A distributed power grid fault monitoring device with built-in dual sensors

Abstract

The present invention relates to a distributed power grid fault monitoring device with built-in dual sensors, including a monitoring body; a current sensing module for obtaining current information; a voltage sensing module for obtaining voltage information; the voltage sensing module includes a measuring electrode and a measuring capacitor, the measuring electrode is arranged in the bottom area of ​​the monitoring body, and the measuring capacitor is arranged above the measuring electrode; one end of the measuring capacitor is electrically connected to the transmission line, and the other end of the measuring capacitor is electrically connected to the measuring electrode; an acquisition module is used to receive current information and voltage information; an energy acquisition module is used to supply energy to the current sensing module, the voltage sensing module, and the acquisition module. The distributed power grid fault diagnosis system of the present invention collects current and voltage signals, judges faults, and provides time. The system integrates voltage and current data, and can complete the calculation of the initial fault time, fault identification, and diagnostic analysis on the spot, thereby further improving the reliability of power grid fault location and identification.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid fault diagnosis, and in particular to a distributed power grid fault monitoring device with built-in dual sensors. Background Art

[0002] The existing distributed power grid fault diagnosis system consists of a fault monitoring terminal and a background. Figure 1 It is a system framework diagram of a distributed power grid fault diagnosis system in the prior art. Figure 2 FIG. 3 is a schematic diagram of the arrangement of the monitoring device of the distributed power grid fault diagnosis system 3 in the prior art. Figure 1 and 2 As shown, several monitoring devices 1 (i.e., fault monitoring terminals) are deployed along the transmission line 2. When a fault occurs in the transmission line 2, the monitoring device 1 collects the fault current and sends it to the backend, which includes a power grid fault diagnosis system 3. Figure 1 As shown, the background completes the positioning calculation and diagnosis analysis and publishes the information.

[0003] In the prior art, the distributed power grid fault diagnosis system 3 only collects the current as the basic data source for background calculation, but does not collect the voltage. The main reason is that it is difficult to solve the problem of high-voltage voltage collection. Compared with the current sensor, which only needs to be connected to the line to realize the current signal collection, the voltage sensor module needs the ground potential as a reference, which requires an insulating structure with a large volume and weight. The common voltage collection in the power system is achieved through ferromagnetic voltage transformers or voltage dividers. Both methods are difficult to meet the requirements of online installation in terms of volume and weight. Therefore, the existing distributed power grid fault location devices do not have voltage sensor modules. Due to the lack of voltage information, the reliability of fault location is relatively reduced when the existing distributed power grid fault diagnosis system is used for multi-branch and distribution network lines, and the reliability of fault identification and diagnosis is difficult to further improve. From the perspective of system functions, overvoltage monitoring cannot be achieved.

[0004] Figure 3 It is a method flow chart of a distributed power grid fault diagnosis system in the prior art, such as Figure 3As shown, in the prior art, the method flow of the distributed power grid fault diagnosis system includes: step S01, data collection; step S02, fault identification; step S03, data storage; step S04, packet sending. Among them, fault identification is the most important link. When the existing power grid fault diagnosis system is used for multi-branch and distribution network line fault location, the reliability is low. This is because compared with high-voltage level lines, the fault current of the distribution network line is smaller, which makes fault identification more difficult, but the voltage drop is more obvious. If the voltage collection can be increased, the reliability of device fault identification can be significantly improved. From a technical point of view, the comprehensive voltage and current can further improve the reliability of fault identification, for example (the current of a lightning fault rises and the voltage drops, while the current of a ground fault rises but the voltage drops), and expand the application scenarios of device data. In addition, the voltage quantity is indispensable for the needs of power grid overvoltage monitoring and load monitoring. The existing technology realizes voltage monitoring. One method is to deploy a voltage sensing module under the distributed fault monitoring device. When the system detects a sudden change in voltage, it notifies the high-potential monitoring device. The voltage and current data are synchronized by clock for fault discrimination and analysis. This method of collecting voltage and current separately requires the hardware to have a large storage cache and communication channel. In actual engineering implementation, the equipment cost is significantly increased and the reliability of the device is greatly affected. Another method is to use the basic principle of electric field sensor to distinguish the electric field by using the potential difference between the two plates. However, due to the small spacing between the two plates, the traditional electric field sensor can only realize live detection and it is difficult to accurately measure the voltage. To solve the above problems, it is proposed to measure the electric field by amplifying the potential difference through a micro-electromechanical structure (i.e., MEMS sensor). However, there are two problems with this electric field: 1) Transient response: The signal bandwidth of the MEMS electric field sensor is limited (generally not more than 1kHz), making it impossible to collect transient voltage (difficult to locate and overvoltage monitoring); 2) When the MEMS electric field sensor is not well shielded, the electric field measurement value is affected by adjacent phases and adjacent lines, making it difficult to ensure good measurement accuracy, and the reliability and accuracy of fault identification and diagnosis are affected.

