CN110470723A - A kind of buried metal pipeline DC influence of protective layer breakage determines method - Google Patents
A kind of buried metal pipeline DC influence of protective layer breakage determines method Download PDFInfo
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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Abstract
The invention discloses a kind of buried metal pipeline DC influences of protective layer breakage to determine method, comprising: according to the characteristic parameter of the earthing pole of acquisition and buried metal pipeline to be analyzed, determines virtual boundary, and determines nonlinear boundary；Determine the Potential distribution of the virtual boundary and the simplification current distribution of the nonlinear boundary；The Potential distribution of soil side on the nonlinear boundary is calculated in soil region；Determine the simplification polarization potential on the nonlinear boundary；According to the Potential distribution of the simplified polarization potential and the soil side, the Potential distribution of metal side on the nonlinear boundary is determined；In metallic region, the process current distribution on the nonlinear boundary is calculated；When difference between the process current distribution and the simplified current distribution is not more than preset convergence threshold, the target polarization potential on the nonlinear boundary is determined.The buried metal pipeline DC influence precision that this method determines is high, high-efficient.
Description
Technical field
The invention belongs to buried metal pipeline DC influence analysis field, damaged more particularly, to a kind of protective layer
Buried metal pipeline DC influence determines method.
Background technique
In recent years, with transferring electricity from the west to the east, the construction of West-East National Gas Transmission Project, direct current grounding pole and buried oil-gas pipeline are neighbouring
Situation is inevitable.
When there is direct current to flow into ground on DC transmission system earthing pole, one will form in the soil near the location of pole directly
Galvanic electricity flow field, and along with there is ground potential raising.DC stray current can circulate on the pipeline near earthing pole, and
Galvano-cautery occurs for the region for flowing out pipeline.
Direct current grounding pole becomes increasingly conspicuous to the corrosion impact and dangerous influence problem of neighbouring buried oil-gas pipeline, some prestige
Coerce national energy delivery safety.Currently, determining that earthing pole is not high to the method precision of buried oil-gas pipeline DC influence, calculate
Low efficiency.
Summary of the invention
Essence when the application aims to solve the problem that the buried metal pipeline DC influence for calculating protective layer local damage in the prior art
Spend the problem not high, efficiency is lower.
The buried metal pipeline DC influence of protective layer breakage proposed by the present invention determines method, comprising:
Step S100: according to the characteristic parameter of the earthing pole of acquisition and buried metal pipeline to be analyzed, fictitious line is determined
Boundary, the metallic region occupied including the buried metal pipeline in the virtual boundary and is located at the virtual boundary and the gold
Belong to the soil region between region；And
Determine nonlinear boundary, the nonlinear boundary is metal side in the side close to metallic region, close to soil
The side in region is soil side；
Step S200: not considering the polarization process of the metallic region of protective layer breakage, based on described in Analogue charge method determination
The simplification current distribution of the Potential distribution of virtual boundary and the nonlinear boundary；
Step S300: using the Potential distribution of the virtual boundary as initial value, the nonlinear boundary is calculated in soil region
The Potential distribution of upper soil side；
Step S400: according to the simplification current distribution of predetermined polarization curve and the nonlinear boundary, institute is determined
State the simplification polarization potential on nonlinear boundary；
Step S500: according to the Potential distribution of the simplified polarization potential and the soil side, the non-linear side is determined
The Potential distribution of metal side in boundary；
Step S600: using the Potential distribution of metal side on the nonlinear boundary as initial value, in metallic region, described in calculating
Process current distribution on nonlinear boundary；
Step S700: the difference between the process current distribution and the simplified current distribution, which is not more than, to be preset
Convergence threshold when,
According to predetermined polarization curve and the process current distribution, the target pole on the nonlinear boundary is determined
Change current potential, the DC influence of the target polarization potential, that is, protective layer breakage buried metal pipeline.
Specifically, the method, further includes:
Step S800: the difference between the process current distribution and the simplified current distribution is greater than preset
When convergence threshold,
According to preset modification rule, the simplified current distribution is updated, and
Repeat step S400 to S700.
In method of the invention, virtual boundary is set by Open region problem and is converted into finite element regional issue, is reduced
Calculation amount；Pass through finite element method and carry out pipe to soil potential distribution and calculate, it is contemplated that the problem of pipeline anticorrosion coating local damage, improves
The computational accuracy and computational efficiency of buried metal pipeline DC influence.
