Electromagnetic transient modeling calculation method for air gap of lightning counterattack circuit and overvoltage of wire insulator string

Abstract

The invention discloses an electromagnetic transient modeling calculation method for an air gap of a lightning counterattack circuit and overvoltage of a wire insulator string. At present, the voltage of a ground wire air gap at a lightning stroke point and the voltage of an adjacent tower wire insulator string cannot be obtained at the instantaneous moment of lightning stroke of an overhead line on site. According to the method, electromagnetic transient simulation modeling is carried out on structure parameters and material parameters of an on-site overhead line and actual structure parameters of a tower, electromagnetic transient simulation modeling is carried out on lightning current, electromagnetic transient modeling is carried out on a normal operation condition and an actual lightning stroke fault condition of a power system, and different lightning current peak values and wave head time are considered; through electromagnetic transient simulation software, a ground wire air gap at a lightning stroke point and a lightning stroke overvoltage maximum value of an adjacent tower wire insulator string after lightning stroke occur are calculated, and a reference basis is provided for ground wire air gap selection and insulation cooperation design of a lightning current invading overhead line. And a foundation is laid for subsequent design evaluation of various line models and tower model selection.

Description

Technical Field

[0001] The invention belongs to the technical field of power transmission and transformation of power grids, and relates to air gap overvoltage calculation. Specifically, the invention provides an electromagnetic transient modeling and calculation method for overvoltage of air gap and conductor insulator string of lightning strike line. Background Art

[0002] High-voltage transmission lines are developing towards high voltage levels and large transmission capacities. Overhead lines are easily affected by extreme weather during operation, including lightning strikes that cause lightning currents to intrude into the lines. This is especially true in areas with many lightning strikes, large spans, and large-span overhead line sections. The probability of tripping due to lightning faults is significant.

[0003] Because lightning strikes occur at microsecond speeds, existing online monitoring devices are unable to consistently detect voltage information such as the lightning strike point. Furthermore, the extensive installation of on-site online monitoring devices can also reduce the economic efficiency of power grid operations. Currently, the characteristics of overvoltages in the air gap between the conductors and the insulators of the upstream conductors caused by lightning current striking the center of the ground wire span are unclear. Consequently, it is impossible to obtain on-site data at the instantaneous moment of a lightning strike on overhead lines, the voltage values ​​of the air gap between the conductors and the ground wires at the lightning strike point, and the voltage values ​​of the insulator strings of conductors on adjacent towers. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the defects of the above-mentioned existing technologies and provide an electromagnetic transient modeling and calculation method for the air gap of the lightning strike line and the overvoltage of the conductor insulator string. The method obtains the maximum value of the overvoltage of the air gap of the ground wire and the overvoltage of the conductor insulator string through electromagnetic transient calculation, thereby providing a reference basis for the selection of the air gap of the ground wire and the insulation coordination design for the lightning current intrusion of overhead lines, and laying the foundation for the subsequent design and evaluation of various line models and pole tower selection.

[0005] To this end, the present invention adopts the following technical solution: an electromagnetic transient modeling and calculation method for the overvoltage of the air gap of the lightning strike line and the conductor insulator string, which comprises the following steps: a) Establish an overhead line model in electromagnetic transient simulation software; b) Establish a tower model in electromagnetic transient simulation software; c) Establish the power supply model in the electromagnetic transient simulation software based on the normal operating parameters of the power system; d) Obtaining the air gap of the ground wire and the dry arc distance of the conductor insulator string on site, and establishing a ground wire air gap model and an insulator string model respectively; e) Obtain the location of the on-site lightning fault point and the magnitude of the lightning current, and establish a lightning current model in the electromagnetic transient simulation software; f) connecting the overhead line model, tower model, power supply model and insulator string model to the ABC three-phase conductors in the electromagnetic transient simulation software; g) The lightning current model is connected to the overhead line model via a single-phase conductor in the electromagnetic transient simulation software, and the lightning current is injected into the ground wire of the overhead line model via the single-phase conductor; h) The conductor-ground air gap model described above is connected to the conductor and ground wire in the overhead line model via a single-phase conductor in the electromagnetic transient simulation software; i) Set different lightning currents and wave front times in the electromagnetic transient simulation software, use the electromagnetic transient simulation software to perform electromagnetic transient calculations, and obtain the maximum overvoltage of the air gap between the conductor and the ground wire and the overvoltage of the conductor insulator string.