[0005] Therefore, in view of the above shortcomings, it is necessary to provide a distributed power grid fault diagnosis system with built-in dual sensors to collect current and voltage signals, judge faults and provide timing. The system integrates voltage and current data to complete the initial fault time calculation, fault identification and diagnostic analysis on site, thereby further improving the reliability of power grid fault location and identification. Summary of the invention

[0006] The technical problem to be solved by the present invention is that in the prior art, a distributed power grid fault diagnosis system only collects current as the basic data source for background calculations, but does not collect voltage. When the distributed power grid fault diagnosis system is used for multi-branch and distribution network lines, the reliability of fault location is relatively reduced, and the reliability of fault identification and diagnosis is difficult to further improve. From the perspective of system functions, overvoltage monitoring cannot be achieved. In view of the defects in the prior art, a distributed power grid fault diagnosis system with built-in dual sensors is provided to collect current and voltage signals, judge faults and provide timing.

[0007] In order to solve the above technical problems, the present invention provides a distributed power grid fault monitoring device with built-in dual sensors, including: a monitoring body, the monitoring body is set on the transmission line; a current sensing module, the current sensing module is arranged inside the monitoring body, and the current sensing module is used to monitor the current of the transmission line and obtain current information; a voltage sensing module, the voltage sensing module is arranged inside the monitoring body, and the voltage sensing module is used to monitor the voltage of the transmission line and obtain voltage information; the voltage sensing module includes a measuring electrode and a measuring capacitor, the measuring electrode is arranged in the bottom area of ​​the monitoring body, and the measuring capacitor is arranged above the measuring electrode; one end of the measuring capacitor is electrically connected to the transmission line, and the other end of the measuring capacitor is electrically connected to the measuring electrode; a collection module, the collection module is used to receive current information and voltage information; an energy acquisition module, the energy acquisition module is used to supply energy to the current sensing module, the voltage sensing module, and the collection module.

[0008] Preferably, the plane where the power transmission line is located and is parallel to the ground is the installation plane, and the voltage sensing module is located below the installation plane.

[0009] Preferably, the monitoring body is constructed as follows: the portion located above the installation plane is made of a first metal material; the area where the measuring capacitor is located is made of a second metal material; and the area where the measuring electrode is located is made of a non-metal material.

[0010] Preferably, the coating thickness of the second metal material coating the measuring capacitor is at least 1 cm; the measuring capacitor is connected to the housing of the monitoring body through a non-metallic material.

[0011] Preferably, the first metal material and the second metal material are both aluminum alloys.

[0012] Preferably, the cross section of the monitoring body is circular, and the center of the monitoring body coincides with the center of the transmission line.

[0013] Preferably, the capacitance of the measuring electrode to the ground is C0, the capacitance value of the measuring capacitor is C1, the transformation ratio coefficient is μ, then C1=μ×C0, the voltage across the measuring capacitor is U1, then the voltage U0 of the transmission line satisfies the following relationship: U0≈μ×U1; wherein, 5000≤μ≤25000.

[0014] Preferably, the acquisition module is composed of an AD chip, an FPGA chip, a DSP chip, a timing chip, and a communication chip.

