Device for detecting alternating voltage based on fiber-optic current sensor

Abstract

The application discloses a device for detecting alternating voltage based on an optical fiber current sensor, and solves the technical problem of low voltage detection accuracy in the prior art. The device comprises a solenoid, a wire wound in a spiral, the wire having a first end and a second end; a plurality of capacitors, the capacitance values of the plurality of capacitors being different, and any capacitor being operatively connected in series with the first end of the wire; and an optical fiber current sensor, a sensing head of the optical fiber current sensor being located in the solenoid; wherein the second end of the wire and the capacitors are respectively used for connecting two different electric potential connectors. The device provided by the application improves the sensitivity and accuracy of alternating voltage detection.

Description

Technical Field

[0001] This application belongs to the field of voltage detection technology, specifically relating to a device for detecting AC voltage based on an optical fiber current sensor. Background Technology

[0002] In the field of voltage measurement in power systems, fiber optic voltage sensing technology has become a research hotspot due to its unique advantages, including excellent electrical insulation and strong resistance to electromagnetic interference. Voltage sensing technology based on fiber optic gratings involves attaching a fiber optic grating to the surface of a piezoelectric material. The deformation of the piezoelectric material under voltage causes a periodic change in the grating, thereby altering the reflected wavelength. The voltage value is then obtained through wavelength demodulation.

[0003] However, voltage sensing technology based on fiber Bragg gratings is susceptible to the combined effects of temperature and vibration on piezoelectric materials, and is also prone to electromagnetic interference, resulting in low voltage detection accuracy. Summary of the Invention

[0004] To address the technical problem of low measurement accuracy of current voltage sensors, this application provides a device for detecting AC voltage based on an optical fiber current sensor.

[0005] This application provides a device for detecting AC voltage based on an optical fiber current sensor, comprising:

[0006] A solenoid is a helically wound conductor having a first end and a second end;

[0007] The capacitor is provided in multiple form, and the capacitance values ​​of the multiple capacitors are all different. Any one of the capacitors is operably connected in series with the first end of the wire.

[0008] An optical fiber current sensor, wherein the sensing head of the optical fiber current sensor is located inside the solenoid;

[0009] The second end of the wire and the capacitor are used to connect two terminals with different electromotive forces.

[0010] In some embodiments, when the sensing head of the fiber optic current sensor is a sensing fiber, the sensing fiber is spirally wound around the sensing shaft, the axis of the solenoid is perpendicular to the sensing shaft, and the sensing fiber passes through the cavity of the solenoid.

[0011] In some embodiments, the winding diameter of the sensing optical fiber is 7cm to 10cm; the ratio of the axial length of the solenoid to the winding diameter of the sensing optical fiber is less than 0.4.

[0012] In some embodiments, when the sensing head of the fiber optic current sensor is a magneto-optical crystal, the magneto-optical crystal is cylindrical, and the central axis of the cylindrical magneto-optical crystal coincides with the axis of the solenoid.

[0013] In some embodiments, the ratio of the outer diameter of the solenoid to the diameter of the magneto-optical crystal is not greater than 4; the ratio of the axial length of the solenoid to the length of the magneto-optical crystal is greater than 5.

[0014] In some embodiments, the ratio of the axial length to the diameter of the solenoid is greater than 10.

[0015] In some embodiments, a controller and a frequency detector are also included, the frequency detector being operatively electrically connected to the controller;

[0016] The fiber optic current sensor is electrically connected to the controller.

[0017] In some embodiments, the solenoid includes a plurality of helical segments, wherein any number of the helical segments are arranged sequentially along the axial direction of the solenoid, and adjacent helical segments are detachably electrically connected.

[0018] The device for detecting AC voltage based on an optical fiber current sensor according to an embodiment of this application includes a solenoid, a capacitor, and an optical fiber current sensor. The solenoid is a helically wound conductor with a first end and a second end. Multiple capacitors are provided, each with a different capacitance value, and any one capacitor is operably connected in series with the first end of the conductor. The sensing head of the optical fiber current sensor is located inside the solenoid. The second end of the conductor and the capacitors are used to connect two terminals with different electromotive forces.

