Protection relay coordination for microgrids

With the increase in demand for renewable energy sources, a large number of distributed generators (DG) have been connected to electrical grids. Since the increase in the use of DGs causes problems in traditional electrical grids, microgrids are preferred. Microgrids help the grids work more efficiently by coordinating DGs and loads. There are critical differences between the DGs that are used in microgrids, and the generators that are used in traditional grids. Generally, DGs are inverter based and unable to produce vast amounts of fault current when a fault occurs in the grid. In addition, due to their relatively low energy generating capacities, they are more affected by the changes that occur regarding the supply and demand balance in the grid. Since current-based protection functions which are used in traditional grids may remain ineffective in microgrids, different protection functions are developed for microgrids. In this study, a traveling wave-based fault location detection system for looped microgrids was developed. In traveling wave-based fault location detection, measurements that are taken from one or both ends of the line are used. However, there is no beginning or end of the lines in looped grids. To allow the use of traveling wave-based protection in loop distribution systems, the system is separated into three zones. To each three separate zone a type D fault locator method was applied, and by ensuring that these algorithms worked in accordance, fault location detection was carried out in a looped microgrid. After the detection of fault location, the protection algorithm isolates the fault and sends a "power on" command to related switches and thus leaves the fault without energy. The developed protection function is tested in Matlab/Simulink setting. In the performed tests it was determined that the fault location could be detected with an error rate of 46.39 meters. After the fault location was detected, a "power on" command was sent to the related switches to ensure that the fault was left without energy.