The stability limit curves in the R-Xc parameteric plane have been determined for EHV lines with series-compensation raking into consideration the nondeterministic nature of the generating system, mechanical system, and transmission system parameters. Studies have shown that the effect of random system parameters is to increase the area of the unstable zone in the parametric plane. First, the border line between the stable and unstable zones has been determined considering a deterministic model of the system. The value of the critical frequency at which the self-excited oscillations including the effect of hunting are set up and the system critical resistance necessary to damp out the oscillations are obtained using a modified D-partition technique. The modification involves the determination of the critical frequency by the Newton method. The nature of the random system parameters is then considered using the results of the deterministic study to calculate the variances of the critical frequency and resistance, and the stability limit curves.