DC ground detection circuit and DC ground detector

Abstract

The invention relates to the technical field of substation direct current, and discloses a direct current grounding detection circuit and a direct current grounding detector, and the direct current grounding detection circuit comprises a test module which is connected with a direct current bus and a ground end, so as to be connected with a to-be-tested feeder line based on the ground end; the acquisition module is respectively connected with the test module and the to-be-tested feeder line and is used for acquiring a voltage signal of the test module and a current signal of the to-be-tested feeder line and sending the voltage signal and the current signal; and the processing module receives the voltage signal and the current signal, calculates a grounding resistance value of the to-be-tested feeder line based on the voltage signal and the current signal, and confirms that the to-be-tested feeder line is short in ground when detecting that the grounding resistance value is within a preset range. The problem that in the prior art, direct-current grounding troubleshooting is conducted through a circuit pulling method, and consequently equipment faults are caused is solved.

Description

Technical Field

[0001] The invention relates to the field of direct current technology of transformer substations, and in particular to a direct current grounding detection circuit and a direct current grounding detector. Background Art

[0002] In the daily operation and maintenance of power plants and substations and abnormal handling work, the most complicated thing is to find and deal with the grounding of the DC system. When a DC system has a single-point grounding, it will not affect the equipment system. If it is not handled and found in time, when two-point grounding occurs, short circuit, device malfunction, refusal to operate and other serious consequences may occur. DC grounding is generally caused by external factors and internal factors.

[0003] External factors: DC circuits are often affected by a variety of adverse factors during operation. For example, rainy or foggy days may cause the outdoor DC system to be grounded or the insulation to be reduced, causing DC grounding. External force squeezing of the DC cable or aging of the DC system insulation may cause grounding. Water entering the cable pipe may cause the cable to freeze in winter, causing grounding.

[0004] Internal factors: grounding caused by design or human error. For example, when working on a live secondary circuit, the DC power supply accidentally touches the equipment housing; when working in a cable trench, the control cable is damaged and grounding occurs. Outdoor external control equipment is not equipped with a rain cover, the secondary circuit terminal, the control cable outer skin insulation is accidentally damaged, and AC and DC are mixed in the same cable during construction, causing DC grounding. All these leave hidden dangers for DC grounding. At this time, the grounding signal may not be sent immediately, but certain external conditions such as moisture or operating equipment may cause DC grounding.

[0005] The existing method for checking DC grounding of secondary circuits is mainly the pull-route method. Although this method is simple, it also has considerable risks: in the case of DC grounding, if the pull-route method is used for troubleshooting, it may cause the protection device to malfunction or refuse to operate, resulting in failure of the protection function, thereby causing power system failure. During the troubleshooting process, if the operation is improper, some secondary equipment may be burned out, causing equipment damage. If the DC grounding problem is not handled properly, it may cause unstable operation of the power system, or even cause larger failures, affecting the normal operation of the entire power system. Summary of the invention

[0006] In view of this, the present invention provides a DC grounding detection circuit and a DC grounding detector to solve the problem of equipment failure caused by DC grounding troubleshooting through the pull-path method in the prior art.

[0007] In a first aspect, the present invention provides a DC grounding detection circuit, the DC grounding detection circuit comprising:

[0008] A test module, wherein the test module is connected to the DC bus and the ground terminal respectively, so as to be connected to the feeder to be tested based on the ground terminal;

[0009] A collection module, the collection module is connected to the test module and the feeder to be tested respectively, and is used to collect the voltage signal of the test module and the current signal of the feeder to be tested and send them;

[0010] A processing module receives the voltage signal and the current signal, calculates the grounding resistance value of the feeder to be tested based on the voltage signal and the current signal, and confirms that the feeder to be tested is short-grounded when the grounding resistance value is detected to be within a preset range.

