A lightning stroke overvoltage detection method and device for a same-tower multi-loop transmission line

Abstract

The application provides a lightning overvoltage detection method and device for a same-tower multi-circuit transmission line. First, the coupling impedance between cross lines at a cross line position in the same-tower multi-circuit transmission line, the cross line head voltage and the cross line head current are obtained. An equivalent impedance matrix of the cross line is constructed through the coupling impedance. The cross line end voltage is calculated according to the equivalent impedance matrix, the cross line head voltage and the cross line head current. Then, a cross line model is established through the equivalent impedance matrix, the cross line head voltage, the cross line head current and the cross line end voltage. A parallel line model is established for the parallel line behind the cross line. Finally, a simulation model is established through the cross line model and the parallel line model. The simulation model is simulated to calculate the lightning overvoltage of the cross line. The lightning overvoltage characteristics obtained by the application are close to the actual working conditions, and the accuracy of lightning level detection of the same-tower multi-circuit transmission line is improved.

Description

Technical Field

[0001] This application relates to the field of power grid construction technology, and in particular to a method and device for detecting lightning overvoltage in multi-circuit transmission lines on the same tower. Background Technology

[0002] With my country's rapid economic growth, the voltage levels and transmission distances of power transmission lines have significantly increased, and user electricity demand has also surged, accelerating the extraordinary development of my country's power grid construction. On the one hand, due to limitations imposed by urban development plans in some cities, land resources for power transmission line construction are limited, so construction and upgrades can only be carried out based on existing transmission line corridors. On the other hand, with the continuous expansion of power grid construction, given a fixed voltage level, the only option is to increase the number of transmission lines. Therefore, multi-circuit lines on the same tower are commonly used. However, compared to single-circuit lines of the same voltage level, multi-circuit lines on the same tower have taller towers and poorer lightning protection. Therefore, the line's backflashover withstand level is low, and lightning-induced tripping problems frequently occur.

[0003] To avoid lightning-induced power outages, lightning withstand levels are measured and lightning damage risks are assessed. This provides a reference for research on the lightning characteristics of transmission lines and for line protection, preventing frequent lightning-induced power outages that could affect transmission efficiency.

[0004] However, current methods for measuring lightning withstand levels and assessing lightning damage risk typically employ parallel line modeling. When multiple circuits on the same tower cross each other, their respective lightning withstand levels are affected. Therefore, using parallel line modeling to measure the lightning withstand levels and assess lightning damage risk of multiple transmission lines on the same tower introduces certain errors, leading to inaccurate detection of the lightning withstand levels of such lines. Summary of the Invention

[0005] This application provides a method and device for detecting lightning overvoltage in multi-circuit transmission lines on the same tower, in order to solve the problem of inaccurate detection of the lightning withstand level of multi-circuit transmission lines on the same tower.

[0006] In a first aspect, this application provides a method for detecting lightning overvoltage in multi-circuit transmission lines on the same tower, including:

[0007] Obtain the coupling impedance, the voltage at the beginning of the crossing line, and the current at the beginning of the crossing line in a multi-circuit transmission line on the same tower; construct the equivalent impedance matrix of the crossing line based on the coupling impedance.

[0008] Calculate the voltage at the end of the cross line based on the equivalent impedance matrix, the voltage at the beginning of the cross line, and the current at the beginning of the cross line.

[0009] A cross-line model is established based on the equivalent impedance matrix, the voltage at the beginning of the cross-line, the current at the beginning of the cross-line, and the voltage at the end of the cross-line.

[0010] Establish a parallel line model for the parallel lines after the crossing lines;

[0011] A simulation model is established based on the cross-line model and the parallel line model;

[0012] The lightning overvoltage of the cross-line is simulated and calculated based on the simulation model.

