Temperature gradient effect on distortion of DC electrical field in polyethylene

Space charge profiles and stress distributions in cable bulk are strongly affected by high voltage direct current (HVDC) voltage, especially with the cooperation of the temperature difference between inner and outer insulations. A modified space charge measurement system suitable for temperature gradient was designed to fulfill the temperature difference via changing the upper and lower electrode temperature. Then space charge profiles and stress distributions in low density polyethylene (LDPE) were measured under different temperature differences (from 0°C to 40°C), as applied DC stresses of 10, 30, 50, and 70 MV/m, respectively. The relationship between temperature difference and stress distribution was obtained. The test results show that the increasing temperature difference and applied stress results in a more distorted stress at the low temperature site of sample. And due to the injection of homo-charges from the electrode under high electrical stress, the distorted stress is reduced with the increasing poling time.