Research On Temperature Online Monitoring Device For Power Cable Based On DTS

With the gradual advancement of urbanization in China,the number of a large number of infrastructure,such as power cables,oil and gas pipelines,bridges and tunnels,large buildings and urban integrated pipe corridors,has increased rapidly,and the resulting fire safety problems have also attracted people's attention.Especially with the rapid expansion of the scale of power network in China,the monitoring level of power cable temperature needs to continue to be improved.The real-time distributed temperature monitoring of power cable can detect the abnormal position of local temperature in time and analyze the insulation problem of the line,so as to prevent the occurrence of cable fire and ensure the continuous and safe operation of the cable.In addition,it can also provide assistance for the calculation of steady-state current carrying capacity.At present,the commonly used methods of power cable temperature measurement are temperature sensing cable,point temperature sensor and infrared temperature measurement and so on.Compared with the traditional methods,distributed optical fiber temperature measurement technology has the advantages of long detection distance,anti-electromagnetic interference,variable shape,intrinsically safe,simple installation and can be used for a long time,which has become the development trend of power cable temperature measurement.In order to solve the problem that it is still difficult to improve the measurement distance and spatial resolution of distributed optical fiber temperature measurement technology,the time division multiplexing distributed optical fiber temperature measurement system based on Raman scattering effect is studied in this paper,which is used for on-line temperature monitoring of power cable.Through time division multiplexing data fusion,the sensing distance is prolonged and the spatial resolution is improved,and the power cable can be monitored in different areas.The research content of this paper has practical significance for the construction of distributed optical fiber sensing network and its application in power cable temperature detection.The main research work includes the following aspects:The principle of time division multiplexing distributed optical fiber temperature measurement is studied,including optical fiber scattering principle and optical time domain reflection positioning technology.a time division multiplexing distributed optical fiber temperature measurement scheme based on Raman scattering effect,pulse laser and wavelength division multiplexer are designed.The key devices such as avalanche photoelectric amplifier are analyzed and studied.according to the demand and cost of the subject,the device selection is carried out.The embedded hardware based on ARM microprocessor is designed,which communicates with the upper computer through SPI protocol,and realizes the reference temperature acquisition and fiber channel switching under the control of the upper computer.The upper computer software is developed on MFC platform,which realizes the functions of measurement channel switching control,scattering signal acquisition,signal wavelet denoising algorithm processing,real-time dynamic temperature curve drawing,temperature database establishment and so on.Finally,the DTS system is tested and the integration of the prototype is completed.The performance parameters are as follows: the temperature measurement range is-25 ? to 200 ?,the temperature measurement accuracy is ±1 ?,the single channel positioning accuracy is ±1m,and the single channel measurement range is 10 km.Through time division multiplex data fitting,the measurement range are improved,and the system can adapt to more complex working conditions.The simulation experiments of power cable temperature field and cable fault DTS detection are carried out,and the results show that the prototype meets the needs of power cable fault monitoring.