A quantum current transformer based on a microwave photon link and a current measurement method

Abstract

The application belongs to the technical field of current measurement, and relates to a quantum current transformer based on a microwave photon link and a current measurement method. The quantum current transformer comprises a high-voltage primary sensor, a low-voltage green light source, a photoelectric detection unit, a merging unit, and an optical fiber composite insulator and a microwave photon link connecting the high-voltage side and the low-voltage side. The microwave photon link comprises a microwave processing unit, a microwave transmitting unit and a microwave receiving unit, and converts the microwave signal into an optical signal for transmission through an optical fiber and then restores the microwave signal at the high-voltage side. The primary sensor comprises an NV color center sensitive unit. The laser and microwave signals are transmitted to the NV color center sensitive unit through the optical fiber and the microwave photon link respectively to generate fluorescence, the fluorescence returns to the photoelectric detection unit through the optical fiber, and the microwave processing unit calculates the primary current value according to the resonance frequency. The application realizes microwave optical fiber transmission through the microwave photon link, has strong anti-interference ability, high insulation reliability and high measurement accuracy.

Description

Technical Field

[0001] This invention belongs to the field of current measurement technology, specifically relating to a quantum current transformer and current measurement method based on a microwave photonic link. Background Technology

[0002] In today's power systems, current transformers, as fundamental measuring devices, are widely used in fields such as power metering and line protection monitoring. With the large-scale grid connection of new energy power generation and the increasing number of nonlinear loads, modern power grids exhibit characteristics such as wide dynamic range, fast time-varying, and strong randomness. These characteristics, coupled with extreme operating conditions such as transient impacts and harmonic overruns, place higher demands on the accuracy and rapid response capabilities of current measurement technology.

[0003] Traditional electromagnetic induction current transformers measure current using the principle of electromagnetic induction. While continuously improved and optimized through long-term practice, they are limited by their core structure, making them prone to magnetic saturation in high-current measurement scenarios. Furthermore, they suffer from narrow measurement bandwidth, limited dynamic range, large size, and high insulation costs. Electronic current transformers, although mitigating some of the shortcomings of traditional transformers, still face challenges such as poor anti-interference capabilities of electronic and optical components, limited operating temperature range, and integral drift. Accuracy and stability remain the main bottlenecks restricting their reliable application.

[0004] Quantum precision measurement technology based on diamond nitrogen-vacancy (NV) centers utilizes the high sensitivity of NV centers to magnetic fields to indirectly obtain the magnitude of current by measuring the magnetic field around a current-carrying conductor. NV centers possess excellent sensitivity and frequency response range, and diamond, as the carrier material, has stable physicochemical properties and can withstand various extreme environments, providing a novel technological approach for current measurement. In recent years, quantum current transformers based on NV centers have been implemented in 110kV substations, achieving a measurement accuracy of 0.05%.

[0005] However, existing quantum current transformers still face many challenges in engineering applications. Patent CN119804944A discloses a non-contact quantum current transformer that places the microwave modulation and processing units on the low-voltage side and uses air wireless transmission to provide microwave signals to the high-voltage side. However, this solution has significant limitations: microwave propagation attenuates severely in adverse weather conditions such as rain, snow, and fog; dust and dirt accumulation on the antenna insulation cover also affect transmission efficiency; and under conditions such as short circuits or wind vibrations, it is difficult to accurately align the transmitting and receiving antennas, resulting in a significant decrease in microwave conversion efficiency. Summary of the Invention

[0006] The purpose of this invention is to provide a quantum current transformer and current measurement method based on microwave photonic links, so as to solve the problems of poor insulation reliability of microwave transmission between high and low voltage, susceptibility of air wireless transmission to environmental interference, and low microwave transmission efficiency caused by difficulty in accurately aligning the transmitting and receiving antennas in the prior art.

[0007] This invention is achieved through the following technical solution: This invention discloses a quantum current transformer based on a microwave photonic link, comprising: A primary sensor is located on the high-voltage side; the primary sensor includes an NV color center sensing unit. Fiber optic composite insulators connect the high-voltage side and the low-voltage side, and have fiber optics integrated inside. The green laser source, photoelectric detection unit, and merging unit are located on the low-voltage side; A microwave photonic link, connecting the low-voltage side and the high-voltage side, includes a microwave processing unit, an optical emitting unit, and a microwave receiving unit. The microwave processing unit is used to regulate the optical emitting unit so that the optical emitting unit emits optical signals at different frequencies. The optical signals are transmitted to the microwave receiving unit through the optical fiber inside the optical fiber composite insulator. The microwave receiving unit is used to restore the optical signals to microwave signals and output them to the NV color center sensing unit. The green laser source is connected to the NV color center sensing unit through an optical fiber inside the optical fiber composite insulator, and is used to transmit excitation laser to the NV color center sensing unit; The fluorescence signal generated by the NV color center sensing unit is transmitted to the photoelectric detection unit through the optical fiber inside the optical fiber composite insulator; the photoelectric detection unit converts the fluorescence signal into an electrical signal and sends it to the microwave processing unit; The microwave processing unit calculates the primary current value based on the resonant frequency and sends the primary current value to the merging unit.

[0008] Furthermore, the optical emitting unit includes a microwave modulation unit and a microwave emitting unit, wherein the microwave modulation unit is disposed between the microwave processing unit and the microwave emitting unit; The microwave modulation unit is used to modulate the microwave signal to generate a microwave modulation signal. The microwave transmitting unit is used to convert the microwave modulation signal into an optical signal via electro-optic conversion.

