Method and system for acquiring zero-sequence impedance to ground of line section, storage medium, and device

Abstract

A method for acquiring the zero-sequence impedance to ground of a line section, comprising: in a power distribution system, selecting any line as a first grounding line (S101); grounding any phase of the first grounding line (S102); determining ground parameter characteristic equations of line sections of a non-grounding line in the power distribution system (S103); releasing a single-phase grounding state of the first grounding line (S104); grounding other phases of the first grounding line one at a time in sequence (S105); obtaining a parameter characteristic equation set composed of each line section to be tested of the non-grounding line in the power distribution system (S106); and determining the zero-sequence impedance to ground of phase-separated sections of lines on the basis of the parameter characteristic equation set (S107). The method can accurately obtain the zero-sequence impedance to ground of phase-separated sections of each line, provide accurate line parameters and topology information for the precise setting calculation of zero-sequence protection of power grids, accurate positioning of grounding faults, real-time power flow calculation, source-grid-load-storage interaction, etc., and facilitate the construction of novel power systems.

Description

Method, system, storage medium and device for obtaining zero-sequence impedance of line section to ground Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a method, system, storage medium and device for obtaining zero-sequence impedance of a line section to ground. Background Art

[0002] To serve the national energy transformation and "dual carbon" goals, a large number of distributed new energy and diversified loads are connected to the power grid, requiring the power grid to achieve multi-directional coordination and flexible interaction. Traditional power grids have shown problems of insufficient transparency and digitalization, especially the distribution network structure is complex and the equipment is numerous. There is an urgent need for transparency of power grid topology and electrical and physical parameters to truly realize the digital twin power grid.

[0003] Current technical means assume that the three-phase zero-sequence impedance of the line section to the ground is balanced. The zero-sequence impedance of the entire bus section and all outgoing lines to the ground is obtained by measuring the capacitor current. However, when the three phases are unbalanced, the obtained results have large errors and cannot build an accurate digital twin power grid.

[0004] In order to solve the problem of segmented and phase-by-phase measurement of the zero-sequence impedance of a line section to ground, the present invention proposes a method for obtaining the zero-sequence impedance of a line section to ground. By measuring the three-phase voltage vector and zero-sequence current vector at each position of the line, a set of characteristic equations for each line section is constructed to obtain the zero-sequence impedance of the line phase section to ground, thereby realizing accurate measurement of the distribution network line-to-ground parameters.

[0005] Summary of the Invention

[0006] Based on this, it is necessary to propose a method for obtaining the zero-sequence impedance of a line section to the ground to address the above problems.

[0007] A method for obtaining zero-sequence impedance of a line section to ground, the method comprising the following steps:

[0008] In the power distribution system, any line is selected as the first grounding line;

[0009] grounding any one phase of the first grounding circuit;

[0010] determining a characteristic equation of ground parameters of each line section of the non-grounded line in the power distribution system;

[0011] releasing the single-phase grounding state of the first grounding line;

[0012] Replace the other phases of the first grounding circuit with the grounding ground in sequence;

[0013] Obtaining a parameter characteristic equation group consisting of each line section to be tested of the non-grounded line in the power distribution system;

[0014] The zero-sequence impedance of the phase-separated section of the line to ground is determined according to the parameter characteristic equation group.

[0015] In the above solution, after selecting any one line as the first grounding line in the power distribution system, the method further includes:

[0016] In the power distribution system, any one line other than the first grounding line is selected as the second grounding line;

[0017] grounding any one phase of the second grounding circuit;

[0018] determining a ground parameter characteristic equation of each line section of the first ground line;

[0019] releasing the single-phase grounding state of the second grounding line;

[0020] Replace the grounding of other phases of the second grounding circuit in sequence;

[0021] Obtaining a parameter characteristic equation group formed by each to-be-tested line section of the first grounding line in the power distribution system;

[0022] The parameter characteristic equation group is solved to determine the zero-sequence impedance to ground of several phase sections corresponding to different line sections.

[0023] In the above solution, determining the characteristic equation of the ground parameters of each line section of the non-grounded line in the power distribution system specifically includes:

[0024] Determining whether both sides of the line section contain measurement points;

[0025] If so, measuring the three-phase voltage vector and the zero-sequence current vector at both ends of each to-be-tested line section of the non-grounded line;

[0026] A first characteristic equation is determined according to the three-phase voltage vector and the zero-sequence current vector.

