CN105974264A - Fault line selection method based on phase current transient characteristic - Google Patents

Abstract

The method discloses a fault line selection method based on a phase current transient characteristic. The method comprises the following steps of S1, continuously measuring a distribution line outlet zero sequence voltage value and determining whether a power distribution network generates a grounding fault; S2, processing collected phase current data, extracting a transient phase-current sudden-change amount of each line, and carrying out interphase pairwise correlation analysis so as to obtain an interphase minimum correlation coefficient rhok min; S3, carrying out spectral analysis on each line fault phase current and calculating a gravity frequency fkg; S4, carrying out normalization processing on a fault characteristic quantity and acquiring normalization values, establishing a two-dimensional coordinate system based on the normalization values, and determining each line fault characteristic coordinate point; and calculating a fault characteristic distance dk between each line fault characteristic coordinate point and a reference point (0, 0) so as to determine a bus fault. The method possesses advantages that a principle is simple; practicality is high; an anti-interference capability is good; accuracy is high and so on.

Description

A kind of fault-line selecting method based on phase current transient characteristic

Technical field

Present invention relates generally to power distribution network grounding technology field, refer in particular to a kind of fault-line selecting method based on phase current transient characteristic.

Background technology

Power distribution network is the important component part of power system, close with customer relationship, and the diagnosis of distribution network failure and repair time will Directly influence power supply quality, one of emphasis in the research of this respect always distribution protection.China's city 10kV distribution System is frequently with neutral by arc extinction coil grounding mode, to reduce instantaneous singlephase earth fault and transient state electric arc for system Impact, but such earthing mode makes fault current less, failure line selection has certain difficulty.

At present, selection method based on transient signal, owing to fault signature is obvious, not by advantages such as earthing mode are affected, and Become the focus of research.Existing power distribution network transient signal method mainly has two kinds, and the first utilizes the route selection side of transient characteristic frequency range Method, carries out route selection by the characteristic quantity of relatively each the determination of route frequency range, but owing to transient frequency content is by network parameter, fault The many factors impacts such as moment, the characteristic spectra distribution of different circuit transients is the most completely the same.The second is based on small echo The method analyzed, this process employs wavelet analysis and has the advantage of good localization at time domain, frequency domain simultaneously, but little wavelength-division Analysis does not possess adaptivity, and is easily affected by the factor such as wavelet basis function and decomposition scale.

From above-mentioned analysis, the transient characterisitics of fault are analyzed the most deep by existing earth-fault protection method, Duo Shuodou Being that amplitude and phase place to transient signal is compared to determine faulty line from different perspectives, fault detect accuracy is relatively low, protects Protect judge setting valve choose difficulty；And due to the impact of interference, the impact of transition resistance, the reason such as multiformity of the method for operation, Even can cause false protection or tripping.

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, practical, capacity of resisting disturbance is strong, degree of accuracy is high fault-line selecting method based on phase current transient characteristic.

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

A kind of fault-line selecting method based on phase current transient characteristic, the steps include:

S1: measure distribution line outlet residual voltage value continuously, if residual voltage is more than voltage setting valve, then judges that power distribution network is sent out Raw earth fault, utilizes and is arranged on the circuit head end FTU device each circuit three-phase current signal of collection；

S2: the phase current data gathered are processed, extracts each circuit transient state difference of phase currents, and it is carried out alternate two Pairwise correlation is analyzed, and calculates the alternate correlation coefficient array [ρ of this circuit_AB ρ_BC ρ_CA], obtain alternate minimum by comparing Correlation coefficient ρ_kmin；

S3: each line fault phase current is carried out spectrum analysis, calculates its gravity frequency f_kg；

S4: be normalized fault characteristic value, obtains normalized valueWithAnd set up two-dimensional coordinate system with this, Determine each line fault characteristic coordinates point

S5: calculate fault signature distance d between each line fault characteristic coordinates point and datum mark (0,0)_k, wherein k=1,2 ..., n；Work as d_max-d_min>d_setTime, then judge d_minCorresponding circuit is faulty line, and tripping operation is isolated this faulty line and realized line Road is protected；Work as d_max-d_min<d_setTime, then judge that bus-bar fault, tripping operation isolation bus realize route protection；Wherein d_maxFor event Barrier characteristic distance maximum, d_minFor fault signature distance maximum, d_setFor fault signature distance setting value.

