With the topic of Smart Grids taking up momentum, challenges to integrate systems from various vendors’ at large scale in a critical infrastructure have arisen. This issue is usually tackled utilizing standards and, therefore, agreements between the various parties. However, the aspect of the interoperability between systems is not only defined by physical connections, but has a multi-faceted dimension which needs to be dealt with at all layers in order for a semantic and cost-efficient integration. Within this contribution, we motivate the need for a procedural way to deal with interoperability in Smart Grids, show the theoretical foundations and the approach taken and present case studies that cover the problem in scope. Based on these case studies, results are critically reflected and conclusions are drawn.