A small current grounding line selection auxiliary selection increment device and method

Abstract

The present application relates to the technical field of small current grounding line selection, and provides a small current grounding line selection auxiliary increment device and method, a grounding transformer module for providing a neutral point for a target power system; the target power system is a system without grounding of the neutral point; a neutral point voltage detection module for detecting the voltage of the neutral point when a grounding fault occurs; an auxiliary increment module for selecting a corresponding input resistor according to the size of the voltage of the neutral point when the grounding fault occurs, so as to obtain an increment current matched with the voltage of the neutral point; the input resistor is used for connecting the neutral point; and a zero sequence current detection module for judging the grounding fault according to the increment current matched with the voltage of the neutral point. Through the above technical solution, the problem that the grounding line selection cannot be accurately judged according to the zero sequence current in the related art is solved.

Description

Technical Field

[0001] This invention relates to the field of low-current grounding fault location technology, specifically to a low-current grounding fault location auxiliary incremental device and method. Background Technology

[0002] With the development of my country's power industry, the current power distribution line system has undergone a leapfrog improvement. The development direction of the line structure is gradually towards systematization and complexity. Faults in power distribution lines can not only lead to instability in the power supply system but also potentially cause power accidents. Therefore, how to quickly and accurately locate the fault point is a major research issue in my country's power sector. This is not only beneficial for improving the speed of fault repair but also for ensuring the reliability of the power supply system, thereby reducing unnecessary losses. Single-phase grounding is one of the common faults in distribution networks. When a single-phase grounding fault occurs in a distribution line, a zero-sequence current is generated. The presence of zero-sequence current affects the stability and safety of the power system. First, zero-sequence current leads to voltage imbalance in the power system, thus affecting the normal operation of power equipment. Second, zero-sequence current causes electromagnetic interference in the power system, thus affecting the normal operation of electronic equipment. Finally, zero-sequence current also affects the protection devices in the power system, thereby affecting the safety of the power system. To ensure the safety of the power system, arc suppression coils are usually used to eliminate the impact of zero-sequence current on the power system. After compensation by the arc suppression coil, the capacitive current at the fault point is canceled by the inductive current of the arc suppression coil, which makes it impossible to accurately determine the ground fault location based on the zero-sequence current, thus making it impossible to eliminate the ground fault in a timely manner. Summary of the Invention

[0003] This invention proposes an incremental device and method for assisting in the selection of grounding lines with low current, which solves the problem in related technologies that cannot accurately determine the grounding line selection based on zero-sequence current.

[0004] The technical solution of the present invention is as follows:

[0005] A first aspect of this disclosure provides a low-current grounding line selection auxiliary incremental device, comprising:

[0006] A grounding transformer module is used to provide a neutral point for a target power system; the target power system is a system with an ungrounded neutral point.

[0007] A neutral point voltage detection module is used to detect the voltage at the neutral point when a ground fault occurs.

[0008] The incremental selection module is used to select a corresponding input resistor based on the voltage of the neutral point when a ground fault occurs, so as to obtain an incremental current that matches the voltage of the neutral point; the input resistor is used to connect the neutral point.

[0009] The zero-sequence current detection module is used to determine grounding faults based on the incremental current matched to the voltage of the neutral point.

[0010] A second aspect of this disclosure provides an incremental method for assisting in the selection of low-current grounding lines, comprising:

[0011] Provide a neutral point for the target power system; the target power system is a system with an ungrounded neutral point.

[0012] Detect the voltage at the neutral point when a ground fault occurs;

[0013] When a ground fault occurs, a corresponding switching resistor is selected based on the magnitude of the neutral point voltage to obtain an incremental current that matches the neutral point voltage; the switching resistor is used to connect the neutral point.

[0014] The ground fault is determined based on the incremental current matching the voltage at the neutral point.

[0015] A third aspect of this disclosure provides an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method as claimed in claim 8.

[0016] A fourth aspect of this disclosure provides a computer-readable storage medium that, when executed by a processor, implements the steps of the method as claimed in claim 8.

