CN117572056A - Weak current detection system based on quantum mixing and method and application thereof - Google Patents
Weak current detection system based on quantum mixing and method and application thereof Download PDFInfo
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Abstract
The invention discloses a weak current detection system based on quantum mixing, a method and application thereof. According to the invention, the current to be detected is changed into a magnetic field through the magnetic field generator, then resonance light is introduced to complete preparation of the alkali metal atom polarization state, the polarized atoms interact with the magnetic field, magnetic field information is transferred to the resonance light, so that the intensity of the resonance light is modulated, and finally, the detection of the current to be detected is realized through signal extraction and processing of the resonance light. The invention provides a quantum mixing mechanism, which adopts atomic air chambers with different relaxation rates and utilizes the voltage amplitude V of p-order harmonic waves Amp (p) to achieve a current amplitude I 0 The measurement can obtain better accuracy, sensitivity, dynamic range and measurement bandwidth, and realize the sectional measurement of the leakage current of the low-frequency insulator.
Description
Technical Field
The invention belongs to the technical field of current sensing, and relates to a weak current detection system based on quantum mixing, a method and application thereof.
Background
In the circuit, if there is a current flowing from the protective earth conductor, this is commonly referred to as leakage current. The damage caused by the leakage current is related to the amplitude of the leakage current, the reliability of the system is affected by the light leakage current, and the safety accident occurs by the heavy leakage current. In an electric power system, an overhead insulator is installed outdoors, is susceptible to the effects of contaminants, humidity, etc., and generates leakage current, and the amplitude thereof is usually kept below several hundred milliamperes. Detailed information on the leakage current of the insulator can be used to monitor the status of the contaminated insulator, measure the aging degree of the contaminated insulator and predict the flashover phase of the contaminated insulator, which has proved to be an important application in the power grid. In particular, accurate measurement of the odd harmonic components (50 Hz, 150Hz and 250 Hz) of insulator leakage current salience is critical to predicting flashover occurrence.
The existing insulator state detection method mainly comprises an effective equivalent salt attaching density (EESDD) method, an infrared thermal imaging method, a leakage current method and the like. Among them, the leakage current method is the most effective and most extensive method for on-line monitoring of insulators, and the measurement accuracy of leakage current is relevant to the current sensing technology used. The traditional electronic current sensor is easy to be subjected to electromagnetic interference, and the problems of high failure rate, poor reliability and the like can occur. The optical current sensor has the characteristics of small size, large dynamic range and no complicated electromagnetic interference, but is easily affected by temperature, and has the problems of poor long-term stability and low measurement accuracy.
Atomic magnetometers based on quantum effects have proven to have superior performance in amperometric applications. The atomic magnetometer has the characteristics of high precision, large dynamic range, large response bandwidth and the like. Different kinds of atomic magnetometers have a certain difference in measuring current. The Mz type optical pump atomic magnetometer can be used for high-precision direct current measurement, and the self-excited optical pump atomic magnetometer can realize high-precision current measurement in a low-frequency range, but has the problem of limited measurement bandwidth. A spin-free relaxation rate (SERF) atomic magnetometer can achieve broadband measurements, but the measured magnetic field is a vector superposition of the target oscillating magnetic field and the residual static magnetic field. The rf atomic magnetometer measures only the magnetic field at larmor frequency and cannot measure multiple frequency components. The atomic magnetometer based on radio frequency two-photon quantum mixing can expand the frequency range and is only suitable for high-frequency measurement.
In summary, although current measurement techniques based on atomic magnetometers and alternating magnetic field measurement techniques have been rapidly developed in recent years, the prior art is not suitable for measuring leakage current of low-frequency insulators. Based on the method, a weak current detection method based on quantum mixing is provided, and the method is suitable for measuring leakage current of a low-frequency insulator.
Disclosure of Invention
The invention provides a weak current detection system based on quantum mixing, a method and application thereof, and aims to realize measurement of leakage current of a low-frequency insulator.
