Validated techniques for modeling shell-form EHV transformers

An EHV (extremely high voltage) shelf-form autotransformer has been thoroughly instrumented and tested for frequency response and step response. The results have been used to develop and validate computer models for predicting the transient behavior of transformers at the design stage. The models are based on relatively simple constant-parameter circuit models. The procedures have been applied to other shell-form EHV transformers with similar results: the dominant response in the 8 to 20 kHz range is easily reproduced, while the model sometimes produces some spurious higher-frequency oscillations. The discrepancies may be a limitation imposed by the constant-parameter circuit model and can frequently be eliminated by lumping two or three coils together. A streamlined, user-friendly impulse calculation program has been developed for a PC, yielding execution times acceptable for the design environment.>