CN116626442A - Novel distribution network fault indicator based on edge calculation and application method thereof - Google Patents
Novel distribution network fault indicator based on edge calculation and application method thereof Download PDFInfo
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Abstract
The invention discloses a novel distribution network fault indicator based on edge calculation and a use method thereof, wherein the novel distribution network fault indicator comprises a high-speed FPGA circuit, a low-speed acquisition module, a high-speed A/D conversion circuit, a trigger module, an SDRAM memory and a communication module, wherein the high-speed FPGA circuit is in bidirectional data connection with the high-speed A/D conversion circuit, a data input end of the high-speed A/D conversion circuit is connected with a signal processing circuit, and 16-bit digital storage bits are adopted for analog-to-digital conversion and transmission of data of an internal circuit of the indicator; according to the distribution network fault indicator, near-end computing service is realized on one side close to a data source through an edge computing method aiming at single-phase ground fault diagnosis, accurate single-phase ground fault positioning is realized on site by comprehensively utilizing a zero sequence current signal, a negative sequence current signal and a three-phase current signal, dependence on communication is reduced, load pressure of a main station server is reduced, and power supply reliability of operation of a power distribution network is effectively improved.
Description
Technical Field
The invention relates to the technical field of power distribution of power grids, in particular to a novel distribution network fault indicator based on edge calculation and a using method thereof.
Background
The safe and stable operation of the power distribution automation equipment is an important guarantee for the power distribution automation system to play a role, and the power distribution automation equipment comprises a feeder terminal FTU, a station terminal DTU, a fault indicator, a secondary fusion complete switch and the like. Particularly, the fault indicator is simple and flexible to install due to relatively low price, so that the fault indicator is distributed in a large quantity in the power distribution network and has a wide point and multiple sides. However, because the running environment and the state of the fault indicator are greatly different, the fault current is small after single-phase earth fault occurs, and the action accuracy of the fault indicator is not high.
The traditional fault indicator has two schemes, wherein the first scheme is that each terminal compares a measured value with a fixed value in real time, when the measured value is found to be larger than the fixed value, the measured value is indicated on site, and meanwhile, remote signaling quantity is uploaded, and the master station obtains action information of each terminal to perform fault location; this approach is clearly unsuitable for single-phase earth faults, because when a single-phase earth fault occurs on a line, zero-sequence currents are generated on each line and each branch (note that not the fault path), and the fixed values are difficult to set. The second scheme is that the sampling values of all terminals are uploaded to a main station in real time for analysis, namely a wave recording type fault indicator, the scheme is theoretically the best, but is often limited by communication and has poor effect, the main station cannot receive accurate data to cause positioning failure due to failure or delay of a communication system, and a complex positioning algorithm is concentrated on the main station, so that the load capacity of the main station is increased, and the real-time processing capacity of the main station is influenced; therefore, it is of great importance to develop key technology to improve the handling capacity of fault indicators for single-phase earth faults.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a novel distribution network fault indicator based on edge calculation and a use method thereof, and fault sections and non-fault sections in a line are distinguished by taking phase current transient state and steady state characteristics and negative sequence current fault characteristics on the line as criteria, so that the problem of single-phase ground fault positioning in the line is solved, and the power supply reliability, safety and economy of a power distribution network are improved.
In order to achieve the above object, the present invention is realized by the following technical scheme:
the invention relates to a novel distribution network fault indicator based on edge calculation, which comprises a high-speed FPGA circuit, a low-speed acquisition module, a high-speed A/D conversion circuit, a trigger module, an SDRAM memory and a communication module, wherein the high-speed FPGA circuit is connected with the high-speed A/D conversion circuit in a bidirectional data manner, the data input end of the high-speed A/D conversion circuit is connected with a signal processing circuit, and the high-speed FPGA circuit is connected with the memory in a bidirectional data manner; the signal output end of the low-speed acquisition module is connected with the trigger input end of the trigger module, and the trigger module controls the high-speed FPGA circuit to start current acquisition according to the output result of the low-speed acquisition module; the communication module drives a first input end of the low-speed acquisition module through threshold voltage, and the communication module performs data transmission inside the indicator and uploading of an external master station.