[0009] Furthermore, it also includes a laser power supply unit located on the low-voltage side and an energy conversion device located on the high-voltage side; The laser power supply unit is connected to the energy conversion device through the optical fiber inside the optical fiber composite insulator. The energy conversion device is connected to the microwave receiving unit and is used to supply power to the microwave receiving unit.

[0010] Furthermore, the primary sensor also includes a magnetic ring, a magnetic shielding cover, and a sensor housing; When the NV color center sensing unit is set up alone, it is used to measure current of Class A and above. Multiple NV color center sensing units are evenly distributed in an array along the circumferential direction of the sensor housing. When the NV color center sensing unit is combined with the magnetic ring, it is used to measure mA-level current. The NV color center sensing unit is located in the air gap of the magnetic ring.

[0011] Furthermore, the magnetic focusing ring is a split-type annular magnetic focusing ring, including a semi-circular magnetic focusing ring and a semi-circular magnetic focusing ring. An air gap is opened on the semi-circular magnetic focusing ring, and the NV color center sensitive unit is disposed in the air gap.

[0012] Furthermore, the sensor housing is a snap-fit ​​circular structure, comprising a semi-circular fixed housing, a semi-circular fixed cover plate, a semi-circular rotating housing, and a semi-circular rotating cover plate. The semi-circular fixed housing and the semi-circular rotating housing are connected by a pin and rotate around the pin as an axis.

[0013] Furthermore, the optical fiber composite insulator includes an epoxy glass core rod, a skirt, and an integrated optical fiber, wherein the integrated optical fiber is integrated between the skirt and the epoxy glass core rod by a helical winding method.

[0014] Furthermore, the integrated optical fiber includes a near-ultraviolet optical fiber transmission unit, a microwave transmission optical fiber, and a laser power transmission optical fiber; The near-ultraviolet fiber optic transmission unit includes a first near-ultraviolet fiber, a second near-ultraviolet fiber, a third near-ultraviolet fiber, a fourth near-ultraviolet fiber, a fifth near-ultraviolet fiber, a sixth near-ultraviolet fiber, a beam splitter, a fiber optic circulator, and a filter. The fourth near-ultraviolet fiber, the microwave transmission fiber, and the laser power transmission fiber together constitute the integrated optical fiber, which is spirally wound between the epoxy glass core rod and the umbrella skirt.

[0015] Furthermore, the near-ultraviolet fiber optic transmission unit has three main optical paths: The first optical path consists of the first near-ultraviolet fiber, the beam splitter, the third near-ultraviolet fiber, the fiber circulator, and the fourth near-ultraviolet fiber, used to transmit the excitation laser from the green laser source to the NV color center sensing unit. The second optical path consists of the fourth near-ultraviolet fiber, the fiber circulator, the fifth near-ultraviolet fiber, the filter, and the sixth near-ultraviolet fiber, used to transmit the fluorescence of the NV color center sensing unit to the photoelectric detection unit. The third optical path consists of the first near-ultraviolet fiber, the beam splitter, and the second near-ultraviolet fiber, used to transmit the reference laser from the green laser source to the photoelectric detection unit.

[0016] This invention also discloses a measurement method for a quantum current transformer based on a microwave photonic link, comprising the following steps: The green laser source transmits a laser signal of a preset wavelength to the NV color center sensing unit via optical fiber; The microwave photonic link converts the microwave signal into an optical signal, transmits it through optical fiber, and then restores it to a microwave signal on the high-voltage side, which is then transmitted to the NV color center sensitive unit. The NV color center sensing unit generates a fluorescence signal under the combined action of laser and microwave, and transmits it to the photoelectric detection unit through optical fiber; The photoelectric detection unit converts the fluorescence signal into an electrical signal and sends it to the microwave processing unit; The microwave processing unit obtains a fluorescence intensity-microwave frequency waveform curve based on fluorescence intensity and microwave frequency. Based on the waveform curve, the microwave frequency corresponding to the trough before power-on is taken as the zero magnetic field resonance frequency f0, and the microwave frequency corresponding to the trough after power-on is taken as the resonance frequency f of the spin color center when a magnetic field is present. B ; According to formula f B =f0±γB calculates the magnetic flux density B; γ is the gyrometry of the quantum spin; The primary current value is calculated according to the formula 2πRB=μ0I; where B is the magnetic induction intensity of the external magnetic field sensed by the primary sensor, R is the distance between the NV color center sensitive unit 11 and the primary conductor, I is the primary current, and μ0 is the vacuum permeability. The microwave processing unit sends the primary current value to the merging unit.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: This invention provides an overall architecture for a quantum current transformer based on a microwave photonic link. Unlike existing technologies that use air-based wireless microwave transmission or microwave sources on the high-voltage side, this invention constructs a microwave photonic link by integrating a microwave processing unit, an optical transmitting unit, and a microwave receiving unit. Optical fiber transmission of microwave signals is achieved through the integration of optical fibers within an optical fiber composite insulator. This fundamentally avoids the problems of air-based wireless transmission being affected by environmental factors such as rain, snow, fog, and dust, as well as the reduced transmission efficiency caused by inaccurate alignment of the transmitting and receiving antennas due to vibration. Furthermore, it eliminates the need for high-power active devices on the high-voltage side, achieving reliable insulation and efficient, stable microwave transmission between high and low voltage levels, providing a stable and reliable microwave signal input for subsequent resonant frequency detection.

