CN103454562B - The route selection of resonant earthed system single-phase earthing clustering procedure - Google Patents

Abstract

The present invention relates to a kind of malfunction route selection method for resonant grounded system adopting time-frequency matrix singular value cluster, comprise the following steps: empirical mode decomposition is done to the transient zero-sequence current waveform of each circuit after fault and bus, obtains multiple IMF component respectively; Hilbert conversion is done to those IMF components, obtains the two-dimentional Hilbert gray scale time-frequency spectrum of transient zero-sequence current; Adopt the time-frequency matrix of HHT bandpass filtering structure transient zero-sequence current waveform; Svd is done to this time-frequency matrix, obtain a series of can the singular value of reflected waveform time-frequency characteristics as the characteristic quantity of each circuit and bus transient zero-sequence current; Fuzzy C-means clustering is done to those singular values, selects faulty line.The present invention can overcome when short-term road fault the impact perfecting long transmission line capacitance current, all can realize accurate route selection at high resistance ground, noise, arc fault etc.

Description

The route selection of resonant earthed system single-phase earthing clustering procedure

Technical field

The present invention relates to intelligent distribution system relay protection field, especially a kind of resonant earthed system single-phase earthing clustering procedure selection method.

Background technology

During resonant earthed system generation singlephase earth fault, due to neutral by arc extinction coil grounding, low impedance short circuit loop cannot be formed, path can only be formed by line mutual-ground capacitor, therefore also little than isolated neutral after arc suppression coil compensation of fault current, and three-phase line voltage keeps symmetrical, does not affect the continued power to load, therefore need not trip immediately, specify to operate with failure 1 ~ 2h according to " power system security code ".But healthy phases voltage rise is line voltage, if starting arc leaps in trouble spot, then the highest transient overvoltage of non-fault line may be made to reach 4 ~ 5 times of phase voltage, cause apparatus insulated damage, form 2 even multipoint earthing short circuits, cause the accident expanded range.In actual motion, the accidents such as the power cable caused due to superpotential explodes, PT fuse melting even burns out, busbar short-circuit, greatly destroy the safe and reliable operation of system.Therefore, the safe reliability of power distribution network in the singlephase earth fault serious threat of power distribution network, quick and precisely selects faulty line, and the tool that restores electricity in time is of great significance.

Obtain residual voltage mainly through voltage transformer secondary open-delta at present, utilize zero sequence current mutual inductor to obtain fault zero-sequence current.Because stable status zero-sequence current route selection method effect is undesirable, containing enrich failure message, than stable state value greatly several times to tens times and the transient route selection method do not affected by arc suppression coil becomes the focus of Recent study.

The route selection criterion overwhelming majority that existing malfunction route selection method for resonant grounded system adopts adopts artificial experience to get threshold method, cannot accomplish Intelligent fault route selection; And accurate route selection is difficult to high resistance earthing fault, short-term road fault.

The present invention is when going deep into resonant earthed system generation singlephase earth fault, on the basis of faulty line and non-fault line transient zero-sequence current characteristic mechanisms relation, in conjunction with singularity value decomposition, a kind of route selection new method based on resonant earthed system single-phase earthing one of transient characteristic quantity cluster is proposed, and a large amount of simulating, verifying is carried out to situations such as high resistance ground, short-term road fault generation singlephase earth faults, Fuzzy C-Means Cluster Algorithm being introduced in failure line selection, realizing Intelligent fault route selection in the situation without the need to arranging threshold value.

Summary of the invention

In view of this, the object of this invention is to provide a kind of malfunction route selection method for resonant grounded system adopting time-frequency matrix singular value cluster, HHT bandpass filtering structure time-frequency matrix is adopted to each feeder line and bus transient zero-sequence current, obtains through svd the resonant earthed system failure line selection that singular value features amount carries out FCM cluster.

The present invention adopts following scheme to realize: a kind of malfunction route selection method for resonant grounded system adopting time-frequency matrix singular value cluster, is characterized in that, comprise the following steps:

S01: empirical mode decomposition is done to the transient zero-sequence current waveform of each circuit after fault and bus, obtains multiple IMF component respectively;

S02: Hilbert conversion is done to those IMF components, obtains the two-dimentional Hilbert gray scale time-frequency spectrum of transient zero-sequence current;

S03: adopt HHT bandpass filtering to obtain the band component of each circuit and bus transient zero-sequence current waveform two dimension Hilbert gray scale time-frequency spectrum, the time-frequency matrix of structure transient zero-sequence current waveform;

S04: do svd to this time-frequency matrix, decomposes different time-frequency subspaces by transient zero-sequence current characteristic information, using obtain a series of can the singular value of reflected waveform time-frequency characteristics as the characteristic quantity of each circuit and bus transient zero-sequence current;

S05: fuzzy C-means clustering is done to those singular values, selects faulty line.