The invention further improves that: the SDRAM memory employs a 16-bit 256M DDR3-SDRAM.
The invention further improves that: the high-speed A/D conversion circuit adopts a 16-bit high-speed A/D conversion chip, and the sampling frequency of the conversion circuit is 2MHz.
The invention further improves that: the communication module comprises a processor, an SD card memory and an Ethernet transmission module, wherein the data end of the processor is in bidirectional transmission communication with the SD card memory, and the communication end of the processor is in bidirectional communication with the Ethernet transmission module.
The application method of the novel distribution network fault indicator based on edge calculation comprises the following steps:
s1, acquiring three-phase current of a line after a fault indicator is started and synthesizing zero sequence current;
s2, comparing the synthesized zero sequence current amplitude with a preset value, if the zero sequence current amplitude exceeds the preset value, performing S3, otherwise, continuously monitoring the zero sequence current amplitude by the indicator;
s3, the indicator judges that the power distribution network breaks down and starts a fault sensing algorithm, and after the algorithm is started, the indicator obtains phase currents in 5 periods before and after the starting time and synthesizes zero sequence currents;
s4, processing the zero-sequence current signal by utilizing improved S transformation to obtain sampling points corresponding to fault occurrence time and high-frequency components of zero-sequence current in a period after fault occurrenceAnd fundamental frequency component->Respectively obtain high frequency components->And fundamental frequency component->Performing self-adaptive fault sensing judgment on the amplitude of the signal;
s5, when a fault sensing criterion is met, judging that a resistor grounding fault occurs in the power distribution network, filtering load current by the indicator, then performing steady-state algorithm calculation, when the fault sensing criterion is not met, judging that an intermittent arc grounding fault occurs in the power distribution network, judging the mutation direction of three-phase current after filtering the load current by the obtained phase current, further judging whether a line fault exists or not, simultaneously extracting negative sequence current fault characteristics, and performing auxiliary judgment;
s6, each indicator completes fault perception judgment on site, and the judgment result is uploaded to the master station for comprehensive centralized judgment.
The invention further improves that: the positioning analysis process based on the phase current steady-state signal characteristics during steady-state algorithm calculation in the step S5 is as follows: three-phase current on each line after failureDivided into load currents->Fault component current +.>The method comprises the steps of carrying out a first treatment on the surface of the The current values corresponding to the phase difference whole period are measured by a detection device before and after the fault occurrence time to be subtracted, so that the fault component current after the fault is obtained>：
The fault component current of the fault path comprises positive sequence, negative sequence and zero sequence three-sequence current, and the non-fault path comprises only zero sequence current, wherein the positive and negative zero three-sequence current at the fault point obtained by the symmetrical component method is respectivelyThree-sequence current on fault path>、/>、/>The following are provided:
direction factorFault components of phases on a fault line +.>、/>、/>The following are provided:
positive sequence, negative sequence and zero sequence three-sequence current on non-fault path、/>、/>The method comprises the following steps:
fault component of three-phase current on non-fault path、/>、/>The method comprises the following steps of: />
By analyzing the fault components of the three-phase current of the fault path and the non-fault path, it is possible to: on the fault path, the fault component of the fault phase is larger than that of the non-fault phase, and the fault components of the non-fault phase are equal; in the non-fault path, the fault components of the three-phase currents are all the same.
The invention further improves that: load current on line after faultLoad current before fault occurrenceEqual.
