Calculation of Maximum DG's Capacity According to their Location for Remaining the Protection Coordination in Distribution Networks

Traditional electric distribution systems are radial in nature. These networks are protected by very simple protection devices such as over-current relays, fuses, and reclosers. Recent trends in distributed generation (DG) and its useful advantages perfectly can be achieved while the relevant concerns are deliberately taken into account. For example, penetration of DG disturbs the radial nature of conventional distribution networks. Therefore, protection coordination will be changed in some cases, and in some other cases it will be lost. In this paper, a new approach is presented for determining the maximum capacity of DG for maintaining the coordination of distribution system's protection devices. In the suggested approach, the contribution of DGs in fault current is limited through considering mathematical equations of characteristics of protection devices. All steps from the beginning to the end were implemented on a simple distribution network using MATLAB and DIgSILENT Power Factory and finally the numerical results are presented in order to confirm the authenticity of suggested approach.