Research on Internal Fault Analysis and Main Protection Design of Zhaoqing Variable-Speed Pumped-Storage Unit

The construction commencement of the Zhaoqing Pumped Storage Power Station represents a significant milestone in China's independent research and development of AC excitation generator-motor technology. This station is set to accommodate one 300MW variable-speed unit alongside three traditional 300MW constant-speed units. To ensure the proper protection of the variable-speed unit, this paper establishes the multi-loop mathematical model for an AC excitation generator-motor, validated through experimental testing. Moreover, by drawing upon quantitative design insights for the main protection of constant-speed units and simulations of typical internal fault scenarios, this paper also determines the appropriate grouping of stator winding branches and devises a scientifically grounded configuration for the Zhaoqing variable-speed unit's main protection scheme. The quantitative and optimized protection design process for the main protection system can provide a reference for the forthcoming construction of domestic variable-speed pumped storage power stations.