A rapid detection device and method for fault grounding points of distribution network overhead lines

Abstract

The present invention discloses a rapid detection device and method for fault grounding points in distribution network overhead lines. The device comprises a main control unit, a detection host, and multiple injection electrodes. The detection host is connected to the injection electrodes, and the injection electrodes are respectively arranged on different phase lines of the overhead line. The detection host generates a pulse signal based on a received pulse instruction, connects to two corresponding injection electrodes based on a received switching instruction, and collects time-domain pulse voltages and sends them to the main control unit. The main control unit generates pulse instructions and switching instructions and sends them to the detection host, and obtains the fault location based on the time-domain pulse voltages collected by the detection host within a predetermined detection period. The injection electrodes inject the pulse signals into the overhead line. The present invention eliminates the step of manually excavating and producing grounding bodies, reducing labor consumption, while achieving more convenient and efficient ground fault detection.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution network fault detection, and in particular to a device and method for quickly detecting a fault grounding point of a distribution network overhead line. Background Art

[0002] Overhead distribution lines are currently widely used in medium-voltage distribution networks in urban areas, suburbs, and vast rural areas. Many of these lines run alongside urban roads or through forested areas between farmlands. Due to factors such as insulator aging, environmental factors, and external damage, the failure rate of overhead insulated lines in distribution networks remains high. Low-resistance ground faults account for over 70% of all faults and are a common type of fault. They often lead to localized power outages and hazards at the fault site, potentially causing casualties and forest fires. Similar problems are a frequent occurrence in distribution networks, and each failure requires significant manpower and time to locate the fault point, making them a major headache for distribution network operations and maintenance.

[0003] At present, the commonly used methods for locating fault grounding points of overhead distribution lines are mostly based on signal injection to accurately locate the fault point. For example, the AC signal injection method injects an AC signal into the overhead line to be tested, and then measures along the line. The point where the signal disappears is the grounding fault point. It is not only affected by the grounding transition resistance and distributed capacitance, but also requires manual inspection along the line. The DC signal injection method injects a DC signal into the overhead line to be tested, and then uses a detection device to manually climb the tower along the line to detect and determine the fault point. Compared with the AC signal injection method, it is not affected by the transition resistance and distributed capacitance, but it still requires manual inspection along the line, and even climbing the tower multiple times for detection. In addition, there are fault detection methods based on other types of injected signals. These signal injection-based methods require a grounding body or lightning conductor, for example, grounding through an induction filter. Some other ground fault detection methods that are not based on signal injection also require a grounding body or lightning conductor. For example, CN105137290A discloses a method for quickly determining the location of the grounding fault of an overhead line, which belongs to the detection field. The method numbers multiple towers on a certain section of overhead lines, installs a first current transformer and a second current transformer on the lightning conductor on both sides of each tower, collects the current detection signals of the first and second current transformers, converts the current detection signals of the first and second current transformers into square wave pulse signals, and compares the phases of the first and second square wave pulse signals. When the superposition of the first and second square wave pulse signals results in a square wave signal group with a gap or negative pulse structure, it determines that a ground fault has occurred on the tower of the overhead line. Although this method can directly determine the specific tower number of the ground fault point, it requires adding a current transformer to the lightning conductor (also called an overhead ground wire) for signal injection. For widely used distribution network overhead lines, many of which do not have lightning conductors, manual excavation and construction of grounding bodies are required, which is difficult to implement in urban areas and requires a lot of work.

[0004] In view of the above industrial status, further research on overhead line ground fault detection technology and the realization of efficient, flexible and low-cost ground fault detection and location are urgent issues to be solved in the fields of such technology research, product design and application. Summary of the Invention

[0005] In response to the defects in the above-mentioned prior art, the present invention provides a device and method for quickly detecting fault grounding points of distribution network overhead lines, which can eliminate the steps of manually excavating and making grounding bodies, reduce manpower consumption, and achieve more convenient and efficient grounding fault detection.

