WO2021248590A1

WO2021248590A1 - Quench detection device and method for high-temperature superconducting magnet

Info

Publication number: WO2021248590A1
Application number: PCT/CN2020/099870
Authority: WO
Inventors: 周考; 任丽; 石晶; 徐颖; 李敬东; 唐跃进
Original assignee: 华中科技大学
Priority date: 2020-06-08
Filing date: 2020-07-02
Publication date: 2021-12-16
Also published as: CN111665462B; CN111665462A

Abstract

A quench detection device and method for a high-temperature superconducting magnet. The device comprises: an optical fiber grating string FBG1, an optical fiber grating string FBG2, a data collection module, and a data processing module. There are multiple optical fiber gratings on FBG1 and FBG2. The optical fiber gratings can promptly sense minor deformations and a rise in temperature of a magnet due to quenching and are sensitive to the temperature and strain of a high-temperature superconducting magnet. FBG1 and FBG2 are wound on the surface of the high-temperature superconducting magnet in parallel. FBG1 is attached to the surface of the high-temperature superconducting magnet. FBG2 is fixed on the surface of the high-temperature superconducting magnet by using an adhesive. The temperature and strain at each position of the high-temperature superconducting magnet can be simultaneously detected quickly. When the magnet experiences local failure, due to the accumulation of heat in a local region, changes in temperature and strain occur quickly in said region, and although the voltage of the magnet does not change at this time, it can still be detected, by means of the changes in temperature and strain, that the magnet experiences failure, thereby significantly increasing the rate of quench detection for the high-temperature superconducting magnet.

Description

Quench detection device and method for high-temperature superconducting magnet

【Technical Field】

The invention belongs to the technical field of quench detection of high-temperature superconducting magnets, and more specifically relates to a quench detection device and method for high-temperature superconducting magnets.

【Background technique】

High-temperature superconducting magnets are currently one of the means to generate high-strength magnetic fields, and high-temperature superconducting magnets have unique advantages such as stable and long-lasting magnetic fields, low loss, and convenient use. They are used in many fields such as medical treatment, electric power, transportation vehicles, environmental protection, and scientific research. It has a wide range of important applications. However, compared with conventional magnet design, the development of superconducting magnets is more difficult and more complex. Since the electromagnetic properties of superconducting materials are very complicated, and their superconducting properties are closely related to factors such as operating current, ambient temperature, and magnetic field, when any of the above factors exceeds the critical value, it is very easy to cause quench failure of high-temperature superconducting magnets. It is necessary Real-time detection of the operating state of the magnet to ensure its reliable operation, so it is of great significance to study a quench detection device and method for high-temperature superconducting magnets.

At present, the commonly used quench detection devices for high-temperature superconducting magnets are mainly based on voltage detection and temperature rise detection to perform quench detection. When the existing voltage-based quench detection device for high-temperature superconducting magnets is used for quench detection, since the quench propagation speed of the high-temperature superconducting magnet is slow, the voltage rises at a relatively slower rate during the quench process of the high-temperature superconducting magnet. Slow, when the voltage change reaches the preset quench threshold, the required time is longer and the detection speed is slower. Therefore, if only the voltage detection device is used to monitor the magnet voltage, the quench critical voltage of the magnet cannot be detected before the magnet is seriously heated, and the protection action cannot be triggered in time to prevent the magnet from being irrecoverably damaged due to quenching; The quench detection devices for high-temperature superconducting magnets based on temperature rise detection generally use temperature sensors such as thermocouples or platinum resistances for measurement, and they have disadvantages such as being unable to be arranged along high-temperature superconducting tapes, not being used for higher voltage levels, and susceptible to electromagnetic interference. , Stability and reliability are low; at the same time, temperature sensors such as thermoelectric resistance are point measurement methods, which can only detect the temperature of a certain point on the magnet. For large high-temperature superconducting magnets, if you want to accurately monitor the temperature change, It is necessary to arrange multiple temperature sensors, which is difficult to achieve in the actual preparation process of the magnet.

[Summary of the invention]

In view of the above defects or improvement requirements of the prior art, the present invention provides a quench detection device and method for high-temperature superconducting magnets to solve the quench detection of high-temperature superconducting magnets due to voltage changes in the prior art. In the process, the slower voltage rise speed leads to the technical problem of slower detection speed.

In order to achieve the above objectives, in the first aspect, the present invention provides a quench detection device for high-temperature superconducting magnets, which includes: a fiber grating string FBG1, a fiber grating string FBG2, a data acquisition module, and a data processing module;

The fiber grating string FBG1 and the fiber grating string FBG2 are wound in parallel on the surface of the high-temperature superconducting magnet. Among them, the fiber grating string FBG1 and the fiber grating string FBG2 each have multiple fiber gratings, and the fiber grating string FBG1 is attached to the surface of the high-temperature superconducting magnet. It is not fixed on the surface of the magnet, the fiber grating string FBG2 is fixed on the surface of the high-temperature superconducting magnet; the high-temperature superconducting magnet is placed in the dewar, and the fiber grating string FBG1 and the fiber grating string FBG2 are drawn from the dewar and collected with the data Modules are connected; multiple voltage probes are led out from the data acquisition module, which are respectively connected to the high-temperature superconducting magnet; the data acquisition module is connected to the data processing module;

The fiber grating string FBG1 is used to sense the temperature of the high-temperature superconducting magnet based on the wavelength change of each fiber grating;

The fiber grating string FBG2 is used to sense the temperature and strain of the high-temperature superconducting magnet based on the wavelength change of each fiber grating;

The data acquisition module is used to collect the center wavelength variation of each fiber grating on the fiber grating string FBG1 and FBG2 and the voltage at each position of the high-temperature superconducting magnet, and send it to the data processing module; wherein, each fiber on the fiber grating string FBG2 The change in the center wavelength of the grating is the sum of the change in the center wavelength of each fiber grating on the FBG2 that is affected by temperature and the change in the center wavelength that is affected by strain;

The data processing module is used to obtain the temperature at each position of the high-temperature superconducting magnet according to the change in the center wavelength of each fiber grating on the fiber grating string FBG1, and perform temperature compensation on the fiber grating string FBG2 based on the obtained temperature, to obtain each of the high-temperature superconducting magnet The strain at each position; according to the temperature at each position of the obtained high-temperature superconducting magnet, the change in the center wavelength of each fiber grating on the fiber grating string FBG2, the strain and voltage at each position of the high-temperature superconducting magnet, the distortion of the high-temperature superconducting magnet Superstate detection.