[0015] Preferably, a current and voltage dual criterion and data preprocessing method are embedded in the acquisition module, wherein the current and voltage dual criterion and data preprocessing method specifically comprises the following steps:

[0016] S11: Calculate the voltage and current power frequency difference: that is, calculate the difference between the current cycle voltage and current (Uk / Ik) and the previous cycle voltage and current (Uk-1 / Ik-1), as shown in the following formula:

[0017] ΔU≈(U k -U k-1 )

[0018] ΔI≈(I k -I k-1 )

[0019] S12: Identify faults based on voltage and current criteria. When the difference between ΔU and ΔI exceeds the limit, it is determined that a fault has occurred and a certain length of data is pre-recorded.

[0020] S13: Fault initial moment determination and data packaging.

[0021] Preferably, the above step S13 specifically includes the following steps:

[0022] S131: extracting the high-frequency components of voltage and current through wavelet transform, assuming that the high-frequency components are DU and DI respectively.

[0023] S132: Obtain high-frequency energy; specifically, voltage and current are highly correlated, and correlation operations can significantly reduce the influence of white noise and sampling noise. The high-frequency energy obtained by multiplying the voltage and current synchronously can more effectively identify the initial moment of the fault.

[0024] DE(i)=DU(i)×DI(i)

[0025] Among them, DE(i), DU(i), and DI(i) represent the high-frequency energy, high-frequency voltage, and high-frequency current sampling values.

[0026] S133: Identify the initial moment of the fault and capture data. Identify the initial moment of the fault based on the modulus maximum method, capture the fixed-length data (1ms) after the initial moment of the fault, and send it to the system background for analysis.

[0027] As described above, the distributed power grid fault diagnosis system implemented in the present invention has the following beneficial effects: current and voltage signals are collected, faults are judged and time is provided. The system integrates voltage and current data to complete the initial fault time calculation, fault identification and diagnostic analysis on site, thereby further improving the reliability of power grid fault location and identification. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a system framework diagram of a distributed power grid fault diagnosis system in the prior art;

[0029] Figure 2 It is a schematic diagram of the arrangement of a monitoring device of a distributed power grid fault diagnosis system in the prior art;

[0030] Figure 3 It is an information flow chart of a distributed power grid fault diagnosis system in the prior art;

[0031] Figure 4 It is a schematic diagram of the installation of a distributed power grid fault monitoring device with built-in dual sensors according to the present invention;

[0032] Figure 5 It is a structural schematic diagram of a distributed power grid fault monitoring device with built-in dual sensors according to the present invention;

[0033] Figure 6 It is a structural schematic diagram of a voltage sensing module of a distributed power grid fault monitoring device with built-in dual sensors according to the present invention;

[0034] Figure 7 It is a schematic diagram of the cross-sectional material composition of the distributed power grid fault monitoring device with built-in dual sensors of the present invention;

[0035] Figure 8 It is a schematic diagram of the cross-sectional material composition of the voltage sensing module of the distributed power grid fault monitoring device with built-in dual sensors of the present invention;

[0036] Fig. 9 It is a calculation principle diagram of the voltage sensing module of the distributed power grid fault monitoring device with built-in dual sensors of the present invention;

[0037] Fig.10 It is a hardware framework diagram of the acquisition module of the distributed power grid fault monitoring device with built-in dual sensors of the present invention;

[0038] Fig.11 It is a schematic diagram of the working process of the acquisition module of the distributed power grid fault monitoring device with built-in dual sensors of the present invention;

[0039] Fig.12 It is a schematic diagram of the working process of the energy acquisition module of the distributed power grid fault monitoring device with built-in dual sensors of the present invention.

[0040] In the figure: 1: monitoring device; 2: transmission line; 3: power grid fault diagnosis system; 4: monitoring body; 5: energy acquisition module; 6: acquisition module; 7: current sensing module; 8: voltage sensing module; 81: measuring electrode; 82: measuring capacitor; 83: wire. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Figure 4 It is a schematic diagram of the installation of a distributed power grid fault monitoring device with built-in dual sensors according to the present invention; Figure 5 It is a structural schematic diagram of a distributed power grid fault monitoring device with built-in dual sensors of the present invention.

