High Voltage Cable Inspection, video.
"There are only three things I'm afraid of, electricity, heights, and women."
I guess this guy likes to face his fears.
I wonder what you actually do to maintain a cable? Is there really warning before one snaps?
As expected, Bert chimes in (is there any tech you don't know about, dude?):
Manufactured and installed to Western world standards, cables last a very long time and never snap on their own. Any significant damage to a cable (I think the most common cause is vandalism by hunters) will cause a localized temperature rise, which will be detected by thermal vision inspection equipment even before the linemen go take a stroll up there.
Close visual inspections are done mainly to detect (and repair) damages to cable spacers, and to assess the state of the insulator chains. Both dirt buildup and cracked insulators can lead to arcing between the line and the tower, which is something to avoid (the line will fail and require important and lengthy repairs).
I wonder: even though the workers apparently don't get any serious shocks, surely there must be some kind of long term effect from working inside a super-electrified suit for hours every day? The body has a significant electrical field, both inside and outside, that must be affected.
I wonder what you actually do to maintain a cable? Is there really warning before one snaps?
ReplyDeleteManufactured and installed to Western world standards, cables last a very long time and never snap on their own. Any significant damage to a cable (I think the most common cause is vandalism by hunters) will cause a localized temperature rise, which will be detected by thermal vision inspection equipment even before the linemen go take a stroll up there.
Close visual inspections are done mainly to detect (and repair) damages to cable spacers, and to assess the state of the insulator chains. Both dirt buildup and cracked insulators can lead to arcing between the line and the tower, which is something to avoid (the line will fail and require important and lengthy repairs).
Thank you very much.
ReplyDeleteDon't the cables have a cover, to protect against the elements/erosion? (And against arches etc.)
Don't the cables have a cover, to protect against the elements/erosion? (And against arches etc.)
ReplyDeleteNope, high voltage aerial wires are bare. The thin oxide coat that forms on the outside surface is an excellent protection against corrosion, and there's no point in providing added electrical insulation (it would be difficult and costly to devise an insulator capable of withstanding the high winds and resulting mechanical stresses anyway).
I wonder: even though the workers apparently don't get any serious shocks, surely there must be some kind of long term effect from working inside a super-electrified suit for hours every day? The body has a significant electrical field, both inside and outside, that must be affected.
Nope. The conductive suit that the lineman wears ensures that his entire body is at one uniform potential (voltage).
As for the voltage reading itself, it's meaningless. Granted, a 500kV line has an average electrical potential of 500,000 Volts apart from ground, but that's like saying that Katmandu is built 1.3km above sea level. Yes, a 1.3km free fall is lethal but, oddly, it's the least of the concerns of the population of Katmandu... ;-) Same thing with power lines: just don't serve as a conductor to ground!
I just realized I said something stupid in my previous comment: a 500kV line has 290kV phase-neutral potential, not 500kV (that's phase-phase potential). In other words, read the sentences as "Granted, a 500kV line has an average electrical potential of 290,000 Volts apart from ground, [...]".
ReplyDeleteI'm surprised nobody corrected me... ;-)
I saw it instantly, but I didn't want to embarrass you.
ReplyDelete