[0006] Furthermore, in step a), by obtaining the actual spatial position and model of the on-site overhead line, the overhead line structural parameters and material parameters are obtained according to the overhead line model, thereby establishing an overhead line model in the electromagnetic transient simulation software; the actual spatial position of the overhead line includes the height of the ABC three-phase line from the ground and the distance from the center crossarm of the tower, as well as the height of the ground wire from the ground and the distance from the center crossarm of the tower; the structural parameters include the conductor outer diameter, conductor inner diameter, number of splits and split spacing of the ABC three-phase line, and the conductor outer diameter, conductor inner diameter, number of splits and split spacing of the ground wire; the material parameters include the DC resistance of the conductor of the ABC three-phase line and the DC resistance of the conductor of the ground wire.

[0007] Furthermore, in step b), by obtaining the actual size and model of the on-site tower, the tower structural parameters are obtained according to the model, and the tower wave impedance parameters are calculated, thereby establishing a tower model in the electromagnetic transient simulation software; the actual size of the tower includes the height above the ground of each cross arm of the tower, the equivalent radius of each main material section, and the equivalent radius of each cross arm section; the tower wave impedance parameters include the wave impedance of each main material section of the tower, the wave impedance of each inclined material section, and the wave impedance of each cross arm section.

[0008] Furthermore, in step c), the normal operating parameters of the power system include the effective value of the power system operating voltage, the power system operating phase angle and the power system operating frequency.

[0009] Furthermore, in step d), the ground wire air gap model and the insulator string model are constructed by an intersection method.

[0010] Furthermore, in step e), the location of the lightning fault point includes the distance from the lightning fault point to the left tower and the distance from the lightning fault point to the right tower; the lightning current model parameters include the lightning current peak, wave front time and half-peak time, and the lightning current is described using a double exponential function model. Furthermore, step f) specifically includes: f1) The overhead line model includes a first overhead line model and a second overhead line model; the tower model includes a first tower model and a second tower model; the power supply model includes a first power supply model and a second power supply model; and the insulator string model includes a first insulator string model and a second insulator string model; f2) The first power supply model, the first insulator string model, the first overhead line model, the second overhead line model, the second insulator string model, and the second power supply model are connected in series in sequence using ABC three-phase conductors; f3) The first insulator string model is connected in series with the three-phase ABC hanging points of the first tower model, and the second insulator string model is connected in series with the three-phase ABC hanging points of the second tower model; f4) The first grounding point, the first overhead line model, the second overhead line model, and the second grounding point are connected in series in sequence using single-phase conductors in the software; f5) the first grounding point is connected in parallel with the ground wire hanging point of the first tower model, and the second grounding point is connected in parallel with the ground wire hanging point of the second tower model; f6) In the software, both the first and second grounding points are at zero potential and are electrically considered to be the same point.

[0011] Furthermore, in step g), when a single-phase conductor is used to connect the lightning current model and the overhead line model, the overhead line model is connected to the ground wire.

[0012] Furthermore, in step h), when a single-phase conductor is used to connect the ground wire air gap model and the overhead line model, the overhead line model selects the ground wire and the A-phase conductor among the ABC three-phase conductors.

[0013] Furthermore, in step i), the maximum values ​​of the ground wire air gap overvoltage and the conductor insulator string overvoltage are obtained by the following steps: i1) setting voltage monitoring points for the ground wire air gap model and the insulator string model described in step d); i2) Based on common lightning current parameters in the atmosphere, set different lightning current peak values ​​and wave front times in the electromagnetic transient simulation software, and record the air gap voltage of the conductor and ground wire and the overvoltage value of the conductor insulator string under each working condition; i3) After the electromagnetic transient simulation software is repeatedly run, compare the overvoltage values ​​of the air gap between the conductor and the ground wire and the overvoltage values ​​of the conductor insulator string to obtain the maximum overvoltage values ​​of the air gap between the conductor and the ground wire and the maximum overvoltage values ​​of the conductor insulator string: , , in, 、 They are the maximum overvoltage of the air gap between the conductor and the ground wire, and the maximum overvoltage of the conductor insulator string;i Representative i A lightning current peak value; j Representative j Wave head time; 、 They are respectively the overvoltage value of the air gap between the conductor and the ground wire and the overvoltage value of the conductor insulator string.