In an embodiment of the present invention, the band component concrete grammar adopting HHT bandpass filtering to obtain each circuit and bus transient zero-sequence current waveform two dimension Hilbert gray scale time-frequency spectrum in described step S03 is: choose a frequency span Δ f, with this, Region dividing is at equal intervals carried out to the instantaneous frequency in described two-dimentional Hilbert gray scale time-frequency spectrum, then the frequency range in i-th region is [(i-1) Δ f, i Δ f], the instantaneous amplitude point of all IMF components outside this frequency range is all set to black, the instantaneous amplitude point gray scale of all IMF components in this frequency range remains unchanged, the gray scale point retained is reconstructed, obtain the band component of original signal in i-th frequency band, in like manner obtain the band component in other frequency band ranges.

In an embodiment of the present invention, suppose that the sampling number of each circuit transient zero-sequence current is n, transient zero-sequence current waveform is broken down into m sub-band after HHT bandpass filtering, and the data point of each sub-band waveform is a _ij, wherein i=1,2 ..., m, j=1,2 ..., n; Then obtain time-frequency matrix

In an embodiment of the present invention, the concrete steps of described step S05 comprise:

1) number of categories c, weighted index p, iteration termination factor ε and maximum iteration time k is preset _max, by constraint condition initialization subordinated-degree matrix U ^(k);

2) cluster centre v is calculated _i, $v_i=\frac{\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{u}_{\mathrm{ij}}^p{x}_j}{\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{u}_{\mathrm{ij}}^p},(1\≤i\≤c);$

3) by v _iupgrade subordinated-degree matrix U ^(k+1),

$U_{\mathrm{ij}}^{(k+1)}={\left[\underset{l=1}{\overset{c}{\mathrm{\Σ}}}{\left(\frac{{\left({\left|\right|x_j-v_i\left|\right|}^2\right)}^{(k+1)}}{{\left({\left|\right|x_j-v_l\left|\right|}^2\right)}^{(k+1)}}\right)}^{1/(p-1)}\right]}^{-1},(i=\mathrm{1,2},...c;j=\mathrm{1,2},...m;l=\mathrm{1,2},...c);$

4) judge whether to reach termination condition, if || U ^(k+1)-U ^(k)||≤ε, then stop iteration, and cluster process terminates, otherwise put k=k+1, forwards step 2 to);

5) an Optimal cluster centers V={v of X is obtained _iand subordinated-degree matrix U={u _ij.

Compared with existing technical scheme, the present invention has the following advantages:

1) Fuzzy C-Means Cluster Algorithm is introduced resonant earthed system failure line selection, avoid artificial experience selected threshold thus realize Intelligent fault route selection;

2) HHT bandpass filtering structure time-frequency matrix is used to the transient zero-sequence current of all circuits of system and bus, describe the time-frequency characteristics of transient zero-sequence current signal under each frequency band imperfectly, contain the localised information of characterization signal essential characteristic;

3) svd is carried out to the time-frequency matrix of structure, can the comparatively stable algebraic characteristic of holding signal, there is good robustness and generalization ability, various complicated situation when can adapt to resonant earthed system singlephase earth fault;

4) for situations such as short-term road fault, high resistance earthing fault generation singlephase earth faults, a large amount of simulation results in ATP-EMTP electromagnetic transient simulation software show, the present invention can overcome when short-term road fault the impact perfecting long transmission line capacitance current, all can realize accurate route selection at high resistance ground, noise, arc fault etc.

For making object of the present invention, technical scheme and advantage clearly understand, below by specific embodiment and relevant drawings, the present invention will be described in further detail.

Accompanying drawing explanation

Fig. 1 is resonant earthed system singlephase earth fault zero-sequence network figure of the present invention.

Fig. 2 is the equivalent circuit diagram of the transient zero-sequence current of Fig. 1.

Fig. 3 be stake resistance of the present invention less time equivalent circuit diagram.

Fig. 4 is the equivalent circuit diagram of the large resistance eutral grounding of the present invention.

Fig. 5 is resonant earthed system realistic model of the present invention.

Fig. 6 is faulty line of the present invention and non-fault line transient zero-sequence current comparison diagram.

