CN105044559B  The subregion method for diagnosing faults of grounding net of transformer substation  Google Patents
The subregion method for diagnosing faults of grounding net of transformer substation Download PDFInfo
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 CN105044559B CN105044559B CN201510475125.4A CN201510475125A CN105044559B CN 105044559 B CN105044559 B CN 105044559B CN 201510475125 A CN201510475125 A CN 201510475125A CN 105044559 B CN105044559 B CN 105044559B
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 Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSSSECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSSREFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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 Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the loadside end user applications
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Abstract
Description
It is August in 2014 20 this application claims the applying date, application No. is 201410412091.X, entitled " substations The priority of the subregion method for diagnosing faults of grounded screen ".
Technical field
The present invention relates to technical field of electric power, and in particular, to a kind of subregion failure of grounding net of transformer substation is examined Disconnected method.
Background technology
Grounding net of transformer substation usually uses band steel or round steel horizontal laying, is arranged in long pass or square groove, is embedded to underground 0.6 ~0.8m, area are substantially identical as the area of power plant and substation.Grounded screen is to the safe operation of electrical equipment to closing weight It wants, in recent years, substation operation accident caused by due to the reduction of grounded screen electric property increases year by year, the wherein corruption of conductor Erosion, fracture or solder skip etc. are the latencies for causing ground connection performance to decline, will if meeting electric system occurs ground short circuit failure Cause earth mat partial potential difference itself and earth mat potential anomalies to increase, except to the safety belt of operations staff come in addition to threatening, it is also possible to Because counterattack or cable skin circulation so that the insulation of secondary device is destroyed, high pressure scurries into control room, makes monitoring or control device Malfunction or tripping occurs and expands accident, brings huge economic loss and undesirable social influence.It can be seen that grounded screen Failure has been a mortal malady of safe operation of power system, and the corrosion condition of the breakpoint and earth mat that diagnose grounded screen has become electric power One great antiaccident measures of department.The ground connection performance of grounded screen is generally sentenced by the size of measure field ground resistance indirectly It is disconnected, but ground net corrosion situation can not be judged accordingly, when the corrosion of earth mat conductor is even broken, ground resistance still may be normal.I.e. So that ground resistance is measured display exception, can not also learn the specific location of failure, and extensive excavate is needed to search fault point, work Work amount is huge and with high costs.Fault Diagnosis for Grounding Grids for scent a hidden danger and take in time corresponding measure have directive significance, Due to by can and interstitial content and its distributing position limited, the difficulty of this work is very big.
Currently, domestic and foreign scholars have been achieved for some achievements in research in Fault Diagnosis for Grounding Grids field, it is mainly reflected in In two class methods：One kind is the detection method based on electromagnetic field method or surface potential, passes through the electromagnetic field parameters or electricity of ground surface The physical signals such as position parameter feedback signal judge that the crack conditions of subsurface conductors, result lack good criterion at present, seriously It relies on the precision of equipment and is vulnerable to the interference at scene, and diagnostic result whether fracture can only be made and can not be known specific Corrosion condition.Also one kind is the method for establishing Fault Diagnosis for Grounding Grids equation based on electric network theory, by grounded screen Equivalent model is established, the relationship side of port resistive value and branch resistance value is established based on the model and using conservation of the similar power principle Journey, and the optimal solution that equation obtains nonlinear equation is solved using the alternative manner of least square.There is scholar to further study Application of the novel intelligent optimization algorithm in solving diagnosis equation, achieves certain effect, but due to fault diagnosis side The Degree of Ill Condition of journey is high, can be obtained that data are relatively fewer, and the result reliability that the above method obtains is still relatively low.It is examined to improve Disconnected reliability, researcher propose according to the structure of grounded screen can and node at network is layered and yojan, obtain Containing only can and node intrinsic grounded screen, and clearbranch branch at all levels is further determined using the method successively traced back Resistance situation reduces the Degree of Ill Condition of diagnostic equation, but wherein uncertainbranch is still more, and algorithm structure complexity, Calculation amount is very big.