Further preferably, the number of fiber gratings on the fiber grating string FBG1 and the fiber grating string FBG2 are the same, and there is a one-to-one correspondence.

Further preferably, glue is used to fix the fiber grating string FBG2 on the surface of the high-temperature superconducting magnet.

Further preferably, the data acquisition module includes an FBG demodulator and a voltage signal acquisition instrument;

The input end of the FBG demodulator is connected to the output ends of the fiber grating string FBG1 and the fiber grating string FBG2, and the input end of the voltage signal acquisition instrument is connected to the high-temperature superconducting magnet through each voltage probe;

The FBG demodulator is used to collect the center wavelength variation of each fiber grating on the fiber grating string FBG1 and fiber grating string FBG2, and send it to the data processing module;

The voltage signal collector is used to collect the voltage at each position of the high-temperature superconducting magnet through the voltage probe and send it to the data processing module.

Further preferably, the high-temperature superconducting magnet quench detection device further includes a display module, the input end of which is connected to the output end of the data processing module, for real-time display of the wavelength information of FBG1 and FBG2, the voltage of the superconducting magnet, and the high-temperature superconducting magnet The temperature and strain at each location, and the state of the high-temperature superconducting magnet.

In the second aspect, the present invention also provides a high-temperature superconducting magnet quench detection method based on the high-temperature superconducting magnet quench detection device provided in the first aspect of the present invention, including the following steps:

S1. Collect the center wavelength change of each fiber grating on the fiber grating string FBG1 and FBG2 and the voltage at each position of the high-temperature superconducting magnet; among them, the center wavelength change of each fiber grating on the fiber grating string FBG2 is each fiber grating on FBG2 The sum of the change in the center wavelength affected by temperature and the change in center wavelength affected by strain;

S2. According to the change of the center wavelength of each fiber grating on the fiber grating string FBG1, obtain the temperature at each position of the high-temperature superconducting magnet, and perform temperature compensation on the fiber grating string FBG2 based on the obtained temperature to obtain the temperature at each position of the high-temperature superconducting magnet strain;

S3. Determine the temperature at each position of the high-temperature superconducting magnet, the change in the center wavelength of each fiber grating on the fiber grating string FBG2, the strain and voltage at each position of the high-temperature superconducting magnet, and the corresponding preset quench judgment threshold. The size of the space and the time when the above-mentioned values exceed their corresponding preset quench judgment thresholds, the quench detection is performed on the high-temperature superconducting magnet.

Further preferably, the above step S2 includes:

S21: Based on the temperature demodulation formula of the fiber grating string FBG1, demodulate the change in the center wavelength of each fiber grating on the FBG1 to obtain the temperature at each position of the high-temperature superconducting magnet;

S22. According to the temperature demodulation formula of the fiber grating string FBG2 and the temperature at each position of the obtained high-temperature superconducting magnet, the temperature-affected central wavelength change of each fiber grating on the fiber grating string FBG2 is obtained, and the temperature is compared with that of the fiber grating string FBG2. The change of the center wavelength of the fiber grating is subtracted, and the absolute value of the result is the change of the center wavelength of each fiber grating on the grating string FBG2 that is affected by the strain. It is demodulated based on the strain demodulation formula of FBG2 to obtain the high temperature superconductor. Strain at each position of the magnet;

Among them, continuously calibrate the change of the center wavelength of each fiber grating on the fiber grating string FBG1 and FBG2 and the corresponding temperature within the range of liquid nitrogen temperature to room temperature, and obtain the temperature demodulation formulas of FBG1 and FBG2 through curve fitting;

In a constant temperature environment, the center wavelength change of each fiber grating on the fiber grating string FBG2 and its corresponding strain are continuously calibrated, and the strain demodulation formula of FBG2 is obtained by curve fitting.

Further preferably, the preset quench judgment threshold includes: a preset maximum magnet operating temperature T _max , a preset quench alarm time threshold Δt _max , a quench judgment value Δλ _2max based on the center wavelength, and a preset maximum allowable strain value of the magnet ε _max and the preset voltage-based quench judgment value ΔV _max ;

If the temperature at each position of the high-temperature superconducting magnet is greater than the preset maximum operating temperature of the magnet T _max and its duration is greater than the preset quench alarm time threshold Δt _max , or the center of each fiber grating on the fiber grating string FBG2 At least one of the wavelength changes is greater than the preset quench determination value Δλ _2max based on the center wavelength, and its duration is greater than the preset quench alarm time threshold Δt _max , or at least one strain at each position of the high-temperature superconducting magnet is greater than the preset Suppose that the maximum allowable strain value of the magnet ε _max and its duration is greater than the preset quench alarm time threshold Δt _max , or the voltage at each position of the high-temperature superconducting magnet is greater than the preset voltage-based quench judgment value ΔV _max , And its duration is greater than the preset quench alarm time threshold Δt _max , the high-temperature superconducting magnet is in a quench state, and it is necessary to prompt that the high-temperature superconducting magnet has a quench failure.

Further preferably, the above-mentioned quench detection method of the high-temperature superconducting magnet further includes step S4. After the execution of step S2 and before the execution of step S3, step S4 is executed to determine the quench state of the high-temperature superconducting magnet. If the magnet is not in the quench state, go to step S1, otherwise, go to step S3 to determine the quench state of the high-temperature superconducting magnet. If the high-temperature superconducting magnet is in the quench state, a quench alarm signal will be issued, and the test ends ; Otherwise, send out the imminent quench alarm signal, and go to step S1;

Wherein, step S4 includes: calculating the average value of the temperature at each position of the high-temperature superconducting magnet, and separately judging the average value of the temperature at each position of the high-temperature superconducting magnet, and the amount of change in the center wavelength of each fiber grating on the fiber grating string FBG2 The magnitude between the corresponding preset threshold for quenching judgment, and the time when each of the above values exceeds the corresponding preset threshold for quenching judgment, to detect and judge whether the high-temperature superconducting magnet is in a quenching state.

