# Smart Grid Protection, Automation and Control: Challenges and Opportunities
## 3 Evolution of Substation Architectures and Digital Modernizations for Smart Substations
### Virtualization of Protection, Automation and Control (VPAC)
Generally, one of the goals includes assigning functionality in a flexible way according to the system requirements, avoiding traditional relay approaches, and making the choice for LD at the station level, which will provide engineering more efficiently adapted to the current technologies. The detailed overview of the architecture of the application in a virtualized substation environment is given in Table 8 below. Classical relay-based protection systems have disadvantages, such as hardware failure due to aging infrastructure or environmental causes. The complexity of these often leads to misconfigurations during installation or maintenance that affect system reliability. Most such systems also suffer from insufficient redundancy, slow response times, and limited interoperability between devices from different manufacturers. CPAC and VPAC system solutions have their own sets of associated risks. In a CPAC system, the centralization of protection functionality creates a problem whereby one single point of failure may affect an entire substation. In VPAC systems, the presence of software and virtualization introduces risks such as software vulnerabilities and performance degradation due to virtualization overhead. \begin{table}
\begin{tabular}{c c} \hline \hline
**Infrastructure** & **Description** \\ \hline Data and & IEC 61850: It is an international standard that defines data models and communication services for substation automation, ensuring seamless interoperability among devices from different manufacturers. \\ \hline Software Virtualization & Software and hardware decoupling: It allows applications to run in virtual environments independent of physical hardware. \\ \multirow{2}{*}{Resource Allocation and} & Virtual Machines (VMs) and containers: Applications can run in VMs or containers, virtualizing different operating system layers. \\ \hline \multirow{4}{*}{Resource Allocation and} & CPU and memory: Exclusive CPU core and memory bandwidth allocation policies for critical applications. \\ \cline{1-1}  & Cache and memory partitioning: Minimizes interference between applications through cache partitioning and the exclusive reservation of memory bandwidth. \\ \hline \multirow{2}{*}{System Interoperability and Efficiency} & Avoiding the duplication of inherited relay logic: Simplify control logic and efficiently distribute functionality. \\ \cline{1-1}  & Adaptability and scalability: Facilitates integration of new technologies and adaptation to changes in the electrical grid. \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Summary of the architecture of applications in virtualized medium-voltage substations. CPAC and VPAC systems depend on communication networks, whereby failures or delays can impact synchronization and protection response times. A proper redundancy setup is crucial to prevent system-wide failures. Enhancing redundancy, strict software management, advanced monitoring, and strong network design are necessary. Modular architectures allow scalability, upgrades, and improved cybersecurity. Regular testing and simulations ensure system reliability and efficiency. Table 9 outlines key differences and considerations between traditional protection, CPAC, and VPAC systems.