A precise calculation method for voltage distribution characteristics along ultra-high voltage transmission lines under series charging.

Abstract

This invention provides a method for accurately calculating the voltage distribution characteristics along ultra-high voltage transmission lines when they are connected in series. The method includes: first, calculating the line wave impedance and propagation constant based on the line's lumped or distributed power frequency parameters, and retrieving the voltage flow calculation results of any node at the beginning, end, and end of the series-connected line from the power system power flow simulation results; second, considering the location of the parallel high-voltage reactors, calculating the voltage distribution along the second section of the line and the current at the beginning based on the voltage readings; then, calculating the current at the end of the first section of the line and the voltage distribution along the first section of the line; finally, plotting the voltage distribution curve along the series-connected line and returning the highest voltage value and its corresponding location. This invention can quickly and accurately calculate the voltage distribution curve along the series-connected ultra-high voltage transmission line when the parallel high-voltage reactors are located at different positions on the series-connected line, effectively avoiding the damage to the insulation of power equipment caused by overvoltage along the line during commissioning.

Description

Technical Field

[0001] This invention relates to the calculation of steady-state voltage during the start-up and commissioning of newly built power transmission projects in power systems, specifically a method for accurately calculating the voltage distribution characteristics along ultra-high voltage transmission lines under series charging. Background Technology

[0002] Before a newly constructed ultra-high voltage transmission project in a power system is put into operation, the commissioning of the newly constructed equipment must be completed. Commissioning work includes switch protection verification, phase verification tests, bus phase verification tests, new line switching tests, and synchronization loop tests. Under no-load charging conditions, the voltage along the line may exceed the maximum operating voltage, which can damage the insulation of the power equipment. When a parallel high-voltage reactor is installed at the beginning or end of a new line, the highest voltage along the line under no-load charging may not appear at the charging end; it is related to the location of the charging power source, the capacity of the parallel high-voltage reactor, and the electrical parameters of the line. When a new transmission project involves π-connection of lines or new lines at adjacent sites, two lines are often connected in series during commissioning. In this case, the highest voltage along the series-connected lines and its location are related to the electrical parameters of both lines, making the voltage distribution characteristics more complex. However, current power system simulation software, typically Power System Analysis and Synthesis Program (PSASP), can only calculate the voltage at the beginning and end of the line and cannot calculate the voltage along the series-connected lines, nor can it provide the highest voltage along the series-connected lines and its location. When the series charging line is segmented, only the voltage simulation results of the nodes at the segment points can be obtained, which cannot accurately describe the voltage distribution characteristics along the series charging line.

[0003] Therefore, for the series charging scenario of ultra-high voltage transmission long lines containing parallel high voltage reactors, it is urgent to study a rapid and accurate calculation method for the voltage distribution characteristics along the series charging line under different installation positions of parallel high voltage reactors, so as to meet the calculation requirements of the highest steady-state voltage along the line during the start-up and commissioning of new transmission projects. Summary of the Invention

[0004] The technical problem this invention aims to solve is a method for calculating the voltage distribution characteristics along a series-charged transmission line. This method is based on the voltage simulation results of any end node of the series-charged line, considers different installation positions of the parallel high-voltage reactors, and sequentially calculates the voltage distribution along the series-charged line. Finally, it returns the voltage distribution curve and the highest value information along the line. This method can be applied to the steady-state voltage calculation scenario during the start-up and commissioning of newly built transmission projects, thereby avoiding damage to power equipment caused by overvoltage along the line during commissioning and ensuring the safe and stable operation of the power grid.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0006] A method for accurately calculating the voltage distribution characteristics along an ultra-high voltage transmission line under series charging, comprising the following steps:

[0007] (1) Calculate the line electrical parameters based on the line power frequency lumped parameters or distributed parameters. The line electrical parameters include the line wave impedance and propagation constant. Then, retrieve the voltage flow calculation results of any node at the beginning, end and end of the series-charged line from the power system power flow simulation results.

[0008] (2) Based on the line electrical parameters and node voltage flow calculation results obtained in step (1), and considering the different locations of the parallel high-voltage reactors in the series charging line, calculate the voltage distribution along the line and the current at the beginning of the second segment of the series charging line.

