Lighting-Gallery.net
Lamps => Vintage & Antique => Topic started by: merc on August 28, 2015, 03:10:38 PM
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Does anybody know what kind of light bulbs was used in streetlights until they were replaced by MV or fluorescent lamps, or in areas where discharge lamps were unsuitable or too expensive?
Since regular incandescent lamp lifetime is 1,000 hrs. it'd mean relamping every 83 days with avg. 12 hrs./daily use. :inc:
In case of rough service 5,000 hrs. lamps, it's about 13 months.
But it's still much less than 4- or 6-year HID lamps typically used these days.
Did they use some special lamps, transformers producing a bit lower voltage for streetlight power supply or did they just relamp as madmen?
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Real incandescent streetlighting used rough service long life lamps. Lantern / lamp and its lifetime :
http://streetlightonline.co.uk/eslabulbgone.htm
Incandescent conversions of Mercury lanterns - esp. the 80W and 125W sizes (E27 base, widely available lamps...) were pretty common in private property here (Israel) in the past
Actually that aren't really conversions. The common 60s/70s Mercury lanterns are remote gear design. The user would get the lantern alone without the gear box (sold separately), and install it as incandescent
I reckon seeing numerous of those (years ago) in the motel village Ramot Shapira in Beit Meir. See at the far corner of the roof here :
https://upload.wikimedia.org/wikipedia/commons/2/26/Ramot_shapira.jpg
The incandescent on Mercury chokes used to happen in East Germany....
http://www.lighting-gallery.net/gallery/displayimage.php?album=2222&pos=0&pid=60476
http://www.lighting-gallery.net/gallery/displayimage.php?album=772&pos=0&pid=81392
The ballast output voltage is dependent on the current drawn through it. At low loads (low power incandescent) the voltage would be near the ballast OCV, the higher load, the lower voltage
On 230V (Europe) :
Ballast OCV is 230V, the incndescents are for 230V
If the incandescent lamp is low power (40W..60W), it won't be very different from using it normally. The higher the lamp power, the less voltage it will get, so the more it will be dimmed by the ballast. At some point, you just can't get any more light as if you use higher power lamp it will just be dimmer
You won't be able to get anywhere near the correct light output, no matter what incandescet you use
Lamp life will be longer, esp for the high wattage lamps (as they are underpowered the most)
On autotransformer ballasts (USA) :
Ballast OCV assume on the order of ~300V, assume incandescents rated for 120V
Low power incandescents will get high voltage, so i guess white light for a time between few seconds and few hours. At some point there may be a lamp that loads the ballast just sufficiently to get its output down to 120V, then itll work as any lamp on 120V. Beyond that point it'll be same as in Europe
When the lamp burns out an arc starts in the bulb. Here it is ballasted by a choke, and won't reach the current it takes to blow the stem fuses
On SON / MH gear it will end up in something melting or exploding and a vacuum loss. On Mercury i am not sure - It is possible the same will happen (if the arc stays), and it is possible that the current will be too low to maintain the arc, then it will extinguish on its own (as there is no ignitor to force it to keep arcing)
At very high wattages you might risk drawing too high current through the Mercury ballast and overheting it
It will happen at lamp wattage that is somewhat higher than the ballast current rating. The underpowered lamp takes less current than at full power, but not proportionally to the voltage since the filament resistance is lower when it is underpowered
Assume 80W Mercury lamp at ~0.8A current. 200W 230V incandescent takes ~0.87A. On the ballast that would be down to maybe 0.6 (guessing), so its fine. 300W lamp takes ~1.3A, now that could end up drawing more than 0.8 through the ballast
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I've seen HPS fixtures relamped with incandescents before, with ballast still connected (USA, 120v 60Hz). Sometimes they're really dim, but I wonder if the ignitor will indeed cause an arc when the bulb does finally burn out?
I've also seen CFLs in there, in one fixture in particular, and it seemed to work perfectly fine for many years, then got a high wattage incandescent, which is much dimmer than it should be!
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On a 100w ballast, the filament breakage has to be small and a gap of a few mm's to src, and the arcs aren't strong. If you put a incandescent into a mh of respective wattage, the higher voltage from the ballast will overdrive and shorten lamp life, and maybe a bigger and stronger arc.
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To the original question:
The bulb replacements of each few months was just common, just nobody thought about it as too short, in the contrary, 100 years ago it was assumed as rather luxuriously long time...
