Direct current system fault detection device based on frequency conversion signal and detection method thereof

Abstract

The invention discloses a frequency conversion signal-based direct current system fault detection device and a detection method thereof. The device comprises a signal source module, a mobile fault detection module and a split core type current transformer module. The detection method comprises the following steps: acquiring bus-to-ground waveform amplitude data of the direct current system and ground insulation state data of the direct current system; acquiring a variable-frequency current characteristic signal of the direct-current system; and judging according to the bus-to-ground waveform amplitude data of the direct current system, the ground insulation state data of the direct current system and the variable frequency current characteristic signal of the direct current system to obtain a ground fault judgment result of the direct current system. According to the embodiment of the invention, the induction of feeder characteristic signals can be improved, the influence of interference signals can be reduced, and more accurate DC system grounding fault detection and positioning can be realized. The method can be widely applied to the technical field of direct-current grounding fault searching.

Description

Technical Field

[0001] The present application relates to the technical field of DC grounding fault detection, and in particular to a DC system fault detection device and a detection method thereof based on a variable frequency signal. Background Art

[0002] In a substation, the DC system normally provides a reliable DC power supply for control signals, relay protection, automatic devices, circuit breaker tripping and closing operation circuits, etc. The reliability of the DC system plays a vital role in the safe operation of the substation and is the guarantee of equipment safety.

[0003] The DC system of the substation adopts the ground-insulated operation mode, but because the DC system is relatively complex and is connected to the terminal box and operating mechanism of the outdoor power distribution device through cables, it is easy to ground. When the DC system is grounded, the signal, protection and control circuits may malfunction or refuse to operate, and there is a possibility of fuse melting and burning relay contacts, which may damage the equipment, causing large-scale power outages and system collapse. When multiple grounding occurs, it is very likely to cause the switch to trip, which will lead to power outages in the power grid and cause economic losses.

[0004] In the related art, the grounding search method of the DC system of a substation is divided into the loop pulling method and the single-frequency AC injection method. The loop pulling method is to stop the DC power supply of the loop, but it is not intuitive for multi-loop grounding faults and is prone to cause false operation or false locking of the protection device; the single-frequency AC injection method is that the injection of AC signals will affect the normal operation of the DC system, and is easily affected by branch distributed capacitance and interference signals, resulting in inaccurate positioning.

[0005] In summary, the technical problems existing in the relevant technologies need to be improved. Summary of the invention

[0006] The main purpose of the embodiments of the present application is to propose a DC system fault detection device and a detection method based on variable frequency signals, which can improve the induction of feeder characteristic signals and reduce the influence of interference signals, thereby achieving more accurate DC system grounding fault detection and positioning.

[0007] To achieve the above-mentioned purpose, one aspect of an embodiment of the present application provides a DC system fault detection device based on a variable frequency signal, the device comprising a signal source module, a mobile fault detection module and a clamp current transformer module, the output end of the signal source module is connected to the first input end of the mobile fault detection module, the output end of the clamp current transformer module is connected to the second input end of the mobile fault detection module, wherein:

[0008] The signal source module is used to obtain the bus-to-ground waveform amplitude data of the DC system and the insulation status data of the DC system to the ground;

[0009] The clamp current transformer module is used to obtain the variable frequency current characteristic signal of the DC system;

[0010] The mobile fault detection module is used to make a judgment based on the busbar-to-ground waveform amplitude data of the DC system, the ground insulation status data of the DC system, and the variable frequency current characteristic signal of the DC system to obtain a ground fault judgment result of the DC system.

[0011] In some embodiments, the signal source module includes a control unit, a main control unit, a first communication unit, a first display unit and a measuring unit, the first output end of the main control unit is connected to the input end of the control unit, the second output end of the main control unit is connected to the input end of the first communication unit, the third output end of the main control unit is connected to the input end of the first display unit, and the output end of the measuring unit is connected to the input end of the main control unit, wherein:

[0012] The measuring unit is used to obtain the ground parameters of the DC system, where the ground parameters of the DC system include ground voltage data of the DC system and ground insulation state data of the DC system;

[0013] The main control unit is used to control the operation of the control unit, the first communication unit, the first display unit and the measuring unit;

[0014] The control unit is used to perform regulation and processing according to the ground parameters of the DC system to obtain the bus-to-ground waveform amplitude data of the DC system;

[0015] The first communication unit is used for wireless communication with the mobile fault detection module;

[0016] The first display unit is used to display the busbar-to-ground waveform amplitude data of the DC system and the insulation status data of the DC system to the ground.