[0018] Furthermore, the optical emitting unit can adopt a split structure, including a microwave modulation unit and a microwave emitting unit, forming a complete signal link for microwave signal generation, modulation, electro-optical conversion, optical fiber transmission, and photoelectric reconstruction. Compared with existing solutions, the microwave modulation unit, controlled by the microwave processing unit, generates a microwave modulation signal of a specific frequency. This signal is then converted into an optical signal by the microwave emitting unit through electro-optical conversion and transmitted through the optical fiber. This effectively avoids frequency drift and attenuation of the microwave signal during air transmission, ensuring that the frequency of the microwave signal transmitted to the NV color center sensing unit is precisely controllable. This provides a strong guarantee for accurately exciting the NV color center magnetic resonance and improving the sensitivity of magnetic field detection.

[0019] Furthermore, by setting up a laser power supply unit and an energy conversion device, remote fiber optic power supply from the low-voltage side to the high-voltage side microwave receiving unit is achieved. Unlike existing solutions that require an independent power supply or high-power laser power supply technology on the high-voltage side, this invention only requires milliwatt-level optical power to drive the high-voltage side microwave receiving unit to operate normally. This effectively avoids the engineering bottleneck of the immature watt-level high-power laser power supply technology, reduces the complexity of high-voltage side equipment and insulation risks, and at the same time enables true passivity on the high-voltage side, improving the safety and reliability of equipment operation.

[0020] Furthermore, through the structural design of the magnetic ring, magnetic shield, and sensor housing, combined with two usage methods of the NV color center sensitive unit, a wide-range current measurement is achieved. Existing quantum current transformers are typically only suitable for a single range, while in this invention, when the NV color center sensitive unit is set up in a separate array, the spatial distribution of multiple sensitive units enhances the magnetic field signal, enabling the measurement of large currents of A level and above. When combined with the split magnetic ring, the magnetic ring concentrates the weak magnetic field to the NV color center sensitive unit located in the air gap, significantly improving the magnetic field detection sensitivity, enabling the measurement of small currents in the mA level. At the same time, the multi-layer magnetic shield effectively suppresses external stray magnetic field interference, ensuring high-precision measurement capabilities across different ranges.

[0021] Furthermore, a split structure for the magnetic focusing ring is defined, comprising a semi-circular magnetic focusing ring and a semi-circular magnetic focusing ring. The semi-circular magnetic focusing ring has an air gap for mounting the NV color center sensing element. This split design is compatible with the snap-on circular sensor housing, allowing the magnetic focusing ring to open and close with the housing. This facilitates installation without cutting the primary conductor. Simultaneously, the air gap precisely fixes the relative position of the NV color center sensing element and the magnetic focusing ring, ensuring consistency in magnetic field focusing effect during each measurement and improving measurement repeatability and accuracy.

[0022] Furthermore, the sensor housing is defined as a snap-fit ​​ring structure, comprising a fixed half-ring and a rotating half-ring connected by pins. Unlike existing current transformer structures that require disconnection of the primary conductor for installation, the snap-fit ​​ring structure of this invention can be directly fastened to the primary conductor to achieve non-contact measurement. This eliminates the need for power outages or modifications to the primary circuitry, significantly reducing installation difficulty and construction costs. Simultaneously, it ensures the coaxiality between the NV color center sensing element and the primary conductor, guaranteeing the spatial positioning accuracy of the magnetic field measurement.

[0023] Furthermore, the specific structure of the fiber optic composite insulator is defined, employing an epoxy glass core rod, sheds, and an integrated helical winding structure of optical fiber. Unlike existing technologies where the optical fiber is merely an independent transmission medium, this invention integrates the optical fiber within the insulator using a helical winding method. This utilizes the epoxy glass core rod and sheds to ensure insulation withstand voltage between high and low voltage levels, while the helical winding structure provides sufficient tensile allowance and flexibility for the optical fiber within the insulator, preventing damage to the fiber due to thermal expansion and contraction or mechanical vibration, thus improving the long-term reliability of optical fiber transmission.

[0024] Furthermore, the specific composition of the integrated optical fiber is defined, integrating the near-ultraviolet fiber transmission unit, microwave transmission fiber, and laser power supply transmission fiber into a single bundle, which respectively undertakes the three functions of excitation laser transmission, microwave modulation optical signal transmission, and power supply laser transmission. Unlike the existing technology where various optical fibers are arranged separately, this invention achieves the integrated integration of the three functional optical fibers, significantly simplifying the internal structure of the insulator, reducing manufacturing costs, and ensuring stable transmission of the three types of optical signals between the high-voltage and low-voltage sides through a helical winding method, providing complete all-optical link support for the system's laser excitation, microwave transmission, and remote power supply.

[0025] Furthermore, the near-ultraviolet fiber optic transmission unit is defined by three optical paths: the first path transmits the excitation laser to the NV color center sensing unit; the second path transmits the fluorescence signal generated by the NV color center sensing unit to the photodetector unit; and the third path directly transmits the reference laser from the green laser source to the photodetector unit to eliminate laser noise in the fluorescence signal. Unlike existing technologies that only include an excitation optical path and a fluorescence detection optical path, this invention introduces a reference laser through the third optical path, enabling the photodetector unit to effectively eliminate measurement noise caused by laser source power fluctuations using the differential detection principle. This significantly improves the signal-to-noise ratio of fluorescence signal detection and the accuracy of current measurement.