Further preferably, the preset impending quench judgment threshold includes: a preset magnet operating temperature alarm value T _al , a preset potential risk alarm time threshold Δt _al and a preset alarm value Δλ _2al based on the center wavelength;

If the average temperature at each position of the high-temperature superconducting magnet is greater than the preset magnet operating temperature alarm value T _al and its duration is greater than the preset potential risk alarm time threshold Δt _al , or the center of each fiber grating on the fiber grating string FBG2 If there is at least one wavelength change greater than the preset central wavelength-based alarm value Δλ _2al and its duration is greater than the preset potential risk alarm time threshold Δt _al , the high-temperature superconducting magnet is in a quench state.

In general, through the above technical solutions conceived in the present invention, the following beneficial effects can be achieved:

1. The present invention proposes a quench detection device for high-temperature superconducting magnets, which includes two fiber grating strings FBG1 and FBG2, and there are multiple fiber gratings on the fiber grating string, making the gratings small in size, easy to install, and free from electromagnetic interference. The optical fiber grating is used as a sensor for quench detection of high-temperature superconducting magnets. The optical fiber grating can timely sense the small deformation and temperature rise of the magnet due to quenching, and is relatively sensitive to the temperature and strain of the high-temperature superconducting magnet, and the present invention Wrap the fiber grating string FBG1 and fiber grating string FBG2 in parallel on the surface of the high-temperature superconducting magnet, attach the fiber grating string FBG1 to the surface of the high-temperature superconducting magnet, and fix the fiber grating string FBG2 on the surface of the high-temperature superconducting magnet. The temperature and strain at each position of the superconducting magnet are quickly detected. When the magnet fails locally, due to the accumulation of heat in the local area, the temperature and strain changes in this area will quickly occur, although the magnet voltage at this time is still not If changes occur, the failure of the magnet can also be detected by changes in temperature and strain, which greatly improves the quench detection speed of the high-temperature superconducting magnet, and can quickly detect the specific position on the high-temperature superconducting magnet in the quench state.

2. The quench detection device for high-temperature superconducting magnets proposed in the present invention can simultaneously monitor the temperature, strain, voltage and other multi-state variables of the magnet, and preset multiple quench determination thresholds for the multi-state variables of the magnet. Quickly respond to different types of failures of magnets, and have a wider range of application scenarios: For quench failures caused by thermal disturbances in local areas, the quench detection device can quickly detect the temperature and strain changes in the failure area based on two fiber grating strings. Once the temperature and strain determination threshold are exceeded, an alarm signal will be issued; for changes in magnet voltage caused by overcurrent and short-circuit faults of the magnet, the quench detection device can quickly detect changes in the magnet voltage based on the voltage probe, and once the voltage determination threshold is exceeded, an alarm signal will be issued .

3. The invention proposes a quench detection device for high-temperature superconducting magnets, which is based on the fiber grating string to perform real-time and rapid detection of the temperature and strain at various positions of the high-temperature superconducting magnet, which can not only accurately locate the local fault location of the magnet, but also It can monitor the direction in which the heat accumulated in the local failure area diffuses to the adjacent area, and then determine the range of other areas affected by the quench failure of the local area of the magnet, which is beneficial to the troubleshooting of the magnet during the maintenance and detection of the magnet, narrowing the scope of the troubleshooting, and reducing Fault handling time.

4. The present invention proposes a quench detection method for high-temperature superconducting magnets, which is based on fiber grating strings for real-time and rapid detection of temperature and strain at various positions of the high-temperature superconducting magnet, and combines the voltage information of the high-temperature superconducting magnet at the same time The quench judgment greatly reduces the probability of misjudgment due to external interference (test device damage, line aging, electromagnetic interference, etc.), the detection speed is fast, and the accuracy of the detection result is high.

【Explanation of the drawings】

Fig. 1 is a schematic diagram of a quench detection device for a high-temperature superconducting magnet according to Embodiment 1 of the present invention;

Figure 2 is a graph of the central wavelength change Δλ-temperature relationship curve of FBG1 and FBG2 and a graph of the central wavelength change Δλ-strain relationship curve of FBG2 provided by Embodiment 2 of the present invention; where (a) is the central wavelength of FBG1 and FBG2 Change Δλ-temperature relationship curve; (b) is the center wavelength change Δλ-strain relationship curve of FBG2;

3 is a flowchart of a quench detection method for a high-temperature superconducting magnet with imminent quench detection provided by Embodiment 2 of the present invention.

【detailed description】

In order to make the objectives, technical solutions, and advantages of the present invention clearer, the following further describes the present invention in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, but not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

Example 1,

A high-temperature superconducting magnet quench detection device, as shown in Figure 1, includes: a fiber grating string FBG1, a fiber grating string FBG2, a data acquisition module, and a data processing module;

Among them, the fiber grating string FBG1 and the fiber grating string FBG2 are wound in parallel on the surface of the high-temperature superconducting magnet. Among them, the fiber grating string FBG1 and the fiber grating string FBG2 each have multiple fiber gratings, and the fiber grating string FBG1 is attached to the high-temperature superconducting magnet. The surface is not fixed with glue to prevent the grating string FBG1 from being affected by the strain and temperature of the magnet, and is only sensitive to temperature; the fiber grating string FBG2 is fixed on the surface of the high-temperature superconducting magnet with glue; the high-temperature superconducting magnet is placed in the low temperature Dewar In the tank, the fiber grating string FBG1 and fiber grating string FBG2 are led out from the Dewar tank through a flange and connected to the data acquisition module; specifically, the flange provides a grating extraction channel for the fiber grating string FBG1 and the fiber grating string FBG2, Except for the grating lead-out channel, the remaining parts are filled with glue for sealing; multiple voltage probes are drawn from the data acquisition module, which are connected to the high-temperature superconducting magnet. In this embodiment, the number of voltage probes is two, respectively Connected to both ends of the high-temperature superconducting magnet; the data acquisition module and the data processing module are connected via Ethernet; preferably, the above-mentioned glue includes epoxy resin or silica gel; when the glue is silica gel, its high and low temperature resistance range is -60 ℃～+200℃. In this embodiment, the usable epoxy resin glue is Loctite Hysol epoxy glue, the model is E-90FL; the usable silica gel is Nanda 703 glue, the model is 703. Specifically, when fixing the fiber grating string FBG2, the grating string FBG2 is bonded to the surface of the superconducting magnet with liquid nitrogen and low temperature resistant epoxy resin, and the epoxy resin is evenly coated during bonding to avoid the adhesive coating. The uneven application causes low-temperature chirp on FBG2.

