CN117434325A - Cable voltage determining method and device - Google Patents
Cable voltage determining method and device Download PDFInfo
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Abstract
The invention discloses a cable voltage determining method and device, wherein the method comprises the following steps: acquiring differential voltages between each of three pairs of probes in different directions around a target cable; the voltage U of the target cable is determined based on the three differential voltages obtained. The invention senses the electric field intensity generated around the cable to be tested based on the electric field radiation principle, and acquires the voltage signal of the line to be tested, thereby having good adaptability and being applicable to AC and DC voltage monitoring; the pair of metal detection points eliminates potential errors to ground and other errors in the measurement process caused by the measurement circuit itself.
Description
Technical Field
The invention relates to the technical field of voltage non-contact measurement, in particular to a cable voltage determining method and device.
Background
The traditional cable voltage measurement mainly utilizes resistance voltage division or a voltage transformer, the mode needs to be directly and electrically connected with a detected circuit, and the method has some defects in aspects of electric isolation, field implementation, user demand and electric energy loss, and is relatively large in equipment volume, relatively high in manufacturing cost, relatively difficult in daily maintenance and the like. Therefore, when voltage values need to be monitored in real time at measurement points where the insulating layer cannot be broken or is inconvenient, a non-contact voltage measurement device needs to be used for voltage measurement.
The non-contact voltage measurement system is not limited by the grade of the power grid, the output voltage value of the non-contact voltage sensor is generally smaller, the operation is safe and reliable, and the service life is long; the non-contact voltage measurement equipment has simple structure, is convenient to carry and can perform measurement without being limited by regions; the non-contact measurement system has no ferromagnetic part, no non-linear conditions such as saturation and the like, and good frequency response; the non-contact measurement system is not directly electrically connected with the power transmission system, so that electromagnetic interference in the measurement process is reduced, and the measurement accuracy is ensured.
At present, a voltage non-contact measurement method based on an electrode plate electric field coupling principle is widely adopted, but at some measurement points with high precision requirements, a traditional voltage non-contact measurement method can generate larger errors due to interference of measurement environments. Thus, current research on this measurement principle focuses on the elimination of measurement errors.
Disclosure of Invention
The invention aims to provide a cable voltage determining method and device, which are characterized in that three pairs of metal detection points which are symmetrical in center are used for inducing the space electric field intensity generated by a cable to be tested, so that 3 induction differential voltages are obtained, 3 algebraic equations about two-dimensional position parameters of the voltage to be tested and the electric field center are obtained, the equation set is solved, a voltage signal of a line to be tested can be obtained, and non-contact measurement of the voltage of the line to be tested is completed. In order to achieve the above purpose, the present invention provides the following technical solutions:
a method of cable voltage determination, the method comprising:
acquiring differential voltages between each of three pairs of probes in different directions around a target cable;
the voltage U of the target cable is determined based on the three differential voltages obtained.
Further, determining the voltage U of the target cable based on the acquired three differential voltages includes:
based on the distance R between the probe close to the cable and the center of the cable of each pair of the three pairs of probes i Electric field strength E at the probe far from the cable for each of the three pairs of probes i (R i ) Dielectric constant epsilon of wire insulation layer 1 Dielectric constant ε of air 2 Dielectric constant epsilon of insulating medium 3 Radius r of cable aluminum core 0 Cable radius r with insulation layer 1 Distance d between the backing probe and the shielding layer of each pair of probe pairs 2 And the i-th pair of probes is deviated from the angle theta of the longitudinal axis y from the line of the central point of the electric field intensity of the cable i Establishing an association relation with the voltage U of the target cable;
and determining the voltage U of the target cable based on the association relation.
Further, the association relationship is as follows:
wherein R is i Representing the distance between the probe of the i-th pair of probes, which is close to the cable, and the center of the cable; e (E) i (R i ) Representing the electric field strength at the probe far from the cable in the i-th pair of probes; epsilon 1 Represent dielectric constant, epsilon of wire insulation layer 2 Represents the dielectric constant, epsilon, of air 3 Represents the dielectric constant, r, of the insulating medium 0 Represents the radius of the cable aluminum core, r 1 Represents the radius of the cable containing the insulating layer, r 2 Indicating the inner diameter of the sensor, d 2 Represents the distance, θ, between the backing probe and the shield of each pair of probe pairs i Indicating the angle of the i-th pair of probes from the longitudinal axis y that is aligned with the center point of the cable's electric field strength.