[0014] The present invention performs electromagnetic transient simulation modeling on the structural parameters and material parameters of on-site overhead lines and the actual structural parameters of towers, performs electromagnetic transient simulation modeling on lightning currents, and performs electromagnetic transient modeling on the normal operation of the power system and actual lightning fault conditions. After considering different lightning current peak values ​​and wave front times, the electromagnetic transient simulation software is used to calculate the maximum lightning overvoltage of the air gap between the conductor and the ground wire at the lightning strike point and the insulator string of the adjacent tower conductor after the lightning strike occurs. This provides a reference basis for the selection of the air gap between the conductor and the ground wire and the insulation coordination design for lightning current intrusion into overhead lines, and lays the foundation for the subsequent design and evaluation of various line models and tower selection. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a flow chart of an electromagnetic transient modeling and calculation method for overvoltage of air gap and conductor insulator string of lightning strike back line according to the present invention; Figure 2 This is a flow chart for obtaining calculation results of the air gap overvoltage of the ground wire and the overvoltage of the conductor insulator string considering different lightning current peak values, wavelengths and times; Figure 3 Schematic diagram of tower structure parameters in a specific embodiment of the present invention; Figure 4 Schematic diagram of tower wave impedance parameters in a specific embodiment of the present invention; Figure 5 The waveforms of the ground wire air gap overvoltage and the conductor insulator string overvoltage in the specific implementation manner of the present invention are shown. DETAILED DESCRIPTION

[0016] The following is an explanation and description of the technical solutions of the embodiments of the present invention in conjunction with the accompanying drawings of the present invention. However, the following embodiments are only preferred embodiments of the present invention and are not exhaustive. Based on the embodiments in the implementation manner, other embodiments obtained by those skilled in the art without making any creative work are all within the scope of protection of the present invention.

[0017] This embodiment is a method for calculating electromagnetic transient modeling of the overvoltage of the air gap and conductor insulator string caused by lightning strike. Figure 1 The steps are as follows: a) Obtain the actual spatial location and model of the on-site overhead line, obtain the structural parameters and material parameters of the overhead line based on the model, and establish the overhead line model in the electromagnetic transient simulation software; b) Obtain the actual size and model of the tower on site, obtain the tower structural parameters based on the model, calculate the tower wave impedance parameters, and establish the tower model in the electromagnetic transient simulation software; c) Establish the power supply model in the electromagnetic transient simulation software based on the normal operating parameters of the power system; d) Obtain the air gap of the ground wire and the dry arc distance of the conductor insulator string on site, and establish the air gap model of the ground wire and the insulator string model; e) Obtain the location of the on-site lightning fault point and the magnitude of the lightning current, and establish a lightning current model in the electromagnetic transient simulation software; f) connecting the overhead line model, tower model, power supply model and insulator string model to the ABC three-phase conductors in the electromagnetic transient simulation software; g) The lightning current model is connected to the overhead line model via a single-phase conductor in the electromagnetic transient simulation software, and the lightning current is injected into the ground wire of the overhead line model via the single-phase conductor; h) The conductor-ground air gap model described above is connected to the conductor and ground wire in the overhead line model via a single-phase conductor in the electromagnetic transient simulation software; i) Set different lightning currents and wave front times in the electromagnetic transient simulation software, use the electromagnetic transient simulation software to perform electromagnetic transient calculations, and obtain the maximum overvoltage of the air gap between the conductor and the ground wire and the overvoltage of the conductor insulator string.