The fiber grating string FBG1 is used to sense the temperature of the high temperature superconducting magnet based on the wavelength change of each fiber grating, and at the same time as the temperature compensation device of the fiber grating string FBG2; the fiber grating string FBG2 is used to sense high temperature superconducting magnets based on the wavelength change of each fiber grating The temperature and strain of the magnet; specifically, the number of fiber gratings on the fiber grating string FBG1 and the fiber grating string FBG2 is the same; the specific number is determined by the size of the high-temperature superconducting magnet; the fiber grating string FBG1 and the fiber grating string FBG2 are one One correspondence can sense the parameters at the same position of the high-temperature superconducting magnet at the same time; among them, the i-th fiber grating on the fiber grating string FBG1 is used to sense the temperature at the i-th position of the high-temperature superconducting magnet, and the parameter on the fiber grating string FBG2 The i-th fiber grating is used to sense the temperature and strain at the i-th position of the high-temperature superconducting magnet. In this embodiment, the fiber grating strings FBG1 and FBG2 are single-mode fibers coated with polyimide and having high bending resistance, and the number of fiber gratings is 10-20.

The data acquisition module is used to collect the center wavelength variation of each fiber grating on the fiber grating string FBG1 and FBG2 and the voltage at each position of the high-temperature superconducting magnet, and send it to the data processing module; wherein, each fiber on the fiber grating string FBG2 The change in the center wavelength of the grating is the sum of the change in the center wavelength of each fiber grating on the FBG2 that is affected by temperature and the change in the center wavelength that is affected by strain. Specifically, the data acquisition module includes an FBG demodulator and a voltage signal acquisition instrument; the input end of the FBG demodulator is connected to the output ends of the fiber grating string FBG1 and the fiber grating string FBG2, and the input end of the voltage signal acquisition instrument passes through each voltage probe Connected to the high-temperature superconducting magnet; FBG demodulator is used to collect the center wavelength change of each fiber grating on the fiber grating string FBG1 and fiber grating string FBG2, and send it to the data processing module; the voltage signal acquisition device is used to pass the voltage probe Collect the voltage at each position of the high-temperature superconducting magnet and send it to the data processing module.

Specifically, the data processing module includes a demodulation unit and a quench judgment unit; wherein the output terminal of the demodulation unit is connected to the input terminal of the quench judgment unit;

The demodulation unit is used to demodulate the center wavelength variation of each fiber grating on the FBG1 based on the temperature demodulation formula of the fiber grating string FBG1 to obtain the temperature at each position of the high-temperature superconducting magnet, and output it to the quench judging unit; Then the temperature and strain cross-induction effects on the fiber grating string FBG2 are decoupled, specifically: according to the temperature demodulation formula of the fiber grating string FBG2 and the temperature at each position of the obtained high-temperature superconducting magnet, the fiber grating string FBG2 is obtained After the change in the center wavelength of each fiber grating affected by temperature is subtracted from the change in the center wavelength of each fiber grating on the fiber grating string FBG2, the absolute value of the result is the center of each fiber grating affected by the strain on the grating string FBG2 The amount of wavelength change is demodulated based on the strain demodulation formula of FBG2, and the strain at each position of the high-temperature superconducting magnet is obtained, and output to the quench judgment unit; among them, the temperature demodulation formula of FBG1 and FBG2 is passed in The results of experimental calibration of the center wavelength change and temperature of each fiber grating on FBG1 and FBG2 within the range of liquid nitrogen temperature (77K) to room temperature; the strain demodulation formula of FBG2 is obtained by setting the temperature at liquid nitrogen temperature (77K) to room temperature The results of experimental calibration of the center wavelength change and strain of each fiber grating on FBG2 in a constant temperature environment within the range; specifically, the center wavelength change and temperature of each fiber grating on FBG1 are tested within the range of liquid nitrogen temperature to room temperature After calibration, the change curve of the center wavelength of each fiber grating on FBG1 with temperature is obtained, and then the curve is fitted to obtain the temperature demodulation formula of FBG1. The center wavelength change and temperature of each fiber grating on FBG2 are calibrated experimentally in the range of liquid nitrogen temperature (77K) to room temperature, and the center wavelength change curve of each fiber grating on FBG2 with temperature is obtained, and then the obtained curve is calculated The temperature demodulation formula of FBG2 is obtained by fitting. The center wavelength change and strain of each fiber grating on FBG2 are calibrated experimentally in a constant temperature environment with a temperature in the range of liquid nitrogen temperature to room temperature, and the center wavelength change curve of each fiber grating on FBG2 with strain is obtained. The curve is fitted to obtain the strain demodulation formula of FBG2.

The quench determination unit is used to determine the temperature at each position of the high-temperature superconducting magnet, the change in the center wavelength of each fiber grating on the fiber grating string FBG2, the strain and voltage at each position of the high-temperature superconducting magnet, and the corresponding preset distortion. The size between the over-judgment thresholds, and the time when the above-mentioned values exceed their corresponding preset quench judging thresholds, the quench detection is performed on the high-temperature superconducting magnet; specifically:

If the temperature at each position of the high-temperature superconducting magnet is greater than the preset maximum operating temperature of the magnet T _max and its duration is greater than the preset quench alarm time threshold Δt _max , or the center of each fiber grating on the fiber grating string FBG2 At least one of the wavelength changes is greater than the preset quench determination value Δλ _2max based on the center wavelength, and its duration is greater than the preset quench alarm time threshold Δt _max , or at least one strain at each position of the high-temperature superconducting magnet is greater than the preset Suppose that the maximum allowable strain value of the magnet ε _max and its duration is greater than the preset quench alarm time threshold Δt _max , or the voltage at each position of the high-temperature superconducting magnet is greater than the preset voltage-based quench judgment value ΔV _max , And its duration is greater than the preset quench alarm time threshold Δt _max , the high-temperature superconducting magnet is in the quench state. At this time, it is necessary to prompt that the high-temperature superconducting magnet has a quench failure and transmit the alarm signal to the superconducting magnet containment system , In order to ensure that the system makes protective actions in time.

In order to provide users with sufficient response and processing time, the data processing module of the high-temperature superconducting magnet quench detection device proposed by the present invention also includes a quenching judgment unit to detect the quenching state of the high-temperature superconducting magnet.

