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australiantroubleman
12-03-2008, 12:03 PM
Had a bad experience with a 11kv vacuum circuit breaker last week , I denergised a 33kv/11kv transformer and noticed some strange voltages existing with both 33kv and 11kv breakers open on the trf voltage transformer . I walked outside and the transformer was humming loudly and erractically in a pulsating sort of way .

I assumed a faulty circuit breaker and was correct it was the 11kv breaker one phase had lost its vacuum and current was flowing though the faulty pole ,back energising the transformer on one phase through the wye connection to ground. The current was jumping a 12 mm gap internally .

The breaker checked ok with a 2.5 kv meggar but broke down when tested with a 5kv meggar.

Dont believe what the manufacturers say about the seals used on vacuum interrupters be wary and dont trust them.

Special ED
12-03-2008, 05:33 PM
Isolate, Open, Test, and Ground is best policy. I don't trust any breakers.

Pootnaigle
12-03-2008, 05:45 PM
Ummmm its best if ya never ever trust an opening that you cannot see. i always made a phyisical opening ( opened both sides of the breaker) or if that was not possible I checked it every way from Sunday n then grounded it. Never ever trust a breaker indicator. If theres no possible way for voltage to get in or out its safe to work on , otherwise lottsa testin needs to be done before gettin onnit.

Special ED
12-03-2008, 05:48 PM
Exactly.. Hell on the Dominion system last time I was up there an open cut out didn't even qualify as a visible opening. But that was due to the large amounts of cut out failures that would track over when open.

Chris
12-16-2008, 05:08 PM
Exactly.. Hell on the Dominion system last time I was up there an open cut out didn't even qualify as a visible opening. But that was due to the large amounts of cut out failures that would track over when open.

Indeed. We often will pull the jumper after opening the cutout switch.

australiantroubleman
07-06-2010, 08:06 AM
We dont generally trust non visual breaks or use breakers as a isolation point, but we leave spare zone substation transformers open on high voltage and low voltage c/bs with automatic standby switching availible.

It was this situation where the breakers are left open and one pole was faulty that caused the problem.

The manufacturers told our company managers that this was the only failure ever recorded, i dont believe that for one minute.

And on the topic of non visual breaks ....

In our and other companies here there is a large scale rollout of SF6 pole mounted switches replacing Air break switches. Us older troublemen do not trust them but company management say its the future and we must accept non visual break equipment that depends on SF6 gas pressure.

Many years of experience makes us skeptical of any mechanical device to be 100% reliable and I will reserve my judgement on how reliable the gas pressure seals will be and how many suffer internal failures after lightning strikes and switching surges once the SF6 gas leaks out.

west coast hand
07-06-2010, 12:02 PM
Indeed. We often will pull the jumper after opening the cutout switch.

I always lift the high side of a cutout if I open it for a visual open and I never trust a breaker always test

thrasher
07-06-2010, 03:44 PM
Basically if you can't see an open it doesn't exist. Also don't forget to test before opening a lead to give you a visual opening. As I related once before we opened a oil switch to a cap bank then pulled open a series non-loadbreak cutout to give us a visual. However back then (1987) we didn't require a test first. The oil switch had welded closed contacts and while the handle dropped it was not open. The resultant load arc went into the steel and knocked out the substation.

slimdalineman
07-08-2010, 12:12 AM
I always lift the high side of a cutout if I open it for a visual open and I never trust a breaker always test

Why? do you feel the cutout is failing and voltage is leaking? Do you then test before lifting the high side in case the cutout is leaking? I have always been taught to work it hot unless it is grounded. Just curious for the reasoning of lifting the high side.

Special ED
07-08-2010, 04:55 AM
Why? do you feel the cutout is failing and voltage is leaking? Do you then test before lifting the high side in case the cutout is leaking? I have always been taught to work it hot unless it is grounded. Just curious for the reasoning of lifting the high side.

Everywhere you go its pretty much the same procedure. Open, test, ground, flag, and tag. The open must be visible meaning leads going to a kyle, recloser, ect must be disconnected since your trusting a piece of equipment that you cant visually see inside of to see if its open or not.

The cutouts high side being removed isn't really a new thing. But more and more places are requiring it to be done when grounding and working a line dead. Yes the cutout is open and you obviously can see that it is but with manufacturing being shipped out of the USA quality control has dropped and alot of cutouts though open still bleed over. Therefore to establish your visible opening prior to grounding at a cutout you must remove the highside jumper to eliminate any possibilities..

It only takes ya couple seconds more to take it off so why not?



Anything built by man has the posibility of failure so why not put it in gods hands?

slimdalineman
07-08-2010, 11:51 PM
Everywhere you go its pretty much the same procedure. Open, test, ground, flag, and tag. The open must be visible meaning leads going to a kyle, recloser, ect must be disconnected since your trusting a piece of equipment that you cant visually see inside of to see if its open or not.

The cutouts high side being removed isn't really a new thing. But more and more places are requiring it to be done when grounding and working a line dead. Yes the cutout is open and you obviously can see that it is but with manufacturing being shipped out of the USA quality control has dropped and alot of cutouts though open still bleed over. Therefore to establish your visible opening prior to grounding at a cutout you must remove the highside jumper to eliminate any possibilities..

It only takes ya couple seconds more to take it off so why not?



