## 1 Introduction
### Basic Principles of the Smart Grid  
The basic electrical power system is a network that consists of the generation, transmission, and distribution of electrical power [2; 50; 51]. The electrical power system that supplies electrical power to the user (e.g., in industry and the home) in a large geographical area is termed an electric grid [51]. The basic smart grid system consists of four major domains, which were mentioned earlier in Section 1.1.1. Figure 2 illustrates the basic structure of the smart grid framework [3; 6; 52; 53]. The smart meter is integrated with the smart grid, which can provide intelligent functionalities such as bidirectional energy trading, decentralized power generation, energy redistribution, request coordination, etc., for the smart and uninterrupted power supply of each key enabler of the smart city [54]. Compared to the conventional power grid, the communication network is integrated with the smart grid architecture to provide different functionalities, such as effective energy redistribution and utilization, as well as price negotiation [15]. The smart grid communication network consists of four distinct kinds of networks (e.g., the Internet, the wide area network (WAN), the substation local area network (LAN), and the premises area network) [55]. By utilizing the various networks, all the major domains of the smart grid are interconnected and would also communicate with the market, operator office, and service provider to perform the functionalities of the smart grid [2; 3; 6; 50; 51; 52; 53]. Moreover, AI, the IoT, and CPS would also be integrated with smart grids to elevate the efficiency of the smart grid system with regard to monitoring, operation, and coordination/management purposes [56].  
The smart grid provides a number of efficient features in terms of power generation, supplies, distribution, and management, such as distribution automation, smart meters, distributed generation, renewable generation integration, automated and intelligent reviving systems, smart meter data coordination, secured communication, demand responses, reduced carbon emissions, the field area network (FAN), etc. These features would provide uninterrupted and effective power supply for the different applications of smart cities [57]. In addition, among the different applications of the smart grid in terms of communication, the crucial applications would be massive wireless connectivity for a huge number of devices (e.g., UAVs, robots, sensors, and IoT devices) and monitoring, the performance of secure communication for resource management and operation, and also the pursuit of real-time monitoring [52; 53]. UAVs and robots are usually utilized for fault detection in transmission lines [52; 53]. It is also difficult to maintain secured communication for operation and resource management, and also to perform time-critical or real-time operations of smart grids in the case of critical situations such as power outages, fault detection, island detection, etc. [58]. The technology of 6G is a suitable communication solution for fulfilling all of the smart grid communication network demands. The basic outline and fundamentals of 6G wireless communication are described in Section 1.3.