[0006] In a first aspect, the present invention provides a rapid detection device for a fault grounding point of a distribution network overhead line, characterized in that it includes a main control unit, a detection host, and a plurality of injection electrodes, wherein the detection host is connected to the injection electrodes, and the injection electrodes are respectively arranged on different phase lines of the overhead line;

[0007] The detection host generates a pulse signal according to the received pulse instruction, connects to the corresponding two injection electrodes according to the received switching instruction, and collects the time domain pulse voltage and sends it to the main control unit;

[0008] The main control unit generates pulse instructions and switching instructions and sends them to the detection host, and obtains the fault location based on the time domain pulse voltage collected by the detection host within a predetermined detection period;

[0009] The injection electrodes inject the pulse signal into the overhead line.

[0010] Furthermore, the detection host includes a microprocessor, a pulse injection unit and a sampling unit;

[0011] The pulse injection unit and the sampling unit are connected in parallel and are respectively connected to two injection electrodes corresponding to the switching instructions. The pulse injection unit and the sampling unit are respectively connected to the microprocessor;

[0012] The microprocessor is used to receive instructions from the main control unit and perform corresponding operations;

[0013] The pulse injection unit is used to send a pulse signal;

[0014] The sampling unit is used to collect the time domain pulse voltage and send it to the main control unit via the microprocessor.

[0015] Furthermore, the instruction received by the microprocessor from the main control unit is a detection instruction, which includes a pulse instruction and a switching instruction.

[0016] Furthermore, the detection host also includes a relay switch unit;

[0017] The pulse injection unit is connected to the injection electrode through the relay switch unit, and the relay switch unit is connected to the corresponding two injection electrodes according to the switching instruction to switch the overhead line phase line to be detected.

[0018] Furthermore, n-1 first switching circuits and n-1 second switching circuits are connected to both ends of the pulse injection unit and the sampling unit in parallel, wherein one first switching circuit and one second switching circuit are connected to two different injection electrodes respectively, and the remaining n-2 first switching circuits and n-2 second switching circuits are connected in pairs to the remaining different injection electrodes; wherein n represents the number of injection electrodes;

[0019] The relay switch unit is composed of a plurality of relays, and each of the first switching circuit and the second switching circuit is provided with at least one relay.

[0020] Furthermore, connecting to the corresponding two injection electrodes according to the received switching instruction includes:

[0021] The detection host obtains and parses the switching instruction to obtain the two injection electrodes to be connected;

[0022] According to the two injection electrodes to be connected, determining a first switching circuit and a second switching circuit respectively connected to the two injection electrodes;

[0023] According to the determined first switching circuit and second switching circuit, all relays thereon are controlled to be connected.

[0024] Furthermore, the pulse injection unit includes a pulse transmitter connected to the microprocessor for communication and a power supply connected to the pulse transmitter, and the pulse transmitter is connected to the relay switch unit.

[0025] Furthermore, the detection host and the injection electrode are connected via a signal cable.

[0026] Furthermore, the injection electrode includes a pulse injection coil, which injects the pulse signal into the overhead line using a capacitive injection method.

[0027] Further, the predetermined detection period includes a plurality of predetermined periods that match the number of injection electrodes and do not overlap;

[0028] The fault location is obtained based on the time domain pulse voltage collected by the detection host within the predetermined detection period, including:

[0029] Obtaining the time domain pulse voltage collected by the detection host in different predetermined periods;

[0030] Plotting the time domain pulse voltages within different predetermined periods as time domain reflection graphs;

[0031] Performing negative value judgment on different time domain reflection graphs to obtain a time domain reflection graph with a negative value;

[0032] The corresponding fault phase line is obtained according to the time domain reflection diagram with negative values.

[0033] Furthermore, negative value judgment is performed on different time domain reflectograms to obtain time domain reflectograms with negative values, including:

[0034] aligning time domain reflectograms of a plurality of predetermined periods according to a starting time of an injected pulse signal;

[0035] Give the corresponding time domain sampling threshold and add the time domain sampling threshold to the aligned time domain reflectogram;

[0036] Filter out the time domain reflectogram that is divided into upper and lower parts by the time domain sampling threshold;

[0037] The filtered time domain reflectogram is regarded as a time domain reflectogram having a negative value.

[0038] Furthermore, the corresponding fault phase line is obtained according to the time domain reflection diagram with negative values, including:

[0039] Obtaining a corresponding predetermined period according to a time domain reflectogram having a negative value;

[0040] Obtaining, according to a predetermined period, injection electrodes connected within the predetermined period;

[0041] Obtain overlapping injection electrodes according to the injection electrodes corresponding to all time domain reflectograms with negative values;

[0042] According to the overlapping injection electrodes, the fault phase line is obtained.

