A single-phase grounding fault identification method and system based on multiple signal sources

Abstract

The present application relates to the technical field of power line detection, and discloses a single-phase grounding fault identification method and system based on multiple signal sources. The method first obtains the distribution network fault signal to match the fault line section, and determines the middle position as the signal injection point. Inject the first high-voltage DC signal, collect DC voltage and current data, calculate the DC resistance of the line, and identify low, medium, high and ultra-high resistance grounding, transient faults and other types according to the comparison with the preset resistance value. Then inject the first AC signal, collect AC voltage and current data, calculate the total impedance of the line, and identify intermittent discharge, medium and low resistance grounding and other fault types according to the preset impedance value and fluctuation amplitude. If it is an intermittent discharge fault, inject a high-voltage signal and measure the three-phase current to determine the fault side. Finally, use the positioning algorithm based on the signal injection point to accurately locate the fault point and output the position. The present application can improve the recognition ability of small current grounding faults.

Description

Technical Field

[0001] The present application relates to the technical field of power line detection, and in particular to a single-phase grounding fault identification method and system based on multiple signal sources. Background Art

[0002] In modern power distribution systems, single-phase grounding faults are a common type of fault, with various causes, including wire breakage, insulator breakdown, and trees touching wires. The diagnosis and location of these faults face major challenges, mainly because the fault signals are weak, susceptible to interference, and the fault current waveform may be distorted. In addition, the complexity and uncertainty of the power grid poses a huge challenge to fault diagnosis, making it extremely difficult to find methods for single-phase grounding faults.

[0003] Weak signals are a major reason why single-phase ground fault diagnosis is difficult. In non-metallic ground faults, the ground fault current of less than one ampere is hidden in the load current of hundreds of amperes, making the load current a great interference in identifying the fault current. In addition, the distortion of the fault current waveform is also a problem, especially in the case of arc ground faults, the waveform distortion of the fault current and voltage is more serious. Furthermore, the grounding form of the power grid is changeable, which may be metal grounding, lightning discharge grounding, tree branch grounding, resistance grounding or various arc grounding, which increases the complexity of fault diagnosis.

[0004] At present, the distribution network fault diagnosis methods mainly include the traditional method of judging the grounding condition based on the voltage change at the open triangle of the voltage transformer, and the method of using the distribution automation system to longitudinally compare the similarity of the transient zero-sequence current waveform recorded at the feeder terminal to achieve ground fault location. However, these methods have limitations in practical applications. The traditional method has limited ability to identify small current ground faults, and although the waveform comparison method of the distribution automation system can improve the accuracy of fault diagnosis, its efficiency and accuracy will also be affected when the number of switches in the distribution network increases. Summary of the invention

[0005] In order to improve the ability to identify small current grounding faults, the present application provides a single-phase grounding fault identification method and system based on multiple signal sources.

[0006] In a first aspect, the present application provides a single-phase ground fault identification method based on multiple signal sources, which adopts the following technical solutions:

[0007] A single-phase grounding fault identification method based on multiple signal sources includes the following steps:

[0008] Obtain distribution network fault signals, and match faulty line sections according to the distribution network fault signals;

[0009] Determine the middle position of the faulty line section and use the middle position as a signal injection point;

[0010] Injecting a first high voltage DC signal from the signal injection point into the fault line section;

[0011] Collecting the DC voltage and DC current on the fault line section in real time to generate DC voltage data and DC current data;

[0012] Stop injecting the first high voltage DC signal;

[0013] Calculate the line DC resistance, where the line DC resistance R=the DC voltage / the DC current;

[0014] If R is less than or equal to a preset first resistance value, the fault type is identified as a low-resistance grounding fault; if R is between the first resistance value and the preset second resistance value, the fault type is identified as a medium-resistance grounding fault; if R is between the second resistance value and the preset third resistance value, the fault type is identified as a high-resistance and ultra-high-resistance grounding fault; if R is greater than the third resistance value, an open circuit alarm is triggered and the fault type is identified as a transient fault;

[0015] Injecting a first AC signal from the signal injection point into the fault line section;

[0016] Collecting the AC voltage and AC current on the fault line section in real time to generate AC voltage data and AC current data;

[0017] Calculate the total line impedance, where the total line impedance Z=the AC voltage / the AC current;

[0018] If Z is greater than or equal to the preset first impedance value, and the fluctuation amplitude of Z exceeds the preset first impedance range, the fault type is identified as an intermittent discharge fault; otherwise, it is a non-intermittent discharge fault;

[0019] If the fault type is identified as an intermittent discharge fault, after injecting a first AC signal from the signal injection point into the fault line section for a preset first time period, if Z is less than or equal to a preset second impedance value, the fault point of the intermittent discharge fault has been broken down;

[0020] If Z is less than the first impedance value, regardless of whether the fluctuation amplitude of Z exceeds the preset first impedance range, the fault type is identified as a medium-low resistance grounding fault;

[0021] If the fault type is identified as the intermittent discharge fault, a high-voltage AC signal of a preset second duration is injected into the signal injection point, and when the high-voltage signal on the line is stable, the three-phase currents of the branches on both sides of the signal injection point are measured;

[0022] If the currents of each phase in the three phases on one side are close to or equal, there is no ground fault on this side; if the current of one phase on this side is greater than the currents of the other two phases and exceeds the preset second AC current value, the phase is determined to be a fault phase, and this side is the side where the signal injection point fails;

[0023] Based on the signal injection point, the fault point is accurately located through a positioning algorithm, and the position of the fault point is output.