Embodiment

During resonant earthed system generation singlephase earth fault, each circuit transient zero-sequence current waveform has nonlinear and nonstationary characteristic, the transient zero-sequence current waveform property of there are differences of faulty line and non-fault line, when analyzing resonant earthed system generation singlephase earth fault, on the basis of faulty line and non-fault line transient zero-sequence current waveform mechanism relation, a kind of failure line selection new method adopting fault transient zero-sequence current waveform time-frequency matrix singular value cluster is proposed.Empirical mode decomposition (empiricalmodedecomposition is done to circuit each after fault and bus transient zero-sequence current waveform, EMD), all can obtain multiple intrinsic mode function (intrinsicmodefunction, IMF) component, Hilbert conversion (Hilbert transform) is done to each IMF component, obtains the two-dimentional Hilbert gray scale time-frequency spectrum of transient zero-sequence current.HHT bandpass filtering is adopted to obtain each band component of circuit transient zero-sequence current waveform, the time-frequency matrix of structure transient zero-sequence current waveform, svd (singularvaluedecompositon is done to it, SVD), transient zero-sequence current characteristic information is decomposed different time-frequency subspaces, using the singular value of a series of energy reflected waveform time-frequency characteristics obtained as the characteristic quantity of each circuit transient zero-sequence current, fuzzy C-means clustering (fuzzyc-meancluster is done to each time-frequency matrix singular value, FCM), faulty line is selected.

Be illustrated in figure 1 resonant earthed system singlephase earth fault zero-sequence network figure.

The equivalent electrical circuit of its transient zero-sequence current as shown in Figure 2.

Wherein u ₀make u for equivalent residual voltage source ₀=U _mcos (ω t+ α), α and U _mbe respectively residual voltage source initial phase angle and amplitude, ω is the angular frequency in residual voltage source.Stake resistance is divided into two parts, and a part is R, and another part is included in R ₀in, L ₀for the equivalent inductance of system in zero sequence loop, R ₀for the substitutional resistance of system in zero sequence loop (comprising arc road resistance and stake resistance), L and r _lbe respectively inductance and the active loss resistance of arc suppression coil, C ₁, C ₂... C _nfor system non-fault line three-phase ground capacitance and order n is system non-fault line number.

When stake resistance R is less, can R be ignored, obtain approximate equivalent circuit as shown in Figure 3.

When stake resistance R is larger, because fault phase zero sequence capacitor charging speed is comparatively slow, for resonant earthed system, can not ignore the impact of arc suppression coil, but the impact of inductance and resistance in Equivalent Circuit can be ignored, the active loss resistance r of arc suppression coil can be ignored simultaneously _limpact, now the equivalent electrical circuit of resonant earthed system single-phase earthing transient characterisitics is as shown in Figure 4.

Stake resistance is very large to resonant earthed system transient zero-sequence current properties influence.When stake resistance changes from small to large, system then experiences from underdamped oscillation to overdamping state again to the underdamped oscillation process of another kind of equivalent electrical circuit form.But no matter how stake resistance changes, between faulty line and non-fault line, the similarity degree of transient zero-sequence current is less than the similarity degree of transient zero-sequence current between non-fault line.As space is limited, little with stake resistance, time be example illustrate, now, if resonant earthed system generation singlephase earth fault, then transient zero-sequence current Equivalent Circuit is as shown in Figure 3.

Faulty line transient zero-sequence current can be obtained according to Fig. 3:

$i_d=(L_{\mathrm{Cm}}-I_{\mathrm{Lm}})\cos (\mathrm{\ωt}+\mathrm{\α})=I_{\mathrm{Cm}}{[\frac{{\mathrm{\ω}}_f}{\mathrm{\ω}}\sin \mathrm{\α}\sin {\mathrm{\ω}}_{f}t-\cos \mathrm{\α}\cos {\mathrm{\ω}}_{f}t]e}^{-\frac{t}{{\mathrm{\τ}}_C}}+I_{\mathrm{Lm}}\cos \mathrm{\α}{e}^{-\frac{t}{{\mathrm{\τ}}_L}}---\left(1\right);$

Non-fault line transient zero-sequence current:

$i_{\mathrm{cn}}=I_{\mathrm{Cm}}^{\′}\cos (\mathrm{\ωt}+\mathrm{\α})+I_{\mathrm{Cm}}^{\′}{[\frac{{\mathrm{\ω}}_f}{\mathrm{\ω}}\sin \mathrm{\α}\sin {\mathrm{\ω}}_{f}t-\cos \mathrm{\α}\cos {\mathrm{\ω}}_{f}t]e}^{-\frac{t}{{\mathrm{\τ}}_C}}---\left(2\right);$