[0043] Furthermore, after obtaining the corresponding fault phase line according to the time domain reflection diagram with a negative value, the method further includes:

[0044] Determine the corresponding time domain reflection diagram according to the fault phase line;

[0045] According to the determined time domain reflection diagram, the time domain pulse voltage reflected by different fault phase lines and the time of injecting pulse signal are obtained;

[0046] The distance between the fault position of the fault phase line and the injection electrode is obtained according to the time of the reflected time domain pulse voltage and the time of the injected pulse signal.

[0047] In a second aspect, a rapid detection method using the above-mentioned rapid detection device for a faulty grounding point of an overhead distribution line comprises:

[0048] The main control unit sends pulse instructions and switching instructions, the detection host connects two injection electrodes, and injects pulse signals into the corresponding phase lines through the injection electrodes;

[0049] The detection host collects the time domain pulse voltage reflection results between the corresponding phase lines through the connected injection electrodes and sends them to the main control unit;

[0050] The main control unit obtains the fault location based on the time domain pulse voltage collected by the detection host within a predetermined detection period.

[0051] Further, the predetermined detection period includes a plurality of predetermined periods that match the number of injection electrodes and do not overlap;

[0052] The fault location is obtained based on the time domain pulse voltage collected by the detection host within the predetermined detection period, including:

[0053] Obtaining the time domain pulse voltage collected by the detection host in different predetermined periods;

[0054] Plotting the time domain pulse voltages within different predetermined periods as time domain reflection graphs;

[0055] Performing negative value judgment on different time domain reflection graphs to obtain a time domain reflection graph with a negative value;

[0056] The corresponding fault phase line is obtained according to the time domain reflection diagram with negative values.

[0057] Furthermore, negative value judgment is performed on different time domain reflectograms to obtain time domain reflectograms with negative values, including:

[0058] aligning time domain reflectograms of a plurality of predetermined periods according to a starting time of an injected pulse signal;

[0059] Give the corresponding time domain sampling threshold and add the time domain sampling threshold to the aligned time domain reflectogram;

[0060] Filter out the time domain reflectogram that is divided into upper and lower parts by the time domain sampling threshold;

[0061] The filtered time domain reflectogram is regarded as a time domain reflectogram having a negative value.

[0062] Furthermore, the corresponding fault phase line is obtained according to the time domain reflection diagram with negative values, including:

[0063] Obtaining a corresponding predetermined period according to a time domain reflectogram having a negative value;

[0064] Obtaining, according to a predetermined period, injection electrodes connected within the predetermined period;

[0065] Obtain overlapping injection electrodes according to the injection electrodes corresponding to all time domain reflectograms with negative values;

[0066] According to the overlapping injection electrodes, the fault phase line is obtained.

[0067] Furthermore, after obtaining the corresponding fault phase line according to the time domain reflection diagram with a negative value, the method further includes:

[0068] Determine the corresponding time domain reflection diagram according to the fault phase line;

[0069] According to the determined time domain reflection diagram, the time domain pulse voltage reflected by different fault phase lines and the time of injecting pulse signal are obtained;

[0070] The distance between the fault position of the fault phase line and the injection electrode is obtained according to the time of the reflected time domain pulse voltage and the time of the injected pulse signal.

[0071] The present invention provides a device and method for quickly detecting a fault grounding point of a distribution network overhead line, which has at least the following beneficial effects:

[0072] (1) By injecting a pulse signal between the two phases of the overhead line, pulse injection without a grounding body is achieved. By detecting the convenient switching between phase lines, that is, using the phase-to-phase pulse injection method, the step of manually digging and making a grounding body can be saved compared to the traditional pulse injection method, thereby reducing manpower consumption.

