Insulated HID Lamps?

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Eddy Current

Senior Member
I was working on a pole light today and opened up the cover to change the lamp and got shocked with 480V! After I turned the power off I inspected the light and found no visible places in the wire insulation and nothing was loose. The only thing I found was that the bolt that bonded the ground was rusted and had come loose. So how did I get shocked through the lamp? Is there some kind of insulation inside the lamp that could have been defective?
 

GoldDigger

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Location
Placerville, CA, USA
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Retired PV System Designer
It would be interesting to see how much current flowed in the ground/bond or EGC connection when you reattached it.
There could be a significant voltage on the pole simply from capacitive coupling from the 480V wires, and it might cause a shock. But it would not support much current.
A more significant current would be a sign of an undetected insulation failure somewhere in the system.
And that could continue to be a hazard even with the EGC connection restored.
 

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
Sounds like something that happened to me once. Had one hand holding the lens cover of a street light (was a little windy that day) and proceeded to remove HPS lamp and whamo I felt like I was welded to the lamp, luckily it caused back muscles to contract and made my arms pull apart.
I had accidentally touched the shell of the bulb which is directly connected to one leg of 480 system (277 volts)
​Always wear your gloves.
 

Eddy Current

Senior Member
This was a pole light that is accessible from the top. It's possible that I could have touched the socket, but the main arm that got shocked was the one unscrewing the bulb. Is it ok to change HID lamps, live? I've alway thought that it's not good on the lamp.
 

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
Possibly your arm was touching the grounded metal of fixture top or parts while unscrewing bulb and your hand touched shell of bulb. Even though the ground wire may or may not have been attached the pole could very well be still in contact with earth which still could have provided some return path.
Which actually was the case with me as the pole lights I were relamping also only had the 2 conductors feeding and no equipment ground ran to them.
 

kwired

Electron manager
Location
NE Nebraska
How clean was the glass envelope of the lamp? Any mildly conductive material on that lamp may be enough to get you if it is energized by the shell of the lampholder. This sits there essentially in free air when installed - but heat from the lamp will burn off a lot of materials that may accumulate there as well.
 

Eddy Current

Senior Member
How clean was the glass envelope of the lamp? Any mildly conductive material on that lamp may be enough to get you if it is energized by the shell of the lampholder. This sits there essentially in free air when installed - but heat from the lamp will burn off a lot of materials that may accumulate there as well.

I don't think it was too dirty.
 

kwired

Electron manager
Location
NE Nebraska
Also keep in mind pulse start type lamp systems use a fairly high voltage for starting, not sure exactly what that voltage is, but if you were working it hot and the lamp is not lit, then it should be trying to start.
 
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