[0024] By adopting the above technical solution, the single-phase grounding fault identification method first injects a high-voltage DC signal into the fault line to detect the line DC resistance R in the line, so as to identify the fault type; then, by injecting a high-voltage AC signal, it passes through the fault position and forms a closed path, captures the change of the total impedance Z of the line, and then identifies the type of intermittent discharge fault; in the fault area, the current of the fault phase and other phases will be different, and each measurement can help determine the location of the fault. By measuring through the positioning algorithm, the scope of the fault area can be gradually narrowed until the fault point is accurately located; this method not only enables the inspection personnel to conduct targeted fault search according to the identified fault type, but also significantly improves the efficiency and accuracy of fault search. It effectively solves the problems of invalid inspection and inefficient inspection faced by the traditional signal injection method for locating grounding fault equipment. By integrating advanced fault diagnosis algorithms, the device realizes the automatic identification and judgment of fault types during fault inspection, which significantly improves the efficiency of fault inspection. In addition, by accurately locating the fault point, the technology shortens the power outage time of the distribution line fault and reduces the workload of fault inspection, thereby improving the reliability and operation and maintenance efficiency of the distribution network.

[0025] Optionally, the method further comprises the following steps:

[0026] Acquire the nearest plurality of the DC resistances R to obtain a DC resistance sequence;

[0027] Fitting the DC resistance sequence into a DC resistance change curve, and calculating the growth change trend of the DC resistance change curve;

[0028] The frequency of the first AC signal is anti-correlatedly adjusted according to the value of the growth trend. The larger the value of the growth trend is, the lower the frequency of the first AC signal is; the smaller the value of the growth trend is, the higher the frequency of the first AC signal is.

[0029] By adopting the above technical solution, the load connected to the power line is mainly inductive load, and the capacitive load is mainly used for compensation of the power line. Therefore, the frequency of the first AC signal is adjusted inversely according to the value of the growth change trend, and the recognition effect can be optimized according to the actual situation of the power line.

[0030] Optionally, the method further comprises the following steps:

[0031] The first AC signal uses a first AC frequency and a second AC frequency with different frequencies to calculate impedance respectively:

[0032] First, a first total impedance Z1 is calculated using a preset first AC frequency;

[0033] Then, using the preset second AC frequency, the second total impedance Z2 is calculated;

[0034] The line total impedance Z is calculated according to the first total impedance Z1 and the second total impedance Z2 by using a first weighted average algorithm.

[0035] By adopting the above technical solution, the first total impedance and the second total impedance are calculated using different AC frequencies, and then the total line impedance is calculated. The line responds differently to different AC frequencies, so the calculated total line impedance can be more in line with the on-site conditions.

[0036] Optionally, the method further comprises the following steps:

[0037] Get the preset frequency change;

[0038] The first AC frequency is adjusted according to the frequency variation to obtain a first variation range of the first total impedance Z1; the second AC frequency is adjusted according to the frequency variation to obtain a second variation range of the second total impedance Z2;

[0039] Based on the comparison between the first variation range and the second variation range, a weighted value of the first total impedance Z1 and a weighted value of the second total impedance Z2 are determined in an anti-correlation manner.

[0040] By adopting the above technical solution, after the first AC frequency and the second AC frequency are changed, the change range is calculated, and the response of the line to the frequency change can be obtained by comparing the change range, so that the weighted value can be more in line with the on-site situation.

[0041] Optionally, the method further comprises the following steps:

[0042] The first AC signal uses a first AC frequency, a second AC frequency, and a third AC frequency with different frequencies to calculate impedance respectively:

[0043] First, a first total impedance Z1 is calculated using a preset first AC frequency;

[0044] Then, using the preset second AC frequency, the second total impedance Z2 is calculated;

[0045] If the difference between the first total impedance Z1 and the second total impedance Z2 is less than the preset first impedance difference, then the third total impedance Z3 is calculated using the preset third AC frequency;

[0046] Calculating a temporary total impedance Z12 according to the first total impedance Z1 and the second total impedance Z2 by using a first weighted average algorithm;

[0047] The line total impedance Z is calculated according to the temporary total impedance Z12 and the third total impedance Z3 by using a second weighted average algorithm.

[0048] By adopting the above technical solution, the temporary total impedance is calculated first, and then the total line impedance is calculated, which can enhance the influence of the third total impedance on the total line impedance and make the total line impedance more suitable for the on-site conditions.

[0049] Optionally, the method further comprises the following steps:

[0050] After stopping injecting the first AC signal, adding a first pulse signal to the signal injection point;

[0051] Performing detection at a preset first distance point at a first distance from the signal injection point to obtain a first electromagnetic induction signal;

[0052] Performing detection at a preset second distance point at a second distance from the signal injection point to obtain a second electromagnetic induction signal;

[0053] calculating a difference between the first electromagnetic induction signal and the second electromagnetic induction signal as an electromagnetic induction difference;

[0054] Matching the fault direction and fault distance according to the electromagnetic induction difference;

[0055] If the fault direction and the fault distance do not correspond to the fault location point, a detection error warning prompt is issued.

[0056] By adopting the above technical solution, a pulse signal is injected into the line. The pulse signal can generate electromagnetic waves through the line. Detecting the electromagnetic waves can generate electromagnetic induction signals. The electromagnetic induction signals can be used to detect the approximate direction and distance of the line fault point, thereby providing an early warning of the fault location.

[0057] Optionally, the method further comprises the following steps:

[0058] Obtaining the number of detection error warning prompts within a recent preset time period;

[0059] The third resistance value, the first impedance value, and the second impedance value are adjusted in a positive correlation according to the number of detection error warning prompts.

[0060] By adopting the above technical solution, the relevant parameters used in the detection are adjusted according to the warning situation. The more warning times there are, the more prominent the atypical characteristics of the fault are, thereby improving the relevant parameters and classifying the fault more reasonably.

[0061] Optionally, the method further comprises the following steps:

[0062] The positioning algorithm is a dichotomy method;

[0063] Obtaining the nearest locations of multiple fault points;

[0064] Calculate the middle point position between two of the fault point positions with adjacent generation times among the multiple fault point positions to obtain a middle point sequence;

[0065] Calculating the discreteness of the intermediate point sequence;

[0066] If the discrete degree is less than a preset discrete value, then calculating the average value of all the intermediate point positions in the intermediate point sequence as the problem recommendation point;

[0067] Next time, the fault point is accurately located from the problem recommended point through the positioning algorithm, and the new position of the fault point is output.

