Assessment of Controlled Backfill Influence on the Service Life of 132 kV XLPE Cables in Duct Bank Installations

Abstract

The increasing demand for reliable underground transmission systems requires accurate evaluation of thermal performance and insulation aging in high-voltage cables. This paper presents an integrated framework for the service-life assessment of 132 kV underground cables in duct-bank configurations. The approach combines thermal simulations, surrogate analytical models for cable ampacity, and load demand profiles with lifetime estimation based on the Arrhenius law and Miner’s rule, adopting experimental aging parameters reported in the literature. Flat and triangular configurations are analyzed for a single circuit, considering scenarios with and without controlled backfill. The results show that controlled backfill significantly enhances heat dissipation, reducing conductor temperature and extending service life by up to 85% for flat configurations and 42% for triangular arrangements. The analysis also reveals the nonlinear evolution of cumulative damage, driven by the interaction between temperature and load demand, which is effectively captured by the Arrhenius-Miner framework. Additionally, annual time discretization for calculating accumulative insulation damage provides conservative estimates, with minor differences compared to finer resolutions. These findings provide practical guidelines for the thermal design and lifetime assessment of underground cable systems.