The invention further improves that: in the step S5, when the fault perception criterion is not satisfied, a transient criterion is applied to perform judgment, which specifically includes the following steps:
fault path fault phase transient fault currentThe method comprises the following steps:
wherein,,is the power frequency angular frequency; />The initial phase of the zero sequence voltage; />Is the free oscillation current angular frequency; />When the transient state is increased, the transient state process is weakened; />Short circuit current amplitude when the fault reaches a steady state; t represents the time after the fault occurs; />The intermediate value resistor is a circuit intermediate value resistor; />Is an arc suppression coil inductance;
non-fault line and fault line non-fault phase transient currentThe method comprises the following steps:
wherein the method comprises the steps ofThe short-circuit current amplitude value of the non-fault line and the non-fault phase of the fault line under the condition that the fault reaches a steady state is used; />Equivalent resistance of non-fault phase of non-fault line and fault line; />The three-phase line and the power supply which are non-fault lines and non-fault phases of the fault lines and the equivalent inductance of the transformer;
filtering the fault component signals, wherein the processed fault component signals are as follows:
wherein:is a sampling point; />Is a current value;
setting the calculation interval asThe function value corresponding to the sampling point at the fault occurrence time is used as a reference value, the absolute value of the difference result between the corresponding function value in the interval and the reference value is calculated respectively, and the sampling point corresponding to the maximum value is found to be used as a mutation point:
maximum, corresponding to
Comparing the abrupt change direction results corresponding to the three-phase current on the same line, when two-phase calculation results appearThe other phase is different, the path is judged to be a fault path, and the direction different phase is a fault phase; when three-phase calculation result on the line appears +.>All are the same, the path can be judged as a non-failure path.
The invention further improves that: the specific operation of the auxiliary judgment in the step S5 is as follows: the extracted negative sequence current is as follows by the basic principle of the three-phase symmetry method:
wherein:，/>，/>and respectively representing the current phasors of abc three phases, filtering out the influence of load current before and after the fault by sampling at equal intervals, and judging whether the terminal is positioned at the upstream or downstream of the fault point through the amplitude value of the negative sequence current.
Compared with the prior art, the invention has the following beneficial effects:
the indicator is arranged at each node in the power distribution network line, and node phase currents are easy to extract for fault location; the phase current is adopted as a judging signal, so that the fault line selection system has extremely strong applicability; the fault position is judged on site by taking the transient state and steady state of the phase current and the fault characteristics of the negative sequence current as criteria, so that the fault is accurately positioned and judged; and under the condition of poor communication signals or lack of communication, the device can still finish fault line selection on site, thereby enhancing the anti-interference performance of an algorithm on a working environment and the independence of processing distribution network faults by the device.
Drawings
FIG. 1 is a schematic diagram of a novel distribution network fault indicator circuit based on edge computation according to the present invention;
FIG. 2 is a flow chart of a novel distribution network fault indicator operation algorithm based on edge calculation according to the present invention;
FIG. 3 is a model diagram of a neutral point through arc suppression coil grounding system;
FIG. 4 is a fault phase transient equivalence circuit;
FIG. 5 is a normal path transient equivalence circuit;
FIG. 6 is a zero sequence circuit equivalent diagram of a neutral point ungrounded system;
FIG. 7 is an equivalent diagram of a zero sequence circuit of a neutral point through arc suppression coil grounding system;
FIG. 8 is an ATP model diagram of a neutral point through arc suppression coil grounding system;
FIG. 9 is a waveform of fault path current when the ground resistor is connected;
FIG. 10 is a graph of a fault point downstream line current waveform at ground resistance;
FIG. 11 is a waveform of the normal line current when the ground resistor is connected;
FIG. 12 is a waveform diagram of a fault path after the ground point is set to arc ground;
FIG. 13 is a graph of a fault point downstream line current waveform after the ground point is set to arc ground;
fig. 14 is a waveform diagram of a normal line current after the ground point is set to be arc grounded.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The novel distribution network fault indicator based on edge calculation comprises a high-speed FPGA circuit, a low-speed acquisition module, a high-speed A/D conversion circuit, a trigger module, an SDRAM memory and a communication module, wherein the high-speed FPGA circuit, the high-speed A/D conversion circuit, the trigger module and the SDRAM memory circuit in the novel distribution network fault indicator all adopt 16-bit data processing units, the high-speed FPGA circuit and the high-speed A/D conversion circuit are connected in a bidirectional data manner, and digital storage data obtained by the high-speed A/D conversion circuit are transferred to the SDRAM memory; the data input end of the high-speed A/D conversion circuit is connected with the signal processing circuit and converts the analog signals acquired by the signal processing module into digital data signals; the high-speed FPGA circuit is in bidirectional data connection with a 16-bit 256M DDR3-SDRAM memory; the signal output end of the low-speed acquisition module is connected with the trigger input end of the trigger module, and the trigger module determines whether to start the high-speed FPGA circuit to trigger the high-speed A/D conversion circuit to perform A/D conversion with the sampling frequency of 2MHz according to the drive input signal of the low-speed acquisition module; the communication module comprises a processor, an SD card memory and an Ethernet transmission module, wherein the data end of the processor is in bidirectional transmission communication with the SD card memory, the communication end of the processor is in bidirectional communication with the Ethernet transmission module, the processor in the communication module drives the first input end of the low-speed acquisition module through threshold voltage, as the data of the 16-bit 256M DDR3-SDRAM memory can disappear due to power failure, the processor in the communication module can transfer the cache data stored in the DDR3-SDRAM memory into the SD card memory through communication with the high-speed FPGA circuit, and the communication module transmits the data in the indicator to an external master station server through the Ethernet.
