Method for measuring the impulse impedance of a power transmission tower and power transmission tower arrangement

Abstract

The application discloses a kind of transmission tower impact impedance measurement method and transmission tower device, the method comprises: obtaining the network equivalent circuit model of transmission tower under lightning state ground connection;According to the network equivalent circuit model, the impedance-frequency characteristic function of the transmission tower is obtained;According to the field measured data, the impedance modulus value of transmission tower under different frequencies is obtained;According to the characteristic function and the field measured data, the fitting curve of frequency-impedance modulus value is obtained;According to the fitting curve, the impact impedance value of the transmission tower corresponding to lightning state is obtained.The technical scheme provided by the application can quickly obtain accurate and effective impact grounding impedance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-voltage electric technology, and in particular to a method for measuring impulse impedance of a power transmission tower and a power transmission tower device. BACKGROUND

[0002] The grounding of a power transmission tower is crucial to the safe and stable operation of a power system. When a lightning strikes the tower top or the lightning conductor, the lightning current flows into the ground through the tower grounding device. The main impact of lightning directly hitting the tower or the lightning conductor is the extremely high transient ground potential rise caused by the lightning current flowing through the tower grounding device, which causes back strike. Therefore, the impulse grounding impedance of the tower grounding device is the main indicator for measuring the lightning protection performance of the tower.

[0003] The impulse grounding impedance of the tower grounding network is closely related to the waveform and amplitude of the impulse current. The impulse grounding characteristics and lightning current dispersion characteristics are quite different from the power frequency steady-state grounding characteristics. Under a lightning impulse current, the tower grounding network has two opposite effects, namely, the nonlinear spark characteristic and the inductive characteristic, and the complexity is large due to the different types, sizes, and soil characteristics of the grounding device.

[0004] The current method for obtaining the impulse grounding impedance of the tower grounding device cannot well meet the requirements of convenience, accuracy, and reliability, and it is not easy to obtain accurate impulse grounding impedance data, so it is not easy to control the lightning protection performance of the tower. SUMMARY

[0005] The embodiments of the present application provide a method for measuring the impulse impedance of a power transmission tower and a power transmission tower device to quickly obtain accurate and effective impulse grounding impedance.

[0006] In a first aspect, the embodiments of the present application provide a method for measuring the impulse impedance of a power transmission tower, comprising:

[0007] obtaining a network equivalent circuit model of the grounding of the power transmission tower in a lightning strike state;

[0008] obtaining a characteristic function of impedance-frequency of the power transmission tower according to the network equivalent circuit model;

[0009] obtaining the impedance modulus of the power transmission tower at different frequencies according to the field measurement data;

[0010] obtaining a fitting curve of frequency-impedance modulus according to the characteristic function and the field measurement data;

[0011] obtaining the impulse impedance value of the power transmission tower corresponding to the lightning strike state according to the fitting curve.

[0012] Secondly, embodiments of the present invention also provide a power transmission tower device, the power transmission tower device comprising: a power transmission line, a grounding grid, an impulse impedance measuring device, and multiple power transmission towers; the power transmission line is used to connect the multiple power transmission towers; each of the power transmission towers is connected to the grounding grid;

[0013] The impact impedance measuring device is used to perform the method for measuring the impact impedance of transmission towers provided in any embodiment of the present invention.

[0014] In this invention, an equivalent circuit model of the transmission tower under lightning strike conditions is obtained based on the constructed transmission tower device. The impedance-frequency characteristic function of the transmission tower is then derived from this model. The frequency-impedance magnitude of the transmission tower measured on-site is substituted into the impedance-frequency characteristic function to obtain a fitting curve of the frequency-impedance magnitude. The impulse impedance value of the transmission tower under lightning strike conditions is then obtained based on this fitting curve. This invention, through a combination of on-site measured data and simulation, considers the inductive effects and spark discharge effects of high-current transmission lines, the tower itself, and the grounding conductor under lightning strike conditions. This allows for convenient and accurate acquisition of the impulse grounding impedance of the grounding device, improving the reliability of transmission tower impulse impedance measurement. Attached Figure Description

[0015] Figure 1 A schematic flowchart illustrating a method for measuring the impact impedance of a transmission tower according to an embodiment of the present invention;

[0016] Figure 2 This is a schematic diagram of the structure of a power transmission tower device under lightning strike conditions, provided by an embodiment of the present invention.