Further, E i (R i ) Is calculated according to the formula:
wherein d 1 For the distance between each pair of probes.
Further, R i Is calculated according to the formula:
where x and y represent the position coordinates of the axis P of the target cable.
Further, the target cable voltage U and R thereof 1 、R 2 、R 3 Electric field strength E at the inner probe of three directions i (R i ) Relation to R 1 、R 2 、R 3 The relation equations are combined to obtain the voltage U of the target cable, and the calculation formula is expressed as follows:
a cable voltage determination device, the device comprises a sensor and a signal processing unit, wherein the sensor comprises three pairs of probe pairs,
each of the three pairs of probes is distributed in a different direction around the target cable for voltage between each pair of probes, respectively;
the signal processing unit is used for determining the voltage U of the target cable based on the acquired three voltages.
Further, determining the voltage U of the target cable based on the acquired three voltages includes:
based on the distance R between the probe close to the cable and the center of the cable of each pair of the three pairs of probes i Electric field strength E at the probe far from the cable for each of the three pairs of probes i (R i ) Dielectric constant epsilon of wire insulation layer 1 Dielectric constant ε of air 2 Dielectric constant epsilon of insulating medium 3 Radius r of cable aluminum core 0 Cable radius r with insulation layer 1 Distance d between the backing probe and the shielding layer of each pair of probe pairs 2 And the i-th pair of probes is deviated from the angle theta of the longitudinal axis y from the line of the central point of the electric field intensity of the cable i Establishing an association relation with the voltage U of the target cable;
and determining the voltage U of the target cable based on the association relation.
Further, the signal processing unit comprises a band-pass filter, an analog-to-digital converter and a data processor, wherein,
the band-pass filter is used for carrying out band-pass filtering on differential voltages before three pairs of probes;
the analog-to-digital converter is used for performing analog-to-digital conversion on the signal output by the band-pass filter;
the data processor is used for determining the voltage U of the target cable based on the acquired three differential voltages.
Further, the sensor further comprises an insulating separation layer, a metal shielding layer and an insulating plastic housing, wherein,
the insulating separation layer is composed of foam and is distributed between each pair of probes and between the probes and the metal shielding layer;
the metal shielding layer is cylindrical copper foil and is used for shielding the influence of other sources around the cable;
the insulating plastic shell is a pair of semi-cylindrical surfaces, a complete cylindrical surface can be formed by buckling, and the inner surface of the insulating plastic shell is adhered with the metal shielding layer.
The invention has the technical effects and advantages that:
1. the invention senses the electric field intensity generated around the cable to be tested based on the electric field radiation principle, and acquires the voltage signal of the line to be tested, thereby having good adaptability and being applicable to AC and DC voltage monitoring; the pair of metal detection points eliminates potential errors to ground caused by the measurement circuit itself and other errors in the measurement process;
2. the voltage sensor comprises 2X 3 (3 pairs) metal detection points and a metal shielding grounding layer, has the characteristics of small volume, portability, low manufacturing cost and the like, is beneficial to mass production and application, and can ensure that the accuracy reaches an acceptable level even if a cable to be measured is positioned at any position instead of the center of the sensor;
3. the digital display platform used by the sensor is built based on MATLAB and C language compiling, and can display information such as measured voltage values and waveforms.
