This paper proposes an Intelligent Protection System for a power transmission network which is based on three principal ideas: A Multi-Agent System, a high performance communications network parallel to the transmission network, and a hierarchical control scheme. It also proposes a Colored Petri Net model of the Intelligent Protection System that represents main system agents (i.e. from protection and transmission systems) and their interaction. The model illustrates the Intelligent Protection System operation by simulating its response to line faults.