A simulation method and device for a building grounding grid

Abstract

The application discloses a kind of simulation method and device of building grounding grid, wherein, method includes: step S1, according to existing building power system, using PEEC to establish the electrical parameter model of building grounding grid;Step S2, according to the electrical parameter obtained from the electrical parameter model, establish building grounding grid multi-port network equivalent circuit model;Step S3, using PEEC to obtain the ground potential distribution curve of grounding grid, for calculating the contact voltage and step voltage of human body;Step S4, according to building model and ground potential distribution curve, the electric shock risk of human body is evaluated.The application adopts the method that PEEC algorithm and multi-port network equivalent circuit model are combined, carries out modeling and simulation calculation to the complex grounding system of building group, can evaluate the contact voltage and step voltage of human body under fault condition, realizes the analysis to electric shock risk;Meanwhile, it will help the design of low-voltage grounding system and the configuration of leakage protector, low-voltage circuit breaker etc.

Description

Technical Field

[0001] This invention relates to the field of electrical engineering technology, specifically to a simulation method and apparatus for building grounding grids. Background Technology

[0002] Grounding grids have always been a key focus of electrical engineering research. Under lightning strikes or short-circuit faults, they can pose a serious threat to the safe and stable operation of power systems. When a short-circuit fault occurs in the system, a considerable potential difference and short-circuit current are applied to related equipment and nearby objects. This is a major cause of system failures and equipment damage. Even worse, if a person touches faulty equipment or metal parts near the grounding grid while standing on the ground, they may suffer electric shock. To mitigate these risks, effective grounding grid design for electrical systems is essential.

[0003] The grounding grid structure of buildings in low-voltage power distribution systems is complex, often constructed of high-density steel mesh, which poses a significant challenge to traditional simulation software. Furthermore, when fault current is injected into the complex grounding grid structure, it raises the surrounding ground potential, creating contact and step voltages for people in the vicinity, thus threatening their personal safety.

[0004] Research on grounding grids initially focused on experimental and theoretical studies using single horizontal grounding wires. With advancements in research on single horizontal and vertical grounding wires, empirical formulas and approximate analytical expressions for grounding system design have been developed. However, these analytical expressions have significant limitations, particularly for analyzing grounding grids with complex geometries. In recent years, with the rapid development of computer technology, numerical calculation methods for grounding grid evaluation and design have emerged. Therefore, researchers have begun calculating or simulating transient voltages or potentials around grounding grids. Numerical methods for transient simulation of grounding grids are classified differently according to various standards. Existing electromagnetic transient simulation software, such as CDEGS and EMTDC, has relatively low efficiency in simulating complex grounding grids in building complexes. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a simulation method and device for building grounding grids, so as to realize the simulation of complex grounding systems and the assessment of electric shock risks.

[0006] To solve the above-mentioned technical problems, the present invention provides a simulation method for building grounding grids, comprising:

[0007] Step S1: Based on the existing building power system, establish an electrical parameter model of the building grounding grid using PEEC;

[0008] Step S2: Based on the electrical parameters obtained from the electrical parameter model, establish an equivalent circuit model of the building grounding grid multi-port network;

[0009] Step S3: Use PEEC to obtain the ground potential distribution curve of the grounding grid, which is used to calculate the contact voltage and step voltage of the human body.

[0010] Step S4: Assess the risk of electric shock to the human body based on the building model and the ground potential distribution curve.

[0011] Furthermore, in step S1, based on the non-uniform distribution of current, all conductors are divided into small segments, and both current segments and charge segments are corrected by half the length of the segment.

[0012] Furthermore, the electrical parameter model of the building grounding grid uses a current-controlled nonlinear grounding resistor, specifically:

[0013]

[0014]

[0015] Where i(t) is the current injected into the electrode, I g It is the current flowing into the grounding grid, E0 is the critical electric field strength of the soil, and R DC It is the grounding resistance at low frequency and low current, σ g It refers to the electrical conductivity of the soil.

[0016] Furthermore, the building grounding grid is grounded through several grounding piles, each of which is composed of a dense steel mesh, and the grounding piles are connected by steel bars; step S2 specifically involves modeling the multi-port network equivalent circuit of the grounding piles.

[0017] Further, step S2 specifically includes:

[0018] Determine all output ports of the grounding grid;

[0019] The voltage to ground of all output ports is calculated by sequentially injecting current sources into each output port.

[0020] The admittance matrix of the grounding grid is established by the ratio of current to voltage, and the size of the admittance matrix is ​​determined by the number of output ports.

[0021] Furthermore, the admittance matrix is ​​expressed as:

[0022]

[0023] Where I = I1, I2, ..., I n and V = C1, V2, ..., V n These represent the current and voltage at each port. Y ij When a current source I is injected into port j js When, current Ijs The ratio of the potential at port i at this time.