As a further improvement on the present invention: described step S2 includes:

S201: by data are carried out pretreatment, extracts each circuit each difference of phase currents waveform, the similarity of two waveforms Being described by correlation coefficient, the computing formula of correlation coefficient ρ is as follows:

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

In formula, x (n), y (n) are 2 discrete signal sequences, and corresponding transient state difference of phase currents sampled value, N represents that discrete sampling is believed The length of number sequence；

S202: under same data window, calculates the relevant array [ρ that each circuit two is alternate_AB ρ_BC ρ_CA], if ρ_kminFor line Road k is correlated with the minima in array, and for faulty line fault phase with to perfect phase Sudden Changing Rate difference relatively big, correlation coefficient is the least, For non-fault line, each difference of phase currents is the most similar, and correlation coefficient is bigger.

As a further improvement on the present invention: in described step S3, the gravity frequency of each line fault phase is calculated, for seeking out The discrete current signal frequency spectrum come uses following formula to calculate gravity frequency:

$f_g=\underset{f=f_1}{\overset{f_2}{\&Sigma;}}\&lsqb;i\left(f\right)gf\&rsqb;/\underset{f=f_1}{\overset{f_2}{\&Sigma;}}i\left(f\right)$

Wherein f_gRepresenting gravity frequency, i (f) is the frequency spectrum of current signal, and f is each corresponding analog frequency of bar spectral line, f₁-f₂ For calculating the interval of frequency, relatively low for faulty line fault phase gravity frequency, and non-fault line fault phase is just the opposite.

As a further improvement on the present invention: in described step S4, logarithm value makees normalized, and correlation coefficient ρ is with 1 On the basis of, gravity frequency using 3000Hz as benchmark, being calculated as follows of its normalized value:

$f_{kg}^{*}=f_{kg}/3000.$

As a further improvement on the present invention: in described step S5, with alternate correlation coefficient minimaAs transverse axis, weight The normalized value of frequency of heartFor the longitudinal axis, set up two-dimensional coordinate system,Represent the transient state phase current event of circuit k Barrier characteristic point, obtains fault signature distance d of each circuit relative datum point (0,0)_kAs the criterion of route selection, its expression formula is:

$d_k=\sqrt{{({\mathrm{\&rho;}}_{k\min }^{*}-0)}^2+{(f_{kg}^{*}-0)}^2}.$

As a further improvement on the present invention: in described step S1, voltage setting valve span is 5%～30% phase voltage value.

As a further improvement on the present invention: in described step S5, d_setTake 0.3.

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

1, two kinds of criterions are effectively combined by the fault-line selecting method based on phase current transient characteristic of the present invention, complementary mutually Fill, further increase protective margin, no matter at high resistant, or when fault initial phase angle is less all can accurately route selection, robustness By force；Can effectively differentiate line fault and bus-bar fault, there is the shadow that capacity of resisting disturbance by force, is not changed by system operation mode The features such as sound；The signal gathered contains the information of each frequency range, improves the arc resistant ability of protection, practical.

2, the fault-line selecting method based on phase current transient characteristic of the present invention, comprehensively utilizes faulty line phase each with non-fault line Two kinds of fault characteristic value are effectively tied by jump-value of current and the difference of faulted phase current signal collection Mid Frequency by fault signature distance Altogether, it is complementary to one another.The present invention, without arranging the setting valve of fault characteristic value, further increases the nargin of protection, has Stronger practicality.

Accompanying drawing explanation

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

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

Fig. 3 is the present invention each line fault characteristic coordinates distribution 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 fault-line selecting method based on phase current transient characteristic of the present invention, the steps include:

S1: measure distribution line outlet residual voltage value continuously, if residual voltage is more than voltage setting valve, then judges that power distribution network is sent out Raw earth fault, utilizes and is arranged on the circuit head end FTU device each circuit three-phase current signal of collection；

S2: the phase current data gathered are processed, extracts each circuit transient state difference of phase currents, and it is carried out alternate two Pairwise correlation is analyzed, and calculates the alternate correlation coefficient array [ρ of this circuit_AB ρ_BC ρ_CA], obtain alternate minimum by comparing Correlation coefficient ρ_kmin；

S3: each line fault phase current is carried out spectrum analysis, calculates its gravity frequency f_kg；

S4: be normalized fault characteristic value, obtains normalized valueWithAnd set up two-dimensional coordinate system with this, Determine each line fault characteristic coordinates point

S5: calculate fault signature distance d between each line fault characteristic coordinates point and datum mark (0,0)_k(k=1,2 ..., n).Work as d_max-d_min>d_setTime, then judge d_minCorresponding circuit is faulty line, and tripping operation is isolated this faulty line and realized line Road is protected；Work as d_max-d_min<d_setTime, then judge that bus-bar fault, tripping operation isolation bus realize route protection.

