A non-contact voltage measurement method with variable ratio parameter adaptive adjustment

Abstract

The application discloses a kind of non-contact voltage measurement methods of variable ratio parameter self-adapting adjustment, belong to power system voltage measurement technology, solve the problem that voltage measurement device cannot adapt to the measurement working condition of ground capacitance variation, the present application includes: step 1: design the double-circuit coupling mechanism of single-phase voltage measurement, combined with the coupling capacitance between the inner and outer copper foil of measurement device and power line and ground, obtain the equivalent circuit model of voltage measurement, establish double-path response voltage equation;Step 2: analyze the numerical characteristics of two-way variable ratio when ground capacitance changes, establish the expression for distinguishing ground capacitance variation, establish the variable ratio coefficient adjustment algorithm suitable for ground capacitance variation;Step 3: design the experimental method of step length w and start threshold tol in calibration adjustment algorithm;Build measurement hardware platform including data acquisition and data processing module.The present application establishes the discriminant of ground capacitance variation and variable ratio adjustment algorithm, realizes the measurement working condition that device adapts to ground capacitance variation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of voltage measurement of power system, and particularly relates to a non-contact voltage measurement method with adaptive adjustment of variable ratio parameters. BACKGROUND

[0002] With the large-scale development of regional Internet projects and the large-scale grid connection of various distributed power sources in China, the world's few super-large complex power grids are formed. It is of great significance to accurately master massive voltage measurement data, which is related to the application effects of power metering, relay protection and other aspects, and provides strong data support for the safe and stable operation of the power system.

[0003] A new type of voltage measurement device based on capacitive coupling is expected to be widely deployed in the power system due to its low cost, small size and easy installation, which is of great significance to the safe operation and precise operation and maintenance of smart grids. However, the ground capacitance of the measurement device is related to the measurement environment, mainly affected by the change of erection height. This parameter is difficult to calibrate by the sensor manufacturer, and the variable ratio parameter of the calibration often depends on the high-voltage probe during the hanging line operation. Moreover, the calibrated variable ratio parameter will change with the environment, which limits the application range of the device. SUMMARY

[0004] The purpose of the application is to:

[0005] To solve the problem that the voltage measurement device cannot adapt to the change of ground capacitance in the measurement working condition, a non-contact voltage measurement method with adaptive adjustment of variable ratio parameters is provided.

[0006] The technical scheme adopted by the application is as follows:

[0007] A non-contact voltage measurement method with adaptive adjustment of variable ratio parameters comprises the following steps:

[0008] Step 1: design a double-circuit coupling mechanism for measuring single-phase voltage, combine the coupling capacitances between the inner and outer copper foils of the measurement device and the power line and the ground, obtain an equivalent circuit model for voltage measurement, and establish a double-path response voltage equation based on the equivalent circuit model;

[0009] Step 2: analyze the numerical characteristics of the variable ratio of each two paths when the ground capacitance changes through the double-path response voltage equation, establish an expression for discriminating the change of the ground capacitance according to the numerical characteristics of the variable ratio coefficient, and establish a variable ratio coefficient adjustment algorithm that adapts to the change of the ground capacitance based on the expression;

[0010] Step 3: design an experimental method for calibrating the step size w and the starting threshold tol in the adjustment algorithm; and build a measurement hardware platform with data acquisition and data processing modules.

[0011] Further, the step 1 specifically comprises the following steps:

[0012] Step 1.1: design a double-circuit coupling mechanism for measuring single-phase voltage;

[0013] The double-circuit coupling mechanism comprises a PVC pipe and two independent copper foil regions, both of which are pasted with copper foil on the inner and outer surfaces of the PVC pipe; the length of the inner copper foil in one side region is the same as that of the outer copper foil; the length of the outer copper foil in the other side region is the same as that of the outer copper foil in the left side, and the length of the outer copper foil is greater than that of the inner copper foil; the inner copper foils of the two independent copper foil regions and the insulating medium of the power line are both air;

[0014] Step 1.2: establish a voltage measurement equivalent circuit model about the coupling capacitances between the inner and outer copper foils in the measuring device and the power line and the ground;

