The Smart Grid is a large networked cyber-physical control system that is part of the critical infrastructure. This paper presents a cyber-physical attack against a substation where the attacker causes a transformer to overheat. The attack is modeled using a hybrid attack graph (HAG), which provides a means to model both the physical and cyber components of the attack. The HAG provides insight into potential attack vectors. Based on this information, key points in the system can be identified where security can be strengthened. Direction for future work to expand the capabilities of HAGs for modeling cyber-physical attacks is presented.