[0019] Multiple capacitors with different capacitance values ​​are provided, so the capacitor with the target capacitance value can be determined based on the frequency of the voltage to be measured. This application connects the capacitor with the target capacitance value in series with a solenoid. The inductive reactance of the solenoid is close to the capacitive reactance of the capacitor with the target value. At this point, the impedance of the closed circuit is at its minimum, resulting in a larger current flowing through the conductor and a larger electromagnetic field from the solenoid. When polarized light is transmitted through the sensing head located inside the solenoid, the deflection angle is also larger, meaning the intensity change of the polarized light is also very large. This makes the current detection result of the fiber optic current sensor more sensitive, thereby improving the current accuracy. Since voltage is the product of current and resistance, higher sensitivity of the current result leads to higher sensitivity of the measured voltage value, thus improving accuracy.

[0020] Since this application uses an optical fiber current sensor to detect current and uses it as a basis to detect voltage, the sensing head of the optical fiber current sensor is a sensing optical fiber or a magneto-optical crystal. The sensing head is less affected by temperature and vibration, thus improving the accuracy of current detection and thereby improving the accuracy of voltage detection.

[0021] The device provided in this application is equipped with a solenoid, which has a large and uniform electromagnetic field at its central axis, reducing external electromagnetic interference and improving the accuracy of current detection, thereby improving the accuracy of voltage detection. Attached Figure Description

[0022] Figure 1 A schematic diagram of the device for detecting AC voltage based on an optical fiber current sensor according to this application is shown.

[0023] Figure 2 A schematic diagram of a fiber optic current sensor with a magneto-optical crystal as the sensing head, combined with a solenoid, is shown.

[0024] Figure 3 A schematic diagram of another fiber optic current sensor using a magneto-optical crystal as the sensing head and coupled with a solenoid is shown.

[0025] Figure 4 This diagram illustrates another type of fiber optic current sensor that uses a magneto-optical crystal as the sensing head in conjunction with a solenoid.

[0026] Figure 5 A schematic diagram of a fiber optic current sensor with a sensing fiber as the sensing head and a solenoid is shown.

[0027] Explanation of reference numerals in the attached figures:

[0028] 10-Capacitor, 20-Solenoid, 30-Fiber optic current sensor, 301-Light source, 302-First single-fiber collimator, 303-Polarizer, 304-Sensing head, 304a-Magneto-optical crystal, 304b-Sensing fiber, 305-45° Faraday rotator, 306-First Wollaston prism, 307-First dual-fiber collimator, 308-Optical circulator, 309-Second dual-fiber collimator, 310-Second Wollaston prism, 311-22.5° Faraday rotator, 312-Faraday reflector, 313-Second single-fiber collimator, 314-Third Wollaston prism, 315-Fourth Wollaston prism, 316-Third single-fiber collimator, 317-Photodetector, 318-Fourth single-fiber collimator. Detailed Implementation

[0029] To enable those skilled in the art to more clearly understand this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0030] According to a first aspect of this application, a device for detecting AC voltage based on an optical fiber current sensor is provided. This device has high detection sensitivity and high accuracy.

[0031] This application is described below with reference to the accompanying drawings and specific embodiments:

[0032] Please see Figure 1 The AC voltage detection device provided in this application includes a solenoid 20, a capacitor 10, and an optical fiber current sensor 30. The solenoid 20 is a helically wound conductor with a first end and a second end. Multiple capacitors 10 are provided, each with a different capacitance value. Any capacitor 10 is operably connected in series with the first end of the conductor. The sensing head 304 of the optical fiber current sensor 30 is located inside the solenoid 20. The second end of the conductor and the capacitors 10 are used to connect two terminals with different electromotive forces.

[0033] When the solenoid 20, capacitor 10, and two connectors are conducting, a closed loop is formed. At this time, the sensing head 304 of the fiber optic current sensor 30 is located inside the solenoid 20, and the wires of the solenoid 20 are energized, forming an "electric-optical" structure. In this way, the magnetic field generated by the solenoid 20 will be concentrated on the optical path where the sensing head 304 is located, thereby improving the ability of the fiber optic current sensor 30 to resist external magnetic field interference and improving the current detection sensitivity of the fiber optic current sensor 30.

[0034] There are multiple capacitors 10, and the capacitance values ​​of the multiple capacitors 10 are different. Therefore, the capacitor 10 with the target capacitance value can be determined according to the frequency of the voltage to be measured. Any capacitor 10 can be operatively connected in series with the first end of the wire, so the capacitor 10 with the target capacitance value can be connected to the circuit to detect the frequency of the voltage to be measured.

