Optimization of Power Transformer Insulation Dry-out Process Using Dielectric Frequency Response (DFR)

Abstract

As with any other manufacturing process, quality of end-product and optimization of resources are reliable monitoring indexes to determine the efficiency, effectiveness, and profitability of a business. Power transformer manufacturers are keenly aware of global economic demands that drive them to rigorous quality control procedures and optimized resource administration. Therefore, for transformer manufacturers, each step in the manufacturing process is critical. Design, material selection, assembly, and testing are all interconnected. If any of these steps fails, the whole process is probably condemned to failure. The dry-out process of the core-coil assembly, the liquid insulation filtration, degasification, and the impregnation process of fluids into solid insulation materials are of utmost importance for the transformer manufacturer and the end-user. Throughout the service life of the transformer, the concentration of moisture in the solid insulation as well as the conductivity of the liquid insulation will rise as part of the insulation system's normal aging process. From a test and monitoring perspective, Dielectric Frequency Response (DFR, aka FDS - Frequency Domain Spectroscopy) has proven its ability to accurately determine the condition of solid, liquid, and solid-liquid insulation systems of power and distribution transformers. After twenty-plus years of field practice, experimental research, and technological development, DFR today can be used to provide high-quality monitoring for the optimization of the dry-out process. The DFR monitoring process for factory and field dry-out is described in this document using representative case studies.