64results about How to "Line selection is accurate" patented technology

The present invention is a distribution network cable-line mixed fault circuit selection method by using HHT detection technology. The invention uses HHT singularity detection technology to calibrate fault occurring time accurately, and implements circuit selection according to a principle that, when a fault occurs transient fault zero-sequence current component of the fault circuit and the regular circuit is opposite in direction. The specific method is using HHT to proceed EMD decomposition to the sampling signal of before and after 1/4 period each circuit fault zero-sequence current that is morphological filter pretreated, obtaining highest frequency IMF component of each circuit fault zero-sequence current and proceeding a first-order backward difference treatment to the IMF component, comparing the polar mutation of the fault zero-sequence current IMF component at fault moment, and then forming a circuit selection criterion. Analysis and simulation of the principle shows that, using fault information of 1/4 period after the fault to select circuit can provide an accurate and reliable circuit selection result and avoid effects of paraphrase and CT saturation on circuit selection accrracy.

The invention discloses an optimal route selection method for overhead transmission line route. Onboard lidar equipment is adopted to acquire laser point cloud data and aerial digital photo data of the transmission line route corridor range; the onboard lidar data is processed after the wave filtering and the sorting of the laser point cloud data, and the points of the ground surface are made into a digital elevation model with high precision; then data processing is carried out by utilizing the data of the digital elevation model with high precision and ortho-rectification is carried out to the aerial photo by utilizing the internal and external orientation elements of the aerial digital photo to generate digital orthophoto maps; through the overlying of the digital elevation model and the digital orthophoto maps, the tridimensional visualization of the transmission line route corridor can be realized to optimize the transmission line route selection; finally prearrangement of power pole and power pole arrangement are carried out according to the data of plane cross sections. The route selection platform of the invention has simple operation and lifelike tridimensional scene, thus being convenient for full roaming and multi-view observation and greatly improving the efficiency of the inner plane cross section survey operation. Compared with the optimal route selection technology based on the aerial photographing measuring method, the efficiency of the inner plane cross section survey operation can be improved by about 75 percent.

The invention relates to a measuring post simulation method of the fault wire selection for a low current grounding system. The invention belongs to the technical field of the power system relay protection. The method is realized by that when the instantaneous value of the voltage of a bus zero exceeds the limit, a fault wire selection device is started immediately and used for recording the wave. The invention adopts a digital filter algorithm to obtain the bus zero voltage and the transient pure fault components of zero current on each feedback line. When a low current grounding system takes place a single-phase earth fault, the waveform of the zero current is quantitatively solved by using measuring post simulation according to the transient pure fault component of the measured value of the bus zero voltage and the feeder zero distribution capacitor parameter under the assumption premise of the perfect feeder of every feeder. The invention carries out correlativity analysis to compare the measured waveform of the current of every zero current with the transient pure fault component solved by the measuring simulation method under a definite data window and calculate both correlative coefficients, thereby the invention forms a line selecting criterion 1 and 2 and can carry out line selection to the system according to the line selecting criterion. The principle analysis and the simulation show that the line selection method has the advantages of accuracy and reliability.

The invention relates to a self-adaptive method for single-phase grounding fault line selection of an electric distribution network by using S transformation energy relative entropy. The method comprises the following steps: when the zero-sequence voltage instantaneous value of a bus is out of limit, starting a fault line selection device immediately; performing S transformation on zero-sequence current in 1/4 cycle after the fault of each line, and calculating transient energy under each frequency of the zero-sequence current of each line by using a complex matrix obtained by the S transformation; and calculating the S transformation energy relative entropy under each frequency of each line and solving the comprehensive S transformation energy relative entropy of each line by using the super-strong recognition capability of the relative entropy to slight differences between signals, and self-adaptively selecting out the fault line by comparing the size of the comprehensive S transformation energy relative entropy of each line under all frequencies. Theoretical analyses and a large number of emulations show that the method effectively avoids the influence caused by a CT saturation discontinuous angle on the line selection, and is applicable to the cable-wire mixed line, pure cable lines and pure aerial lines.

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, and the 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 size 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.

