Coordinated and comprehensive protection scheme for the transitional period with increasing DG incorporation

This paper introduces the scheme for protection based on the needs of DG growth and automatic device control, which is to minimize fault duration, to prevent the DG damage by changing the substation grounding mode, configuration of protective device, the scheme for fixed value setting, automatic switch-on device and low-frequency low-voltage separation mode. Among them, the corresponding "Islands" operating scheme can maximize continuous power supply of Level I load. This scheme has solved the complex problems in the transition of DG from the character of pure "load" to the character of "Small Power Source by the change of the grounding mode and optimizing secondary protection system, under the circumstance of existing protective and automatic devices, by virtue of related technological means, to basically achieve safe operation of regional power grid after DG access.