[0035] For high-frequency AC voltage under test, the inductive reactance of solenoid 20 is very high after the circuit is closed. This reduces the current flowing through the wire to a very small value, which means that the point magnetic field inside solenoid 20 is also very small. When polarized light propagates through the sensing head 304 located inside solenoid 20, the deflection angle is also relatively small, which means that the change in the intensity of polarized light is also very small. As a result, the sensitivity of the current measured by fiber optic current sensor 30 is reduced. Therefore, the voltage value calculated using the low-accuracy current is also very low in sensitivity, and thus the accuracy is also poor.

[0036] This application connects a capacitor 10 with a target capacitance value and a solenoid 20 in series. The inductive reactance of the solenoid 20 is close to the capacitive reactance of the capacitor 10 with the target capacitance value. At this time, the impedance of the closed circuit is the minimum, so the current flowing through the conductor of the solenoid 20 will be relatively large, and the electromagnetic field of the solenoid 20 will also be relatively large. When polarized light is transmitted through the sensing head 304 located inside the solenoid 20, the deflection angle is also relatively large, which means that the intensity change of the polarized light is also very large. This makes the current detection result of the fiber optic current sensor 30 more sensitive, thereby improving the current accuracy. Since voltage is the product of current and resistance, the higher the sensitivity of the current result, the higher the sensitivity of the measured voltage value, and thus the higher the accuracy.

[0037] In some embodiments, the solenoid 20 includes a plurality of helical segments, wherein any number of helical segments are arranged sequentially along the axial direction, and adjacent helical segments are detachably electrically connected.

[0038] In the closed loop of voltage measurement, the inductive reactance of solenoid 20 is exactly equal to the capacitive reactance of capacitor 10, thus forming a resonant series circuit. When current flows through solenoid 20, it exhibits inductive reactance. Since the capacitance values ​​of different capacitors 10 are not continuously changing, it is difficult to make the inductive reactance of solenoid 20 exactly equal to the capacitive reactance of capacitor 10. By configuring solenoid 20 as a multi-segment structure, the number of solenoid segments can be adjusted according to the existing capacitance value of capacitor 10 and the frequency of the voltage to be measured. This allows for adjustment of the inductive reactance of solenoid 20, making it as close as possible to the capacitive reactance, thereby reducing the impedance in the closed circuit, increasing the current in the closed circuit, and improving the sensitivity and accuracy of voltage detection.

[0039] In some embodiments, the axial lengths of the multiple solenoid segments can be different or the same, meaning the internal resistances of the multiple solenoid segments can be the same or different. The winding directions of the multiple solenoid segments are the same, so that electromagnetic fields with the same direction can be generated within them. This application does not impose limitations. For electrical connections between multiple solenoid segments, quick-connect fittings can be provided at the ends of the wires of the solenoid segments to achieve rapid connection and disconnection.

[0040] The sensing head 304 of the fiber optic current sensor 30 can be either a sensing fiber 304b or a magneto-optical crystal 304a. The two cases will be described below.

[0041] When the sensing head 304 of the fiber optic current sensor is a sensing fiber 304b: the sensing fiber 304b is spirally wound around the sensing shaft, the axis of the solenoid 20 is perpendicular to the sensing shaft, and the sensing fiber 304b passes through the cavity of the solenoid 20.

[0042] Similar to solenoid 20, sensing fiber 304b is wound around the sensing axis in the form of a coil. When polarized light is transmitted to sensing fiber 304b located inside solenoid 20, the portion of sensing fiber 304b inside solenoid 20 extends along the axial direction of solenoid 20. That is, sensing fiber 304b is placed in the axial region of the strongest magnetic field inside solenoid 20. The transmission direction of polarized light is parallel to the direction of the magnetic field inside solenoid 20. At this time, the conditions of Faraday effect are met, thereby realizing the rotation of polarized light and expanding the rotation angle, enhancing the current detection sensitivity, and thus improving the sensitivity and accuracy of voltage detection.

[0043] In some embodiments, the winding diameter of the sensing fiber 304b is 7cm to 10cm, for example, 8cm or 9cm. The portion of the sensing fiber 304b located inside the solenoid 20 can coincide with the axis of the solenoid 20, precisely in the region of the solenoid 20 where the axial magnetic field is strongest and most uniform, maximizing the accumulation of the Faraday magneto-optical effect, improving the sensitivity of current detection, and thus ensuring the sensitivity of voltage detection. Simultaneously, this allows for a smaller size of the fiber optic current sensor 30, saving space.