[0013] In conjunction with the first aspect, in one possible implementation of the first aspect, the formula for calculating the coupling impedance is:

[0014]

[0015]

[0016] Among them, Z′ ii As the self-impedance, Z′ ik For mutual impedance, R′ i,int Let μ be the AC resistance of wire i, μ0 be the permeability, and h be the resistance of wire i. i Let D be the average height of conductor i above the ground. ik Let d be the distance between the mirror images of conductor i and conductor k. ik Let r be the distance between conductors i and k. i Let X' be the radius of conductor i. i,int Let be the internal reactance of conductor i, γ be the angle of crossing between lines, w be the angular frequency, and ΔR′ and ΔX′ be the Karsson ground return effect correction terms.

[0017] In conjunction with the first aspect, in one possible implementation of the first aspect, if the conductor is made of a magnetic material, the formula for calculating the internal reactance is:

[0018]

[0019] Where GMR is the geometric mean radius of the conductor.

[0020] In conjunction with the first aspect, in one possible implementation of the first aspect, the formula for calculating the end voltage of the cross line based on the equivalent impedance matrix, the voltage at the beginning of the cross line, and the current at the beginning of the cross line is as follows:

[0021] ΔU i =Z′ ii ×I i +Z′ ik ×I k

[0022] ΔU k =Z′ik ×I i +Z′ kk ×I k

[0023] U′ i =U i -ΔU i

[0024] U′ k =U k -ΔU k

[0025] In the formula, I i Let I be the current at the beginning of line i. k Let ΔU be the current at the beginning of line k. i Let ΔU be the voltage drop of line i in the crossing line. k Let U′ be the voltage drop of line k in the crossing line. i Let U′ be the voltage at the end of line i through the crossover line. k Let be the voltage at the end of line k through the cross line.

[0026] In conjunction with the first aspect, in one possible implementation of the first aspect, before establishing the parallel line model, parallel line model parameters are obtained, including conductor and ground wire types, spatial locations, tower types, height, wave impedance and grounding resistance, insulator string length, and final jump distance.

[0027] In conjunction with the first aspect, in one possible implementation of the first aspect, the parallel line model includes tower drawing information and conductor parameters.

[0028] In conjunction with the first aspect, in one possible implementation of the first aspect, when establishing a parallel line model for the parallel line after the cross line, the voltage at the end of the cross line is taken as the voltage at the beginning of the parallel line.

[0029] In conjunction with the first aspect, in one possible implementation of the first aspect, after calculating the lightning overvoltage of the cross-line according to the simulation model, the lightning withstand level information of each tower is calculated.

[0030] Secondly, this application provides a lightning overvoltage detection device for multi-circuit transmission lines on the same tower, comprising:

[0031] The calculation unit is configured to obtain the coupling impedance between the crossing lines, the voltage at the beginning of the crossing line, and the current at the beginning of the crossing line in a multi-circuit transmission line on the same tower; construct an equivalent impedance matrix of the crossing line based on the coupling impedance; and calculate the voltage at the end of the crossing line based on the equivalent impedance matrix, the voltage at the beginning of the crossing line, and the current at the beginning of the crossing line.

[0032] The modeling unit is configured to establish a cross-line model based on the equivalent impedance matrix, the voltage at the beginning of the cross-line, the current at the beginning of the cross-line, and the voltage at the end of the cross-line, and to establish a parallel line model for the parallel lines following the cross-line.

[0033] The simulation unit is configured to establish a simulation model based on the cross-line model and the parallel line model, and to simulate and calculate the lightning overvoltage of the cross-line based on the simulation model.

[0034] In conjunction with the second aspect, in one possible implementation of the second aspect, the simulation module is further configured to calculate the lightning withstand level information of each tower after calculating the lightning overvoltage of the cross line.

