Organization of the numerical-field calculations of electromagnetic processes in a turbogenerator at its asymmetrical loading

Представлены принципы подготовки расчетной модели турбогенератора (ТГ) для численно-полевого анализа электромагнитных процессов в нем при несимметричной нагрузке. Исходя из стандартных ограничений такой эксплуатации ТГ, с использованием метода симметричных составляющих, получаются токи его обмоток вместе с их фазовыми соотношениями. Анализируются временные дискретные функции электромагнитных величин ТГ, которые получаются многопозиционными расчетами вращающихся магнитных полей. В качестве примера проведена оценка фазных ЭДС, напряжений, мощностей и других величин при несимметричной нагрузке ТГ мощностью 35 МВт.Design and presentation of the method of organization of the numerical-field calculations of the electromagnetic processes at asymmetry of turbo-generators load. Preparation of the calculation model of turbo-generator is based on the method of symmetric constituents. Values and the phase relationship of the currents of their windings are obtained within the limits of the existing standard constraints. The temporal functions of the electromagnetic quantities are derived in a discrete form by the multi-position calculations of the rotating magnetic fields. A harmonic analysis is applied to these functions. The calculations for testing of the presented method are performed on a three-phase 35 MW turbo-generator by during its work under autonomous unbalanced loading. The example of analysis of phase EMFs, tensions, powers and other quantities are presented in that load. The basis of this are the temporal functions of the magnetic flux linkage of phase windings which are expanded to the harmonic series. The novelty of the results is achieved by a combination of the new features of the numerical methods for the calculation of magnetic fields, high-performance computers and effective software. Problems of exploitation of turbo-generators under unbalanced loading are detected by the consideration of their electromagnetic system as a whole, and not their simplified local parts as usual. It is shown that the temporal functions of the magnetic flux linkage and EMF of phase stator windings under unbalanced loading significantly differ in shape from sine waves and from each other and contain a number of significant upper harmonics. Analysis of the turbo-generator work under unbalanced loading showed the "top" level of problems of electromagnetic character although excluding reaction of eddy and contour currents of the rotor core. Adequate such reaction which effectively transports these problems on the above currents occurs to their "smoothing" to an acceptable level. They are also a serious problem of turbo-generator exploitation under unbalanced loading and require a depth study. All this allows us to provide for measures to ensure a durable and reliable operation of turbo-generators