Why do street lights flicker in snowy weather?

wrote:


Oh sure, carbon arc street lights... with gilded hand-carved capitals, chromium plated motors and a Rolls-Royce gearbox.
http://upload.wikimedia.org/wikipedia/commons/6/6c/Staite-Petrie_Lamp_1847.png
http://en.wikipedia.org/wiki/File:Arc_lamp-ignition_%CE%940035.JPG
We use 'em in our refrigerators too, striking an arc when the door opens; it saves having a little man inside to operate a switch.
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Androcles wrote:

The first electricity in Middletown, Ohio was generated for one large Carbon Arc light mounted on a tower. According to the town's history, people cold read a newspaper over a mile from the tower. From there, electricity was provided to the downtown area, then the suburbs. Later, the system was sold to CG&E.
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Street lamps are usually sodium vapor some old installations may be mercury vapor. It's simple economics.

Absolutely. Tadchem wins the poster who actually has a brain prize! When cold high pressure sodium or mercury vapor lamps will flicker or repeatedly restart if they have lots of hours on them. As someone noted they are usually just replaced en mass at a certain age so by that time it's common for many to be at the flicker to not work at all stage.

Possible, but not very likely. More likely is that because of snow being white and reflective (as opposed to black pavement) people just tend to NOTICE the flickering more which was really there all the time.

What is this verbal diarrhea? You are just babbling on about nothing at all. NONE of it is from a "practical standpoint". Moron.

Great bunch of information all leading to the totally WRONG conclusion. Never met a mercury vapor or sodium vapor lamp in person did you? Hey, I've got one that lights my parking lot. And when it gets cold and when it has lots of hours on it, the damn thing flickers, Buster! I take it you came here to pontificate and show everyone how much you know and all you did was show the world how little practical knowledge you actually have.
It's simple. Streetlights these days are sodium vapor for economic reasons. The one I've got produces an AMAZING amount of light for consuming 35 watts. Street lights are somewhat though not extremely larger. As they age the arc gets harder and harder to strike. Also as it heats up the arc may not sustain leading to restarting. In this mix there is also flickering as the gas pressure begins to creep out of the stable arc range as the bulb ages. These conditions are much exacerbated by low temperatures. Hence a lamp that was working fine in warmer weather will suddenly turn cantankerous if the temperature suddenly drops. And finally snow reflects the light making the flickering much more obvious. And THAT kiddies is the real story about flickering street lights. (Even if Terry has never seen it. Judging from his bluster I take it he probably works for the government designing street lights that flicker)
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TKM comes from sci.engr.lighting. He worked in the lighting industry. His answer is typical of the long, technical answers from the very sharp people on sci.engr.lighting. His "babbling" is all from a "practical standpoint".
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On Mon, 21 Dec 2009 17:58:39 -0800 (PST), tadchem

[snip]
As Terry said, cold ambient temperatures effect only fluorescent lamps.
Fluorescent lamps operate at wall temperatures of 40C or about 313K in a 25C ambient; and the mercury pressure is a strong function of wall temperature. (The mercury pressure, in turn, has a strong impact on the lamp's electrical characteristics.)
Metal halide lamps operate at wall temperatures of about 1000C or about 1275K in a 25C ambient, while HPS lamps operate at wall temperatures of about 1225C or 1500K. A reduction of 40C in ambient temperature has a much greater relative effect on the relatively low wall temperature of fluorescent lamps than on the much higher wall temperature of metal halide lamps or HPS lamps.
In metal halide lamps the mercury dose is fully vaporized when the lamps are at operating temperature. Therefore, even a moderate decrease in wall temperature can change the lamp color, by reducing the metal halide pressure, but will not significantly reduce the mercury pressure, so the electrical characteristics will remain substantially unchanged.
In HPS lamps the mercury and sodium are typically not fully vaporized. A lower than normal wall temperature will reduce the mercury and sodium pressures, and can impact the electrical characteristics. However, the very high temperature of arc tube makes even HPS lamps relatively immune to changes in ambient temperature.
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wrote:

I presume "wall temperature" is the temperature at the inside of the glass tube right next to the glass.

I'd no idea that these lights operated at such high temperatures - even hotter that an indcandescent light. I tend to think of discharge bulbs as being "cold" compared with incandescent, but evidently this is not always the case!
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Incandescent lamp filament is about 2700K, which is quite a bit hotter than these arc tubes.
When you switch off a HID lamp (mercury, sodium, ...) the electrodes and arc tube are glowing bright red hot until they cool down.
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writes:

Yes but the wall temperature (well, the outside wall, anyway!) isn't that hot.

Are they? Didn't know that. How hot are the electrode tips for an arc light?
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On Wed, 23 Dec 2009 20:01:42 +0000 (UTC), snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:

The color temperature of the light emitted, and the operating temperature of the bulb are two entirely different and unrelated things. Light bulb nomenclature, when referring to a temperature measured in Kelvins, is referring to the light color temp, not the operating temp of the bulb or filament.
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With tungsten incandescent lamps, the filament temperature and the color temperature of the emitted light are about the same. Color temperature refers to the temperature of an ideal incandescent radiator (namely, a "blackbody") producing light of the color temperature in question. The color of light from incandescent tungsten is not much different from the color of light from a blackbody at the same temperature.
- Don Klipstein ( snipped-for-privacy@misty.com)
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On Thu, 24 Dec 2009 01:53:43 +0000 (UTC), snipped-for-privacy@manx.misty.com (Don Klipstein) wrote:

I used to make a black body source that used a foot long calibrated filament.
I used to make another that used coils of 'coiled' heater wire wrapped around the ceramic 'wool' wrap and silica 'plaster of paris', then we wrapped around the outside of that. The base form inside all of it was a basketball. After the form set, we bake it in a kiln and after that, with the actual excitation coils. Put a foot long ceramic feeder tube onto that, and one "looks" into a perfect black body cavity.
Those were fun to slather together, and quite profitable too.
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On Wed, 23 Dec 2009 18:19:39 -0000, "Martin"

The temperatures quoted are for the wall temperature of the arc tube. The arc tube is contained in an outer bulb that operates at much lower temperature.
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