[0017] In some embodiments, the measurement unit includes a busbar-to-ground insulation measurement unit and a busbar-to-ground voltage measurement unit, the ground insulation state data of the DC system includes ground resistance data of the DC system and ground capacitance data of the DC system, the output end of the busbar-to-ground insulation measurement unit is connected to the first input end of the main control unit, and the output end of the busbar-to-ground voltage measurement unit is connected to the second input end of the main control unit, wherein:

[0018] The busbar-to-ground insulation measurement unit is used to obtain the voltage data of the DC system to the ground;

[0019] The busbar-to-ground voltage measurement unit is used to obtain the ground resistance data of the DC system and the ground capacitance data of the DC system.

[0020] In some embodiments, the control unit includes an adjustable frequency control unit, an adjustable resistance control unit and a polarity control unit, the first output end of the main control unit is connected to the input unit of the adjustable frequency control unit, the output end of the adjustable frequency control unit is connected to the input end of the adjustable resistance control unit, and the output end of the adjustable resistance control unit is connected to the input end of the polarity control unit, wherein:

[0021] The adjustable frequency control unit is used to perform frequency control processing on the ground parameters of the DC system to obtain a variable frequency signal, wherein the variable frequency signal includes a signal with a first frequency and a signal with a second frequency;

[0022] The adjustable resistance control unit is used to convert the frequency conversion signal to obtain a frequency conversion current signal;

[0023] The polarity control unit is used to transmit the variable frequency current signal to the DC system to obtain bus-to-ground waveform amplitude data of the DC system.

[0024] In some embodiments, the mobile fault detection module includes an operational amplifier unit, a microprocessing unit, a voice unit, a second display unit and a second communication unit, the output end of the operational amplifier unit is connected to the first input end of the microprocessing unit, the first output end of the microprocessing unit is connected to the input end of the voice unit, the second output end of the microprocessing unit is connected to the input end of the second display unit, and the output end of the second communication unit is connected to the second input end of the microprocessing unit, wherein:

[0025] The operational amplifier unit is used to perform operational amplification and filtering processing on the variable frequency current characteristic signal of the DC system to obtain a pre-processed variable frequency current characteristic signal;

[0026] The microprocessor unit is used to control the operation of the operational amplifier unit, the voice unit, the second display unit and the second communication unit;

[0027] The voice unit is used to broadcast the ground fault judgment result of the DC system;

[0028] The second display unit is used to display the ground fault judgment result of the DC system;

[0029] The second communication unit is used for wireless communication with the signal source module.

[0030] To achieve the above object, another aspect of the embodiment of the present application provides a detection method of a DC system fault detection device based on a variable frequency signal, the method comprising the following steps:

[0031] Acquiring busbar-to-ground waveform amplitude data of a DC system and insulation status data of the DC system to ground;

[0032] Acquiring a variable frequency current characteristic signal of the DC system;

[0033] A judgment is made based on the busbar-to-ground waveform amplitude data of the DC system, the insulation status data of the DC system to ground, and the variable frequency current characteristic signal of the DC system to obtain a ground fault judgment result of the DC system.

[0034] In some embodiments, the obtaining of bus-to-ground waveform amplitude data of a DC system and insulation status data of the DC system to ground includes:

[0035] Acquire the ground parameters of the DC system, where the ground parameters of the DC system include ground voltage data of the DC system and ground insulation status data of the DC system;

[0036] According to the ground parameters of the DC system, regulation and processing are performed to obtain bus-to-ground waveform amplitude data of the DC system.

[0037] In some embodiments, the step of performing control processing according to the ground parameters of the DC system to obtain the bus-to-ground waveform amplitude data of the DC system includes:

[0038] Performing frequency control processing on the ground parameters of the DC system to obtain a variable frequency signal, wherein the variable frequency signal includes a signal with a first frequency and a signal with a second frequency;

[0039] Converting the frequency conversion signal to obtain a frequency conversion current signal;

[0040] The variable frequency current signal is transmitted to the DC system to obtain bus-to-ground waveform amplitude data of the DC system.