Due to the ground lead of its power transformation station equipment be it is limited, no matter the grounded screen fault of which kind of method structure Diagnostic equation is all underdetermined equation, and the result obtained has uncertainty.For engineering reality, if it is possible to determine grounded screen Fault zone position, for guidance scene targetedly excavate safeguard it is very significant, therefore, how according to such Model is imitated, validity and the accuracy to Fault Diagnosis for Grounding Grids is improved using a kind of new method, is to special procure solution at present The problem of.
Invention content
The purpose of the present invention is to provide a kind of subregion method for diagnosing faults of grounding net of transformer substation, this method is a kind of Grounded screen subregion method for diagnosing faults based on topological hierarchy yojan, theme be for grounded screen can and node distribution Situation carries out layer reduction to grounded screen to grounded screen topological structure subregion, according to division result and obtains intrinsic grounded screen, to this The changing value of each branch resistance is calculated in intrinsic grounded screen application and trouble diagnostic equation group model and optimization algorithm, according to every Fault condition in branch corresponding grounded screen region decision region, underdetermined problem when this method avoids solving equation group, Significantly improve the reliability and accuracy of diagnostic result.
In order to achieve the above objectives, the present invention provides a kind of subregion method for diagnosing faults of grounding net of transformer substation, this method, Include the following steps：
Step 1：For given grounded screen original design topological structure, application circuit network theory is to grounded screen topology knot Structure carries out yojan, prunes unreachable node,:By a grounded screen be decomposed into grounded screen, accurate first column, first column, metanetwork, can And 6 levels of grounded screen and intrinsic grounded screen；
Step 2：The result decomposed according to accurate first column stage topology divides the geographic location area of grounded screen, and compiles successively Number；
Step 3：To every branch in intrinsic grounded screen successively trace each branch region or by which region about Letter obtains, and records the corresponding zone number of each branch in the table；
Step 4：According to the original design data of grounded screen, the nominal value parameter of the branch resistance of intrinsic grounded screen is calculated, Common node is selected, incidence matrix A and branch admittance matrix Y is generated；
Step 5：According to intrinsic grounded screen topological structure, simulation circuit model is built, scheme is measured using abundant, in circuit Middle selection node i applies direct current source forcing I between j_{0}, test it is selected can and node voltage U_{ij}, i is obtained, the port electricity between j Hinder R_{ij}；
Step 6：After grounded screen fault, node i, the port resistive measured value between j becomes R '_{ij}, with grounded screen normal condition Under can and port resistive comparison, obtain port resistive difference value vector Δ R_{ij}, according to Fault Diagnosis for Grounding Grids model, establish failure and examine Disconnected equation group；
Step 7：Diagnosis equation group is solved using Leastsquares minimization algorithm, obtains result of calculation to the end；
Step 8：According to the solving result in step 7, branch resistance value is relatively nominal after calculating intrinsic grounded screen fault The multiple of value, according to the fault condition in each item intrinsic branch trouble situation region decision corresponding with its each region.
According to the subregion method for diagnosing faults of the grounding net of transformer substation described in present preferred embodiments, in step 1：
The accurate first column be one group can and node at grounded screen is torn after obtained minimum unit network；
The member column is merged to obtain by accurate first version series and parallel branch in the block, at the same retain it is all can and node；
The metanetwork be by each piece in first column by conversion of circuits be changed into containing only can and node it is equivalent Network；
It is described can and grounded screen be in whole metanetworks with same node point branch be attached composition containing only can and The network of node；
The intrinsic grounded screen be by can and grounded screen in whole parallel branches merge to obtain, any two can and section At most there are a branch, referred to as intrinsic branch between point.
