An indirect measurement method for grounding resistance of complex grounding grid

Abstract

The present invention relates to an indirect measurement method of the grounding resistance of a complex grounding network, comprising the following steps: step 1, measuring the resistance value of a simple grounding network not far from the complex grounding network; step 2, connecting the complex grounding network with the simple grounding network, injecting current at both ends of the connecting lead, and then obtaining the total loop resistance; step 3, correcting the loop resistance by measuring the lifting potential of the simple grounding network, and then obtaining the grounding resistance of the complex grounding network. The present invention obtains the resistance value of the complex grounding network through indirect testing while establishing a small grounding body and accurately measuring its grounding resistance.

Description

Technical Field

[0001] The invention relates to the technical field of ground grid resistance measurement, and in particular to an indirect measurement method for the grounding resistance of a complex ground grid. Background Art

[0002] The measurement of ground grid resistance is an important basis for judging whether the ground grid design and construction are qualified or not, and it is also an effective means to evaluate the ground grid status. The theory and practice of existing ground grid test methods are all based on isolated simple grids for derivation or practice, but the actual ground grid structure is complex, there are many interferences in the test process, and the accuracy and effectiveness of the ground grid test results are affected by various factors.

[0003] In the ground network test, in order to accurately obtain the ground network resistance value, the frequency test technology can be used to eliminate the interference of the power frequency component, and the long overhead line can be used instead of the manual line to obtain the zero potential point more accurately. For the power grid that cannot disconnect the measured ground network from the outside ground network, in order to eliminate the interference of the external ground network, some researchers suggest correcting the measurement results by measuring the shunt. However, most of the actual ground networks are complex ground networks. The so-called complexity means that the boundary of the ground network is not clear, that is, the ground network body is often connected to the tower grounding body and the external ground network through the overhead ground wire and the cable shielding layer. In actual testing, except for the overhead ground wire as a shunt, other external and shunt conductors are unknown, and the extension of the ground network is often unclear. The influence of the extension part on the earth potential distribution will cause a great change in the position of the zero potential point. If the zero potential point cannot be accurately found, the measurement result itself is inaccurate, and it is impossible to obtain the ideal result through shunt correction. Summary of the invention

[0004] The purpose of the present invention is to provide an indirect measurement method for the grounding resistance of a complex ground grid. First, the resistance value of a simple grid that is not too far away from the complex ground grid is measured, and then the complex ground grid is connected to the simple grid, and current is injected at both ends of the connecting lead to obtain the total loop resistance. By measuring the lifting potential of the simple grid, the loop resistance is corrected to obtain the grounding resistance of the complex ground grid.

[0005] The present invention provides an indirect measurement method for the grounding resistance of a complex grounding grid, comprising the following steps:

[0006] Step 1, measure the resistance value of a simple ground grid not far from the complex ground grid;

[0007] Step 2, connect the complex ground grid with the simple ground grid, inject current at both ends of the connecting lead, and then obtain the total loop resistance;

[0008] Step 3: By measuring the lifting potential of the simple ground grid, the loop resistance is corrected to obtain the grounding resistance of the complex ground grid.

[0009] Furthermore, the step 1 comprises:

[0010] A simple grid analysis model is established, the potential distribution on the observation line is calculated, and the grounding resistance of the grid is measured by the straight-line method.

[0011] Furthermore, the step 2 comprises:

[0012] Assuming that there is an isolated ground grid near the complex ground grid, first obtain the grounding resistance of the isolated ground grid. After obtaining the grounding resistance of the isolated ground grid, use the isolated ground grid as a current electrode, set a power supply at the complex ground grid to form a current loop between the two ground grids, and measure the voltage difference between the pressurized leads at the same time to obtain the total loop resistance.

[0013] Furthermore, in step 2, by establishing a complex power grid analysis model with a small isolated ground grid, injecting current, calculating the potential distribution on the observation line of the small isolated grid, and further obtaining the grounding resistance of the isolated grid.

[0014] Furthermore, in step 2, based on the potential distribution on the observation line, the resistance in the entire loop is obtained by calculating the difference between the potential on the complex ground network and the potential on the simple ground network.

[0015] By means of the above scheme, through the indirect measurement method of the grounding resistance of the complex ground grid, a small grounding body is established and its grounding resistance is accurately measured, and the resistance value of the complex ground grid is obtained through indirect testing.

[0016] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Simple grid ground resistance measurement principle diagram;

[0018] Figure 2 Simply observe the potential distribution on the network line;

[0019] Figure 3 Schematic diagram of small isolated ground network test;

[0020] Figure 4 Potential distribution of ground resistance test of small isolated ground grid. Among them: (a) observation line potential distribution; (b) surface potential distribution contour map (absolute value of potential);

[0021] Figure 5 Schematic diagram of indirect measurement method for complex ground network;

[0022] Figure 6 The indirect measurement method observes the potential distribution on the line. DETAILED DESCRIPTION

[0023] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0024] This embodiment provides an indirect measurement method for the grounding resistance of a complex grounding network. Through the indirect measurement method for the grounding resistance of a complex grounding network, the resistance value of the complex grounding network is obtained through indirect testing while building a small grounding body and accurately measuring its grounding resistance. The method first measures the resistance value of a simple grounding network that is not too far from the complex grounding network, and then connects the complex grounding network to the simple grounding network, injects current at both ends of the connecting lead, and then obtains the total loop resistance. By measuring the lifting potential of the simple grounding network, the loop resistance is corrected to obtain the grounding resistance of the complex grounding network. The specific scheme is as follows:

[0025] 1. Use ground grid analysis software for modeling analysis.