[0041] In some embodiments, the determining according to the busbar-to-ground waveform amplitude data of the DC system, the ground insulation state data of the DC system, and the variable frequency current characteristic signal of the DC system to obtain the ground fault determination result of the DC system includes:

[0042] Determine the current value of the variable frequency current characteristic signal of the DC system to obtain the current value of the variable frequency current characteristic signal with a first frequency and the current value of the variable frequency current characteristic signal with a second frequency;

[0043] Determine the impedance value of the variable frequency current characteristic signal of the DC system according to the bus-to-ground waveform amplitude data of the DC system in combination with Ohm's law, and obtain the impedance value of the variable frequency current characteristic signal with a first frequency and the impedance value of the variable frequency current characteristic signal with a second frequency;

[0044] Calculate the grounding resistance value of the DC system by combining the insulation state data of the DC system with the impedance value of the variable frequency current characteristic signal of the DC system;

[0045] A ground fault judgment result of the DC system is obtained by performing a judgment based on the ground resistance value of the DC system, the current value of the variable frequency current characteristic signal with the first frequency, and the current value of the variable frequency current characteristic signal with the second frequency.

[0046] In some embodiments, the determining according to the grounding resistance value of the DC system, the current value of the variable frequency current characteristic signal with the first frequency, and the current value of the variable frequency current characteristic signal with the second frequency to obtain the grounding fault determination result of the DC system includes:

[0047] If the current value of the variable frequency current characteristic signal with the first frequency and the current value of the variable frequency current characteristic signal with the second frequency are both 0, the ground fault judgment result of the DC system is that there is no ground fault;

[0048] If the current value of the variable frequency current characteristic signal with the first frequency and the current value of the variable frequency current characteristic signal with the second frequency are both not 0, and the grounding resistance value of the DC system is less than a preset threshold, the grounding fault judgment result of the DC system is that a grounding fault exists.

[0049] The embodiments of the present application include at least the following beneficial effects: The present application provides a DC system fault detection device and a detection method based on a variable frequency signal. The scheme obtains the busbar-to-ground waveform amplitude data of the DC system and the insulation status data of the DC system to the ground, and then judges the ground fault of the DC system based on the feedback variable frequency current characteristic signal of the DC system. The variable frequency current characteristic signal of the DC system is used to improve the induction of the feeder characteristic signal and avoid some useless interference signals. The frequency conversion method is used for calculation to avoid the influence of excessive distributed capacitance and excessive grounding resistance, thereby achieving more accurate DC system grounding fault detection and positioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a structural schematic diagram of a DC system fault detection device based on variable frequency signals provided in an embodiment of the present application;

[0051] Figure 2It is a schematic diagram of the steps of a detection method of a DC system fault detection device based on a variable frequency signal provided in an embodiment of the present application;

[0052] Figure 3 is a schematic diagram of the structure of the signal source module provided in an embodiment of the present application;

[0053] Figure 4 is a structural schematic diagram of a clamp-on current transformer module provided in an embodiment of the present application;

[0054] Figure 5 It is a structural schematic diagram of the mobile fault detection module provided in an embodiment of the present application. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the embodiments of the present application. They are only examples of systems and methods consistent with some aspects of the embodiments of the present application as detailed in the attached claims.

[0056] It is understood that the terms "first", "second", etc. used in this application can be used to describe various concepts in this article, but unless otherwise specified, these concepts are not limited by these terms. These terms are only used to distinguish one concept from another concept. For example, without departing from the scope of the embodiment of the present application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the words "if" and "if" as used herein can be interpreted as "at the time of" or "when" or "in response to determination".