Detailed description of the invention
By reference to the following drawings, exemplary embodiments of the present invention can be more fully understood by:
Fig. 1 is that the buried metal pipeline DC influence of the protective layer local damage of one embodiment of the invention determines method
Flow diagram；
Fig. 2 is that the hybrid analog-digital simulation charge method of one embodiment of the invention and finite element method calculate earthing pole to buried pipeline
DC influence implementation steps schematic diagram；
Fig. 3 is charge simulation configuration diagram when calculating earthing pole and pipeline distribution of charges in the embodiment of the present invention；
Fig. 4 is to measure in the simulated soil solution that conductivity is 100 Ω m, Ph=8 in another embodiment of the invention
The polarization curve of obtained X80 pipe line steel；
Fig. 5 is the nonlinear boundary configuration schematic diagram in the embodiment of the present invention at virtual boundary interior conduit local damage
Fig. 6 be in another of the invention embodiment pipeline and earthing pole in the schematic diagram of spatial relationship；
Fig. 7 is the polarization potential distribution curve on the determining pipeline.
Specific embodiment
Exemplary embodiments of the present invention are introduced referring now to the drawings, however, the present invention can use many different shapes
Formula is implemented, and is not limited to the embodiment described herein, and to provide these embodiments be at large and fully disclose
The present invention, and the scope of the present invention is sufficiently conveyed to person of ordinary skill in the field.Show for what is be illustrated in the accompanying drawings
Term in example property embodiment is not limitation of the invention.In the accompanying drawings, identical cells/elements use identical attached
Icon note.
Unless otherwise indicated, term (including scientific and technical terminology) used herein has person of ordinary skill in the field
It is common to understand meaning.Further it will be understood that with the term that usually used dictionary limits, should be understood as and its
The context of related fields has consistent meaning, and is not construed as Utopian or too formal meaning.
Currently, the calculating of earthing pole DC influence is mainly based upon moment method, principle of moment method itself causes it can not
Consider the local damage feature of metallic conductor protective layer.Therefore, currently, considering influence of the earthing pole for buried metal pipeline
When, often have ignored the activation polarization process of metal surface.Pipe to soil potential and the Leakage Current that so will cause calculating are close
Degree inaccuracy.
Finite element method has advantage when handling local damage problem.But because the current field coverage area of earthing pole is very
Greatly, when calculating the problem of direct current interference of buried pipeline using finite element method, subdivision difficulty is big, calculation amount is excessive.
The buried metal pipeline DC influence of protective layer local damage provided by the invention determines method, by Analogue charge method
It is combined with finite element method, reduces the subdivision difficulty of the finite element method in extensive area, reduces finite element
Calculation amount can accurately calculate the DC influence of the metallic conduit with protective layer local damage feature.
It is construed as, in the following contents, " pipeline ", " buried pipeline ", " metallic conduit ", and " buried metal pipeline ", tool
There is identical meaning.
It is construed as, in the following contents, " current density ", " Leakage Current density ", " current distribution ", " current density
Distribution " has the same meaning.
Virtual boundary is arranged by the adjacent domain in metallic conduit in method provided by the invention, thus by current field from nothing
Limit regional issue is converted into finite region problem；And finite region problem then passes through finite element method and is calculated.
As shown in Figure 1, the buried metal pipeline DC influence of the protective layer breakage of the embodiment of the present invention determines method, packet
It includes:
Step S100: according to the characteristic parameter of the earthing pole of acquisition and buried metal pipeline to be analyzed, fictitious line is determined
Boundary, the metallic region occupied including the buried metal pipeline in the virtual boundary and is located at the virtual boundary and the gold
Belong to the soil region between region；And
Determine nonlinear boundary, the nonlinear boundary is metal side in the side close to metallic region, close to soil
The side in region is soil side；
It is construed as, includes the buried metal pipeline in the virtual boundary and do not include the earthing pole；
The buried metal of nonlinear boundary protective layer breakage between the metallic region and the soil region
Pipe section.