The invention provides a weak current detection system based on quantum mixing, which comprises a resonance light source (1), a quantum mixing module (2) and a signal processing module (3) which are connected in sequence through a laser light path;
the resonant light source (1) comprises a resonant light emitter (4), a convex lens (5) and a triple prism (6), wherein resonant light (4 a) generated by the resonant light emitter (4) is collimated by the convex lens (5), and the collimated resonant light is divided into two parts by the triple prism (6) to form a first sub-resonant light (4 b) and a second sub-resonant light (4 c) which are transmitted in equal quantity and opposite directions;
the quantum mixing module (2) comprises a magnetic field generator (7), a small relaxation rate atomic gas chamber (8) and a large relaxation rate atomic gas chamber (9); the magnetic field generator (7) is used for converting the current to be measured into a magnetic field; the small relaxation rate atomic gas chamber (8) and the large relaxation rate atomic gas chamber (9) are both positioned in a uniform magnetic field area generated by the magnetic field generator (7); the atoms in the atomic gas chamber (8) with small relaxation rate are loaded on the first sub-resonance light (4 b) in a mixing mode under the combined action of the magnetic field generated by the magnetic field generator (7) and the first sub-resonance light (4 b); the atoms in the atomic gas chamber (9) with large relaxation rate are loaded on the second sub-resonance light (4 c) in a mixing mode under the combined action of the magnetic field generated by the magnetic field generator (7) and the second sub-resonance light (4 c);
the signal processing module (3) comprises a first photoelectric detector (10), a second photoelectric detector (11), a first spectrum analysis module (12) and a second spectrum analysis module (13); the first photoelectric detector (10) is used for collecting electric signals generated by the first sub-resonance light (4 b) loaded with magnetic field information, and the electric signals pass through the first frequency spectrum analysis module (12) to obtain p-order harmonic voltage signals V 1 The second photodetector (11) is used for collecting an electric signal generated by second sub-resonance light (4 c) loaded with magnetic field information, and the electric signal passes through the second spectrum analysis module (13) to obtain a p-order harmonic voltage signal V 2 。
Preferably, the measured current is a low frequency insulator leakage current, typically with regard to components having frequencies of 50Hz, 150Hz and 250 Hz.
Preferably, the resonance light (4 a) is a circularly polarized laser beam which is frequency stabilized and can resonate with alkali metal atoms.
Preferably, the small relaxation rate atomic gas chamber (8) is composed of glass bubbles containing alkali metal saturated steam and other buffer gases, the relaxation rate of the small relaxation rate atomic gas chamber (8) is [125Hz-a,125Hz+a ], a is a set value, and the range of the set value is [0, 20].
Preferably, the large relaxation rate atomic gas chamber (9) is formed by adopting glass bubbles which contain alkali metal saturated steam and do not contain other buffer gases, the relaxation rate of the large relaxation rate atomic gas chamber (9) is [2700Hz-b,2700Hz+b ], b is a set value, and the range of the set value is [0, 100].
Preferably, the magnetic field generated by the magnetic field generator (7) is perpendicular to the propagation direction of the first sub-resonance light (4 b) and the second sub-resonance light (4 c).
Preferably, the signals output by the first spectrum analysis module (12) and the second spectrum analysis module (13) are second harmonic voltage amplitudes.
In a second aspect, the present invention provides a method for implementing a weak current detection system, including the steps of:
the method comprises the following steps that (1) resonance light (4 a) generated by a resonance light emitter (4) is collimated through a convex lens (5), and the collimated resonance light is divided into two parts through a triple prism (6) to form first sub-resonance light (4 b) and second sub-resonance light (4 c) which are transmitted in equal quantity and opposite directions;
step (2), a magnetic field generator (7) converts the measured current I (t) into a magnetic field B (t), wherein the magnetic field and the current satisfy the relation:
B(t)＝kI(t) (1)
in the formula, the measured current I (t) =I 0 cos (ωt), magnetic field B (t) =b 0 cos (ωt), where I 0 For the current amplitude, B 0 The magnetic field amplitude, T is time, omega is the measured current frequency, k is a fixed coefficient related to the structure of the magnetic field generator (7), and the unit is T/A;
ratio frequency Ω and magnetic field amplitude B 0 The following relationships are satisfied:
Ω＝γB 0 (2)
wherein, gamma is the atomic gyromagnetic ratio, and the unit is Hz/nT;
the atoms in the atomic gas chamber (8) with small relaxation rate are loaded on the first sub-resonance light (4 b) in a mixing mode under the combined action of the magnetic field generated by the magnetic field generator (7) and the first sub-resonance light (4 b);
the atoms in the atomic gas chamber (9) with large relaxation rate are loaded on the second sub-resonance light (4 c) in a mixing mode under the combined action of the magnetic field generated by the magnetic field generator (7) and the second sub-resonance light (4 c);
step (4), a first photoelectric detector (10) collects an electric signal generated by first sub-resonance light (4 b) loaded with magnetic field information, and the electric signal passes through a first frequency spectrum analysis module (12) to obtain a p-order harmonic voltage signal V 1 ；
The second photoelectric detector (11) is used for collecting electric signals generated by second sub-resonance light (4 c) loaded with magnetic field information, and the electric signals pass through the second frequency spectrum analysis module (13) to obtain p-order harmonic voltage signals V 2 ；
The output V of the first photodetector (10) and the second photodetector (11) is due to the fact that the quantum mixing module (2) is in a zero magnetic environment out The method comprises the following steps:
wherein p is the harmonic order, A dc As a direct current component, A acc (p) is a cosine component, A acs (p) is a sinusoidal component, specifically:
wherein, R is relaxation rate, X in Is the population difference of unbalanced particle numbers of each energy level, n is the order, omega is the Rayleigh frequency, omega is the measured current frequency, J n Is a first class of n-order Bessel functions, and the numerical values appearing are coefficient constants related to a theoretical model;
from equations (5) - (6), the p-order harmonic signal amplitude V output by the signal processing module (3) Amp (p) is:
signal amplitude V by p-th harmonic amp And (p) obtaining current, and realizing measurement of the current.
