CN101587159B - Power distribution network outgoing feeder fault route selecting method by S transform amplitude detection - Google Patents

Abstract

The invention relates to a power distribution network outgoing feeder fault route selecting method by S transform amplitude detection, namely, when the power distribution network generates single-phase ground fault, the bus zero sequence voltage before and after the fault can be performed for S transform to find out the moment corresponding to a module maximal value on the S transform highest frequency component position for accurately calibrating the fault moment; the each line zero sequence current before and after the fault moment can be performed for S transform to obtain the S transform complex matrix of each line zero sequence current; the amplitudes of highest frequency component at fault moment in the each line zero sequence current S transform complex matrix can be worked out, andthe amplitude difference can be worked out; the integrative amplitude difference of each line zero sequence current can be worked out; the fault route selecting can be implemented by comparing the si ze of the integrative amplitude difference. The invention can avoid the route selecting failure caused by CT saturation and phase alternation, the invention implements the route selecting by using high-frequency components, without being influenced by arc-suppression coil compensation degree. The accurate route selecting under different fault conditions comprising small fault angle can be implemented.

Description

The power distribution network outgoing fault-line selecting method that utilizes S conversion argument to detect

Technical field

The present invention relates to the relay protection of power system technical field, the power distribution network outgoing fault-line selecting method that specifically utilizes S conversion argument to detect.

Background technology

The resonant earthed system single-phase earth fault line selection is the difficult point of one-phase earthing failure in electric distribution network route selection.During resonant earthed system generation singlephase earth fault, the capacitance current that the inductive current compensate for failed of arc suppression coil produces, make that the fault steady-state current in the faulty line is very little, even less than perfecting circuit, therefore traditional detection method based on fault stable state information is difficult to satisfactory for resonant earthed system route selection effect.Utilize the transient state component after the fault to carry out failure line selection, and utilize steady-state signal to compare to have an enormous advantage: the one, the transient signal amplitude is far longer than steady-state signal, is the several times to tens times of steady-state signal, and fault detect is highly sensitive; The 2nd, be not subjected to the influence of arc suppression coil; The 3rd, be not subjected to that trouble spot electric arc is unsettled to be influenced, in fact the intermittence of trouble spot punctures, and can constantly produce the transient zero-sequence current signal, helps detection failure.Along with the development of modern microelectric technique, the transient signal that can more easily write down and produce with complex mathematical algorithm process earth fault, so the transient state component method has great vitality.

The S conversion is to be the extension of the continuous wavelet transform of basic small echo with the Morlet small echo.Be equivalent to add the Short Time Fourier Transform of normalization Gaussian window or through the wavelet transformation of phase correction, its inherits and developed the localization thought of continuous wavelet transform and Short Time Fourier Transform.The S conversion has the resolution with frequency dependence, and its transformation results can be passed through the time-frequency expression matrix, has concentrated the advantage of Short Time Fourier Transform and wavelet transformation.The complex matrix that signal obtains after the S conversion can be explained amplitude, frequency and the phase propetry of signal, is suitable for analyzing the signal after the power distribution network resonant earthed system fault.

Summary of the invention

The purpose of this invention is to provide the power distribution network outgoing fault-line selecting method that a kind of S of utilization conversion argument detects.Can realize to the different faults situation the accurate route selection when comprising the glitch angle.

Technical scheme of the present invention is as follows:

1, S conversion basic theories

The S conversion is a kind of reversible local Time-Frequency Analysis Method, and its thought is the development to continuous wavelet transform and Short Time Fourier Transform.The S conversion S of signal x (t) (τ f) is defined as follows:

$S(\mathrm{\&tau;},f)={\&Integral;}_{-\&infin;}^{\&infin;}x\left(t\right)w(\mathrm{\&tau;}-t,f)e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H2009100946192E00021.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;ft}}\mathrm{dt}---\left(1\right)$

$w(\mathrm{\&tau;}-t,f)=\frac{\left|f\right|}{\sqrt{2\mathrm{\&pi;}}}{e}^{\left|\frac{-f^2{(\mathrm{\&tau;}-t)}^2}{2}\right|}---\left(2\right)$

Wherein, (τ-t f) is Gauss's window (Gaussian Window) to w, and τ is the location parameter of control Gauss window at time shaft t, and f is a frequency, and j is an imaginary unit.