[0073] (2) The distance to the ground fault is calculated by the time domain reflectometry method to accurately locate the fault, avoiding the tedious work of manual line inspection in the traditional positioning method, thereby achieving more convenient and efficient ground fault detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 A schematic diagram of a rapid detection device for a faulty grounding point of a distribution network overhead line provided by the present invention;

[0075] Figure 2 A schematic diagram of a detection host according to an embodiment of the present invention;

[0076] Figure 3 A schematic diagram of a pulse injection unit according to an embodiment of the present invention;

[0077] Figure 4 A schematic diagram showing the principle of locating a fault grounding point according to an embodiment of the present invention;

[0078] Figure 5 A flowchart of a method for quickly detecting a faulty grounding point of an overhead distribution line provided by the present invention;

[0079] Figure 6 A schematic diagram of phase A and phase B detection according to an embodiment of the present invention;

[0080] Figure 7 A schematic diagram of phase A and C detection according to an embodiment of the present invention;

[0081] Figure 8 A schematic diagram of phase B and C detection according to an embodiment of the present invention;

[0082] Figure 9 A schematic diagram of a time domain reflectometry diagram according to an embodiment of the present invention;

[0083] Figure 10 This is a schematic diagram of the application effect of the rapid detection device provided by the present invention.

[0084] Explanation of the reference numerals: 1-main control unit, 2-detection host, 3-injection electrode, 4-signal cable. DETAILED DESCRIPTION

[0085] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0086] The terms used in the embodiments of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The singular forms "a," "an," "the," and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, and unless the context clearly indicates otherwise, "a plurality" generally includes at least two.

[0087] It should also be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or device comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or device. In the absence of further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the product or device comprising the element.

[0088] like Figure 1 As shown, the present invention provides a rapid detection device for a fault grounding point of a distribution network overhead line, comprising a main control unit, a detection host, and a plurality of injection electrodes, wherein the detection host is connected to the injection electrodes, and the injection electrodes are respectively arranged on different phase lines of the overhead line;

[0089] The detection host generates a pulse signal according to the received pulse instruction, connects to the corresponding two injection electrodes according to the received switching instruction, and collects the time domain pulse voltage and sends it to the main control unit; wherein, the amplitude of the pulse signal is not less than 50V and the pulse width is less than 200ns;

[0090] The main control unit generates pulse instructions and switching instructions and sends them to the detection host, and obtains the fault location based on the time domain pulse voltage collected by the detection host within a predetermined detection period;

[0091] The injection electrodes inject the pulse signal into the overhead line.

[0092] The detection host of the present invention may include a microprocessor, a pulse injection unit and a sampling unit;

[0093] The pulse injection unit and the sampling unit are connected in parallel and are respectively connected to two injection electrodes corresponding to the switching instructions. The pulse injection unit and the sampling unit are respectively connected to the microprocessor;

[0094] The microprocessor is used to receive instructions from the main control unit and perform corresponding operations;

[0095] The pulse injection unit is used to send a pulse signal;

[0096] The sampling unit is used to collect the time domain pulse voltage and send it to the main control unit via the microprocessor.

[0097] In practical application scenarios, the rapid detection device of the present invention is mainly composed of a detection host, a signal cable, an injection electrode and a main control unit. Figure 2 As shown in the figure, the detection host mainly includes a microprocessor, a pulse injection unit, a relay switch unit, and a sampling unit; the pulse injection unit is connected in parallel with the sampling unit, and the pulse injection unit and the sampling unit are respectively connected to the external main control unit; the pulse injection unit is connected to the external signal cable through the relay switch unit. The sampling unit adopts a data acquisition module with a sampling rate of not less than 100MS / s and a sampling bit number of not less than 12 bits. The microprocessor module adopts FPGA+ARM architecture and has a parallel processing capability of more than 1Gbyte. Figure 3 As shown, the pulse injection unit mainly consists of a pulse transmitter and a battery, and the injection electrode mainly consists of a pulse injection coil and a housing. The pulse injection coil uses a material with a magnetic permeability of not less than 2000 as its magnetic core, and the number of turns does not exceed 10. The pulse transmitter can generate a pulse signal with an amplitude of not less than 50V and a pulse width of less than 200ns. The battery uses an 8.4V lithium battery. The circuits of the pulse injection unit and the sampling unit are existing circuits, and only need to be able to implement the functions of the present invention, so they are not described here in detail.

