Method for calculating electric field distribution of human body under ultra-high voltage direct current transmission line

Abstract

The present application relates to a kind of methods for calculating the electric field distribution of human body under UHV DC transmission line, belong to high voltage transmission technical field.The method includes the following contents: a, calculation, the electric charge method is applied to calculate the electric charge density of UHV DC transmission line conductor and the electric field line method is calculated to calculate the potential of any point in space under transmission line;B, human body modeling, reference the basic data of human body modeling size, according to the relative position of human body and transmission line and the actual height of transmission line, establish the space area for calculating the electric field distribution of human body;C, region division, according to the influence of finite element region boundary condition by the presence or absence of human body, select appropriate calculation area, analyze the internal and surface field intensity distribution of human body under UHV DC transmission line.The present application can provide technical reference for electromagnetic protection of the people who move under UHV DC transmission line.

Description

Technical Field

[0001] This invention belongs to the field of high-voltage power transmission technology and relates to a method for calculating the electric field distribution of the human body under ultra-high voltage direct current transmission lines. Background Technology

[0002] Direct current (DC) transmission is a long-distance, high-capacity power transmission technology and the preferred solution for reversing energy and load distribution. However, with increasing voltage levels, high-voltage DC transmission systems face a series of electromagnetic environment problems. These mainly involve the DC composite electric field, ion current density, DC magnetic field, audible noise, and radio interference, which are crucial factors that must be considered in engineering design, construction, and operation and maintenance. Among these, the composite electric field and space charge are unique to DC transmission systems, resulting in significant differences between the electromagnetic environment of DC transmission and that of AC transmission. When the electric field strength on the surface of high-voltage DC transmission lines and fittings exceeds a certain critical value, corona discharge occurs, leading to various hazards such as continuous power loss, electric field distortion, biological effects from the ion current field, audible noise, and radio interference.

[0003] Because the polarity of a DC electric field does not change over time, the space charges generated around the surface corona move into the surrounding air under the influence of the electric field. These space charges, together with the nominal electric field generated by the conductor potential, form a composite electric field. This charge drift increases the strength of the composite electric field in the drift direction, resulting in a ground electric field strength that can be 2 to 3 times the nominal electric field strength. The directional movement of space charges around the transmission line creates an ion flow. People standing under a DC transmission line may experience some of this ion flow, which flows through their bodies to the ground, potentially having uncertain effects on their health. A US research institute conducted long-term observational studies of wild flora and fauna near ±400kV DC transmission lines and discovered some subtle differences in wild animals. The Dallas Test Center in the United States conducted a human sensation test under high-voltage direct current (HVDC) lines. The results showed that when the electric field strength under the line was 30 kV / m, the hair and scalp on the human body could feel a slight tingling sensation; when the electric field strength was greater than 30 kV / m, the tingling sensation was more pronounced and intense, mainly in the torso and face. my country's power industry standards, implemented in 2008, stipulate that when HVDC transmission lines are close to residential buildings, the maximum combined electric field strength must not exceed 25 kV / m, and the maximum combined electric field strength around the line must be less than 30 kV / m.

[0004] However, as things stand, there is no definitive conclusion yet regarding whether high-voltage direct current (HVDC) transmission lines will have adverse effects on people. On the one hand, some international organizations or institutions have given their own conclusions or safety guidelines. For example, in 2004, the World Health Organization (WHO) summarized the research conclusions on the effects of direct current electric fields on the human body: no research has concluded that direct current electric fields have any adverse effects on human health. The International Agency for Research on Cancer (IARC) has also stated that, to date, there is insufficient evidence to determine that electrostatic fields have a carcinogenic effect on the human body. The International Commission on Non-Ionizing Protection believes that when the ion current density under a HVDC transmission line exceeds 100 nA / m... 2 When exposed to electromagnetic fields, these fields can affect the nervous system and heart. Therefore, it is essential to study the effects of ultra-high voltage direct current (UHVDC) on the human body's electric field and to conduct a safety assessment of the electromagnetic fields under UHVDC transmission lines, in conjunction with relevant limit standards. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for calculating the electric field distribution of the human body under ultra-high voltage direct current transmission lines.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for calculating the electric field distribution of a human body under an ultra-high voltage direct current transmission line, the method comprising the following steps:

[0008] S1: Calculate the potential at any point under an ultra-high voltage direct current transmission line using the simulated charge method;

[0009] S2: Calculate the spatial ion current density and potential under UHVDC transmission lines using the electric field line method based on the Deutsch assumption;

[0010] S3: Solve for the potential of the spatial region under the combined influence of conductor charge and space ions. Based on the requirement that the height of the transmission line and the presence of human beings have approximately no effect on the boundary conditions of the finite element region, the region under the transmission line is divided into a finite element region and other spatial regions, and the boundary potentials are determined.

[0011] S4: Human body modeling. A three-dimensional human body simulation model is established with reference to the basic data of human body modeling dimensions in "Chinese Adult Human Body Dimensions". Based on the relative position of the human body and the power transmission line and the actual height of the power transmission line, a spatial region for calculating the electric field distribution of the human body is established.

[0012] S5: Calculate and analyze the distribution of electric field intensity inside and on the surface of the human body under ultra-high voltage direct current transmission lines using the finite element method.

[0013] Optionally, in step S1, the specific steps for determining the surface charge density of the conductor using the simulated charge method are as follows:

[0014] S11: Set n simulated charges Q outside the computational region. j (j = 1, 2, ..., n);

[0015] S12: On the electrode surface with a known surface potential value, set n matching points M, the same number as the number of simulated charges. i (i = 1, 2, ..., n), the potential value of each matching point Equal to the electrode surface potential;

[0016] S13: According to the superposition principle, corresponding to each matching point M i List out the linear potential equations established by the given simulated charges one by one.

[0017]

[0018] In the formula, P is the potential coefficient;

[0019] S14: Solve the linear equation system above to obtain the simulated charge value [Q];

[0020] S15: Take a certain number of verification points on the electrode surface—usually the midpoint between two adjacent matching points, calculate its potential value, and compare it with the known potential. If the absolute difference between the two is less than the set value, the arrangement is considered valid and proceed to S16. If it is greater than the set value, the simulated charge state and parameters need to be adjusted and return to S11 until the calculation accuracy requirements are met.

[0021] S16: Based on the final obtained discrete solution of the simulated charge [Q], calculate the potential at any field point using analytical formulas.

[0022] Optionally, in step S2, the specific steps for calculating the ion current density using the electric field line method based on the Deutsch assumption are as follows:

[0023] Deutsch's assumptions are as follows:

[0024] (1) It is assumed that the existence of space charge only affects the magnitude of the electric field and does not change its direction, i.e., the Deutsch assumption is:

[0025] E s =AE

[0026] In the formula, A is a scalar greater than zero;

[0027] (2) After the conductor begins to corona, the surface potential remains at the corona initiation voltage value V0. When the conductor-to-ground voltage is U, the conductor surface proportionality coefficient A... e The value is:

[0028] A e =V0 / U=E on / E0

[0029] E in the formula on E0 and E0 are the initial electric field strength of the corona discharge and the maximum electric field strength on the surface of the conductor, respectively.

[0030] (3) Ion mobility is independent of electric field strength and is considered a constant; the mobility of positive and negative ions is considered to be equal.

[0031] k = k + =k -

[0032] (4) The corona initiation voltage of the positive and negative terminals is considered to be the same;

[0033] (5) The effect of space charge diffusion is negligible compared to the directional motion under the action of electric field force, and it is assumed that all charges move along the direction of electric field lines;

[0034] Based on the above assumptions, the key to solving the composite electric field lies in solving for the nominal electric field and A. The method of simulated charge is used to solve for the nominal electric field and the horizontal component E of the electric field intensity at a point in space. x E y and E z Let the coordinates of a point P1 arbitrarily close to P(x,y,z) on the electric field line be (x1,y1,z1), then we have:

[0035]

[0036] d represents the step size for plotting electric field lines. A larger step size should be chosen when the field is far from the conductor, and a smaller step size should be chosen when the field is close to the conductor. The specific formula is as follows:

