Grounding grid safety assessment method
By treating the grounding network as a whole and setting auxiliary current electrodes, analyzing the equivalent impedance, and using the equivalent impedance circuit to calculate parameters, the accuracy of the safety assessment of the substation grounding network in urban areas is solved, and safety under limited measurement distance is achieved Sexual assessment.
Patent Information
- Application Number
- CN202310615928.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-05-29
- Publication Date
- 2024-12-13
AI Technical Summary
Due to space limitations and overhead ground wire access in substations in urban areas, traditional methods are difficult to accurately measure ground grid parameters, which reduces the accuracy of ground grid safety assessment.
Consider the grounding network as a whole, set up auxiliary current electrodes, collect voltage data in the direction of voltage drop, analyze and obtain equivalent impedance, and use equivalent impedance circuit to calculate relevant index parameters for safety evaluation.
The accuracy of the safety evaluation of the grounding network is improved under the limited measurement distance, and can effectively determine whether the grounding network meets the safety threshold, reducing the difficulty of evaluation.
Smart Images
Figure CN119125750A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the electrical field, and more particularly to a grounding network safety assessment method. Background Art
[0002] Substations located in urban areas are one of the important guarantees for urban power supply. As one of the important guarantees for the normal operation of substations, good grounding performance is directly related to the safety of substations and on-site personnel, so the safety assessment of grounding grids is particularly critical. However, due to urban environmental restrictions, substations in urban areas are usually surrounded by various types of buildings and facilities. When measuring the safety performance of their grounding grid systems, the surrounding measurement space is limited; at the same time, the overhead ground wires connected to various types of power equipment are directly incorporated into the grounding grid, and the environment is complex. In traditional impedance methods or electromagnetic methods, the grounding grid needs to be equivalent to a pure resistance loop network, and the signals collected after injecting current are used to analyze the grounding grid parameters. However, due to the direct access of overhead ground wires, the structure of the grounding grid is complicated. In extreme cases, it will not be equivalent to a circuit loop, that is, it is difficult to measure its parameters by traditional methods, which increases the difficulty of grounding grid safety assessment and reduces the accuracy of the assessment. Summary of the invention
[0003] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a grounding grid safety assessment method. This method aims at the problems of limited space in substations and access to overhead ground wires. Under limited measurement distance, firstly, the grounding grid system is regarded as a whole, and auxiliary current electrodes are set. On the connection line between the electrode and the grounding grid, voltage is collected along the voltage drop direction, and then the equivalent impedance of the grounding grid is obtained by analysis. Secondly, the equivalent impedance circuit is used to further obtain the relevant index parameters of the grounding grid, and finally the safety of the grounding grid is evaluated according to the parameters.
[0004] A grounding grid safety assessment method, the method is used to detect the grounding grid laid in a substation to assess whether the laying is safe; comprising:
[0005] S1. Set up an auxiliary current source near the substation;
[0006] S2, measure the voltage data of the grounding grid, analyze the resistor arrangement, and obtain the overall equivalent impedance Req of the grounding grid;
[0007] S3, construct an equivalent impedance circuit of the grounding grid and calculate the laying evaluation parameters of the grounding grid;
[0008] S4. Conduct safety assessment of the grounding grid.
[0009] The grounding grid is regarded as a whole, the current auxiliary electrode of the auxiliary current source is at a distance D from the center of the grounding grid, the diagonal length of the grounding grid is d, and 3d≤D≤5d.
[0010] The obtaining of the overall equivalent impedance Req of the grounding grid comprises:
[0011] S2.1 Measure the surface x at fixed intervals from the center of the grounding grid to the current source auxiliary electrode position. i The potential rise value V(x i ), i=1, ..., k; finally, k groups of measurement data are obtained;
[0012] S2.2 Calculate position x i The resistance at Get the resistor arrangement;
[0013] Among them, V x (x i ) is the soil surface x i The theoretical value of the potential at the position, I is the current injected by the current auxiliary electrode;
[0014] S2.3 uses a pattern search algorithm to solve the resistor arrangement and obtain the overall equivalent resistance Req of the grounding grid.