[0043] like Figure 4 As shown, the distributed power grid fault monitoring device with built-in dual sensors of the present invention includes a monitoring body 4 mounted on a transmission line 2.

[0044] like Figure 5 As shown, the monitoring body 4 includes a current sensing module 7 and a voltage sensing module 8, wherein the current sensing module 7 is used to monitor the current of the transmission line 2 and obtain current information; the voltage sensing module 8 is used to monitor the voltage of the transmission line 2 and obtain voltage information.

[0045] Figure 6 Schematic diagram of the structure of the voltage sensing module of the distributed power grid fault monitoring device with built-in dual sensors of the present invention. Figure 6 As shown, the voltage sensing module 8 includes a measuring electrode 81, a measuring capacitor 82, and a wire 83. The measuring electrode 81 is arranged at the bottom area of ​​the monitoring body 4, and the measuring capacitor 82 is arranged above the measuring electrode 81; one end of the measuring capacitor 82 is electrically connected to the transmission line 2, and the other end of the measuring capacitor 82 is electrically connected to the measuring electrode 81; the acquisition module 6, the acquisition module 6 is used to receive current information and voltage information; the energy acquisition module 5, the energy acquisition module 5 is used to supply energy to the current sensing module 7, the voltage sensing module 8, and the acquisition module 6.

[0046] As described above, the distributed power grid fault diagnosis system proposed in the embodiment of the present invention adopts a distributed power grid fault diagnosis design scheme with dual sensors such as built-in current sensor module 7 and voltage sensor module 8. The device adopts a dual sensor design, and the voltage and current dual sensor collector is responsible for current and voltage signal collection, fault judgment and timing. Since the device integrates voltage and current data, it can complete the initial fault time calculation, fault identification and diagnostic analysis on-site, thereby further improving the reliability of power grid fault location and identification.

[0047] Figure 7 Schematic diagram of the cross-sectional material composition of the distributed power grid fault monitoring device with built-in dual sensors of the present invention. Figure 7 As shown, in the distributed power grid fault monitoring device provided by the embodiment of the present invention, the middle circular hole is crossed by the transmission line 2. The plane parallel to the ground where the transmission line 2 is located is the installation plane. Figure 5 It can be seen that the voltage sensing module 8 is located below the installation plane. The material composition of the monitoring body 4 is as follows: the part located above the installation plane is composed of a first metal material; the area where the measuring capacitor 82 is located is composed of a second metal material; and the area where the measuring electrode 81 is located is composed of a non-metal material. The first metal material and the second metal material can be aluminum alloy.

[0048] Figure 8 Schematic diagram of the cross-sectional material composition of the voltage sensor module of the distributed power grid fault monitoring device with built-in dual sensors of the present invention. Figure 8 As shown, the voltage sensing module 8 of the distributed power grid fault monitoring device of the present invention includes a measuring electrode 81 and a measuring capacitor 82 .

[0049] Also refer to Figure 6 The measuring electrode 81 is located below the monitoring device 1 and may be rectangular in shape and may have a size of 40 cm*20 cm.

[0050] The measuring capacitor 82 is connected to the housing of the monitoring body 4 through non-metallic materials. The cross section of the monitoring body 4 is circular, and the center of the monitoring body 4 coincides with the center of the transmission line 2.

[0051] In the distributed power grid fault monitoring device provided by the embodiment of the present invention, the coating thickness of the second metal material coating the measuring capacitor 82 is at least 1 cm. In the present invention, the measuring electrode 81 is arranged inside the monitoring body 4, and the device shell forms a shielding structure to suppress the influence from the adjacent phase voltage. The built-in voltage sensor module 8 is located under the metal shielding of the device shell and slightly penetrates the shielding by 1 cm, suppressing the influence of external interference and the adjacent relative voltage sensor module 8 measurement.

[0052] In the distributed power grid fault monitoring device provided by the embodiment of the present invention, the height of the measuring electrode 81 from the ground is H, the height of the measuring electrode 81 itself is h, then H>20h, the measuring electrode 81 is located below the monitoring body 4, is rectangular, and is typically designed to be 40cm×20cm. According to electromagnetic field theory, when the conductor is far enough away from the zero potential point (greater than 20 times the size of the conductor, for example, when the conductor is a 40cm square metal plate, it can be more than 8m from the ground), the conductor-to-ground stray capacitance is a stable value.