[0068] By adopting the above technical solutions, through this integrated data management and analysis system, we can not only monitor the operating status of the device in real time during fault finding, but also identify potential fault points in this section of the faulty line through in-depth analysis of historical data and real-time data; historical data will be stored and constructed into a database. When new measurement data are entered into the database, they will be compared with potential fault data or abnormal fault data in the historical fault line. If the new data matches the data characteristics of the abnormal fault situation, further diagnosis and detection can be carried out according to the established methods of abnormal fault detection.

[0069] In the second aspect, the present application provides a single-phase grounding fault identification system based on multiple signal sources, which adopts the following technical solutions:

[0070] A single-phase grounding fault identification system based on multiple signal sources comprises a processor, wherein the processor executes the steps of any one of the above-mentioned single-phase grounding fault identification methods based on multiple signal sources.

[0071] In summary, the present application includes at least one of the following beneficial technical effects:

[0072] Accurate identification of fault types: This technology can realize early identification of fault types, allowing inspection personnel to select the most appropriate inspection strategy for targeted processing based on the specific type of fault. This "symptomatic treatment" approach greatly improves the efficiency and accuracy of inspections.

[0073] Innovation of high-voltage fault finding device: When an intermittent discharge fault occurs, the high-voltage fault finding device of the present invention can effectively break down the fault point, making the difficult fault point that was originally difficult to locate easy to identify and handle, thereby simplifying the fault handling process.

[0074] Significant improvement in fault detection efficiency and accuracy: Compared with traditional methods, the use of this technology for single-phase grounding fault detection can significantly reduce the time spent by maintenance personnel in the fault location process. Actual cases show that the fault location efficiency has been improved by more than 50%. At the same time, this technology significantly enhances the detection accuracy of grounding faults. Test data shows that the fault detection rate has increased by about 30%, greatly improving the stability and safety of the power system.

[0075] In summary, the technical solution of the present invention not only improves the efficiency of fault handling, but also enhances the reliability and safety of the power system, and provides strong technical support for the stable operation of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 It is the data collection logic model.

[0077] Figure 2 It is a flow chart of fault type identification.

[0078] Figure 3 This is the DC resistance measurement (DC signal) output diagram.

[0079] Figure 4 is the fault finding mode (AC signal) output graph.

[0080] Figure 5 It is the output open circuit alarm diagram. DETAILED DESCRIPTION

[0081] Embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings.

[0082] In the description of this specification, the description with reference to the terms "certain embodiments", "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0083] The present application embodiment discloses a single-phase ground fault identification method based on multiple signal sources, referring to Figure 1-Figure 5 , including the following steps:

[0084] Obtain distribution network fault signals, and match faulty line sections according to the distribution network fault signals;

[0085] Determine the middle position of the faulty line section and use the middle position as the signal injection point;

[0086] Injecting a first high voltage DC signal from a signal injection point into the faulty line section;

[0087] The DC voltage and DC current on the faulty line section are collected in real time to generate DC voltage data and DC current data.

[0088] The high voltage DC signal is injected to obtain the DC parameters of the line. The specific steps include:

[0089] Selection of signal injection point: First, determine the approximate center position of the faulty line section and select this position as the signal injection point.

[0090] Device connection: Correctly connect the power supply, signal source and booster of the fault detection device, and ensure that all interfaces are matched and secure.

[0091] Grounding operation: After the device is connected, fix the grounding wire clamp to the grounding flat iron or a reliable grounding point to ensure the safety of the operation.

[0092] Output line connection: Connect the output lines to the A, B, and C phases of the faulty line respectively to ensure good contact to facilitate signal transmission.

[0093] Gear setting: Turn the device's toggle switch to the impedance measurement gear, that is, the DC output gear, to prepare for the subsequent signal output.

[0094] Signal output: Turn the output gear to start the device for signal output. The output voltage can reach 10KV and the current can reach 4.9mA. At this time, the device will inject a high-voltage DC signal into the fault line.

[0095] Data acquisition and storage: The signal source will collect the DC voltage U0 and DC current I0 on the fault line in real time. These analog data will be processed by the signal source and stored in the microcontroller unit (MCU) for subsequent fault analysis and processing.

[0096] Stop injecting the first high voltage DC signal, analyze the system data, and identify the fault type:

[0097] Calculate the line DC resistance R, which is DC voltage U0 / DC current I0. According to the calculation results, the faults can be classified into the following types:

[0098] If R is less than or equal to a preset first resistance value, in this embodiment, the first resistance value is 10K, that is, when R is in the range of 0≤R≤10K, the fault type is identified as a low-resistance grounding fault.

[0099] If R is between the first resistance value and the preset second resistance value, in this embodiment, the second resistance value is 100K, that is, when R is in the range of 10K<R≤100K, the fault type is identified as a medium-resistance grounding fault.

[0100] If R is between the second resistance value and the preset third resistance value, in this embodiment, the third resistance value is 5000K, that is, when R is in the range of 100K<R≤5000K, the fault type is identified as a high resistance and an ultra-high resistance grounding fault.

[0101] If R is greater than the third resistance value, that is, 5000K<R, an open circuit alarm is triggered and the fault type is identified as a transient fault.

[0102] Injecting a first AC signal from a signal injection point into the faulty line section;

[0103] The AC voltage and AC current on the fault line section are collected in real time to generate AC voltage data and AC current data.

[0104] Inject AC signals to obtain line AC parameters. The specific steps include:

[0105] Position switching: Switch the device's toggle switch from the impedance measurement position (DC signal input) to the fault finding position (AC signal input).

[0106] Signal output: After the fault finding gear is set, a 22HZ AC signal is output to the faulty line section, with an output voltage of up to 8KV and a current of up to 80mA.

[0107] Data acquisition: The signal source will collect the AC voltage U1 and AC current I1 on the fault line in real time. These parameters are crucial for analyzing fault characteristics.

[0108] Data processing and storage: The collected analog data of AC voltage U1 and AC current I1 will be processed by the signal source and then stored in the microcontroller unit (MCU). This process ensures the accuracy and reliability of the data and provides a basis for subsequent fault analysis.