The invention discloses a single-phase grounding fault line selection method for a small current grounding system based on transient zero-mode current. Three-phase modeling is performed on the power grid, and different fault conditions are selected for single-phase grounding fault simulation experiments to obtain various lines Transient zero-mode current; extract the above data; perform empirical mode decomposition EMD on the above data; calculate the time-domain energy of multiple IMFs and residual components; add the energy of IMF and residual components to obtain the energy sum of a line , repeat the above steps to obtain the energy sum of all lines; calculate the energy weight coefficients of each line, compare the energy weight coefficients of each line, and the line corresponding to the maximum energy weight coefficient is the faulty line. Comparing the peak value and polarity of the first zero-mode current pulse and the polarity of the first instantaneous power peak value, the zero-mode current amplitude of the faulty line is larger than that of the non-faulty line, and the polarity of the two is opposite. The invention is not affected by arc suppressing coils and fault conditions and can accurately select fault lines.

The invention relates to a small current earth fault line selection method for a radial distribution network. The small current earth fault line selection method for the radial distribution network comprises the steps that firstly, the line reference values of fault lines and non-fault lines are calculated according to the number of branch lines of a current radial distribution network system; secondarily, taking a Gabor atom dictionary as the index, a matching tracing algorithm is utilized to carry out time frequency atomic decomposition on transient zero-sequence current of each fault branch line within the first one quarter cycle, and attenuation sinusoidal quantity atoms representing the fault feature information of branch lines are further obtained; thirdly, an improved gray correlation analytic method is adopted to carry out correlation degree analysis on the attenuation sinusoidal quantity atom of each branch line, so that the feature value of each branch line is obtained; and finally, Euclidean distance is obtained by using the feature value of each branch line and the reference values of the fault lines and the non-fault lines, the Euclidean distances are compared, so that the accurate line selection is realized through the comparison of the Euclidean distances. The small current earth fault line selection method for the radial distribution network realizes low calculated amount and high line selection accuracy and is particularly applicable to radial distribution network systems with multiple branch lines.

An adaptive method of fault wire selection includes starting up fault wire selection device to record zero sequence current and voltage of each outlet on two cycles before fault and three cycles after fault when bus zero sequence transient voltage value uo ( t ) is over KuUn as Ku value of 0.35 and Un referring to bus rated voltage; searching sample point with value being less than 0.01 Un on bus; finding out corresponding time when single phase earthing fault is occurred; calculating phase angle theta uo and each line I DC to obtain criteria 1, 2, 3 and 4; selecting wire for system fault as per criteria.

The invention relates to a fault line selection fusion method of a power distribution network cable-line mixing line which utilizes an extensive theory, and belongs to the electric power system relaying protection technology field. The application of a distribution network cable-line mixing line is increased in cities, a cable in a unit length has larger capacitance for the earth than a trolly wire, frequency dependent character of a cable parameter is serious, and a voltage current fault transient state component is more distinct when the cable-line mixing line is connected with the ground in a single phase way. Perceptual decay direct current component characteristic of each feeding outgoing line fault zero-sequence current is fused with a disintegrating and integrating relative coefficient of a transient component small waving bag through utilizing the extensive theory. Possible fault line assembly, fault characteristic assembly and an amount domain which is set by the characteristic are used as three factors for the extendable merging matter, and the decay direct current component and the small waving bag disintegrating and integrating relative coefficient are used as the characteristic assembly. A weight function can be objectively confirmed according to the size of a fault close angle, a fault confident degree of each line can be calculated through utilizing the extensive correlation function, and the fault outgoing line is judged according to the confident degree. A great number of artificial results indicate that the line chosen by the method is accurate and reliable.

A single-phase-to-ground fault line selection method for small current comprises the following steps of first determining a signal sampling period, using an A/D converter to collect the zero-sequencevoltage of a bus and the zero-sequence current of feeders of the system, monitoring the zero-sequence voltage of the bus in real time, and starting a line selection algorithm when the zero-sequence voltage is greater than a set voltage; performing smoothing pre-treatment on the transient zero-sequence current spectrum of each of the extracted feeders, carrying out empirical wavelet transform decomposition to extract an intrinsic mode function that best characterizes the original signal, calculating energy relative entropies by using the amplitude of the signal obtained after Hilbert transform,selecting the line with the largest relative entropy as the fault candidate line, determining that the line with the largest relative entropy is faulty if the line with the largest relative entropy is larger than the sum of the relative entropies of the line with the second largest relative entropy and the line with the third largest relative entropy, and otherwise determining that the bus is faulty. The single-phase-to-ground fault line selection method is accurate in line selection and good in real-time performance without being affected by the neutral point grounding mode, the fault distance, the initial fault angle or the transition resistance fault condition.