Step 3 is specially：Since every branch in intrinsic grounded screen is by all accurate first versions several columns in the block What interior branch obtained after conversion of circuits, and each accurate first column corresponds to a region in original grounded screen.Cause This successively traces its region or by which according to conversion of circuits process to every branch in intrinsic grounded screen Branch in quasi member column converts to obtain, and corresponds to each region in step 2 according to its region or these accurate first columns Number, records the corresponding zone number of each branch in the table.
According to the subregion method for diagnosing faults of the grounding net of transformer substation described in present preferred embodiments, in step 4, tool Body is the resistance value that each branch of original grounded screen is calculated according to the original design data of grounded screen, each of original grounded screen Obtain connecing after the equivalent transformation of Lu Jing oversampling circuits accurate first column, first column, metanetwork, can and grounded screen and intrinsic grounded screen, According to conversion of circuits principle, the resistance value of each branch of each level grounded screen is successively calculated, finally reckoning obtains intrinsic The nominal value parameter of the branch resistance of grounded screen；Then, it selects common node and defines A to select network after a reference mode Incidence matrix；Y_{b}For branch admittance matrix；Y_{n}For node admittance matrix；Have between branch admittance matrix and node admittance matrix There is following relationship：
Y_{n}=A*Y_{b}*A^{T} (1)
In formula, A^{T}For the transposed matrix of incidence matrix A.
According to the subregion method for diagnosing faults of the grounding net of transformer substation described in present preferred embodiments, step 5 is specific For：
If a normal ground connection pessimistic concurrency control N has b+1 branch, n+1 node, to the grounded screen equivalent resistance network All nodes and branch press following rule numbers：Node serial number：It is subject to final topology figure, from top to down, until it is left and right, into Row number, the last one node is not numbered, and is set to datum mark, and when measurement does not also allow to use；Branch number：With final Subject to topological diagram, from top to down, until it is left and right, it is numbered, first transverse legs is numbered, then to longitudinal branch number.B+1 Branch is connected to the i of ground lead, and the ends j add DC current source forcing, current value I in the ports ith, j_{0}, according to electricity Road principle seeks R_{ij}, define I_{b}For branch current square；U_{n}For node voltage column vector；I_{n}It is nonactuated for the current source column vector of node The current value of node is 0；
The Kirchhoff's current law (KCL) and Kirchhoff's second law equation of resistor network are expressed as：
AI_{b}=0 (2)
U_{b}=A^{T}U_{n} (3)
U in formula_{b}Indicate the voltage of node b.
It can be obtained in conjunction with formula (1), (2), (3)
Y_{n}U_{n}=I_{n} (4)
Port resistive R_{ij}Calculating formula is：
R_{ij}=U_{b+1}/I_{0} (5)
U in formula_{b+1}Indicate the voltage of node b+1.
