CN104914351A - Area power network fault positioning method based on optimal wave velocity - Google Patents

Abstract

The invention relates to a fault positioning method for power system automation, and especially relates to an area power network fault positioning method based on an optimal wave velocity. The method, based on a genetic algorithm and a signal spectrum analysis, carries out fault positioning by use of branch line refracted waves correlated with fault lines in a power network. The method comprises the following steps: (1), analyzing a power grid structure and carrying out data pairing; (2), constructing a target function, and generating variable constraining conditions; (3), carrying out the signal spectrum analysis on the branch line refracted waves, and determining frequency components of signals and a frequency correction coefficient scope; (4), solving an optimal solution of the target function by use of the genetic algorithm to obtain the optimal wave velocity; and (5), according to the optimal wave velocity, obtaining a fault point position and outputting a result. The method provided by the invention takes the influences of the frequency and the path of each branch line into full consideration, and compared to a conventional area power network fault positioning algorithm, obviously improves the precision.

Description

A kind of regional power grid Fault Locating Method based on optimum velocity of wave

Technical field

The present invention relates to the Fault Locating Method of Automation of Electric Systems, be specifically related to a kind of regional power grid Fault Locating Method based on optimum velocity of wave.

Background technology

After transmission line of electricity breaks down, even if successful reclosing, also need track walker's looking up the fault point, judge can continue to run or palpus interruption maintenance, to remove a hidden danger according to the damaged condition that fault causes.Therefore, after line fault, fast searching trouble spot (measuring distance of transmission line fault technology is also referred to as Fault-Locating Test) just becomes the gordian technique ensureing power network safety operation.

Transmission line travelling wave fault location device (hereinafter referred to as traveling wave ranging device), according to the difference adopting electric parameters, can be divided into single-ended traveling wave method, both-end traveling wave method and impulse method.At present, practical traveling wave ranging device mainly adopts both-end traveling wave method, its principle is as follows: both-end traveling wave method principle is first the wavefront signal utilizing fault to produce, the mistiming arriving circuit two ends by calculating fault initial row ripple calculates abort situation, as shown in Figure 1, computing formula is as follows:

$l_1=\frac{L^{\″}{(t_2-t_1)}^v}{2}$ ①；

In above formula: l ₁for fault distance; t ₁, t ₂be respectively the time that initial row ripple arrives circuit two ends, L'' is total track length, v is row velocity of wave propagation, both-end traveling wave method only needs the initial wave head of identification signal in calculating, principle is simple and reliable, but it needs circuit both sides device data, requires the support of communication and GPS, System's composition relative complex.

At present, transmission line travelling wave fault location device is applied widely in China's electric system, and the regional faults positioning system that traveling wave ranging device networking is formed has been built up in the provinces such as domestic Liaoning, Sichuan.As previously mentioned, what existing traveling wave ranging device great majority adopted is both-end traveling wave method, relate to sampling, GPS time service, the multiple link of communication, more intermediate link reduces entire system reliability, if circuit side plant failure, then system just cannot normally work, and this just have impact on the global reliability of system.

After transmission line malfunction, transient state travelling wave can be refracted on branched line by bus, branched line distance measuring equipment due to algorithm, definite value design on to avoid tripping, therefore record ripple can be started under most failure condition, this condition that has been just feasible region electric network fault Positioning Creates.Regional power grid localization of fault has following meaning in engineering:

1) improve system reliability, utilize multiterminal data to complete range finding, avoid side plant failure causing trouble to locate unsuccessfully;

2) reduce system Construction cost, can suitably reduce terminal configuration quantity.

At present, the research of regional power grid localization of fault has achieved certain achievement, but in general, existing regional power grid Fault Locating Method mainly chooses shortest path by network structure generator matrix, or exploitation right coefficient is used for localization of fault with reference to multi-group data, substantially do not relate to the signal attenuation in traveling wave process and wave form distortion, and this is the key factor affecting localization of fault precision.In practical engineering application, the precision of existing regional power grid localization of fault is lower than both-end traveling wave method.

Summary of the invention

For the deficiencies in the prior art, the object of this invention is to provide a kind of regional power grid Fault Locating Method based on optimum velocity of wave, the method utilizes branched line refraction wave relevant to faulty line in electrical network to carry out localization of fault calculating, the method has taken into full account the impact in each branched line frequency, path, significantly improves relative to existing regional power grid fault location algorithm precision.

