Optical fiber Raman cable temperature monitoring and alarm system with attenuation self-compensation

Abstract

The invention discloses an optical fiber Raman cable temperature monitoring and alarm system with attenuation self-compensation. The system comprises an optical fiber pulse laser, an optical fiber wavelength division multiplexer, a first photoelectric receiving module, a second photoelectric receiving module, a data acquisition module, a computer, a calibrating optical cable, a sensing optical cable, a reflector and a point type temperature sensor. The computer software comprises three parts, namely real-time temperature monitoring, historical data retention and temperature rise fault alarm. An optical fiber Raman distributed temperature sensor with attenuation self-compensation can eliminate influence of optical fiber attenuation change along the cable caused by bend, strain, node loss and particularly long-term operation and working environment difference, attenuation self-compensation is realized, and the temperature-sensing stability and reliability of the system are improved. The cable temperature monitoring and alarm computer software can realize early warning and alarm by comparing the current data and historical data to obtain an operating state of the cable.

Description

technical field [0001] The invention belongs to the field of distributed optical fiber sensing and temperature measurement, in particular to an attenuation self-compensating optical fiber Raman cable temperature monitoring and alarm system, which is a system for monitoring the temperature distribution of power cables and abnormal alarming. Background technique [0002] At present, with the development of smart grid, there are higher and higher requirements for the monitoring of the working status of cables. Traditional temperature sensors bring great inconvenience to installation and networking due to their point-type temperature measurement characteristics. The temperature sensing system based on optical fiber Raman scattering is a distributed temperature sensing system in the true sense. The optical fiber can not only transmit optical signals, but also itself is a sensor, so its temperature measurement and monitoring range is large, and it is not affected by electromagneti...

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Problems solved by technology

The first method is the most ideal installation method, that is, the optical fiber is directly built into the cable conductor core (or between the insulation shielding layers), so that the temperature of the optical fiber is the temperature of the cable, and the information obtained on the working status of the cable is more accurate. But this also brings two problems: 1. A special cable is required, 2. The installation and connection of this special cable is inconvenient, so this solution has not been promoted at present

The second method is a more practical installation method, which is to install the optical fiber on the outer surface of the cable. This method is more convenient to install, but there are two problems. On the one hand, although the temperature of the cable fiber core is high when a fault occurs, the cable cannot The surface temperature is low, and the average temperature rise is about 10 degrees Celsius. However, due to the difference in the location of the cable laying, and the temperature of the cable surface is greatly affected by the external environment, the temperature difference of the cable at different locations and at different times is 10 degrees Celsius. Therefore, the temperature The alarm needs to be determined according to the temperature rise of different locations; on the other hand, after a period of time, the optical fiber has been in different environments (such as temperature and humidity) for a period of time, which will lead to differences in the attenuation coefficients of each section of the optical fiber, and this It has a great influence on the accurate calibration of the temperature value, so in such a system, the temperature measurement noise level is not a particularly prominent problem, and it is particularly important to eliminate the influence of the attenuation change along the optical fiber on the temperature calibration, thereby improving the accuracy of the temperature calibration

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