According to the subregion method for diagnosing faults of the grounding net of transformer substation described in present preferred embodiments, step 6 is specific For：
Grounded screen to that the illustraton of model after corrosion failure occur and is considered as Wang LuoN ', still in its i, the ends j add the current source, current value to be I_{0}, find out R_{ij}'；Network N and Wang LuoN 'Topological structure is identical；To circuit N and N&apos with identical topological structure;, and corresponding branch Road and node, which take, to be identically numbered, and the reference direction of each branch is identical, is then had with theorem according to Teller：
In formula, I_{k}'、U_{k}'Respectively electric network N'Branch current and branch voltage, I_{k}、U_{k}The respectively branch of electric network N Road electric current and branch voltage；When corrosion or fracture defect occur for branch k, branch resistance is by R_{k}Become R_{k}', i.e.,：
ΔR_{k}=R_{k}'R_{k} (8)
The resistance at the both ends i at this time, j is by R_{ij}Become R_{ij}'I.e.：
ΔR_{ij}=R_{ij}'R_{ij} (9)
Because two networks in i, the electric current of the b+1 articles branch at the ends j is all I_{0}, i.e.,：
I_{b+1}=I'_{b+1}=I_{0} (10)
U_{b+1}=R_{ij}I_{0} (11)
U'_{b+1}=R'_{ij}I_{0} (12)
Formula (10), (11), (12) are substituted into formula (6), in (7)：
Formula formula (13) subtracts formula (14) and obtains：
Formula (8), (9) are substituted into formula (15) and obtained：
Formula (16) indicates the relationship of branch resistance changing value and the variation of port resistive value, due to branch resistance in the network Variable have b, it is therefore desirable to measure a series of port resistive, it is assumed that the different port numbers of measurement are m, to obtain Equation group：
According to the subregion method for diagnosing faults of the grounding net of transformer substation described in present preferred embodiments, step 7 includes Following steps：
Step 71：The topological structure and branch resistance R of grounded screen are obtained from design drawing_{k}；It is calculated according to circuit theory I_{k(s)}, choose measuring node group and find out resistance R between theoretical node_{ij(s)}(s=1~m)；
Step 72：Measurement port resistance R '_{ij(s)}, calculate port resistive changing value Δ R_{ij(s)}=R '_{ij(s)}R_{ij(s)}；
Step 73：Enable I '_{k(s)}(0)=I_{k(s)}, I '_{k(s)}(0) when being first iteration each branch current value；
Step 74：With equation group (17) Δ R is calculated in conjunction with least square optimization_{k} ^{(t)}(s), t=0,1 ..., t are Iterations, Δ R_{k} ^{(t)}(s) when being the t times iteration branch resistance difference；Since original leg resistance is R_{k}, in addition the t times changes For when branch resistance difference DELTA R_{k} ^{(t)}(s), the t times branch resistance value is obtained
Step 75：If the Er Qies of t >=1 ΔR_{k} ^{(t)}ΔR_{k} ^{(t1)}< ε are obtained then stopping iterative calculationIt is last As a result, ε is the constant of setting；It is no to then follow the steps 76；
Step 76：WithCalculate I '_{k(s)} ^{(t+1)}, I '_{k(s)} ^{(t+1)}The current value of each article of branch when being the t+1 times iteration；Weight Multiple step 74 and step 75.
According to the subregion method for diagnosing faults of the grounding net of transformer substation described in present preferred embodiments, described minimum two Multiplying optimization method formula is：
In formula,The resistance calculations difference of the b articles branch when being the t times iteration,It is the t times and t1 iteration When port resistive difference.
According to the subregion method for diagnosing faults of the grounding net of transformer substation described in present preferred embodiments, least square is excellent The value lower limit of parameter in change method is the nominal value of branch resistance, and the upper limit is 50 times of nominal value, the upper limit value, lower limiting value Constraints in corresponding formula (18).
According to the subregion method for diagnosing faults of the grounding net of transformer substation described in present preferred embodiments, in step 8, electricity It is as follows that resistance value increases multiple situation corresponding with fault degree：
It is normal if μ is 1~2 if it is μ that resistance value, which increases multiple,；There is minor failure if μ is 2~4；If μ is 4~10 there is moderate failure；There is heavier failure if μ is 10~20；There is catastrophe failure if μ is 20~40；If μ is 40 or more are then broken.
Compared with prior art, the present invention has the following advantages due to taking above technical scheme：
1, the mathematical model that grounded screen subregion fault diagnosis is established in the present invention, by complicated Fault Diagnosis for Grounding Grids Problem is converted into the solution to mathematical model, quantifies to grounded screen fault degree, and diagnostic result is easy to understand.
2., the present invention avoid solve equation group when underdetermined problem grounded screen is changed by topological structure layer reduction For containing only can and node intrinsic network, using abundant testing scheme, it is less qualitative to reduce diagnostic equation group, significantly improves diagnosis knot The reliability and accuracy of fruit.
