78results about How to "Improve line selection accuracy" patented technology

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.

A method for selecting wire of single phase earthing in neutral point noneffective earthing system includes making instant short circuit between neutral point and ground at position near two ends voltage polarity from positive to negative over zero by short circuiter set between neutral point and ground when single phase earthing is occurred in neutral point noneffective earthing system and state is stabilized in order to generate a short circuit pulse current being used to judge earthing line through short circuit detector. The device for realizing said method is also disclosed.

The invention provides a small current grounding system single-phase earth fault direction detecting method utilizing the linearity relation between a line zero sequence current and a voltage derivative and belongs to the field of relay protection of power distribution networks. The linearity relation between upstream and downstream voltages and currents of a fault point is analyzed when a single-phase earth fault occurs in an unearthed and arc suppression coil grounded system, a method for fault direction detection by utilizing the linearity relation between the line zero sequence current andthe voltage derivative at a detection point is provided. The zero-sequence voltage and zero-sequence current at each detection point are acquired, linear fitting is conducted on a zero-sequence current sample value sequence and a corresponding zero-sequence voltage difference value sequence, it is judged whether the detection points having the fit goodness greater than a threshold value and the fitting function slope greater than 0 are located at the downstream of fault points or not, if not, the detection points are located at the upstream of the fault points. The method can be simultaneously suitable for low-resistance and high-resistance earth faults of a small current grounding system, improves the adaptability of a fault direction detection algorithm and has a wide actual applicationvalue.

The invention discloses a high-accuracy arc extinguishing coil grounding system single-phase grounding wire selection method. The method comprises the steps of parallelly connecting a series loop which is composed of a grounding resistor and a circuit breaker with two ends of an arc extinguishing coil, wherein in normal operation, the circuit breaker is in an on state; additionally mounting a zero-sequence current transformer on each outlet wire of a transformer station without the zero-sequence current transformer; in single-phase grounding, acquiring the zero-sequence current of the zero-sequence current transformer by means of an existing microcomputer protecting device of a transformer substation, when flowing zero-sequence current is larger than a setting value Izd0, transmitting a fault signal after setting time T1, and determining a faulted line; and when the zero-sequence voltage of a bus voltage transformer increases to a certain value Uzd0, determining single-phase grounding, and performing tripping-out on the circuit breaker which is serially connected with the grounding resistor after a time period T2. The high-accuracy arc extinguishing coil grounding system single-phase grounding wire selection method has advantages of realizing simple reconstruction, greatly improving wire selection accuracy on the condition that safe and stable system operation is not affected, reducing economic loss caused by wire selection error and ensuring continuous electric power supplying to electric power users.

Disclosed is a line selection method which is applied to an arc suppression coil earth power system. Firstly, the zero sequence current of each feed line and the compensation current of the arc suppression coil can be sampled synchronously, and the zero sequence current of each feed line sampling value is added to the compensation current of the arc suppression coil sampling value point-to-point, and then a quarter of cycle (5mS) is moved forwards, furthermore, the signal is multiplied by the zero sequence current of corresponding feed line sampling value, and the algebraic mean value of a cycle can be obtained. Providing that only one value is negative and the others are positive numbers among the algebraic mean values, and the corresponding feed line with the negative value is the malfunction feed line; if all the algebraic mean values are positive numbers, the main line has malfunction. Because only the zero sequence current is used in line-selecting judgment and the zero sequence current is the zero sequence current of the feed line, the judgment is not affected by the angle error between the zero sequence voltage transformer and the zero sequence current transformer, and also is not affected by the dispersion characteristic of the zero sequence current transformer which has weak excitation (small current), and the line selection accuracy is high.

The invention relates to a three-dimensional fault line selection method based on random resonance and a transient current signal. The method comprises the following steps of: (1) after a power distribution network is faulted, recording the zero-sequence current iZn(t) and the fault phase current iXn(t) of each branch line fault, and computing transient zero-sequence current izn(t) and transient fault phase current ixn(t); (2) performing variable-scale bistable treatment on the transient zero-sequence current izn(t) and transient fault phase current ixn(t); (3) computing a cross correlation coefficient matrix M and an integrated correlation coefficient Mn among the transient characteristic zero-sequence current iczn(t) of the branch lines and selecting the line ln with the minimum Mn; (4) performing seven-layer db10 wavelet packet decomposition on the transient characteristic phase current icxn(t) of each branch line and computing simplified energy E*sn and simplified gravity center frequency f*gn; and (5) forming a three-dimensional coordinate system by using the simplified gravity center frequency f*gn as a horizontal ordinate, the simplified energy E*sn as a vertical coordinate, and a polarity parameter value as a longitudinal coordinate. Compared with a method in the prior art, the method is high in reliability and is not liable to suffer from external interference.