Step S200: not considering the polarization process of the metallic region of protective layer breakage, based on described in Analogue charge method determination
The simplification current distribution of the Potential distribution of virtual boundary and the nonlinear boundary；
Step S300: using the Potential distribution of the virtual boundary as initial value, the nonlinear boundary is calculated in soil region
The Potential distribution of upper soil side；
Step S400: according to the simplification current distribution of predetermined polarization curve and the nonlinear boundary, institute is determined
State the simplification polarization potential on nonlinear boundary；
Step S500: according to the Potential distribution of the simplified polarization potential and the soil side, the non-linear side is determined
The Potential distribution of metal side in boundary；
Step S600: using the Potential distribution of metal side on the nonlinear boundary as initial value, in metallic region, described in calculating
Process current distribution on nonlinear boundary；
Step S700: the difference between the process current distribution and the simplified current distribution, which is not more than, to be preset
Convergence threshold when,
According to predetermined polarization curve and the process current distribution, the target pole on the nonlinear boundary is determined
Change current potential, the DC influence of the target polarization potential, that is, protective layer breakage buried metal pipeline.
Further, the method, further includes:
Step S800: the difference between the process current distribution and the simplified current distribution is greater than preset
When convergence threshold,
According to preset modification rule, the simplified current distribution is updated, and
Repeat step S400 to S700.
Specifically, the preset modification rule, comprising:
Using the average value of the process current distribution and the simplified current distribution as updated simplified current distribution；
Using the process current distribution as the updated simplified current distribution updated.
Further, the method in the step S200, does not consider the polarization of the metallic region of protective layer breakage
Journey determines the Potential distribution of the virtual boundary based on Analogue charge method, comprising:
M charge simulation is set on the earthing pole, and charge simulation value is denoted as Q respectivelyi, wherein 1≤i≤m；It is corresponding
There is m match point on ground on the outside of earthing pole；Current potential on the m charge simulation and the m match point is
N charge simulation is set on the buried metal pipeline, and charge simulation value is denoted as Qj, 1≤j≤m；It is corresponding
There is n match point on ground on the outside of pipeline；Current potential on the n charge simulation and the n match point is
In conjunction with following formula:
Following equation is solved, determines the distribution of charges Q on earthing pole with the charge simulation being arranged on buried metal pipeline0With
Q1；
Wherein, Q0For the column vector of the charge value for the charge simulation being arranged on earthing pole；
Q1For the column vector of the charge value for the charge simulation being arranged on buried metal pipeline；
Value for the column vector of the potential value for the charge simulation being arranged on earthing pole, either element is
For the column vector of the potential value for the charge simulation being arranged on buried metal pipeline, either element value is
[Pst] it is coefficient of potential matrix, PstFor the element that s row t in the matrix is arranged, determined by following formula:
Wherein,The respectively position vector of s-th of charge simulation and t-th of match point, 1≤s≤(m+n), 1≤t
≤(m+n)；
ε is dielectric constant；
By the virtual boundary it is discrete be y analysis site, solve following equation, determine that current potential on the virtual boundary divides
Cloth
Wherein, Q is the column vector being arranged on earthing pole with the charge value of the charge simulation on pipeline composition；
[Pab] virtual boundary coefficient of potential matrix, PabFor the element that a row b in the matrix is arranged, it is given by:
Wherein,Respectively indicate the position vector of a-th of charge simulation and b-th of analysis site, 1≤a≤(m+n), 1≤
b≤y。
Further, in the step S200, the polarization process of the metallic region of protective layer breakage is not considered, based on simulation
Charge method determines that the simplification current distribution of the nonlinear boundary includes:
By the nonlinear boundary it is discrete be k analysis site, determine the simplification electric current of the nonlinear boundary according to the following formula
Distribution:
Wherein, σ is soil conductivity；
For electric field coefficient matrix, FghFor the element that g row h in the matrix is arranged, determined by following formula:
Wherein,The respectively position vector of g-th of charge simulation and h-th of analysis site, 1≤g≤(m+n), 1≤h
≤k；
Q is the column vector being arranged on earthing pole with the charge value of the charge simulation on pipeline composition.