The discrete representation form S[m of S conversion, n] be:

$S[m,n]=\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}X[n+k]e^{-2{\mathrm{\&pi;}}^2{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="H2009100946192E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}^2/n^2}{\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="H2009100946192E00021.png"\; state="\{\{state\}\}">e</figure-callout>}}^j$ n≠0 (3)

$S[m,n]=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x\left[k\right]$ n＝0 (4)

Wherein

$X\left[n\right]=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x\left[k\right]e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H2009100946192E00021.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;kn}/N}---\left(5\right)$

In the following formula, the row of the matrix that the matrix column that m obtains for the S conversion, n obtain for the S conversion, k is the location parameter of control Gauss window at time shaft t, N is a sampling number.So to N the discrete signal point x[i that collects] (i=0,1 ..., N-1) the S conversion is carried out in employing formula (3), (4), and transformation results is a multiple time-frequency matrix, and note is made s-matrix, the corresponding sampling time point of its row, the row respective frequencies, the difference on the frequency Δ f between the adjacent lines is:

$\mathrm{\&Delta;f}=\frac{f_s}{N}---\left(6\right)$

The frequency f of the capable correspondence of n _nFor:

$f_n=\frac{f_s}{N}n---\left(7\right)$

F wherein _sBe sample frequency.

Each element of s-matrix asked obtain matrix behind the mould and be designated as the S modular matrix, its column vector is represented signal amplitude versus frequency characte at a time, and the time domain of its row vector representation signal under a certain frequency distributes.

2, the fault-line selecting method that utilizes S conversion argument to detect

For ease of analyzing, set up the one-phase earthing failure in electric distribution network system as shown in Figure 2.This system shown in Figure 2 is a 110kV/35kV electric substation that 6 circuits are arranged, and Z font transformer neutral point adopts LSJC-35 type current transformer by arc suppression coil resistance in series ground connection.Circuit adopts overhead transmission line (L ₁, L ₃, L ₅), line-cable joint line (L ₄) and cable line (L ₂, L ₆), wherein, overhead transmission line adopts JS ₁The bar type, LGJ-70 type lead, span are 80m, cable line adopts YJV23-35/95 type cable.

Among Fig. 2, T is a step-down transformer, and Tz is a Z font transformer, and K is a switch, and L is the arc suppression coil inductance, and R is the arc suppression coil resistance in series, R _fBe earth fault transition resistance, i ₀₁, i ₀₄, i ₀₆Be respectively circuit L ₁, L ₄, L ₆Zero-sequence current.

Utilize the S conversion amplitude variation characteristic on each frequency component of analytic signal independently, observe the moment that the corresponding frequency amplitude situation of change in time of row in the complex matrix that the S conversion obtains can be judged sign mutation.During power distribution network generation singlephase earth fault, the bus residual voltage raises suddenly, therefore, can utilize the accurate demarcation signal sudden change of S conversion constantly, i.e. fault moment.Power distribution network shown in Figure 2, cable line L ₂When at distance bus 2km place singlephase earth fault taking place, the fault transition resistance is 200 Ω, and the fault switching angle is 60 °.The bus residual voltage is carried out the S conversion, utilize synoptic diagram that the S conversion accurately demarcates fault moment as shown in Figure 3.

Among Fig. 3, u/V represents voltage/volt, t/ms express time/millisecond.As seen from Figure 3, carry out the S conversion for the bus residual voltage, time-the amplitude distribution that obtains 250kHz and 500kHz by the row of S conversion modular matrix correspondence as can be seen, the extreme point of different frequency point place time-amplitude curve is all constantly corresponding with sign mutation, and strengthen gradually to this character pair of high frequency by low frequency, therefore, a plurality of following times of Frequency point of comprehensive observing S modular matrix-amplitude curve, can determine fault moment by the modulus maximum of high fdrequency component.The modulus maximum moment corresponding of high fdrequency component is fault moment.

