CN113946923A - Electromagnetic interference calculation method of power grid to buried pipe network - Google Patents

Electromagnetic interference calculation method of power grid to buried pipe network Download PDF

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CN113946923A
CN113946923A CN202111141265.XA CN202111141265A CN113946923A CN 113946923 A CN113946923 A CN 113946923A CN 202111141265 A CN202111141265 A CN 202111141265A CN 113946923 A CN113946923 A CN 113946923A
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conductor
current
pipe network
potential
section
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张金鹏
丁梁
寇晓适
郭磊
张科
董曼玲
徐碧川
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State Grid Zhejiang Electric Power Co Ltd Zhuji Power Supply Co
Electric Power Research Institute of State Grid Henan Electric Power Co Ltd
Electric Power Research Institute of State Grid Jiangxi Electric Power Co Ltd
Shaoxing Power Supply Co of State Grid Zhejiang Electric Power Co Ltd
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State Grid Zhejiang Electric Power Co Ltd Zhuji Power Supply Co
Electric Power Research Institute of State Grid Henan Electric Power Co Ltd
Electric Power Research Institute of State Grid Jiangxi Electric Power Co Ltd
Shaoxing Power Supply Co of State Grid Zhejiang Electric Power Co Ltd
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/10—Geometric CAD
    • G06F30/18—Network design, e.g. design based on topological or interconnect aspects of utility systems, piping, heating ventilation air conditioning [HVAC] or cabling
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
    • G06F17/10—Complex mathematical operations
    • G06F17/11—Complex mathematical operations for solving equations, e.g. nonlinear equations, general mathematical optimization problems
    • G06F17/12—Simultaneous equations, e.g. systems of linear equations
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2111/00—Details relating to CAD techniques
    • G06F2111/10—Numerical modelling
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2113/00—Details relating to the application field
    • G06F2113/04—Power grid distribution networks
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2113/00—Details relating to the application field
    • G06F2113/14—Pipes

Abstract

The invention discloses a method for calculating electromagnetic interference of a power grid on a buried pipe network, which comprises the following steps: dividing a conductor into conductor micro-sections, wherein the potential difference between two ends of the outer surface of each conductor micro-section is equal to the potential difference between two ends in each conductor micro-section, establishing an equation set according to the characteristics of the continuity, working out the potential difference between two ends of the outer surface of each conductor micro-section according to leakage current, and working out the potential difference between two ends in each conductor micro-section by the product of the impedance of each conductor micro-section and axial current; and obtaining a relational expression between the axial current and the leakage current on each conductor micro-section according to kirchhoff's law, comprehensively establishing a group of linear algebraic equations, and solving the linear algebraic equations to obtain the leakage current distribution on the conductors. The result of the invention is used for evaluating the influence of electromagnetic interference on the buried pipe network, thereby controlling the risk in advance and realizing the harmonious symbiosis of the power grid and the oil and gas pipe network.

Description

Electromagnetic interference calculation method of power grid to buried pipe network
Technical Field
The invention relates to a power grid engineering technology, in particular to an electromagnetic interference analysis technology of a power grid on a buried pipe network.
Background
Oil gas pipeline and electric wire netting are the life pulse of energy security, the economic rapid development makes our country demand for energy increasing day by day in recent years, but our country's special geographic environment has created energy layout and electric power consumption with fossil energy as the main and has geographic reverse distribution, this makes large-scale, long distance energy transmission necessary, until now, our country has 16 kilometers oil gas pipeline in transit, in order to give full play to the advantages of limited country's resources, the electric power line and oil gas pipeline inevitably will appear the crossing situation of the route, in some land tight areas even have long distance share public corridor the situation, a large number of electric power channels and oil gas pipeline are parallel, the electromagnetic compatibility problem (including magnetic field coupling and electric field coupling) between the two is more and more serious, once the pipeline system is damaged, will cause the serious destruction to the ecological environment, and may bring about serious safety production accidents, so the safety influence of the large-area power grid on the buried metal pipeline becomes a very acute problem.
When the power grid normally transmits power, the alternating electromagnetic field can generate induced voltage on an adjacent oil and gas pipeline. If the alternating current transmission line is too close to the oil gas pipeline or the parallel coupling relationship is too strong, the voltage to earth of the pipeline is high, the normal work of construction, maintenance or measurement personnel can be influenced, and the pipeline can be corroded in serious cases.