[0044] In other embodiments, the winding diameter of the sensing fiber 304b can be less than 7cm, such as 6cm, or greater than 10cm, such as 12cm. The fiber optic current sensor 30 can still detect current and thus obtain voltage. However, it should be noted that if the winding diameter of the sensing fiber 304b is less than 7cm, such as 5cm, it may lead to an excessively small bending diameter, which can introduce mechanical stress and cause birefringence in the sensing fiber 304b. This results in unstable polarization state of polarized light during transmission, interfering with the detection of the Faraday rotation angle. Consequently, the current value measured by the fiber optic current sensor 30 may have errors and low accuracy, leading to low accuracy in the voltage detection value.

[0045] In some embodiments, the ratio of the axial length of the solenoid 20 to the winding diameter of the sensing fiber 304b is less than 0.4, for example, a ratio of 0.38, 0.3, or 0.2. This ratio ensures that each fiber in the loop formed by the sensing fiber 304b is located in a region with a high and uniform magnetic field strength near the central axis of the solenoid 20, maximizing the Faraday magneto-optical effect, resulting in a larger Faraday rotation angle and higher demodulation sensitivity, thus leading to higher voltage detection sensitivity and accuracy. Furthermore, the uniform magnetic field of the sensing fiber 304b reduces noise interference, further improving the accuracy and stability of current measurement by the fiber optic current sensor 30, thereby affecting the accuracy and stability of voltage detection. Additionally, it allows for a smaller size of the fiber optic current sensor 30, saving space.

[0046] In other embodiments, the ratio of the axial length of the solenoid 20 to the winding diameter of the sensing fiber 304b can also be greater than 0.4. The fiber optic current sensor 30 can still detect current and thus obtain voltage. However, it should be noted that if the ratio of the axial length of the solenoid 20 to the winding diameter of the sensing fiber 304b is greater than 0.4, for example, when the axial length of the solenoid 20 is 1 relative to the winding diameter of the sensing fiber 304b, the radius of curvature of the sensing fiber 304b is small, and the portion of the sensing fiber 304b located inside the solenoid 20 is bent and difficult to be parallel to the axis of the solenoid 20. Therefore, the electromagnetic induction intensity is high at some positions and low at others in the portion of the sensing fiber 304b located inside the solenoid 20. This will cause the Faraday rotation angle experienced by the polarized light at different positions in the sensing fiber 304b to be different, ultimately leading to an error in the overall Faraday rotation angle measurement.

[0047] When the sensing head 304 of the fiber optic current sensor is a magneto-optical crystal 304a: the magneto-optical crystal 304a is cylindrical, and the central axis of the cylindrical magneto-optical crystal 304a coincides with the axis of the solenoid 20.

[0048] The propagation direction of polarized light in magneto-optical crystal 304a is along the central axis of magneto-optical crystal 304a, and the direction of magnetic field in solenoid 20 is along the axis of solenoid 20. Therefore, by aligning the central axis of magneto-optical crystal 304a with the axis of solenoid 20, the polarized light undergoes the Faraday effect, and the polarization is deflected, so that fiber optic current sensor 30 can detect accurate current.

[0049] In some embodiments, the ratio of the outer diameter of the solenoid 20 to the diameter of the magneto-optical crystal 304a may not exceed 4. For example, the ratio may be 2.0, 2.5, 3.0, or 3.5. The outer diameter of the solenoid 20 is larger than the diameter of the magneto-optical crystal 304a, which facilitates the entry of the magneto-optical crystal 304a into the solenoid 20. The ratio of the outer diameter of the solenoid 20 to the diameter of the magneto-optical crystal 304a is not greater than 4, meaning the outer diameter of the solenoid 20 cannot be infinitely large but is kept within a suitable range. This ensures that the center of the solenoid 20 is properly positioned. The electromagnetic field at the axis is uniformly distributed and has a relatively large magnetic field strength with no obvious edge effects. This more uniform magnetic field amplifies the electromagnetic signal. The magnetic field strength and direction experienced by the magneto-optical crystal 304a are essentially consistent, ensuring that the polarized light deflects at different positions within the crystal with essentially the same degree of polarization. The magneto-optical effect of the crystal 304a maintains a good linear relationship; that is, there is a linear correspondence between the light polarization rotation angle and the magnetic field strength, and consequently, the current magnitude. This makes demodulating the current magnitude through the polarization rotation angle more reliable and accurate, thus ensuring the accuracy of voltage detection. The ratio of the outer diameter of the solenoid 20 to the diameter of the magneto-optical crystal 304a is no greater than 4. This region is less susceptible to interference from external stray magnetic fields and other sources, improving the accuracy and stability of current detection, thereby ensuring the accuracy and stability of voltage detection. This also allows for a smaller size of the fiber optic current sensor 30, saving space.

