Electric Transformer

[supersurgilator]

What would cause something like this to occur, and how often do you suppose it happens?

 

[toggleswitch2]

Overload, stressed metal, compromised insulators.

I've seen transformetrs pop in Provinctown Massachusetts were the poulation swells for the summer and the electrical system can't handle it.

 

[sudsmaster]

Heat.

Perhaps the transformer has aged and the dielectric (oil) has broken down. With high load perhaps a short occurs at some point, creating an arc. The oil (or other dielectric, like tar) inside is flammable, and what you see is basically an oil explosion.

It may be wise to steer clear of older exploding transformers, even after the fire has died out. The oil may contain PCB's which are carcinogenic. I understand that utility companies have been replacing the PCB laden transformers but I don't know if it's 100% done.

 

[sudsmaster]

This may shed some light on the problem.

http://www.transproco.com/why-transformers-explode.htm

 

[redcarpetdrew]

This could happen outside Kevin's House...

In his case, it's caused by having too many lit consoles on at the same time. It was only a matter of time... LOL!!!

RCD

 

[sudsmaster]

But wait, there's more...

http://www.ehow.com/how-does_4578514_why-do-transformers-explode.html

 

[toploader55]

OMG Drew...

I just had a sip of wine shoot out through my nose reading your post. You are too funny !!!

Do you really think it could happen ?

 

[a440]

Very interesting!

I was at a traffic light once during an electrical storm and a transformer blew to the left of me. Besides the huge boom metal flew everywhere. I almost crapped my pants!
There was an interesting video on youtube awhile back and I can't find it to post! Darn! In the video a tree company is doing tree work cutting limbs that were about to touch the high power lines. The company accidentally (of course) hit the high power lines with the boom. This causes the expected flashes. The issue was that the "line breakers" did not trip. Within 5 minutes of the video (that I think a resident on the street was filming) you see smoke start to come out of the attics of most of the homes on the block. My guess is that since the transformers blew and the "breakers" did not trip the homes were getting raw full power.
Such a scary thing.
I will keep searching and if I find the video will post here.
It really makes you think and respect electricity!
Great thread!
Brent

 

[supersurgilator]

I hope you can find that link, I cannot believe that would happen. So did basically all of the houses have electrical fires then as a result?

 

[sudsmaster]

All the homes should have had main breakers mounted on the OUTSIDE of the homes, which should have tripped to prevent the "raw full power" from getting inside the structures.

Theoretically, that is.

I once lived in a town nearby that had terrible electric service. It seemed like every time there was a winter storm, the power would go out. The home was a rental and had only fuses with ungrounded outlets. Needless to say, I lost a fair amount of electronic equipment due to this situation (several VCR's, a TV, etc...).

One winter night there was a fierce storm and I woke up to a blinding white flash coming through my second story bedroom windows (which looked out on the street) and the sound of the transformer down the block exploding. Or something. There was no fire, that I recall. But the power went out of course.

I finally moved to this town where the electrical service is much more reliable. Even has grounded outlets, mostly.

 

[a440]

I found the Video!

This is terrible, but it does happen Bruce. More than you would like to think.
Brent

<object width=425 height=344><param name=movie value=></param><param name=allowFullScreen value=true></param><param name=allowscriptaccess value=always></param><embed src= type=application/x-shockwave-flash allowscriptaccess=alwaysallowfullscreen=true width=425 height=344></embed></object>

 

[tolivac]

Transformer failers like what was filmed is rare-but spectacular.At my workplace I am sorrounded by various transformers in the building in in the transmitters and their transformer vaults.Most of the ones we have here have pressure ratings and limits on their tanks-5Psi and 15 Psi as I have read on them-and their is a guage to tell what the pressure is-and venting to let off the gas and oil in case of overpressure.These have been tested.In one of our transmitters the transformers have Buchholtz protection-a two level gas pressure sensor that responds to minor arcs in a transformer case-warning-to major-trips off the primary power to the transformer.Power companies have that too on substation trasnformers.And transfromers have expansion tanks-a tank above the main transformer tank that holds expanded gas and oil.also serves as a reserve for when the transformer is cold and warming up.Substation transforemrs have these-the transformers provided by the power co out here have them.The transformers for our site step down 115Kv to 4160V-10Mva.A very powerful feeder.The 4160v current per phase can go up to 1400A!SCARY!!