[0035] As can be seen from the above technical solution, the lightning overvoltage detection method and device for multi-circuit transmission lines on the same tower provided by this application first obtains the coupling impedance, the voltage at the beginning of the crossing line, and the current at the beginning of the crossing line in the multi-circuit transmission line on the same tower. An equivalent impedance matrix of the crossing line is constructed using the coupling impedance. Based on the equivalent impedance matrix, the voltage at the beginning of the crossing line, and the current at the beginning of the crossing line, the voltage at the end of the crossing line is calculated. Then, a model of the crossing line is established using the equivalent impedance matrix, the voltage at the beginning of the crossing line, the current at the beginning of the crossing line, and the voltage at the end of the crossing line; a model of the parallel line is established for the parallel line following the crossing line. Finally, a simulation model is established using the crossing line model and the parallel line model. Simulation is performed using the simulation model to calculate the lightning overvoltage of the crossing line. This application can calculate the equivalent impedance of the crossing line based on the line information when the crossing occurs, and represent the coupling relationship of the crossing line using the equivalent impedance matrix. The lightning overvoltage of the crossing line is calculated in a transient circuit, and the obtained lightning characteristics are closer to those under actual operating conditions, improving the accuracy of lightning withstand level detection for multi-circuit transmission lines on the same tower. Attached Figure Description

[0036] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a flowchart of the lightning overvoltage detection method for multi-circuit transmission lines on the same tower in the embodiments of this application;

[0038] Figure 2 This is an example diagram of a lightning overvoltage detection model for multi-circuit transmission lines on the same tower, as described in this application.

[0039] Figure 3This is an example diagram of the LCC verification model for lightning overvoltage detection of multi-circuit transmission lines on the same tower in the embodiments of this application;

[0040] Figure 4 The embodiments of this application are adopted Figure 2 Voltage diagram of node 7 without lightning current during modeling;

[0041] Figure 5 The embodiments of this application are adopted Figure 2 The model includes a voltage diagram of node 7 for lightning current.

[0042] Figure 6 The embodiments of this application are adopted Figure 3 Voltage diagram of node 7 without lightning current during modeling;

[0043] Figure 7 The embodiments of this application are adopted Figure 3 The model includes a voltage diagram of node 7 for lightning current.

[0044] Figure 8 The embodiments of this application are adopted Figure 2 Voltage diagram of node 7 when the cross angle is 60° during modeling;

[0045] Figure 9 This is a structural diagram of a lightning overvoltage detection device for a multi-circuit transmission line on the same tower, as described in an embodiment of this application. Detailed Implementation

[0046] To make the objectives and implementation methods of the present invention clearer, the exemplary embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the exemplary embodiments of the present invention. Obviously, the exemplary embodiments described are only some embodiments of the present invention, and not all embodiments.

[0047] With the continuous expansion of the power grid, in economically developed and densely populated areas, adopting multi-circuit transmission lines on the same tower is an effective way to improve the utilization rate of transmission corridors and solve the problem of scarce land resources. Multi-circuit transmission lines on the same tower refer to two or more lines erected on the same tower, including lines with different voltage levels sharing the same tower. For a long time, lightning strikes have been a major cause of transmission line failures, especially for multi-circuit transmission lines on the same tower, which have taller towers and a higher probability of being struck by lightning. Furthermore, multiple circuits arranged on the same tower are prone to simultaneous flashover. When multiple circuits trip simultaneously due to lightning strikes, the power supply requirement of N-1 circuits is not met, causing a power outage and significantly impacting the power grid. Particularly for the Southern Power Grid, the total length and proportion of multi-circuit transmission lines on the same tower have been increasing year by year, and the number of simultaneous trips of multiple circuits on the same tower caused by lightning strikes is also increasing, posing a significant challenge to the safe operation of the power grid.

[0048] Therefore, it is necessary to test and evaluate the lightning withstand level of transmission lines. The lightning withstand level of a transmission line is an important technical characteristic reflecting its ability to resist lightning strikes. It is expressed by the magnitude of the lightning current, referring to the maximum lightning current value that will not cause flashover of the line insulation when struck by lightning. Parallel line modeling is usually used to evaluate the lightning strike characteristics of transmission lines. However, because multiple transmission lines on the same tower cross each other, their respective lightning withstand levels are also affected. In this case, parallel line modeling cannot reflect the true lightning withstand situation of the lines when they cross, so there will be some error, leading to inaccurate testing of the lightning withstand level of multiple transmission lines on the same tower.