The invention discloses a small-current single-phase earth fault line selection method based on spiking neural P systems. The method comprises the following steps: extracting zero sequence characteristics, comprising steady state and transient characteristics, of each line of a power distribution network at the fault moment, and establishing a fault measurement function of each line; obtaining theline selection criterion weight and line selection decision rule based on an information gain degree and a rough set theory; and performing fuzzy reasoning on the spiking neural P systems to obtain the fused fault measures, and determining the faulty line. According to the method disclosed by the invention, the fault information is fully utilized, the acquired steady state zero sequence current amplitude, steady state zero sequence current phase angle, zero sequence reactive power amplitude, zero sequence admittance amplitude, transient zero sequence current energy value and transient zero sequence current effective value are taken as the line selection criterions, the maximal fault measure is obtained by performing fuzzy reasoning on the spiking neural P systems, line selection results can be accurately obtained, the defect that a single line selection criterion cannot adapt to a complex fault condition is overcome, the small-current fault line selection precision is improved, and safe and reliable power supply of the power system is ensured.

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 low current grounding intelligent route selecting method comprises: firstly judging whether the grounding fault happens or not; then acquiring the zero sequence current data before or after the fault to judge the route selecting. The steps for processing the obtained current data by sampling comprise: selecting the appropriate wavelet function; performing the wavelet decomposition for the fault signal; selecting the decomposition dimension with the maximum value as the characteristic dimension information of the fault; performing the wavelet reconstruction for the characteristic dimension information; judging the fault line. The apparatus for implementing the method comprises an event management module, a data processing module, a data acquiring module, a data communication module, a power supply module, a display and control module and a CAN communication module; the power supply module is connected with each module for supplying power; the output signal of the data acquiring module is transferred to the data processing module, the data processing module is connected with the event management module to perform the data communication; the event management module output is connected with the display and control module and the CAN communication module. The invention solves the problems existing in the prior art.

The invention provides a small-current grounding fault line selection system, which comprises zero sequence current transformers, a voltage transformer, a grounding transformer, a grounding loop and a grounding line selection device, wherein the zero current transformers are arranged on each feed line, the voltage transformer is arranged on a bus, the grounding transformer is connected with the bus, the grounding loop is connected between a high-voltage side neutral point of the grounding transformer and the ground, and is connected in series with a grounding resistor and a contactor used for controlling the on-off state of the loop, the grounding line selection device is respectively connected with the zero sequence current transformer, the voltage transformer and the contactor, and is used for controlling the conduction of the grounding loop when the voltage transformer detects the zero sequence voltage, and then, a fault line is judged according to the current data collected by the zero sequence current transformer.

The invention discloses a power distribution network fault line selection method based on dominant frequency zero sequence power, aiming to solve the problem that when a complex small current grounding system generates a single-phase earth fault, present line selection methods based on dependency may cause misjudgment due to insufficient criterion margin. In order to solve the problem of insufficient criterion margin, the invention provides a power distribution network fault line selection method based on dominant frequency zero sequence power, which selects lines by employing dominant frequency zero sequence power as characteristic quantity, and calculates the dominant frequency zero sequence power integrated correlation coefficient corresponding to each feeder line, wherein a fault line integrated correlation coefficient is less than zero, and a perfect line integrated correlation coefficient is greater than zero. A lot of simulation results show that the method increases line selection criterion margin and line selection accuracy, and is not influenced by switching angles and fault resistors.

