High voltage cables that are directly buried or laid through pipes are usually buried underground. In addition to their own manufacturing quality or underground corrosion, the important factors causing damage to high-voltage cables are human mechanical external forces. Due to the weak awareness of power facility protection and unorganized and barbaric construction by some construction units, large construction machinery such as pipe jacking machines, pile drivers, and crushers often damage the high-voltage cable body, causing varying degrees of damage to the cable body, and even causing line tripping. According to statistics, there have been 75 failures of high-voltage cable bodies in the past decade, mainly due to external damage caused by construction, accounting for as much as 70% 67% is the main cause of the main body failure; Next are product quality reasons and improper construction and installation, which are 12% and 6% respectively 7%
At present, for the supervision of the construction of high-voltage cable lines, the operation and maintenance units mainly adopt methods such as manual irregular inspections, distributing promotional materials, and signing safety disclosure agreements. However, the inspection personnel need to complete the prescribed inspections and defect elimination work every month, resulting in blind spots in the inspection cycle and the inability to achieve external damage hazard warning. Therefore, traditional operation and maintenance methods cannot achieve the expected results, and there are still many barbaric constructions. Some construction sites have installed simple video surveillance devices, which to some extent strengthen real-time supervision of the construction site. However, this method can only achieve limited monitoring of fixed construction points, and the outdoor power supply method adopts solar energy+battery, which is greatly affected by weather factors. In most cases, manual detection of external hidden danger information is required for early warning, which has certain limitations.
A monitoring and early warning system for preventing external damage of high-voltage cables based on distributed fiber optic vibration sensing. This system does not require the installation of other equipment along the pipeline. By utilizing the vibration signal of laying optical fibers in the same trench as the high-voltage cables, it intelligently identifies the types of mechanical external damage of the entire high-voltage cable line and actively sends warning information.
Fiber optic is both a sensor and a transmission channel. Compared with traditional electrical sensors, fiber optic sensors have advantages such as high measurement accuracy, strong resistance to electromagnetic interference, lightweight materials, good channel safety, long measurement distance, and continuous distributed measurement. By burying or laying detection optical fibers in the monitored structure, various physical information such as temperature, stress, strain, etc. of the structure can be obtained through optical signals, thereby achieving real-time monitoring of abnormal conditions.
The entire system consists of a distributed fiber optic vibration sensing monitoring host, an analysis host, and an anti external damage monitoring system platform. All host equipment is installed in the same cabinet in the communication room of the substation. The monitoring host can achieve all-weather monitoring of external damage hazards along high-voltage cables laid in the same trench by utilizing one core of spare single-mode optical fiber already laid in the pipeline, which includes communication business optical cables. There is no need to lay another multi-mode optical fiber for transmitting and sensing vibration signals.
Characteristics of distributed fiber optic cable monitoring
① No installation is required along the route, and one core of spare optical fiber from the communication optical cable is taken as the sensing and transmission channel to connect to the monitoring host;
② No blind spots in the entire construction line, achieving monitoring of external damage to high-voltage cables throughout the line;
③ The system architecture is simple, requiring only the installation of monitoring and analysis hosts in the communication room of the substation, without the need to install any additional sensors on the line;
④ A comprehensive warning system is in place. When there is a large machinery operating near the optical cable, the system will issue a warning and distinguish the alarm levels based on different threshold settings. If the large machinery is traveling near the optical cable or intersects with the optical cable route for a short time, the system will only record external damage hazards and will not issue warning messages It can identify the vibration signals of crushers, excavators, pipe jacking machines, exploration machines, pile drivers, handheld machinery (such as air picks), and underground pipe threading operations. The movement and operation signals of large construction machinery can be accurately distinguished.