CN-115879282-B - Method for analyzing and calculating magnetic field of low-frequency near-field region of finite-length electrified straight wire in conductive medium

Abstract

The invention relates to a method for analyzing and calculating a magnetic field in a low-frequency near field region of a finite-length electrified straight wire in a conductive medium, which comprises the steps of taking the center of the electrified straight wire as an origin, taking the length of the electrified straight wire as an X axis, taking the length of the electrified straight wire as a Y axis, taking a plane vertical to the X axis and the Y axis as a Z axis, establishing a coordinate system, wherein coordinates of two endpoints A and B of the electrified straight wire in the coordinate system are (0.5L, 0) and (-0.5L, 0), and the real part and the imaginary part of the magnetic field induction intensity of any point P (X, Y, Z) in the coordinate system are obtained by a formula:

Inventors

• WANG XINYI
• JIAO YUCHENG
• ZHANG GUOGUANG

Assignees

• 中国船舶重工集团公司七五0试验场

Dates

Publication Date

20260512

Application Date

20221122

Claims (6)

1. 1. A method for analyzing and calculating a magnetic field in a low-frequency near field region of a finite-length electrified straight wire in a conductive medium is characterized in that the center of the electrified straight wire (1) is taken as an original point, the direction of the electrified straight wire (1) is taken as an X axis, the direction vertical to the electrified straight wire (1) is taken as a Y axis, a plane vertical to the X axis and the Y axis is taken as a Z axis, a coordinate system is established, and coordinates of two end points A and B of the electrified straight wire (1) in the coordinate system are respectively (0.5L, 0) and (-0.5L, 0) in the coordinate system, wherein the real part and the imaginary part of the magnetic field induction intensity of any point P (X, Y, Z) in the coordinate system are obtained by a formula: ; ; Wherein: ; ; B 0 is the induction intensity of a magnetic field in air, r 1 and r 2 are the distances between two end points A and B of the electrified straight wire (1) and the point P respectively, r 0 is the vertical distance from the point P to the electrified straight wire (1), I is the alternating current peak value of the electrified straight wire, omega is the angular frequency of the alternating current, sigma is the conductivity of a medium, mu is the magnetic conductivity of the medium, Post-rounding the whole number; the application range of the formula (1) and the formula (2) is that the vertical distance r 0 between the P point and the electrified straight wire (1) is as follows Is within the range of (2); The θ 1 ＝arcsin(r 0 /r 1 ), the θ 2 ＝arcsin(r 0 /r 2 ); L is the length of the electrified straight wire (1).
2. 2. The method for analyzing and calculating the magnetic field in the low-frequency near-field region of a finite length energized straight wire in a conductive medium according to claim 1, wherein the method is characterized in that 。
3. 3. The method for analyzing and calculating the magnetic field of the low-frequency near-field region of the finite-length electrified straight wire in the conductive medium according to claim 2, wherein the method is characterized in that 。
4. 4. The method for analyzing and calculating the magnetic field in the low-frequency near-field region of the finite-length electrified straight wire in the conductive medium according to claim 3, wherein the method is characterized in that 。
5. 5. The method for analyzing and calculating the magnetic field of the low-frequency near field region of the finite-length electrified straight wire in the conductive medium according to claim 4, wherein the length of the electrified straight wire (1) is less than 1000 meters.
6. 6. The method for analyzing and calculating the magnetic field in the low-frequency near field region of the finite-length electrified straight wire in the conductive medium according to claim 5, wherein the method comprises the following steps of: the conductive medium is water, oil, alcohol or their mixture.

Description

Method for analyzing and calculating magnetic field of low-frequency near-field region of finite-length electrified straight wire in conductive medium Technical Field The invention belongs to the field of electromagnetic fields, and relates to a method for analyzing and calculating a low-frequency near field of a limited-length electrified straight wire in a conductive medium such as underwater. Background In the prior art, a finite length of energized straight wire is a basic way to generate a magnetic field, and a magnetic field calculation method can be deduced through a Maxwell equation. The finite length of electrically conductive straight wire along the x-axis is shown in FIG. 1, where the time domain expression of the Maxwell equation in the conductive medium is: Due to So that the magnetic field can be appliedExpressed as a loss of rotation, namely: Carry the upper part into Obtaining: The following variants are available: Since the rotation of the divergence is constantly equal to 0, the Can be expressed as a scalar divergence, i.e Thus, the first and second substrates are bonded together,AndOne loss function and scalar function may be expressed as follows: from knowledge of the correlation of the loss of quantity, it is necessary to determine a loss of quantity, and to define both the divergence and the rotation of the loss of quantity, for the uniqueness of the expression, the loss of quantity field Lorentz specification: Thus, under Lorenz's standard condition Damage toThe satisfied darabal equation is: When the electromagnetic field is a time-harmonic field, it can be written as: Wherein the method comprises the steps of The solution of the above formula is: The current element is a basic radiation unit for energizing a straight wire, and assuming that the length of the current element is L, the center of the current element is positioned at the origin of coordinates and is placed along the x axis, the vector magnetic bit on the current element can be expressed as: as a result of the line current, lr, The current on the wire is in phase,Thus, the above formula can be written as: Under the spherical coordinate system can be expressed as: the spatial distribution of the magnetic field of the available line current is: The magnetic field of the electrified straight wire in the consumable medium is obtained as follows: expressed in rectangular coordinate system as Bx=0, Wherein L is the length of the electrified straight wire, K is the complex wave number Obviously, for the near field magnetic field, integral operation is needed, an original function expression cannot be obtained, only numerical integration can be adopted in software design, and the operation amount is large, so that real-time processing is not facilitated. In the actual operation of active electromagnetic detection under water, the detector can detect the low-frequency magnetic field near the limited-length linear wire towed by the underwater vehicle or the surface ship, wherein the magnetic field comprises the low-frequency magnetic field generated by the limited-length linear wire and the low-frequency magnetic field generated by nearby metal, in order to find out whether the metal exists near the limited-length linear wire, the low-frequency magnetic field in the space around the limited-length linear wire needs to be calculated rapidly and in real time, and the calculated low-frequency magnetic field in the space around the limited-length linear wire is compared with the low-frequency magnetic field detected by the detector to obtain whether other metal substances exist near the limited-length linear wire. Disclosure of Invention The invention provides an integral calculation method for a magnetic field in a low-frequency near field region of a limited-length electrified straight wire in an existing conductive medium, and provides an analytic calculation method for the magnetic field in the low-frequency near field region of the limited-length electrified straight wire in the conductive medium, which can avoid numerical integral calculation with great operand and remarkably improve calculation speed. In order to achieve the aim of the application, the application adopts the following technical scheme: The invention relates to a method for analyzing and calculating a magnetic field in a low-frequency near field region of a finite-length electrified straight wire in a conductive medium, which is characterized in that the center of the electrified straight wire is taken as an origin, the length of the electrified straight wire is taken as an X axis, the length of the electrified straight wire is taken as a Y axis, a plane perpendicular to the X axis and the Y axis is taken as a Z axis, a coordinate system is established, two endpoints A and B of the electrified straight wire are respectively (0.5L, 0) and (-0.5L, 0) in the coordinate system, wherein the real part and the imaginary part of the magnetic field induction intensity at