[0053] The monitoring body 4 of the present invention constructs a built-in voltage sensor by measuring electrodes and measuring capacitors. The voltage sensor utilizes the metal isolated conductor effect to construct a stable stray capacitance, and constructs a capacitive voltage divider structure through stray capacitance and measuring capacitance to achieve high potential voltage collection. Since the capacitance value of the stray capacitance is small, the voltage sensor has better transient response characteristics.

[0054] In the invention, the built-in voltage sensor is located under the metal shield of the device housing and slightly penetrates into the shield by 1 cm, suppressing the influence of external interference and the adjacent relative voltage sensor measurement.

[0055] The current sensor module 7 adopts a protection-level CT, and the dynamic range of the protection-level CT measurement signal is: 10A-5000A, and the signal frequency band range is 0.1-1MHz, which meets the relevant national and industry standards for distributed monitoring devices.

[0056] Fig. 9 1 is a calculation principle diagram of the voltage sensing module of the distributed power grid fault monitoring device with built-in dual sensors of the present invention. Fig. 9As shown, in the distributed power grid fault monitoring device provided by the embodiment of the present invention, the capacitance of the measuring electrode 81 to the ground is C0, the capacitance value of the measuring capacitor 82 is C1, and the transformation ratio is μ, then C1=μ×C0, the voltage across the measuring capacitor 82 is U1, and the voltage U0 of the transmission line 2 satisfies the following relationship: U0≈μ×U1; wherein, 5000≤μ≤25000, preferably μ=20000. The distributed power grid fault monitoring device constructs a built-in voltage sensing module 8 by measuring the electrode 81 and the measuring capacitor 82. The voltage sensing module 8 constructs a stable stray capacitance by using the metal isolated conductor effect, and constructs a capacitive voltage division structure by using the stray capacitance and the measuring capacitor 82 to realize high potential voltage collection. Since the capacitance value of the stray capacitance is small, the voltage sensing module 8 has a good transient response characteristic. A measuring capacitor 82 is connected in series between the high-voltage conductor and the measuring electrode 81. At this time, the measuring electrode 81 and the measuring capacitor 82 constitute a complete capacitive voltage division structure; the line voltage value can be obtained by detecting the voltage across the measuring capacitor 82. In a specific embodiment, the capacitance of the measuring electrode 81 to the ground is C0. Through electromagnetic simulation tools such as ANSYS, it can be obtained that its capacitance to the ground is approximately 0.15pF. If it is designed according to a 20000:1 ratio, the capacitance value of the measuring capacitor 82 is 3nF, and the voltage across the measuring capacitor 82 is U1. At this time, the voltage of the transmission line 2 is approximately 20000×U1.

[0057] Fig.10 FIG. 1 is a hardware framework diagram of the acquisition module of the distributed power grid fault monitoring device with built-in dual sensors of the present invention; Fig.10 As shown, the acquisition module 6 is composed of an AD chip, an FPGA chip, a DSP chip, a timing chip, and a communication chip. Fig.10 As shown, the analog signal is conditioned; the AD chip completes the digital-to-analog conversion; the DSP chip is responsible for fault identification; when a line fault occurs, the DSP identifies that the line has a fault, stores the fault time data, and composes a data packet for transmission.

[0058] The method flow chart of the distributed power grid fault diagnosis system in the prior art is shown in FIG. Figure 3 And text description related to background technology.

[0059] Fig.11 This is a schematic diagram of the workflow of the acquisition module of the distributed power grid fault monitoring device with built-in dual sensors of the present invention. There are two main links in the above workflow that may cause problems:

[0060] 1) Fault identification: Grid faults can generally be divided into ground faults and lightning strikes. In actual projects, high-resistance ground faults have a greater impact on existing distributed fault monitoring devices. Under high-resistance faults, the fault current is small, and traditional starting criteria such as current over-limit are invalid.