Among them, the input terminal of the quench judgment unit is connected with the output terminal of the demodulation unit;

That is, the quench judging unit is used to calculate the average temperature at each position of the high-temperature superconducting magnet, and judge the average temperature at each position of the high-temperature superconducting magnet, and the center wavelength of each fiber grating on the fiber grating string FBG2. The magnitude between the amount of change and the corresponding preset threshold for quenching judgment, and the time when each of the above values exceeds its corresponding preset threshold for quenching judgment, to detect the quenching state of the high-temperature superconducting magnet; specifically:

Preferably, the high-temperature superconducting magnet quench detection device further includes a display module, the input end of which is connected to the output end of the data processing module for real-time display of the wavelength information of FBG1 and FBG2 (specifically including the amount of change of each central wavelength of each fiber grating ), the voltage of the superconducting magnet, the temperature and strain at each position of the high-temperature superconducting magnet, and the state of the high-temperature superconducting magnet.

Example 2,

A quench detection method for high-temperature superconducting magnets based on the quench detection device for high-temperature superconducting magnets provided in embodiment 1, including the following steps:

Specifically, it includes the following steps:

S22. According to the temperature demodulation formula of the fiber grating string FBG2 and the temperature at each position of the obtained high-temperature superconducting magnet, the temperature-affected central wavelength change of each fiber grating on the fiber grating string FBG2 is obtained, and the temperature is compared with that of the fiber grating string FBG2. The change of the center wavelength of the fiber grating is subtracted, and the absolute value of the result is the change of the center wavelength of each fiber grating on the grating string FBG2 that is affected by strain. Based on the strain demodulation formula of FBG2, the fiber grating on the obtained grating string FBG2 is The change in the center wavelength affected by the strain is demodulated to obtain the strain at each position of the high-temperature superconducting magnet;

Specifically, since the change of the center wavelength of the fiber grating is affected by temperature and strain at the same time, and the wavelength and temperature of the fiber grating are not linearly changed in the low temperature operating environment of the high-temperature superconducting magnet. Therefore, it is necessary to perform low-temperature calibration experiments on two fiber grating strings to obtain temperature and strain calibration formulas suitable for the low-temperature operating environment of superconducting magnets. Specifically, firstly calibrate the temperature of FBG1 and FBG2, specifically: continuously calibrate the center wavelength variation and the corresponding temperature of each grating on the fiber grating string FBG1 and FBG2 within the range of liquid nitrogen temperature (77K) to room temperature, respectively, and obtain FBG1 and upper FBG2 grating center wavelength variation curve with temperature, through curve fitting, the calibration formulas between the wavelength variation and temperature of FBG1 and FBG2 are as follows:

FBG1: Δλ _1i =f ₁ (T _i ), T _i =f ₁ ^-1 (Δλ _1i )

FBG2: Δλ _21i =f ₂ (T _i ), T _i =f ₂ ^-1 (Δλ _21i )

Among them, T _i =f ₁ ^-1 (Δλ _1i ) and T _i =f ₂ ^-1 (Δλ _21i ) are the temperature demodulation formulas of FBG1 and FBG2; i=1, 2,...M, M is FBG1 or the number of fiber grating FBG2, Δλ _1i of the i-th FBG FBG1 central wavelength change amount; Δλ _21i FBG2 the i-th FBG central wavelength change amount; Δλ _21i of the i-th fiber grating FBG2 center wavelength the amount of change, when the calibration experiment for temperature FBG2 only attached to the superconducting magnet, the center wavelength change amount at this time is only affected by temperature; T _i is the temperature of the high temperature superconducting magnet at the i-th fiber gratings FBG1 positions; as fiber gratings FBG1 string and a fiber grating FBG2 parallel series wound surface of a high temperature superconducting magnet, and the fiber grating correspondence, so FBG2 T _i is the temperature of the first high temperature superconducting magnet at the position of the i-th FBG.

Specifically, in this embodiment, the central wavelength variation Δλ-temperature curve of FBG1 and FBG2 obtained through temperature calibration experiments is shown in Figure 2(a). The polynomial fitting method can be used to obtain the central wavelength variation and temperature. The relationship is:

Secondly, perform strain calibration on FBG2, specifically: experimentally calibrate the center wavelength change and strain of each fiber grating on FBG2 in a constant temperature environment in the range of liquid nitrogen temperature to room temperature, and obtain the center of each fiber grating on FBG2 The curve of wavelength change with strain, and the curve is fitted to obtain the calibration formula between the wavelength change of FBG2 and the strain as follows:

FBG2: Δλ _2i = f ₃ (ε _i ), ε _i = f ₃ ^-1 (Δλ _22i )

Among them, ε _i =f ₃ ^-1 (Δλ _22i ) is the strain demodulation formula of FBG2, Δλ _22i and ε _i are respectively the center wavelength change of the i-th fiber grating on FBG2 and the corresponding strain of the high-temperature superconducting magnet, It should be noted that when doing the strain calibration experiment, the FBG2 is fixed on the superconducting magnet. Since the temperature is constant, the change in the center wavelength is only affected by the strain at this time.

Specifically, in this embodiment, the center wavelength change Δλ-strain relationship curve of FBG2 obtained by the calibration experiment is shown in Figure 2(b), and the relationship between the center wavelength change and strain can be obtained by linear fitting. The formula is:

Since the fiber grating string FBG2 is fixed on the high-temperature superconducting magnet by epoxy resin in the quench detection device of the high-temperature superconducting magnet, the center wavelength of the fiber grating on the FBG2 will be affected by temperature and strain at the same time. Therefore, FBG2 is used in practical applications. Will be affected by temperature and strain. Δλ _{2i is} the change in the center wavelength of the i-th fiber grating on FBG2 that is simultaneously affected by temperature and strain. The relationship with temperature and strain is as follows:

Δλ _2i =f ₂ (T _i )+f ₃ (ε _i )=Δλ _21i +Δλ _22i ;

Among them, Δλ _21i is the variation of the wavelength of the i-th grating on FBG2 affected by temperature, specifically: Δλ _21i = f ₂ (T _i ); since T _i =f ₂ ^-1 (Δλ _21i ) = f ₁ ^-1 ( Δλ _1i ), according to Δλ _21i =f ₂ (T _i ) and Δλ _22i =f ₃ (ε _i )=Δλ _2i -Δλ _21i _{, the amount of change Δλ 22i of the} i-th grating wavelength on FBG2 affected by strain can be obtained _{, Combined with the strain demodulation formula of FBG2, the strain ε i} =f ₃ ^-1 (Δλ _22i ) of the high-temperature superconducting magnet at the position of the i-th fiber grating on the FBG2 is obtained.

