A three-phase voltage indirect measurement method considering the height of electric field sensor

Abstract

The present invention discloses a three-phase voltage indirect measurement method considering the height of an electric field sensor, which belongs to the field of voltage measurement technology. The mirror method is used to analyze the electric field of the upper surface of an electric field sensor located below a single-phase overhead transmission line to be measured; the electric field expression of the upper surface of the electric field sensor is derived; the number and position of the electric field sensor array are designed for three-phase voltage measurement, and the horizontal and vertical components of the electric field measured by the electric field sensor and the corresponding ratio coefficients are determined; a three-phase voltage measurement equation group is constructed based on the superposition theorem, and the conductor position information of the overhead transmission line is obtained by solving; a proportional coefficient matrix of the horizontal or vertical components of the electric field is constructed, and the instantaneous value of the three-phase voltage to be measured is calculated in real time in combination with the corresponding proportional coefficient matrix. The present invention provides a three-phase voltage indirect measurement method considering the height of an electric field sensor, which greatly reduces the number of sensors and improves the convenience and accuracy of measurement.

Description

Technical Field

[0001] The invention belongs to the technical field of voltage measurement, and in particular relates to a three-phase voltage indirect measurement method taking into account the height of an electric field sensor. Background Art

[0002] Voltage is a very important operating parameter in the power grid. The ability to conveniently measure the voltage of the transmission line is of great significance for the safe, reliable and economical operation of the power system. Voltage measurement methods are generally divided into direct measurement and indirect measurement. The traditional direct voltage measurement method mainly uses the voltage transformer to make a direct electrical connection with the line to be measured, and reflects the voltage of the conductor to be measured by measuring the low-voltage small signal on the secondary side of the voltage transformer. Voltage transformers are mainly divided into electromagnetic and capacitive types. Generally speaking, electromagnetic voltage transformers are used for 35kV and below, and capacitive voltage transformers are used for 110kV and above, but there are some problems. Electromagnetic transformers have ferromagnetic saturation due to the iron core, which makes it easy to produce ferromagnetic resonance; capacitive voltage transformers have poor transient characteristics due to the capacitive inertial element, and high-frequency oscillation may occur on the secondary side under high-frequency overvoltage. In addition, the volume and insulation difficulty of the voltage transformer will increase with the increase of voltage level, and the position of its measurement point is relatively fixed, which cannot achieve massive measurement.

[0003] With the development of sensing technology, the performance of electric field sensors has been continuously improved. The electric field in the space around the conductor can be used to indirectly calculate the conductor voltage without touching the conductor, thus achieving safe, convenient and efficient measurement. At present, there are research schemes that use the relationship between electric field and voltage to measure the conductor voltage, but the height of the electric field sensor during actual measurement is not considered, which increases the measurement error; and in three-phase measurement, the existing scheme requires 9 electric field sensors, which is a large number of sensors. Therefore, it is necessary to study the influence of the height of the electric field sensor on the measurement and propose a new indirect voltage measurement scheme. Summary of the invention

[0004] The purpose of the present invention is to provide a three-phase voltage indirect measurement method taking into account the height of an electric field sensor, so as to solve the problem of measurement error caused by not taking into account the actual height of the electric field sensor in the existing measurement scheme in the prior art.

[0005] To achieve the above object, the present invention provides a three-phase voltage indirect measurement method considering the height of the electric field sensor, comprising the following steps:

[0006] Step 1: Using the mirror image method, an electric field analysis is performed on the position of the upper surface of the electric field sensor located below the single-phase overhead transmission line to be tested;

[0007] Step 2, deriving an electric field expression on the upper surface of the electric field sensor, including an electric field vertical component and an electric field horizontal component, and an expression of a ratio coefficient of the two components;

[0008] Step 3: Design the number and position of the electric field sensor array for three-phase voltage measurement, and determine the horizontal component and vertical component of the electric field measured by the electric field sensor, as well as the ratio coefficient of the measured horizontal component and vertical component of the electric field;

