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Pressure washing insulators? — Parallax Forums

Pressure washing insulators?

Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
edited 2010-09-12 20:51 in General Discussion
This is a new one for me. I looked out my front window, where I can see the high-tension lines that service the town I live in, and a crew from the power company was pressure washing the insulators on one of the power poles:

attachment.php?attachmentid=72706&stc=1&d=1282671209

Now this is a bit of maintenance I've never seen before or even imagined necessary -- despite the number of seagulls that abound around here. And what a maintenance nightmare if they have to do that to every pole! Moreover, it seems as if it would be a rather hazardous undertaking for the crew. After all, the water column in the hose is grounded, and water (unless it's deionized or distilled) does conduct electircity.

'Anyone here familiar with electric utility practices who can shed some light?

Thanks,
-Phil
washing_insulators.jpg
726 x 568 - 122K

Comments

  • John R.John R. Posts: 1,376
    edited 2010-08-24 10:44
    First, I would be surprised if the lines were not powered down while they were doing that. Besides the water, just being the physically close to powered high voltage lines is generally frowned upon by the safety type folks.

    Second, I have no idea why they are doing this, other than possibly to make sure that the view you have stays pleasing, with nice white insulators.

    Third, with that view, how do you get any work done?

    John R.
  • ercoerco Posts: 20,261
    edited 2010-08-24 10:54
    That is some serious stuff. My buddy was a linesman for Conn-Ed in upstate New York. He dealt with 13 kV lines for many years, but was wise to retire after many years when several transformers exploded, killing two friends of his.

    There are some nasty and disturbing graphic images online of a poor chap who was killed trying to steal copper wire with a hacksaw. The safety rubber gloves he wore failed to protect him from the high-tension line. I won't post a link, but the curious and strong-stomached can google "thou shalt not steal copper wire".
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-08-24 11:37
    John R. wrote: »
    First, I would be surprised if the lines were not powered down while they were doing that.
    I hadn't thought about that, but I'm sure you're right. There are two redundant sets of supply lines coming into town, joining at the substation (about a block from where those guys were working). They could easily disconnect one set to work on them, while the other supplied the town. (Ever since the second set went in, our power has been a lot more reliable during winter storms.)

    -Phil
  • Tim-MTim-M Posts: 522
    edited 2010-08-24 13:29
    The film of dirt and grime that develops on the surface of an insulator string holds moisture and that starts the formation of a conductive path, especially for high voltage. If left to build up, it can lead to mold, mildew and other growth... this leads to arcing, melt down and expensive failure. Pressure washing cleans it up back to full insulating value and prevents the chain reaction toward failure. If you get a chance, listen to a clean high voltage line versus a dirty one... the dirty one sizzles much more than a clean one does.
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2010-08-24 15:16
    Erco In Torrance ther are some 96kV lines nere grevella( street ) and sam ash music .

    they arc all the time from salt on the insulators
    they are 3
  • LynnLynn Posts: 33
    edited 2010-08-24 19:11
    I work at a power plant with a very large switch yard. We have 345kv and 500kv DC systems that we pressure wash the insulators every year. I have seen both of these system flash over due to a combination of dirt and moisture. It grabs your attention real quick like and leaves a nasty trail of destruction.
  • LilDiLilDi Posts: 229
    edited 2010-08-24 20:14
    Yep!, I worked 4 years on a line crew. We couldn't de-energize the 250K lines, so we brought the insulators to the ground and removed the dust and put them back in place. The dust indeed would cause arcing. Water was not a problem since the water would bead up with lots of space between the water beads. Power washing live 250K lines would have make the area look like World War III had just started. Judging from the size of those insulator, I would say they are at least 250K volts.
  • RavenkallenRavenkallen Posts: 1,057
    edited 2010-08-24 21:37
    Whoa, Erco. I just looked up the picture. Is that even real? Can a high voltage line really deform somebody that much? That was intense...
  • BradCBradC Posts: 2,601
    edited 2010-08-25 03:48
    Phil Pilgrim (PhiPi) wrote: »
    This is a new one for me. I looked out my front window, where I can see the high-tension lines that service the town I live in, and a crew from the power company was pressure washing the insulators on one of the power poles:

    We do it from choppers over here for the more rural stuff. The lines are down while it's being done and generally they earth them at the nearest sub (HV lines can have large residual static charges. They make great capacitors.)