In concrete application example, in above-mentioned steps S2, by data are carried out pretreatment, extract each phase current of each circuit and dash forward Variant waveform, the similarity of two waveforms can be described by correlation coefficient, and the computing formula of correlation coefficient ρ is as follows:

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

In formula, x (n), y (n) are 2 discrete signal sequences, and corresponding transient state difference of phase currents sampled value, N represents that discrete sampling is believed The length of number sequence.

Under same data window, calculate the relevant array [ρ that each circuit two is alternate_AB ρ_BC ρ_CA], if ρ_kminFor circuit k phase Closing the minima in array, for faulty line fault phase with to perfect phase Sudden Changing Rate difference relatively big, correlation coefficient is the least, for non- Faulty line, each difference of phase currents is the most similar, and correlation coefficient is bigger.

In concrete application example, in above-mentioned steps S3, calculate the gravity frequency of each line fault phase, for ask for out from The current signal frequency spectrum dissipated can use following formula to calculate gravity frequency:

$f_g=\underset{f=f_1}{\overset{f_2}{\&Sigma;}}\&lsqb;i\left(f\right)gf\&rsqb;/\underset{f=f_1}{\overset{f_2}{\&Sigma;}}i\left(f\right)$

Wherein f_gRepresenting gravity frequency, i (f) is the frequency spectrum of current signal, and f is each corresponding analog frequency of bar spectral line, f₁-f₂ For calculating the interval of frequency, generally take 0:3000Hz section, relatively low for faulty line fault phase gravity frequency, rather than fault wire Road fault phase is just the opposite.

In concrete application example, in above-mentioned steps S4, logarithm value makees normalized, and correlation coefficient ρ is on the basis of 1, Therefore without processing.Gravity frequency then using 3000Hz as benchmark, being calculated as follows of its normalized value:

$f_{kg}^{*}=f_{kg}/3000$

In concrete application example, in above-mentioned steps S5, with alternate correlation coefficient minimaAs transverse axis, gravity frequency Normalized valueFor the longitudinal axis, set up two-dimensional coordinate system,Represent the transient state phase current fault signature of circuit k Point, obtains fault signature distance d of each circuit relative datum point (0,0)_kAs the criterion of route selection, its expression formula is:

$d_k=\sqrt{{({\mathrm{\&rho;}}_{k\min }^{*}-0)}^2+{(f_{kg}^{*}-0)}^2}.$

As the presently preferred embodiments, in step S1 in this example, voltage setting valve span is 5%～30% phase voltage value.

As the presently preferred embodiments, in step S4 in this example, it is with alternate least correlativing coefficientFor transverse axis,It is vertical Axle (k=1,2 ..., n) sets up two-dimensional coordinate system.

As the presently preferred embodiments, in step S5 in this example, d_setGenerally take 0.3.

As in figure 2 it is shown, be present invention earth fault experiment schematic diagram in concrete application example, with L on bus₁、L₂、 L₃、L₄Article four, feeder line, L₁For the overhead transmission line of 20km, L₂For the cable run of 10km, L₃For joint line, by 10km Overhead transmission line and 5km cable run composition, L₄For the overhead transmission line of 30km, each line parameter circuit value is shown in Table 1, at each feeder line Outlet protection device for installing.

Table 1

Respectively with circuit L₁、L₂And bus (includes fault distance, earth resistance, fault initial phase angle etc.) under the conditions of different faults Occurring to carry out experiment test during singlephase earth fault, the protection device being arranged on line port obtains the transient current signal of each circuit； Go out the frequecy characteristic of corresponding difference of phase currents and fault phase from signal extraction, calculate the alternate minimum phase relation of each circuit Number ρ_kminWith fault phase gravity frequency f_kg；After normalized, set up coordinate system, as shown in (a) and (b) in Fig. 3, Points different in coordinate represents the distribution situation of various circuits and non-fault line characteristic coordinates.

After determining fault signature coordinate, calculate fault signature distance d of each circuit respectively_k, judge corresponding according to the size of distance Circuit whether break down.Result of calculation is as shown in table 2.

Table 2

As can be seen from Table 2, either when high resistance ground or fault initial phase angle are less, the fault signature of faulty line away from From being minima, and affected not quite by resistance variations and angle, much smaller than non-fault line, it is easy to judge fault Circuit；During bus-bar fault, each line fault characteristic distance is more or less the same, and the difference of its maximum and minima is respectively less than setting value 0.3, Therefore, can determine that as bus-bar fault.Test result indicate that the inventive method has higher accuracy, validity and reliability.

