CN105929297A - Ground fault line selection method based on high-frequency component correlation - Google Patents

Abstract

The invention discloses a baseThe method for selecting the line of the ground fault with the high-frequency component correlation degree comprises the following steps: s1: monitoring zero sequence voltage values of outlets of the distribution lines in real time; if the zero sequence voltage value is larger than the limit value, determining that the power distribution network has a ground fault, and collecting the zero sequence current of each line; s2: carrying out noise elimination treatment on the zero sequence current of each line to obtain a pure fault component; s3: EMD decomposition is carried out on the pure fault components to obtain various transient frequency components, then, power frequency components are removed through transient frequency analysis, and corresponding high-frequency transient components are extracted; s4: carrying out pairwise correlation analysis on the high-frequency transient components of each line to obtain a correlation coefficient matrix M, and solving a comprehensive correlation coefficient rho of each line_i. The invention has the advantages of simple principle, anti-interference capability, high protection precision and the like.

Description

A kind of ground fault line selecting method based on high fdrequency component degree of association

Technical field

Present invention relates generally to power distribution network grounding technology field, refer in particular to a kind of earth fault line selection based on high fdrequency component degree of association Method.

Background technology

China's power distribution network widely used neutral non-effective grounding mode, this operation can be effectively increased the reliability of power supply, but During its singlephase earth fault, fault residual flow is little, the impact of factor, earth-fault protection precision and poor reliability, the choosing such as is disturbed Line accuracy rate is the most relatively low.

Existing method based on steady-state signal route selection mainly includes that zero-sequence current is than width phase comparing method, negative-sequence current method, Harmonic Method etc.. Generally speaking, steady state method main difficulty is that fault current is faint, easily by the shadow of the factors such as earthing mode, arc suppression coil overcompensation Ringing, the signal reliability therefore recorded is the highest, even produces erroneous judgement, the phenomenon failed to judge.It is artificially injected during method is applied at the scene and has Certain effect, but instantaneity and intermittent defect can not be detected, and need to increase signal injection device, investment is big.Transient state is believed Number method is obvious due to fault signature, and is not affected by arc suppression coil and electric arc instability, has the advantage that detection sensitivity is high, And become the focus of Recent study.

The transient characterisitics of fault are analyzed the most deep by the method for existing transient state earth-fault protection, and majority is the most from different perspectives Transient characterisitics are done general analysis, has lacked comprehensive analysis.Wherein have than more typical: 1. utilize zero-sequence current route selection method, But cause wave distortion easily to bring route selection to lose efficacy due to CT saturation when in zero-sequence current containing relatively strong DC component Problem, therefore, if not being acted upon, can cause the erroneous judgement of route selection.2. utilize wavelet analysis to carry out route selection, but wavelet analysis is not Possess adaptivity, and easily affected by the factor such as wavelet basis function and decomposition scale.3. characteristic spectra is utilized to select Line, but owing to transient frequency content is affected by the many factors such as network parameter, fault moment, the feature of different circuit transients Frequency range distribution is the most completely the same.

Summary of the invention

The technical problem to be solved in the present invention is that the technical problem existed for prior art, and the present invention provides a kind of principle Simply, capacity of resisting disturbance, ground fault line selecting method based on high fdrequency component degree of association that protection precision is high.

For solve above-mentioned technical problem, the present invention by the following technical solutions:

A kind of ground fault line selecting method based on high fdrequency component degree of association, the steps include:

S1: monitoring distribution line outlet residual voltage value in real time；If residual voltage value is more than limit value, then it is judged to power distribution network There is earth fault, gather the zero-sequence current of each circuit；

S2: obtain pure fault component after the zero-sequence current of each circuit is carried out denoising Processing；

S3: pure fault component is carried out EMD decomposition, obtains various transient frequency component IMF1, IMF2 ..., then passes through Instantaneous frequency is analyzed, and rejects power frequency component, extracts corresponding high frequency transient component；

S4: each circuit high frequency transient component is carried out correlation analysis two-by-two, obtains correlation matrix M, obtain each circuit Integrated correlation coefficient ρ_i, wherein i=1,2 ..., n represent circuit number；Work as ρ_max-ρ_min>ρ_setTime, it is determined that ρ_minInstitute is right The circuit answered is faulty line；Work as ρ_max-ρ_min<ρ_setTime, it is determined that bus-bar fault；Wherein ρ_minMinimum for integrated correlation coefficient Value, ρ_maxFor integrated correlation coefficient maximum, ρ_setFor integrated correlation coefficient setting value.