Further, the step S300, comprising:
Using the Potential distribution of the virtual boundary as initial value, in soil region using non-linear side described in Finite element arithmetic
The Potential distribution of soil side in boundary:
The soil region ΩDThe current potential of current field meet following formula:
(x,y,z)∈ΩD
The Potential distribution of the virtual boundary is the First Boundary Condition in the current field of the soil region:
Further, the step S600, comprising:
Using the Potential distribution of metal side on the nonlinear boundary as initial value, in metallic region, with Finite element arithmetic institute
State the process current distribution on nonlinear boundary:
The metal conductor regions ΩpipeThe current potential of current field meet Laplace's equation, it may be assumed that
The conductor and the intact boundary of protective layer meet second in the current field of the metal conductor regions
Class boundary condition:
In the nonlinear boundary, meet with downstream condition:
Wherein,For the current distribution on the nonlinear boundary.
The characteristic parameter of the earthing pole and buried metal pipeline to be analyzed includes:
The protective layer of the structural parameters and location parameter of earthing pole, the structural parameters of pipeline and location parameter, many places breakage
Size and location parameter.
Further,
Charge simulation on the earthing pole is arranged on the axis of the guide rod of earthing pole, and corresponding match point is located at ground connection
On the excircle of the guide rod of pole, the distance between two adjacent charge simulations are greater than charge simulation between corresponding match point
Distance；
Charge simulation on pipeline is arranged in pipeline, along the central axis that duct length extends, corresponding matching
Point be located at pipeline excircle on, the distance between two adjacent charge simulations be greater than charge simulation to corresponding match point it
Between distance.
Further, the difference in the step S700, between the process current distribution and the simplified current distribution
For mean square deviation, the preset convergence threshold is 1e-5.
Further, in the step S100, determine that virtual boundary is to be with the central axis of the buried metal pipeline
Central axis, radius 5m, length cylindrical surface identical with the length of the buried metal pipeline.
To sum up, this method does not consider polarization process according to direct current grounding pole and the characteristic parameter of metallic conduit, foundation
Current field distributed computing model is converted into Analogue charge method according to electrostatic analogy principle and carries out initial current distribution calculating；According to
The distribution of charges that the geometric parameter and charge simulation of virtual boundary are calculated calculates the Potential distribution on virtual boundary；According to
Current continuity theorem establishes the finite element model of soil region and metallic region, chooses the pipeline that Analogue charge method is calculated
Initial current density of the leakage current density as nonlinear boundary.Non-linear side is calculated by the finite element model of soil region
The Potential distribution of boundary soil side calculates the current distribution of nonlinear boundary pipe side, knot by the finite element model of metallic region
The current density that actual measurement polarization curve obtains nonlinear boundary is closed, the first of nonlinear boundary current density is corrected according to calculated result
Value repeats finite element model and calculates step until result restrains.
Specifically, in the step of calculating field distribution using Analogue charge method, activation polarization process is not considered, by quiet
Electrical analogy method converts electrostatic field problem from current field problem to the interference of buried pipeline for earthing pole.
Specifically, charge simulation is respectively set on earthing pole and pipeline, in conjunction with ground connection pole surface potential condition with
And the charge conservation condition on pipeline arranges the potential equation group for writing charge simulation respectively, solves equation group, ground connection can be obtained
Charge simulation distribution on pole and pipeline.
Because the normal direction current density on the earth boundary is 0, big ground boundary is substituted by setting image charge.
Specifically, pass through the other side on the earth boundary, setting and the symmetrical (edge of charge simulation on earthing pole and pipeline
Ground is to two sides mirror image) another group of charge simulation, to indicate that the normal direction current density on the earth boundary is 0 this known conditions.
As shown in figure 3, m charge simulation is arranged in the inside of earthing pole, n charge simulation is set in the inside of pipeline.
Each match point is located at the outside of earthing pole or pipeline, and is located on earthing pole or pipeline, not in the soil.
Repeat no more the charge simulation current potential individually listed on the potential equation of the charge simulation on earthing pole (1) and pipeline
The step of equation group (2).
In addition, the charge simulation configured on pipeline meets current continuity theorem, therefore net charge on the whole is 0.
By equations simultaneousness, can acquire on earthing pole with the current potential on the charge value and pipeline of charge simulation each on pipeline
Value.
It is construed as, because of the electric current that earthing pole has DC transmission system to inject, the simulation configured on earthing pole
Charge is unsatisfactory for current continuity theorem.
