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.

MIDWEST Uncategorized 2000 Kva Dry Transformer, 2000 KVA Oil Filled Substation Power Transformer, Combustible Gas-in-Oil Tests, dielectric fluid, Dielectric Fluid Tests, dry type transformers, Electrical Power Engineers, Engineering Technician, Field Service, Furan Tests, Kva Dry Type Transformer, Oil Filled Power Transformer, Oil Transformer, Power Distribution Equipment, Power Factor Tests

MIDWEST frequently gets calls from someone wanting to sell used electrical equipment. We are very cautious of the biography of the equipment when the seller is someone other than the original owner. When there are any concerns, the equipment is shipped to MIDWEST, then thoroughly inspected and tested, before we consider purchasing. There are many concerns relating to the condition of used electrical equipment, so we may request pictures, prior use, nameplate data, and other details. Usually a visual inspection is the first line of rejection. With a little biographical information we can frequently determine that the equipment is scrap. As an example, we received a request to sell us three used 1000 kva 13,200 volt to 480/277 volt air cooled, dry type power transformers. The seller was not the company that had used the transformer and the condition was described as “In great condition.” He said he had the transformers for over two years and just wanted to sell them. We asked for pictures before shipping. We got the pictures and the transformers look great. No indications of structural damage. Paint condition indicated the transformers were probably used in a clean environment, a commercial building for example, rather than a manufacturing plant. But, the pictures showed the transformers stored outdoors. Outdoors in the rain and whatever might blow into the windings. Immediate rejection. The windings would be wet and contaminated. Because of the location, the moisture in the windings would have frozen in the winter. The steel structure would be rusted. And if they stored these transformers outside, they had little knowledge of the proper handling of 15 kv dry type general purpose transformers. The pictures said it all. Junk. 

MIDWEST Uncategorized 1000 KVA Dry Transformers, 15 KV Air Cooled Transformers, dry type transformers, General Purpose Transformers, Nameplate Data, Transformer Stored Outdoors, Transformer Windings, Used Dry Type Transformers, Used Electrical Equipment, Used Transformers

When Infrared Scanning electrical power distribution systems, including general purpose dry type transformers, MIDWEST frequently finds interesting, strange, and even dangerous situations that have nothing to do with Infrared Thermography.  Visualize a make shift rest area in a manufacturing plant. This area was next to the tool room.  There were two panel boards, some wire way with switches above it, and two small general purpose dry type transformers next to the panel boards. One transformer looked like an old 75 kva 480 volt to 208 volt transformer and the other looked like a new, maybe 25 kva general purpose transformer.  Both of the dry type transformers were very warm. On top of the large dry type transformer was a small microwave and a coffee maker.  On top of the small dry type transformer was a cushion.  This looked like a pretty comfortable kitchenette set up.

Anyone electrical should recognize the danger of coffee, liquid, around an open air, air cooled, general purpose dry type transformer. A liquid spill would seem inevitable.  Just a matter of time. Even if the transformer had weather shields, no one should ever be around it with liquid.

The smaller electrical power transformer was just a nice warm seat.  We have seen this a million times, especially in warehouse and other unheated or poorly heated manufacturing and industrial areas.  Usually the folks using these transformers as seat warmers are not electrical and have no idea of the danger below. 

A 75 kva 480 volt air cooled transformer can let out a horrific blast if the primary conductors short out. The transformer would become an instant hot seat and the arc blast from the open top vents could cause horrible burns to anyone nearby.  Add to this the shock hazard. An arcing fault could go to ground and some one touching the transformer could receive a deadly shock. Or something could easily be stuck into the vents and contact live conductors. We see these general purpose air cooled dry type transformers everywhere, and in sizes ranging from 5 kva to 500 kva.  When we see this danger, we politely let the person know the risk of shock or burn.  In a second, that nice warm seat could turn into a deadly hot seat. And that coffee pot stand could be the source of a deadly shock or horrible arcing burn, in a second.

MIDWEST Uncategorized air cooled transformer, arc blast, arcing fault, dry type transformers, electrical hazards, electrical power transformer, electrical transformer, general purpose dry type transformers, Infrared Scanning, infrared thermography, shock hazard

225 KVA Dry Type Transformer For Sale

Many facilities are declaring their maintenance budget to be revenue neutral. Our recommendations for maintenance of old transformers are both condition based and time based. For example, one may recommend annual infrared scanning and annual dielectric fluid analysis on fluid filled power transformers, especially old or obsolete transformers. Whereas, old indoor dry type transformer should be cleaned and maintained based on their condition, their environment. A foundry would be more condition based than a commercial facility. A problem occurs when the conditioned based maintenance costs are unusually high in a particular year, say this year. Some maintenance supervisors have been told if they add cost in one area, they must remove cost somewhere else. Revenue neutral decision making. This can be roulette in some facilities that have a lot of old or aging equipment that really needs attention.  Unfortunately what often happens is time scheduled maintenance is postponed in favor of condition based service. MIDWEST suggests a compromise. Review “Schedule Services” and perform those services on equipment that is most critical and has the poorest service condition. Likewise, service “Condition Based” equipment that is both the most critical and most in need of service.  These decisions are only good “if nothing goes wrong.” If something goes wrong, then, of course, it will be attributed to you choosing poorly. You can’t win.  You might escape the first year.  But as the financial stress on the maintenance dollar continues, what seemed to work last year, now appears more reasonable to “do the same” this year.  And next.  Until something goes wrong.  Then you lose. You chose poorly. We recommend reviewing the maintenance services on obsolete, old, and new equipment each year using the cumulative information of all the prior years. Do not go back just one year.  Also, good luck.

MIDWEST General Transformer Information dry type transformers, fluid filled power transformers, obsolete transformers, old transformers