[0050] In other embodiments, the ratio of the outer diameter of the solenoid 20 to the diameter of the magneto-optical crystal 304a can also be greater than 4, and the fiber optic current sensor 30 can still detect current to obtain voltage.

[0051] In some embodiments, the axial length of the solenoid 20 is at least 10 times its diameter. A ratio of axial length to diameter greater than 10 makes the solenoid 20 closer to an ideal infinitely long solenoid model. According to the Biot-Savart law, in this case, a more uniform axial magnetic field can be generated in the central region of the solenoid 20's axis. The magneto-optical crystal 304a is placed on the central axis of the solenoid 20, in a relatively stable environment with both magnetic field strength and direction. This ensures that the Faraday rotation angle generated by the polarized light passing through the magneto-optical crystal 304a is consistent, guaranteeing a linear relationship between the current and the light polarization rotation angle, improving the accuracy of current detection, and ensuring the accuracy of voltage detection. In other embodiments, the axial length of the solenoid 20 can also be 8 or 9 times its diameter, etc., and the fiber optic current sensor 30 can still detect the current, thereby measuring the voltage value.

[0052] In some embodiments, the ratio of the axial length of the solenoid 20 to the length of the magneto-optical crystal 304a can be greater than 5. For example, the ratio of the axial length of the solenoid 20 to the length of the magneto-optical crystal 304a can be 5.2, 5.5, 5.8, 6.0, 6.5, or 7.0. A ratio greater than 5 and a sufficiently long axial length of the solenoid 20 ensures that the magneto-optical crystal 304a is completely within the region of the uniform magnetic field inside the solenoid 20. This allows all parts of the magneto-optical crystal 304a to be subjected to a stable and uniform magnetic field, ensuring that the Faraday rotation angle generated when polarized light propagates within the magneto-optical crystal 304a is linearly related only to the current magnitude, without errors caused by differences in the magnetic field at different locations. This improves the accuracy and reliability of current detection. Simultaneously, a relatively strong magnetic field makes it less susceptible to interference from external magnetic fields, improving the stability and qualitative nature of current measurement, thereby ensuring the stability of voltage detection. In other embodiments, the ratio of the axial length of the solenoid 20 to the length of the magneto-optical crystal 304a may not be greater than 5, and the fiber optic current sensor 30 can still detect the current, thereby measuring the voltage value.

[0053] In some embodiments, the fiber optic current sensor 30 includes a first controller, and the device includes a second controller, which are electrically connected. The first controller may be a built-in controller of the fiber optic current sensor 30, and the second controller is a controller that calculates voltage based on current and impedance. The two are electrically connected so that the second controller can obtain the current value calculated by the first controller. In other embodiments, the device includes a controller electrically connected to the photodetector 317 of the fiber optic current sensor 30. In this way, the controller can not only realize the signal acquisition and current calculation functions of the photodetector 317 of the first controller of the fiber optic current sensor 30, but also has the function of calculating voltage based on current and impedance. Therefore, the controller integrates the functions of the first controller and the second controller into one controller, which can improve space utilization.

[0054] In some embodiments, the device may further include a frequency detector operably electrically connected to the controller, so that the frequency detector can obtain the frequency signal of the voltage to be measured, thereby selecting from a plurality of capacitors 10 with different capacitance values ​​that makes the inductive reactance of the solenoid 20 in the closed circuit under the voltage to be measured relatively close, to ensure the accuracy and sensitivity of subsequent voltage detection. In other embodiments, the frequency of the voltage to be measured can also be determined by reading the signal output by the fiber optic current sensor 30, thereby determining the capacitor 10 with the target capacitance value.

[0055] Please see Figure 2The fiber optic current sensor 30 may include a light source 301, a first single-fiber collimator 302, a polarizer 303, a magneto-optical crystal 304a, a 45° Faraday rotator 305, a first Wollaston prism 306, a first dual-fiber collimator 307, and two photodetectors 317. The light source 301, the first single-fiber collimator 302, the polarizer 303, the magneto-optical crystal 304a, the 45° Faraday rotator 305, the first Wollaston prism 306, and the first dual-fiber collimator 307 are arranged sequentially along the direction of light transmission. The first dual-fiber collimator 307 is provided with two pigtails, and the two photodetectors 317 are respectively connected to the two pigtails. The first single-fiber collimator 302, polarizer 303, magneto-optical crystal 304a, 45° Faraday rotator 305, first Wollaston prism 306, and first dual-fiber collimator 307 are arranged sequentially along the axis of the solenoid 20 and are all located inside the solenoid 20.