[0011] In the DC grounding detection circuit provided by the present invention, the test module is respectively connected to the DC bus and the ground terminal, the acquisition module respectively acquires the current signal of the feeder to be tested and the voltage signal of the test module, and calculates the grounding resistance value of the feeder to be tested based on the voltage signal and the current signal. When the grounding resistance value is detected to be within a preset range, it is confirmed that the feeder to be tested is short-grounded. Therefore, compared with the DC grounding troubleshooting by the pull-through method that causes equipment failure, the stability is greatly improved. In addition, by calculating the grounding resistance value, the DC grounding position can be accurately determined without an external injection source.

[0012] In an optional implementation, the processing module is further used to perform harmonic filtering on the current signal to obtain a filtered current signal, and calculate the grounding resistance value of the feeder to be tested based on the voltage signal and the filtered current signal.

[0013] In an optional implementation, the processing module performs a Fourier forward transform on the current signal to obtain a Fourier forward transformed current signal, and then performs an inverse transform on the Fourier forward transformed current signal to obtain an inverse Fourier transformed current signal to filter out harmonics of the current signal, and uses the inverse Fourier transformed current signal as a filtered current signal.

[0014] In an optional implementation, the acquisition module includes:

[0015] A current acquisition unit, which is arranged close to the feeder to be tested, connected to the processing module, and is used to acquire a current signal of the feeder to be tested and then output it to the processing module;

[0016] A voltage acquisition unit is connected to the test module and the processing module respectively, and is used for acquiring the voltage signal of the test module and then outputting it to the processing module.

[0017] In an optional implementation, the current acquisition unit includes:

[0018] A handheld current clamp, which is arranged close to the feeder to be tested and is used to collect the current signal of the feeder to be tested and then output it;

[0019] A current collection subunit, wherein the current collection subunit is connected to the handheld current clamp and the processing module respectively, and is used to receive the current signal and transmit it to the processing module.

[0020] In an optional implementation, the current collection subunit and the processing module are connected based on a communication line.

[0021] In an optional implementation, the voltage acquisition unit includes:

[0022] An analog-to-digital converter, wherein the analog-to-digital converter is connected to the test module and the processing module respectively, and is used for collecting the voltage signal of the test module and then outputting it to the processing module.

[0023] In an optional implementation manner, the DC bus includes: a DC bus negative terminal and a DC bus positive terminal, and the test module includes:

[0024] A first resistor, wherein a first end of the first resistor is respectively connected to the positive end of the DC bus and the acquisition module, and a second end of the first resistor is grounded;

[0025] A second resistor, wherein a first end of the second resistor is respectively connected to the negative end of the DC bus and the acquisition module, and a second end of the second resistor is grounded.

[0026] In an optional implementation manner, the DC grounding detection circuit further includes:

[0027] An alarm module, which is connected to the processing module and is used to output an alarm signal after receiving an alarm control signal;

[0028] The processing module outputs the alarm control signal when confirming that the feeder to be tested is short-grounded.

[0029] In a second aspect, the present invention further provides a DC grounding detector, which includes the DC grounding detection circuit as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 is a structural diagram of a DC grounding detection circuit according to an embodiment of the present invention;

[0032] Figure 2 is a structural diagram of a collection module in a DC grounding detection circuit according to an embodiment of the present invention;

[0033] Figure 3 is a detailed structural diagram of a collection module of a DC grounding detection circuit according to an embodiment of the present invention;

[0034] Figure 4 is a structural diagram of another DC grounding detection circuit according to an embodiment of the present invention.

[0035] Description of Figure Numbers:

[0036] Rd-grounding resistance; 10-test module; 20-acquisition module; 30-processing module; 21-current acquisition unit; 22-voltage acquisition unit; R1-first resistor; R2-second resistor; A-handheld current clamp; B-current acquisition subunit. DETAILED DESCRIPTION

[0037] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0039] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0041] In the daily operation and maintenance of power plants and substations and abnormal handling work, the most complicated thing is to find and deal with the grounding of the DC system. When a DC system has a single-point grounding, it will not affect the equipment system. If it is not handled and found in time, when two-point grounding occurs, short circuit, device malfunction, refusal to operate and other serious consequences may occur. DC grounding is generally caused by external factors and internal factors.