[0049] To address the above problems, this application provides a method for detecting lightning overvoltage in multi-circuit transmission lines on the same tower. (See [link to relevant documentation]). Figure 1 This is a flowchart of a lightning overvoltage detection method for multi-circuit transmission lines on the same tower, as described in this application. The method includes:

[0050] Obtain the coupling impedance between the crossing lines, the voltage at the beginning of the crossing line, and the current at the beginning of the crossing line in a multi-circuit transmission line on the same tower.

[0051] In obtaining the coupling impedance between crossing lines, the shielding effect of multiple crossing lines on the same tower in actual lines is approximately 200 meters. Considering the coupling effect between lines, the coupling impedance between crossing lines is calculated. Calculating the coupling impedance requires obtaining the AC resistance of each conductor, the average height to ground, the distance between conductors, the internal reactance, and the Karsun ground return effect correction term. Based on the above information, the coupling impedance is calculated using the following formula:

[0052]

[0053]

[0054] In the formula, Z′ ii As the self-impedance, Z′ ik For mutual impedance, R′ i,int Let μ be the AC resistance of wire i, μ0 be the permeability, and h be the resistance of wire i. i Let D be the average height of conductor i above the ground. ik Let d be the distance between the mirror images of conductor i and conductor k. ik Let r be the distance between conductors i and k. i Let X' be the radius of conductor i. i,int Let be the internal reactance of conductor i, γ be the angle of crossing between lines, w be the angular frequency, and ΔR' and ΔX' be the Karsson ground return effect correction terms.

[0055] If the conductor is made of magnetic material, the internal reactance can be calculated based on the geometric mean radius (GMR), as shown in the following formula:

[0056]

[0057] Therefore,

[0058]

[0059] The Carson geodetic return correction terms ΔR' and ΔX' take into account the geodetic return coefficient. These correction terms are functions of angle θ and parameter a, where a is calculated as follows:

[0060]

[0061] In the formula, when D is used for self-impedance, D = 2h i When used for mutual impedance, D = D ik f is the system frequency, and ρ is the earth resistivity.

[0062] When a≤5, the formulas for calculating the Kathon correction terms ΔR' and ΔX' are as follows:

[0063]

[0064] ΔX'=4ω×10 -4 (0.5×(0.61593-lna)+b1acosθ-d2a 2 cos2θ)

[0065] Wherein, parameter b is:

[0066]

[0067]

[0068] The formula for calculating parameter c is:

[0069] c1 = 1.3659315

[0070]

[0071] The formula for calculating parameter d is:

[0072]

[0073] The formula for calculating the parameter θ is:

[0074]

[0075]

[0076] Furthermore, the parameter θ also satisfies the following equation:

[0077] ai cosiθ=(a i-1 cos(i-1)θcosθ-a i-1 sin(i-1)θsinθ)a

[0078] a i siniθ=(a i-1 cos(i-1)θcosθ+a i-1 sin(i-1)θcosθ)a

[0079] After calculating the coupling impedance between lines, an equivalent impedance matrix for the crossing lines is constructed based on the values ​​of each coupling impedance. This coupling impedance matrix, formed by the coupling relationships between single conductors, represents the impedance coupling relationship between multiple lines on the same tower, thus reflecting the crossing situation of transmission lines. After obtaining the equivalent impedance matrix, the voltage and current at the beginning of the crossing line are used to calculate the voltage at the end of the crossing line. The voltage at the end of the crossing line can be calculated through programming simulation. For example, based on the actual situation of the transmission line, an ATP-EMTP model can be built. The Probe Current element in ATP-EMTP outputs the current at the beginning of the crossing line, the ProbeVoltage element outputs the voltage at the beginning of the crossing line, and the Probe TACS element outputs the TACS signals of the current and voltage at the beginning of the crossing line. Finally, the difference between the voltage at the beginning of the crossing line and the voltage drop across the crossing line is calculated using the DIFF2 element or the MODEL module, thus calculating the voltage at the end of the crossing line.