[0009] (3) Based on the calculation results of step (2), obtain the voltage and current information at the beginning of the second line segment, and calculate the current at the end of the first line segment and the voltage distribution along the first line segment.

[0010] (4) Identify the highest voltage point and location along the line based on the voltage distribution along the second line obtained in step (2) and the voltage distribution along the first line obtained in step (3), and draw the voltage distribution curve along the series charging line.

[0011] Furthermore, in step (1), the line power frequency lumped parameters or distributed parameters are obtained based on the basic database of the power system simulation software PSASP. The lumped parameters include π-type equivalent impedance and susceptance, rated capacity and rated voltage of the line parallel high-voltage reactor, and line length. The distributed parameters include impedance and susceptance per unit length, rated capacity and rated voltage of the line parallel high-voltage reactor, and line length.

[0012] Furthermore, in step (2), based on the line electrical parameters obtained in step (1), for the three cases where the parallel high-voltage reactor is located at the end of the first line segment, the beginning of the second line segment, and the end of the second line segment, the voltage power flow calculation results of any node at the beginning, end, and end of the series-charged line segment are read from the power flow simulation results, the voltage distribution along the second line segment and the current at the beginning are calculated, where the series-charged point is the end of the first line segment or the beginning of the second line segment.

[0013] Furthermore, when the parallel high-voltage reactor is located at the end of the first line segment or the beginning of the second line segment, assuming that the parameters of each line segment are uniformly distributed along the line, the voltage and current at any location on the second line segment are as follows:

[0014]

[0015]

[0016] In the formula, These represent the voltage and current at a node n meters from the end of the line, respectively. The voltage at the end of the second line segment; γ2, Z C2 Let n represent the line propagation constant and wave impedance of the second line segment, respectively; n is the line length at any point from the end of the second line segment.

[0017] Based on the voltage and power flow calculation results of any node at the beginning, end, and end of the series-charged line retrieved from the PSASP power flow simulation, the voltage and current at the beginning of the second section of the line are calculated:

[0018] 1) Given the voltage at the series charging point

[0019]

[0020]

[0021] 2) Given the voltage at the end of the line

[0022]

[0023]

[0024] 3) Given the voltage at the beginning of the line

[0025]

[0026]

[0027] In the formula, γ1 and Z C1 These represent the line propagation constant and wave impedance of the second segment of the line, respectively. This indicates the voltage at the end of the first segment of the line; This refers to the current at the beginning of the second segment of the line; L1 is the voltage at the end of the second line segment; L2 is the line length of the second line segment; X L The reactance value of the parallel high-voltage reactor located at the end of the first section of the line or the beginning of the second section of the line is calculated based on the rated capacity and rated voltage.

[0028] Furthermore, when the parallel high-voltage reactor is located at the end of the second line segment, assuming that the parameters of each line segment are uniformly distributed along the line, the voltage and current at any location on the second line segment are as follows:

[0029]

[0030]

[0031] In the formula, X L2The reactance value of the parallel high-voltage reactor located at the end of the second line segment is calculated based on the rated capacity and rated voltage.

[0032] Based on the voltage and power flow calculation results of any node at the beginning, end, and end of the series-charged line retrieved from the PSASP power flow simulation, the voltage and current at the beginning of the second section of the line are calculated:

[0033] 1) Given the voltage at the series charging point

[0034]

[0035]

[0036] 2) Given the voltage at the end of the line

[0037]

[0038]

[0039] 3) Given the voltage at the beginning of the line

[0040]

[0041]

[0042] In the formula, γ2, Z C2 Let n represent the line propagation constant and wave impedance of the second line segment, respectively; n is the line length at any point from the end of the second line segment. These represent the voltage and current at a node n meters from the end of the line, respectively. This is the voltage at the end of the second line segment.

