# Smart Grid Protection, Automation and Control: Challenges and Opportunities
## 3 Evolution of Substation Architectures and Digital Modernizations for Smart Substations
### Migration from Conventional to Digital Substations  
Migration from conventional substations to digital substations represents a big transformation in electrical infrastructure [40]. The challenges of conventional substations are shown in Table 4, summarizing the main drawbacks of conventional substations. \begin{table}
\begin{tabular}{c c} \hline \hline
**Aspect** & **Drawbacks** \\ \hline \multirow{3}{*}{Hardwiring} & Copper wiring not supervised \\  & High costs of hardwiring CT/VTs \\  & Long installation and manual testing \\ \hline \multirow{3}{*}{Control Panels} & Conventional protection relays \\  & Different relays for different functions \\ \cline{1-1}  & The low-impedance busbar 87B requires additional secondary windings \\ \cline{1-1}  & on CTs \\ \cline{1-1}  & Lower flexibility: new function requires a new relay \\ \cline{1-1}  & High costs for construction of the panels \\ \hline \multirow{3}{*}{Substation} & High costs for the protection and control room inside the substation \\ \cline{1-1}  & Separate panels for gateways and local SCADA \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Main issues associated with traditional substations. \begin{table}
\begin{tabular}{l l l l l l l l} \hline \hline
**Characteristic** & **SIFROTEC 7 SX85** & **MULTLIN B90** & **MICOM Agile F747** & **Easergy MiCOM P0** & **SEL-487E** & **ABB SSC600** \\ \hline \multirow{3}{*}{Brand} & \multirow{3}{*}{SIEMENS} & \multirow{3}{*}{GE} & \multirow{3}{*}{GE} & \multicolumn{3}{c}{SCHENDER} & \multirow{3}{*}{SEL} & \multirow{3}{*}{ABB} \\  & & & & ELECTRIC & & & \\ \hline \multirow{3}{*}{Protection} & Feeders, lines, transformers, motors, generators, capacitor & Low-impedance & \multirow{3}{*}{Busbars} & Lines, transformers, generators, busbars & Transformers, feeders & Lines, transformers, busbars, generators \\  & & & & & & & \\ \hline \multirow{3}{*}{Control and Automation} & \multirow{3}{*}{Yes} & \multirow{3}{*}{Yes}  
A conventional substation is burdened with several disadvantages, such as a shortage of supervision, high installation and maintenance expenses, and a lack of flexibility. Standardization through the introduction of digital technologies and standards such as IEC 61850 holds the key to overcoming most of these drawbacks, and provides a boost toward operational efficiency, security, and flexibility to meet future demands. Conventional protection relays can only provide a very basic level of protection by acting on preset settings and thresholds. Their principle of operation is the invasion of these threshold values. Central protection systems with high computing capabilities can offer sophisticated concepts, which continuously monitor the network for aberrant conditions and disturbances. Real-time data analysis, along with advanced algorithms, provides proactive and adaptive protection guarantees for a higher degree of reliability and efficiency, in line with IEC/IEEE standards [41; 42]. The digitalization of a substation, in simple words, encompasses critical steps that range from conventional architecture to a completely digital AI-powered infrastructure. The road ahead from the existing scenario of conventional substations to a fully digital AI-powered substation is presented in Table 5. This holistic strategy discusses the shortcomings of the present conventional substations and probes for the latest digital technologies to develop an electrical infrastructure that would be more efficient, flexible, and future-friendly. Presently, the commercially available models of the SSC600 from ABB have the capacity for recording anomalies, which they have had since firmware version 1.4. [37]. Table 6 summarizes the benefits, risks, challenges, and research directions of integrating Software-Defined Networks (SDN) and Programmable Data Planes (PDP) into IEC 61850 substations, focusing on network management, security, and automation. Ad