With the application of power cables in large industrial enterprises such as power grids and power cables, their usage is increasing, and monitoring their operational reliability is also receiving more and more attention. Although the cable trench laying method has disadvantages such as high cost, large investment, and inconvenient maintenance, it is isolated from the outside world, has high operational reliability, and does not occupy the bottom and overhead lines. Therefore, this laying method is often the best choice.
Why does cable trench need temperature measurement
As a power transmission medium, cables in cable trenches contain a certain resistance value. Therefore, during power transmission, the cables themselves will emit a certain amount of heat, especially at the joints of two cables. The heat emitted by the cables will significantly increase, ultimately causing the insulation on the surface of the cables to melt or even burn, posing a safety hazard. Especially for cables installed inside cable trenches, as they are buried underground, temperature monitoring is required at the joints of the cables to monitor their working status. There are relatively few cable temperature measurement devices specifically designed for cable trenches in the market. Important power equipment such as high-voltage cables (such as 10kV high-voltage cables in substations) are usually installed in cable trenches, and they must have a suitable working environment (such as suitable temperature) to ensure the normal operation of the power equipment. If the temperature inside the cable trench is too high or there are other severe environments that affect the normal operation of the corresponding power equipment, the power equipment inside the cable trench will accelerate the aging of the cable insulation, significantly reduce the current carrying capacity of the cable and other voltage equipment, greatly shorten the service life of the power equipment, and even cause damage to the power equipment. Therefore, it is necessary to monitor the environmental status inside the cable trench so that it can be detected in a timely manner and corresponding measures can be taken when the environmental status inside the cable trench is abnormal. This is crucial for the normal operation of the power equipment installed in the cable trench. During operation, cables generate heat and age due to the passage of current. When the temperature exceeds its tolerance temperature, it causes accelerated aging, ultimately shortening the lifespan of the cable, and even leading to serious accidents such as fire and power outages. Therefore, real-time monitoring of cable operating temperature is of great significance for understanding the working condition of cables, preventing major accidents, ensuring personnel safety, and avoiding economic losses.
Why does cable trench temperature need to be monitored
Cable trench is an underground dedicated passage for laying cables, as well as an enclosure structure for the laid cable facilities. It can be in the form of rectangular, circular, arched and other pipeline structures. During the operation of cables, there may be heating problems, where heat accumulates in the cable trench and cannot be dissipated in a timely manner, making it prone to high temperatures; Due to the large number of cables in the cable trench and the long length of the cable trench, it is difficult to quickly detect the heating position, making the detection and maintenance process very inconvenient. Each inspection requires measuring the temperature of each section of the cable trench, resulting in a long detection time. If the heating problem is not eliminated in time, it is very easy to cause safety operation accidents. Cables are important energy and information transmission channels in substations, and the safe operation of cables is extremely important for the safe operation of substations. Generally, cables are arranged in cable trenches, and the operating environment is harsh. Major accidents such as complete shutdown of substations caused by cable fires in the power grid often occur. Cables are buried underground through cable trenches, making it difficult to detect a fire, especially since substations are generally unmanned. Once a fire occurs, it often takes a long time to be detected through fire alarms or other means. At this time, many power cables in the cable trench have been damaged, leading to large-scale power outages and seriously affecting the reliability of power supply for power supply enterprises. Based on this, it is necessary to regularly detect the temperature inside the cable trench. The cable trench is covered with a cement cover plate outdoors, and it is difficult and labor-intensive to open the cover plate for infrared temperature measurement of the cable. Long term heavy overload of cables can cause cable heating, and long-term high temperatures can lead to a decrease in the insulation performance of the cable insulation layer, accelerating the degradation of the insulation layer. High temperatures also increase resistance, exacerbate heating, and increase electrical energy loss. Therefore, it is necessary to measure the temperature of the cable line and cool the cable trench once. At present, the temperature measurement of cable trenches is usually carried out through traditional infrared temperature measurement devices and other methods for one or more real-time measurements. The current temperature measurement method can only use portable equipment such as infrared thermometers to measure the temperature of cable lines during peak load periods on site, and cannot grasp real-time changes in cable temperature.
Distributed fiber optic temperature measurement system for cables
The temperature monitoring and over temperature alarm of cables in cable trays and cable trenches can be carried out using FJINNO’s distributed fiber optic temperature measurement system. Temperature measuring optical fibers are laid along each layer of cable tray, and key monitoring areas such as the middle end of the cable are expanded. Temperature sensing optical fibers collect the temperature on the optical fibers and are connected to the distributed fiber optic temperature measurement host. The fiber optic temperature measurement host is installed in the main control room of the power equipment. Using temperature sensing optical fibers laid at the monitoring point of the monitored cable, compared with traditional temperature measurement methods, optical fiber temperature measurement has the advantages of passive, intrinsic safety, ability to measure temperature along the line, resistance to electromagnetic interference, low false alarm rate, long service life, and low maintenance cost. The distributed fiber optic temperature measurement system effectively avoids the shortcomings of traditional cable temperature monitoring methods. By utilizing the inherent insulation and distributed characteristics of fiber optic, it has the characteristics of long monitoring distance, high reliability, and no electromagnetic interference, making it suitable for temperature measurement in harsh industrial environments.