[0037]

[0038] in The potential at this point in a zero space charge region;

[0039] Solving the equations together, we get:

[0040]

[0041] If the product of Aρ at any point along the direction of the electric field lines is a constant, then

[0042] Aρ=A e ρ e =A l ρ l

[0043] Where A e and ρ e A is the value of the conductor surface. l and ρ l Let A and ρ be the values ​​of any point in the electric field;

[0044] Ignoring the recombination effect of ions, the result simplifies to:

[0045]

[0046] Simplifying along the direction of the electric field lines, we get:

[0047]

[0048] Where s is the integral variable along the direction of the electric field lines;

[0049] Solving the above equations simultaneously, we get:

[0050]

[0051] Simplifying, we get:

[0052]

[0053] When using the secant-chord iteration method to solve the problem simultaneously, improper selection of the surface charge density of the conductor can easily lead to non-convergence of the results. Therefore, it is necessary to predict the charge density of the conductor, specifically in the following form:

[0054]

[0055] Where ρ m The average charge density of each electric field line is magnified and used as the initial value of the charge density on the surface of the conductor.

[0056] After solving for the charge density at the nodes of the conductor, the charge density at other nodes on the electric field line and its corresponding A value are obtained, and then the distribution of ion current density at any location on the ground is obtained.

[0057] Optionally, in S2, after calculating the combined electric field under the UHVDC transmission line according to the electric field line method, the electric field is the negative gradient of the potential. The potential of the region under the DC transmission line is solved. The boundary potential of the finite element region is generated by the combined action of the surface charge of the conductor and the space charge. The induced electric field inside and outside the human body is calculated using the finite element method.

[0058] Optionally, in step S3, based on the influence of the presence or absence of a human body on the boundary conditions of the finite element region, the finite element calculation region is defined as a 4×4×4m area centered on the human body. 3 Cube space.

[0059] Optionally, in S5, when simulating in finite element software, the human body is considered as a non-magnetic entity consisting of four parts: head, arms, torso, and legs, and each part is assigned a dielectric constant ε and a conductivity γ.

[0060] Optionally, in S5, the electric field distribution inside and on the surface of the human body is calculated in finite element software under both grounding and insulation conditions; the electric field distribution of the human body at different positions under the DC transmission line is analyzed, as well as the influence of the transmission line erection height and electrode spacing on the electric field distribution of the human body.

[0061] The beneficial effects of this invention are as follows:

[0062] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0063] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0064] Figure 1 The three-view drawing of the constructed human body model;

[0065] Figure 2 A schematic diagram showing the position of a human body under an ultra-high voltage direct current transmission line;

[0066] Figure 3 A diagram showing the potential distribution around and inside a grounded human body; Figure 3 (a) is a front view of the potential distribution in the area near the human body; Figure 3 (b) is a side view of the potential distribution in the area near the human body. Figure 3 (c) shows the internal potential distribution;

[0067] Figure 4 A diagram showing the potential distribution around and inside the human body, which is insulated from the ground; Figure 4 (a) is a front view of the potential distribution in the area near the human body; Figure 4 (b) is a side view of the potential distribution in the area near the human body; Figure 4 (c) shows the internal potential distribution. Detailed Implementation

[0068] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0069] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0070] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0071] Figure 1 Three-dimensional human body model (three-view drawing); Figure 2 The location of a human body under an ultra-high voltage direct current transmission line; Figure 3 A diagram showing the potential distribution around and inside a grounded human body; Figure 3 (a) is a front view of the potential distribution in the area near the human body; Figure 3 (b) is a side view of the potential distribution in the area near the human body. Figure 3 (c) shows the internal potential distribution; Figure 4 This is a diagram showing the potential distribution around and inside a human body that is insulated from the ground. Figure 4 (a) is a front view of the potential distribution in the area near the human body; Figure 4 (b) is a side view of the potential distribution in the area near the human body; Figure 4 (c) shows the internal potential distribution.