Anything built by man has the posibility of failure so why not put it in gods hands?

removing the high side of the cutout is not something done around here. do i feel it is a big deal, no. but if i am grounding, and i test the line dead, then i do not see the reason why removing the high side makes any sense. why not remove it...redundancy. we have enough of that through safety rules above and beyond what is necessary (i.e. bucksqueeze, etc). I am not trying to be a smartass but do you test the line before removing the high side? just curious. p.s. i do not begrudge a man for working safe, nor for making the top of the pole orange...whatever the man in the air chooses as his comfort level and i don't see him endangering himself or others do as you please. i was just wondering why.

Special ED
07-09-2010, 03:22 AM
I am not trying to be a smartass but do you test the line before removing the high side? just curious. p.s. i do not begrudge a man for working safe, nor for making the top of the pole orange...whatever the man in the air chooses as his comfort level and i don't see him endangering himself or others do as you please. i was just wondering why.

Actually I test before and after. Before to insure the cutout is not bleeding over. And after prior to installing my grounds. I've personally seen many cutouts bleedin over some up to full system voltage and you'd never know. (no smoke, burns, or anything)

Its just eliminating the possibility cause the chance cutouts that are part of the bad batch are unrecognizable from any other chance cutouts. One hair line crack in a cutout may not do a thing till your up there workin then you bump the wire the wrong way and "KAPOW" there ya go phase to ground all up in your face.. To each their own.. I dont feel the need to better my tan since I got a nice one already without being subject to arc blasts..

australiantroubleman
07-13-2010, 09:42 AM
There is no way our company would allow you to break connections in series with a visual break type isolation point .

There arguement would be you wasting time and being ineffient when a device purchased as suitable to use as a isolation point is availible.

The testing of the isolated mains and equipment with a approved tester is considered enough to detect leakages across faulty isolation devices and effective grounding procedures are considered adequent if a isolation device fails.

I like the extra procedures some of you people follow but it would never be excepted by management in my company on efficency grounds .

Special ED
07-13-2010, 04:40 PM
[QUOTE=australiantroubleman;83837]

The testing of the isolated mains and equipment with a approved tester is considered enough to detect leakages across faulty isolation devices and effective grounding procedures are considered adequent if a isolation device fails.

QUOTE]

You ever see a lightning arrestor blow while workin out a hot pole just cause you accidently bumped it or the pole a little causing the hairline cracks with water in them to grow just the slightest? Same concept. Porceline is a good insulator but fragile. It can be cracked and not leaking over and you would never know that it was till you bumped it the wrong way or just shook the pole then "Ka POW" phase to ground as glass flies everywhere and your sitting there goin "What just happend?".

Same thing. Its been known and well documented about the faulty cutouts from Mexico so we just eliminate the risks. As for the kyles and OCRs? Do ya really trust something you cant visually see? In reality your trusting your life to a little spring inside the damn reclosures. Mechanical devices can and will fail eventually. And even if you have the line grounded thats a false sense of hope and a whole nother thread cause they wont protect you. You will still be subjected to a dangerous volatge with more than enough power to kill unless you use equipotental grounding methods that lots of places aint even heard of let alone practice.

glover
10-25-2010, 02:44 PM
that equipotential ground method will save you butt everytime. but ya gotta use it. its a pain to install and climb around but if you want that little bit of extra protection USE IT.

Trbl639
10-25-2010, 09:30 PM
Open, Test, Ground, Flag, and Tag !! If you can't see that there is a physical open/Air Gap...I don't trust it any farther than I can see it with my eyes closed!!

Had situations with the Cooper VXE single phase vaccum kyles before......indicator showed open...still had lights burning downstream of the kyle........for umpteen years, on 1 phase we hung the kyle with jumpers and a bypass fuse........now standard installation is solid barrels (line and load side) and a fused bypass,,makes for a nicer installation and eliminates the need to lift the high side jumpers.......unless you are concerned with the cut-out bleeding..........

Can't tell you how many times I've worked behind and open line fuse without lifting the clamp...no reg says it was necessary, again unless you were leary of the cutout bleeding, and after all of the chance cut-out failures......I damn sure took the time to lift that clamp....regardless of whether we/i was working it dead and grounded..or 'As Hot', meaning working it with rubbers etc..........of course, when I retired, anything working 'As Hot' was outlawed, it was either Hot or Dead and Grounded....

As a word of caution......to anybody out there, who has never seen the inside of a kyle/OCR/electronic or vaccum breaker......find one in the shop to look at..it will scare ya when you see how close the contacts are to each other when open...........downright spooky..........

Seen too many guys rely on them being open, in my younger days, been known to myself...but age/experience teach ya things!!

Like special Ed said about LA's.....can't tell you how many I/we have heated up by hand, just turning the old noggin away and slappin it on the phase............see one go south and that old habit will disappear real quick!! Most outfits, now days, it's done with a suck-em-up!! Damn near got my ass kicked by a young Tman, one night when he went to slap one on with just gloves..long story, he thought he was God's gift, needless to say, he didn't whoop my ass, but he didn't put anymore LA's on by hand, when I worked with him after that night!!:D At least when I was around.........

climbsomemore
10-28-2010, 02:13 PM
The old adage I grew up with is... if you cannot see into it (regarding any switch, recloser, breaker, etc) you can't take clearance from that device.

The older oil- filled reclosers have been know to "make noise" and stay hot as the linkage broke and the contacts stayed closed.

Any good company standard will have some sort of seperable device or scheme that positivly insures a "visual open"....if they intend for folks to clear line sections from that point on.

Phoenix-7
11-02-2010, 09:42 PM
Yes, you cannot trust them, one blew up on me last year!!