[0042] External factors: DC circuits are often affected by a variety of adverse factors during operation. For example, rainy or foggy days may cause the outdoor DC system to be grounded or the insulation to be reduced, causing DC grounding. External force squeezing of the DC cable or aging of the DC system insulation may cause grounding. Water entering the cable pipe may cause the cable to freeze in winter, causing grounding.

[0043] Internal factors: grounding caused by design or human error. For example, when working on a live secondary circuit, the DC power supply accidentally touches the equipment housing; when working in a cable trench, the control cable is damaged and grounding occurs. Outdoor external control equipment is not equipped with a rain cover, the secondary circuit terminal, the control cable outer skin insulation is accidentally damaged, and AC and DC are mixed in the same cable during construction, causing DC grounding. All these leave hidden dangers for DC grounding. At this time, the grounding signal may not be sent immediately, but certain external conditions such as moisture or operating equipment may cause DC grounding.

[0044] The existing method for checking DC grounding of secondary circuits is mainly the pull-route method. Although this method is simple, it also has considerable risks: in the case of DC grounding, if the pull-route method is used for troubleshooting, it may cause the protection device to malfunction or refuse to operate, resulting in failure of the protection function, thereby causing power system failure. During the troubleshooting process, if the operation is improper, some secondary equipment may be burned out, causing equipment damage. If the DC grounding problem is not handled properly, it may cause unstable operation of the power system, or even cause larger failures, affecting the normal operation of the entire power system.

[0045] In this regard, a DC grounding detection circuit is provided in this embodiment, such as Figure 1 As shown, the DC grounding detection circuit includes:

[0046] A test module 10, wherein the test module 10 is connected to the DC bus and the ground terminal respectively, so as to be connected to the feeder to be tested based on the ground terminal;

[0047] A collection module 20, which is connected to the test module and the feeder to be tested respectively, and is used to collect the voltage signal of the test module and the current signal of the feeder to be tested and send them;

[0048] The processing module 30 receives the voltage signal and the current signal, calculates the grounding resistance value of the feeder to be tested based on the voltage signal and the current signal, and confirms that the feeder to be tested is short-grounded when the grounding resistance value is detected to be within a preset range.

[0049] Specifically, refer to Figure 1 , the DC bus is respectively connected to a plurality of feeders, and there is a grounding resistance Rd between the feeder and the ground terminal, and the feeder to be tested is used as the feeder to be tested. The test module 10 is used to provide test values ​​such as voltage signals and current signals. Current flows between the DC bus, the test module 10, the ground terminal, the grounding resistance Rd, the feeder to be tested and the DC bus, thereby generating a loop. At this time, the voltage of the test module 10 and the current of the feeder to be tested are collected by the acquisition module 20. It should be understood that the current flowing through the feeder to be tested is the same as the current flowing through the test module 10. Thus, the grounding resistance value of the grounding resistance Rd is calculated by the current signal and the voltage signal, and when it is detected that the grounding resistance value is within a preset range, it is confirmed that the feeder to be tested is short-grounded.

[0050] It should be noted that the presence of a DC grounding fault is inferred by the magnitude of the current of the feeder to be tested. Then the magnitude of the grounding resistance value of the grounding resistor Rd is specifically calculated, and the grounding condition of the grounding fault is specifically obtained. Specifically, if the current flowing through the feeder to be tested is larger, the grounding resistance value of the grounding resistor Rd is smaller, and the DC grounding fault is deeper at this time. If the current flowing through the feeder to be tested is smaller, the grounding resistance value of the grounding resistor Rd is larger, and the DC grounding fault is shallower at this time. The preset range can be less than the preset resistance value. When the grounding resistance value is monitored to be within the preset range, it is confirmed that the feeder to be tested is short-grounded.