[0061] 2) Data preprocessing: including data storage and packet transmission. Since the distributed device is based on local collection and wireless communication, the hardware storage space and communication data packet size are limited. Therefore, the actual recording time of fault data is generally no more than 1ms. Under high-resistance faults, the fault current changes slowly. Even if the device correctly identifies the fault, it often misses the data at the initial moment of the fault and only records the data after the fault. In this case, it is difficult for the device to complete fault location and diagnosis.

[0062] In view of the above problems, the present invention proposes to embed the current and voltage dual criteria and data preprocessing method in the acquisition module 6. The basic principle is to use the power frequency voltage to identify the fault and integrate the high-frequency current and voltage to identify the initial moment of the fault. The current and voltage dual criteria and data preprocessing method specifically include the following steps:

[0063] S11: Calculate the voltage and current power frequency difference: that is, calculate the difference between the current cycle voltage and current (Uk / Ik) and the previous cycle voltage and current (Uk-1 / Ik-1), as shown in the following formula:

[0064] ΔU≈(U k -U k-1 )

[0065] ΔI≈(I k -I k-1 )

[0066] S12: Identify faults based on voltage and current criteria. When the difference between ΔU and ΔI exceeds the limit, it is determined that a fault has occurred and a certain length of data is pre-recorded, such as 5 to 10 ms.

[0067] S13: Fault initial moment determination and data packaging.

[0068] Wherein, the step S13 specifically includes the following steps:

[0069] S131: extracting the high-frequency components of voltage and current through wavelet transform, assuming that the high-frequency components are DU and DI respectively.

[0070] S132: Obtain high-frequency energy; specifically, voltage and current are highly correlated, and correlation operations can significantly reduce the influence of white noise and sampling noise. The high-frequency energy obtained by multiplying the voltage and current synchronously can more effectively identify the initial moment of the fault.

[0071] DE(i)=DU(i)×DI(i)

[0072] Among them, DE(i), DU(i), and DI(i) represent the high-frequency energy, high-frequency voltage, and high-frequency current sampling values.

[0073] S133: Identify the initial moment of the fault and capture data. Identify the initial moment of the fault based on the modulus maximum method, capture the fixed-length data (1ms) after the initial moment of the fault, and send it to the system background for analysis.

[0074] Existing distributed monitoring devices can only determine whether a fault has occurred by current, and their reliability is relatively low when used for distribution network line fault determination. In the invention, the device synchronously collects the hardware design of voltage and current, and on this basis, a dual judgment and preprocessing method of voltage and current is proposed. The integrated power frequency voltage and current are used to identify faults. After the fault is determined, the initial moment of the fault is accurately captured based on high-frequency energy identification to accurately capture post-fault data. Compared with existing methods, the combination of voltage and high-frequency energy judgment reduces the impact of high-resistance faults on device fault identification and data capture.

[0075] Fig.12 Schematic diagram of the working process of the energy acquisition module of the distributed power grid fault monitoring device with built-in dual sensors of the present invention. Fig.12 As shown, the energy acquisition module is composed of an energy acquisition coil, a lithium battery and an energy management module.

[0076] When the line current flows through a current of a certain amplitude, the energy harvesting coil couples out a voltage to power the collector module. The energy harvesting module has a built-in energy management module. When the energy output of the energy harvesting coil is greater than the power consumption of the collector, the energy harvesting coil charges the lithium battery at the same time. When the power supply of the energy harvesting coil is lower than the power consumption of the collector module, the energy management module automatically switches to lithium battery power supply.

