On the way to compare the polarity reversal withstand capability of HVDC mass-impregnated and extruded cable systems

​The reversal of voltage polarity is essential in HVDC cablesystems with Current Source Converters (CSC), since it enables to revert the direction of the power flow. Mass Impregnated Non-Draining (MIND) cables are known tobe able to withstand the voltage polarity reversal without particular problems. TERNA, the Italian Transmission System Operator (TSO), has introduced since many years in its test protocols for HVDC MIND-insulated cable systems the so-called “sustained polarity reversal loading cycle test”. This test has proved to be very effective for a thorough assessment of the cable system performances in the presence of polarity reversal during cable tests of different HVDC interties: the Italy-Greece and SAPEI and the up-coming Italy-Montenegro. This paperdescribes a broad test campaign for comparing the performances of extruded cable systems under polarity reversal with those of MIND cable systems. The campaign, based on a partnership between TERNA, CESI, and a few major cable manufacturers worldwide, is being performed in the new HVDC test labs of CESI in Mannheim, Germany. The tests include a mixed arrangement of both load cycles and voltage polarity reversals tests. The test protocol has been selected from TERNA’s experience in testing MIND cables, and aging and life models for extruded cables developed together with the University of Bologna, Italy .​