Pressure and temperature dependence of the dielectric breakdown of polyethylene used in submarine power cables

The dielectric strength of low-density polyethylene is measured under high hydrostatic pressure (25–800 bars) at temperature of 20, 45, and 70 °C. First results show that the breakdown field Eb decreases at 20 °C and increases with pressure in the range 45–70 °C for short-time tests. The significant variations of Eb are noted for 70 °C; for example, Eb=3.2 and 4.48 MV/cm for P=25 and 300 bars, respectively.