Aging Evaluation of Retired 220 kV XLPE Cables: Correlating Long-Term Breakdown Performance with Short-Term Characteristics

As China's cross-linked polyethylene (XLPE) cable approach their designed service life, researchers have shown increasing interest in studying their aging characteristics. This investigation analyzed six retired 220 kV XLPE cable to systematically quantify the relationships between short-term characteristics and long-term breakdown performance. The Voltage Endurance Coefficient (VEC, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$n$</tex>) is commonly adopted to characterize the long-term breakdown performance of XLPE insulation. Results demonstrate significant positive correlations between VEC and both short-term breakdown strength (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$r=0.74$</tex>) and crystallinity (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$r=0.50$</tex>). Conversely, pronounced negative correlations are observed with electrical conductivity (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$r=-0.54$</tex>) and low-frequency dielectric loss tangent (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$r=-0.52$</tex>). However, no statistically significant relationships are identified between VEC and either dielectric constant or carbonyl index. Based on these findings, four robust indicators for insulation aging assessment are established: crystallinity, breakdown strength, conductivity, and low-frequency dielectric loss characteristics.