3 phase 14.4 tub toubles

[otis-mn]

Anybody ever had any trouble heating up a 3 phase trans.??
We just switched to 14.4 prim. on one of sub stations. We where pulling some dumbie caps off to plug on the 3 elbows to heat up the tub. when we pulled the last cap we had a small blow up. (sparking and arcing) Got that cleaned up and went to plug on the elbows when we got to the last one we had some arcing on the elbow . I 'll admit this 14.4 is new to us, but what did we do wrong??? thanks

[lewy]

Is this phase to ground or phase to phase?
What was the temp?
What kind of load if any were you picking up?

[Boomer gone soft]

ferroresonance.

Check out the posts on that topic.

[Fiberglass Cowboy]

If it had no load on it; it does sound like ferroresonance. Chances are higher in 3 phase padmount transformers fed from urd cable, with no load on them and higher distribution voltages like 14.4/24.9kv or 19.9/34.5kv.

[topgroove]

It would add cost to the job but a three phase switchgear on the line side of the transformer would make life alot easier for everyone. Including troublemen like me down the road:) If you can make and break all three phases at the same time ferroressonence is not an issue:D

[slimdalineman]

I'm guessing by your handle you are in Minn...that being said ferro could be an issue as others stated, also are you using enhanced elbows?..weather may also be a cause of your "arcing" if it is damp out particularly on 14.4 and up

[Trbl639]

It would add cost to the job but a three phase switchgear on the line side of the transformer would make life alot easier for everyone. Including troublemen like me down the road:) If you can make and break all three phases at the same time ferroressonence is not an issue:D

Amen!...........................

[MI-Lineman]

Anybody ever had any trouble heating up a 3 phase trans.??
We just switched to 14.4 prim. on one of sub stations. We where pulling some dumbie caps off to plug on the 3 elbows to heat up the tub. when we pulled the last cap we had a small blow up. (sparking and arcing) Got that cleaned up and went to plug on the elbows when we got to the last one we had some arcing on the elbow . I 'll admit this 14.4 is new to us, but what did we do wrong??? thanks

Hopefully you all are usin new equipment and the "dust cap" you're referrin to was "posi break?" Same with your elbows? They got the yellow band around them to signify posi break? Doesn't sound like ferro to me when it's the dust cap? We had major issues with our 14.4 urd dust caps and elbows doin this!

Climbsome should be jumpin all over this soon! He'll tell ya!

Read this, it happens a lot on 14.4 24.9! http://www.cooperpowercentral.com/Repository/EpicDocs/B235-07047.pdf

[Orgnizdlbr]

ferroresonance.

Check out the posts on that topic.

Exactly......

[rcdallas]

Almost all of our new 3 phase transformers have a switch. Open the switch close in the feed then close the switch...all 3 phases close at once.

What about putting a small load like a hair dryer on the secondary, close two phases then close in the third, if you don't have a switch.

[lewy]

Hopefully you all are usin new equipment and the "dust cap" you're referrin to was "posi break?" Same with your elbows? They got the yellow band around them to signify posi break? Doesn't sound like ferro to me when it's the dust cap? We had major issues with our 14.4 urd dust caps and elbows doin this!

Climbsome should be jumpin all over this soon! He'll tell ya!

Read this, it happens a lot on 14.4 24.9! http://www.cooperpowercentral.com/Repository/EpicDocs/B235-07047.pdf
I was thinking along the same lines as you that is why I asked the ?
We use vented bushings on all of our transformers, but we only had problems on our 27.6/16 kv.

[MI-Lineman]

I was thinking along the same lines as you that is why I asked the ?
We use vented bushings on all of our transformers, but we only had problems on our 27.6/16 kv.

Yeah it sounds like the dust cap was the problem and probably damaged or flashed over the bushin causin a little show when they plugged in the elbow? He only mentions some "arcing" on the last elbow not anything about fuses or such blowin or sh!t just plain ol blowin up? I wonder if it was the same bushing the problematic dust cap was on as the elbow that arced was parked on? Just don't sound like ferro???

[Boomer gone soft]

Yeah it sounds like the dust cap was the problem and probably damaged or flashed over the bushin causin a little show when they plugged in the elbow? He only mentions some "arcing" on the last elbow not anything about fuses or such blowin or sh!t just plain ol blowin up? I wonder if it was the same bushing the problematic dust cap was on as the elbow that arced was parked on? Just don't sound like ferro???

