Corona Location in Transformers by Radio Frequency Spectrum Analysis, Part I: Theory

After discussing transformer types, ¿values, and location of voltage generators in capacitive ladder networks and equivalent transmission lines, a new electrical technique for locating transformer partial discharges or corona is described. It is based on the measurement of the radio frequency spectra at the transformer terminals. Provided the transforner winding can be approximated to a uniform transmission line for the frequency range considered, the method is shown to be theoretically sound. Measurements on model networks and actual transformers suggest that, at least over certain frequency ranges, the winding can be regarded as a uniform transmission line. Apart from locating corona, the method provides a quick and accurate means of measuring actual transformer ¿values.