[0027] In the above solution, the three-phase voltage vector and the zero-sequence current vector are vector values ​​at the same moment in a unified time scale.

[0028] In the above solution, the first characteristic equation includes:

[0029] in, The voltages of phases A, B, and C measured at the measurement point on the load side of the kth line section of line m when phase P is single-phase grounded; is the zero-sequence impedance to ground of the kth line section of line m; is the zero-sequence current measured at the measurement point close to the busbar side in the kth line section of line m when the P phase is single-phase grounded; It is the zero-sequence current measured at the measurement point close to the load side of the kth line section of line m when the P phase is single-phase grounded.

[0030] In the above solution, the first characteristic equation also includes:

[0031] in, The voltages of phases A, B, and C measured at the measurement point on the busbar side of the kth line section of line m when phase P is single-phase grounded; is the zero-sequence impedance to ground of the kth line section of line m; is the zero-sequence current measured at the measurement point close to the busbar side in the kth line section of line m when the P phase is single-phase grounded; It is the zero-sequence current measured at the measurement point close to the load side of the kth line section of line m when the P phase is single-phase grounded.

[0032] In the above solution, after determining whether both sides of the line section contain measurement points, the method further includes:

[0033] When the line section has a measurement point only at one end close to the power supply side;

[0034] measuring the three-phase voltage vector and the zero-sequence current vector of the terminal line section of the non-grounded line close to one end of the busbar side;

[0035] A second characteristic equation is determined according to the three-phase voltage vector and the zero-sequence current vector.

[0036] In the above solution, the second characteristic equation includes:

[0037] in, The voltages of phases A, B, and C are measured at the measurement point on the busbar side of the kth line section at the end of line m when phase P is single-phase grounded; is the zero-sequence impedance to ground of the kth line section of line m; It is the zero-sequence current measured at the measurement point on the busbar side of the kth line section at the end of line m when the P phase is single-phase grounded.

[0038] In the above solution, obtaining a parameter characteristic equation group formed by each line section to be tested of the first grounding line in the power distribution system specifically includes:

[0039] When there are measurement points on both sides of each line section to be measured, the corresponding parameter characteristic equation group is:

[0040] in, The voltages of phases A, B, and C measured at the measurement point on the load side of the kth line section of line m when phase P is single-phase grounded; is the zero-sequence impedance to ground of the kth line section of line m; is the zero-sequence current measured at the measurement point close to the busbar side in the kth line section of line m when the P phase is single-phase grounded; It is the zero-sequence current measured at the measurement point close to the load side of the kth line section of line m when the P phase is single-phase grounded.

[0041] In the above solution, obtaining a parameter characteristic equation group formed by each line section to be tested of the first grounding line in the power distribution system specifically includes:

[0042] When there are measurement points on both sides of each line section to be measured, the corresponding parameter characteristic equation group is:

[0043] in, The voltages of phases A, B, and C measured at the measurement point on the busbar side of the kth line section of line m when phase P is single-phase grounded; is the zero-sequence impedance to ground of the kth line section of line m; is the zero-sequence current measured at the measurement point close to the busbar side in the kth line section of line m when the P phase is single-phase grounded; It is the zero-sequence current measured at the measurement point close to the load side of the kth line section of line m when the P phase is single-phase grounded.

[0044] In the above solution, obtaining a parameter characteristic equation group formed by each line section to be tested of the first grounding line in the power distribution system specifically includes:

[0045] When each of the line sections to be measured has a measurement point only at one end of the line section close to the power supply side, the corresponding parameter characteristic equation group is:

[0046] in, The voltages of phases A, B, and C are measured at the measurement point on the busbar side of the kth line section at the end of line m when phase P is single-phase grounded; is the zero-sequence impedance to ground of the kth line section of line m; It is the zero-sequence current measured at the measurement point on the busbar side of the kth line section at the end of line m when the P phase is single-phase grounded.

[0047] The present application also proposes a system for obtaining zero-sequence impedance to ground of a phase-separated line section, the system comprising: a line obtaining unit, a phase selecting unit, a characteristic equation determining unit, and a solving unit;

[0048] The line acquisition unit is configured to select any line as a first grounding line in the power distribution system;

[0049] The phase selection unit is used to ground any one phase of the first grounding line, release the single-phase grounding state of the first grounding line, and sequentially replace the other phases of the first grounding line for grounding;

[0050] The characteristic equation determination unit is used to determine the ground parameter characteristic equations of each line section of the non-grounded line in the power distribution system, and obtain a parameter characteristic equation group consisting of each line section to be tested of the non-grounded line in the power distribution system;

[0051] The solving unit is used to determine the zero-sequence impedance of the phase section of the line to ground according to the parameter characteristic equation group.