Had a little "windshield time" yesterday and was letting the squirrel rattle around in the old cage.....after the drool dried to the chin, I was kicking this problem around some.;)

I am still thinking ferro because if there was arcing when the dusty cap was taken off, that means at least one other phase was hot and plugged in. If there was no load on the tx, then that's high time for ferro especially at that voltage.

He never said, but I was wondering if that tx had an oil switch? How did they resolve the issue? Did they replace the bushing?

[T-Man]

Like slim mentioned 14.4 will have some arcing on the caps and terminators. we use a drain wire to check that. If you are energizing a new transformer you should be doing that remotely. we never fire up a tub standing in front of it the first time. Once it's proved and we are just energizing or de-energizing we can do that standing with a shot gun stick for clearance in front of the unit with two men, one standing with his back to a possible arc so if it should happen he can control the stick if the switcher gets temporarily blinded by a flash.

Mi mentioned enhanced caps and terminators with the yellow band or they may even have a yellow painted dot up near the pulling ring. If you are not using these, in temps below 30 and in damp conditions you can get a significant blow/flash from terminator to case.

You can read the Ferroresonance info on another post but in my opinion I wouldn't think that as the first choice in this problem.

T-man

[climbsomemore]

Switching in cold weather is always a problem. Are you folks buying those improved elbows, bushings and caps that are supposed to work better in the cold?

In the worse case... you may need to tarp over the padmount and heat things up with a salamander (kerosene heater) to warm the elbows up. A buddy in Montana tells me that's SOP in prolonged cold spells.

Are you connecting the Dust covers to ground? The should be bonded.

I doubt your seeing ferro resonace unless your switching load... but dust covers have been know to flash over (for a wide range of reasons)

[lewy]

Had a little "windshield time" yesterday and was letting the squirrel rattle around in the old cage.....after the drool dried to the chin, I was kicking this problem around some.;)

I am still thinking ferro because if there was arcing when the dusty cap was taken off, that means at least one other phase was hot and plugged in. If there was no load on the tx, then that's high time for ferro especially at that voltage.

He never said, but I was wondering if that tx had an oil switch? How did they resolve the issue? Did they replace the bushing?

In the earlier days of switching 27.6/16 they would get a lot of flashes pulling elbows or caps anytime the temp was around freezing, but not at the warmer temps. They determined that part of the problem was caused by a partial vacuum that would only flash at the cold temps, because of this we went to vented bushings & the problem went away.

[MI-Lineman]

It would be nice if the guy who started this thread could respond to the questions!!

Gish!:rolleyes:

[otis-mn]

Sorry About not getting back to you sooner! We are just using the plain elbows and dumbie caps. Sounds like we should switch!!!

It was below freezing about 10. Just pulling caps off to put elbows on in 3 phase cabinet to heat up tub that had no loadand was 250 feet away.

THANKS FOR ALL THE INFO YOU HAVEN GIVEN US!!!

[MI-Lineman]

Sorry About not getting back to you sooner! We are just using the plain elbows and dumbie caps. Sounds like we should switch!!!

It was below freezing about 10. Just pulling caps off to put elbows on in 3 phase cabinet to heat up tub that had no loadand was 250 feet away.

THANKS FOR ALL THE INFO YOU HAVEN GIVEN US!!!

Yep! Partial vacuum flash! You need "posi break" elbows and dust caps! Also, are you sayin your elbows are in a dead front switch cabinet or coffin? Was it a direct fed live front tub from there with no fuses in it or were the elbows in the transformer? Just curious cause I hate those dam things!:(

[otis-mn]

Ya there are elbows in the tub. With 3 fuses on the high side.(bayonet style)

We were plugging the elbows on in the 3 phase cabinet. (dead front)

I think you are right , it's some type of vacum flash.

thanks for for the info!!

[MI-Lineman]

Ya there are elbows in the tub. With 3 fuses on the high side.(bayonet style)

We were plugging the elbows on in the 3 phase cabinet. (dead front)

I think you are right , it's some type of vacum flash.

thanks for for the info!!

Good luck!

[swanny]

If it had no load on it; it does sound like ferroresonance. Chances are higher in 3 phase padmount transformers fed from urd cable, with no load on them and higher distribution voltages like 14.4/24.9kv or 19.9/34.5kv.

had small splashes-closing cut-out-no load-just picking up 3rd coil-no load