Low-voltage distribution network fault monitoring method and system based on sensor network technology

Abstract

The invention discloses a low-voltage power distribution network fault monitoring method and system based on a sensor network technology, and relates to the technical field of power distribution network fault monitoring, and the method comprises the steps: collecting sensor data in real time, and obtaining the frequency response of a power distribution network channel; comparing and analyzing change amplitudes of frequency responses of different power receiving equipment channels, and determining a branch where a fault is located; and calculating the impedance amplitude of the fault branch, and determining the accurate position of the fault point according to the relevance between the impedance and the distance. A fault branch is positioned by comparing the channel frequency response variation amplitudes of different power receiving devices, the impedance amplitude of the fault branch is calculated, and the accurate positioning of a fault point is further realized by combining the relation between impedance and distance. The method is accurate and stable, and can effectively monitor the grounding fault in the low-voltage power distribution network. Under the condition that signal interference is not considered or interference is small, fault branch detection accuracy is high.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution network fault monitoring, in particular to a fault monitoring method and system for low-voltage distribution networks based on sensor network technology. Background Art

[0002] As an important part of the power system, the reliability of the distribution network operation is directly related to the stability of the entire power system and the power consumption safety of users. The distribution network is responsible for delivering electric energy from the substation to the user side and is a key part connecting the substation and users in the power system. Therefore, ensuring the safe and stable operation of the distribution network is of great significance for guaranteeing grid safety and improving power supply reliability.

[0003] The decentralized access of distributed power sources has transformed the low-voltage distribution network from a traditional passive distribution network to a more active one, becoming a low-voltage active distribution network with characteristics such as complex topological structure, flexible operation mode, bidirectional and variable power flow, and uncertain output of distributed power sources. This leads to significant differences in its fault characteristics compared with traditional distribution networks, making the existing relay protection in the distribution network prone to maloperation and refusal to operate. Therefore, a fast fault location method is needed in the low-voltage active distribution network to ensure that faults can be quickly and accurately located and isolated. At the same time, fault type identification in the low-voltage active distribution network can provide more comprehensive fault diagnosis information based on fault location.

[0004] The research on fault location methods for distribution networks with distributed power sources at home and abroad can be divided into two categories according to the location accuracy: fault point location methods and fault section location methods. Fault point location methods are generally applicable to fault distance measurement of long straight wires and are rarely used in low-voltage active distribution networks with short line lengths. Fault section location methods are mainly divided into two categories: methods based on distribution automation information and methods based on wide-area information. Methods based on distribution automation information are only applicable to distribution networks with low penetration rates (not exceeding 25%) and cannot adapt to the development trend of distribution network automation and intelligence. With the development of smart distribution networks, the power consumption fluctuations will greatly increase the operation complexity of low-voltage active distribution networks, which requires their fault location methods to have self-adaptability. In order to quickly and accurately isolate faults and diagnose faults in a timely and comprehensive manner in low-voltage active distribution networks, fast fault location and fault type identification are needed. Summary of the Invention

[0005] In view of the above existing problems, the present invention is proposed.

[0006] Therefore, the problem to be solved by the present invention is that the existing fault point location methods are generally applicable to fault distance measurement of long straight wires and are rarely used in low-voltage active distribution networks with short line lengths. The existing fault section location methods are mainly divided into two categories: methods based on distribution automation information and methods based on wide-area information. The methods based on distribution automation information are only applicable to distribution networks with low penetration rates (not exceeding 25%), and cannot adapt to the development trends of distribution network automation and intelligence.

[0007] To solve the above technical problems, the present invention provides the following technical solutions: A fault monitoring method for low-voltage distribution networks based on sensor network technology, which includes collecting sensor data in real time to obtain the channel frequency response of the distribution network; comparing and analyzing the change amplitudes of the channel frequency responses of different power receiving devices to determine the branch where the fault is located; calculating the impedance amplitude of the fault branch, and determining the exact location of the fault point according to the correlation between impedance and distance.

[0008] As a preferred solution of the fault monitoring method for low-voltage distribution networks based on sensor network technology of the present invention, wherein: the sensors are deployed on electrical equipment of the distribution network for collecting power data of the electrical equipment and the environmental status around the electrical equipment; the sensors perform information interaction with intelligent measurement terminals through micro-power wireless; the intelligent measurement terminals are equipped with transmitters to continuously send high-frequency carrier signals to the network, and one carrier device in each power line is selected as the receiver for receiving signals, and each receiver is set at the node of the monitored line, and each receiver synchronously receives the signals sent by the transmitter at a fixed frequency together; the frequency of the high-frequency carrier is higher than 2×10^7 Hz.

