Power distribution network single-phase grounding fault discrimination system and method using different frequency signals

Abstract

A power distribution network single-phase ground fault discrimination system and method using different frequency signals, a discrimination signal sending device is arranged between the neutral point and the ground of the distribution transformer in the substation; a plurality of discrimination signal receiving devices are arranged on each line of the same bus connected with the distribution transformer; the discrimination signal receiving device realizes signal sensing function based on the magneto-electric stress coupling type sensing element, can select frequency to identify the different frequency current signal with the same identification frequency point as the magneto-electric stress coupling type sensing element; when judging that the single-phase ground fault of the power distribution network is suspected to occur, the discrimination signal sending device injects the different frequency current signal to the neutral point; each discrimination signal receiving device on the fault phase of each line obtains the different frequency current signal through adaptive adjustment detection to determine the single-phase ground fault line. The application has the advantages of adaptive adjustment of the identification frequency according to the current frequency, low dependence of the injected current intensity, simple structure, reliable method, convenient use, small size, low cost, large-scale deployment and the like.

Description

Technical Field

[0001] This invention belongs to the field of single-phase grounding fault identification, specifically relating to a single-phase grounding fault identification system and method for power distribution networks using heterogeneous frequency signals.

[0002] Background Technology Introduction

[0003] In medium and low voltage distribution networks, over 80% of faults are single-phase-to-ground faults, and most phase-to-phase faults develop from single-phase-to-ground faults. After such a fault occurs, the line voltage remains unchanged, allowing the system to continue operating for a period of time. However, if the fault is not correctly identified and promptly isolated, it may lead to more serious secondary faults such as phase-to-phase short circuits, threatening the safe operation of the system. Therefore, it is crucial to quickly identify and isolate the faulty line after a single-phase-to-ground fault occurs.

[0004] Methods for identifying single-phase grounding faults are mainly divided into methods based on steady-state and transient information, as well as comprehensive methods combining intelligent algorithms. Steady-state methods, such as the current amplitude and phase method and the fifth harmonic method, are limited in effectiveness due to factors such as arc suppression coil compensation and arc grounding. Transient methods, including transient zero-sequence current analysis and traveling wave methods, are limited in effectiveness due to the difficulty of data acquisition and changes in system parameters. Intelligent algorithms, such as empirical mode decomposition and Fourier transform, can handle complex signals, but still have shortcomings in processing nonlinear and non-stationary signals.

[0005] Active current injection is currently the main technology for ground fault detection. Its principle is to inject a different frequency characteristic signal into the power frequency current signal, and then detect the injected signal through a sensing device to achieve fault detection. The active signal injection method is not affected by weak steady-state signals or short-lived transient signals, and has a high success rate in most cases. This method is simple and easy to implement, requiring only a few devices to determine the faulty line, and is not affected by the neutral grounding method.

[0006] For example, the prior art CN102221660A discloses an online location method for small current grounding faults and a location device based on the method. The method is applicable to 3-60kV neutral point non-effectively grounded power grids. When the line is operating with a single-phase grounding fault, an AC signal of 130-230Hz (excluding integer multiples of the power frequency of 50Hz) is injected from the substation PT. The voltage phasor of the injected signal is measured in the substation, and the current phasor of the injected signal is measured on the line. The section location of the fault point is determined according to the phase relationship between the voltage and current phasors of the injected signal.

[0007] CN102778636A discloses a method and device for locating single-phase grounding faults. The method involves installing a signal injection device at the three-phase busbar or outlet of a substation; suspending multiple monitoring instruments on the three-phase power line; injecting a specific frequency current signal into the ground when a grounding fault occurs; only monitoring instruments located between the signal injection device and the grounding fault point can extract the current signal from the carrier signal; the monitoring instrument locally displays fault judgment information and outputs this information via radio frequency.

[0008] CN116626440A discloses a method and system for locating traveling wave faults in distribution networks based on active injection. The method includes the following steps: Step 1, after detecting a single-phase ground fault in the distribution network, a detection signal of a characteristic frequency is injected from the neutral point of the distribution network by controlling an active inverter; Step 2, the traveling wave signal reflected back from the fault point is measured using a line-end detection device; Step 3, the traveling wave front is calibrated using phase mode transformation and the Teager energy operator, and the fault distance is calculated based on the traveling wave location method. This achieves accurate location of faults in distribution networks using active injection.