[0009] Step 4: Based on the superposition theorem, a three-phase voltage measurement equation group is constructed according to the horizontal component of the electric field and the vertical component of the electric field obtained in step 3, and the corresponding ratio coefficients, and the three-phase voltage measurement equation group is solved to obtain the conductor position information of the overhead transmission line;

[0010] Step 5: Use the wire position information obtained in step 4 to construct a proportional coefficient matrix of the horizontal or vertical component of the electric field. When the electric field sensor subsequently measures the horizontal or vertical component of the electric field, the corresponding proportional coefficient matrix is ​​combined to calculate the instantaneous value of the three-phase voltage to be measured in real time.

[0011] Preferably, in step 1, when the electric field generated by the single-phase overhead transmission line to be measured in space is analyzed by using the mirror method, assuming that the overhead line radius is r0, the overhead line height is h, and the overhead line voltage is u, the electric field intensity of the overhead line at point P (x, y) in space is specifically expressed as follows:

[0012]

[0013] In the formula, E x is the horizontal component of the electric field at point P; E y is the vertical component of the electric field at point P; r is the distance from the equivalent charge Q of the wire to point P; r′ is the distance from the image charge Q′ of the wire to point P.

[0014] Preferably, the specific calculation expressions of the distance r from the wire equivalent charge Q to the point P and the distance r′ from the wire image charge Q′ to the point P are as follows:

[0015] r 2 =(xd) 2 +(yh) 2

[0016] r′ 2 =(xd) 2 +(y+h) 2

[0017] Where d is the horizontal position of the overhead line.

[0018] Preferably, in step 2, considering the influence of the height of the electric field sensor on the measurement, assuming that the height of the electric field sensor is n, and the horizontal distance of the electric field sensor from the origin is m0, the position is expressed as (m0, n); the electric field of the wire on the upper surface of the electric field sensor is expressed as follows:

[0019] Horizontal component of the electric field:

[0020]

[0021] Vertical component of the electric field:

[0022]

[0023] The ratio of the vertical component to the horizontal component of the electric field is:

[0024]

[0025] Preferably, the specific process of step 3 is as follows:

[0026] S31, assuming that the number of overhead lines is 3, the number of electric field sensors installed on the ground is 3, the position of the first electric field sensor is set at the origin, and a rectangular coordinate system is established;

[0027] S32, setting the spacing between each electric field sensor equal to m, and keeping the placement direction of the electric field sensor array perpendicular to the longitudinal direction of the overhead line;

[0028] S33, at the beginning of the measurement, using the first electric field sensor to perform single-phase electric field measurement on the three-phase overhead line respectively, determine the vertical component and horizontal component of the electric field at this time, and calculate the ratios of the three phases to l1, l2, and l3;

[0029] S34. Determine the actual values ​​measured by the three electric field sensors.

[0030] Preferably, the specific expression of the three-phase voltage measurement equation group constructed in step 4 is as follows:

[0031]

[0032] In the formula, E jy (j=1,2,3) is the vertical component of the electric field strength measured by the jth sensor; E jx (j=1,2,3) is the horizontal component of the electric field strength measured by the jth sensor; r0 is the radius of the overhead line; m is the distance between each electric field sensor; u i (i=1,2,3) is the voltage of the ith overhead line; h i (i=1,2,3) is the height of the ith overhead line; d i(i=1,2,3) represents the horizontal position of the ith overhead line; Newton's method is used to solve the three-phase voltage measurement equations to obtain the conductor position information of the overhead transmission line, including the height h of the three-phase overhead line. i , horizontal position of three-phase overhead line d i And the instantaneous value of a voltage at the corresponding moment.

