Phase difference measurement device and electric facility with the same

Abstract

To measure a phase difference between a plurality of physical fields with high sensitivity.SOLUTION: A phase difference measurement device (10) comprises: an electric magnetic wave irradiation part (2) which repeatedly irradiates a quantum sensor element (1) with an electromagnetic wave for operating an electron spin state of the quantum sensor element (1) changing with an interaction with a first physical field or second physical field generated with an AC signal; and a phase difference measurement part (3) which acquires a plurality of electron spin states after the interaction with the first physical field or second physical field, and measures the phase difference between a plurality of physical fields based upon the plurality of acquired electron spin states.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to technology using quantum sensors, and more particularly to an apparatus and method for measuring the phase difference of magnetic and electric fields using quantum sensors, and electrical equipment equipped with a phase difference measuring apparatus. [Background technology]

[0002] When AC is supplied through power lines in a power system, reactive power flows through the lines. As an increase in reactive power increases power loss, a device for adjusting the power factor is connected to the power system, which is highly effective in improving the stability of the power system and suppressing power fluctuations. For example, Patent Document 1 discloses a system for adjusting reactive power in distribution lines.

[0003] Devices that adjust the power factor are called phase modifying equipment. Phase modifying equipment includes power capacitors, shunt reactors, synchronous phase modifying machines, and static VAR compensators (SVCs). When using phase modifying equipment to adjust and improve the power factor of a power system, the reactive power flowing through the power system is measured. Reactive power is expressed using the effective value of the voltage, the effective value of the current, and the phase difference between the voltage and current.

[0004] Large currents and high voltages flow through power lines. For example, in extra-high voltage substations, high voltages of tens of thousands of volts flow through transmission lines, while in distribution substations, high voltages of several thousand to tens of thousands of volts flow through distribution lines. To measure the large currents and high voltages flowing through power lines, substations are equipped with transformers such as current transformers and voltage transformers in addition to phase modifying equipment. Until now, the phase difference between the voltage phase and current phase of the alternating current flowing through power lines has been measured by measuring the voltage phase and the current phase respectively in non-insulated transformers connected to the transmission or distribution line (or in circuits surrounding the transformers). Phase modifying equipment adjusts the power factor of the power system based on the measured phase difference.

[0005] In recent years, diamond has also been attracting attention as a material for sensor elements that measure magnetic fields. Complex defects called nitrogen-vacancy centers can be found in the crystal structure of diamond. These nitrogen-vacancy centers consist of a pair of a nitrogen atom that replaces a carbon atom in the crystal lattice, and a vacancy (missing a carbon atom) located adjacent to the nitrogen atom; they are also called NV centers (Nitrogen Vacancy centers). In addition to NV centers, complex defects called silicon-vacancy centers and germanium-vacancy centers can also be found in the crystal structure of diamond. These complex defects, including NV centers, are called color centers.

[0006] The NV center is in a state where an electron is trapped in a vacancy (negative charge state, hereafter referred to as "NV - In this NV state, the electron spin exhibits a magnetic property. - is the state in which no electrons are captured (neutral state, hereafter referred to as "NV 0 NV exhibits a long transverse relaxation time (decoherence time, hereafter referred to as "T2") compared to NV. - In the electron spin state of NV, after the magnetization of the electron spins aligned in the vertical direction of the external magnetic field (hereinafter referred to as the "quantization axis") is tilted to the transverse direction, the individual spins are displaced due to the precession of the individual spins, and it takes a long time for the overall transverse magnetization to disappear. - exhibits a long T2 value even at room temperature (approximately 300 K).

[0007] NV - The electron spin state of diamond changes in response to an external magnetic field, and this electron spin state can be measured at room temperature. Therefore, diamond containing NV centers can be used as a material for magnetic field sensor elements.

[0008] For example, Patent Document 2 discloses a method for measuring an AC magnetic field by magnetic resonance of electron spins in diamond, in which a pulse sequence based on the spin echo method is applied to the spins.

[0009] For example, Patent Document 3 discloses a method for measuring an AC magnetic field by optically detected magnetic resonance (ODMR) of electron spins in diamond. NV centers are excited by laser light, and magnetic resonance signals (phase information) related to the spin state are detected by measuring changes in the intensity of fluorescence emitted from the NV centers.

[0010] In addition to sensors using diamond color centers, there are various other types of sensors used as magnetic field sensor elements, such as sensors using color centers in silicon carbide (SiC), optically pumped atomic magnetometers (OPMs), and superconducting quantum interference devices (SQUIDs). These diamond color centers, silicon carbide color centers, optically pumped magnetometers, and superconducting quantum interference devices are called quantum sensors because they measure physical quantities using quantum effects. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-105488 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-103171 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-75964 Summary of the Invention [Problem to be solved by the invention]

[0012] When attempting to measure the phase difference between voltage and current in a non-insulated transformer (or in a circuit surrounding the transformer) for AC currents flowing through an electric power line carrying large currents and high voltages, the transformer requires a protection circuit to protect the circuit from the large currents and high voltages. As a result, electrical equipment, including power transmission and transformation equipment such as transformers and switches, and electric power lines, becomes large and expensive. In recent years, various equipment has been installed to connect DC power from solar power generation facilities to the power grid, and the scale of electrical equipment is also increasing. There is a need to measure the phase difference between voltage and current for AC currents flowing through electrical equipment without the need for a protection circuit.

[0013] Furthermore, when signs of failure appear in electrical equipment due to aging, a phase difference occurs between the minute electric field and minute magnetic field generated by fluctuations in the alternating current flowing through the electrical equipment. In order to detect signs of failure in electrical equipment as quickly as possible, there is a need to measure the phase difference between the magnetic and electric fields with high sensitivity.

[0014] An object of the present invention is to measure the phase difference between a plurality of physical fields with high sensitivity. [Means for solving the problem]

[0015] The present invention for solving the above problems includes, for example, the following aspects.

[0016] (Section 1) an electromagnetic wave irradiation unit that repeatedly irradiates the quantum sensor element with electromagnetic waves for manipulating the electron spin state of the quantum sensor element, which changes due to interaction with the first physical field or the second physical field generated by the AC signal; a phase difference measurement unit that acquires a plurality of electron spin states after interacting with the first physical field or the second physical field, and measures a phase difference between a plurality of physical fields based on the acquired plurality of electron spin states; A phase difference measuring device comprising: (Section 2) The phase difference measurement unit a first physical field phase calculation unit that calculates a phase of the first physical field based on the plurality of electron spin states after interacting with the first physical field; a second physical field phase calculation unit that calculates a phase of the second physical field based on the plurality of electron spin states after interacting with the second physical field; Including, Item 2. The phase difference measuring device according to item 1, wherein the phase difference is measured based on the calculated phase of the first physical field and the calculated phase of the second physical field. (Section 3) the first physical field phase calculation unit calculates a phase of the first physical field by fitting a plurality of time-series data corresponding to a plurality of the electron spin states after interacting with the first physical field; Item 3. The phase difference measuring device according to Item 2, wherein the second physical field phase calculating unit calculates the phase of the second physical field by fitting a plurality of time series data corresponding to a plurality of the electron spin states after interacting with the second physical field. (Section 4) 4. The phase difference measuring device according to any one of items 1 to 3, wherein the electromagnetic wave irradiation unit is a pulse sequence for observing a free induction decay (FID) signal of the electron spin state, and repeatedly irradiates the quantum sensor element with the electromagnetic wave using a pulse sequence including a plurality of π / 2 pulses. (Section 5) the electromagnetic wave irradiation unit is a pulse sequence for observing a spin echo signal of the electron spin state, and repeatedly irradiates the quantum sensor element with the electromagnetic wave using a pulse sequence including a plurality of π / 2 pulses and a π pulse between the plurality of π / 2 pulses; Item 4. The phase difference measuring device according to item 3, wherein each of the first physical field phase calculating unit and the second physical field phase calculating unit fits the plurality of data of the time series corresponding to the curvature of the AC signal. (Section 6) The phase difference measurement unit a light irradiation unit that irradiates the quantum sensor element with light for reading out phase information of the electron spin state after interacting with the first physical field or the second physical field; a change detection unit that detects a change that occurs in the quantum sensor element due to the irradiation of the light; a data processing unit that reads out phase information of the electron spin state from the detected change, and measures the phase difference between the phase of the first physical field and the phase of the second physical field based on the readout phase information of the electron spin state; Item 6. The phase difference measuring device according to any one of items 1 to 5, further comprising: (Section 7) Item 7. The phase difference measurement device according to item 6, further comprising a pulse pattern generator that outputs a pulse signal for operation timing to the electromagnetic wave irradiation unit and the light irradiation unit using the fluorescence intensity when the electron spin state is initialized as a trigger, and corrects a deviation in the measurement period. (Section 8) Item 8. The phase difference measurement device according to item 7, wherein the pulse signals for operation timing are connected in series among a plurality of the phase difference measurement devices. (Section 9) Item 9. The phase difference measuring device according to any one of items 1 to 8, wherein the AC signal is an AC signal that flows through an electrical facility. (Section 10) a step of repeatedly irradiating the quantum sensor element with electromagnetic waves for manipulating the electron spin state of the quantum sensor element, which changes due to interaction with a first physical field or a second physical field generated by an AC signal; acquiring a plurality of electron spin states after interacting with the first physical field or the second physical field, and measuring a phase difference between a phase of the first physical field and a phase of the second physical field based on the acquired plurality of electron spin states; A phase difference measuring method comprising: (Section 11) The step of measuring the phase difference includes: calculating a phase of the first physical field based on the plurality of electron spin states after interacting with the first physical field; calculating a phase of the second physical field based on the plurality of electron spin states after interacting with the second physical field; Including, Item 11. The phase difference measuring method according to Item 10, wherein the phase difference is measured based on the calculated phase of the first physical field and the calculated phase of the second physical field. (Section 12) the step of calculating the phase of the first physical field includes calculating the phase of the first physical field by fitting a plurality of time series data corresponding to a plurality of the electron spin states after interacting with the first physical field; Item 12. The phase difference measurement method according to Item 11, wherein the step of calculating the phase of the second physical field calculates the phase of the second physical field by fitting a plurality of time series data corresponding to a plurality of the electron spin states after interaction with the second physical field. (Section 13) Item 10. An electrical installation comprising the phase difference measuring device according to any one of items 1 to 9. [Effects of the Invention]