[0017] Figure 3 for Figure 2 A schematic diagram of the network equivalent circuit model of a China transmission tower.

[0018] Figure 4 A schematic flowchart illustrating another method for measuring the impact impedance of a transmission tower provided in an embodiment of the present invention;

[0019] Figure 5 A schematic diagram of a frequency-impedance modulus fitting curve provided in an embodiment of the present invention;

[0020] Figure 6 This is a simulation diagram of the power transmission tower device provided in an embodiment of the present invention;

[0021] Figure 7 This is a schematic diagram of another power transmission tower device provided in an embodiment of the present invention. Detailed Implementation

[0022] The application will be described in further detail below with reference to the drawings and embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application. In addition, it should be noted that, for the sake of brevity, only the parts of the drawings that are related to the present application are shown.

[0023] Currently, the acquisition of the impulse grounding resistance (impulse impedance) mainly includes the following three ways:

[0024] First, based on power frequency test and impulse coefficient empirical formula. At present, in the lightning protection practice of transmission lines, the evaluation of the tower grounding device is still based on the measured results of the tower power frequency grounding resistance, and the impulse coefficient of different types of tower grounding devices is obtained according to the empirical calculation formula given in the relevant standards (such as GB / T 50065 "Design Specification for Grounding of AC Electrical Installations") and the impulse grounding impedance is calculated. Although this method is simple and easy to implement, the empirical formula recommended in the relevant standards is a fitting value obtained through experiments, and these experiments are conducted under specific experimental conditions. However, the working conditions in actual use cannot completely match the above experimental conditions, so the impulse grounding resistance obtained by this method has a large error. Moreover, the relevant standards are obtained based on different shapes of grounding devices, and the shape of the buried grounding device may not be known, so the above relevant standards are no longer applicable.

[0025] Second, based on impulse current field test. In order to obtain the grounding resistance of the grounding device under lightning current impulse, a large current impulse test can also be directly conducted. The main idea of this method is to apply actual amplitude level current impulse wave to the actual tower grounding net, at least to produce soil spark discharge, and a large power mobile high-voltage impulse current generator capable of generating lightning waveform with amplitude between 1kA and 100kA and a large measurement system need to be built on site. However, this method has a large workload, and large-scale measurement is not practical at present. It is currently only in the theoretical and basic research of impulse grounding impedance measurement method. Due to the limitations of technical conditions, large impulse current test equipment and field test conditions, it is difficult to realize the measurement of impulse characteristics under real lightning wave amplitude level for different types of towers and different soil conditions, and it does not yet have the conditions for practical field measurement and application.

[0026] Third, based on numerical simulation. The method is based on the electromagnetic field numerical calculation method and the vector matching method to study the transmission line tower impulse impedance and the equivalent circuit model. First, the impedance frequency domain characteristic function of the tower is analyzed by the electromagnetic field numerical software, and then the tower frequency response is calculated and fitted, and then the network synthesis method is used to establish the equivalent circuit model of the tower, so as to obtain the potential change of any part of the tower when any point of the tower is struck by lightning, and then the possible discharge channel overvoltage situation can be simulated, which is used to analyze the lightning back strike process of the transmission line tower. However, in fact, the premise of this fitting method is that the material and structure parameters of the tower itself are known, and the soil resistivity stratified structure is assumed to be a strict horizontal or vertical structure, which obviously does not match the actual situation. Therefore, the results obtained by using the numerical calculation method cannot fully reflect the real situation of the soil, so the simulation results are unreliable.

