E. Chiodo et D. Lauria, TRANSIENT STABILITY EVALUATION OF MULTIMACHINE POWER-SYSTEMS - A PROBABILISTIC APPROACH BASED UPON THE EXTENDED EQUAL-AREA CRITERION, IEE proceedings. Generation, transmission and distribution, 141(6), 1994, pp. 545-553
The probabilistic aspects of transient stability evaluation of electri
cal power systems are discussed. The stability properties of the syste
m after a given fault are characterised by means of the instability pr
obability, which is defined in terms of the critical clearing time and
the fault clearing time. Particular attention is devoted to the proba
bilistic description of the load demand, characterised by a random vec
tor, and its effect on the critical clearing time. The instability pro
bability is evaluated by using an analytical approach, already proved
satisfactory in the single-machine case, as shown in a previous paper
by the authors. The method is illustrated with reference to a simple s
ystem: the critical clearing time is calculated, for each value of the
random inputs, by means of the extended equal area criterion. Its pro
bability distribution is then evaluated, by means of a regression tech
nique, in terms of the load demand distribution. Such distribution is
then used to calculate the instability probability as a function of th
e basic statistical parameters of the system. The proposed method allo
ws a straight-forward analytical determination of the influence of the
system parameters on the instability probability. A peculiar aspect r
egarding a multinode system, which is also analysed in the paper, is t
he effect of the statistical correlation among the loads on the stabil
ity.