The invention discloses a low-current grounding comprehensive line selection method. Various methods are adopted for calculation; a faulty line is comprehensively selected according to data modeling comparison; each method is in allusion to specific characteristics of a signal; different methods are complementary. The method is applicable to both a power grid with a non-grounded neutral point anda power grid with a neutral point is grounded by using an arc suppression coil. The method is particularly suitable for scenarios with complicated fault conditions and disordered fault waveforms, andis complementary to a steady-state-content line selection method. The comprehensive line selection method is very reliable in line selection result and is a continuous line selection technology; underthe condition that a fault does not disappear, a device repeatedly performs line selection calculation every other second until the fault disappears, so that several misjudgments can be effectively eliminated, and the faulty line can be accurately selected within short time; the economical loss is greatly reduced, and the power supply reliability is improved.

The invention relates to a low-current line selection device and a control method for inhibiting unbalanced current by way of differential filtration. The low-current grounding line selection device comprises a multi-channel alternating-current sampled signal input interface, an operational amplifier filter module, an analog/digital conversion module, a central processor module, a power module, a human-computer module and a communication module, wherein the multi-channel alternating-current sampled signal input interface, the operational amplifier filter module and the analog/digital conversion module are sequentially connected, the analog/digital conversion module, the human-computer module and the communication module are respectively bidirectionally connected with the central processor module, and the power module is connected with each part to supply power. The device adopts a zero-sequence current differential filtration algorithm which can effectively extract zero-sequence current fault component, and therefore can effectively extract the zero-sequence current fault component in a high-unbalanced current power supply system during normal operation, and thereby the line selection accuracy of the low-current grounding line selection device can be increased.

A method for selecting wire of single phase earthing fault in small current earthing system measures zero sequence current increment of each circuit at bus side before and after fault and selects wire according to principle that zero sequence current increment of fault circuit is equal to negative value of nonfault circuit zero sequence current increment sum.

The invention discloses an MMC converter DC power distribution network single-pole high-resistance grounding fault protection method, which mainly comprises the following steps of: judging whether a single-pole grounding fault occurs or not by taking the change rate of positive and negative pole voltages to ground of a DC power distribution network as a starting criterion and taking the voltage variation as a fault criterion; when a single-pole grounding fault occurs, firstly, determining a fault pole according to the magnitude of positive and negative pole voltages; preliminarily judging a fault line according to the magnitude and the direction of the fault electrode charging and discharging current detected at the head end of each line; and finally, injecting a detection signal into the fault electrode, and verifying the accuracy of the judgment according to the size of the detection signal detected at the head end of each line. When the two data are consistent, determining that the line is the fault line; and when the two data are inconsistent, re-determining the fault line by using the charging and discharging current criterion and the detection signal criterion and using a comprehensive weight method.

The invention is used for solving the problem of miss selection of line in rapidly automatic arc suppressing coil ground system by using current line selection scheme. It firstly selects three lines having maximum abrupt change value of zero sequence current, and then the zero sequence current abrupt change value is integrated to get comparable polarity at maximum value or minimal value from which the fault line is picked up.

A method for selecting out single phase earthing in small current system includes injecting a current signal with specific frequency intermittently to three phase circuit; carrying out voltage preprocessing, synchronous sampling and digital filtering to detect the current signal comparing resistive current size of the current signal in each subcircuit and confirming that subcircuit with the largerst resistive current is earthing subcircuit.

The invention discloses a method for locating a single phase ground fault locating system, for real-time detecting current signals, rapidly detecting and locating the faults,,capturing overhead line errors and increasing wire selection accuracy of the single phase ground faults. The method is realized by the following technical scheme: the method for locating the single phase ground fault locating system comprises the following steps of: selecting wires, selecting testing circuits by an arc suppression coil control module, sending notice messages to a main station via a communication interface; distributing fault judging instructions, after the main station receiving the notice messages, broadcasting the fault judging instructions to an overhead line error alarm of the testing circuit; monitoring; reporting the faults; judging fault points, the main station judging the fault points according to fault report information; and alarming, the main station alarming and notifying the fault point information to maintainers.

The invention discloses a power distribution network single-phase high-resistance grounding fault line selection method, system and device. According to the invention, a plurality of fault characteristic quantities are obtained, a weight is distributed to each fault characteristic quantity, the significance degree of each fault characteristic quantity is quantitatively represented, normalization processing is performed on each fault characteristic quantity after weight distribution, the information of each feeder line when a single-phase high-resistance fault occurs in a system is reflected, and dimensionality reduction processing is performed on each fault characteristic normalization value, so that data redundancy can be reduced, and the calculation speed can be improved; and finally, afinal line selection result is obtained by a fusion line selection model constructed by combining a support vector machine, a Logistic regression classifier and a random forest classifier. The line selection accuracy of the fusion line selection model is improved by acquiring a plurality of fault characteristic quantities and combining a plurality of classifiers, and the technical problem that a line selection result is wrong when the fault characteristic quantity is very weak in a line selection method based on a single fault characteristic quantity in the prior art is solved.