The invention constructs a three-polar plate-dual-detection-point annular cable voltage measurement structure based on the electric field radiation principle, and deduces the voltage of the cable to be measured and the position of the center point of the electric field according to the differential voltage detected by the detection points. The measuring system has the advantages that: on the basis of theoretical analysis of the electric field in the space around the cable, the voltage to be measured is solved by establishing a ternary equation system containing the position coordinates of the center point, and the solved voltage eliminates errors caused by the fact that the center point of the electric field of the cable to be measured is not located at the geometric center of the cable and errors caused by induction of the environmental electric field at detection points, so that measurement accuracy is high.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
FIG. 1 is a schematic diagram of a cable voltage determination device system of the present invention;
FIG. 2 is a schematic diagram of a three pole-dual sensing point sensor in accordance with an embodiment of the present invention;
FIG. 3 is a spatial medium distribution of a cable in an embodiment of the invention when the cable is centered in the sensor;
FIG. 4 illustrates the eccentricity measurement of a three pole-dual sensing point sensor in accordance with an embodiment of the present invention;
FIG. 5a is an equivalent diagram of the electric field distribution in the first pole direction of the sensor when the cable is eccentric in an embodiment of the invention;
FIG. 5b is an equivalent diagram of the electric field distribution in the second direction of the sensor when the cable is eccentric in an embodiment of the present invention;
FIG. 5c is an equivalent diagram of electric field distribution in the third pole direction of the sensor when the cable is eccentric in an embodiment of the invention;
FIG. 6 is a flow chart of formula derivation in an embodiment of the invention;
FIG. 7 is a schematic diagram of a voltage non-contact measurement circuit based on a three pole-dual sense point voltage sensor in accordance with an embodiment of the present invention;
fig. 8 is a real test scenario of a hardware device of a measurement system in an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
To address the deficiencies of the prior art, the present invention discloses a method of determining cable voltage, the method comprising,
the method comprises the steps that induction voltage signals between each pair of probes in three pairs of probes in different directions around a target cable are obtained through a metal probe pair in a sensor, and the induction voltage signals are subjected to signal processing to obtain at least 3 groups of differential voltage signals of the target cable; determining a voltage U of the target cable from the at least 3 sets of differential voltage signals; and displaying the measured target cable voltage result by a digital platform.
In one embodiment of the present invention, in conjunction with fig. 1, the signal processing includes:
when voltage non-contact measurement is carried out, each pair of probes in the sensor acquire an induced voltage signal, and the induced voltage signal is subjected to band-pass filtering and filtering treatment to obtain an analog voltage signal with good waveform; converting the filtered analog voltage signal into a digital voltage signal through analog-to-digital conversion (A/D conversion); based on the digital voltage signal, obtaining a corresponding differential voltage; wherein the number of the sensor metal probes is more than or equal to 3; the number of the differential voltages is the same as the number of the metal probe pairs in the sensor, and the differential voltage acquired by the ith pair of the metal probe pairs is u i I=1, 2,3 … …. And the differential voltage is processed by MCU data to obtain the target cable voltage.
Fig. 2 shows a three pole-dual sense point voltage sensor structural model in an embodiment of the invention. In the figure, the low-voltage power transmission cable is a long straight cylindrical conductor, and the tripolar-double detection point structure consists of 3 pairs of metal detection points (A, B and C) which are annularly and radially arranged, an insulating separation layer, a metal shielding layer and an insulating plastic shell; wherein 3 metal detection points are symmetrically distributed about the center of the sensor, the metal detection points are composed of 3 x 2 iron probes with consistent shapes, each pair of probes is isolated by a separation layer and connected to a PCB (printed circuit board) for filtering and digital-to-analog conversion processing, and then is calculated by MCU (micro control Unit) data processing to obtain a voltage value to be measured; the insulating separation layer is composed of foam and is distributed between each pair of probes and between the probes and the metal shielding layer; the metal shielding layer is cylindrical copper foil and can shield the influence of other sources around the cable; the insulating plastic shell is a pair of semi-cylindrical surfaces, a complete cylindrical surface can be formed by buckling, and a shielding copper foil is adhered to the inner surface of the insulating plastic shell; the cable voltage determination method of the invention is highly dependent on the key technical principle of the voltage sensor, and the theory basis is as follows.