[0009] Signal injection methods offer flexible applications, but the strength of the injected signal is limited by the equipment's capacity, and the positioning accuracy is influenced to some extent by line distributed capacitance and grounding resistance. Especially with the increasing integration of new energy sources, the accuracy of signal extraction is crucial. Simultaneously, various interference sources exist in the power grid system, such as harmonics and noise, which may confuse or mask signals from different frequency characteristic currents. Existing current sensors mainly include current transformers, resistive current sensors, and Hall effect sensors, but each has its own limitations in application. Current transformers are bulky; resistive current sensors have poor applicability for accurately detecting grid-injected currents; and Hall effect sensors are limited in their applicability due to external magnetic field interference. Therefore, single-phase ground fault detection based on the active current injection method places extremely high demands on the sensitivity and accuracy of the sensing device. Summary of the Invention

[0010] To address the shortcomings of existing technologies, this invention provides a system and method for identifying single-phase grounding faults in power distribution networks using heterogeneous frequency signal sensing.

[0011] The present invention adopts the following technical solution.

[0012] This application claims protection for a single-phase ground fault detection system for a distribution network using heterogeneous frequency signals, comprising a detection signal transmitting device and multiple detection signal receiving devices, characterized in that:

[0013] The discrimination signal transmitting device is installed between the neutral point of the substation distribution transformer and ground;

[0014] Multiple discrimination signal receiving devices are installed on each line connected to the same busbar of the distribution transformer;

[0015] When a single-phase ground fault is detected in the distribution network, the discrimination signal transmitting device injects a different frequency current signal into the neutral point;

[0016] Each discrimination signal receiving device on the faulty phase of each line determines the single-phase ground fault line by detecting and acquiring the different frequency current signal.

[0017] Further, the following preferred options are included:

[0018] The discrimination signal transmitting device includes a first main control module, a different frequency current signal injection module, and a voltage sensing module;

[0019] The voltage sensing module monitors the neutral point zero-sequence voltage in real time. When the zero-sequence voltage is greater than the set threshold, it is determined that a single-phase grounding fault has occurred in the distribution network. The first main control module controls the heterogeneous frequency current signal injection module to generate heterogeneous frequency current signals and inject them into the neutral point.

[0020] The heterogeneous current signal injection module generates a heterogeneous current signal between the transformer neutral point and ground by controlling the automatic short-term connection of a dynamic resistive load signal source. The characteristic parameters of the heterogeneous current signal include the peak value of the injected current, the frequency of the injected current signal, and the duration of the injected current.

[0021] The peak injection current shall not exceed 10A;

[0022] The frequency of the injected current signal is set to 200-1000Hz, while avoiding the frequencies of odd and even harmonics.

[0023] The duration of the injected current shall not exceed 2 seconds.

[0024] The discrimination signal transmitting device also includes a first communication module for receiving instructions. When a single-phase ground fault occurs, the master station system selects the faulty phase through the three-phase voltage detection value. The master station system sends instructions on the characteristic parameters of the heterogeneous current signal to be injected to the discrimination signal transmitting device and each discrimination signal receiving device on the faulty phase line.

[0025] The discrimination signal transmitting device generates and injects a corresponding heterogeneous frequency current signal according to the instruction;

[0026] The discrimination signal receiving device adapts and adjusts the signal sampling frequency and identification frequency point according to the instructions.

[0027] The discrimination signal receiving device realizes the signal sensing function based on a magnetoelectric stress coupling sensing element.

[0028] The discrimination signal receiving device further includes a second communication module and a second main control module;

[0029] The second communication module receives the characteristic parameter instruction of the heterogeneous current signal to be injected from the main station system. The second control module adapts and adjusts the sampling frequency and identification frequency of the discrimination signal receiving device according to the characteristic parameter of the heterogeneous current signal to achieve the perception of the heterogeneous current signal.

