The utility domain is facing new problems in both transmission and distribution systems.Better reliability and more efficiency of the overall systems is one of the main goals of thesmart grid. The smart grid incorporates a lot of stakeholders, it has to deal with a very highcomplexity of the system, it should facilitate a whole industry transition, it brings up newsecurity and safety issues and it has to be an enabler for a consensus on standards as well astheir development and support. Technically, there are many challenges in terms of smartequipment, communication systems, data management, cyber security, information and dataprivacy and new software applications. In our research activities Semantic Web Technologiesare emphasized as an appropriate solution to face the beforehand mentioned challenges. Inthis contribution, we present three different use cases concerning the issues interoperability,security and communication as follows.In the context of our interoperability use cases, we particularly model IEC TC 57 Standards asontologies and develop ontology alignments in order to harmonize the data quality codesaccording to IEC 62361.The security use case deals with creating an overall security management ontology, byconnecting three different ontology parts (i) domain specific data models (ii) non-functionalrequirements and (iii) security concepts. The overall ontology provides important informationwhich can allow users to gain additional information by allowing search and reasoningfacilities.In the communication use case it is essential to have a common basis for semantics and syntaxprovided by a domain specific ontology. Thus, the Common Information Model (CIM, IEC61970/61968) should be the basis for all communication processes on the different layersusing semantic web services. Focusing on the power infrastructure communication the OPCUA (IEC 62541) is the choice.