[0017] According to the present invention, it is possible to measure with high sensitivity the phase difference between a plurality of physical fields, such as the magnetic and electric fields generated around electrical equipment through which alternating current flows. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a diagram showing a schematic configuration of a phase difference measuring device 10 according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram schematically illustrating an example of a specific configuration of the phase difference measuring device 10 shown in FIG. [Figure 3] 1 is a schematic diagram of an electrical installation 9 equipped with a phase difference measuring device 10 according to an embodiment of the present invention. [Figure 4] 1 is a schematic diagram of an electrical installation 9 equipped with a phase difference measuring device 10 according to an embodiment of the present invention. [Figure 5] FIG. 1 is a diagram schematically showing the energy levels of electrons in the NV-center of diamond. [Figure 6] 1 is an exemplary pulse sequence for sensing a magnetic field by an optically detected magnetic resonance (ODMR) method, and is a pulse sequence for observing a free induction decay (FID) signal. [Figure 7] FIG. 1 is a diagram for explaining one aspect of the concept of phase difference measurement of the present invention. [Figure 8] FIG. 1 is a diagram for explaining one aspect of the concept of phase difference measurement of the present invention. [Figure 9] 1 is a flowchart showing the steps of a phase difference measuring method according to an embodiment of the present invention. [Figure 10] 10A and 10B are diagrams for explaining another aspect of the phase difference measurement concept of the present invention. [Figure 11] 10A and 10B are diagrams for explaining another aspect of the phase difference measurement concept of the present invention. [Figure 12] 10 is another exemplary pulse sequence for sensing a magnetic field by a method using optically detected magnetic resonance (ODMR), which is a pulse sequence for observing a spin echo signal. [Figure 13] 10 shows the results of a numerical simulation regarding the phase measurement of the magnetic field and the electric field according to the first embodiment. [Figure 14] 10 shows the results of a numerical simulation regarding the phase measurement of the magnetic field and the electric field according to the second embodiment. [Figure 15] 10 shows the results of a numerical simulation regarding the phase measurement of the magnetic field and the electric field according to the third embodiment. [Figure 16] FIG. 10 is a diagram for explaining a first improvement concept according to the fourth embodiment. [Figure 17] FIG. 10 is a diagram schematically illustrating the general configuration of a phase difference measuring device 10 to which a first improvement according to a fourth embodiment has been applied. [Figure 18] 10 shows magnetic resonance signals before and after the first improvement according to the fourth embodiment is performed. [Figure 19] FIG. 10 is a diagram for explaining the concept of a second improvement according to the fourth embodiment, showing a first connection mode when a trigger signal is applied to a plurality of phase difference measurement devices. [Figure 20] FIG. 10 is a diagram for explaining the concept of a second improvement according to the fourth embodiment, showing a second connection mode when a trigger signal is applied to a plurality of phase difference measurement devices. [Figure 21]20 shows a magnetic resonance signal obtained by the first connection mode shown in FIG. [Figure 22] 21 shows a magnetic resonance signal obtained by the second connection mode shown in FIG. 20. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and drawings, the same reference numerals will denote the same or similar components, and therefore, redundant descriptions of the same or similar components will be omitted.

[0020] In this specification, a physical quantity refers to a quantity whose dimensions are determined under a certain system in physics and which can be expressed as a multiple of a defined physical unit. Examples of physical quantities include magnetic fields, electric fields, temperature, and mechanical quantities (mechanical stress, pressure, etc.). Magnetic fields, electric fields, and mechanical quantities include physical quantities that do not change over time and physical quantities whose direction repeatedly changes over time. In other words, magnetic fields include static magnetic fields and AC magnetic fields, electric fields include electrostatic fields and AC electric fields, and mechanical quantities include static mechanical quantities and AC mechanical quantities.

[0021] In the embodiment of the present invention described below, a magnetic field and an electric field are defined as a first physical field and a second physical field, respectively, and a phase difference between the voltage phase and the current phase of an alternating current flowing through an electrical facility is measured. Illustratively, the frequency of the alternating current is about 50 Hz to about 60 Hz.

[0022] <Relationship between the phase of the magnetic and electric fields and the phase of the voltage and current> The following describes the relationship between the phase of the magnetic field and the phase of the electric field generated around the electrical equipment 9 and the phase of the voltage and the phase of the current related to the AC flowing through the electrical equipment 9. For the magnetic field and the electric field generated around the electrical equipment 9 through which AC flows, the phase of the magnetic field correlates with the phase of the AC current, and the phase of the electric field correlates with the phase of the AC voltage.

[0023] The phase of the current is measured by measuring the phase of the magnetic field generated by the current flow. The phase of the magnetic field is calculated from the first term of the spin Hamiltonian of the electron spin, which is described later, due to the Zeeman effect, which functions as a magnetic field sensor. The magnetic field strength is calculated from the first term, and the magnetic field phase is calculated from the temporal fluctuations of the calculated multiple magnetic field strengths.

[0024] The voltage phase is measured by the sensor element 1 measuring the magnetic resonance signal at zero magnetic field splitting, where the signal intensity is contributed by the electric field but not by the magnetic field. The electric field phase is calculated from the third term of the spin Hamiltonian of the electron spin, which functions as an electric field sensor, as described below. The electric field strength is calculated from the third term, and the electric field phase is calculated from the temporal fluctuations of the calculated multiple electric field strengths. When measuring the voltage phase (electric field phase), the zero point of the phase is adjusted in advance. For example, the time rate of change of the voltage is maximum at the zero crossing point of the voltage strength, so this point is used as the reference zero point.

[0025] As will be described later with reference to Figure 5, when a magnetic field is applied to the sensor element 1, the quantum state of the sensor element 1 is split in proportion to the strength of the applied magnetic field due to the Zeeman effect. In contrast, when no magnetic field is applied to the sensor element 1, the first term due to the Zeeman effect of the spin Hamiltonian of the electron spin, which will be described later, does not contribute to the magnetic resonance signal. When the sensor element 1 is split in zero magnetic field, the third term (and the second term) that functions as an electric field sensor contributes to the magnetic resonance signal.

[0026] [Device configuration] Fig. 1 is a diagram showing a schematic configuration of a phase difference measurement device 10 according to one embodiment of the present invention. Fig. 2 is a diagram showing a schematic example of a specific configuration of the phase difference measurement device 10 shown in Fig. 1.

[0027] The phase difference measuring device 10 (hereinafter simply referred to as the measuring device 10) includes a sensor element 1, an electromagnetic wave irradiating unit 2, and a phase difference measuring unit 3. In this embodiment, the sensor element 1 is attached to the tip of a probe 11 of the measuring device 10.

[0028] The sensor element 1 is a quantum sensor element. In this embodiment, the sensor element 1 is a diamond crystal having a color center, and an NV center is used as the color center. The NV center is a complex (complex defect) of nitrogen (N) substituting a carbon atom and a vacancy (V) adjacent to the nitrogen. In this embodiment, the sensor element 1 is generated in advance by a known method in a predetermined region on the diamond crystal 12. Illustratively, the region contains approximately several thousand particles (concentration: 1×10 12 / cm -3 ) A plurality of sensor elements 1 are generated. In this embodiment, the sensor elements 1 are ensemble NV centers.

[0029] The electron spin state of the sensor element 1 is changed by an interaction 8 with an object 9. In this embodiment, the object 9 is an electrical equipment, and the interaction 8 is an interaction between a magnetic field and an electric field. Due to the interaction 8 with the object 9, the electron spin state of the color center of the sensor element 1 changes to a state that corresponds to the strength of the magnetic field and electric field generated around the object 9, which is the electrical equipment.