First, the equation about the electric displacement vector in maxwell's equations is In the form of a hamiltonian,electric displacement vector whose two ends of equation are integrated +.>ρ f Is the charge density, S is a closed curved surface, q f Is the total amount of free charge in a curved surface, and is the gaussian theorem describing how the charge creates an electric field. In reality, we can consider the low-voltage power transmission cable to be a long straight cylindrical conductor, and we can consider the electric field in the space around the conductor as a quasi-electrostatic field on the premise of neglecting the influence of the radial conduction time of the electromagnetic field. The method is characterized in that a closed cylindrical Gaussian surface with the length of l and the radius of R can be taken to coaxially wrap a wire with the corresponding unit length, and based on the Gaussian theorem, the electric displacement vector is integrated at the radius of R by the Gaussian surface to obtain +.>So the electric displacement vector is +.>From the corresponding physical equation->It can be seen that the space around the cable and the conductorThe electric field strength at the position with the distance R between the axes of the lines is +.>Wherein q is the total Gaussian surface charge of the conductor, ρ is the bulk charge density of a single conductor of the overhead line, and ε is the dielectric constant of the space medium at R.
Taking a low voltage power aluminum core cable as an example, fig. 3 shows the dielectric profile of the sensor in the spatial region where the cable is located in the center of the sensor. In FIG. 3, r 0 Represents the radius of the cable aluminum core, r 1 Represents the radius of the cable containing the insulating layer, r 2 For the inner diameter of the sensor, R is the radius of the metal wire core, d 1 D for the distance between each pair of probes 2 Epsilon for the distance between the backing probe and the shielding layer for each pair of probe pairs 1 Is the dielectric constant epsilon of the insulating layer of the wire 2 Is the dielectric constant, epsilon, of air 3 Is the dielectric constant of the insulating medium.
Fig. 6 shows the flow of deriving the equation set, and the theoretical derivation logic can be intuitively seen, in conjunction with fig. 6:
let the radius of the inner aluminum core conductor of the cable be r 0 The electric field distribution around the conductor is as follows.
From the following componentsIt is known that the potential difference of the space around the cable at any two point positions can be expressed in terms of electric field integration. Namely: />
In actual measurement, the three pairs of pole-double probe electric field sensors are wrapped around the cable, and the shielding layer is grounded. But in general we cannot guarantee that the cable must be in the centre of the sensor, so we will describe in the general case that the cable is offset from the centre of the sensor.
Fig. 4 shows the case of eccentric measurement of a three-pair pole-double probe voltage sensor. In the figure, the electric field around the wire is R under the condition that the central axis of the wire is not deviated from the center of the sensor 1 、R 2 、R 3 The distribution in the three directions is not uniform, but we can consider the electric field strength E in the vicinity of the probe in each direction i Is in accordance with R 1 、R 2 、R 3 The electric field strength near the probe when the wire is at the center of the sensor when the wire is at the radius of the shielding layer, respectively, can be regarded as three equivalent cases, as shown in fig. 5a-5c, and satisfies the following functional relationship:
from the relation (1) and the formula (2), the voltage U of the target cable and the electric field intensity E of the target cable at the probes on the inner sides in three directions can be deduced i (R i ) Is the relation of:
where U represents the voltage of the target cable. From equation (3), we determine the relationship between the wire's own voltage to ground and the strength of the electric field around it.
Next, we do the electric field strength E at the polar plate i (R i ) Is calculated by the computer. Taking the sensor double-probe substructure at the point a as an example, we can get the electric field strength at probe a in fig. 4.
Voltage u between probe pair (double probes) a and a 1 Can be measured by an externally applied sampling circuit, and the voltage u between the double probe and the ground layer 1 ' and u 1 "can be obtained from the following relation.
So we can obtain the electric field intensity E at the probe a position 1 (R 1 )。
Similarly, we can obtain the electric field strength E in other directions i (R i )。
By combining the relations (3) and (9), we can obtain a preliminary expression of the voltage U of the target cable as follows:
next, we do an analysis of the cable's axial center position relative to the sensor's center position. To further simplify the positional relationship, the distance R is more easily obtained 1 、R 2 、R 3 Mathematical relationship with the relative position coordinates (x, y) of the cable axes. In fig. 4, P is the cable axis, O is the sensor center point, and the three positions of A, B, C are the dual-probe substructure of the voltage sensor (1), (2) and (3), respectively, we use O as the origin, the line of OA as the y-axis, and the line perpendicular to OA and passing through the point O as the x-axis to establish the rectangular planar coordinate system. At three position pointsThe distance between the probe close to the cable and the center P of the cable is R 1 、R 2 、R 3 The position coordinates of the cable axis P are (x, y). Angle aob= angle boc= angle coa= 120 °, and through geometric analysis we can apply pythagorean theorem to obtain axis position coordinates (x, y) and R 1 、R 2 、R 3 Relationship between them.