When determining the virtual boundary of pipeline adjacent domain, closed fictitious line is selected in the adjacent domain of buried pipeline
Boundary, entity area in the virtual boundary is by the target area as subsequent finite element analysis.This target area includes completely
There is buried metal pipeline, and does not include earthing pole.
It is construed as, the entity area in the virtual boundary includes soil region and conduit region.And the sky in pipeline
Gas region is then not belonging to the target area.
It is distributed according on the earthing pole obtained in the first step with the charge simulation on pipeline, solves equation, it is available to be somebody's turn to do
Potential distribution on virtual boundary.
It is construed as, it can be according to the needs of subsequent finite element analysis, by discrete point for any scale of virtual boundary
Analysis point quantity, and the Potential distribution on the virtual boundary is sought using equation.
Be construed as, the Potential distribution on the virtual boundary respectively from earthing pole with the charge simulation on pipeline
Effect.
It should be noted that not considering local protective layer for this condition of damaged state above.In following step,
Introduce local protective layer then as this condition of damaged state.That is, in " buried metal pipeline " in the following contents, at least one
A regional area, protective layer are damaged state.
It should be noted that metal surface area corresponding with damaged protective layer directly connects with soil in buried pipeline
Touching；In the activation polarization process that the metal surface area occurs, so that the region of protective layer breakage and soil region on pipeline
Interface condition and pipeline on the intact region and soil region of other protective layers interface condition it is not identical.
Specifically, the activation polarization between the metal layer for the buried pipeline being in direct contact with it for any soil environment
Process can be tested by laboratory test or engineering site, determine the boundary of metallic region and soil region as shown in Figure 5
Polarization potential-current density polarization curve on face
It is construed as, current density, J is vector, and direction is the normal orientation on boundary.
The soil region of pending finite element analysis, has inside and outside two boundaries, and outer boundaries are determined in second step
Virtual boundary；Inboard boundary is neighbouring with pipeline, including the intact pipeline outer wall part of protective layer, protective layer breakage and soil and gold
The part that metal surface directly contacts.
The metal conductor regions of pending finite element analysis have inside and outside two boundaries, and inboard boundary is adjacent with air
Inner wall outside；Outer boundaries are neighbouring with soil, including the intact pipeline outer wall part of protective layer, protective layer breakage and and soil
The metal surface part of the pipeline outer wall directly contacted.
As shown in figure 4, by nonlinear between the damaged corresponding metal surface area of protective layer and soil region
Polarization boundary is contacted.It is construed as, illustrates the nonlinear boundary in Fig. 4 in order to strengthen, with whole metallic conduits
Illustrated for protective layer breakage.
According to current continuity theorem, the finite element model of soil region and metallic region is established respectively, to solve each point
The current potential and current density at place.
The soil region is constant current field, and the divergence of current density is zero.In the current field of the soil region, mark
Virtual boundary ΓDFor First Boundary Condition, have
Wherein, fD(x, y, z) is the potential value of each point on the virtual boundary, on the virtual boundary as obtained in second step
Potential distribution
The metal conductor regions are constant current field, and the divergence of current density is zero.
In the current field of the metal conductor regions, conductor and the intact boundary Γ of protective layerinPlace meets the second class
Boundary condition, i.e.,
Wherein, n here indicates the normal component on boundary；In the boundary Γ that conductor and protective layer are intactinPlace,
On its normal component direction, the variable quantity of current potential is zero.
3) the damaged corresponding metal surface Γ of protective layerMBelong to nonlinear boundary, meets nonlinear boundary condition, i.e.,
Wherein, n here indicates the normal component on boundary；
For the Leakage Current density on nonlinear boundary；
σ is soil conductivity.
In FEM calculation, it is distributed according to determining charge simulation and determines that the Leakage Current on the nonlinear boundary is close
Degree, and the initial current density as the nonlinear boundary.