[0056] After the light source 301 emits transmitted light, the two photodetectors 317 output voltage signals, which are then processed to obtain the current value. The first single-fiber collimator 302, polarizer 303, magneto-optical crystal 304a, 45° Faraday rotating mirror 305, first Wollaston prism 306, and first dual-fiber collimator 307 are distributed along the axis of the solenoid 20 and are all located inside the solenoid 20. This ensures that the magneto-optical crystal 304a is located at the center of the length of the solenoid 20, guaranteeing a more uniform electromagnetic field with a strong magnetic field, making it less susceptible to external interference and improving the accuracy, stability, and zero-degree current detection.

[0057] In other embodiments, please refer to Figure 3The fiber optic current sensor 30 may further include a light source 301, an optical circulator 308, a second dual-fiber collimator 309, a second Wollaston prism 310, a 22.5° Faraday rotation mirror, a magneto-optical crystal 304a, a Faraday reflector 312, and two photodetectors 317. The optical circulator 308 has a first port, a second port, and a third port. The first port is coupled to the light source 301. The second dual-fiber collimator 309 has a first transmission interface, a second transmission interface, a third transmission interface, and a fourth transmission interface. The second port is coupled to the first transmission interface of the second dual-fiber collimator 309. Both the second and third transmission interfaces face the second Wollaston prism 310. The second transmission interface is used to output transmitted light to the second Wollaston prism 310 and to input the first transmitted light returned from the second Wollaston prism 310. The third transmission interface is used to input the first transmitted light returned from the second Wollaston prism 310. A second transmission light is set at an angle to the first transmission light. The fourth transmission interface is coupled to the second photodetector 317, and the third port is coupled to one of the photodetectors 317. The second Wollaston prism 310, the 22.5° Faraday rotator, the magneto-optical crystal 304a, and the Faraday reflector 312 are arranged in sequence to form an incident light path. The Faraday reflector 312 can reflect the incident light and transmit it in sequence to the 22.5° Faraday rotator, the magneto-optical crystal 304a, and the second Wollaston prism 310. The second Wollaston prism 310 can separate the reflected transmission light into two orthogonal linearly polarized beams, which are transmitted to the second transmission interface and the third transmission interface of the second dual fiber collimator 309, respectively. The transmission light transmitted through the second transmission interface is collimated and diffused, then input through the second port of the optical circulator 308, and output through the third port to transmit this linearly polarized beam to one of the photodetectors 317. The transmitted light from the third transmission interface of the second dual-fiber collimator 309 is collimated and diffused, and then transmitted to another photodetector 317 via the fourth transmission interface of the second dual-fiber collimator 309. After the light source 301 emits the transmitted light, the two photodetectors 317 output voltage signals respectively, which are then demodulated by the controller to obtain the current value.

[0058] The second dual-fiber collimator 309, the second Wollaston prism 310, the 22.5° Faraday rotator, the magneto-optical crystal 304a, and the Faraday reflector 312 are arranged sequentially along the axis of the solenoid 20 and are all located inside the solenoid 20. This ensures that the magneto-optical crystal 304a is located at the center of the length of the solenoid 20, guaranteeing that the electromagnetic field it is in is more uniform and has a strong magnetic field, making it less susceptible to external interference and improving the zero degree, accuracy, and stability of current detection.

[0059] In some other embodiments, please refer to Figure 4The fiber optic current sensor 30 includes a light source 301, a second single-fiber collimator 313, a third Wollaston prism 314, a magneto-optical crystal 304a, a fourth Wollaston prism 315, a third single-fiber collimator 316, and a photodetector 317. The light source 301, the second single-fiber collimator 313, the third Wollaston prism 314, the magneto-optical crystal 304a, the fourth Wollaston prism 315, and the third single-fiber collimator 316 are arranged sequentially along the direction of light transmission. The photodetector 317 is connected to the pigtail of the third single-fiber collimator 316. The second single-fiber collimator 313, the third Wollaston prism 314, the magneto-optical crystal 304a, the fourth Wollaston prism 315, and the third single-fiber collimator 316 are arranged sequentially along the axial direction of the solenoid 20, and all of them are located inside the solenoid 20.