[0057] The terms "at least one", "multiple", "each", "any", etc. used in this application, at least one includes one, two or more, multiple includes two or more, each refers to each of the corresponding multiple, and any refers to any one of the multiple.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0059] Reference Figure 1 , Figure 1A schematic diagram of a DC system fault detection device based on a variable frequency signal according to an embodiment of the present invention is provided. Figure 1 The device includes a signal source module, a mobile fault detection module and a clamp current transformer module, the output end of the signal source module is connected to the first input end of the mobile fault detection module, and the output end of the clamp current transformer module is connected to the second input end of the mobile fault detection module, wherein:

[0060] The signal source module is used to obtain the busbar-to-ground waveform amplitude data of the DC system and the insulation status data of the DC system to the ground;

[0061] In this embodiment, after the signal source module detects the insulation of the DC system to the ground, it will cause the DC system bus to generate a current characteristic signal with a regularly changing frequency to the ground.

[0062] Specifically, Figure 3 As shown, the signal source module includes a control unit, a main control unit, a first communication unit, a first display unit and a measuring unit, wherein the first output end of the main control unit is connected to the input end of the control unit, the second output end of the main control unit is connected to the input end of the first communication unit, the third output end of the main control unit is connected to the input end of the first display unit, and the output end of the measuring unit is connected to the input end of the main control unit, wherein the measuring unit is used to obtain the ground parameters of the DC system, and the ground parameters of the DC system include the ground voltage data of the DC system and the ground insulation status data of the DC system; the main control unit is used to control the operation of the control unit, the first communication unit, the first display unit and the measuring unit; the control unit is used to perform regulation and processing according to the ground parameters of the DC system to obtain the bus-to-ground waveform amplitude data of the DC system; the first communication unit is used to perform wireless communication with the mobile fault detection module; and the first display unit is used to display the bus-to-ground waveform amplitude data of the DC system and the ground insulation status data of the DC system.

[0063] Further, the measuring unit in the embodiment of the present invention is described, the measuring unit includes a busbar-to-ground insulation measuring unit and a busbar-to-ground voltage measuring unit, the ground insulation status data of the DC system includes the ground resistance data of the DC system and the ground capacitance data of the DC system, the output end of the busbar-to-ground insulation measuring unit is connected to the first input end of the main control unit, and the output end of the busbar-to-ground voltage measuring unit is connected to the second input end of the main control unit, wherein the busbar-to-ground insulation measuring unit is used to obtain the ground voltage data of the DC system; the busbar-to-ground voltage measuring unit is used to obtain the ground resistance data of the DC system and the ground capacitance data of the DC system.

[0064] Furthermore, the control unit in the embodiment of the present invention is explained, and the control unit includes an adjustable frequency control unit, an adjustable resistance control unit and a polarity control unit. The first output end of the main control unit is connected to the input unit of the adjustable frequency control unit, the output end of the adjustable frequency control unit is connected to the input end of the adjustable resistance control unit, and the output end of the adjustable resistance control unit is connected to the input end of the polarity control unit, wherein the adjustable frequency control unit is used to perform frequency control processing on the ground parameters of the DC system to obtain a variable frequency signal, and the variable frequency signal includes a signal with a first frequency and a signal with a second frequency; the adjustable resistance control unit is used to convert the variable frequency signal to obtain a variable frequency current signal; the polarity control unit is used to transmit the variable frequency current signal to the DC system to obtain the bus-to-ground waveform amplitude data of the DC system.

[0065] The clamp-on current transformer module is used to obtain the variable frequency current characteristic signal of the DC system;

[0066] The mobile fault detection module is used to make a judgment based on the busbar-to-ground waveform amplitude data of the DC system, the insulation status data of the DC system to the ground, and the variable frequency current characteristic signal of the DC system to obtain the ground fault judgment result of the DC system.

[0067] In this embodiment, the mobile fault detection device detects the presence and magnitude of the variable frequency characteristic signal of the feeder through a clamp-on current transformer to determine whether the DC feeder has a ground fault.

[0068] Specifically, Figure 5 As shown, the mobile fault detection module includes an operational amplifier unit, a microprocessing unit, a voice unit, a second display unit and a second communication unit, the output end of the operational amplifier unit is connected to the first input end of the microprocessing unit, the first output end of the microprocessing unit is connected to the input end of the voice unit, the second output end of the microprocessing unit is connected to the input end of the second display unit, and the output end of the second communication unit is connected to the second input end of the microprocessing unit, wherein the operational amplifier unit is used to perform operational amplification and filtering processing on the variable frequency current characteristic signal of the DC system to obtain a pre-processed variable frequency current characteristic signal; the microprocessing unit is used to control the operation of the operational amplifier unit, the voice unit, the second display unit and the second communication unit; the voice unit is used to broadcast the ground fault judgment result of the DC system; the second display unit is used to display the ground fault judgment result of the DC system; and the second communication unit is used to communicate wirelessly with the signal source module.

