Thermal Degradation in Underground Cable Joints: Techniques, Causes, and Diagnostic Advances – A Review

ASM Sc. J., 21(2), 2026

Published on October 20, 2026

https://doi.org/10.32802/asmscj.2026.1018

Author: Ahmad Luqman Che Rani, Tze Mei Kuan, Mohamed Ansari Mohamed Nainar, Azrul Mohd Ariffin, Miszaina Osman

Abstract

Underground cable (UC) joints are among the most failure-prone components in power distribution networks, particularly under thermal stress. This review explores a range of jointing methods and diagnostic approaches used to assess thermal degradation (TD) in UC joints. The discussion begins with the structural components of high-voltage cables, followed by a comparison of mechanical, electromagnetic, heat-shrink, cold-shrink, and exothermic welding techniques. Each method is evaluated based on materials, performance, application principles, and known limitations. The paper also analyses key contributors to TD, including electrical overloading, improper joint construction, and environmental exposure, with attention to material-level effects such as insulation embrittlement and conductor oxidation. Several diagnostic strategies are assessed, including infrared thermography (IRT), partial discharge (PD) testing, real-time thermal monitoring, and emerging tools like acoustic emission (AE) and AI-driven sensing. A comparative evaluation highlights the trade-offs between sensitivity, practicality, and field performance under various conditions. Accordingly, this review synthesises recent and foundational research to address three questions: (1) What are the dominant causes and pathways of TD in UC joints? (2) How do joint technologies and installation/maintenance practices influence thermal aging risk? (3) Which diagnostic techniques are most effective for detecting TD, and what are their limitations in field deployment? The findings emphasise the importance of integrated monitoring, standardised practices, and appropriate material selection to enhance long-term reliability. Future research should focus on the integration of advanced diagnostic technologies such as AI-driven predictive maintenance systems and real-time thermal monitoring to improve the detection of early-stage TD.

Keywords: diagnostic methods, jointing techniques, partial discharge monitoring, thermal degradation, underground cable joints