The novel distribution network fault indicator performs algorithm processing in the multipoint acquisition fault work of the power grid circuit according to the following steps:
s1, acquiring three-phase current of a line after a fault indicator is started and synthesizing zero sequence current;
s2, comparing the synthesized zero sequence current amplitude with a preset value, if the zero sequence current amplitude exceeds the preset value, performing S3, otherwise, continuously monitoring the zero sequence current amplitude by the indicator;
s3, the indicator judges that the power distribution network breaks down and starts a fault sensing algorithm, and after the algorithm is started, the indicator obtains phase currents in 5 periods before and after the starting time and synthesizes zero sequence currents;
s4, processing the zero-sequence current signal by utilizing improved S transformation to obtain sampling points corresponding to fault occurrence time and high-frequency components of zero-sequence current in a period after fault occurrenceAnd fundamental frequency component->Respectively obtain high frequency components->And fundamental frequency component->Performing self-adaptive fault sensing judgment on the amplitude of the signal; at the position ofIn the step, the fault perception judgment algorithm can decompose and acquire the amplitude-frequency characteristic of the fault moment and extract the amplitude of the high-frequency component by utilizing the improved S transformation>Amplitude +.>Setting upAs adaptive sensing criterion, the localization technique is allowed to select by itself the criterion suitable for the fault feature, wherein +.>Is an adaptive coefficient; when the criteria are met, the harmonic content in the line is low, the steady-state process is stable, and the steady-state algorithm can complete the fault positioning task; on the contrary, the harmonic content in the representative line is higher, the arc-through ground fault is likely to occur, and the steady-state criterion cannot be accurately judged, so that the transient-state criterion is applied for judgment. Wherein (1)>Can be determined according to the field actual measurement data and engineering experience, and is subjected to a large number of actual data tests>The value range is 0.4-0.5, so that most situations can be satisfied;
s5, when a fault perception criterion is met, judging that a resistor grounding fault occurs in the power distribution network, filtering load current by the indicator, then performing steady-state algorithm calculation, when the fault perception criterion is not met, judging that an intermittent arc grounding fault occurs in the power distribution network, filtering load current by the obtained phase current, then performing transient algorithm calculation, judging the mutation direction of three-phase current, further judging whether a line is faulty or not, simultaneously extracting negative sequence current fault characteristics, and performing auxiliary judgment; in the step, the positioning analysis process based on the phase current steady-state signal characteristics during steady-state algorithm calculation is as follows: three-phase on each line after failureElectric currentCan be divided into load current->Fault component current +.>At the same time the probability of a sudden change of the load at the very moment of failure is very low, so it is assumed that the load current on the line after failure is +.>Load current before failure>Equal. Therefore, the current values corresponding to the whole period of the phase difference measured by the detection device before and after the occurrence time of the fault can be subtracted, so that the fault component current +.>：
According to the symmetrical component method, positive and negative zero sequence currents of the system can be obtained through a sequence network diagram, and the zero sequence impedance of a neutral point ungrounded system is different from that of a neutral point through the arc suppression coil grounding system due to the arc suppression coil, so that the current of each sequence changes accordingly. However, as zero sequence current flows through all lines of the system, the steady state characteristics of the lines are obviously affected; the positive and negative sequence current only exists in the fault path, so that the influence on the steady-state characteristics of the line is small; the zero sequence current distribution under two grounding modes is analyzed, and a neutral point ungrounded system model and a neutral point with the overcompensation degree of 5% are respectively analyzed by taking an arc suppression coil grounding system model as examples.
