CFL lamps, bad power factor

Re: CFL lamps, bad power factor

RCinFLA wrote: »

You pay for true power (I*V*pf.) not apparent power (I*V)

Not quite a true statement for everyone...

Businesses (as I understand) typically pay for "true power" for their monthly billing--but their "reservation/max power" is billed in kVA (apparent power).

For the typical business customer in California, roughly 1/2 of their power costs are the Monthly kWhr charges. And the other 1/2 are the kVA reservation charges.

So, it is very easy to see a large office building (lights, computers) could be significantly impacted if the majority of their lighting has a PF of 0.5 (the peak kVA charges would be 2x vs kWhr charges).

Also, from what I remember some 30 years ago--large users (such as oil refineries) will have a PF meter on their billing too... Basically, the cost was $$kWhr/PF -- So the effective charges where for kVAhr (apparent power) and not KWhr (or true power).

Next--we in California are now starting to get "Smart Meters" installed. I have seen a couple places where it has been mentioned that Smart Meters will be billing kVAhr--not kWhr. And it was going to be recommended that homes may need PF correction hardware to bring their inductive loads back near unity Power Factor (i.e., 1.00).

The ugly part is that while it is relatively easy (and cheap) to correct PF for the typical induction motor (such as a well pump, A/C pump and fans)--it is not easy (at least the little bit I know and understand) to correct PF of non-linear electronic loads (i.e., older computers, CFLs, dimmer circuits, possibly older microwaves, etc.).

And the issue is the same for utilities--pumps, motors, etc., bad power factors are relatively easy and cheap to correct at their distribution points (near customers--such as we can see in the central valley of California where there are banks of capacitors that are typically switched on during the summer when well pumping and A/C loads are the heaviest).

However, any non-linear PF issues (such as CFL's)--cannot be--and (I would guess) the harmonic energy is eventually converted to waste heat during transmission/transformer conversion.

I think I have seen in a couple places that lighting was responsible for some 1/3 of the electric consumption in the US (may be one of those urban legends too)--so the mass conversion to CFL/electronic ballasts may be a pretty huge issue for power companies (and eventually) for the consumer.

What does it mean in the "real world" for the Utility Grid--basically transformers and wiring must be sized to the load/PF... So, if you have a string of CFL's (or other devices) with a PF of 0.5, then the wiring and transformer basically have to be twice as large and they distribution system losses could be 4x larger (I^2 * R losses) because of this (increased infrastructure costs and increase of wasted energy costs to the utility.

Supposedly--there may also be other issues if the majority of lighting goes "electronic"... For example, these devices (including power supplies and such) are basically "constant power" devices... Or, in English-- P=I*V... So if V goes up, I goes down (to keep P=constant). And if V goes down, I will go up.

This is a "negative resistance". It would be possible to setup a resonance condition in the grid... You get some heavy loads and/or generator failure--voltage starts to drop, and current increases (negative resistance because of active loads)--causing the voltage to plunge even faster... The utility pumps more current in to bring back up the voltage--and now the current drops. And the voltage will overshoot it regulation set-point. Classic feedback for an oscillator.

I don't know enough about the US grid to know if this is a real issue or not--but I have read a few discussions where this issue has been raised.

-Bill