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- For practical electrical insulation design of high temperature superconducting (HTS) power apparatuses, knowledge of the dielectric behavior of both liquid nitrogen (LN2) and subcooled liquid nitrogen (SLN2) are essential. To achieve SLN2 at atmospheric pressure, cryostat was designed and constructed. By pumping up the LN2 in the outer dewar, the temperature of LN2 in the inner dewar at atmospheric pressure can be controlled. The breakdown characteristics of LN2 in quasi-uniform and non-uniform electrical fields for temperatures ranging from 77 K to 65 K at atmospheric pressure and pressure ranging from 0.1 to 0.5 MPa were investigated experimentally. The experimental data suggested that the breakdown voltage (BDV) of LN2 is both highly temperature and pressure dependent. We also carried out statistical analysis of the experimental results using the Weibull distribution. The Weibull shape parameter m for the sphere-to-plane electrodes in SLN2 was estimated to be 11 to 18.