[0009] As a preferred solution of the fault monitoring method for low-voltage distribution networks based on sensor network technology of the present invention, wherein: based on transmission line theory, channel modeling is performed on the cables in the distribution network, and equivalent calculations are performed using a distributed parameter model, and the formula is expressed as

[0010]

[0011] wherein, R, L, C, and G respectively represent the resistance, inductance, capacitance, and conductance per unit length, r and D respectively represent the conductor radius and the distance between two adjacent conductors; σ c and μ c respectively represent the conductivity and permeability, δ represents the skin depth, X g represents a correlation factor related to the skin depth and radius; after obtaining the basic parameters of the cable, the corresponding characteristic impedance γ and propagation constant Z c are expressed as

[0012]

[0013] Among them, j represents the imaginary unit, and f represents the frequency.

[0014] As a preferred solution of the low-voltage distribution network fault monitoring method based on sensor network technology according to the present invention, wherein: the obtaining of the distribution network channel frequency response includes, after calculating the distribution parameters of each cable in the system, performing topological modeling of the network, and after constructing the network topology model, further obtaining the channel frequency response by calculating the voltage ratio between the signal receiver and the transmitter. The voltage ratio H(f) is expressed as

[0015]

[0016] Among them, V RX (f) and V TX (f) respectively represent the single-phase-to-ground voltage of a certain phase using the receiver and the transmitter; when a fault occurs, the change magnitude ΔH(f) of the channel frequency response signal is expressed as

[0017]

[0018] Among them, H0(f) represents the magnitude of the channel frequency response after a fault occurs, and H t (f) represents the magnitude of the channel frequency response when no fault occurs; the determination of the branch where the fault is located includes that when a fault occurs in the main part between the sending end and the receiving node, the frequency response change of the main line is larger and negative than the change of the fault frequency response at the branch position. By comparing the amplitude of the frequency response change at each receiver end, the branch where the fault belongs is detected; when multiple faults occur in the network, if the faults occur on different lines, multiple fault lines will be identified and detected, and the frequency response change of each line is larger than that of the normal line.

[0019] As a preferred solution of the low-voltage distribution network fault monitoring method based on sensor network technology according to the present invention, wherein: the calculation of the impedance amplitude of the fault branch includes, according to the relationship between the frequency signal change and the impedance spectrum, using the variable-mode decomposition technology to extract the frequency signal characteristics, obtaining the key factors affecting the impedance, and obtaining the impedance estimation result through inverse analysis; the inverse analysis includes that the voltage is the electromagnetic coupling voltage of the carrier machine, the channel frequency response is reflected by the voltage ratio, by iterating forward from the last unit, calculating the transfer function of each unit, and determining the overall transfer function by multiplying the transfer function of each unit. By using the characteristic impedance, transmission constant and length to calculate the transfer function, and then obtaining the input impedance formula expressed as

[0020]

[0021] Among them, Z c1 Z c2 and Z cbAre respectively represented as the previous part, the next part of the main trunk, and the branch line. And Is represented as the transmission constant. And Is represented as the cable length. And Are represented as the input impedance of the main trunk and the input impedance of the previous section of branch unit n. Is represented as the main trunk impedance of branch unit n. Is represented as the impedance of the branch line of branch unit n. Is represented as the characteristic impedance of the previous part of branch unit n. Is represented as the characteristic impedance of the next part of branch unit n. Is represented as the characteristic impedance of the branch line of branch unit n.

[0022] As a preferred solution of the low-voltage distribution network fault monitoring method based on sensor network technology according to the present invention, wherein: the determining the exact location of the fault point according to the correlation between impedance and distance includes that when the fault branch detection link detects a fault line, the input impedance of the fault line is predicted through impedance estimation technology to obtain the change of the system input impedance, which is expressed by the formula

[0023]

[0024] Wherein, Δ Z (f) is represented as the impedance change in the frequency domain, Z(f) is represented as the input impedance of the system under normal conditions, Z d (f) is represented as the input impedance after the fault occurs, Δ Z (f) is represented as the change of the input impedance.