[0052] The present application also provides a readable storage medium storing a computer program. When the computer program is executed by a processor, the processor performs the following steps:

[0053] In the power distribution system, any line is selected as the first grounding line;

[0054] grounding any one phase of the first grounding circuit;

[0055] determining a characteristic equation of ground parameters of each line section of the non-grounded line in the power distribution system;

[0056] releasing the single-phase grounding state of the first grounding line;

[0057] Replace the other phases of the first grounding circuit with the grounding ground in sequence;

[0058] Obtaining a parameter characteristic equation group consisting of each line section to be tested of the non-grounded line in the power distribution system;

[0059] The zero-sequence impedance of the phase-separated section of the line to ground is determined according to the parameter characteristic equation group.

[0060] The present application also proposes a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the processor executes the following steps:

[0061] In the power distribution system, any line is selected as the first grounding line;

[0062] grounding any one phase of the first grounding circuit;

[0063] determining a characteristic equation of ground parameters of each line section of the non-grounded line in the power distribution system;

[0064] releasing the single-phase grounding state of the first grounding line;

[0065] Replace the other phases of the first grounding circuit with the grounding ground in sequence;

[0066] Obtaining a parameter characteristic equation group consisting of each line section to be tested of the non-grounded line in the power distribution system;

[0067] The zero-sequence impedance of the phase-separated section of the line to ground is determined according to the parameter characteristic equation group.

[0068] The embodiment of the present invention has the following beneficial effects: in a power distribution system, any one line is selected as the first grounding line; any one phase of the first grounding line is grounded; the characteristic equations of the ground parameters of each line section of the non-grounded line in the distribution system are determined; the single-phase grounding state of the first grounding line is released; the other phases of the first grounding line are replaced with ground in turn; a group of parameter characteristic equations consisting of each line section to be tested of the non-grounded line in the distribution system is obtained; the zero-sequence impedance of the phase section of the line section to the ground is determined according to the group of parameter characteristic equations; the present invention can accurately obtain the zero-sequence impedance of the phase section to the ground of each line section, combines the grounding switching of different phases of each line and specifies the corresponding characteristic equations of the ground parameters, and can realize the accurate measurement of the ground parameters of the distribution network line, provide accurate line parameters and topology information for real-time power flow calculation of the power grid, and assist in the construction of new power systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0070] in:

[0071] FIG1 is a schematic flow chart of a method for obtaining zero-sequence impedance of a line section to ground according to an embodiment;

[0072] FIG2 is a circuit diagram of a power distribution network system according to an embodiment;

[0073] FIG3 is a partially simplified circuit diagram based on FIG2 ;

[0074] FIG4 is a simplified circuit diagram based on FIG3 ;

[0075] FIG5 is a partially simplified circuit diagram based on FIG2 . DETAILED DESCRIPTION

[0076] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0077] In the following description, numerous specific details are given to provide a more thorough understanding of the present invention; however, it will be apparent to those skilled in the art that the present invention may be practiced without one or more of these details; in other examples, some technical features known in the art are not described to avoid confusion with the present invention, and it should be understood that the present invention may be practiced in different forms and should not be construed as limited to the embodiments set forth herein; on the contrary, these embodiments are provided to make the disclosure thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0078] The terminology used herein is intended only to describe specific embodiments and is not intended to limit the present invention. When used herein, the singular forms "a," "an," and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "including," when used in this specification, identify the presence of the recited features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0079] In the power system, the zero-sequence impedance of a line phase section to ground is the basic data for power system flow calculation, short-circuit calculation, relay protection setting, and fault analysis. Current technical means assume that the three-phase zero-sequence impedance of the line section to ground is balanced. The zero-sequence impedance of the entire busbar section for all outgoing lines is obtained by measuring the capacitance current. When the three phases are unbalanced, the error is large. To obtain the zero-sequence impedance of the section to ground for each outgoing line, the line to be measured needs to be put into operation in a time-sharing manner, which affects the power supply reliability and also places a large workload on the distribution network. In addition, current technology cannot obtain the zero-sequence impedance of the phase section to ground, nor can it obtain the zero-sequence impedance of the section of a line (part of a line of an outgoing line). To solve the problem of segmented and phased measurement of the zero-sequence impedance of the line section to ground, the present invention proposes to construct a set of characteristic equations for each line section by measuring the three-phase voltage vector and zero-sequence current vector at each position of the line, and obtain the zero-sequence impedance of the phase section of the line. This is especially useful for sections with unbalanced line parameters, thereby achieving accurate measurement of the zero-sequence impedance of the phase section of the distribution network line to ground parameters.

