remarks Transparent. I can see from some of your posts you have a lot of knowledge in this subject area.

I have some decades of technical experience with equipment suppliers, mainly low voltage (240/400V) and some higher voltage distribution applications, both for revenue metering and energy information systems (so larger customers can see where all the power is going).  Also electronic motor drives, generator protection systems, and fault tolerant distribution systems.

I'm interested to see your views on future developments. I'm not involved in government or regulatory authorities, so fire away!

@sparky

If consumer's were only billed for kWh's of energy supplied, then why would some go to the expense of installing power factor correction equipment?

Below is an extract from Wikipedia which explains the power triangle, which you may find of use. I think that we both agree that Power = RMS Volts x RMS Amps, which at a Power factor of 1, kWh = kVAh.

As detailed below, when the Power Factor is less than 1, the Apparent Power (RMS Volts x RMS Amps) designated as VA, is greater than the Real Power, designated as W. As far as I am aware the domestic energy meter measures Volts and Amps and therefore Apparent Power, which is actually Volt-Amperes. Most consumer's are confused about kWh's, so for suppliers to then say that you are actually paying for kVAh would not go down very well.

In alternating current circuits, energy storage elements such as inductance and capacitance may result in periodic reversals of the direction of energy flow. The portion of energy flow (power) that, averaged over a complete cycle of the AC waveform, results in net transfer of energy in one direction is known as real power (also referred to as active power).^[2] The amplitude of that portion of energy flow (power) that results in no net transfer of energy but instead oscillates between the source and load in each cycle due to stored energy, is known as the absolute value of reactive power.^[2][3][4] The product of the RMS value of the voltage wave and the RMS value of the current wave is known as apparent power. The real power P in watts consumed by a device is given by

where

• V_p is the peak voltage in volts
• I_p is the peak current in amperes
• V_rms is the root-mean-square voltage in volts
• I_rms is the root-mean-square current in amperes
• θ = θ_v − θ_i is the phase angle by which the voltage sine wave leads the current sine wave, or equivalently the phase angle by which the current sine wave lags the voltage sine wave

The relationship between real power, reactive power and apparent power can be expressed by representing the quantities as vectors. Real power is represented as a horizontal vector and reactive power is represented as a vertical vector. The apparent power vector is the hypotenuse of a right triangle formed by connecting the real and reactive power vectors. This representation is often called the power triangle. Using the Pythagorean Theorem, the relationship among real, reactive and apparent power is:

I have no idea why domestic consumers would install power factor correction equipment. 

Meters that measure only RMS current and voltage will not pass statutory tests (see Transparent's earlier post for details), as they can have large kWh errors on reactive or non linear loads and cannot be used for revenue metering.

It may help if you have a look at the datasheet of an IC which meters power, for example:

and look at section 2.3.  This chip is now obsolete but does explain the algorithms used and how it calculates kW as well as kVA and kvar.

Posted by: @sparky

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I have no idea why domestic consumers would install power factor correction equipment. 

Meters that measure only RMS current and voltage will not pass statutory tests (see Transparent's earlier post for details), as they can have large kWh errors on reactive or non linear loads and cannot be used for revenue metering.

It may help if you have a look at the datasheet of an IC which meters power, for example:

ANALOG.COM "https://www.analog.com/media/en/technical-documentation/data-sheets/78M6610PSU.pdf"

and look at section 2.3.  This chip is now obsolete but does explain the algorithms used and how it calculates kW as well as kVA and kvar.

Domestic consumers would not install power factor correction, because it would not be cost effective to do so for the quantity of energy involved, and most would not have a clue about it anyway.

So if I understand correctly what you are saying, today's Smart meters have a similar type of IC to the one that you specified, and the consumer is billed for True Power (Watts) rather than Apparent Power (Volt-Amperes), since the difference between the two could be quite small. If that is the case then I stand corrected and apologise.

No apologies necessary - this is after all a forum to share information and learn from others.  I'm certainly learning from the RHH forum.

@sparky

I still find it strange that in our modern 'rip off the customer whenever possible' society, that electrical energy suppliers are happy to provide the overall 'Apparent Power' but only charge for the 'True Power'.

But the UK's Smart Meter specification was drawn up by Government in consultation with Ofgem.

The meter manufacturers built to that standard in order to gain certification,
and the Energy Suppliers had very little say in anything apart from the installations process (for which they are responsible).

Contrast that with the way in which the Suppliers were in direct communication with Ofgem as the EV Charging Regulations were being drawn up.
And we can then see that they've succeeded in not having to implement any of the features within our Smart Meters which are designed for that purpose.