[0069] In summary, the DC system fault detection device in the embodiment of the present invention consists of three parts: a signal source, a mobile fault detection device and a clamp-on current transformer. After the signal source is connected to the DC system, it will detect the insulation state of the DC system, and generate a characteristic signal with a regularly changing frequency between the bus and the ground by frequency conversion and switching variable resistance. The signal source transmits the detection data to the mobile fault detection device through a wireless communication unit; the mobile fault detection device detects the presence of a frequency conversion characteristic signal in the DC system feeder through the connected clamp-on current transformer to determine whether there is a ground fault, and then analyzes and calculates the insulation resistance of the cable according to the size of the frequency conversion characteristic signal, thereby quickly and accurately locating the ground fault of the DC system.

[0070] See also Figure 2 The embodiment of the present application further provides a detection method of a DC system fault detection device based on a variable frequency signal, which can implement the above-mentioned DC system fault detection device based on a variable frequency signal, and the system includes:

[0071] S100, obtaining busbar-to-ground waveform amplitude data of a DC system and insulation status data of the DC system to ground;

[0072] It should be noted that, in some embodiments, step S100 may include:

[0073] S110, obtaining ground parameters of the DC system, where the ground parameters of the DC system include ground voltage data of the DC system and ground insulation status data of the DC system;

[0074] Specifically, in this embodiment, the signal source is connected to the DC system, the positive interface of the signal source is connected to the positive pole of the DC system, the negative interface of the signal source is connected to the negative pole of the DC system, and the ground interface of the signal source is connected to the ground of the DC system. After the signal source is connected to the DC system, the signal source is started. The signal source will detect the DC system voltage to ground through the bus-to-ground measurement unit, and detect the DC system resistance to ground and the system capacitance to ground through the bus-to-ground insulation measurement unit.

[0075] S120, performing control processing according to the ground parameters of the DC system to obtain busbar-to-ground waveform amplitude data of the DC system.

[0076] In some embodiments, step S120 may include:

[0077] S121, performing frequency control processing on the ground parameter of the DC system to obtain a variable frequency signal, where the variable frequency signal includes a signal with a first frequency and a signal with a second frequency;

[0078] In some specific embodiments, the signal source has an adjustable frequency control unit that controls the frequency of the signal output according to the detected insulation condition to the ground and the system capacitance. The regularly changing frequencies are low frequencies f1=0.5Hz and f2=0.1Hz, and the signal time of the output frequencies f1 and f2 are each a complete cycle.

[0079] S122, converting the frequency conversion signal to obtain a frequency conversion current signal;

[0080] In some specific embodiments, the frequency-converted signal is converted into an adjustable current signal after passing through the adjustable resistance control unit, so that after being connected to the DC system, the DC system voltage to ground is fixed at an amplitude U, and U is not greater than 10% of the DC bus voltage.

[0081] S123, transmitting the variable frequency current signal to the DC system to obtain the bus-to-ground waveform amplitude data of the DC system

[0082] In some specific embodiments, the signal source then connects the regulated variable frequency current signal to the DC system through a polarity control unit. When the positive voltage to ground of the DC system is less than the negative voltage to ground, the signal is connected between the positive pole of the DC system and the ground; when the negative voltage to ground of the DC system is less than the positive voltage to ground, the signal is connected between the negative pole of the DC system and the ground.

[0083] Finally, the signal source displays the detection information through the LCD display unit, namely the first display unit, and transmits the busbar-to-ground waveform amplitude U and the ground insulation status information to the mobile fault detection device through the first wireless communication unit.