[0033] Preferably, the specific expression for constructing the proportional coefficient matrix of the horizontal or vertical component of the electric field in step 5 is as follows:

[0034] The proportional coefficient matrix of the vertical component of the electric field is:

[0035]

[0036] The proportional coefficient matrix of the horizontal component of the electric field is:

[0037]

[0038] Preferably, in step 5, the overhead line voltage vector U=[u1,u2,u3] T The vertical component E of the electric field measured by the electric field sensor y =[E 1y , E 2y , E 3y ] T , horizontal component of electric field E x =[E 1x , E 2x , E 3x ] T The following relationship exists:

[0039] E y =K y U

[0040] E x =K x U

[0041] Wherein, the superscript T represents the matrix transpose symbol;

[0042] In subsequent measurements, the horizontal component of the electric field or the vertical component of the electric field is measured by the electric field sensor, and the real-time conductor voltage is inferred by combining the corresponding proportional coefficient matrix. The specific expression is as follows:

[0043] U=K y + E y

[0044] U=K x + E x

[0045] In the formula, K y+ is the matrix K y The generalized inverse matrix of x + is the matrix K x The generalized inverse matrix of .

[0046] Therefore, the present invention adopts the above-mentioned three-phase voltage indirect measurement method taking into account the height of the electric field sensor, solves the measurement error caused by not considering the actual height of the electric field sensor in the existing measurement scheme, and proposes a three-phase voltage indirect measurement scheme taking into account the height of the electric field sensor. In addition, when measuring three-phase, the number of sensors is greatly reduced compared with the existing scheme, thereby improving the convenience and accuracy of measurement.

[0047] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is an overall flow chart of a three-phase voltage indirect measurement method considering the height of the electric field sensor of the present invention;

[0049] Figure 2 A schematic diagram of a cross section of a single overhead line and an electric field sensor analysis according to an embodiment of the present invention;

[0050] Figure 3 This is a schematic diagram of analyzing the electric field on the upper surface of the electric field sensor according to an embodiment of the present invention;

[0051] Figure 4 This is a schematic diagram of three-phase voltage measurement according to an embodiment of the present invention;

[0052] Figure 5 It is a curve diagram of the measured values ​​of the vertical component of the electric field within 100 milliseconds of three electric field sensors in an example of the present invention;

[0053] Figure 6 It is a curve diagram of three-phase voltage measurement values ​​within 100 milliseconds in an example of the present invention;

[0054] Figure 7 It is a curve diagram of three-phase voltage measurement error within 100 milliseconds in an example of the present invention. DETAILED DESCRIPTION

[0055] The following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] See also Figure 1-7, a three-phase voltage indirect measurement method considering the height of electric field sensors, comprising the following steps:

[0057] Step 1: Use the mirror image method to perform electric field analysis on the upper surface of the electric field sensor located below the single-phase overhead transmission line to be tested; in this step, Figure 2 The figure shows a schematic diagram of a cross section of a single overhead line and an electric field sensor analysis according to an embodiment of the present invention. The following assumptions need to be made about the actual overhead line:

[0058] 1) The electric field of overhead lines in space is a quasi-static field, that is, the electric field generated by the alternating magnetic field is ignored.

[0059] 2) The ground potential is 0, the wire is infinitely long, and considering the wire sag, select the two-dimensional plane at the lowest point of the wire.

[0060] 3) The equivalent charge of the wire can be regarded as an ideal line charge, and the position of the charge can be regarded as the geometric center of the wire cross section.

[0061] 4) Ignore the conductor end effect and the impact of surrounding buildings on overhead lines.

[0062] When using the mirror image method to analyze the electric field generated by the single-phase overhead transmission line to be tested in space, assuming that the overhead line radius is r0, the overhead line height is h, and the overhead line voltage is u, the electric field intensity of the overhead line at point P (x, y) in space is specifically expressed as follows:

[0063]

[0064] In the formula, E x is the horizontal component of the electric field at point P; E y is the vertical component of the electric field at point P; r is the distance from the equivalent charge Q of the wire to point P; r′ is the distance from the image charge Q′ of the wire to point P.

