Partial discharge sensing system for power cable joints based on distributed fiber optic sensing technology

With the continuous development of society and the economy, the proportion of power tunnels and utility corridors in urban power grids has been steadily increasing. However, as their scale expands and aging issues intensify, the safety challenges associated with their operation have become increasingly prominent. As the weakest point in cable insulation, cable joints are prone to various types of insulation defects over time due to factors such as operational aging, limited installation conditions, and constrained manual handling methods. These defects can induce partial discharges (PD), which, under the influence of localized strong electric fields, may lead to the formation of penetrating discharge channels in the insulation medium. This can result in overheating of the cable insulation and, in severe cases, carbonization that degrades insulation performance, potentially causing serious safety incidents such as fires or explosions. Therefore, monitoring PD in cable joints within utility corridors is of significant importance for ensuring economic and societal stability. Distributed optical fiber sensing technology, which utilizes optical fibers as sensing elements, offers remarkable advantages for monitoring power tunnels and utility corridors. The complex electromagnetic environment around cable joints poses challenges for traditional HFCT sensors, which are highly susceptible to electromagnetic interference, resulting in lower reliability and difficulty in providing accurate monitoring results. The passive nature of optical fibers makes them particularly well-suited for sensing cable conditions in such high electromagnetic environments. Furthermore, optical fibers can be installed along the length of power cables, aligning well with the long-distance and distributed characteristics of cable systems, thereby leveraging the strengths of distributed optical fiber sensing technology. This study proposes a PD monitoring system for power cable joints based on distributed optical fiber sensing technology. By tightly and meticulously wrapping the optical fiber around the surface of the cable joint, the system can detect disturbance signals generated by internal PD within the joint. The system is capable of online monitoring of PD across transmission lines up to 10km in length, covering approximately 50 cable joints, with a signal-to-noise ratio of 14dB.