By combining the theoretical formulas, we can obtain an equation set with three unknowns of U, x and y, which satisfies the uniqueness of the solution.
And finally, obtaining the line voltage to be measured by solving an equation set. The solving formula is obtained based on an electric field radiation theory, wherein only three unknowns U, x and y are obtained, and the condition that an equation set has a unique solution is met.
Fig. 6 shows the flow of deriving the equation set, and the theoretical derivation logic can be intuitively seen.
The invention also provides a cable voltage determining device, as shown in fig. 1, which comprises a sensor and a signal processing unit, wherein the sensor comprises three pairs of probes, an insulating separation layer, a metal shielding layer and an insulating plastic shell, wherein the probes consist of iron needles with consistent shapes, and each pair of probes is symmetrically distributed about the center of the sensor; the insulation separation layer is composed of foam and is distributed between each pair of probes and between the probes and the metal shielding layer; the metal shielding layer is cylindrical copper foil and is used for shielding the influence of other sources around the cable; the insulating plastic shell is a pair of semi-cylindrical surfaces, a complete cylindrical surface can be formed by buckling, and the inner surface of the insulating plastic shell is adhered with the metal shielding layer.
Each of the three pairs of probes is distributed in a different direction around the target cable for the voltage between each pair of probes, respectively; the signal processing unit is used for determining the voltage U of the target cable based on the acquired three voltages.
In a specific embodiment of the present invention, the determining device further includes a digital display platform, which is constructed based on MATLAB and C language, and is configured to display information such as measured voltage values and waveforms.
In one specific embodiment of the present invention, determining the voltage U of the target cable based on the acquired three voltages includes: based on the distance R between the probe close to the cable and the center of the cable of each pair of the three pairs of probes i Electric field strength E at the probe far from the cable for each of the three pairs of probes i (R i ) Dielectric constant epsilon of wire insulation layer 1 Dielectric constant ε of air 2 Dielectric constant epsilon of insulating medium 3 Radius r of cable aluminum core 0 Cable radius r with insulation layer 1 Distance d between the backing probe and the shielding layer of each pair of probe pairs 2 And the i-th pair of probes is deviated from the angle theta of the longitudinal axis y from the line of the central point of the electric field intensity of the cable i Establishing an association relation with the voltage U of the target cable;
and determining the voltage U of the target cable based on the association relation.
In a specific embodiment of the present invention, the signal processing unit includes a band-pass filter, an analog-to-digital converter, and a data processor, wherein the band-pass filter is configured to band-pass filter a voltage before each pair of probes; the analog-to-digital converter is used for performing analog-to-digital conversion on the signal output by the band-pass filter; the data processor is used for determining the voltage U of the target cable based on the acquired three voltages.
The inventive determination device ensures that the accuracy reaches an acceptable level even if the cable to be measured is located at any position other than the center of the sensor; the differential voltages measured at the pairs of sense points (probe pairs) eliminate potential errors to ground and other errors in the measurement process caused by the measurement circuit itself; the sensor is suitable for alternating current and direct current voltage monitoring; the measurement results are finally displayed by the digitizing platform.
The three-pair pole-double probe electric field sensor used in the invention reversely pushes the cable voltage by collecting the electric field at the probe close to the cable, and actually adopts the electric field intensity at the probe surface space at one side of the probe close to the cable. In addition, the cable selected by the measurement model is general, and the voltage measured by the system must have larger access to some special cables. In addition, the accuracy of the measured result of the measuring system has no correlation with the cable position, and even if the cable to be measured is positioned at any position instead of the center of the sensor, the accuracy can be ensured to reach an acceptable level, and the measuring device of the measuring system is more accurate than the measuring result of the traditional fixed-parameter type non-contact measuring device.