[0043] Furthermore, step (3) involves obtaining the voltage and current at the beginning of the second line segment based on the calculation results of step (2), and calculating the current at the end of the first line segment and the voltage distribution along the first line segment. Specifically, this includes:

[0044] 1) When the parallel high-voltage reactor is located at the end of the first section of the line or the beginning of the second section of the line, the current at the end of the first section of the line and the voltage at any location are as follows:

[0045]

[0046]

[0047] In the formula, This refers to the current at the end of the first line segment; This refers to the current at the beginning of the second segment of the line; Indicates the voltage at the beginning of the second line segment; X L The reactance value of the parallel high-voltage reactor located at the end of the first section of the line or the beginning of the second section of the line is calculated based on the rated capacity and rated voltage. This represents the voltage at a node located m meters from the end of the first line segment; Indicates the voltage at the beginning of the second line segment; γ1, Z C1 represents the line propagation constant and wave impedance of the first line segment, respectively; m is the line length at any point from the end of the first line segment.

[0048] 2) When the parallel high-voltage reactor is located at the end of the second section of the line, the current at the end of the first section of the line and the voltage at any location are as follows:

[0049]

[0050]

[0051] The beneficial effects of this invention are as follows: This invention explores a precise calculation method for the voltage distribution characteristics along ultra-high voltage transmission lines during series charging. It can quickly and accurately calculate the voltage distribution curves along ultra-high voltage transmission lines when the parallel high-voltage reactors are located at different positions in the series charging line. This effectively overcomes the limitation of existing power system simulation software, which can only calculate the voltage at the beginning and end of the line. It can provide the highest value and location information of the highest voltage along the series charging line when it is not at the end of the charging line. This method is superior to traditional segmented simulation or segmented iterative methods and is suitable for the steady-state voltage calculation scenario during the start-up and commissioning of newly built transmission projects. It has important guiding significance for the boundary conditions of engineering commissioning. Attached Figure Description

[0052] Figure 1 This is a flowchart illustrating a method for accurately calculating the voltage distribution characteristics along an ultra-high voltage transmission line under series charging, according to an embodiment of the present invention.

[0053] Figure 2 This is a voltage distribution curve along the series charging lines AB and BC of the present invention.

[0054] Figure 3 This is a voltage distribution curve along the DE and EF lines of the present invention. Detailed Implementation

[0055] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0056] like Figure 1As shown, this embodiment of the invention provides a method and program for accurately calculating the voltage distribution characteristics along an ultra-high voltage transmission line undergoing series charging. First, the line wave impedance and propagation constant are calculated based on the line's power frequency lumped or distributed parameters, and the voltage flow calculation results of any node at the beginning, end, and end of the series charging line are retrieved from the power system power flow simulation results. Second, considering the location of the parallel high-voltage reactors on the line, the voltage distribution along the second segment of the line and the current at the beginning are calculated based on the voltage readings. Then, the current at the end of the first segment of the line and the voltage distribution along the first segment are calculated. Finally, the voltage distribution curve along the series charging line is plotted, and the highest voltage value and corresponding location along the line are returned.

[0057] The lumped or distributed parameters of each line segment are obtained from the basic database of the power system simulation software PSASP: 1) Lumped parameters: π-type equivalent impedance, susceptance, rated capacity and rated voltage of the parallel high-voltage reactor, and line length; 2) Distributed parameters: impedance and susceptance per unit length, rated capacity and rated voltage of the parallel high-voltage reactor, and line length. Then, the wave impedance and propagation constant of each line segment in series are calculated based on the lumped / distributed parameters.

[0058] The voltage distribution and head current calculation of the second line segment will be calculated based on the voltage and current flow calculation results of any node at the head, the charging point (head of the first line / head of the second line), and the end of the series-charged second line segment, taking into account different cases where the parallel high-voltage reactor is located at the end of the first line segment, the head of the second line segment, and the end of the second line segment.

[0059] The voltage distribution and current calculation at the beginning of the second line segment when the parallel high-voltage reactor is located at the end of the first line segment or the beginning of the second line segment are as follows:

[0060] Assuming the parameters of each line segment are uniformly distributed along the line, the voltage and current at any location on the second line segment are as follows:

[0061]

[0062]

[0063] In the formula, γ2, Z C2 Let n represent the line propagation constant and wave impedance of the second line segment, respectively; n is the line length at any point from the end of the second line segment. These represent the voltage and current at a node n meters from the end of the line, respectively. This is the voltage at the end of the second line segment.