Because the zero sequence current forms a loop between the capacitance to ground and the fault point on each line, the zero sequence current can be split at the fault point and flows to all lines of the system, and the neutral point is not grounded to the zero sequence of the systemThe value circuit is as in fig. 6, wherein,is zero sequence voltage;for the earth capacitance of each line>，/>For the line-to-ground capacitance upstream of the fault point, < >>Is the line-to-ground capacitance downstream of the fault point.
The shunt coefficients of zero sequence current on the ith line on the non-fault path can be obtained as follows:
since the zero-sequence current on the fault path is the sum of the zero-sequence currents except the fault point, the shunt coefficient is as follows:the zero sequence equivalent circuit of the neutral point through arc suppression coil grounding system is as shown in figure 7,
wherein,,is zero sequence voltage; />For the earth capacitance of each line>，/>For the line-to-ground capacitance upstream of the fault point, < >>Capacitance to ground for line downstream of fault point；/>Is the arc suppression coil inductance.
The shunt coefficients of zero sequence current on the ith line on the non-fault path can be obtained as follows:
wherein,,is the power frequency angular frequency.
Since the zero-sequence current on the fault path is the sum of the zero-sequence currents except the fault point, the shunt coefficient is as follows:
for ease of description, the shunt coefficients of the fault paths are unified asThe shunt coefficient of the non-faulty path is +.>. According to the foregoing, positive, negative and zero sequence three-sequence currents are contained in the fault component current of the fault path, while only zero sequence currents are contained in the non-fault path.
Only zero sequence current is contained in the non-fault path.
In order to not lose the generality, the positive and negative zero three-sequence currents at the fault point obtained by the system through a symmetrical component method are respectivelyThree-sequence current on fault path +.>、/>、/>The following is shown:
direction factorFault components of phases on a fault line +.>、/>、/>The following are provided:
positive sequence, negative sequence and zero sequence three-sequence current on non-fault path、/>、/>The method comprises the following steps:
fault component of three-phase current on non-fault path、/>、/>The method comprises the following steps of:
by analyzing the fault components of the three-phase current of the fault path and the non-fault path, it is possible to: on the fault path, the fault component of the fault phase is larger than that of the non-fault phase, and the fault components of the non-fault phase are equal; in the non-fault path, the fault components of the three-phase currents are all the same.
In the step, the positioning analysis process based on the transient signal characteristics of the phase current when the transient algorithm is calculated is as follows:
as shown in figure 3 of the drawings,is the electromotive force of a power supply; />For the earth capacitance of each line>；/>Is an arc suppression coil inductance; />Is the ground resistance. Single phase earth fault occurs in phase a in the middle section of line 2,/-phase a>A line-to-ground capacitance upstream of the fault point; />Is the line-to-ground capacitance downstream of the fault point.
Transient process after fault occurrence can be regarded as neutral point offset voltageActing on the inductance and capacitance in the line. The transient current on each line flows back to the line through the fault point, bus and transformer.
To simplify the calculation of the current transient characteristics, multiple inductors and capacitors in the equivalent circuit can be combined into one inductor and capacitor, and the approximation can lead to the loss of high-frequency components, but the transient process can be qualitatively analyzed. The fault path fault phase fault current transient equivalence circuit diagram is as follows:
wherein the method comprises the steps ofThe capacitance to ground of the power distribution network; />The intermediate value resistor is a circuit intermediate value resistor; />Is fault phase voltage>Is the ground resistance. Thereby obtaining transient fault current +.>：
Wherein,,is the power frequency angular frequency; />The initial phase of the zero sequence voltage; />Is the free oscillation current angular frequency; />When the transient state is increased, the transient state process is weakened; />Short circuit current amplitude when the fault reaches a steady state; t represents the time after the occurrence of the fault.