[0084] S200, obtaining a variable frequency current characteristic signal of a DC system;

[0085] It should be noted that in some specific embodiments, the clamp-on current transformer uses the principle of electromagnetic induction to measure current, and the magnetic core of the clamp-on current transformer is in a clamp-shaped shape, such as Figure 4 As shown, the measured current wire is placed in the jaws and the magnetic core is closed. n1 The conductor is the primary side n1 of the transformer, so an induced current i will be generated on the secondary side n2 of the transformer core winding. n2 According to the principle of electromagnetic induction, n1×i n1 =n2×i n2 ,i n2 The size of is related to the number of turns of the primary side and the secondary side of the transformer and the current. n2 The current magnitude i of the secondary current conductor can be obtained. n1 =k×i n2 , k represents the clamp calibration current coefficient.

[0086] S300, determining according to the busbar-to-ground waveform amplitude data of the DC system, the insulation status data of the DC system to the ground, and the variable frequency current characteristic signal of the DC system to obtain a ground fault determination result of the DC system;

[0087] It should be noted that, in some embodiments, step S300 may include:

[0088] S310, determining a current value of a variable frequency current characteristic signal of a DC system, and obtaining a current value of a variable frequency current characteristic signal having a first frequency and a current value of a variable frequency current characteristic signal having a second frequency;

[0089] In this embodiment, the mobile fault detection device receives the DC system bus voltage signal amplitude U sent by the signal source through the wireless communication unit, the clamp current transformer is connected to the mobile fault detection device, the device performs operational amplification and filtering on the current signal induced by the transformer, and further performs calculation and analysis on the processed signal waveform. The DC system voltage signal amplitude is U, and the current magnitude i1 of the mobile fault detection device detection signal frequency f1 is expressed as:

[0090]

[0091] The current magnitude of the mobile fault detection equipment detection signal frequency f2 is i2, and its expression is:

[0092]

[0093] S320, determining the impedance value of the variable frequency current characteristic signal of the DC system according to the bus-to-ground waveform amplitude data of the DC system in combination with Ohm's law, and obtaining the impedance value of the variable frequency current characteristic signal with a first frequency and the impedance value of the variable frequency current characteristic signal with a second frequency;

[0094] In this embodiment, the total impedances Z1 and Z1 of the feeder at frequencies f1 and f2 are calculated according to Ohm's law, and the expressions are:

[0095]

[0096] In the above formula, Z1 represents the impedance value of the variable frequency current characteristic signal with a first frequency, Z2 represents the impedance value of the variable frequency current characteristic signal with a second frequency, U represents the bus-to-ground waveform amplitude data of the DC system, i1 represents the current value of the variable frequency current characteristic signal with the first frequency, and i2 represents the current value of the variable frequency current characteristic signal with the second frequency.

[0097] S330, calculating the grounding resistance value of the DC system by combining the insulation state data of the DC system with the impedance value of the variable frequency current characteristic signal of the DC system;

[0098] In this embodiment, according to the parallel model of the grounding resistance R and the capacitor C, the expression is:

[0099]

[0100] In summary, the grounding resistance value of the DC system can be obtained, and its expression is:

[0101]

[0102] S340, making a judgment based on the grounding resistance value of the DC system, the current value of the variable frequency current characteristic signal with the first frequency, and the current value of the variable frequency current characteristic signal with the second frequency, to obtain a grounding fault judgment result of the DC system.

[0103] It should also be noted that the grounding fault judgment result of the DC system includes no grounding fault and the presence of a grounding fault, wherein, if the current value of the variable frequency current characteristic signal with the first frequency and the current value of the variable frequency current characteristic signal with the second frequency are both 0, then the grounding fault judgment result of the DC system is that there is no grounding fault; if the current value of the variable frequency current characteristic signal with the first frequency and the current value of the variable frequency current characteristic signal with the second frequency are both not 0, and the grounding resistance value of the DC system is less than the preset threshold value, then the grounding fault judgment result of the DC system is that there is a grounding fault.

[0104] In some specific embodiments, the mobile fault detection device will determine whether the feeder branch clamped by the clamp-on transformer has a ground fault through the size of R, i1 and i2. When i1 or i2 is equal to 0, the device will determine that the feeder has no ground fault; when i1 or i2 is not equal to 0 and R is less than the set 500kΩ threshold, the device will determine that the feeder has a ground fault. Finally, the mobile fault detection device will display the measurement results through the display unit and broadcast them through the voice unit.

