CN105226616A - A kind of bus bar protecting method based on row wave height frequency component coefficient correlation - Google Patents

Abstract

The present invention relates to a kind of bus bar protecting method based on row wave height frequency component coefficient correlation, belong to Relay Protection Technology in Power System field.During system generation single phase ground fault, under sample rate 1MHz, first the three-phase current sampled value utilizing each bar circuit measuring end to obtain calculates line mould electric current, then wavelet transformation is carried out to the line mould electric current of each bar circuit, and the high fdrequency component extracted under the first yardstick carries out correlation analysis between two, ask for the coefficient correlation between circuit, form correlation matrix.Finally calculate the mean value of other each element absolute values except diagonal entry in every a line of correlation matrix respectively, obtain the integrated correlation coefficient of every bar circuit relative to All other routes, form integrated correlation coefficient matrix.When the integrated correlation coefficient of all circuits is all less than threshold value, then decision-making system generation line fault; When the integrated correlation coefficient of all circuits is all greater than threshold value, then decision-making system generation busbar fault.Theory analysis and emulation show that the present invention is respond well.

Description

A kind of bus bar protecting method based on row wave height frequency component coefficient correlation

Technical field

The present invention relates to a kind of bus bar protecting method based on row wave height frequency component coefficient correlation, belong to Relay Protection Technology in Power System field.

Background technology

Bus connects many into and out of circuit, is the hinge of power transmission and distribution, occupies extremely important status in electric power system.During busbar fault; if can not detect in time and excise fault bus; accident scope will be expanded; damage more equipment; destruction power system safety and stability runs; even disintegrate whole electric power system, therefore, research reliability is high, selectivity good, highly sensitive bus protection principle is necessary.Existing PC bus protection is generally based on power frequency electric flow, and protecting group originally can meet system for reliability and optionally requirement, but faces the problem of anti-current instrument transformer saturability difference.In addition, along with the expansion gradually of net capacity and scale, the responsiveness of existing bus protection more and more can not meet the requirement of electric power system for protection quick-action.Scholar is had to propose to utilize the bus protection new method of theory of travelling wave and wavelet theory; shorten the operate time of protection to a certain extent; but utilize the detection method of wavelet theory large by high-frequency noise interference, be often difficult to selecting properly fault wave head and compare, actual effect is not high.Therefore, be badly in need of proposing one bus protection new method more reliably.

Summary of the invention

The object of the invention is, in order to overcome the not high problem of traditional bus protection reliability, to propose a kind of bus bar protecting method based on row wave height frequency component coefficient correlation.

Technical scheme of the present invention is: a kind of bus bar protecting method based on row wave height frequency component coefficient correlation; when system generation single phase ground fault; under sample rate 1MHz; first the three-phase current sampled value utilizing each bar circuit measuring end to obtain calculates line mould electric current; then wavelet transformation is carried out to the line mould electric current of each bar circuit; and the high fdrequency component extracted under the first yardstick carries out correlation analysis between two, asks for the coefficient correlation between circuit, form correlation matrix.Finally calculate the mean value of other each element absolute values except diagonal entry in every a line of correlation matrix respectively, obtain the integrated correlation coefficient of every bar circuit relative to All other routes, form integrated correlation coefficient matrix.When the integrated correlation coefficient of all circuits is all less than threshold value, then decision-making system generation line fault; When the integrated correlation coefficient of all circuits is all greater than threshold value, then decision-making system generation busbar fault.Construct the bus bar protecting method based on row wave height frequency component coefficient correlation thus.

Specifically follow these steps to realize:

(1) under 1MHz sample rate, the three-phase current that the measuring end of every bar circuit obtains is sampled, obtain each bar circuit phase current sampling value sequence i _n,a(k), i _n,b(k), i _n,c(k), wherein k represents sampled point, k=1,2 ... N, and N is total number of sample points; N represents system line number, n=1,2,

(2) formula (1) is utilized to calculate the discrete series i of each bar circuit line mould electric current respectively _{n, ab}(k):

i _n,ab(k)＝i _n,a(k)-i _n,b(k)(1)

(3) utilize formula (2) to the discrete series i of each bar circuit line mould electric current _{n, ab}k () carries out wavelet analysis respectively, extract the high fdrequency component d under wavelet transformation first yardstick _n(k):

$d_n\left(k\right)=\underset{p=1}{\overset{8}{\Σ}}{i}_{n,ab}(k-p)h\left(p\right)---\left(2\right)$

In formula (2), h [p] is small echo high pass filter coefficient, h [p]=[0.0625,0.125,0.375,0.375,0.125,0.0625]; P is discrete signal p sampled point.

