CN110261799B - High-temperature superconducting magnet quench detection system using distributed optical fiber sensing technology - Google Patents
High-temperature superconducting magnet quench detection system using distributed optical fiber sensing technology Download PDFInfo
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Abstract
The invention discloses a high-temperature superconducting magnet quench detection system utilizing a distributed optical fiber sensing technology, which comprises a distributed sensing optical fiber, an optical fiber switching module, distributed optical fiber sensing equipment, an upper computer control module and a quench judgment module. According to the invention, a flexible distributed sensing optical fiber is used as a sensor and is implanted into the surface of a magnet in an insulation part, a back Rayleigh scattering spectrum of the sensing optical fiber after the superconducting magnet quenches is detected in real time by adopting an optical frequency domain reflection technology, a low temperature resistant coating optical fiber is adopted in an ultralow temperature region, the spatial resolution and the acquisition frequency of the distributed sensing optical fiber are set by an upper computer control module, and the discrimination of a quenching detection signal is completed by a preset threshold module in a quenching discrimination module. The method can not only continuously measure the high spatial resolution of the high-temperature superconducting magnet, but also can position the quench area range, can completely avoid the influence of high voltage and electromagnetic back field noise, can complement the defects of conventional quench detection in the quench detection technology of the high-temperature superconducting magnet and the technical bottleneck of the conventional temperature measurement, and can be effectively used as a safety interlocking rear-stage quench detection means.
Description
Technical Field
The invention relates to the technical field of quench detection for high-temperature superconducting coils, in particular to a quench detection system for a high-temperature superconducting magnet by using a distributed optical fiber sensing technology.
Background
The use of a high temperature superconducting magnet makes it possible to increase the operating temperature or field strength of the coils used in tokamaks (such as CFETR or EU-DEMO). Furthermore, the temperature (safety) margin can be increased during operation. However, this puts higher demands on quench protection of the magnet. The high-temperature superconducting magnet has the characteristic of slow propagation speed in a normal area, and is approximately 2-3 orders of magnitude lower than the low-temperature superconducting magnet. When the resistivity is increased locally and unexpectedly, the high-temperature superconducting magnet is easy to form multiple hot spots and the like under the condition of quench, because the quench propagation speed is low, the temperature begins to change before the resistivity reaches a detectable value, which has adverse factors for accurate and rapid quench detection under high parameters, and thus parameters such as temperature strain of the superconducting magnet after quench and close to the essence of physical phenomena are prominent in the quench detection of the high-temperature superconducting magnet. The operation condition of the magnet needs to be rapidly monitored in real time, and the quench propagation rule of high-temperature superconductivity needs to be further researched.
The detection method in the quench detection of the high-temperature superconducting magnet mainly comprises the following steps: temperature sensing, voltage sensing, ultrasonic sensing, acoustic emission sensing techniques, Fiber Bragg Gratings (FBGs), and the like.
According to the traditional temperature detection, a resistance thermometer is arranged on the surface of a superconducting magnet, and due to the fact that operating parameters of the superconducting magnet are high, the resistance-based thermometer is easily affected by high-voltage damage when the resistance-based thermometer is directly arranged, a certain insulation measure is adopted on the surface of the thermometer and the surface of a magnet of a large superconducting magnet of an EAST fusion device at present, or a thermometer is installed on an insulator at the rear end of a cooling loop. Very good accuracy can be achieved based on resistance thermometers, but the problems facing superconducting magnets are evident: the resistance thermometer belongs to a point measurement mode, can only measure the temperature change of a certain point, needs to arrange a large number of thermometers for a magnet needing to detect a certain area, obviously has higher difficulty, is influenced by high voltage and electromagnetic noise, has certain hysteresis because the detected temperature is not the actual temperature of the magnet, is not beneficial to the quench detection of the superconducting magnet, can only be used as a backup reference, and has a technical bottleneck to be solved for the accurate real-time detection of physical parameters such as temperature and the like for the current large superconducting magnet.
The traditional voltage signal detection-based method is convenient to use, needs few quench detection circuits, and needs to overcome the problem of strong electromagnetic interference caused by high operation parameters. Meanwhile, the voltage signal after quenching is weak, and a certain lag time may occur relative to the temperature or strain change of the magnet, especially for a high-temperature superconducting magnet, the actual quenching condition of the conductor cannot be reflected in time only by detecting the voltage signal.
