Power Transformers Blog – Expert Safety and Usage Info

There are many technical reasons for using an oil filled power transformer or for using a dry type power transformer. But sometimes the reasons might be a bit of self interest. One example that MIDWEST runs into deals with customers that have a great need to monitor the condition of their power distribution equipment. There may be many reasons for this. Some, certainly justified, say for a mission critical facility, and some less important. But for a MIDWEST field service engineering technician, they would much rather test the dielectric fluid, oil, of a transformer than go through the work of testing an equal Kva dry type transformer. Dry type transformers have to be taken out of service and that usually means weekend or holiday work. Weekend or holiday work is not family friendly. It would take a technician maybe 10 minutes to sample the fluid in a 2000 kva oil filled substation power transformer, including a thorough technical and safety inspection of the transformer. The sample is turned over to the lab for a complete battery of tests. The results of these tests are very informative, especially when there is a history of test results. Lots of data and Electrical Power Engineers love lots of data. The tests may include a group of standard dielectric fluid tests, plus combustible gas-in-oil tests, furan tests, and power factor tests. And, of course, the ever important and super sophisticated smell and visual test performed by the experienced service technician on site.  A nice technical package. The site inspection of the transformer by an experienced technician is extremely important.  Whereas the visual inspection and dielectric tests performed on a 2000 kva dry transformer have very limited value in real time or for historical data tracking. So, if the choice is 4 hours during a weekend or over a holiday versus 15 minutes during normal work hours and with much better information, the choice would be 15 minutes and the oil filled transformer.