Research On Engineering Application Of Distributed Optical Fiber Temperature Measurement Technology In High Temperature Superconducting Cables

The high-temperature superconducting（HTS）power cables have large transimission capacity,once HTS cables occur quench,it will seriously threaten the safety of cable body and power system.Therefore,the fault detection and protection is one of the key technologies for the large-scale engineering applocations of HTS cables.Conventional fault detection of HTS cable is generally based on the HTS cable port characteristics.It is difficult for thermocouple and voltage detection methods to detect the local faults of HTS cables,timely and effectively.It is necessary to explore and study the local fault detection and location technology of HTS cables.Based on this,this paper has carried out research on the engineering application of distributed optical fiber temperature measurement technology in HTS cables.The main research contents and results are as follows:（1）Aiming at the distributed optical fiber temeperature measurement system has not been calibrated at the cryogenic operating temperature of HTS cables,a cryogenic calibration experiment is carried out on this system,and a method of optical fiber segmental calibration by adding gain and offset is proposed.After calibration,the temperature measurement accuracy of this system is within±1K in liquid nitrogen（LN₂）,and it can measure temperature stably and reliably in the temperature range of 77K to283K.（2）Aiming at HTS cables operating at LN₂ temperature zone and its complex construction environment,the model of the packaged optical fiber used in HTS cables is determined.The effects of different packaging materials and packaging forms on the low-temperature sensing characteristics and mechanical properties of optical fibers are experimentally studied.Combing with the low-temperature resistance and mechanical properties of these optical fibers,a miniature armored optical fiber with a diameter of0.75mm suitable for superconducting cable engineering applications is selected.（3）The exploration and verification of optical fiber winding process are completed on a 30m copper cable.Aiming at the engineering problems in the optical fiber winding process,the optical fiber winding scheme and the winding process flow are given.Aiming at the cryogenic-sealed operation and regular maintenance of HTS cables,the design and optimition of optical fiber lead-out connector on the HTS cable terminationl are completed.The optical fiber is lead out of the HTS cable terminal without demage,and the lead-out connector has stable sealing performance in the HTS cable type test for 3 months.（4）The distributed optical fiber temperature measurement test is carried out on a30m/10k V/2.5k A HTS cable,and the optical fiber winding and integration scheme on HTS cable for engineering practice are summarized.The test results show that the optical fiber has good low-temperature measurement performance and insulation performance:the uneven temperature distribution along this HTS cable during the thermocycling is detected timely by the optical fiber,and the abnormal temperature fluctuation（>1K）during HTS cable load cycle is also identified effectively by the optical fiber.The engineering feasibility of the application of the optical fiber temperature measurement technology in HTS cable is verified.