CN112462195A - Small current fault positioning method based on fault characteristic value - Google Patents

Abstract

The invention discloses a fault characteristic value-based small current fault positioning method, which comprises the following steps: step S10, periodically collecting three-phase and zero-mode voltage signals by each line terminal in the power distribution network, and detecting whether the line has a single-phase earth fault; step S11, each line terminal obtains a fault waveform, and a fault characteristic value corresponding to each line terminal is calculated; step S12, each line terminal uniformly uploads the fault characteristic values carrying address information and time labels to a main control terminal; and step S13, the main controller positions the line fault according to the predetermined fault unified judgment strategy according to all fault characteristic values and the topology identification matrix corresponding to the line. The invention can simplify the fault positioning process and the data transmission quantity between the terminals and improve the positioning efficiency.

Description

Small current fault positioning method based on fault characteristic value

Technical Field

The invention belongs to the technical field of fault location, and particularly relates to a fault characteristic value-based low-current fault location method.

Background

The neutral point of the distribution network in China is widely operated in a non-grounded or arc suppression coil grounding mode, when a single-phase (small current) grounding fault occurs in a line, a fault signal is weak and is difficult to detect, and the grounding fault accounts for a high proportion of the faults of the distribution network; in addition, the distribution network side load distribution randomness, the topology complexity, the data processing scale and the like are continuously enlarged, and the fault processing difficulty is increased, so that the single-phase earth fault positioning speed is increased, the fault occurrence time is shortened, and the method becomes a research hotspot of the fault processing of the distribution network. The fault indicator is used as an effective means for section positioning and is widely applied to a power distribution network, but a centralized fault positioning mode needs reliable coordination of the fault indicator, a communication system, a substation or a main station, the participation links are many, the fault processing time is long, the dependence degree of the main station is high, and in field practical application, the limitation of software property rights, system management authorities and the like exists.

The low-current ground fault is mainly divided into a centralized control mode and an intelligent distributed control mode according to different fault location modes. In the centralized control mode, fault information is collected by line terminals (FTUs or fault indicators) installed along the line and is uniformly uploaded to a distribution automation main station, and the main station executes a fault positioning algorithm to determine a fault section. Fault location is realized by comparing the correlation or energy similarity of transient zero-sequence current waveforms between adjacent terminals in a time domain; giving a fault positioning method based on a matrix by using a transient zero sequence current phase relation; the method only needs to detect zero sequence current signals, has strong adaptability, needs to upload a large amount of wave recording data to a main station for centralized processing, and has the advantages of multiple participation links, high communication cost and large data centralized processing pressure.

The existing small current ground fault positioning method based on current similarity is a common method for determining a fault section by using the characteristics of low similarity degree of transient zero-mode currents on two sides of the fault section and high similarity degree of transient zero-mode currents on two sides of a healthy section, and is called as a zero-sequence current similarity method. However, there are some disadvantages, specifically, in engineering, it is difficult to record the transient current signal accurately and synchronously between the monitoring points on the line, each line monitoring point needs to upload the fault recording data to the master station, the transmission data volume is large, and the communication pressure is large. The positioning algorithm of the master station is complex, and the matching of products of different manufacturers has certain difficulty.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a fault characteristic value-based low-current fault positioning method, which can simplify the fault positioning process and the data transmission quantity between terminals and improve the positioning efficiency.

The technical scheme adopted by the invention is that a fault characteristic value-based small current fault positioning method is provided, and the method comprises the following steps:

step S10, periodically collecting three-phase and zero-mode voltage signals by each line terminal in the power distribution network, and detecting whether the line has a single-phase earth fault;

step S11, each line terminal obtains a fault waveform, performs fitting and correction on the fault waveform, and calculates a fault characteristic value corresponding to each line terminal;

step S12, each line terminal uniformly uploads the fault characteristic values carrying address information and time labels to a main control terminal;

step S13, the main control locates the line fault according to the predetermined fault unified judgment strategy according to all fault characteristic values and the topology identification matrix corresponding to the line;

and step S14, the main control terminal uploads the positioning result to the main station or the mobile equipment of the operation and maintenance personnel.

