Charging Models For Airborne Suspended Particles Around Hvdc Lines

Ground total electric field (GTEF) is a vital parameter in the field of electromagnetic environment of high voltage direct current (HVDC) lines. Some experimental works reported that airborne suspended particles can be charged in the corona ion flow of the lines and thus affect GTEF. This paper aims at studying the charging models for particles. Equivalent unipolar charging models (EUCMs) and bipolar charging models (BCMs) for describing field and diffusion charging mechanisms in bipolar ion environments are introduced and the Maxwell-Wagner relaxation is proposed to be incorporated. Besides, the EUCMs and BCMs are analysed and validated through comparisons with experimental data. The results show that BCMs are applicable to describing the particle charging in a bipolar ion environment, while EUCMs are not. The predictions made by BCM that takes into account the Maxwell-Wagner relaxation are in good agreement with experimental results. Moreover, the BCMs are proposed to analyse the experimental results about GTEF in the presence of particles, which are not understood before. It is demonstrated that the BCMs are able to qualitatively explain these results. Finally yet importantly, a new charging model combining field and diffusion charging mechanism is proposed for airborne suspended particles around HVDC lines and validated by experiments. The results show that the proposed hybrid field-diffusion charging model is able to give predictions consistent with experiments.