[0051] Optionally, the test module 10 may be a voltage drop device, the acquisition module 20 may be a current acquisition and voltage acquisition device, and the processing module 30 may be a CPU (Central Processing Unit). The processing module 30 also has a signal processing function. The processing module 30 may be a monitoring host.

[0052] In the DC grounding detection circuit provided by the present invention, the test module 10 is connected to the DC bus and the ground terminal respectively, and the acquisition module 20 respectively acquires the current signal of the feeder to be tested and the voltage signal of the test module 10, and calculates the grounding resistance value of the feeder to be tested based on the voltage signal and the current signal. When the grounding resistance value is detected to be within a preset range, it is confirmed that the feeder to be tested is short-grounded. Therefore, compared with the DC grounding troubleshooting by the pull-through method that causes equipment failure, the stability is greatly improved. In addition, by calculating the grounding resistance value, the DC grounding position can be accurately determined without an external injection source.

[0053] In some optional implementations, the processing module 30 is further configured to perform harmonic filtering on the current signal to obtain a filtered current signal, and calculate the grounding resistance value of the feeder to be tested based on the voltage signal and the filtered current signal.

[0054] Specifically, after receiving the current signal sent by the acquisition module 20, the processing module 30 performs harmonic filtering on the current signal to obtain a filtered current signal, and then calculates the grounding resistance value of the feeder to be tested based on the filtered current signal and the voltage signal. Thus, the interference of harmonic current on DC grounding search is eliminated, and the stability of DC grounding search is further improved.

[0055] In some optional implementations, the processing module 30 performs a Fourier forward transform on the current signal to obtain a Fourier forward transformed current signal, and then performs an inverse transform on the Fourier forward transformed current signal to obtain an inverse Fourier transformed current signal to filter out harmonics of the current signal, and uses the inverse Fourier transformed current signal as a filtered current signal.

[0056] Specifically, x(n) is used to represent the current signal, that is, the total number of sampling points for synchronous sampling of the continuous current signal is N, and a finite-length discrete time series x(n) is obtained, where x(n) is:

[0057]

[0058] First, perform discrete Fourier transform DEF[x(n)] on x(n) to obtain the Fourier forward transform current signal X(k), where X(k) is:

[0059]

[0060] Then, perform inverse discrete Fourier transform IDEF[x(n)] on X(k) to obtain the inverse Fourier transform current signal x(n)', where x(n)' is:

[0061]

[0062] Finally, x(n)' is used as the filtered current signal. The test module is connected to the DC bus and the ground terminal respectively, and the acquisition module respectively acquires the current signal of the feeder to be tested and the voltage signal of the test module, and calculates the grounding resistance value of the feeder to be tested based on the voltage signal and the current signal. When the grounding resistance value is detected to be within a preset range, it is confirmed that the feeder to be tested is short-grounded. Therefore, compared with the DC grounding troubleshooting through the pulling method that leads to equipment failure, the stability is greatly improved. In addition, by calculating the grounding resistance value, the DC grounding position can be accurately determined without an external injection source.

[0063] In some optional embodiments, Figure 2 As shown, the acquisition module 20 includes:

[0064] A current acquisition unit 21, which is disposed close to the feeder to be tested and connected to the processing module 30, and is used for acquiring a current signal of the feeder to be tested and then outputting it to the processing module 30;

[0065] The voltage acquisition unit 22 is connected to the test module 10 and the processing module 30 respectively, and is used for acquiring the voltage signal of the test module 10 and outputting it to the processing module 30 .

[0066] Specifically, the current acquisition unit 21 is used to collect the current signal of the loop composed of the DC bus, the test module 10, the ground terminal, the grounding resistor Rd, and the feeder to be tested. The voltage acquisition unit 22 collects the voltage signal of the test module 10. Specifically, the voltage of the connection terminal where the module 10 is connected to the DC bus can be tested. Thus, the grounding resistance value of the grounding resistor Rd is calculated by the current signal and the voltage signal. When the grounding resistance value is detected to be within a preset range, it is confirmed that the feeder to be tested is short-grounded. At the same time, the harmonics of the current signal are filtered out, eliminating the interference of the harmonic current on the DC grounding search.