In a third aspect, the present invention provides a weak current detection method based on quantum mixing, specifically comprising:
step (1), building a quantum mixing weak current detection device;
step (2), constructing p-order harmonic voltage amplitude V under different relaxation Amp (p) and current amplitude I 0 Is a theoretical curve of (2);
step (3), flowing leakage current of the low-frequency insulator to be detected through a magnetic field generator (7) of the quantum mixing weak current detection device, and outputting p-order harmonic voltage amplitude V according to the signal processing module (3) Amp (p) substituting the current value into the theoretical curve in the step (2) to obtain the corresponding current amplitude I 0 The leakage current of the low-frequency insulator to be detected can be obtained.
The invention has the advantages that: 1) The quantum mixing mechanism is proposed, so that the current detection limit is smaller; 2) Atomic air chambers with different relaxation rates are adopted, and the p-order harmonic voltage amplitude V is utilized Amp (p) to achieve a current amplitude I 0 The measurement can obtain better accuracy, sensitivity, dynamic range and measurement bandwidth, and realize the sectional measurement of the leakage current of the low-frequency insulator.
Drawings
FIG. 1 is a schematic diagram of a quantum mixing weak current detection device;
FIG. 2 is a detailed schematic diagram of a quantum mixing weak current detection device;
FIG. 3 is a schematic diagram of a magnetic field generator;
FIG. 4 is a magnetic field simulation vector diagram of a magnetic field generator;
FIG. 5 second harmonic Voltage amplitude V at different relaxation rates Amp (2) And current amplitude I 0 A theoretical graph;
FIG. 6 is a graph comparing experimental and theoretical data at small relaxation rates;
FIG. 7 is a graph comparing experimental and theoretical data at a large relaxation rate.
Detailed Description
For the purposes of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the present application will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some, but not all, embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.
The terms "comprising" and "having" and any variations thereof, as used in the embodiments of the present application, are intended to cover non-exclusive inclusion. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those listed but may optionally include other steps or elements not listed or inherent to such process, method, article, or apparatus.
The existing insulator state detection method is easy to be interfered by external environment, and has the problems of high failure rate, poor reliability, low measurement precision and the like. Current measurement based on atomic magnetometers is currently used for high frequency and narrow band measurements. Therefore, in order to implement the weak current detection method, the problems to be solved are: how to realize the low-frequency weak current detection based on the atomic magnetometer, and ensure the accuracy, the sensitivity, the dynamic range and the measurement bandwidth.
Based on the above, the embodiment of the application provides a weak current detection system based on quantum mixing, a method and application thereof, and the method can be used for relieving the technical problem that the current detection of a low-frequency insulator is not applicable in the existing atomic magnetometer technology.
According to the invention, through a series of theoretical deductions and simulations, theoretical curves with voltage on the ordinate and current on the abscissa are drawn under different relaxation rates, and in order to realize a wider linear measurement range, two atomic air chambers with different relaxation rates are adopted, so that curves with voltage on the ordinate and current on the abscissa can be obtained in a segmented manner, and based on the curves, segmented measurement of the leakage current of the insulator is realized.
