Non-Invasive Method for Evaluating and Detecting Failures in Bentonite Filling in High-Voltage Cable Ducts during Project Execution

Bentonite is widely used as a filling material in underground ducts for high-voltage cables due to its high thermal conductivity, which enhances heat dissipation and enables optimization of conductor sizing. However, even localized application failures may create hot spots that reduce the system current-carrying capacity and accelerate insulation aging. This paper proposes a noninvasive method to assess bentonite filling quality during the project execution phase. The method is validated through simulated filling failures and is based on circulating high-intensity direct current through the cable metallic screen to induce heating, monitored by an optical fiber– based Distributed Temperature Sensing (DTS) system. Thermal profile analysis allowed accurate detection and localization of…