Analysis of small disturbances of transmission lines in dynamic stability studies

The inherent small-magnitude fluctuations of transmission line parameters, often attributed to the cause of an unstable and oscillatory behaviour of electric power systems, which operate in unfaulted and normal states under moderate load conditions, are investigated. Due to the limited nature of the deterministic theory to describe the dynamics of a large-scale power system, a stochastic theory is presented. On the basis of recent mathematical studies of stochastic processes, a performance index is derived to measure the small-disturbance stability limits of the system. The viability of this performance index is tested on a power system model.