[0080] To facilitate understanding, the relevant terms involved in this application are first introduced below.

[0081] (1) The zero-sequence impedance of the phase section to ground refers to the ratio of the phase sequence voltage across any component to the corresponding phase sequence current flowing through the component, which is the zero-sequence impedance (impedance) of the phase section to ground of the component. The zero-sequence impedance (impedance) of the phase section to ground is related to the network structure, especially the wiring method and neutral point grounding method of the transformer;

[0082] (2) Single-phase grounding is a common fault in the power system, indicating that a short circuit occurs between one phase of the three-phase system and the ground;

[0083] (3) Characteristic equation refers to some equations introduced to study the corresponding mathematical objects, which vary depending on the mathematical objects.

[0084] In order to thoroughly understand the present invention, a detailed structure will be presented in the following description to illustrate the technical solution proposed by the present invention; optional embodiments of the present invention are described in detail below, but in addition to these detailed descriptions, the present invention may also have other implementation methods.

[0085] As shown in FIG1 , in one embodiment, a method for obtaining zero-sequence impedance of a line section to ground is provided. The method for obtaining zero-sequence impedance of a line section to ground includes steps S101 to S107, which are described in detail as follows:

[0086] S101. In a power distribution system, select any line as a first grounding line;

[0087] S102, grounding any one phase of the first grounding circuit;

[0088] That is, a phase (phase A, phase B or phase C) is connected to the ground at any position of the grounding line, resulting in a single-phase grounding state for the phase.

[0089] S103, determining characteristic equations of ground parameters of each section of the non-grounded line in the power distribution system;

[0090] Specifically, determine the ground parameter characteristic equation corresponding to each section of the non-grounded line when a specific phase (phase A, phase B or phase C) is single-phase grounded; as shown in Figure 2, E a 、E b 、E c They are three-phase power supply, For each measuring point; is the zero-sequence impedance of each line section to ground; wherein, the line section is a line with a certain distance, which in this scheme refers to the line between any two measurement points, and a section of the line after the end measurement point.

[0091] In some embodiments, determining a characteristic equation of ground parameters of each line section of a non-grounded line in a power distribution system specifically includes:

[0092] Determine whether both sides of the line section contain measurement points;

[0093] As shown in FIG3 , line section 1 satisfies the requirement of whether both sides contain measurement points (the first case), while line section 2 has measurement points on only one side, which does not satisfy the first case.

[0094] If so, measure the three-phase voltage vector and zero-sequence current vector at both ends of each line section to be tested of the non-grounded line;

[0095] A first characteristic equation is determined according to the three-phase voltage vector and the zero-sequence current vector.

[0096] In some embodiments, the first characteristic equation comprises:

[0097] in, The voltages of phases A, B, and C measured at the measurement point on the load side of the kth line section of line m when phase P is single-phase grounded; is the zero-sequence impedance to ground of the kth line section of line m; is the zero-sequence current measured at the measurement point close to the busbar side in the kth line section of line m when the P phase is single-phase grounded; It is the zero-sequence current measured at the measurement point close to the load side of the kth line section of line m when the P phase is single-phase grounded.

[0098] In some embodiments, the first characteristic equation further includes:

[0099] in, The voltages of phases A, B, and C measured at the measurement point on the busbar side of the kth line section of line m when phase P is single-phase grounded; is the zero-sequence impedance to ground of the kth line section of line m; is the zero-sequence current measured at the measurement point close to the busbar side in the kth line section of line m when the P phase is single-phase grounded; It is the zero-sequence current measured at the measurement point close to the load side of the kth line section of line m when the P phase is single-phase grounded.

[0100] In some embodiments, after determining whether both sides of the line segment contain measurement points, the method further includes:

[0101] When the line section has a measuring point only at one end close to the power supply side (the second case);

[0102] Measure the three-phase voltage vector and zero-sequence current vector at one end of the terminal line section of the non-grounded line close to the busbar side;

[0103] The second characteristic equation is determined according to the three-phase voltage vector and the zero-sequence current vector.