[0015] In one side copper foil region of the voltage measurement equivalent circuit model, there exists coupling capacitance: the coupling capacitance C1 of the inner copper foil in this side to the line, the coupling capacitance C w1 of the line to the outer copper foil, and the coupling capacitance C x of the outer copper foil to the ground; in

[0016] In the other side copper foil region of the voltage measurement equivalent circuit model, there also exists coupling capacitance: the coupling capacitance C2 of the inner copper foil in this side to the line, the coupling capacitance C w2 of the line to the outer copper foil, and the coupling capacitance C x of the outer copper foil to the ground; the heights of the outer copper foils in the two side regions to the ground are consistent, both being C w1 ; an equivalent circuit model for double-circuit measurement of single-phase power line based on displacement current method is established through the coupling capacitances;

[0017] According to the double-circuit measurement model, the length of the inner copper foil in the other side is half of that in one side, so there is:

[0018] C1+C w2 > C2+C w2 (22)

[0019] From the equivalent circuit, under the action of ideal amplifier virtual short, the inner and outer copper foils in the two sides are equivalent to short circuit, and through analysis, the double-circuit response voltage equation is obtained:

[0020]

[0021]

[0022] From the above formula, it can be seen that the response voltages u1 and u2 of the measurement model are in linear relationship with the line voltage U, and the two-way variable ratios are defined as k1 and k2.

[0023] Further, the step 2 specifically comprises the following steps:

[0024] Step 2.1: Analyze the numerical characteristics of the two-way variable ratio when the ground capacitance changes through the double-path response equation, and establish an expression for distinguishing the response voltage change with the ground capacitance according to the numerical characteristics of the variable ratio coefficient:

[0025] When the device measurement circuit is erected on a line with two independent measurement circuits, the response voltages in the two measurement circuits are divided, i.e., the variable ratio is divided to obtain the following:

[0026]

[0027] Through equation (5) and in combination with equation (1), it has the following characteristics:

[0028]

[0029] Since With the monotone decrease of the outer copper foil ground capacitance Cx, the change trend of the ground capacitance Cx is judged according to the change trend of

[0030] In the calibration of the variable ratio during the preliminary installation of the device, it is assumed that when the device is installed, Cx=Cx*, and the variable ratios of the two sides of the circuit at this time are k1* and k2* respectively. It is assumed that at any time after calibration, the coupling capacitance of the outer copper foil to the ground of the two sides of the circuit is disturbed, at which time the ground capacitance changes to Cx=Cx', and the variable ratios of the two sides of the circuit are k1' and k2' respectively. According to the monotonicity of The following conclusions are drawn:

[0031]

[0032] Therefore, the change trend of the variable capacitance Cx is obtained through the sign of the equation k1'k2*-k2'k1*;

[0033] The variable replacement is performed on the determination equation to obtain real-time k1' and k2', and the process is as follows:

[0034] The equations and U'=k1'·u1'=k2'·u2' are obtained.

[0035]

[0036] Since Therefore, the response voltages u1' and u2' are used to distinguish the sign of k1'k2*-k2'k1*, and to identify whether the coupling capacitance Cx of the two sides of the mechanism to the ground has changed;

[0037] Step 2.2: According to the numerical characteristics of the variable ratio coefficient, a variable ratio coefficient adjustment model suitable for the change of the ground capacitance is established.​

[0038] Let Δ = u2'·k2*-u1'·k1*, the adjustment of the variable ratio is expressed as follows according to the method of line search:

[0039] k1 n+1 = k1 n + λ·Δ (29)

[0040] The variable ratio state is judged and the variable ratio is adjusted accordingly;

[0041] The expression of the step length λ is found to optimize the step length of the variable ratio coefficient adjustment, and the expression of the step length λ is derived as follows:

[0042] For any moment, the response voltages measured by the two side circuits satisfy:

[0043] U = k1·u1 = k2·u2 (30)

[0044] Taking the differential of both ends at the same time, we get:

