Dynamic-response analysis of interconnected synchronousߝasynchronous-machine groups. Computer correlation studies with site-test results

Prior to instrumented site tests being carried out on a group of power-station auxiliary motors, computer studies of the site-test conditions were undertaken, and the paper reports the analytical methods developed for the pretest dynamic analyses, together with the correlation achieved between site-test and computed results. For the purposes of the tests, the motors were isolated from the turbogenerator for which they normally function as auxiliaries, and supplied from a neighbouring power station. To assess their recovery to, or divergence from, steady running conditions subsequent to disturbances in the system from which they are supplied, controlled-duration faults were applied at the power station supplying the induction-motor group. In the pretest analyses, 12 subgroups, of a total of 23 motors tested, were independently represented, as was the trubogenerator unit at the neighbouring unit at the neighbouring power station. Central to the analysis is Kron´s concept of a synchronously rotating frame of reference, into which the equations of all machines in the group are transformed. It is shown, in the paper, that, after transformation, the machine equations may be arranged in a form particularly suitable for multimachine-system analysis by computer. The overall method of analysis is developed in detail, and its validity is checked by comparisons, made in the paper, of site-test recordings of the principal machine variables, and solutions obtained for them in the pretest computer studies.