 

[mielabor]

Never seen or heard of anything like this here. But then, all above ground electrical wiring with exception of high voltage long distance lines has been replaced with underground cables many years ago.

 

[alr2903]

mielabor, in our urban areas lines are underground usually covered with a grate to allow air ciculation. The poor homeless often sleep over these grates. Now thats a frightening thought. alr2903

 

[mielabor]

Underground lines covered with a grate? Also new for me. I have only seen cables buried in soil. To avoid damage by digging a tough plastic strip of about one foot wide is laid over the cable. This serves as a warning that further digging can damage the cable. The strips are colour coded: red for electricity, blue for telephone, yellow for gas, green for cable tv.

 

[toggleswitch2]

~in our urban areas lines are underground usually covered with a grate to allow air ciculation.

And when the salt gets in there (that the streets are treated/coated with), it rots and rusts everything and that causes problems also. *KABOOM* We had a massive transformer fire not long ago in NYC due to salt and snow.

Not to metninon salt makes water mor conductive.........

 

[mielabor]

So why do they do it then, covering cables with grates. Are the cables overrated and made too thin so that they get hot in use? Is this an outcome of the 110V system?

 

[whirlcool]

They really had a mess on their hands with that last transformer. I was putting out some real noise!

 

[supersurgilator]

Thanks for posting that link. That is absolutely unbelieveable. Like others have said why didn't these people's breakers trip? Would that have even been strong enough to protect against that mass amount of energy going into the homes?

 

[a440]

I don't think it would matter if the breakers tripped or not.
I think the raw power was strong enough to melt their breaker boxes.

 

[sudsmaster]

Um, what is meant by "raw power"?

Do you mean extremely (by household standards) high voltage and amperage?

I suppose sufficient voltage running down the wires to the home might cause arcing over in the breaker box... But then I'd also expect it to arc on the way down to the breaker box... Something seems non standard about the way those homes were wired... perhaps not to code or code not followed?

It looks however that the guy in the bucket survived. The arcing on the high tension wires seems to have gone on waaaay too long.

 

[sudsmaster]

Apparently the high tension power line broke and contacted the ground wire. I guess the ground wire also must have had a one-way route to the block of homes. Since ground wires are not normally protected by breakers on the homes, that current would have gone through the homes' ground location seeking the path of least resistance. Apparently the homes had interconnected the service ground to the homes' gutters and plumbing, which caused these to heat up and start the blazes. Possibly some of that smoke is really steam from overheated water in the plumbing (some homes built on slabs have the plumbing running through the attics instead of under the slabs). At least this is what I gather from looking at few web sites that talk about the incident.

I do remember what an electronics instructor told our class back in 1984: "Never trust the ground wire coming in from the utility"...

Which reminds me... I need to install another ground rod at the electrical service entrance...

 

[alr2903]

mielabor, Togs and i are speaking of runs of electric cable in the urban jungle, these large grates are present in the sidewalk, where i would guess several tranformers and lines tie together, kind of like one kitchen table sized grate in an entire block of concrete sidewalk, so to speak. alr2903

 

[toggleswitch2]

110v or 220 at end use is of no importance, in this case.

More and more use of air-conditioning in summer has lead to catastrophic loss of power and burnt cables.

Air-conditioners were over $250 in the 1970's and are now $80 to $100 (Thank you China). Everyone including the poorest of the poor now has one in this city.

My apartment building was buit in 1945 and has only 30a 110v service (say 3,300w)per apartment. To make it worse, I think 8 apartments have only 100a 110/220v main service coming in. With 4 apts per 110v leg, there is only 100a to split between 4 units. (4 x 30= 120a demand)

We are so far behind in so may ways it is scary!