[0098] Among them, the detection host includes a relay switch unit that realizes convenient switching of the detection phase line;

[0099] The pulse injection unit is connected to the injection electrodes via a relay switch unit. The relay switch unit connects to the corresponding two injection electrodes according to a switching instruction to switch the overhead line phase line to be detected. Specifically, after the pulse injection unit and the sampling unit are connected in parallel, n-1 first switching circuits and n-1 second switching circuits are connected to both ends, respectively. One first switching circuit and one second switching circuit are connected to two different injection electrodes, respectively. The remaining n-2 first switching circuits and n-2 second switching circuits are paired and connected to the remaining different injection electrodes. Where n represents the number of injection electrodes. The relay switch unit is composed of multiple relays, and each of the first switching circuit and the second switching circuit is equipped with at least one relay.

[0100] The pulse injection unit of the present invention is used to send a detection pulse signal, which is sent to the injection electrode through the relay switch unit and the signal cable. The injection electrode injects the pulse into the overhead line through the induction coil; the relay switch unit is used to switch the phase line of the overhead line to be detected; the sampling unit is used to collect the injected and reflected time domain pulse voltage and send it to the main control unit.

[0101] When connecting to two corresponding injection electrodes according to the received switching instruction, the present invention may include:

[0102] The detection host obtains and parses the switching instruction to obtain the two injection electrodes to be connected;

[0103] According to the two injection electrodes to be connected, determining a first switching circuit and a second switching circuit respectively connected to the two injection electrodes;

[0104] According to the determined first switching circuit and second switching circuit, all relays thereon are controlled to be connected.

[0105] In actual application scenarios, the function of the main control unit is to control the relay switch unit to switch the phase line of the connected overhead line for detection (for example, it can include phase A, phase B, and phase C), and to collect the detection data between three different phases AB, BC, and AC together to draw a time domain reflection diagram to evaluate the existence and location of the ground fault.

[0106] Additionally, the predetermined detection period includes a plurality of predetermined periods that match the number of injection electrodes and do not overlap;

[0107] The main control unit of the present invention obtains the fault location based on the time domain pulse voltage collected by the host during the predetermined detection period, which may include:

[0108] Obtaining the time domain pulse voltage collected by the detection host in different predetermined periods;

[0109] The time domain pulse voltages within different predetermined periods are plotted as time domain reflection graphs respectively; the plotting process may include: plotting the time domain reflection graph with the sampling time of the sampling unit as the horizontal axis and the time domain pulse voltage measured by the sampling unit as the vertical axis;

[0110] Performing negative value judgment on different time domain reflection graphs to obtain a time domain reflection graph with a negative value;

[0111] The corresponding fault phase line is obtained according to the time domain reflection diagram with negative values.

[0112] The step of performing negative value judgment on different time domain reflectograms to obtain a time domain reflectogram having a negative value may include:

[0113] aligning time domain reflectograms of a plurality of predetermined periods according to a starting time of an injected pulse signal;

[0114] Give the corresponding time domain sampling threshold and add the time domain sampling threshold to the aligned time domain reflectogram;

[0115] Filter out the time domain reflectogram that is divided into upper and lower parts by the time domain sampling threshold;

[0116] The filtered time domain reflectogram is regarded as a time domain reflectogram having a negative value.

[0117] In the present invention, the time domain sampling threshold is related to the ambient noise; the filtered time domain reflectogram is regarded as a time domain reflectogram with a negative value, which means that the negative value in the time domain reflectogram exceeds the ambient noise and can be observed. At this time, the time domain reflectogram is correspondingly divided into two parts, upper and lower, by the time domain sampling threshold, such as Figure 9 The negative value starts to appear at time t2 shown in the figure.

[0118] Wherein, obtaining the corresponding fault phase line according to the time domain reflection diagram having a negative value may include:

[0119] Obtaining a corresponding predetermined period according to a time domain reflectogram having a negative value;

[0120] Obtaining, according to a predetermined period, injection electrodes connected within the predetermined period;

[0121] Obtain overlapping injection electrodes according to the injection electrodes corresponding to all time domain reflectograms with negative values;

[0122] According to the overlapping injection electrodes, the fault phase line is obtained.