[0080] In some embodiments, the process of calculating the voltage at the end of a cross-line involves retrieving the voltage and current of each conductor 200m before the cross-line and calculating the voltage after the point where multiple lines cross on the same tower, i.e., the voltage at the end of the cross-line. The formula for calculating the voltage at the end of a cross-line is shown below:

[0081] ΔU i =Z′ ii ×I i +Z′ ik ×I k

[0082] ΔU k =Z′ ik ×I i +Z' kk ×I k

[0083] U′ i =U i -ΔU i

[0084] U′k =U k -ΔU k

[0085] In the formula, I i Let I be the current at the beginning of line i. k Let ΔU be the current at the beginning of line k. i Let ΔU be the voltage drop of line i in the crossing line. k Let U′ be the voltage drop of line k in the crossing line. i U' is the voltage at the end of line i through the crossover line. k Let be the voltage at the end of line k through the cross line.

[0086] A model of the crossing line is established based on the obtained equivalent impedance matrix, the voltage at the beginning of the crossing line, the current at the beginning of the crossing line, and the voltage at the end of the crossing line. A parallel line model is then constructed for the parallel lines following the crossing line, and the voltage at the end of the crossing line is set as the voltage at the beginning of the parallel line. It should be noted that some parallel line model parameters need to be obtained based on the actual situation before modeling the parallel lines.

[0087] In some embodiments, the parallel line model parameters include transmission line parameters: conductor and ground wire types and spatial locations; tower parameters: tower type, height, surge impedance, and grounding resistance; and insulator parameters: insulator string length and final transition distance. All these parameters are obtained based on the actual operating conditions of the transmission line. A parallel line model is built using these parameters to simulate the line. The height, also known as the tower's nominal height or tower marking height, is the vertical distance from the lower plane of the conductor crossarm to the construction base of the tower's center pile, i.e., the vertical distance from the lowest conductor crossarm to the base plate of the longest leg or the top surface of the foundation. The insulator string length is the length of the insulator string, which refers to an assembly of two or more insulator elements combined together to flexibly suspend the conductor. The insulator string is a protective device with fixing and operational requirements, used to suspend the conductor and insulate it from the tower and the ground.

[0088] In some embodiments, the information contained in the parallel line model includes tower drawing information and conductor parameters, so as to simulate the line using the parallel line model.

[0089] After establishing models for crossing and parallel lines, simulation models are used to simulate the transmission lines and calculate the lightning overvoltage of the crossing lines. Following the calculation of the lightning overvoltage, the lightning withstand level of each tower is calculated based on information data from different towers.

[0090] The above steps allow for modeling and simulation of multi-circuit transmission lines on the same tower. Based on the line information at the point of crossing, the equivalent impedance of the crossing lines is calculated and then performed in a transient circuit. The resulting lightning strike characteristics closely approximate actual operating conditions, improving the accuracy of lightning withstand level testing for multi-circuit transmission lines on the same tower.

[0091] See Figure 2 This is an example diagram of a lightning overvoltage detection model for a multi-circuit transmission line on the same tower, as described in this application. The model uses two parallel conductors struck by lightning as an example, with conductor type LGJ-400 / 35. The lightning overvoltage detection method for multi-circuit transmission lines on the same tower provided in this application is based on ATP-EMTP for calculation and model establishment. The coupling impedance is simulated using the MODEL module. The transmission line is simulated using the J.Marti model, with a total length of 700m, of which 200m is simulated using the MODEL module. The model is shown below. Figure 2 The model example diagram shown is a transient model of a lightning-struck power line. Furthermore, in the construction... Figure 2 In addition to the model, an LCC model was also built for comparison. See [link / reference]. Figure 3 This is an example diagram of the LCC verification model for lightning overvoltage detection of multi-circuit transmission lines on the same tower in the embodiments of this application.

[0092] The lightning current amplitude was 20kA, and the waveform parameters were 2.6 / 50μs. (Using...) Figure 2 During modeling, the voltage condition of node 7 under no lightning current is as follows: Figure 4 As shown; when there is lightning current, the voltage condition of node 7 is as follows. Figure 5 As shown. Using Figure 3 During modeling, the voltage condition of node 7 under no lightning current is as follows: Figure 6 As shown; the voltage condition of node 7 during lightning current is as follows. Figure 7 As shown. When considering line crossings, only one method can be used. Figure 2 Modeling and calculation. This involves inputting the cross angle into the MODEL module. For example, when the cross angle is 90°, input this cross angle information into the MODEL module, and the voltage situation at node 7 will be as follows. Figure 8 As shown.