Therefore, in order to avoid serious accidents caused by overlarge influence of an alternating electromagnetic field generated during normal operation of the power grid on the oil and gas pipeline, the influence of electromagnetic interference on the buried pipe network in a normal operation state of the power grid is deeply analyzed, so that risks are controlled in advance, and harmonious symbiosis of the power grid and the oil and gas pipe network is realized.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a method for calculating the electromagnetic interference of a power grid on a buried pipe network, so that the risk is controlled in advance according to the result, and the harmonious symbiosis of the power grid and an oil and gas pipe network is realized.
The technical scheme adopted by the invention is as follows: the method for calculating the electromagnetic interference of the power grid on the buried pipe network comprises the following steps of:
dividing a conductor into conductor micro-sections, wherein the potential difference between two ends of the outer surface of each conductor micro-section is equal to the potential difference between two ends in each conductor micro-section, establishing an equation set according to the characteristics of the continuity, working out the potential difference between two ends of the outer surface of each conductor micro-section according to leakage current, and working out the potential difference between two ends in each conductor micro-section by the product of the impedance of each conductor micro-section and axial current;
and obtaining a relational expression between the axial current and the leakage current on each conductor micro-section according to kirchhoff's law, comprehensively establishing a group of linear algebraic equations, and solving the linear algebraic equations to obtain the leakage current distribution on the conductors.
Preferably, the electromagnetic interference of the power grid to the pipe network is realized by an electromagnetic field, so that the Maxwell equation system is followed:
Figure BDA0003284029100000021
in the formula, H is the magnetic field intensity; b is the magnetic flux density; d is a potential shift vector; e is the electric field strength; ρ is the space charge density; j. the design is a squaresIs the conduction current density;
introducing a vector magnetic bit A and a scalar bit function phi to make B equal to rotA, and then the second formula of the Maxwell equation system has:
Figure BDA0003284029100000022
in the formula, omega is angular frequency, and the angular frequency is substituted into the first and fourth formulas of the Maxwell equation set to obtain the Dalnberg equation set:
Figure BDA0003284029100000023
in the formula (I), the compound is shown in the specification,
Figure BDA0003284029100000031
as the phase constant, mu and epsilon are respectively the magnetic conductivity and the dielectric constant;
the interference of the interfering source to the interfered point is given by the following general solution:
Figure BDA0003284029100000032
wherein R is the distance between the interfered point and the interference source;
segmenting a grid conductor into nsSegment, pipe network conductor is segmented into npA current I flows in the I-th conductor after the segmentationiAnd the induced potential of the ith segment conductor at the kth segment conductor is:
Figure BDA0003284029100000033
the induced potential on the kth section of pipe network conductor micro-section is the sum of the potentials induced on the conductor by the current on all the section of pipe network conductor micro-sections, namely:
Figure BDA0003284029100000034
under the action of induced potential, the pipe network forms a through-flow loop with soil through the anticorrosive coating, a certain current field distribution is formed in the ground, and b end points exist in the micro-section of the segmented pipe network conductor, so that the potential U on the ith section of pipeline is reduced due to the fact that the segmented pipe network conductor is shortiTaken as the voltage V of two adjacent terminalsj1And Vj2I.e.:
Figure BDA0003284029100000035
writing is in matrix form:
U＝KV
in the same way, the current I of each section of conductor is disperseddThe two parts are divided into two parts, and the two parts flow into the ground from two nodes connected with the two parts, then:
J＝KTId
in the formula, J is equivalent current dissipation of each node;
the application of KCL and KVL to the segmented pipe network conductor comprises the following steps:
Figure BDA0003284029100000036
in the formula, Y is a branch admittance matrix; a is a correlation matrix; i is1Current flows through each pipe network conductor;
thus, the node admittance equation is established as:
AYATV＝AYE-J
according to the green function, the relationship between the potential of each conductor and the current is as follows:
U＝ZId
in the formula, Z is a mutual impedance matrix among conductor micro-sections, and comprises an inductive component, a resistive component and an inductive component;
the above formula is combined to calculate the pipeline potential as:
U＝K(AYAT+KTZ-1K)-1AYE
under the condition of lightning stroke, because a time domain solving method of electromagnetic coupling between conductors is complex and large in calculation amount, the potential distribution problem of a system under the impact current is generally calculated by a time-frequency conversion method, and the grounding grid potential under the impact current is firstly calculated by a moment method. The inrush current in the time domain can be described by a bi-exponential function as follows:
I(t)＝Im(e-αt-e-βt)
in the formula: t is time; alpha is a wavefront attenuation index; beta is the wave tail attenuation index; i ismIs the current amplitude.