[0030] The electromagnetic wave irradiating unit 2 irradiates the sensor element 1 with electromagnetic waves for manipulating the electron spin state of the sensor element 1 by magnetic resonance. As an example, in this embodiment, the electromagnetic wave irradiating unit 2 includes a known microwave (MW) oscillator 21, a switch 22 for irradiating the electromagnetic waves in a pulsed form, and an amplifier 23. The switch 22 and the amplifier 23 may have any configuration. In this embodiment, the electromagnetic wave irradiating unit 2 irradiates the sensor element 1 with electromagnetic waves in a pulsed form for manipulating the electron spin state of the sensor element 1.

[0031] The pulse sequence of the electromagnetic waves that the electromagnetic wave irradiating unit 2 irradiates to the sensor element 1 can be any of various pulse sequences that cause magnetic resonance.

[0032] Illustratively, in this embodiment, a pulse sequence for observing a free induction decay (FID) signal is used as a magnetic resonance signal. Such a pulse sequence for observing a free induction decay (FID) signal is a simpler pulse sequence than pulse sequences based on the Hahn echo method or the Ramsey method, which are exemplified as examples of pulse sequences used to detect magnetic resonance signals. Illustratively, in other embodiments, a pulse sequence for observing a spin echo signal as a magnetic resonance signal can be used.

[0033] The electromagnetic wave irradiating unit 2 irradiates the sensor element 1 with electromagnetic waves through an antenna 14 for irradiating electromagnetic waves that is arranged in the vicinity of the sensor element 1. The antenna 14 is formed on the diamond crystal 12 using a conductive metal, for example, by lithography technology.

[0034] The phase difference measurement unit 3 calculates the magnetic field phase and the electric field phase individually based on changes in the multiple electron spin states of the sensor element 1 after changes due to the interaction 8 with the target object 9, and measures the phase difference between the magnetic field phase and the electric field phase. Both the magnetic field phase and the electric field phase are calculated by fitting time-series data of magnetic resonance signals. In this embodiment, the magnetic field phase and the electric field phase are calculated by fitting time-series data of multiple free induction decay (FID) signals. The phase difference measurement unit 3 includes a light irradiation unit 31, a change detection unit 32, and a data processing unit 33.

[0035] The light irradiating unit 31 irradiates the sensor element 1 with light for reading out phase information of the electron spin state of the sensor element 1 after interacting with the object 9. The light irradiating unit 31 also irradiates the sensor element 1 with light for initializing the electron spin state of the sensor element 1. As an example, in this embodiment, the light irradiating unit 31 includes a light source 311, an acousto-optical modulator (AOM) 312, and an objective lens 313. The acousto-optical modulator 312 and the objective lens 313 can have any configuration.

[0036] The light source 311 emits light for reading out phase information of the electron spin state of the sensor element 1 after interaction with the object 9. The light source 311 also emits light for exciting and initializing the electron spin state of the sensor element 1. The wavelength of the light emitted by the light source 311 is determined depending on the type of the sensor element 1. In this embodiment, the light source 311 emits laser light with a wavelength of 532 nm (green). For example, various known laser generating devices can be used as the light source 311. In this embodiment, the light source 311 is a semiconductor laser that emits green laser light.

[0037] The objective lens 313 focuses the light emitted from the light source 311 and irradiates it onto the area on the diamond crystal 12 where the sensor element 1 is being generated. Illustratively, the spot size of the laser light focused on the diamond crystal 12 has a diameter of about 2 μm. As the spot size of the laser light decreases, the intensity of the laser light per unit area increases, and the efficiency of the photocurrent generated in the conduction band of the diamond also increases.

[0038] 2, the spot of the laser light is positioned so as to cover the area where the sensor element 1 is generated on the diamond crystal 12. Preferably, the spot of the laser light can be positioned at a position offset from approximately the center of the area where the sensor element 1 is generated.

[0039] The change detection unit 32 detects changes occurring in the sensor element 1. In this embodiment, the change detection unit 32 detects light emitted from the sensor element 1, and detects a magnetic resonance signal as a change in light emission intensity by a known optically detected magnetic resonance (ODMR) method. In this case, the change detection unit 32 can be, for example, a known photodiode. The photodiode can be, for example, an avalanche photodiode.

[0040] In this embodiment, the electromagnetic wave for operation is irradiated in a pulsed form in the electromagnetic wave irradiation unit 2. Therefore, in this embodiment, specifically, detection is performed by the Pulsed Optically Detected Magnetic Resonance (pODMR) method.

[0041] The data processing unit 33 is connected to the change detection unit 32, and reads out phase information of the electron spin state of the sensor element 1 after interaction with the object 9 from the change detected by the change detection unit 32, and measures the phase difference between the phase of the magnetic field and the phase of the electric field based on the read out phase information. The data processing unit 33 includes a magnetic field phase calculation unit 331, an electric field phase calculation unit 332, and a phase difference signal output unit 333.

[0042] Various information terminal devices such as a known general-purpose computer or a smartphone can be used as the data processing unit 33. The data processing unit 33 may be configured as an integral part of the measuring device 10, or, as shown in the figure, may be provided externally to the measuring device 10 and connected to the measuring device 10 via a wired or wireless network 99.

[0043] The magnetic field phase calculation unit 331 calculates the phase of the magnetic field based on the multiple electron spin states after interacting with the magnetic field. The observed magnetic resonance signals reflect the electron spin states, and the magnetic field phase is calculated by fitting the time-series data of the multiple magnetic resonance signals after interacting with the magnetic field.

[0044] The electric field phase calculation unit 332 calculates the phase of the electric field based on the multiple electron spin states after interacting with the electric field. The observed magnetic resonance signals reflect the electron spin states, and the electric field phase is calculated by fitting the time-series data of the multiple magnetic resonance signals after interacting with the electric field.

[0045] In this embodiment, the magnetic field phase calculation unit 331 and the electric field phase calculation unit 332 calculate the phase of the magnetic field and the phase of the electric field, respectively, by fitting time-series data of a plurality of free induction decay (FID) signals.

[0046] The phase difference signal output unit 333 outputs a signal containing information about the phase difference between the phase of the magnetic field and the phase of the electric field. The phase difference signal is transmitted, for example, via a network 99, to a computer device (not shown) that centrally manages the operating status of other electrical equipment. The centralized management computer device then determines whether or not power factor adjustment is necessary based on the received phase difference signal, and transmits information about the power factor adjustment along with the phase difference signal to a phase modifying device (not shown). The phase modifying device adjusts the power factor of the power system based on the received phase difference signal and the information about the power factor adjustment. Alternatively, the phase difference signal is transmitted directly to a phase modifying device (not shown), for example, via the network 99, and the phase modifying device adjusts the power factor of the power system based on the received phase difference signal.

[0047] 3 and 4 are schematic diagrams of electrical equipment 9 equipped with a phase difference measuring device 10 according to one embodiment of the present invention. As the electrical equipment 9, a current transformer 9a is illustrated in FIG. 3, and a voltage transformer 9b is illustrated in FIG. 4. The locations of the measuring device 10 illustrated in these figures are merely examples.

[0048] The measuring device 10 is placed in a position where it can sense the magnetic and electric fields generated around the electrical equipment 9 (9a, 9b). Preferably, the measuring device 10 is placed so that the axis along which the sensor element 1 senses the magnetic or electric field is aligned with the direction of the magnetic or electric field generated around the electrical equipment 9.

[0049] In another embodiment, multiple measurement devices 10, 10 can be placed in one piece of electrical equipment 9. For example, a first measurement device 10 for measuring the phase of the voltage can be placed at a location in the current transformer 9a where the electric field strength is strongest, and a second measurement device 10 for measuring the phase of the current can be placed at a location in the current transformer 9a where the magnetic field strength is strongest. The same applies when the electrical equipment 9 is a transformer 9b.

[0050] [Measurement principle] In the present invention, the phase difference between the magnetic field and electric field generated around the electrical equipment 9 is measured using a sensor element 1. The sensor element 1 is a quantum sensor element, which measures with high sensitivity the phase difference between the voltage and current related to the AC current flowing through the electrical equipment 9. The magnetic resonance signals used to calculate the phase of the magnetic field and the phase of the electric field are detected by optically detected magnetic resonance (ODMR). This allows the phase difference between the voltage and current related to the AC current to be measured contactlessly, without being directly electrically connected to the electrical equipment 9.

[0051] First, we will explain the principle and procedure for detecting magnetic resonance signals using optically detected magnetic resonance (ODMR). Next, we will explain how to calculate the intensities of magnetic and electric fields from the detected magnetic resonance signals. Finally, we will explain the phase difference measurement concept of the present invention, which measures the phase difference between the voltage phase and the current phase of an alternating current.

[0052] <Detection of magnetic resonance signals by optically detected magnetic resonance (ODMR)> Figure 5 shows the NV of diamond. - FIG. 2 is a diagram schematically illustrating the energy levels of electrons at the center.

[0053] In this embodiment, the NV center of diamond is used as the sensor element 1. The ground state of the NV center has a magnetic quantum number m s = -1, 0, +1 spin triplet states, and in the steady state at room temperature, all levels are equally distributed in the ground state.

[0054] Ground state magnetic quantum number m s When irradiated with a laser beam with a wavelength of 532 nm (green), the electron with a magnetic quantum number m s =0 ground state.