In formula:

$I_{\mathrm{Lm}}=\frac{U_m}{\sqrt{r_L^2+{\mathrm{\ω}}_2{L}_2}},I_{\mathrm{Cm}}=\frac{{\mathrm{\ωCU}}_m}{\sqrt{{\left(R_0\mathrm{C\ω}\right)}^2+{(1-L_0{\mathrm{C\ω}}^2)}^2}},I_{\mathrm{Cm}}^{\′}=\frac{{\mathrm{\ωC}}_n{U}_m}{\sqrt{{\left(R_0\mathrm{C\ω}\right)}^2+{(1-L_0{\mathrm{C\ω}}^2)}^2}},{\mathrm{\τ}}_C=\frac{2L_0}{R_0},$ ${\mathrm{\τ}}_L=\frac{\mathrm{\ωL}}{r_L},{\mathrm{\ω}}_f=\sqrt{\frac{1}{L_{0}C}-{\left(\frac{R_0}{2L_0}\right)}^2};$

Formula (1), (2) are by two compositions, and Section 1 is steady-state component, and Section 2 is transient state component.

Because of the over-compensation effect of arc suppression coil during stable state, faulty line steady-state component is identical with non-fault line steady-state component oscillation frequency, be power frequency, phase place is consistent, and the amplitude of faulty line may be less than non-fault line, now the zero-sequence current similarity degree of faulty line and non-fault line strengthens, and pure steady-state component failure line selection method will lose efficacy.

Faulty line transient state component is the high frequency free oscillation component of all non-fault line transient state capacitance currents and superposing of arc suppression coil transient DC component.Due to fault initial stage both frequency difference great disparity, its amplitude not only can not compensate mutually, also may be superposed on one another, and faulty line transient zero-sequence current amplitude is obviously increased.And the transient state component of non-fault line has identical expression formula, variation tendency is identical, phase place is consistent, amplitude there are differences because each line parameter circuit value is different, a large amount of emulation experiment shows, amplitude difference between non-fault line is less than the difference between non-fault line and faulty line far away, and therefore between faulty line and non-fault line, the similarity degree of transient zero-sequence current is less than the similarity degree of transient zero-sequence current between non-fault line.

Other failure conditions are also used for the same analysis, and can lead to the same conclusion, and namely between faulty line and non-fault line, the similarity degree of transient zero-sequence current is little more than the similarity degree of transient zero-sequence current between non-fault line.Research shows, when there is dissimilar singlephase earth fault in resonant earthed system, transient zero-sequence current is mainly concentrated after a failure in 1/8-1/4 power frequency period, there is notable difference in faulty line and non-fault line transient zero-sequence current, therefore the characteristic quantity of transient zero-sequence current can be extracted, failure line selection is carried out by fuzzy C-mean algorithm (fuzzyc-meancluster, FCM) cluster.

During resonant earthed system generation single-phase earthing, there are differences between its faulty line and non-fault line transient zero-sequence current waveform, extract each sub-band component that they comprise and do comparative analysis and can be grounded route selection.If directly adopt each transient zero-sequence current waveform to do com-parison and analysis through the corresponding IMF component in a few rank that EMD obtains, then because frequency range may be inconsistent, comparability is not strong.HHT bandpass filtering is adopted to solve said frequencies inconsistence problems.Carry out Hilbert conversion to each rank IMF component that each line fault transient zero-sequence current obtains after EMD, obtain two-dimentional Hilbert gray scale time-frequency spectrum, each instantaneous amplitude of each IMF component correspond to a gray scale point in Hilbert spectrogram.Choose suitable frequency span Δ f as required, with this, Region dividing is at equal intervals carried out to the instantaneous frequency in spectrogram, then the frequency range in i-th region is [(i-1) Δ f, i Δ f], the instantaneous amplitude point of outer for this frequency range all IMF components is all set to black (corresponding gray-scale value is zero), in this frequency range, the instantaneous amplitude point gray scale of all IMF components remains unchanged, the gray scale point retained is reconstructed, the band component of original signal in i-th frequency band can be obtained, in like manner can obtain the band component in other frequency bands.

