Subharmonic Oscillations in Power Systems-Theory and Practice

This work makes a comprehensive single phase study of the most commonly observed subharmonic oscillation, that is the one- third order subharmonic. The theoretical methods employed may be extended to other subharmonic frequencies and also to combinations of subharmonics. A theory is developed to enable the calculation of the existence region for all practical cases concerned with static magnetic circuits. Further, in a detailed comparison of the theoretical results of all commonly used static magnetic circuits with the results obtained in experimental studies using a specially designed Transient Network Analyser, TNA, differences of less than 5% in every case were recorded. This TNA includes a new method of simulation of the power transformer and its associated nonlinearities, and an outline of the method of representation is given.