The object of the invention is to adopt following technical proposals to realize:

The invention provides a kind of regional power grid Fault Locating Method based on optimum velocity of wave, its improvements are, described method is based on genetic algorithm and signal spectrum analysis, and utilize branched line refraction wave relevant to faulty line in electrical network to carry out localization of fault, described method comprises the steps:

(1) Power grid structure analysis carry out data pair;

(2) establishing target function, generates variable bound condition;

(3) the signal spectrum analysis of branched line refraction wave, determines frequency content and the frequency correction factor scope of signal;

(4) utilize the optimum solution of genetic algorithm for solving objective function, obtain optimum velocity of wave;

(5) obtain position of failure point according to optimum velocity of wave, and result is exported.

Further, in described step (1), after transmission line malfunction, transient state travelling wave is refracted on each branched line by bus, branched line refraction wave signal is all gathered to regional power grid Nei Ge transformer station, consider the impact of transient state travelling wave signal dispersion in reality, select the data of faulty line adjacent substations;

Transmission line travelling wave distance measuring equipment adopts both-end traveling wave method: both-end traveling wave method principle is first the wavefront signal utilizing fault to produce, and the mistiming arriving circuit two ends by calculating fault initial row ripple calculates abort situation, and expression formula is as follows:

$l_1=\frac{L^{\″}{(t_2-t_1)}^v}{2}$ ①；

In above formula: l ₁for fault distance; t ₁, t ₂be respectively the time that initial row ripple arrives circuit two ends, L'' is total track length, and v is row velocity of wave propagation;

Regional power grid is made to comprise transformer station M, N and transformer station S ₁, S ₂s _n; Described transformer station M is connected with transformer station N by circuit L '; Described transformer station S ₁be connected with transformer station M by branched line 1; Described transformer station S ₂be connected with transformer station M by branched line 2; Described transformer station S _nbe connected with transformer station M by branched line n; Branched line 1, branched line 2 and branched line n are in parallel.

Further, in described step (2), when faulty line is MN section, after transient state travelling wave arrives transformer station M end, hold bus to be refracted on branched line 1 ~ n through transformer station M, the branched line refraction wave and the transformer station N that choose transformer station S end hold initial row ripple to form both-end distance measuring; Transformer station S end comprises transformer station S ₁, S ₂and S _nend;

Transformer station S holds the both-end distance measuring formed with transformer station N end data to calculate respectively, and formula is as follows:

$\left\{\begin{array}{c}{d}_1=\frac{L+L_1-(t_1^{\′}-t_2)*v_1}{2}\\ d_2=\frac{L+L_2-(t_2^{\′}-t_2)*v_2}{2}\\ ......\\ d_n=\frac{L+L_n-(t_n^{\′}-t_2)*v_n}{2}\end{array}\right.$ ②；

Wherein, t ' ₁, t' ₂, t' _nmeet following formula:

t' _n＝t ₁+(L _n/v _n) ③；

Formula 2., 3. in, L, L ₁, L ₂, L _nbe respectively faulty line and branched line 1,2, the line length of n; T1, t2 are respectively initial row ripple and arrive M, N end moment; T ' ₁, t' ₂, t' _nfor branched line refraction wave arrives S ₁, S ₂, S _nthe moment of end; d ₁, d ₂, d _nbe respectively different end device data both-end result of calculation; v ₁, v ₂, v _nbe branched line 1,2, traveling wave speed on n; Due to d in theory ₁, d ₂, d _nequal, namely meet the following conditions:

$t_1^{\′}-t_2^{\′}-t_n^{\′}-\frac{L_1}{v_0\×k_{f1}\×k_{s1}}+\frac{L_2}{v_0\×k_{f2}\×k_{s2}}+\frac{L_n}{v_0\×k_{\mathrm{fn}}\×k_{\mathrm{sn}}}=0$ ④；

$t_1=t_1^{\′}-\frac{L_1}{v_0\×k_{f1}\×k_{s1}}$ ⑤；

Formula 4. in, v ₀for supposition benchmark velocity of wave; k _f1, k _f2, k _fnfrequency correction factor respectively, for revising the velocity of wave difference that each branched line refraction wave different frequency signals causes; k _s1, k _s2, k _snbe respectively path modification coefficient, for revising the velocity of wave difference that each branched line refraction wave different transmission path causes;

Establishing target function as shown in the formula:

$f(k_{f1},k_{f2},k_{\mathrm{fn}},k_{s1},k_{s2},k_{\mathrm{sn}},v_0)=t_1^{\′}-t_2^{\′}-t_n^{\′}-\frac{L_1}{v_0\×k_{f1}\×k_{s1}}+\frac{L_2}{v_0\×k_{f2}\×k_{s2}}+\frac{L_n}{v_0\×k_{\mathrm{fn}}\×k_{\mathrm{sn}}}$ ⑥；

The variable bound condition of objective function is as follows:

$\left\{\begin{array}{c}{v}_{\min }<v_0<v_{\max }\\ k_{f\min }<k_{\mathrm{fn}}<k_{f\max }\\ k_{s\min }<k_{\mathrm{sn}}<k_{s\max }\end{array}\right.$ ⑦；

Formula 7. in, v _max, v _minbe respectively the upper lower limit value of velocity of wave; k _fmax, k _fminbe respectively the upper lower limit value of frequency correction factor; k _smax, k _sminbe respectively the upper lower limit value of path modification coefficient.