[0026] This invention also discloses a measurement method based on the aforementioned quantum current transformer. The method involves first obtaining the zero-magnetic-field resonant frequency, then obtaining the resonant frequency under magnetic field conditions, using the resonant frequency offset to infer the magnetic flux density, and finally calculating the primary current value. Unlike existing technologies that rely solely on single frequency detection, this invention effectively eliminates the systematic error caused by the zero-field splitting frequency drift of the NV color center by comparing the trough frequencies before and after power-on. Furthermore, by performing the calculations of magnetic flux density and current value step-by-step, the physical meaning of each step is clear and verifiable, ensuring the accuracy and traceability of the measurement results. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure of a quantum current transformer based on a microwave photonic link according to the present invention. Figure 2 This is a schematic diagram of the operation of the quantum current transformer of the present invention; Figure 3 This is a flowchart illustrating the working process of the quantum current transformer of the present invention. Figure 4 The fluorescence spectrum of the NV color center under laser excitation; Figure 5 The fluorescence spectrum of the NV color center under combined laser and microwave excitation (without an external magnetic field); Figure 6 The fluorescence spectrum of the NV color center under combined excitation by laser, microwave and magnetic field (Zeeman splitting). Figure 7 The fluorescence spectrum of the NV color center under combined excitation by laser, microwave, and magnetic field. Figure 8 This is a schematic diagram of the first application method of the NV color center sensing unit (high current measurement); Figure 9 This is a schematic diagram of the NV color center sensitive unit structure; Figure 10 This is a schematic diagram of the primary sensor housing structure; Figure 11 This is a schematic diagram illustrating the second application method of the NV color center sensing unit (small current measurement); Figure 12 This is a schematic diagram of an optical fiber composite insulator structure. Figure 13 This is a schematic diagram of the optical transmission unit structure; Figure 14 This is a schematic diagram illustrating the working principle of a microwave photonic link (including a microwave modulation unit) scheme.

[0028] The components include: 1. Primary sensor; 2. Fiber optic composite insulator; 3. Green laser source; 4. Photoelectric detection unit; 5. Microwave processing unit; 6. Microwave modulation unit; 7. Microwave transmitting unit; 8. Microwave receiving unit; and 9. Merging unit. 11. NV color center sensing unit; 12. Magnetic ring; 13. Magnetic shielding cover; 14. Primary sensor housing; 15. Primary conductor; 16. Near-ultraviolet fiber optic transmission unit; 17. Microwave transmission fiber optic; 18. Laser-powered transmission fiber optic; 21. Epoxy glass core rod; 22. Umbrella skirt; 23. Integrated optical fiber; 24. Lower flange; 25. Upper flange; 101. Laser power supply unit; 102. Energy conversion device; 111. Laser receiving unit; 112. NV color center probe; 113. Microwave antenna; 114. Circuit board; 121. Semi-circular magnetic focusing ring; 122. Semi-circular magnetic focusing ring; 141. Semicircular ring fixed outer shell; 142. Semicircular ring fixed cover plate; 143. Semicircular ring rotating outer shell; 144. Semicircular ring rotating cover plate; 145. Pin; 161. First near-ultraviolet fiber; 162. Second near-ultraviolet fiber; 163. Third near-ultraviolet fiber; 164. Fourth near-ultraviolet fiber; 165. Fifth near-ultraviolet fiber; 166. Sixth near-ultraviolet fiber; 167. Optical splitter; 168. Fiber circulator; 169. Filter. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0030] The components described and illustrated in the accompanying drawings and embodiments of this invention can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely to illustrate one selected embodiment of the invention. All other embodiments obtained by those skilled in the art based on the accompanying drawings and embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0031] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0032] like Figure 1 and Figure 2As shown, this invention provides a quantum current transformer based on a microwave photonic link, comprising a primary sensor 1, an optical fiber composite insulator 2, a green laser source 3, a photoelectric detection unit 4, a microwave processing unit 5, a microwave modulation unit 6, a microwave transmitting unit 7, a microwave receiving unit 8, and a merging unit 9. The primary sensor 1 is located on the high-voltage side, while the green laser source 3, photoelectric detection unit 4, microwave processing unit 5, microwave modulation unit 6, microwave transmitting unit 7, and merging unit 9 are located on the low-voltage side. The optical fiber composite insulator 2 connects the high-voltage side and the low-voltage side.

[0033] The fiber optic composite insulator 2 integrates optical fibers for transmitting green laser light, fluorescent signals, microwave modulated optical signals, and power laser light.

[0034] like Figure 2 As shown, a green laser source 3 generates a laser signal, which is transmitted through the optical fiber inside the fiber-optic composite insulator 2 to the NV color center sensing unit 11 in the primary sensor 1. A microwave processing unit 5 controls the microwave modulation unit 6, which generates a microwave signal and modulates it to generate a microwave modulation signal. A microwave transmitting unit 7 processes the microwave modulation signal into an optical signal via electro-optic modulation, which is then transmitted through the optical fiber inside the fiber-optic composite insulator 2 to a microwave receiving unit 8. The microwave receiving unit 8 performs photoelectric detection on the optical signal and modulates it to generate a microwave modulation signal, which is finally transmitted to the NV color center sensing unit 11. The NV color center sensing unit 11 generates fluorescence under the combined action of the laser and microwave. The fluorescence signal is transmitted through the optical fiber inside the fiber-optic composite insulator 2 to a photoelectric detection unit 4. The photoelectric detection unit 4 receives the fluorescence signal and converts it into an electrical signal. The microwave processing unit 5 demodulates the electrical signal to generate a demodulated signal and controls the microwave modulation unit 6 to match the microwave signal frequency with the resonant frequency of the NV color center sensing unit 11. After resonant frequency matching, microwave processing unit 5 processes the primary current information and sends it to merging unit 9. Merging unit 9 then sends the primary current information to the relay protection device according to the prescribed protocol.