[0109] Calculate the total line impedance Z, which is AC voltage U1 / AC current I1.

[0110] If Z is greater than or equal to the preset first impedance value, and the fluctuation amplitude of Z exceeds the preset first impedance range, in this embodiment, the first impedance value is 100K; the first impedance range is -50K to +50K; that is, the initial Z ≥ 100K, but Z fluctuates within the range of ≥ ± 50K, then the fault type is identified as an intermittent discharge fault.

[0111] If the fault type is identified as an intermittent discharge fault, after the first AC signal is injected from the signal injection point to the faulty line section for a preset first time period, the first time period is 10 minutes. If Z is less than or equal to a preset second impedance value, in this embodiment, that is, the ratio of Z suddenly decreases to (Z≤10K), then the fault point whose fault type is an intermittent discharge fault has been broken down.

[0112] In AC mode, if Z is less than the first impedance value, that is, the total line impedance Z is lower than 100k, regardless of whether the fluctuation amplitude of Z exceeds the preset first impedance range, the fault type is identified as a medium-low resistance grounding fault. If the total line impedance is lower than 100k, an intermittent discharge fault may occur. This type of fault can be directly detected by the device in conjunction with a clamp meter. Therefore, for medium-low resistance intermittent discharge faults below 100k, they are all treated as medium-low resistance grounding faults.

[0113] Note: When the total line impedance Z fluctuates within a range of more than 50k, the phenomenon is identified as an intermittent discharge fault. This identification is based on the following principle: During the process of injecting AC signals into the device, the current will fluctuate to a certain extent. Only when this fluctuation exceeds the error threshold of the device can it be considered as a current change caused by fault discharge. Specifically, the error threshold of the device is the key criterion for judging the change in fault discharge current. When the current fluctuation exceeds this error range, it can be confirmed as an intermittent discharge fault, thus providing an accurate basis for fault location and processing.

[0114] In order to achieve real-time monitoring and remote management of data, we will seamlessly transmit these measurement data, including DC characteristic data U0, I0, AC measurement data U1, I1, and three-phase current data IA, IB, IC and Ia, Ib, Ic at the injection point, to the data cloud platform through wireless communication units. On the data cloud platform, we will establish a structured database to store and manage these data. The database will use the latest data storage technology to ensure high availability and fast access to data.

[0115] Through this integrated data management and analysis system, we can not only monitor the operating status of the device in real time during fault detection, but also identify potential fault points in this section of the faulty line through in-depth analysis of historical data and real-time data (historical data will be stored and built into a database. When new measurement data are entered into the database, they will be compared with potential fault data or abnormal fault data in the historical faulty line. If the new data matches the data characteristics of the abnormal fault condition, further diagnosis and detection can be performed based on the established methods of abnormal fault detection).

[0116] If the fault type is identified as an intermittent discharge fault, a high-voltage signal of a preset second duration is injected into the signal injection point. When the high-voltage signal on the line is stable, the three-phase current of the branches on both sides of the signal injection point on the line is measured. In this embodiment, the specific method of intermittent discharge fault processing and current measurement is as follows: If it is an intermittent discharge fault, when discharging at the fault point, the device can continuously output a high-voltage signal to the fault point for 10 minutes. The continuous output can break through part of the fault point, making it a low-resistance fault, thereby greatly increasing the fault detection rate. After the signal injection process is stable, an intelligent clamp ammeter is used to accurately measure the current of the three phases A, B, and C. During the measurement process, current measurements must be performed on the two directions of the injection point, namely the large side and the small side, respectively, to determine the approximate direction of the fault point.

[0117] If the difference between the currents of each phase in the three phases on one side is less than the preset first AC current value, there is no ground fault on this side; if the current of a phase on this side is greater than the currents of the other two phases and exceeds the preset second AC current value, the phase is determined to be a fault phase, and this side is the side where the signal injection point fails. In this embodiment, the specific fault identification method is as follows: If the values ​​of the three-phase currents A, B, and C measured on the large side are equal, it can be inferred that there is no ground fault in the large measurement direction. If it is found that the current of a phase is significantly greater than that of the other two phases when measuring on the large side, it can be determined that this phase is the fault phase, and the direction of the large side is the direction where the ground fault occurs. The measurement method on the small side is analogous to that on the large side. This measurement and judgment method is based on the principle of symmetry of current distribution, and can effectively assist the fault diagnosis process through high-precision measurement of the intelligent clamp ammeter.

[0118] Based on the signal injection point, the fault point is accurately located through the positioning algorithm and the fault point position is output. After determining the fault phase and fault direction, the binary method should be used to accurately locate the fault point. The binary method is an effective fault location technology, and its specific operation steps are as follows:

[0119] 1. Reduction of the fault area: According to the midpoint measurement results, if the currents on one side of the midpoint are equal, it indicates that the fault is on the other side of the line; if the current on one side is abnormal, it indicates that the fault is on that side. In this way, the fault area is reduced to half of the line.

[0120] 2. Recursively apply the binary method: Repeat the binary measurement process in the reduced fault area, continue to measure the midpoints of the remaining lines, and gradually reduce the fault area until the fault point is accurately located.

[0121] 3. Final determination of the fault point: Through continuous binary measurements, the fault point can be located within a very small range, thereby achieving accurate fault finding. Through this step-by-step refinement method, the binary method can efficiently locate the fault point, reduce troubleshooting time, and improve the accuracy of fault handling.

[0122] Here’s how it works:

[0123] 1. The fault detection system is based on signal injection technology. This technology introduces a 22Hz frequency signal into the fault line, passing through the fault location and forming a closed path. In the fault area, the current of the fault phase will be different from that of other phases, and each measurement can help determine the location of the fault. By using the binary method for measurement, the scope of the fault area can be gradually narrowed until the fault point is accurately located.