[0027] As can be seen from the above, the three methods of obtaining the impulse grounding impedance of the grounding device cannot well meet the requirements of convenience, accuracy and reliability. In order to meet the above test requirements and obtain relatively accurate impulse grounding impedance, the embodiment of the present application provides a method for measuring the impulse impedance of a transmission tower, as shown in Figure 1 Figure 1 The flowchart of the method for measuring the impulse impedance of a transmission tower provided by the embodiment of the present application is shown in the figure, and the specific steps are as follows:

[0028] Step S101, obtaining the network equivalent circuit model of the transmission tower grounding under lightning state.

[0029] Because the current frequency is high under lightning state, and there is a certain destructive and dangerous, the actual environment of the transmission tower under lightning state is difficult to simulate or test, and the embodiment is based on the actual arrangement of the transmission tower device to build the network equivalent circuit model of the transmission tower grounding under lightning state. As shown in Figure 2 Figure 2 The structure diagram of the transmission tower device under lightning state provided by the embodiment of the present application is shown in the figure, and the lightning tower device includes a plurality of transmission towers 21, and the adjacent transmission towers 21 are connected by transmission lines 22, so as to complete high-voltage power transmission. In addition, in order to withstand lightning state, each transmission tower 21 is connected to the grounding net 23, and the high-frequency current of lightning is transmitted to the grounding net 23, so as to prevent the transmission tower 21 from being damaged and improve the reliability of high-voltage power transmission of the transmission tower device.

[0030] As can be seen, the transmission tower device includes the transmission tower 21, the transmission line 22 and the grounding net 23, and when building the network equivalent circuit model, the parameters of the above parts need to be considered, so as to realize a model closer to the actual transmission tower device, and then the accuracy of the subsequent impulse impedance measurement. ​​

[0031] Optionally, the network equivalent circuit model of the grounding of the power transmission tower under lightning stroke state can comprise: obtaining parameters of a measurement loop of the power transmission tower under lightning stroke state; the parameters of the measurement loop of the power transmission tower at least comprise power transmission line parameters, tower parameters and grounding net parameters; and obtaining the network equivalent circuit model of the power transmission tower according to the parameters of the measurement loop of the power transmission tower. In order to obtain the network equivalent circuit model of the grounding of the power transmission tower under lightning stroke state, it is necessary to obtain the parameters of the grounding loop (measurement loop) of the power transmission tower under lightning stroke state, and the parameters of the grounding loop (measurement loop) of the power transmission tower under lightning stroke state can be obtained by the method for obtaining the network equivalent circuit model of the grounding of the power transmission tower under lightning stroke state. Figure 2 It can be known that the parameters of the measurement loop of the power transmission tower at least comprise power transmission line parameters, tower parameters and grounding net parameters. The power transmission line parameters, the tower parameters and the grounding net parameters can be equivalent to the power transmission line, the power transmission tower itself and the grounding net respectively in the network equivalent circuit model. Thus, the embodiment can build a more accurate network equivalent circuit model of the power transmission tower according to the above-mentioned parameters of the measurement loop of the power transmission tower. In addition, it needs to be noted that when the measurement loop of the power transmission tower or the grounding loop of the power transmission tower comprises other components, the parameters corresponding to the other components also need to be obtained to build the network equivalent circuit model. For example, the power transmission tower is also connected with other discharge devices, and the parameters of the other discharge devices need to be referred to to build the network equivalent circuit model, that is, the network equivalent circuit model needs to be set according to the actual or current connection structure of the power transmission tower device, and the embodiment does not limit the specific connection structure of the power transmission tower device.

[0032] In step S102, the impedance-frequency characteristic function of the power transmission tower is obtained according to the network equivalent circuit model.

[0033] According to the above-mentioned network equivalent circuit model, the equivalent equation about the power transmission tower device can be listed, and because each parameter of the network equivalent circuit model is related to the current cycle (frequency) of the test loop, the above-mentioned equivalent equation can finally be transformed into the impedance-frequency characteristic function of the power transmission tower.