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.

A single-phase grounding fault locating method for a distribution network without a master station of the invention comprises the following steps: (1) each distribution terminal detects the zero sequence voltage value of a distribution network, and judges whether there is a single-phase grounding fault; (2) when there is a single-phase grounding fault, each distribution terminal takes the derivative of zero sequence voltage, compares the polarity of transient zero sequence current with the polarity of the derivative of zero sequence voltage, and identifies a single-phase grounding fault line; (3) a line meeting the condition that the polarity of transient zero sequence current and the polarity of the derivative of zero sequence voltage are opposite is selected as a fault line, and each distribution terminal sends a grounding fault locking signal containing level information to a higher-level line distribution terminal; (4) the distribution terminal at the fault point does not receive a grounding fault locking signal, and acts first to remove the grounding fault, and the distribution terminals upstream of the fault do not malfunction; and (5) if the distribution terminal at the fault point fails to remove the fault in time, the higher-level feeder distribution terminal delays the action exit gradually according to the received locking signal. Through the method, a grounding fault point can be located accurately even when a distribution terminal on a switch loses communication connection with a distribution monitoring master station system.

The invention discloses a DC resistance selection method and system for a complex power distribution network comprehensive optimization device. The DC resistance selection method comprises the following steps: 1) constructing positive-sequence, negative-sequence and zero-sequence three-sequence fundamental frequency equivalent circuits and equivalent circuits at a sampling frequency for the complex power distribution network comprehensive optimization device; 2) constructing positive-sequence, negative-sequence and zero-sequence three-sequence equivalent circuits at a fundamental frequency anda sampling frequency of a power distribution system at a fault point; 3) calculating to obtain a relationship between fault current and DC resistance; 4) determining a lower limit value of the DC resistance; 5) calculating to obtain a relationship between the current of the sampling frequency at the fault point and the DC resistance; 6) determining an upper limit value of the DC resistance; and 7) obtaining the DC resistance according to the lower limit value and the upper limit value as well as a relationship between the lower limit value and the upper limit value. The DC resistance selection method and system disclosed by the invention have the benefits that a selected DC resistance value can take into account effective arc suppression and accurate line selection of the power distribution system, effectively improve the control performance of the comprehensive optimization device and realize the substitution effect on an arc suppression coil.

The invention relates to a single-phase ground fault locating method based on zero sequence voltage starting. Zero sequence voltage is adopted as a single-phase ground fault break variable starting component, when a ground fault appears, a bus zero sequence voltage starting device can record zero sequence voltage waveforms at the break moment T, three-phase current waveforms of all high-precisiontransient wave recording type fault indicators installed along a transformer substation outgoing line at the same moment are called, and finally fault positioning is achieved based on wide area synchronous information. The purpose of single-phase ground fault locating in an existing power distribution network is achieved.

A method for selecting out fault circuit in small earthing current system uses DC constituent of the first cycle after the fault to replace attenuation DC constituent for calculation and selects out fault circuit of small earthing current system with arc suppression coil based on DC constituent size. The rationale of the method is also listed in the present invention.

The invention relates to a resonant earthed system fault line selection method with invariant moments. The method comprises the following steps that S1, zero-sequence current waveforms measured at the head ends of all circuits within a working frequency period are recorded after a fault occurs; S2, the point gray levels of curves of all the measured zero-sequence current waveforms are one, the other point gray levels are zero, and an image gray level distribution function F(t, i) is obtained; S3, the image gray level distribution function F(t, i) of the obtained zero-sequence current waveforms is substituted in an invariant moment formula, 11 invariant moments reflecting image characteristics are obtained, and four invariant moment characteristic quantities, psi4, psi6, psi9 and psi11 expressing an image axial symmetry relation are extracted; S4, spectrum clustering analysis is carried out on the invariant moment characteristic quantities, psi4, psi6, psi9 and psi11, and a cluster tree is output; S5, according to cluster validity indexes, the optimal cluster tree is selected out, and fault line selection is carried out. The method is accurate in line selection, and can improve reliability of power distribution network fault line selection.