[0045] dk1·u1+k1·du1 = dk2·u2+k2·du2 (31)

[0046] By discretizing and rearranging equation (11), we get:

[0047] (k1 n+1 -k1 n )·u1 = (k2 n+1 -k2 n )·u2+k2 n ·(u 2(n+1) -u 2(n) )-k1 n ·(u 1(n+1) -u 1(n) ) (32)

[0048] According to formulas (2) and (3), the variable ratio coefficient is eliminated to eliminate the parameters Cx related to the height change, and k1 and k2 satisfy the linear relationship shown in the following formula:

[0049]

[0050] Taking the differential of both sides of equation (13), we get:

[0051]

[0052] Let Write equation (14) in the form of discrete difference as follows:

[0053] k1 n+1 -k1 n = w·(k2 n+1 -k2n ) (35)

[0054] Substitute (12) and (15) into (13), we have:

[0055]

[0056] If k2 n , k1 n are regarded as the variable ratio at the calibration time, the corresponding voltage at the calibration time is u 1(n) , u 2(n) , that is:

[0057] k2 n =k2*, k1 n =k1*, u 1(n) =u1*, u 2(n) =u2* (37)

[0058] Since the calibration time must satisfy the condition: u2*·k2 n -u1*·k1 n =0, substitute (16) and (17) into (13), we have:

[0059]

[0060] In the measurement of the response voltage after calibration, u 2(n+1) , u 1(n+1) ; from (18) and (9), we have the step expression:

[0061]

[0062] Set the iteration start threshold tol, and the algorithm suitable for variable ratio changes is as follows:

[0063]

[0064] Further, the step 3 specifically comprises the following steps:

[0065] Step 3.1: design an experimental method for the step length w and the start threshold tol in the calibration adjustment algorithm:

[0066] Measure the response voltage of the two sides of the circuit at a certain height, and use the least square method to calibrate k1* and k2* respectively;

[0067] Based on the simulated annealing algorithm, give the range of parameters w and tol; the range of w: when the device is fixed relative to the power line, according to (6) and w is the zero point of function (6), and it is monotonically decreasing, so The value range of tol: when the device is erected at the same height, at this time, only the line voltage affects delta in formula (20), that is, u2' * k2' - u1' * k1', so the threshold of the ratio adjustment start filters out the case of 10kV line voltage fluctuation ±7%, tol >= max (|u2' * k2' - u1' * k1'|), wherein u2', u1' correspond to the response voltage measured when U fluctuates ±7%;

[0068] Optimize w and tol through the objective function (22) in the simulated annealing algorithm and the cost function difference (23) of the updated solution;

[0069]

[0070]

[0071] Wherein v(i) is the voltage after the ratio adjustment algorithm when the actual hanging line is running, v real The voltage measured by the actual measurement is optimized to obtain the parameters w and tol, and the non-contact voltage measurement is completed by using the experimental calibration value;

[0072] Step 3.2: Build a measurement hardware platform containing data acquisition and data processing module: on the built hardware platform, test the error of the inverse-propagation voltage after the algorithm adjustment under the working condition of the change of the device ground capacitance.

[0073] As described above, since the above technical solutions are adopted, the beneficial effects of the present application are:

[0074] The present application proposes a variable ratio parameter self-adaptive adjustment non-contact voltage measurement method, uses the response equation of the double-circuit non-contact voltage measurement, establishes a discriminant for the change of the ground capacitance, and on this basis, establishes a variable ratio adjustment algorithm, so that the measurement device can adapt to the measurement working condition of the change of the ground capacitance, greatly expanding the application range of the device, and combining the simulated annealing method, designing an experimental method for calibrating the step size parameter w and the start threshold tol in the variable ratio adjustment algorithm, so that the measurement device can complete the non-contact voltage measurement without the help of a high-voltage probe after calibration. BRIEF DESCRIPTION OF DRAWINGS

[0075] Figure 1 The method flowchart of the present application;

[0076] Figure 2 The single-phase power line double-circuit measurement schematic diagram based on the displacement current method of the present application;