The working mechanism of the invention is as follows: according to the method, firstly, the current to be detected is changed into a magnetic field through a magnetic field generator 7, then resonance light is introduced to complete preparation of the alkali metal atom polarization state, the polarized atoms interact with the magnetic field, magnetic field information is transferred to the resonance light, so that the intensity of the resonance light is modulated, and finally, the current to be detected is detected through signal extraction and processing of the resonance light.
Embodiments of the present application are further described below with reference to the accompanying drawings.
The embodiment of the application provides a quantum mixing weak current detection device, as shown in fig. 1-2, which comprises a resonance light source 1, a quantum mixing module 2 and a signal processing module 3 which are sequentially connected through a laser light path;
the resonant light source 1 comprises a resonant light emitter 4, a convex lens 5 and a triangular prism 6, wherein resonant light 4a generated by the resonant light emitter 4 is collimated by the convex lens 5, and the collimated resonant light is divided into two parts by the triangular prism 6 to form a first sub-resonant light 4b and a second sub-resonant light 4c which are transmitted in equal quantity and opposite directions;
specifically, the resonance light 4a is a circularly polarized laser beam which is frequency-stabilized and can resonate with alkali metal atoms;
specifically, the triangular prism 6 is a right-angle triangular prism, and the resonance light 4a is struck on the top end of the triangular prism 6 in a direction perpendicular to the bottom surface of the triangular prism 6;
the quantum mixing module 2 comprises a magnetic field generator 7, a small relaxation rate atomic gas chamber 8 and a large relaxation rate atomic gas chamber 9; the magnetic field generator 7 is used for converting the measured current into a magnetic field; the small relaxation rate atomic gas chamber 8 and the large relaxation rate atomic gas chamber 9 are respectively positioned at two sides of the triangular prism 6, and the small relaxation rate atomic gas chamber 8 and the large relaxation rate atomic gas chamber 9 are positioned in a region where a uniform magnetic field is generated by the magnetic field generator 7; the atoms in the small relaxation rate atomic gas chamber 8 are loaded on the first sub-resonance light 4b in a frequency mixing mode under the combined action of the magnetic field generated by the magnetic field generator 7 and the first sub-resonance light 4b, and the atoms in the large relaxation rate atomic gas chamber 9 are loaded on the second sub-resonance light 4c in a frequency mixing mode under the combined action of the magnetic field generated by the magnetic field generator 7 and the second sub-resonance light 4c;
in particular, the small relaxation rate atomic gas cell 8 is constituted by using a glass bubble containing alkali metal saturated vapor and containing other buffer gas, the relaxation rate of the small relaxation rate atomic gas cell 8 being 125Hz; a large relaxation rate atomic gas chamber 9 constituted by using a glass bulb containing alkali metal saturated vapor and containing no other buffer gas, the relaxation rate of the large relaxation rate atomic gas chamber 9 being 2700Hz;
specifically, as shown in fig. 3, the magnetic field generator 7 adopts red copper with a semicircular section as the magnetic field generator 7, copper wires are welded at two ends of the magnetic field generator 7, and the measured current flows in from one end copper wire and flows out from the other end copper wire along the arrow direction, so that a uniform magnetic field shown by the arrow can be generated in the magnetic field generator; the magnetic field generated by the magnetic field generator 7 is perpendicular to the propagation direction of the first sub-resonance light 4b and the second sub-resonance light 4c;
the signal processing module 3 comprises a first photoelectric detector 10, a second photoelectric detector 11, a first spectrum analysis module 12 and a second spectrum analysis module 13; the first photodetector 10 is configured to collect an electrical signal generated by the first sub-resonance light 4b loaded with magnetic field information, and the electrical signal passes through the first spectrum analysis module 12 to obtain a p-harmonic voltage signal V 1 The second photodetector 11 is configured to collect an electrical signal generated by the second sub-resonance light 4c loaded with magnetic field information, and the electrical signal passes through the second spectrum analysis module 13 to obtain a p-order harmonic voltage signal V 2 ；
The magnetic field generator 7 converts the measured insulator current I (t) into a magnetic field B (t), wherein the magnetic field and the current satisfy the relation:
B(t)＝kI(t) (1)