[0124] 2. Fault type identification technology first injects a high-voltage DC signal into the fault line to detect the resistive load in the line to identify the fault type. Then, by injecting a high-voltage AC signal, the change in the reactance (Z) of the fault line is captured to identify the type of intermittent discharge fault. This method not only enables inspection personnel to conduct targeted fault finding based on the identified fault type, but also significantly improves the efficiency and accuracy of fault finding.

[0125] The single-phase grounding fault identification method first injects a high-voltage DC signal into the fault line and detects the line DC resistance R in the line to identify the fault type; then, by injecting a high-voltage AC signal, it passes through the fault location and forms a closed path to capture the change in the total impedance Z of the line, and then identify the type of intermittent discharge fault; in the fault area, the current of the fault phase will be different from that of other phases, and each measurement can help determine the direction of the fault. By measuring with a positioning algorithm, the scope of the fault area can be gradually narrowed until the fault point is accurately located; this method not only enables inspection personnel to conduct targeted fault finding based on the identified fault type, but also significantly improves the efficiency and accuracy of fault finding.

[0126] The best implementation method of this embodiment is: when a ground fault occurs in the distribution network, a 10kV DC signal is first injected into the fault line section using a signal source. The signal source body will accurately calculate the DC parameters of the line and stop signal output after the calculation is completed.

[0127] When a ground fault occurs in the distribution network, the signal source is first used to inject a 10kV DC signal into the faulty line section. The signal source body will accurately calculate the DC parameters of the line and stop signal output after the calculation is completed.

[0128] The inspectors use a clamp ammeter to measure the line current to obtain the current parameters of the line.

[0129] After completing the above steps, the signal source will comprehensively identify the fault type based on the collected DC and AC parameter data.

[0130] After identifying the fault type, inspection personnel can accurately locate and find the line fault point based on the analysis results of the signal source.

[0131] This invention not only realizes the function of automatically identifying the fault type through the signal source, but also can effectively assist the inspection personnel to quickly locate the grounding fault point, significantly improving the efficiency and accuracy of fault finding. Through this method, the operation and maintenance personnel of the distribution network can quickly respond to the grounding fault, reduce the power outage time, and improve the reliability and safety of the power grid.

[0132] The method further comprises the steps of:

[0133] The most recent multiple DC resistances R are obtained to obtain a DC resistance sequence; the value of the DC resistance R is collected once every 1 minute, and the collection is performed continuously for 10 times. The DC resistance values ​​obtained are 5, 5.2, 5.3, 5.5, 5.6, 5.8, 6, 6.2, 6.3, and 6.5, respectively. These values ​​are arranged in sequence according to the collection order to form a DC resistance sequence.

[0134] Fit the DC resistance sequence into a DC resistance change curve, and calculate the growth trend of the DC resistance change curve. Use professional data analysis software (such as MATLAB, etc.) to fit this DC resistance sequence into a DC resistance change curve through a fitting algorithm (such as least squares fitting). Calculate its growth trend by performing related mathematical operations such as calculating the slope of the curve. If the calculation shows that the slope of this curve is gradually increasing, it means that the value of its growth trend is increasing.

[0135] The frequency of the first AC signal is adjusted inversely according to the value of the growth change trend. The larger the value of the growth change trend, the lower the frequency of the first AC signal, and the smaller the value of the growth change trend, the higher the frequency of the first AC signal. According to the set adjustment rules, the larger the value of the growth change trend, the lower the frequency of the first AC signal. Assuming that the initial frequency of the first AC signal is originally set to 22Hz, when it is detected that the growth change trend of the DC resistance change curve increases significantly (for example, the slope reaches a certain set threshold), the frequency of the first AC signal should be lowered accordingly according to the rules, for example, it should be lowered to 20Hz. On the contrary, if after a period of monitoring, the growth change trend of the DC resistance change curve becomes smaller (the slope becomes smaller), then the frequency of the first AC signal needs to be increased, for example, adjusted back to 23Hz.

[0136] In this way, by dynamically adjusting the frequency of the first AC signal according to the growth trend of the DC resistance change curve, it is possible to better adapt to the actual operation of the power line and optimize the fault identification effect. For example, different types of ground faults can be more accurately distinguished, making the entire single-phase ground fault identification method more accurate and effective.

[0137] The loads connected to the power line are mainly inductive loads, and the capacitive loads are mainly used for compensation of the power line. Therefore, by adjusting the frequency of the first AC signal inversely according to the value of the growth trend, the recognition effect can be optimized according to the actual situation of the power line.

[0138] The method further comprises the following steps: the first AC signal uses a first AC frequency and a second AC frequency with different frequencies to respectively calculate impedance:

[0139] First, use the first AC signal with a preset first AC frequency to calculate the first total impedance Z1; and inject the first AC signal with a preset first AC frequency of 22Hz into the power line as required. While injecting, use professional measuring instruments to collect the corresponding AC voltage and AC current values ​​on the line in real time. For example, the measured AC voltage is 220V and the AC current is 10A. According to the total line impedance calculation formula (total line impedance Z=AC voltage / AC current), the first total impedance Z1=220V / 10A=22 can be calculated.

[0140] The second total impedance Z2 is calculated using the first AC signal of the preset second AC frequency.

[0141] When a 30Hz AC signal is injected into the line, the AC voltage at this time is collected by the measuring instrument again, which is 210V and the AC current is 8A. Then, according to the same calculation method, the corresponding total impedance at this time (temporarily recorded as Z2-30Hz) is 210V / 8A=26.25.

[0142] The line total impedance Z is calculated according to the first total impedance Z1 and the second total impedance Z2 by using a first weighted average algorithm: Z=Z1×0.5+Z2×0.5=24.125.

[0143] The method further comprises the steps of:

[0144] Get the preset frequency change; for example, the frequency change is -5hz.

