A customer of mine has two transformers adjacent to their building for 2400 2ph 3 wire to 240v 2 ph 5 wire conversion. Inside the building the oil switch was hit by lightning which fried one of the coils for the fault trip. Anyway we are going to repair it, which involves interupting power from the street. Question is, these xfmrs are probably 50 years old easy. We are going to rebug the connections, and retape, since the power will be off anyway. Should the oil be changed? Will changing the oil help? or will it possibly alter the performance and possibly cause rapid failure due to the fact it has never been changed? I am comparing it to my experiences with say automatic transmissions. The fluid should be changed every 15000 or so. But if never changed and the vehicle has very high miles, changing the fluid could cause failure to the tranny. Can someone shed some light and experience please?
It's very likely that the oil in the transformers contain PCB's (a carcinogen). If this is the case, it could be an expensive proposition to change the oil. An environmental services company would likely have to be involved with the draining and removal of the oil, depending on the regulations in your area.
[This message has been edited by CTwireman (edited 12-05-2002).]
IMHO: You should be extreemly careful persuing an "oil change". If the xfrs are "50 yrs old" they probably are PCB contaminated, unless they were "cleaned" previously. They should have a tag indicating that they were "cleaned". I believe that this is a FEDERAL EPA (DEP) regulation.
THE PCB'S ARE A VERY SERIOUS MATTER. If you create a "spill" the clean-up costs can be astronomical. There used to be a test kit for a quick field analsys of xfr oil, but I don't recall who it was from.
BTW, If your "switches" are oil filled, be careful also, if they are old.
There are no easy answers to your questions. There could be PCBs in the transformer and also in the switch. A local utility might be able to refer you to a lab that does their oil testing.
Aside from the regulatory aspect, the oil should at minimum be tested for dielectric breakdown. There is a standardized tests and portable testers for this purpose, but if the process is unfamiliar, get an experienced firm to do it. If dielectric breaksdown is OK, [and it is pure mineral oil] then you can decide on an oil handling course.
Three phase to two phase—Wow! That’s cool! The particular transformer arrangement for the conversion is quite historic—first demonstrated by the pioneer CF Scott in 1894. It’s a true part of electrical evolution—called the “Scott-Tee” connection.
The most important comment I have, and I forgot to type it......
Hire a certified, licensed, company to do this phase of the job you outlined. Here in NJ, I use an enviornmental contractor, who is licensed, INSURED, state and Federal EPA/DEP certified, etc. And make sure you get all the proper documentation for the disposal.
To Bjarney, it is very common here. In Philadelphia 2 pase is all over. To the rest thank you. I have all ready dealt with the problem. A electrical testing company is going to test the oil for PCB's among other things. They can tell if the xfmrs are failing as well. They stopped using PCB's around thirty years ago. Xfmrs were assembled using mineral oil and PCB's even in the same factory, at the same time. It was finally discovered that PCB'S are dangerous so they dumped alot of it into the Hudson River. I have discovered that even if the xfmrs have PCB's, as long as it does not exceed a limited "parts per million" it is ok, but they still need to be labled as Haz Mat, in case of an emergency, say a leak!
As previously mentioned by other members, the original oil in the Pot[s] may contain PCB - therefore becoming a Hazardous material [like Asbestos (ACM) abatement]. I say "May" only because maybe the original oil was previously changed to a Non-PCB type??? [not an easy thing to verify looking at the oil!]. This is added just as a "BTW" thing-ee
I would imagine that changing the oil is something that would not only be a good idea - due to possible dielectric breakdown from age, the Lightning surge, and since you are doing some "R&R" on the coils -, but also would be mandatory replacement with non-PCB materials since it's being "Exposed".
Sounds like an "Icky, Sticky" job!
On the subject of the 2 phase systems:
PLEASE, PLEASE, PLEASE!!! get some pictures of active systems [open delta Tee and the "full" three xformer systems, if any], along with the one you are servicing. Man, I would love to add those images to the Tech Center's archives!!!
Send them to me for posting.
Scott " 35 " Thompson Just Say NO To Green Eggs And Ham!