[0077] In summary, the present invention proposes a distributed fault diagnosis system with built-in dual sensors. First, a built-in voltage sensor module 8 design is proposed, and a capacitive voltage divider structure is constructed using the stray capacitance of the measuring plate to the ground and the measuring capacitor 82 to achieve voltage measurement; on this basis, the device acquisition unit realizes synchronous monitoring and acquisition of current and voltage, thereby improving the reliability of fault location and diagnosis, and adding an overvoltage monitoring function.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A distributed power grid fault monitoring device with built-in dual sensors, characterized in that: include: A monitoring body, wherein the monitoring body is mounted on the transmission line; The cross section of the monitoring body is circular, and the center of the monitoring body coincides with the center of the transmission line; The circular hole in the middle of the monitoring body is crossed by the power transmission line; A current sensing module, which is disposed inside the monitoring body and is used to monitor the current of the power transmission line and obtain current information; A voltage sensing module, the voltage sensing module is arranged inside the monitoring body, the voltage sensing module is used to monitor the voltage of the transmission line and obtain voltage information; the voltage sensing module includes a measuring electrode and a measuring capacitor, the measuring electrode is arranged in the bottom area of ​​the monitoring body, and the measuring capacitor is arranged above the measuring electrode; one end of the measuring capacitor is electrically connected to the transmission line, and the other end of the measuring capacitor is electrically connected to the measuring electrode; The plane where the power transmission line is located and is parallel to the ground is the installation plane, and the voltage sensor module is located below the installation plane; A collection module, the collection module is used to receive the current information and the voltage information; An energy acquisition module, the energy acquisition module is used to supply energy to the current sensing module, the voltage sensing module, and the acquisition module; The energy acquisition module is composed of an energy acquisition coil, a lithium battery and an energy management module; When the line current flows through a current of a certain amplitude, the energy harvesting coil couples out a voltage to power the collector module. The energy harvesting module has a built-in energy management module. When the energy output of the energy harvesting coil is greater than the power consumption of the collector, the energy harvesting coil charges the lithium battery at the same time. When the power supply of the energy harvesting coil is lower than the power consumption of the collector module, the energy management module automatically switches to lithium battery power supply. Wherein, the current and voltage dual criteria and data preprocessing method are embedded in the acquisition module, wherein the current and voltage dual criteria and data preprocessing method specifically include the following steps: S11: Calculate the voltage and current power frequency difference: that is, calculate the difference between the current cycle voltage and current (Uk / Ik) and the previous cycle voltage and current (Uk-1 / Ik-1), as shown in the following formula: ΔU≈(U k -IN k-1 ) ΔI≈(I k -I k-1 ) S12: Identify faults based on voltage and current criteria. When the difference between ΔU and ΔI exceeds the limit, it is determined that a fault has occurred and a certain length of data is pre-recorded. S13: fault initial moment determination and data packaging; Wherein, the step S13 specifically includes the following steps: S131: extracting the high-frequency components of voltage and current by wavelet transform, assuming that the high-frequency components are DU and DI respectively; S132: Acquire high-frequency energy; wherein, the voltage and current are highly correlated, and the correlation operation can significantly reduce the influence of white noise and sampling noise. The high-frequency energy obtained by multiplying the voltage and current synchronously can more effectively identify the initial moment of the fault. DE(i)=DU(i)×DI(i) Among them, DE(i), DU(i), and DI(i) represent the high-frequency energy, high-frequency voltage, and high-frequency current sampling values; S133: Fault initial moment determination and data interception: the fault initial moment is identified based on the modulus maximum method, and fixed-length data packets after the fault initial moment are intercepted and sent to the system background for analysis; Wherein, the capacitance of the measuring electrode to the ground is C0, the capacitance value of the measuring capacitor is C1, the transformation ratio coefficient is μ, then C1=μ×C0, the voltage across the measuring capacitor is U1, then the voltage U0 of the transmission line satisfies the following relationship: U0≈μ×U1; Among them, 5000≤μ≤25000.

2. The distributed power grid fault monitoring device according to claim 1, characterized in that: The monitoring subject is composed of: The portion located above the mounting plane is made of a first metal material; The area where the measuring capacitor is located is made of a second metal material; The area where the measuring electrode is located is made of non-metallic material.

3. The distributed power grid fault monitoring device according to claim 2, characterized in that: The coating thickness of the second metal material covering the measuring capacitor is at least 1 cm, and the measuring capacitor is connected to the outer shell of the monitoring body through a non-metallic material.

4. The distributed power grid fault monitoring device according to claim 3, characterized in that: The first metal material and the second metal material are both aluminum alloys.

5. The distributed power grid fault monitoring device according to any one of claims 1 to 4, characterized in that: The acquisition module is composed of an AD chip, an FPGA chip, a DSP chip, a timing chip, and a communication chip.

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