In summary, the temperature expression of the high-temperature superconducting magnet at the i-th fiber grating position of FBG1 is: T _i =f ₁ ^-1 (Δλ _1i ); the temperature of the high-temperature superconducting magnet at the i-th fiber grating position on FBG2 And the strain expressions are respectively: T _i =f ₂ ^-1 (Δλ _21i )=f ₁ ^-1 (Δλ _1i ) and ε _i =f ₃ ^-1 (Δλ _22i )=f ₃ ^-1 (Δλ _2i -Δλ _21i )=f ₃ ^-1 [Δλ _2i- f ₂ (T _i )].

Through the above process, using FBG1 which is not affected by strain as the temperature compensation device of FBG2, the temperature of FBG2 can be measured by FBG1, and then the change of the grating wavelength on FBG2 affected by temperature can be calculated from the measured temperature value, and then can be calculated Obtain the strain of each fiber grating on FBG2.

In this embodiment, the high-temperature superconducting cable is subjected to quench detection and judgment. Specifically, the above-mentioned preset quench judgment threshold includes: the preset maximum magnet operating temperature T _max , the preset quench alarm time threshold Δt _max , based on the center The wavelength quench judgment value Δλ _2max , the preset maximum allowable magnet strain value ε _max and the preset voltage-based quench judgment value ΔV _max . Step S3 includes:

_{If at least one of the temperatures (T i} ) at each position of the high-temperature superconducting magnet is greater than the preset maximum magnet operating temperature T _max and its duration is greater than the preset quench alarm time threshold Δt _max , or each of the fiber grating string FBG2 At least one of the central wavelength change (Δλ _2i ) of the fiber grating is greater than the preset quench judgment value Δλ _2max based on the central wavelength, and its duration is greater than the preset quench alarm time threshold Δt _max , or each position of the high-temperature superconducting magnet At least one strain (ε _i ) is greater than the preset maximum allowable strain value of the magnet ε _max and its duration is greater than the preset quench alarm time threshold Δt _max , or the voltage at each position of the high-temperature superconducting magnet (ΔV _j ) If there is at least one greater than the preset voltage-based quench determination value ΔV _max and its duration is greater than the preset quench alarm time threshold Δt _max , the high-temperature superconducting magnet is in the quench state. At this time, it is necessary to prompt that the high-temperature superconducting magnet has been A quench failure occurs, and the alarm signal is transmitted to the superconducting magnet containing system to ensure that the system makes a timely protection action; where j∈[1,M], M is the number of voltage probes.

Specifically, in the foregoing preset quench judgment thresholds, the preset maximum operating temperature _{of the magnet T max} is the highest operating temperature at which the magnet can operate normally, which is 80K in this embodiment; the quench judgment value based on the center wavelength is preset Δλ _2max is the maximum change in the center wavelength of the magnet when a quench failure occurs, which is taken as 30 pm in this embodiment; the preset maximum allowable strain value _{of the magnet ε max} is the magnet surface along the axis of the superconducting tape when the magnet fails a quench failure The maximum strain sent is 36 με in this embodiment; the preset voltage-based quench judgment value ΔV _max is the voltage threshold value when the magnet has a quench failure, which is conventionally taken as 0.1 μV/cm; the preset quench alarm The time threshold Δt _max is the maximum duration that the magnet is allowed to continue to run after a quench failure occurs. In this embodiment, it is 0.5s. Once the duration is exceeded, the magnet quench alarm signal is sent to start the protection action.

Further, in order to provide users with sufficient response and processing time, the above-mentioned high-temperature superconducting magnet quench detection method further includes step S4. After step S2 is executed and before step S3 is executed, step S4 is executed to determine the high-temperature superconducting magnet If the high-temperature superconducting magnet is not in the quench state, go to step S1, otherwise, go to step S3 to determine the quench state of the high-temperature superconducting magnet, if the high-temperature superconducting magnet is in the quench state , The quench alarm signal is issued, and the detection is over; otherwise, the high-temperature superconducting magnet is in the state of quenching. At this time, the high-temperature superconducting cable has the risk of quench failure. After the quenching alarm signal is issued, go to step S1;

Step S4 includes: calculating the average value of the temperature at each position of the high-temperature superconducting magnet, and separately judging the average value of the temperature at each position of the obtained high-temperature superconducting magnet, the change of the center wavelength of each fiber grating on the fiber grating string FBG2 and the corresponding Detect and judge whether the high-temperature superconducting magnet is in the state of quenching soon by the size between the preset thresholds for quenching judgment and the time when each of the above values exceeds its corresponding preset threshold for quenching judgment;

Among them, the preset impending quench judgment threshold includes: a preset magnet operating temperature alarm value T _al , a preset potential risk alarm time threshold Δt _al and a preset alarm value Δλ _2al based on the center wavelength;

_{Specifically, if the average value T av} of the temperature at each position of the high-temperature superconducting magnet is greater than the preset magnet operating temperature alarm value T _al , and its duration is greater than the preset potential risk alarm time threshold Δt _al , or the fiber grating string FBG2 At least one of the center wavelength changes (Δλ _2i ) of each fiber grating is greater than the preset alarm value Δλ _2al based on the center wavelength, and its duration is greater than the preset potential risk alarm time threshold Δt _al , then the high-temperature superconducting magnet is about to lose Super state.

Specifically, in the foregoing preset threshold for quench determination, the value of the preset magnet operating temperature alarm value T _al is the average operating temperature to ensure the normal operation of the magnet, which is set to 77K in this embodiment; the alarm value Δλ _2al of the center wavelength is The maximum change in the central wavelength of the local area of the magnet where thermal disturbance occurs but the timeout does not occur. In this embodiment, it is 21 pm; the potential risk alarm time threshold Δt _al is the maximum time allowed for the temperature and wavelength to exceed the corresponding alarm value. In the embodiment, it is 2s. Once the duration exceeds Δt _al, it indicates that the magnet may have a quench failure, and the detection device will send an alarm signal.