[0015] The equivalent impedance circuit of the grounding grid is constructed, comprising:
[0016] S3.1 regards the grounding grid system as a whole, defines external power equipment and overhead ground wire as external equivalent impedance Zext, and constructs an equivalent impedance circuit; where Zeq is the equivalent impedance converted from the equivalent resistance Req measured in step 2; It and Vt are the current and voltage on Zeq respectively; and Zext is the external equivalent impedance.
[0017] The calculation of the laying evaluation parameters of the grounding grid includes:
[0018] S3.2 inject a circulating current It between the grounding grid of the substation under test and the auxiliary current electrode;
[0019] S3.3 Measure the voltage Vt of the grounding grid;
[0020] S3.4 Use Kirchhoff's current law to calculate the current Im flowing through the grounding resistance Rm of the grounding grid and the current Iext flowing through the external equivalent impedance Zext.
[0021] The laying evaluation parameters include: grounding resistance Rm of the grounding grid, current Im flowing through Rm, and current Iext flowing through the external equivalent impedance Zext.
[0022] The safety assessment of the grounding grid includes: comparing the laying assessment parameters with the safety threshold range, and if one of the parameters exceeds the threshold range, determining that it does not meet the safety laying requirements.
[0023] The present invention has the following advantages and beneficial effects:
[0024] 1. The present invention proposes a method for evaluating the safety status of a substation grounding grid, which is mainly aimed at the situation where the substation grounding grid is located in an urban area (or there are obstacles nearby) and there is an overhead ground wire of a transmission line directly connected to the grounding grid.
[0025] 2. Under limited measurement distance, the present invention regards the grounding grid system as a whole, and sets auxiliary current electrodes. Voltage is collected along the voltage drop direction on the connection line between the electrode and the grounding grid, and then the equivalent impedance of the grounding grid is obtained by analysis. Secondly, the equivalent impedance circuit is used to further obtain relevant index parameters of the grounding grid, and finally the safety of the grounding grid is evaluated based on the parameters. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 The figure is a flow chart of the method of the present invention.
[0027] Figure 2 The present invention discloses a process for obtaining the equivalent resistance of a grounding grid system.
[0028] Figure 3 This is the calculation process of grounding grid system parameters.
[0029] Figure 4 This is a schematic diagram of an equivalent impedance circuit. DETAILED DESCRIPTION
[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation method of the present invention is described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the invention, so the present invention is not limited by the specific implementation disclosed below.
[0031] like Figure 1 As shown, it is a flow chart of the method of the present invention, and the specific implementation steps are as follows;
[0032] 1. Under limited measurement space conditions, set up an auxiliary current source near the substation;
[0033] 2. Measure the voltage data of the grounding grid system and analyze to obtain the equivalent impedance of the grounding grid;
[0034] 3. Construct the equivalent impedance circuit of the grounding grid system and calculate the current and other parameters of the grounding grid system;
[0035] 4. Use the calculation results to evaluate the safety of the grounding grid system.
[0036] Among them, in step 1, the grounding grid is regarded as a whole. Assuming that the distance between the current auxiliary electrode and the center of the grounding grid is D, and the diagonal length of the grounding grid system is d, it is required that 3d≤D≤5d to ensure the calculation error.
[0037] The specific implementation method of step 2 is as follows: Figure 2 :
[0038] 2.1 Measure the surface x at fixed intervals from the center of the grounding grid to the current auxiliary electrode position. i Position potential rise V(x i ), i=1, ..., k, and finally obtain k groups of measurement data;
[0039] 2.2 Using the theoretical value of the potential at point x on the soil surface as V x (x i ) and V(x i ), we can calculate x i The resistance at Where I is the current injected by the current auxiliary electrode, which will be offset in the calculation, so no special agreement is made;
[0040] 2.3 Use the pattern search algorithm to solve and obtain the equivalent resistance Req of the grounding grid system.