[0018] Specifically, in step a), the actual spatial position of the overhead line includes the height of the ABC three-phase line from the ground and the distance from the center cross arm of the tower, as well as the height of the ground wire from the ground and the distance from the center cross arm of the tower.

[0019] Specifically, in step a), the structural parameters include: the conductor outer diameter, conductor inner diameter, number of splits and split spacing of the ABC three-phase line, and the conductor outer diameter, conductor inner diameter, number of splits and split spacing of the ground wire; the material parameters include: the DC resistance of the conductor of the ABC three-phase line, and the DC resistance of the conductor of the ground wire.

[0020] Specifically, in step b), the actual size of the tower includes the height from the ground of each cross arm of the tower, the equivalent radius of each main material section, and the equivalent radius of each cross arm section.

[0021] Specifically, in step b), the tower wave impedance parameters, including the wave impedance of each main material section of the tower, the wave impedance of each inclined material section, and the wave impedance of each cross-arm section, are calculated by the following steps: b1) Obtain the actual dimensions of the tower, including the height of each cross arm from the ground, the equivalent radius of each main material section, and the equivalent radius of each cross arm section.

[0022] b2) Calculation of the main material wave impedance of each section of the tower, see formula (1).

[0023] (1) Where, Z Tk For the k Equivalent wave impedance of the main material of the segment tower, Ω; h k For the k Height of cross arm from ground, m; r Tk For the k Equivalent radius of main material of segment tower, m.

[0024] b3) Calculation of the wave impedance of each section of the tower, see formula (2).

[0025] (2) Where, Z Lk For the k Equivalent wave impedance of the inclined material of the tower segment, Ω.

[0026] b4) Calculation of the wave impedance of each cross arm of the tower, see formula (3).

[0027] (3) Where, Z Ak For the k Equivalent wave impedance of cross arm, Ω; r Ak For the k Equivalent radius of segment cross arm, m.

[0028] Specifically, in step c), the normal operating parameters of the power system include the effective value of the power system operating voltage, the power system operating phase angle, and the power system operating frequency.

[0029] Specifically, in step d), the ground wire air gap model and the insulator string model are constructed by the intersection method and obtained by the following steps: d1) Obtain the air gap of the ground wire L air , conductor insulator string dry arc distance L insulator ; d2) Construct the volt-second characteristic curve of the air gap between the conductor and the ground wire (i.e., the air gap model between the conductor and the ground wire), see formula (4).

[0030] (4) Where, is the volt-second characteristic curve of the air gap between the conductor and the ground, kV; t is the flashover time, μs; L air is the air gap between the conductor and the ground wire, m.

[0031] d3) Construct the volt-second characteristic curve of the insulator string (i.e., the insulator string model), see formula (5).

[0032] (5) Where, is the volt-second characteristic curve of the insulator string, kV; t is the flashover time, μs; L insulator is the dry arc distance of the conductor insulator string, m.

[0033] Specifically, in step e), the location of the lightning fault point includes the distance from the lightning fault point to the left pole tower and the distance from the lightning fault point to the right pole tower.

[0034] Specifically, in step e), the lightning current model parameters include the lightning current peak value, wave front time and half-peak time, and the lightning current is described by a double exponential function model, as shown in formulas (6) and (7).

[0035] (6) in, Indicates lightning current; Indicates the initial lightning current peak value, kA; is the peak current correction factor; t Indicates time, seconds; is the wave head time coefficient; is the half-wave peak time coefficient; e is a natural constant; (7) in, is the peak value of lightning current, 、 and Jointly decided; the wave head time is determined by The half-peak time is determined by Decide.

[0036] Specifically, step f) includes: f1) the overhead line model includes a first overhead line model and a second overhead line model; the tower model includes a first tower model and a second tower model; the power supply model includes a first power supply model and a second power supply model; and the insulator string model includes a first insulator string model and a second insulator string model; f2) The first power supply model, the first insulator string model, the first overhead line model, the second overhead line model, the second insulator string model, and the second power supply model are connected in series in sequence using ABC three-phase conductors; f3) The first insulator string model is connected in series with the three-phase ABC hanging points of the first tower model, and the second insulator string model is connected in series with the three-phase ABC hanging points of the second tower model; f4) The first grounding point, the first overhead line model, the second overhead line model, and the second grounding point are connected in series in sequence using single-phase conductors in the software; f5) the first grounding point is connected in parallel with the ground wire hanging point of the first tower model, and the second grounding point is connected in parallel with the ground wire hanging point of the second tower model; f6) In the software, the first and second grounding points are both at zero potential and are electrically considered to be the same point.

