The work aims at developing a new stability approach used to cany out
transient stability studies of a rnultimachine power system when the generator
int~rnsl voltage components E' and E' d are changing with the time. Consider‌ing the generator mechanical damping and the generator control systems ( that
is, the vol~dge regulator and speed governor), each generator is represented by
a 6th-order dynamic model, then the mathenlatical model of the whole system
is derived. Applying the decomposition-aggresdion method, the system is de‌composed by using the triple-wise decomposition. Then avector Lyapunov
function is constructed and used for aggregating the system. An aggregation
matrix is obtained. the stability of which implies asymptotic stability of the sy‌stem equilibrium state.
As an iiiustsative example, the developed stability approach is used to ca-
1ry out transient stability studies of a i'machine, 14-bus power system assumi‌ng a %phase short c~rcnit (with successfill reclosure) near a generator,or a load,
bus. The faulted line is tripped out for clearing the fault. An estimate for the sy‌stem asymptotic stability dom& is determined and used to determine directly
the critical time for reconnectin? the isolated Ime. It is found that the proposed