smart meters resisted

[SimonH2]

At church we have a "3 line" meter, with two lines connected to the same phase - in practice, all modern "3 phase" meters should be "3 line" since apart from sharing 1 neutral, they simply measure 3off single phases. Really no idea why they did it that way, other than there having been 5 fuseboards and hence multiple connections. Now we have one DB fed off one of the fitted* isolators, and another supply that goes no further than the isolator.
* I say "fitted" in the loosest meaning of the word. It was a mess, and whoever did it clearly had not been taught that terminal screws are intended to be tightened

 

[SimonH2]

When 3 phases are connected there is no way of knowing how much 240v is drawn from each.

Modern electronic meters offer per-line metering. You can cycle through registers showing per-line consumption (including VAr when that's being measured) as well as a total.

 

[JohnW2]

Modern electronic meters offer per-line metering. You can cycle through registers showing per-line consumption (including VAr when that's being measured) as well as a total.

I don't really get that.

For a start, for what it's worth, my 'modern electronic (3-phase) meter' certainly does not offer such a facility.

More to the point, I don't really understand how it would work, unless it were effectively three separate single-phase meters in the same box - as I understand it (maybe wrongly!) they work on the basis of the vector sum of all three phase currents.

Kind Regards, John

 

[ajohn]

I do know that some people in "houses" in B'ham wanted 3 phase for hobbies and due to the mains wiring used for a period it was easy and cheap to do. The meters recorded total use 3 phase and any 240v use. Main thing that interested me was one standing charge for one meter and also not being able to get 2 dual fuel deals having 2 gas meters as well. They would just say one deal per address even though each had a different address.

This is the set up with one phase disconnected - the space for the fuse can be seen - a dedicated 2 phase head.



And this is the isolator just fitted to the smart meter when that was installed



Which shows another problem. An electrician that looked for CU upgrade wants to fit a new backboard.

 

[SimonH2]

I don't really get that.
For a start, for what it's worth, my 'modern electronic (3-phase) meter' certainly does not offer such a facility.

It may depend on how the meter is set up. The one at church can (from memory) cycle through three readings - two registers and a total.

More to the point, I don't really understand how it would work, unless it were effectively three separate single-phase meters in the same box

That's exactly what they are - or at least some of them are. Measure the current and phase angle for each of three lines, then you can do the maths to derive a total consumption and power factor regardless of whether it's 3 phase or single phases fed into it.[/QUOTE]

And this is the isolator just fitted to the smart meter when that was installed

Curious isn't it. There's clearly different policies in place - and not just across different DNOs. In our rental properties, there are isolators with one pole marked "do not connect" and a separate henley for the neutral. While in our house and at church, both line and neutral are switched. Both in the same DNO area, but I guess this is a meter operator thing rather than a DNO thing.

And if you're thinking that backboard shows signs of water damage, you're correct. From an early age we were taught that electricity and water don't mix - yet we insist these days on putting unsuitable electrical equipment outside, protected only by a flimsy plastic box that often ends up with the door flapping about.

Which shows another problem. An electrician that looked for CU upgrade wants to fit a new backboard.

Well he can't It's not his board to be fitting a CU on anyway, so if the DNO and meter operator are both happy with what's there, it's not for the electrician to be changing it.

 

[JohnW2]

It may depend on how the meter is set up. The one at church can (from memory) cycle through three readings - two registers and a total.

Well, I would say that it depends upon how the meter is designed. As I said. mine certainly doesn't offer that facility - although it strictly is not, and is not being used as, a 'smart meter', it has umpteen registers, they all relate to to the total 3-phase consumption.

That's exactly what they are - or at least some of them are. Measure the current and phase angle for each of three lines, then you can do the maths to derive a total consumption and power factor regardless of whether it's 3 phase or single phases fed into it.

Again, fair enough, but I've certainly never seen or heard of such an animal, and nor do I really understand when one would be required. Meters are, after all, primarily for metering - so do you envisage that there would ever be a need for different tariffs/charges to be applied to different phases (and, if so, why?)?

Kind Regards, John

 

[ajohn]

It seems that the electronic meters measure and do calculations to work out consumption. That means software. Sometimes additions in that area means that things can be added at near zero cost. ie it's measuring them, has a button and a display so the ability to scroll though readings is likely to work out at just a few lines of code. LOL In software providing they decide to do it from day one. The mechanical 3ph ones as far as I am aware just use more coils to drive the disk.

That white thing next to the isolator appears to be the bit that does the coms back to base so the actual smart meter isn't that smart. The bottom of the meter display can just be seen

This what I am left with - economy 7 x2 disconnected by the suppliers some time ago.

I have been told by the electrician that looked that I shouldn't put various things in the cupboard. From long ago as far as oil etc goes - an ancient Shogun used to tow a caravan and since then out of site out of mind but did add the screenwash a few months ago.

 

[JohnW2]

It seems that the electronic meters measure and do calculations to work out consumption. That means software. Sometimes additions in that area means that things can be added at near zero cost. ie it's measuring them, has a button and a display so the ability to scroll though readings is likely to work out at just a few lines of code.

In terms of what Simon was talking about, software can do nothing about separate-phase registering if the hardware does not monitor the current and phase in the three phases separately - and, as I've said, I somewhat struggle to think of reasons why that would be required.

 

[Leofric]

I have been told by the electrician that looked that I shouldn't put various things in the cupboard.

surprised you haven't got a can of petrol in the meter cupboard

 

[AndyPRK]

So there is no display on your smart meter ?

 

[JohnW2]

So there is no display on your smart meter ?

Is not the top part of the meter (with the display) obscured in that photo?

Kind Regards, John

 

[ajohn]

So there is no display on your smart meter ?

If you look at the top of the meter in the shot you can just see the start of the display, it's darker than the rest I'd have had to lie on the floor to get it all in,

 

[ajohn]

In terms of what Simon was talking about, software can do nothing about separate-phase registering if the hardware does not monitor the current and phase in the three phases separately - and, as I've said, I somewhat struggle to think of reasons why that would be required.

They probably use current transformers on each phase and measure phase voltage directly. Much the same as the plug in power consumption meters that can be bought and used on single phase. Hope the meters are more accurate. Much like amper clamp meters really.

 

[SimonH2]

In terms of what Simon was talking about, software can do nothing about separate-phase registering if the hardware does not monitor the current and phase in the three phases separately - and, as I've said, I somewhat struggle to think of reasons why that would be required.

And I struggle to see how an electronic meter could measure the total without measuring the 3 phases. In a Ferraris disk meter, as far as I can make out they have 3 sets of coils (and 3 disks ?) - so 3 sets of power measurement, with the torques added mechanically.
There's a diagram on the face of the meter at church which shows three separate metering elements - though this could be just "convenient illustration" to show the connections.
Of course, what is measured, and what is made visible on the display are two separate things once there's a layer of software in between.

 

[JohnW2]

They probably use current transformers on each phase and measure phase voltage directly.

Yes, they probably do - but whether the amalgamation of the three phases is done in hardware of software in a different question.

My meter already has and awful lot of resisters - if there was one for each phase, that would obviously multiply by three. However, as I've said, I'm not sure why anyone would want/need that.