in the formula, the measured current I (t) =I 0 cos (ωt), magnetic field B (t) =b 0 cos (ωt), where I 0 For the current amplitude, B 0 The magnetic field amplitude, T is time, omega is the measured current frequency, k is a fixed coefficient related to the structure of the magnetic field generator 7, and the unit is T/A;
ratio frequency Ω and magnetic field amplitude B 0 The following relationships are satisfied:
Ω＝γB 0 (2)
wherein, gamma is the atomic gyromagnetic ratio, and the unit is Hz/nT;
the quantum mixing module 2 is in a zero magnetic environment, and the outputs V of the first photoelectric detector 10 and the second photoelectric detector 11 are out The method comprises the following steps:
wherein p is the harmonic order, A dc As a direct current component, A acc (p) is a cosine component, A acs (p) is a sinusoidal component, specifically:
wherein, R is relaxation rate, X in Is the population difference of unbalanced particle numbers of each energy level, n is the order, omega is the Rayleigh frequency, omega is the measured current frequency, J n Is a first class of n-order Bessel functions, and the numerical values appearing are coefficient constants related to a theoretical model;
from equations (5) - (6), the p-order harmonic signal amplitude V outputted from the signal processing module 3 Amp (p) is:
from formulas (1) to (7), it can be seen that: (1) When the harmonic frequency p is odd, A acc (p)＝0，A acs (p) =0, so the signal processing module 3 outputs only even harmonics; (2) The signal processing module 3 outputs harmonic signal amplitude and the ratio frequency omega to form a first n-order Bessel modulation relation; (3) Signal amplitude V by p-th harmonic amp (p) current can be obtained, and measurement of the current is realized;
specifically, the signals output by the first spectrum analysis module 12 and the second spectrum analysis module 13 are second harmonic voltage amplitudes;
for the measurement of leakage current, because the quantum mixing weak current detection device does not have odd harmonics in a zero magnetic environment, V is generated at different relaxation rates out Second harmonic signal amplitude V of (2) Amp (2) The curve of the current has good enough sensitivity and linear interval, and the formula (7) can know the signal amplitude V of the second harmonic outputted by the signal processing module 3 Amp (2) The method comprises the following steps:
after the measured current passes through the quantum mixing weak current detection device, according to the range of the measured current, the first spectrum analysis module 12 and the second spectrum analysis module 13 of the system have different response outputs, in the first section of current interval, the second spectrum analysis module 13 has no signal output, and the second harmonic voltage signal V output by the first spectrum analysis module 12 1 Is a valid signal, V in the formula (8) Amp (2) Equal to V 1 The method comprises the steps of carrying out a first treatment on the surface of the In the second section of the current interval, the second spectrum analysis module 13 outputs a signal, and the second harmonic voltage signal V output by the second spectrum analysis module 13 2 Is a valid signal, V in the formula (8) Amp (2) Equal to V 2 The method comprises the steps of carrying out a first treatment on the surface of the In the two-section current interval, the current amplitude I 0 And second harmonic signal amplitude V Amp (2) There is a one-to-one correspondence, which can be determined by the second harmonic signal amplitude V Amp (2) The measurement of the current is achieved.
The embodiment of the invention also provides a specific implementation method for detecting weak current, which comprises the following steps:
step (1), constructing a quantum mixing weak current detection device;
the resonance light source 1, the quantum mixing module 2 and the signal processing module 3 are sequentially connected through a laser light path;
the resonant light emitter 4, the convex lens 5 and the triangular prism 6 which are included in the resonant light source 1 are connected through a laser light path along the vertical direction, the resonant light emitter 4 used in the embodiment can generate circularly polarized resonant light 4a with the wavelength of 894nm and capable of resonating with cesium atoms, the convex lens 5 is perpendicular to the resonant light 4a, the triangular prism 6 adopts a right-angle triangular prism, and the bottom edge of the triangular prism is perpendicular to the resonant light 4a; the resonance light 4a is collimated by the convex lens 5, and the collimated resonance light is divided into two beams of first sub-resonance light 4b and second sub-resonance light 4c which are horizontally transmitted in opposite directions at the top end of the triangular prism 6, wherein the first sub-resonance light 4b and the second sub-resonance light 4c are used for preparing atomic polarization states and optically detecting magnetic field signals;