Concretely comprising the following steps of described step S3:

S301: utilizing EMD adaptive by the fluctuation of different scale in signal or trend decomposition step by step out, obtaining one is The data sequence of row different frequency yardstick, each sequence is an intrinsic mode function IMF, and frequency the most from high to low, is counted The formula calculated is as follows:

$s\left(t\right)=\underset{i=1}{\overset{n}{\&Sigma;}}{c}_i+r$

Component c in above formula₁、c₂、...、c_nBeing respectively input signal medium frequency different frequency range composition from high to low, r is for averagely to take advantage of Gesture；

S302: utilize Hilbert conversion to carry out instantaneous frequency analysis to decompositing each frequency component, reject power frequency by frequency characteristic Component and the DC component of decay, obtain one of transient characteristic quantity the most substantially high fdrequency component.

As a further improvement on the present invention: concretely comprising the following steps of described step S4:

S401: each circuit high fdrequency component waveform is carried out Controlling UEP, and the similarity of two waveforms is described by correlation coefficient, Its computing formula is:

$\mathrm{\&rho;}=\frac{\underset{n=1}{\overset{N}{\&Sigma;}}x\left(n\right)y\left(n\right)}{\sqrt{\underset{n=1}{\overset{N}{\&Sigma;}}{x}^2\left(n\right)\underset{n=1}{\overset{N}{\&Sigma;}}{y}^2\left(n\right)}}$

In formula, x (n), y (n) are 2 discrete signal sequences, and corresponding transient high-frequency component sampled value, N represents discrete sample signals sequence Length；

S402: under same data window, carries out correlation analysis two-by-two to each circuit transient high-frequency component, obtains correlation coefficient square Battle array:

$M=\left[\begin{array}{cccc}{\mathrm{\&rho;}}_{11}& {\mathrm{\&rho;}}_{12}& L& {\mathrm{\&rho;}}_{1n}\\ {\mathrm{\&rho;}}_{21}& {\mathrm{\&rho;}}_{22}& L& {\mathrm{\&rho;}}_{2n}\\ M& M& O& M\\ {\mathrm{\&rho;}}_{n1}& {\mathrm{\&rho;}}_{n2}& L& {\mathrm{\&rho;}}_{nn}\end{array}\right]$

ρ in formula_ijFor the correlation coefficient of transient high-frequency component between each circuit, n is the bar number of circuit；

S403: correlation matrix M is done normalized, obtains each circuit integrated correlation coefficient, and formula is as follows:

${\mathrm{\&rho;}}_i=\frac{1}{N-1}\underset{j=1,j\&NotEqual;i}{\overset{N}{\&Sigma;}}{\mathrm{\&rho;}}_{ij}$

ρ in formula_iFor each circuit integrated correlation coefficient, ρ_ijFor the correlation coefficient between circuit, N is the number of lines.

As a further improvement on the present invention: in described step S2, when residual voltage is more prescribed a time limit, each before and after gathering fault moment The zero-sequence current in 1/4 cycle, after subtracting each other, obtains pure fault component；The described residual voltage sudden change moment is that fault occurs the moment.

As a further improvement on the present invention: in described step S1, the span of described voltage limit is the electricity mutually of 15% Pressure.

Compared with prior art, it is an advantage of the current invention that:

1, the ground fault line selecting method based on high fdrequency component degree of association of the present invention, only need to measure the voltage of protected object, electricity Stream, it is easy to accomplish；Fully utilize amplitude and the phase property of each high frequency transient component, using the size of correlation coefficient as route selection Criterion, eliminates the impact of asymmetrical component, system noise and power frequency component effectively, has computing simple, practical Feature, further increase the nargin of route selection；And not by the shadow of the factors such as system operation mode, transition resistance, fault moment Ring.