[0064] Based on the voltage and power flow calculation results of any node at the beginning, end, and end of the series-charged line retrieved from the PSASP power flow simulation, the voltage and current at the beginning of the second section of the line are calculated.

[0065] 1) Given the voltage at the series charging point

[0066]

[0067]

[0068] 2) Given the voltage at the end of the line

[0069]

[0070]

[0071] 3) Given the voltage at the beginning of the line

[0072]

[0073]

[0074] In the formula, γ1 and Z C1 These represent the line propagation constant and wave impedance of the second segment of the line, respectively. This indicates the voltage at the end of the first line segment; This refers to the current at the beginning of the second segment of the line; L1 is the voltage at the end of the second line segment; L2 is the line length of the second line segment; X L The reactance value of the parallel high-voltage reactor located at the end of the first section of the line or the beginning of the second section of the line can be calculated based on the rated capacity and rated voltage.

[0075] The voltage distribution and head current calculation of the second line segment when the parallel high-voltage reactor is located at the end of the second line segment are as follows:

[0076] Assuming the parameters of each line segment are uniformly distributed along the line, the voltage and current at any location on the second line segment are as follows:

[0077]

[0078]

[0079] In the formula, X L2 The reactance value of the parallel high-voltage reactor located at the end of the second line segment is calculated based on the rated capacity and rated voltage.

[0080] Based on the voltage and power flow calculation results of any node at the beginning, end, and end of the series-charged line retrieved from the PSASP power flow simulation, the voltage and current at the beginning of the second section of the line are calculated.

[0081] 1) Given the voltage at the series charging point

[0082]

[0083]

[0084] 2) Given the voltage at the end of the line

[0085]

[0086]

[0087] 3) Given the voltage at the beginning of the line

[0088]

[0089]

[0090] The method for calculating the voltage distribution along the first section of the line is as follows:

[0091] Based on the aforementioned calculations, the voltage and current at the beginning of the second line segment are obtained. Further calculations are then performed on the current at the end of the first line segment and the voltage distribution along the first line segment.

[0092] 1) When the parallel high-voltage reactor is located at the end of the first section of the line or the beginning of the second section of the line, the current at the end of the first section of the line and the voltage at any location are as follows:

[0093]

[0094]

[0095] In the formula, m is the length of the line at any point from the end of the first line segment; This represents the voltage at a node located m meters from the end of the first line segment; This refers to the current at the end of the first line segment; This indicates the voltage at the beginning of the second line segment.

[0096] 2) When the parallel high-voltage reactor is located at the end of the second section of the line, the current at the end of the first section of the line and the voltage at any location are as follows:

[0097]

[0098]

[0099] Example Verification Analysis 1:

[0100] Taking the series charging of a newly built power transmission and transformation project during commissioning as an example, the method for accurately calculating the voltage distribution characteristics along the line for series charging of ultra-high voltage transmission lines is verified and analyzed on the MATLAB 2018a simulation platform.

[0101] First, the lumped parameters of the series charging line obtained from the basic database of the power system simulation software PSASP are as follows:

[0102] The length of the ultra-high voltage line AB is 179.586km, and the length of the ultra-high voltage line BC is 44.7km. The line parameters are shown in Table 1 below. The B side of line AB has a line parallel high voltage reactor with a rated capacity of 150Mvar and a rated voltage of 550kV.

[0103] Table 1. Per-unit reference values ​​of lumped parameters for 500kV lines AB and BC: U b =525kV, S b =100MVA

[0104] Line Name <![CDATA[R1]]> <![CDATA[X1]]> <![CDATA[B1 / 2]]> <![CDATA[R0]]> <![CDATA[X0]]> <![CDATA[B0 / 2]]> BC 0.000230 0.004296 0.266711 0.002944 0.012127 0.151395 AB 0.001162 0.017533 1.056712 0.012132 0.047886 0.688674