In order to portray the local feature of one dimension each line fault transient zero-sequence current waveform in time domain and frequency domain better, HHT bandpass filtering is utilized to construct the time-frequency matrix of transient zero-sequence current waveform.Suppose that the sampling number of each circuit transient zero-sequence current is n, transient zero-sequence current waveform is broken down into m sub-band after HHT bandpass filtering, and the data point of each sub-band waveform is a _ij(i=1,2 ..., m, j=1,2 ..., n), then can obtain time-frequency matrix:

The row of time-frequency matrix A represents the reconfiguration waveform of transient zero-sequence current each sub-band after HHT bandpass filtering, and the sampling time point of transient zero-sequence current is shown in list.Time-frequency matrix A describes the time-frequency characteristics of transient zero-sequence current waveform in each sub-band imperfectly, contains the localised information characterizing transient zero-sequence current waveform essential characteristic.

After constructing time-frequency matrix A, svd is carried out to it.

Matrix singular value decomposition essence is a kind of orthogonal transformation, can by diagonalization of matrix, and it is defined as: for a real matrix A=(a _ij) _{m × n}, r (A)=r, A ^tthe eigenwert being greater than zero of A is λ ₁, λ ₂..., λ _r, then be called the singular value of A, wherein r (A) be A order, r (A)=min (m, n).Then must there are 2 unitary matrix V _{m × m}, U _{n × n}with a diagonal matrix make A=VDU ^tset up, wherein v=(v ₁, v ₂..., v _m) be AA ^tunit character vector, U=(u ₁, u ₂..., u _n) be A ^tthe unit character vector of A.

Carry out svd to the time-frequency matrix A of resonant earthed system fault transient zero sequence current signal structure, each transient zero-sequence current signal can obtain a series of submatrix A _iand N number of singular value of correspondence 1≤N≤min (m, n), both reflect this matrix comprise signal Time-Frequency Information number, represent the feature mode that this matrix is intrinsic to a certain extent, and non-zero singular value number reflects the number that this signal time-frequency matrix A comprises different mode, its value size reflects the proportion that respective frequencies pattern accounts in assemble mode, characterizes the feature of this signal waveform.After the element of matrix A is interfered, the quadratic sum of singular values of a matrix variable quantity is no more than the norm of perturbation matrix, singular value change is less, stability is better, it is the comparatively stable algebraic characteristic of matrix, there is good robustness and generalization ability, various complicated situation when can adapt to resonant earthed system singlephase earth fault.

Time-frequency matrix singular value obtains singular value as characteristic quantity after decomposing, and by FCM cluster after normalized, by faulty line and non-fault line classification, can select faulty line when without the need to arranging threshold value.

FCM cluster is that each data point is belonged to a certain cluster centre by certain degree of membership, realizes dividing the Flexible Fuzzy of data.

If X={x ₁, x ₂..., x _mbe sample space, the time-frequency matrix A of corresponding resonant earthed system, each sample is n-dimensional vector, i.e. x _i={ x _i1, x _i2..., x _in, m is sample size.X is divided into c class 2≤c≤m, each sample is under the jurisdiction of this c inhomogeneity, with u with certain degree _ijrepresent that in X, a jth sample belongs to the degree of membership of the i-th class arbitrarily, meet following 3 conditions:

$\left\{\begin{array}{c}\underset{i=1}{\overset{c}{\mathrm{\Σ}}}{u}_{\mathrm{ij}}=1\\ u_{\mathrm{ij}}\∈\left[\mathrm{0,1}\right]\\ \underset{j=1}{\overset{n}{\mathrm{\Σ}}}{u}_{\mathrm{ij}}\∈(0,m)\end{array}\right.---\left(3\right);$

Then U _{c × n}={ u _ijbe called subordinated-degree matrix.FCM cluster adopts process of iteration to make objective function minimum, namely

$\min \mathrm{imize}{J}_{\mathrm{fcm}}(U,V)=\underset{j=1}{\overset{m}{\mathrm{\Σ}}}\underset{i=1}{\overset{c}{\mathrm{\Σ}}}{u}_{\mathrm{ij}}^p{\left|\right|x_j-v_i\left|\right|}^2---\left(4\right);$

J in formula _fcm(U, V) is objective function, and U is subordinated-degree matrix, and v is cluster centre, v _ibe the cluster centre of the i-th class, p>1 is FUZZY WEIGHTED index, generally gets p=2.Concrete steps are as follows:

1) number of categories c, weighted index p, iteration termination factor ε and maximum iteration time k is preset _max, by constraint condition initialization subordinated-degree matrix U ^(k);

2) cluster centre v is calculated _i, $v_i=\frac{\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{u}_{\mathrm{ij}}^p{x}_j}{\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{u}_{\mathrm{ij}}^p},(1\≤i\≤c);$