[0035] The laser power supply unit 101 on the low-voltage side performs electro-optical conversion and supplies power to the energy conversion device 102 on the high-voltage side through the optical fiber inside the optical fiber composite insulator 2. The energy conversion device 102 then supplies power to the microwave receiving unit 8.

[0036] This invention transmits microwaves via a microwave photonic link, effectively solving the insulation problem of microwave transmission between high and low voltage levels and the stability problem of microwave wireless transmission; through microwave frequency modulation, it achieves accurate measurement of high-voltage side current.

[0037] principle: When a primary conductor (circular) carries a primary current, a magnetic field is generated around it. This magnetic field can be detected by a primary sensor to determine its magnitude. The magnetic field generated by the primary conductor is related to the primary current as follows: 2πRB=μ0I(1) Where B is the magnetic flux density of the external magnetic field sensed by the primary sensor, R is the distance between the NV color center sensing unit 11 and the primary conductor, I is the primary current, and μ0 is the vacuum permeability. Based on the magnitude of the magnetic field detected by the probe, the primary current can be calculated according to formula (1), thus realizing the measurement of the primary current.

[0038] like Figure 4 As shown, the quantum current transformer measures primary current based on diamond ensemble NV center magnetometry. NV centers have three spin states: 0, +1, and -1. NV centers can be polarized to the 0 state under laser pumping, exhibiting strong fluorescence, for example, emitting fluorescence under 532nm wavelength laser excitation.

[0039] If a polarized NV center is irradiated with microwaves at a frequency equal to its resonant frequency, electrons in the 0 state will undergo magnetic resonance, transitioning to the +1 or -1 state, resulting in a decrease in the fluorescence intensity of the NV center. The resonant frequency of the NV center is related to the magnetic field strength; by measuring the resonant frequency, the magnetic field strength around the NV center can be calculated.

[0040] Therefore, by irradiating the NV color center with microwaves of different frequencies and simultaneously recording the changes in the fluorescence intensity of the NV color center, the magnetic field strength around the NV color center can be obtained.

[0041] like Figure 5 As shown, in the absence of an external magnetic field, the spin energy levels corresponding to the first and second resonance frequencies are in the ±1 degenerate state, corresponding to one trough, and the fluorescence intensity darkens. At this time, the spin color center resonance frequency of the degenerate state is f0.

[0042] like Figure 6 As shown, when the spin color center senses an external magnetic field B, the waveform undergoes Zeeman splitting, with one trough splitting into two troughs, corresponding to the +1 and -1 states of the spin color center. The resonant frequencies f of the +1 and -1 states of the spin color center are also shown. B+ and f B- Move +γB and -γB relative to f0 respectively.

[0043] The resonant frequency f of the spin color center when a magnetic field is present B The resonance frequency f0 of the spin color center in the absence of a magnetic field satisfies the following equation: f B =f0±γB(2) Where f0 is the zero magnetic field resonance frequency of the quantum spin color center, γ is the gyromagnetic ratio of the quantum spin, and B is the magnetic induction intensity of the magnetic field induced by the quantum spin color center.

[0044] When the microwave frequency is f B+ and f B- When one of them is present, only one trough will appear on the fluorescence intensity-microwave frequency waveform diagram, and formula (2) still applies.

[0045] When the applied microwave frequency is equal to the resonant frequency of the spin center, a decreasing peak in the fluorescence intensity emitted by the spin center can be observed under continuous laser excitation. The magnetic flux density of the external magnetic field induced by the spin center can then be obtained using formula (2). Therefore, the fluorescence signal spectrum emitted by the spin center reflects the magnitude of the external magnetic field induced by the spin center, and the magnitude of the primary current can be calculated.

[0046] like Figure 8 and Figure 11 As shown, the primary sensor 1 includes an NV color center sensing unit 11, a magnetic ring 12, a magnetic shielding cover 13, a primary sensor housing 14, and a primary conductor 15.

[0047] like Figure 9 As shown, the NV color center sensing unit 11 is a MENS integrated component, including a laser receiving unit 111, an NV color center sensing unit 112, a microwave antenna 113, a circuit board 114, etc. The laser receiving unit 111 and the microwave antenna 113 are located on both sides of the NV color center sensing unit 112, and the microwave antenna 113 is located on the circuit board 114.

[0048] The NV color center sensing unit 11 has two usage modes: The first type: such as Figure 8 As shown, the NV color center sensing units 11 are evenly distributed in an array along the circumference of the primary sensor housing, and are used to measure large currents from A-level to kA-level. The magnetic shielding cover 13 is a multi-layered shield, including plate-type and cage-type magnetic shielding covers, located between the NV color center sensitive unit 11 and the primary sensor housing 14, and can shield static magnetic fields such as the Earth's magnetic field as well as low-frequency and high-frequency electromagnetic fields.