[0055] On the other hand, the magnetic quantum number m in the ground state s When an electron with a magnetic quantum number m = 0 is irradiated with microwaves with a resonant frequency of 2.87 GHz, electron spin resonance (ESR) occurs, and the magnetic quantum number m sThe magnetic quantum number m s When irradiated with a laser beam with a wavelength of 532 nm (green), the electrons with magnetic quantum number m s = 0. This series of processes is a non-radiative transition that does not emit fluorescence.

[0056] In this way, the process of emitting red fluorescence occurs when magnetic resonance occurs and the electrons have a magnetic quantum number m s This is unlikely to occur when the magnetic quantum number m s The doubly degenerate ground states of = ±1 are split by Zeeman splitting in proportion to the strength of the external magnetic field, so the fluorescence intensity also changes depending on the magnetic quantum number m of the electron. s = ±1. Therefore, when the microwave frequency is swept around 2.87 GHz, the magnetic resonance signal can be detected as a point where the red fluorescence intensity decreases.

[0057] Fig. 6 shows an exemplary pulse sequence for sensing a magnetic field using an optically detected magnetic resonance (ODMR) method. The pulse sequence of the operating electromagnetic wave shown in Fig. 6 is a pulse sequence including two π / 2 pulses for observing a free induction decay (FID) signal.

[0058] We will now explain states I to V of the pulse sequence shown in Fig. 6. State I represents a state in which electron spins are initialized by irradiation with laser light. In the Bloch sphere, which is a notation for representing a quantum state on a unit spherical surface, electron spins are aligned in the direction along the z-axis, which is the quantization axis.

[0059] Next, in state II, a π / 2 pulse is applied to tilt the electron spins along the quantization axis to a plane perpendicular to the quantization axis. The electron spins are tilted to the xy plane of the Bloch sphere. After that, in state III, the electron spins tilted to the xy plane are dephased while rotating in the xy plane of the Bloch sphere due to interaction with the magnetic field for a predetermined time τ. The strength of the interaction corresponds to the strength of the magnetic field felt by the electron spins. In this state III, the electron spins are dephased while rotating in the xy plane of the Bloch sphere due to interaction with the magnetic field. This process is observed as a free induction decay (FID) signal in the subsequent state V.

[0060] After a certain time τ has elapsed while the phase is being relaxed in state III, a π / 2 pulse is applied in state IV to project the relaxed electron spins onto the quantization axis. The electron spins, which were located within the xy plane of the Bloch sphere, are projected onto the z-axis, which is the quantization axis, and aligned along the z-axis.

[0061] Thereafter, in state V, the sensor element is irradiated with laser light and the light emitted from the sensor element is detected, thereby reading out the phase information of the electron spin state after the interaction.

[0062] In the pulse sequence including two π / 2 pulses shown in Figure 6, electron spins relax while rotating in the xy plane of the Bloch sphere in state III, and in magnetic resonance imaging, the signal generated when the electron spins relax is detected as a magnetic resonance signal. The time τ between the π / 2 pulses corresponds to the period in state III during which the electron spins relax, and this time τ determines the sensitivity of the measurement. This is because the degree to which the electron spins relax due to interaction with a magnetic field corresponds to the strength of the magnetic field felt by the electron spins.

[0063] As with the magnetic field, the electric field can be sensed using the pulse sequence shown in FIG.

[0064] <Method for calculating magnetic field and electric field strength based on magnetic resonance signals> In the optically detected magnetic resonance (ODMR) method, phase information (magnetic resonance signal) of the electron spin state of the sensor element 1 after interaction with the object 9 is detected as a change in emission intensity. The detected phase information corresponds to the physical quantity of the object. Therefore, by appropriately processing the detected phase information of the electron spin state after interaction, the physical quantity of the object can be calculated. The physical quantity of the object can be calculated based on the Hamiltonian of the electron spin.

[0065] Electron spin Hamiltonian H gs is expressed by the following formula:

number

[0066] First term

number

[0067] The second and third terms are due to dipole interactions (i.e., spin-spin interactions).

number

number

[0068] Thus, the strength of the magnetic field can be calculated based on the first term, the strength of the temperature and mechanical quantities can be calculated based on the second term, and the strength of the electric field can be calculated based on the third term.

[0069] In the present invention, the absolute values of the magnetic field and electric field strength are not required, but the magnitude of the magnetic resonance signal after interacting with the magnetic field is determined by the Hamiltonian H of the electron spin. gs The magnitude of the magnetic resonance signal after interaction with the electric field can be calculated based on the first term, and the magnitude of the magnetic resonance signal after interaction with the electric field can be calculated based on the third term. This allows the magnetic resonance signal after interaction with the magnetic and electric fields to be separated into a component due to interaction with the magnetic field and a component due to interaction with the electric field.

[0070] <Phase difference measurement concept> 7 and 8 are diagrams for explaining the concept of phase difference measurement according to the present invention.

[0071] In Fig. 7, the upper part shows the temporal fluctuation of an alternating current flowing through an electrical facility, which is the object 9, and the lower part shows an exemplary pulse sequence for sensing a magnetic field and an electric field by a technique using optically detected magnetic resonance (ODMR). Illustratively, the frequency of the alternating current is about 50 Hz to about 60 Hz. Fig. 8 is an enlarged view of the portion surrounded by a dashed line in the pulse sequence shown in the lower part of Fig. 7. Symbols I to V in Fig. 8 correspond to states I to V of the pulse sequence shown in Fig. 6.

[0072] As described above, with regard to the magnetic field and electric field generated around electrical equipment 9 through which AC flows, the phase of the magnetic field correlates with the phase of the AC current, and the phase of the electric field correlates with the phase of the AC voltage. In the present invention, the phase difference between the magnetic field and electric field generated around electrical equipment 9 through which AC flows is measured using sensor element 1. This allows the phase difference between the voltage and current related to the AC flowing through electrical equipment 9 to be measured with high sensitivity.

[0073] The phase difference between the magnetic field phase and the electric field phase is calculated based on a plurality of electron spin states after interacting with the magnetic field and the electric field. The electron spin states are acquired by measuring magnetic resonance signals using the pulse sequences exemplified in, for example, Figures 7 and 8 (more specifically, Figure 6). As exemplified in Figures 7 and 8, the pulse sequence shown in Figure 6 is repeatedly executed a plurality of times during one cycle of the alternating current, thereby acquiring a plurality of pieces of magnetic resonance signal data.

[0074] If the frequency of the AC current flowing through the electrical equipment 9 is, for example, approximately 60 Hz, measurement using the pulse sequence illustrated in FIG. 8 is repeated approximately 512 times during one cycle of the AC current, thereby obtaining approximately 512 magnetic resonance signals representing multiple electron spin states after interaction with the magnetic and electric fields. These approximately 512 magnetic resonance signal data are time-series data corresponding to multiple electron spin states after interaction with the magnetic field. The phase of the magnetic field is calculated by curve-fitting these approximately 512 magnetic resonance signal data. Trigonometric functions such as sine and cosine functions are used as functions for fitting the data, and four parameters are used: signal offset, amplitude, frequency, and phase. As with the magnetic field, the phase of the electric field is calculated by curve-fitting the multiple magnetic resonance signal data after interaction with the electric field.

[0075] If the frequency of the alternating current flowing through the electrical equipment 9 is, for example, approximately 50 Hz, measurement using the pulse sequence illustrated in FIG. 8 is repeated approximately 614 times during one cycle of the alternating current, and approximately 614 magnetic resonance signals can be acquired as multiple electron spin states after interacting with the magnetic and electric fields.

[0076] [Measurement procedure] 9 is a flowchart showing the steps of a phase difference measurement method according to one embodiment of the present invention. Steps S1 to S5 are steps for calculating the phase of the magnetic field, and steps S6 to S10 are steps for calculating the phase of the electric field. In step S11, the phase difference between the magnetic field and the electric field is calculated, and information about the calculated phase difference is output in step S12.

[0077] In step S1, the sensor element 1 is irradiated with laser light to initialize the electron spin of the color center (NV center) of the sensor element 1. Then, the initialized electron spin of the NV center is caused to interact with the magnetic and electric fields generated around the object 9. After allowing the interaction for a sufficient time, the electron spin state of the NV center becomes a state corresponding to the strength of the magnetic field. The state of step S1 corresponds to state I of the pulse sequence shown in FIG. 6.

[0078] In step S2, magnetic field sensing is performed by irradiating the sensor element 1 with electromagnetic waves for spin manipulation. In this embodiment, magnetic field sensing is performed by irradiating two π / 2 pulses according to the pulse sequence shown in Fig. 6. That is, in this embodiment, the electron spin state of the NV center is manipulated to correspond to states II to IV of the pulse sequence shown in Fig. 6.

[0079] In step S3, the sensor element 1 is irradiated with laser light and changes occurring in the sensor element 1 are detected, thereby reading out phase information of the electron spin state after the interaction. In this embodiment, the phase information of the electron spin state after the interaction is read out by detecting light emitted from the sensor element 1. The phase information of the electron spin state after the interaction is detected as a change in emission intensity by the optically detected magnetic resonance (ODMR) method using the change detection unit 32. The magnetic resonance signal detected as a change in emission intensity represents the phase information of the electron spin state after the interaction. The state in step S3 corresponds to state V of the pulse sequence shown in FIG. 6.