3) by v _iupgrade subordinated-degree matrix U ^(k+1),

$U_{\mathrm{ij}}^{(k+1)}={\left[\underset{l=1}{\overset{c}{\mathrm{\Σ}}}{\left(\frac{{\left({\left|\right|x_j-v_i\left|\right|}^2\right)}^{(k+1)}}{{\left({\left|\right|x_j-v_l\left|\right|}^2\right)}^{(k+1)}}\right)}^{1/(p-1)}\right]}^{-1},(i=\mathrm{1,2},...c;j=\mathrm{1,2},...m;l=\mathrm{1,2},...c);$

4) judge whether to reach termination condition, if || U ^(k+1)-U ^(k)||≤ε, then stop iteration, and cluster process terminates, otherwise put k=k+1, forwards step 2 to);

5) an Optimal cluster centers V={v of X is obtained _iand subordinated-degree matrix U={u _ij.

Between faulty line and non-fault line, the similarity degree of transient zero-sequence current is less than the similarity degree of transient zero-sequence current between non-fault line, eigenwert difference singular value features amount then shown as between non-fault line is very little, and eigenwert between faulty line and non-fault line is widely different, subordinated-degree matrix U identifiable design is therefore utilized to be out of order circuit.

Method of the present invention is described in detail below in conjunction with a specific embodiment of the present invention:

Build 10kV resonant earthed system realistic model with EMTP, as shown in Figure 5, wherein JL is pole line, and DL is cable.110kV main-transformer model is SZ-31500/110, connects group Yd11, transformer noload losses Δ P ₀=19.5kW, short circuit loss Δ P _k=118.9kW, no-load current percentage I ₀%=0.12, short-circuit voltage percentage U _k%=14.99.Overhead transmission line parameter is: R ₀=0.23 Ω/km, C ₀=0.008 μ F/km, L ₀=5.478mH/km; R ₁=0.17 Ω/km, C ₁=0.00969 μ F/km, L ₁=1.21mH/km.Cable-line parameter is: R ₀=2.7 Ω/km, C ₀=0.28 μ F/km, L ₀=1.019mH/km; R ₁=0.27 Ω/km, C ₁=0.339 μ F/km, L ₁=0.255mH/km.Z-type transformer is made up of three single-phase saturation transformers, and model is JSC-200/10.5, and primary side and the secondary side parameter of each single-phase saturation transformer are set to: V _rp=V _rs=10.5kV, R _p=R _s=13.7675 Ω, L _p=L _s=65.8mH.Load equiva lent impedance (100+j40) Ω equivalence replaces.The over-compensation degree of arc suppression coil gets 10%, and calculate the inductance of arc suppression coil is 0.6853H, arc suppression coil active loss is about 2.5% ~ 3% of perceptual loss, gets 3%, calculates resistance is 6.4592 Ω.

Utilize the present invention to carry out route selection to the singlephase earth fault in different faults situation, as space is limited, only enumerate part typical fault situation.

When circuit 1 crosses peak value in phase voltage, stake resistance is 5 Ω, C phase earth fault occurs at distance bus 1km place, the transient zero-sequence current waveform of faulty line 1 and certain 2 non-fault line as shown in Figure 6.

As can be seen from Figure 6, faulty line is contrary with non-fault line transient zero-sequence current direction, between non-fault line, transient zero-sequence current variation tendency is consistent, and phase place is identical, and amplitude difference between non-fault line is less than the amplitude difference between non-fault line and faulty line far away; When transient decay complete enter stable state after, faulty line is consistent with the phase place of non-fault line, and difference in magnitude mutation is between the two little, waveform similarity enhancing, be unfavorable for failure line selection.Therefore to utilize in transient state process transient zero-sequence current similarity degree between non-fault line large, and the feature that the transient zero-sequence current similarity degree of faulty line and non-fault line is little, can failure line selection be realized.

Respectively HHT bandpass filtering is done to the transient zero-sequence current of 1/5 cycle after a failure of 6 circuits and bus in system, fault transient zero-sequence current waveform is decomposed in 10 different frequency bands, obtain corresponding time-frequency matrix A, respectively SVD is done to time-frequency matrix A, the corresponding size of each transient zero-sequence current waveform is the singular value vector of 1 × 10, the singular value vector of 7 transient zero-sequence currents merges the eigenvectors matrix X of formation 7 × 10, shown in (9).