[0077] Figure 3 The equivalent capacitance diagram of the digital bridge measurement power line and outer copper foil of the present application;

[0078] Figure 4A non-contact voltage measurement system framework of the present application;

[0079] Figure 5 A convergence curve diagram of the simulated annealing algorithm of the present application;

[0080] Figure 6 A relative error and input voltage relationship diagram of the present application. DETAILED DESCRIPTION

[0081] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0082] The present application is a non-contact voltage measurement method with variable ratio parameter adaptive adjustment, comprising the following steps:

[0083] Step 1: design a double-circuit coupling mechanism for measuring single-phase voltage, combine the coupling capacitors between the inner and outer copper foils of the measuring device and the power line and the ground, obtain an equivalent circuit model for voltage measurement, and establish a double-path response voltage equation based on the same;

[0084] Step 2: analyze the numerical characteristics of the left and right variable ratios when the ground capacitance changes through the double-path response equation, establish an expression for discriminating the change of the ground capacitance according to the numerical characteristics of the variable ratio coefficient, and establish a variable ratio coefficient adjustment algorithm that adapts to the change of the ground capacitance on this basis;

[0085] Step 3: design an experimental method for calibrating the step size w and the start threshold tol in the adjustment algorithm; build a measurement hardware platform with data acquisition and data processing modules;

[0086] The step 1 comprises the following steps:

[0087] Step 1.1: design a double-circuit coupling mechanism for measuring single-phase voltage;

[0088] The double-circuit measuring device structure based on the displacement current method is shown in Figure 1 : It contains a PVC pipe and two independent copper foil areas on the left and right, and the copper foils are pasted on the inner and outer surfaces of the PVC pipe in the left and right areas. The length of the inner copper foil in the left area is the same as that of the outer copper foil; the length of the outer copper foil in the right area is the same as that of the outer copper foil in the left area, but the length of the outer copper foil is twice the length of the inner copper foil; the insulating medium of the inner copper foil in the left and right areas and the power line is air.

[0089] Step 1.2: establish an equivalent circuit model for voltage measurement about the coupling capacitors between the inner and outer copper foils of the measuring device and the power line and the ground;

[0090] The measurement model described above exhibits coupling capacitance in the copper foil region on the left: the coupling capacitance C1 between the inner copper foil and the circuit, and the coupling capacitance C between the circuit and the outer copper foil. w1 And the coupling capacitance C of the outer copper foil to ground x Coupling capacitance exists in the copper foil region on the right side of the measurement model: the coupling capacitance C2 between the inner copper foil and the circuit, and the coupling capacitance C between the circuit and the outer copper foil. w2 And the coupling capacitance of the outer copper foil to ground, because the height of the outer copper foil to ground is the same on both the left and right sides, it is C. x These coupling capacitors can be used to establish an equivalent circuit model for single-phase power line two-circuit measurement based on the displacement current method, such as... Figure 2 As shown.

[0091] According to the dual-circuit measurement model described above, the length of the inner copper foil on the right side is half the length of the inner copper foil on the left side. Therefore:

[0092] C1+C w1 >C2+C w2 (43)

[0093] From equivalent circuit Figure 2 It can be seen that under the effect of the "virtual short" of the ideal amplifier, the inner and outer copper foils on the left and right sides are equivalent to a short circuit. Through analysis... Figure 2 The dual-path response voltage equation can be obtained as follows:

[0094]

[0095]

[0096] As can be seen from the above formula, the response voltages u1 and u2 of the measurement model are linearly related to the line voltage U, and the two "turn ratios" can be defined as k1 and k2 respectively.