[0080] In step S4, it is determined whether the series of measurement processes from steps S1 to S3 has been repeated a predetermined number of times. If the series of measurement processes has been repeated a predetermined number of times (Yes in step S4), the process of step S5 is performed, and if it has not been repeated the predetermined number of times (No in step S4), the process is performed again from step S1.

[0081] As mentioned above, if the frequency of the AC current flowing through the electrical equipment 9 is, for example, about 50 Hz to about 60 Hz, it is possible to perform measurements using the pulse sequence illustrated in FIG. 8 about 512 times during one cycle of the AC current, and as an example, the series of measurement processes from steps S1 to S3 can be repeatedly executed about 512 times.

[0082] In step S5, the phase of the magnetic field is calculated based on a predetermined number of electron spin states after interacting with the magnetic field and electric field, which are obtained by the series of measurement processes in steps S1 to S4.

[0083] The strength of the magnetic field is calculated from the phase information of the electron spin state after the interaction read out in step S3. The phase information of the electron spin state after the interaction detected by the change detection unit 32 corresponds to the magnetic field and electric field of the object 9. Therefore, the strength of the magnetic field can be calculated by appropriately processing the magnetic resonance signal representing the phase information of the detected electron spin state after the interaction. For example, the strength of the magnetic field can be calculated by calculating the Hamiltonian H of the electron spin described above from the measurement result of the electron spin state in the ground state after the interaction. gs can be calculated based on the first term due to the Zeeman effect.

[0084] By calculating the magnetic field strength for each of the phase information of the multiple electron spin states obtained by the series of measurement processes in steps S1 to S4, data on the temporal fluctuation of the magnetic field strength can be obtained. The phase of the magnetic field is calculated by curve fitting the obtained data on the temporal fluctuation of the magnetic field strength.

[0085] In steps S6 to S9, the same processes as in steps S1 to S4 are performed. In step S6, the sensor element 1 is irradiated with laser light to initialize the electron spin of the color center (NV center) of the sensor element 1. Then, the initialized electron spin of the NV center is caused to interact with the magnetic and electric fields generated around the object 9. In step S7, the sensor element 1 is irradiated with an electromagnetic wave for spin manipulation, thereby performing electric field sensing. In step S8, the sensor element 1 is irradiated with laser light to detect changes occurring in the sensor element 1, thereby reading out phase information of the electron spin state after the interaction. In step S9, it is determined whether the series of measurement processes in steps S6 to S8 have been repeated a predetermined number of times. If the series of measurement processes have been repeated a predetermined number of times (Yes in step S9), the process of step S10 is performed. If the series of measurement processes have not been repeated a predetermined number of times (No in step S9), the process is performed again from step S6.

[0086] In step S10, the phase of the electric field is calculated based on a predetermined number of electron spin states after interacting with the magnetic and electric fields, which are obtained by the series of measurement processes in steps S6 to S9.

[0087] The electric field strength is calculated from the phase information of the electron spin state after the interaction read out in step S8. The phase information of the electron spin state after the interaction detected by the change detection unit 32 corresponds to the magnetic field and electric field of the object 9. Therefore, the electric field strength can be calculated by appropriately processing the magnetic resonance signal representing the phase information of the detected electron spin state after the interaction. For example, the electric field strength can be calculated by using the above-mentioned Hamiltonian H of the electron spin from the measurement result of the electron spin state in the ground state after the interaction. gs can be calculated based on the third term, which acts as an electric field sensor.

[0088] For each of the phase information of the multiple electron spin states obtained by the series of measurement processes in steps S6 to S9, the electric field strength is calculated to obtain data on the temporal fluctuation of the electric field strength. The phase of the electric field is calculated by curve fitting the obtained data on the temporal fluctuation of the electric field strength.

[0089] In step S11, the phase difference between the magnetic field phase and the electric field phase is calculated from the difference between the magnetic field phase calculated in step S5 and the electric field phase calculated in step S10.

[0090] In step S12, a signal containing information about the phase difference between the phase of the magnetic field and the phase of the electric field calculated in step S11 is output. The signal containing information about the phase difference is transmitted, for example, via a network 99, and is used to adjust the power factor by a phase modifying device.

[0091] [effect] As described above, according to the present invention, it is possible to measure with high sensitivity the phase difference between the magnetic and electric fields generated around electrical equipment through which alternating current flows. As a result, even in electrical equipment through which large currents and high voltages flow, it is possible to measure the phase difference between the voltage and current related to alternating current without requiring a protection circuit to protect the circuit from large currents and high voltages. Because no protection circuit is required, the electrical equipment can be made smaller in scale and less expensive.

[0092] In this invention, the phase difference between the magnetic and electric fields generated around electrical equipment through which AC flows is measured using the sensor element of a quantum sensor. This makes it possible to measure the phase difference between the voltage and current related to the AC flowing through the electrical equipment with high sensitivity. The magnetic resonance signals used to calculate the phase of the magnetic field and the electric field are detected by optically detected magnetic resonance (ODMR). This makes it possible to measure the phase difference between the voltage and current related to the AC flowing through the electrical equipment without contact, without directly connecting electrically to the electrical equipment.

[0093] [Other forms] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the above-described embodiments.

[0094] In the above-described embodiment, the pulse sequence of the electromagnetic waves irradiated to the sensor element 1 by the electromagnetic wave irradiating unit 2 is a pulse sequence for observing a free induction decay (FID) signal, as exemplified in Fig. 6, but the pulse sequence used for detecting a magnetic resonance signal is not limited to this. As will be described with reference to Figs. 10 to 12, instead of observing a free induction decay (FID) signal, a spin echo signal may be observed as a magnetic resonance signal using a pulse sequence based on the Hahn echo method.

[0095] <Pulse sequence for measuring the curvature of an AC signal> 10 and 11 are diagrams for explaining another embodiment of the concept of phase difference measurement of the present invention.

[0096] In Fig. 10, the upper part shows the temporal fluctuation of an alternating current flowing through an electrical facility, which is the object 9, and the lower part shows another exemplary pulse sequence for sensing a magnetic field and an electric field by a technique using optically detected magnetic resonance (ODMR). Illustratively, the frequency of the alternating current is about 50 Hz to about 60 Hz. Fig. 11 is an enlarged view of the portion surrounded by a dashed line in the pulse sequence shown in the lower part of Fig. 10. Symbols I to VII in Fig. 11 correspond to states I to VII of the pulse sequence shown in Fig. 12.

[0097] In another aspect of the concept of phase difference measurement of the present invention, the electron spin state is acquired by measuring the magnetic resonance signal using the pulse sequence exemplified in Figures 10 and 11 (more specifically, Figure 12). As in the concept of phase difference measurement of the present invention described with reference to Figures 6 to 8, the pulse sequence shown in Figure 12 is repeatedly executed multiple times during one period of the AC current, as exemplified in Figures 10 and 11, thereby acquiring multiple pieces of magnetic resonance signal data.

[0098] Fig. 12 shows another exemplary pulse sequence for sensing a magnetic field using an optically detected magnetic resonance (ODMR) method. The pulse sequence of an operating electromagnetic wave shown in Fig. 12 is a pulse sequence based on the spin echo method (Hahn echo method) in which a spin echo signal is observed using a pulse sequence including two π / 2 pulses and a π pulse therebetween.

[0099] We will now explain states I to VII of the pulse sequence shown in Fig. 12. State I represents a state in which electron spins are initialized by irradiation with laser light. In a Bloch sphere, which is a notation for representing a quantum state on a unit spherical surface, electron spins are aligned in the direction along the z-axis, which is the quantization axis.

[0100] Next, in state II, a π / 2 pulse is applied to tilt the electron spins along the quantization axis to a plane perpendicular to the quantization axis. The electron spins are tilted to the xy plane. After that, in state III, the electron spins tilted to the xy plane undergo dephasing due to interactions with the AC magnetic field and static magnetic field over a predetermined time τ0. The strength of the interaction corresponds to the strength of the magnetic field felt by the electron spins, which corresponds to region B in Figure 11.

[0101] After a predetermined time τ0 has elapsed in state III, a π pulse is applied in state IV to invert the electron spins, which have been dephasised by interaction with the object being measured, in the plane. From state III to state IV, the electron spins rotate in the xy plane. In this case, in state V after inversion, the electron spins refocus, canceling out the static magnetic field component, but the AC magnetic field component is not cancelled out because its strength has been inverted compared to state III.

[0102] After that, while a predetermined time τ has elapsed in state V, the electron spins undergo dephasing due to the interaction with the AC magnetic field and the static magnetic field, as in state III. The strength of the interaction corresponds to the strength of the magnetic field felt by the electron spins, and corresponds to region A in Figure 11.

[0103] After a predetermined time τ0 has elapsed in state V, a π / 2 pulse is applied in state VI to project the dephasing electron spins onto the quantization axis. The electron spins, which were located in the xy plane, are projected onto the z-axis, which is the quantization axis, and aligned along the z-axis.

