A novel approach to reliable determination of surge armature current of a synchronous machine

Abstract

Calculation of a short circuit current of a symmetrical fault in a high-power synchronous machine in accordance with national standards is time-consuming and imprecise. The process involves multiple graphic operations and a triple transition from an analog transient process to its discrete form and back. As a result, optimizing procedures cannot be applied to transient identification techniques that meet national standards and it is impossible to compensate for random factors in the identification process. Therefore, a surge current derived from experimental data is not adequate for transients in high-power synchronous machines. Modern equipment for recording of short-term transients solves many processing problems. Express determination of a surge current is obtained using a digital waveform recorder, which allows precise calculation of 50-Hz peaks and discrete representation of the 100-Hz component of the transients. This method of information extraction and processing replaces all the time-consuming graphic operations of the national standards. Results of a study of a 110-MW synchronous machine based on laboratory tests for various stator voltages are presented. The study has confirmed the viability of the proposed approach for express determination of a surge current without the need to determine the parameters of transients.