Single to 3 phase invertor and smart meters

Spinning disc meters did measure power - see here. When I was a student we built a crude charger for NiCads with a half-wave rectifier - interestingly when connected to the shilling in the slot meter in our flat, the disc went slowly backwards (as long as it was the only thing conencted). However they were obviously wise to this and there must have been a ratchet in the gear train because the dials did not wind back.

I rest my case, we will see!

As John Haine has pointed out, the old spinning disk meters did consume power, some of which you pay for and some you don't. Basically you pay for the I^2R loss in the current coil but don't pay for the V^2/R loss in the voltage coil.

Those meters don't charge for the reactive part of the load current, at least ideally. This is fair since the reactive part does not convey any power to you, nor does it cost the power company the full cost of the equivalent power. Why they don't like it is that the reactive current does cost them the loss in all the conductors leading to your house. So for instance if you have nothing connected in your house other than a large capacitor, there will be no net power delivered to your house, but there will be a reactive current flowing, and there will be losses in the power lines due to that current. Domestic users usually do not have enough reactive load to worry them very much, but in most countries the company has the right to insist that large users correct their power factor. It would be fair for the company to charge you something for having a very reactive load, but not the full V x A figure since that amount of real power is not having to be generated.

The power companies are also not all that keen on non linear loads like switch mode power supplies and vfd's, inverter welders and so on, which generally all present a rectifier to the power line. This means that they tend to take their current as a pulse at the peak of the AC waveform, which generates harmonics, which are not really welcome in the power distribution network. This can be alleviated by using a choke input filter on the DC side of the rectifier, but such chokes are bulky, heavy, and expensive so naturally do not form part of the usual circuits. Of course they will hate half wave rectifiers even more, these cause DC to flow in the secondary of the pole transformer. Too much DC will saturate the iron core, potentially causing a very high current to flow in the primary.

Here in NZ, if I put in solar power, I have to get a new meter. This is because if I am generating excess, the existing old style meter will not register any power fed back into the mains...that ratchet that someone mentioned above. So a smart meter in that case at least would mean that I did get paid for the power I supply to them, even if they only pay a miserable fraction of what they charge me for power going the other way. They only charge a quite reasonable installation cost for the new meter. I'd quite like to put in some solar cells, at the moment in the hot weather we have been getting I would be able to run the heat pump as a cooler in the daytime which would be very welcome. (Meanwhile in winter it sits idle as we have a wood burner which is much cheaper to run!)

John

I cannot listen to my little LW/MW/FM transistor radio in one corner of the living room since having a smart meter fitted. Lots of interference from the meter on the other side of the wall......but that's another can of worms!

Gordon.

John, in the UK there is no facility for monitoring how much generated power is fed back to the grid with domestic metering, the government assumes that 50% of kWh that are paid for with the feed in tariff will be exported to the grid so they pay every PV generator for the deemed 50%. That could change with smart meters if they can detect exported kw hours.

Dave W

I wonder what the new little kWh meter installed next to the main meter when the solar panels were installed, the reading on which I have to enter when the FIT claim is put in, is measuring then? And the online monitoring page also says how much is being exported. So there is certainly the facility in the installation to monitor it.

As for things interfering with radios, it's a fact of life that electronic devices radiate. Anything like a smart meter will need to meet emc standards. Unfortunately the same is not true of a broadcast receiver, and if it is in a place with low signal strength it's going to be affected by locally generated noise.

That is what is deemed as export (gleefully agreed by the suppliers, with the overseers) for normal installations up to the 3.68kW export limit, allowed for the full FIT payments.

Larger domestic installations can/will have an export meter. They are paid a far lower FIT payment per kWh than the usual domestic systems. Clearly they agreed this level of ‘deemed export’ because they were getting a good deal at the time! All might change when the FIT payments cease, for new installations, come next month-end.

I think many systems will not only have PV-generated kWh meters, but also export meters installed anyway - even if they do not indicate the export. (Some) electronic meters indicate a reverse electricity flow by the normal white flashing light changing to a pink/red continuous light. I expect those meters are totting up the export.

Smart meters would soon tell if the owner was getting paid for too many kWh, so the rules will doubtless be changed when smart meters are nearly universal, if the suppliers are still not benefitting by the present system.

Larger systems likely have to have a 3 phase supply so exported power would not unbalance the local substation transformer.

People are getting wise about so called smart meters.

