Study On Large Generator Protection Fault Simulation And Protection Test Technology

With the development of ultra-high voltage AC/DC parallel transmission network,the large-scale access of wind and solar power and the application of flexible AC/DC transmission technology make a big difference to the structure and characteristics of grid.As the main supply,the steady increasing of large generator unit capacity makes it play a more important role in the power grid.In order to make full use of its supporting ability,coordinating the grid and the generator unit by relaying protection is very important.Considering the dynamic test is the key to ensure the relaying protection equipment operation,and there is no practical test platform,this paper studies on the fault simulation and protection testing technology of large generator unit,including the establishment of relaying protection test platform based on RTDS,the typical generator unit faults test scheme and simulation analysis,and the generator unit modeling method for stator grounding and short circuit faults,etc.Considering the high real-time performance of dynamic test,this paper establishes the large generator unit fault simulation and protection test platform based on RTDS.After studying the characteristics of excitation system and stator winding model,the PDSM model has been partially revamped to meet the test requirement and the typical test scheme for generator unit relaying protection has been proposed.The test result shows the applicability and validity of test platform and the model limitation for stator grounding and short circuit faults.For stator grounding fault,the PDSM model can't reflect the distributed winding,stator grounding distributed capacitance,the third harmonic voltage and the injection protection test.Based on the stator grounding fault feature analysis,the generator stator grounding fault quasi-distributed parameter model has been proposed.In the process of modeling,all factors are taken into account,including the injected low frequency source,the third harmonic voltage and the stator grounding capacitance.The simulation result shows the model can effectively reflect the characteristics of stator grounding fault and can be used to analyze the performance of typical stator grounding protection,including the fundamental zero sequence voltage protection,the third harmonic voltage protection,and the injection stator grounding protection.For stator short circuit fault,the PDSM model ignores the influence of branch winding,distributed potential and distributed inductance.In order to established the generator stator short circuit fault model,two key problem are studied.One is the the stator inductance splitting method considering stator struction and phase belt distribution.The other is transient calculation model for different fault,including same branch short circuit fault,same phase interbranch short circuit fault and interphase short circuit fault.In this paper,an actual nuclear generator unit is analyzed and the the performance of typical main protection is evaluated,including differential protection,longitudinal zero-sequence voltage protection,rotor second harmonic protection and negative-sequence power protection.At the end of this dissertation,the research work and results are summarized and the directions of further research are pointed out.