The smart grid as a large-scale system of systems has an exceptionally large surface exposed to cyber-attacks, including highly evolved and sophisticated threats such as Advanced Persistent Threats (APT) or Botnets. When addressing this situation the usual cyber security technologies are prerequisite, but not sufficient. The smart grid requires developing and deploying an extensive ICT infrastructure that supports significantly increased situational awareness and enables detailed and precise command and control. The paper presents one of the studies related to the development and deployment of the Situation Awareness Platform for the smart grid, namely the evaluation of open source Security Information and Event Management systems. These systems are the key components of the platform.