[0065] The specific calculation expressions of the distance r from the wire equivalent charge Q to point P and the distance r′ from the wire image charge Q' to point P are as follows:

[0066] r 2 =(xd) 2 +(yh) 2

[0067] r′ 2 =(xd) 2 +(y+h) 2

[0068] Where d is the horizontal position of the overhead line

[0069] Step 2: Derive the electric field expression on the upper surface of the electric field sensor, including the vertical component of the electric field and the horizontal component of the electric field, as well as the expression of the ratio coefficient of the two components; in this step, since the electric field sensor has a height, it cannot be equivalent to the ground in actual measurement. If it is equivalent to the ground, the electric field sensor needs to be embedded underground, and its upper surface coincides with the ground. However, it is not easy to embed the sensor underground in the actual field, so it is necessary to further consider the impact of the height of the electric field sensor on the measurement. Figure 3 As shown in the figure, considering the influence of the height of the electric field sensor on the measurement, assuming that the height of the electric field sensor is n and the horizontal distance between the electric field sensor and the origin is m0, the position is expressed as (m0, n); the electric field of the wire on the upper surface of the electric field sensor is expressed as follows:

[0070] Horizontal component of the electric field:

[0071]

[0072] Vertical component of the electric field:

[0073]

[0074] The ratio of the vertical component to the horizontal component of the electric field is:

[0075]

[0076] Step 3. Design the number and position of the electric field sensor array for three-phase voltage measurement, and determine the horizontal component and vertical component of the electric field measured by the electric field sensor, as well as the ratio coefficient of the measured horizontal component and vertical component of the electric field. In this step, the height and horizontal position of each overhead line are unknown during actual measurement, plus there are three unknowns in the voltage to be measured. From the above, we can see that we can obtain the vertical component and horizontal component of the electric field, as well as their ratio equations through a single electric field sensor. The number of equations and unknowns are equal, and the equation is solvable. From the above, we can conclude that each phase of the overhead line corresponds to at least one electric field sensor. For three-phase voltage measurement, at least three electric field sensors are required. Figure 4 The figure shows a schematic diagram of three-phase voltage measurement according to an embodiment of the present invention, and the specific process is as follows:

[0077] S31, assuming that the number of overhead lines is 3, the number of electric field sensors installed on the ground is 3, the position of the first electric field sensor is set at the origin, and a rectangular coordinate system is established;

[0078] S32, setting the spacing between each electric field sensor equal to m, and keeping the placement direction of the electric field sensor array perpendicular to the longitudinal direction of the overhead line;

[0079] S33, at the beginning of the measurement, using the first electric field sensor to perform single-phase electric field measurement on the three-phase overhead line respectively, determine the vertical component and horizontal component of the electric field at this time, and calculate the ratios of the three phases to l1, l2, and l3;

[0080] S34. Determine the actual values ​​measured by the three electric field sensors.

[0081] Step 4: Based on the superposition theorem, a three-phase voltage measurement equation group is constructed according to the horizontal component of the electric field and the vertical component of the electric field obtained in step 3, and the corresponding ratio coefficient, and the three-phase voltage measurement equation group is solved to obtain the conductor position information of the overhead transmission line; in this step, the electric field generated by each phase voltage on the upper surface of the electric field sensor obeys the formula introduced above, and this system is a linear system, so the three-phase voltage measurement equation group is constructed by the superposition theorem, and the specific expression is as follows:

[0082]