[0034] In step S103, the impedance modulus value of the power transmission tower under different frequencies is obtained according to the field measurement data.

[0035] Because the frequency under the lightning state is high, for example, generally reaches 1MHz or more, the test condition is not easy to achieve. The present application can obtain the on-site measured data in the low frequency range, for example, the actual measurement is carried out on the low frequency environment in the range of 45Hz-20kHz, so that the impedance module value of the transmission tower under different frequencies is obtained. In the embodiment, the impedance module value refers to that, for the high frequency lightning signal, the transmission line parameters, tower parameters and ground net parameters in the transmission tower form a loop in turn, so that the impedance between the two ends of the high frequency lightning signal is the impedance module value of the transmission tower, which can also be called the port impedance module value of the high frequency lightning signal. The impedance module value refers to that, under the on-site measurement condition of the transmission tower impulse impedance, the measurement value of a certain impedance corresponds to the measurement value of the frequency of the transmission tower.

[0036] Step S104, obtaining the fitting curve of the frequency-impedance module value according to the characteristic function and the on-site measured data.

[0037] The on-site measured data has high accuracy. In the embodiment, the measurement data of the frequency-impedance module group in the series of on-site measured data can adjust and correct the characteristic function of the impedance-frequency of the transmission tower obtained according to the network equivalent circuit model, so that the parameters in the characteristic function tend to be more actual data, and the fitting curve of the frequency-impedance module value obtained according to the characteristic function tends to be more close to the corresponding value of the frequency-impedance of the transmission tower under the actual condition. The corresponding relationship of the frequency-impedance under the lightning state (high frequency) obtained according to the fitting curve is more accurate, so that the impedance module value of the fitting curve under the specific high frequency (lightning state) is found, and the impedance module value is the impulse impedance value of the transmission tower corresponding to the lightning state. Therefore, the impulse impedance value is more close to the actual data, and the accuracy of obtaining the impulse impedance value is improved.

[0038] Step S105, obtaining the impulse impedance value of the transmission tower corresponding to the lightning state according to the fitting curve.

[0039] In the embodiment of the present application, the network equivalent circuit model of the transmission tower under the lightning state is obtained according to the transmission tower device built, and the characteristic function of the impedance-frequency of the transmission tower is obtained according to the model. The on-site measured frequency-transmission tower impedance module value is substituted into the characteristic function of the impedance-frequency of the transmission tower, so that the fitting curve of the frequency-impedance module value is obtained, and the impulse impedance value of the transmission tower under the lightning state is obtained according to the fitting curve. The present application only needs to combine the on-site measured data and the simulation in the first end, considers the inductive effect and spark discharge effect of the impulse high current transmission line, tower itself and grounding conductor under the lightning state, conveniently and accurately obtains the impulse grounding impedance of the grounding device, and improves the reliability of the measurement of the transmission tower impulse impedance.

[0040] The above is the core idea of ​​this invention. The technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0041] This invention proposes a method for effectively obtaining impulse impedance values ​​based on low-frequency impedance measurement data of transmission towers. First, it studies and analyzes the network equivalent state parameter circuit model corresponding to the grounding of transmission towers under lightning strike conditions. Based on this circuit model, a third-order frequency domain characteristic function of the tower impedance is proposed. Port impedance magnitudes at different frequencies (45Hz–20kHz) are obtained based on field measurement data. Using the third-order function and low-frequency measurement data, a minimum variance iterative solution is applied to obtain the fitting curve and correlation coefficient between frequency and impedance magnitude. The impulse impedance value of the tower under lightning strike conditions is obtained based on the impedance value in the measurable frequency band, thereby accurately evaluating the state of the transmission tower grounding device.

[0042] like Figure 3 As shown, Figure 3 for Figure 2 A schematic diagram of the network equivalent circuit model of a transmission tower. Optionally, obtaining the network equivalent circuit model of the transmission tower based on the parameters of the measurement loop of the transmission tower may include: connecting the impedance of the transmission line, the impedance of the tower, and the impedance of the tower grounding device in series; and connecting the impedance of the transmission line to the impedance of the tower grounding device through a lightning current source AC.