Further, path modification coefficient is by obtaining the analysis of line construction, and frequency correction factor passes through to obtain signal spectrum analysis, namely based on the frequency correction factor of signal spectrum analysis and the correction factor defining method based on line construction;

Correction factor defining method based on line construction comprises: according to line parameter circuit values such as each branched line lead wire and earth wire spacing, tower structure, length, contrast, obtain the path modification coefficient of each branched line with basis point branch line;

Specific as follows: according to the characteristic impedance of each branched line of route parameter calculation, attenuation coefficient and phase coefficient, expression formula is as follows respectively:

$\mathrm{\&alpha;}=\sqrt{[R_m{G}_m-{\mathrm{\&omega;}}^2{L}_m{C}_m+\sqrt{(R_m^2+{\mathrm{\&omega;}}^2{L}_m^2)(G_m^2+{\mathrm{\&omega;}}^2{C}_m^2)}]/2}$ ⑩；

$\mathrm{\&beta;}=\sqrt{[{\mathrm{\&omega;}}^2{L}_m{C}_m-R_m{G}_m+\sqrt{(R_m^2+{\mathrm{\&omega;}}^2{L}_m^2)(G_m^2+{\mathrm{\&omega;}}^2{C}_m^2)}]/2}$ ；

In above formula, α is attenuation coefficient, and β is phase coefficient; R _m, G _m, ω, L _mdistinguish the mould resistance of corresponding unit length circuit, inductance, conductance and electric capacity; Obtaining in circuit phase coefficient situation, row velocity of wave propagation is as follows:

$v=\frac{\mathrm{\&omega;}}{\mathrm{\&beta;}}$ 。

With basis point branch line for standard, calculate the same frequency Signal transmissions velocity of wave difference because each branched line transmission path difference causes, in Practical Project, transfer relative value and path modification coefficient to.

Further, in described step (3), adopt Hilbert-yellow HHT to convert marginal spectrum and spectrum analysis is carried out to each branched line refraction wave, calculate the frequency of refraction wave high fdrequency component, contrast with basis point branch line again, obtain the frequency correction factor of each branched line;

Hilbert-yellow HHT converts marginal spectrum based on decomposition base intrinsic mode function IMF, and obtain multiple decomposition base intrinsic mode function IMF by empirical mode decomposition EMD, conversion net result is as follows:

$s\left(t\right)=\underset{k=1}{\overset{n}{\mathrm{\&Sigma;}}}{C}_k+r$ ⑧；

In above formula: s (t) is original signal, r is residual components, C _kfor decomposing base intrinsic mode function IMF, Hilbert-yellow HHT converts marginal spectrum and is defined as follows:

$h\left(w\right)={\&Integral;}_0^{T}H(w,t)\mathrm{dt}$ ⑨；

The cumulative distribution that what Hilbert-yellow HHT converted that marginal spectrum characterizes is on Frequency point, i.e. energy distribution, with basis point branch line for standard, calculates the frequency difference of each branched line refraction wave frequency component, and transfers relative value and frequency correction factor to.

Further, in described step (4), 6. branched line length, velocity of wave, frequency correction factor and path modification coefficient are substituted into formula, calculating target function;

In genetic algorithm: coded system adopts binary coding; Fitness function is objective function; Genetic manipulation and controling parameters is utilized to calculate; 6. solve to obtain optimum velocity of wave by formula, substitute into formula 5. initial wave head arrives transformer station M and holds the bus time, finally transformer station M, N are held bus initial time to substitute into formula and 1. obtain position of failure point.

Compared with the prior art, the beneficial effect that the present invention reaches is:

(1) area fault location algorithm does not affect by factors such as terminal fault, GPS, communicating interrupt substantially, and the relatively existing device of global reliability of fault location system significantly improves.

(2) localization of fault precision is high, and algorithm of the present invention has taken into full account the impact in each branched line frequency, path, significantly improves relative to existing regional power grid fault location algorithm precision.Through testing Liaoning Province 2009 ~ 2011 annual data, area fault location algorithm precision reaches the precision of existing both-end traveling wave method substantially.

