Performance of an optimized XLPE material for controlling space charge in HVDC transmission cable system

We have developed special XLPE material (DC-XLPE) suitable for DC insulation. It was optimized for well-control of space charge. Basic properties of the material and reliability of cable system were evaluated in numbers of measurements and test programs. Higher volume resistivity, controlled behavior of space charge even in case of polarity reversal and excellent long term performance of DC-XLPE were confirmed by measurements of sheet samples. Higher capability of system performance including combinations of cable and accessories was also confirmed by tests using model cable system. Finally, 320kV full size DC cable system was tested in accordance with prequalification test program of CIGRE TB-496. It was completed successfully. After that, a part of test loop was dismantled for space charge measurement. Space charge behavior was still well-controlled even after 1 year-long test.