[0037] Specifically, in step g), when a single-phase conductor is used to connect the lightning current model and the overhead line model, the overhead line model is connected to the ground wire.

[0038] Specifically, in step h), when a single-phase conductor is used to connect the ground wire air gap model and the overhead line model, the overhead line model selects the ground wire and the A-phase conductor among the ABC three-phase conductors.

[0039] Specifically, in step i), the maximum overvoltage of the air gap of the ground wire and the overvoltage of the conductor insulator string are obtained as follows: Figure 2 As shown, it is obtained by the following steps: i1) setting voltage monitoring points for the ground wire air gap model and the insulator string model described in step d); i2) Based on common lightning current parameters in the atmosphere, set different lightning current peak values ​​and wave front times in the electromagnetic transient simulation software, and record the air gap voltage of the conductor-to-ground wire and the overvoltage value of the conductor insulator string under each operating condition; i3) After the electromagnetic transient simulation software is repeatedly run, the overvoltage values ​​of the air gap between the conductor and the ground wire and the overvoltage values ​​of the conductor insulator string are compared to obtain the maximum overvoltage values ​​of the air gap between the conductor and the ground wire and the maximum overvoltage values ​​of the conductor insulator string, as shown in Equations (8) and (9).

[0040] (8) (9) in, 、 They are the maximum overvoltage of the air gap between the conductor and the ground wire, and the maximum overvoltage of the conductor insulator string; i represents the peak value of the i-th lightning current; j represents the j-th wave head time; 、 They are respectively the overvoltage value of the air gap between the conductor and the ground wire and the overvoltage value of the conductor insulator string.

[0041] Taking a 220kV lightning-struck line fault as an example, the electromagnetic transient modeling and calculation method for the lightning strike line air gap and conductor insulator string overvoltage of the present invention is applied below to obtain the ground wire air gap overvoltage and conductor insulator string overvoltage values ​​of the line. The specific steps are as follows: 1) Obtain the actual spatial location and model of the on-site overhead line, obtain the structural parameters and material parameters of the overhead line, and establish the overhead line model in the electromagnetic transient simulation software; 1.1) Obtain the actual spatial location of overhead lines, including: the heights of the three-phase lines ABC at 21m, 27.5m, and 34m above the ground, and the distances from the center crossarm of the tower at 4.2m, 2.2m, and 2.2m, respectively; and the height of the ground wire at 38.5m above the ground and 7.6m from the center crossarm of the tower.

[0042] 1.2) The actual overhead line conductor model on site is obtained as JL / G1A-300 / 40, and the structural parameters and material parameters of the corresponding overhead line model are obtained. The structural parameters include: a conductor outer diameter of 2.394 m, a conductor inner diameter of 0 m, a number of splits of 4, and a split spacing of 400 mm for the ABC three-phase line; and a conductor outer diameter of 1.52 m, a conductor inner diameter of 0 m, a number of splits of 0, and a split spacing of 0 mm for the ground wire; the material parameters include: a conductor DC resistance of 0.0960 Ω / km for the ABC three-phase line, and a conductor DC resistance of 0.274 Ω / km for the ground wire.

[0043] 1.3) Establish an overhead line model in the simulation software ATP-EMTP.

