Induced voltage calculation method and system for short-circuit working condition of multiple ground wires at end of double-circuit line in same tower

Abstract

This invention discloses a method and system for calculating induced voltage under the condition of multiple conductors and ground wires being short-circuited at the ends of a double-circuit transmission line on the same tower. The method obtains the line's geometric and operating parameters and calculates the line's self-capacitance and mutual capacitance. Based on the capacitance parameters, it calculates the coupling coefficients of normally operating and out-of-operation lines to other lines. Then, it writes induced voltage equations including coupling effects for each out-of-operation line. According to the actual end-short-circuit condition, the relevant equations are specially processed: the left-hand sides of the equations for the short-circuited lines are added to form new equations, and a constraint equation for equal voltage between the short-circuited lines is added, thereby constructing an accurate set of induced voltage calculation equations. Solving this set of equations yields the precise induced voltage of all out-of-operation lines. This invention significantly improves the calculation accuracy of induced voltage under complex short-circuit conditions by accurately modeling the physical constraint of end-short-circuit, providing key technical support for formulating scientific de-icing strategies and ensuring the safety of maintenance operations.

Description

Technical Field

[0001] This invention belongs to the field of power system relay protection, and specifically relates to a method for calculating induced voltage of lines on the same tower. Background Technology

[0002] With the rapid growth of electricity load, the construction of double-circuit transmission lines on the same tower is becoming increasingly common in order to save land resources and optimize transmission corridors. However, complex electromagnetic coupling exists between lines on the same tower, bringing new problems to line operation and maintenance. Especially during line de-icing and maintenance operations, some lines may be out of service or in special operating conditions. Taking the de-icing process as an example, it often happens that when one conductor is running, the ends of several conductors and ground wires on the same tower are short-circuited and suspended, while the remaining conductors and ground wires may be suspended and not short-circuited. Regardless of whether they are short-circuited or not, the strong electromagnetic field generated by the nearby normally operating lines will induce high voltages on the deactivated conductors and ground wires. This induced voltage is difficult to calculate, and the deactivated lines affect each other. Without accurate calculation and evaluation of the induced voltage, it may not only lead to overload damage to the de-icing device and forced interruption of maintenance operations, but also pose safety risks to on-site personnel. Therefore, it is necessary to calculate the induced voltage distribution characteristics of lines on the same tower under complex operating conditions. This technology has crucial engineering significance for formulating scientific de-icing strategies, ensuring the safety of maintenance operations, and improving the level of power grid operation and maintenance. Summary of the Invention

[0003] To address the challenge of induced voltage calculation under the condition of short-circuiting the ends of multiple conductors and ground wires in a double-circuit line on the same tower, this invention proposes a method and system for calculating induced voltage under the same condition of short-circuiting the ends of multiple conductors and ground wires in a double-circuit line on the same tower. The induced voltage calculation takes into account the coupling effect of the out-of-operation lines. By accurately obtaining the coupling parameters and accurately analyzing the coupling effect between the out-of-operation lines, the accuracy of induced voltage calculation is greatly improved, which can provide key guidance for the de-icing and maintenance plan formulation of the line.

[0004] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, this invention proposes a method for calculating the induced voltage under the condition of short-circuiting the ends of multiple conductors and ground wires in a double-circuit line on the same tower, comprising the following steps: Obtain the geometric parameters and operating parameters of a double-circuit line on the same tower. The geometric parameters include the spatial distribution and model parameters of the conductors and ground wires in the double-circuit line on the same tower. The operating parameters include at least the voltage of the normally operating circuit. Based on the geometric parameters, calculate the capacitance parameters between each line in the double-circuit line on the same tower; Based on the capacitance parameters, the equivalent coupling coefficient of the normal operating circuit to each line and the mutual coupling coefficient between the out-of-operation lines are determined. Based on the equivalent coupling coefficient, the mutual coupling coefficient, and the voltage of the normal operating circuit, an induced voltage equation is established for each out-of-operation line. The induced voltage equation characterizes the coupling relationship between the induced voltage of the out-of-operation line, the voltage of the normal operating circuit, and the induced voltage of other out-of-operation lines. Based on the actual short-circuit connection relationship at the end of each out-of-service line, constraints are applied to the induced voltage equation to construct a closed set of equations; wherein, for each group of out-of-service lines whose ends are short-circuited to each other, the applied constraints include: the induced voltage of all out-of-service lines in the group is equal, and the total coupling current flowing through the short-circuit point is zero. Solve the system of equations to obtain the induced voltage of all out-of-service lines.