[0025] As a preferred solution of the low-voltage distribution network fault monitoring method based on sensor network technology according to the present invention, wherein: the determining the exact location of the fault point according to the correlation between impedance and distance further includes that after obtaining the impedance change in the frequency domain, the impedance change is converted from the frequency domain form to the time domain form through the inverse fast Fourier transform to obtain the change of impedance with time, which is expressed by the formula

[0026] Δ z (f) → Δ z (t)

[0027] After obtaining the time-domain impedance change Δ z (t), the fault distance measurement is realized according to the relationship between the impedance change and the distance. The distance l is obtained by multiplying the propagation speed v of the electromagnetic wave in the cable by the time t, which is expressed by the formula

[0028] l = v·t

[0029] The propagation speed of high-frequency electromagnetic waves is independent of frequency and depends on the line inductance L and capacitance C. It is expressed by the formula

[0030]

[0031] Multiply the time t in Δ z (t) by the propagation speed v to obtain a function equation related to distance. The relationship between impedance change and distance is expressed as

[0032] Δ Z (l) = Δ Z (v·t)

[0033] where the peak position of Δ Z (l) is the distance from the fault point. When there are multiple faults on the same line, the input impedance at each fault point changes. Then, there will be multiple peaks in Δ Z (l), each peak represents a fault, and the position of each peak is the position of each fault point.

[0034] Another object of the present invention is to provide a low-voltage distribution network fault monitoring system based on sensor network technology. This system

[0035] To solve the above technical problems, the present invention provides the following technical solutions: A system for a low-voltage distribution network fault monitoring method based on sensor network technology, including: a data acquisition module, a fault branch determination module, and a fault point position determination module; the data acquisition module collects sensor data in real time to obtain the channel frequency response of the distribution network; the fault branch determination module compares and analyzes the change amplitude of the channel frequency response of different power receiving devices to determine the branch where the fault is located; the fault point position determination module calculates the impedance amplitude of the fault branch and determines the exact position of the fault point according to the correlation between impedance and distance.

[0036] A computer device includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements the steps of the above-mentioned low-voltage distribution network fault monitoring method based on sensor network technology.

[0037] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it implements the steps of the above-mentioned low-voltage distribution network fault monitoring method based on sensor network technology.

[0038] The beneficial effects of the present invention are as follows: By comparing the amplitude changes of the channel frequency responses of different power-receiving devices to locate the faulty branch, calculating the impedance amplitude of the faulty branch, and combining the relationship between impedance and distance, the accurate location of the fault point is further realized. This method is accurate and stable, and can effectively monitor the grounding faults in low-voltage distribution networks. Under the condition of not considering signal interference or with less interference, the detection accuracy of the faulty branch reaches a relatively high level. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0040] Figure 1 It is a specific category diagram of the background indicators of the low-voltage distribution network fault monitoring method based on sensor network technology in Embodiment 1.

[0041] Figure 2 It is a specific category diagram of the safety indicators of the low-voltage distribution network fault monitoring method based on sensor network technology in Embodiment 1.

[0042] Figure 3 It is a flow chart of the fault monitoring algorithm of the low-voltage distribution network fault monitoring method based on sensor network technology in Embodiment 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following will describe the specific embodiments of the present invention in detail with reference to the accompanying drawings of the specification.

[0044] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0045] Embodiment 1, referring to Figures 1 - 3 , which is the first embodiment of the present invention. This embodiment provides a low-voltage distribution network fault monitoring method based on sensor network technology, including

[0046] Step 1: Collect sensor data in real time to obtain the channel frequency response of the distribution network.

[0047] The low-voltage distribution network fault monitoring design system of the sensor network technology of the present invention is established as Figure 1 and Figure 2The new evaluation system shown classifies the data monitored by the sensor module anew. For monitoring the operation status of the distribution area, by deploying devices such as primary-secondary integrated devices and intelligent measurement terminals with edge computing functions, the operation data of the transformer is collected and analyzed in real time, and early warnings are given for possible faults of the transformer in a timely manner.

[0048] The sensors are deployed on the electrical equipment of the distribution network and are used to collect the power data of the electrical equipment and the environmental status around the electrical equipment; the sensors interact with the intelligent measurement terminal through micro-power wireless.

[0049] The intelligent measurement terminal is equipped with a transmitter to continuously send high-frequency carrier signals to the network. A carrier device in each power line is selected as the receiver of the received signal, and each receiver is set at the node of the monitored line. Each receiver synchronously receives the signal sent by the transmitter at a fixed frequency together.

