Oil Filled Transformers 101 First Post July 2011
This blog is to introduce you to the maintenance testing and care of oil filled transformers. I have spent 15 years in the industry in my younger days and now I think it’s time to start disseminating some of the insider knowledge about the testing servicing and repair of oil filled transformers.
We could see the market beginning to shrink years ago. When the first president Bush made the declaration that we were going to a service economy it pretty much sounded the death knell for the growth aspects of the industry. I knew that in the future everyone would be fighting over a much smaller pie. Most of the huge industrial plants are gone due to inefficiency, high labor costs, higher costs of doing business due to regulation and other reasons.
What we are left with is a few small manufacturers and utilities who own their own transformers. With fewer manufacturers, testing and maintenance is becoming more and more important to those few. In the decade of the eighties it was customary for owners to just run it until it blows rather than invest in testing and maintenance. Only those that absolutely could not afford a shutdown were interested in testing and PM. Utilities usually had spares on hand to replace the smaller KVA units and only performed testing on the larger more expensive units (some of which take months/years to replace).
Testing and maintenance companies had come up with the theory that a transformer theoretically could last over 400 years if properly maintained. That worked out great for business but when the customers learned how much they could save by purchasing newer much more efficient equipment they lost a lot of wind in their sails. The industry quickly recognized that this turn of events could be beneficial because the newer equipment was built with virtually no safety margin. It not only ran hotter causing it to deteriorate faster and it could not stand up to the abuse and fluctuations that the older transformers could handle with ease.
Basically you only have a few materials in a transformer:
Oil
Wood
Iron
Steel
Copper
Paper
Ceramic
Some cloth or plastic/rubber type insulation
And some cork or other gasketing material
The iron, steel, copper, and ceramic will easily last 400 years if protected from corrosion. It’s the organic stuff, the oil, paper, wood, gasketing that deteriorates, and the whole process is fueled by oxygen and heat and aggravated by vibration. We will get into all of the details of this process later.
Some of the companies take oil samples for testing without power shutdown. If shutdown is not possible then you should be testing this equipment on a regular basis. This is something else that we will be discussing in detail at a later date. That being said ALWAYS leave energized sampling to the experts, the people who do it everyday. There are so many hazards that could trip you up and a mistake can be fatal.
As I told you above this is an introduction to Oil filled Transformer Testing Maintenance and Repair. I would appreciate any feedback from you on any of the writings here as well as any questions that you may have. Subjects for future logs will be:
Field tests
Lab Tests
Dissolved Gas Analysis
Moisture
Re-gasketing
Filtering
Oil Reclamation (Energized or Shutdown)
Leak Repair
Painting
Bushing and insulator repair/Replacement
Vacuum Processing
Heat
Interpretation of test results
And anything else that I may be able to help you with. As far as direction, I will take this blog anywhere YOU want to go by your questions (within my areas of expertise). Please don’t hesitate to email me at TransformerBob@gmail.com.
Best Regards,
Transformer Bob"Classic." A book which people praise and don't read.
MARK TWAIN, Following the Equator
