Air gap correction method considering long wave head impact effect

Abstract

The application provides an air gap correction method considering the influence of long wave head impact, comprising the following steps: S1. obtaining environmental parameters of actual environment of different positions of long power transmission line, including air pressure, temperature and humidity; S2. simulating the power transmission line by using simulation software, and determining the operating overvoltage and long wave head waveform of different positions by the simulation software; and determining the equivalent wave front time and 2% maximum operating overvoltage of the long wave head; S3. selecting the air gap suitable for the equivalent wave front time and 2% maximum operating overvoltage of the long wave head waveform determined in step S2; S4. performing impact discharge experiment on the selected air gap under different environmental parameters, and determining the 50% flashover voltage U5 1 0％ of the air gap; S5. constructing a 50% flashover voltage and environmental parameter influence coefficient relationship model, and fitting and solving the relationship model by using ORIGIN software to obtain the environmental parameter influence coefficient; S6. substituting the environmental parameters of different positions of the power transmission line into the relationship model to calculate the 50% flashover voltage U5 2 0％ , and determining the corresponding air gap distance based on the calculated 50% flashover voltage U5 2 0％ .

Description

Technical Field

[0001] This invention relates to an air gap correction method, and more particularly to an air gap correction method that takes into account the impact of long wavefronts. Background Technology

[0002] In long-distance power transmission, transmission lines inevitably pass through areas with extreme environments, such as high altitudes and high humidity. Under the influence of various extreme environmental factors, the safety and reliability of transmission lines will be severely tested. As the voltage level increases and the line length increases, the waveform characteristics of the operating overvoltage during the oscillation process are different, and the distribution of overvoltage along the line varies significantly. The actual operating overvoltage waveform of the line differs significantly from the standard operating waveform, exhibiting a long wavefront. Under these conditions, the selection of air gaps becomes extremely important. Different air gap distances result in different impulse voltages. In existing technologies, the distance of air gaps is often determined based on experience and some power industry standards or regulations. This method ignores the influence of environmental factors, making the air gaps unsuitable for long-distance transmission lines, thus posing serious safety hazards.

[0003] In view of this, in order to solve the above-mentioned technical problems, it is urgent to propose a new technical approach. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide an air gap correction method that takes into account the impact of long wavefronts. The method determines the air gap distance by taking into account the long wavefront waveform and operating overvoltage of the transmission line, as well as the environmental factors of the actual operating conditions of the transmission line. This effectively ensures the compatibility between the transmission line and the air gap, ensures the insulation performance of long transmission lines, and thus effectively ensures the safe operation of long transmission lines.

[0005] This invention provides an air gap correction method that takes into account the impact of long-wave head impact, comprising the following steps:

[0006] S1. Obtain environmental parameters of the actual environment at different locations along the long transmission line, including air pressure, temperature, and humidity;

[0007] S2. The transmission line is simulated using simulation software, and the switching overvoltage and long wavefront waveform at different locations are determined by the simulation software; the equivalent wavefront time of the long wavefront and the maximum switching overvoltage of 2% are also determined.

[0008] S3. Select an air gap that matches the equivalent wavefront time of the long wavefront waveform determined in step S2 and the maximum operating overvoltage of 2%.

[0009] S4. Conduct impulse discharge experiments on the selected air gap under different environmental parameters to determine the 50% flashover voltage of the air gap.

[0010] S5. Construct a model relating 50% flashover voltage to environmental parameter influence coefficients, and use ORIGIN software to fit and solve the model to obtain the environmental parameter influence coefficients.

[0011] S6. Substitute the environmental parameters at different locations along the transmission line into the relational model to calculate the 50% flashover voltage. And based on the calculated 50% flashover voltage Determine the corresponding air gap distance.

[0012] Furthermore, in step S5, the relationship model between the 50% flashover voltage and the influence coefficient of environmental parameters is as follows:

[0013]

[0014] Where: A is the comprehensive influence coefficient, P0 is the standard atmospheric pressure, h is the absolute humidity, d is the air gap distance, c is the additional influence coefficient of absolute humidity, m is the characteristic influence index of air gap distance, n is the characteristic influence index of absolute humidity, and P is the air pressure at the current location of the transmission line.

[0015] Furthermore, step S3 specifically includes:

[0016] Operational overvoltages include planned closing operation overvoltages, reclosing operation overvoltages, operational overvoltages caused by single-phase ground faults, and fault clearing operation overvoltages.

[0017] Select the target operating overvoltage in the operating overvoltage section;

[0018] The target operating overvoltages are arranged in descending order, and 2% of the target operating overvoltage data are selected as a reference.

[0019] Determine whether the impulse voltage range of the candidate air gap includes 2% of the maximum operating overvoltage. If so, use the current air gap as the target air gap.