[0123] The present invention uses time domain reflectometry to accurately locate ground faults on overhead lines. If a ground fault exists in an overhead line, the impedance of the line at the ground fault point will be mismatched. A pulse signal is injected into the overhead line. When the pulse signal propagates in the overhead line, it will be reflected and refracted when it encounters the ground fault point due to impedance mismatch. The reflected wave propagates from the ground fault point in the opposite direction of the injected pulse. The reflection coefficient (the ratio of the amplitude of the reflected pulse to the amplitude of the incident pulse) can be calculated using the following formula:

[0124]

[0125] Where β is the voltage wave reflection coefficient; Z1 and Z2 are wave impedances. The wave propagates from the medium with wave impedance Z1 to the medium with wave impedance Z2. At the ground fault site, the wave impedance is approximately 0, smaller than the wave impedance of the overhead line, and the amplitude of the reflected pulse is negative. Therefore, adding a measurement device (sampling unit) at the pulse injection point can capture the reflected wave.

[0126] In addition, after the main control unit of the present invention obtains the corresponding fault phase line according to the time domain reflection diagram with a negative value, it may further include:

[0127] Determine the corresponding time domain reflection diagram according to the fault phase line;

[0128] According to the determined time domain reflection diagram, the time domain pulse voltage reflected by different fault phase lines and the time of injecting pulse signal are obtained;

[0129] The distance between the fault position of the fault phase line and the injection electrode is obtained according to the time of the reflected time domain pulse voltage and the time of the injected pulse signal.

[0130] Specifically, the position of the ground fault point can be located by calculating the time difference between the injected pulse signal and the reflected pulse signal arriving at the detection device. The basic principle is as follows: Figure 4 As shown in Figure 2, the distance between the ground fault point and the pulse injection end can be calculated using the following formula:

[0131]

[0132] Where l is the distance from the ground fault point to the pulse injection end, Δt is the time difference between the injected pulse signal and the reflected pulse signal reaching the detection device, and v is the propagation speed of the pulse signal on the overhead line. The advantage of this time domain reflectometry method is that it accurately locates ground faults with high efficiency.

[0133] Compared with other methods for diagnosing and locating overhead line faults by injecting pulses and reflecting pulses, the present invention is characterized in that it adopts the method of injecting pulses and sampling between different phases of the overhead line, eliminating the steps of manually excavating and making grounding bodies. At the same time, a relay switch unit is used to realize convenient switching of the detection phase line, reducing manpower consumption in the pulse injection and measurement links, and realizing more convenient and efficient grounding fault detection.

[0134] See also Figure 5 As shown, the present invention also provides a rapid detection method using the above-mentioned rapid detection device for fault grounding points of overhead distribution lines, comprising:

[0135] The main control unit sends pulse instructions and switching instructions, the detection host connects two injection electrodes, and injects pulse signals into the corresponding phase lines through the injection electrodes;

[0136] The detection host collects the time domain pulse voltage reflection results between the corresponding phase lines through the connected injection electrodes and sends them to the main control unit;

[0137] The main control unit obtains the fault location based on the time domain pulse voltage between the phase lines collected by the detection host within a predetermined detection period.

[0138] Specifically, it may include:

[0139] Step S1: Send pulse instructions and switching instructions through the main control unit, detect that the host is connected to two injection electrodes, and inject pulse signals into the corresponding phase lines through the injection electrodes;

[0140] Step S2: The detection host collects the time domain pulse voltage reflection results between the corresponding phase lines through the connected injection electrodes and sends them to the main control unit;

[0141] Step S3: The main control unit draws a time domain reflection diagram based on the time domain pulse voltage reflection result between the phase lines;

[0142] Step S4, repeating steps S1-S3 to complete the drawing of the time domain reflectogram between all phase lines;

[0143] Step S5: Screen the time domain reflectograms between all phase lines and provide the time domain reflectograms with reflection amplitudes;

[0144] Step S6: Obtain the phase line where the single-phase grounding fault is located based on the filtered time domain reflection diagram;

[0145] Step S7: Obtain the reflected pulse and the injected pulse time according to the screened time domain reflectogram;

[0146] Step S8: Obtain the distance between the single-phase grounding fault position and the injection electrode according to the reflected pulse and the injection pulse time.