(4) utilize formula (3) to the high fdrequency component d under each bar circuit line mould electric current wavelet transformation first yardstick _nk () carries out correlation analysis between two, ask for the coefficient correlation between circuit, forms correlation matrix M:

${\mathrm{\ρ}}_{ij}=\underset{k=0}{\overset{N-1}{\Σ}}{d}_i\left(k\right)d_j\left(k\right){\[\underset{k=0}{\overset{N-1}{\Σ}}{d}_i{\left(k\right)}^2\underset{k=0}{\overset{N-1}{\Σ}}{d}_j{\left(k\right)}^2\]}^{-1/2}---\left(3\right)$

$M=\left[\begin{array}{cccc}{\mathrm{\ρ}}_1& {\mathrm{\ρ}}_{12}& ...& {\mathrm{\ρ}}_{ln}\\ & & .& \\ & & .& \\ & & .& \\ {\mathrm{\ρ}}_{n1}& {\mathrm{\ρ}}_{n2}& ...& {\mathrm{\ρ}}_{nn}\end{array}\right]---\left(4\right)$

In formula (3), n is system line number; In correlation matrix M, diagonal entry is the auto-correlation coefficient of each circuit line mould electric current wavelet conversion coefficient, and its value is 1, and all the other elements are the cross-correlation coefficient between two of each circuit line mould electric current wavelet conversion coefficient; d _ik () represents the line mould electric current wavelet conversion coefficient of i-th circuit, d _jthe line mould electric current wavelet conversion coefficient of (k) jth bar circuit; ρ _ijrepresent the coefficient correlation of i-th circuit and jth bar circuit.

(5) utilize formula (5) to calculate the mean value of other each element absolute values except diagonal entry in every a line of correlation matrix respectively, obtain the integrated correlation coefficient ρ of every bar circuit relative to All other routes _i, i=1,2 ..., n, forms integrated correlation coefficient matrix Q:

${\mathrm{\ρ}}_i=\frac{1}{n-1}\underset{j=1,j\≠i}{\overset{n}{\Σ}}\left|{\mathrm{\ρ}}_{ij}\right|---\left(5\right)$

Q=[ρ ₁ρ ₂ρ _i] in (6) formula (5), | ρ _ij| represent the coefficient correlation absolute value of i-th circuit and jth bar circuit; ρ _irepresent the integrated correlation coefficient of every bar circuit relative to All other routes.

(6) when the integrated correlation coefficient of all circuits is all less than threshold value time, then decision-making system generation line fault; When the integrated correlation coefficient of all circuits is all greater than threshold value time, then decision-making system generation busbar fault.By a large amount of simulating, verifying, definite threshold

The invention has the beneficial effects as follows:

The present invention adopts wavelet transformation to extract circuit capable wave height frequency component and to go forward side by side line correlation analysis, compares according to integrated correlation coefficient and threshold value the differentiation realizing busbar fault and line fault.Principle is simple, and reliability is strong, does not affect by CT saturation and system oscillation etc.

Accompanying drawing explanation

Fig. 1 is the analogue system figure of embodiment 1,2,3;

Fig. 2 (a), (b), (c), (d) are respectively circuit L when AG fault occurs embodiment 1 median generatrix M ₁, L ₂, L ₃and L ₄line mould current traveling wave;

Fig. 3 (a), (b), (c), (d) are respectively circuit L when AG fault occurs embodiment 1 median generatrix M ₁, L ₂, L ₃and L ₄line mould electric current wavelet transform result;

Fig. 4 (a), (b), (c), (d) are respectively L in embodiment 2 ₁circuit L during generation AG fault ₁, L ₂, L ₃and L ₄line mould current traveling wave;

Fig. 5 (a), (b), (c), (d) are respectively L in embodiment 2 ₁circuit L during generation AG fault ₁, L ₂, L ₃and L ₄line mould electric current wavelet transform result.