Acoustic emission detection technology belongs to passive detection: the conductor can not emit sound waves under normal conditions, once the conductor is quenched, the microstructure or stress of the conductor changes, a weak sound wave can be emitted, and whether the quenching is performed or not is judged by detecting a sound wave signal;
ultrasonic waves belong to active detection, and the ultrasonic waves propagate through a conductor, and the original (t) changes into (t) due to the transmission of the conductor, and the transfer function of the (t) is ℎ (t). The quench will cause the change of h (t) and further g (t), and whether the quench is caused is judged by detecting g (t);
ultrasonic waves and acoustic emission detection are mechanical waves, and do not need more signal lines, but signals are weak and are greatly influenced by noise, so that the ultrasonic waves and the acoustic emission detection cannot be used as a reliable quench basis. And a certain number of probes are required to be installed on the surface of the magnet, and the insulation structure of the large high-temperature superconducting magnet is not allowed to be damaged.
The high-temperature superconducting quench detection is a necessary guarantee for the safe operation of all magnets, and the high-temperature quench detection technology is based on the low-temperature superconducting magnet quench detection technology, is different from the quench propagation characteristic and needs to be explored.
Disclosure of Invention
The invention aims to make up for the defects of the prior art and provides a high-temperature superconducting magnet quench detection system utilizing a distributed optical fiber sensing technology.
The invention is realized by the following technical scheme:
a high-temperature superconducting magnet quench detection system utilizing a distributed optical fiber sensing technology comprises a distributed sensing optical fiber, an optical fiber switching module, a distributed optical fiber sensing device, an upper computer control module and a quench discrimination module, wherein the distributed sensing optical fiber is attached to the surface of a superconducting magnet, the distributed optical fiber sensing device comprises a linear sweep light source, a signal detection module and a signal processing module, the distributed sensing optical fiber is connected with the signal detection module through the optical fiber switching module, the linear sweep light source emits linear continuous light, the quench physical quantity of the distributed sensing optical fiber after the superconducting magnet is quenched affects the occurrence of backward Rayleigh scattering of optical signals in the distributed sensing optical fiber as signal light, the signal light is mixed with preset reference light on the signal detection module, and the signal processing module is used for processing the mixed signal, obtaining the spectral quantity of backward Rayleigh scattering to represent the physical information of a superconducting magnet after quenching, calculating the change position of the superconducting magnet quenching optical fiber through the frequency difference of different positions of the optical fiber to realize the positioning of the quenching optical fiber, measuring the quenching condition of the magnet at the position through the spectral offset, including the temperature or strain change condition, setting the spatial resolution and acquisition frequency of the distributed sensing optical fiber through the upper computer control module, judging the spectral offset and the time threshold of real-time sensing through the preset threshold in the quenching judgment module, and finishing the judgment of a quenching detection signal.
The signal detection module comprises a first coupler, a second coupler and a detector, continuous light of linear scanning of the scanning light wave emitted by the linear scanning light source is divided into two paths by the coupler, one path of light wave is injected into the distributed sensing optical fiber, Rayleigh scattering signals are continuously generated when the light wave propagates in the distributed sensing optical fiber, the Rayleigh scattering signals become signal light and are coupled into the detector through the second coupler, the other path of light coming out of the first coupler is directly coupled into the detector as reference light, the signal light and the reference light are mixed in the detector to obtain difference frequency signals, and the difference frequency signals are analyzed by the signal processing module.
The optical fiber switching module is a communication connector, a connector of the distributed sensing optical fiber led out of the superconducting magnet is protected by a copper pipe and is connected with the signal detection module through the communication connector and a communication optical fiber G652, the distributed sensing optical fiber is a bending insensitive single-mode optical fiber, and a low temperature resistant coating optical fiber is applied to liquid helium temperature zone detection.
The quench judging module comprises a threshold setting unit and a judging unit, wherein the threshold setting unit and the judging unit are connected with logic to evaluate the spectral offset of the sensing optical fiber after quench, quench judgment is set according to the property of the high-temperature superconducting material, the threshold setting unit sets the quench threshold, and quench judgment and quench area positioning are completed by the judging unit through combination and logic.
The distributed optical fiber sensing equipment adopts an optical frequency domain reflection technology to calibrate the position of a signal in a frequency domain.
The distributed optical fiber sensing device adopts tunable wavelength interference technology, so that the integrated physical quantity of distributed temperature or strain can have millimeter-scale spatial resolution on a standard optical fiber with the length of tens of meters.
The linear sweep frequency light source of the distributed optical fiber sensing equipment is characterized in that sweep frequency light waves emitted by the light source are continuous light which is linearly scanned.
