Distance protection of a renewable energy plant in electric power distribution systems

This paper presents a scheme of distance protection for a renewable energy plant in electric power distribution systems. In many developing countries where renewable energy power plants are typically located in rural remote areas, they must be connected to weak power distribution systems inevitably. Although over-current relays are used to protect feeders at substations, fuses are only available elsewhere along feeder lines. To secure the system operation, distance protection is assigned to protect feeders. In this paper, distance relays are placed in the feeder along with over-current relays and fuses. Design of the distance protection of multi-source systems is described. This study considered the system consisting of a renewable energy plant. The power plant was a 6-MW unit of firmed power generation. The test feeder was simplified to be an equivalent four-bus test feeder for relaying purpose. Fault analysis in this paper was performed by using PowerWorld™ software. Obtained fault currents were used to establish protective zones of distance relays. In addition, this paper also compared the result of using distance protection with those of using directional over-current protection. As a result, protection of the power feeder with renewable power plants by using distance relaying can reduce complication in relay setting due to the impedance-based setting of the distance relay.