[0043] according to Figure 2 and Figure 3 As can be seen, for the lightning signal loop, that is, the measurement loop of the transmission tower in this embodiment, the lightning current source AC, the impedance of the transmission line, the impedance of the tower, and the impedance of the tower grounding device are connected sequentially, and the lightning current source AC is connected to the impedance of the tower grounding device. Thus, the lightning current source AC, the impedance of the transmission line, the impedance of the tower, and the impedance of the tower grounding device form a loop. The resistance value measured across the lightning current source AC is the port impedance modulus of the measurement loop of the transmission tower.

[0044] Continue to refer to Figure 3Optionally, the impedance of the transmission line may include a first resistor R1 and a first capacitor C1 connected in parallel; the impedance of the tower may include a second resistor R2, a second capacitor C2, and a first inductor L1 connected in parallel; and the tower grounding device may include a third resistor R3 and a second inductor L2 connected in series. Because different components have different impedances—for example, the impedance of the transmission line has capacitive impedance, while the impedance of the tower grounding device is more inclined towards inductive impedance, and the impedance of the tower includes both capacitive and inductive impedance—this embodiment sets the impedance of the transmission line in the network equivalent circuit model to include a first resistor R1 and a first capacitor C1 connected in parallel, the tower grounding device to include a third resistor R3 and a second inductor L2 connected in series, and the tower impedance to include a second resistor R2, a second capacitor C2, and a first inductor L1 connected in parallel, thereby more accurately reflecting the specific impedance values ​​of different components.

[0045] In another embodiment, the specific steps for obtaining the characteristic function are described in detail, such as... Figure 4 As shown, Figure 4 A flowchart illustrating another method for measuring the impact impedance of a transmission tower provided in an embodiment of the present invention is shown, which specifically includes the following steps:

[0046] Step S201: Obtain the equivalent circuit model of the grounding network of the transmission tower under lightning strike conditions.

[0047] For example, such as Figure 3 As shown, the impedance of the transmission line, the impedance of the tower, and the impedance of the tower grounding device are connected in series. The impedance of the transmission line is connected to the impedance of the tower grounding device through the lightning current source AC. Then, the impedance of the transmission line, the impedance of the tower, the impedance of the tower grounding device, and the lightning current source form a loop. This loop is the network equivalent circuit model of the transmission tower grounding under lightning conditions.

[0048] Step S202: Obtain the impedance formula Z = Z1 + Z2 + Z3 of the network equivalent circuit model; where Z1 is the impedance of the transmission line; Z2 is the impedance of the tower; Z3 is the impedance of the tower grounding device; and Z is the impedance of the transmission tower.

[0049] Step S203: Substitute ω=2πf into the impedance formula to obtain the impedance-frequency multi-order equation of the transmission tower.

[0050] Step S204: Convert the multi-order equation of impedance-frequency of the transmission tower into a triangular form characteristic function of impedance-frequency of the transmission tower.

[0051] Steps S202 to S204 are the specific operations of step S102 above, "obtaining the impedance-frequency characteristic function of the transmission tower based on the network equivalent circuit model".

[0052] based on Figure 3The network equivalent circuit model shown can be used to propose the third-order frequency domain characteristic function of the transmission tower's impedance. For example, based on the KVL equations in circuit theory, the equations are derived and solved as follows:

[0053] Z = Z1 + Z2 + Z3 (1)

[0054]

[0055]

[0056]

[0057]

[0058]

[0059] Substituting ω = 2πf into the above formula, we get...