And a copper pipe protection optical fiber structure is adopted at the magnet joint of the low-temperature area, and a common communication optical fiber is adopted to connect the sensing optical fiber and the optical fiber sensing equipment in the room-temperature area.
And the upper computer control module is used for carrying out communication control on the distributed optical fiber sensing equipment and displaying the spectrum change condition of each sensing point of the distributed sensing optical fiber in real time.
The invention aims to sense the quench physical quantity change of a high-temperature superconducting magnet by using a distributed optical fiber sensing technology, and quench detection is realized by demodulating the change condition of a backward Rayleigh scattering spectrum of a sensing optical fiber after the magnet quenches. The distributed optical fiber sensing equipment measures a backward Rayleigh scattering signal by using a tunable wavelength scanning interference method, so that the comprehensive measurement of distributed temperature and strain can have millimeter-level spatial resolution on a distributed sensing optical fiber with the length of dozens of meters, and the spectral shift precision corresponding to the comprehensive quantity of characterization quench information can reach 0.1 pm. And calibrating the quench area in a frequency domain according to the corresponding relation between the frequency interval and the space interval by demodulating the mixing signal of the signal detection module by adopting an optical frequency domain reflection technology.
The invention has the advantages that: the invention adopts the flexible distributed sensing optical fiber as a sensor, is implanted on the surface of a magnet in the insulation, detects the backward Rayleigh scattering spectrum of the sensing optical fiber after the superconducting magnet quenches in real time by adopting the optical frequency domain reflection technology, adopts the low temperature resistant coating optical fiber in an ultralow temperature area, not only can continuously measure with high spatial resolution, but also can reach dozens of meters of magnitude on the detection length of the optical fiber, can position the range of the quenching area, can completely avoid the influence of high voltage and electromagnetic background noise, can complement the defects of the conventional quenching detection in the high temperature superconducting magnet quenching detection technology, and can effectively serve as a safety interlocking rear-stage quenching detection means.
Drawings
FIG. 1 is a schematic structural diagram of the present invention.
Fig. 2 is a block diagram of a distributed optical fiber sensing apparatus.
Fig. 3 is a schematic diagram of wiring at a joint of the distributed sensing optical fiber superconducting magnet.
Detailed Description
As shown in fig. 1 and 2, a high temperature superconducting magnet quench detection system using distributed optical fiber sensing technology includes a distributed sensing optical fiber 1, an optical fiber switching module 2, a distributed optical fiber sensing device 3, an upper computer control module 4 and a quench discrimination module 5, wherein the distributed sensing optical fiber 1 is attached to the surface of a superconducting magnet 6, the distributed optical fiber sensing device 3 includes a linear sweep light source 7, a signal detection module 8 and a signal processing module 9, the distributed sensing optical fiber 1 is connected with the signal detection superconducting magnet module 8 through the optical fiber switching module 2, the linear sweep light source 7 emits linear continuous light, the quench physical quantity of the distributed sensing optical fiber 1 after quench affects the optical signal in the distributed sensing optical fiber to generate backward rayleigh scattering as signal light, and the signal light is mixed with preset reference light on the signal detection module 8, the frequency mixing signal is processed by the signal processing module 9, the spectrum quantity of the backward Rayleigh scattering is obtained to represent the physical information of the superconducting magnet after quenching, the quenching position of the superconducting magnet is calculated through the frequency difference of different positions of the optical fiber, quenching positioning is realized, the quenching condition of the magnet at the position is measured through the spectrum offset, the quenching condition comprises the temperature or strain change condition, the spatial resolution and the acquisition frequency of the distributed sensing optical fiber are set through the upper computer control module 4, the spectrum offset and the time threshold of real-time sensing are judged through the preset threshold in the quenching judging module 5, and the judgment of the quenching detection signal is completed.
As shown in fig. 2, the signal detection module 8 includes a first coupler 10, a second coupler 11, and a detector 12, where continuous light obtained by linearly scanning a swept optical wave emitted by the linear swept optical source 7 is divided into two paths by the first coupler 10, one path of the continuous light is injected into the distributed sensing optical fiber 1, the optical wave continuously generates rayleigh scattering signals while propagating in the distributed sensing optical fiber 1, the rayleigh scattering signals become signal light and are coupled to the detector 12 through the second coupler 11, the other path of the continuous light coming out of the first coupler 10 is directly coupled to the detector 12 as reference light, the signal light and the reference light are mixed in the detector 12 to obtain a difference frequency signal, and the difference frequency signal is analyzed by the signal processing module 9.