[0024] Furthermore, step S3 obtains the ground potential distribution curve under the fault voltage by solving the PEEC matrix. The PEEC matrix is ​​discretized based on the backward Euler method and solved using the time step method.

[0025] Further, step S4 specifically includes: determining the contact voltage or step voltage of the human body when an electric shock occurs based on the ground potential distribution curve; and assessing the risk of electric shock to the human body based on its relationship with a predetermined danger voltage.

[0026] The present invention also provides a simulation device for a building grounding grid, comprising:

[0027] The first modeling module is used to establish an electrical parameter model of the building grounding network based on the existing building power system using PEEC.

[0028] The second modeling module is used to establish an equivalent circuit model of the multi-port network of the building grounding grid based on the electrical parameters obtained from the electrical parameter model.

[0029] The acquisition module is used to acquire the ground potential distribution curve of the grounding grid using PEEC, and to calculate the contact voltage and step voltage of the human body.

[0030] The assessment module is used to assess the risk of electric shock to the human body based on the building model and the ground potential distribution curve.

[0031] Furthermore, the second modeling module is specifically used to: determine all output ports of the grounding grid; calculate the voltage to ground of all output ports by sequentially injecting current sources into each output port; and establish the admittance matrix of the grounding grid by the ratio of current to voltage, so that the size of the admittance matrix is ​​determined by the number of output ports.

[0032] The admittance matrix is ​​expressed as:

[0033]

[0034] Where I = I1, I2, ..., I n and V = V1, V2, ..., V n These represent the current and voltage at each port. Y ij When a current source I is injected into port j js When, current I js The ratio of the potential at port i at this time.

[0035] Implementing this invention has the following beneficial effects: This invention uses a combination of the PEEC algorithm and the equivalent circuit model of a multi-port network to model and simulate the complex grounding system of a building complex. It can evaluate the human contact voltage and step voltage under fault conditions, thereby achieving the purpose of analyzing the risk of electric shock. At the same time, it will help in the design of low-voltage grounding systems and the configuration of leakage current protectors, low-voltage circuit breakers, etc. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a flowchart illustrating a simulation method for a building grounding grid according to an embodiment of the present invention.

[0038] Figure 2a This is a schematic diagram of the current line segmentation in an embodiment of the present invention.

[0039] Figure 2b This is a schematic diagram of the equivalent circuit of the current line segment in an embodiment of the present invention.

[0040] Figure 3 This is a schematic diagram of the basic model of the grounding line in an embodiment of the present invention.

[0041] Figure 4 This is a schematic diagram of the equivalent model of the grounding network in an embodiment of the present invention.

[0042] Figure 5 This is a schematic diagram of the equivalent circuit model of the multi-port grounding grid in an embodiment of the present invention.

[0043] Figure 6 This is a schematic diagram of the ground potential distribution curves under different grounding grids in an embodiment of the present invention. Detailed Implementation

[0044] The following description of the embodiments is taken with reference to the accompanying drawings, which illustrate specific embodiments in which the invention can be implemented.

[0045] With the development of new power systems, low-voltage distribution networks are becoming increasingly complex and sophisticated, demanding higher levels of simulation expertise. The Partial Element Equivalent Circuit (PEEC) method is advantageous in simulating complex conductor structures and is widely used in electromagnetic simulation. Furthermore, utilizing multi-port network equivalent circuit models can accelerate the simulation of complex grounding networks. Therefore, this invention proposes a PEEC method combined with a multi-port network equivalent circuit model to achieve simulation and electric shock risk assessment of complex grounding systems.

[0046] Please refer to Figure 1 As shown, this embodiment of the invention provides a simulation method for a building grounding grid, including:

[0047] Step S1: Based on the existing building power system, establish an electrical parameter model of the building grounding grid using PEEC;

[0048] Step S2: Based on the electrical parameters obtained from the electrical parameter model, establish an equivalent circuit model of the building grounding grid multi-port network;

[0049] Step S3: Use PEEC to obtain the ground potential distribution curve of the grounding grid, which is used to calculate the contact voltage and step voltage of the human body.

[0050] Step S4: Assess the risk of electric shock to the human body based on the building model and the ground potential distribution curve.

[0051] Specifically, in the PEEC method, to account for the non-uniform distribution of current, all conductors need to be divided into small segments. In the T-type circuit model, as shown in Figure 2(a), both the current segment and the charge segment are corrected by half the length of the segment. The segment length is typically chosen to be 1 / 10 of the wavelength of the primary frequency of interest. The volume current and the voltage across the segment are unknown parameters to be determined.