Accompanying drawing explanation

Fig. 1 is both-end travelling wave ranging schematic diagram;

Fig. 2 is area fault location algorithm schematic diagram provided by the invention;

Fig. 3 is the area fault location algorithm process flow diagram based on optimum velocity of wave provided by the invention;

Fig. 4 is the network structure of specific embodiment provided by the invention;

Fig. 5 is genetic algorithm iteration convergence curve map provided by the invention.

Embodiment

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in further detail.

The invention provides a kind of regional power grid Fault Locating Method based on optimum velocity of wave, the method is based on genetic algorithm and signal spectrum analysis, and utilize branched line refraction wave relevant to faulty line in electrical network to carry out localization of fault, described method comprises the steps:

(1) Power grid structure analysis carry out data pair;

After transmission line malfunction, transient state travelling wave can be refracted on each branched line by bus, in theory, regional power grid Nei Ge transformer station all can collect branched line refraction wave signal, but in practical engineering application, consider transient state travelling wave signal dispersion, main selection faulty line adjacent substations data.

Transmission line travelling wave distance measuring equipment adopts both-end traveling wave method: both-end traveling wave method principle is first the wavefront signal utilizing fault to produce, and the mistiming arriving circuit two ends by calculating fault initial row ripple calculates abort situation, and expression formula is as follows:

$l_1=\frac{L^{\&Prime;}{(t_2-t_1)}^v}{2}$ ①；

In above formula: l ₁for fault distance; t ₁, t ₂be respectively the time that initial row ripple arrives circuit two ends, L'' is total track length, and v is row velocity of wave propagation;

Area fault location algorithm schematic diagram as shown in Figure 2, makes regional power grid comprise transformer station M, N and transformer station S ₁, S ₂s _n; Described transformer station M is connected with transformer station N by branched line L '; Described transformer station S ₁be connected with transformer station M by branched line 1; Described transformer station S ₂be connected with transformer station M by branched line 2; Described transformer station S _nbe connected with transformer station M by branched line n; Branched line 1, branched line 2 and branched line n are in parallel.

(2) establishing target function, generates variable bound condition;

When faulty line is MN section, after transient state travelling wave arrives M end, can pass through M and hold bus to be refracted on branched line 1 ~ n, therefore, branched line refraction wave and the N that can choose S end hold initial row ripple to form both-end distance measuring.Consider that S end may have multiple transformer station (to be defined as S ₁, S ₂, S _nend), then S holds the both-end distance measuring computing formula formed with N end data as follows:

$\left\{\begin{array}{c}{d}_1=\frac{L+L_1-(t_1^{\&prime;}-t_2)*v_1}{2}\\ d_2=\frac{L+L_2-(t_2^{\&prime;}-t_2)*v_2}{2}\\ ......\\ d_n=\frac{L+L_n-(t_n^{\&prime;}-t_2)*v_n}{2}\end{array}\right.$ ②；

Wherein, t ' ₁, t' ₂, t' _nmeet following formula:

t' _n＝t ₁+(L _n/v _n) ③；

Formula 2., 3. in, L, L ₁, L ₂, L _nbe respectively faulty line and branched line 1,2, the line length of n; T1, t2 are respectively initial row ripple and arrive M, N end moment; T ' ₁, t' ₂, t' _nfor branched line refraction wave arrives S ₁, S ₂, S _nthe moment of end; d ₁, d ₂, d _nbe respectively different end device data both-end result of calculation; v ₁, v ₂, v _nbe branched line 1,2, traveling wave speed on n; Due to d in theory ₁, d ₂, d _nequal, namely meet the following conditions:

$t_1^{\&prime;}-t_2^{\&prime;}-t_n^{\&prime;}-\frac{L_1}{v_0\&times;k_{f1}\&times;k_{s1}}+\frac{L_2}{v_0\&times;k_{f2}\&times;k_{s2}}+\frac{L_n}{v_0\&times;k_{\mathrm{fn}}\&times;k_{\mathrm{sn}}}=0$ ④；

$t_1=t_1^{\&prime;}-\frac{L_1}{v_0\&times;k_{f1}\&times;k_{s1}}$ ⑤；

Formula 4. in, v ₀for supposition benchmark velocity of wave; k _f1, k _f2, k _fnfrequency correction factor respectively, for revising the velocity of wave difference that each branched line refraction wave different frequency signals causes; k _s1, k _s2, k _snbe respectively path modification coefficient, for revising the velocity of wave difference that each branched line refraction wave different transmission path causes; By solution formula 4., result is substituted into formula and 5. obtain t ₁then hold the initial wave head moment for final M, be combined can complete localization of fault with N end data.But frequency, path modification coefficient climate condition affect astable value, and often there is error therefore in Practical Project, therefore, the accurate Calculation of velocity of wave and correction factor is difficult to realize in engineering.