According to initial current density determined above, the electricity of the polarization on the pipeline of local damage is determined by following iteration
Position:
Step 1): the Potential distribution according to the finite element model of soil region calculating nonlinear boundary in soil side,
Specifically, from the current potential on virtual boundary, determine the nonlinear boundary in the Potential distribution of soil side；
Step 2) is according to initial current density, according to the determining polarization curve of test, by tabling look-up, interior fitting, outer fitting
The methods of, determine corresponding with above-mentioned initial current density polarization potential (that is, nonlinear boundary is in soil side and pipe side
Potential difference)；
Above-mentioned polarization potential is added with the Potential distribution of soil side, can determine nonlinear boundary pipe side (namely
Metal side) Potential distribution；
Nonlinear boundary is initial value in the Potential distribution of pipe side (namely metal side) by step 3), according to metallic conductor area
The finite element model in domain determines the nonlinear boundary in the process current density of pipe side；
Step 4) judges the difference for the process current density and the process current density determined in last round of circulation that epicycle determines
Does the absolute value of value meet preset iteration error
If it is satisfied, then the polarization curve determining according to test, the determining intermediate current density determined with epicycle is corresponding
Polarization potential is the DC influence of the polarization potential namely local damage region on the nonlinear interface；
If not satisfied, the process current density for then taking epicycle to determine is obtained with the process current density determined in last round of circulation
Average value repeats step 2)-step 4) as updated initial current density.
In above step, persistently it is modified by the current density to nonlinear boundary, improves nonlinear boundary
The accuracy of current density, and then ensure that the accuracy of the polarization potential on the nonlinear interface that solution obtains.
As shown in Fig. 2, buried metal pipeline of the invention includes: by the calculation method of DC influence
A, charge simulation distribution calculates
Under conditions of not considering polarization process, by electrostatic analogy method by earthing pole to the interference of buried pipeline from electricity
Flow field problems are converted into electrostatic field problem, and physical simulation charge arrangement is as shown in Figure 3.
In earthing pole, charge simulation is arranged inside earthing pole and inside pipeline, guarantees that calculating field domain inside is not present mould
Quasi- charge；Charge simulation potential equation is write in conjunction with the charge conservation condition column on the potential condition and pipeline for being grounded pole surface
Group finally obtains the charge simulation distribution of earthing pole and pipeline；In conjunction with charge simulation distribution can solving virtual boundary current potential
The initial Leakage Current Density Distribution of metallic region at the protective layer of distribution and breakage.
Specifically, in charge simulation configuration, as shown in figure 3, the charge simulation of earthing pole is placed in the inside of earthing pole, preferably
Ground is arranged on the central axis of guide rod；Match point on earthing pole is located in the outer circumference of earthing pole.
Specifically, in charge simulation configuration, as shown in figure 3, the charge simulation of pipeline is placed in inside pipeline, it is preferable that set
It sets on mandrel line in the duct；Match point on pipeline is located in the outer circumference of pipeline conductor.
It is construed as, earthing pole and pipeline are separated by a distance in spatial vertical, and spatially.
The cross section of guide rod is circle, and the central axis of guide rod is a closed circle；Pipe centerline refers to pipeline
The central axis for the cylindrical body that inside radius is constituted, is straight line.
Pipeline is usually thin-wall part, and charge simulation is arranged on the central axis of duct wall, causes not can be carried out substantially quiet
The calculating of electric field；And field domain is unrelated field domain inside pipeline, therefore, the charge simulation of pipeline may be provided at central axis
On.
B, pipeline adjacent domain virtual boundary determines
Virtual boundary is set by the cylindrical surface at the central axis 5m apart from buried pipeline, to guarantee that the boundary can be complete
It entirely include metallic conduit.
C, in finite region nonlinear boundary processing
In the region of protective layer local damage, finite element region can be divided into soil region and metallic region, two regions it
Between contacted by nonlinear boundary (namely polarization boundary).Specific boundary configuration diagram is as shown in Figure 5.
Soil region and metallic region are arranged respectively and write FEM equations, i.e.,
When FEM calculation, design conditions of the calculated result of soil region as metallic region；In turn, metallic region
Design conditions of the calculated result as soil region.
D, initial value is determining and iteratively solves
It is distributed according to charge simulation, the current density initial value on the pipeline for the breakage being calculated.
The Potential distribution of nonlinear boundary is solved by the FEM equations of soil region；Then it is obtained by polarization curve
Obtain the current potential boundary condition in tube metal region；The FEM calculation for carrying out metallic region later, obtains the electric current of metallic region
Density.
It is modified by current density of the successive ignition to metallic region, until after certain wheel iteration, the electricity of epicycle iteration
The difference of the current density results of the result of current density and last round of iteration is less than some in a small amount, then iteration convergence, and terminates and change
Generation.