[0097] Step 2 includes the following steps:

[0098] Step 2.1: Analyze the numerical characteristics of the left and right turns ratios as the capacitance to ground changes using the dual-path response equation. Based on the numerical characteristics of the turns ratio coefficients, establish an expression to determine the response voltage as a function of the capacitance to ground:

[0099] When the installed device measures the circuit, such as Figure 1 As shown, this is equivalent to having two independent measuring circuits on the left and right sides of a single line. Dividing the response voltages of the left and right measuring circuits, or in other words, dividing the turns ratios, yields the following result:

[0100]

[0101] By observing equation (5) and combining it with equation (1), it has the following characteristics:

[0102]

[0103] Since With the monotonic decrease of the outer copper foil to ground capacitance Cx, the change trend of the ground capacitance Cx can be determined according to the change trend of

[0104] Since the calibration of the variable ratio can be completed when the device is initially installed, assuming that the device is installed, Cx=Cx*, and assuming that the variable ratios corresponding to the left and right circuits at this time are k1* and k2* respectively. Assuming that the same interference is received by the coupling capacitance of the outer copper foil to ground of the left and right circuits at any time after calibration, at this time the ground capacitance changes to Cx=Cx'(the corresponding left and right variable ratios are k1' and k2'), and by the monotonicity of

[0105] Therefore, by observing the sign of the formula k1'k2*-k2'k1*, the change trend of the variable capacitance Cx can be known.

[0106] However, after the device is initially installed, only the real-time measurement values u1' and u2' of the device can be obtained, and k1' and k2' cannot be obtained in real time. Variable substitution needs to be made to the determination formula, and the process is as follows:

[0107] The formula

[0108] and U'=k1'·u1'=k2'·u2' can be obtained:

[0109] Since

[0110] Therefore, the sign of k1'k2*-k2'k1* can be determined by using the response voltages u1' and u2', so as to identify whether the coupling capacitance Cx of the left and right mechanisms to ground changes. Step 2.2: According to the numerical characteristics of the variable ratio coefficient, a variable ratio coefficient adjustment model suitable for the change of the ground capacitance is established;

[0111] Let Δ=u2'·k2*-u1'·k1*, and according to the method of line search, the adjustment of the variable ratio can be written as the following formula:

[0112] k1 n+1 =k1 n +λ·Δ (50)

[0113] The variable ratio state can be judged and adjusted accordingly.

[0114]

[0115] ​​The key of equation (9) is to find the expression of step length λ, so that the step length of the variable ratio coefficient adjustment is appropriate. The derivation of the expression of step length λ is as follows:

[0116] For any moment, the response voltages measured by the left and right circuits should satisfy:

[0117] U=k1·u1=k2·u2 (51)

[0118] Taking the differential of both ends of the equation can obtain:

[0119] dk1·u1+k1·du1=dk2·u2+k2·du2 (52)

[0120] Through the discretization and arrangement of equation (11), the following equation can be obtained:

[0121] (k1 n+1 -k1 n )·u1=(k2 n+1 -k2 n )·u2+k2 n ·(u 2(n+1) -u 2(n) )-k1 n ·(u 1(n+1) -u 1(n) ) (53)

[0122] According to equations (2) and (3), the variable ratio coefficient is eliminated from the parameters Cx related to the height change, and the linear relationship of k1 and k2 is obtained as shown in the following equation:

[0123]

[0124] Taking the differential of both sides of equation (13) can obtain:

[0125]

[0126] Let Equation (14) is written in the discrete difference form as follows:

[0127] k1 n+1 -k1 n =w·(k2 n+1 -k2 n ) (56)

[0128] By combining equations (12) and (15), the following equation can be obtained:

[0129]

[0130] If k2 n , k1 nThe ratio at the calibration time is regarded as the variable ratio, and the corresponding voltage at the calibration time is u 1(n) , u 2(n) , that is,

[0131] k2 n = k2*, k1 n = k1*, u 1(n) = u1*, u 2(n) = u2* (58)

[0132] Since the calibration time must satisfy the condition: u2*·k2 n - u1*·k1 n = 0, the simultaneous equations (16) and (17) can be obtained:

[0133]

[0134] The measured value of the response voltage after calibration can be regarded as u 2(n+1) , u 1(n+1) . The step expression can be obtained from equation (18) and equation (9):

[0135]

[0136] In order to prevent the problem of incorrect iteration of the variable ratio k caused by the change of the measured value of the response voltage when the line voltage of 10kV fluctuates ±7%, an iteration start threshold tol is set here, and finally the algorithm suitable for the change of the variable ratio is established as follows:

[0137]

[0138] The step 3 includes the following steps:

[0139] Step 3.1: Design an experimental method for the step size w and the start threshold tol in the calibration adjustment algorithm:

[0140] The response voltages of the left and right circuits are measured at a certain lower height, and k1* and k2* are calibrated by the least square method respectively.