[0050] These receivers allow real-time monitoring of the frequency response changes of the network. The carrier frequency used in the method of the present invention is higher than 2×10^7Hz. Through a large number of simulation tests, we found that the fault recognition effect increases with the increase of the frequency, and a good monitoring effect can be achieved above 2×10^7Hz, and the carrier signal in this frequency band is relatively less affected by noise and other interference signals.

[0051] Step 2: Compare and analyze the change range of the channel frequency response of different power receiving devices to determine the branch where the fault is located.

[0052] The existing devices in the distribution network that can send and receive high-frequency carriers are used to monitor single-phase grounding faults, including intelligent devices, carrier devices and other devices in the smart grid. By real-time online monitoring of the frequency response changes of the low-voltage distribution network channel to identify faults and locate the fault branch, and calculating the impedance amplitude change of the fault branch with respect to distance, the precise location of the fault point can be further realized. The method of the present invention adopts two-stage detection. First, the fault branch is determined, and then the fault distance is accurately estimated. Based on the transmission line theory, a bottom-up method can be used to determine the channel model of the power line in the distribution network, and a distributed parameter model is used for equivalent calculation. The formula is expressed as,

[0053]

[0054] Among them, R, L, C, and G respectively represent the resistance, inductance, capacitance, and conductance per unit length, r and D respectively represent the conductor radius and the distance between two adjacent conductors; σ c and μ c respectively represent the conductivity and permeability, δ represents the skin depth, X g represents the relevant factor related to the skin depth and radius.

[0055] After obtaining the basic parameters of the cable, the corresponding characteristic impedance γ and propagation constant Z c are expressed as,

[0056]

[0057] where j represents the imaginary unit and f represents the frequency.

[0058] After calculating the distribution parameters of each cable in the system, perform the topological modeling of the network. Since the topological structure of the power network may be very complex, it can be divided into multiple small units, and then a detailed topological model can be constructed by describing the structure of each small unit. After obtaining the equivalent topology of the distribution network, divide the network topology into several small units from the transmitter to the receiver, and each small unit consists of a main trunk and a branch (the main trunk is the shortest path between two nodes, and the rest are branches).

[0059] After constructing the network topology model, further obtain the channel frequency response by calculating the voltage ratio between the signal receiver and the transmitter. The voltage ratio H(f) is expressed as,

[0060]

[0061] where V RX (f) and V TX (f) respectively represent the single-phase-to-ground voltage of a certain phase using the receiver and the transmitter.

[0062] When a single-phase grounding fault occurs in the distribution network, the channel characteristics of the power grid will change. Therefore, the occurrence of a single-phase grounding fault can be detected by monitoring the sudden change in the frequency response of the low-voltage distribution network channel. First, the faulty branch detection is realized by comparing the changes in the frequency signals received by different lines, and then the fault distance location is realized by using the relationship between the impedance and the distance of the faulty line. Figure 3 The algorithm flow chart of the method of the present invention is shown, where N is the total number of lines in the distribution network, and the change magnitude of the channel frequency response signal of the nth line is ΔH(f).

[0063] When the change magnitude ΔH(f) of the channel frequency response signal after the fault occurs is expressed as,

[0064]

[0065] where H0(f) represents the magnitude of the channel frequency response after the fault occurs, and H t (f) represents the magnitude of the channel frequency response when no fault occurs.

[0066] Determining the branch where the fault lies specifically includes using a device as the signal transmitter of the network and devices on different lines as receivers. When a fault occurs in the main part between the transmitting end and the receiving node, the frequency response of the main line changes greatly and is negative, while other receiving end faults are located at the branch positions, and the frequency response change of the branch line is relatively small. Using this function, by comparing the amplitude of the frequency response change at each receiver end, the faulty branch can be effectively detected. When multiple faults occur in the network, if the faults occur on different lines, the method of the present invention will identify and detect multiple faulty lines, and the frequency response change of each line is larger than that of the normal line. If multiple faults occur at different positions on the same line, the method of the present invention will detect the line and perform distance positioning in the next stage. Since signals such as noise in the low-voltage distribution network will affect the carrier signal, signal filtering devices can be added to areas with severe interference to reduce interference.

[0067] Step 3: Calculate the impedance amplitude of the faulty branch, and determine the exact position of the fault point according to the correlation between impedance and distance.