[0049] The primary sensor housing 14 is a snap-fit ​​circular structure, coaxially arranged with the primary conductor. For example... Figure 10 As shown, the primary sensor housing 14 includes a semi-circular ring fixed housing 141, a semi-circular ring fixed cover plate 142, a semi-circular ring rotating housing 143, and a semi-circular ring rotating cover plate 144. The semi-circular ring fixed housing 141 and the semi-circular ring rotating housing 143 are connected by a pin 145 and rotate around the pin 145 as an axis.

[0050] The second type: such as Figure 11 As shown, the NV color center sensing unit 11 and the magnetic ring 12 are used together to measure small currents in the mA range.

[0051] The magnetic focusing ring 12 is a split-type annular magnetic focusing ring, comprising a semi-circular magnetic focusing ring 121 and a semi-circular magnetic focusing ring 122. The semi-circular magnetic focusing ring 121 is installed inside the semi-circular ring fixed housing 141, and the semi-circular magnetic focusing ring 122 is installed inside the semi-circular ring rotating housing 143. A gap is opened on the semi-circular magnetic focusing ring 121, and the NV color center sensitive unit 11 is installed in the gap.

[0052] like Figure 12 As shown, the optical fiber composite insulator 2 includes an epoxy glass core rod 21, a shed 22, an integrated optical fiber 23, a lower flange 24, and an upper flange 25. The integrated optical fiber 23 is integrated between the shed 22 and the epoxy glass core rod 21 by a helical winding method.

[0053] like Figure 13 As shown, the optical transmission unit includes a near-ultraviolet optical fiber transmission unit 16, a microwave transmission optical fiber 17, and a laser power transmission optical fiber 18.

[0054] The near-ultraviolet fiber optic transmission unit includes a first near-ultraviolet fiber 161, a second near-ultraviolet fiber 162, a third near-ultraviolet fiber 163, a fourth near-ultraviolet fiber 164, a fifth near-ultraviolet fiber 165, a sixth near-ultraviolet fiber 166, a beam splitter 167, a fiber optic circulator 168, and a filter 169.

[0055] The fourth near-ultraviolet fiber 164, microwave transmission fiber 17 and laser power transmission fiber 18 together constitute the integrated fiber 23, which is spirally wound between the epoxy glass core rod 21 and the umbrella skirt 22, and leads out from the upper flange 25 and the lower flange 24 at both ends.

[0056] The first near-ultraviolet fiber 161, the second near-ultraviolet fiber 162, the third near-ultraviolet fiber 163, the fifth near-ultraviolet fiber 165, the sixth near-ultraviolet fiber 166, the beam splitter 167, the fiber optic circulator 168, and the filter 169 are all located at the lower end of the fiber optic composite insulator. The third near-ultraviolet fiber 163, the fourth near-ultraviolet fiber 164, and the fifth near-ultraviolet fiber 165 are connected to the fiber optic circulator 168; the first near-ultraviolet fiber 161, the second near-ultraviolet fiber 162, and the third near-ultraviolet fiber 163 are connected to the beam splitter 167, and the fifth near-ultraviolet fiber 165 and the sixth near-ultraviolet fiber 166 are connected to the filter 169.

[0057] Near-ultraviolet optical fibers are divided into three main optical paths based on the direction of light flow.

[0058] The first optical path consists of a first near-ultraviolet fiber 161, a beam splitter 167, a third near-ultraviolet fiber 163, a fiber optic circulator 168, and a fourth near-ultraviolet fiber 164, used to send the excitation laser from the green laser source 3 to the NV color center sensing unit 11; the second optical path consists of a fourth near-ultraviolet fiber 164, a fiber optic circulator 168, a fifth near-ultraviolet fiber 165, a filter 169, and a sixth near-ultraviolet fiber 166, used to send the fluorescence from the NV color center sensing unit 11 to the photoelectric detection unit 4; the third optical path consists of a first near-ultraviolet fiber 161, a beam splitter 167, and a second near-ultraviolet fiber 162, used to send the reference laser from the green laser source 3 to the photoelectric detection unit 4.

[0059] The two ends of the microwave transmission optical fiber 17 are used to connect the microwave transmitting unit 7 and the microwave receiving unit 8.

[0060] The laser power transmission fiber 18 is used to connect the laser power supply unit 101 and the energy conversion device 102.

[0061] The green laser source 3 can be a solid-state green laser source or a semiconductor green laser source, with a preferred wavelength of 532nm. The laser signal used to generate the preset wavelength is transmitted to the NV color center sensing unit 11 via a path consisting of a first near-ultraviolet fiber 161, a beam splitter 167, a third near-ultraviolet fiber 163, a fiber optic circulator 168, and a fourth near-ultraviolet fiber 164. The near-ultraviolet fiber is suitable for transmitting light with a wavelength of 532nm, exhibiting low energy loss.

[0062] The microwave modulation unit 6 is used to modulate the microwave signal to generate a microwave modulation signal of the required frequency, which is then transmitted to the NV color center sensing unit 11 via a microwave photonic link. The microwave photonic link includes a coaxial cable, a microwave transmitting unit 7, an optical fiber inside the optical fiber composite insulator 2, a microwave receiving unit 8, and the coaxial cable.

[0063] The NV color center sensing unit 11 generates a fluorescence signal, which is transmitted to the photoelectric detection unit 4 through the fourth near-ultraviolet fiber 164, fiber optic circulator 168, fifth near-ultraviolet fiber 165, filter 169, and the fifth near-ultraviolet fiber 165. The filter 169 is used to filter out noise in the fluorescence signal.