[0017] The working principle and beneficial effects of this invention are as follows:

[0018] In this invention, the grounding transformer provides an artificial neutral point for a system with an ungrounded neutral point, facilitating the use of arc suppression coils for grounding. This reduces the impact of zero-sequence current on the power system and improves the reliability of the power distribution system. However, after compensation by the arc suppression coil, the capacitive current at the fault point is sometimes canceled out by the inductive current of the arc suppression coil, resulting in a low current value detected by the zero-sequence current detection module, making it impossible to accurately select the grounding fault line. When a single-phase grounding fault occurs in the power system, the three-phase power becomes unbalanced, causing the neutral point voltage to be non-zero. The neutral point voltage detection module detects the neutral point voltage and, based on this voltage, switches resistors of different values ​​to the neutral point to ensure that the incremental current provided by the auxiliary selection module to the zero-sequence current detection module is controlled within a set range. This allows for accurate grounding line selection based on the zero-sequence current. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of a small current grounding line selection aid incremental device provided in an embodiment of this disclosure;

[0021] Figure 2 This is a circuit diagram of the selection assistance incremental module provided in the embodiments of this disclosure;

[0022] Figure 3 This is a circuit diagram of the neutral point voltage detection module provided in an embodiment of this disclosure;

[0023] Figure 4 This is a schematic flowchart of an incremental method for selecting low-current grounding lines, provided in an embodiment of this disclosure.

[0024] Figure 5 This is a schematic block diagram of an electronic device provided in an embodiment of this disclosure. Detailed Implementation

[0025] To enable those skilled in the art to better understand this solution, the technical solutions in the embodiments of this solution will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this solution, not all of them. Based on the embodiments of this solution, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this solution.

[0026] The term "comprising" and any other variations thereof in the specification, claims, and accompanying drawings of this invention mean "including but not limited to," and are intended to cover a non-exclusive inclusion, not limited to the examples listed herein. Furthermore, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order.

[0027] The implementation of this disclosure will be described in detail below with reference to the specific accompanying drawings:

[0028] First Embodiment

[0029] like Figure 1 As shown, this embodiment proposes a small current grounding line selection auxiliary incremental device 10, including:

[0030] Grounding transformer module 11 is used to provide a neutral point for the target power system; the target power system is a system with an ungrounded neutral point.

[0031] In power systems, 6kV, 10kV, and 35kV grids generally operate with an ungrounded neutral point. The low-voltage side of the main transformer in this grid is typically delta-connected, lacking a groundable neutral point. When a single-phase ground fault occurs in an ungrounded system, the line voltage delta remains symmetrical, allowing the power system to continuously supply power to users for 1 to 2 hours. Furthermore, the capacitive current is relatively small (less than 10A), preventing intermittent arcing, and some transient ground faults can dissipate spontaneously. This is highly effective in improving power supply reliability and reducing power outages. However, with the continuous expansion of urban power grids and the increasing number of cable outgoing lines, the system's ground capacitive current has increased dramatically. After a single-phase ground fault, the capacitive current flowing through the fault point is substantial (exceeding 10A). Arcs are difficult to extinguish, easily triggering ferroresonant overvoltages and intermittent arcing ground faults, potentially leading to insulation damage, line tripping, and escalating the accident. To reduce the ground capacitance current during a single-phase ground fault, compensation devices such as arc suppression coils need to be installed at the neutral point of the transformer. Therefore, a neutral point needs to be artificially established so that an arc suppression coil can be connected to the neutral point to reduce the ground fault current and improve the reliability of the power supply system.

[0032] The function of a grounding transformer is to provide an artificial neutral point for a system where the neutral point is not grounded, so as to facilitate the use of arc suppression coils for grounding, thereby reducing the magnitude of the ground capacitance current when a single-phase ground fault occurs in the distribution network and improving the power supply reliability of the distribution system.

[0033] Neutral point voltage detection module 12 is used to detect the voltage of the neutral point when a ground fault occurs.

[0034] In this embodiment, when the power system is operating normally, the vector sum of the currents of the three phases of the power system is 0. Therefore, ideally, the current at the neutral point is 0, that is, the voltage at the neutral point is also 0. When a single-phase ground fault occurs in the power system, the three phases of the power system become unbalanced, resulting in different magnitudes and phases of the currents in the three phases, which leads to the neutral point voltage not being 0. The neutral point voltage detection module 12 is used to detect the magnitude of the neutral point voltage. When a single-phase ground fault occurs in the power system, different grounding types can be identified based on the neutral point voltage. In this embodiment, when the neutral point voltage exceeds 70V, it is a low-resistance grounding; when the neutral point voltage is below 25V, it is an ultra-high-resistance grounding; and when the neutral point voltage is between 25V and 70V, it is a high-resistance grounding.

[0035] The incremental selection module 13 is used to select the corresponding input resistor according to the magnitude of the neutral point voltage when a ground fault occurs, so as to obtain an incremental current that matches the neutral point voltage; the input resistor is used to connect the neutral point.

