Impacts Of Atmospheric Particles On The Ionized Field Of The High Voltage Direct Current Conductor And Application Research

Corona generated ionized field is an essential parameter to describe the electromagnetic environment of ultra-high voltage direct current(UHVDC)transmission lines.The ionized field,ion current density,radio interference,and audible noise determine the design factors of conductor type,conductor height,polar separation,bundle separation,and corridor width.Hazy weather has occurred in northern China in specific seasons.The atmospheric particles in haze may be charged due to the corona discharge of the UHVDC power lines,and then impact the ionized field and ion current density of the lines.The ionized field distributions are computed by the calculation model with the particles’ charging processes.The ionized field distributions under HVDC conductors are also measured.The impacts of the atmospheric particles’ mass concentration,diameter,and permittivity on the ionized field have been revealed in this dissertation.Firstly,the impacts of space charges generated in corona discharge on the measurement of ground-level ionized field,and the distortion of the field mill probe on the nearby ionized field distribution are investigated.The ionized field strength,ion current density,and space charge density are extracted through calculation and measurement in the configuration of parallel electrodes.The ionized field distribution on the field mill probe is calculated by the flux finite element method(flux FEM)in the cylindrical coordinate.The ionized field distortion due to the probe is analyzed quantitatively and is also verified by experiments.An additional electrode to restrict the field distortion near the field mill probe is proposed and the design is also verified by calculations and experiments.Secondly,the measurement methods of ionic mobility in air are presented,and are utilized in the equivalent mobility investigation of the mixture with air and atmospheric particles.The configurations of parallel and cylindrical electrodes to measure the ionic mobility in DC corona discharge are both applied.An indoor closed laboratory is established to investigate the impact of incense particles’ mass concentration on the equivalent mobility of the mixture with air and the particles.Thirdly,the upstream boundary element method(upstream BEM)is proposed in this dissertation to compute the ionized field on the boundaries or electrodes accurately.Poisson’s equation and current continuity equation are solved by boundary elements and upstream elements.The ionized field strength and space charge density are calculated iteratively.The calculation method is verified by the measurement of ionized field.Lastly,the impact mechanisms and rules of atmospheric particles’ mass concentration,diameter,and permittivity on the ionized field of the HVDC conductor are attained.The field charging and diffusion charging are considered in the upstream BEM for calculating ionized field.The ionized field distributions at ground level under HV conductors with the presence of incense particles in the indoor closed laboratory are measured to verify the computation method.The contributions of charged particles and small ions to space charges,and the contribution of charged particles to the ionized field are obtained through measurements and calculations.The ground-level ionized fields of ±1100 k V UHVDC transmission lines with various values of atmospheric particles’ mass concentration,diameter,and permittivity are calculated to acquire the impact rules.