[0030] The sampling frequency of the receiving device for the heterogeneous current signal is not less than 4kHz, and is an integer multiple of the power frequency and the injected signal frequency.

[0031] The identification frequency point of the signal receiving device is adjusted accordingly as follows:

[0032] The second main control module selects a magnetoelectric stress-coupled sensing element with the same frequency as the injected small current signal, based on the characteristic parameter instructions of the signal to be injected from the main station system, to realize the signal sensing function.

[0033] Once the signal receiving device detects an abnormal frequency current signal, it determines that the line in question is faulty and reports the fault information to the main station via the second communication module.

[0034] This application also claims protection for a method for identifying single-phase ground faults in a distribution network using heterogeneous frequency signals based on the aforementioned discrimination system, the method comprising the following:

[0035] Step 1: Monitor the zero-sequence voltage of the distribution network in real time. When it exceeds the set threshold, determine that a single-phase ground fault has occurred in the distribution network.

[0036] Step 2: After determining that a single-phase ground fault has occurred, determine that the signal transmitting device injects a different frequency current signal with set characteristic parameters into the neutral point;

[0037] Step 3: Each discrimination signal receiving device on the faulty phase of each line determines the single-phase ground fault line by detecting and acquiring the different frequency current signal.

[0038] Another aspect of this application discloses an electronic device, including a processor and a storage medium; characterized in that:

[0039] The storage medium is used to store instructions;

[0040] The processor is configured to operate according to the instructions to execute the aforementioned method for identifying single-phase grounding faults in a distribution network using heterogeneous frequency signals.

[0041] This application also discloses a computer-readable storage medium having a computer program stored thereon, characterized in that the program, when executed by a processor, implements the method for identifying single-phase grounding faults in a power distribution network using heterogeneous frequency signals.

[0042] The beneficial effects of this invention are that, compared with the prior art,

[0043] (1) This invention is the first to systematically propose a discrimination signal receiving device and method using a magnetoelectric stress-coupled sensing element. The discrimination signal receiving device using a magnetoelectric stress-coupled sensing element has resonant characteristics, enabling it to obtain the most effective output within a specific frequency range. When the frequency of the different frequency current signal matches the resonant frequency of the sensing element, the sensitivity of the sensing element reaches its maximum, thus effectively receiving and amplifying the signal. The maximum output in the resonant state can be 1000 times that in the non-resonant state. In power systems, background noise and interference are unavoidable. These interferences may originate from environmental noise, other equipment in the power grid, or the lines themselves. Due to its resonant characteristics, the sensing element can effectively filter out these interferences, allowing only specific signals to pass through. It can effectively acquire and identify different frequency current signals under complex background current conditions, exhibiting outstanding filtering and anti-interference capabilities.

[0044] (2) This invention is the first to fully propose a single-phase ground fault detection system and method with low injection current of 10A and below. Traditional active current injection methods typically use current values ​​in the tens of A range, making low injection current identification difficult. The detection effect under low injection current conditions is improved by using a detection signal receiving device. This invention, through its ultra-high sensitivity, can achieve accurate fault detection under low injection current conditions. This method not only improves the accuracy and efficiency of fault detection but also reduces interference to the power system, improving system stability and safety.

[0045] (3) This invention is the first to propose a single-phase grounding fault identification method with an adaptively adjustable identification frequency. Based on the ultra-high sensitivity and filtering anti-interference capability of the identification signal receiving device, it can effectively receive and identify different frequency current signals, thereby significantly improving the success rate of single-phase grounding fault identification, improving the speed and accuracy of fault handling, and thus ensuring the stable operation of the power system and the power supply to users.

[0046] (4) The present invention utilizes a single-phase grounding fault identification system and method for distribution networks using different frequency signals. It also has the advantages of simple structure, reliable method, convenient use, small size, low cost, and large-scale deployment. Attached Figure Description

[0047] Figure 1 This is a model diagram of the single-phase grounding fault detection system of the present invention;

[0048] Figure 2 It is the characteristic waveform current injected by the discrimination signal generating device of the present invention;

[0049] Figure 3 It is the basic structure of a magnetoelectric stress-coupled sensing element;

[0050] Figure 4This is a flowchart of the single-phase grounding fault identification method of the present invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, other embodiments obtained by those skilled in the art without creative effort are all within the protection scope of this invention.