[0093] By comparison Figure 4 and Figure 6 , Figure 5 and Figure 7 The voltage situation revealed that when simulating coupling impedance using the MODEL module, the line voltage was slightly lower than that of the LCC line. Through observation... Figure 8The voltage analysis revealed that when dense lines cross each other, altering the line coupling based on the crossing angle further reduces the line voltage. Simultaneously, it increases the line's lightning withstand level, making the measured voltage values ​​more consistent with reality. Therefore, it can be seen that the lightning overvoltage detection method for multi-circuit transmission lines on the same tower in this application's embodiments detects lightning characteristics that are quite close to actual operating conditions.

[0094] See Figure 9 This is a structural diagram of a lightning overvoltage detection device for a multi-circuit transmission line on the same tower, according to an embodiment of this application. The lightning overvoltage detection device for a multi-circuit transmission line on the same tower provided in this application includes:

[0095] The calculation unit is configured to obtain the coupling impedance between the crossing lines, the voltage at the beginning of the crossing line, and the current at the beginning of the crossing line in a multi-circuit transmission line on the same tower; construct an equivalent impedance matrix of the crossing line based on the coupling impedance; and calculate the voltage at the end of the crossing line based on the equivalent impedance matrix, the voltage at the beginning of the crossing line, and the current at the beginning of the crossing line.

[0096] The modeling unit is configured to establish a cross-line model based on the equivalent impedance matrix, the voltage at the beginning of the cross-line, the current at the beginning of the cross-line, and the voltage at the end of the cross-line, and to establish a parallel line model for the parallel lines following the cross-line.

[0097] The simulation unit is configured to establish a simulation model based on the cross-line model and the parallel line model, and to simulate and calculate the lightning overvoltage of the cross-line based on the simulation model.

[0098] In some embodiments, the simulation unit is further configured to calculate the lightning withstand level information of each tower after calculating the lightning overvoltage of the cross line.

[0099] As can be seen from the above technical solution, this application provides a method and device for detecting lightning overvoltage in multi-circuit transmission lines on the same tower. First, the coupling impedance, the voltage at the beginning of the crossing line, and the current at the beginning of the crossing line are obtained at the crossing points in the multi-circuit transmission line on the same tower. An equivalent impedance matrix of the crossing line is constructed using the coupling impedance. Based on the equivalent impedance matrix, the voltage at the beginning of the crossing line, and the current at the beginning of the crossing line, the voltage at the end of the crossing line is calculated. Then, a model of the crossing line is established using the equivalent impedance matrix, the voltage at the beginning of the crossing line, the current at the beginning of the crossing line, and the voltage at the end of the crossing line. A parallel line model is also established for the parallel lines following the crossing line. Finally, a simulation model is established using the crossing line model and the parallel line model. The simulation model is then used to calculate the lightning overvoltage of the crossing line.

[0100] The lightning overvoltage detection method and apparatus for multi-circuit transmission lines on the same tower provided in this application can construct the equivalent impedance matrix of the crossing lines based on the line information at the time of crossing. Calculations are then performed in a transient circuit based on the equivalent impedance matrix. Since the downstream line is farther away and has weaker coupling, parallel modeling can be used. The resulting lightning characteristics are closer to those under actual operating conditions, improving the accuracy of lightning withstand level detection for multi-circuit transmission lines on the same tower.

[0101] Similar parts between the embodiments provided in this application can be referred to mutually. The specific implementation methods provided above are only a few examples under the overall concept of this application and do not constitute a limitation on the scope of protection of this application. For those skilled in the art, any other implementation methods extended from the solution of this application without creative effort shall fall within the scope of protection of this application.

