Exploded transformer Pics

[hockeyoligist2]

We got called in at 2 AM the other night and found this. Wires shorted phase to phase in the conduit and blew the doors off of the transformer. Good thing no one was in front of it!

 

[hurk27]

it appears that the lightning arrestors took a hit, as they seem to have the most damage?
Did you have a storm in the area?

 

[jim dungar]

Another reminder how doors, alone, do not mitigate the effects of an arc flash. When something decides to 'blow up' there is little that can be done to handle it. Prevention is critical.

 

[iwire]

Another reminder how doors, alone, do not mitigate the effects of an arc flash. When something decides to 'blow up' there is little that can be done to handle it. Prevention is critical.

And another example of this equipment being located in areas open to the general public.

A 'easy' fix would be to make a section of the top weak so that the force of a fault is sent upwards and not outward. Much like the ammunition storage is on a tank.

 

[jim dungar]

A 'easy' fix would be to make a section of the top weak so that the force of a fault is sent upwards and not outward. Much like the ammunition storage is on a tank.

For sure.

But I was thinking along the lines of proper protective device settings. Many padmount transformers feeders are protected by fusing chosen as large as possible to 'save the power grid at the expense of the equipment' in order to prevent nuisance trips.

 

[hockeyoligist2]

it appears that the lightning arrestors took a hit, as they seem to have the most damage?
Did you have a storm in the area?

Nope, no storm! And the short was on the secondary side, inside the conduit. If you look closely at pic#2 you can see the bolts are melted on the ends where it arced between them. I'm guessing that is what took out the arrestors. I had to grind the bolts off because they had so much damage.

Iwire, the top did go up about 6 inches on the left side, kinda hard to see in the pic. I was using my phone camera and I shot too low.

 

[iwire]

But I was thinking along the lines of proper protective device settings. Many padmount transformers feeders are protected by fusing chosen as large as possible to 'save the power grid at the expense of the equipment' in order to prevent nuisance trips.

Point taken, thanks.

 

[iwire]

Iwire, the top did go up about 6 inches on the left side, kinda hard to see in the pic. I was using my phone camera and I shot too low.

It would have been exciting to watch ........ from a good distance.

 

[hockeyoligist2]

It would have been exciting to watch ........ from a good distance.

I thought the same! Top of the hill 100' away!

 

[hurk27]

Nope, no storm! And the short was on the secondary side, inside the conduit. If you look closely at pic#2 you can see the bolts are melted on the ends where it arced between them. I'm guessing that is what took out the arrestors. I had to grind the bolts off because they had so much damage.

Iwire, the top did go up about 6 inches on the left side, kinda hard to see in the pic. I was using my phone camera and I shot too low.

Ok maybe someone could clue me in as to how a fault between the secondaries and ground (the pipe) will cause a higher voltage on the primary bushing's and lightning arrestors to the point it melts the terminal bolts of the primary connections and blows apart the arrestors?

I have seen allot of damage over the years, but this one sure seems like the primaries got a surge of higher voltage somewhere down the line and if no storm then maybe a tree limb came between a 69kv line and a 7200 volt line for just long enough to cause this, (voltages might very place to place) I have seen this result around here.

 

[jim dungar]

Ok maybe someone could clue me in as to how a fault between the secondaries and ground (the pipe) will cause a higher voltage on the primary bushing's and lightning arrestors to the point it melts the terminal bolts of the primary connections and blows apart the arrestors?

The 'fireball', created by the fault on the secondary, could easily have propagated into the primary compartment causing a HV fault.

 

[hurk27]

The 'fireball', created by the fault on the secondary, could easily have propagated into the primary compartment causing a HV fault.

It would had to go out then back in the primary side as the separator steel wall is solid and still intact, and not that burnt?

I just never seen arrestors blown apart like this except when hit by over voltage, mostly lightning strikes, but have seen 69 kv blow a few 7200v ones apart.

But I guess its possible.
Put this one down as a learning for future referance.

 

[hurk27]

After looking at the last photo a little more, I think I can see a pattern that might be because of a slight gap between the separator and the transformer bulkhead wall, if hot gases were to have escaped behind this panel through that gap, who knows what kind of damage it would have done to the arrestors because their right there?

 

[masterinbama]

I have seen where the smoke and soot created by a secondary conductor failure allowed the exposed primary voltage to flash over.

 

[weressl]

It would had to go out then back in the primary side as the separator steel wall is solid and still intact, and not that burnt?

I just never seen arrestors blown apart like this except when hit by over voltage, mostly lightning strikes, but have seen 69 kv blow a few 7200v ones apart.

But I guess its possible.
Put this one down as a learning for future referance.

I am with you on the lightning arrrestors being the initiating culprits. Look at the smoke patetrn on the back of the wall, it is moving toward the top FROM the LA's, but largely leaving the primary bulkheads out of the picture. There may have been an arcover on the primary bushing but does not seem to have sustained itself. There may have been reclosers at work and there may have been two separate events closely spaced together.

 

[jim dungar]

I am with you on the lightning arrrestors being the initiating culprits.

Then how do you account for all of the soot and in the LV compartment?
Read post #6.

And the short was on the secondary side, inside the conduit.

I will stick with my theory, that the fireball went from the secondary into the primary compartment at which time it contacted the LA's. The interior wall of the transformer would definitely allow this scenario.