[0052] This invention discloses a single-phase ground fault detection system for distribution networks using heterogeneous frequency signals, comprising a detection signal transmitting device and multiple detection signal receiving devices; see appendix. Figure 1 This is a diagram of a single-phase ground fault detection model. Figure 1 Taking a 10kV distribution network as an example, the distribution transformer is a 35kV / 10kV double-winding transformer, using a Δ-Y connection. The 10kV low-voltage side connects multiple distribution lines via bus couplers, including overhead lines, cable lines, and composite lines of overhead and cable lines. A single-phase ground fault detection signal transmitting device (hereinafter referred to as the detection signal transmitting device) is installed between the neutral point of the low-voltage winding of the distribution transformer and ground. Multiple single-phase ground fault detection signal receiving devices (hereinafter referred to as detection signal receiving devices) are installed on each distribution line. In overhead distribution line sections, a detection signal receiving device can be installed at regular intervals; in circuit line sections, detection signal receiving devices can be installed at both ends of the cable and at intermediate nodes.

[0053] When it is determined that a single-phase ground fault is suspected to have occurred in the distribution network, the discrimination signal transmitting device injects a different frequency current signal into the neutral point;

[0054] The signal transmission device includes a first communication module, a first main control module, a heterogeneous current signal injection module, and a voltage sensing module. The voltage sensing module monitors the neutral point zero-sequence voltage in real time. When the zero-sequence voltage exceeds a set threshold, it determines that a single-phase ground fault has occurred in the distribution network. After a single-phase ground fault occurs, the first main control module controls the heterogeneous current signal injection module to generate a heterogeneous current signal and inject it into the neutral point.

[0055] As a further preferred option, the main control system can also determine the single-phase ground fault phase based on the changes in the neutral point zero-sequence voltage and the three-phase voltage. The main station system sends an injection of heterogeneous current command to the discrimination signal transmitting device, and at the same time sends heterogeneous current signal detection command to each discrimination signal receiving device on each faulty phase of the line.

[0056] After the discrimination signal transmitting device receives the instruction from the master station system through the first communication module, the first main control module controls the heterogeneous frequency current signal injection module to generate heterogeneous frequency current with corresponding characteristic parameters according to the instruction and inject it into the neutral point of the distribution transformer. The first communication module can use LoRa or RS485 to implement communication functionality.

[0057] Furthermore, the heterogeneous current signal injection module generates a heterogeneous current signal between the transformer neutral point and ground by controlling the automatic short-term connection of the dynamic resistive load signal source. The characteristic parameters of the heterogeneous current signal include the peak value of the injected current, the frequency of the injected current signal, and the duration of the injected current.

[0058] In this invention, the peak value of the injected current preferably does not exceed 10A. The frequency of the injected current signal is set as high as possible within the range of 200-1000Hz, while avoiding the frequencies of odd and even harmonics of the power frequency. The duration of the injected current does not exceed 2 seconds.

[0059] See appendix Figure 2 This is an example of the different frequency current injected by the signal generation device of the present invention. The different frequency current signal is composed of multiple consecutive current sequences with the same characteristic parameters. The characteristic parameters of the different frequency current signal include the peak value of the injected current, the frequency of the injected current signal, and the duration of the injected current. Figure 2 The different frequency current shown consists of four sequences of current square waves.

[0060] Each discrimination signal receiving device on each faulty phase of the line determines the single-phase ground fault line by detecting and acquiring the different frequency current signal.

[0061] The main installation locations of the discrimination signal receiving device include overhead line towers and cable line ring network cabinets / switching stations.

[0062] The discrimination signal receiving device realizes the signal sensing function based on the magnetoelectric stress coupling sensing element. In addition to the sensor array composed of multiple magnetoelectric stress coupling sensing elements, it also includes a second communication module and a second main control module.

[0063] The second communication module receives the instruction to inject heterogeneous current from the main station system. The second control module selects / adjusts the sampling frequency and identification frequency of the discrimination signal receiving device according to the characteristic parameters of the heterogeneous current signal to be injected, so as to realize the perception of the heterogeneous current signal.