[0147] For the injection method of measuring pulses, one of the key technologies is how to realize pulse injection without a grounding body. The traditional signal injection method requires the excavation and production of an artificial grounding body. The present invention proposes to adopt a phase-to-phase pulse injection method with switchable detection phase line, which realizes pulse injection without a grounding body by injecting the pulse signal between the two phases of the overhead line, and realizes convenient switching of the detection phase line through the relay switch unit. The present invention takes the three-phase lines A, B, and C as an example. The end of the A phase and the pulse injection unit and the sampling unit are connected in parallel through the relay K1, the end of the B phase and the pulse injection unit and the sampling unit are connected in parallel through the relay K2, the other end of the B phase and the pulse injection unit and the sampling unit are connected in parallel through the relay K3, and the other end of the C phase and the pulse injection unit and the sampling unit are connected in parallel through the relay K4. The basic working process is described as follows (reference Figures 6 to 8 ):

[0148] Step 1: The main control unit sends a command to the microprocessor, which controls the relay switch unit K1 and K3 to close, and the pulse injection unit is connected between the overhead line A and B phases (such as Figure 6 shown).

[0149] Step 2: The main control unit sends instructions to the microprocessor, which controls the pulse injection unit to generate a pulse signal. The measured pulse signal amplitude is not less than 50V, and the pulse width is less than 200ns. The pulse is injected between phases A and B of the overhead line through the signal cable and the injection electrode, and propagates on the overhead line.

[0150] Step 3: The voltage value between phases A and B starting from the start of the injection of the measurement pulse is measured by the acquisition unit, and the measured voltage value between phases A and B is sent to the main control unit through the microprocessor.

[0151] Step 4: The main control unit receives the voltage measurement results from the acquisition unit, draws a time domain reflection diagram between phases A and B with the sampling time as the horizontal axis and the voltage value between phases A and B measured by the sampling unit as the vertical axis.

[0152] Step 5: Control K1 and K4 to close respectively (such as Figure 7 As shown) and K2, K4 closed (as shown) Figure 8 Repeat the above steps to obtain the time domain reflection diagram between phases A and C and the time domain reflection diagram between phases B and C.

[0153] Step 6: Compare the time domain reflection diagrams between phases A and B, between phases A and C, and between phases B and C (such as Figure 9 (as shown in the figure), by comparing the time domain sampling threshold, it is determined whether there are obvious negative amplitude reflection pulses in the time domain reflectogram. If a time domain reflectogram contains obvious negative amplitude reflection pulses, it means that there is a ground fault in the two phases corresponding to the time domain reflectogram. Based on this, it is determined whether there is a single-phase ground fault. Based on the predetermined period corresponding to the time domain reflectogram with negative amplitude and all corresponding injection electrodes, overlapping injection electrodes are obtained. Based on the phase lines corresponding to the overlapping injection electrodes, the phase line where the single-phase ground fault is located is determined.

[0154] Step 7: If a single-phase ground fault exists, the distance between the ground fault point and the pulse injection end is calculated based on the time information of the waveform in the time domain reflection diagram. Since the injected pulse signal will propagate in both directions, the distances on both sides of the injection end are the two possible locations of the ground fault point (if there is a fault on both sides of the measurement point and the distance to the injection end is close, the two negative reflected pulses will be more obvious after superposition). The two possible locations are confirmed one by one to eliminate the ground fault. The distance calculation process specifically includes:

[0155]

[0156] Where l is the distance between the ground fault point and the pulse injection end, Δt is the time difference between the injected pulse signal and the reflected pulse signal reaching the detection device, and v is the speed at which the pulse signal propagates on the overhead line, that is, the propagation speed.

[0157] When the overhead line to be tested is located in a city and it is difficult to dig and make an artificial grounding body, the switchable phase-to-phase pulse injection method will provide great convenience for on-site ground fault location applications, greatly improving the efficiency of ground fault detection.

[0158] like Figure 10 The figure shows the application effect of the detection method and device, which can carry out ground fault detection of several kilometers of overhead lines and accurately locate the specific location of the ground fault, significantly improving the efficiency of fault detection and providing clear guidance for overhead line operation and maintenance.

[0159] Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the invention. Thus, the present invention is intended to include such changes and modifications as fall within the scope of the claims and their equivalents.