[0005] Furthermore, determining the coupling coefficient based on the capacitance parameters specifically includes: The conductors of the double-circuit lines on the same tower are numbered 1 to 6, and the ground wires are numbered 7 and 8. Among them, numbers 1 to 3 are the lines of the normally operating circuit. The equivalent coupling coefficient of the normal operating circuit to line number q Calculated using the following formula:

[0006] In the formula, , , These are the mutual capacitances between lines 1, 2, and 3 and line q, respectively. , For the preset phase operator, It is the sum of the self-capacitance of line q and the mutual capacitance between all other lines; The mutual coupling coefficient between the out-of-service line numbered p and the line numbered q Calculated using the following formula:

[0007] in, Let be the mutual capacitance between line p and line q.

[0008] Furthermore, the capacitance parameters include the self-capacitance of each line obtained by the method of images. and the mutual capacitance between any two lines .

[0009] Furthermore, the step of establishing an induced voltage equation for each outage line specifically involves establishing an equation of the following form: For the line numbered... The induced voltage of the out-of-service lines satisfy:

[0010] in, This is a set of numbers for all the suspended lines. This refers to the induced voltage of other out-of-service lines. For the line For the line The mutual coupling coefficient, For normal operation of the circuit, the line The equivalent coupling coefficient, The voltage of the normally operating circuit is denoted as .

[0011] Furthermore, the constraint that the total coupling current flowing through the short-circuit point is zero is achieved by summing the left-hand sides of the induced voltage equations corresponding to all out-of-operation lines within the short-circuit group to zero.

[0012] Furthermore, the method is applied to the safety assessment of induced voltage during DC de-icing operations or power outage maintenance of transmission lines. Furthermore, the geometric parameters include the spatial coordinates, type, number of splits, outer diameter, and sag of each conductor and ground wire.

[0013] Secondly, this invention also proposes an induced voltage calculation system for a double-circuit line on the same tower under the condition of short-circuiting at the ends of multiple conductors and ground wires, implementing the method described in any one of the claims, including: The parameter acquisition module is used to acquire the geometric parameters and operating parameters of the double-circuit line on the same tower. The operating parameters include at least the voltage of the normally operating circuit. The parameter calculation module is used to calculate the capacitance parameters between each line in the double-circuit line on the same tower based on the geometric parameters. The coupling coefficient determination module is used to determine the equivalent coupling coefficient of the normal operating circuit to each line, and the mutual coupling coefficient between the out-of-operation lines, based on the capacitance parameters. The equation establishment module is used to establish an induced voltage equation for each out-of-operation line based on the equivalent coupling coefficient, the mutual coupling coefficient and the voltage of the normal operation circuit. The induced voltage equation characterizes the coupling relationship between the induced voltage of the out-of-operation line and the voltage of the normal operation circuit and the induced voltage of other out-of-operation lines. The equation system construction module is used to impose constraints on the induced voltage equations based on the actual short-circuit connection relationship at the end of each out-of-service line, and construct a closed equation system; wherein, for each group of out-of-service lines whose ends are short-circuited to each other, the imposed constraints include: the induced voltage of all out-of-service lines in the group is equal, and the total coupling current flowing through the short-circuit point is zero. The solver module is used to solve the system of equations to obtain the induced voltage of all out-of-service lines.

[0014] Furthermore, the parameter calculation module is specifically used to calculate the self-capacitance and mutual capacitance of each line using the mirror method; the coupling coefficient determination module is specifically used to perform the calculation.

