Optimal Design of Main Protection for Generator-motor Based on Flexible Optical Current Transformer

Abstract

Renovation projects of generator main protection in large and medium hydropower stations in China are gradually increasing. Limited by the existing branch wiring mode and installation condition for electromagnetic current transformer (CT), there is still a protection dead zone in the final selection of the main protection configuration scheme, despite the quantitative design for the generator main protection. Taking the renovation project of main protection for Tankeng Hydropower Station in China as an example, a suboptimal main protection configuration scheme has to be selected due to the installation limitation of electromagnetic CT. As a result, safety risks still exist in generator operation after the renovation. Because of the high speed and small foundation space of large generator-motor, the problem above is more prominent. In the renovation project of main protection for Shenzhen pumped storage generator-motor, based on the advantages of the flexibility of flexible optical CT winding, the wiring mode of branches is virtually changed through the flexible installation of optical CT without changing the existing branch grouping or the copper ring wiring mode of the generator. And the branch currents and branch group currents connected to the generator protection devices are recombined. Then the configuration scheme of main protection for Shenzhen pumped storage generator-motor is optimized based on quantitative analysis, thereby eliminating the dead zone of main protection.