[0060] In some embodiments, please refer to Figure 5 The fiber optic current sensor 30 and Figure 3 The reflective magneto-optical crystal 304a shown is similar to the fiber optic current sensor 30 of the sensing head 304, except that the magneto-optical crystal 304a between the 22.5° Faraday rotator 311 and the Faraday reflector 312 is replaced by a third single-fiber collimator 316 and a sensing fiber 304b. After the light source 301 emits transmitted light, the two photodetectors 317 output voltage signals, which are demodulated by the controller to obtain the current value.

[0061] The structure of the fiber optic current sensor 30 described above is merely an example. The structure of the fiber optic current sensor 30 is existing technology. More details about the fiber optic current sensor 30 and other forms of fiber optic current sensors 30 can be selected according to actual needs, and will not be elaborated further in this application.

[0062] Based on the same technical concept as the first aspect, the second aspect of this application provides a method for detecting AC voltage, which is applicable to the apparatus for detecting AC voltage based on an optical fiber current sensor according to any embodiment of the first aspect.

[0063] The method provided in this application includes the following steps:

[0064] S1. Select a capacitor 10 with the target capacitance value and connect it in series with the first end of the wire.

[0065] S2. Connect capacitor 10 and the second end of the wire to two terminals with different electromotive forces to be measured, and obtain the current value output by fiber optic current sensor 30.

[0066] S3. Substitute the current value into the voltage detection model to obtain the AC voltage between the two terminals.

[0067] When capacitor 10 with the target capacitance value is connected to a closed loop, the capacitive reactance of capacitor 10 and the inductive reactance of solenoid 20 in the closed loop are relatively close. This makes the impedance in the closed current mainly come from the resistance of the solenoid 20's own wires, resulting in a larger current flowing through the solenoid 20's wires. Consequently, the electromagnetic field of solenoid 20 is also larger. When polarized light is transmitted through the sensing head 304 located inside solenoid 20, the deflection angle is also larger, meaning that the intensity change of polarized light is also very large. This makes the current detection result of fiber optic current sensor 30 more sensitive, thereby improving the current accuracy. Since voltage is the product of current and resistance, the higher the sensitivity of the current result, the higher the sensitivity of the measured voltage value, and thus the higher the accuracy.

[0068] In some embodiments, the method for determining the target capacitance value may include:

[0069] S11. Connect the first and second ends of the wire to two connectors with different electromotive forces to be measured, and obtain the signal output by the fiber optic current sensor 30.

[0070] S12. Determine the theoretical capacitance value of capacitor 10 based on the frequency of the signal;

[0071] S13. Determine the target capacitance value of capacitor 10 based on the theoretical capacitance value, wherein the difference between the target capacitance value and the theoretical capacitance value is less than a set value.

[0072] In step S11, the signal output by the fiber optic current sensor 30 can be a current signal, a light intensity signal, or a voltage characteristic signal output by the photodetector 317; this application does not impose any limitations. To improve the frequency acquisition efficiency of the signal, in some embodiments, a frequency detector can be electrically connected to the controller. Simultaneously with the output signal from the fiber optic current sensor, the frequency of the voltage to be measured can be acquired, thereby determining the theoretical capacitance value of capacitor 10 when the closed circuit has only the resistance of solenoid 20. That is, when the capacitor with the theoretical capacitance value is connected in series with the closed circuit under the voltage to be measured, resonance occurs, capacitive reactance and inductive reactance cancel each other out, and the impedance of the closed circuit is only the internal resistance of the solenoid 20 wire.

[0073] However, in reality, the capacitance value of capacitor 10 is not continuously changing. There may not be a capacitor 10 with the theoretical capacitance value that causes the closed circuit to resonate. In this case, a capacitor 10 with the target capacitance value can be selected. Since the target capacitance value is close to the theoretical capacitance value, the difference is small, and it is easy to obtain, connecting a capacitor 10 with the target capacitance value in series with the closed circuit can still result in a relatively large current, thereby improving the sensitivity and accuracy of voltage detection. Of course, if a capacitor 10 with the theoretical capacitance value is available, it can be directly connected to the circuit to further increase the current, thereby improving the sensitivity and accuracy of voltage detection.

[0074] Between steps S1 and S2, the following may also be included: adjusting the number of solenoid segments on solenoid 20 according to the target capacitance value and the theoretical capacitance value, so that the capacitive reactance of capacitor 10 with the target capacitance value is close to the inductive reactance of solenoid 20 after the number adjustment.