[0104] Thereafter, in state VII, the sensor element is irradiated with laser light and the light emitted from the sensor element is detected, thereby reading out the phase information of the electron spin state after the interaction.

[0105] As with the magnetic field, the electric field can be sensed by the pulse sequence shown in FIG.

[0106] As will be described with reference to FIG. 12, a pulse sequence based on the spin echo method includes a π pulse between two π / 2 pulses. As shown in state IV, irradiation with a π pulse flips the electron spin along the z-axis in the Bloch sphere. As a result, the observed spin echo signal reflects the curvature of the magnetic and electric fields to be sensed, as shown in FIG. 11. As shown in FIG. 11, due to the flipping of the electron spin in state IV, the phase information (magnetic resonance signal) of the electron spin state after the interaction read out in state VII reflects the difference (AB) between region A shown in FIG. 11 and region B shown in FIG. 12.

[0107] As shown in Figure 11, the AC repeatedly increases and decreases periodically. As the AC fluctuates periodically, the periods of the magnetic and electric fields to be sensed also fluctuate. In a periodically fluctuating AC, when the AC signal increases, the difference (AB) represented by the magnetic resonance signal read out in state VII becomes a positive value. At the peak of the signal where the AC signal takes an extreme value, the difference (AB) becomes 0 (zero), and when the AC signal decreases, the difference (AB) becomes a negative value.

[0108] In the above-described embodiment, the magnetic resonance signals used to calculate the strength of the magnetic and electric fields are detected by optically detected magnetic resonance (ODMR), but the method used to detect the magnetic resonance signals is not limited to optically detected magnetic resonance (ODMR). Instead of optically detected magnetic resonance (ODMR), magnetic resonance signals can also be detected by, for example, electrically detected magnetic resonance (EDMR). In this case, a pair of measurement electrodes for detecting the magnetic resonance signals is electrically connected to the sensor element 1. A bias voltage is applied between the pair of measurement electrodes, and an electric field is applied to the sensor element 1 through the measurement electrodes.

[0109] In the above-described embodiment, the phase difference measurement device 10 measures the phase difference between the magnetic field and electric field generated around the electrical equipment 9, and although transformers such as current transformers 9a and voltage transformers 9b are given as examples of the electrical equipment 9, the electrical equipment 9 is not limited to these. The electrical equipment 9 can be, for example, power transmission and transformation equipment such as transformers and switchgears, or electric lines such as power transmission lines and distribution lines, and the phase difference measurement device 10 is attached to such electrical equipment 9 to measure the phase difference between the magnetic field and electric field generated around the electrical equipment 9.

[0110] In the above embodiment, one measuring device 10 is arranged in one electrical facility 9, and the one measuring device measures the phase of the magnetic field and the phase of the electric field, but multiple measuring devices 10, 10 may be arranged in one electrical facility 9, and each measuring device 10 may measure the phase of the magnetic field and the phase of the electric field, respectively. In this case, the multiple measuring devices 10, 10 may coordinate their operations and data and share the processing of steps S1 to S12.

[0111] For example, a first measuring device 10 performs the processes of steps S1 to S5 to calculate the phase of the magnetic field, a second measuring device 10 performs the processes of steps S6 to S10 to calculate the phase of the electric field, and either the first measuring device or the second measuring device 10 performs the processes of steps S11 to S12 to calculate the phase difference between the magnetic field and the electric field. By having multiple measuring devices 10, 10 operate in coordination with each other in terms of their operations and data, the processes of steps S1 to S5 to calculate the phase of the magnetic field and the processes of steps S6 to S10 to calculate the phase of the electric field can be performed in parallel.

[0112] In the above-described embodiment, the phase difference between the phase of the magnetic field and the phase of the electric field generated around the electrical equipment 9 is measured, but the types of physical quantities for which the phase difference is measured are not limited to the magnetic field and the electric field. The types of physical quantities measured by the phase difference measuring device 10 include the spin Hamiltonian H of the electron spin described above. gsThe physical fields can be magnetic fields, electric fields, temperatures, and mechanical quantities described in [Document 1], and the phase difference measurement device 10 can measure the phase difference between these multiple physical fields, i.e., measure the phase difference between two physical fields selected from multiple types of physical fields (magnetic fields, electric fields, temperatures, and mechanical quantities).

[0113] The combination of two physical fields may be of different types, such as a magnetic field and an electric field, or may be of the same type, such as two different magnetic fields. In the former case, as exemplified in the above-described embodiment, the phase difference measurement device 10 may focus on a single piece of electrical equipment 9 and measure the phase difference between the phase of the magnetic field and the phase of the electric field generated around the electrical equipment 9. In the latter case, the phase difference measurement device 10 may focus on two different pieces of electrical equipment 9 and measure the phase difference between the phase of the magnetic field generated around one piece of electrical equipment 9 and the phase of the magnetic field generated around the other piece of electrical equipment 9.

[0114] The physical fields that the phase difference measuring device 10 measures are not limited to those occurring around the electrical equipment 9, and the phase difference measuring device 10 can measure the phase difference between multiple physical fields occurring around various devices through which alternating current flows.

[0115] [Example] Examples of the present invention will be described below to clarify the features of the present invention. [Example]

[0116] In Example 1, a numerical simulation was carried out using a free induction decay (FID) signal.

[0117] <Conditions for numerical simulation> The pulse sequence was a simple FID sequence. Since each measurement relies on a single sequence, no accumulation of magnetic resonance signals was performed. The AC frequency was 60 Hz, and the pulse sequence was repeated approximately 512 times.

[0118] The assumed conditions (a) to (f) for the sensor element sample and pulse sequence are as follows:

[0119] (a) Coherence time T2 * is 1 μs. T2 * = 1 μS, the total concentration of NV centers is about 10 ppm. (b) The diameter of the laser spot is 10 μm, and the NV center density "NV" is 0.5 ppm (= 8.8 × 3 × 10 16 cm -3 ). Therefore, the number of NV centers in a spherical volume is approximately 4.6 × 10 7 . (c) 1% contrast, which can be about 10% between spin states. (d) On average, 0.1 photons per readout per NV center. (e) The pulse sequence for measuring the FID signal is a pulse sequence including two π / 2 pulses as exemplified in FIG. (f) The laser pulse length is 30 μs, the waiting time between the laser pulse and the first π / 2 pulse is 1 μs, the π / 2 pulse length is 40 ns, and the delay between these pulses is 0.5 μs.

[0120] In Example 1, the magnetic field strength was assumed to have an amplitude of 40 μT, and the electric field strength was assumed to have an amplitude of 20 kV / cm.

[0121] <Numerical simulation results> 13 shows the results of a numerical simulation relating to the phase measurement of the magnetic field and the electric field according to Example 1. (A) shows the results of the simulation relating to the phase measurement of the magnetic field, and (B) shows the results of the simulation relating to the phase measurement of the electric field.

[0122] The amplitude of the magnetic field strength depends on the distance r from the current line (wire). When the distance r is 0.1 m, the amplitude of the magnetic field strength is about 2 mT and decays at a rate of 1 / r. The amplitude of the magnetic field strength of 40 μT assumed in the numerical simulation of Example 1 corresponds to a distance of about 5 m from the current line. For reference, the effect of the magnetic field on the spin Hamiltonian is about 28 GHz T. -1 The results are shown in Figure 13(A).

[0123] In FIG. 13A, the multiple points plotted with cross symbols "x" are simulated values of the signal intensity of the free induction decay (FID) signal corresponding to the magnetic field intensity. By curve fitting these multiple points plotted with cross symbols "x", the phase of the magnetic field φ B =101.3±5.6mrad was obtained.

[0124] The amplitude of the electric field strength depends on the distance d between the current wire and the ground plane on which the diamond NV center sample is placed. When the distance d is 1 m, the amplitude of the electric field strength is about 0.2 kV / cm and decays at a rate of 1 / d. The amplitude of the electric field strength of 20 kV / cm assumed in the numerical simulation of Example 1 corresponds to a distance of about 1 cm from the current wire. For simple reference, the effect of the perpendicular electric field on the spin Hamiltonian is about 17 Hz / cm. -1 It is known that the direction of the electric field has no effect, and in the simulations this effect was modeled in the same way as the magnetic field. The results are shown in Figure 13(B).

[0125] In FIG. 13B, the multiple points plotted with cross symbols "x" are simulated values of the signal intensity of the free induction decay (FID) signal corresponding to the electric field intensity. By curve fitting these multiple points plotted with cross symbols "x", the phase of the electric field φ E =86.2mrad, with an error of +16.4mrad to -15.74mrad. [Example]

[0126] In Example 2, a numerical simulation was performed by changing the distance from the current line (wire) from Example 1. Unless otherwise specified, the conditions for the numerical simulation in Example 2 were the same as those in Example 1.

[0127] In Example 2, the magnetic field strength was assumed to have an amplitude of 200 μT, and the electric field strength was assumed to have an amplitude of 200 kV / cm.

[0128] <Numerical simulation results> 14 shows the results of a numerical simulation relating to the phase measurement of the magnetic field and the electric field according to Example 2. (A) shows the results of the simulation relating to the phase measurement of the magnetic field, and (B) shows the results of the simulation relating to the phase measurement of the electric field.