Don't forget the arc lamp rods had the life of just one or two days, Yablochkoff's candles only one night, the gas lanterns had required the lamp man to light each of them (the pressure wave ignition systems came later), so an incandescent bulb with life of three months was already a tremendous improvement.
And don't forget the early discharges didn't had the rated life much longer, 1500 hour was rather common for fluorescents, the medium pressure MV's had rated life of about 3000hours, so the same as the long life incandescents already available at the time.
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@Medved: Yeah, I didn't realise there really wasn't an alternative with better lifespan at that time. Also manpower used to be cheaper than today so no problem with employing more electricians-relampers.
I can imagine times (and it might not be so distant future) when streetlights will be relamped (or rather replaced in a plug-in style) by drones. :)
@Ash: Thanks for interesting information and links.
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I can imagine times (and it might not be so distant future) when streetlights will be relamped (or rather replaced in a plug-in style) by drones. :)
Not that much the drones, but just treated as e.g. the guard rails: Sometimes someone smashes them, so they need repair, sometimes some fault would require a repair, if inferior quality materials would be used, it deteriorate and need replacement in a short time and so on.
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That allready is how you maintain proper HID lighting....
Good HPS lamps (ie. before Philips and Osram started selling Yaming lamps) can go unmaintained for ~10 years before they start failing in mass, and being HPS, they maintain well the light output levels. When the 10 years are up you have to do maintenance anyway eg. cleaning, repainting (the column) - sometimes..... Could as well do that along with repairing/replacing other outdoor stuff like guard rails, trash cans etc
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Here in the UK I'm sure I heard that they simply used 260 volt bulbs in streetlights so on a nominal 240 volt supply they lasted nicely. On other mains voltages say 210 volt they used 220 volt lamps you get the idea
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According to the McGraw- Hill book," Street Lighting Practice" (1930),the life of standard "multiple" incandescent street light lamps(120volt) was 1000 hours. The life of "series" incandescent street light lamps was 1350 hours. They have a sample street light maintenance contract that would be negotiated between a town and utility to provide and maintain series street lighting fixtures. Under a 4000 hour lighting schedule( from 15 minutes after sunset to 30 minutes before sunrise)it would be required that every bulb be replaced"within 10 days of April first,September first and December twentieth". It was far more economical to "group relamp" than to have trucks going out every night to "spot relamp" burned out bulbs.
By the 1950's,all the large lamp makers listed series bulbs of 2000 and 3000 hours,and 120 volt multiple lamps of 1500 and 3000 hours. This allowed group relamping intervals of three or two times per year. By the 1960's 6000 hour lamps were listed that allowed a once per year relamp.
But these longer relamping intervals came at a price. For example, if you were using a 10,000 lumen lamp on your major avenue,you could install a 575 watt bulb that you replaced three times a year,or a 620 watt bulb that you replaced twice a year,or a 690 watt lamp that you replaced annually. You had to balance the cost of the higher electricity against the labor of lamp replacement.
In the late 1950's,New York City had about 200,000 incandescent street lamps and were group relamping twice a year. That meant electricians were going up and down ladders 400,000 times a year! ( yes ladders,no bucket trucks 'till 1962!) And that does not count the trips for early burnouts or fixture cleaning!
When the conversion to mercury vapor began in earnest in NYC in 1961, the group relamping period went to once every three years,a tremendous savings in labor.
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Forgot to mention that in the mid 1970's,most of the lamp makers were offering krypton filled incandescent multiple lamps in the 1000 lumen(105watt) and 2500 lumen (205watt) with a 12,000 hour rated life. This gave a little better than a two year relamp interval. Worth it if the fixtures were in the boondocks and hard to get to.
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With group relamping schedule I doubt there were special trips fro lantern cleaning, I would rather guess all the cleaning, inspection and eventually some fixes were done at once with the relamping...
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Incandescent lamps were also made for street series operation. They made special lamps for 5.5A, 6.6A, 7.5A, 15A, and 20A circuits, 6.6A being the most common. They actually have low voltage filaments, like for example a 2500 lumen street series lamp was 24V and 6.6A. Such circuits were regulated by constant current series regulators which adjusted the voltage to properly operate the number of working lamps on the loop.
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What happened when one lamp on a series loop burnt out ? Did they have a mechanism similar to Christmas lights to shunt out the bad lamp ?