[0072] The surface density of ion flux under ±800kV transmission lines is calculated using the electric field line method based on the Deutsch assumption, including the following:

[0073] a. Modeling: Referencing the basic data of human body modeling dimensions, "GB10000-1988 Chinese Adult Human Body Dimensions", a three-dimensional human body simulation model is established. Combined with the actual height of the power transmission line, the relative position of the human body and the power transmission line is determined, and a three-dimensional calculation model of the actual spatial area is established.

[0074] b. Regional Division: In reality, power transmission lines are high and long, and are far from people active near the ground, resulting in a large overall modeling and calculation area. Furthermore, calculating the ion flow field in three-dimensional space requires solving nonlinear partial differential equations and repeatedly solving finite element equations, which is much more computationally intensive than calculating the electric field. Therefore, when considering the impact of power transmission lines on the human body, it is necessary to introduce appropriate boundary conditions to divide the area where the human body is located in order to reasonably reduce the computational workload.

[0075] When a person is located under a DC transmission line, the size of the human body is very small relative to the height of the DC line. Therefore, it is reasonable to assume that the presence of the human body has little effect on the space charge density and potential at a distance from it. When the human body is not present, the potential and charge density at the corresponding location in the calculation results of the simulated charge method and the electric field line method will be used as the space potential and charge density boundaries at the boundary of this three-dimensional region. The size of the human body is very small relative to the entire calculation model, making this method reasonable for calculating the synthetic electric field and ion current of a human body under a DC transmission line. To avoid the situation where the three-dimensional region is too small and affects the calculation accuracy, or too large and wastes computational resources, a calculation region is selected. If the three-dimensional region continues to increase without having a significant impact on the calculation results, it is approximately considered to be large enough to meet the calculation requirements. Finally, a 4×4×4m area around the human body is determined. 3 The cube is used as the finite element region.

[0076] c. Calculate the nominal electric field of UHVDC transmission lines using the simulated charge method;

[0077] d. Calculate the ion flow field of UHVDC transmission lines using the electric field line method based on the Deutsch assumption;

[0078] e. Solve for the potential of the region under the DC transmission line using the total field, thereby determining the boundary potential of the finite element region;

[0079] f. Calculate and analyze the electric field intensity distribution inside and on the surface of the human body under ultra-high voltage direct current transmission lines using finite element software.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for calculating the electric field distribution of a human body under an ultra-high voltage direct current (UHVDC) transmission line, characterized in that: The method comprises the following steps: S1: applying the simulation charge method to calculate the surface charge distribution of the UHV DC transmission line and the electric field and potential of any point under the line; the specific steps of the simulation charge method to calculate the nominal electric field are as follows: S11: setting outside of the calculation region n analog charge ; S12: On the electrode surface whose surface potential value is known, the same number of matching points as the number of simulation charges is set n Matching points , the potential value of each matching point is equal to the electrode surface potential; S13: According to the superposition principle, for each matching point M i linear potential equations established by the set of analog charges are listed one by one [ P ][ Q ]=[ ] In the formula, P is the potential coefficient; S14: Solve the linear equations of the above formula to obtain the analog charge value Q ] S15: taking a certain number of check points on the surface of the electrode, usually the middle position of two adjacent matching points, calculating the potential value thereof, comparing the potential value with the known potential, if the absolute value difference between the two is less than a set value, it is considered that the arrangement is effective, and S16 is entered, if the absolute value difference is greater than the set value, the simulation charge state and parameters need to be adjusted and returned to S11 until the calculation precision requirement is met; S16: Discretize the final obtained simulation charge [ Q ] and calculate the electric field and potential on the finite element region interface according to it; S2: applying the electric field line method based on the Deutsch assumption to calculate the space ion current density and potential under the UHV DC transmission line; S3: according to the relative position of the human body and the transmission line and the actual height of the transmission line, combining the limiting conditions of the regional boundary calculated by the finite element method when the human body exists, dividing the space region for calculating the electric field distribution of the human body in the whole space, and determining the boundary conditions of the finite element method by the space potential under the joint action of the wire charge and the space ion; S4: human body modeling, establishing a three-dimensional human body simulation model according to the basic data of human body modeling size in “Chinese adult human body size”; S5: calculating and analyzing the internal and surface electric field intensity distribution of the human body under the UHV DC transmission line by using the finite element method.

