The low frequency cable system shows promise in wind power transmission due to enhanced transmission capacity and distance. Despite the operation of two low frequency (20 Hz) projects in China, there is a noticeable gap in research concerning the dielectric properties of XLPE insulation material and the electric field distribution characteristics of the XLPE cable under low frequency voltage. To evaluate the feasibility and potential of cables designed according to power frequency applications for low frequency power transmission, this paper firstly measures the dielectric parameters of XLPE samples under different frequencies and temperatures. Subsequently, a simulation model of a 35 kV cable is constructed to investigate the electric field distribution in XLPE insulation with typical defects under the 20 Hz voltage. Lastly, by integrating test data and simulation results, the allowable defect sizes in low frequency cable insulation are deduced.