[0064] The green laser source 3 emits a laser as a reference laser through the third optical path splitter. The photoelectric detection unit uses the reference laser to remove the reference laser component from the fluorescence signal emitted by the NV color center sensitive unit 11.

[0065] The photoelectric detection unit 4 converts the fluorescence signal into an electrical signal and sends it to the microwave processing unit 5.

[0066] like Figure 14As shown in the figure below, the structure of the microwave photonic link comprises a microwave processing unit 5, an optical transmitting unit, and a microwave receiving unit 8. The optical transmitting unit includes a microwave modulation unit 6 and a microwave transmitting unit 7. The microwave processing unit 5 demodulates the microwave signal and adjusts the microwave modulation unit 6 according to the demodulated signal to match the frequency of the microwave signal with the resonant frequency of the NV color center sensitive unit 11. The microwave modulation unit 6 modulates and generates a microwave modulation signal, which is transmitted to the microwave transmitting unit 7 via a coaxial cable. The microwave modulation unit 6 includes a signal amplifier and a filter.

[0067] like Figure 14 As shown, the microwave transmitting unit 7 converts the microwave modulation signal into an optical signal via electro-optical conversion, and transmits it to the microwave receiving unit 8 through the optical fiber inside the optical fiber composite insulator 2. The microwave receiving unit 8 performs photoelectric conversion on the optical signal and generates a microwave signal, which is finally transmitted to the NV color center sensing unit 11 through a coaxial cable.

[0068] The microwave processing unit 5 calculates the magnetic field strength and primary current based on the resonant frequency.

[0069] The microwave processing unit 5 sends the primary current value to the merging unit 9.

[0070] The merging unit 9 sends the primary current value to the background measurement, protection device and online monitoring device.

[0071] An alarm unit is set on the merging unit 9, which is connected to the status monitoring units of the green laser source 3, photoelectric detection unit 4, microwave transmission unit, microwave modulation unit 6, and microwave processing unit 5 respectively.

[0072] like Figure 3 As shown, the specific working process of the quantum current transformer of the present invention is as follows: Step 1: The green laser source 3 transmits a laser signal with a preset wavelength and adjustable power to the NV color center sensing unit 11; Step 2: The NV color center sensing unit 11 generates fluorescence and sends it to the photoelectric detection unit 4; Step 3: The photoelectric detection unit 4 removes the laser component contained in the fluorescence, converts the fluorescence signal into an electrical signal, and sends it to the microwave processing unit 5; Step 4: The microwave processing unit 5 controls the microwave modulation unit 6 to change the frequency within the set frequency band according to the set power, and transmits it to the NV color center sensing unit 11 through the microwave transmitting unit 7 and the microwave receiving unit 8. Step 5: Microwave processing unit 5 obtains the fluorescence intensity-microwave frequency waveform curve based on fluorescence intensity and microwave frequency; Step 6: Based on the fluorescence intensity-microwave frequency waveform obtained in Step 5, determine the frequency. When the microwave frequency equals the spin center resonance frequency, the waveform of microwave processing unit 5 produces a trough, corresponding to the ±1 degenerate state or the +1 or -1 split state. Take the microwave frequency corresponding to the trough before power-on as the zero-field splitting frequency f0, and the microwave frequency corresponding to the trough after power-on as the resonance frequency f of the spin center under that magnetic field. B ; Step 7: Use formula f B =f0±γB Calculate the magnetic field; Step 8: Calculate the primary current using the formula 2πRB=μ0I; Step 9: Microwave processing unit 5 sends primary current to merging unit 9.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. A quantum current transformer based on a microwave photonic link, characterized in that, include: A primary sensor (1) is located on the high-voltage side; the primary sensor (1) includes an NV color center sensing unit (11). Fiber optic composite insulator (2) connects the high-voltage side and the low-voltage side, and has fiber optics integrated inside; The green laser source (3), photoelectric detection unit (4), and merging unit (9) are located on the low-voltage side; The microwave photonic link connects the low-voltage side and the high-voltage side, including a microwave processing unit (5), an optical emitting unit and a microwave receiving unit (8). The microwave processing unit (5) is used to regulate the optical emitting unit so that the optical emitting unit emits optical signals at different frequencies. The optical signals are transmitted to the microwave receiving unit (8) through the optical fiber inside the optical fiber composite insulator (2). The microwave receiving unit (8) is used to restore the optical signals to microwave signals and output them to the NV color center sensitive unit (11). The green laser source (3) is connected to the NV color center sensing unit (11) through the optical fiber inside the optical fiber composite insulator (2) and is used to transmit excitation laser to the NV color center sensing unit (11); The fluorescence signal generated by the NV color center sensing unit (11) is transmitted to the photoelectric detection unit (4) through the optical fiber inside the optical fiber composite insulator (2); the photoelectric detection unit (4) converts the fluorescence signal into an electrical signal and sends it to the microwave processing unit (5). The microwave processing unit (5) calculates the primary current value based on the resonant frequency and sends the primary current value to the merging unit (9).

2. A quantum current transformer based on a microwave photonic link according to claim 1, characterized in that, The light emitting unit includes a microwave modulation unit (6) and a microwave emitting unit (7), wherein the microwave modulation unit (6) is disposed between the microwave processing unit (5) and the microwave emitting unit (7); The microwave modulation unit (6) is used to modulate the microwave signal to generate a microwave modulation signal. The microwave transmitting unit (7) is used to convert the microwave modulation signal into an optical signal via electro-optic conversion.