The non-fault path and the fault path non-fault phase line transient equivalence circuit are as shown in figure 5,
thereby obtaining the non-fault line and the non-fault phase transient current of the fault lineThe following are provided:
wherein the method comprises the steps ofThe short-circuit current amplitude value of the non-fault line and the non-fault phase of the fault line under the condition that the fault reaches a steady state is used; />Equivalent resistance of non-fault phase of non-fault line and fault line; />The three-phase line and the power supply which are non-fault lines and non-fault phases of the fault lines and the equivalent inductance of the transformer;
in the neutral point through arc suppression coil grounding system, because the arc suppression coil compensation current only flows through the fault path fault phase, and the arc suppression coil time constant is large, the arc suppression coil compensation current is extremely small in the initial stage of fault occurrence, and the arc suppression coil can be regarded as open circuit. Thus, when analyzing fault component current transients, the neutral point via the arc suppression coil grounding system is approximately the same as the neutral point ungrounded system.
Because the phase current contains harmonic waves and load current interference, a signal with high reliability cannot be obtained only by subtracting the current before and after the fault. In order to avoid the influence of high-frequency components on the abrupt change direction of signals, an algorithm firstly utilizes improved S transformation to carry out filtering treatment on three-phase current signals, and finds abrupt change points of phase currents to determine the abrupt change direction after fundamental frequency components are obtained.
The invention designs an algorithm for determining the phase current abrupt change direction, and assumes that the processed fault component signal is:
wherein:is a sampling point; />Is a current value; the sampling point corresponding to the fault occurrence time obtained by the improved S transformation is +.>An appropriate calculation section is defined in the vicinity of the sampling point to calculate, and the calculation section is set to +.>。
Then the function value corresponding to the sampling point at the moment of fault occurrence is used as a reference value, the absolute value of the difference result between the corresponding function value in the interval and the reference value is calculated respectively, and the maximum value is foundThe sampling point corresponding to the value is taken as the mutation point:
maximum, corresponding to
Comparing the abrupt change direction results corresponding to the three-phase current on the same line, when two-phase calculation results appearWhen the other phase is different, the path can be judged to be a fault path, and the direction different phase is a fault phase; when three-phase calculation result on the line appears +.>All are the same, the path can be judged as a non-failure path.
In the step, based on the negative sequence current fault characteristics, auxiliary judgment is carried out as follows:
after single-phase earth fault, the negative sequence current only exists in the fault path, namely from the power supply point to the fault point, so that if the negative sequence current is extracted, the negative sequence current can be used as the basis for fault judgment. The basic principle of the three-phase symmetry method can obtain the negative sequence current as follows:
wherein:，/>，/>the current phasors of the abc three phases are represented, respectively. The influence of load current is filtered before and after the fault by sampling at equal intervals, and the terminal can be judged to be positioned at the upstream or downstream of the fault point through the amplitude value of the negative sequence current.
S6, each indicator completes fault perception judgment on site, and the judgment result is uploaded to the master station for comprehensive centralized judgment.
The calculation result obtained by carrying out the simulation test by using the physical test platform according to the above step flow is as follows:
simulation verification is carried out on high-resistance grounding and arc grounding in an arc suppression coil grounding system aiming at a neutral point with high positioning difficulty, and the device is provided with0.49. The neutral point is divided into an upstream line of the fault point and a downstream line of the fault point in the fault line through an arc suppression coil grounding system model as shown in the following figure 8;
after setting the ground resistance to 2000 q, the fault phase is phase a, the three-phase current waveforms of the fault path and the non-fault path are shown in fig. 9, 10 and 11,
the waveform can be obtained, and the transient process of the grounding resistance with larger current has larger attenuation, so that the phase current has no obvious abrupt change, and the transient process is fuzzy and cannot be judged. Under the condition of high-resistance grounding, the ratio of the amplitude of the high-frequency component to the amplitude of the fundamental frequency component of the three circuits is as follows: 0.0527, 0.0374 and 0.0288, so the positioning technology uses steady state characteristics to judge, and the calculation results are shown in the following table:
under the high-resistance grounding condition, the fault perception algorithm judges and utilizes the steady-state characteristics to judge, the current steady-state characteristics are obvious, the calculated result shows that the fault path variance is far greater than that of the non-fault path, the analysis of the steady-state process is verified, and the fault positioning can be correctly completed.