[0064] Magnetoelectric stress-coupled sensing elements have good bending resonant frequency, i.e., the ability to adjust the identification frequency.

[0065] Magnetoelectric stress-coupled sensing elements have resonant characteristics, enabling them to effectively acquire and identify weak heterogeneous frequency current signals under complex background current conditions, and possess outstanding filtering and anti-interference capabilities.

[0066] The magnetoelectric stress-coupled sensing element used in this invention includes a magnetostrictive layer and a piezoelectric layer; the magnetostrictive layer is formed by bonding multiple layers of magnetostrictive materials with a bonding material and has a magnetostrictive effect; the magnetostrictive layer can sense changes in the external magnetic field and use the magnetostrictive effect to generate stress changes that are transmitted to the piezoelectric layer.

[0067] The piezoelectric layer is composed of piezoelectric material and flexible electrode material. The piezoelectric layer, through the magnetoelectric stress coupling effect generated by its combination with the magnetostrictive layer, utilizes the piezoelectric effect of the piezoelectric material to convert the stress deformation of the piezoelectric layer caused by the deformation of the magnetostrictive layer into voltage form, which is output by two flexible electrodes symmetrically arranged on the upper and lower sides of the piezoelectric material in the piezoelectric layer.

[0068] See appendix Figure 3 The basic sensing structure of the magnetoelectric stress-coupled sensing element used in this invention consists of a magnetostrictive layer composed of multiple layers of magnetostrictive material, symmetrically arranged on the upper and lower sides of a piezoelectric layer composed of piezoelectric material, forming a magnetoelectric composite layer. The magnetoelectric stress-coupled sensing element senses a magnetic field component H parallel to the long side of its magnetoelectric composite layer. The relationship between the thickness of the magnetoelectric composite layer and the thicknesses of the magnetostrictive layer and the piezoelectric layer is as follows:

[0069] d = 2w + z;

[0070] Where w is the thickness of the magnetostrictive layer, the magnetostrictive layers on the upper and lower sides of the piezoelectric layer are of equal thickness, both being w, z is the thickness of the piezoelectric layer, and d is the thickness of the magnetoelectric composite layer.

[0071] In a preferred embodiment of the present invention, the signal receiving device includes an array of multiple magnetoelectric stress-coupled sensing elements, each with a different identification frequency and sampling frequency. When the second communication module receives a command from the master station system to inject a different frequency current, the second control module selects and connects the magnetoelectric stress-coupled sensing element whose characteristic parameters are closest to those of the different frequency current signal, based on the characteristic parameters of the signal to be injected, for sensing the different frequency current signal.

[0072] In another preferred embodiment, the signal receiving device is equipped with a magnetoelectric stress-coupled sensing element with adjustable characteristic parameters. When the second communication module receives the instruction to inject a different frequency current from the main station system, the second control module adjusts the sampling frequency and bending resonant frequency of the magnetoelectric stress-coupled sensing element according to the characteristic parameters of the different frequency current signal to be injected. For example, those skilled in the art can adjust the bending resonant frequency using the following formula:

[0073]

[0074] Where f is the bending resonant frequency, l is the length of the magnetoelectric composite layer, ρ is the average density of the magnetoelectric composite layer, s is the average flexibility coefficient of the magnetoelectric composite layer, and n is a positive integer representing the vibration level of the magnetoelectric composite layer. When the vibration level is 1, i.e., n=1, the calculated bending resonant frequency that is the same as the frequency of the measured heterogeneous current signal is the bending resonant frequency with the highest matching degree between the magnetoelectric stress-coupled sensing element and the measured heterogeneous current signal, which can maximize the piezoelectric layer voltage output value of the magnetoelectric stress-coupled sensing element; when the vibration level is 2, i.e., n=2 At that time, the calculated bending resonant frequency, which is the same as the frequency of the heterogeneous signal, is the bending resonant frequency with the second highest matching degree between the magnetoelectric stress-coupled sensing element and the heterogeneous current signal to be measured. At this bending resonant frequency, the piezoelectric layer voltage output value of the magnetoelectric stress-coupled sensing element is the second largest. The larger the value of the vibration level n, the lower the matching degree between the magnetoelectric stress-coupled sensing element and the heterogeneous current signal to be measured at the calculated bending resonant frequency, and the smaller the piezoelectric layer voltage output value of the magnetoelectric stress-coupled sensing element.