Adopt optimum velocity of wave to instead of tradition in the method for the invention and preset velocity of wave, and frequency, path modification coefficient are transferred to relative value and calculate.With wall scroll branched line for benchmark, coefficient value scope between given each branched line, establishing target function, and utilize genetic algorithm be optimized calculate ask the optimum solution of objective function (i.e. optimum velocity of wave), be shown below:

$f(k_{f1},k_{f2},k_{\mathrm{fn}},k_{s1},k_{s2},k_{\mathrm{sn}},v_0)=t_1^{\&prime;}-t_2^{\&prime;}-t_n^{\&prime;}-\frac{L_1}{v_0\&times;k_{f1}\&times;k_{s1}}+\frac{L_2}{v_0\&times;k_{f2}\&times;k_{s2}}+\frac{L_n}{v_0\&times;k_{\mathrm{fn}}\&times;k_{\mathrm{sn}}}$ ⑥；

For ensureing the rationality of separating, in research, also proposed formula following variable bound condition 6.:

$\left\{\begin{array}{c}{v}_{\min }<v_0<v_{\max }\\ k_{f\min }<k_{\mathrm{fn}}<k_{f\max }\\ k_{s\min }<k_{\mathrm{sn}}<k_{s\max }\end{array}\right.$ ⑦；

Formula 7. in, v _max, v _minbe respectively the upper lower limit value of velocity of wave; k _fmax, k _fminbe respectively the upper lower limit value of frequency correction factor; k _smax, k _sminbe respectively the upper lower limit value of path modification coefficient.In Practical Project, path modification coefficient is by obtaining the analysis of line construction, and frequency correction factor then needed to obtain the analysis of spectrum of signal, namely based on the frequency correction factor of signal spectrum analysis and the correction factor defining method based on line construction;

Correction factor defining method based on line construction comprises: according to line parameter circuit values such as each branched line lead wire and earth wire spacing, tower structure, length, contrast, obtain the path modification coefficient of each branched line with basis point branch line.

Concrete grammar is as follows: according to the characteristic impedance of each branched line of route parameter calculation, attenuation coefficient and phase coefficient, and expression formula is as follows respectively:

$\mathrm{\&alpha;}=\sqrt{[R_m{G}_m-{\mathrm{\&omega;}}^2{L}_m{C}_m+\sqrt{(R_m^2+{\mathrm{\&omega;}}^2{L}_m^2)(G_m^2+{\mathrm{\&omega;}}^2{C}_m^2)}]/2}$ ⑩；

$\mathrm{\&beta;}=\sqrt{[{\mathrm{\&omega;}}^2{L}_m{C}_m-R_m{G}_m+\sqrt{(R_m^2+{\mathrm{\&omega;}}^2{L}_m^2)(G_m^2+{\mathrm{\&omega;}}^2{C}_m^2)}]/2}$

In above formula, α is attenuation coefficient, and β is phase coefficient; R _m, G _m, ω, L _mdistinguish the mould resistance of corresponding unit length circuit, inductance, conductance and electric capacity; Obtaining in circuit phase coefficient situation, row velocity of wave propagation is as follows:

$v=\frac{\mathrm{\&omega;}}{\mathrm{\&beta;}}$

With basis point branch line for standard, calculate the same frequency Signal transmissions velocity of wave difference because each branched line transmission path difference causes, in Practical Project, transfer relative value and path modification coefficient to.

(3) the signal spectrum analysis of branched line refraction wave, determines frequency content and the frequency correction factor scope of signal;

Adopt Hilbert-yellow HHT to convert marginal spectrum and spectrum analysis is carried out to each branched line refraction wave, calculate the frequency of refraction wave high fdrequency component, then contrast with basis point branch line, obtain the frequency correction factor of each branched line;

Hilbert-yellow HHT converts marginal spectrum based on decomposition base intrinsic mode function IMF, and obtain multiple decomposition base intrinsic mode function IMF by empirical mode decomposition EMD, conversion net result is as follows:

$s\left(t\right)=\underset{k=1}{\overset{n}{\mathrm{\&Sigma;}}}{C}_k+r$ ⑧；

In above formula: s (t) is original signal, r is residual components, C _kfor decomposing base intrinsic mode function IMF, Hilbert-yellow HHT converts marginal spectrum and is defined as follows:

$h\left(w\right)={\&Integral;}_0^{T}H(w,t)\mathrm{dt}$ ⑨；

From formula 9., the cumulative distribution that what Hilbert-yellow HHT converted that marginal spectrum characterizes is on Frequency point, i.e. energy distribution, therefore, is more suitable for analyzing row wave frequency composition.By can obtain the span of frequency correction factor to the signal spectrum analysis of each branched line refraction wave.

