Study On Prediction Model Of Galloping And Anti-galloping Method For Bundle Conductors

Galloping of transmission lines caused by the uneven ice accreted on the conductor and the sustained wind loads is a low-frequency,large-amplitude and self-excited vibration.Galloping of iced lines threatens the safe operation of power grids seriously and gives rise easily to the electrical fault and structural damage.With the great development of extra-high and ultra-high voltage transmission lines in China and increase of the extreme weather,the galloping accidents take place more frequently.The galloping features of lines are the basis of the design of transmission lines,development of the anti-galloping technology and galloping warning system.Therefore,the promotion of researches on the prediction of galloping and anti-galloping method benefits to the steady supply of electric power and behaves great theoretical significance and engineering values.Firstly,a prediction model for aerodynamic coefficients of iced quad bundle conductors is established in this paper by combining the numerical simulation for aerodynamic characteristics of iced conductors and machine learning algorithm.Compared with the high-cost wind tunnel test and time-consuming numerical simulation,the model can predict the aerodynamic coefficients of each sub-conductor quickly and provide basis for researching the galloping of lines with different conditions.The developed simulation software is used to study the aerodynamic characteristics of iced quad bundle conductors and the influences of various parameters are identified.The sampling points are designed using Latin hypercube sampling method and the lift,drag and moment coefficients varying the wind attack angle are obtained to create the datasets by the numerical simulation.Set the number of subconductors,wind attack angle,bundle spacing,ice accretion angle,ice thickness,wind velocity and diameter of the conductor as the input variables,a prediction model for the lift,drag and moment coefficients of iced quad bundle conductors is created,trained and tested by using the dataset and extra-trees algorithm.In addition,a software for aerodynamic characteristics of iced lines is developed based on the model.The prediction model is further validated by applying the predicted coefficients to simulate the galloping and study the influences of bundle spacing and conductor type on the galloping.It’s demonstrated that the prediction model can provide coefficients quickly and effectively for the research of galloping of lines with different parameters.A galloping classification model and a galloping feature prediction model for transmission lines are established respectively,and a prediction method for galloping features is proposed by combining the two models,which provides basis for the design of lines,establishment of galloping prediction system and development of anti-galloping technology.The galloping of iced quad conductor lines with different ice,wind and structural conditions is simulated by using the developed galloping simulation platform,and the various galloping features are analyzed.The corresponding extraction method for the galloping features are studied to construct a dataset.The galloping classification model is established to predict the galloping mode and vertical galloping mode(loop number)using random forests algorithm.Further,the galloping feature prediction model is also developed to predict the galloping frequencies,vibration amplitudes and maximum conductor tension.A prediction method for galloping features of transmission lines is proposed by combining the classification and prediction models,which can predict the galloping features quickly and effectively.The test demonstrates that the accuracy of classification model is about 90%and the average R~2 value for each galloping feature by prediction model for is greater than 0.85,and the efficiency and accuracy of the method are validated.Considering the ice distribution and aerodynamic characteristics of sub-conductors along the span,an evaluation method for the anti-galloping efficiency of rotary clamp spacers is researched,and the anti-galloping efficiencies of rotary clamp spacers for eight bundle conductors are researched and the optimal schemes are acquired.The distribution of cross-section shapes of accreted ice along the twistable sub-conductor connected with the rotation-free clamps are numerically modeled.The air flows around the iced eight bundle conductor installed with the rotary clamp spacers are then simulated and the aerodynamic coefficients of the sub-conductors varying with the wind attack angle are obtained.Considering the ice shape distribution along the span,the aerodynamic loads on the sub-conductors are applied sectionally using ABAQUS and its subroutine UEL,and the galloping of iced eight bundle conductor lines with different installation schemes of rotary clamp spacers are numerically investigated.The anti-galloping efficiencies of rotary clamp spacers are evaluated under different parameters,including initial wind attack angle,ice thickness,ice accretion angle,span length,conductor type and continuous spans,and the optimal schemes are proposed.Further more,the acquired evaluation method is used to research the anti-galloping design of the actual ultra-high voltage(UHV)alternating current one-span eight bundle conductor line and direct current four-span six bundle conductor line respectively.The distribution of ice shape and aerodynamic characteristics along the span are studied,and the galloping of two lines installed with different schemes of rotary clamp spacers and double swinging protectors is simulated.The galloping features and anti-galloping efficiencies of different schemes are analyzed and evaluated,and the optimal schemes are proposed.The obtained results may provide instructions to the design of anti-galloping for actual UHV lines.Considering the spatial correlation effect of wind filed and the time variability of wind velocity,the anti-efficiencies of different arrangements of interphase spacers for three-phase eight bundle conductor lines under stochastic wind load are researched.Two finite element models of three-phase eight bundle conductor lines with triangle and vertical layouts are established,and various arrangements of interphase spacers are installed respectively.Based on the Kaimal spectrum and the Davenport coherence function,the time interval curves of pulsation wind velocity at typical points along the span are obtained using WAWS method and then the stochastic aerodynamic loads of iced sub-conductors are applied.The galloping of lines with different arrangements are simulated numerically and the corresponding galloping features are compared to evaluate the anti-galloping efficiencies and acquire the best arrangement.Research results in this paper provide important theoretical and technical supports for the design of transmission lines,development of the anti-galloping technology and galloping warning system,and behave good application prospects.