[0068] According to the relationship between the frequency signal change and the impedance spectrum, the variable mode decomposition technology is used to extract the frequency signal characteristics, obtain the key factors affecting the impedance, and obtain the impedance estimation result through inverse analysis.

[0069] Inverse analysis includes that the voltage is the electromagnetic coupling voltage of the carrier machine, the channel frequency response is reflected by the voltage ratio, by iterating forward from the last unit, calculating the transfer function of each unit, and determining the overall transfer function by multiplying the transfer function of each unit. The transfer function is calculated by using the characteristic impedance, transmission constant and length, and then the input impedance formula is obtained as

[0070]

[0071] where, Z c1 , Z c2 and Z cb represent the previous part, the next part of the main trunk and the branch line respectively, and represent the transmission constant, and represent the cable length, and represent the main trunk input impedance and the input impedance of the previous section of branch unit n, represents the main trunk impedance of branch unit n, represents the impedance of the branch line of branch unit n, represents the characteristic impedance of the previous part of branch unit n, represents the characteristic impedance of the next part of branch unit n, Denoted as the characteristic impedance of the n-th branch of the branch unit.

[0072] After identifying the faulty branch, it is necessary to further accurately locate the fault point. The input impedance of the line can reflect the changes in the power grid and relevant location information. By monitoring the relationship between the impedance change and the distance in the faulty line, the location of the impedance mutation is determined, thus realizing the distance positioning of the fault point on the faulty line. According to the relationship between the frequency signal change and the impedance spectrum, the variable mode decomposition technology is used to extract the frequency signal characteristics, obtain the key factors affecting the impedance, and then the impedance estimation result is obtained through inverse analysis. When the fault branch detection link detects a faulty line, the input impedance of the faulty line is predicted through impedance estimation technology to obtain the change in the system input impedance, which is expressed by the formula

[0073]

[0074] where, Δ Z (f) is denoted as the impedance change in the frequency domain, Z(f) is denoted as the input impedance of the system under normal conditions, Z d (f) is denoted as the input impedance after the fault occurs, and Δ Z (f) is denoted as the change in the input impedance.

[0075] After obtaining the impedance change in the frequency domain, the impedance change is converted from the frequency domain form to the time domain form through the inverse fast Fourier transform to obtain the change of impedance with time, which is expressed by the formula

[0076] Δ z (f) → Δ z (t)

[0077] After obtaining the time-domain impedance change Δ z (t), the fault distance measurement is realized according to the relationship between the impedance change and the distance. The distance l is obtained by multiplying the propagation speed v of the electromagnetic wave in the cable by the time t, which is expressed by the formula

[0078] l = v·t

[0079] The propagation speed of high-frequency electromagnetic waves is independent of frequency and depends on the line inductance L and capacitance C, which is expressed by the formula

[0080]

[0081] Multiplying the time t in Δ z (t) by the propagation speed v, a function equation related to the distance is obtained, and the relationship between the impedance change and the distance is expressed as

[0082] Δ Z (l) = Δ Z (v·t)

[0083] According to the transmission line theory, the input impedance of a line can be calculated by the last unit of forward iteration. When a fault occurs at a certain point on the line, the input impedance of the faulty line will change, and the input impedance at the fault point will change suddenly. By detecting the position of the impedance mutation, fault location can be achieved. Therefore, the Z peak position of Δ(l) is the distance from the fault point. When multiple faults occur on the same line, the input impedance at each fault point changes, and then there will be multiple peaks in Δ Z (l). Each peak represents a fault, and the position of each peak is the position of each fault point.

[0084] Embodiment 2 is the second embodiment of the present invention. The difference from the first embodiment is: A system for a low-voltage distribution network fault monitoring method based on sensor network technology, including a data acquisition module, a fault branch determination module, and a fault point location determination module; The data acquisition module collects sensor data in real time to obtain the channel frequency response of the distribution network; The fault branch determination module compares and analyzes the change amplitude of the channel frequency responses of different power receiving devices to determine the branch where the fault is located; The fault point location determination module calculates the impedance amplitude of the fault branch and determines the exact position of the fault point according to the correlation between impedance and distance.