[0104] Preferably, the three-phase voltage vector and zero-sequence current vector are vector values ​​at the same moment in a unified time scale.

[0105] In some embodiments, the second characteristic equation comprises:

[0106] in, The voltages of phases A, B, and C are measured at the measurement point on the busbar side of the kth line section at the end of line m when phase P is single-phase grounded; is the zero-sequence impedance to ground of the kth line section of line m; It is the zero-sequence current measured at the measurement point on the busbar side of the kth line section at the end of line m when the P phase is single-phase grounded.

[0107] Below, with reference to FIG3 , two cases of whether a line section includes a measurement point are explained:

[0108] In this figure, there are measurement points on both sides of line section 1, namely measurement point k-1 and measurement point k. Line section 2 is the terminal line section and has only one measurement point close to the busbar, namely measurement point k. Measurement point k-1 measures the three-phase voltage vector and zero-sequence current vector of this point, and measurement point k measures the three-phase voltage vector and zero-sequence current vector of this point.

[0109] In the power system, since the zero-sequence current of the distribution network line only flows in the zero-sequence loop, the zero-sequence current only flows through the zero-sequence impedance of the line section to the ground. To the ground, without passing through the load, so the above Figure 3 can be simplified to Figure 4, according to which the zero-sequence current flowing through the measuring point k-1 can be determined The relationship between the zero-sequence current and the measuring point k is as follows:

[0110] in is the zero-sequence current at the measuring point k-1; is the zero-sequence current flowing through the zero-sequence impedance of line section 1; To measure the zero-sequence current at k; is the zero-sequence current flowing through the zero-sequence impedance of line section 2, and equal;

[0111] Furthermore, for line section 1:

[0112] For line section 2:

[0113] Referring to FIG4 , based on the concept of zero-sequence current, it can be determined that the current flowing through the zero-sequence impedance of line section 1 is:

[0114] The current flowing through the zero-sequence impedance of line section 2 is:

[0115] Furthermore, the three-phase voltages measured at the measuring point k-1 and the measuring point k are respectively equal. According to Formula 5, Formula 7 and Formula 8, Formula 1 and Formula 2 can be obtained, and according to Formula 6 and Formula 8, Formula 3 can be obtained.

[0116] S104, releasing the single-phase grounding state of the first grounding line;

[0117] S105, sequentially replacing the grounding of other phases of the first grounding circuit;

[0118] In some embodiments, in the power distribution system, after selecting any one line as the first grounding line, the method further includes:

[0119] (1) In a power distribution system, any line other than the first grounding line is selected as the second grounding line;

[0120] (2) grounding any phase of the second grounding circuit;

[0121] (3) determining the ground parameter characteristic equations of each line section of the first ground line;

[0122] As shown in FIG2 , a line section is a line with a certain distance. In this solution, it refers to the line between any two measuring points and a section of the line after the end measuring point.

[0123] (4) Release the single-phase grounding state of the second grounding line;

[0124] (5) Replace the other phases of the second grounding circuit in turn;

[0125] (6) obtaining a set of parameter characteristic equations for each line segment to be tested of the first grounding line in the power distribution system;

[0126] (7) Solve the parameter characteristic equation group to determine the zero-sequence impedance to ground of several phase sections corresponding to different line sections.

[0127] S106, obtaining a parameter characteristic equation group consisting of each line section to be tested of the non-grounded line in the power distribution system;

[0128] In some embodiments, obtaining a parameter characteristic equation group formed by each to-be-tested line section of the first grounding line in the power distribution system specifically includes:

[0129] When there are measurement points on both sides of each line section to be measured, the corresponding parameter characteristic equation group is:

[0130] in, The voltages of phases A, B, and C measured at the measurement point on the load side of the kth line section of line m when phase P is single-phase grounded; is the zero-sequence impedance to ground of the kth line section of line m; is the zero-sequence current measured at the measurement point close to the busbar side in the kth line section of line m when the P phase is single-phase grounded; It is the zero-sequence current measured at the measurement point close to the load side of the kth line section of line m when the P phase is single-phase grounded.