[0036] In this embodiment, when a single-phase ground fault occurs in the power system, the three-phase power becomes unbalanced, resulting in zero-sequence current in the three-phase power. The presence of zero-sequence current affects the stability and safety of the power system. First, zero-sequence current causes voltage imbalance in the power system, thus affecting the normal operation of power equipment. Second, zero-sequence current causes electromagnetic interference in the power system, thus affecting the normal operation of electronic equipment. Finally, zero-sequence current also affects the protection devices in the power system, thus affecting the safety of the power system. To reduce the generation of zero-sequence current, arc suppression coils are usually used in power systems to reduce the impact of zero-sequence current on the power system. However, after compensation by the arc suppression coil, the capacitive current at the fault point is canceled out by the inductive current of the arc suppression coil, resulting in the current value detected by the zero-sequence current detection module 14 being too small, making it impossible to accurately select the ground fault line.

[0037] To improve the accuracy of grounding line selection, this embodiment adds an auxiliary selection increment module 13. Based on the neutral point voltage, it switches resistors of different values ​​to the neutral point, ensuring that the incremental current provided by the auxiliary selection increment module 13 to the zero-sequence current detection module 14 is controlled within the range of 25A-50A. The switching resistor is 400Ω for low-resistance grounding, 200Ω for high-resistance grounding, and 133Ω for ultra-high-resistance grounding.

[0038] The zero-sequence current detection module 14 is used to determine grounding faults based on the incremental current matched to the neutral point voltage.

[0039] When a single-phase ground fault occurs in the power system, there is a zero-sequence current in the three-phase power of the power system. The zero-sequence current detection module 14 is used to detect the magnitude of the zero-sequence current, and then the amplitude method and the change method are used to comprehensively determine the ground fault selection line.

[0040] like Figure 2 As shown, in this embodiment, the resistors in the selection increment module 13 include a first resistor, a second resistor, and a third resistor, and the resistance values ​​of the first resistor, the second resistor, and the third resistor are different. When the voltage at the neutral point is greater than a first set value, the selection increment module selects to activate the first resistor. When the voltage at the neutral point is less than a second set value, the selection increment module selects to activate the second resistor. When the voltage at the neutral point is between the first set value and the second set value, the selection increment module selects to activate the third resistor.

[0041] In this embodiment, the resistance of the first resistor is 400Ω, the resistance of the second resistor is 200Ω, and the resistance of the third resistor is 133Ω. When the voltage of the neutral point is greater than 70V, the auxiliary selection increment module 13 selects to switch the first resistor; when the voltage of the neutral point is lower than 40V, the auxiliary selection increment module 13 selects to switch the third resistor; when the voltage of the neutral point is between 40V and 70V, the auxiliary selection increment module 13 selects to switch the second resistor.

[0042] like Figure 3 As shown, in this embodiment, the incremental selection module is also used to select the corresponding input resistor according to the magnitude of the neutral point voltage when the duration of the ground fault exceeds the first preset time.

[0043] In this embodiment, when the power system is normal, the neutral point voltage is ideally 0. However, in actual operation, the three phases of the power system cannot be perfectly symmetrical. Even when the power system is operating normally, the neutral point will still have a certain range of voltage values. Furthermore, due to the complex operating environment of the power system, the neutral point voltage may increase for short periods due to environmental influences. Such short-term voltage increases are considered false grounding. To avoid misjudgment, this embodiment sets a first preset time of 3 seconds. When the fault voltage at the neutral point lasts for more than 3 seconds without significant changes, a single-phase grounding fault (actual grounding) is determined to have occurred in the power system. Then, the appropriate switching resistor is selected based on the specific voltage value of the neutral point.

[0044] like Figure 4 As shown, in this embodiment, the incremental selection module 13 is also used to select the corresponding input resistor according to the magnitude of the neutral point voltage when the occurrence time of the ground fault does not exceed the second preset time and the duration of the ground fault is greater than the third preset time; the occurrence time is the time from the start of the ground fault to the current moment.

[0045] In this embodiment, when a single-phase ground fault occurs in the power system, it may be an intermittent ground fault. This would cause the resistor to be switched too frequently, which would affect the normal operation of the auxiliary selection incremental module 13 over a long period of time. Therefore, in this embodiment, when an intermittent ground fault occurs in the power system, the corresponding resistor will be switched according to the neutral point voltage value as long as the ground fault time exceeds 3 seconds.