FIG. 7 shows that if the coordinate of the disturbance electric field source A is (x ', y'), the electric field strength is E r The distance from the center point of the cable to be tested is D 0 . Taking a-a' detection point as an example, the distance between the point A and the point a is D 1 A' distance is D 2 The detection point senses that the interference electric field intensity is:
due to D 0 >>R 0 (sensor radius) and spacing between a-a<<D 1 And D 2 This results in D 1 ≈D 2 Then E ra ≈E ra’ From this, it is possible to:
wherein E is ra 、E ra’ The strength of the interference electric field induced at the detection points a and a' respectively; u's' error1 、u″ error1 The ground disturbance voltages measured at the detection points a and a' are respectively; u (u) error 1 Is the interference differential voltage measured at detection point a-a';d1 'is the distance between the detection point a' and the interference electric field source a and the shielding layer; d2' is the distance between the detection point a and the shielding layer connected with the interference electric field source a.
According to the analysis, the voltage non-contact measurement is performed by adopting the method, so that the measurement environment error signal in the embodiment can be eliminated, and the measurement accuracy is effectively improved.
Fig. 8 shows a voltage non-contact measurement circuit diagram based on a three-pair pole-double probe voltage sensor.
Three pairs of probes of the sensor respectively acquire potential differences between each pair of probes in the electric field space and serve as input voltage signals of a circuit processing module, and the input voltage signals are respectively named as u 1 、u 2 And u 3 . Then, the three voltage signals sequentially pass through a filtering module, an A/D conversion module and an MCU digital processing module in the signal processing circuit to carry out a series of processing. The filtering module comprises three identical filtering circuits, wherein the input end of each circuit is connected with the double probes to receive input voltage signals, and the input voltage signals are output to the A/D conversion module after being filtered by the three circuits. The filtered output voltage signal is an analog signal, and the analog signal is converted into a digital signal by an A/D conversion module in order to facilitate the data processing of the MCU data processing module. In this embodiment, the analog signal is digitized using an analog-to-digital converter ADC. For a nominal 50Hz input signal, the ADC may sample the output signal from the signal processing circuit with a sampling frequency of 10.24KHz for ease of sampling, to provide 1024 samples in 100ms ready for fast fourier transform and voltage reconstruction algorithms in the MCU data processing block. The MCU data processing module acquires the digital signals output by the digital-to-analog conversion module, and the voltage to be measured is solved by programming a computer program through the voltage reconstruction equation set, so that an accuracy measurement result is obtained and displayed. The measuring system can finish the work of voltage non-contact measurement through a single wire, can measure direct current voltage and alternating current voltage, is convenient to operate, and has good practicability.
The invention constructs a three-polar plate-dual-detection-point annular cable voltage measurement structure based on the electric field radiation principle, and deduces the voltage of the cable to be measured and the position of the center point of the electric field according to the differential voltage detected by the detection points. The measuring system has the advantages that: on the basis of theoretical analysis of the electric field in the space around the cable, the voltage to be measured is solved by establishing a ternary equation system containing the position coordinates of the center point, and the solved voltage eliminates errors caused by the fact that the center point of the electric field of the cable to be measured is not located at the geometric center of the cable and errors caused by induction of the environmental electric field at detection points, so that measurement accuracy is high.
The invention relates to a hardware device physical test scene of a voltage non-contact measurement system.
The hardware device of the measuring system consists of a sensor probe and two parts of circuit boards, wherein the two circuit boards are connected by an HDMI interface. One of the circuit boards is provided with a signal input interface and a signal processing circuit, and the other circuit board is provided with a data processing circuit, a data transmission interface and a power interface.
Finally, it should be noted that: the foregoing description is only illustrative of the preferred embodiments of the present invention, and although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described, or equivalents may be substituted for elements thereof, and any modifications, equivalents, improvements or changes may be made without departing from the spirit and principles of the present invention.
Claims (10)
1. A method of cable voltage determination, the method comprising:
acquiring differential voltages between each of three pairs of probes in different directions around a target cable;
the voltage U of the target cable is determined based on the three differential voltages obtained.