2. The method of claim 1, wherein the method comprises: In the S2, the specific steps of the electric field line method based on the Deutsch assumption to calculate the ion current density are as follows: The Deutsch assumption conditions are as follows: (1) it is assumed that the existence of space charge only affects the size of the electric field and does not change its direction, that is, the Deutsch assumption is as follows: E s = AE wherein A is a scalar greater than zero; (2) After the wire is corona, the surface potential is maintained at the corona starting voltage value V 0, the voltage of the wire to the ground is U , the surface proportion coefficient of the wire A e The value is: A e = V 0 / U = E on / E 0 in the formula E on and E 0 are the corona inception field strength and the maximum field strength at the surface of the wire, respectively (3) the ion mobility is independent of the electric field intensity and is considered as a constant, and the mobilities of positive and negative ions are considered to be equal; k = k + = k - (4) the corona inception voltage of the positive and negative poles is considered to be the same; (5) the diffusion of space charge is ignored compared with the directional motion under the action of electric field force, and it is considered that all charges move along the electric field line direction; Based on the above assumptions, the key to solving the resultant electric field lies in the nominal electric field and A The solution is obtained by using the simulated charge method to determine the nominal electric field and the horizontal component of the electric field intensity at a point in space. E x , E y and E z Assume the electric field line is connected to P ( x , y , z any point that is close to P 1. Coordinates are ( x 1, y 1, z 1), then we have: d To draw the step of electric field line, the step should be large far from the wire and small near the wire, the specific formula is: wherein is the potential at this point in the space-charge-free medium; The above formula is solved together to obtain: ▽( Aρ )=0 The product of the electric field and the displacement vector at any point along the direction of the electric field lines is constant. Aρ The product of the electric field and the displacement vector at any point along the Aρ= A e ρ e = A l ρ l wherein A e and ρ e is the value of the surface of the wire, A l and ρ l is the value of the electric field at any point in the electric field, A and ρ the value of the magnetic field at any point in the magnetic field. Ignoring the recombination effect of ions, it is simplified as: Simplify along the electric field line direction to obtain: Where s is the integral variable along the electric field line direction; The above formula is solved together to obtain: Simplify to obtain: The chord intersection iteration method is used to solve together, at this time, improper selection of the wire surface charge density can easily make the result not converge, and the wire charge density needs to be estimated, and the specific form is as follows: wherein ρ m is the average charge density per electric field line, which after amplification serves as the initial value for the surface charge density of the wire; After the charge density of the conductor nodes is solved, the charge density of other nodes on the electric field line and their corresponding A values are obtained, and the ion flow density distribution at any place on the ground is solved.

3. The method of claim 2, wherein the method comprises: In the S2, after the charge density under the transmission line is determined according to the simulation charge method and the electric field line method, the potential of any point in the region is solved, the boundary potential of the finite element region is generated by the joint action of the wire surface charge and the space charge, and finally the method of finite element is used to calculate the induced electric field inside and outside the human body.

4. The method of claim 3, wherein the method comprises: In the S3, according to the requirement that the human body has little influence on the boundary of the finite element region, the three-dimensional model is divided into 4x4x4m 3 The cube is taken as the finite element method to calculate the region of the human body affected by the power transmission line.

5. The method of claim 4, wherein the method comprises: In the S5, when the finite element method is used for simulation calculation, the non-magnetic of the human body composition is considered, and the head, arm, torso and leg are composed of four parts, and the dielectric constant ε and the conductivity γ of each part are set.

6. The method of claim 5, wherein the method further comprises: In the S5, the finite element method is used to calculate the electric field distribution of the human body inside and on the surface under the conditions of grounding and insulation from the ground; the electric field distribution of the human body in different positions under the DC transmission line is analyzed, and the influence of the height of the transmission line and the pole spacing on the electric field distribution of the human body is analyzed.

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