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 (7)

1. a fault-line selecting method based on phase current transient characteristic, it is characterised in that step is:

S1: measure distribution line outlet residual voltage value continuously, if residual voltage is more than voltage setting valve, then judges that power distribution network is sent out Raw earth fault, utilizes and is arranged on the circuit head end FTU device each circuit three-phase current signal of collection；

S2: the phase current data gathered are processed, extracts each circuit transient state difference of phase currents, and it is carried out alternate two Pairwise correlation is analyzed, and calculates the alternate correlation coefficient array [ρ of this circuit_AB ρ_BC ρ_CA], obtain alternate minimum by comparing Correlation coefficient ρ_kmin；

S3: each line fault phase current is carried out spectrum analysis, calculates its gravity frequency f_kg；

S4: be normalized fault characteristic value, obtains normalized valueWithAnd set up two-dimensional coordinate system with this, Determine each line fault characteristic coordinates point

S5: calculate fault signature distance d between each line fault characteristic coordinates point and datum mark (0,0)_k, wherein k=1,2 ..., n；Work as d_max-d_min＞ d_setTime, then judge d_minCorresponding circuit is faulty line, and tripping operation is isolated this faulty line and realized line Road is protected；Work as d_max-d_min<d_setTime, then judge that bus-bar fault, tripping operation isolation bus realize route protection；Wherein d_maxFor event Barrier characteristic distance maximum, d_minFor fault signature distance maximum, d_setFor fault signature distance setting value.

Fault-line selecting method based on phase current transient characteristic the most according to claim 1, it is characterised in that described step S2 includes:

S201: by data are carried out pretreatment, extracts each circuit each difference of phase currents waveform, the similarity of two waveforms Being described by correlation coefficient, the computing formula of correlation coefficient ρ is as follows:

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

In formula, x (n), y (n) are 2 discrete signal sequences, and corresponding transient state difference of phase currents sampled value, N represents that discrete sampling is believed The length of number sequence；

S202: under same data window, calculates the relevant array [ρ that each circuit two is alternate_AB ρ_BC ρ_CA], if ρ_kminFor line Road k is correlated with the minima in array, and for faulty line fault phase with to perfect phase Sudden Changing Rate difference relatively big, correlation coefficient is the least, For non-fault line, each difference of phase currents is the most similar, and correlation coefficient is bigger.

Fault-line selecting method based on phase current transient characteristic the most according to claim 1, it is characterised in that described step In S3, calculating the gravity frequency of each line fault phase, the discrete current signal frequency spectrum for asking for out uses following formula to calculate Gravity frequency:

$f_g=\underset{f=f_1}{\overset{f_2}{\&Sigma;}}\&lsqb;i\left(f\right)gf\&rsqb;/\underset{f=f_1}{\overset{f_2}{\&Sigma;}}i\left(f\right)$

Wherein f_gRepresenting gravity frequency, i (f) is the frequency spectrum of current signal, and f is each corresponding analog frequency of bar spectral line, f₁-f₂ For calculating the interval of frequency, relatively low for faulty line fault phase gravity frequency, and non-fault line fault phase is just the opposite.

Fault-line selecting method based on phase current transient characteristic the most according to claim 1, it is characterised in that described step In S4, logarithm value makees normalized, and correlation coefficient ρ is on the basis of 1, gravity frequency using 3000Hz as benchmark, its Being calculated as follows of normalized value:

$f_{\mathrm{kg}}^{*}=f_{\mathrm{kg}}/3000.$

Fault-line selecting method based on phase current transient characteristic the most according to claim 1, it is characterised in that described step In S5, with alternate correlation coefficient minimaAs transverse axis, the normalized value of gravity frequencyFor the longitudinal axis, set up two dimension and sit Mark system,Represent the transient state phase current fault signature point of circuit k, obtain each circuit relative datum point (0,0) Fault signature distance d_kAs the criterion of route selection, its expression formula is:

$d_k=\sqrt{{({\mathrm{\&rho;}}_{kmin}^{*}-0)}^2+{(f_{kg}^{*}-0)}^2}.$

6. according to the fault-line selecting method based on phase current transient characteristic described in any one in Claims 1 to 5, its feature Being, in described step S1, voltage setting valve span is 5%～30% phase voltage value.

7. according to the fault-line selecting method based on phase current transient characteristic described in any one in Claims 1 to 5, its feature It is, in described step S5, d_setTake 0.3.