[0046] like Figure 5 As shown, in this embodiment, the incremental selection module 13 is also used to select the corresponding input resistor according to the magnitude of the neutral point voltage when the occurrence time of the ground fault does not exceed the second preset time and the duration of the ground fault is less than the fourth preset time; the occurrence time is the time from the start of the ground fault to the current moment.

[0047] If the power system experiences intermittent grounding, the grounding begins between 0 and 7 seconds. If the grounding duration is less than 3 seconds within any time period, the incremental selection module 13 will select an appropriate switching resistor and select the line after 7 seconds based on the voltage limit of the neutral point.

[0048] like Figure 2As shown, in this embodiment, the incremental selection module includes a Zener diode D1, a resistor R1, a Zener diode D2, a resistor R2, a voltage detector U1, a voltage detector U2, a switch Q1, a switch Q2, a relay K1, a relay K2, a switch Q3, a NAND gate U5, a switch Q5, a resistor RX1, and a resistor RX2. The cathode of Zener diode D1 is used to receive the voltage signal output by the neutral point voltage detection module. The cathode of Zener diode D2 is connected to the cathode of Zener diode D1. The anode of Zener diode D1 is grounded through resistor R1 and connected to the input terminal of voltage detector U1. The anode of Zener diode D2 is grounded through resistor R2 and connected to the input terminal of voltage detector U2. The output terminal of voltage detector U1 is connected to the cathode of Zener diode D1 and the control terminal of switch Q1. The output terminal of voltage detector U2 is connected to the cathode of Zener diode D1 and the control terminal of switch Q2. The first terminal of switch Q1... Connect the first input terminal of relay K1, connect the second input terminal of relay K1 to the VCC power supply, ground the second terminal of switching transistor Q1, ground the common terminal of relay K1 through resistor RX1, connect the normally open terminal of relay K1 to the neutral point, connect the normally closed terminal of relay K1 to the normally open terminal of relay K2, connect the first terminal of switching transistor Q3 to the neutral point, connect the second terminal of switching transistor Q3 to the normally open terminal of relay K2, and connect the control terminal of switching transistor Q3 to the first terminal of switching transistor Q2. Connect the first terminal of switching transistor Q2 to the first input terminal of relay K1, ground the second terminal of switching transistor Q2, connect the second input terminal of relay K2 to the VCC power supply, ground the common terminal of relay K2 through resistor RX2, connect the normally closed terminal of relay K2 to the first terminal of switching transistor Q5, connect the second terminal of switching transistor Q5 to the neutral point, connect the control terminal of switching transistor Q5 to the output terminal of NAND gate U5, connect the first input terminal of NAND gate U5 to the first terminal of switching transistor Q1, and connect the second input terminal of NAND gate U5 to the first terminal of switching transistor Q2.

[0049] In this embodiment, when a single-phase ground fault occurs in the power system, a resistor needs to be switched to the neutral point. The value of the switching resistor is mainly determined by the neutral point voltage. The neutral point voltage is used to distinguish the actual ground fault type. In this embodiment, it can be divided into low-resistance ground fault, high-resistance ground fault, and ultra-high-resistance ground fault. The switching resistor corresponding to low-resistance ground fault is 400Ω, the switching resistor corresponding to high-resistance ground fault is 200Ω, and the switching resistor corresponding to ultra-high-resistance ground fault is 133Ω. By incrementally selecting the small-current ground fault, regardless of whether a high-resistance ground fault, ultra-high-resistance ground fault, or low-resistance ground fault occurs, the output current of the auxiliary selection incremental module is controlled between 25A and 50A. Then, the actual faulty line is determined according to the amplitude method and the change method. In this embodiment, resistors RX1 and RX2 are used as switching resistors. The resistance of resistor RX1 is 400Ω, the resistance of resistor RX2 is 200Ω, and the resistance of resistors RX1 and RX2 connected in parallel is 133Ω. These two resistors represent the first resistance, the second resistance, and the third resistance, respectively.

[0050] Specifically, the working principle of the incremental selection module is as follows: the breakdown voltage of Zener diode D1 is greater than that of Zener diode D2. When the voltage output by the neutral point voltage detection module is greater than 70V, both Zener diodes D1 and D2 are broken down and turned on. The input terminals of voltage detectors U1 and U2 are both at high level. Therefore, both voltage detectors U1 and U2 output high level, switch Q1 is turned on, switch Q2 is turned off, relay K1 is energized, and relay K2 does not operate. At this time, the first terminal of switch Q2 can be regarded as low level, NAND gate U5 outputs high level, switch Q5 is turned off, the common terminal of relay K1 is connected to the normally open terminal of relay K1, and resistor RX1 is connected to the neutral point.