atomic air chambers with different relaxation rates are respectively arranged at two sides of the triangular prism 6 along the transmission directions of the first sub-resonance light 4b and the second sub-resonance light 4c, the atomic air chamber 8 with small relaxation rate is arranged in the transmission direction of the first sub-resonance light 4b, and the atomic air chamber 9 with large relaxation rate is arranged in the transmission direction of the second sub-resonance light 4c; cesium atom gas cells with a relaxation rate of 125Hz and containing buffer gas are used as small relaxation rate atom gas cells 8 in this example, and pure cesium atom gas cells with a relaxation rate of 2700Hz are used as large relaxation rate atom gas cells 9;
the measured current is converted into a magnetic field by a magnetic field generator 7, and a small relaxation rate atomic gas chamber 8 and a large relaxation rate atomic gas chamber 9 contained in the quantum mixing module 2 are positioned in a uniform magnetic field area generated by the magnetic field generator 7; in the example, red copper with a semicircular section is adopted as the magnetic field generator 7, and when current flows, a uniform magnetic field is generated inside the red copper;
the first sub-resonance light 4b passes through the atomic gas chamber 8 with small relaxation rate and is detected by the first photoelectric detector 10, the output end of the first photoelectric detector 10 is connected with the input end of the first spectrum analysis module 12, and the voltage amplitude V of the second harmonic signal is obtained 1 The method comprises the steps of carrying out a first treatment on the surface of the The second sub-resonance light 4c passes through the atomic gas chamber 9 with large relaxation rate and is detected by the second photoelectric detector 11, the output end of the second photoelectric detector 11 is connected with the input end of the second spectrum analysis module 13, and the voltage amplitude V of the second harmonic signal is obtained 2 。
Step (2) constructing the second harmonic voltage amplitude V under different relaxation Amp (2) And current amplitude I 0 Theoretical curves to obtain linear intervals at different relaxation rates;
as shown in fig. 4, which is a simulation vector diagram of the magnetic field inside the magnetic field generator 7; the simulation software of Ansys Maxwell electromagnetic field is adopted in the embodiment, a low-frequency alternating current is input to the magnetic field generator 7, the internal magnetic field of the magnetic field generator 7 is simulated, a magnetic field vector diagram in the magnetic field generator 7 is obtained, and the uniformity of the magnetic field in the middle area in the magnetic field generator 7 is verified. The magnetic field simulation selects current amplitudes of 30 muA, 100 muA, 1mA, 50mA and 100mA, the magnetic field amplitudes corresponding to the central axis of the magnetic field generator 7 are 97.49pT, 324.55pT, 3.25nT, 162.28nT and 324.55nT respectively, and the magnetic field generated by the magnetic field generator 7 has a linear relation with the current, so that the linear coefficient is about:
k＝3.25×10 -6 T/A (9)
the example adopts a cesium atom air chamber, and the gyromagnetic ratio is as follows:
γ＝3.5Hz/nT (10)
according to formulas (1) - (2), (5) - (6) and (8) - (10), the second harmonic voltage amplitude V under different relaxation can be obtained Amp (2) And current amplitude I 0 Theoretical curves to obtain linear intervals under different relaxation;
step (3) given the current, outputting the second harmonic voltage amplitude V according to the signal processing module 3 Amp (2) Obtaining the second harmonic voltage amplitude V Amp (2) And current amplitude I 0 An actual curve;
according to the linear interval obtained in the step (2), the current input system is given from small to large in sequence, the first spectrum analysis module 12 outputs a signal in advance, and the second spectrum analysis module 13 outputs no signal at the moment, so that the current I at the moment is obtained 1 Is a curve S 1 Starting value of abscissa corresponds to voltage amplitude V of second harmonic Amp (2) Is a curve S 1 On the ordinate, the current is increased until the second spectrum analysis module 13 has a signal output, at which point the current I 2 Is a curve S 1 Termination value of abscissa and curve S 2 Establishing the starting value of the abscissa and establishing the ordinate as the voltage amplitude V of the second harmonic Amp (2) The abscissa is the current amplitude I 0 Is a curve S of (2) 1 ，S 1 Current amplitude I of middle abscissa 0 The value range of (C) is [ I ] 1 ,I 2 ]Increasing the current again, and when the voltage and current slopes decrease, using the current I at that time 3 As a curve S 2 Establishing the termination value of the abscissa and establishing the ordinate as the voltage amplitude V of the second harmonic Amp (2) The abscissa is the current amplitude I 0 Is a curve S of (2) 2 ，S 2 Middle abscissa electric powerFlow amplitude I 0 The value range of (C) is [ I ] 2 ,I 3 ]Thereby completing curve S 1 And S is 2 Is established;