[0085] The system of the present invention accesses the total meter of the substation area, the main protection, the leakage protection, the intelligent capacitor, and the environmental sensors (temperature and humidity sensors, smoke sensors, water immersion sensors), etc. to realize the monitoring of the substation environment. Various sensors perform information interaction with the intelligent measurement terminal through micro-power wireless. Taking the multi-dimensional sensor information intelligent fusion technology as the core, it realizes the real-time perception function of the auxiliary monitoring equipment in the substation building, monitors the operating conditions of the equipment on the substation side in real time, and realizes the panoramic perception of the wide range of distribution network operating states. Taking the main equipment of the edge IoT component in the situation awareness complete set of equipment as the core, by enabling the corresponding function application software and adopting the passive low-power IoT sensor technology, it collects and analyzes the data such as the operating temperature, voltage, and current of the transformer in real time, monitors the electrical equipment, the transformer, and the surrounding environment all-weather, performs intelligent control, accurately predicts the possible faults in time, realizes functions such as equipment operating state analysis, visual on-line monitoring, and automatic alarm for foreign object intrusion, and ensures the safe, stable, and economic operation of the distribution network.

[0086] If the above-described functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. The foregoing storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs.

[0087] The logic and / or steps represented in the flowchart or described in other ways herein, for example, can be considered as a predefined sequence list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other systems that can fetch instructions from the instruction execution system, apparatus, or device and execute the instructions), or in combination with these instruction execution systems, apparatus, or devices. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by or in combination with an instruction execution system, apparatus, or device.

[0088] More specific examples (non-exhaustive list) of computer-readable media include the following: electrical connection parts with one or more wirings (electronic devices), portable computer disk cartridges (magnetic devices), random access memories (RAM), read-only memories (ROM), erasable programmable read-only memories (EPROM or flash memories), fiber optic devices, and portable compact disc read-only memories (CDROM). Additionally, the computer-readable medium can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other media, then editing, interpreting, or processing it in other suitable ways as necessary, and then storing it in a computer memory.

[0089] It should be understood that each part of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, any one or a combination of the following techniques well known in the art can be used: discrete logic circuits having logic gate circuits for implementing logical functions on data signals, application specific integrated circuits having appropriate combinational logic gate circuits, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.

[0090] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A low-voltage distribution network fault monitoring method based on sensor network technology, characterized in that: Including, Collecting sensor data in real time to obtain the channel frequency response of the distribution network; Comparing and analyzing the change amplitudes of the channel frequency responses of different power receiving devices to determine the branch where the fault is located; The obtaining of the channel frequency response of the distribution network includes, after calculating the distribution parameters of each cable in the system, performing topological modeling of the network. After constructing the network topology model, the channel frequency response is further obtained by calculating the voltage ratio between the signal receiver and the transmitter. The voltage ratio H(f) is expressed as where V RX (f) and V TX (f) respectively represent the single-phase-to-ground voltage of a certain phase using the receiver and the transmitter; When a fault occurs, the change magnitude ΔH(f) of the channel frequency response signal is expressed as Among them, H0(f) represents the magnitude of the channel frequency response after a fault occurs, and H t (f) represents the magnitude of the channel frequency response when no fault occurs; The determining of the branch where the fault is located includes that when a fault occurs in the main part between the sending end and the receiving node, the frequency response change of the main line is larger and negative than the frequency response change of the fault at the branch position. By comparing the change amplitudes of the frequency responses at each receiver end, the branch to which the fault belongs is detected; When multiple faults occur in the network, if the faults occur on different lines, multiple fault lines will be identified and detected, and the frequency response change of each line is larger than that of the normal line; Calculating the impedance amplitude of the fault branch, and determining the exact location of the fault point according to the correlation between the impedance and the distance.

2. The method for monitoring faults in a low-voltage distribution network based on sensor network technology according to claim 1, wherein: The sensors are deployed on the electrical equipment of the distribution network and are used to collect the power data of the electrical equipment and the environmental state around the electrical equipment; The sensors perform information interaction with the intelligent measurement terminal through micro-power wireless; The intelligent measurement terminal is equipped with a transmitter to continuously send high-frequency carrier signals to the network. One carrier device in each power line is selected as the receiver of the received signal. Each receiver is set at the node of the monitored line, and each receiver synchronously receives the signal sent by the transmitter at a fixed frequency together; The frequency of the high-frequency carrier is higher than 2×10^7Hz.