With Fourier transform, the impulse current waveform in the time domain can be converted into a frequency domain response:
Figure BDA0003284029100000041
in the formula: omega is angular frequency; i (ω) is the lightning current in the frequency domain.
Linearly varying current I (l ') on the conductor axis l' and uniformly distributed line charges
Figure BDA0003284029100000042
The intensity of the scattered electric field generated in the space is
Figure BDA0003284029100000043
Wherein, in an infinite space, there are
Figure BDA0003284029100000044
Figure BDA0003284029100000045
In the formula: e is the axial direction of the current of the cylindrical conductor wire; a is the vector magnetic potential generated by the axial current I (l'); r is the distance between the field point and the source point in the space; phi is the line charge uniformly distributed on the surface of the conductor
Figure BDA0003284029100000051
A generated scalar potential; mu and epsilon are respectively the magnetic permeability and the dielectric constant of the space where the conductor is located; k is the wave number.
Integral equation of electric field strength obtained simultaneously
Figure BDA0003284029100000052
If the whole conductor structure is divided into n sections of conductors
Figure BDA0003284029100000053
In the formula: i isiAnd UjRespectively the current on the ith segment of conductor and the potential of the midpoint of the jth segment of conductor; zijFor the transfer impedance between the i-th conductor and the j-th conductor
Figure BDA0003284029100000054
When lightning current is injected into one end of a conductor, the current injected into one end of the conductor is a known quantity and can be represented in a matrix form:
Z-1U＝I
since the injection conductor micro-segment current vector I is known, other unknown currents and branch voltages can be solved. Thus, the problems of space current distribution, electromagnetic field and the like can be solved. And finally, obtaining scalar voltage in the time domain, the electric field intensity and the magnetic field intensity through Fourier inverse transformation.
Figure BDA0003284029100000055
Figure BDA0003284029100000056
Figure BDA0003284029100000057
In the formula: u shape0(ω)、E0(omega) and H0(ω) is the scalar voltage in the frequency domain, the electric field strength and the magnetic field strength, respectively, produced by the unit current source.
According to the technical scheme, electromagnetic interference of the power transmission line on the pipeline is calculated based on a moment method, and the influence of the electromagnetic interference on the buried pipe network is evaluated according to the result, so that risks are controlled in advance, and harmonious symbiosis of the power grid and the oil and gas pipe network is realized.
The following detailed description and the accompanying drawings are included to provide a further understanding of the invention.
Drawings
The invention is further described with reference to the accompanying drawings and the detailed description below:
FIG. 1 is a circuit diagram of a buried pipeline-earth equivalent circuit model;
FIG. 2 is a schematic overhead line;
FIG. 3 is a schematic view of an underground cable;
FIG. 4 is a model diagram of an overhead conductor and a buried conductor when the soil is uniform;
FIG. 5 is a schematic diagram of a single-phase ground short equivalent circuit;
FIG. 6 is a schematic view of the dispersion of the conductor segments of the pipe network.
Detailed Description
The electromagnetic interference problem of an alternating current transmission line on an adjacent buried metal pipeline is mainly caused by alternating current in the line in a space electromagnetic field and a ground current, and the electromagnetic interference problem can be divided into three types of inductive coupling influence, resistive coupling influence and capacitive coupling influence from a mechanism level. The analysis of the electromagnetic influence mechanism is the basis for determining the electromagnetic influence object and the calculation method, and is also beneficial to making a relevant limit value, determining a safety distance and implementing a protection measure.
Inductive coupling: alternating current in the power transmission line can generate an alternating magnetic field in the surrounding space of the power transmission line, so that the buried metal pipeline generates an induced voltage. The alternating magnetic field exists in the air and the ground, and when a buried metal pipeline is close to a power transmission line, the magnetic field has strong action and can generate longitudinal electromotive force on two sides of the pipeline. The metal pipeline is generally coated with an anticorrosive layer, the anticorrosive layer is not an absolute insulating material, but a substance with certain conductivity, namely, electric leakage exists between the pipeline and the ground. The longitudinal electromotive force acts on a loop formed by the pipeline and the ground to generate longitudinal current and leakage current, and potential difference, namely coating voltage, is generated on two sides of the anti-corrosion layer of the pipeline.