[0075] Preferably, the sampling frequency of the heterogeneous current signal of the receiving device is not less than 4kHz, and is an integer multiple of the power frequency and the injected signal frequency. Since the peak value of the power frequency current in the distribution network is much higher than the peak value of the injected heterogeneous current signal, the power frequency current signal exists as a small noise in the heterogeneous current signal identified by the discrimination signal receiving device; therefore, the sampling frequency is also defined as an integer multiple of the power frequency.

[0076] After the magnetoelectric stress-coupled sensing element senses the heterogeneous current signal and converts it into a voltage output, the voltage output is sampled according to the sampling frequency. Since the waveform of the output voltage, except for the peak value, should be consistent with the sensed heterogeneous current signal, comparing the sampled signal with the heterogeneous current signal characteristic parameters, except for the injected current peak value, can achieve the effect of determining whether the sensed heterogeneous current signal is the injected heterogeneous current signal.

[0077] When the signal receiving device detects an abnormal frequency current signal, it determines that the line in question is faulty and reports the fault information to the main station. The fault information refers to the installation location of the signal receiving device that detected the abnormal frequency current signal.

[0078] The master station system determines the single-phase grounding fault line based on the installation location of the discrimination signal receiving device that senses the different frequency current signal; if none of the discrimination signal receiving devices report fault information, the master station system determines that no single-phase grounding fault has occurred.

[0079] Example 1

[0080] If a change in the three-phase line voltage is detected, and a single-phase ground fault is suspected, the master station system selects the faulty phase based on the three-phase voltage detection value. The master station system then sends instructions on the characteristic parameters of the differential frequency current signal to be injected to the discrimination signal sending device and each discrimination signal receiving device on the faulty phase line.

[0081] The discrimination signal transmitting device generates and injects a corresponding heterogeneous frequency current signal into the neutral point of the transformer according to the instruction.

[0082] The discrimination signal receiving device adapts to the signal sampling frequency and identification frequency point according to the instructions to realize the signal sensing function.

[0083] The identification frequency of the signal receiving device is adjusted as follows:

[0084] The second main control module selects a magnetoelectric stress-coupled sensing element with the same frequency as the injected small current signal, based on the characteristic parameter instructions of the signal to be injected from the main station system, to realize the signal sensing function.

[0085] Once the signal receiving device detects an abnormal frequency current signal, it determines that the line in question is faulty and reports the fault information to the main station.

[0086] The main station system determines the single-phase grounding fault line based on the installation location of the discrimination signal receiving device that senses the heterogeneous current signal; if none of the discrimination signal receiving devices acquire the heterogeneous current signal, it is determined that no single-phase grounding fault has occurred.

[0087] Example 2

[0088] If a change in the three-phase line voltage is detected, and a single-phase ground fault is suspected, the master station system selects the faulty phase based on the three-phase voltage detection value. The master station system then sends instructions on the characteristic parameters of the differential frequency current signal to be injected to the discrimination signal sending device and each discrimination signal receiving device on the faulty phase line.

[0089] The discrimination signal transmitting device generates and injects a corresponding heterogeneous frequency current signal into the neutral point of the transformer according to the instruction.

[0090] The discrimination signal receiving device adapts to the signal sampling frequency and identification frequency point according to the instructions to realize the signal sensing function.

[0091] Adjust the identification frequency of the discrimination signal receiving device, that is, adjust the identification frequency of the magnetoelectric stress coupling sensing element.

[0092] The identification frequency of the magnetoelectric stress-coupled sensing element is adjusted according to the formula relating the piezoelectric layer voltage output value to the AC magnetic field strength generated by the measured heterofrequency current signal, the formula for the thickness of the magnetostrictive layer on both sides of the piezoelectric layer, the relationship between the thickness of the magnetoelectric composite layer and the thickness of the magnetostrictive layer and the piezoelectric layer, and the formula for the bending resonant frequency of the magnetoelectric composite layer.

