depends on how severe the bushing was damaged. The open porcelan should be covered and sealed with "glyptol" or another insulating paint. I would get a replacement bushing on order if you don't already have one.
Problems down the road are tracking and bushing failure in severe cases.
It's not a question about bushing repair or replacement or problems down the road, but about the possible extent of damage and result. Thought I might get some first hand knowledge here.
it really depends on where the bullet hit. Chipping a small fragment from the edge of the skirt isn't a big deal. A direct hit into the center of the bushing is a far bigger deal. Most I have seen were chipped skirts with no outage.
I have seen more outages from line insulators being shot than substations. Most subs have outages caused by animals that I have worked with. Nothing like the smell of fried raccoon in the morning...
Assume that the alcohol's affect on accuracy is made up for by determination along with a large supply of ammo, and that the location is remote enough that chances of discovery are low.
Many times it is not a full understanding of how far away those insulator really are. They don't have as big of a surface area either, so that factors in.
Have not seen such a case - but hopefully such a shot will totally miss the transformer. I think I would rather prefer a damaged bushing than a few holes in the transformer body.
Regards
Ralph
[red]Failure seldom stops us, it is the fear for failure that stops us - Jack Lemmon[/red]
Make the best use of Eng-Tips.com
Read the Site Policies at FAQ731-376
Most people do not have bullets that will go through the body of a transformer. They are hard to get your hands on. Even high powered big game rifles will not go through a transformer wall.
I am sure most big game rifles (.303, .308, .3006, etc) which are very ordinary here (South Africa) will at least penetrate into the first wall of the transformer. Also, the transformers of today have mush thinner metal sheets than the older transformers, meaning penetration will be much easier.
Oil containment or not - it is beter to replace a bushing and top a few litres of oil up, than to patch a hole/holes at the bottom and totally refill the transformer.
Wfowfo
Radiators or not, hole/holes in the bottom of the transformer = spilled oil.
Regards
Ralph
[red]Failure seldom stops us, it is the fear for failure that stops us - Jack Lemmon[/red]
Make the best use of Eng-Tips.com
Read the Site Policies at FAQ731-376
If you are meaning smaller stuff, like children with "ketties" (sorry, do not know a suitable English word) or small guns, then I agree with you. In that case the bushing will be the most vulnerable part on the transformer.
We have had experience of bullets piercing the tanks of transformers (mainly distribution - 11kV/415 around the 1000kVA mark). Mainly someone in a block of units taking pot-shots at a harmless target. They shoot the tank, then the oil drains, then there is the failure of the transformer, fairly simple. The bullet pierced the tank wall, glanced off the outer winding and rattled round the bottom of the tank after it lost all its energy.
Also HV instrument transformers shot in the tank. Again the oil drains out and then you have a flying procelain safety issue. Unfortunately these events aren't instantaneous, they take time for the oil to drain, and hence the "perp" (perpetrator for those not used to the police vernacular) is long gone. The investigation of the failure only recognised the bullet hole and hence the bullet in the sand filled tank some days later. Bullets are not high on the list of common failure modes.
The first incident mentioned above would be a perfect situation to get Grissolm and the CSI team to investigate, you can work out the angle of entry of the bullet, get your laser pointer and identify the balcony from which the bullet was shot - case closed.
I'm not sure of the extent of the original post, but I would certainly be replacing the bushings if they were shot, unless it is clear that the damage is purely to the porcelain surface. If it is an oil filled bushing (or gas filled for that matter) you cannot be sure of what damage that the force of the bullet hitting it has had on the seals, and hence possible leaks can occur, resulting in an unsavoury failure.