[0105] Substations A and B are located on either side of line AB, and substations B and C are located on either side of line BC. Considering a scenario where line BC (operating with a parallel high-voltage reactor) is charged from substation A, with the line electrical parameters and the location of the parallel high-voltage reactor known, the voltage at the beginning node of the series line is obtained as 531.53∠-25.68°kV based on PSASP. The proposed method and program for accurately calculating the voltage distribution characteristics along the series charging line are used to calculate the voltage distribution characteristics along line BC charged from line AB. Starting from side A of line AB, the voltage distribution curves along lines AB and BC are as follows: Figure 2 As shown, the highest voltage along the line is 535.17 kV, located 108.7 km from side A of line AB; the voltage at side B at the end of line AB is 533.63 kV; and the voltage at side C at the end of line BC is 534.24 kV.

[0106] Example Verification Analysis 2:

[0107] Taking the series charging of a newly built power transmission and transformation project during commissioning as an example, the method for accurately calculating the voltage distribution characteristics along the line for series charging of ultra-high voltage transmission lines is verified and analyzed on the MATLAB 2018a simulation platform.

[0108] First, the lumped parameters of the series charging line obtained from the basic database of the power system simulation software PSASP are as follows:

[0109] The length of the ultra-high voltage line DE is 62.98km, and the length of the ultra-high voltage line EF is 162.68km. The line parameters are shown in Table 2 below. The F side of line EF has a line parallel high-voltage reactor with a rated capacity of 150Mvar and a rated voltage of 550kV.

[0110] Table 2. Per-unit reference values ​​of lumped parameters DE and EF for 500kV lines: U b =525kV, S b =100MVA

[0111] Line Name <![CDATA[R1]]> <![CDATA[X1]]> <![CDATA[B1 / 2]]> <![CDATA[R0]]> <![CDATA[X0]]> <![CDATA[B0 / 2]]> DE 0.000217 0.006138 0.396357 0.004623 0.020431 0.218591 EF 0.000561 0.015853 1.023769 0.011940 0.052771 0.564608

[0112] Substations D and E are located on either side of line DE, and substations E and F are located on either side of line EF. Considering a scenario where line DE is charged in series with line EF (operating with a parallel high-voltage reactor) using substation D as the power source, given the line electrical parameters and the location of the parallel high-voltage reactor, and based on PSASP, the series node voltage of the series line is obtained as 527.25∠-6.82°kV. The proposed method and program for accurately calculating the voltage distribution characteristics along the series charging line are used to calculate the voltage distribution characteristics along line DE and line EF. Starting from side D of line DE, the voltage distribution curves along lines DE and EF are as follows: Figure 3 As shown. The highest voltage along the line is 528.21 kV, located 54.3 km from the E side of the line EF; the voltage at the F side of the end of the line EF is 524.40 kV.

[0113] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for accurately calculating the voltage distribution characteristics along an ultra-high voltage transmission line under series charging, characterized in that, Includes the following steps: (1) Calculate the line electrical parameters based on the line power frequency lumped parameters or distributed parameters. The line electrical parameters include the line wave impedance and propagation constant. Then, retrieve the voltage flow calculation results of any node at the beginning, end and end of the series-charged line from the power system power flow simulation results. (2) Based on the line electrical parameters and node voltage flow calculation results obtained in step (1), and considering the different locations of the parallel high-voltage reactors in the series charging line, calculate the voltage distribution along the line and the current at the beginning of the second segment of the series charging line. (3) Based on the calculation results of step (2), obtain the voltage and current information at the beginning of the second line segment, and calculate the current at the end of the first line segment and the voltage distribution along the first line segment. (4) Identify the highest voltage point and location along the line based on the voltage distribution along the second line segment calculated in step (2) and the voltage distribution along the first line segment calculated in step (3), and draw the voltage distribution curve along the series charging line. Step (3) involves obtaining the voltage and current at the beginning of the second line segment based on the calculation results of step (2), and calculating the current at the end of the first line segment and the voltage distribution along the first line segment. Specifically, this includes: 1) When the parallel high-voltage reactor is located at the end of the first section of the line or the beginning of the second section of the line, the current at the end of the first section of the line and the voltage at any location are as follows: ； In the formula, This refers to the current at the end of the first line segment; This refers to the current at the beginning of the second segment of the line; This indicates the voltage at the beginning of the second line segment; The reactance value of the parallel high-voltage reactor located at the end of the first section of the line or the beginning of the second section of the line is calculated based on the rated capacity and rated voltage. This represents the voltage at a node located m meters from the end of the first line segment; , represents the line propagation constant and wave impedance of the first line segment, respectively; m is the line length at any point from the end of the first line segment. 2) When the parallel high-voltage reactor is located at the end of the second section of the line, the current at the end of the first section of the line and the voltage at any location are as follows: 。 2. The method for accurately calculating the voltage distribution characteristics along an ultra-high voltage transmission line under series charging as described in claim 1, characterized in that, In step (1), the line power frequency lumped parameters or distributed parameters are obtained based on the basic database of the power system simulation software PSASP. The lumped parameters include π-type equivalent impedance and susceptance, rated capacity and rated voltage of the line parallel high-voltage reactor, and line length. The distributed parameters include impedance and susceptance per unit length, rated capacity and rated voltage of the line parallel high-voltage reactor, and line length.