[0015] This invention addresses the challenge of accurately calculating the induced voltage of double-circuit power lines on the same tower when some lines are out of service and complex short-circuit connections exist at their ends during de-icing, maintenance, and other operations. It proposes a technical solution that "applies physical constraints to the induced voltage equation based on coupling relationships according to the actual short-circuit connections at the ends of the out-of-service lines, thereby constructing and solving a closed set of equations." This achieves accurate calculation of the induced voltage of each out-of-service line under such complex conditions. Compared to existing technologies, it achieves the following significant technical advantages: 1. Existing methods often struggle to handle complex electrical connections formed by shorting the ends of multiple lines. This invention addresses this problem by explicitly applying two sets of physical constraints—"equal induced voltages" and "zero total coupling current"—to the shorted line group, thus constructing a closed and solvable mathematical model. This provides the first systematic solution to the problem of accurate calculation under this specific operating condition.

[0016] 2. The technical solution derives the constraint conditions from the physical essence of "short circuit", so that the established equations rigorously reflect the real coupling and boundary conditions between lines. It overcomes the shortcomings of large errors in traditional simplification methods, significantly improves the calculation accuracy of induced voltage, and provides a reliable basis for subsequent de-icing power setting and safety distance verification.

[0017] 3. By providing accurate induced voltage distribution data, it can directly guide the formulation of scientific de-icing strategies (such as optimizing short-circuit schemes and setting safe currents), and accurately assess the risk of electric shock during maintenance operations, thereby effectively ensuring equipment safety and personnel safety, and improving the precision and intelligence level of power grid operation and maintenance. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the induced voltage calculation method for a double-circuit line on the same tower under the condition of short-circuiting at the ends of multiple conductors and ground wires, as described in this invention.

[0019] Figure 2 This is a schematic diagram of the tower structure of a double-circuit line on the same tower, according to an embodiment of the present invention.

[0020] Figure 3 This is a block diagram of the induced voltage calculation system for a double-circuit line on the same tower under the condition of short-circuiting at the ends of multiple conductors and ground wires. Detailed Implementation

[0021] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0022] Step 1: Obtain the geometric and operational parameters of the line; wherein, the geometric parameters include the spatial distribution and model parameters of the conductors and ground wires in a double-circuit line on the same tower, and the operational parameters include at least the voltage of the normally operating circuit; a detailed description is as follows: Based on the tower structure, obtain the spatial distribution and model parameters of the line. Specifically, this includes: the distance of each double-circuit conductor to the ground and its distance to the center crossarm of the tower, as well as the distance of the ground wire to the ground and its distance to the center crossarm of the tower. In addition, the number of strands, outer diameter, and sag parameters of the conductors and ground wire should also be obtained.

[0023] Based on the actual operation of the line, obtain the A-phase voltage of the normally operating circuit on the tower. .

[0024] Step 2: Based on the geometric parameters, calculate the capacitance parameters between each line in the double-circuit line on the same tower; specifically, the line parameters are calculated based on the image method, as described below: Based on the above geometric parameters, the self-capacitance of each line to ground in a double-circuit line on the same tower is calculated using the image method. and the mutual capacitance between any two lines Where p and q represent the line numbers (usually two circuits with six conductors numbered 1-6, and two ground wires numbered 7-8). The capacitance parameters will be used to solve the subsequent circuit equations. For example... Figure 2 The diagram shows a schematic of the tower structure for a double-circuit transmission line provided in an embodiment of the present invention. The diagram clearly indicates the line numbers: 1-3 represent the three-phase conductors of the first circuit (operating circuit), 4-6 represent the three-phase conductors of the second circuit (out of service circuit), and 7 and 8 represent the two ground wires. This numbering system corresponds one-to-one with the solution for line parameters (such as capacitance and coupling coefficient) and induced voltage in subsequent calculations, forming the basis for establishing an accurate mathematical model and performing calculations.

[0025] Step 3: Based on the capacitance parameters, determine the equivalent coupling coefficient of the normally operating circuit to each line, and the mutual coupling coefficient between the out-of-operation lines; the specific description is as follows: The equivalent coupling coefficient of the normal operating circuit to line number q Calculated using the following formula: (1) In the formula: This indicates the phase difference between line 2 and line 1 (phase A); This indicates the phase difference between line 3 and line 1 (phase A). This represents the sum of the self-capacitance of line q and the mutual capacitance between it and other lines.