[0060]

[0061] From the above formula (7), we know that Z = F(f 2 The impedance is a second-order equation about frequency. Since formula (7) is expressed in the algebraic form of complex numbers, for the convenience of curve fitting analysis, the above formula is transformed into a third-order trigonometric function as follows:

[0062] y=a0+a1 cos(x*w)+b1 sin(x*w)+a2 cos(2*x*w)+b2 sin(2*x*w)+a3 cos(3*x*w)+b3 sin(3*x*w) (8)

[0063] It is important to note that ω refers to angular frequency, a physical quantity that describes how fast an object vibrates, and the unit of angular frequency is radians per second (rad / s); y is the impedance of the transmission tower; and x is the current frequency of the test circuit of the transmission tower.

[0064] Step S205: Obtain the impedance modulus of the transmission tower at different frequencies based on the on-site measured data.

[0065] The field-measured data are impedance-frequency pairs actually measured on the transmission towers. Currently, the instrument can measure frequencies below 20kHz, as shown in Table 1 below. Table 1 shows the impedance-frequency comparison values ​​obtained from the field-measured data. The table below shows multiple sets of field-measured data within the range of 45Hz to 20kHz. Because the field-measured data is relatively accurate, the impedance of the transmission tower at different frequencies can be recorded separately, which we can call the impedance modulus.

[0066] Table 1: Impedance-Frequency Comparison Values ​​Obtained from Field Measurements

[0067]

[0068] Step S206: Using the minimum variance iteration method, the field measured data are substituted into the characteristic function in sequence.

[0069] Step S207: Obtain the coefficients of the characteristic function based on the field measured data, thereby obtaining the fitting curve of frequency-impedance modulus.

[0070] Steps S206 to S207 above are the specific steps of step S104 above, "obtaining the fitting curve of frequency-impedance magnitude based on the characteristic function and field measured data." In this embodiment, when determining and correcting the coefficients of the above characteristic function, the above multiple sets of field measured data can be directly substituted, and multiple sets of different multivariate linear equations can be obtained through impedance data at multiple different frequencies. By solving multiple sets of equations, the coefficients of each term of the characteristic function can be obtained, thereby determining the characteristic function. This characteristic function can yield a fitting curve of frequency-impedance magnitude. Because this fitting curve is obtained based on field measured data, it is close to the accurate data.

[0071] Furthermore, to further improve the accuracy of obtaining the coefficients of the characteristic function, the variance of the discrete data is first obtained through discrete impedance-frequency reference values. The minimum variance is then identified, and the coefficients of the characteristic function are determined using the minimum variance iteration method. This yields a fitting curve for the frequency-impedance magnitude. Compared to directly substituting the impedance-frequency reference values ​​into the characteristic function, this method further improves the accuracy of the coefficients, thereby enhancing the accuracy of the fitting curve for the frequency-impedance magnitude.

[0072] For example, such as Figure 5 As shown, Figure 5 This is a schematic diagram of a frequency-impedance magnitude fitting curve provided in an embodiment of the present invention. The horizontal axis represents frequency (Hz), and the vertical axis represents impedance magnitude (Ω). By using a characteristic function and field measurement data, and employing minimum variance iteration, the fitting curve and correlation coefficients between frequency and impedance magnitude are obtained. For example, the fitting coefficients are: a0 = 108.4; a1 = -22.26; b1 = -37.23; a2 = -116.6; b2 = -23.56; a3 = 32.47; b3 = 39.32; w = 1.882e-6. Therefore, the impulse impedance at 1MHz (lightning state) is approximately 190Ω.

[0073] Step S208: Obtain the frequency value corresponding to the current lightning strike state; substitute the frequency value into the fitting curve to obtain the impulse impedance value of the transmission tower corresponding to the current lightning strike state.

[0074] Optionally, obtaining the impulse impedance value of the transmission tower corresponding to the lightning strike state based on the fitted curve may include: obtaining the frequency value corresponding to the current lightning strike state; substituting the frequency value into the fitted curve to obtain the impulse impedance value of the transmission tower corresponding to the current lightning strike state. This embodiment obtains a relatively accurate frequency-impedance modulus fitting curve using field measurement data. This fitting curve also includes the high-frequency range. Although it is difficult to simulate high-frequency currents in the actual environment, the impedance corresponding to high frequencies can be obtained from the aforementioned fitting curve. This embodiment obtains the frequency corresponding to the lightning strike state (high-frequency state) and obtains the impedance value on the fitted curve corresponding to that frequency. This impedance value is the impulse impedance value of the transmission tower corresponding to the current lightning strike state.