Capacitive coupling: high voltage is applied to a high-voltage alternating current transmission line wire, a strong electric field exists around the high-voltage alternating current transmission line wire, and a ground potential can be induced on a pipeline due to the principle of electrostatic induction. But generally the ground has better shielding effect on the electric field, and the capacitive coupling influence of the transmission line on the buried pipeline is smaller.
Resistive coupling: when the single-phase grounding short circuit fault occurs to the line, the short circuit current flows into the ground through the tower grounding device, the ground potential of the area near the fault point can be greatly increased by the large short circuit current, when a buried oil and gas pipeline is arranged near the tower, the metal pipeline can be kept at a low potential due to the fact that the resistivity of the oil and gas pipeline anticorrosive coating is high, and therefore a high potential difference is formed between the metal pipeline and the ground around the pipeline.
Method for calculating influence of power grid on pipe network
Theoretical basis
The view ground is taken as a reference conductor, the long-distance oil and gas pipeline is subjected to infinitesimal processing, a pipeline-ground loop transmission line equivalent model can be established, and a pipeline-ground loop equivalent circuit is shown in figure 1.
The corresponding frequency domain telegraph equation is:
Figure BDA0003284029100000071
Figure BDA0003284029100000072
wherein, U and I are respectively voltage and current along the pipeline; z and Y are the unit length series impedance and the parallel admittance of the pipeline-ground loop transmission line model respectively; and E is induced electromotive force generated by the transmission line on the pipeline with the unit length. The formula above can be combined to obtain:
Figure BDA0003284029100000073
Figure BDA0003284029100000074
assuming that the induced electromotive force generated by the transmission line on each pipe infinitesimal does not change along with the coordinate x, i.e. E is a constant, a general solution can be obtained:
U(x)＝Aeγx+Be-γx
Figure BDA0003284029100000081
wherein Z isCFor the characteristic impedance of the pipe-to-ground loop transmission line model,
Figure BDA0003284029100000082
gamma is a propagation constant and is a linear function,
Figure BDA0003284029100000083
alpha and beta are the decay constant and the phase constant, respectively.
Two additional terminal constraints are required to solve the equation. According to the constraint condition of end of transmission line U (0) ═ Z1I (0) and U (L) ═ Z2(l), substitution can be solved to obtain:
Figure BDA0003284029100000084
Figure BDA0003284029100000085
wherein
Figure BDA0003284029100000086
The situation frequently encountered in practical engineering is that the pipeline is parallel to the line and close to one end, then extends to far positions at two ends infinitely, is embodied in a mathematical model that two ends of the pipeline are connected with matched impedance,
namely Z1＝Z2＝ZC,ρ1＝ρ2＝0。
The earth return impedance is an important parameter used when calculating the induced voltage generated by the power transmission line on a buried oil and gas pipeline, and for a complex conductor system consisting of an overhead conductor and a buried conductor, the earth return impedance can be divided into three types:
as shown in fig. 2, the first type is the earth return self-impedance and the mutual impedance of the overhead conductor system, the carson formula is the most classical one, but the carson formula is only suitable for the case of uniform soil, and the correction term contains infinite integral and is inconvenient to calculate, so that the formula of calculating the impedance of the overhead line with unit length on the layered soil based on the concept of 'complex depth' proposed by Dubanton, the self-impedance ZsAnd mutual impedance ZmRespectively as follows:
Figure BDA0003284029100000087
Figure BDA0003284029100000091
wherein p is the complex transmission depth of the electromagnetic wave in the soil.
As shown in fig. 3, the second type is the earth return self-impedance and the mutual impedance of the buried conductor system, and for calculating the self-mutual impedance of the buried conductor, the formula of polaczek is usually adopted to perform:
Figure BDA0003284029100000092
Figure BDA0003284029100000093
wherein the content of the first and second substances,
Figure BDA0003284029100000094
Figure BDA0003284029100000095
α＝ωμ0/ρe
in the above formula, hm＝(hi+hj)/2，djkIs the distance between cable j and cable k, djk'Is the distance, x, between cable j and the mirror image of cable kjkIs the horizontal separation between cable j and cable k.