Preferably, the step S10 further includes:

step S100, when the system operates normally, each line terminal in the power distribution network periodically collects three-phase and zero-mode voltage signals, and whether the mutation quantity of 2 or more sampling points in 3 continuous sampling points meets the following conditions is compared:

|u₀(n)-u₀(n-mT)|≥k_rel|u₀(n-mT)|

wherein u is₀(n) is the instantaneous voltage value of the nth sampling point of the zero-sequence current; u. of₀(n-mT) is an instantaneous voltage value corresponding to the nth sampling point of the zero-sequence current before m power frequency cycle waves T, and the value of m is 1; the moment corresponding to the nth sampling point is called the fault starting moment t₀，k_relThe value range is 1-5 for the reliability coefficient;

step S101, checking fault recording data according to the following formula, and if the fault recording data meet the formula, determining that a fault occurs; if not, returning to the step S100 to continue monitoring;

|I₀(t₀+2T)-I₀(t₀+T)|-|I₀(t₀-2T)-I₀(t₀-T)|>k_actI_act

wherein, I₀(t₀+2T) is T₀The effective value of the second cycle zero sequence current, the meaning of the formula is t₀The difference between the effective values of the last two cycles and t₀The difference of the difference between the effective values of the first two cycles; the effective value calculation formula is as follows:

preferably, the step S11 further includes:

line termination fetch t₀Acquiring low-frequency waveforms through a low-pass filter according to the last three power frequency cycle zero-sequence current recording data, judging the positive and negative slopes of the previous sampling point of the first extreme point, and fitting and correcting fault waveforms according to a curve fitting principle;

cutting off a fitting curve t₀Calculating the fault characteristic value according to the following formula from the data of the second half cycle or the first zero crossing point;

S_i(n)＝i₀(n)-4i₀(n-1)+6i₀(n-2)-4i₀(n-3)+i₀(n-4)

wherein S is_iAnd (n) is the i-order difference of the signals, namely the fault characteristic value.

Preferably, the step S13 further includes:

step S130, when the line normally runs, the terminal where the transformer substation is located issues a topology query command to the line terminal, obtains the topology information of the line terminal on the outgoing line in a step-by-step query mode, and forms a topology description matrix D; the method comprises the following steps that each line terminal in a control domain is used as a node to uniformly code address information of the line terminal, and meanwhile, the positive power flow direction is set to be the positive direction of a main line and each branch line; if there are n lines of nodes, an n × n square matrix is constructed, matrix D_n×nElement d in (1)_ijThe definition is as follows:

step S131, the main control terminal receives the sudden change eigenvalue uploaded by each line terminal in the centralized control domain, and a fault information diagonal matrix G is formed, wherein the definition formula of G is as follows:

G＝Diag[S_m]

wherein S is_mIs the aforementioned S_i(n) corresponding values;

step S132, a fault judgment matrix P is obtained by adding the topology description matrix D and the fault information matrix G, namely:

P＝D+G

step S133, finding a fault path by using the fault matrix P and combining a predetermined fault unified determination policy, and determining a section where the fault is located.

Preferably, the step S133 is specifically:

if p is_ii>0(p_ii<0)，p_ij1 is ═ 1; if p is_jj<0(p_jj>0) If yes, judging that the fault is positioned between the node i and the node j;

if p is_ii>0(p_ii<0)，p_ij1 and p_ik1 is ═ 1; if p is_jj<0(p_jj>0) And p is_kk<0(p_kk>0) If yes, judging that the fault is positioned among the nodes i, j and k;

if p is_jj<0(p_jj>0) But p is_kk>0(p_kk<0) If yes, judging that the fault is positioned at the downstream of the node k;

if p is satisfied in both of the failure finding paths_ii>0(p_ii<0) Then it is determined that the point of failure is downstream of the last node of the path.

