Tan Delta Test Result Verification

Install dehumidifier

The only "correction factor" for humidity is to thoroughly clean and dry the bushings of the transformer or other device being tested. It's not the humidity in the air that is directly the problem, is the humidity that is absorbed into contamination on the surface of the bushings, which causes lower resistance for leakage currents. THe cleaner and drier your bushings, the less leakage is possible.

We have had good results using a quality paste wax (carnauba or similar) on apparatus bushings after the contamination has been cleaned off. There are commercial products manufactured for electrical bushing polishing, but I have not seen that they work significantly better than good quality paste wax. Apply a thin film of the wax as if polishing your car or furniture, then buff to a glossy shine. It has the added effect of helping to reduce future contamination from sticking as easily, and helps water (rain, etc.) to bead and run off better.

Thanks peter.....