[0145] The first AC frequency is adjusted according to the frequency change to obtain the first change range of the first total impedance Z1; it is known that the initial first AC frequency is 22Hz, and after adjusting according to the set frequency change, the frequency becomes 17Hz. At 22Hz, by injecting an AC signal of this frequency into the line, and measuring the AC voltage to be 440V and the AC current to be 20A, according to the total impedance calculation formula of the line (Z=AC voltage / AC current), it can be calculated that the first total impedance Z1 (at 22Hz) at this time is 440V / 20A=22. When the first AC frequency changes to 17Hz, it is measured again. Assuming that the measured AC voltage at this time becomes 360V and the AC current becomes 16A, it can be calculated that the corresponding total impedance at this time (recorded as Z1-17Hz) is 360V / 16A=22.5. Therefore, the change of the first total impedance Z1 is 22.5-22=0.5, that is, the first change range can be expressed as a change from 22 to 22.5, with a change range of 0.5.

[0146] The second AC frequency is adjusted according to the frequency variation to obtain the second variation range of the second total impedance Z2. The initial second AC frequency is 30Hz, which is adjusted to 25Hz according to the frequency variation of -5Hz. At 30Hz, the measured AC voltage is 600V and the AC current is 20A. The second total impedance Z2 (at 30Hz) is calculated to be 600V / 20A=30.

[0147] When the frequency changes to 25Hz, the AC voltage is re-measured to be 480V and the AC current is 18A. The corresponding total impedance (recorded as Z2-25Hz) is 480V / 18A=26.67 (keep two decimal places). Therefore, the change of the second total impedance Z2 is 26.67-30=-3.33, that is, the second change range is from 30 to 26.67, and the change range is 3.33.

[0148] Based on the comparison between the first variation range and the second variation range, the weighted value of the first total impedance Z1 and the weighted value of the second total impedance Z2 are determined by anti-correlation, that is, the weighted value of the first total impedance Z1: the weighted value of the second total impedance Z2 = the second variation range / (first variation range+second variation range): first variation range / (first variation range+second variation range)=3.33 / (3.33+0.5):0.5 / (3.33+0.5)=0.87:0.13.

[0149] After the first AC frequency and the second AC frequency are changed, the change range is calculated, and the response of the line to the frequency change can be obtained by comparing the change range, so that the weighted value can be more in line with the on-site situation.

[0150] The method further comprises the following steps: the first AC signal uses a first AC frequency, a second AC frequency and a third AC frequency with different frequencies to respectively calculate impedance:

[0151] First, use the first AC signal with a preset first AC frequency to calculate the first total impedance Z1. As required, use the first AC signal with a preset first AC frequency of 22Hz to inject into the power line. While injecting, we use professional measuring instruments to collect the corresponding AC voltage and AC current values ​​on the line in real time. For example, the measured AC voltage is 220V and the AC current is 10A. According to the total line impedance calculation formula (total line impedance Z=AC voltage / AC current), the first total impedance Z1=220V / 10A=22 can be calculated.

[0152] Then use the first AC signal of the preset second AC frequency to calculate the second total impedance Z2. Using the first AC signal of the preset second AC frequency, the second AC frequency is 30Hz, and the AC voltage at this time is collected by the measuring instrument again, which is 210V and the AC current is 8A. Then, according to the same calculation method, the corresponding total impedance at this time (temporarily recorded as Z2-30Hz) is 210V / 8A=26.25.

[0153] If the difference between the first total impedance Z1 and the second total impedance Z2 is less than the preset first impedance difference, the first AC signal of the preset third AC frequency is used to calculate the third total impedance Z3. Assuming that the preset first impedance difference is 10, the first total impedance Z1=22, the second total impedance Z2 (corresponding to Z2-30Hz at 30Hz)=26.25, their difference is: 26.25-22=4.25, 4.25 is less than the preset first impedance difference of 10, so it is necessary to continue to calculate the third total impedance Z3. Assuming that the preset third AC frequency is 40Hz, after the corresponding first AC signal is injected into the line, the AC voltage collected by the measuring instrument at this time is 300V and the AC current is 10A. According to the line total impedance calculation formula, the third total impedance Z3=300V / 10A=30 can be obtained.

[0154] The temporary total impedance Z12 is calculated by a first weighted average algorithm according to the first total impedance Z1 and the second total impedance Z2. The temporary total impedance Z12 is calculated by a first weighted average algorithm according to the first total impedance Z1 and the second total impedance Z2.

[0155] Assuming that the weighted value of the first total impedance Z1 is 0.5 and the weighted value of the second total impedance Z2 is 0.5, the calculation formula of the temporary total impedance Z12 is: Z12=Z1×0.5+Z2×0.5=24.125.

[0156] The line total impedance Z is calculated by the second weighted average algorithm based on the temporary total impedance Z12 and the third total impedance Z3. Assuming that the weighted value of the temporary total impedance Z12 is 0.5 and the weighted value of the third total impedance Z3 is 0.5, the calculation formula of the line total impedance Z is:

[0157] Z=Z12×0.5+Z3×0.5=(Z1×0.5+Z2×0.5)×0.5+Z3×0.5=Z1×0.25+Z2×0.25+3×0.5.

[0158] Calculating the temporary total impedance first and then calculating the total line impedance can enhance the influence of the third total impedance on the total line impedance and make the total line impedance more in line with the on-site conditions.

[0159] The method further comprises the steps of:

[0160] After the injection of the first AC signal is stopped, a first pulse signal is added to the signal injection point.

[0161] A first electromagnetic induction signal is obtained by detecting at a preset first distance point which is a first distance away from the signal injection point.

[0162] A second electromagnetic induction signal is obtained by detecting at a preset second distance point which is a second distance away from the signal injection point.

[0163] The difference between the first electromagnetic induction signal and the second electromagnetic induction signal is calculated as an electromagnetic induction difference.

[0164] The fault direction and distance are matched according to the electromagnetic induction difference. The matching method is table lookup.

[0165] If the fault direction and fault distance do not match the fault location point, a detection error warning prompt is issued. The matching method is table lookup.

[0166] For example, first, after stopping the injection of the first AC signal as required, a first pulse signal is added to the signal injection point. For example, the signal injection point is located at the starting end of the line.