The invention relates to an undercurrent grounding line selection method and device. The method is characterized in that when a ground fault of a line is detected, active and reactive components in the fault current are compensated, so the fault current is reduced to a fault current setting threshold; after the setting time, compensation of the active and reactive components in the fault current is stopped, and whether the ground fault disappears is determined; if not, the zero sequence current, the fifth harmonic current and the transient first half wave voltage current peak of each line arecollected, the collected data is preprocessed to obtain a corresponding fault index of each line, the fault index corresponding to each line is inputted into a logistic regression model to determine the fault line, and thereby faulty and non-faulty lines are obtained. The method is advantaged in that the faulty and non-faulty lines can be accurately distinguished, line selection accuracy is substantially improved, and problems of low reliability and accuracy of a traditional single line selection method are effectively solved.

The invention provides a fault line selection method and device for a small-current grounding system, and the method comprises the steps: respectively collecting transient zero sequence currents of all lines in the small-current grounding system from a fault moment according to a preset sampling frequency; calculating the optimal atoms of all lines according to the transient zero sequence currents of all lines; calculating the atom singular entropies of all lines according to the optimal atoms of all lines; calculating the atom actual energy of all lines according to the atom singular entropies of all lines; calculating the fault confidence degrees of all lines based on a pre-constructed fault confidence degree function according to the atom singular entropies of all lines; correcting the fault confidence degrees of all lines according to the atom actual energy of all lines, and obtaining the fault integrated measurement values of all lines; comparing the fault integrated measurement values of all lines, and carrying out fault line selection. The method improves the reliability and accuracy of fault line selection, and can meet the requirements of fault conditions of various types of complex power grid structures.

The invention discloses a small current grounding line selection device and line selection method, thereby improving the line selection precision. The device comprises an AC input conversion module for isolating and transforming an input analog signal and transmitting the converted analog signal to an A/D conversion module, the A/D conversion module for collecting an analog signal and transmittingthe signal to a CPU module, a switch input module for collecting a switch-in amount and transmitting the information to the CPU module, the CPU module for selecting the collected analog amount as line selection sample data, carrying out fault line determination, and outputting a switch-out amount to a switch-out output module, and the switch-out output module for receiving the switch-out amount outputted by the CPU module and controlling turning on/off of an external device.

The invention discloses a detection method of an S injecting signal. The problem that the S injecting signal is so small to be detected currently is solved. When a power distribution system has a single-phase grounded error, the weak S injecting signal is detected by utilizing a random resonance theory so that the aim of selecting lines is fulfilled. The method comprises the following steps that:1), when a power distribution net has the single-phase grounded error, zero sequence currents of various lines can be sine signals mainly at 50Hz, a weak current signal with special frequency being 220Hz is injected into a system through a signal injecting device; 2), the injected weak current signal with the special frequency only flows through an error phase, and then is grounded through a grounded point, and the signal is a line selection judgment signal required to be detected; and 3), the output of the system can be enhanced based on the random resonance theory under a certain condition,and therefore, the weak current signal injected by the signal injection device can be detected by utilizing the random resonance theory, so that the line selection can be carried out completely.

The invention discloses a low-current grounding system single-phase grounding line selection method and system. The method comprises the steps: decomposing zero-sequence current, collected under a single-phase grounding fault, of each feeder line into a transient component and an attenuation direct-current component; judging whether the transient component of each feeder line is normal or not according to the transient threshold value, and constructing a transient energy line selection matrix according to a judgment result; judging whether the attenuation direct-current component of each feeder line is normal or not according to the attenuation direct-current threshold value, and constructing an attenuation direct-current component line selection matrix according to a judgment result; andmerging the transient energy line selection matrix and the attenuation direct current component line selection matrix to obtain a comprehensive line selection matrix, and comparing the comprehensive line selection matrix with a preset normal matrix to obtain a line where the fault point is located. A fault line can be rapidly locked, and fault time is reduced.