step (4) the measured current passes through the signal analysis module 3 to obtain the second harmonic voltage amplitude V Amp (2) Combining the curve S in the step (3) 1 、S 2 The measured current is measured by a table look-up method;
after the measured current passes through the system, the first spectrum analysis module 12 and the second spectrum analysis module 13 have different output responses according to the amplitude range to which the measured current belongs; if the second spectrum analysis module 13 outputs V 2 Not 0, the second spectrum analysis module 13 outputs V 2 Is a valid signal, V in the formula (8) Amp (2) Equal to V 2 At this time, the voltage amplitude V of the second harmonic Amp (2) Sum curve S 2 Looking up a table to obtain current; if the second spectrum analysis module 13 outputs V 2 0, the first spectrum analysis module 12 outputs V 1 Is a valid signal, V in the formula (8) Amp (2) Equal to V 1 At this time, the voltage amplitude V of the second harmonic Amp (2) Sum curve S 1 Looking up a table to obtain current;
as shown in FIG. 5, the plot is of the second harmonic voltage amplitude V at different relaxation rates Amp (2) And current amplitude I 0 A theoretical graph; in the case of small relaxation rate, the system has larger measurement sensitivity, but the linear range is narrow; under the condition of large relaxation rate, the system measurement sensitivity is smaller, but the linear range is widened; in order to obtain better measurement sensitivity and linearity, the system adopts atomic gas chambers with different relaxation rates to realize the sectional measurement of current; the applicable current amplitude measurement range of the embodiment is 30 mu A-70mA, the current amplitude is taken as a boundary, the current measurement is realized by adopting the atomic gas chamber 8 with small relaxation rate at 30 mu A-10mA, and the current measurement is realized by adopting the atomic gas chamber 9 with large relaxation rate at 10mA-70 mA;
as shown in fig. 6, which is a graph comparing experimental data with theoretical data at a small relaxation rate; as shown in fig. 7, which is a graph comparing experimental data with theoretical data at a large relaxation rate; as can be seen from fig. 6-7, a segmented measurement of the current can be achieved by using atomic gas cells with different relaxation rates.
Claims (9)
1. The weak current detection system based on quantum mixing is characterized by comprising a resonance light source (1), a quantum mixing module (2) and a signal processing module (3) which are connected in sequence through a laser light path;
the resonant light source (1) comprises a resonant light emitter (4), a convex lens (5) and a triple prism (6), wherein resonant light (4 a) generated by the resonant light emitter (4) is collimated by the convex lens (5), and the collimated resonant light is divided into two parts by the triple prism (6) to form a first sub-resonant light (4 b) and a second sub-resonant light (4 c) which are transmitted in equal quantity and opposite directions;
the quantum mixing module (2) comprises a magnetic field generator (7), a small relaxation rate atomic gas chamber (8) and a large relaxation rate atomic gas chamber (9); the magnetic field generator (7) is used for converting the current to be measured into a magnetic field; the small relaxation rate atomic gas chamber (8) and the large relaxation rate atomic gas chamber (9) are both positioned in a uniform magnetic field area generated by the magnetic field generator (7); the atoms in the atomic gas chamber (8) with small relaxation rate are loaded on the first sub-resonance light (4 b) in a mixing mode under the combined action of the magnetic field generated by the magnetic field generator (7) and the first sub-resonance light (4 b); the atoms in the atomic gas chamber (9) with large relaxation rate are loaded on the second sub-resonance light (4 c) in a mixing mode under the combined action of the magnetic field generated by the magnetic field generator (7) and the second sub-resonance light (4 c);
the signal processing module (3) comprises a first photoelectric detector (10), a second photoelectric detector (11), a first spectrum analysis module (12) and a second spectrum analysis module (13); the first photoelectric detector (10) is used for collecting electric signals generated by the first sub-resonance light (4 b) loaded with magnetic field information, and the electric signals pass through the first frequency spectrum analysis module (12) to obtain p-order harmonic voltage signals V 1 The second photodetector (11) is used for collecting an electric signal generated by second sub-resonance light (4 c) loaded with magnetic field information, and the electric signal passes through the second spectrum analysis module (13) to obtain a p-order harmonic voltage signal V 2 。
2. The system of claim 1, wherein the current to be measured is a low frequency insulator leakage current.
3. The system according to claim 1, characterized in that the resonating light (4 a) is a circularly polarized laser beam which is frequency stabilized and is capable of resonating with alkali atoms.