2, the ground fault line selecting method based on high fdrequency component degree of association of the present invention, is the deficiency for tradition selection method, On the basis of low current grounding transient signal feature analysis, by HHT conversion when analyzing non-linear, non-stationary signal Good Time-Frequency Localization characteristic, utilizes EMD to decompose circuit zero-sequence current each after fault, obtains frequency from high to low Each frequency content so that extract the features such as its corresponding phase and amplitude of high fdrequency component, under certain data window, it is carried out Controlling UEP.The method of the present invention is not affected by the method for operation, it is possible to eliminate power frequency component, system noise, not to component Interference, realize fault line detection exactly, there is capacity of resisting disturbance, protection precision high.

Accompanying drawing explanation

Fig. 1 is the schematic flow sheet of the inventive method.

Fig. 2 is present invention experimental principle schematic diagram in concrete application example.

Detailed description of the invention

Below with reference to Figure of description and specific embodiment, the present invention is described in further details.

As it is shown in figure 1, the ground fault line selecting method based on high fdrequency component degree of association of the present invention, the steps include:

S1: monitoring distribution line outlet residual voltage value in real time；If residual voltage value is more than limit value, then it is judged to power distribution network There is earth fault, gathered the zero-sequence current of each circuit by FTU；The residual voltage sudden change moment is that fault occurs the moment；

S2: obtain pure fault component after the zero-sequence current of each circuit is carried out denoising Processing；

S3: pure fault component is carried out EMD decomposition, obtains various transient frequency component IMF1, IMF2 ..., then passes through Instantaneous frequency is analyzed, and rejects power frequency component, extracts corresponding high fdrequency component；

S4: each circuit high frequency transient component is carried out correlation analysis two-by-two, obtains correlation matrix M, obtain each circuit Integrated correlation coefficient ρ_i(i=1,2 ..., n represent circuit number).Work as ρ_max-ρ_min>ρ_setTime, it is determined that ρ_minCorresponding Circuit is faulty line；Work as ρ_max-ρ_min<ρ_setTime, it is determined that bus-bar fault.

As preferred embodiment, in step S1 of this example, the span of voltage limit is the phase voltage of 15%.

When specifically applying, in step S3 of this example, utilize EMD adaptive by the fluctuation of different scale in signal or become Gesture decomposition step by step out, obtains the data sequence of a series of different frequency yardstick, and each sequence is an intrinsic mode function IMF, the most from high to low, the formula of calculating is as follows for frequency:

$s\left(t\right)=\underset{i=1}{\overset{n}{\&Sigma;}}{c}_i+r$

Component c in above formula₁、c₂、...、c_nBeing respectively input signal medium frequency different frequency range composition from high to low, r is for averagely to take advantage of Gesture.

Then, recycling Hilbert conversion carries out instantaneous frequency analysis to decompositing each frequency component, rejects work by frequency characteristic Frequency component and the DC component of decay, obtain one of transient characteristic quantity the most substantially high fdrequency component.

When specifically applying, in step S4 of this example, each circuit high fdrequency component waveform is carried out Controlling UEP, two waveforms Similarity can be described by correlation coefficient, its computing formula is:

$\mathrm{\&rho;}=\frac{\underset{n=1}{\overset{N}{\&Sigma;}}x\left(n\right)y\left(n\right)}{\sqrt{\underset{n=1}{\overset{N}{\&Sigma;}}{x}^2\left(n\right)\underset{n=1}{\overset{N}{\&Sigma;}}{y}^2\left(n\right)}}$

In formula, x (n), y (n) are 2 discrete signal sequences, and corresponding transient high-frequency component sampled value, N represents discrete sample signals sequence Length.

Under same data window, each circuit transient high-frequency component is carried out correlation analysis two-by-two, obtains correlation matrix:

$M=\left[\begin{array}{cccc}{\mathrm{\&rho;}}_{11}& {\mathrm{\&rho;}}_{12}& L& {\mathrm{\&rho;}}_{1n}\\ {\mathrm{\&rho;}}_{21}& {\mathrm{\&rho;}}_{22}& L& {\mathrm{\&rho;}}_{2n}\\ M& M& O& M\\ {\mathrm{\&rho;}}_{n1}& {\mathrm{\&rho;}}_{n2}& L& {\mathrm{\&rho;}}_{nn}\end{array}\right]$

ρ in formula_ijFor the correlation coefficient of transient high-frequency component between each circuit, n is the bar number of circuit.