[0141] The range of the parameters w and tol needs to be given for the simulated annealing algorithm; regarding the range of the value of w: when the device is fixed relative to the power line, observe that equation (6) and w is actually the zero point of function (6), and since the function is monotonically decreasing, Regarding the value range of tol: when the device is erected at the same height, at this time, the formula (20) is only affected by the line voltage, so the threshold value of the ratio adjustment start should filter out the case of 10kV line voltage fluctuation ±7%, tol>=max(|u2'·k2*-u1'·k1*|)(u2', u1' corresponds to the response voltage measured when U fluctuates ±7%)

[0142] Optimize w, tol through the objective function (22) in the simulated annealing algorithm and the cost function difference (23) of the updated solution.

[0143]

[0144]

[0145] Where v(i) is the voltage after the ratio adjustment algorithm in the actual hanging line operation, v real is the voltage measured, and the parameters w, tol can be obtained after optimization. Thereafter, the non-contact voltage measurement will be completed with the experimental calibration value.

[0146] Step 3.2: Build a measurement hardware platform containing data acquisition and data processing modules, and test the error of the algorithm adjustment when the ground capacitance changes on the measurement hardware platform.

[0147] The voltage measurement system diagram built by the present application is shown in Figure 4 The system is composed of a non-contact voltage measurement double-circuit analog front end and a data processing part. The signal processing process of the system is as follows: first, the sinusoidal signal of the non-contact voltage measurement double response voltage is converted into a signal suitable for the ADC voltage amplitude 0-3.3V range in STM32 through the conditioning circuit; then, STM32 transmits the signal to the receiving end through the NRF24L01 communication module; in the receiving end, the signal is transmitted to the host computer through STM32 and the data is processed, the processing part includes the ratio adjustment algorithm and the calibration parameter method proposed in this paper. Finally, on the hardware platform built, the error of the inverse voltage after the algorithm adjustment is tested under the working condition of the device when the ground capacitance changes. The error of the inverse voltage after the algorithm adjustment is shown in Figure 6 .

[0148] The specific experiments of the calibration of the present application are as follows:

[0149] 1) When the line height is 80cm, the voltage regulation range is 4kV-12kV, and the voltage data measured by machine 1 and machine 2 is shown in Table 1. When the line height is 160cm, the voltage regulation range is 4kV-12kV, and the voltage measured by machine 1 and machine 2 is shown in Table 2.

[0150] Table 1 Voltage data measured in the experiment at 80cm

[0151]

[0152] Table 2 Experimental measurement of voltage data at 160cm

[0153]

[0154] 2) By least square of machine 1 voltage and input voltage in table 1, the ratio k1* = 18360 can be obtained, and the least square ratio of machine 2 voltage and input voltage k2* = 18360 can be obtained.

[0155] Substitute k1*, k2* into the algorithm and combine simulated annealing algorithm, as shown in the following formula: Figure 5 The convergence curve is shown in the following figure, and the total error converges to 0.4791 when tol = 35.5, w = 0.5102.

[0156] 3) Experimental based on tol, w of measured data

[0157] Table 3 Experimental measurement of voltage data at 160cm Tab.3Experimental measurement of voltage data at 160cm

[0158]

[0159]

[0160] Substitute the values of tol and w obtained by simulated annealing algorithm into the algorithm (20), and the ratio iteration calculation of the data in table 3 is carried out, and the error curve is attached Figure 6 When the height changes from 80cm to 160cm, the voltage measurement error obtained by iteration is less than 3.5%.

