Factories charged per kVA?, why not get PF and charge in kWh?

[eveares]

If I understand correct; factories and other large energy consumers have their energy usage measured kVA and not in kWh, are they just simply charged for their apparent power usage or do they also have their Power factor measured and only get charged for their true power usage?

In other words, why do they not have their PF measured to, or do they?

Is it also true that factories get penalized for having a poor power factor and thus having a high reactive power usage.

 

[westie101]

The charge consists of usually four parts
Network capacity charge - to ensure there is sufficient availability of the maximum load they require
Actual demand often measured every 30 minutes (it can in some cases be above the capacity which gets expensive
Power Factor usually with an extra charge if it is less than 0.9. This is usually done by charging separately for the kVAr load i.e the reactive load
Units used as a domestic tariff

 

[eveares]

Actual demand often measured every 30 minutes (it can in some cases be above the capacity which gets expensive

So a reading is taken every 30 minutes, or just their current consumption in the moment every 30 minutes?

Although impracticable and unrealistic, surely there can't be a loop hole of where you could turn everything off a few seconds before a actual demand reading and then turn everything back on after to avoid paying the demand part of the charge. I amuse they have a allotted capacity, if they exceed that then that is what gets expensive as you said.

Also

Units used as a domestic tariff

Do you mean they are still charged per kWh in the end.

Also is the Power factor measured in real time, or is it based on a predetermined/average/worst case scenario value for them?

 

[ericmark]

In some cases it is down to demand at peak times. As with domestic there are different deals. Where my father worked at a steel works they both imported and exported power. Their own power stations used multi-fuel could run on blast furnace gas, coke oven gas, oil or coal although latter was never used and his job was to decide when to use each idea being if possible to be exporting at peak times. It was only a small power station just 12 MW but a real power station controlling steam, air, gas and electric supplies to the works.

It is common to be charged for peak power rather than actual power used.

On Anglesey the Aluminium plant had a special deal with the national grid and it used the power from the Wylfa Nuclear Power Station and the Dinorwig Power Station and was all about taking power when not required else where. When the national grid was privatised it caused huge problems which resulted in the 299MW Biomass Energy Centre at Anglesey Aluminium.

Even where I worked at a small concrete plant it was still the peak demand which was a major factor in the cost. We were considering making concrete bricks for storage heaters and I had to work out the cost of power. But the problem was there was no fixed cost so near impossible to work out costs when you don't know until after how much power will cost. We did experiments and found there was a chemical reaction the first time a brick was heated which resulted in pools of water on the floor under the storage heater after first use. We would need to pre-heat the bricks to 250°C to remove the water so the idea was dropped.

 

[Lectrician]

Actual demand often measured every 30 minutes (it can in some cases be above the capacity which gets expensive

So a reading is taken every 30 minutes, or just their current consumption in the moment every 30 minutes?

Although impracticable and unrealistic, surely there can't be a loop hole of where you could turn everything off a few seconds before a actual demand reading and then turn everything back on after to avoid paying the demand part of the charge. I amuse they have a allotted capacity, if they exceed that then that is what gets expensive as you said.

Also

Units used as a domestic tariff

Do you mean they are still charged per kWh in the end.

Also is the Power factor measured in real time, or is it based on a predetermined/average/worst case scenario value for them?

Half hourly metering simply remotely sends the data every 30 minutes, for the consumption up to that point. There is no way to grab free lecky between the 30 min reads.

There is too many variables, too many suppliers and too many ages of installs/meters.

You used to have a kWh meter and PF meter, and your supplier would charge you per kWh, and may charge for poor PF.

These days the meters are all digital and measure everything, usually charging kWh and PF if poor. On a site recently though, the PF capacitor failed, and took out the supply fuse. It was decided not to repair as there was no penalty for poor PF from the supplier. The PF was not too bad anyway.

Large supplies, typically at HV, over around 1MW demand are usually charged at kVA to reflect the true demands placed on the network. Obviously no PF charges then apply.

You will also have a monthly "availability charge" which reflects the size of your connection. Large connections place large demands on the network and an availability charge is levied. If you exceed your stated maximum demand (which is essentially what your availability charge is based on), you will be fined monthly.

 

[bernardgreen]

Back in the 1980's the control room of one of London's first sky scraper office towers had a "clock" on the wall. Nothing to do with time. It had a red hand that moved at a constant speed around the clock face and a black hand that followed it but not at a constant speed. The black hand was the amount of power being used and the red hand was the maximum allowed to be used. When the black hand was catching up to the red one the staff started shutting down services to slow the black hand. I never saw what happened if the black hand over took the red one. I assume the cost of electricity increased a lot if the black over took the red.

 

[ban-all-sheds]

I never saw what happened if the black hand over took the red one.

Total protonic reversal?

 

[Dave54]

Back in the 70s I worked in the steel industry. Maximum demand meter was on a 30 minute period, and if exceeded the penalty had to be paid for the month IIRC. I assume there was an alarm somewhere when it reached a certain level, because the shift engineer would come and instruct an electrician to arrange the shut down of some of the annealing furnaces until the meter reset. We had to check that visually in the sub station.
Interestingly PF was never an issue there because the main DC generators for the mill motors was driven by a 5000HP synchronous motor running directly off 11Kv. That gave us a leading PF. Can't remember how much, but I remember being told that the electricity supplier liked us running it because of the PF correction it gave.

 

[bernardgreen]

One large building in London had the escalators running 24 hours 7 days a week. This was to compensate for the PF of the flourescent lighting. The building manager told me that running the escalators resulted in a lower electricity costs.

 

[westie101]

Poor power factor is seen as an issue, with turbo generators having to be operated purely for power factor correction.
There are experimental steps afoot I understand to fit power factor protection at an LV network level in domestic areas to correct it at that level

 

[Dave54]

One large building in London had the escalators running 24 hours 7 days a week. This was to compensate for the PF of the flourescent lighting. The building manager told me that running the escalators resulted in a lower electricity costs.

I think I have a vague recollection of having heard that before.

 

[eveares]

It is common to be charged for peak power rather than actual power used.

vs.

Half hourly metering simply remotely sends the data every 30 minutes, for the consumption up to that point.

Contradiction!?

 

[JohnW2]

It is common to be charged for peak power rather than actual power used.

vs.

Half hourly metering simply remotely sends the data every 30 minutes, for the consumption up to that point.

Contradiction!?

I'm no authority on the details of these contracts, but I don't see that as necessarily being a contradiction. If one didn't measure the consumption regularly (or continuously), how could one work out (at least approximately) what the peak consumption had been?

Kind Regards, John

 

[eveares]

I'm no authority on the details of these contracts, but I don't see that as necessarily being a contradiction. If one didn't measure the consumption regularly (or continuously), how could one work out (at least approximately) what the peak consumption had been?

I guess that makes sense, also I guess in reality it's unfeasible that there power consumption would drastically change every few minutes. Also even if they only have a reading taken every 30 minutes, maybe the meter would also send back the average kWhs consumed in that half hour; and even if not, I suppose it's perfectly fine as a large energy consumer like a factory would not be able to disconnect from the grid or drastically save power every 30 minutes.

On a side note; does anyone know of a public interactive map showing all the transmission lines, sub stations, power stations, etc.. in the country and the routes they take. (i.e. If i see a transmission line going across a motorway or a local substation, can I find it on a map what covers the nation.)

 

[EFLImpudence]

The transmission lines are on OS maps.