3. A quantum current transformer based on a microwave photonic link according to claim 1, characterized in that, It also includes a laser power supply unit (101) located on the low-voltage side and an energy conversion device (102) located on the high-voltage side. The laser power supply unit (101) is connected to the energy conversion device (102) through the optical fiber inside the optical fiber composite insulator (2). The energy conversion device (102) is connected to the microwave receiving unit (8) and is used to supply power to the microwave receiving unit (8).

4. A quantum current transformer based on a microwave photonic link according to claim 1, characterized in that, The primary sensor (1) also includes a magnetic ring (12), a magnetic shield (13), and a sensor housing (14). When the NV color center sensing unit (11) is set up alone, it is used to measure current of Class A and above. Multiple NV color center sensing units (11) are evenly distributed in an array along the circumferential direction of the sensor housing (14). When the NV color center sensing unit (11) is combined with the magnetic ring (12), it is used to measure mA-level current. The NV color center sensing unit (11) is located in the air gap of the magnetic ring (12).

5. A quantum current transformer based on a microwave photonic link according to claim 4, characterized in that, The magnetic ring (12) is a split-type circular magnetic ring, including a semi-circular magnetic ring (121) and a semi-circular magnetic ring (122). The semi-circular magnetic ring (121) has an air gap, and the NV color center sensitive unit (11) is disposed in the air gap.

6. A quantum current transformer based on a microwave photonic link according to claim 1, characterized in that, The sensor housing (14) is a snap-fit ​​circular structure, comprising a semi-circular fixed housing (141), a semi-circular fixed cover plate (142), a semi-circular rotating housing (143), and a semi-circular rotating cover plate (144). The semi-circular fixed housing (141) and the semi-circular rotating housing (143) are connected by a pin (145) and rotate around the pin (145).

7. A quantum current transformer based on a microwave photonic link according to claim 1, characterized in that, The fiber composite insulator (2) includes an epoxy glass core rod (21), a skirt (22) and an integrated optical fiber (23). The integrated optical fiber (23) is integrated between the skirt (22) and the epoxy glass core rod (21) by spiral winding.

8. A quantum current transformer based on a microwave photonic link according to claim 7, characterized in that, The integrated optical fiber (23) includes a near-ultraviolet optical fiber transmission unit (16), a microwave transmission optical fiber (17), and a laser power transmission optical fiber (18). The near-ultraviolet fiber transmission unit (16) includes a first near-ultraviolet fiber (161), a second near-ultraviolet fiber (162), a third near-ultraviolet fiber (163), a fourth near-ultraviolet fiber (164), a fifth near-ultraviolet fiber (165), a sixth near-ultraviolet fiber (166), a beam splitter (167), a fiber optic circulator (168), and a filter (169). The fourth near-ultraviolet fiber (164), the microwave transmission fiber (17), and the laser power transmission fiber (18) together constitute the integrated fiber (23), which is spirally wound between the epoxy glass core rod (21) and the umbrella skirt (22).

9. A quantum current transformer based on a microwave photonic link according to claim 8, characterized in that, The near-ultraviolet fiber optic transmission unit (16) has three main optical paths: The first optical path consists of the first near-ultraviolet fiber (161), the beam splitter (167), the third near-ultraviolet fiber (163), the fiber circulator (168), and the fourth near-ultraviolet fiber (164), used to transmit the excitation laser of the green laser source (3) to the NV color center sensing unit (11). The second optical path consists of the fourth near-ultraviolet fiber (164), the fiber circulator (168), the fifth near-ultraviolet fiber (165), the filter (169), and the sixth near-ultraviolet fiber (166), which are used to transmit the fluorescence of the NV color center sensitive unit (11) to the photoelectric detection unit (4). The third optical path consists of the first near-ultraviolet fiber (161), the beam splitter (167), and the second near-ultraviolet fiber (162), used to transmit the reference laser from the green laser source (3) to the photoelectric detection unit (4).

10. A measurement method for a quantum current transformer based on a microwave photonic link according to any one of claims 1 to 9, characterized in that, Includes the following steps: The green laser source (3) transmits a laser signal of a preset wavelength to the NV color center sensing unit (11) through an optical fiber. The microwave photonic link converts the microwave signal into an optical signal, transmits it through an optical fiber, and then restores it to a microwave signal on the high-voltage side, which is then transmitted to the NV color center sensitive unit (11). The NV color center sensing unit (11) generates a fluorescence signal under the combined action of laser and microwave, and transmits it to the photoelectric detection unit (4) through optical fiber. The photoelectric detection unit (4) converts the fluorescence signal into an electrical signal and sends it to the microwave processing unit (5). The microwave processing unit (5) obtains the fluorescence intensity-microwave frequency waveform curve based on the fluorescence intensity and microwave frequency. Based on the waveform curve, the microwave frequency corresponding to the trough before power-on is taken as the zero magnetic field resonance frequency f0, and the microwave frequency corresponding to the trough after power-on is taken as the resonance frequency f of the spin color center when a magnetic field is present. B ; According to formula f B =f0±γB calculates the magnetic flux density B; γ is the gyrometry of the quantum spin; The primary current value is calculated according to the formula 2πRB=μ0I; where B is the magnetic induction intensity of the external magnetic field sensed by the primary sensor, R is the distance between the NV color center sensing unit 11 and the primary conductor, I is the primary current, and μ0 is the vacuum permeability. The microwave processing unit (5) sends the primary current value to the merging unit (9).

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