Utility companies worldwide are facing a multitude of new challenges, which can not be met with the historically grown, monolithic IT systems currently in use. Service oriented architectures are heavily used to integrate heterogeneous systems. One key aspect of this integration is the use of a common language, such as the Common Information Model (CIM). Important use cases are exchange of topologies and storage of topology histories. This paper describes the development and implementation of CIM Topology Store (CTS). CTS introduces new difference models for CIM/XML-serialized topologies.