## 1 Introduction  
Power generation from fossil fuels is one of the contributions factors to the global warming issue. Thus, various countries have launched power development policies to reduce fossil fuel utilisation. Renewable energy is important to rapidly increase the power system. Most private sectors develop the distributed generator (DG) to combine with the grid individually. Renewable sources of DG are connected to the grid, such as PV power, wind power, and biomass power, which are populated to complied on grid connections. The advantages of DG sizing placement [1] involve the characteristics of the voltage level, short circuit current magnitude, and power flow direction changing. Renewable DG placement can be supported in terms of the economic and lower effect on the environment [2]. However, each DG has been provided with the protection system which depends on the network configuration. Several DG technologies are connected to the grid, which differently impact the existing protection system. Thus, the provincial electricity authority (PEA) provides the grid connection code regulation notice that is used for applying all DG connections. However, DGs must be connected from the system in case of abnormal conditions such as short circuit occurrences as calling in \"islanding mode\". Therefore, these events cannot be controlled in case of fault in the distribution system. Nonetheless, when the fault situation occurs, the system energies the power back immediately, which cannot be interrupted for all power systems. In addition, the fault characteristics are of two types, i.e., permanent and temporary failures [3]. Various solutions are presented to the system by improving the protection scheme to prevent the malfunction of protective devices. The protective devices are installed on the system, which is used for monitoring and detecting the fault location or defected point. When a fault occurs in the system, the protective devices can be operatedon time due to a wrong relay coordination. Hence, the coordination between the protective devices must be performed by zone protection to increase the reliability of the distribution system. Therefore, protective coordination is divided into three main feature correlations such as current, timing, and both of current and timing. DG installation is impacted by and related to the impedance bus value [4; 5], when connected to the grid. Thus, the magnitude current value also increases, causing malfunction of protective devices as well. Simple protective devices are proposed and utilised on the radial distribution system, such as the overcurrent [6; 7; 8], reclosers [9; 10], and fuses [11; 12]. Losses of coordinated protective devices are concerned with the processes observed, such as loss of tripping, loss of action, and loss of trip command to another device [13; 14]. However, the protection characteristics are applied to the distribution system, in which the operation has to be correctly performed and perfectly functional as per the conceptual providing. For instance, the reliability, dependability, security, selectivity, and speedy functions of protective devices are used for reinforcement of the stability of a distribution system. Additionally, various protective coordination is proposed under different conditions to prevent the high-risk impact to the grid [15; 16]. The optimal coordinate of protective devices is proposed in cases between positive, negative, and zero sequences [17; 18] to comply and consider with overcurrent and voltage aspects in case DG connection to the grid. For this reason, the point of failure will be separated from the system correctly and accurately for saving and reducing the time to protect the device breakdown. The major impacts after DG connection to the grid are summarised on three critical points. For instance, the sensitivity problem concerns the power, selectivity, recloser, and islanding problems.