[0105] In summary, the embodiment of the present invention uses the frequency conversion signal method for the first time to locate the DC system feeder grounding fault, and uses a high-precision clamp-on mutual inductor and a high-order operational amplifier filter circuit to improve the induction of the feeder characteristic signal and avoid some useless interference signals, and uses the frequency conversion method to calculate the grounding resistance to avoid the influence of excessive distributed capacitance and excessive grounding resistance, thereby effectively solving the problems of signal interference, excessive branch capacitance, and high branch resistance in the process of searching for grounding, and further solving the problem of overall insulation degradation of the DC system branch, thereby more accurately locating the grounding fault.

[0106] It can be understood that the contents of the above method embodiments are all applicable to the present system embodiments, the functions specifically implemented by the present system embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0107] The preferred embodiments of the present invention are described above with reference to the accompanying drawings, but the scope of the rights of the present invention is not limited thereto. Any modification, equivalent substitution and improvement made by a person skilled in the art without departing from the scope and essence of the present invention should be within the scope of the rights of the present invention.

Claims

1. A DC system fault detection device based on variable frequency signal, characterized in that: The device comprises a signal source module, a mobile fault detection module and a clamp current transformer module, wherein the output end of the signal source module is connected to the first input end of the mobile fault detection module, and the output end of the clamp current transformer module is connected to the second input end of the mobile fault detection module, wherein: The signal source module is used to obtain the bus-to-ground waveform amplitude data of the DC system and the insulation status data of the DC system to the ground; The clamp current transformer module is used to obtain the variable frequency current characteristic signal of the DC system; The mobile fault detection module is used to make a judgment based on the busbar-to-ground waveform amplitude data of the DC system, the ground insulation status data of the DC system, and the variable frequency current characteristic signal of the DC system to obtain a ground fault judgment result of the DC system.

2. The device according to claim 1, characterized in that The signal source module includes a control unit, a main control unit, a first communication unit, a first display unit and a measuring unit, wherein the first output end of the main control unit is connected to the input end of the control unit, the second output end of the main control unit is connected to the input end of the first communication unit, the third output end of the main control unit is connected to the input end of the first display unit, and the output end of the measuring unit is connected to the input end of the main control unit, wherein: The measuring unit is used to obtain the ground parameters of the DC system, where the ground parameters of the DC system include ground voltage data of the DC system and ground insulation state data of the DC system; The main control unit is used to control the operation of the control unit, the first communication unit, the first display unit and the measuring unit; The control unit is used to perform regulation and processing according to the ground parameters of the DC system to obtain the bus-to-ground waveform amplitude data of the DC system; The first communication unit is used for wireless communication with the mobile fault detection module; The first display unit is used to display the busbar-to-ground waveform amplitude data of the DC system and the insulation status data of the DC system to the ground.

3. The device according to claim 2, characterized in that The measuring unit includes a busbar-to-ground insulation measuring unit and a busbar-to-ground voltage measuring unit, the ground insulation state data of the DC system includes ground resistance data of the DC system and ground capacitance data of the DC system, the output end of the busbar-to-ground insulation measuring unit is connected to the first input end of the main control unit, and the output end of the busbar-to-ground voltage measuring unit is connected to the second input end of the main control unit, wherein: The busbar-to-ground insulation measurement unit is used to obtain the voltage data of the DC system to the ground; The busbar-to-ground voltage measurement unit is used to obtain the ground resistance data of the DC system and the ground capacitance data of the DC system.

4. The device according to claim 2, characterized in that The control unit includes an adjustable frequency control unit, an adjustable resistance control unit and a polarity control unit, the first output end of the main control unit is connected to the input unit of the adjustable frequency control unit, the output end of the adjustable frequency control unit is connected to the input end of the adjustable resistance control unit, and the output end of the adjustable resistance control unit is connected to the input end of the polarity control unit, wherein: The adjustable frequency control unit is used to perform frequency control processing on the ground parameters of the DC system to obtain a variable frequency signal, wherein the variable frequency signal includes a signal with a first frequency and a signal with a second frequency; The adjustable resistance control unit is used to convert the frequency conversion signal to obtain a frequency conversion current signal; The polarity control unit is used to transmit the variable frequency current signal to the DC system to obtain bus-to-ground waveform amplitude data of the DC system.