3., the present invention to grounded screen dividing regions domain, diagnostic result is as a result reliable accurate for the fault condition in region, The reference that grounded screen is excavated when checking is may be used as to be easy to use for instructing substation field maintenance more efficient and practical Into Practical Project.
Description of the drawings
Fig. 1 is the subregion method for diagnosing faults method flow diagram of grounding net of transformer substation of the present invention；
Fig. 2 is the grounded screen equivalent model figure of the present invention；
Fig. 3 is the grounded screen topological diagram of the present invention；
Fig. 4 is the first column figure of standard of the present invention；
Fig. 5 is first column figure of the present invention；
Fig. 6 is the metanetwork figure of the present invention；
Fig. 7 be the present invention can and grounded screen figure；
Fig. 8 is the intrinsic grounded screen figure of the present invention；
Fig. 9 is the grounded screen subregion figure of the present invention；
Figure 10 is that Matlab exports branch resistance with respect to nominal value multiple block diagram.
Specific implementation mode
Below with reference to the attached drawing of the present invention, technical solution in the embodiment of the present invention carries out clear, complete description And discussion, it is clear that as described herein is only a part of example of the present invention, is not whole example, based on the present invention In embodiment, the every other implementation that those of ordinary skill in the art are obtained without making creative work Example, belongs to protection scope of the present invention.
For the ease of the understanding to the embodiment of the present invention, make further by taking specific embodiment as an example below in conjunction with attached drawing It illustrates, and embodiment does not constitute the restriction to the embodiment of the present invention.
First principles analysis：
Be embedded in underground grounded screen water mean pressure conductor be connected with each other constitute circuit network, ignore the influence of edphic factor, Grounded screen can regard pure resistance network as.After net is completed, since the length of each section of conductor, sectional area and conductivity are true It is fixed, their resistance value, i.e. nominal value can be calculated；Rear certain section of conductor occurs fracture or corrodes local network operation for many years When (its topological structure is unchanged), its branch resistance becomes larger compared with nominal value at this time.Meanwhile Substation Electric Equipment have and The ground lead that earth mat is connected, if grounded screen to be regarded as to the black box of a resistive network, and ground lead can With regard as it can and port, as shown in Figure 2.Wherein original network port resistance (resistance i.e. between ground lead, similarly hereinafter) Because of topological structure, branch resistance according to electric network theory it is known that can be calculated；And corrode after grounded screen port resistive Value can measure corrosion by ground lead and be followed by because Substation Electric Equipment has the ground lead being connected with grounded screen The port resistive value of earth mat.It can be obtained by port resistive changing value in this way, port electricity can be found out using Tellegen The relationship for hindering changing value and branch resistance changing value, reapplies mathematical method appropriate, can be released from noderesistance changing value The increased resistance value of grounded screen branch, to judge Grounding Grid and breakpoint situation.
A kind of subregion method for diagnosing faults of grounding net of transformer substation, includes the following steps：
Step 1：For given grounded screen original design topological structure, application circuit network theory is to grounded screen topology knot Structure carries out yojan, prunes unreachable node, by a grounded screen be decomposed into grounded screen, accurate first column, first column, metanetwork, can And 6 levels of grounded screen and intrinsic grounded screen；
The accurate first column be one group can and node at grounded screen is torn after obtained minimum unit network；
The member column is merged to obtain by accurate first version series and parallel branch in the block, at the same retain it is all can and node；
The metanetwork be by each piece in first column by conversion of circuits be changed into containing only can and node it is equivalent Network；
It is described can and grounded screen be in whole metanetworks with same node point branch be attached composition containing only can and The network of node；
The intrinsic grounded screen be by can and grounded screen in whole parallel branches merge to obtain, any two can and section At most there are a branch, referred to as intrinsic branch between point.
Step 2：The result decomposed according to accurate first column stage topology divides the geographic location area of grounded screen, and compiles successively Number.