[0020] Determine whether the equivalent wavefront time of the long wavefront waveform of the target air gap is equal to the equivalent wavefront time. If so, the target air gap is used as the air gap for the impulse discharge test in step S4.

[0021] Furthermore, the equivalent wavefront time is determined using the following method:

[0022] T f =η(T) p -T 85％ ), where η is the equivalent wavefront time calculation coefficient, T f This is the equivalent wavefront time.

[0023] Furthermore, the 50% flashover voltage was determined using the following method.

[0024]

[0025] Among them: U i Let n be the voltage applied during the i-th breakdown of the air gap, and n be the total number of effective tests. i The number of experiments conducted under the same impulse voltage.

[0026] The beneficial effects of this invention are as follows: By using the long-waveform and overvoltage of the transmission line, and combining the environmental factors of the actual operating conditions of the transmission line, the distance of the air gap can be determined, thereby effectively ensuring the compatibility between the transmission line and the air gap, ensuring the insulation performance of long transmission lines, and thus effectively ensuring the safe operation of long transmission lines. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0028] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0029] The present invention will be further described in detail below:

[0030] This invention provides an air gap correction method that takes into account the impact of long-wave head impact, comprising the following steps:

[0031] S1. Obtain the actual environmental parameters of different locations along the long transmission line, including air pressure, temperature, and humidity. Different locations refer to different sections along the transmission line. In other words, a long transmission line can be divided into several sections, and the environmental parameters of different sections will be different. For example, the temperature and humidity of adjacent sections may not differ significantly, but the air pressure data will be different. Similarly, the environmental parameters of non-adjacent sections, such as the first and last sections along the transmission direction, may differ considerably. Therefore, it is necessary to obtain the environmental parameters of different locations to provide sufficient data support for subsequent processing.

[0032] S2. The transmission line is simulated using simulation software, and the switching overvoltage and long wavefront waveform at different locations are determined by the simulation software; the equivalent wavefront time and the maximum switching overvoltage of 2% of the long wavefront are also determined; the simulation software uses PSCAD to simulate the long transmission line and conduct corresponding operational tests, which is existing technology. By performing simulation processing through simulation software, the switching overvoltage and long wavefront waveform can be determined.

[0033] S3. Select an air gap that matches the equivalent wavefront time of the long wavefront waveform determined in step S2 and the maximum operating overvoltage of 2%.

[0034] S4. Conduct impulse discharge experiments on the selected air gap under different environmental parameters to determine the 50% flashover voltage of the air gap.

[0035] S5. Construct a model relating 50% flashover voltage to environmental parameter influence coefficients, and use ORIGIN software to fit and solve the model to obtain the environmental parameter influence coefficients; that is, the 50% flashover voltage... Substituting these values ​​into the calculation model and fitting them using ORIGIN software, the corresponding simulation coefficients can be determined. Since step S4 only selects set data points for testing (e.g., 100 environmental parameter data points), but in reality, there are more than 100 combinations of environmental parameters, it's necessary to determine the relationship model. Then, the actual environmental parameters and their influence coefficients are substituted into the model to obtain the corresponding 50% flashover voltage.

[0036] S6. Substitute the environmental parameters at different locations along the transmission line into the relational model to calculate the 50% flashover voltage. And based on the calculated 50% flashover voltage Determining the corresponding air gap distance is crucial. Under different impulse voltages, there is a correlation between the 50% flashover voltage and the air gap distance. Since we know the voltage of a long transmission line, such as a 500kV line, the 50% flashover voltage and air gap distance correspond. By obtaining the 50% flashover voltage, we can look up the corresponding air gap distance in a table and arrange the air gaps accordingly. Of course, the air gap distance may differ at different locations on the same transmission line; in this case, the above steps can be used to determine it. By using the above method, considering the long-wavelength waveform and switching overvoltage of the transmission line, and combining it with environmental factors related to the actual operating conditions of the transmission line, the air gap distance can be determined. This effectively ensures the compatibility between the transmission line and the air gap, guarantees the insulation performance of the long transmission line, and thus effectively ensures the safe operation of the long transmission line.

[0037] In this embodiment, the relationship model between the 50% flashover voltage and the influence coefficient of environmental parameters in step S5 is as follows:

[0038]

[0039] Where: A is the comprehensive influence coefficient, P0 is the standard atmospheric pressure, h is the absolute humidity, d is the air gap distance, c is the additional influence coefficient of absolute humidity, m is the characteristic influence index of air gap distance, n is the characteristic influence index of absolute humidity, and P is the air pressure at the current location of the transmission line. In this model, A, c, m, and n are unknowns, so it is necessary to use the values ​​determined in step S4... Substituting these values ​​into the model and then inputting them into ORIGIN software for fitting to obtain A, c, m, and n, the relationship model between 50% flashover voltage and environmental parameter influence coefficients is determined. Substituting the real-time environmental parameters into the model then allows us to calculate the influence coefficients on the current transmission line segment. Alright.