[0041] The specific implementation method of step 3 is as follows Figure 3 :
[0042] 3.1 Consider the grounding grid system as a whole, and convert external power equipment, overhead ground wires, etc. into external equivalent impedances. The equivalent impedance circuit constructed is as follows: Figure 4 , where Zeq is the equivalent impedance converted from the equivalent resistance Req measured in step 2, It and Vt are the current and voltage on Zeq respectively; Zext is the external equivalent impedance, and Rm represents the grounding resistance of the grounding grid.
[0043] 3.2 Inject circulating current It between the grounding system of the substation under test and the current electrode;
[0044] 3.3 Measure the voltage Vt of the grounding system;
[0045] 3.4 Use Kirchhoff's current law to calculate the grounding current Im flowing through the grounding resistance Rm of the grounding grid and the current Iext flowing through the external equivalent impedance Zext.
[0046] After the above steps, the grounding grid safety can be diagnosed and analyzed based on the laying parameters: Im, Iext and Rm, combined with the design values of the grounding grid safety performance standards: by comparing the laying evaluation parameters with the safety threshold range, if one of the parameters exceeds the threshold range, it is determined that it does not meet the safety laying requirements.
[0047] The present invention is described above by way of example in conjunction with the accompanying drawings. Obviously, the present invention is not limited to the above embodiments, and may also have many variations. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.
Claims
1. A grounding grid safety assessment method, characterized in that: The method is used to detect the grounding network laid in the substation and evaluate whether the laying is safe; it includes: S1. Set up an auxiliary current source near the substation; S2, measure the voltage data of the grounding grid, analyze the resistor arrangement, and obtain the overall equivalent impedance Req of the grounding grid; S3, construct an equivalent impedance circuit of the grounding grid and calculate the laying evaluation parameters of the grounding grid; S4. Conduct safety assessment of the grounding grid.
2. A grounding grid safety assessment method according to claim 1, characterized in that: The grounding grid is regarded as a whole, the current auxiliary electrode of the auxiliary current source is at a distance D from the center of the grounding grid, the diagonal length of the grounding grid is d, and 3d≤D≤5d.
3. A grounding grid safety assessment method according to claim 1, characterized in that: The obtaining of the overall equivalent impedance Req of the grounding grid comprises: S2.1 Measure the surface x at fixed intervals from the center of the grounding grid to the current source auxiliary electrode position. i The potential rise value V(x i ), i=1, ..., k; finally, k groups of measurement data are obtained; S2.2 Calculate position x i The resistance at Get the resistor arrangement; Among them, V x (x i ) is the soil surface x i The theoretical value of the potential at the position, I is the current injected by the current auxiliary electrode; S2.3 uses a pattern search algorithm to solve the resistor arrangement and obtain the overall equivalent resistance Req of the grounding grid.
4. A grounding grid safety assessment method according to claim 1, characterized in that: The equivalent impedance circuit of the grounding grid is constructed, comprising: S3.1 regards the grounding grid system as a whole, defines external power equipment and overhead ground wire as external equivalent impedance Zext, and constructs an equivalent impedance circuit; where Zeq is the equivalent impedance converted from the equivalent resistance Req measured in step 2; It and Vt are the current and voltage on Zeq respectively; and Zext is the external equivalent impedance.
5. A grounding grid safety assessment method according to claim 4, characterized in that: The calculation of the laying evaluation parameters of the grounding grid includes: S3.2 inject a circulating current It between the grounding grid of the substation under test and the auxiliary current electrode; S3.3 Measure the voltage Vt of the grounding grid; S3.4 Use Kirchhoff's current law to calculate the current Im flowing through the grounding resistance Rm of the grounding grid and the current Iext flowing through the external equivalent impedance Zext.
6. A grounding grid safety assessment method according to claim 1, characterized in that: The laying evaluation parameters include: grounding resistance Rm of the grounding grid, current Im flowing through Rm, and current Iext flowing through the external equivalent impedance Zext.
7. A grounding grid safety assessment method according to claim 1, characterized in that: The safety assessment of the grounding grid includes: comparing the laying assessment parameters with the safety threshold range, and if one of the parameters exceeds the threshold range, determining that it does not meet the safety laying requirements.