[0026] For the out-of-service line, let its number be p (p is 4-8), then its coupling coefficient with line q is: (2) Step 4: Establish an induced voltage equation for each out-of-operation line; the induced voltage equation characterizes the coupling relationship between the induced voltage of the out-of-operation line, the voltage of the normal operating circuit, and the induced voltage of other out-of-operation lines; Since the voltage of the normally operating line is the same as the running voltage, there is no need to calculate the induced voltage. Therefore, we only need to solve for the induced voltage of the out-of-operation line. The relationship between the induced voltage of the out-of-operation line and other line voltages is expressed by the following formula: Line number 4 that is out of service: (3) Line number 5 that is out of service: (4) Line number 6 that is out of service: (5) Line number 7 that is out of service: (6) Line number 8 that is out of service: (7) in, ~ These are the induced voltages to be solved on each line, and The voltage of phase A of the normal line that was not shut down in step (1).

[0027] Step 5: Construct a closed system of equations; the equations for calculating the induced voltage are listed below: Based on the induced voltage equation for each line, and according to the number and number of short-circuited lines in actual operating conditions, a set of induced voltage calculation equations can be further formulated. Adding the left sides of the induced voltage equations for all short-circuited lines, with the sum of the right sides still being 0, yields the first new induced voltage calculation equation. The remaining equations in the set represent the same induced voltage for each out-of-operation line. For lines that are not short-circuited but are only in a floating state, their form in the equation set remains unchanged. For example, when lines 4 and 5 are short-circuited in actual operating conditions, the first equation obtained by adding the equations is: (8) The second equation states that the induced voltages in lines 4 and 5 are equal: (9) For lines 6-8, the equations remain unchanged, as shown in equations (5)-(7).

[0028] Combining the above equations, the system of equations for calculating the induced voltage can be written as follows: (10) According to equation (10), the induced voltage equation for each outage line is established, specifically, the equation is established in the following form: For the line numbered... The induced voltage of the out-of-service lines satisfy:

[0029] in, This is a set of numbers for all the suspended lines. This refers to the induced voltage of other out-of-service lines. For the line For the line The mutual coupling coefficient, For normal operation of the circuit, the line The equivalent coupling coefficient, The voltage of the normally operating circuit is denoted as .

[0030] Step 6: Solve the system of equations to obtain the induced voltage of all out-of-service lines; Since the number of unknowns and equations in equation system (10) is the same as the number of out-of-service lines, the equation system has a unique solution. By solving higher-order equation systems, the induced voltage of each out-of-service line, including both short-circuited and unshort-circuited lines, can be obtained.

[0031] The above description is merely an embodiment of the present invention and is not intended to limit the methods proposed in this invention. The scope of protection of this invention is defined by the claims. Any obvious modifications or variations in form and detail made by those skilled in the art without departing from the spirit and scope of this invention should fall within the scope of protection of this invention.

Claims

1. A method for calculating the induced voltage under the condition of short-circuiting the ends of multiple conductors and ground wires in a double-circuit line on the same tower, characterized in that, Includes the following steps: Obtain the geometric parameters and operating parameters of a double-circuit line on the same tower. The geometric parameters include the spatial distribution and model parameters of the conductors and ground wires in the double-circuit line on the same tower. The operating parameters include at least the voltage of the normally operating circuit. Based on the geometric parameters, calculate the capacitance parameters between each line in the double-circuit line on the same tower; Based on the capacitance parameters, the equivalent coupling coefficient of the normal operating circuit to each line and the mutual coupling coefficient between the out-of-operation lines are determined. Based on the equivalent coupling coefficient, the mutual coupling coefficient, and the voltage of the normal operating circuit, an induced voltage equation is established for each out-of-operation line. The induced voltage equation characterizes the coupling relationship between the induced voltage of the out-of-operation line, the voltage of the normal operating circuit, and the induced voltage of other out-of-operation lines. Based on the actual short-circuit connection relationship at the end of each out-of-service line, constraints are applied to the induced voltage equation to construct a closed set of equations; wherein, for each group of out-of-service lines whose ends are short-circuited to each other, the applied constraints include: the induced voltage of all out-of-service lines in the group is equal, and the total coupling current flowing through the short-circuit point is zero. Solve the system of equations to obtain the induced voltage of all out-of-service lines.