It is carried out directly to shown in fig. 6 with the defeated buried metal pipeline 200 of the neighbouring length of direct current grounding pole 100 using above method
Flow interference calculation.Ground connection electrode potential is 600V, and material is 70 round steel of φ；The diameter of section of the guide rod of earthing pole is de=10cm；
The polar ring outer diameter D of earthing polee=200m, the buried depth h of earthing polee=1.5m；Internal diameter of the pipeline 0.59m, outer diameter 0.61m, wall thickness 2cm；
Pipeline overall length 200km, buried depth of pipeline hp=1m；Distance of the earthing pole away from pipeline is D=10km, and soil conductivity takes 100 Ω
m；Pipeline anticorrosion coating breakage is upper to be uniformly distributed along pipeline, and breakage rate is 1% (in terms of area), and single breaking point area is
4cm2。
The polarization potential calculated result along pipeline after final iteration convergence and assignment is as shown in fig. 7, the electricity that polarizes in Fig. 6
Position refers both to the polarization potential for damaged area occur.
It should be noted that direct current grounding pole is located at the middle part of long defeated buried metal pipeline in Fig. 6.
It is construed as, polarization potential is not present in non-damaged area；Only exist remote ground potential.The remote ground potential is entirely managed
Difference on road is very little, and numerical value can take the pipeline current potential being calculated in Analogue charge method.
The present invention is described by reference to a small amount of embodiment above.However, it is known in those skilled in the art,
As defined by subsidiary Patent right requirement, in addition to the present invention other embodiments disclosed above equally fall in this hair
In bright range.
Normally, all terms used in the claims are all solved according to them in the common meaning of technical field
It releases, unless in addition clearly being defined wherein.All references " one/described/be somebody's turn to do [device, component etc.] " are all opened ground
At least one example being construed in described device, component etc., unless otherwise expressly specified.Any method disclosed herein
Step need not all be run with disclosed accurate sequence, unless explicitly stated otherwise.
Claims (10)
1. a kind of buried metal pipeline DC influence of protective layer breakage determines method characterized by comprising
Step S100: according to the characteristic parameter of the earthing pole of acquisition and buried metal pipeline to be analyzed, virtual boundary is determined, institute
It states the metallic region occupied in virtual boundary including the buried metal pipeline and is located at the virtual boundary and the metal area
Soil region between domain；And
Determine nonlinear boundary, the nonlinear boundary is metal side in the side close to metallic region, close to soil region
Side be soil side；
Step S200: not considering the polarization process of the metallic region of protective layer breakage, is determined based on Analogue charge method described virtual
The simplification current distribution of the Potential distribution on boundary and the nonlinear boundary；
Step S300: using the Potential distribution of the virtual boundary as initial value, soil on the nonlinear boundary is calculated in soil region
The Potential distribution of earth side；
Step S400: it according to the simplification current distribution of predetermined polarization curve and the nonlinear boundary, determines described non-
Simplification polarization potential on linear barrier；
Step S500: it according to the Potential distribution of the simplified polarization potential and the soil side, determines on the nonlinear boundary
The Potential distribution of metal side；
Step S600: it using the Potential distribution of metal side on the nonlinear boundary as initial value, in metallic region, calculates described non-thread
The borderline process current distribution of property；
Step S700: the difference between the process current distribution and the simplified current distribution is not more than preset receipts
When holding back threshold value,
According to predetermined polarization curve and the process current distribution, the target polarization electricity on the nonlinear boundary is determined
Position, the DC influence of the target polarization potential, that is, protective layer breakage buried metal pipeline.
2. the method according to claim 1, wherein further include:
Step S800: the difference between the process current distribution and the simplified current distribution is greater than preset convergence
When threshold value,
According to preset modification rule, the simplified current distribution is updated, and
Repeat step S400 to S700.