[0040] In this embodiment, step S3 specifically includes:

[0041] Operational overvoltages include planned closing operation overvoltages, reclosing operation overvoltages, operation overvoltages caused by single-phase ground faults, and fault clearing operation overvoltages. In other words, there are four types of operational overvoltages. Therefore, the selection should be based on the current focus. If the current focus of the transmission line is planned closing operation overvoltages, then planned closing operation overvoltages will be used as the target operational overvoltage.

[0042] Select the target operating overvoltage in the operating overvoltage section;

[0043] The target operating overvoltages are arranged in descending order, and 2% of the target operating overvoltage data are selected as references. For example, if there are 100 data points of planned closing operation overvoltages and they are arranged in order of size, then the first two maximum values ​​are selected, which are the first two data points of the sequence.

[0044] Determine whether the impulse voltage range of the candidate air gap includes 2% of the maximum operating overvoltage. If so, the current air gap is taken as the target air gap. For example, if the impulse voltage range of the current air gap is 0-300V and the 2% maximum operating overvoltage is 350V and 300V, then the impulse voltage range of the air gap is 0-300V. In this case, the air gap distance is increased until the impulse voltage range of the air gap is adjusted to include 350V. Then the air gap at the current distance is the target air gap.

[0045] Determine whether the equivalent wavefront time of the long-wavehead waveform of the target air gap is equal to the equivalent wavefront time. If so, the target air gap is used as the air gap for the impulse discharge test in step S4. The equivalent wavefront time of the target air gap is also calculated through PSCAD simulation.

[0046] The equivalent wavefront time is determined by the following method:

[0047] T f =η(T) p -T 85％ ), where η is the equivalent wavefront time calculation coefficient, T f This is the equivalent wavefront time.

[0048] In this embodiment, the 50% flashover voltage is determined by the following method.

[0049]

[0050] Among them: U i Let n be the voltage applied during the i-th breakdown of the air gap, and n be the total number of effective tests. i The number of experiments conducted under the same impulse voltage.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for correcting air gaps considering the impact of long-wavehead impacts, characterized in that: Includes the following steps: S1. Obtain environmental parameters of the actual environment at different locations along the long transmission line, including air pressure, temperature, and humidity; S2. The transmission line is simulated using simulation software, and the switching overvoltage and long wavefront waveform at different locations are determined by the simulation software; the equivalent wavefront time of the long wavefront and the maximum switching overvoltage of 2% are also determined. S3. Select an air gap that matches the equivalent wavefront time of the long wavefront waveform determined in step S2 and the maximum operating overvoltage of 2%. S4. Conduct impulse discharge experiments on the selected air gap under different environmental parameters to determine the 50% flashover voltage of the air gap. ; S5. Construct a model relating 50% flashover voltage to environmental parameter influence coefficients, and use ORIGIN software to fit and solve the model to obtain the environmental parameter influence coefficients. S6. Substitute the environmental parameters at different locations along the transmission line into the relational model to calculate the 50% flashover voltage. Based on the calculated 50% flashover voltage Determine the corresponding air gap distance; In step S5, the relationship model between the 50% flashover voltage and the influence coefficient of environmental parameters is as follows: ； Where: A is the comprehensive influence coefficient, P0 is the standard atmospheric pressure, h is the absolute humidity, d is the air gap distance, c is the additional influence coefficient of absolute humidity, m is the characteristic influence index of air gap distance, n is the characteristic influence index of absolute humidity, and P is the air pressure at the current location of the transmission line. Step S3 specifically includes: Operational overvoltages include planned closing operation overvoltages, reclosing operation overvoltages, operational overvoltages caused by single-phase ground faults, and fault clearing operation overvoltages. Select the target operating overvoltage in the operating overvoltage section; The target operating overvoltages are arranged in descending order, and 2% of the target operating overvoltage data are selected as a reference. Determine whether the impulse voltage range of the candidate air gap includes 2% of the maximum operating overvoltage. If so, use the current air gap as the target air gap. Determine whether the equivalent wavefront time of the long wavefront waveform of the target air gap is equal to the equivalent wavefront time. If so, the target air gap is used as the air gap for the impulse discharge test in step S4. The equivalent wavefront time is determined by the following method: ,in, The coefficients are calculated for the equivalent wavefront time. This is the equivalent wavefront time.

2. The air gap correction method considering the impact of long-wave head impact according to claim 1, characterized in that: The 50% flashover voltage is determined using the following method. : Among them: U i Let n be the voltage applied during the i-th breakdown of the air gap, and n be the total number of effective tests. i The number of experiments conducted under the same impulse voltage.

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