[0167] When the distance from the signal injection point reaches a first distance, for example, the first distance is set to a preset first distance point of 2 kilometers, a professional electromagnetic induction detection instrument is used to detect to obtain a first electromagnetic induction signal. It is assumed that the detected first electromagnetic induction signal strength is 80 millivolts (mV).

[0168] Next, a detection is performed at a preset second distance point at a second distance of 3 kilometers from the signal injection point to obtain a second electromagnetic induction signal. It is assumed that the intensity of the second electromagnetic induction signal detected this time is 50 mV.

[0169] Then, the difference between the first electromagnetic induction signal and the second electromagnetic induction signal is calculated as the electromagnetic induction difference, that is, the electromagnetic induction difference=80mV-50mV=30mV.

[0170] According to the electromagnetic induction difference, the fault direction and fault distance are matched through a pre-defined lookup table. For example, the lookup table shows that when the electromagnetic induction difference is in the range of 25mV-35mV, the corresponding fault direction is roughly toward the end of the line (relative to the signal injection point), and the fault distance is about 3.5 kilometers away from the signal injection point.

[0171] A pulse signal is injected into the line, which can generate electromagnetic waves through the line. Detecting the electromagnetic waves can generate electromagnetic induction signals. The electromagnetic induction signals can be used to detect the approximate direction and distance of the line fault point, thereby providing an early warning of the fault location.

[0172] The method further comprises the steps of:

[0173] Get the number of detection error warning prompts in the most recent preset time period; set the preset time period to the past week, and use the fault monitoring system's recording function to count the number of detection error warning prompts generated during this week. For example, after checking the system records, it is found that a total of 10 detection error warning prompts occurred in the past week.

[0174] The third resistance value, the first impedance value and the second impedance value are adjusted in a positive correlation according to the number of detection error warning prompts.

[0175] Assume that the originally set third resistance value is 500, the first impedance value is 100, and the second impedance value is 50 (the values ​​are only for example display, not the specific values ​​in actual application). Now, since there are 10 detection error warning prompts, it means that in the past fault detection process, the faults showed many situations that did not meet the conventional expectations, that is, the atypical characteristics of the faults were more prominent. In order to classify and identify the faults more reasonably, these parameter values ​​need to be increased accordingly.

[0176] For example, the following adjustment rules are formulated: every time there are 5 detection error warning prompts, the third resistance value increases by 100, the first impedance value increases by 20, and the second impedance value increases by 10. Then, when there are 10 detection error warning prompts, the third resistance value needs to be increased by 200, and the adjusted third resistance value becomes 500+200=700; the first impedance value increases by 40, becoming 100+40=140; the second impedance value increases by 20, becoming 50+20=70.

[0177] The relevant parameters used in the detection are adjusted according to the warning situation. The more warning times there are, the more prominent the atypical characteristics of the fault are, thereby improving the relevant parameters and making a more reasonable classification of the fault.

[0178] In other embodiments, the method further comprises the steps of:

[0179] The positioning algorithm is a dichotomy method;

[0180] Obtain the nearest multiple fault point locations; First, obtain the nearest multiple fault point locations, which are relevant data recorded in the previous troubleshooting process of the power line.

[0181] Calculate the midpoint position between two fault point positions with adjacent generation times among multiple fault point positions to obtain a midpoint sequence. Next, for these multiple fault point positions obtained, calculate the midpoint position between two fault point positions with adjacent generation times, and arrange all the midpoint positions calculated in this way in sequence to obtain a midpoint sequence. For example, if there are fault point positions A, B, and C (in order of generation time), then calculate the midpoint position between A and B, and the midpoint position between B and C, etc., and summarize these midpoints to form a sequence.

[0182] Calculate the degree of dispersion of the intermediate point sequence. Then, further calculate the degree of dispersion of the intermediate point sequence. The degree of dispersion can reflect the concentration or dispersion of the position distribution of these intermediate points. The degree of dispersion can be measured by appropriate mathematical statistical methods such as variance and standard deviation.

[0183] If the degree of discreteness is less than the preset discrete value, the average value of all the intermediate points in the intermediate point sequence is calculated as the problem recommendation point. If the calculated degree of discreteness is less than the preset discrete value, it means that the positions of these intermediate points are relatively concentrated and have certain common characteristics. At this time, the average value of all the intermediate points in the intermediate point sequence is calculated, and the position corresponding to this average value is used as the problem recommendation point.

[0184] Next time, the fault point is accurately located by the positioning algorithm from the problem recommendation point, and the new fault point location is output. The next time the fault point needs to be located, it is based on the problem recommendation point, and the binary positioning algorithm is used to accurately locate the fault point, and finally the new fault point location is output. In this way, with the help of previously accumulated data information and reasonable data analysis and processing, the fault location can be locked more efficiently and accurately.

[0185] Through this integrated data management and analysis system, we can not only monitor the operating status of the device in real time during fault finding, but also identify potential fault points in this section of the faulty line through in-depth analysis of historical data and real-time data; historical data will be stored and built into a database. When new measurement data are entered into the database, they will be compared with potential fault data or abnormal fault data in the historical fault line. If the new data matches the data characteristics of the abnormal fault situation, further diagnosis and detection can be carried out according to the established methods of abnormal fault detection.

[0186] Note: The unit of resistance or impedance in this embodiment is Ω.

[0187] An embodiment of the present application further discloses a single-phase grounding fault identification system based on multiple signal sources, including a processor, wherein the processor executes the steps of the single-phase grounding fault identification method based on multiple signal sources as described in any one of the above.