2. The method of claim 1, wherein determining the voltage U of the target cable based on the acquired three differential voltages comprises:
proximity cable based on each of the three pairs of probesDistance R of probe from cable center i Electric field strength E at the probe far from the cable for each of the three pairs of probes i (R i ) Dielectric constant epsilon of wire insulation layer 1 Dielectric constant ε of air 2 Dielectric constant epsilon of insulating medium 3 Radius r of cable aluminum core 0 Radius r of cable containing insulating layer 1 Distance d between the backing probe and the shielding layer of each pair of probe pairs 2 And the i-th pair of probes is deviated from the angle theta of the longitudinal axis y from the line of the central point of the electric field intensity of the cable i Establishing an association relation with the voltage U of the target cable;
and determining the voltage U of the target cable based on the association relation.
3. The method of claim 2, wherein the association relationship is:
wherein i=1, 2,3
Wherein R is i Representing the distance between the probe of the i-th pair of probes, which is close to the cable, and the center of the cable; e (E) i (R i ) Representing the electric field strength at the probe far from the cable in the i-th pair of probes; epsilon 1 Represent dielectric constant, epsilon of wire insulation layer 2 Represents the dielectric constant, epsilon, of air 3 Represents the dielectric constant, r, of the insulating medium 0 Represents the radius of the cable aluminum core, r 1 Represents the radius of the cable containing the insulating layer, r 2 Indicating the inner diameter of the sensor, d 2 Represents the distance, θ, between the backing probe and the shield of each pair of probe pairs i Indicating the angle of the i-th pair of probes from the longitudinal axis y that is aligned with the center point of the cable's electric field strength.
4. The method of claim 3, wherein the step of,
E i (R i ) Is calculated according to the formula:
wherein d 1 Represents the distance between each pair of probes, u i Representing the differential voltage acquired by the i-th pair of probes.
5. The method of claim 3, wherein the step of,
R i is calculated according to the formula:
wherein x and y represent the position coordinates of the axis P of the target cable, R 0 Representing the radius of the sensor shield.
6. The method according to any one of claims 3-5, characterized in that the target cable voltage U is set to R thereof 1 、R 2 、R 3 Electric field strength E at the inner probe of three directions i (R i ) Relation to R 1 、R 2 、R 3 The relation equations are combined to obtain the voltage U of the target cable, and the calculation formula is expressed as follows:
7. a cable voltage determining device is characterized by comprising a sensor and a signal processing unit, wherein the sensor comprises three pairs of probe pairs,
each pair of the three pairs of probes is distributed in different directions around the target cable and is used for acquiring differential voltage between each pair of probes;
the signal processing unit is used for determining the voltage U of the target cable based on the acquired three differential voltages.
8. The determination device according to claim 7, wherein determining the voltage U of the target cable based on the acquired three voltages includes:
based on the distance R between the probe close to the cable and the center of the cable of each pair of the three pairs of probes i Electric field strength E at the probe far from the cable for each of the three pairs of probes i (R i ) Dielectric constant epsilon of wire insulation layer 1 Dielectric constant ε of air 2 Dielectric constant epsilon of insulating medium 3 Radius r of cable aluminum core 0 Cable radius r with insulation layer 1 Distance d between the backing probe and the shielding layer of each pair of probe pairs 2 And the i-th pair of probes is deviated from the angle theta of the longitudinal axis y from the line of the central point of the electric field intensity of the cable i Establishing an association relation with the voltage U of the target cable;
and determining the voltage U of the target cable based on the association relation.
9. The determining apparatus according to claim 7 or 8, wherein the signal processing unit comprises a band-pass filter, an analog-to-digital converter, a data processor, wherein,
the band-pass filter is used for carrying out band-pass filtering on differential voltages before three pairs of probes;
the analog-to-digital converter is used for performing analog-to-digital conversion on the signal output by the band-pass filter;
the data processor is used for determining the voltage U of the target cable based on the acquired three differential voltages.
10. The determining apparatus of claim 7 or 8, wherein the sensor further comprises an insulating spacer layer, a metallic shielding layer and an insulating plastic housing, wherein,
the insulating separation layer is composed of foam and is distributed between each pair of probes and between the probes and the metal shielding layer;
the metal shielding layer is cylindrical copper foil and is used for shielding the influence of other sources around the cable;
the insulating plastic shell is a pair of semi-cylindrical surfaces, a complete cylindrical surface can be formed by buckling, and the inner surface of the insulating plastic shell is adhered with the metal shielding layer.
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