[0051] When the voltage output by the neutral point voltage detection module is less than 40V, both Zener diodes D1 and D2 are cut off, and both voltage detectors U1 and U2 output a low level. Switch Q1 is cut off, and switch Q2 is turned on. At this time, the first terminal of switch Q2 can be regarded as a low level. Switch Q3 is turned on, and relay K1 does not operate. At this time, relay K2 is energized and connected. The common terminal of relay K2 is connected to the normally open terminal of relay K2. At this time, resistors RX1 and RX2 are connected in parallel and then connected to the neutral point through switch Q3.

[0052] When the voltage output by the neutral point voltage detection module is between 40V and 70V, Zener diode D1 is cut off and Zener diode D2 is turned on. At this time, voltage detector U1 outputs a low level and voltage detector U2 outputs a high level. Switches Q1 and Q2 are both cut off, and relays K1 and K2 do not operate. The first terminals of switches Q1 and Q2 can be regarded as high level. Therefore, NAND gate U5 outputs a low level, and switch Q5 is turned on. At this time, resistor RX2 is connected to the neutral point.

[0053] Therefore, this embodiment can automatically select a suitable resistor to switch to the neutral point based on the output voltage of the neutral point voltage detection module, providing a larger zero-sequence current for subsequent circuits, and then determine the actual faulty line based on the amplitude method and the change method.

[0054] like Figure 3 As shown, in this embodiment, the neutral point voltage detection module includes a transformer T1, a filter U4, a capacitor C1, resistors R7 and R8, an operational amplifier U3, a resistor R9, a Zener diode D3, and a switching transistor Q4. The first input terminal of transformer T1 is connected to the neutral point, the second input terminal of transformer T1 is grounded, the first output terminal of transformer T1 is connected to the first input terminal of filter U4, the second output terminal of transformer T1 is connected to the second input terminal of filter U4, the second output terminal of filter U4 is connected to the non-inverting input terminal of operational amplifier U3 through resistor R7, and the second output terminal of filter U4 is connected to the positive terminal of capacitor C1. The negative terminal of 1 is grounded, the second output terminal of filter U4 is grounded, the inverting input terminal of operational amplifier U3 is grounded through resistor R8, the output terminal of operational amplifier U3 is connected to the inverting input terminal of operational amplifier U3 through resistor R9, the output terminal of operational amplifier U3 is connected to the cathode of Zener diode D1, the output terminal of operational amplifier U3 is connected to the cathode of Zener diode D3, the anode of Zener diode D3 is connected to the control terminal of switch transistor Q4, the first terminal of switch transistor Q4 is connected to the neutral point, the second terminal of switch transistor Q4 is connected to the normally open terminal of relay K1, the second terminal of switch transistor Q4 is connected to the first terminal of switch transistor Q3, and the second terminal of switch transistor Q4 is connected to the normally closed terminal of relay K2.

[0055] In this embodiment, the neutral point voltage detection module is used to detect the voltage at the neutral point. The working principle of the neutral point voltage detection module is as follows: Transformer T1 converts the high AC voltage at the neutral point into a low AC voltage signal, which is then rectified and filtered by rectifier U4 and capacitor C1 to become a DC signal. However, this DC signal is relatively weak. Operational amplifier U3 forms an amplification circuit to amplify the DC voltage signal, and finally, the amplified voltage is sent to the input terminal of the auxiliary selection incremental module. Ideally, the neutral point voltage is 0 during power system operation. However, in actual operation, due to uncontrollable factors, even without a single-phase ground fault, the neutral point voltage will not be 0. In this case, the neutral point voltage will have a reasonable fluctuation range. In this embodiment, when the voltage output by operational amplifier U3 is less than 15V, it indicates that no single-phase ground fault has occurred in the power system, therefore, it is not necessary to switch the neutral point resistor. When the output voltage of operational amplifier U3 is less than 15V, Zener diode D3 is cut off and switching transistor Q4 is not turned on. Therefore, resistors RX1 and RX2 are disconnected from the neutral point. When the output voltage of operational amplifier U3 exceeds 15V, it indicates that a single-phase ground fault has occurred in the power system. Zener diode D3 breaks down and conducts, the control terminal of switching transistor Q4 becomes high level, and switching transistor Q4 is turned on. Then, the auxiliary incremental module will switch resistors of different values ​​to the neutral point according to the specific voltage value output by operational amplifier U3.