The third type is the ground return mutual impedance between the overhead conductor and the buried conductor, the mutual impedance between the transmission line and the oil transmission pipeline buried in the soil can be calculated by using Pollaczek formula, and because some functions in the formula are too complex and difficult to integrate, the functions are usually simplified to obtain an approximate formula.
The aerial conductor and buried conductor model is shown in figure 4, the mutual impedance Z between the aerial conductor 1 and the buried conductor 2jm12The expression is as follows:
the formula:
Figure BDA0003284029100000096
wherein h is1Is the height of the overhead conductor to the ground h2For the depth of the buried conductor, y12Is the horizontal distance between the two. Is air permeability, mu0For complex transmission depth, w is the angular frequency.
The loop impedance formed by the conductor and the ground is called the ground return self-impedance, the mutual impedance between the loops formed by different conductors and the ground return channel is called the ground return mutual impedance, and if a unit current flows on the conductor, the ground return mutual impedance is the longitudinal induced voltage generated on the conductor. When a single-phase grounding short-circuit fault occurs in a power transmission line, overvoltage is generated on a pipeline through inductive coupling when a non-fault phase is the same as a fault phase, electromagnetic interference is generated on the pipeline through resistive coupling after partial short-circuit fault current enters the ground through a tower grounding grid, the pipeline coating is punctured due to the fact that the tolerance voltage of the pipeline coating is too high under the combined action of the non-fault phase and the fault phase, and pipeline explosion accidents can be caused under severe conditions. Fig. 5 is a schematic diagram of an inductive coupling calculation model in the case of a single-phase ground short circuit.
Principle of calculation
The interference of the transmission line on the pipeline is researched based on a moment method. Firstly, a conductor is divided into conductor micro-segments, the potential difference between two ends of the outer surface of each conductor segment is equal to the potential difference between two ends in each conductor segment, an equation set is established according to the characteristics of continuity, the potential difference between two ends of the outer surface of each conductor segment is solved according to leakage current, the potential difference between two ends in each conductor segment is solved by the product of the impedance of each conductor segment and axial current, then the relational expression between the axial current and the leakage current on each conductor segment is obtained according to kirchhoff's law, a group of linear algebraic equations is comprehensively established, and then the leakage current distribution on the conductor can be obtained. The specific implementation process is as follows:
since the electromagnetic interference of the power grid to the pipe network is realized through an electromagnetic field, the electromagnetic interference follows Maxwell equations:
Figure BDA0003284029100000101
in the formula, H is the magnetic field intensity; b is the magnetic flux density; d is a potential shift vector; e is the electric field strength; ρ is the space charge density; j. the design is a squaresIs the conduction current density.
Introducing a vector magnetic bit A and a scalar bit function phi to make B equal to rotA, and then the second formula of the Maxwell equation system has:
Figure BDA0003284029100000102
in the formula, ω is an angular frequency. Substituting the first expression and the fourth expression of the Maxwell equation set to obtain a Dalnberg equation set:
Figure BDA0003284029100000111
in the formula (I), the compound is shown in the specification,
Figure BDA0003284029100000112
as the phase constant, μ and ε are the permeability and permittivity, respectively.
The interference of the interfering source to the interfered point is given by the following general solution:
Figure BDA0003284029100000113
wherein R is the distance between the interfered point and the interference source.
Since the inductive coupling component is much larger than the capacitive coupling component, the effect of the capacitive coupling component is ignored. Segmenting a grid conductor into nsSegment, pipe network conductor is segmented into npSegment, divided intoThe current flowing in the ith conductor after the section is IiAnd the induced potential of the ith segment conductor at the kth segment conductor is:
Figure BDA0003284029100000114
the induced potential on the kth section of the pipe network conductor section is the sum of the potentials induced on the conductor by the currents on all the sections of the pipe network conductor, namely:
Figure BDA0003284029100000115
under the action of induced potential, the pipe network forms a through-flow loop with soil through the anticorrosive coating, and forms a certain current field distribution in the ground. A schematic of the flow dispersion of the segmented ductwork conductor segments is shown in fig. 6.
If b endpoints exist in the segmented pipe network, the potential U on the ith segment of pipeline can be adjusted due to the short conductor of the segmented pipe networkiTaken as the voltage V of two adjacent terminalsj1And Vj2I.e.:
Figure BDA0003284029100000116
writing is in matrix form:
U＝KV
in the same way, the current I of each section of conductor is disperseddThe two parts are divided into two parts, and the two parts flow into the ground from two nodes connected with the two parts, then:
J＝KTId
in the formula, J is the equivalent current of each node.