After the grounding point is set to be grounded through an arc, the fault phase is a C phase, and fault path and non-fault path phase current waveforms are shown in fig. 11, 12 and 13.
As can be seen from the waveforms, the transient process is quite evident through the arc grounding process, and a significant abrupt change can be observed. Under the condition of arc grounding, the ratio of the amplitude of the high-frequency component to the amplitude of the fundamental frequency component of the three circuits is as follows: 0.6297, 0.5941 and 0.5100, so that the positioning technology judges a fault path result by utilizing transient characteristics, and the transient result obtained by S-transformation of signals is shown in the following table:
the characteristic of large arc grounding harmonic content enables the fault perception algorithm to select transient characteristics for judgment, current transient characteristics are obvious, three-phase abrupt change directions in a fault path are different, but three-phase abrupt change directions in a fault path are the same, analysis of the fault component current transient process is verified, and the fault location can be accurately completed by a location technology.
Embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein. The scheme in the embodiment of the invention can be realized by adopting various computer languages, such as object-oriented programming language Java, an transliteration script language JavaScript and the like.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (9)
1. Novel distribution network fault indicator based on edge calculation, its characterized in that: the distribution network fault indicator comprises a high-speed FPGA circuit, a low-speed acquisition module, a high-speed A/D conversion circuit, a trigger module, an SDRAM memory and a communication module, wherein the high-speed FPGA circuit is connected with the high-speed A/D conversion circuit in a bidirectional data manner, the data input end of the high-speed A/D conversion circuit is connected with the signal processing circuit, and the high-speed FPGA circuit is connected with the memory in a bidirectional data manner; the signal output end of the low-speed acquisition module is connected with the trigger input end of the trigger module, and the trigger module controls the high-speed FPGA circuit to start current acquisition according to the output result of the low-speed acquisition module; the communication module drives a first input end of the low-speed acquisition module through threshold voltage, and the communication module performs data transmission inside the indicator and uploading of an external master station.
2. A novel distribution network fault indicator based on edge computation according to claim 1, wherein: the SDRAM memory employs a 16-bit 256M DDR3-SDRAM.
3. A novel distribution network fault indicator based on edge computation according to claim 1, wherein: the high-speed A/D conversion circuit adopts a 16-bit high-speed A/D conversion chip, and the sampling frequency of the conversion circuit is 2 multiplied by 1MHz.
4. A novel distribution network fault indicator based on edge computation according to claim 1, wherein: the communication module comprises a processor, an SD card memory and an Ethernet transmission module, wherein the data end of the processor is in bidirectional transmission communication with the SD card memory, and the communication end of the processor is in bidirectional communication with the Ethernet transmission module.
5. The utility model provides a novel distribution network fault indicator's operation method based on edge calculation which characterized in that: the method comprises the following steps:
s1, acquiring three-phase current of a line after a fault indicator is started and synthesizing zero sequence current;
s2, comparing the synthesized zero sequence current amplitude with a preset value, if the zero sequence current amplitude exceeds the preset value, performing S3, otherwise, continuously monitoring the zero sequence current amplitude by the indicator;
s3, the indicator judges that the power distribution network breaks down and starts a fault sensing algorithm, and after the algorithm is started, the indicator obtains phase currents in 5 periods before and after the starting time and synthesizes zero sequence currents;
s4, processing the zero-sequence current signal by utilizing improved S transformation to obtain sampling points corresponding to fault occurrence time and high-frequency components of zero-sequence current in a period after fault occurrenceAnd fundamental frequency component->Respectively obtain high frequency components->And fundamental frequency component->Performing self-adaptive fault sensing judgment on the amplitude of the signal;
s5, when a fault sensing criterion is met, judging that a resistor grounding fault occurs in the power distribution network, filtering load current by the indicator, then performing steady-state algorithm calculation, when the fault sensing criterion is not met, judging that an intermittent arc grounding fault occurs in the power distribution network, judging the mutation direction of three-phase current after filtering the load current by the obtained phase current, further judging whether a line fault exists or not, simultaneously extracting negative sequence current fault characteristics, and performing auxiliary judgment;
s6, each indicator completes fault perception judgment on site, and the judgment result is uploaded to the master station for comprehensive centralized judgment.
