## 1 Introduction  
The Smart Grid exhibits a high complexity regarding organisational and technological issues. The key challenge of the Smart Grid is integration, which in turns affects all the components, systems, applications and information involved. Telecommunications play an important role for the realisation of the smart grid, since they enable data exchange between components. There is a plethora of telecommunication technologies that can be utilized for the smart grid depending on the application, either wireless or wired [1; 2]. In general, there are three main domains of applications for the smart grid network: the High Voltage (HV) network used for the electricity transmission, the Medium Voltage (MV) network used for the electricity distribution and the Low Voltage (LV) network used to provide electricity to end-users [3]. In addition, functionalities and interfaces should enable interaction so as to execute all the necessary processes within the system. Thus interoperability is an essential requirement for the Smart Grid interoperability, a technical imperative, and the enabler of an open market where innovation can flourish. Interoperability refers to the ability of two or more devices from the same vendor, or different vendors, to exchange information and use that information for correct co-operation [4]. As stated by the CEN-CENELEC-ETSI Smart Grid Coordination Group (SG-CG) [5], this definition is extended to \"The ability of two or more networks, systems, devices, applications, or components to interwork, to exchange and use information in order to perform required functions.\" In addition, \"Interoperability between systems in a smart grid must be considered and well specified in use cases, in order to develop interoperable Smart Grid systems by design. Use cases provide a basis for the specification of functional requirements, non-functional requirements, Test Cases (TC) and test profiles\". A framework that has been used for Interoperability purposes is the Smart Grid Architecture Model SGAM model, which stands for \"Smart Grid Architecture Model\" and is the main outcome of Reference Architecture working group mandated by the EU's 490 Mandate [6] entitled \"Smart Grid Mandate-Standardization Mandate to European Standardization Organizations (ESOs) to support European Smart Grid deployment\". Based on the SGAM framework there are five different layers of interoperability:  
* Business layer which represents the business view on the information (business models, market structures, business portfolios etc.) * Functional layer specifying the functions and services
* Information layer which is the data model to be used to ensure a common understanding of the data exchanged
* Communication layer which is the communication technology (e.g., PLC or Ethernet) and the communication protocol for data transmission
* Component layer which is the hardware to connect systems or devices such as power cables (physical distribution)  
This means that all interactions (i.e., physical, information-based and process-based) should satisfy the interoperability principle. This includes the field level (e.g., substation automation, distribution automation, distributed energy resources), to remote operations (e.g., remote grids management), market management, service management, customer management, etc. A major challenge for interoperability is the integration across domains. Figure 1 presents the SGAM model with the mapping of different types of interoperability. The additions made clarify the field regarding the different types of interoperability available and their connection to different interoperability layers. Figure 1: SGAM model and Interoperability Types, as extracted by reference [7]. There have been several attempts in the literature to address the issue of interoperability on the smart grid. Interoperability for digital substation devices and the information exchange among them is the topic of reference [8]. In particular, they assess the interoperability between such devices which use the IEC 61850 standard.