Space charge accumulation is an important issue to be considered in power transmission systems. However, due to the limitation of the spatial and temporal resolution of the detection system, the detection of space charge under AC is difficult. The numerical simulation of space charge under the AC field can qualitatively explain the source and transport principle of the space charge, and thus can preliminarily explain the charge transport process under the AC field. In this paper, based on the bipolar carrier transport model, the numerical simulation of the space charge transport process in LDPE (Low-density polyethylene) under different frequency AC fields is carried out. The results show that the accumulation of space charges is less in the AC field, and is mainly concentrated on the surface side of the sample. There is almost no space charge accumulation on the sample surface when the electric field applied frequency is 50Hz and above. Under the 0.1 Hz electric field, a small amount of the same polarity as the electrode appears on the surface side of the sample, there is obvious charge hysteresis at the zero-crossing point of the electric field. Under the 0.01Hz and the 0.005Hz electric field, the amount of charge accumulation increases significantly,and the hysteresis phenomenon at the zero-crossing point of the electric field is more obvious. Only under the low-frequency AC field, obvious space charge accumulation appears on the surface side of the sample, and the charge polarity is the same as that of the electrode field. The above phenomenon may be related to traps inside the medium.

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