[0188] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A single-phase grounding fault identification method based on multiple signal sources, characterized in that: The steps include: Obtain distribution network fault signals, and match faulty line sections according to the distribution network fault signals; Determine the middle position of the faulty line section and use the middle position as a signal injection point; Injecting a first high voltage DC signal from the signal injection point into the fault line section; Collecting the DC voltage and DC current on the fault line section in real time to generate DC voltage data and DC current data; Stop injecting the first high voltage DC signal; Calculate the line DC resistance, where the line DC resistance R=the DC voltage / the DC current; If R is less than or equal to a preset first resistance value, the fault type is identified as a low-resistance grounding fault; if R is between the first resistance value and the preset second resistance value, the fault type is identified as a medium-resistance grounding fault; if R is between the second resistance value and the preset third resistance value, the fault type is identified as a high-resistance and ultra-high-resistance grounding fault; if R is greater than the third resistance value, an open circuit alarm is triggered and the fault type is identified as a transient fault; Injecting a first AC signal from the signal injection point into the fault line section; Collecting the AC voltage and AC current on the fault line section in real time to generate AC voltage data and AC current data; Calculate the total line impedance, where the total line impedance Z=the AC voltage / the AC current; If Z is greater than or equal to the preset first impedance value, and the fluctuation amplitude of Z exceeds the preset first impedance range, the fault type is identified as an intermittent discharge fault; Otherwise, it is a non-intermittent discharge fault; If the fault type is identified as an intermittent discharge fault, after injecting a first AC signal from the signal injection point into the fault line section for a preset first time period, if Z is less than or equal to a preset second impedance value, the fault point of the intermittent discharge fault has been broken down; If Z is less than the first impedance value, regardless of whether the fluctuation amplitude of Z exceeds the preset first impedance range, the fault type is identified as a medium-low resistance grounding fault; If the fault type is identified as the intermittent discharge fault, a high-voltage AC signal of a preset second duration is injected into the signal injection point, and when the high-voltage signal on the line is stable, the three-phase currents of the branches on both sides of the signal injection point are measured; If the currents of each phase in the three phases on one side are close to or equal, there is no ground fault on this side; if the current of one phase on this side is greater than the currents of the other two phases and exceeds the preset second AC current value, the phase is determined to be a fault phase, and this side is the side where the signal injection point fails; Based on the signal injection point, the fault point is accurately located through a positioning algorithm, and the position of the fault point is output.

2. The single-phase grounding fault identification method based on multiple signal sources according to claim 1 is characterized in that: The method further comprises the steps of: Acquire the nearest plurality of the DC resistances R to obtain a DC resistance sequence; Fitting the DC resistance sequence into a DC resistance change curve, and calculating the growth change trend of the DC resistance change curve; The frequency of the first AC signal is anti-correlatedly adjusted according to the value of the growth trend. The larger the value of the growth trend is, the lower the frequency of the first AC signal is; the smaller the value of the growth trend is, the higher the frequency of the first AC signal is.

3. The single-phase grounding fault identification method based on multiple signal sources according to claim 1 is characterized in that: The method further comprises the steps of: The first AC signal uses a first AC frequency and a second AC frequency with different frequencies to calculate impedance respectively: First, a first total impedance Z1 is calculated using a preset first AC frequency; Then, using the preset second AC frequency, the second total impedance Z2 is calculated; The line total impedance Z is calculated according to the first total impedance Z1 and the second total impedance Z2 by using a first weighted average algorithm.

4. The single-phase grounding fault identification method based on multiple signal sources according to claim 3 is characterized in that: The method further comprises the steps of: Get the preset frequency change; The first AC frequency is adjusted according to the frequency variation to obtain a first variation range of the first total impedance Z1; the second AC frequency is adjusted according to the frequency variation to obtain a second variation range of the second total impedance Z2; Based on the comparison between the first variation range and the second variation range, a weighted value of the first total impedance Z1 and a weighted value of the second total impedance Z2 are determined in an anti-correlation manner.

5. The single-phase grounding fault identification method based on multiple signal sources according to claim 1 is characterized in that: The method further comprises the steps of: The first AC signal uses a first AC frequency, a second AC frequency, and a third AC frequency with different frequencies to calculate impedance respectively: First, a first total impedance Z1 is calculated using a preset first AC frequency; Then, using the preset second AC frequency, the second total impedance Z2 is calculated; If the difference between the first total impedance Z1 and the second total impedance Z2 is less than the preset first impedance difference, then the third total impedance Z3 is calculated using the preset third AC frequency; Calculating a temporary total impedance Z12 according to the first total impedance Z1 and the second total impedance Z2 by using a first weighted average algorithm; The line total impedance Z is calculated according to the temporary total impedance Z12 and the third total impedance Z3 by using a second weighted average algorithm.

6. The single-phase grounding fault identification method based on multiple signal sources according to claim 1 is characterized in that: The method further comprises the steps of: After stopping injecting the first AC signal, adding a first pulse signal to the signal injection point; Performing detection at a preset first distance point at a first distance from the signal injection point to obtain a first electromagnetic induction signal; Performing detection at a preset second distance point at a second distance from the signal injection point to obtain a second electromagnetic induction signal; calculating a difference between the first electromagnetic induction signal and the second electromagnetic induction signal as an electromagnetic induction difference; Matching the fault direction and fault distance according to the electromagnetic induction difference; If the fault direction and the fault distance do not correspond to the fault location point, a detection error warning prompt is issued.

7. The single-phase grounding fault identification method based on multiple signal sources according to claim 6 is characterized in that: The method further comprises the steps of: Obtaining the number of detection error warning prompts within a recent preset time period; The third resistance value, the first impedance value, and the second impedance value are adjusted in a positive correlation according to the number of detection error warning prompts.

8. The single-phase grounding fault identification method based on multiple signal sources according to claim 1 is characterized in that: The method further comprises the steps of: The positioning algorithm is a dichotomy method; Obtaining the nearest locations of multiple fault points; Calculate the middle point position between two of the fault point positions with adjacent generation times among the multiple fault point positions to obtain a middle point sequence; Calculating the discreteness of the intermediate point sequence; If the discrete degree is less than a preset discrete value, then calculating the average value of all the intermediate point positions in the intermediate point sequence as the problem recommendation point; Next time, the fault point is accurately located from the problem recommended point through the positioning algorithm, and the new position of the fault point is output.

9. A single-phase grounding fault identification system based on multiple signal sources, characterized in that: It comprises a processor, in which the steps of the single-phase grounding fault identification method based on multiple signal sources as described in any one of claims 1 to 8 are executed.

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