Development Of An Integrated Device For Stator And Rotor Insulation Monitoring And Grounding Protection Of Small And Medium Generators

The generator is an important equipment of the power plant,and the rotor grounding is a common fault of the generator set.Although these two faults are less harmful to the unit,they are not dealt with in time,causing interphase and inter-turn short circuit of the stator winding and rotor winding.When other serious faults such as two-point grounding are involved,the safe operation of the generator will be seriously affected.Therefore,it is of great theoretical and engineering significance to carry out effective grounding protection and operation status monitoring of the generator and carry out related technical research and engineering applications.This paper first compares the existing domestic and foreign research methods and technical solutions of stator and rotor grounding protection,analyzes its advantages and disadvantages,and selects the signal injection method according to the electrical characteristics and stator and rotor grounding fault characteristics of small and medium-sized hydropower units As the research basis of this subject.In this paper,the 20 Hz signal injection type stator insulation monitoring grounding resistance detection principle,insulation resistance basic algorithm,as well as the rotor one-point grounding protection and two-point grounding protection principle,rotor grounding resistance detection algorithm and fault location algorithm are deeply analyzed,Using MATLAB simulation tools,based on the electrical parameters of small and medium-sized hydropower units,the above principles and algorithms were verified by simulation,and the stator single-phase grounding,rotor one-point and two-point grounding resistance detection sensitivity and error influencing factors and application conditions were carried out Verification simulation.This paper presents an integrated solution for the measurement and control of stator and rotor grounding protection of small and medium-sized generators.According to the two integrated design principles of stator and rotor grounding protection as one,measurement and control function and protection function as one,the sensitivity of online monitoring of stator and rotor grounding is considered On the premise of quickness and selectivity of performance,accuracy and protection action,the integrated design of measurement and control of the fixed rotor grounding protection meets the application requirements of small and medium-sized generator sets with high protection integration and high cost performance.Completed the design of CPU basic system,analog signal sampling,etc.,and integrated the design of stator injection power module,rotor injection power module,and hardware circuits of additional equipment.Based on the current hardware circuit,the signal source generation,signal processing and system anti-interference are improved,and the correctness and reliability of the hardware design are verified by the actual system operation.In the software design,because the signal processing involves the accurate acquisition of 20 Hz injected signal source voltage,ground current and 50 Hz zero-sequence voltage signal and avoids the influence of the third harmonic signal that often occurs in the stator current of small and medium-sized units,this article uses 10 Hz as the basis for sampling The frequency-corrected FFT algorithm is added with a filtering function to achieve the purpose of automatically tracking the frequency change of the signal source and achieving accurate measurement,which meets the goal of high-resistance grounding sensitivity detection of small and medium-sized units.The correctness and stability of the software design are verified by the actual system operation.Aiming at the different working conditions of generator static,boost and grid-connected states,on the basis of demonstrating the main factors affecting the fixed rotor grounding protection performance of the unit,the setting principles of fixed and rotor insulation monitoring related fixed values are proposed to determine the rotor grounding protection Test methods and operating steps provide important experience for engineering applications.The actual operation and test prove the rationality and feasibility of the principle research,hardware design and software design of this article.