[0056] Second Embodiment

[0057] A small-current grounding line selection auxiliary incremental device corresponding to the above embodiment, Figure 4 This is a flowchart illustrating an incremental method for assisting in the selection of low-current grounding lines, as provided in one embodiment of this disclosure. For ease of explanation, only the parts relevant to the embodiment of this disclosure are shown. References Figure 4 An incremental method for assisting in the selection of low-current grounding lines includes:

[0058] S1: Provides a neutral point for the target power system; the target power system is a system with an ungrounded neutral point.

[0059] S2: Detects the voltage at the neutral point when a ground fault occurs;

[0060] S3: When a ground fault occurs, select the corresponding switching resistor according to the magnitude of the neutral point voltage to obtain an incremental current that matches the neutral point voltage; the switching resistor is used to connect the neutral point.

[0061] S4: Determine the grounding fault based on the incremental current matched to the neutral point voltage.

[0062] Third Embodiment

[0063] See Figure 5 , Figure 5 This is a schematic block diagram of an electronic device provided according to an embodiment of the present disclosure. Figure 5The electronic device 300 in this embodiment may include one or more processors 301, one or more input devices 302, one or more output devices 303, and one or more memories 304. The processors 301, input devices 302, output devices 303, and memories 304 communicate with each other via a communication bus 305. The memories 304 store computer programs, including program instructions. The processors 301 execute the program instructions stored in the memories 304. Specifically, the processors 301 are configured to invoke the program instructions to perform the functions of the modules in the aforementioned device embodiments, for example... Figure 1 The functions of modules 101 to 104 are shown.

[0064] It should be understood that, in the embodiments of this disclosure, the processor 301 may be a central processing unit (CPU), or it may be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor.

[0065] Input device 302 may include a touchpad, a fingerprint sensor (for collecting the user's fingerprint information and fingerprint orientation information), a microphone, etc., and output device 303 may include a display (LCD, etc.), a speaker, etc.

[0066] The memory 304 may include read-only memory and random access memory, and provides instructions and data to the processor 301. A portion of the memory 304 may also include non-volatile random access memory. For example, the memory 304 may also store device type information.

[0067] In specific implementations, the processor 301, input device 302, and output device 303 described in the embodiments of this disclosure can execute the implementation methods described in the first and second embodiments of the incremental method for assisting in the selection of small current grounding lines provided in the embodiments of this disclosure, or they can execute the implementation methods of the electronic devices described in the embodiments of this disclosure, which will not be repeated here.

[0068] Fourth embodiment

[0069] In another embodiment of this disclosure, a computer-readable storage medium is provided. This computer-readable storage medium stores a computer program, which includes program instructions. When executed by a processor, the program instructions implement all or part of the processes in the methods described above. The computer program can also instruct related hardware to complete the process. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include any entity or device capable of carrying computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals.

[0070] The computer-readable storage medium can be an internal storage unit of the electronic device in any of the foregoing embodiments, such as a hard disk or memory of the electronic device. The computer-readable storage medium can also be an external storage device of the electronic device, such as a plug-in hard disk, smart media card (SMC), secure digital card (SD), flash card, etc., equipped on the electronic device. Furthermore, the computer-readable storage medium can include both internal and external storage units of the electronic device. The computer-readable storage medium is used to store computer programs and other programs and data required by the electronic device. The computer-readable storage medium can also be used to temporarily store data that has been output or will be output.

[0071] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this disclosure.

[0072] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the electronic devices and units described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0073] In the several embodiments provided in this application, it should be understood that the disclosed electronic devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces or units, or it may be an electrical, mechanical, or other form of connection.

[0074] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of the embodiments of this disclosure, depending on actual needs.