4. The system according to claim 1, characterized in that the small relaxation rate atomic gas chamber (8) is constituted by glass bubbles containing alkali metal saturated vapour and containing other buffer gases, the relaxation rate of the small relaxation rate atomic gas chamber (8) being [125Hz-a,125hz+a ], a being a set value.
5. The system according to claim 1, characterized in that the large relaxation rate atomic gas chamber (9) is constituted by glass bubbles containing alkali metal saturated vapor and no other buffer gas, the relaxation rate of the large relaxation rate atomic gas chamber (9) being [2700Hz-b,2700hz+b ], b being a set value.
6. The system according to claim 1, wherein the magnetic field generated by the magnetic field generator (7) is perpendicular to the propagation direction of the first sub-resonance light (4 b) and the second sub-resonance light (4 c).
7. The system according to claim 1, characterized in that the signals output by the first (12) and second (13) spectral analysis modules are second harmonic voltage amplitudes.
8. A method of implementing the system of any one of claims 1-7, the method comprising the steps of:
the method comprises the following steps that (1) resonance light (4 a) generated by a resonance light emitter (4) is collimated through a convex lens (5), and the collimated resonance light is divided into two parts through a triple prism (6) to form first sub-resonance light (4 b) and second sub-resonance light (4 c) which are transmitted in equal quantity and opposite directions;
step (2), a magnetic field generator (7) converts the measured current I (t) into a magnetic field B (t), wherein the magnetic field and the current satisfy the relation:
B(t)＝kI(t) (1)
in the formula, the measured current I (t) =I 0 cos (ωt), magnetic field B (t) =b 0 cos (ωt), where I 0 For the current amplitude, B 0 The magnetic field amplitude, T is time, omega is the measured current frequency, k is a fixed coefficient related to the structure of the magnetic field generator (7), and the unit is T/A;
ratio frequency Ω and magnetic field amplitude B 0 The following relationships are satisfied:
Ω＝γB 0 (2)
wherein, gamma is the atomic gyromagnetic ratio, and the unit is Hz/nT;
the atoms in the atomic gas chamber (8) with small relaxation rate are loaded on the first sub-resonance light (4 b) in a mixing mode under the combined action of the magnetic field generated by the magnetic field generator (7) and the first sub-resonance light (4 b);
the atoms in the atomic gas chamber (9) with large relaxation rate are loaded on the second sub-resonance light (4 c) in a mixing mode under the combined action of the magnetic field generated by the magnetic field generator (7) and the second sub-resonance light (4 c);
step (4), a first photoelectric detector (10) collects an electric signal generated by first sub-resonance light (4 b) loaded with magnetic field information, and the electric signal passes through a first frequency spectrum analysis module (12) to obtain a p-order harmonic voltage signal V 1 ；
The second photoelectric detector (11) is used for collecting electric signals generated by second sub-resonance light (4 c) loaded with magnetic field information, and the electric signals pass through the second frequency spectrum analysis module (13) to obtain p-order harmonic voltage signals V 2 ；
The output V of the first photodetector (10) and the second photodetector (11) is due to the fact that the quantum mixing module (2) is in a zero magnetic environment out The method comprises the following steps:
in the middle ofP is harmonic order, A dc As a direct current component, A acc (p) is a cosine component, A acs (p) is a sinusoidal component, specifically:
wherein, R is relaxation rate, X in Is the population difference of unbalanced particle numbers of each energy level, n is the order, omega is the Rayleigh frequency, omega is the measured current frequency, J n Is a first class of n-order Bessel functions, and the numerical values appearing are coefficient constants related to a theoretical model;
from equations (5) - (6), the p-order harmonic signal amplitude V output by the signal processing module (3) Amp (p) is:
signal amplitude V by p-th harmonic amp And (p) obtaining current, and realizing measurement of the current.
9. A weak current detection method based on quantum mixing is characterized by comprising the following steps:
step (1), building a quantum mixing weak current detection device according to the system of any one of claims 1-7;
step (2) of constructing the p-th harmonic voltage amplitudes V under different relaxation according to the method of claim 8 Amp (p) and current amplitude I 0 Is a theoretical curve of (2);
step (3), flowing leakage current of the low-frequency insulator to be detected through a magnetic field generator (7) of the quantum mixing weak current detection device, and outputting p-order harmonic voltage amplitude V according to the signal processing module (3) Amp (p) substituting the current value into the theoretical curve in the step (2) to obtain the corresponding current amplitude I 0 The leakage current of the low-frequency insulator to be detected can be obtained.
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