5. The device according to claim 1, characterized in that The mobile fault detection module comprises an operational amplifier unit, a microprocessing unit, a voice unit, a second display unit and a second communication unit, wherein the output end of the operational amplifier unit is connected to the first input end of the microprocessing unit, the first output end of the microprocessing unit is connected to the input end of the voice unit, the second output end of the microprocessing unit is connected to the input end of the second display unit, and the output end of the second communication unit is connected to the second input end of the microprocessing unit, wherein: The operational amplifier unit is used to perform operational amplification and filtering processing on the variable frequency current characteristic signal of the DC system to obtain a pre-processed variable frequency current characteristic signal; The microprocessor unit is used to control the operation of the operational amplifier unit, the voice unit, the second display unit and the second communication unit; The voice unit is used to broadcast the ground fault judgment result of the DC system; The second display unit is used to display the ground fault judgment result of the DC system; The second communication unit is used for wireless communication with the signal source module.

6. A detection method for a DC system fault detection device based on a variable frequency signal, characterized in that: The method comprises the following steps: Acquiring busbar-to-ground waveform amplitude data of a DC system and insulation status data of the DC system to ground; Acquiring a variable frequency current characteristic signal of the DC system; A judgment is made based on the busbar-to-ground waveform amplitude data of the DC system, the insulation status data of the DC system to ground, and the variable frequency current characteristic signal of the DC system to obtain a ground fault judgment result of the DC system.

7. The method according to claim 6, characterized in that The obtaining of bus-to-ground waveform amplitude data of a DC system and insulation status data of the DC system to the ground includes: Acquire the ground parameters of the DC system, where the ground parameters of the DC system include ground voltage data of the DC system and ground insulation status data of the DC system; According to the ground parameters of the DC system, regulation and processing are performed to obtain bus-to-ground waveform amplitude data of the DC system.

8. The method according to claim 7, characterized in that The step of performing control processing according to the ground parameters of the DC system to obtain the bus-to-ground waveform amplitude data of the DC system includes: Performing frequency control processing on the ground parameters of the DC system to obtain a variable frequency signal, wherein the variable frequency signal includes a signal with a first frequency and a signal with a second frequency; Converting the frequency conversion signal to obtain a frequency conversion current signal; The variable frequency current signal is transmitted to the DC system to obtain bus-to-ground waveform amplitude data of the DC system.

9. The method according to claim 6, characterized in that The step of determining the ground fault determination result of the DC system according to the busbar-to-ground waveform amplitude data of the DC system, the ground insulation state data of the DC system, and the variable frequency current characteristic signal of the DC system comprises: Determine the current value of the variable frequency current characteristic signal of the DC system to obtain the current value of the variable frequency current characteristic signal with a first frequency and the current value of the variable frequency current characteristic signal with a second frequency; Determine the impedance value of the variable frequency current characteristic signal of the DC system according to the bus-to-ground waveform amplitude data of the DC system in combination with Ohm's law, and obtain the impedance value of the variable frequency current characteristic signal with a first frequency and the impedance value of the variable frequency current characteristic signal with a second frequency; Calculate the grounding resistance value of the DC system by combining the insulation state data of the DC system with the impedance value of the variable frequency current characteristic signal of the DC system; A ground fault judgment result of the DC system is obtained by performing a judgment based on the ground resistance value of the DC system, the current value of the variable frequency current characteristic signal with the first frequency, and the current value of the variable frequency current characteristic signal with the second frequency.

10. The method according to claim 9, characterized in that The step of determining the ground fault judgment result of the DC system according to the ground resistance value of the DC system, the current value of the variable frequency current characteristic signal with the first frequency, and the current value of the variable frequency current characteristic signal with the second frequency includes: If the current value of the variable frequency current characteristic signal with the first frequency and the current value of the variable frequency current characteristic signal with the second frequency are both 0, the ground fault judgment result of the DC system is that there is no ground fault; If the current value of the variable frequency current characteristic signal with the first frequency and the current value of the variable frequency current characteristic signal with the second frequency are both not 0, and the grounding resistance value of the DC system is less than a preset threshold, the grounding fault judgment result of the DC system is that a grounding fault exists.

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