No abstract

Distribution networks are usually protected by directional overcurrent relays (DOCRs). Besides, autoreclosers and fuses can be used for protecting lateral feeders to minimize power cuts. Coordinated operation of protection device must be maintained to ensure optimal fault isolation. Typically, steady-state fault current and static protective device characteristics are used to determine optimal settings of devices such that coordinated operation is verified. Sine fault current is not a steady signal and protection devices have dynamic behaviors, the conventionally-determined settings of devices can lead to loss of coordination jeopardizing system reliability. In this paper, a two-layer protection scheme is proposed for a distribution network with distributed generators (DGs). The first layer has DOCRs to protect main feeders. The second has autoreclosers and fuses to protect lateral feeders. Optimal settings of devices are determined to achieve both local-layer and inter-layer coordination of devices by constrained nonlinear optimization. Full dynamic models of every component and transient data of fault current are considered. Furthermore, to sustain coordination under DGs, a hybrid superconducting fault current limiter (HSFCL) with high temperature superconducting resistive element is connected in series to each DG. Dynamic modeling-based HSFCL cost minimization is searched by multi-objective optimization. The approach is applied to two distribution networks and simulation results are analyzed.

the desire of the consumers for a cheap and reliable energy source in comparison to the large generators, DGs penetration increased as they have smaller capacities, cheap operating costs, low environmental pollution, high efficiency, voltage profile improvement, and enhance the capacity of the electrical grid [1,2].Despite the huge benefits gained from the penetration of DGs, the large penetration leads to conflicts in the protection system of distribution systems as the design of distribution networks is a radial network, and penetration of DGs changes the nature of the network [2].The protection system in the distribution network contains different types of protection devices such as overcurrent relays, and a combination of fuses, and reclosers. These devices are configured in the distribution network as the overcurrent relay is suited at the distribution system substations, reclosers are installed on main feeders, and fuses