With the rapid development of the power grid and the acceleration of urban network renovation, the proportion of cables in the power grid has significantly increased, and the frequency of cable fire accidents has also increased. The traditional method of cable fire prevention is to install fire prevention boxes on the exposed parts of the cable, but these methods are very passive and the effect is not significant. It is impossible to timely understand the temperature of the cable, nor can it effectively prevent fire accidents. Therefore, in order to effectively prevent cable fire accidents, it is necessary to design an intelligent fiber optic temperature measurement system to monitor the temperature of cables in real time. Distributed fiber optic temperature measurement technology is a good cable temperature measurement technology with broad application prospects in China.
distributed temperature sensing
Principle of Distributed Fiber Optic Temperature Measurement Technology
Distributed fiber optic temperature measurement technology is a real-time, online, and multi-point fiber optic temperature measurement technology. It can monitor the spatial temperature field in real time. It is a new type of intelligent cable temperature monitoring technology widely used in industrial process control. Distributed fiber optic temperature measurement technology can achieve continuous real-time measurement of measurement points along the fiber optic cable in cable temperature measurement. Real time measurement of cable temperature can be achieved within a range of 1-30 kilometers. The spatial positioning accuracy is less than 0.5 meters, with a temperature resolution of up to 0.5 degrees Celsius, which can achieve real-time continuous measurement of cable temperature. Continuous and automatic measurement provides better results in a wide range of multi-point measurement applications. The distributed fiber optic temperature measurement technology mainly applies the principle of optical time-domain reflection and the influence of fiber Raman scattering temperature. Distributed fiber optic temperature measurement technology, as a new type of intelligent temperature measurement technology, has many advantages and characteristics. Distributed fiber optic temperature measurement technology can achieve large-scale, multi-point, and high-precision temperature measurement, and can achieve automatic measurement, providing reliable technical support for online detection of cable insulation.
Application of Distributed Fiber Optic Temperature Measurement Technology
Taking the environmental monitoring system of 220KV Line 1 and Line 2 tunnels in college student cities as an example. The system environment is a mixture of overhead lines and cable lines for 220KV lines 1 and 2, with the cable section located in the middle of the entire line. The length of the cable is 1.7 kilometers. The entire monitoring system is controlled by a computer, programmable logic controller (PLC), and distributed fiber optic cable temperature measurement system. The temperature of the cable, water in the tunnel, combustible gases, and other cable environments. Through computer software and PLC for monitoring, real-time remote monitoring, analysis of potential hazards in cable tunnels, and remote alarm information. The system mainly includes computers, fiber optic communication, sensors, etc., and is composed of a host, multiple switches, etc.
Layout of Distributed Fiber Optic Temperature Measurement System
The length of the entire cable temperature measurement cable is 4.2 kilometers. The two cores of the cable are used as communication channels, with temperature information connected to the local area network of the power supply company and corresponding equipment configured.
Implementation of Distributed Fiber Optic Temperature Measurement System
Using a programmable controller (PLC) with 485 bus to connect the upper computer and sensors of the temperature measurement system. Each measurement unit, upper computer, and temperature measurement control layer are connected to form a complete network system, achieving centralized measurement and alarm information display, and achieving centralized management and control effects.
Distributed fiber optic temperature measurement technology can achieve automatic, continuous, and real-time monitoring, timely grasp the temperature changes of cables in the control area, and timely alert various hazardous information. The host is placed in the indoor workstation. The temperature sensing cable is connected to the host and laid along the cable. Set up a monitoring point every 0.5 meters for continuous monitoring, fully understand the working condition of the cables, and timely transmit the cable information of the monitoring point to the monitoring control station to display the monitoring information. Such as monthly alarm data, accident alarm data, abnormal cable temperature, average cable temperature data, etc. Temperature sensors have excellent characteristics such as thermal conductivity and mechanization. They can not only transmit temperature signals, but also transmit signal channels. They can receive signals from optical fibers at different positions on the cable, receive temperature information, and monitor cable temperature in various complex environments.
The optical channel switching multiplexer is a device that controls the optical path, plays a role in switching the optical path, is not affected by external wavelengths, and has high measurement accuracy. It can be connected to a temperature measurement host and perform function switching. Select the start channel and end channel, and switch freely through optical switches. The main interface can display real-time monitoring of temperature changes for the current cable.
When the cable temperature in the temperature measurement system is abnormal, first record the abnormal temperature data and specific location information, analyze and classify the abnormal data, and promptly issue an alarm message. Secondly, alarm information such as sound and light is transmitted through relays, and the alarm information is transmitted to the established address through Ethernet. Alarm information is transmitted to the industrial control station in a timely manner through the COM port. In the process of processing alarm information, cable temperature measurement data can be analyzed.
distributed temperature sensing
The distributed fiber optic temperature measurement system can timely obtain cable temperature information and changes in any complex environment. The temperature measurement system can set one or more monitoring points and alarm temperature points. If the cable temperature in the environment is abnormal, and the cable temperature changes abnormally, if the cable temperature reaches or exceeds the set temperature, the temperature curve of the cable will be displayed in the system of the workstation. Display: The temperature measurement system sends alarm messages to the PLC at any time. After receiving instructions from various monitoring points, the internal program can control the environment of the cable based on the set temperature data. It can open the exhaust system, automatically close the fire doors, prevent fire from spreading, and ensure that the entire system is in a safe control and control environment.
The distributed optical cable temperature monitoring technology is supported by advanced DTS technology. The cable is laid along the cable. It can achieve continuous monitoring of various temperature information along the cable, and real-time grasp of the dynamic information and temperature changes of the cable. Configuring cables is very valuable. Distributed fiber optic cable temperature monitoring technology can also achieve real-time online monitoring of cable temperature changes, and can set warning information for multiple monitoring points to prevent dangerous accidents from occurring. Based on the temperature of the cable, the load variation of the cable can be determined, the load of the cable can be optimized, the capacity of the cable can be effectively increased, and the utilization efficiency of the cable can be improved. Distributed optical cable temperature monitoring technology has improved the shortcomings of traditional technology through intelligent control technology, improved the operational level of cables in China, and reduced the incidence of cable accidents.