[0044] 2) Obtain the actual size and model of the on-site tower, obtain the tower structural parameters, calculate the tower wave impedance parameters, and establish the tower model in the electromagnetic transient simulation software; 2.1) Get the actual size of the tower, such as Figure 3 As shown, the heights of the first to fourth cross arms of the tower from the ground are h1=21m, h2=27.5m, h3=34m, and h4=38.5m respectively; the equivalent radii of the first to fourth main materials are r T1 =0.85m, r T2 =0.75m, r T3 =0.5m, r T4 =0.32m; the equivalent radii of the first to fourth cross arms are r A1 =2.2m,r A2 =4.2m, r A3 =2.2m, r A4 =1.6m; 2.2) Calculate the tower wave impedance parameters, such as Figure 4 As shown, including: the main material wave impedances of the first to fourth sections of the tower are Z T1 =98.3Ω, Z T2 =109.4Ω, Z T3 =95.4Ω, Z T4 =69.5Ω; the wave impedance of the inclined material from the first to the fourth section of the tower is Z L1 =884.5Ω, Z L2 =984.7Ω, Z L3 =858.8Ω, Z L4 =625.9Ω; the cross-arm impedances from the first to the fourth section of the tower are Z A1 =461.8Ω, Z A2 =454.3Ω, Z A3 =426.5Ω, Z A4 =410.3Ω; 2.3) Establish a tower model in the simulation software ATP-EMTP.

[0045] 3) Obtain the normal operating parameters of the power system and establish the power supply model in the electromagnetic transient simulation software; 3.1) Obtain the normal operating parameters of the power system, including: the effective value of the power system operating voltage is 127.017 kV, the power system operating phase angle is -151.95°, and the power system operating frequency is 50 Hz; 3.2) Establish a power supply model in the simulation software ATP-EMTP.

[0046] 4) Obtain the air gap of the ground wire and the dry arc distance of the conductor insulator string on site, and establish the air gap model of the ground wire and the insulator string model; 4.1) Obtain the air gap between the conductor and the ground wire and the arc distance between the conductor and the insulator string, including: the air gap between the conductor and the ground wire is 9.31m, and the arc distance between the conductor and the insulator string is 2.044m; 4.2) Establish the volt-second characteristic curve of the air gap between the conductor and the ground wire, which is ; Establish the volt-second characteristic curve of the insulator string, ; 4.3) Establish the ground wire air gap model and insulator string model in the simulation software ATP-EMTP.

[0047] 5) Obtain the location of the on-site lightning fault point and the magnitude of the lightning current, and establish a lightning current model in the electromagnetic transient simulation software; 5.1) Obtain the location of the lightning fault point, including: the distance from the lightning fault point to the left tower is 420m, and the distance from the lightning fault point to the right tower is 283m; 5.2) Obtain lightning current model parameters, including: lightning current peak value -100kA, wave front time 2.6μs, half-peak time 50μs; 5.3) Establish a lightning current model in the simulation software ATP-EMTP.

[0048] 6) Connect the overhead line model, tower model, power supply model, and insulator string model to the ABC three-phase conductors in the simulation software ATP-EMTP; 7) Connect the overhead line model, tower model, power supply model, and insulator string model to the ABC three-phase conductors in the simulation software ATP-EMTP; 8) Connect the lightning current model to the overhead line model using a single-phase conductor in the simulation software ATP-EMTP, and inject the lightning current into the ground wire of the overhead line model through the single-phase conductor; 9) Connect the conductor and ground wire in the overhead line model to the single-phase conductor in the simulation software ATP-EMTP in the air gap model of the conductor-ground wire; 10) Different lightning current peak values ​​of 50kA, 80kA, 100kA, 120kA, 150kA, and 200kA, and wave head time of 1.2μs, 2.6μs, 5μs, and 10μs were set in the electromagnetic transient simulation software. Electromagnetic transient calculations were performed in the simulation software ATP-EMTP. The calculation results are shown in Tables 1 and 2. The overvoltage waveform is shown in Figure 5 shown.

[0049] According to Table 1 and Table 2, the maximum overvoltage of the air gap of the conductor and the ground wire is 9190.8 kV, and the maximum overvoltage of the conductor insulator string is 5883.7 kV.

