Power Transformers Blog – Expert Safety and Usage Info

MIDWEST was called to check out an old 3750 kva oil filled transformer. The owner was trying to decide whether to reclaim the oil in the old power transformer or to go ahead and replace it with a new 5000 Kva transformer. They actually needed a 5 Mva replacement power transformer. They had the history of the oil test results. It was apparent the transformer had slowly absorbed moisture over the years and there was serious paper degredation. They wanted MIDWEST to do an under the cover inspection to see if there were visual signs of sludge and tank rust. Pretty straight forward stuff. Their electricians asked if they could look inside the transformer while we had the access cover open. They had to follow our safety precautions.  They were absolutely amazed to see all the wood used inside the transformer. Almost the entire top of the core and coils was hidden under wood.  The wood was used for blocking, for support of the tap changer, and for making the high voltage connects going to the line side of the windings. The electricians were a little skeptical when we explained how much wood was actually used in transformer construction. How common it was. And that 15 Kv high voltage terminations were made on the wood. They were also surprised how clean the inside of the transformer looked, even though the oil was dark and there was visible sludge on flat surfaces, especially on the wood. For the electricians, seeing was believing. High voltage oil filled power transformers are made with wood.