In this paper a fully parametrized finite element simulation model of the stator bar end is created using the COMSOL Multiphysics.The model allows conducting the comparison of different corona protection structures’d...In this paper a fully parametrized finite element simulation model of the stator bar end is created using the COMSOL Multiphysics.The model allows conducting the comparison of different corona protection structures’design,various materials properties,and finally optimizing the corona protection system.Several samples of SiC based nonlinear conductivity materials for corona protection were fabricated in laboratory and then investigated.The conductivity dependencies on electric field(0.05 to 1 kV/mm)and temperature(20 to 155℃)were measured.By comparing the heat-resistant grades of the corona protection material and the insulating material,the maximum working temperature of the corona protection material corresponds to the heat-resistant grade F of the insulating material.As the temperature increases,the nonlinear characteristics of the corona protection material in the experiment decrease dramatically,reducing the heat-resistant grade of the corona protection material.The decrease in the nonlinear characteristics of the corona protection material at the maximum operating temperature causes the maximum electric field strength at the end of the HV rotating machines end corona protection(ECP)exceeding the corona discharge electric field strength,resulting in corona phenomenon.展开更多
This paper analyzes lightning surge on the stator windings of wind turbine generators.The path of lightning in the wind turbines was analyzed.An equivalent circuit model for megawatt direct-driven wind turbine system ...This paper analyzes lightning surge on the stator windings of wind turbine generators.The path of lightning in the wind turbines was analyzed.An equivalent circuit model for megawatt direct-driven wind turbine system was developed,in which high-frequency distributed parameters of the blade conducts,tower,power cables and stator windings of generator were calculated based on finite element method,and the models of converter,grounding,loads, surge protection devices and power grid were established.The voltage distribution along stator windings,when struck by lightning with 10/350μs wave form and different amplitude current between 50 kA and 200 kA,was simulated using electro-magnetic transient analysis method.The simulated results show that the highest coil-to-core voltage peak appears on the last coil or near the neutral of stator windings,and the voltage distribution along the windings is nonuniform initially.The voltage drops of each coil fall from first to last coil,and the highest voltage drop appears on the first coil.The insulation damage may occur on the windings under lightning overvoltage.The surge arresters can restrain the lightning surge in effect and protect the insulation.The coil-to-core voltage in the end of windings is nearly 19.5 kV under the 200 kA lightning current without surge arresters on the terminal of generator,but is only 2.7 kV with arresters.展开更多
文摘In this paper a fully parametrized finite element simulation model of the stator bar end is created using the COMSOL Multiphysics.The model allows conducting the comparison of different corona protection structures’design,various materials properties,and finally optimizing the corona protection system.Several samples of SiC based nonlinear conductivity materials for corona protection were fabricated in laboratory and then investigated.The conductivity dependencies on electric field(0.05 to 1 kV/mm)and temperature(20 to 155℃)were measured.By comparing the heat-resistant grades of the corona protection material and the insulating material,the maximum working temperature of the corona protection material corresponds to the heat-resistant grade F of the insulating material.As the temperature increases,the nonlinear characteristics of the corona protection material in the experiment decrease dramatically,reducing the heat-resistant grade of the corona protection material.The decrease in the nonlinear characteristics of the corona protection material at the maximum operating temperature causes the maximum electric field strength at the end of the HV rotating machines end corona protection(ECP)exceeding the corona discharge electric field strength,resulting in corona phenomenon.
基金Supported by National Natural Science Foundation of China(50877063)
文摘This paper analyzes lightning surge on the stator windings of wind turbine generators.The path of lightning in the wind turbines was analyzed.An equivalent circuit model for megawatt direct-driven wind turbine system was developed,in which high-frequency distributed parameters of the blade conducts,tower,power cables and stator windings of generator were calculated based on finite element method,and the models of converter,grounding,loads, surge protection devices and power grid were established.The voltage distribution along stator windings,when struck by lightning with 10/350μs wave form and different amplitude current between 50 kA and 200 kA,was simulated using electro-magnetic transient analysis method.The simulated results show that the highest coil-to-core voltage peak appears on the last coil or near the neutral of stator windings,and the voltage distribution along the windings is nonuniform initially.The voltage drops of each coil fall from first to last coil,and the highest voltage drop appears on the first coil.The insulation damage may occur on the windings under lightning overvoltage.The surge arresters can restrain the lightning surge in effect and protect the insulation.The coil-to-core voltage in the end of windings is nearly 19.5 kV under the 200 kA lightning current without surge arresters on the terminal of generator,but is only 2.7 kV with arresters.