[0050] Table 1 Overvoltage at different lightning current peaks

[0051] Table 2 Overvoltage at different wave front times

[0052] Table 1 shows that, maintaining a constant crest / half-crest time of 2.6 / 50μs, the breakdown voltage across the conductor-to-ground gap gradually increases as the peak lightning current increases. When the peak lightning current increases from 50kA to 200kA, the breakdown voltage increases from 3003.9kV to 9005.5kV, a 3.0-fold increase. Table 1 also shows that, maintaining a constant crest / half-crest time, the overvoltage on the upper phase insulator also exhibits a positive correlation with the peak lightning current. When the peak lightning current increases from 80kA to 200kA, the overvoltage on the upper phase insulator increases from 2853.2kV ​​to 5741.2kV, a 2.0-fold increase.

[0053] Table 2 shows that, while maintaining the peak lightning current, the overvoltage across the air gap between the conductor and the upper phase insulator decreases with increasing surge front time. When the surge front time increases from 1.2 μs to 10 μs, the overvoltage across the air gap between the conductor and the ground decreases from 9190.8 kV to 1720.7 kV, a decrease of 81.28%. The overvoltage across the upper phase insulator decreases from 5883.7 kV to 209.4 kV, a decrease of 96.44%.

[0054] The above description of the embodiments is intended to facilitate understanding and application of the present invention by those skilled in the art. It is apparent that those skilled in the art can readily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without requiring creative effort. Therefore, the present invention is not limited to the above embodiments. Any improvements or modifications made by those skilled in the art based on the disclosure of the present invention should fall within the scope of protection of the present invention.

Claims

1. The electromagnetic transient modeling and calculation method for the overvoltage of the air gap and conductor insulator string of the lightning strike line is characterized by: Including steps: a) Establish an overhead line model in electromagnetic transient simulation software; b) Establish a tower model in electromagnetic transient simulation software; c) Establish the power supply model in the electromagnetic transient simulation software based on the normal operating parameters of the power system; d) Obtaining the air gap of the ground wire and the dry arc distance of the conductor insulator string on site, and establishing a ground wire air gap model and an insulator string model respectively; e) Obtain the location of the on-site lightning fault point and the magnitude of the lightning current, and establish a lightning current model in the electromagnetic transient simulation software; f) connecting the overhead line model, tower model, power supply model and insulator string model to the ABC three-phase conductors in the electromagnetic transient simulation software; g) The lightning current model is connected to the overhead line model via a single-phase conductor in the electromagnetic transient simulation software, and the lightning current is injected into the ground wire of the overhead line model via the single-phase conductor; h) The conductor-ground air gap model described above is connected to the conductor and ground wire in the overhead line model via a single-phase conductor in the electromagnetic transient simulation software; i) Set different lightning currents and wave front times in the electromagnetic transient simulation software, use the electromagnetic transient simulation software to perform electromagnetic transient calculations, and obtain the maximum overvoltage of the air gap between the conductor and the ground wire and the overvoltage of the conductor insulator string.

2. The electromagnetic transient modeling and calculation method for the air gap of a lightning strike line and the overvoltage of a conductor insulator string according to claim 1 is characterized in that: In step a), the overhead line model in the electromagnetic transient simulation software is established by obtaining the actual spatial position and model of the on-site overhead line and obtaining the structural parameters and material parameters of the overhead line according to the overhead line model; the actual spatial position of the overhead line includes the height of the ABC three-phase line from the ground and the distance from the center cross arm of the tower, and the height of the ground wire from the ground and the distance from the center cross arm of the tower; the structural parameters include the conductor outer diameter, conductor inner diameter, number of splits and split spacing of the ABC three-phase line, and the conductor outer diameter, conductor inner diameter, number of splits and split spacing of the ground wire; and the material parameters include the DC resistance of the conductor of the ABC three-phase line and the DC resistance of the conductor of the ground wire.

3. The electromagnetic transient modeling and calculation method for the air gap and conductor insulator string overvoltage of a lightning strike line according to claim 1 is characterized in that: In step b), the tower model in the electromagnetic transient simulation software is established by obtaining the actual size and model of the tower on site, obtaining the tower structural parameters according to the model, and calculating the tower wave impedance parameters; the actual size of the tower includes the height above the ground of each cross arm of the tower, the equivalent radius of each main material section, and the equivalent radius of each cross arm section; the tower wave impedance parameters include the wave impedance of each main material section of the tower, the wave impedance of each inclined material section, and the wave impedance of each cross arm section.

