Space charge measurement in LPDE films under temperature gradient and DC stress

Space charge profiles and field distributions in the cable bulk are strongly affected by high voltage direct current (HVDC) voltage especially with the cooperation of the temperature gradient across the cable insulation. In this paper, a modified space charge measurement system suitable for temperature gradient was designed to fulfill the temperature difference through changing the upper and lower electrodes´ temperature. The effect of temperature gradient on the PEA measurement system was analyzed and the space charge waveform was recovered. Space charge profiles and field distributions in low density polyethylene (LDPE) films were measured under different temperature differences (ΔT=0-40°C), and dc stresses of 10, 30, 50, and 70 kV/mm, respectively. The results show that the increasing temperature difference as well as the applied stress results in a more enhanced field at the low temperature side of sample. Along with the poling time, the enhanced field is reduced due to the injection of homocharges from the electrode under high electrical stress.