[0075] Based on the above embodiments, optionally, the method for measuring the impulse impedance of transmission towers may further include: verifying the fitted curve based on the parameters of a typical transmission tower measurement loop. Optionally, verifying the fitted curve based on the parameters of a typical transmission tower measurement loop may include: substituting the network equivalent circuit model into the parameters of the typical transmission tower measurement loop to obtain the simulated impulse impedance value of the transmission tower; comparing the simulated impulse impedance value with the impulse impedance value of the transmission tower obtained from the fitted curve to verify the fitted curve. The parameters of the aforementioned typical transmission tower measurement loop can be selected from commonly used parameters, or the parameters can be set within a conventional range; this embodiment does not limit this. The accuracy of the fitted curve is verified by comparing the simulated impulse impedance value obtained from the software simulation with the impulse impedance value of the transmission tower obtained from the fitted curve.

[0076] The error verification method in this invention can simulate a network equivalent circuit model using typical data parameters and compare the simulation results with the impedance values ​​calculated from the derived function. For example, ... Figure 6 As shown, Figure 6 The diagram below is a simulation illustration of a power transmission tower device provided in an embodiment of the present invention. The first resistance R1 of the transmission line is 0.02205Ω, and the first capacitor C1 is 10μF. The second resistance R2 of the tower is 200Ω, the second capacitor C2 is 2232.3pF, and the first inductance L1 is 8.57μH. The third resistance R3 of the tower grounding device is 2Ω, and the second inductance L2 is 8.57μH.

[0077] As shown in Table 2 below, Table 2 compares the theoretical simulation values ​​and the analytical values ​​of the characteristic function of the transmission tower at different frequencies. Based on the above error data analysis, it can be seen that the maximum error is 0.44Ω at a frequency of 20kHz, and the error is only 0.1Ω near the lightning strike frequency of 1MHz. Therefore, the impulse impedance measurement method for transmission towers in this embodiment of the invention has high accuracy.

[0078] Table 2: Comparison of theoretical simulation values ​​and analytical values ​​of characteristic functions for transmission towers at different frequencies

[0079]

[0080]

[0081] This invention also provides a power transmission tower device. Figure 7 This is a schematic diagram of another power transmission tower device provided in an embodiment of the present invention. The power transmission tower device includes: a power transmission line 22, a grounding grid 23, an impulse impedance measuring device 24, and multiple power transmission towers 21. The power transmission line 22 is used to connect multiple power transmission towers 21. Each power transmission tower 21 is connected to the grounding grid 23. The impulse impedance measuring device 24 is used to perform the power transmission tower impulse impedance measurement method of any embodiment of the present invention.

[0082] The transmission tower device provided in this invention includes the technical features of the method for measuring the impulse impedance of transmission towers provided in any embodiment of this invention, and possesses the beneficial effects of the corresponding technical features. The transmission tower device provided by this invention can conveniently, accurately, and reliably obtain the impulse grounding resistance of the grounding device by combining on-site measured data and simulation, considering the inductive effect and spark discharge effect of the transmission line, the tower itself, and the grounding conductor under the action of a large impulse current. This results in a more accurate and referable final impulse grounding resistance value. It improves the reliability of the transmission tower impulse impedance measurement, effectively saves measurement and labor costs, and is not limited by the environment in which the transmission tower is located, improving the adaptability of the transmission tower device to various environments. For example, in areas where it is difficult to simulate lightning conditions due to geographical or weather conditions, the transmission tower device shown in this invention can be installed. This allows for accurate acquisition of the transmission tower impulse impedance under lightning conditions, precise control of the transmission tower, and expansion of the installation range of the transmission tower device, facilitating the transmission of high-voltage signals in various locations and improving the user experience.

