Study of Transient Stability of A divided Rotor Synchronous Machine

Abstract

Instability in long transmission lines especially when on light load constitutes a major obstacle which prevents the most efficient and eccentric utlisation of the system. Previous investigations have proved the usefulness of adopting the divided winding rotor for improving the system stability under different operating conditions. The work conducted in this project, dealt with a lightly loaded alternator with leading paver factor relative to the busbar voltage This operating condition is the main difficulty in system stability involving long transmission lines. The disturbance considered is a symmetrical 3-Phase short circuit applied about the middle of the transmission line. The work consisted of two parts: 1) an analytical solution in which an exact solution of the generalised equations of the alternator using RungeKutta fourth order integration method is obtained and 2) an experimental part in which the effect of injected voltages in the D- and Q field windings separately or simultaneously are tested, Also the improvement produced by the use of some practical angle and voltage regulators is examined. It was shown, clearly that the two winding excitation system will give smaller swings compared with a one field excitation system for the same loading conditions and the same fault duration. This means that the true winding alternator will stand greater fault duration before synchronism is lost.