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In Reply to: Tweaking via parallel chokes/transformers on AC line harmful to grid? posted by Christopher Witmer on April 27, 2007 at 01:42:44:
In my area the power from the 69kV power line goes to a substation first. From there it is distributed to many large "neighborhood" transformers. From that huge tranny it is sent out again to several street transformers. I think any correction that you do at home is pretty well isolated from the original power lines. At the most it is quite insignificant.Also, if there is any "loss", reactive or otherwise, wouldn't it show up on your bill?
Follow Ups:
With regard to your last sentence, electricity utilities measure reactive power used by high demand customers and charge higher rates accordingly. (Some industrial users install power factor correction schemes at their factories to cut down on these higher costs.) But we small fry are not charged for reactive power.Inductors are said to consume reactive power . . . that makes me wonder if perhaps our use of inductors in AC power tweaking is putting a disproportionate burden on the grid . . . not that the sum total of what we do makes a great deal of difference compared with impact of indstrial users . . .
I work for a power utility, responsible for the automated meter reading of both commercial and residiential accounts.I don't know of any utility that charges by power factor. We do monitor it, more to keep demands balanced on 3 phase lines, but it's not billed that way. Billing is typically done based upon demand, not reactance.
I have seen plenty of off balance meter reads caused by reactive loads. You can see it at the specific meter, but any negative effect tends to stay at the site; these customers typically have power and current transformers before the meter, so they tend to mitigate the issue.
At a residential site, I really doubt that any type of reactance from an A/C filtering system would be worse than that of a fridge, heat pump, central air compressor, or any other large motors.
I agree utility companies do install a demand meter for large users of electrical power.I would also agree any inductor that would be used across the mains for an audio system would not be enough to cause any problem.
Problem with too much inductive reactance, heat..... It can cause feeders and panel boards to run hot. This in turn can causes fuses to blow even though the load may be below the rating of the fuse. Same is true for breakers. The electrical wire as well as the terminations temperatures will run above their normal temperatures and sometimes be very hot.... And in this case capacitors are added to bring the lagging out of phase current back in phase with the voltage. Thus PF correction. Problem? Motor Frequency Drives hate capacitor banks...
I think we can both agree that large scale inductive reactance is an industrial problem moreso than a residential one. And most larger industries will have the means to compensate for the loads, either through conductor oversizing, time shifting of loads, or even taking a feed directly from a substation.You are right, while capacitance is the mathematical solution to inductive lag, it doesn't always work well in practice.
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