[0075] First, determine the capacitance 10, then adjust the number of solenoid segments in solenoid 20. Through these two adjustments, the capacitive reactance of capacitor 10 in the closed circuit is made almost the same as the inductive reactance of solenoid 20, which further reduces the impedance in the closed circuit and further increases the current, thereby improving the sensitivity and accuracy of voltage detection.

[0076] The number of solenoid segments in solenoid 20 can be determined by calculation or by adjusting the number and trying multiple times with power applied, so that the capacitive reactance of capacitor 10 in the closed circuit is almost the same as the inductive reactance of solenoid 20. This application does not impose specific limitations.

[0077] In some embodiments, the voltage detection model can be:

[0078]

[0079] Where U is the voltage between the two connectors, I is the current value measured by the fiber optic current sensor, R0 is the internal resistance of the solenoid, L0 is the inductance of the solenoid, ω is the angular frequency of the AC voltage, and C is the target capacitance value.

[0080] When the capacitive reactance of capacitor 10 is the same as that of solenoid 20, the voltage model above is U = I × R0.

[0081] The device and method for detecting AC voltage based on an optical fiber current sensor provided in this application have at least the following advantages:

[0082] (1) Based on the detection of AC voltage by fiber optic current sensor, the sensing head of the fiber optic current sensor is a sensing fiber or a magneto-optical crystal. The sensing head is less affected by temperature and vibration, so the accuracy of current detection can be improved, thereby improving the accuracy of voltage detection.

[0083] (2) The device provided in this application is equipped with a solenoid, and the electromagnetic field at the central axis is large and uniform, which reduces the interference of external electromagnetic fields, resulting in high accuracy of current detection and thus improving the accuracy of voltage detection.

[0084] (3) By combining the fiber optic current sensor with a solenoid, the deflection angle of the linearly polarized light is amplified, which improves the sensitivity of current detection and thus improves the sensitivity of voltage detection.

[0085] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0086] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", and "counterclockwise" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0087] In this application, unless otherwise expressly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0088] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0089] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A device for detecting AC voltage based on an optical fiber current sensor, characterized in that, include: A solenoid is a helically wound conductor having a first end and a second end; The capacitor is provided in multiple form, and the capacitance values ​​of the multiple capacitors are all different. Any one of the capacitors is operably connected in series with the first end of the wire. An optical fiber current sensor, wherein the sensing head of the optical fiber current sensor is located inside the solenoid; The second end of the wire and the capacitor are used to connect two terminals with different electromotive forces.

2. The device for detecting AC voltage based on an optical fiber current sensor according to claim 1, characterized in that, When the sensing head of the fiber optic current sensor is a sensing fiber, the sensing fiber is spirally wound around the sensing shaft, the axis of the solenoid is perpendicular to the sensing shaft, and the sensing fiber passes through the cavity of the solenoid.

3. The device for detecting AC voltage based on an optical fiber current sensor according to claim 2, characterized in that, The diameter of the winding of the sensing optical fiber is 7cm to 10cm.

4. The device for detecting AC voltage based on an optical fiber current sensor according to claim 2, characterized in that, The ratio of the axial length of the solenoid to the winding diameter of the sensing optical fiber is less than 0.

4.

5. The device for detecting AC voltage based on an optical fiber current sensor according to claim 1, characterized in that, When the sensing head of the fiber optic current sensor is a magneto-optical crystal, the magneto-optical crystal is cylindrical, and the central axis of the cylindrical magneto-optical crystal coincides with the axis of the solenoid.

6. The device for detecting AC voltage based on an optical fiber current sensor according to claim 5, characterized in that, The ratio of the outer diameter of the solenoid to the diameter of the magneto-optical crystal is no greater than 4.

7. The device for detecting AC voltage based on an optical fiber current sensor according to claim 5, characterized in that, The ratio of the axial length of the solenoid to the length of the magneto-optical crystal is greater than 5.

8. The apparatus for detecting AC voltage based on an optical fiber current sensor according to any one of claims 1-7, characterized in that, The ratio of the axial length to the diameter of the solenoid is greater than 10.

9. The apparatus for detecting AC voltage based on an optical fiber current sensor according to any one of claims 1-7, characterized in that, It also includes a controller and a frequency detector, the frequency detector being operatively electrically connected to the controller; The fiber optic current sensor is electrically connected to the controller.

10. The apparatus for detecting AC voltage based on an optical fiber current sensor according to any one of claims 1-7, characterized in that, The solenoid includes multiple helical segments, and any number of the helical segments are arranged sequentially along the axial direction of the solenoid, with adjacent helical segments being detachably electrically connected.

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