Preferably, further comprising: and if the fault position is judged to be in the current area, performing fault isolation operation.

The implementation of the invention has the following beneficial effects:

in the embodiment of the invention, a line monitoring point does not need to exchange recording data any more, and fault information can be converted into a fault characteristic value through local data processing, so that the data transmission quantity between a fault positioning process and terminals is simplified, the time synchronization precision requirement between the terminals is reduced, and the positioning efficiency is improved;

the invention does not depend on zero-mode voltage or line voltage, only needs a zero-mode current signal, has small data transmission quantity and can adapt to all detection points and communication modes. .

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is within the scope of the present invention for those skilled in the art to obtain other drawings based on the drawings without inventive exercise.

Fig. 1 is a schematic main flow diagram of an embodiment of a fault characteristic value-based low-current fault location method provided by the present invention;

FIG. 2 is a more detailed flowchart of step S13 in FIG. 1;

FIG. 3 is a schematic diagram of the topology query principle involved in FIG. 1;

fig. 4 is a timing diagram of a cooperation process between the main control terminal and the line terminal referred to in fig. 1;

fig. 5 is a more detailed flow chart of an embodiment to which the present invention relates.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.

For those skilled in the art to more clearly understand the objects, technical solutions and advantages of the present invention, the following description will be further provided in conjunction with the accompanying drawings and examples.

As shown in fig. 1, a schematic structural diagram of an embodiment of a fault characteristic value-based small current fault location method provided by the present invention is shown, and is shown in fig. 2 to fig. 5, in this embodiment, the method includes the following steps:

step S10, periodically collecting three-phase and zero-mode voltage signals by each line terminal in the power distribution network, and detecting whether the line has a single-phase earth fault;

specifically, in one example, the step S10 further includes:

step S100, when the system operates normally, each line terminal in the power distribution network periodically collects three-phase and zero-mode voltage signals, and whether the mutation quantity of 2 or more sampling points in 3 continuous sampling points meets the following conditions is compared:

|u₀(n)-u₀(n-mT)|≥k_rel|u₀(n-mT)|

wherein u is₀(n) is the instantaneous voltage value of the nth sampling point of the zero-sequence current; u. of₀(n-mT) is an instantaneous voltage value corresponding to the nth sampling point of the zero-sequence current before m power frequency cycle waves T, and the value of m is 1; the moment corresponding to the nth sampling point is called the fault starting moment t₀，k_relThe value range is 1-5 for the reliability coefficient;

step S101, checking fault recording data according to the following formula, and if the fault recording data meet the formula, determining that a fault occurs; if not, returning to the step S100 to continue monitoring;

|I₀(t₀+2T)-I₀(t₀+T)|-|I₀(t₀-2T)-I₀(t₀-T)|>k_actI_act

wherein, I₀(t₀+2T) is T₀Effective value, k, of zero-sequence current of the second cycle_actFor starting the sensitivity coefficient, it is usually set according to the unbalanced voltage level of the system, and 1, I is usually taken_actThe starting current threshold value is in a value range of (0.15-0.3) I₀The meaning of the formula is t₀The difference between the effective values of the last two cycles and t₀The difference of the difference between the effective values of the first two cycles; the effective value calculation formula is as follows:

wherein T is the period of power frequency signal, I_0kIs the effective value of zero sequence current i_0kIs the instantaneous value of the zero sequence current.

Step S11, each line terminal obtains a fault waveform, performs fitting and correction on the fault waveform, and calculates a fault characteristic value corresponding to each line terminal;

specifically, in one example, the step S11 further includes:

line termination fetch t₀Acquiring low-frequency waveforms through a low-pass filter according to the last three power frequency cycle zero-sequence current recording data, judging the positive and negative slopes of the previous sampling point of the first extreme point, and fitting and correcting fault waveforms according to a curve fitting principle;

cutting off a fitting curve t₀Calculating the fault characteristic value according to the following formula from the data of the second half cycle or the first zero crossing point;

S_i(n)＝i₀(n)-4i₀(n-1)+6i₀(n-2)-4i₀(n-3)+i₀(n-4)

wherein S is_i(n) is the i-th order difference of the signals, i₀And (n) is the instantaneous value of the zero-sequence current of n points.