Embodiment

Below in conjunction with drawings and Examples, the present invention is further elaborated.

During system generation single phase ground fault, under sample rate 1MHz, first the three-phase current sampled value utilizing each bar circuit measuring end to obtain calculates line mould electric current, then wavelet transformation is carried out to the line mould electric current of each bar circuit, and the high fdrequency component extracted under the first yardstick carries out correlation analysis between two, ask for the coefficient correlation between circuit, form correlation matrix.Finally calculate the mean value of other each element absolute values except diagonal entry in every a line of correlation matrix respectively, obtain the integrated correlation coefficient of every bar circuit relative to All other routes, form integrated correlation coefficient matrix.When the integrated correlation coefficient of all circuits is all less than threshold value, then decision-making system generation line fault; When the integrated correlation coefficient of all circuits is all greater than threshold value, then decision-making system generation busbar fault.

Embodiment 1:

With as shown in the figure 1 the simulation model of 3/2 mode of connection emulate, bus direct-to-ground capacitance is 0.01 μ F, circuit L ₁total length 400km, circuit L ₂total length 400km, circuit L ₃total length 400km, circuit L ₄total length 400km.If A phase earth fault occurs bus M, transition resistance is 10 Ω.Sample frequency is set to 1MHz.The measuring end of each bar circuit obtains the three-phase current after fault respectively.The three-phase fault electric current of every bar circuit is carried out phase-model transformation respectively and obtains line mould electric current, as shown in Figure 2.Carry out wavelet transformation such as Fig. 3 to the line mould electric current of each bar circuit to show, and extract the high fdrequency component d under wavelet transformation first yardstick _n(k).Coefficient correlation between computational scheme, forms correlation matrix P

$P=\left[\begin{array}{cccc}1& 1& 1& 1\\ 1& 1& 1& 1\\ 1& 1& 1& 1\\ 1& 1& 1& 1\end{array}\right]$

Finally calculate the mean value of other each element absolute values except diagonal entry in every a line of correlation matrix respectively, obtain the integrated correlation coefficient of every bar circuit relative to All other routes, form integrated correlation coefficient matrix Q

Q＝[1111] ^T

Therefore decision-making system generation busbar fault.

Embodiment 2:

With as shown in the figure 1 the simulation model of 3/2 mode of connection emulate, bus direct-to-ground capacitance is 0.01 μ F, circuit L ₁total length 400km, circuit L ₂total length 400km, circuit L ₃total length 400km, circuit L ₄total length 400km.Set out line L ₁hold 200km place that A phase earth fault occurs apart from bus M, transition resistance is 10 Ω.Sample frequency is set to 1MHz.Sample frequency is set to 1MHz.The measuring end of each bar circuit obtains the three-phase current after fault respectively.The three-phase fault electric current of every bar circuit is carried out phase-model transformation respectively and obtains line mould electric current, as shown in Figure 4.Wavelet transformation is carried out as shown in Figure 5 to the line mould electric current of each bar circuit, and extracts the high fdrequency component d under wavelet transformation first yardstick _n(k).Coefficient correlation between computational scheme, forms correlation matrix P

$P=\left[\begin{array}{cccc}1& -0.9514& -0.9515& -0.9515\\ -0.9514& 1& 1& 1\\ -0.9515& 1& 1& 1\\ -0.9515& 1& 1& 1\end{array}\right]$

Finally calculate the mean value of other each element absolute values except diagonal entry in every a line of correlation matrix respectively, obtain the integrated correlation coefficient of every bar circuit relative to All other routes, form integrated correlation coefficient matrix Q

Q＝[0.95150.98380.98380.9838] ^T

Therefore decision-making system generation line fault.

Claims (2)

1. the bus bar protecting method based on row wave height frequency component coefficient correlation, it is characterized in that: when system generation single phase ground fault, under sample rate 1MHz, first the three-phase current sampled value utilizing each bar circuit measuring end to obtain calculates line mould electric current, then wavelet transformation is carried out to the line mould electric current of each bar circuit, and the high fdrequency component extracted under the first yardstick carries out correlation analysis between two, asks for the coefficient correlation between circuit, form correlation matrix; Finally calculate the mean value of other each element absolute values except diagonal entry in every a line of correlation matrix respectively, obtain the integrated correlation coefficient of every bar circuit relative to All other routes, form integrated correlation coefficient matrix; When the integrated correlation coefficient of all circuits is all less than threshold value, then decision-making system generation line fault; When the integrated correlation coefficient of all circuits is all greater than threshold value, then decision-making system generation busbar fault.

