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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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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:
Power factor (pf) of tiny devices isn't much of an issue as stated. pf is an issue for the power companies. Most if not all end users whether home of companies, factories, etc., are inductive pf loads. The end effect is that at some point, even on lines serving only houses, the pf must be corrected. This is because even though the load is reactive and not "consumed" so-to-speak, it increase the total current that puts a load on the lines and also ultimately reflects back to the generating and transmission stations.The extra line load current can ultimately exceed the rating of the lines and also will cause losses in the conductors. Power companies routinely conduct distribution load studies (that was my first job as an EE) to forecast growth and anticipate where and when lines will need to be upgraded. This can be increasing the conductor gauge, adding phases (going from single to 3-phase) to spread the line drops, moving load from one phase of an existing 3-phase to another phase to balance the load on the three phases or it may be adding line capacitors to counter the pf of the load. You'll likely see capacitors on any local distribution line. They're often the box-like cans mounted on poles separate from the transformer drops. These may also be distributed on the line, not all located at the same point, depending on how long the line is and what the distribution is of the load.
Large companies that have large motors are billed additionally if their load is too excessive with regard to pf. Power companies generally have specific contracts with them that state that if the pf drops below some value (pf=1 is purely resistive), then they will be charge additionally. Those companies that have large inductive current draws often install their own capacitors to prevent this.
When I left the power company I interviewed with a steel company that made only rebar. They were in the process of installing an electronically controlled fast-switching capacitor bank for nearly instantaneous switching of capacitors. Their process involved lowering a high-current probe into a tank to melt the metal. The capacitive loading was so extreme that the power company was charging them enough to make an expensive dedicated capacitor system economically feasible. My sole job would have been to start up and manage the capacitor bank project. I declined.
I wouldn't be at all concerned with anything you'd do in the home. Your refrigerator alone will swamp almost anything else you might connect.
dlr
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Follow Ups
- Re: Tweaking via parallel chokes/transformers on AC line harmful to grid? - dlr 07:27:07 04/28/07 (0)
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