What's "Dirty Power"

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Could someone please explain what dirty power is and how it could effect us. According to CEO man we may have it for a year...how should I prepare for this?

-- (thegigco@erols.com), December 03, 1999


Clean power: 60-cycle AC, approximately 110 volts peak-to-peak, clean sine-wave (no "surges" or "brown-outs"). No grounding problems.

Dirty power: Anything not in above definition.

Brown-out problem - Low voltage actually RAISES current-flow through some devices, creating overheating (especially motors). Cheap solution? Unplug your stuff. Good solution? Line conditioner capable of compensating for brown-outs (transformer with solenoids which automatically "kick in" to alter windings depending on voltage).

Surge problem - Very short-duration very high voltage can hurt sensitive electronics. Cheap solution? Surge suppressor. Good solution? Line conditioner (a transformer).

Grounding problem - If your home wiring is not properly grounded, you can have all sorts of "dirty power" problems, mostly "ground-loops", which adversely affect the 60-cycle AC sine-wave. Solution? Good ground.

-- Anonymous999 (Anonymous999@Anonymous999.xxx), December 03, 1999.

A few weeks ago we had a very powerful rain storm. At some point during it about half of the UPS units in the shop here kicked in and started beeping there alarms. What was weird was that all the lights were still on, the monitors glowing and our TV was still up. At first we were totally perplexed and couldnt figure it out. The lights didnt dim nor did we see the "trigger" that caused it. In about 15 minutes most of the UPS units ran out of juice and shut down, while about half of them remained in standby as if nothing happened. We had to disconnect all the equiptment from the UPS units and plug them straight into the power because we were down as if we had a power outtage but you sure couldnt tell from walking around the place.

Turns out we had a small dip in voltage for a few hours, due to what I dont know. What bothered me was how some of the UPS units (about 15) acted as if there was a power loss and the other 18 or so didnt.

UPS units are useful for sudden drops of voltage but moderate drops will trigger them to think its too low even though your equiptment would normally still work fine with that "dirty power".

-- hamster (hamster@mycage.com), December 03, 1999.

Don't forget power factor. That's when the voltage and current are out of phase of each other. Large inductive loads can cause it, especially in the summer. It does nasty things to motors.


-- Y2Kook (Y2Kook@usa.net), December 03, 1999.

Mr. 999, if you have "clean power", at 110 volts, you will burn your electrical equipment up. The industry standard for voltage is 120 volts, plus or minus 6 volts.

-- Pl (Powerlineman@u.com), December 03, 1999.


Do your UPS's have switches to set the low voltage trigger point? If so, set them to the lowest value. I had to do this due to a problem with an A/C that caused a momentary voltage drop during start up.

-- pho (owennos@bigfoot.com), December 03, 1999.

If you have access to older darkroom equipment suppliers, you may be able to pick up an old Omega constant voltage transformer for a song. They were used to maintain a stable color temperature at the enlarger bulb. If the power line voltage raises or drops, they'll automatically compensate to give you the correct output voltage. They were fairly expensive when new, but I picked up a used one on the cheap a few years ago, and I suspect there are quite a few of them gathering dust around the country. If you use one to feed your UPS, it would probably take care of the problem you described.

-- Ron Schwarz (rs@clubvb.com.delete.this), December 03, 1999.

In short its when the voltage, current, and harmonic distortion exceed the operating standards. The power isnt pure sinusoidal, nor at rated voltage and current all the time. However the fluctuations are within the limits of your operating equipment. That has changed as more ASDs are being used. A lot of equipment is more sensitive to fluctuations then in the old days. Basically 5% is a good rule. Voltages, currents, harmonic distortion should all be within 5% of nominal.

-- The Engineer (The Engineer@tech.com), December 03, 1999.

FWIW, after I saw that my Coleman generator output voltage varied from 138 volts no-load to 115 volts full-load (This is typical, I checked with them), I bought a couple of American Power's Line-R power conditioners to regulate the voltage to my computer, satellite and TV equipment. I am also using them with the normal AC feed. Here is the link if anyone is interested.


-- John (jh@NotReal.ca), December 03, 1999.

I guess I've lived with dirty power all my life, per A999's definition. Normal power everywhere I've lived (three different states) has been about 300 volts peak-to-peak.

But usually I measure it as 120 Volts RMS.


-- Mikey2k (mikey2k@he.wont.eat.it), December 03, 1999.

Could someone clarify the implications of dirty power for the homeowner. Some questions:

1. Would circuit breakers be tripped by voltage levels that were outside operating standards (whether high or low)?

2. If the answer to #1 is Yes, and they were (tripped), what is a good way to determine whether service is back to normal?

3. If current levels went outside operating standards (assuming that voltage remained normal), would the effect depend on how much current was being drawn at the time?

4. Would circuit breakers be tripped by harmonic distortion that was outside operating standards?

-- David L (bumpkin@dnet.net), December 05, 1999.

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