(4) utilize the optimum solution of genetic algorithm for solving objective function, obtain optimum velocity of wave;

6. branched line length, velocity of wave, frequency correction factor and path modification coefficient are substituted into formula, calculating target function;

In genetic algorithm: coded system adopts binary coding; Fitness function is objective function; Genetic manipulation and controling parameters is utilized to calculate; 6. solve to obtain optimum velocity of wave by formula, substitute into formula 5. initial wave head arrives transformer station M and holds the bus time, finally transformer station M, N are held bus initial time to substitute into formula and 1. obtain position of failure point.Based on optimum velocity of wave area fault location algorithm process flow diagram as shown in Figure 3.

(5) obtain position of failure point according to optimum velocity of wave, and result is exported.

Embodiment

Be recorded as example with one group of physical fault below to illustrate: in August, 2011 Qingyuan County, liaoning Province prosperous second line fault, because Yi Xian Qinghe, Qinghe Power Plant Side distance measuring equipment damages, cannot provide range measurement in time, the network structure of specific embodiment as shown in Figure 4, adopts the inventive method calculation process as follows:

(1) Qinghe power plant neighbor stations is selected: Shen Dong, Niu Gang, Tieling, brave Shitai County, station, Changtu data carry out regional power grid localization of fault.

(2) structure of objective function and parameter initialization, hold the initial wave head moment based on each branched line initial wave head moment precomputation M.Because measuring error generally presents normal distribution principle, in repetitive measurement situation, average should close to exact value, and therefore, using the branched line closest to average as reference line, its velocity of wave, frequency, transmission path are as reference reference value.

Table 1 physical fault analyzes data

Remarks: initial value first supposes in calculating that each branched line velocity of wave is consistent, only as subsequent analysis reference.

The M calculated based on each branched line holds initial wave head moment (t ₁, primary fault wave head arrives the Qinghe power plant time) and as shown in table 2, mean value =100725.26us, considers that distance measuring equipment average error (σ) is in 500 meters (3 ~ 4us) left and right, when differing 3 more than σ with average, namely thinking and belonging to bad measurement data, being rejected in the calculation.After the clear brave second line of cancellation, calculating each branched line average is 100716.16us, and actual M holds initial wave head moment 100706.49us error to be about about 9.67us, in subsequent calculations, then using the branched line 1 closest to average as reference value.Calculate velocity of wave by average error ± σ (3 ~ 4us) equally, can obtain benchmark velocity of wave interval is 284.9 ~ 300m/us.

(3) the signal spectrum analysis of branched line refraction wave, determines frequency content and the frequency correction factor span of signal.

Table 2 frequency correction factor and path modification coefficient

Remarks: consider that same electric pressure lead wire and earth wire spacing is basically identical, path modification coefficient mainly considers the impact of line construction and length.

(4) generate genetic algorithm according to formula 4 and calculate required objective function, determine the parameters needed for genetic algorithm, solve best fit approximation solution (namely solving the most reasonable velocity of wave), substitute into formula 5,1 and can obtain final position of failure point.

The value of the frequency in physical fault data analysis, path modification coefficient is see table 2, and with clear prosperous second line for basis of reference value, calculate from simplification and improve precision and consider, engineer applied medium frequency, path modification coefficient value scope suitably expand.The parameter such as length, velocity of wave, correction factor is substituted into formula 6 calculate required objective function.

In this fault, after successive ignition calculates, trying to achieve equation optimum solution (i.e. the optimum velocity of wave of clear prosperous second line) is 285.54m/us, and corresponding M holds bus moment 100710.3us.3us is reduced relative to branched line 1 and initial calculation mean value error, 3.81us is differed with the physical fault moment, the 0.5us extra error that in deduction station, bus brings, error is 3.31us, corresponding transmission open acess error is about about 484m (supposing that velocity of wave is 293m/us), close to existing both-end travelling wave ranging precision, the iteration convergence curve ginseng of algorithm as shown in Figure 5.

Finally should be noted that: above embodiment is only in order to illustrate that technical scheme of the present invention is not intended to limit, although with reference to above-described embodiment to invention has been detailed description, those of ordinary skill in the field are to be understood that: still can modify to the specific embodiment of the present invention or equivalent replacement, and not departing from any amendment of spirit and scope of the invention or equivalent replacement, it all should be encompassed in the middle of right of the present invention.