In order to describe the above method more clearly, the following is an explanation with reference to Figure 3, where Δt _l is the duration when the _{average temperature T av} at each position of the high-temperature superconducting magnet is greater than the preset magnet operating temperature warning value T _al, Δλ _2k _{is the center wavelength change (Δλ 2i} ) of each fiber grating on the fiber grating string FBG2 that is greater than the preset center-wavelength-based alarm value Δλ _2al , and Δt ₂ is Δλ _2k greater than the preset center-based The duration of the wavelength warning value Δλ _2al ; if not satisfied in step S4 ((T _av ＞T _al )∩(Δt ₁ ＞Δt _al ))∪((Δλ _2k ＞Δλ _2al )∩(Δt ₁ ＞Δt _al )), go to step S1; otherwise, go to step S3 to determine the quench state _{of the high-temperature superconducting magnet, where T m} _{is the temperature (T i} ) at each position of the high-temperature superconducting magnet greater than the preset magnet A certain temperature value of the maximum operating temperature T _max _{, Δt 3} is the duration when _{T m is} greater than the preset maximum operating temperature T _max _{of the magnet; Δλ 2l} is the central wavelength change of each fiber grating on the fiber grating string FBG2 (Δλ _2i ) is greater than a predetermined center wavelength based on the loss of a certain amount of wavelength variation is determined over the center value of Δλ _2max, Δt ₄ is greater than the predetermined Δλ _2l loss center wavelength based on the duration of the super-determined value Δλ _2max; ε _n is a high temperature strain (ε _i) at each position is greater than a preset magnet superconducting magnet allows a maximum strain the strain ε _max, Δt ₅ ε _n is greater than a predetermined maximum permitted duration magnets strain ε _max of; ΔV _b is _{Among the voltages (ΔV j} ) at each position of the high-temperature superconducting magnet, a certain voltage value greater than the preset voltage-based quench judgment value ΔV _max _{, Δt 6} is the _{value where ΔV b is} greater than the preset voltage-based quench judgment value ΔV _max Duration; in S3, if ((T _m ＞T _max )∩(Δt ₃ ＞Δt _max ))∪((Δλ _2l ＞Δλ _2max )∩(Δt ₄ ＞Δt _max )∪((ε _n ＞ε _max )∩(Δt ₅ ＞Δt _max ))∪((ΔV _b ＞ΔV _max )∩(Δt ₆ ＞Δt _max )), the quench alarm signal is issued, and the test ends; otherwise, the high-temperature superconducting magnet is about to quench Status, at this time, a quenching alarm signal is issued, indicating that the high-temperature superconducting cable has a risk of quench failure, and then go to step S1.

In summary, the present invention uses fiber grating as a sensor, combined with a voltage probe, and simultaneously detects the voltage, temperature, strain and wavelength information of the fiber grating during the operation of the high-temperature superconducting magnet in real time, and calculates the obtained detection quantities And processing, according to the processing results to make a comprehensive judgment, timely find and locate the quench fault location on the high-temperature superconducting magnet, the detection speed is fast, and the accuracy of the detection result is high, which can help the magnet protection system to quickly and accurately perform the quench protection action In addition, the present invention can also quickly detect the quenching state of the high-temperature superconducting magnet, and the specific position on the high-temperature superconducting magnet that is in the quenching state.

It is easy for those skilled in the art to understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modification, equivalent replacement and improvement, etc. made within the spirit and principle of the present invention, All should be included in the protection scope of the present invention.

Claims

A high-temperature superconducting magnet quench detection device, which is characterized by comprising: a fiber grating string FBG1, a fiber grating string FBG2, a data acquisition module and a data processing module;

The fiber grating string FBG1 and the fiber grating string FBG2 are wound in parallel on the surface of the high-temperature superconducting magnet, wherein the fiber grating string FBG1 and the fiber grating string FBG2 each have multiple fiber gratings, and the fiber grating string FBG1 is attached to the high-temperature superconducting magnet On the surface, the fiber grating string FBG2 is fixed on the surface of the high-temperature superconducting magnet; the high-temperature superconducting magnet is placed in the dewar, and the fiber grating string FBG1 and the fiber grating string FBG2 are drawn from the dewar and connected to the data acquisition module; A plurality of voltage probes are led out from the data acquisition module, which are respectively connected to the high-temperature superconducting magnet; the data acquisition module is connected to the data processing module;

The fiber grating string FBG1 is used to sense the temperature of the high-temperature superconducting magnet based on the wavelength change of each fiber grating;

The fiber grating string FBG2 is used to sense the temperature and strain of the high-temperature superconducting magnet based on the wavelength change of each fiber grating;

The data acquisition module is used to collect the center wavelength variation of each fiber grating on the fiber grating string FBG1 and FBG2 and the voltage at each position of the high-temperature superconducting magnet, and send it to the data processing module; wherein, the fiber grating string FBG2 The change in the center wavelength of each fiber grating is the sum of the change in the center wavelength of each fiber grating on the FBG2 that is affected by temperature and the change in the center wavelength that is affected by strain;

The data processing module is used to obtain the temperature at each position of the high temperature superconducting magnet according to the change in the center wavelength of each fiber grating on the fiber grating string FBG1, and perform temperature compensation on the fiber grating string FBG2 based on the obtained temperature to obtain the high temperature superconductor The strain at each position of the magnet; according to the temperature at each position of the obtained high-temperature superconducting magnet, the change in the center wavelength of each fiber grating on the fiber grating string FBG2, the strain and voltage at each position of the high-temperature superconducting magnet, the high-temperature superconducting magnet The quench state is detected.
The quench detection device for a high-temperature superconducting magnet according to claim 1, wherein the number of fiber gratings on the fiber grating string FBG1 and the fiber grating string FBG2 are the same, and there is a one-to-one correspondence.
The quench detection device for a high-temperature superconducting magnet according to claim 1, wherein the fiber grating string FBG2 is fixed on the surface of the high-temperature superconducting magnet by using glue.
The high-temperature superconducting magnet quench detection device according to claim 1, wherein the data acquisition module includes an FBG demodulator and a voltage signal acquisition device;

The input end of the FBG demodulator is connected to the output ends of the fiber grating string FBG1 and the fiber grating string FBG2, and the input end of the voltage signal collector is connected to the high temperature superconducting magnet through each voltage probe;