6. The method for using the novel distribution network fault indicator based on edge calculation according to claim 5, wherein the method comprises the following steps: the positioning analysis process based on the phase current steady-state signal characteristics during steady-state algorithm calculation in the step S5 is as follows: three phases on each line after failurePhase currentDivided into load currents->Fault component current +.>The current values corresponding to the phase difference whole period are measured by a detection device before and after the fault occurrence time to be subtracted, so that the fault component current after the fault is obtained>：
The fault component current of the fault path comprises positive sequence, negative sequence and zero sequence three-sequence current, and the non-fault path comprises only zero sequence current, wherein the positive and negative zero three-sequence current at the fault point obtained by the symmetrical component method is +.>Three-sequence positive sequence, negative sequence and zero sequence currents on fault path->、/>、/>The following are provided:
Directionfactor->Fault components of phases on a fault line +.>、/>、The following are provided:
positive, negative and zero sequence three-sequence currents on non-faulty paths->、/>、/>The method comprises the following steps: /> Fault component of three-phase current on non-fault path +.>、/>、/>The method comprises the following steps of:
wherein (1)>For the shunt coefficient of the fault path +.>Shunt coefficients for non-faulty paths;
by analyzing the fault components of the three-phase current of the fault path and the non-fault path, it is possible to: on the fault path, the fault component of the fault phase is larger than that of the non-fault phase, and the fault components of the non-fault phase are equal; in the non-fault path, the fault components of the three-phase currents are all the same.
7. The method for using the novel distribution network fault indicator based on edge calculation according to claim 6, wherein the method comprises the following steps: load current on line after faultLoad current before failure>Equal.
8. The method for using the novel distribution network fault indicator based on edge calculation according to claim 5, wherein the method comprises the following steps: in the step S5, when the fault perception criterion is not satisfied, a transient criterion is applied to perform judgment, which specifically includes the following steps:
fault path fault phase transient fault currentThe method comprises the following steps:
wherein (1)>Is the power frequency angular frequency; />The initial phase of the zero sequence voltage; />Is the free oscillation current angular frequency; />When the transient state is increased, the transient state process is weakened; />Short circuit current amplitude when the fault reaches a steady state; t represents the time after the fault occurs; />The intermediate value resistor is a circuit intermediate value resistor; />Is an arc suppression coil inductance;
non-fault line and fault line non-fault phase transient currentThe method comprises the following steps:
wherein->The short-circuit current amplitude value of the non-fault line and the non-fault phase of the fault line under the condition that the fault reaches a steady state is used; />Equivalent resistance of non-fault phase of non-fault line and fault line; />The three-phase line and the power supply which are non-fault lines and non-fault phases of the fault lines and the equivalent inductance of the transformer;
filtering the fault component signals, wherein the processed fault component signals are as follows:
wherein: />Is a sampling point; />Is a current value;
setting the calculation interval asThe function value corresponding to the sampling point at the fault occurrence time is used as a reference value, the absolute value of the difference result between the corresponding function value in the interval and the reference value is calculated respectively, and the sampling point corresponding to the maximum value is found to be used as a mutation point:
at the time of maximum value, the maximum value,
corresponding to By comparing the abrupt direction results corresponding to the three-phase currents on the same line, when the two-phase calculation result +.>The other phase is different, the path is judged to be a fault path, and the direction different phase is a fault phase; when three-phase calculation result on the line appears +.>All are the same, the path can be judged as a non-failure path.
9. The method for using the novel distribution network fault indicator based on edge calculation according to claim 5, wherein the method comprises the following steps: the specific operation of the auxiliary judgment in the step S5 is as follows: the extracted negative sequence current is as follows by the basic principle of the three-phase symmetry method:
wherein: />，/>，/>And respectively representing the current phasors of abc three phases, filtering out the influence of load current before and after the fault by sampling at equal intervals, and judging whether the terminal is positioned at the upstream or downstream of the fault point through the amplitude value of the negative sequence current.
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