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Power Factor Testing for Transformers and Relays

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In transformers and relays the function of the component relies on the integrity of the insulation in the windings. The insulation can break down over time due to factors such as moisture getting into the component windings, and in some cases, this can lead to violent explosive destruction of the equipment.


The most effective method for early detection of contamination and deterioration is a power factor measurement or Doble test. In the Doble testing procedure, AC current is measured to determine the capacitance of the insulation. There are various forms of the power factor test using different types of equipment. In the main, the procedure is carried out by measuring insulation properties between the current-carrying conductor and the bushing. Another test is to determine the moisture content by pushing a red-hot rod into compound-filled bushings. If moisture is present, the insertion of the rod will cause noisy melting of the compound, and if no moisture is present, the compound will melt quietly.

For many jobs, you will want to rent a relay test set rather than buy one.  When you rent your electrical test equipment from us, you preserve capital that can be used in your business without a large cash outlay for testing equipment. We also clean, calibrate and maintain the test equipment so you can take care of the important parts of your project without having to worry about keeping testing equipment operational. 
To learn more about our budget saving rental programs, call or 
contact us online.