As shown in fig. 3, the optical fiber switching module 2 is a communication joint 13, a joint of the distributed sensing optical fiber 1 leading out of the superconducting magnet 6 is protected by a copper pipe 14, and is connected with a signal detection module through the communication joint 13 and a communication optical fiber G652, the distributed sensing optical fiber is a bending insensitive single-mode optical fiber, and a low temperature resistant coating optical fiber is used for detecting a liquid helium temperature zone.
The quench judging module 5 comprises a threshold setting unit and a judging unit, wherein the threshold setting unit and the judging unit are connected with logic to evaluate the spectral offset of the sensing optical fiber after quench, quench criterion is set according to the property of the high-temperature superconducting material, the threshold setting unit sets the quench threshold, and quench judgment and quench area positioning are completed by the judging unit through combining and logic.
The invention adopts flexible distributed sensing optical fiber as a sensor, the distributed sensing optical fiber is tightly attached to the surface of a high-temperature superconducting magnet in an insulating layer to be measured, the optical fiber is led out of a superconducting magnet joint safely by designing a protection structure, the backward Rayleigh scattering spectrum of the sensing optical fiber after the superconducting magnet quenches is demodulated by using distributed optical fiber sensing equipment based on an optical frequency domain reflection technology in real time, not only can high-spatial resolution continuous measurement be realized, but also the detection length of the optical fiber can reach dozens of meters, and simultaneously the quenching area range can be positioned, in a liquid helium temperature region and a high-parameter high-temperature superconducting magnet operating environment, the influence of high voltage and electromagnetic background noise can be completely avoided by adopting the superconducting magnet insensitive distributed sensing optical fiber, the defects of conventional quenching detection and the technical bottleneck of traditional temperature measurement can be complemented in the high-temperature quenching detection technology, the early warning function of safe operation of the high-temperature superconducting magnet can be effectively realized.
Claims (1)
1. A high-temperature superconducting magnet quench detection system using distributed optical fiber sensing technology is characterized in that: the superconducting magnet quenching device comprises a distributed sensing optical fiber, an optical fiber switching module, a distributed optical fiber sensing device, an upper computer control module and a quenching distinguishing module, wherein the distributed sensing optical fiber is attached to the surface of a superconducting magnet, the distributed optical fiber sensing device comprises a linear sweep light source, a signal detection module and a signal processing module, the distributed sensing optical fiber is connected with the signal detection module through the optical fiber switching module, the linear sweep light source emits linear continuous light, the quenching physical quantity of the distributed sensing optical fiber after the superconducting magnet is quenched affects the occurrence of backward Rayleigh scattering of optical signals in the distributed sensing optical fiber as signal light, the signal light is mixed with preset reference light on the signal detection module, the signal processing module is used for processing the mixed frequency signals, and the spectral quantity of the backward Rayleigh scattering is obtained to represent the physical information after the superconducting magnet is quenched, calculating the quench position of the superconducting magnet through the frequency difference of different positions of the optical fiber to realize quench positioning, measuring the quench condition of the magnet at the position through the spectral offset, wherein the quench condition comprises the temperature or strain change condition, setting the spatial resolution and acquisition frequency of the distributed sensing optical fiber through the upper computer control module, judging the spectral offset and the time threshold of real-time sensing through a preset threshold in the quench judging module, and finishing the judgment of a quench detection signal;
the signal detection module comprises a first coupler, a second coupler and a detector, continuous light of linear scanning of the scanning light wave emitted by the linear scanning light source is divided into two paths by the coupler, one path of light wave is injected into the distributed sensing optical fiber, rayleigh scattering signals are continuously generated when the light wave propagates in the distributed sensing optical fiber, the rayleigh scattering signals become signal light and are coupled into the detector through the second coupler, the other path of light coming out of the first coupler is directly coupled into the detector as reference light, the signal light and the reference light are subjected to frequency mixing in the detector to obtain difference frequency signals, and the difference frequency signals are subjected to spectral signal analysis by the signal processing module;
the optical fiber switching module is a communication connector, a connector of the distributed sensing optical fiber led out of the superconducting magnet is protected by a copper pipe, the connector and the communication optical fiber G652 are connected with the signal detection module through the communication connector, and the distributed sensing optical fiber is a bending insensitive single-mode optical fiber;
the quench judging module comprises a threshold setting unit and a judging unit, wherein the threshold setting unit and the judging unit are connected with logic to evaluate the spectral offset of the sensing optical fiber after quench, quench judgment is set according to the property of the high-temperature superconducting material, the threshold setting unit sets the quench threshold, and quench judgment and quench area positioning are completed by the judging unit through combination and logic.
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