    I remember about 16 years ago we had a huge incident where they had not been washing the insulators regularly enough (cost cutting) and on one particularly humid day the number of flashovers and the ensuing fire risk (wooden poles 'n all that) made them literally shut down the entire grid (and I mean the whole of the south west of western australia) for the best part of a day. I was home from work with Chicken Pox. No telly, No PC, No radio.. not amused.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-08-25 10:23
    BradC wrote: »
    We do it from choppers over here for the more rural stuff.
    Wow. Based on the amount of water I saw being sprayed, the copters must have to reload quite often. Or maybe they add a surfactant to make the water more effective.

    BTW, I fear that we may soon be faced with the same sort of cost cutting you mentioned. Our local Public Utility District is taking over the power company's assets in the coming days. 'Big mistake, IMO. I don't think the people who voted for it realize what a good job the power company was doing or the immensity of the maintenance and infrastructure burden that will now be shouldered by us taxpayers.

    -Phil
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2010-08-25 10:52
    Whats HV again ?

    http://farm1.static.flickr.com/194/493256164_c7afb28a32_o.jpg

    http://farm1.static.flickr.com/207/493249008_8e047f7c03_o.jpg

    Its funny how I have to wet the GND so I don't blow holes in the concrete.
    BTW this is my hair after a long run :freaked:
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2010-09-09 04:42
    You mention seagulls?

    Rachel Carson in 'The Sea Around Us' mentions some very surprising figures about the amount of salt that drops out of the air near a sea shore. Just how far are you from the ocean?

    It seems that the primary reason for doing this is to eliminate leakage in the power line. It may be new and it may be a study. But unless the atmosphere is heavily polluted, I doubt that washing insulators in necessary when far in land.

    Of course, I could be completely wrong and some bugs could be nesting in and around the insulators and causing mayhem.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-09-09 09:20
    The insulators in question are about two city blocks from the bay (salt water).

    -Phil
  • Dave HeinDave Hein Posts: 6,347
    edited 2010-09-09 09:40
    The power transformers on South Padre Island always have an "aura" around the high voltage connectors. It's very entertaining to watch at night. It's hard to believe they can maintain electrical power on the island.
  • davejamesdavejames Posts: 4,047
    edited 2010-09-09 11:44
    I'm gonna guess that those lines are not "high tension" as in the multi-kV that run cross-country, but the lower 240/480/600+ lines that run through suburban areas. Not as much arcing potential with those voltages.

    I would also guess that the water source is from a tank and not city water; that would at least keep one end of the circuit floating.

    In the end - definitely NOT a job I'd want!


    DJ

    P.S. I've vacationed in around Gig Harbor just a bit south of you - gorgeous country!!!
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-09-09 11:50
    No, they really are multi-kV lines that feed a large substation next to where the guys were working. The substation distributes power to the entire city. A sub-kV line would not need such big insulators.

    -Phil
  • davejamesdavejames Posts: 4,047
    edited 2010-09-09 11:55
    ...well, I sit corrected then (can't see the insulator under all the water).

    Still gorgeous country!

    DJ
  • logan996logan996 Posts: 281
    edited 2010-09-09 14:56
    *shiver* looked up the pictures *shiver* freaked the heck out of me, i swear if i have nightmares tonight im blaming it on you erco! :D (i am never stealing copper wire!)
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2010-09-10 00:40
    Salt fallout near the ocean is dependent on stormy weather, but can go into kilos/acre. If you car tends to prematurely rust and so does your lawn furniture, it is salt fallout. I lived a block from the ocean in Newport, Oregon and outside electric meter boxes would often start a house on fire due to corrosion.
  • JavalinJavalin Posts: 892
    edited 2010-09-10 01:43
    >Third, with that view, how do you get any work done?
    +1

    There was a thing on TV here in the UK, a while ago on "most dangerous jobs" or similar. That had guys with helicopters servicing live power lines. There was a few sparks and the guy transfered himself to the wire from the chopper. He had a basket thingy to sit in.

    Not for me!

    J
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-09-10 07:38
    I've often wondered about birds perched on the lines on a humid day and whether they can feel any corona discharge. Even the 2.2kV neighborhood feeders will "sing" a little when the humidity is high.

    -Phil
  • User NameUser Name Posts: 1,451
    edited 2010-09-10 10:52
    John R. wrote: »
    Third, with that view, how do you get any work done?

    When all you do is whatever you feel like, it really doesn't matter.
  • ElectricAyeElectricAye Posts: 4,561
    edited 2010-09-12 20:51
    Phil Pilgrim (PhiPi) wrote: »
    ...Anyone here familiar with electric utility practices who can shed some light?

    ....

    Maybe it wasn't the power company.

    Maybe a cat had climbed up there and they called in the fire department to help it down???
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