Claims (6)

1. the regional power grid Fault Locating Method based on optimum velocity of wave, it is characterized in that, described method is based on genetic algorithm and signal spectrum analysis, and utilize branched line refraction wave relevant to faulty line in electrical network to carry out localization of fault, described method comprises the steps:

(1) Power grid structure analysis carry out data pair;

(2) establishing target function, generates variable bound condition;

(3) the signal spectrum analysis of branched line refraction wave, determines frequency content and the frequency correction factor scope of signal;

(4) utilize the optimum solution of genetic algorithm for solving objective function, obtain optimum velocity of wave;

(5) obtain position of failure point according to optimum velocity of wave, and result is exported.

2. regional power grid Fault Locating Method as claimed in claim 1, it is characterized in that, in described step (1), after transmission line malfunction, transient state travelling wave is refracted on each branched line by bus, branched line refraction wave signal is all gathered to regional power grid Nei Ge transformer station, consider the impact of transient state travelling wave signal dispersion in reality, select the data of faulty line adjacent substations;

Transmission line travelling wave distance measuring equipment adopts both-end traveling wave method: both-end traveling wave method principle is first the wavefront signal utilizing fault to produce, and the mistiming arriving circuit two ends by calculating fault initial row ripple calculates abort situation, and expression formula is as follows:

$l_1=\frac{L^{\&Prime;}{(t_2-t_1)}^v}{2}$ ①；

In above formula: l ₁for fault distance; t ₁, t ₂be respectively the time that initial row ripple arrives circuit two ends, L'' is total track length, and v is row velocity of wave propagation;

Regional power grid is made to comprise transformer station M, N and transformer station S ₁, S ₂s _n; Described transformer station M is connected with transformer station N by circuit L '; Described transformer station S ₁be connected with transformer station M by branched line 1; Described transformer station S ₂be connected with transformer station M by branched line 2; Described transformer station S _nbe connected with transformer station M by branched line n; Branched line 1, branched line 2 and branched line n are in parallel.

3. regional power grid Fault Locating Method as claimed in claim 1, it is characterized in that, in described step (2), when faulty line is MN section, after transient state travelling wave arrives transformer station M end, hold bus to be refracted on branched line 1 ~ n through transformer station M, the branched line refraction wave and the transformer station N that choose transformer station S end hold initial row ripple to form both-end distance measuring; Transformer station S end comprises transformer station S ₁, S ₂and S _nend;

Transformer station S holds the both-end distance measuring formed with transformer station N end data to calculate respectively, and formula is as follows:

$\left\{\begin{array}{c}{d}_1=\frac{L+L_1-(t_1^{\&prime;}-t_2)*v_1}{2}\\ d_2=\frac{L+L_2-(t_2^{\&prime;}-t_2)*v_2}{2}\\ ......\\ d_n=\frac{L+L_n-(t_n^{\&prime;}-t_2)*v_n}{2}\end{array}\right.$ ②；

Wherein, t ' ₁, t' ₂, t' _nmeet following formula:

t' _n＝t ₁+(L _n/v _n) ③；

Formula 2., 3. in, L, L ₁, L ₂, L _nbe respectively faulty line and branched line 1,2, the line length of n; T1, t2 are respectively initial row ripple and arrive M, N end moment; T ' ₁, t' ₂, t' _nfor branched line refraction wave arrives S ₁, S ₂, S _nthe moment of end; d ₁, d ₂, d _nbe respectively different end device data both-end result of calculation; v ₁, v ₂, v _nbe branched line 1,2, traveling wave speed on n; Due to d in theory ₁, d ₂, d _nequal, namely meet the following conditions:

$t_1^{\&prime;}-t_2^{\&prime;}-t_n^{\&prime;}-\frac{L_1}{v_0\&times;k_{f1}\&times;k_{s1}}+\frac{L_2}{v_0\&times;k_{f2}\&times;k_{s2}}+\frac{L_n}{v_0\&times;k_{\mathrm{fn}}\&times;k_{\mathrm{sn}}}=0$ ④；

$t_1=t_1^{\&prime;}-\frac{L_1}{v_0\&times;k_{f1}\&times;k_{s1}}$ ⑤；

Formula 4. in, v ₀for supposition benchmark velocity of wave; k _f1, k _f2, k _fnfrequency correction factor respectively, for revising the velocity of wave difference that each branched line refraction wave different frequency signals causes; k _s1, k _s2, k _snbe respectively path modification coefficient, for revising the velocity of wave difference that each branched line refraction wave different transmission path causes;

Establishing target function as shown in the formula:

