Study on Last Break Trip Fault of Inverter Station in ±800 kV UHVDC Project From Yunnan to Guangdong

The last breaker trip of inverter station, i.e., the load shedding of AC system at inversion side, will lead to severe over-voltage at converter bus and equipments in DC side, so it is one of the major faults to be considered in the research on DC over-voltage and insulation coordination. By means of simulation, the authors research the over-voltage level at AC and DC sides of converter station as well as arrestor operation condition caused by last breaker trip occurred in inverter station of UHVDC power transmission project from Yunnan to Guangdong; analyze and reveal the interrelations among over-voltage level, various operation conditions and different action delay of DC protections and propose the requirement to the time of protection coordination to ensure secure and reliable operation of equipments for the project. The results of this research can offer basic data and technological basis for the design of practical engineering project and are available for reference to on-site commissioning and protection configuration for system operation.