[0129] The amplitude of the magnetic field strength assumed in the numerical simulation of Example 2, 200 μT, corresponds to a distance of approximately 1 m from the current line. The results are shown in FIG. 14A. By curve fitting these multiple points plotted with cross symbols "x" in FIG. 14A, the phase of the magnetic field φ B =100.2±1.1mrad was obtained.

[0130] The amplitude of the electric field strength assumed in the numerical simulation of Example 2, 200 kV / cm, corresponds to a distance of approximately 1 mm from the current line. The results are shown in Figure 14(B). By curve fitting these multiple points plotted with cross symbols "x" in Figure 14(B), the phase of the electric field φ E =100.2±1.9mrad was obtained.

[0131] <Consideration> Assuming the magnitude of the large currents and high voltages that actually flow through the power system lines and assuming the following measurement conditions, the measurement accuracy required to measure the phase difference between the magnetic and electric fields during one cycle of alternating current supplied through a current line (wire) is approximately 5.82 mrad.

[0132] [Measurement conditions] ·Frequency f: 50 / 60Hz Voltage V amplitude : Approximately 2×10 4 V ·Current I amplitude : about 10 3 A At the distance from the current line assumed in Example 1, i.e., the distance between the current line and the diamond NV center sample, the phase φ of the magnetic field obtained by the numerical simulation B The error is ±5.6 mrad, and the phase of the electric field φ E The error was +16.4 mrad or -15.74 mrad. B and φ E Among the errors in E This far exceeds the required measurement accuracy of about 5.82 mrad, and it was thought that there would be a hurdle to achieving this at the distance from the current line assumed in Example 1.

[0133] In contrast, at the distance from the current line assumed in Example 2, which was assumed to be shorter than that in Example 1, the phase φ of the magnetic field obtained by the numerical simulation B The error is ±1.1 mrad, and the phase of the electric field φ E The error was ±1.9 mrad.

[0134] Therefore, numerical simulations have shown that by placing diamond NV center samples at a distance of approximately 1 m for magnetic field measurements and approximately 1 mm for electric field measurements, which are the distances from the current line assumed in Example 2, it is possible to actually measure the phase difference between voltage and current with sufficient measurement accuracy for large currents and high voltage alternating currents that actually flow through power system lines. [Example]

[0135] In Example 3, a numerical simulation was carried out using a spin echo signal.

[0136] <Conditions for numerical simulation> The pulse sequence was based on the spin echo (Hahn echo) method. Since each measurement relies on a single sequence, magnetic resonance signal accumulation was not performed. The AC frequency was 60 Hz, and the pulse sequence was repeated approximately 204 times.

[0137] The assumed conditions (a) to (f) for the sensor element sample and pulse sequence are as follows:

[0138] (a) Coherence time T2 is 100 μs. (b) The sensor volume is 8.5 × 10 -4 mm 3 , the number of NV centers is 10 11 . (c) 0.5% contrast, which can be as high as 7.5% when the NV centers are misaligned and as high as 30% when they are aligned between spin states. (d) On average, 0.1 photons per readout per NV center. (e) The pulse sequence for measuring the spin echo signal is a pulse sequence including a π pulse between two π / 2 pulses, as exemplified in FIG. (f) The laser pulse length is 30 μs, the waiting time between the laser pulse and the first π / 2 pulse is 1 μs, the π / 2 pulse length is 40 ns, and the delay between the π / 2 pulses is 50 μs.

[0139] In Example 3, it was assumed that the diamond NV center sample was placed at the same distance as in Example 1. That is, as in Example 1, the magnetic field strength was assumed to have an amplitude of 40 μT, and the electric field strength was assumed to have an amplitude of 20 kV / cm.

[0140] <Numerical simulation results> 15 shows the results of a numerical simulation relating to the phase measurement of the magnetic field and the electric field according to Example 3. (A) shows the results of the simulation relating to the phase measurement of the magnetic field, and (B) shows the results of the simulation relating to the phase measurement of the electric field.

[0141] In a pulse sequence based on the spin echo technique, electron spins are flipped along the z-axis in a Bloch sphere by irradiation with a π pulse. As a result, the observed spin echo signal contains information corresponding to the curvature of the AC current. Since the curvature is measured using the derivative, the curve shown in Figure 15 looks like a cosine wave rather than a sinusoidal wave.

[0142] In FIG. 15A, the points plotted with cross symbols "x" are simulation values of the signal intensity of the spin echo signal corresponding to the magnetic field intensity. By curve fitting these points plotted with cross symbols "x", the phase of the magnetic field φ B =100.3mrad, with an error of +0.8mrad to -0.9mrad.

[0143] In FIG. 15B, the points plotted with cross symbols "x" are simulation values of the signal intensity of the spin echo signal corresponding to the electric field intensity. By curve fitting these points plotted with cross symbols "x", the phase of the electric field φ E =101.5±2.2mrad was obtained.

[0144] In the results of Example 3, the phase φ of the magnetic field B and the phase of the electric field φ E It was confirmed that both of the errors were significantly below the required measurement accuracy of approximately 5.82 mrad.

[0145] <Consideration> The measurement accuracy of the phase obtained by the numerical simulation was compared between Example 1 and Example 3. The phase φ of the magnetic field B and the phase of the electric field φ EIn both cases, the results of the numerical simulation in Example 3 were superior to the results of the numerical simulation in Example 1. The assumed distance from the current line, i.e., the distance between the current line and the diamond NV center sample, was the same in Example 1 and Example 3. For the detection of magnetic resonance signals, simulations were performed assuming a pulse sequence for observing free induction decay (FID) signals in Example 1, and a pulse sequence based on the spin echo method for observing spin echo signals in Example 3.

[0146] Therefore, numerical simulations showed that when a diamond NV center sample is placed at the same distance from the current line, it is preferable to observe magnetic resonance signals using a pulse sequence based on the spin echo method, which observes spin echo signals, rather than a pulse sequence that observes free induction decay (FID) signals. [Example]

[0147] In Example 4, improvements were made to the phase difference measurement device to verify whether the improvements improved performance. Two improvements were made in Example 4. In the first improvement, an improvement was made to the phase difference measurement device to correct the shift in pulse period. In the second improvement, an improvement was made to multiple phase difference measurement devices to correct the shift in phase.

[0148] FIG. 16 is a diagram for explaining the concept of a first improvement according to the fourth embodiment. The pulse sequence shown in FIG. 16 corresponds to the pulse sequence shown in FIG. 6 or the part surrounded by a dashed line in the pulse sequence shown in FIG. 8. Symbols I to IV in the diagram correspond to states I to IV shown in FIG. 6 or 8, etc. FIG. 16 illustrates the relationship between the pulse sequence and the timing of reading out data (phase information of the electron spin state) by irradiating with laser light. In the diagram, symbol Rd indicates the range of data read out by laser light.

[0149] The ideal pulse sequence and data readout timing to be set in the device are shown in (A). In contrast, the pulse sequence and data readout timing during actual measurement were as shown in (B). As shown in (B), in actual measurements, deviations in the pulse period can occur due to limitations in the clock frequency generated by the pulse pattern generator. This can cause the range Rd of the readout data by the laser light to deviate by the time indicated by the symbol Td from the timing of laser light irradiation (timing of fluorescence emission) corresponding to state V. A pulse pattern generator is a waveform signal generator such as a pattern generator, function generator, or pulse streamer.

[0150] In the first improvement, as shown in (C), a predetermined level of fluorescence intensity was set as the trigger Trg and applied to timing adjustment to correct the pulse period deviation. In this example, the level of fluorescence intensity set as the trigger (trigger level of the pulse pattern generator) was approximately 5% to approximately 90% of the rising portion of the fluorescence intensity emitted from the sensor element during electron spin initialization by laser light irradiation, as shown in state I. If the trigger level is set above 90%, the trigger cannot be read when a large magnetic resonance of approximately 10% occurs. Furthermore, if it is set below 5%, there is a risk of misreading shot noise as the trigger. The set trigger was applied to adjust the timing of data readout by laser light irradiation, as shown in state V. Timing correction by trigger application was performed for each pulse. The trigger fluorescence intensity was set by the data processing unit 33 (PC). The lower limit of the trigger level can be set based on quantum noise or shot noise, and the upper limit can be set based on the maximum spin contrast ratio. The trigger level range can be set within these ranges.

[0151] 17 is a diagram schematically showing the general configuration of a phase difference measurement device 10 with the first improvement. As shown in Fig. 17, the phase difference measurement device 10 with the first improvement further includes a pulse pattern generator 4 in which a trigger for correcting a deviation in the pulse period is set. The pulse pattern generator 4 uses the fluorescence intensity upon initialization of the electron spin state as a trigger to output a pulse signal for operation timing to the electromagnetic wave irradiation unit 2 and the light irradiation unit 31, thereby correcting a deviation in the measurement period.