Claims

1. A method for detecting lightning overvoltage in multi-circuit transmission lines on the same tower, characterized in that, include: Obtain the coupling impedance between crossing lines, the voltage at the beginning of the crossing line, and the current at the beginning of the crossing line in a multi-circuit transmission line on the same tower. Construct the equivalent impedance matrix of the cross line based on the coupling impedance; The formula for calculating the coupling impedance is: in, It is self-impedance. For mutual impedance, Let be the AC resistance of wire i. Permeability, Let be the average height of conductor i above the ground. Let i be the distance between the mirror images of wire i and wire k. Let i be the distance between conductors i and k. Let be the radius of conductor i. Let i be the internal reactance of conductor i. The angle at which the lines intersect. Angular frequency, and This is a correction term for the Carson land return effect; Calculate the voltage at the end of the cross line based on the equivalent impedance matrix, the voltage at the beginning of the cross line, and the current at the beginning of the cross line. The formula for calculating the voltage at the end of the cross line based on the equivalent impedance matrix, the voltage at the beginning of the cross line, and the current at the beginning of the cross line is as follows: In the formula, Let be the current at the beginning of line i. Let be the current at the beginning of line k. Let be the voltage drop of line i in the crossing line. Let k be the voltage drop across the crossing line. The voltage at the end of line i through the cross line. The voltage at the end of line k through the cross line; A cross-line model is established based on the equivalent impedance matrix, the voltage at the beginning of the cross-line, the current at the beginning of the cross-line, and the voltage at the end of the cross-line. Establish a parallel line model for the parallel lines after the crossing lines; When establishing a parallel line model for the parallel line after the crossing line, the voltage at the end of the crossing line is taken as the voltage at the beginning of the parallel line. A simulation model is established based on the cross-line model and the parallel line model; The lightning overvoltage of the cross-line is simulated and calculated based on the simulation model.

2. The method for detecting lightning overvoltage in multi-circuit transmission lines on the same tower according to claim 1, characterized in that, If the conductor is made of magnetic material, the formula for calculating the internal reactance is: Where GMR is the geometric mean radius of the conductor.

3. The method for detecting lightning overvoltage in multi-circuit transmission lines on the same tower according to claim 1, characterized in that, Before establishing the parallel line model, the parallel line model parameters are obtained. The parallel line model parameters include conductor and ground wire type, spatial location, tower type, height, wave impedance and grounding resistance, insulator string length, and final jump distance.

4. The method for detecting lightning overvoltage in multi-circuit transmission lines on the same tower according to claim 1, characterized in that, The parallel line model includes tower drawings and conductor parameters.

5. The method for detecting lightning overvoltage in multi-circuit transmission lines on the same tower according to claim 1, characterized in that, After calculating the lightning overvoltage of the cross line based on the simulation model, the lightning withstand level information of each tower is calculated.

6. A lightning overvoltage detection device for multi-circuit transmission lines on the same tower, applied to the lightning overvoltage detection method for multi-circuit transmission lines on the same tower as described in claim 1, characterized in that, include: The calculation unit is configured to obtain the coupling impedance between the crossing lines, the voltage at the beginning of the crossing line, and the current at the beginning of the crossing line in a multi-circuit transmission line on the same tower; construct an equivalent impedance matrix of the crossing line based on the coupling impedance; and calculate the voltage at the end of the crossing line based on the equivalent impedance matrix, the voltage at the beginning of the crossing line, and the current at the beginning of the crossing line. The modeling unit is configured to establish a cross-line model based on the equivalent impedance matrix, the voltage at the beginning of the cross-line, the current at the beginning of the cross-line, and the voltage at the end of the cross-line; and to establish a parallel line model for the parallel lines following the cross-line. The simulation unit is configured to establish a simulation model based on the cross-line model and the parallel line model, and to simulate and calculate the lightning overvoltage of the cross-line based on the simulation model.

7. The lightning overvoltage detection device for multi-circuit transmission lines on the same tower according to claim 6, characterized in that, The simulation unit is also configured to calculate the lightning withstand level information of each tower after calculating the lightning overvoltage of the cross line.

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