The application of KCL and KVL to the segmented pipe network conductor comprises the following steps:
Figure BDA0003284029100000117
in which Y is the branch admittance momentArraying; a is a correlation matrix; i is1And current flows through each pipe network conductor.
The node admittance equation can thus be established as:
AYATV＝AYE-J
according to the green function, the relationship between the potential of each conductor and the current is as follows:
U＝ZId
wherein Z is a mutual impedance matrix between the conductor segments, and comprises an inductive component, a resistive component and an inductive component. By combining the above formula, the pipeline potential can be calculated as:
U＝K(AYAT+KTZ-1K)-1AYE
under the condition of lightning stroke, because a time domain solving method of electromagnetic coupling between conductors is complex and large in calculation amount, the potential distribution problem of a system under the impact current is generally calculated by a time-frequency conversion method, and the grounding grid potential under the impact current is firstly calculated by a moment method. The inrush current in the time domain can be described by a bi-exponential function as follows:
I(t)＝Im(e-αt-e-βt)
in the formula: t is time; alpha is a wavefront attenuation index; beta is the wave tail attenuation index; i ismIs the current amplitude.
With Fourier transform, the impulse current waveform in the time domain can be converted into a frequency domain response:
Figure BDA0003284029100000121
in the formula: omega is angular frequency; i (ω) is the lightning current in the frequency domain.
Linearly varying current I (l ') on the conductor axis l' and uniformly distributed line charges
Figure BDA0003284029100000122
The intensity of the scattered electric field generated in the space is
Figure BDA0003284029100000123
Wherein, in an infinite space, there are
Figure BDA0003284029100000124
Figure BDA0003284029100000125
In the formula: e is the axial direction of the current of the cylindrical conductor wire; a is the vector magnetic potential generated by the axial current I (l'); r is the distance between the field point and the source point in the space; phi is the line charge uniformly distributed on the surface of the conductor
Figure BDA0003284029100000131
A generated scalar potential; mu and epsilon are respectively the magnetic permeability and the dielectric constant of the space where the conductor is located; k is the wave number.
Integral equation of electric field strength obtained simultaneously
Figure BDA0003284029100000132
If the whole conductor structure is divided into n sections of conductors
Figure BDA0003284029100000133
In the formula: i isiAnd UjRespectively the current on the ith segment of conductor and the potential of the midpoint of the jth segment of conductor; zijFor the transfer impedance between the i-th conductor and the j-th conductor
Figure BDA0003284029100000134
When lightning current is injected into one end of a conductor, the current injected into one end of the conductor is a known quantity and can be represented in a matrix form:
Z-1U＝I
since the injected conductor segment current vector I is known, other unknown currents and branch voltages can be found. Thus, the problems of space current distribution, electromagnetic field and the like can be solved. And finally, obtaining scalar voltage in the time domain, the electric field intensity and the magnetic field intensity through Fourier inverse transformation.
Figure BDA0003284029100000135
Figure BDA0003284029100000136
Figure BDA0003284029100000137
In the formula: u shape0(ω)、E0(omega) and H0(ω) is the scalar voltage in the frequency domain, the electric field strength and the magnetic field strength, respectively, produced by the unit current source.
The method for calculating the electromagnetic interference of the power grid to the buried pipe network adopts CDEGS as calculation software. CDEGS (Current Distribution, electronic Interference, grouping and Soil Structure Analysis) is an integrated Engineering software package, introduced by SES corporation of Canada (Safe Engineering Services & technologies Itd.). The software is compiled based on an electromagnetic theory, has a series of functions of grounding system design analysis, electromagnetic interference research and the like, and mainly calculates electromagnetic field distribution, conductor and surface potential distribution and the like around a network formed by conductors with any shapes on the ground or underground under transient conditions such as steady state, fault, lightning stroke and the like.