Step 3：To every branch in intrinsic grounded screen successively trace each branch region or by which region about Letter obtains, and records the corresponding zone number of each branch in the table；
Specifically, every branch in intrinsic grounded screen is to be passed through by the branch in all accurate first versions several columns in the block It is obtained after oversampling circuit equivalent transformation, and each accurate first column corresponds to a region in original grounded screen.Therefore, according to circuit Equivalent transformation process successively traces its region or by which accurate first column to every branch in intrinsic grounded screen Branch converts to obtain, and corresponds to the number in each region in step 2 according to its region or these accurate first columns, in the table Record the corresponding zone number of each branch.
Step 4：According to the original design data of grounded screen, the nominal value parameter of the branch resistance of intrinsic grounded screen is calculated, The resistance value of each branch of original grounded screen is specially calculated according to the original design data of grounded screen, original grounded screen is each Branch obtain connecing after the equivalent transformation through oversampling circuit accurate first column, first column, metanetwork, can and grounded screen and intrinsic ground connection Net successively calculates the resistance value of each branch of each level grounded screen according to conversion of circuits principle, finally calculates and obtains this Levy the nominal value parameter of the branch resistance of grounded screen；Then selection common node generates incidence matrix A and branch admittance matrix Y.
Define the incidence matrix that A is network after selecting a reference mode；Y_{b}For branch admittance matrix；Y_{n}For node admittance Matrix；There is following relationship between branch admittance matrix and node admittance matrix：
Y_{n}=A*Y_{b}*A^{T} (1)
In formula, A^{T}For the transposed matrix of incidence matrix A.
Step 5：According to intrinsic grounded screen topological structure, simulation circuit model is built in Multisim simulation softwares, is answered Scheme is measured with abundant, node i is chosen in circuit, applies direct current source forcing I between j_{0}, test it is selected can and node voltage U_{ij}, i is obtained, the port resistive R between j_{ij}。
If a normal ground connection pessimistic concurrency control N has b+1 branch, n+1 node, to the grounded screen equivalent resistance network All nodes and branch press preset rule numbers node serial number：Be subject to final topology figure, from top to down, until it is left and The right side is numbered, the last one node opened up in complement is not numbered, and is set to datum mark and (is used as incidence matrix below Reference mode), when measurement, does not also allow to use；Branch number：It is subject to final topology figure, from top to down, until it is left and right, into Row number first numbers transverse legs, then to longitudinal branch number.The b+1 articles branch is connected to the i of ground lead, the ends j, The port ith, j adds DC current source forcing, current value I_{0}, R is asked according to circuit theory_{ij}, define I_{b}For branch current square； U_{n}For node voltage column vector；I_{n}Current value for the current source column vector of node, nonactuated node is 0；
The KCL (Kirchhoff's current law (KCL)) and KVL (Kirchhoff's second law) journey of resistor network are expressed as：
AI_{b}=0 (2)
U_{b}=A'U_{n} (3)
U in formula_{b}Indicate the voltage of node b.
It can be obtained in conjunction with formula (1), (2), (3)
Y_{n}U_{n}=I_{n} (4)
Port resistive R_{ij}Calculating formula is：
R_{ij}=U_{b+1}/I_{0} (5)。
U in formula_{b+1}Indicate the voltage of node b+1.
Step 6：After grounded screen fault, node i, the port resistive measured value between j becomes R^{’} _{ij}, with grounded screen normal condition Under can and port resistive comparison, obtain port resistive difference value vector Δ R_{ij}, according to Fault Diagnosis for Grounding Grids model, establish failure and examine Disconnected equation group.