Power distribution network generation singlephase earth fault moment, the faulty line zero-sequence current with perfect circuit zero sequence current opposite in direction, each circuit zero-sequence current before and after the fault moment is carried out the S conversion, obtain the S conversion complex matrix of each circuit zero-sequence current.In the S conversion complex matrix of each circuit zero-sequence current, high fdrequency component has embodied the phase relation of fault zero-sequence current at fault moment in the argument size of fault moment.Therefore, can ask for the method for its phase angle according to the actual place of plural number quadrant, ask for the argument θ of the zero-sequence current of circuit i at fault moment according to a known plural number _i, i=1,2 ..., h, h are power distribution network circuit sum.The argument difference θ of circuit i zero-sequence current and all the other circuit zero-sequence currents then _IjFor:

i＝1，2，...，h；j＝1，2，...，h (8)

In the formula, θ _jBe the zero-sequence current of circuit j argument at fault moment.This shows θ _IjIt is the matrix on a h * h rank.The comprehensive argument difference φ of definition circuit i zero-sequence current and all the other circuit zero-sequence currents _iFor:

According to the phase relation of distribution fault zero-sequence current, can get the failure line selection criterion and be at fault moment:

1, if φ _i〉=150 °, i=1,2 ..., h, then circuit i is a faulty line;

2, if φ _i＜150 °, for i=1,2 ..., h all sets up, and then is bus-bar fault.

In sum, the power distribution network outgoing fault-line selecting method that the S of utilization conversion argument of the present invention detects is: when power distribution network generation singlephase earth fault, bus residual voltage before and after the fault is carried out the S conversion, find out the modulus maximum moment corresponding at S conversion highest frequency component place, be fault moment, each circuit zero-sequence current before and after the fault moment is carried out the S conversion, obtain the S conversion complex matrix of each line zero stream electric current; Ask in each line zero sequence current S transform complex matrix highest frequency component at the argument of fault moment, and it is poor to ask for argument; The comprehensive argument of asking for each line zero stream electric current is poor; Realize failure line selection by more comprehensive argument extent.

The specific implementation step is:

(1) as bus residual voltage instantaneous value u _n(t) greater than K _uU _n, fault line selection device starts immediately, and the sample frequency of employing 1MHz is noted bus residual voltage and each feeder line zero-sequence current, wherein K of 1 cycle in fault front and back _uGeneral value is 0.15, U _nExpression bus rated voltage;

(2) utilize the discrete form S[m of S conversion, n] the bus residual voltage is analyzed, take place constantly with accurate demarcation fault;

$S[m,n]=\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}X[n+k]e^{-2{\mathrm{\&pi;}}^2{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="H2009100946192E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}^2/n^2}{\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="H2009100946192E00021.png"\; state="\{\{state\}\}">e</figure-callout>}}^j$ n≠0

$S[m,n]=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x\left[k\right]$ n＝0

Wherein

$X\left[n\right]=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x\left[k\right]e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H2009100946192E00021.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;kn}/N}$

In the following formula, the signal that x (k) expression need be carried out the S conversion, the row of the matrix that the matrix column that m obtains for the S conversion, n obtain for the S conversion, k is the location parameter of control Gauss window at time shaft t, N is a sampling number; The modulus maximum moment corresponding of high fdrequency component is fault moment in the S transformation results;

(3) adopt the discrete form of S conversion in the step (2) that each circuit zero-sequence current is carried out the S conversion, obtain the S conversion complex matrix of each circuit zero-sequence current;

(4) highest frequency component of taking out the S conversion complex matrix of each the circuit zero-sequence current that obtains in the step (3) is analyzed, ask for the method for its phase angle according to a known plural number according to the actual place of plural number quadrant, ask for the argument θ of the zero-sequence current of circuit i at fault moment _i, i=1,2 ..., h, h are power distribution network circuit sum, and ask for the argument difference θ of circuit i zero-sequence current and all the other circuit zero-sequence currents according to following formula _Ij

i＝1，2，...，h；j＝1，2，...，h

In the formula, θ _jBe the zero-sequence current of circuit j argument at fault moment;

(5) the comprehensive argument difference φ of definition circuit i zero-sequence current and all the other circuit zero-sequence currents _iFor:

(6), can get the failure line selection criterion and be according to the phase relation of distribution fault zero-sequence current at fault moment:

1) if

I=1,2 ..., h, then circuit i is a faulty line;

2) if

For i=1,2 ..., h all sets up, and then is bus-bar fault.

