LINEAR, LUMPED, PARAMETER TRANSFORMER MODEL-REDUCTION TECHNIQUE

The behavior of large power transformers under transient conditions is of significant interest to both transformer designers and power syste m engineers [1]. The designer employs computer programs to construct d etailed electrical models enabling him to compute the transformer's in ternal transient voltage distribution. Using this information, and var ious other tools, the design engineer can develop a reliable and cost effective insulation structure; The power engineer requires a reduced model that accurately represents the transformer's behavior to investi gate the effects of power system transients. Reduced models are genera lly obtained either from detailed design models, or from measurements on fully constructed transformers. The later technique has the major d isadvantage that in the absence of an expensive prototype design, impr ovements cannot be made. Presently, both methods are subject to varyin g degrees of error. This paper presents a reduction technique that sta rts with the linear, detailed design model, and provides a reduced. mo del of any specified size, while retaining the same computational accu racy as the original model. The method is mathematically exact, relati vely straight-forward and compatible with time domain transient analys is programs. Application of the technique to the detailed model of a 7 65/345/34.5 kV, 500 MVA single phase autotransformer is provided.