[0093] Once the signal receiving device detects an abnormal frequency current signal, it determines that the line in question is faulty and reports the fault information to the main station.

[0094] The main station system determines the single-phase grounding fault line based on the installation location of the discrimination signal receiving device that senses the heterogeneous current signal; if none of the discrimination signal receiving devices acquire the heterogeneous current signal, it is determined that no single-phase grounding fault has occurred.

[0095] This application also discloses a method for identifying single-phase ground faults in distribution networks using heterogeneous frequency signals based on the aforementioned discrimination system. (See appendix) Figure 4 The process includes: Step 1: Real-time monitoring of the zero-sequence voltage of the distribution network. When a sudden change or increase in the zero-sequence voltage occurs at a certain moment, and it exceeds a set threshold, it is determined that a single-phase grounding fault may have occurred in the distribution network.

[0096] Step 2: After determining that a single-phase ground fault has occurred, the signal transmitting device injects a different frequency current signal with set characteristic parameters into the neutral point;

[0097] Step 3: Each discrimination signal receiving device on the faulty phase of each line determines the single-phase ground fault line by detecting and acquiring the different frequency current signal; if none of the discrimination signal receiving devices acquire the different frequency current signal, it is determined that no single-phase ground fault has occurred.

[0098] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0099] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0100] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0101] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A single-phase ground fault detection system for a distribution network using heterogeneous frequency signals, comprising a master station system, a detection signal transmitting device, and multiple detection signal receiving devices, characterized in that: The discrimination signal transmitting device is installed between the neutral point and ground of the substation distribution transformer; the discrimination signal transmitting device includes a voltage sensing module and a heterogeneous current signal injection module; the voltage sensing module monitors the neutral point zero-sequence voltage in real time, and when the zero-sequence voltage is greater than a set threshold, it preliminarily judges that a single-phase grounding fault has occurred in the distribution network; the heterogeneous current signal injection module generates a heterogeneous current signal between the transformer neutral point and ground by controlling the automatic short-term connection of a dynamic resistive load signal source; the characteristic parameters of the heterogeneous current signal include the injected current signal frequency, the injected current peak value, and the injected current duration; The frequency of the injected current signal simultaneously avoids both odd and even harmonic frequencies of the power frequency. Multiple discrimination signal receiving devices are installed on each line connected to the same busbar of the distribution transformer; When a single-phase ground fault is detected in the distribution network, the main station system selects the faulty phase through the three-phase voltage detection value, and then sends the characteristic parameter instruction of the differential frequency current signal to be injected to the discrimination signal sending device and the discrimination signal receiving device on the phase line corresponding to the fault in each line. The discrimination signal transmitting device injects a different frequency current signal into the neutral point; The peak injection current shall not exceed 10A; The frequency of the injected current signal is set to 200~1000 Hz; The duration of the injected current shall not exceed 2 seconds; The discrimination signal receiving device includes an array of multiple magnetoelectric stress-coupled sensing elements with different bending resonant frequencies and sampling frequencies. In each discrimination signal receiving device on each faulty phase of the line, the second main control module selects the sampling frequency and bending resonant frequency of the magnetoelectric stress-coupled sensing element from the array according to the characteristic parameters of the injected heterofrequency current signal. The sampling frequency is not lower than 4kHz and is an integer multiple of the power frequency and the injected signal frequency. The bending resonant frequency of the discrimination signal receiving device is selected as follows: the second main control module selects a magnetoelectric stress-coupled sensing element with a bending resonant frequency consistent with the frequency of the injected heterofrequency small current signal according to the instruction of the characteristic parameters of the injected heterofrequency current signal issued by the main station system to achieve the signal sensing function. After the magnetoelectric stress-coupled sensing element senses the heterofrequency current signal and converts it into a voltage output, the voltage output is sampled according to the sampling frequency. The second main control module compares the sampled signal with the characteristic parameters of the heterofrequency current signal, excluding the peak value of the injected current, to determine whether the sensed heterofrequency current signal is the heterofrequency current signal injected this time. Once the discrimination signal receiving device determines that the sensed heterogeneous current signal is the heterogeneous current signal injected this time, it will report the fault information to the main station system. The fault information is the installation location of the discrimination signal receiving device. The main station system determines the single-phase grounding fault line based on the installation location. If none of the signal receiving devices report fault information, the main station system determines that no single-phase grounding fault has occurred.