3. The method for accurately calculating the voltage distribution characteristics along an ultra-high voltage transmission line under series charging as described in claim 1, characterized in that, In step (2), based on the line electrical parameters obtained in step (1), for the three cases where the parallel high-voltage reactor is located at the end of the first line segment, the beginning of the second line segment, and the end of the second line segment, the voltage power flow calculation results of any node at the beginning, end, and end of the series-charged line segment are read from the power flow simulation results, and the voltage distribution and the beginning current of the second line segment are calculated. The series-charged point is either the end of the first line segment or the beginning of the second line segment.

4. The method for accurately calculating the voltage distribution characteristics along an ultra-high voltage transmission line under series charging as described in claim 3, characterized in that, When the parallel high-voltage reactor is located at the end of the first section of the line or the beginning of the second section of the line, assuming that the parameters of each section of the line are uniformly distributed along the line, the voltage and current at any location on the second section of the line are as follows: ； In the formula, These represent the voltage and current at a node n meters from the end of the line, respectively. This refers to the voltage at the end of the second line segment; , Let n represent the line propagation constant and wave impedance of the second line segment, respectively; n is the line length at any point from the end of the second line segment. Based on the voltage and power flow calculation results of any node at the beginning, end, and end of the series-charged line retrieved from the PSASP power flow simulation, the voltage and current at the beginning of the second section of the line are calculated: 1) Given the voltage at the series charging point ; ； 2) Given the voltage at the end of the line : ； 3) Given the voltage at the beginning of the line : ； In the formula, , These represent the line propagation constant and wave impedance of the first segment of the line, respectively. This indicates the voltage at the end of the first segment of the line; This refers to the current at the beginning of the second segment of the line; This refers to the voltage at the end of the second line segment; This is the length of the second segment of the line; The reactance value of the parallel high-voltage reactor located at the end of the first section of the line or the beginning of the second section of the line is calculated based on the rated capacity and rated voltage.

5. The method for accurately calculating the voltage distribution characteristics along an ultra-high voltage transmission line under series charging as described in claim 3, characterized in that, When the parallel high-voltage reactor is located at the end of the second line segment, assuming that the parameters of each line segment are uniformly distributed along the line, the voltage and current at any location on the second line segment are as follows: ； In the formula, The reactance value of the parallel high-voltage reactor located at the end of the second line segment is calculated based on the rated capacity and rated voltage. Based on the voltage and power flow calculation results of any node at the beginning, end, and end of the series-charged line retrieved from the PSASP power flow simulation, the voltage and current at the beginning of the second section of the line are calculated: 1) Given the voltage at the series charging point : ； 2) Given the voltage at the end of the line : ； 3) Given the voltage at the beginning of the line : ； In the formula, , These represent the line propagation constant and wave impedance of the second segment of the line, respectively. , Let n represent the line propagation constant and wave impedance of the first line segment, respectively; n is the line length at any point from the end of the second line segment. These represent the voltage and current at a node n meters from the end of the line, respectively. This is the voltage at the end of the second line segment. This represents the current at the beginning of the second segment of the line.

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