$X=\left[\begin{array}{cccccccccc}417.7728& 148.9942& 61.2506& 22.3767& 16.6020& 14.1358& 7.8811& 4.7887& 0.0000& 0.0000\\ 58.3098& 42.7062& 29.9541& 9.2013& 6.0886& 4.6996& 3.6672& 2.8049& 1.3066& 0.8914\\ 68.3852& 41.6720& 29.2079& 14.8035& 4.1075& 2.4861& 2.0440& 1.7424& 1.1242& 0.0457\\ 111.4240& 55.2297& 37.6699& 6.5040& 5.3835& 2.0695& 1.8593& 1.5015& 1.0913& 0.4619\\ 137.4414& 23.5374& 16.1765& 5.6983& 1.4585& 0.0000& 0.0000& 0.0000& 0.0000& 0.0000\\ 77.1604& 45.0986& 30.2724& 16.1744& 3.3772& 2.3446& 2.1424& 2.0763& 1.5776& 1.0024\\ 69.0944& 35.1537& 9.7675& 1.4959& 0.0000& 0.0000& 0.0000& 0.0000& 0.0000& 0.0000\end{array}\right]---\left(9\right);$

X is adopted normalized obtains new matrix wherein x _ijfor element in X, min (X) is minimum value element in X, and max (X) is maximal value element in X, then new matrix element value is in [0,1].

Will as the input of FCM cluster, failure line selection only needs Judging fault and non-faulting two states, therefore to arrange FCM clusters number be 2, and setting weighted index is p=2, and the iteration termination factor is ε=10 ^-5, maximum iteration time is k _max=100.Through 8 iteration, objective function J _fcm(U, V)=0.083701, subordinated-degree matrix is:

$U=\left[\begin{array}{ccccccc}\underset{\‾}{1.0000}& 0.0059& 0.0028& 0.0095& 0.0300& 0.0014& 0.0048\\ 0.0000& \underset{\‾}{0.9941}& \underset{\‾}{0.9972}& \underset{\‾}{0.9905}& \underset{\‾}{0.9700}& \underset{\‾}{0.9986}& \underset{\‾}{0.9952}\end{array}\right];$

The row of subordinated-degree matrix U represents status categories, and 1 ~ 7 row represent circuit 1 ~ 6 and bus respectively, and in U, the row at each row maximal value place is state corresponding to this column line.Between faulty line and non-fault line, the similarity degree of transient zero-sequence current is less than the similarity degree of transient zero-sequence current between non-fault line, eigenwert difference singular value features amount then shown as between non-fault line is very little, and eigenwert between faulty line and non-fault line is widely different, subordinated-degree matrix U identifiable design is therefore utilized to be out of order circuit.Can find out from U acceptance of the bid underscore element, by FCM cluster, circuit 1 constitutes a class by itself, and all the other circuits all belong to another kind of, judges that circuit 1 is as faulty line accordingly, consistent with actual conditions.

Typical fault route selection result:

1) short-term road fault

There is singlephase earth fault apart from bus 0.5km place in pure overhead transmission line 1, route selection the results are shown in Table 1.

Route selection result during table 1 short-term road fault

2) line end high resistance ground

Circuit 5 end generation stake resistance is the earth fault of 5000 Ω, and route selection the results are shown in Table 2.

Table 2 line end high resistance earthing fault route selection result

3) bus-bar fault

Table 3 bus-bar fault route selection result

4) there is singlephase earth fault in the white Gaussian noise interference line 3,6 being 20dB in signal to noise ratio (S/N ratio), route selection the results are shown in Table 4.

Failure line selection result under the interference of table 4 white Gaussian noise

5) signal sampling is asynchronous

There is singlephase earth fault in circuit 2,4, circuit 1,2,3 zero-sequence current sampling time delayed circuit 4,5,6 zero-sequence current sampling time 0.001s, route selection the results are shown in Table 5.

Failure line selection result under table 5 signal sampling is asynchronous

6) two points ground fault fault

For circuit 5,6, emulate homophase diverse location on same circuit respectively and occur two points ground fault fault occurs for two points ground fault fault and different circuit simultaneously simultaneously, route selection result is respectively in table 6 and table 7.

Table 6 is with circuit two points ground fault failure line selection result

Table 7 different circuit two points ground fault failure line selection result

7) arc fault

Adopt Mayr Arc Modelling analog electrical arc property, under the various condition of simulated line 3,4, arc fault occurs, route selection the results are shown in Table 8.

