Application On Temperature Morning In Nuclear Power System By Distributed Fiber Temperature-measured System

Nuclear power is a safe, economical and clean energy. It is widely used and occupies a large proportion in national strategy. And it has entered a rapid development stage in the new century. Under the guidance of the principle which is "actively promoting nuclear power development" the government has developed a nuclear power plan, which is "70 million kilowatts by 2020, 30 million kilowatts under-construction " . Therefore, the safety monitoring of nuclear power facilities such as cables, transformers and other equipment is a major task.Traditional temperature sensors which based on electrical-signal have been very mature. They are simple, high precision, low cost and widely used in the national economy, scientific research, defense and other fields. However, the traditional temperature sensor is greatly restricted in the strong electromagnetic interference or flammable occasions.As the development of semiconductor, laser technology, optical fiber sensing technology and digital signal processing technology, distributed fiber temperature measurement has greatly developed. Distributed Fiber Temperature-measured System (Distributed Fiber Temperature-measured System , referred to as DFTS ) is a real-time, online, multi-point fiber optic temperature measurement system. And it has become a new methods and technologies in industrial control system.DFTS based on Optical Time-Domain Reflectometry (Optical Time-Domain Reflectometry, referred to as OTDR) and Raman-scattering Effect. OTDR technology is used to get coordinates. And Raman-scattering Effect is used to get the value of temperature.Compared with conventional temperature sensors, DFTS takes optical fiber as the sensing element and the information transmission channel. This system has electrical insulation, corrosion resistance, wide signal bandwidth and low loss for long distance transmission. So, it's a very new method for temperature mesurement in strong electromagnetic fields, high voltage high current, inflammable, explosive, complex geometry of space and other harsh environment (such as underground cables, ships, etc.). This paper presents a method which based on principles of distributed fiber optic temperature measurement on temperature morning in nuclear power system. The DFTS consists of laser emission system, wavelength division multiplexing systems, temperature calibration system, APD receiver, dual-channel high-speed USB data acquisition system and the microprocessor system.The working process of DFTS is divided into four stages. First, the laser controlled by microprocessor produces high-power laser pulse. Then couples the pulse into sensing fiber; Secondly, strips out of the Stokes and anti-Stokes light; Third, takes care of the isolated light signals by data acquisition unit; Finally, the microprocessor demodulates the value of temperature by calculating.DFTS mainly uses ARM9 microprocessor system and high-speed usb data acquisition circuit as hardware platform. And its software design bases on MiniGUI and embedded linux. So DFTS is a real-time, dynamic temperature morning system. Futhermore, it has the network, storage, high-speed data processing and other functions.System test shows that the system indicators such as spatial resolution, temperature resolution and response time meet the design requirements. And it has high reliability and strong anti-interference ability in practical applications.