4. The electromagnetic transient modeling and calculation method for the air gap and conductor insulator string overvoltage of a lightning strike line according to claim 1 is characterized in that: In step c), the normal operating parameters of the power system include the effective value of the power system operating voltage, the power system operating phase angle and the power system operating frequency.

5. The electromagnetic transient modeling and calculation method for the overvoltage of the air gap and conductor insulator string of the lightning strike line according to claim 1 is characterized in that: In step d), the ground wire air gap model and the insulator string model are constructed by the intersection method.

6. The electromagnetic transient modeling and calculation method for lightning strike line air gap and conductor insulator string overvoltage according to claim 1 is characterized in that: In step e), the location of the lightning fault point includes the distance from the lightning fault point to the left tower and the distance from the lightning fault point to the right tower; the lightning current model parameters include the lightning current peak, wave front time and half-peak time, and the lightning current is described by a double exponential function model.

7. The electromagnetic transient modeling and calculation method for lightning strike line air gap and conductor insulator string overvoltage according to claim 1 is characterized in that: Step f) specifically includes: f1) The overhead line model includes a first overhead line model and a second overhead line model; the tower model includes a first tower model and a second tower model; the power supply model includes a first power supply model and a second power supply model; and the insulator string model includes a first insulator string model and a second insulator string model; f2) The first power supply model, the first insulator string model, the first overhead line model, the second overhead line model, the second insulator string model, and the second power supply model are connected in series in sequence using ABC three-phase conductors; f3) The first insulator string model is connected in series with the three-phase ABC hanging points of the first tower model, and the second insulator string model is connected in series with the three-phase ABC hanging points of the second tower model; f4) The first grounding point, the first overhead line model, the second overhead line model, and the second grounding point are connected in series in sequence using single-phase conductors in the software; f5) the first grounding point is connected in parallel with the ground wire hanging point of the first tower model, and the second grounding point is connected in parallel with the ground wire hanging point of the second tower model; f6) In the software, both the first and second grounding points are at zero potential and are electrically considered to be the same point.

8. The electromagnetic transient modeling and calculation method for lightning strike line air gap and conductor insulator string overvoltage according to claim 1 is characterized in that: In step g), when a single-phase conductor is used to connect the lightning current model and the overhead line model, the overhead line model is connected to the ground wire.

9. The electromagnetic transient modeling and calculation method for lightning strike line air gap and conductor insulator string overvoltage according to claim 1 is characterized in that: In step h), when a single-phase conductor is used to connect the ground wire air gap model and the overhead line model, the overhead line model selects the ground wire and the A-phase conductor of the ABC three-phase conductors.

10. The electromagnetic transient modeling and calculation method for lightning strike line air gap and conductor insulator string overvoltage according to claim 1, characterized in that: In step i), the maximum values ​​of the ground wire air gap overvoltage and the conductor insulator string overvoltage are obtained by the following steps: i1) setting voltage monitoring points for the ground wire air gap model and the insulator string model described in step d); i2) Based on common lightning current parameters in the atmosphere, set different lightning current peak values ​​and wave front times in the electromagnetic transient simulation software, and record the air gap voltage of the conductor and ground wire and the overvoltage value of the conductor insulator string under each working condition; i3) After the electromagnetic transient simulation software is repeatedly run, compare the overvoltage values ​​of the air gap between the conductor and the ground wire and the overvoltage values ​​of the conductor insulator string to obtain the maximum overvoltage values ​​of the air gap between the conductor and the ground wire and the maximum overvoltage values ​​of the conductor insulator string: ， ， in, 、 They are the maximum overvoltage of the air gap between the conductor and the ground wire, and the maximum overvoltage of the conductor insulator string; i Representative i A lightning current peak value; j Representative j Wave head time; 、 They are respectively the overvoltage value of the air gap between the conductor and the ground wire and the overvoltage value of the conductor insulator string.

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