The present invention compared with prior art has following advantage:

1, the present invention can avoid because the route selection failure that CT is saturated and paraphase causes.

2, the present invention adopts high fdrequency component to realize route selection, is not subjected to the influence of arc suppression coil compensation degree.

3, the present invention can realize the different faults situation, and the accurate route selection when comprising the glitch angle is good to the adaptability of arc fault.

4, the present invention does not rely on the line construction parameter, when the short-term road fault, is not subjected to the influence of long line capacitance electric current, can accurately discern faulty line.

Description of drawings:

Fig. 1 is a failure line selection process flow diagram of the present invention.

Fig. 2 is an one-phase earthing failure in electric distribution network system schematic of the present invention.

Fig. 3 is circuit L of the present invention ₂The S conversion of fault bus residual voltage, (a) bus residual voltage; (b) 250kHz time-amplitude curve; (c) 500kHz time-amplitude curve.

Fig. 4 is circuit L of the present invention ₁The S conversion of fault bus residual voltage, (a) bus residual voltage; (b) 500kHz time-amplitude curve.

Embodiment:

The concrete steps of line selection algorithm of the present invention are as follows:

1, as bus residual voltage instantaneous value u _n(t) greater than K _uU _n, fault line selection device starts immediately, and the sample frequency of employing 1MHz is noted bus residual voltage and each feeder line zero-sequence current, wherein K of 1 cycle in fault front and back _uGeneral value is 0.15, U _nExpression bus rated voltage;

2, utilize the discrete form S[m of S conversion, n] the bus residual voltage is analyzed, take place constantly with accurate demarcation fault;

$S[m,n]=\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}X[n+k]e^{-2{\mathrm{\&pi;}}^2{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="H2009100946192E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}^2/n^2}{\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="H2009100946192E00021.png"\; state="\{\{state\}\}">e</figure-callout>}}^j$ n≠0

$S[m,n]=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x\left[k\right]$ n＝0

Wherein

$X\left[n\right]=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x\left[k\right]e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H2009100946192E00021.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;kn}/N}$

In the following formula, the signal that x (k) expression need be carried out the S conversion, the row of the matrix that the matrix column that m obtains for the S conversion, n obtain for the S conversion, k is the location parameter of control Gauss window at time shaft t, N is a sampling number.

The modulus maximum moment corresponding of high fdrequency component is fault moment in the S transformation results;

3, adopt the discrete form of S conversion in the step 2 that each circuit zero-sequence current is carried out the S conversion, obtain the S conversion complex matrix of each circuit zero-sequence current;

4, the highest frequency component of taking out the S conversion complex matrix of each the circuit zero-sequence current that obtains in the step 3 is analyzed, and asks for the method for its phase angle according to a known plural number according to the actual place of plural number quadrant, asks for the argument θ of the zero-sequence current of circuit i at fault moment _i, i=1,2 ..., h, h are power distribution network circuit sum, and ask for the argument difference θ of circuit i zero-sequence current and all the other circuit zero-sequence currents according to following formula _Ij

i＝1，2，...，h；j＝1，2，...，h

In the formula, θ _jBe the zero-sequence current of circuit j argument at fault moment.This shows θ _IjIt is the matrix on a h * h rank.

5, the comprehensive argument difference φ of definition circuit zero-sequence current i and all the other circuit zero-sequence currents _iFor:

6,, can get the failure line selection criterion and be according to the phase relation of distribution fault zero-sequence current at fault moment:

1) if

I=1,2 ..., h, then circuit i is a faulty line;

2) if

For i=1,2 ..., h all sets up, and then is bus-bar fault.

For example:

When resonant earthed system generation singlephase earth fault as shown in Figure 2, circuit L ₁Apart from bus 5km place, A phase ground connection is taken place, transition resistance is 200 Ω, the fault switching angle is 90 degree.Carry out route selection with method of the present invention, detailed process is as follows:

1) the bus residual voltage is carried out the S conversion, data window length is 0.2ms, and its result as shown in Figure 4.