**LINK**

At our current property, smart meters were already installed by the energy supplier, EON. We switched to Scottish Power last April. We supply readings to SP every three months and receive a bill accordingly. We pay by direct debit.

Our previous property had meters supplied by British Gas, as we hadnt sold it yet, we transferred to SP to take advantage of their costs, again last April. We supply readings to them as we do for the home where we live now.

Bottom line here is, Smart Meters dont provide me with any advantage, its no issue for me providing a reading. I keep my energy useage down by switching off lights in unoccupied rooms, turning down the room stats on unoccupied rooms etc.

There is some confusion above about the FIT. All installations have an extra meter to record the actual power generated regardless of where it goes. The next stage is dependent on the supplier you are with. Some suppliers, especially in the early days knew the main meter wouldn't go backwards to record the actual flow back into the mains so just agreed a 50% rule. Others especially more recently got wise to the fact that there were devices on the market to feed excess into heaters etc so ensure none went back n to the grid, yet the homeowner still got the 50%. So they took the trouble to change the meter for one that registers what goes in both directions. More detail on the Navitron forum.

I agree that all the predicted "savings" for the consumer are complete bullsh*t for the majority of customers. I finally relented because I was getting so fed up of being bombarded with information. I have had a new meter for about a month now. My supplier has not yet caught up with the billing. It is a bit of a novelty to see what does and doesn't consume energy, but as others have said, the vast majority of usage is essential. The house is heated by a ground source heat pump, which is 2.3kW. I pay my bill on monthly standing order, whch means I spread the cost of the winter over the year, but on the slipside my account is also in credit for most of the year. It will be interesting to see how more accurate usage impacts this. Time will tell

Believe me, if the suppliers were not getting a good deal, they would never have so gleefully accepted the arbitrary figure of 50% export. Many systems placed on houses, where both occupants were at work all day long (maximum PV output) would be using far less than 50% of the system output.

That probably changed a bit when immersuns, solics, etc came on the market and diverted excess generated power to domestic hot water heating, but they have still not complained re the 50/50 split, so are quietly raking in profits of buying cheap and selling at full retail price! Not a bad mark up? About 400%? Out of one house and used in the next, so no grid costs? Diverters are not a good way to use high grade energy, but better than being scammed by the leccy retailers.

Smart meters will lead to increased prices. They already have and are still not worth it. It is the customers who are paying for the suppliers to screw them further, later!

I call my wife ‘switch on and never switch off’ or ‘turn it but never turn it down’. Describes her quite succinctly!

In respect of generated solar being exported back to the grid I was under the impression that all systems generating 3.68 kw or less were subject to the deemed 50% rule, was unaware that some were subject to export metering. As a point of interest we have an energy monitor on our meter feed, this has a transmitter clamped around the live feed from the meter and displays the flow in watts on a portable unit indoors. Since having the solar panels fitted there is now two way flow on the live feed because exported power now travels the opposite way to incoming power, unfortunately as the meter is unable to detect the direction of electron flow it just records a figure of flow irrespective of direction. It is therefore not possible to know whether we are importing or exporting to the grid so I have told the wife that to be efficient we need the number of watts displayed to be as low as possible, ideally zero, that means when the sun is shining and we are generating we are using what is generated and conversely when we are drawing from the grid the figure is as low as possible. When the tumble dryer is switched on the reading rockets up, although it is an energy + appliance it uses about 4.2 kw, by far the biggest consumer of energy that we have, we have always operated an energy consumption of if we need it we use it, the solar panels mean that with a little thought and rescheduling we can use as much as possible of the solar generated energy which of course is free and we get paid for it.

Dave W

About the old type meters,back before the 2011 earthquake in Christchurch NZ Whispertech, the manufacturer of the Whispergen Stirling Engine domestic power supply had one of their units set up in the workshop with an old rotating disc meter on it, and most of the time it rotated backwards with the hands on the dials moving backward.

Ian S C

If you are referring to your supply meter logging import and export as import, you are getting hammered every time you export!

NDIY, not referring to the utilities meter but a small energy monitor that I acquired and fitted on the live input from the utilities meter. I have been monitoring our unit consumption in respect of readings from the utilities meter and compared to 12 months ago there is so far a 10% drop in power used, this is since day one of the solar panels generating, quite pleased with that result as we are generating in the darkest winter months I.e. December, January and February so expect a lot more solar to be utilised in the Summer period and therefore a significant reduction in units purchased from the grid.

Dave W