Table 8 arc fault route selection result

Use HHT bandpass filtering to construct its time-frequency matrix to the inlet wire of resonant earthed system and the fault transient zero-sequence current waveform of each outlet, time-frequency matrix obtains time-frequency singular value matrix through SVD, does FCM cluster, select faulty line to it.The simulation result of various different faults situation is shown:

1) the time-frequency matrix obtained through HHT bandpass filtering can describe the time-frequency characteristics of fault transient zero-sequence current waveform in each sub-band imperfectly, contains the Time-Frequency Localization information characterizing transient zero-sequence current waveform essential characteristic.

2) singular value is the comparatively stable algebraic characteristic of matrix, both effectively can characterize fault transient zero sequence current signal characteristic information, and can reduce intrinsic dimensionality again.

3) FCM cluster is adopted, for last route selection criterion, without the need to arranging the route selection threshold value just optional circuit that is out of order.

4) selection method can overcome when short-term road fault the impact perfecting long transmission line capacitance current, all can accurately route selection in the situations such as high resistance ground, noise, asynchronous sampling, two points ground fault fault.

Above-listed preferred embodiment; the object, technical solutions and advantages of the present invention are further described; be understood that; the foregoing is only preferred embodiment of the present invention; not in order to limit the present invention; within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (3)

1. adopt a malfunction route selection method for resonant grounded system for time-frequency matrix singular value cluster, it is characterized in that, comprise the following steps:

S01: empirical mode decomposition is done to the transient zero-sequence current waveform of each circuit after fault and bus, obtains multiple IMF component respectively;

S02: Hilbert conversion is done to those IMF components, obtains the two-dimentional Hilbert gray scale time-frequency spectrum of transient zero-sequence current;

S03: adopt HHT bandpass filtering to obtain the band component of each circuit and bus transient zero-sequence current waveform two dimension Hilbert gray scale time-frequency spectrum, the time-frequency matrix of structure transient zero-sequence current waveform;

S04: do svd to this time-frequency matrix, decomposes different time-frequency subspaces by transient zero-sequence current characteristic information, using obtain a series of can the singular value of reflected waveform time-frequency characteristics as the characteristic quantity of each circuit and bus transient zero-sequence current;

S05: fuzzy C-means clustering is done to those singular values, selects faulty line;

The band component concrete grammar adopting HHT bandpass filtering to obtain each circuit and bus transient zero-sequence current waveform two dimension Hilbert gray scale time-frequency spectrum in described step S03 is: choose a frequency span Δ f, with this, Region dividing is at equal intervals carried out to the instantaneous frequency in described two-dimentional Hilbert gray scale time-frequency spectrum, then the frequency range in i-th region is [(i-1) Δ f, i Δ f], the instantaneous amplitude point of all IMF components outside this frequency range is all set to black, the instantaneous amplitude point gray scale of all IMF components in this frequency range remains unchanged, the gray scale point retained is reconstructed, obtain the band component of original signal in i-th frequency band, in like manner obtain the band component in other frequency band ranges.

2. the malfunction route selection method for resonant grounded system of employing time-frequency matrix singular value cluster according to claim 1, it is characterized in that: suppose that the sampling number of each circuit transient zero-sequence current is n, transient zero-sequence current waveform is broken down into m sub-band after HHT bandpass filtering, and the data point of each sub-band waveform is a _ij, wherein i=1,2 ..., m, j=1,2 ..., n; Then obtain

Time-frequency matrix

3. the malfunction route selection method for resonant grounded system of employing time-frequency matrix singular value cluster according to claim 1, it is characterized in that, the concrete steps of described step S05 comprise:

1) number of categories c, weighted index p, iteration termination factor ε and maximum iteration time k is preset _max, by constraint condition initialization subordinated-degree matrix U ^(k);

2) cluster centre v is calculated _i, $v_i=\frac{\underset{j=1}{\overset{m}{\Σ}}{u}_{ij}^p{x}_j}{\underset{j=1}{\overset{m}{\Σ}}{u}_{ij}^p}(1\≤i\≤c);$

3) by v _iupgrade subordinated-degree matrix U ^(k+1),

$U_{ij}^{(k+1)}={\[\underset{l=1}{\overset{c}{\Σ}}{\left(\frac{{\left(\right||x_j-v_i|{|}^2)}^{(k+1)}}{{\left(\right||x_j-v_l|{|}^2)}^{(k+1)}}\right)}^{1/(p-1)}\]}^{-1},(i=1,2,...c;j=1,2,...m;i=1,2,...c);$

4) judge whether to reach termination condition, if || U ^(k+1)-U ^(k)||≤ε, then stop iteration, and cluster process terminates, otherwise put k=k+1, forwards step 2 to);

5) an Optimal cluster centers V={v of X is obtained _iand subordinated-degree matrix U={u _ij.