Finally, correlation matrix M being done normalized, obtain each circuit integrated correlation coefficient, formula is as follows:

${\mathrm{\&rho;}}_i=\frac{1}{N-1}\underset{j=1,j\&NotEqual;i}{\overset{N}{\&Sigma;}}{\mathrm{\&rho;}}_{ij}$

ρ in formula_iFor each circuit integrated correlation coefficient, ρ_ijFor the correlation coefficient between circuit, N is the number of lines.

From the foregoing, it will be observed that the present invention realizes on the spot by making proposed guard method be suitable on distribution power automation terminal unit, select The transient zero-sequence current of each circuit of In situ Measurement, residual voltage.When residual voltage more in limited time, gather before and after fault moment each 1/4 The zero-sequence current in individual cycle, after subtracting each other, obtains pure fault component；Decomposed by EMD again and Hibert instantaneous frequency is analyzed Obtain the transient high frequency fault signature component of each circuit: the high fdrequency component of each circuit.Calculate comprehensive by Waveform Correlation analysis meter again Close correlation coefficient ρ_i, work as ρ_max-ρ_min>ρ_setTime, ρ_minCorresponding circuit is judged to faulty line, works as ρ_max-ρ_min<ρ_set Time, it is determined that for bus-bar fault.

As in figure 2 it is shown, in a concrete application example, with L on bus₁、L₂、L₃、L₄Article four, feeder line, L₁For 20km Overhead transmission line, L₂For the cable run of 10km, L₃For joint line, by overhead transmission line and the cable run of 5km of 10km Composition, L₄For the overhead transmission line of 30km, export protection device for installing at each feeder line.Present invention 10.5kV as shown in Figure 1 joins Electricity system is tested, and feeder line parameter is shown in Table 1.

Table 1

Point Not with circuit L₁、L₂And bus (includes fault distance, earth resistance, fault initial phase angle etc.) under the conditions of different faults and occurs Carrying out experiment test during singlephase earth fault, the protection device being arranged on line port obtains the transient zero-sequence current signal of each circuit； After pretreatment de-noising, extract transient high frequency fault characteristic value, it is carried out correlation analysis, obtain comprehensive phase relation Number ρ_i。

In ground fault protection method of distribution network test process, taking residual voltage setting valve is 10% phase voltage.Route selection result is such as Shown in table 2.

Table 2

As known from Table 2, the most under what circumstances, the integrated correlation coefficient of faulty line is respectively less than 0, much smaller than All other routes Integrated correlation coefficient, it is easy to determine faulty line.During bus-bar fault, each circuit integrated correlation coefficient is more or less the same, its The difference of maximum and minima is respectively less than setting value, therefore, can determine that as bus-bar fault.Test result indicate that, the side of the present invention Method is not changed by transition resistance, fault moment and system operation mode to be affected, and has higher accuracy, effectiveness and reliable Property.

Below being only the preferred embodiment of the present invention, protection scope of the present invention is not limited merely to above-described embodiment, all belongs to Technical scheme under thinking of the present invention belongs to protection scope of the present invention.It should be pointed out that, the ordinary skill for the art For personnel, some improvements and modifications without departing from the principles of the present invention, should be regarded as protection scope of the present invention.

