| China is currently implementing a new type of infrastructure construction represented by UHV,indicating that C hina will usher in the peak of a large-scale planning and construction of UHV transmission lines,and the current transmission corridors are becoming more and more scarce,and there are many places where HVAC and HVDC lines are erected in parallel,the electromagnetic environment problems caused by it have also attracted more and more attention.Because of the coupling effect between high voltage AC and DC parallel lines,making the parallel lines’ hybrid electric field calculation is more complex.At the same time,different environmental variables will also have different effects on the hybrid electric field.In different seasons,the distribution of the hybrid electric field of the transmission lines forms a seasonal difference.In this paper,the hybrid electric field distribution of HVAC and HVDC parallel lines is calculated according to the fully coupled finite element method.Consider the influence of space charge and the combined influence of various environmental factors.By analyzing the influence mechanism of different environmental factors on the hybrid electric field,combined with the characteristics of the environmental factors in the four seasons,the calculation parameters and distribution rules of the hybrid electric field of HVAC and HVDC parallel lines under different seasonal conditions are calculated;Finally,through the long-term electromagnetic environment monitoring of an actual HVAC-HVDC parallel lines,the measurement results of the combined electric field and power frequency electric field of the parallel line in different seasons are sorted out and analyzed.The main innovative work of this article includes:(1)For ultra-high voltage AC / DC parallel lines,considering the effect of space charge,a fully coupled finite element method for calculating the hybrid electric field is proposed.The field enhancement factor is used to correct the phenomenon of reduced electric field on the surface of the wire due to simplified wire shape.This method takes into account the interplay between the HVAC lines and the HVDC lines,the interaction between the space electric field and space charges,the influence of environmental factors on the space charge distribution,and the recombination and migration of the negative and positive ions.By eliminating the influence of Kaptzov hypothesis and Deutsch hypothesis on the calculation accuracy,the corona electric field with space charge propagation was accurately solved.(2)The effects of environmental parameters such as humidity,wind,haze and temperature on parallel-line hybrid electric fields are studied,the characteristics of the meteorological variables in the four seasons were analyzed,and the calculation parameters and distribution rules of the HVAC and HVDC parallel lines hybrid electric field under four season conditions were calculated.Results show that space charges increase the hybrid electric field,and among the environmental factors,wind has the greatest influence on the hybrid electric field.(3)The long-term monitoring records of the combined electric field and power frequency electric field was carried out on an actual HVAC-HVDC parallel transmission lines.Combined with the operating conditions of the lines and weather conditions,the distribution rule of the hybrid electric field was obtained.The conclusion is that the magnitude of the hybrid electric field varies greatly between different seasons,and the absolute value of combined electric field of the HVDC positive conductor are generally smal er than that of the negative conductor. |
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