[0161] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A non-contact voltage measurement method with variable ratio parameter adaptive adjustment, characterized in that, The method comprises the following steps: Step 1: designing a double-circuit coupling mechanism for measuring single-phase voltage, combining the coupling capacitors between the inner and outer copper foils of the measuring device and the power line and the ground to obtain an equivalent circuit model of voltage measurement, and establishing a double-path response voltage equation based on the equivalent circuit model; Step 2: analyzing the numerical characteristics of the two-path variable ratios when the ground capacitance changes through the double-path response voltage equation, establishing an expression for judging the change of the ground capacitance according to the numerical characteristics of the variable ratio coefficients, and establishing a variable ratio coefficient adjustment algorithm that adapts to the change of the ground capacitance on the basis; Step 3: designing an experimental method for calibrating the step size w and the starting threshold tol in the adjustment algorithm; and building a measuring hardware platform comprising a data acquisition module and a data processing module.

2. The non-contact voltage measurement method with variable ratio parameter adaptive adjustment according to claim 1, characterized in that, The step 1 specifically comprises the following steps: Step 1.1: designing a double-circuit coupling mechanism for measuring single-phase voltage; The double-circuit coupling mechanism comprises a PVC pipe and two independent copper foil regions, and the inner and outer copper foils are attached to the inner and outer surfaces of the PVC pipe, respectively; the length of the inner copper foil in one region is the same as that of the outer copper foil; the length of the outer copper foil in the other region is the same as that of the outer copper foil in the left region, and the length of the outer copper foil is greater than that of the inner copper foil; the inner copper foils in the two independent copper foil regions are both air; Step 1.2: establishing an equivalent circuit model of voltage measurement about the coupling capacitors between the inner and outer copper foils of the measuring device and the power line and the ground; The coupling capacitance exists in one side copper foil area of the voltage measurement equivalent circuit model, the coupling capacitance C1 of the inner layer copper foil to the line, the coupling capacitance C w1 of the line to the outer layer copper foil, and the coupling capacitance C x of the outer layer copper foil to the ground; in There is also a coupling capacitor in the other side copper foil area of the voltage measurement equivalent circuit model: the coupling capacitor C2 of the inner layer copper foil in this side to the line, the coupling capacitor C w2 of the line to the outer layer copper foil, and the coupling capacitor of the outer layer copper foil to the ground, the ground height of the outer layer copper foil in both side areas is consistent, and is C x ; an equivalent circuit model of single-phase power line double-circuit measurement based on displacement current method is established through the coupling capacitor; According to the double-circuit measurement model, the length of the inner copper foil in the other region is half of that in one region, so there is: C1 + C w1 C2 + C w2 (1) Under the action of the ideal amplifier virtual short, the inner and outer copper foils on both sides are equivalent to be short-circuited, and the double-path response voltage equation is obtained through analysis: It can be seen from the above formula that the response voltages u1 and u2 of the measurement model have a linear relationship with the line voltage U, and the two-path variable ratios are defined as k1 and k2, respectively.