The theoretical basis of the CDEGS software programming analysis procedure is various relevant electromagnetic theories, which are not constrained by various frequencies, so that the processing result is more accurate, and various grounding systems can be designed to analyze and process relevant problems such as electromagnetic interference. The primary purpose of the CDEGS package is to calculate the electromagnetic field distribution and the distribution of conductive objects, soil surface potential, around a network constructed from any shape of conductor above the earth's surface or buried in the soil under various steady state and transient conditions such as short circuit faults, lightning strikes, etc. The software has strong function when the high-voltage transmission line is calculated to electromagnetically influence the buried oil and gas pipeline at the adjacent position, and is recommended to be used by the international large power grid conference
The CDEGS software is widely applied to the over-voltage calculation of the oil and gas pipeline and can analyze the influence rule of the over-voltage of the pipeline under various operating conditions of the power transmission line. Meanwhile, potential distribution of the conductors on the ground or underground is calculated by establishing different working condition models, and the method can be applied to gradient control lines and elimination of electromagnetic interference. The CDEGS mainly contains 8 engineering modules. In the pipeline overvoltage protection, the MALZ module, the HIFREQ module and the FFTSES module are mainly used. The MALZ module can analyze the frequency domain grounding of any soil structure and calculate grounding resistance values of grounding grids of different types, the HIFREQ module can perform frequency domain analysis on an electromagnetic field generated by any electrified conductor network, and can establish an overground transmission tower line and underground simplified grounding grid model for calculation and analysis. The FFTSES module is also called as fast Fourier transform and is mainly matched with the HIFREQ module to carry out simulation calculation under the condition of lightning striking of the power transmission line.
While the invention has been described with reference to specific embodiments thereof, it will be understood by those skilled in the art that the invention is not limited thereto, and may be embodied in many different forms without departing from the spirit and scope of the invention as set forth in the following claims. Any modification which does not depart from the functional and structural principles of the present invention is intended to be included within the scope of the claims.

Claims (2)

1. The method for calculating the electromagnetic interference of the power grid on the buried pipe network is characterized by comprising the following steps of:
dividing a conductor into conductor micro-sections, wherein the potential difference between two ends of the outer surface of each conductor micro-section is equal to the potential difference between two ends in each conductor micro-section, establishing an equation set according to the characteristics of the continuity, working out the potential difference between two ends of the outer surface of each conductor micro-section according to leakage current, and working out the potential difference between two ends in each conductor micro-section by the product of the impedance of each conductor micro-section and axial current;
and obtaining a relational expression between the axial current and the leakage current on each conductor micro-section according to kirchhoff's law, comprehensively establishing a group of linear algebraic equations, and solving the linear algebraic equations to obtain the leakage current distribution on the conductors.
2. The method for calculating the electromagnetic interference of the power grid to the pipe network according to claim 1, wherein the method comprises the following steps: the electromagnetic interference of the power grid to the pipe network is realized through an electromagnetic field, so that the Maxwell equation system is followed:
Figure FDA0003284029090000011
in the formula, H is the magnetic field intensity; b is the magnetic flux density; d is a potential shift vector; e is the electric field strength; ρ is the space charge density; j. the design is a squaresIs the conduction current density;
introducing a vector magnetic bit A and a scalar bit function phi to make B equal to rotA, and then the second formula of the Maxwell equation system has:
Figure FDA0003284029090000012
in the formula, omega is angular frequency, and the angular frequency is substituted into the first and fourth formulas of the Maxwell equation set to obtain the Dalnberg equation set:
Figure FDA0003284029090000013
in the formula (I), the compound is shown in the specification,
Figure FDA0003284029090000014
as the phase constant, mu and epsilon are respectively the magnetic conductivity and the dielectric constant;
the interference of the interfering source to the interfered point is given by the following general solution:
Figure FDA0003284029090000015
wherein R is the distance between the interfered point and the interference source;
segmenting a grid conductor into nsSegment, pipe network conductor is segmented into npA current I flows in the I-th conductor after the segmentationiAnd the induced potential of the ith segment conductor at the kth segment conductor is:
Figure FDA0003284029090000021
the induced potential on the kth section of pipe network conductor micro-section is the sum of the potentials induced on the conductor by the current on all the section of pipe network conductor micro-sections, namely:
