ABSTRACT
Power transformer reliability is enhanced considerably by a well-written test plan, which should include specifications for transformer tests. This chapter covers testing to verify or measure the following: Voltage ratio and proper connections, Insulation condition, Control devices and control wiring, Dielectric withstand, Performance characteristics and other tests. Tests for checking the winding ratios, and for checking the polarity and phase relationships of winding connections, are carried out on all transformers during factory tests. The transformer test sets used to determine voltage ratio and polarity are designed for single-phase operation, but supplemental switching arrangements are employed to facilitate testing of three-phase transformers. The quality of the transformer insulation and the efficacy of the insulation processing for moisture removal are evaluated through the results of insulation power-factor tests and insulation resistance tests. In substations and factory test floors, interference control circuits may be required to achieve the desired sensitivity at balance.