The invention discloses neutral-point grounding control equipment of a medium-voltage power grid. The neutral-point grounding control equipment comprises a bus voltage transformer, a grounding transformer, a circuit zero-sequence current transformer and a controller, wherein the bus voltage transformer is connected with a bus and the controller, the grounding transformer is connected with the busand an arc extinguishing coil, a neutral point current transformer and a neutral point voltage transformer are arranged between the grounding transformer and the arc extinguishing coil and are connected with the controller, a branch is arranged between the neutral voltage transformer and the arc extinguishing coil and is connected with a resistor by a switch connected with the controller, the controller is connected with at least two branch lines by the circuit zero-sequence current transformer, and the branch lies are connected with the bus. The advantages of two grounding modes of neutral-point resonant grounding and resistance grounding are combined, the advantage that a line can be accurately selected by resistance grounding is maintained, residual current of a grounding point also canbe reduced, an arc light grounding overvoltage is limited, an appropriate working mode can be selected according to different conditions of a short-term grounding fault or a permanent grounding fault, the safety running of the line is guaranteed, and the power supply reliability is also improved.

The invention discloses an arc grounding overvoltage limiting device applied to a medium-voltage power distribution system, which includes a single-phase fast electronic switch controlled by an intelligent controller and a high-energy nano-zinc oxide energy-absorbing arc extinguishing device; the single-phase fast electronic switch is three Only, the main circuits of the three single-phase fast electronic switches are connected in a star shape, and the three high-voltage terminals are respectively connected to the three-phase busbar of the system, and the other ends are connected in parallel to the upper end of the high-energy nano-zinc oxide energy-absorbing arc-extinguishing device The high-energy nano-zinc oxide energy-absorbing arc-extinguishing device is composed of a high-energy zinc oxide linear resistor, a nano-damping absorber, a high-energy zinc oxide non-linear resistor and a high-voltage thyristor, wherein the high-voltage thyristor is connected in parallel to the high-energy zinc oxide Linear resistors and nano-damping absorbers at both ends. Compared with the prior art, the invention can effectively limit the single-phase intermittent arc grounding overvoltage in various operating modes of the 3-35KV neutral point non-directly grounded power grid.

The invention provides a distribution line single-phase earth fault line selection method based on phase current traveling wave comparison. The method comprises the following steps: collecting three-phase current traveling waves on a distribution line, and taking a bus pointing line as a current positive direction; when a single-phase earth fault occurs in the distribution line, comparing the amplitude and the polarity relationship of the difference before and after the three-phase current traveling wave fault; when the amplitude of one phase of current traveling wave difference is greater than the amplitude of the other two phases of current traveling wave differences by more than 1.5 times, and the polarity of the phase of current traveling wave difference with the maximum amplitude is opposite to the polarity of the other two phases of current traveling wave differences, judging that the fault occurs on the line on the load side of the measurement point and the phase with the maximum current traveling wave difference amplitude is a fault phase; and if the three-phase current traveling wave difference amplitudes are the same and the polarities are the same, judging that the faultoccurs on the line at the power supply side of the measurement point. Through the technical scheme of the invention, accurate line selection of the single-phase earth fault of the distribution line can be realized.

The invention discloses a distribution network small current neutral grounding line selection method based on multi-source information fusion. The distribution network small current neutral groundingline selection method comprises the steps that a distribution network grounding line selection switch matrix (DGSM) is established to describe feeder and outlet switch models of related buses of all grounding substations in the distribution network; a feeder switch pull path sequence table (FSST) is established to describe the brake separating action sequence of each feeder and outlet switch on the bus; priority adjustment rules are established to perform necessary adjustments on the switch sequence in the feeder switch pull path sequence table (FSST); and according to the distribution networkgrounding line selection switch matrix (DGSM) and the adjusted feeder switch pull path sequence table (FSST), the distribution network grounding fault is subjected to comprehensive line selection processing until a grounding fault feeder is found. The distribution network small current neutral grounding line selection method has good adaptability to a substation line selection device under the conditions of accurate and inaccurate of line selection.

The invention discloses a low-current earthing line-selection method based on tabu search optimization RBF network. A tabu algorithm is adopted, undermined RBF network structural parameters are trained so as to ensure that the RBF network structural parameters trend to optimal, and the optimized RBF network is used as a line selection model, so that low-current earthing fault comprehensive line selection is realized, automatic and quick determination of fault lines is realized, and stable operation of a power grid and safe equipment can be ensured.