Transient stability angular increment computer

DETERMINATION of the transient-stability limit of a power system requires expressing the rotor angle of each machine or group of machines in the system as a function of time following the initial disturbance. This problem has been solved using miniature dynamic systems, digital computers, and differential analyzers. The latter two methods require a-c network analyzer measurements of the transfer impedances and prefault conditions. Other methods use special-purpose synchronous machine analogues coupled to the a-c network analyzer to represent power system behavior on an expanded time scale. Transient swings following a disturbance are then automatically determined. Such equipment is expensive and does not integrate readily into existing analyzer installations. At present most multimachine transient-stability problems are solved on a-c network analyzers using the step-by-step method.