Claims

1. A rapid detection device for fault grounding points of distribution network overhead lines, characterized in that: It includes a main control unit, a detection host and multiple injection electrodes, the detection host is connected to the injection electrodes, and the injection electrodes are respectively arranged on different phase lines of the overhead line; The detection host generates a pulse signal according to the received pulse instruction, connects to the corresponding two injection electrodes according to the received switching instruction, and collects the time domain pulse voltage and sends it to the main control unit; The injection electrode injects the pulse signal between the two phases of the overhead line; The main control unit generates a pulse instruction and a switching instruction and sends them to the detection host, and obtains the fault location according to the time domain pulse voltage collected by the detection host within the predetermined detection period, including: obtaining the time domain pulse voltage collected by the detection host within different predetermined periods; plotting the time domain pulse voltages within different predetermined periods as time domain reflection diagrams; performing negative value judgment on different time domain reflection diagrams to obtain time domain reflection diagrams with negative values; obtaining the corresponding predetermined period according to the time domain reflection diagrams with negative values; obtaining the injection electrodes connected within the predetermined period according to the predetermined period; obtaining overlapping injection electrodes according to the injection electrodes corresponding to all time domain reflection diagrams with negative values; obtaining the fault phase line according to the overlapping injection electrodes; wherein the predetermined detection period includes multiple predetermined periods that match the number of injection electrodes and do not overlap.

2. The rapid detection device according to claim 1, characterized in that The detection host includes a microprocessor, a pulse injection unit and a sampling unit; The pulse injection unit and the sampling unit are connected in parallel and are respectively connected to two injection electrodes corresponding to the switching instructions. The pulse injection unit and the sampling unit are respectively connected to the microprocessor; The microprocessor is used to receive instructions from the main control unit and perform corresponding operations; The pulse injection unit is used to send a pulse signal; The sampling unit is used to collect the time domain pulse voltage and send it to the main control unit via the microprocessor.

3. The rapid detection device according to claim 2, characterized in that The detection host also includes a relay switch unit; The pulse injection unit is connected to the injection electrode through the relay switch unit, and the relay switch unit is connected to the corresponding two injection electrodes according to the switching instruction to switch the overhead line phase line to be detected.

4. The rapid detection device according to claim 3, characterized in that The two ends of the pulse injection unit and the sampling unit after being connected in parallel are respectively connected to n-1 first switching circuits and n-1 second switching circuits, wherein one first switching circuit and one second switching circuit are respectively connected to two different injection electrodes, and the remaining n-2 first switching circuits and n-2 second switching circuits are connected in pairs to the remaining different injection electrodes; wherein n represents the number of injection electrodes; The relay switch unit is composed of a plurality of relays, and each of the first switching circuit and the second switching circuit is provided with at least one relay.

5. The rapid detection device according to claim 4, characterized in that Connecting to two corresponding injection electrodes according to the received switching instruction includes: The detection host obtains and parses the switching instruction to obtain the two injection electrodes to be connected; According to the two injection electrodes to be connected, determining a first switching circuit and a second switching circuit respectively connected to the two injection electrodes; According to the determined first switching circuit and second switching circuit, all relays thereon are controlled to be connected.

6. The rapid detection device according to claim 1, wherein Perform negative value judgment on different time domain reflectograms to obtain time domain reflectograms with negative values, including: aligning time domain reflectograms of a plurality of predetermined periods according to a starting time of an injected pulse signal; Give the corresponding time domain sampling threshold and add the time domain sampling threshold to the aligned time domain reflectogram; Filter out the time domain reflectogram that is divided into upper and lower parts by the time domain sampling threshold; The filtered time domain reflectogram is regarded as a time domain reflectogram having a negative value.

7. The rapid detection device according to claim 1, characterized in that After obtaining the corresponding fault phase line according to the time domain reflection diagram with negative values, the method further includes: Determine the corresponding time domain reflection diagram according to the fault phase line; According to the determined time domain reflection diagram, the time domain pulse voltage reflected by different fault phase lines and the time of injecting pulse signal are obtained; The distance between the fault position of the fault phase line and the injection electrode is obtained according to the time of the reflected time domain pulse voltage and the time of the injected pulse signal.

8. A rapid detection method using the rapid detection device for fault grounding points of distribution network overhead lines according to any one of claims 1 to 7, characterized in that: include: The main control unit sends pulse instructions and switching instructions, the detection host connects two injection electrodes, and injects pulse signals into the corresponding phase lines through the injection electrodes; The detection host collects the time domain pulse voltage reflection results between the corresponding phase lines through the connected injection electrodes and sends them to the main control unit; The main control unit obtains the fault location based on the time domain pulse voltage collected by the detection host within a predetermined detection period.

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