Breakdown voltage of polypropylene laminated paper (PPLP) in plain samples and a full scale cable

Polypropylene laminated paper (PPLP) has been used as ac power cable insulation for a number of years. However, reports on the use of PPLP in high voltage direct current (HVDC) cables are sparse. In this paper we report dc breakdown strength of impregnated PPLP samples. Experimental breakdown data from identically treated samples both from Kraft paper and PPLP have been analyzed assuming a Weibull distribution. The results suggest that PPLP insulation is superior to paper insulation on a lab scale but more sensitive to volume effects than paper insulation. A full scale mass-impregnated PPLP cable has been type-tested successfully according to CIGRE recommendations. Additional impulse tests on the cable suggest a higher Lightning Impulse Withstand Level (LIWL) compared with a similar mass-impregnated paper cable. The performance ratio of PPLP vs. paper is substantially higher for dc breakdown tests on plain lab samples than for impulse breakdown test on full scale cables