A more insightful dimension of standard electrical field tests for transformer diagnostics

The Variable Frequency Power Factor (VFPF), Frequency Response of Stray Losses (FRSL), and Dynamic DC Winding Resistance tests are reviewed in this paper. These electrical field tests provide significant new diagnostic detail resulting in a more comprehensive assessment of the condition of a transformer. These tools are not radically different from three standard electrical tests that have been in use for decades in the industry. In fact, the test set up, connections, and test implementation requirements from a tester´s perspective are identical to those for the Power Factor, Leakage Reactance and DC Winding Resistance tests, respectively. The subject diagnostics have progressed from these traditional tests, gaining their unique, diagnostic prowess by simply expanding the related, standard test´s measurement(s) in the frequency or time domains. VFPF, FRSL, and Dynamic DC Winding Resistance tests do not displace these older diagnostic tools but rather supplement them, bringing considerable and, in the case of the VFPF test, disproportionately more value.