A Protective Method to Detect Short Circuit Fault on Distribution Line Applied to PV Power Generation Systems interconnected to the Grid with High Density

Abstract

In near future, it expects that PV systems will be interconnected to the utility distribution lines with high density. The PV systems are required to detect short circuit fault on the distribution line in order to prevent serious failure of the utility's protection device installed in the substation, caused by reduction of the fault current flowing at the substation. The establishment of proper detection method for the PV systems to detect the fault with high resistance in the high voltage distribution line has remained as an unresolved issue because PV systems cannot detect the fault by UVR recommended on the current guide line for grid interconnection. In the study, a new protection method to detect the fault for PV systems is designed by a numerical simulation. In the method, a new AND condition of voltage absolute value change and voltage phase change of the grid is adopted as a detective parameter for achieving enhancement of detective performance including the prevention of unnecessary detection in normal operation. Moreover, a new integration method of the voltage phase change is also devised to get high reliability of the detection under the high density interconnection to the grid. Simulation results indicate the number of detective PV system remarkably increases with the devised methods to improve the fault current flowing at substation in 20% to 40% as compared with conventional method. From above, applicability of the designed method to PV systems is confirmed.