3. the method according to claim 1, wherein
In the step S200, the polarization process of the metallic region of protective layer breakage is not considered, and institute is determined based on Analogue charge method
State the Potential distribution of virtual boundary, comprising:
M charge simulation is set on the earthing pole, and charge simulation value is denoted as Q respectivelyi, wherein 1≤i≤m；Accordingly, In
There is m match point on the outside of earthing pole；
N charge simulation is set on the buried metal pipeline, and charge simulation value is denoted as Qj, 1≤j≤m；Accordingly, in pipe
There is n match point on the outside of road；
In conjunction with following formula:
Following equation is solved, determines the distribution of charges Q on earthing pole with the charge simulation being arranged on buried metal pipeline0And Q1；
Wherein, Q0For the column vector of the charge value for the charge simulation being arranged on earthing pole；
Q1For the column vector of the charge value for the charge simulation being arranged on buried metal pipeline；
Value for the column vector of the potential value for the charge simulation being arranged on earthing pole, either element is
For the column vector of the potential value for the charge simulation being arranged on buried metal pipeline, either element value is
[Pst] it is coefficient of potential matrix, PstFor the element that s row t in the matrix is arranged, determined by following formula:
Wherein,The respectively position vector of s-th of charge simulation and t-th of match point, 1≤s≤(m+n), 1≤t≤(m+
n)；
ε is dielectric constant；
By the virtual boundary it is discrete be y analysis site, solution following equation, determine the Potential distribution on the virtual boundary
Wherein, Q is the column vector being arranged on earthing pole with the charge value of the charge simulation on pipeline composition；
[Pab] virtual boundary coefficient of potential matrix, PabFor the element that a row b in the matrix is arranged, it is given by:
Wherein,Respectively indicate the position vector of a-th of charge simulation and b-th of analysis site, 1≤a≤(m+n), 1≤b≤y.
4. according to the method described in claim 3, it is characterized in that, not considering the gold of protective layer breakage in the step S200
Belong to the polarization process in region, the simplification current distribution for determining the nonlinear boundary based on Analogue charge method includes:
By the nonlinear boundary it is discrete be k analysis site, determine the simplification current distribution of the nonlinear boundary according to the following formula:
Wherein, σ is soil conductivity；
For electric field coefficient matrix, FghFor the element that g row h in the matrix is arranged, determined by following formula:
Wherein,The respectively position vector of g-th of charge simulation and h-th of analysis site, 1≤g≤(m+n), 1≤h≤k；
Q is the column vector being arranged on earthing pole with the charge value of the charge simulation on pipeline composition.
5. the method according to claim 1, wherein the step S300, comprising:
Using the Potential distribution of the virtual boundary as initial value, in soil region using on nonlinear boundary described in Finite element arithmetic
The Potential distribution of soil side:
The soil region ΩDThe current potential of current field meet following formula:
The Potential distribution of the virtual boundary is the First Boundary Condition in the current field of the soil region:
6. according to the method described in claim 5, it is characterized in that, the step S600, comprising:
Using the Potential distribution of metal side on the nonlinear boundary as initial value, in metallic region, with non-described in Finite element arithmetic
Process current distribution on linear barrier:
The metal conductor regions ΩpipeThe current potential of current field meet Laplace's equation, it may be assumed that
The conductor and the intact boundary of protective layer meet the second class side in the current field of the metal conductor regions
Boundary's condition:
In the nonlinear boundary, meet with downstream condition:
Wherein,For the current distribution on the nonlinear boundary.
7. the method according to claim 1, wherein
The characteristic parameter of the earthing pole and buried metal pipeline to be analyzed includes:
The structural parameters and location parameter of earthing pole, the structural parameters of pipeline and location parameter, many places breakage protective layer ruler
Very little and location parameter.
8. according to the method described in claim 3, it is characterized in that,
Charge simulation on the earthing pole is arranged on the axis of the guide rod of earthing pole, and corresponding match point is located at earthing pole
On the excircle of guide rod, the distance between two adjacent charge simulations be greater than charge simulation between corresponding match point away from
From；
Charge simulation on pipeline is arranged in pipeline, along the central axis that duct length extends, corresponding matching point
In on the excircle of pipeline, the distance between two adjacent charge simulations are greater than charge simulation between corresponding match point
Distance.
9. the method according to claim 1, wherein
In the step S700, the difference between the process current distribution and the simplified current distribution is mean square deviation, described
Preset convergence threshold is 1e-5.
10. the method according to claim 1, wherein
In the step S100, determine that virtual boundary is using the central axis of the buried metal pipeline as center axis, radius
For 5m, length cylindrical surface identical with the length of the buried metal pipeline.
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