[0083] In the formula, E jy (j=1,2,3) is the vertical component of the electric field strength measured by the jth sensor; E jx (j=1,2,3) is the horizontal component of the electric field strength measured by the jth sensor; r0 is the radius of the overhead line; m is the distance between each electric field sensor; u i (i=1,2,3) is the voltage of the ith overhead line; h i (i=1,2,3) is the height of the ith overhead line; d i (i=1,2,3) represents the horizontal position of the ith overhead line; the above completes the construction of the three-phase voltage measurement equation group, which belongs to a multivariate nonlinear equation group. There are many methods for solving this type of equation group, such as Newton's method, gradient method, chord intercept method, fixed point method, ant colony algorithm, etc. According to factors such as the specific equation volume, convergence speed requirements, and hardware computing power conditions, the appropriate method can be selected to solve the problem by balancing various contradictions. The measurement object in this embodiment is the overhead line voltage, but in the actual site, the height and horizontal position of the overhead line can be roughly determined by observation, that is, the initial value can be well determined, so this implementation selects Newton's method, and Newton's method has a fast iteration speed and high solution accuracy. The three-phase voltage measurement equation group is solved using Newton's method to obtain the conductor position information of the overhead transmission line, including the height h of the three-phase overhead line. i , horizontal position of three-phase overhead line d i And the instantaneous value of a voltage at the corresponding moment. In the specific implementation, the detailed process of solving using Newton's method is not the focus of this article and has been ignored.

[0084] Step 5: Use the wire position information obtained in step 4 to construct a proportional coefficient matrix of the horizontal or vertical component of the electric field. When the electric field sensor measures the horizontal or vertical component of the electric field, the corresponding proportional coefficient matrix is ​​combined to calculate the instantaneous value of the three-phase voltage to be measured in real time. The specific expression for constructing the proportional coefficient matrix of the horizontal or vertical component of the electric field is as follows:

[0085] The proportional coefficient matrix of the vertical component of the electric field is:

[0086]

[0087] The proportional coefficient matrix of the horizontal component of the electric field is:

[0088]

[0089] Overhead line voltage vector U = [u1, u2, u3] T The vertical component E of the electric field measured by the electric field sensor y =[E 1y , E 2y , E 3y ] T , horizontal component of electric field E x =[E 1x , E 2x , E 3x ] T The following relationship exists:

[0090] E y =K y U

[0091] E x =K x U

[0092] Wherein, the superscript T represents the matrix transpose symbol;

[0093] As long as the relative position of the overhead line and the electric field sensor array does not change, the proportional coefficient matrix Ky or Ex will not change, so only one round of iteration is needed to obtain the matrix proportional coefficient matrix E y or E x ;

[0094] In subsequent measurements, only the horizontal component or vertical component of the electric field is measured by the electric field sensor. Combined with the corresponding proportional coefficient matrix, the real-time conductor voltage can be inferred. The specific expression is as follows:

[0095] U=K y + E y

[0096] U=K x + Ex

[0097] In the formula, K y + is the matrix K y The generalized inverse matrix of x + is the matrix K x The generalized inverse matrix of .

[0098] Example

[0099] For ease of understanding, the method of the present invention is simulated and tested in conjunction with a specific scenario example. This example simulation test selects a 10kV (line voltage effective value) three-phase overhead line scenario, and the relevant parameters are as follows:

[0100] There are 3 overhead lines, and the parameters of the overhead lines are: r0=0.004, h1=2, h2=2.1, h3=2.2, d1=0.5, d2=1.5, d3=2.5, unit: meter.

[0101] The number of electric field sensors is 3, the height of the electric field sensors is n=0.8, and the spacing is m=1, unit: meter.

[0102] Initially, the first electric field sensor measures the electric field value of each phase: E' 1y =-1038.00, E' 1x =-230.03, E' 2y =633.70, E' 2x =252.64, E' 3y =-28.01, E' 3x = -10.72, unit: V / m. It can be deduced that the relative value coefficients l1 = 4.51, l2 = 2.51, and l3 = 2.61.

[0103] The electric field value output by the electric field sensor at a certain moment: E 1y =-432.30, E 2y =-25.78, E 3y =392.53, E 1x =11.89, E 2x =423.55, E 3x =29.75, unit: V / m.

