# Smart Grid Protection, Automation and Control: Challenges and Opportunities
## 4 Time Management and Synchronization
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**Aspect** & **Description** \\ \hline Atomic Clocks vs. Grandmaster Clocks (GMC) [60] & Atomic Clocks: The vibration of atoms, such as those of cesium or rubidium, can be harnessed to provide an exceptionally precise measure of time. These atoms are a standard component in a multitude of scientific and telecommunications applications. \\ GMC: Can use atomic technologies, high-quality crystal oscillators, or GPS to maintain network time accuracy. They act as the primary synchronization source in a network \\ \hline \hline \end{tabular} Standards: Synchronization must comply with IEEE 1588 v2 (Precision Time Protocol, PTP) for station bus and process bus environments, and with the data models specified in IEC 61850. Requirements: Support for SNMP MIB from Annex E of UNE-EN IEC 62439-3:2022, and automatic adjustments for daylight saving time changes.  
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Table 12: Technologies and considerations for time synchronization in electrical systems. \begin{table}
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**Synchronization Method [66]** & **Typical Accuracy** & **Description** & **Application** \\ \hline GPS & 10 ns & Synchronization based on the Global Navigation Satellite System (GNSS) with Coordinated Universal Time (UTC). Requires a hardware receiver and antenna. Generally used as a master time source. & High-precision synchronization for critical applications such as power utilities and telecommunications. \\ \hline PTP & 100 ns & High-precision time distribution protocol with error correction through boundary or transparent clocks. Supports multiple sources with Best Master Clock Algorithm (BMCA) and LAN or WAN switching. & Critical and time-sensitive applications such as sample values (SV) and synchrophasors. \\ \hline IRIG-B [67,68] & 1 us & Precise time distribution requiring local cabling. Generally sourced from GPS clocks. For Intelligent Electronic Devices (IEDs), the typical accuracy of IRIG-B time synchronization is as follows: - & Unmodulated IRIG-B (DC-level shift): \(\pm\)1 microsecond. This version is preferred in IEDs used in critical applications such as protection relays and automation systems, ensuring precise event logging and deterministic behavior, - & Less critical applications such as GOOSE, MMS, and supervisory data in utility substations. \\ \hline \multirow{7}{*}{NTP} & \multirow{2}{*}{200 μs (over LAN)} & \multirow{2}{*}{While less precise, this variant is sometimes used for compatibility with legacy equipment. Most modern IEDs adopt unmodulated IRIG-B to meet the stringent timing requirements of standards like IEC 61850, ensuring reliable event sequencing (SOE) and precise fault location through synchronized measurements. \\ \hline \hline \end{tabular}
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Table 13: Most common synchronization methods used in the field of electric utility automation. \begin{table}
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**Aspect** & **Description** \\ \hline Network Configuration & Ensure the network infrastructure, including switches and routers, supports PTP and is appropriately configured. \\ \hline Latency and jitter & Solutions that minimize latency and jitter are preferable. Enabling “latency-sensitive” features in the hypervisor can help reduce these issues. \\ \hline Consistency in the Environment & Ensure that all components in the virtualized environment are synchronized with the same time source to avoid time drift issues. \\ \hline Testing and Validation & Before deploying PTP in a production environment, it is crucial to test and validate the configuration to ensure the required level of precision. \\ \hline Round Trip Time (RTT) & Conduct RTT tests using GOOSE messages between synchronized \\ Testing & applications to verify the accuracy of synchronization. \\ \hline \hline \end{tabular}
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Table 14: Best practices and considerations for PTP.