No abstract

No abstract

A number of computer models have been recently proposed for simulation of the impulse voltage distribution in the winding of power transformers. Some of these models can predict the winding behavior at high frequencies, some other were developed as a practical tool for designers of lower voltage transformers. The time and expenditure put in development of these models shall be balanced by a similar effort to check the model validity. Such check consists in comparison of the predicted voltages to the actually measured ones.With the advent of high resolution, fast digital recorders and signal processing techniques, this validation can be performed to a much higher accuracy and completeness than the conventional comparison of analog oscillograms to simulated graphs. The paper presents such validation technique applied to a computer model of transformer winding.Problem.An accurate simulation of the transient voltage distribution in HV windings of a large power transformer allows the designer to apply a sufficient insulation in the areas of high stress, and at the same time reduce an excessive insulation of the wires and discs, in order to make the transformer more competitive. A practical importance of a reliable simulation of the winding characteristics has been long recognized by manufacturers of large and expensive transformers. They have found that the savings on an optimized insulation represent a significant amount of money These savings project on the overall cost of a transformer, and often decide on the choice of supplier With the increasingly competitive market, the importance of simulation has also been noticed by makers of medium size and smaller transformers. In general, they do not have a sufficient engineering and research staff to develop and implement the computer model required for simulation of the dielectric stress in the insulating system. However, they would like to use a commercially available program that has been proved in industrial applications.In addition, the very fast transients appearing in the SF6 insulated bus bar add to the complexity of the model that shall take into account the natural winding resonances occurring in the megahertz frequency range This situation has created demand for a computer model of power transformer HV windings applicable at manufacturing and repair facilities of lower voltage transformers, as well as for a highly specialized model that can simulate the winding behaviour up to say 1 MHZ. Several research centers and universities have recently reported progress in development of such scientific tools, or even announced the final product [l to 31. It may be taken for granted that the highly specialized knowledge of the authors of these models warrants the accuracy and practical usehlness of these models.. WM 148-7 PWRDA paper recommended and approved by the IEEE Power System Instrumentation & Measurements Committee of the IEEE Power Engineering Society for presentation at the IEEE/PES 1994 Winter Meeting,However, it should be recognized that an actual HV winding...

No abstract

No abstract