[0131] In some embodiments, obtaining a parameter characteristic equation group formed by each to-be-tested line section of the first grounding line in the power distribution system specifically includes:

[0132] When there are measurement points on both sides of each line section to be measured, the corresponding parameter characteristic equation group is:

[0133] in, The voltages of phases A, B, and C measured at the measurement point on the busbar side of the kth line section of line m when phase P is single-phase grounded; is the zero-sequence impedance to ground of the kth line section of line m; is the zero-sequence current measured at the measurement point close to the busbar side in the kth line section of line m when the P phase is single-phase grounded; It is the zero-sequence current measured at the measurement point close to the load side of the kth line section of line m when the P phase is single-phase grounded.

[0134] In some embodiments, obtaining a parameter characteristic equation group formed by each to-be-tested line section of the first grounding line in the power distribution system specifically includes:

[0135] When each line section to be measured has a measurement point only at one end of the line section close to the power supply side, the corresponding parameter characteristic equation group is:

[0136] in, The voltages of phases A, B, and C are measured at the measurement point on the busbar side of the kth line section at the end of line m when phase P is single-phase grounded; is the zero-sequence impedance to ground of the kth line section of line m; It is the zero-sequence current measured at the measurement point on the busbar side of the kth line section at the end of line m when the P phase is single-phase grounded.

[0137] S107. Determine the zero-sequence impedance of the phase section of the line to ground according to the parameter characteristic equation group.

[0138] With reference to FIG5 , the steps S101 to S107 are explained below using a specific embodiment:

[0139] As shown in the figure, there are four line sections (Section 1, Section 2, Section 3, and Section 4) and two ground outgoing lines (Line 1 and Line 2). Each outgoing line is divided into two line sections. Line 1 consists of Section 1 and Section 2, and Line 2 consists of Section 3 and Section 4. Sections 2 and 4 are the terminal line sections. The line lengths of Line Sections 1 to 4 are 10 km, 20 km, 30 km, and 40 km, respectively. The measured single-phase distributed impedance values ​​are 61978 Ω, 30363 Ω, 20242 Ω, and 15182 Ω, respectively.

[0140] According to the implementation steps, first, a single-phase metallic grounding of phase A is set at a certain position on line 2. Under this state, the three-phase voltage vectors and zero-sequence current vectors of the measuring points of line sections 1 and 2 are measured respectively to determine the characteristic equations of each line section of line 1 under the phase A grounding state. At this time, the three-phase voltage vectors and zero-sequence current vectors of the two measuring points of line 1 are shown in the following table:

[0141] The characteristic equation of line section 1 when phase A is single-phase grounded is:

[0142] The characteristic equation of line section 2 when phase A is single-phase grounded is:

[0143] According to the implementation steps, we continue to assume that line 2 has a single-phase grounding of phase B. Similarly, the characteristic equation of line section 1 when the single-phase grounding of phase B is obtained:

[0144] The characteristic equation of line section 2 when phase B is single-phase grounded is obtained as follows:

[0145] Remove the state of single-phase grounding of phase B in line section 2 and set the state of single-phase grounding of phase C in line 2. Similarly, the characteristic equation of line section 1 when single-phase grounding of phase C is obtained as follows:

[0146] The characteristic equation of line section 2 when phase C is single-phase grounded is obtained as follows:

[0147] Among them, the above equations 12, 14, and 16 constitute the characteristic equation group of line section 1, and equations 13, 15, and 17 constitute the characteristic equation group of line section 2. The zero-sequence impedance of line section 1 to ground is obtained by solving:

[0148] The zero-sequence impedance of line section 2 to ground is obtained as follows:

[0149] Assume that line 1 is grounded, list the characteristic equations of line sections 3 and 4, and solve them. The zero-sequence impedance of line section 3 to ground is obtained as follows:

[0150] The zero-sequence impedance of line section 4 to ground is obtained as:

[0151] In summary, by measuring the three-phase voltage vector and zero-sequence current vector at each position of the line and constructing a set of characteristic equations for each line section, the zero-sequence impedance of the line phase section to ground can be obtained, and the accurate measurement of the distribution network line-to-ground parameters can be achieved, which facilitates the formulation or adjustment of the distribution network implementation plan.

[0152] The present application also proposes a system for obtaining zero-sequence impedance to ground in a phase-separated section of a line, the system comprising: a line obtaining unit, a phase selecting unit, a characteristic equation determining unit, and a solving unit;

[0153] A line acquisition unit, configured to select any line as a first grounding line in a power distribution system;

[0154] A phase selection unit is used to ground any one phase of the first grounding line, release the single-phase grounding state of the first grounding line, and sequentially replace the other phases of the first grounding line for grounding;

[0155] A characteristic equation determination unit is used to determine the ground parameter characteristic equations of each line section of the non-grounded line in the power distribution system, and obtain a parameter characteristic equation group consisting of each line section to be tested of the non-grounded line in the power distribution system;

[0156] The solving unit is used to determine the zero-sequence impedance of the phase section of the line to ground according to the parameter characteristic equation group.