As shown in Figure 4, the modulus maximum of the highest frequency component 500kHz of bus residual voltage S conversion appears at 0.025ms, and promptly fault moment is 0.025ms.

2) each circuit zero-sequence current is carried out the S conversion, the highest frequency component 500kHz of S conversion complex matrix that asks for each circuit zero-sequence current is at the argument at fault moment 0.025ms place: θ ₁=-158.2 °, θ ₂=21.8 °, θ ₃=21.8 °, θ ₄=21.8 °, θ ₅=21.8 °, θ ₆=21.8 °.

3) utilize formula (8) to ask for the argument difference θ of circuit i zero-sequence current and all the other circuit zero-sequence currents _IjFor:

4) the comprehensive argument difference of utilizing formula (9) to ask for circuit i zero-sequence current is:

φ ₁＝180°，φ ₂＝36°，φ ₃＝36°，φ ₄＝36°，φ ₅＝36°，φ ₆＝36°

And φ is only arranged ₁=180 ° 〉=150 °.Thus, decidable is circuit L ₁Fault.

Claims (1)

1. power distribution network outgoing fault-line selecting method that utilizes S conversion argument to detect, it is characterized in that: during power distribution network generation singlephase earth fault, bus residual voltage before and after the fault is carried out the S conversion, find out the modulus maximum moment corresponding at S conversion highest frequency component place, this is fault moment constantly; Each circuit zero-sequence current before and after the fault moment is carried out the S conversion, obtain the S conversion complex matrix of each line zero stream electric current; Ask in each line zero sequence current S transform complex matrix highest frequency component at the argument of fault moment, and it is poor to ask for argument; The comprehensive argument of asking for each line zero stream electric current is poor; Realize failure line selection by more comprehensive argument extent; The specific implementation step is:

(1) as bus residual voltage instantaneous value u _n(t) greater than K _uU _n, fault line selection device starts immediately, and the sample frequency of employing 1MHz is noted bus residual voltage and each feeder line zero-sequence current, wherein K of 1 cycle in fault front and back _uValue is 0.15, U _nExpression bus rated voltage;

(2) utilize the discrete form S[m of S conversion, n] the bus residual voltage is analyzed, take place constantly with accurate demarcation fault;

$S[m,n]=\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}X[n+k]e^{-2{\mathrm{\&pi;}}^2{k}^2/n^2}{e}^{j2\mathrm{\&pi;km}/N},n\&NotEqual;0$

$S[m,n]=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x\left[k\right],n=0$

Wherein

$X\left[n\right]=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}x\left[k\right]e^{-j2\mathrm{\&pi;kn}/N}$

In the following formula, the signal that x (k) expression need be carried out the S conversion, the row of the matrix that the matrix column that m obtains for the S conversion, n obtain for the S conversion, k is the location parameter of control Gauss window at time shaft t, N is a sampling number; The modulus maximum moment corresponding of high fdrequency component is fault moment in the S transformation results;

(3) adopt the discrete form of S conversion in the step (2) that each circuit zero-sequence current is carried out the S conversion, obtain the S conversion complex matrix of each circuit zero-sequence current;

(4) highest frequency component of taking out the S conversion complex matrix of each the circuit zero-sequence current that obtains in the step (3) is analyzed, ask for the method for its phase angle according to a known plural number according to the actual place of plural number quadrant, ask for the argument θ of the zero-sequence current of circuit i at fault moment _i, i=1,2 ..., h, h are power distribution network circuit sum, and ask for the argument difference θ of circuit i zero-sequence current and all the other circuit zero-sequence currents according to following formula _Ij

i＝1，2，…，h；j＝1，2，...，h

In the formula, θ _jBe the zero-sequence current of circuit j argument at fault moment;

(5) the comprehensive argument difference φ of definition circuit i zero-sequence current and all the other circuit zero-sequence currents _iFor:

(6), can get the failure line selection criterion and be according to the phase relation of one-phase earthing failure in electric distribution network zero-sequence current at fault moment:

1) if I=1,2 ..., h, then circuit i is a faulty line;

2) if

For i=1,2 ..., h all sets up, and then is bus-bar fault.

Images