| In order to realize the energy allocation of the long-distance and high-capacity,it is inevitable to develop the ultra high voltage direct current transmission.At present,the highest voltage transmission in China is ±1100kV UHVDC transmission.And its transmission capacity and distance have been greatly improved compared with ±800kV UHVDC transmission.With the increase of voltage level,the problem of power line carrier interference noise also has been increasingly significant,PLC(Power Line Carrier)reactor effectively inhibits the influence of interference noise.However,in order to prevent the surface of ±1100kV PLC reactor from being discharged due to excessive electric field intensity,it is particularly of importance to improve the structure of the grading ring of the ±1100kV PLC reactor reasonably,in view to the high switching impulse voltage that±1100kV PLC reactor may withstand,.Firstly,in this thesis,several common structures of the potential grading device are listed;and the feasibility of adopting electrostatic field calculation equivalent to transient field calculation under switching impulse voltage is studied;the calculation principle of 3D electrostatic field of ANSOFT MAXWELL is introduced.Secondly,to verify the reliability of modeling and calculations,aiming at the taikai±1100kV PLC reactor model,the dichotomy is used to carry out numerical calculation with different grading ring's height to the ground,and the calculated switching impulse voltage value is compared with the test results.The test and calculation results show that the higher the grading ring at the end of reactor to the ground is,the greater the corresponding switching impulse voltage is.When the height is constant,the numerical calculation value is basically consistent with the switching impulse voltage value measured by the test.Therefore,it is feasible to calculate the electric field distribution of the given±1100kV PLC reactor by using this calculation method.Then,the numerical calculation is carried out in two cases,with or without the grading ring for given ±1100 kV PLC reactor.The results show that the electric field intensity of the PLC reactor without the grading ring is concentrated on the upper and lower edges of the coil winding and the lower edge of the high voltage flange.The electric field intensity of the PLC reactor with the grading ring is concentrated on the outer surface of the grading ring.And the electric field intensity distribution on the surface of the reactor is more uniform,and the maximum electric field intensity value is smaller than the first case.In order to reduce the maximum electric field intensity value of each layer,aiming at grading ring with larger electric field intensity value,we change outside diameter,pipe diameter or height of both grading ring and its adjacent grading rings following certain logic.By analyzing the electric field distribution on the surface of the grading ring at the end of the improved ±1 100kV PLC reactor,it shows that the improved reactor has a more uniform electric field intensity distribution,and the electric field intensity gradient between layers is smaller.Therefore,it is reasonable to improve the structure of the grading ring in this way.In the end,based on the improved ±1 100kV PLC reactor,modeling wiring terminals that may affect the electric field intensity on the surface of the grading ring of the±1 100kV PLC reactor,and the influence of wiring terminals on the electric field intensity distribution on the surface of the grading ring is analyzed.The result shows that the wiring terminals have little effect on the distribution of the electric field intensity on the surface of the grading ring.By changing the inner and outer diameters of the coil winding,the influences on the distribution of the electric field intensity on the surface of the grading ring is analyzed.In practical application,we can combine analysis results and adjust the inner and outer diameters of coil windings properly to reduce the maximum electric field intensity value of the surface of the grading ring. |
PDF Full Text Request