[0052] Figure 2(b) shows the equivalent circuit of the conductor in Figure 2(a). Each circuit segment can be called a PEEC unit, and each PEEC unit includes a resistor, a self-inductance, a mutual inductance, a self-capacitance, and a controlled source.

[0053] The simplified calculation formulas for the basic cell of the PEEC equivalent method are shown in Table 1 below:

[0054] Table 1. Basic Cells of PEEC

[0055]

[0056] Where, σ iε0, μ0 are the conductivity, permeability and permittivity of the conductor, respectively. a and S are the cross-sectional area and surface area, respectively. V is the volume of the conductor and R is the distance from the observation point to the source point.

[0057] Because the ionization process of the soil is introduced, calculating the resistance of the grounding line is much more complex than calculating the parameters above ground. To improve computational efficiency and simplify the model, the effect of capacitance is temporarily ignored in the grounding line model. Therefore, the grounding line model only considers the effects of line resistance, inductance, and grounding resistance. Its basic model and network model are as follows: Figure 3 express.

[0058] Ionization reduces soil conductivity, necessitating the use of current-controlled nonlinear grounding resistors. The nonlinear grounding resistors recommended by CIGRE are defined as follows:

[0059]

[0060]

[0061] Where i(t) is the current injected into the electrode, I g It is the current flowing into the grounding grid, E0 is the critical electric field strength of the soil, and R DC It is the grounding resistance at low frequency and low current, σ g It refers to the electrical conductivity of the soil.

[0062] For example Figure 4 As shown, a typical building includes a reinforced concrete structure above ground, internal electrical wiring, and a grounding system beneath the ground. The grounding system is connected to the ground via several grounding stakes, each composed of a dense steel mesh, with the stakes linked together by steel reinforcement. This embodiment uses the obtained PEEC parameters to model the equivalent circuit of the grounding stakes as a multi-port network.

[0063] First, determine all output ports of the grounding grid: port 1, port 2, port 3, ... . Figure 5 As shown, the voltage to ground of all output ports is calculated by sequentially injecting current sources into each output port.

[0064] The admittance matrix of the grounding grid can be established using the ratio of current to voltage, as shown below:

[0065]

[0066] Where I = I1, I2, ..., I n and V = V1, V2, ..., V n These represent the current and voltage at each port. Y ij When a current source I is injected into port j js When, current Ijs The ratio of the potential at port i at this time. In this way, the size of the resulting admittance matrix depends only on the number of output ports, not on the number of reinforcing bars or circuit components.

[0067] As described above, this embodiment uses the underlying PEEC algorithm to model the grounding grid of a single building. By solving the PEEC matrix, the ground potential distribution under fault voltage can be obtained. The PEEC matrix is ​​discretized based on the backward Euler method and solved using the time-stepping method. Figure 6 The figures show the ground potential distribution curves under grounding grids of different densities, including (1) a single grounding electrode; (2) a grounding grid with a cell size of 10m × 10m; (3) a grounding grid with a cell size of 5m × 5m; and (4) a grounding grid with a cell size of 1m × 1m. Based on the distribution of ground potential, the contact voltage (voltage between a person's hand and foot) or step voltage (voltage between a person's two feet) at the time of electric shock can be determined. Assuming that voltages above 50V are defined as dangerous voltages and voltages below 50V are defined as safe voltages, the risk of electric shock to the human body can be assessed by combining the building model and the ground potential distribution curves.

[0068] Corresponding to the simulation method for a building grounding grid in Embodiment 1 of the present invention, Embodiment 2 of the present invention also provides a simulation device for a building grounding grid, comprising:

[0069] The first modeling module is used to establish an electrical parameter model of the building grounding network based on the existing building power system using PEEC.

[0070] The second modeling module is used to establish an equivalent circuit model of the multi-port network of the building grounding grid based on the electrical parameters obtained from the electrical parameter model.

[0071] The acquisition module is used to acquire the ground potential distribution curve of the grounding grid using PEEC, and to calculate the contact voltage and step voltage of the human body.

[0072] The assessment module is used to assess the risk of electric shock to the human body based on the building model and the ground potential distribution curve.

[0073] Furthermore, the second modeling module is specifically used to: determine all output ports of the grounding grid; calculate the voltage to ground of all output ports by sequentially injecting current sources into each output port; and establish the admittance matrix of the grounding grid by the ratio of current to voltage, so that the size of the admittance matrix is ​​determined by the number of output ports.

[0074] The admittance matrix is ​​expressed as:

[0075]

[0076] Where I = I1, I2, ..., I n and V = V1, V2, ..., V n These represent the current and voltage at each port. Y ij When a current source I is injected into port j js When, current I js The ratio of the potential at port i at this time.

[0077] For the working principle and process of this embodiment, please refer to the description of the aforementioned Embodiment 1 of the present invention, which will not be repeated here.