It is understood that the fault characteristic value calculation formula is obtained based on the following principle:

according to the characteristics of the ground fault, the polarity of transient zero-mode current on the upstream and downstream of a fault point is opposite, the characteristic that the sudden change direction of a fitting curve is opposite, and the fault characteristics are defined by using the transformation of a mathematical algorithm SOD (SOD). The SOD is a high-order differential method, and the higher the differential order is, the more the calculation result can reflect the mutation direction of the high-frequency transient quantity of the signal, and the definition formula is:

in the formula, m is the order of difference; s_m(n) is the m-order difference of the signals; q (n) is the original fault signal; (c)_j)_mIs SOD transformation coefficient. (c)_j)_mThe value of the coefficient is (c)₁)_m＝(c_m+1)_m＝1，(c₂)_m＝m，(c_j)_m＝(c_j)_m-1+(c_j-1)_m-1，∑(-1)^j+1(c_j)_m＝0。

The invention takes the application effect and the actual operation capability of the monitoring equipment into comprehensive consideration, and selects a 4-order difference series, wherein the calculation formula is as follows:

S_i(n)＝i₀(n)-4i₀(n-1)+6i₀(n-2)-4i₀(n-3)+i₀(n-4)

if a positive angle fault occurs, if Si (n)>0, judging that the detection point i is positioned at the upstream of the fault point, otherwise, the detection point i is positioned at the downstream section; if Si (n) occurs when a negative angle fault occurs<And 0, judging that the detection point i is positioned at the upstream of the fault point, otherwise, judging that the detection point i is positioned at the downstream section. Namely, the signs of Si (n) at the upstream and downstream of a fault point at any angle are opposite, the transient zero-sequence current mutation direction can be accurately reflected, so that S is converted into S_iDefined as the characteristic value of the mutation amount. Under normal conditions, selecting half power frequency cycle of fitting curve as S_iThe calculated data window of (1); considering that under certain fault conditions, the non-periodic components in the zero-sequence current are more, so that the fitting waveform has zero-crossing points, and S is reduced_iThe calculated point number and the offset effect of the sampling point in the reverse direction under the fixed data window on the characteristic value are obtained, and the fitting curve 0S is intercepted to the first zero crossing point data set for calculation S_i。

Step S12, each line terminal uniformly uploads the fault characteristic values carrying address information and time labels to a main control terminal;

step S13, the main control locates the line fault according to the predetermined fault unified judgment strategy according to all fault characteristic values and the topology identification matrix corresponding to the line;

specifically, as shown in fig. 2, in one example, the step S13 further includes:

step S130, circuitWhen the system normally operates, a terminal where a transformer substation is located issues a topology query command to a line terminal, an outlet monitoring terminal serves as a main control line terminal of the feeder line, topology information of the line terminal on the outgoing line is obtained in a step-by-step query mode, and a topology description matrix D is formed; the method comprises the following steps that each line terminal in a control domain is used as a node to uniformly code address information of the line terminal, and meanwhile, the positive power flow direction is set to be the positive direction of a main line and each branch line; if there are n lines of nodes, an n × n square matrix is constructed, matrix D_n×nElement d in (1)_ijThe definition is as follows:

as shown in fig. 3, the final topology query result includes 6 nodes, and the network description matrix D is determined by the above principle as follows:

wherein the rows and columns of the matrix D each represent a node, referred to herein by the action, e.g. element D₁₂1, the terminal corresponding to the node 1 and the node 2 is adjacent; if two elements equal to 1 appear in the second row at the same time, the position of the node 2 can be judged to be a T-shaped wiring; and the row 3 and row 6 elements are both 0, then the node can be determined to be an end node. In addition, it should be noted that in the actual application process, it is not necessary to number the IP address of the terminal in sequence from the first terminal, and the IP address of the terminal only needs to be corresponding to the number, so that the IP address can be numbered out of sequence.