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Yep. If i understand correctly it was a thin ceramic(?) part holding springy contacts apart. At open circuit voltage it would break down, shatter and let the contacts close
Wonder how reliable it is if some sort of vibration or earthquake makes filaments in few lamps break at the same time during the day, and then the voltage is applied to the circuit with few of the isolators in series. Will the leakages to Earth present along the circuit make for sufficiently inequal voltage drop so that there is a 1st one to go, or they will stay like that without lighting ?
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Even the earthquake is spreading in waves, so the peak acceleration hits the lights sequentially, one after one. So even with that the lamps never break many at once, the time differences could be in 10's of ms for the shunts to activate.
What I've seen on a few pictures, the cutouts were made of some kind of hardened paper, so very brief overvoltage is sufficient to ignite the arc through the paper and carbonize that area within few ms. And when carbonized, it becomes at least somehow conductive, so it allows breakdown of the discs as well. Then the resistive nature of the carbonized paper makes it heat so it burns out, so allows the contacts completely to short circuit, but that does not need the elevated voltage anymore.
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That is, why i noted them breaking in day time when there is no power. Then when the night comes the power is applied at once
Since there are leakage resistance to Earth from each of the "floating" sections of the circuit, i would expect near full OCV to appeaer across the isolator at the high end, so there is one from which the reaction starts. But, would such discharge (into leakage, so very small current) even be sufficient to destroy the isolator ?
In case with the paper, some initial carbonization will make it drop in resistance from "infinity" to some high value. As it is getting to the same order of magnitude as the leakage to Earth, the voltage across it goes down, and across the next one goes up, so same process repeat with the next one while it slows down with the 1st. I wonder if it may happen that they all go into some high resistance value that is about balanced, and get "stuck" in this condition for some time (minutes, hours) before carbonization advances sufficiently to make for a final breakdown in one, after which the rest will follow
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I assume there is also a fuse that will blow if too many burnt out lamps are left installed and with shunts activated. I don't imagine the shunts to offer the same resistance as the lamps so the current in the other still working lamps would be higher and higher as more lamps burn out and the shunts activate. When too many shunts have activated, the current goes over the fuse limit and it blows.
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When too many shunts have activated, the current goes over the fuse limit and it blows.
These use to be fed from a constant current transformer (http://www.tpub.com/celec/5.htm), which deliver the same current from zero volts till the full voltage of all lamps. So all what happens while more bulbs get broken is, the secondary winding in the transformer is moving further away from the primary...
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I think there would be very little leakage to earth after all any leakage like that presents a shock hazard and the power company's don't want that on there minds. I think the paper shunts are treated chemically so that when a voltage is applied when the filament fails it quickly burns up then 2 wire touch and complete an almost zero ohms link to keep things running
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The leakage does not pose any hazard to who is standing on the Earth
Leakages are a fact in any electrical grid. They are not a fault, it is simply not possible to build a grid without leakage. At voltages in the 100s-V or few-kV range i'd expect the leakage current will be sufficient to destroy breaking-down isolation in series with it
Paper ot its own is fair enough for this task. It burns through and the metal contacts touch directly....Though i would expect there something like a tab made of clay or such, that would shatter from the heat of the arc when it breaks down
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If I understand correctly, the transformer adjusts itself to deliver the correct current to all lamps by lowering the voltage of the entire loop. This means all lamps see the voltage and current they were designed for regardless of the number of EOL lamps. There is no need for a fuse that has the same purpose as the one in Christmas lights, and other lamps can still remain in the circuit when a number of them have blown. It even compensates enough to light a single lamp if all others are bad.
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In large yep thats how it is
I think there may be some minimum load requirement though (ie. minimum voltage that must drop on the loop). To get working current regulation, the secondary armature must be floating above the primary, so f = mg. The higher load, higher magnetic field produced, so the point where f = mg is further up away from the primary (where mg is independent of the load). But with too low load, f may be too low to lift the armature up even when it is in the bottom position....
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There is indeed maximum voltage limit, where exceeding that means the current would drop.
But with near short circuit there is always the same current, so the same force lifting the winding (or it's counterweight - depend in which position it is supposed to operate).
The transformer regulates the current in fact by varying the leakage inductance between primary and secondary. So higher the voltage difference between the OCV and load voltage, less movement is necessary when the load voltage changes, when the load is the range of 25% or lower, the winding won't move at all and yet the current stays within 5% even till a short circuit...
Of course, a difference is, when the secondary power (so voltage) is boosted by an extra fixed transformer (extra voltage in series with the secondary), this extra voltage might be, what pushes the moving coil till the end of it's regulation range at short circuit, then the current may become higher than rated.