This research presents a methodology for the creation of a novel computational algorithm, which allowed the automation of the simulation activities associated to the determination of critical times of fault clearance in the Peruvian National Interconnected System. For its development, interesting iterative stability analyzes were carried out and Ward reductions were introduced to the network model of the Peruvian electrical system. The above, in order to obtain adequate processing times, in such a way that this algorithm was applicable to the analysis of planning and operation of the power system. The secondary arc model has been developed using MODELS in ATP, which brings together the strengths of the main existing models and implements a pseudorandom variation of the secondary arc length, in order to provide accurate results for the determination of extinction times of Secondary arch in studies of monopolar reclosures. The approach of the developed model also proposes a methodology in which the extinction times are obtained as the result of a statistical simulation. The comparison of the proposed model with cases of studies of the double circuit line 500 kV with satisfactory results was carried out.