The FBG demodulator is used to collect the center wavelength variation of each fiber grating on the fiber grating string FBG1 and the fiber grating string FBG2, and send it to the data processing module;

The voltage signal collector is used to collect the voltage at each position of the high-temperature superconducting magnet through a voltage probe and send it to the data processing module.
The high-temperature superconducting magnet quench detection device according to claim 1, wherein the high-temperature superconducting magnet quench detection device further comprises a display module, the input end of which is connected with the output end of the data processing module for real-time Display the wavelength information of FBG1 and FBG2, the voltage of the superconducting magnet, the temperature and strain at each position of the high-temperature superconducting magnet, and the state of the high-temperature superconducting magnet.
A high-temperature superconducting magnet quench detection method based on the high-temperature superconducting magnet quench detection device according to any one of claims 1 to 5, characterized in that it comprises the following steps:

S1. Collect the center wavelength change of each fiber grating on the fiber grating string FBG1 and FBG2 and the voltage at each position of the high-temperature superconducting magnet; among them, the center wavelength change of each fiber grating on the fiber grating string FBG2 is each fiber grating on FBG2 The sum of the change in the center wavelength affected by temperature and the change in center wavelength affected by strain;

S2. According to the change of the center wavelength of each fiber grating on the fiber grating string FBG1, obtain the temperature at each position of the high-temperature superconducting magnet, and perform temperature compensation on the fiber grating string FBG2 based on the obtained temperature to obtain the temperature at each position of the high-temperature superconducting magnet strain;

S3. Determine the temperature at each position of the high-temperature superconducting magnet, the change in the center wavelength of each fiber grating on the fiber grating string FBG2, the strain and voltage at each position of the high-temperature superconducting magnet, and the corresponding preset quench judgment threshold. The size of the space, and the time when each of the above values exceeds its corresponding preset quench judgment threshold, the quench detection is performed on the high-temperature superconducting magnet.
The quench detection method of a high-temperature superconducting magnet according to claim 6, wherein the step S2 comprises:

S21: Based on the temperature demodulation formula of the fiber grating string FBG1, demodulate the center wavelength variation of each fiber grating on the FBG1 to obtain the temperature at each position of the high-temperature superconducting magnet;

S22. According to the temperature demodulation formula of the fiber grating string FBG2 and the temperature at each position of the obtained high-temperature superconducting magnet, the temperature-affected central wavelength change of each fiber grating on the fiber grating string FBG2 is obtained, and the temperature is compared with the temperature on the fiber grating string FBG2. The change of the center wavelength of the fiber grating is subtracted, and the absolute value of the result is the change of the center wavelength of each fiber grating on the grating string FBG2 affected by strain. Demodulate it based on the strain demodulation formula of FBG2 to obtain the high temperature superconductor Strain at each position of the magnet;

Among them, continuously calibrate the change of the center wavelength of each fiber grating on the fiber grating string FBG1 and FBG2 and the corresponding temperature within the range of liquid nitrogen temperature to room temperature, and obtain the temperature demodulation formulas of FBG1 and FBG2 through curve fitting;

In a constant temperature environment, the center wavelength change of each fiber grating on the fiber grating string FBG2 and its corresponding strain are continuously calibrated, and the strain demodulation formula of FBG2 is obtained by curve fitting.
The quench detection method for a high-temperature superconducting magnet according to claim 7, wherein the preset quench judgment threshold includes: a preset maximum magnet operating temperature T max , a preset quench alarm time threshold Δt max , The quench judgment value Δλ 2max based on the center wavelength, the preset maximum allowable strain value of the magnet ε max and the preset voltage-based quench judgment value ΔV max ;

If the temperature at each position of the high-temperature superconducting magnet is greater than the preset maximum operating temperature of the magnet T max and its duration is greater than the preset quench alarm time threshold Δt max , or the center of each fiber grating on the fiber grating string FBG2 At least one of the wavelength changes is greater than the preset quench determination value Δλ 2max based on the center wavelength, and its duration is greater than the preset quench alarm time threshold Δt max , or at least one strain at each position of the high-temperature superconducting magnet is greater than the preset Suppose that the maximum allowable strain value of the magnet ε max and its duration is greater than the preset quench alarm time threshold Δt max , or the voltage at each position of the high-temperature superconducting magnet is greater than the preset voltage-based quench judgment value ΔV max , And its duration is greater than the preset quench alarm time threshold Δt max , the high-temperature superconducting magnet is in a quench state, and it is necessary to prompt that the high-temperature superconducting magnet has a quench failure.
The quench detection method of a high-temperature superconducting magnet according to claim 6, characterized in that it further comprises step S4. After step S2 is executed and before step S3 is executed, step S4 is executed to determine the imminent quench of the high-temperature superconducting magnet If the high-temperature superconducting magnet is not in the quench state, then go to step S1, otherwise, go to step S3 to determine the quench state of the high-temperature superconducting magnet. If the high-temperature superconducting magnet is in the quench state, then the quench If the alarm signal is exceeded, the detection is over; otherwise, an alarm signal about quenching is issued, and go to step S1;

Among them, step S4 includes: calculating the average value of the temperature at each position of the high-temperature superconducting magnet, and separately judging the average value of the temperature at each position of the high-temperature superconducting magnet, and the change of the center wavelength of each fiber grating on the fiber grating string FBG2 The magnitude between the corresponding preset threshold for quenching judgment and the time when each of the above values exceeds the corresponding preset threshold for quenching judgment is used to detect and judge whether the high-temperature superconducting magnet is in a quenching state.
The quench detection method of a high-temperature superconducting magnet according to claim 9, characterized in that the preset threshold for judgment of imminent quench comprises: a preset magnet operating temperature alarm value T al and a preset potential risk alarm time threshold Δt al And preset the alarm value Δλ 2al based on the center wavelength;

If the average temperature at each position of the high-temperature superconducting magnet is greater than the preset magnet operating temperature alarm value T al and its duration is greater than the preset potential risk alarm time threshold Δt al , or the center of each fiber grating on the fiber grating string FBG2 If there is at least one wavelength change greater than the preset central wavelength-based alarm value Δλ 2al and its duration is greater than the preset potential risk alarm time threshold Δt al , the high-temperature superconducting magnet is in a quench state.