Grounded screen to that the illustraton of model after corrosion failure occur and is considered as Wang LuoN ', still in its i, the ends j add the current source, current value to be I_{0}, find out R_{ij}'；Network N and Wang LuoN 'Topological structure is identical；To circuit N and N&apos with identical topological structure;, and corresponding branch Road and node, which take, to be identically numbered, and the reference direction of each branch is identical, is then had with theorem according to Teller：
In formula, I_{k}'、U_{k}'Respectively electric network N'Branch current and branch voltage, I_{k}、U_{k}The respectively branch of electric network N Road electric current and branch voltage；When corrosion or fracture defect occur for branch k, branch resistance is by R_{k}Become R_{k}', i.e.,：
ΔR_{k}=R_{k}'R_{k} (8)
The resistance at the both ends i at this time, j is by R_{ij}Become R_{ij}'I.e.：
ΔR_{ij}=R_{ij}'R_{ij}(9)
Because two networks in i, the electric current of the b+1 articles branch at the ends j is all I_{0}, i.e.,：
I_{b+1}=I'_{b+1}=I_{0} (10)
U_{b+1}=R_{ij}I_{0} (11)
U'_{b+1}=R'_{ij}I_{0} (12)
Formula (10), (11), (12) are substituted into formula (6), in (7)：
Formula formula (13) subtracts formula (14) and obtains：
Formula (8), (9) are substituted into formula (15) and obtained：
Formula (16) indicates the relationship of branch resistance changing value and the variation of port resistive value, due to branch resistance in the network Variable have b, it is therefore desirable to measure a series of port resistive, it is assumed that the different port numbers of measurement are m, to obtain Equation group：
Step 7：Diagnosis equation group is solved using Leastsquares minimization algorithm in MATLAB softwares, is obtained Last result of calculation.
Formula (17) belongs to Nonlinear System of Equations, can not direct solution, alternative manner can be introduced.First, I ' is enabled_{k}(0)= I_{k}, equation group becomes system of linear equations, but m < b equation groups owe fixed, need to use Optimization Method, herein be it is nonnegative most Small square law.Thus find out Δ R_{k}(0) and R '_{k}(0), R ' is then used_{k}(0) I ' is calculated_{k}(1)；Then I ' is used_{k}(1) R ' is calculated_{k} (1).Calculating above is repeated, until the resistance delta found out is met the requirements, obtains result of calculation to the end.It specifically includes following Step：
Step 71：The topological structure and branch resistance R of grounded screen are obtained from design drawing_{k}；It is calculated according to circuit theory I_{k(s)}, choose measuring node group and find out resistance R between theoretical node_{ij(s)}(s=1~m)；
Step 72：Measurement port resistance R '_{ij(s)}, calculate port resistive changing value Δ R_{ij(s)}=R '_{ij(s)}R_{ij(s)}；
Step 73：Enable I '_{k(s)}(0)=I_{k(s)}, I '_{k(s)}(0) when being first iteration each branch current value；
Step 74：With equation group (17) Δ R is calculated in conjunction with least square optimization_{k} ^{(t)}(s) (t=0,1 ..., t are Iterations), Δ R_{k} ^{(t)}(s) when being the t times iteration branch resistance difference；Since original leg resistance is R_{k}, in addition the t times The difference DELTA R of branch resistance when iteration_{k} ^{(t)}(s), the t times branch resistance value is obtained
Step 75：If the Er Qies of t >=1 ΔR_{k} ^{(t)}ΔR_{k} ^{(t1)}< ε are obtained then stopping iterative calculationFor most Afterwards as a result, ε is the constant of setting；It is no to then follow the steps 76；
Step 76：WithCalculate I '_{k(s)} ^{(t+1)}, I '_{k(s)} ^{(t+1)}The current value of each article of branch when being the t+1 times iteration；Weight Multiple step 74 and step 75.
Because the number of unknown quantity is b in equation group (17), the exact value of these variables is obtained, the number of equation number is answered It is less than the branch quantity of grounded screen for the quantity of b, but general substation grounding lead, solution of equations is not unique.In view of engineering Practical problem often only has range very small percentage to be reasonable, introduces constrained linear programming problem in these solutions To obtain optimal solution.Preferable exact value in order to obtain needs to use Techniques of Optimum, specifically, least square optimization Formula is：
In formula,The resistance calculations difference of the b articles branch when being the t times iteration,It is the t times and t1 iteration When port resistive difference.The formula is during solution formula (17) as adaptation value function so that the difference of port resistive Variation reaches minimum.