2. The single-phase grounding fault detection system for power distribution networks according to claim 1, characterized in that: The discrimination signal transmitting device further includes a first main control module; The first main control module controls the heterogeneous frequency current signal injection module to generate heterogeneous frequency current signals and inject them into the neutral point.

3. The single-phase grounding fault detection system for power distribution networks according to claim 2, characterized in that: The discrimination signal transmitting device further includes a first communication module for receiving instructions; The discrimination signal transmitting device generates and injects a corresponding heterogeneous frequency current signal according to the instruction; The discrimination signal receiving device adapts and adjusts the signal sampling frequency and bending resonant frequency according to the instructions.

4. The single-phase grounding fault detection system for power distribution networks according to claim 1, characterized in that: The discrimination signal receiving device further includes a second communication module; The second communication module receives the characteristic parameter command of the heterogeneous frequency current signal to be injected from the master station system.

5. The single-phase grounding fault detection system for power distribution networks according to claim 4, characterized in that: The bending resonant frequency of the signal receiving device can also be adjusted in the following manner: The formula for adjusting the bending resonant frequency is: Where f is the bending resonant frequency, l is the length of the magnetoelectric composite layer, ρ is the average density of the magnetoelectric composite layer, s is the average flexibility coefficient of the magnetoelectric composite layer, n is a positive integer representing the vibration level of the magnetoelectric composite layer, and when the vibration level is 1, i.e., n=1, the bending resonant frequency calculated to be the same as the frequency of the measured heterogeneous current signal is the bending resonant frequency with the highest matching degree between the magnetoelectric stress-coupled sensing element and the measured heterogeneous current signal; d is the thickness of the magnetoelectric composite layer; each discrimination signal receiving device determines the single-phase grounding fault line by detecting and acquiring heterogeneous current signals.

6. A method for identifying single-phase grounding faults in a distribution network using heterogeneous frequency signals, based on the discrimination system described in any one of claims 1-5, characterized in that, The method includes the following: Step 1: Monitor the neutral point zero-sequence voltage in real time. When the zero-sequence voltage is greater than the set threshold, it is preliminarily judged that a single-phase grounding fault may have occurred in the distribution network. Step 2: The main station system selects the faulty phase through the three-phase voltage detection value and sends the characteristic parameter command of the inter-frequency current signal to be injected to the discrimination signal sending device and the discrimination signal receiving device corresponding to the fault in each line. Step 3: The signal transmitting device injects a different frequency current signal into the neutral point according to the characteristic parameters of the different frequency current signal to be injected; Step 4: The signal receiving device, according to the characteristic parameter instruction of the signal to be injected, selects a magnetoelectric stress-coupled sensing element whose bending resonant frequency is consistent with the frequency of the injected current signal from multiple magnetoelectric stress-coupled sensing element arrays with different bending resonant frequencies and sampling frequencies, and samples its voltage output according to the corresponding sampling frequency. Step 5: Compare the parameters other than the peak value of the injected current in the characteristic parameters of the sampled signal and the heterogeneous current signal to determine whether the sensed heterogeneous current signal is the heterogeneous current signal injected this time. Step 6: After the discrimination signal receiving device determines that the sensed heterogeneous current signal is the heterogeneous current signal injected this time, it reports its installation location to the main station system. The main station system determines the single-phase grounding fault line based on the installation location. If none of the discrimination signal receiving devices report fault information, the main station system determines that no single-phase grounding fault has occurred.

7. An electronic device, comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the method for identifying single-phase grounding faults in a distribution network using heterogeneous frequency signals as described in claim 6.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the method for identifying single-phase grounding faults in a distribution network using heterogeneous frequency signals as described in claim 6.

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