Step S131, the main control terminal receives the sudden change eigenvalue uploaded by each line terminal in the centralized control domain, and a fault information diagonal matrix G is formed, wherein the definition formula of G is as follows:

G＝Diag[S_m]

wherein S is_mIs the aforementioned S_i(n) corresponding values;

step S132, a fault judgment matrix P is obtained by adding the topology description matrix D and the fault information matrix G, namely:

P＝D+G

here, the fusion of the topological structure and the fault characteristic value is realized;

step S133, finding a fault path by using the fault matrix P and combining a predetermined fault unified determination policy, and determining a section where the fault is located.

Preferably, the step S133 is specifically:

if p is_ii>0(p_ii<0)，p_ij1 is ═ 1; if p is_jj<0(p_jj>0) If yes, judging that the fault is positioned between the node i and the node j;

if p is_ii>0(p_ii<0)，p_ij1 and p_ik1 is ═ 1; if p is_jj<0(p_jj>0) And p is_kk<0(p_kk>0) If yes, judging that the fault is positioned among the nodes i, j and k;

if p is_jj<0(p_jj>0) But p is_kk>0(p_kk<0) If yes, judging that the fault is positioned at the downstream of the node k;

if p is satisfied in both of the failure finding paths_ii>0(p_ii<0) Then it is determined that the point of failure is downstream of the last node of the path.

And step S14, the main control terminal uploads the positioning result to the main station or the mobile equipment of the operation and maintenance personnel.

Specifically, the method further comprises the following steps: and if the fault position is judged to be in the current area, performing fault isolation operation.

It can be understood that, in the present invention, the mode adopted for distributed fault location is a master-slave control mode, as shown in fig. 4, the line terminal collects fault information, calculates the fault characteristic value in situ according to the fault location algorithm, and then uploads the fault characteristic value to the master control terminal in a unified manner; and the master control terminal realizes fault positioning by combining the topological structure and the fault unified criterion. The method avoids remote transmission of a large amount of wave recording data in the traditional master-slave control mode, reduces the operation pressure of centralized processing of the master control terminal, and can exert the advantages of the master-slave control mode. The decision terminals only receive the fault characteristic values at last, so that the data processing pressure of the master control terminal is reduced; the latter positioning mode has little uploading amount of information from the terminal.

The implementation of the invention has the following beneficial effects:

the invention provides a low-current fault positioning method based on fault characteristic values. The fault information can be converted into the fault characteristic value through local data processing without exchanging fault full information between adjacent terminals, so that the time synchronization precision requirement between the terminals is reduced, the fault positioning process and the data transmission quantity between the terminals are simplified, and the positioning efficiency is improved.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims (6)

1. A fault characteristic value-based low-current fault positioning method is characterized by comprising the following steps:

step S10, periodically collecting three-phase and zero-mode voltage signals by each line terminal in the power distribution network, and detecting whether the line has a single-phase earth fault;

step S11, each line terminal obtains a fault waveform, performs fitting and correction on the fault waveform, and calculates a fault characteristic value corresponding to each line terminal;

step S12, each line terminal uniformly uploads the fault characteristic values carrying address information and time labels to a main control terminal;

step S13, the main control locates the line fault according to the predetermined fault unified judgment strategy according to all fault characteristic values and the topology identification matrix corresponding to the line;

and step S14, the main control terminal uploads the positioning result to the main station or the mobile equipment of the operation and maintenance personnel.