[0026] For the sake of simplicity, the soil is set to be uniform soil, the soil resistivity is 100Ω·m, the burial depth of the grounding body is 0.5m, the grounding body material is a copper rod, and the diameter of the copper rod is 12mm. For the convenience of explaining the principle, the straight line method is used for explanation.

[0027] 2. Establish a simple grid analysis model, calculate the potential distribution on the observation line and accurately measure the grounding resistance of the ground grid by the straight line method.

[0028] Depend on Figure 1 , a simple grid analysis model was established. The diagonal length of the ground grid is 141.4m, the straight-line distance between the current pole and the center of the ground grid is 500m, which is 3.5 times the diagonal length. The observation line is located on the ground surface, and the test current is 10A.

[0029] Depend on Figure 2 Under the action of the test current, the surface potential between the ground grid and the current electrode gradually changes from positive to negative, forming a zero potential zone in the area between 246 and 256 m from the ground grid, that is, the voltage electrode is arranged here to accurately measure the grounding resistance of the ground grid by the straight line method. In this example, the potential at the ground grid is 4.1V, the potential at the current electrode is -271.9V, and the injected current is 10A. From this, it can be obtained that the grounding resistance of the ground grid is 0.41Ω, the grounding resistance of the current electrode grounding body is 27.19Ω, the voltage applied by the measuring device is 275V, and the power is 2750W.

[0030] 3. Assume that there is an isolated ground grid near the complex ground grid, first obtain the grounding resistance of the isolated ground grid. After obtaining the grounding resistance of the isolated ground grid, use the isolated ground grid as the current pole, set the power supply at the complex ground grid to form a current loop between the two ground grids, and measure the voltage difference between the pressurized leads at the same time to obtain the total loop resistance. By measuring the lifting potential of the simple grid, the loop resistance is corrected to obtain the grounding resistance of the complex ground grid.

[0031] Depend on Figure 3 , a complex power grid analysis model with a small isolated ground grid is established, and the injection current of 10A is still used to calculate the potential distribution on the observation line of the small isolated power grid. Figure 4 .

[0032] Furthermore, the grounding resistance of the isolated power grid is obtained.

[0033] Depend on Figure 5 Indirect test wiring method, the isolated ground network is used as the current electrode, and a power supply is set at the complex ground network to form a current loop between the complex ground network and the isolated ground network. The current amplitude is 10A. At the same time, the voltage difference between the pressurized leads is measured to perform indirect measurement of the resistance of the complex power grid.

[0034] Furthermore, the potential distribution on the observation line is obtained as follows: Figure 6 The potential on the complex ground network is 2.22V, and the potential on the simple network is -45.93V, which means that the potential difference at the output end of the measuring device current injection is 48.15V, and the resistance in the entire loop is 4.82Ω.

[0035] Since the potential of 45.9396V on the current electrode at this time is affected by the voltage rise of the measured ground network, it needs to be corrected. When correcting, the current leads measured in the original simple ground network are used to obtain a potential difference of 44.6955 between the leads. The correction value is 0.12Ω, and the measurement result of the complex ground network is 4.82-4.48-0.12=0.22Ω.

[0036] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the technical principles of the present invention, and these improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. An indirect measurement method for the grounding resistance of a complex ground grid, characterized in that: The steps include: Step 1: Measure the resistance value of a simple grid not far from the complex grid, including: Establish a simple grid analysis model, calculate the potential distribution on the observation line and measure the grounding resistance of the ground grid by the straight line method; Step 2: Connect the complex ground grid to the simple ground grid, inject current at both ends of the connecting lead, and then obtain the total loop resistance, including: Assuming that there is an isolated ground grid near the complex ground grid, first obtain the grounding resistance of the isolated ground grid. After obtaining the grounding resistance of the isolated ground grid, use the isolated ground grid as a current electrode, set a power supply at the complex ground grid to form a current loop between the two ground grids, and measure the voltage difference between the pressurized leads at the same time, so as to obtain the total loop resistance; By establishing a complex power grid analysis model with a small isolated ground grid, injecting current, calculating the potential distribution on the observation line of the small isolated grid, and further obtaining the grounding resistance of the isolated grid; Based on the potential distribution on the observation line, the resistance of the entire circuit is obtained by calculating the difference between the potential on the complex ground network and the potential on the simple network; Step 3: By measuring the lifting potential of the simple ground grid, the loop resistance is corrected to obtain the grounding resistance of the complex ground grid.

Images