[0104] At this time, the voltage measurement equations are as follows:

[0105]

[0106] In this example, Newton's method is used to solve the measurement equations. The solution process is ignored, and the wire position information can be obtained as shown in Table 1:

[0107] Table 1

[0108] Wire parameters <![CDATA[h1]]> <![CDATA[h2]]> <![CDATA[h3]]> <![CDATA[d1]]> <![CDATA[d2]]> <![CDATA[d3]]> Measurement value / m 2.0001 2.1002 2.2000 0.5000 1.5003 2.5002

[0109] In this case, the electric field vertical component proportional coefficient matrix is ​​used for calculation. The electric field vertical component proportional coefficient matrix is ​​as follows:

[0110]

[0111] Its generalized inverse matrix is ​​as follows:

[0112]

[0113] like Figure 5 The graph shows the measured values ​​of the vertical component of the electric field of three electric field sensors within 100 milliseconds in the example of the present invention, combined with the matrix K y + The three-phase conductor voltage can be obtained, such as Figure 6 The graph of the three-phase voltage measurement value within 100 milliseconds in the example of the present invention is shown as follows: Figure 7 The figure shows the three-phase voltage measurement error curve within 100 milliseconds in the example of the present invention. It can be seen that the absolute error of voltage measurement is less than 10 -9 , indicating that this method has high measurement accuracy.

[0114] It can be seen that the measurement scheme of the embodiment of the present invention measures the vertical component and horizontal component of the electric field through the electric field sensor array under the overhead line, and indirectly measures the three-phase voltage to be measured by utilizing the relationship between the electric field and the voltage. It improves the measurement accuracy while taking into account the height of the electric field sensor and reduces the number of electric field sensors.

[0115] Therefore, the present invention adopts the above-mentioned three-phase voltage indirect measurement method considering the height of the electric field sensor. The electric field information obtained by measuring the electric field sensor array below the overhead line can solve the unknown height and horizontal position parameters of the overhead line; when facing three-phase voltage measurement, only 3 electric field sensors are needed (the principle is shown in the specific implementation method), which greatly reduces the number of electric field sensors and improves the economy and convenience of measurement; and the height of the electric field sensor during actual measurement is taken into account, eliminating the measurement error caused by the sensor height and improving the measurement accuracy; at the same time, as long as the relative position of the electric field sensor array and the conductor to be measured does not change, it is only necessary to measure the horizontal component and the vertical component of the electric field sensor once, and subsequently, by measuring only the horizontal component or the vertical component of the electric field, combined with the corresponding proportional coefficient matrix, the real-time conductor voltage can be inferred, thereby improving the measurement efficiency.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A three-phase voltage indirect measurement method considering the height of the electric field sensor, characterized in that: The following steps are involved: Step 1: Using the mirror image method, an electric field analysis is performed on the position of the upper surface of the electric field sensor located below the single-phase overhead transmission line to be tested; Step 2, deriving an electric field expression on the upper surface of the electric field sensor, including an electric field vertical component and an electric field horizontal component, and an expression of a ratio coefficient of the two components; Step 3: Design the number and position of the electric field sensor array for three-phase voltage measurement, and determine the horizontal component and vertical component of the electric field measured by the electric field sensor, as well as the ratio coefficient of the measured horizontal component and vertical component of the electric field; Step 4: Based on the superposition theorem, a three-phase voltage measurement equation group is constructed according to the horizontal component of the electric field and the vertical component of the electric field obtained in step 3, and the corresponding ratio coefficients, and the three-phase voltage measurement equation group is solved to obtain the conductor position information of the overhead transmission line; Step 5: construct a proportional coefficient matrix of the horizontal or vertical component of the electric field using the wire position information obtained in step 4, and calculate the instantaneous value of the three-phase voltage to be measured in real time by combining the corresponding proportional coefficient matrix when the electric field sensor measures the horizontal or vertical component of the electric field in the subsequent process; In step 2, the influence of the height of the electric field sensor on the measurement is considered. Assume that the height of the electric field sensor is n, and the horizontal distance between the electric field sensor and the origin is m0. Then the position is expressed as (m0, n). The electric field of the wire on the upper surface of the electric field sensor is expressed as follows: Horizontal component of the electric field: Vertical component of the electric field: The ratio of the vertical component to the horizontal component of the electric field is: The specific process of step 3 is as follows: S31, assuming that the number of overhead lines is 3, the number of electric field sensors installed on the ground is 3, the position of the first electric field sensor is set at the origin, and a rectangular coordinate system is established; S32, setting the spacing between each electric field sensor equal to m, and keeping the placement direction of the electric field sensor array perpendicular to the longitudinal direction of the overhead line; S33, at the beginning of the measurement, using the first electric field sensor to perform single-phase electric field measurement on the three-phase overhead line respectively, determine the vertical component and horizontal component of the electric field at this time, and calculate the ratios of the three phases to l1, l2, and l3; S34, determining actual values ​​measured by three electric field sensors; The specific expression of the three-phase voltage measurement equation group constructed in step 4 is as follows: In the formula, E jy is the vertical component of the electric field strength measured by the jth sensor, where j = 1, 2, 3; E jx is the horizontal component of the electric field strength measured by the jth sensor, where j = 1, 2, 3; r0 represents the radius of the overhead line; m represents the distance between each electric field sensor; u i is the voltage of the ith overhead line, where i = 1, 2, 3; h i is the height of the ith overhead line, where i = 1, 2, 3; d i represents the horizontal position of the i-th overhead line, where i = 1, 2, 3; Newton's method is used to solve the three-phase voltage measurement equations to obtain the conductor position information of the overhead transmission line, including the height h of the three-phase overhead line i , horizontal position of three-phase overhead line d i And the instantaneous value of a voltage at the corresponding moment.