[0075] Furthermore, the functional units in the various embodiments of this disclosure can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0076] The above are merely specific embodiments of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this disclosure, and these modifications or substitutions should all be covered within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A low-current grounding line selection auxiliary incremental device, characterized in that, include: Grounding transformer module, used to provide a neutral point for the target power system; The target power system is a system with an ungrounded neutral point; A neutral point voltage detection module is used to detect the voltage at the neutral point when a ground fault occurs. The incremental selection module is used to select the corresponding input resistor according to the magnitude of the neutral point voltage when a ground fault occurs, so as to obtain an incremental current that matches the neutral point voltage. The input resistor is used to connect the neutral point; The zero-sequence current detection module is used to determine grounding faults based on the incremental current matched to the voltage of the neutral point. The resistor includes a first resistor, a second resistor, and a third resistor, and the resistance values ​​of the first resistor, the second resistor, and the third resistor are different. When the voltage at the neutral point is greater than the first set value, the auxiliary selection incremental module selects to connect the first resistor; When the voltage at the neutral point is less than the second set value, the auxiliary selection incremental module selects to engage the second resistor. When the voltage of the neutral point is between the first set value and the second set value, the auxiliary selection incremental module selects to connect the third resistor; The incremental selection module is also used to select the corresponding input resistor according to the magnitude of the neutral point voltage when the duration of the ground fault exceeds the first preset time. The incremental selection module includes a Zener diode D1, a resistor R1, a Zener diode D2, a resistor R2, a voltage detector U1, a voltage detector U2, a switch Q1, a switch Q2, a relay K1, a relay K2, a switch Q3, a NAND gate U5, a switch Q5, a resistor RX1, and a resistor RX2. The cathode of Zener diode D1 is used to receive the voltage signal output by the neutral point voltage detection module. The cathode of Zener diode D2 is connected to the cathode of Zener diode D1. The anode of Zener diode D1 is grounded through resistor R1 and connected to the input terminal of voltage detector U1. The anode of Zener diode D2 is grounded through resistor R2 and connected to the input terminal of voltage detector U2. The output terminal of voltage detector U1 is connected to the cathode of Zener diode D1, the output terminal of voltage detector U1 is connected to the control terminal of switching transistor Q1, the output terminal of voltage detector U2 is connected to the cathode of Zener diode D1, the output terminal of voltage detector U2 is connected to the control terminal of switching transistor Q2, the first terminal of switching transistor Q1 is connected to the first input terminal of relay K1, the second input terminal of relay K1 is connected to VCC power supply, the second terminal of switching transistor Q1 is grounded, the common terminal of relay K1 is grounded through resistor RX1, the normally open terminal of relay K1 is connected to the neutral point, the normally closed terminal of relay K1 is connected to the normally open terminal of relay K2, the first terminal of switching transistor Q3 is connected to the neutral point, the second terminal of switching transistor Q3 is connected to the normally open terminal of relay K2, and the control terminal of switching transistor Q3 is connected to the first terminal of switching transistor Q2. The first terminal of the switching transistor Q2 is connected to the first input terminal of the relay K1, the second terminal of the switching transistor Q2 is grounded, the second input terminal of the relay K2 is connected to the VCC power supply, the common terminal of the relay K2 is grounded through the resistor RX2, the normally closed terminal of the relay K2 is connected to the first terminal of the switching transistor Q5, the second terminal of the switching transistor Q5 is connected to the neutral point, the control terminal of the switching transistor Q5 is connected to the output terminal of the NAND gate U5, the first input terminal of the NAND gate U5 is connected to the first terminal of the switching transistor Q1, and the second input terminal of the NAND gate U5 is connected to the first terminal of the switching transistor Q2.

2. The incremental device for selecting low-current grounding lines according to claim 1, characterized in that, The incremental selection module is also used to select the corresponding input resistor based on the voltage of the neutral point when the occurrence time of the ground fault does not exceed the second preset time and the duration of the ground fault is greater than the third preset time; the occurrence time is the time from the start of the ground fault to the current moment.

3. The incremental device for selecting low-current grounding lines according to claim 1, characterized in that, The incremental selection module is also used to select the corresponding input resistor according to the magnitude of the neutral point voltage when the occurrence time of the ground fault does not exceed the second preset time and the duration of the ground fault is less than the fourth preset time; the occurrence time is the time from the start of the ground fault to the current moment.