Claims (5)

1. a ground fault line selecting method based on high fdrequency component degree of association, it is characterised in that step is:

S1: monitoring distribution line outlet residual voltage value in real time；If residual voltage value is more than limit value, then it is judged to power distribution network There is earth fault, gather the zero-sequence current of each circuit；

S2: obtain pure fault component after the zero-sequence current of each circuit is carried out denoising Processing；

S3: pure fault component is carried out EMD decomposition, obtain various transient frequency component IMF1, IMF2, then pass through Instantaneous frequency is analyzed, and rejects power frequency component, extracts corresponding high frequency transient component；

S4: each circuit high frequency transient component is carried out correlation analysis two-by-two, obtains correlation matrix M, obtain each circuit Integrated correlation coefficient ρ_i, wherein i=1,2 ..., n represent circuit number；Work as ρ_max-ρ_min>ρ_setTime, it is determined that ρ_minInstitute is right The circuit answered is faulty line；Work as ρ_max-ρ_min<ρ_setTime, it is determined that bus-bar fault；Wherein ρ_minMinimum for integrated correlation coefficient Value, ρ_maxFor integrated correlation coefficient maximum, ρ_setFor integrated correlation coefficient setting value.

Ground fault line selecting method based on high fdrequency component degree of association the most according to claim 1, it is characterised in that described Concretely comprising the following steps of step S3:

S301: utilizing EMD adaptive by the fluctuation of different scale in signal or trend decomposition step by step out, obtaining one is The data sequence of row different frequency yardstick, each sequence is an intrinsic mode function IMF, and frequency the most from high to low, is counted The formula calculated is as follows:

$s\left(t\right)=\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{c}_i+r$

Component c in above formula₁、c₂、...、c_nBeing respectively input signal medium frequency different frequency range composition from high to low, r is for averagely to take advantage of Gesture；

S302: utilize Hilbert conversion to carry out instantaneous frequency analysis to decompositing each frequency component, reject power frequency by frequency characteristic Component and the DC component of decay, obtain one of transient characteristic quantity the most substantially high fdrequency component.

Ground fault line selecting method based on high fdrequency component degree of association the most according to claim 1, it is characterised in that described Concretely comprising the following steps of step S4:

S401: each circuit high fdrequency component waveform is carried out Controlling UEP, and the similarity of two waveforms is described by correlation coefficient, Its computing formula is:

$\mathrm{\&rho;}=\frac{\underset{n=1}{\overset{N}{\&Sigma;}}x\left(n\right)y\left(n\right)}{\sqrt{\underset{n=1}{\overset{N}{\&Sigma;}}{x}^2\left(n\right)\underset{n=1}{\overset{N}{\&Sigma;}}{y}^2\left(n\right)}}$

In formula, x (n), y (n) are 2 discrete signal sequences, and corresponding transient high-frequency component sampled value, N represents discrete sample signals sequence Length；

S402: under same data window, carries out correlation analysis two-by-two to each circuit transient high-frequency component, obtains correlation coefficient square Battle array:

$M=\left[\begin{array}{cccc}{\mathrm{\&rho;}}_{11}& {\mathrm{\&rho;}}_{12}& L& {\mathrm{\&rho;}}_{1n}\\ {\mathrm{\&rho;}}_{21}& {\mathrm{\&rho;}}_{22}& L& {\mathrm{\&rho;}}_{2n}\\ M& M& O& M\\ {\mathrm{\&rho;}}_{n1}& {\mathrm{\&rho;}}_{n2}& L& {\mathrm{\&rho;}}_{nn}\end{array}\right]$

ρ in formula_ijFor the correlation coefficient of transient high-frequency component between each circuit, n is the bar number of circuit；

S403: correlation matrix M is done normalized, obtains each circuit integrated correlation coefficient, and formula is as follows:

${\mathrm{\&rho;}}_i=\frac{1}{N-1}\underset{j=1,j\&NotEqual;i}{\overset{N}{\&Sigma;}}{\mathrm{\&rho;}}_{ij}$

ρ in formula_iFor each circuit integrated correlation coefficient, ρ_ijFor the correlation coefficient between circuit, N is the number of lines.

4. according to the ground fault line selecting method based on high fdrequency component degree of association described in any one in claims 1 to 3, its It is characterised by, in described step S2, when residual voltage is more prescribed a time limit, the zero-sequence current in each 1/4 cycle before and after collection fault moment, After subtracting each other, obtain pure fault component；The described residual voltage sudden change moment is that fault occurs the moment.

5. according to the ground fault line selecting method based on high fdrequency component degree of association described in any one in claims 1 to 3, its Being characterised by, in described step S1, the span of described voltage limit is the phase voltage of 15%.