2. The three-phase voltage indirect measurement method considering the height of the electric field sensor according to claim 1 is characterized in that: In step 1, when the mirror image method is used to analyze the electric field generated by the single-phase overhead transmission line to be tested in space, the overhead line radius is set to r0, the overhead line height is h, the overhead line voltage is u, and the electric field intensity of the overhead line at point P (x, y) in space is specifically expressed as follows: In the formula, E x is the horizontal component of the electric field at point P; E y is the vertical component of the electric field at point P; r is the distance from the equivalent charge Q of the conductor to point P; r' is the distance from the mirror charge Q' of the conductor to point P, and d is the horizontal position of the overhead line.

3. The three-phase voltage indirect measurement method considering the height of the electric field sensor according to claim 2, characterized in that: The specific calculation expressions of the distance r from the wire equivalent charge Q to point P and the distance r′ from the wire image charge Q' to point P are as follows: r 2 =(x-d) 2 +(y-h) 2 r′ 2 =(x-d) 2 +(y+h) 2 Where d is the horizontal position of the overhead line.

4. The three-phase voltage indirect measurement method considering the height of the electric field sensor according to claim 3 is characterized in that: The specific expression for constructing the proportional coefficient matrix of the horizontal or vertical component of the electric field in step 5 is as follows: The proportional coefficient matrix of the vertical component of the electric field is: The proportional coefficient matrix of the horizontal component of the electric field is:

5. The three-phase voltage indirect measurement method considering the height of the electric field sensor according to claim 4, characterized in that: In step 5, the overhead line voltage vector U = [u1, u2, u3] T The vertical component E of the electric field measured by the electric field sensor y =[E 1y , E 2y , E 3y ] T , horizontal component of electric field E x =[E 1x , E 2x , E 3x ] T The following relationship exists: E y =K y YOU E x =K x YOU Wherein, the superscript T represents the matrix transpose symbol; In subsequent measurements, the horizontal component of the electric field or the vertical component of the electric field is measured by the electric field sensor, and the real-time conductor voltage is inferred by combining the corresponding proportional coefficient matrix. The specific expression is as follows: U=K y + E y U=K x + E x In the formula, K y + is the matrix K y The generalized inverse matrix of x + is the matrix K x The generalized inverse matrix of .

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