2. The method of claim 1, wherein the step S10 further comprises:

step S100, when the system operates normally, each line terminal in the power distribution network periodically collects three-phase and zero-mode voltage signals, and whether the mutation quantity of 2 or more sampling points in 3 continuous sampling points meets the following conditions is compared:

|u₀(n)-u₀(n-mT)|≥k_rel|u₀(n-mT)|

wherein u is₀(n) is the instantaneous voltage value of the nth sampling point of the zero-sequence current; u. of₀(n-mT) is an instantaneous voltage value corresponding to the nth sampling point of the zero-sequence current before m power frequency cycle waves T, and the value of m is 1; the moment corresponding to the nth sampling point is called the fault starting moment t₀，k_relThe value range is 1-5 for the reliability coefficient;

step S101, checking fault recording data according to the following formula, and if the fault recording data meet the formula, determining that a fault occurs; if not, returning to the step S100 to continue monitoring;

|I₀(t₀+2T)-I₀(t₀+T)|-|I₀(t₀-2T)-I₀(t₀-T)|>k_actI_act

wherein, I₀(t₀+2T) is T₀The effective value of the second cycle zero sequence current, the meaning of the formula is t₀The difference between the effective values of the last two cycles and t₀The difference of the difference between the effective values of the first two cycles; the effective value calculation formula is as follows:

3. the method of claim 2, wherein the step S11 further comprises:

line termination fetch t₀Obtaining low-frequency waveform through a low-pass filter from the last three power frequency cycle zero-sequence current recording data, judging whether the slope of the previous sampling point of the first extreme point is positive or negative, and fitting the curve to the fault according to the principle of fitting the curveFitting and correcting the waveform;

cutting off a fitting curve t₀Calculating the fault characteristic value according to the following formula from the data of the second half cycle or the first zero crossing point;

S_i(n)＝i₀(n)-4i₀(n-1)+6i₀(n-2)-4i₀(n-3)+i₀(n-4)

wherein S is_iAnd (n) is the i-order difference of the signals, namely the fault characteristic value.

4. The method of claim 3, wherein the step S13 further comprises:

step S130, when the line normally runs, the terminal where the transformer substation is located issues a topology query command to the line terminal, obtains the topology information of the line terminal on the outgoing line in a step-by-step query mode, and generates a topology description matrix D; the method comprises the following steps that each line terminal in a control domain is used as a node to uniformly code address information of the line terminal, and meanwhile, the positive power flow direction is set to be the positive direction of a main line and each branch line; if there are n lines of nodes, an n × n square matrix is constructed, matrix D_n×nElement d in (1)_ijThe definition is as follows:

step S131, the main control terminal receives the sudden change eigenvalue uploaded by each line terminal in the centralized control domain, and a fault information diagonal matrix G is formed, wherein the definition formula of G is as follows:

G＝Diag[S_m]

wherein S is_mIs the aforementioned S_i(n) corresponding values;

step S132, a fault judgment matrix P is obtained by adding the topology description matrix D and the fault information matrix G, namely:

P＝D+G

step S133, finding a fault path by using the fault matrix P and combining a predetermined fault unified determination policy, and determining a section where the fault is located.

5. The method according to claim 4, wherein the step S133 is specifically:

if p is_ii>0(p_ii<0)，p_ij1 is ═ 1; if p is_jj<0(p_jj>0) If yes, judging that the fault is positioned between the node i and the node j;

if p is_ii>0(p_ii<0)，p_ij1 and p_ik1 is ═ 1; if p is_jj<0(p_jj>0) And p is_kk<0(p_kk>0) If yes, judging that the fault is positioned among the nodes i, j and k;

if p is_jj<0(p_jj>0) But p is_kk>0(p_kk<0) If yes, judging that the fault is positioned at the downstream of the node k;

if p is satisfied in both of the failure finding paths_ii>0(p_ii<0) Then it is determined that the point of failure is downstream of the last node of the path.

6. The method of any of claims 1 to 5, further comprising: and if the fault position is judged to be in the current area, performing fault isolation operation.

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