Off-Grid Microgrid Protection Based on the Combination of Current and Temperature Measurement

There is a large difference in the fault current between the grid-connected operation and the island operation of the microgrid. When operating off-grid, the fault current of new energy sources does not increase significantly. Therefore, the protection based on current amplitude calculation in the traditional distribution network is an incorrect action risk. To solve this problem, an off-grid microgrid cable fault identification method based on the combination of distributed optical fiber temperature measurement and current measurement is proposed, which can accurately determine the fault area. Based on the characteristics of the temperature change caused by the accumulation of fault current on the time scale after the cable insulation is damaged, this paper uses distributed optical fiber temperature measurement technology to sense the relationship between temperature and distance to determine the location of the fault. In order to solve the problem of the small fault current of the distributed power supply, it is difficult to form with the load current. For problems with obvious differences, the mapping relationship between current and temperature is used to judge the fault, and the method of combining electrical and non-electrical quantities is adopted to avoid the risk of incorrect fault judgment under weak fault characteristics in a single electrical or non-electrical measurement method. Finally, the effectiveness of the method is verified by the simulation current data of PSCAD and the COMSOL temperature field modeling simulation results.