[0152] We verified whether there was any performance improvement before and after the first improvement. Figure 18 shows the magnetic resonance signals before and after the first improvement. (A) is the magnetic resonance signal before the first improvement was made, and (B) is the magnetic resonance signal after the first improvement was made. Comparing the magnetic resonance signals shown in Figure 18 confirmed that the physical field signal was accurately read without any deviation in the pulse sequence period.

[0153] 19 and 20 are diagrams for explaining the concept of a second improvement according to Example 4, showing connection modes when a trigger signal is applied to a plurality of phase difference measurement devices. Fig. 19 shows a first connection mode, and Fig. 20 shows a second connection mode.

[0154] As shown in FIGS. 19 and 20 , a pulse pattern generator 4 is connected to realize the pulse sequences exemplified in FIGS. 6 and 8 across multiple phase difference measurement devices 10a and 10b. The pulse pattern generator 4 outputs pulse signals for operation timing to each component (switch 22, acousto-optic modulation element 312) of the multiple phase difference measurement devices, causing the multiple phase difference measurement devices 10a and 10b to operate in synchronization. A trigger signal set in a data processing unit 33 (PC) is input to the pulse pattern generator 4, and time information is fed back from the data processing unit 33 to the pulse pattern generator 4. In this example, for the same object 9 (electrical equipment 9 in the example shown in the embodiment), a magnetic field (first physical field) was measured using the phase difference measurement device 10a shown on the left side of the figure, and an electric field (second physical field) was measured using the phase difference measurement device 10b shown on the right side of the figure.

[0155] 19 , pulse signals for operation timing are input in parallel from the pulse pattern generator 4 to each unit of the multiple measuring devices 10a, 10b via signal lines 41, 42, 43, and 44. Similarly, trigger signals are input in parallel from the data processing units 33 of the respective measuring devices 10a, 10b to the pulse pattern generator 4 via signal lines 51 and 52.

[0156] 20 , pulse signals for operation timing are input in series from pulse pattern generator 4 to each unit of multiple measuring devices 10a, 10b via serially connected signal lines 41A, 41B and serially connected signal lines 42A, 42B. Similarly, trigger signals are input in series from data processing units 33 of each measuring device 10a, 10b to pulse pattern generator 4 via serially connected signal lines 51A, 51B.

[0157] The performance improvement achieved by the second improvement was compared between the first and second connection modes. FIG. 21 shows magnetic resonance signals obtained by the first connection mode shown in FIG. 19. (A) is a magnetic resonance signal obtained by the phase difference measurement device 10a shown on the left side of FIG. 19, and (B) is a magnetic resonance signal obtained by the phase difference measurement device 10b shown on the right side of FIG. 19. FIG. 22 shows magnetic resonance signals obtained by the second connection mode shown in FIG. 20. (A) is a magnetic resonance signal obtained by the phase difference measurement device 10a shown on the left side of FIG. 20, and (B) is a magnetic resonance signal obtained by the phase difference measurement device 10b shown on the right side of FIG. 20. To facilitate comparison, the horizontal scales of the graphs in (A) and (B) are the same.

[0158] 21(A) and 21(B), in the first connection mode, a phase shift (peak position) of the magnetic resonance signal occurred between the multiple phase difference measurement devices 10a and 10b each time a measurement was performed. In contrast, as shown in FIGS. 22(A) and 22(B), in the second connection mode, the phase shift of the magnetic resonance signal was reduced and generally eliminated compared to the first connection mode, and the magnetic resonance signal was always acquired with the same phase between the multiple phase difference measurement devices 10a and 10b. As a result, the second connection mode shown in FIG. 20, in which an operation timing pulse signal is input in series to each of the multiple phase difference measurement devices 10a and 10b, reduces the phase shift of the magnetic resonance signal obtained by measurement compared to the first connection mode shown in FIG. 19, in which an operation timing pulse signal is input in parallel to each of the multiple phase difference measurement devices 10a and 10b. This confirms that the second connection mode has improved performance compared to the first connection mode.

[0159] The embodiments disclosed in this specification are illustrative in all respects and should not be considered limiting. The technical scope of the present invention is not limited to the above-described exemplary embodiments, and also includes cases where phases are measured by a combination of measuring a magnetic field (current) with a continuous wave (CW) and measuring an electric field (voltage) with a pulse sequence. [Explanation of symbols]

[0160] 1. Sensor element (Nuclear-Voltage center in diamond) 2 Electromagnetic wave irradiation section 3 Phase difference measurement section 8 Interaction 9(9a,9b) Electrical equipment (current transformers, voltage transformers) 10(10a,10b) Phase difference measuring device 11 Probe 12 Diamond Crystal 14 Antenna 21 Microwave (MW) Oscillator 22 Switch 23 Amplifier 31 Light irradiation unit 311 Light source 312 Acousto-optic Modulator (AOM) 313 Objective Lens 32 Change detection unit 33 Data Processing Unit 331 Magnetic Field Phase Calculation Unit 332 Electric field phase calculation unit 333 Phase difference signal output section 99 Network

Claims

1. an electromagnetic wave irradiation unit that repeatedly irradiates the quantum sensor element with electromagnetic waves for manipulating the electron spin state of the quantum sensor element, which changes due to interaction with the first physical field or the second physical field generated by an AC signal; a phase difference measurement unit that acquires a plurality of electron spin states after interacting with the first physical field or the second physical field, and measures a phase difference between a plurality of physical fields based on the acquired plurality of electron spin states; A phase difference measuring device comprising:

2. The phase difference measurement unit a first physical field phase calculation unit that calculates a phase of the first physical field based on the plurality of electron spin states after interacting with the first physical field; a second physical field phase calculation unit that calculates a phase of the second physical field based on the plurality of electron spin states after interacting with the second physical field; Including, 2. The phase difference measuring device according to claim 1, wherein the phase difference is measured based on the calculated phase of the first physical field and the calculated phase of the second physical field.

3. the first physical field phase calculation unit calculates a phase of the first physical field by fitting a plurality of time-series data corresponding to a plurality of the electron spin states after interacting with the first physical field; 3. The phase difference measurement device according to claim 2, wherein the second physical field phase calculation unit calculates the phase of the second physical field by fitting a plurality of time-series data corresponding to a plurality of the electron spin states after interacting with the second physical field.

4. 2. The phase difference measuring device according to claim 1, wherein the electromagnetic wave irradiating unit is a pulse sequence for observing a free induction decay (FID) signal of the electron spin state, and repeatedly irradiates the quantum sensor element with the electromagnetic wave using a pulse sequence including a plurality of π / 2 pulses.

5. the electromagnetic wave irradiation unit is a pulse sequence for observing a spin echo signal of the electron spin state, and repeatedly irradiates the quantum sensor element with the electromagnetic wave using a pulse sequence including a plurality of π / 2 pulses and a π pulse between the plurality of π / 2 pulses; The phase difference measuring device according to claim 3 , wherein each of the first physical field phase calculating section and the second physical field phase calculating section fits the plurality of data of the time series corresponding to the curvature of the AC signal.

6. The phase difference measurement unit a light irradiation unit that irradiates the quantum sensor element with light for reading out phase information of the electron spin state after interacting with the first physical field or the second physical field; a change detection unit that detects a change that occurs in the quantum sensor element due to the irradiation of the light; a data processing unit that reads out phase information of the electron spin state from the detected change, and measures the phase difference between the phase of the first physical field and the phase of the second physical field based on the readout phase information of the electron spin state; The phase difference measuring device according to claim 1 , further comprising:

7. 7. The phase difference measurement device according to claim 6, further comprising a pulse pattern generator that outputs a pulse signal for operation timing to the electromagnetic wave irradiation unit and the light irradiation unit using the fluorescence intensity when the electron spin state is initialized as a trigger, and corrects a deviation in the measurement period.

8. 8. The phase difference measurement device according to claim 7, wherein the pulse signals for operation timing are connected in series among a plurality of the phase difference measurement devices.

9. 2. The phase difference measuring device according to claim 1, wherein the AC signal is an AC signal that flows through an electrical installation.

10. a step of repeatedly irradiating the quantum sensor element with electromagnetic waves for manipulating the electron spin state of the quantum sensor element, the state changing due to interaction with a first physical field or a second physical field generated by an AC signal; acquiring a plurality of electron spin states after interacting with the first physical field or the second physical field, and measuring a phase difference between a phase of the first physical field and a phase of the second physical field based on the acquired plurality of electron spin states; A phase difference measuring method comprising:

11. The step of measuring the phase difference includes: calculating a phase of the first physical field based on the plurality of electron spin states after interacting with the first physical field; calculating a phase of the second physical field based on the plurality of electron spin states after interacting with the second physical field; Including, The phase difference measuring method according to claim 10 , wherein the phase difference is measured based on the calculated phase of the first physical field and the calculated phase of the second physical field.

12. the step of calculating the phase of the first physical field includes calculating the phase of the first physical field by fitting a plurality of time series data corresponding to a plurality of the electron spin states after interacting with the first physical field; 12. The phase difference measurement method according to claim 11, wherein the step of calculating the phase of the second physical field calculates the phase of the second physical field by fitting a plurality of time series data corresponding to a plurality of the electron spin states after interaction with the second physical field.

13. An electrical installation comprising the phase difference measuring device according to any one of claims 1 to 9.

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