4. The incremental device for selecting low-current grounding lines according to claim 1, characterized in that, The neutral point voltage detection module includes a transformer T1, a filter U4, a capacitor C1, a resistor R7, a resistor R8, an operational amplifier U3, a resistor R9, a Zener diode D3, and a switching transistor Q4. The first input terminal of transformer T1 is connected to the neutral point, the second input terminal of transformer T1 is grounded, the first output terminal of transformer T1 is connected to the first input terminal of filter U4, the second output terminal of transformer T1 is connected to the second input terminal of filter U4, the second output terminal of filter U4 is connected to the non-inverting input terminal of operational amplifier U3 through resistor R7, the second output terminal of filter U4 is connected to the positive terminal of capacitor C1, the negative terminal of capacitor C1 is grounded, the second output terminal of filter U4 is grounded, and the inverting input terminal of operational amplifier U3 is connected to the non-inverting input terminal of operational amplifier U3 through resistor R7. R8 is grounded. The output terminal of operational amplifier U3 is connected to the inverting input terminal of operational amplifier U3 through resistor R9. The output terminal of operational amplifier U3 is connected to the cathode of Zener diode D1. The output terminal of operational amplifier U3 is connected to the cathode of Zener diode D3. The anode of Zener diode D3 is connected to the control terminal of switching transistor Q4. The first terminal of switching transistor Q4 is connected to the neutral point. The second terminal of switching transistor Q4 is connected to the normally open terminal of relay K1. The second terminal of switching transistor Q4 is connected to the first terminal of switching transistor Q3. The second terminal of switching transistor Q4 is connected to the normally closed terminal of relay K2.

5. A method for incremental selection of grounding faults with low current, characterized in that, include: Provide a neutral point for the target power system; The target power system is a system with an ungrounded neutral point; Detect the voltage at the neutral point when a ground fault occurs; When a ground fault occurs, the corresponding switching resistor is selected according to the magnitude of the neutral point voltage to obtain an incremental current that matches the neutral point voltage. The input resistor is used to connect the neutral point; The ground fault is determined based on the incremental current matched to the voltage at the neutral point; The resistor includes a first resistor, a second resistor, and a third resistor, and the resistance values ​​of the first resistor, the second resistor, and the third resistor are different. When the voltage at the neutral point is greater than the first set value, the auxiliary selection incremental module selects to connect the first resistor; When the voltage at the neutral point is less than the second set value, the auxiliary selection incremental module selects to engage the second resistor. When the voltage of the neutral point is between the first set value and the second set value, the auxiliary selection incremental module selects to connect the third resistor; The incremental selection module is also used to select the corresponding input resistor according to the magnitude of the neutral point voltage when the duration of the ground fault exceeds the first preset time. The incremental selection module includes a Zener diode D1, a resistor R1, a Zener diode D2, a resistor R2, a voltage detector U1, a voltage detector U2, a switch Q1, a switch Q2, a relay K1, a relay K2, a switch Q3, a NAND gate U5, a switch Q5, a resistor RX1, and a resistor RX2. The cathode of Zener diode D1 is used to receive the voltage signal output by the neutral point voltage detection module. The cathode of Zener diode D2 is connected to the cathode of Zener diode D1. The anode of Zener diode D1 is grounded through resistor R1 and connected to the input terminal of voltage detector U1. The anode of Zener diode D2 is grounded through resistor R2 and connected to the input terminal of voltage detector U2. The output terminal of voltage detector U1 is connected to the cathode of Zener diode D1, the output terminal of voltage detector U1 is connected to the control terminal of switching transistor Q1, the output terminal of voltage detector U2 is connected to the cathode of Zener diode D1, the output terminal of voltage detector U2 is connected to the control terminal of switching transistor Q2, the first terminal of switching transistor Q1 is connected to the first input terminal of relay K1, the second input terminal of relay K1 is connected to VCC power supply, the second terminal of switching transistor Q1 is grounded, the common terminal of relay K1 is grounded through resistor RX1, the normally open terminal of relay K1 is connected to the neutral point, the normally closed terminal of relay K1 is connected to the normally open terminal of relay K2, the first terminal of switching transistor Q3 is connected to the neutral point, the second terminal of switching transistor Q3 is connected to the normally open terminal of relay K2, and the control terminal of switching transistor Q3 is connected to the first terminal of switching transistor Q2. The first terminal of the switching transistor Q2 is connected to the first input terminal of the relay K1, the second terminal of the switching transistor Q2 is grounded, the second input terminal of the relay K2 is connected to the VCC power supply, the common terminal of the relay K2 is grounded through the resistor RX2, the normally closed terminal of the relay K2 is connected to the first terminal of the switching transistor Q5, the second terminal of the switching transistor Q5 is connected to the neutral point, the control terminal of the switching transistor Q5 is connected to the output terminal of the NAND gate U5, the first input terminal of the NAND gate U5 is connected to the first terminal of the switching transistor Q1, and the second input terminal of the NAND gate U5 is connected to the first terminal of the switching transistor Q2.

6. An electronic device, characterized in that, include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the steps of the method as claimed in claim 5.

7. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the method as described in claim 5.

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