3. The variable ratio parameter self-adapting adjustment non-contact voltage measurement method according to claim 2, characterized in that, The step 2 specifically comprises the following steps: Step 2.1: analyzing the numerical characteristics of the two-path variable ratios when the ground capacitance changes through the double-path response equation, and establishing an expression for judging the change of the response voltage with the ground capacitance according to the numerical characteristics of the variable ratio coefficients: When the device measuring circuit is erected on two independent lines, the response voltages in the two measuring circuits are divided, that is, the variable ratios are divided to obtain the following formula: Through formula (4) and formula (1), the following characteristics are obtained: Since As the outer layer copper foil to ground capacitance Cx increases monotonically decreases, so according to The change trend of the ground capacitance Cx is judged according to the change trend of In the device preliminary installation carries on the ratio of the calibration, set device installation, Cx = Cx*, and set this time two sides circuit corresponding ratio respectively: k1*, k2*; set in the calibration after any time, two sides circuit outside copper skin to the ground coupling capacitance receives the same interference, this time to the ground capacitance change Cx = Cx', corresponding two sides ratio k1', k2', by Monotonicity of the following conclusions: Cx* < Cx' when, i.e. k1'k2* - k2'k1* < 0 Cx* = Cx' when, i.e. k1'k2* - k2'k1* = 0 Therefore, the change trend of the variable capacitance Cx is obtained through the sign of formula k1′k2*-k2′k1*; The real-time k1′ and k2′ are obtained through variable substitution on the judgment formula, and the process is as follows: Simultaneous equations and U' = k1' - u1' = k2' - u2' gives: Since Therefore, the sign of k1'k2*-k2'k1*is determined by the measured values of the response voltages u1', u2', and whether the coupling capacitances Cx of the two sides to ground have changed is identified. Step 2.2: establishing a variable ratio coefficient adjustment model that adapts to the change of the ground capacitance according to the numerical characteristics of the variable ratio coefficients; Let Δ=u2′·k2*-u1′·k1*, and the adjustment of the variable ratio is expressed as the following formula according to the line search method: k1 n+1 = k1 n + λ · Δ (8) to implement the variable ratio state judgment and make variable ratio adjustment accordingly; The expression of the step size λ is found to optimize the step size of the variable ratio coefficient adjustment, and the expression of the step size λ is derived as follows: For any moment, the response voltages measured by the two sides satisfy the following formula: U=k1·u1=k2·u2 (9) The differential of both ends is taken to obtain: dk1·u1+k1·du1=dk2·u2+k2·du2 (10) Through discrete arrangement of formula (10), the following formula is obtained: (k1 n+1 -k1 n )·u1= (k2 n+1 -k2 n )·u2+ k2n·(u 2(n+1) -u 2(n) ) - k1n·k(u 1(n+1) -u 1(n) ) (11) According to formula (2), (3), the variable ratio coefficient eliminates the parameters Cx related to the change of height, and k1, k2 satisfy the linear relationship shown in the following formula: Simultaneously differentiating both sides of formula (12) gives: Let Equation (13) can be written in discrete difference form as follows: k1 n+1 -k1 n = w · (k2 n+1 -k2 n ) (14) Simultaneously formula (11), (14) gives: If k2n, k1n are regarded as the variable ratio at the calibration, the corresponding voltage at the calibration is u 2(n) That is: k2 n = k2*, k1 n = k1*, u 1(n) = u1*, u 2(n) = u2* (16) Since the condition must be satisfied at the calibration time: u2* · k2 n - u1* · k1 n = 0, the equations (15), (16) can be solved simultaneously. The measured value of the response voltage after calibration is considered as u 2(n+1) ,u 1(n+1) The step expression is obtained from equation (17) and equation (8): Set the iteration start threshold tol, and the algorithm suitable for variable ratio change is as follows:

4. The non-contact voltage measurement method of variable ratio parameter self-adaptive adjustment according to claim 3, characterized in that, The step 3 specifically comprises the following steps: Step 3.1: design the experimental method of step length w and start threshold tol in the calibration adjustment algorithm: At a height of the erected, the response voltages of the two sides of the circuit are measured, and k1* and k2* are calibrated by the least square method respectively; Based on the simulated annealing algorithm, the range of given parameters w, tol; the range of w: when the device is fixed relative to the power line, according to formula (5) and w is the zero point of function (5), and it is monotonically decreasing from the function The range of tol: when the device is erected at the same height, at this time, Δ = u2'·k2*-u1'·k1* in formula (19) is only affected by the line voltage, so the threshold of the transformation ratio adjustment start filters out the case of ±7% fluctuation of 10kV line voltage, tol≥max(|u2'·k2*-u1'·k1*|), where u2', u1' correspond to the response voltage measured when U fluctuates ±7%. Through the objective function (20) in the simulated annealing algorithm and the cost function difference (21) of the updated solution, w and tol are optimized; Where v(i) is the voltage after the transformation ratio adjustment algorithm during actual string operation, v real is the actual measured voltage, and the parameters w and tol are obtained through optimization to complete the non-contact voltage measurement with the experimental calibration value. Step 3.2: build a measurement hardware platform containing data acquisition and data processing module: on the built hardware platform, the error of the adjusted inverse voltage is tested under the working condition of the change of the device to ground capacitance.

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