## 2 Smart Grid Background
### Key Components of Smart Grid  
Recent SGs are very complex in structure, where various subsystems are interconnecting. An IoT-based smart grid might have a complex structure with various components such as ICT devices, power generation, transmission and substations, a distribution system, consumers, smart meters and AMIs, regional and central control centers, intelligent electronic devices (IEDs), protocol gateways, a remote terminal unit (RTU), a phasor measuring unit (PMU), SCADA, a tap changer, log services, human-to-machine interface (HMI), circuit breakers, protecting relays, and home appliances [24]. ICT (information and communication technology) devices in a smart grid include sensors, controllers, communication equipment, and computing systems that enable real-time data collection, transmission, and processing. These devices help to monitor system performance, predict failures, and enable the efficient control of the grid. Regional control centers (RCCs) and central control centers (CCC) are facilities where operators monitor and control grid operations. They use real-time data to ensure stability, handle emergency situations, and optimize power distribution across the grid. Intelligent electronic devices (IEDs) are smart devices used to monitor, protect, and control power system equipment, such as circuit breakers, transformers, and relays. They incorporate microprocessors to provide real-time data processing, protection, and automation. Protocol gateways facilitate  
Figure 2: Domains of smart grid—conceptual model [22]. communication between different devices and systems within the grid by translating various communication protocols. For example, they enable interoperability between legacy equipment and newer smart devices. Remote terminal units (RTUs) are devices that collect data from remote locations, such as substations or generation plants, and send it to a control center. They also receive commands from the control center to operate equipment like circuit breakers or switches. PMUs measure the electrical waves on an electricity grid to determine the health of the system. They track phase angle differences, which are key to understanding system stability and managing grid congestion. PMUs feed real-time data into the control center for analysis. Circuit breakers are safety devices that automatically disconnect a section of the grid if there is a fault, preventing damage to equipment and ensuring safety. Protective relays are devices that detect abnormal conditions, such as overcurrent or under-voltage, and initiate protective actions like tripping circuit breakers to isolate faults. Finally, home appliances in a smart grid context refer to consumer devices such as HVAC systems, lighting, and home automation systems [24]. The two most important components of a smart grid that are prone to cyber threats are the supervisory control and data acquisition (SCADA) and the advanced metering infrastructure (AMI). Supervisory Control and Data Acquisition (SCADA) functions as control systems for industrial process control and monitoring, including electric power grid, oil mining, nuclear facilities, traffic control systems, and water treatment systems. Because they run on isolated networks, traditional SCADA systems are less vulnerable to Internet threats. Due to this isolated nature, it is argued that the original SCADA was developed without any focus on security. Modern SCADA systems, on the other hand, have developed from isolated, relatively simple systems into complex, open, advanced systems that are linked to the Internet [25; 26; 27]. Modern SCADA systems come with many features that make them more complex and challenging to manage. Communication protocols, control logic, security, and user interfaces are a few of the new features. Since they use open access networks to maximize efficiency, these systems have been vulnerable to a variety of cyber threats.