2. the bus bar protecting method based on row wave height frequency component coefficient correlation according to claim 1, is characterized in that concrete steps are:

(1) under 1MHz sample rate, the three-phase current that the measuring end of every bar circuit obtains is sampled, obtain each bar circuit phase current sampling value sequence i _n,a(k), i _n,b(k), i _n,c(k), wherein k represents sampled point, k=1,2 ... N, and N is total number of sample points; N represents system line number, n=1,2 ...;

(2) formula (1) is utilized to calculate the discrete series i of each bar circuit line mould electric current respectively _{n, ab}(k):

i _n,ab(k)＝i _n,a(k)-i _n,b(k)(1)

(3) utilize formula (2) to the discrete series i of each bar circuit line mould electric current _{n, ab}k () carries out wavelet analysis respectively, extract the high fdrequency component d under wavelet transformation first yardstick _n(k):

$d_n\left(k\right)=\underset{p=1}{\overset{8}{\Σ}}{i}_{n,ab}(k-p)h\left(p\right)---\left(2\right)$

In formula (2), h [p] is small echo high pass filter coefficient, h [p]=[0.0625,0.125,0.375,0.375,0.125,0.0625]; P is discrete signal p sampled point;

(4) utilize formula (3) to the high fdrequency component d under each bar circuit line mould electric current wavelet transformation first yardstick _nk () carries out correlation analysis between two, ask for the coefficient correlation between circuit, forms correlation matrix M:

${\mathrm{\ρ}}_{ij}=\underset{k=0}{\overset{N-1}{\Σ}}{d}_i\left(k\right)d_j\left(k\right){\[\underset{k=0}{\overset{N-1}{\Σ}}{d}_i{\left(k\right)}^2\underset{k=0}{\overset{N-1}{\Σ}}{d}_j{\left(k\right)}^2\]}^{-1/2}---\left(3\right)$

$M=\left[\begin{array}{cccc}{\mathrm{\ρ}}_{11}& {\mathrm{\ρ}}_{12}& ...& {\mathrm{\ρ}}_{1n}\\ & & .& \\ \begin{array}{c}\\ \end{array}& \begin{array}{c}\\ \end{array}& \begin{array}{c}.\\ .\end{array}& \begin{array}{c}\\ \end{array}\\ {\mathrm{\ρ}}_{n1}& {\mathrm{\ρ}}_{n2}& ...& {\mathrm{\ρ}}_{nn}\end{array}\right]---\left(4\right)$

In formula (3), n is system line number; In correlation matrix M, diagonal entry is the auto-correlation coefficient of each circuit line mould electric current wavelet conversion coefficient, and its value is 1, and all the other elements are the cross-correlation coefficient between two of each circuit line mould electric current wavelet conversion coefficient; d _ik () represents the line mould electric current wavelet conversion coefficient of i-th circuit, d _jthe line mould electric current wavelet conversion coefficient of (k) jth bar circuit; ρ _ijrepresent the coefficient correlation of i-th circuit and jth bar circuit;

(5) utilize formula (5) to calculate the mean value of other each element absolute values except diagonal entry in every a line of correlation matrix respectively, obtain the integrated correlation coefficient ρ of every bar circuit relative to All other routes _i, i=1,2 ..., n, forms integrated correlation coefficient matrix Q:

${\mathrm{\ρ}}_i=\frac{1}{n-1}\underset{j=1,j\≠i}{\overset{n}{\Σ}}\left|{\mathrm{\ρ}}_{ij}\right|---\left(5\right)$

Q＝[ρ ₁ρ ₂…ρ _i](6)

In formula (5), | ρ _ij| represent the coefficient correlation absolute value of i-th circuit and jth bar circuit; ρ _irepresent the integrated correlation coefficient of every bar circuit relative to All other routes;

(6) when the integrated correlation coefficient of all circuits is all less than threshold value time, then decision-making system generation line fault; When the integrated correlation coefficient of all circuits is all greater than threshold value time, then decision-making system generation busbar fault.