Automatic resynchronisation of synchronous machines

The theme of the project was the development of a scheme to re-establish synchronism automatically in the contingency of a synchronous machine falling out-of-step while in operation. To establish the necessary criteria on which the proposed scheme for resynchronisation could be based, machine behaviour during asynchronous operation and the process of resynchronisation has been studied in detail. Rotors in common use are of two different types; laminated and solid. The two types produce different damping effects and both have been studied. All the studies have been performed on a general-purpose analogue computer. To study the two types of rotor, mathematical models have been developed. Each of these models is suitable for cylindrical or salient-pole construction. Results obtained on the analogue computer have been verified by comparison with results obtained on both actual large alternators and laboratory micro-machines. Auxiliary equipment can play a significant part during asynchronous operation and in the process of resynchronisation. The effects of various auxiliary equipment, different machine parameters and system conditions on out of-synchronous operation and resynchronisation, have been studied. Investigations have been made into the process of pulling--into-step from the state of steady asynchronous operation using an entirely different approach and the process is explained in simple physical terms. Based on the results obtained from various studies, a transistor relay, for the automatic resynchronisation of synchronous machines, using static relaying techniques is proposed. This relay has been constructed and its effectiveness has been demonstrated on a micro-machine. The proposed scheme for automatic resynchronisation is particularly adaptable to the controls of the future and is suited to 'on line' computer control.