2. The method for calculating induced voltage under the condition of short-circuiting the ends of multiple conductors and ground wires in a double-circuit line on the same tower as described in claim 1, characterized in that, The determination of the coupling coefficient based on the capacitance parameters specifically includes: The conductors of the double-circuit lines on the same tower are numbered 1 to 6, and the ground wires are numbered 7 and 8. Among them, numbers 1 to 3 are the lines of the normally operating circuit. The equivalent coupling coefficient of the normal operating circuit to line number q Calculated using the following formula: In the formula, , , These are the mutual capacitances between lines 1, 2, and 3 and line q, respectively. , For the preset phase operator, It is the sum of the self-capacitance of line q and the mutual capacitance between all other lines; The mutual coupling coefficient between the out-of-service line numbered p and the line numbered q Calculated using the following formula: in, Let be the mutual capacitance between line p and line q.

3. The method for inducing voltage under the condition of short-circuiting the ends of multiple conductors and ground wires of a double-circuit line on the same tower according to claim 1 or 2, characterized in that, The capacitance parameters include the self-capacitance of each line obtained by the method of images. and the mutual capacitance between any two lines .

4. The method for inducing voltage under the condition of short-circuiting the ends of multiple conductors and ground wires of a double-circuit line on the same tower according to claim 1, characterized in that, The aforementioned process establishes an induced voltage equation for each outage line, specifically an equation of the following form: For line numbered... The induced voltage of the out-of-service lines satisfy: in, This is a set of numbers for all the suspended lines. This refers to the induced voltage of other out-of-service lines. For the line For the line The mutual coupling coefficient, For normal operation of the circuit, the line The equivalent coupling coefficient, The voltage of the normally operating circuit is denoted as .

5. The method for inducing voltage under the condition of short-circuiting the ends of multiple conductors and ground wires of a double-circuit line on the same tower according to claim 1, characterized in that, The constraint that the total coupling current flowing through the shorting point is zero is achieved by summing the left-hand sides of the induced voltage equations corresponding to all out-of-service lines in the shorting group to zero.

6. The method for inducing voltage under the condition of short-circuiting the ends of multiple conductors and ground wires of a double-circuit line on the same tower according to claim 1, characterized in that, The method is applied to the safety assessment of induced voltage during DC de-icing operations or power outage maintenance operations on transmission lines.

7. The method for inducing voltage under the condition of short-circuiting the ends of multiple conductors and ground wires of a double-circuit line on the same tower according to claim 1, characterized in that, The geometric parameters include the spatial coordinates, type, number of splits, outer diameter, and sag of each conductor and ground wire.

8. A system for calculating induced voltage under the condition of short-circuiting the ends of multiple conductors and ground wires of a double-circuit line on the same tower, implementing the method according to any one of claims 1-7, characterized in that, include: The parameter acquisition module is used to acquire the geometric parameters and operating parameters of the double-circuit line on the same tower. The operating parameters include at least the voltage of the normally operating circuit. The parameter calculation module is used to calculate the capacitance parameters between each line in the double-circuit line on the same tower based on the geometric parameters. The coupling coefficient determination module is used to determine the equivalent coupling coefficient of the normal operating circuit to each line, and the mutual coupling coefficient between the out-of-operation lines, based on the capacitance parameters. The equation establishment module is used to establish an induced voltage equation for each out-of-operation line based on the equivalent coupling coefficient, the mutual coupling coefficient and the voltage of the normal operation circuit. The induced voltage equation characterizes the coupling relationship between the induced voltage of the out-of-operation line and the voltage of the normal operation circuit and the induced voltage of other out-of-operation lines. The equation system construction module is used to impose constraints on the induced voltage equations based on the actual short-circuit connection relationship at the end of each out-of-service line, and construct a closed equation system; wherein, for each group of out-of-service lines whose ends are short-circuited to each other, the imposed constraints include: the induced voltage of all out-of-service lines in the group is equal, and the total coupling current flowing through the short-circuit point is zero. The solver module is used to solve the system of equations to obtain the induced voltage of all out-of-service lines.

9. The induced voltage calculation system for a double-circuit line on the same tower under the condition of short-circuiting at the ends of multiple conductors and ground wires as described in claim 8, characterized in that, The parameter calculation module is specifically used to calculate the self-capacitance and mutual capacitance of each line using the mirror method; the coupling coefficient determination module is specifically used to perform the calculation as described in claim 2.

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