Figure FDA0003284029090000022
under the action of induced potential, the pipe network forms a through-flow loop with soil through the anticorrosive coating, a certain current field distribution is formed in the ground, and b end points exist in the micro-section of the segmented pipe network conductor, so that the potential U on the ith section of pipeline is reduced due to the fact that the segmented pipe network conductor is shortiTaken as the voltage V of two adjacent terminalsj1And Vj2I.e.:
Figure FDA0003284029090000023
writing is in matrix form:
U＝KV
in the same way, the current I of each section of conductor is disperseddThe two parts are divided into two parts, and the two parts flow into the ground from two nodes connected with the two parts, then:
J＝KTId
in the formula, J is equivalent current dissipation of each node;
the application of KCL and KVL to the segmented pipe network conductor comprises the following steps:
Figure FDA0003284029090000024
in the formula, Y is a branch admittance matrix; a is a correlation matrix; i is1Current flows through each pipe network conductor;
thus, the node admittance equation is established as:
AYATV＝AYE-J
according to the green function, the relationship between the potential of each conductor and the current is as follows:
U＝ZId
in the formula, Z is a mutual impedance matrix among conductor micro-sections, and comprises an inductive component, a resistive component and an inductive component;
the above formula is combined to calculate the pipeline potential as:
U＝K(AYAT+KTZ-1K)-1AYE
under the condition of lightning stroke, the potential distribution problem of a system under the impact current is calculated by a time-frequency conversion method, firstly, the grounding grid potential under the impact current is calculated by a moment method, and the impact current in a time domain is described by the following double exponential function:
I(t)＝Im(e-αt-e-βt)
in the formula: t is time; alpha is a wavefront attenuation index; beta is the wave tail attenuation index; i ismIs the current amplitude; converting the impulse current waveform in the time domain into a frequency domain response by using Fourier transform:
Figure FDA0003284029090000031
in the formula: omega is angular frequency; i (omega) is lightning current in the frequency domain;
linearly varying current I (l ') on the conductor axis l' and uniformly distributed line charges
Figure FDA0003284029090000032
The intensity of the scattered electric field generated in the space is
Figure FDA0003284029090000033
Wherein, in an infinite space, there are
Figure FDA0003284029090000034
Figure FDA0003284029090000035
In the formula: e is the axial direction of the current of the cylindrical conductor wire; a is the vector magnetic potential generated by the axial current I (l'); r is the distance between the field point and the source point in the space; phi is the line charge uniformly distributed on the surface of the conductor
Figure FDA0003284029090000036
A generated scalar potential; mu and epsilon are respectively the magnetic permeability and the dielectric constant of the space where the conductor is located; k is the wave number;
integral equation of simultaneous electric field strength
Figure FDA0003284029090000037
If the whole conductor structure is divided into n sections of conductors
Figure FDA0003284029090000038
In the formula: i isiAnd UjRespectively the current on the ith segment of conductor and the potential of the midpoint of the jth segment of conductor; zijFor the transfer impedance between the i-th conductor and the j-th conductor
Figure FDA0003284029090000041
When lightning current is injected into one end of a conductor, the current injected into one end of the conductor is a known quantity and is represented in a matrix form:
Z-1U＝I
the vector I of the current injected into the conductor micro-section is known, other unknown currents and branch voltage are obtained, and finally scalar voltage in a time domain, electric field intensity and magnetic field intensity can be obtained through Fourier inverse transformation
Figure FDA0003284029090000042
Figure FDA0003284029090000043
Figure FDA0003284029090000044
In the formula: u shape0(ω)、E0(omega) and H0(ω) is the scalar voltage in the frequency domain, the electric field strength and the magnetic field strength, respectively, produced by the unit current source.
CN202111141265.XA 2021-09-28 2021-09-28 Electromagnetic interference calculation method of power grid to buried pipe network Pending CN113946923A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114169119A (en) * 2022-02-11 2022-03-11 国网江西省电力有限公司电力科学研究院 Big data analysis system and method for influence of power transmission and transformation network on metal buried pipe network
CN114709782A (en) * 2022-04-11 2022-07-05 国网陕西省电力有限公司电力科学研究院 Method for reducing potential difference in transformer substation grounding network caused by impact current

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114169119A (en) * 2022-02-11 2022-03-11 国网江西省电力有限公司电力科学研究院 Big data analysis system and method for influence of power transmission and transformation network on metal buried pipe network
CN114169119B (en) * 2022-02-11 2022-06-14 国网江西省电力有限公司电力科学研究院 Big data analysis system and method for influence of power transmission and transformation network on metal buried pipe network
CN114709782A (en) * 2022-04-11 2022-07-05 国网陕西省电力有限公司电力科学研究院 Method for reducing potential difference in transformer substation grounding network caused by impact current
CN114709782B (en) * 2022-04-11 2024-04-05 国网陕西省电力有限公司电力科学研究院 Method for reducing potential difference in transformer substation grounding grid caused by impact current

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