3. The low-voltage distribution network fault monitoring method based on sensor network technology according to claim 2, characterized in that: Based on the transmission line theory, channel modeling is performed on the cables in the distribution network, and equivalent calculations are performed using the distributed parameter model. The formula is expressed as wherein, R, L, C, and G respectively represent the resistance, inductance, capacitance, and conductance per unit length, r and D respectively represent the conductor radius and the distance between two adjacent conductors; σ c and μ c respectively represent the conductivity and the permeability, δ represents the skin depth, X g represents a correlation factor related to the skin depth and the radius; After obtaining the basic parameters of the cable, the corresponding characteristic impedance γ and propagation constant Z c are expressed as where j represents the imaginary unit and f represents the frequency.

4. The low-voltage distribution network fault monitoring method based on sensor network technology according to claim 3, characterized in that: The calculating of the impedance amplitude of the fault branch includes, according to the relationship between the frequency signal change and the impedance spectrum, using the variable-mode decomposition technology to extract the frequency signal characteristics, obtaining the key factors affecting the impedance, and obtaining the impedance estimation result through inverse analysis; The inverse analysis includes that the voltage is the electromagnetic coupling voltage of the carrier machine, the channel frequency response is reflected by the voltage ratio, by iterating forward from the last unit, calculating the transfer function of each unit, and determining the overall transfer function by multiplying the transfer functions of each unit. The input impedance formula is obtained by calculating the transfer function using the characteristic impedance, transmission constant, and length, which is expressed as Among them, Z c1 , Z c2 and Z cb represent the previous section, the next part of the main trunk, and the branch line respectively, and represent the transmission constants, and represent the cable lengths, and represent the input impedance of the main trunk and the input impedance of the previous section of branch unit n, represents the main trunk impedance of branch unit n, represents the impedance of the branch line of branch unit n, represents the characteristic impedance of the previous section of branch unit n, represents the characteristic impedance of the next part of branch unit n, represents the characteristic impedance of the branch line of branch unit n.

5. The low-voltage distribution network fault monitoring method based on sensor network technology according to claim 4, characterized in that: The determining of the exact location of the fault point according to the correlation between the impedance and the distance includes that when the fault branch detection link detects a fault line, the input impedance of the fault line is predicted through impedance estimation technology to obtain the change of the system input impedance. The formula is expressed as where, Δ Z (f) represents the impedance change in the frequency domain, Z(f) represents the input impedance of the system under normal conditions, Z d (f) represents the input impedance after a fault occurs, Δ Z (f) represents the change in the input impedance.

6. The method for monitoring faults in a low-voltage distribution network based on sensor network technology according to claim 5, wherein: Determining the exact location of the fault point according to the correlation between impedance and distance further includes, after obtaining the impedance change in the frequency domain form, converting the impedance change from the frequency domain form to the time domain form through inverse fast Fourier transform to obtain the change of impedance over time, which is expressed by the formula as Δ z (f)→Δ z (t) After obtaining the time-domain impedance change Δ z (t), fault location is achieved according to the relationship between the impedance change and the distance. The distance l is obtained by multiplying the propagation speed v of the electromagnetic wave in the cable by the time t, and the formula is expressed as l = v·t The propagation speed of high-frequency electromagnetic waves is independent of frequency and depends on the line inductance L and capacitance C, which is expressed by the formula as Multiply the time t in Δ z (t) by the propagation speed v to obtain a function equation related to distance. The relationship between the impedance change and the distance is expressed as Δ Z l) = Δ Z (v·t) Among them, Δ Z (l) the peak position is the distance from the fault point. When there are multiple faults on the same line, the input impedance of each fault point changes. Then Δ Z (l) will have multiple peaks, each peak representing a fault, and the position of each peak is the position of each fault point.

7. A system adopting the low-voltage distribution network fault monitoring method based on sensor network technology according to any one of claims 1 to 6, characterized in that: including a data acquisition module, a fault branch determination module, and a fault point location determination module; The data acquisition module collects sensor data in real time to obtain the channel frequency response of the distribution network; The fault branch determination module compares and analyzes the change amplitudes of the channel frequency responses of different power receiving devices to determine the branch where the fault is located; The fault point location determination module calculates the impedance amplitude of the fault branch and determines the exact location of the fault point according to the correlation between impedance and distance.

8. A computer device, comprising a memory and a processor, the memory storing a computer program, characterized in that: When the processor executes the computer program, it implements the steps of the low-voltage distribution network fault monitoring method based on sensor network technology described in any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by the processor, it implements the steps of the low-voltage distribution network fault monitoring method based on sensor network technology described in any one of claims 1 to 6.

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