[0083] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A method for measuring the impulse impedance of a transmission tower, characterized in that, include: Obtain the network equivalent circuit model of the transmission tower grounded under lightning strike conditions; The impedance-frequency characteristic function of the transmission tower is obtained based on the network equivalent circuit model. The impedance modulus of the transmission tower at different frequencies was obtained based on on-site measured data. Based on the characteristic function and the field measured data, the fitting curve of frequency-impedance modulus is obtained; The impulse impedance value of the transmission tower corresponding to the lightning strike state is obtained based on the fitted curve. The process of obtaining the network equivalent circuit model of the transmission tower grounded under lightning strike conditions includes: The parameters of the measurement circuit of the transmission tower under lightning strike conditions are obtained; the parameters of the measurement circuit of the transmission tower include at least the transmission line parameters, tower parameters, and grounding grid parameters. The network equivalent circuit model of the transmission tower is obtained based on the parameters of the measurement circuit of the transmission tower. The network equivalent circuit model of the transmission tower is obtained based on the parameters of the measurement loop of the transmission tower, including: The impedance of the transmission line, the impedance of the tower, and the impedance of the tower grounding device are connected in series; and the impedance of the transmission line is connected to the impedance of the tower grounding device through a lightning current source. The impedance-frequency characteristic function of the transmission tower is obtained based on the network equivalent circuit model, including: The impedance formula for the equivalent circuit model of the network is obtained as Z = Z1 + Z2 + Z3; where Z1 is the impedance of the transmission line; Z2 is the impedance of the tower; Z3 is the impedance of the tower grounding device; and Z is the impedance of the transmission tower. Substituting ω=2πf into the impedance formula, we obtain the multi-order impedance-frequency equation of the transmission tower. The impedance-frequency multi-order equation of the transmission tower is transformed into a trigonometric characteristic function of the impedance-frequency of the transmission tower.

2. The method for measuring the impulse impedance of a transmission tower according to claim 1, characterized in that, The impedance of the transmission line includes a first resistor and a first capacitor connected in parallel; The impedance of the tower includes a second resistor, a second capacitor, and a first inductor connected in parallel; The tower grounding device includes a third resistor and a second inductor connected in series.

3. The method for measuring the impact impedance of transmission towers according to claim 1, characterized in that, Based on the characteristic function and the field measured data, a fitting curve for the frequency-impedance modulus is obtained, including: The minimum variance iteration method is used to sequentially substitute the field measured data into the characteristic function; The coefficients of the characteristic function are obtained based on the field measurement data, thereby obtaining the fitting curve of the frequency-impedance modulus.

4. The method for measuring the impulse impedance of a transmission tower according to claim 1, characterized in that, The impulse impedance value of the transmission tower corresponding to the lightning strike state is obtained based on the fitted curve, including: Get the frequency value corresponding to the current lightning strike status; The frequency value is substituted into the fitted curve to obtain the impulse impedance value of the transmission tower corresponding to the current lightning strike state.

5. The method for measuring the impact impedance of a transmission tower according to claim 1, characterized in that, Also includes: The fitted curve was verified based on the parameters of the measurement loop of a typical transmission tower.

6. The method for measuring the impact impedance of a transmission tower according to claim 5, characterized in that, The fitted curve was validated based on parameters of a typical transmission tower's measurement loop, including: The simulated impulse impedance value of the transmission tower is obtained by substituting the network equivalent circuit model into the parameters of the measurement loop of a typical transmission tower. The simulated impact impedance value is compared with the impact impedance value of the transmission tower obtained from the fitted curve to verify the fitted curve.

7. A transmission tower device, characterized in that, include: Transmission lines, grounding grids, impulse impedance measuring devices, and multiple transmission towers; The transmission line is used to connect the plurality of transmission towers; each of the transmission towers is connected to the grounding grid; The impact impedance measuring device is used to perform the method for measuring the impact impedance of transmission towers as described in any one of claims 1-6.

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