## 4 Standards Enabling CPES
### Other Standards  
The IEC 61850 [62] standard was originally defined for the automation of legacy substations and distributed generators. The aim of IEC 61850 is the interoperability of electrical systems in substations of all types and brands [63]. By now, IEC 61850 (in combination with other standards, such as IEC 61499) has gained considerable importance for the implementation of smart grids [64; 65]. With an abstract, tree-like data model, as well as an abstract data interface, the standard enables the virtualization of physical components in the sense of CPES. To describe all objects, the XML-based Substation Configuration Language (SCL) is used. SCL is often found in electrical substation devices to perform an offline exchange of the configuration between tools. An OPC UA IEC 61850 Companion Specification [49] exists for mapping the data and object model into the address space of OPC UA without loss of semantics.  
The Common Information Model (CIM), standardized in IEC 61970/61968, is an energy-specific information model for objects and their relations in the context of energy supply [66]. The model considers numerous aspects, such as generation, transmission, maintenance, and asset management in its objects. Therefore, CIM can also be considered as large domain ontology, and is often used for simulation purposes. The exchange of messages is XML-based. For the exchange of the topology itself, CIM provides a serialization with the Resource Description Framework (RDF) [50]. CIM can be integrated into an OPC UA server by translating the UML descriptions into the OPC UA address space [67]. This combination is suitable for the description of complex CPES.  
AutomationML is a data format for the exchange of technical data between heterogeneous production systems. AutomationML enables the modeling of physical and logical plant components as a hierarchical structure of data objects. The description language thus follows an object-oriented paradigm. These objects contain information about plants and plant components, such as topology, interfaces, geometry, kinematics, logic, and behavior. AutomationML is standardized in IEC 62714 [68] and is based on IEC 62424 [69] (CAEX), and the open description language XML. These standards can be combined with OPC UA by applying the AutomationML Companion Specification for OPC UA [70], so the AutomationML data models can make use of the OPC UA functionality for data exchange, communication, and security. In addition, the data model can be used to specify the configuration of an OPC UA server in a standardized way and to make it exchangeable [71]. Other standards more related to smart grids can be found in the review studies [72; 73].  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt}} \hline \hline
**CPES Requirements** & **OPC UA Features** \\
**according to [4]** & The concept of OPC UA considers a migration, so not every component in the overall system has to be a CPES from the beginning, but it can be. \\
**(iv)** CPS-property of every component & As OPC UA is basically based on IP-based networks, it can adopt the scalability of this technology. The architecture provides unrestricted horizontal and vertical integration. \\
**(vi)** Complexity at multiple temporal and spatial scales & OPC UA cannot yet be used in time-sensitive networks (TSN), an extension of the standard is still in preparation. A spatial scaling is, however, problem-free. In addition, OPC UA also offers scalability of functionality owing to its flexible address space. \\ \hline \hline \end{tabular}
\end{table}
Table 2: _Cont._