Study On Multi-channel Optical Fiber Temperature-supervising System Based On Optic Absorption

Nowadays, with the development of industry and agriculture at high speed, higher and higher requirements of reliability and security for electric power system are put forward. There are many means to improve the reliability and security for electric power system, temperature supervise on line is a significant and efficient means for working condition supervise of large electric power equipment. This subject is aimed to achieve working condition supervise of high voltage equipment such as high voltage transformer, super generator, high voltage switch etc. At the same time, temperature supervise is crucial to the safe and economical operation and the work life-span of the high voltage equipment. So, it is necessary to supervise the hottest spot temperature of this equipment in order to ensure them to work at their best condition. The information about temperature supervise of high voltage equipment is consulted and analyzed at large near the last forty years. A novel scheme based on optic absorption of semiconductor is proposed, which can overcome the problem of low accuracy and bad reliability in this field. The system configuration of optical and electric portion is given. The major reasons, which cause the low accuracy and bad long-term stability, are the unsteadiness of the optical radiation of the light source and photodetector. An optic-feedback circuit is designed to adjust the drive current of the optic source according to the optic power radiating from the light source. And we get the more steady optic power then before. A reference light source is added in the system. The measurement optical signal and the reference optical signal are coupled into the same optical fiber, and transmitted into the electric signal by the same photodetector, therefore the effect of the photodetector drift to the measurement optical signal and the reference optical signal are coincident. A unique signal pick-up circuit is designed, which can automatic track the measurement signal and the reference signal respectfully, even they are submerged by the noise, and the noises caused by the background light and the photodetector are removed. A higher SNR is gotten. Furthermore, watchdog circuit and software anti-interference measures are designed also. The working steadiness of system is buildup further. The experimental result shows that the system we designed can achieve the following properties: the accuracy is approximately ? 0c over the range covered; the resolution 0.1 0c, respond time is about lms. Furthermore, this system is insensitive to fluctuation of the light source intensity, fiber losses, and photodetector drifts.