[0157] The present application also provides a readable storage medium storing a computer program. When the computer program is executed by a processor, the processor performs the following steps:

[0158] In the power distribution system, any line is selected as the first grounding line;

[0159] Ground any one phase of the first grounding circuit;

[0160] Determine the characteristic equations of the ground parameters of each line section of the non-grounded line in the distribution system;

[0161] releasing the single-phase grounding state of the first grounding line;

[0162] Replace the other phases of the first grounding circuit with the grounding ground in sequence;

[0163] Obtaining a parameter characteristic equation group consisting of each line section to be tested of the non-grounded line in the power distribution system;

[0164] The zero-sequence impedance of the phase-separated section of the line to ground is determined based on the parameter characteristic equation group.

[0165] The present application also proposes a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the computer program is executed by the processor to perform the following steps:

[0166] In the power distribution system, any line is selected as the first grounding line;

[0167] Ground any one phase of the first grounding circuit;

[0168] Determine the characteristic equations of the ground parameters of each line section of the non-grounded line in the distribution system;

[0169] releasing the single-phase grounding state of the first grounding line;

[0170] Replace the other phases of the first grounding circuit with the grounding ground in sequence;

[0171] Obtaining a parameter characteristic equation group consisting of each line section to be tested of the non-grounded line in the power distribution system;

[0172] The zero-sequence impedance of the phase-separated section of the line to ground is determined based on the parameter characteristic equation group.

[0173] Those skilled in the art will understand that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program. The program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0174] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0175] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. The above disclosures are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for obtaining zero-sequence impedance of a line section to ground, characterized in that: The method comprises: In the power distribution system, any line is selected as the first grounding line; grounding any one phase of the first grounding circuit; determining a characteristic equation of ground parameters of each line section of the non-grounded line in the power distribution system; releasing the single-phase grounding state of the first grounding line; Replace the other phases of the first grounding circuit with the grounding ground in sequence; Obtaining a parameter characteristic equation group consisting of each line section to be tested of the non-grounded line in the power distribution system; The zero-sequence impedance of the phase-separated section of the line to ground is determined according to the parameter characteristic equation group.

2. The method for obtaining zero-sequence impedance of a line section to ground according to claim 1, characterized in that: In the power distribution system, after selecting any one line as the first grounding line, the method further includes: In the power distribution system, any one line other than the first grounding line is selected as the second grounding line; grounding any one phase of the second grounding circuit; Determining a section-to-ground parameter characteristic equation of each line of the first grounding line; releasing the single-phase grounding state of the second grounding line; Replace the other phases of the second grounding circuit with the grounding phases in sequence; Obtaining a parameter characteristic equation group formed by each to-be-tested line section of the first grounding line in the power distribution system; The parameter characteristic equation group is solved to determine the zero-sequence impedance to ground of several phase sections corresponding to different line sections.

3. The method for obtaining zero-sequence impedance of a line section to ground according to claim 2, characterized in that: The determining of the ground parameter characteristic equations of each line section of the non-grounded line in the power distribution system specifically includes: Determining whether both sides of the line section contain measurement points; If so, measuring the three-phase voltage vector and the zero-sequence current vector at both ends of each to-be-tested line section of the non-grounded line; A first characteristic equation is determined according to the three-phase voltage vector and the zero-sequence current vector.

4. The method for obtaining zero-sequence impedance of a line section to ground according to claim 3, characterized in that: The three-phase voltage vector and the zero-sequence current vector are vector values at the same moment in a unified time scale.

5. The method for obtaining zero-sequence impedance of a line section to ground according to claim 4, characterized in that: The first characteristic equation includes: in, The voltages of phases A, B, and C measured at the measurement point on the load side of the kth line section of line m when phase P is single-phase grounded; is the zero-sequence impedance to ground of the kth line section of line m; is the zero-sequence current measured at the measurement point close to the busbar side in the kth line section of line m when the P phase is single-phase grounded; It is the zero-sequence current measured at the measurement point close to the load side of the kth line section of line m when the P phase is single-phase grounded.