[0078] As can be seen from the above description, compared with the prior art, the beneficial effects of the present invention are as follows: The present invention adopts a method combining the PEEC algorithm and the equivalent circuit model of multi-port networks to model and simulate the complex grounding system of building groups, which can evaluate the human contact voltage and step voltage under fault conditions, thereby achieving the purpose of analyzing the risk of electric shock; at the same time, it will help in the design of low-voltage grounding systems and the configuration of leakage current protectors, low-voltage circuit breakers, etc.

[0079] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A simulation method of a building grounding grid, characterized by, include: Step S1: Based on the existing building electrical system, establish the electrical parameter model of the building grounding grid using the PEEC (Power Equivalent Circuit for Partial Components). Step S2: Based on the electrical parameters obtained from the electrical parameter model, establish an equivalent circuit model of the building grounding grid multi-port network; Step S3: Use PEEC to obtain the ground potential distribution curve of the grounding grid, which is used to calculate the contact voltage and step voltage of the human body. Step S4: Assess the risk of electric shock to the human body based on the building model and the ground potential distribution curve; In step S1, based on the uneven distribution of current, all conductors are divided into small segments, and both current segments and charge segments are corrected by half the length of the segment. The electrical parameter model of the building grounding grid uses a current-controlled nonlinear grounding resistor, which is specifically: wherein, is a non-linear grounding resistance, is the current injected into the electrode, is the current flowing into the grounding grid, is the critical electric field strength of the soil, is a low-frequency low-current grounding resistance, is the electrical conductivity of the soil; The building grounding grid is grounded through a number of grounding piles, each of which is composed of a dense steel mesh, and the grounding piles are connected by steel bars; step S2 specifically involves modeling the equivalent circuit of a multi-port network for the grounding piles. Step S4 specifically includes: determining the contact voltage or step voltage of the human body when an electric shock occurs based on the ground potential distribution curve; and assessing the risk of electric shock to the human body based on its relationship with a predetermined danger voltage.

2. The method of claim 1, wherein, Step S2 specifically includes: Determine all output ports of the grounding grid; The voltage to ground of all output ports is calculated by sequentially injecting current sources into each output port. The admittance matrix of the grounding grid is established by the ratio of current to voltage, and the size of the admittance matrix is ​​determined by the number of output ports.

3. The method of claim 2, wherein, The admittance matrix is ​​expressed as: in, and These represent the current and voltage at each port, respectively. For when at port j Injected current At that time, the current With the port at this time i voltage V i The ratio, .

4. The method of claim 1, wherein, Step S3 obtains the ground potential distribution curve under the fault voltage by solving the PEEC matrix. The PEEC matrix is ​​discretized based on the backward Euler method and solved using the time step method.

5. A simulation device of a building grounding grid, characterized by, include: The first modeling module is used to establish the electrical parameter model of the building grounding network based on the existing building power system and using the PEEC equivalent circuit of some components. The second modeling module is used to establish an equivalent circuit model of the multi-port network of the building grounding grid based on the electrical parameters obtained from the electrical parameter model. The acquisition module is used to acquire the ground potential distribution curve of the grounding grid using PEEC, and to calculate the contact voltage and step voltage of the human body. The assessment module is used to assess the risk of electric shock to the human body based on the building model and the ground potential distribution curve; The first modeling module divides all conductors into small segments based on the uneven distribution of current, and both current segments and charge segments are corrected by half the length of the segment. The electrical parameter model of the building grounding grid uses a current-controlled nonlinear grounding resistor, which is specifically: in, It is a non-linear grounding resistance. It is the current injected into the electrode. It is the current flowing into the grounding grid. It is the critical electric field strength of the soil. It is a grounding resistance with low frequency and low current. It is the electrical conductivity of the soil; The building's grounding grid is grounded through several grounding stakes, each of which is composed of a dense steel mesh, and the grounding stakes are connected by steel bars; the second modeling module specifically performs multi-port network equivalent circuit modeling for the grounding stakes; The assessment module is specifically used to: determine the contact voltage or step voltage of the human body when an electric shock occurs based on the ground potential distribution curve; and assess the risk of electric shock to the human body based on its relationship with a predetermined danger voltage.

6. The apparatus of claim 5, wherein, The second modeling module is specifically configured to determine all output ports of the grounding net; calculate the voltage to ground of all output ports by sequentially injecting a current source at each output port; and establish an admittance matrix of the grounding net through the ratio of current to voltage, so that the size of the admittance matrix is determined by the number of output ports. The admittance matrix is expressed as: in, and These represent the current and voltage at each port, respectively. For when at port j Injected current At that time, the current With the port at this time i voltage V i The ratio, .

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