Limitation with constraints to domain can make solution more reasonable, while be also beneficial to planning problem in reality The effect that border calculates.Being constrained to for lower variable is nonnegative, ensures that solution is of practical significance in engineering；Steplength limit is made to upper variable System, it is ensured that the solution acquired is the optimal solution near every singlestep iteration initial value, meets the actual conditions of iterative process.Specifically Ground, the value lower limit (descending variable) of the parameter in least square optimization are the nominal value of branch resistance, and the upper limit is (i.e. upper to become Amount) it is 50 times of nominal value.
Step 8：According to the solving result in step 7, branch resistance value is relatively nominal after calculating intrinsic grounded screen fault The multiple of value, according to the fault condition in the corresponding region decision each region of each branch.
Specifically, it is as shown in table 1 to increase multiple situation corresponding with fault degree for resistance value.
1 resistance value of table increases multiple situation corresponding with fault degree
The subregion method for diagnosing faults of the grounding net of transformer substation of the present invention is done further below in conjunction with specific embodiment It is described in detail.
Embodiment one
Fig. 3 show certain grounding net of transformer substation network topological diagram, have 16 nodes, wherein 2,4,5,7,8,10,11, 14,16 for can and node, the grounded screen it is specific decompose can be referring to Fig. 4~8 this paper.Under normal condition, every branch is nominally electric Resistance value is 60m Ω, and existing three branches break down, are followed successively by：12 branches become 300m Ω, and 78 branches become 600m Ω, 1115 branch become 900m Ω.Fig. 4~8 are the quasi member that the Grounding net topology structural stratification yojan obtains respectively Column, first column, metanetwork, can and grounded screen and intrinsic grounded screen, Fig. 9 be that grounded screen divides administrative division map.Then according to accurate first version Block yojan is the process of intrinsic grounded screen, successively traces back every branch in intrinsic grounded screen to grounded screen, every branch in Fig. 8 Shown in the correspondence situation table 1 converted by ground connection web area.
1 intrinsic branch of table situation corresponding with ground connection web area
Ground connection pessimistic concurrency control is built in Multisim, applies the continuous current excitation of 10A, according to ideal optimal abundant test side Case selects measurement port, and the port resistive situation of change for measuring intrinsic grounded screen before and after failure is as shown in table 2.
2 intrinsic grounded screen port resistive situation of change of table
Using the method for the invention, diagnosis equation group is established, least square is applied in Matlab calculation procedures Iterative algorithm is solved, and it is as shown in Figure 10 to obtain diagnostic result.
From diagnostic result as can be seen that obvious fault, wherein branch 25 electricity occur in branch 25,78,1114,1116 Resistance is increased to original 2.5 times, and branch 78 resistance is increased to original 9.4 times, and branch 1114 resistance is increased to original 10.6 times, branch Road 1116 resistance is increased to original 1.9 times, and the region of grounded screen is corresponded to according to branch, it can be determined that 1., 4., 5., 9.,Area There are fault branches in domain.Since 4., 9. other branches of the intrinsic grounded screen corresponding to region do not have failure, so 4., 9. Region is pseudo fault zone.Therefore, in grounded screen there are the region of failure be 1., 5.,, and 1. region is minor failure, 5.,For more serious failure.The diagnostic result is consistent with the case where actual set, illustrates that the method for diagnosing faults of this paper can be just The fault condition being really diagnosed to be in smallsized grounded screen each region.
Disclosed above is only several specific embodiments of the present invention, but the present invention is not limited to this, any this field Technical staff can think variation, should all be within the scope of the present invention.
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