6. The method for obtaining zero-sequence impedance of a line section to ground according to claim 4, characterized in that: The first characteristic equation also includes: in, The voltages of phases A, B, and C measured at the measurement point on the busbar side of the kth line section of line m when phase P is single-phase grounded; is the zero-sequence impedance to ground of the kth line section of line m; is the zero-sequence current measured at the measurement point close to the busbar side in the kth line section of line m when the P phase is single-phase grounded; It is the zero-sequence current measured at the measurement point close to the load side of the kth line section of line m when the P phase is single-phase grounded.

7. The method for obtaining zero-sequence impedance of a line section to ground according to claim 5 or 6, characterized in that: After determining whether both sides of the line section contain measurement points, the method further includes: When the line section has a measurement point only at one end close to the power supply side; measuring the three-phase voltage vector and the zero-sequence current vector of the terminal line section of the non-grounded line close to one end of the busbar side; A second characteristic equation is determined according to the three-phase voltage vector and the zero-sequence current vector.

8. The method for obtaining zero-sequence impedance of a line section to ground according to claim 7, characterized in that: The second characteristic equation includes: in, The voltages of phases A, B, and C measured at the measurement point on the busbar side of the kth line section at the end of line m when phase P is single-phase grounded; is the zero-sequence impedance to ground of the kth line section of line m; It is the zero-sequence current measured at the measurement point on the busbar side of the kth line section at the end of line m when the P phase is single-phase grounded.

9. The method for obtaining zero-sequence impedance of a line section to ground according to claim 8, characterized in that: The step of obtaining a parameter characteristic equation group formed by each to-be-tested line section of the first grounding line in the power distribution system specifically includes: When there are measurement points on both sides of each line section to be measured, the corresponding parameter characteristic equation group is: in, The voltages of phases A, B, and C measured at the measurement point on the load side of the kth line section of line m when phase P is single-phase grounded; is the zero-sequence impedance to ground of the kth line section of line m; is the zero-sequence current measured at the measurement point close to the busbar side in the kth line section of line m when the P phase is single-phase grounded; It is the zero-sequence current measured at the measurement point close to the load side of the kth line section of line m when the P phase is single-phase grounded.

10. The method for obtaining zero-sequence impedance of a line section to ground according to claim 9, characterized in that: The step of obtaining a parameter characteristic equation group formed by each to-be-tested line section of the first grounding line in the power distribution system specifically includes: When there are measurement points on both sides of each line section to be measured, the corresponding parameter characteristic equation group is: in, The voltages of phases A, B, and C measured at the measurement point on the busbar side of the kth line section of line m when phase P is single-phase grounded; is the zero-sequence impedance to ground of the kth line section of line m; is the zero-sequence current measured at the measurement point close to the busbar side in the kth line section of line m when the P phase is single-phase grounded; It is the zero-sequence current measured at the measurement point close to the load side of the kth line section of line m when the P phase is single-phase grounded.

11. The method for obtaining zero-sequence impedance of a line section to ground according to claim 10, characterized in that: The step of obtaining a parameter characteristic equation group formed by each to-be-tested line section of the first grounding line in the power distribution system specifically includes: When each of the line sections to be measured has a measurement point only at one end of the line section close to the power supply side, the corresponding parameter characteristic equation group is: in, The voltages of phases A, B, and C measured at the measurement point on the busbar side of the kth line section at the end of line m when phase P is single-phase grounded; is the zero-sequence impedance to ground of the kth line section of line m; It is the zero-sequence current measured at the measurement point on the busbar side of the kth line section at the end of line m when the P phase is single-phase grounded.

12. A system for obtaining zero-sequence impedance of a line phase section to ground, characterized in that: The system comprises: a line acquisition unit, a phase selection unit, a characteristic equation determination unit and a solution unit; The line acquisition unit is configured to select any line as a first grounding line in the power distribution system; The phase selection unit is used to ground any one phase of the first grounding line, release the single-phase grounding state of the first grounding line, and sequentially replace the other phases of the first grounding line for grounding; The characteristic equation determination unit is used to determine the ground parameter characteristic equations of each line section of the non-grounded line in the power distribution system, and obtain a parameter characteristic equation group consisting of each line section to be tested of the non-grounded line in the power distribution system; The solving unit is used to determine the zero-sequence impedance of the phase section of the line to ground according to the parameter characteristic equation group.

13. A readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 11.

14. A computer device comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 11.

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