 

[tolivac]

Grates in the city-When I was in Wash DC-these grates were common-esp in front of buildings-and the buildings power feeder transformer was under the grate.Hate to be the utility tech who have to work on the equipment-its covered with cigarette butts,dried spit and food remains-not to mention dead mice and rats,snakes,etc.
And yes I have seen people sitting on power transformers in front of buildings,houses while waiting for their bus-if only they knew what they were sitting on!-sometimes these let go!!I would want to pick something else as a seat.
At my workplace some electric renovations are underway-all of our MV and LV breaker panels are being replaced-it has to be timed to keep airtime loss at a min.And the contractors have gotten rid of some older transformers no longer used-and they held PCB dielectric cooling fluid.From the substation out here-the 4160V cables run thru a water filled area that is always wet-high water table here-so the cables have to be specially waterproofed-imagine if one or more failed-that water would be boiling!!I have seen other buildings where their power cables go thru water filled basements and conduits.SCARY!!!

 

[sudsmaster]

Not just debris...

One of the sites I visited mentions that underground cabling and transformers in the Northeast has a special challenge - the salt used on roads in the winters there gets into the chambers and corrodes the wiring, which then can lead to wiring/transformer failure/explosion.

 

[circlew]

Yikes! That would be very scary to see something like that. The closest thing to that around here was when the power co. (municipal owned) replaced a 120/240 volt 1ph transformer with a 480 volt by mistake. They had bought some used units, and they claimed it was mis-marked, but I also heard from others they just picked up the wrong one. This transformer served 5 houses. Due to the higher voltage going in to the buildings, it burned out the motors in the people's refrigerators and some other appliances, and ruined their TVs, VCRs, and other electronics. The power co. didn't want to pay, so the homeowner's insurance had to.
In another instance, a vehicle hit a power pole a couple miles from here. A high voltage line fell onto a lower voltage line, causing a momentary surge to the area served by the lower voltage line. This cause some electronic items to be ruined. The main substation breakers did trip, causing a widespread power outage - knocking out power to all of Goshen, Blanchester and Newtonsville.

 

[tomturbomatic]

Transformer failure is a major threat to the world's electrical grid. Transformers are not mass-produced items. If a plasma discharge from a solar storm were to breach Earth's magnetosphere, transformers would be overloaded and destroyed. The electrical grid could be down for months and even years. We would be shoved back in time more than a hundred years without the resources of those times. Even natural gas service would be disrupted without electricity to power the pumps, likewise water and sewer systems.

http://www.examiner.com/x-2383-Hono...grid-failure-from-2012-solar-storms-avoidable

 

[tolivac]

WHAT Tran sformers not mass produced-yes they are!!!That is a big reason there is so many of them.Visit a transformer factory sometime!even the larger substation transformers are mass produced-and factories produce custom ones like for our facility-IE as a replacement for one of our transmitters a rectifier transformer-primary 4160V 3p sec-two 10Kv 3Ph secondaries for 6 phase rectifier to get 30Kv DC at up to 20A.Distribution transformers are the most mass produced(pole pigs and URD transformer) that feed into your home or business.Most common 13.8-7.4Kv primary-240-120V secondaries for homes-13.8Kv primary-208-120V secondary in a 3 ph bank-pole pig-and another pole pig-ground mount 13.8Kv primary-480-277V secondary pole pig or ground mount.I had to oversee and specify a 3 phase bank of transformers for a 50Kw AM radio station transmitter site-3 pole pigs 100Kva each-13.8Kv primary voltage 480-277V secondary.Lower power station use 208-120V or 230V transmformer banks.or one ground mount 3 ph transmformer-these are becoming more common.
The 480V screwup by that power company-a 480V transformer in a residentual feeder--you bet your A?? they would be responsible-negigence on their part-anyone got hurt?The homeowners should hire a lawyer and sue-would be an open-shut case!!If the power co tech can't read a nameplate on a transformer--they aren't qualified for the job!!A transformer that has its plate missing should not be used.A turn ratio tester could determine its specs though.none the less unmarked transformers shouldn't be used.That power co or the contractor that did the work would indeed be reponsible for any injuires and damages.

 

[tolivac]

Transformers are pretty interesting electrical-electronic devices-they do the function without any moving parts or vacuum tubes or semiconductors-just two or more coils of wire wound on a soft iron core.(soft iron has low periability-does not retain a magnetic charge)and the transformer can do its job for years or even decades with surpizingly little care or mainteanance!