Synchronous Machine Problems Requiring Step-by-Step Computations

  • Bernard Adkins
  • Ronald G. Harley


A synchronous generator connected to an infinite bus runs stably at synchronous speed and at a constant rotor angle if the mechanical input power from the prime mover exactly balances the generator losses and electrical output power, and if the conditions for steady-state stability are met. Any disturbance to the balance results in a change of speed and rotor angle. The generator is transiently stable only if after some temporary fluctuations the speed returns to synchronism and the rotor angle to a constant value. In the unstable condition the speed does not return to synchronism and the rotor angle consequently varies continuously. The calculation of the swing curve of rotor angle as a function of time, is therefore the prime objective of any transient stability study. This chapter studies the effect of a symmetrical three-phase short-circuit cleared after a short period of time. Although it occurs less often, the three-phase fault is particularly chosen since its effect is more severe than that of an unbalanced fault or any other disturbance.


Rotor Angle Synchronous Generator Synchronous Speed Common Reference Frame Synchronous Reference Frame 
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Copyright information

© B. Adkins and R. G. Harley 1975

Authors and Affiliations

  • Bernard Adkins
    • 1
  • Ronald G. Harley
    • 2
  1. 1.Imperial CollegeLondonUK
  2. 2.University of NatalDurbanSouth Africa

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