Misoperation and hidden failures of protections in electric power systems have been recognized as a contributing factor to power system cascading outages and catastrophic events. For that reason, it is important to develop new tools to study the sequence of the operation of protections given a contingency in the system. This paper proposes a methodology for modeling the operating sequences of protections in the IEEE 493 system and a meshed transmission system using generalized stochastic petri nets (GSPNs), contemplating main and back-up protections, and specially how they interact.