$f(k_{f1},k_{f2},k_{\mathrm{fn}},k_{s1},k_{s2},k_{\mathrm{sn}},v_0)=t_1^{\&prime;}-t_2^{\&prime;}-t_n^{\&prime;}-\frac{L_1}{v_0\&times;k_{f1}\&times;k_{s1}}+\frac{L_2}{v_0\&times;k_{f2}\&times;k_{s2}}+\frac{L_n}{v_0\&times;k_{\mathrm{fn}}\&times;k_{\mathrm{sn}}}$ ⑥；

The variable bound condition of objective function is as follows:

$\left\{\begin{array}{c}{v}_{\min }<v_0<v_{\max }\\ k_{f\min }<k_{\mathrm{fn}}<k_{f\max }\\ k_{s\min }<k_{\mathrm{sn}}<k_{s\max }\end{array}\right.$ ⑦；

Formula 7. in, v _max, v _minbe respectively the upper lower limit value of velocity of wave; k _fmax, k _fminbe respectively the upper lower limit value of frequency correction factor; k _smax, k _sminbe respectively the upper lower limit value of path modification coefficient.

4. regional power grid Fault Locating Method as claimed in claim 3, it is characterized in that, path modification coefficient is by obtaining the analysis of line construction, frequency correction factor passes through to obtain signal spectrum analysis, namely based on the frequency correction factor of signal spectrum analysis and the correction factor defining method based on line construction;

Correction factor defining method based on line construction comprises: according to line parameter circuit values such as each branched line lead wire and earth wire spacing, tower structure, length, contrast, obtain the path modification coefficient of each branched line with basis point branch line;

Specific as follows: according to the characteristic impedance of each branched line of route parameter calculation, attenuation coefficient and phase coefficient, expression formula is as follows respectively:

$\mathrm{\&alpha;}=\sqrt{[R_m{G}_m-{\mathrm{\&omega;}}^2{L}_m{C}_m+\sqrt{(R_m^2+{\mathrm{\&omega;}}^2{L}_m^2)(G_m^2+{\mathrm{\&omega;}}^2{C}_m^2)}]/2}$ ⑩；

$\mathrm{\&beta;}=\sqrt{[{\mathrm{\&omega;}}^2{L}_m{C}_m-R_m{G}_m+\sqrt{(R_m^2+{\mathrm{\&omega;}}^2{L}_m^2)(G_m^2+{\mathrm{\&omega;}}^2{C}_m^2)}]/2}$

In above formula, α is attenuation coefficient, and β is phase coefficient; R _m, G _m, ω, L _mdistinguish the mould resistance of corresponding unit length circuit, inductance, conductance and electric capacity; Obtaining in circuit phase coefficient situation, row velocity of wave propagation is as follows:

$v=\frac{\mathrm{\&omega;}}{\mathrm{\&beta;}}$

With basis point branch line for standard, calculate the same frequency Signal transmissions velocity of wave difference because each branched line transmission path difference causes, in Practical Project, transfer relative value and path modification coefficient to.

5. regional power grid Fault Locating Method as claimed in claim 1, it is characterized in that, in described step (3), adopt Hilbert-yellow HHT to convert marginal spectrum and spectrum analysis is carried out to each branched line refraction wave, calculate the frequency of refraction wave high fdrequency component, contrast with basis point branch line again, obtain the frequency correction factor of each branched line;

Hilbert-yellow HHT converts marginal spectrum based on decomposition base intrinsic mode function IMF, and obtain multiple decomposition base intrinsic mode function IMF by empirical mode decomposition EMD, conversion net result is as follows:

$s\left(t\right)=\underset{k=1}{\overset{n}{\mathrm{\&Sigma;}}}{C}_k+r$ ⑧；

In above formula: s (t) is original signal, r is residual components, C _kfor decomposing base intrinsic mode function IMF, Hilbert-yellow HHT converts marginal spectrum and is defined as follows:

$h\left(w\right)={\&Integral;}_0^{T}H(w,t)\mathrm{dt}$ ⑨；

The cumulative distribution that what Hilbert-yellow HHT converted that marginal spectrum characterizes is on Frequency point, i.e. energy distribution, with basis point branch line for standard, calculates the frequency difference of each branched line refraction wave frequency component, and transfers relative value and frequency correction factor to.

6. regional power grid Fault Locating Method as claimed in claim 1, is characterized in that, in described step (4), 6. branched line length, velocity of wave, frequency correction factor and path modification coefficient is substituted into formula, calculating target function;

In genetic algorithm: coded system adopts binary coding; Fitness function is objective function; Genetic manipulation and controling parameters is utilized to calculate; 6. solve to obtain optimum velocity of wave by formula, substitute into formula 5. initial wave head arrives transformer station M and holds the bus time, finally transformer station M, N are held bus initial time to substitute into formula and 1. obtain position of failure point.