[0067] In some optional embodiments, Figure 3 As shown, the current acquisition unit 21 includes:

[0068] A handheld current clamp A, which is arranged close to the feeder to be tested and is used to collect the current signal of the feeder to be tested and then output it;

[0069] The current collection subunit B is connected to the handheld current clamp A and the processing module 30 respectively, and is used to receive the current signal and transmit it to the processing module 30.

[0070] Specifically, the handheld current clamp A is clamped on the feeder to be tested, and the current signal of the feeder to be tested is collected by the handheld current clamp A and sent to the current collection subunit B. The current collection subunit B transmits the current signal to the processing module 30. Of course, the current collection unit 21 can also collect current in other ways, which are not limited here. The test module is connected to the DC bus and the ground terminal respectively, and the collection module collects the current signal of the feeder to be tested and the voltage signal of the test module respectively, and calculates the grounding resistance value of the feeder to be tested based on the voltage signal and the current signal. When the grounding resistance value is detected to be within a preset range, it is confirmed that the feeder to be tested is short-grounded. Therefore, compared with the DC grounding troubleshooting through the pulling method that causes equipment failure, the stability is greatly improved. In addition, by calculating the grounding resistance value, the DC grounding position can be accurately determined without an external injection source. The interference of harmonics on the current signal is also eliminated.

[0071] In addition, it should be noted that the reference Figure 3 The first end of the grounding resistor Rd is the feeder to be tested, and the second end of the grounding resistor Rd is connected to the first resistor R1 and the second resistor R2 through the ground terminal.

[0072] In some optional implementations, the current collection subunit B and the processing module 30 are connected based on a communication line.

[0073] Specifically, the current acquisition subunit B can be a communication device. After receiving the current signal sent by the handheld current clamp A, the current acquisition subunit B converts the current signal into a communication signal and transmits it to the processing module 30 through the communication line. Optionally, the communication line can be specifically RS485 (a remote weighing data acquisition method of a communication interface). Of course, the current acquisition subunit B and the processing module 30 can also be connected based on other communication methods. The test module is connected to the DC bus and the ground terminal respectively, and the acquisition module respectively acquires the current signal of the feeder to be tested and the voltage signal of the test module, and calculates the grounding resistance value of the feeder to be tested based on the voltage signal and the current signal. When the grounding resistance value is detected to be within a preset range, it is confirmed that the feeder to be tested is short-grounded. Thus, compared with the DC grounding troubleshooting through the pull-through method that causes equipment failure, the stability is greatly improved. In addition, by calculating the grounding resistance value, the DC grounding position can be accurately determined without an external injection source. The interference of harmonics on the current signal is also eliminated.

[0074] In some optional implementations, the voltage acquisition unit 22 includes:

[0075] An analog-to-digital converter, wherein the analog-to-digital converter is connected to the test module 10 and the processing module 30 respectively, and is used for collecting the voltage signal of the test module and outputting it to the processing module 30 .

[0076] Specifically, the voltage acquisition unit 22 may be an analog-to-digital converter, which acquires the analog voltage signal of the test module 10 , and converts the analog voltage signal into a digital voltage signal before transmitting it to the processing module 30 .

[0077] In some optional embodiments, Figure 4 As shown, the DC bus includes: a DC bus negative terminal and a DC bus positive terminal, and the test module 10 includes:

[0078] A first resistor R1, wherein a first end of the first resistor R1 is respectively connected to the positive end of the DC bus and the acquisition module 20, and a second end of the first resistor R1 is grounded;

[0079] A second resistor R2, wherein a first end of the second resistor R2 is respectively connected to the negative end of the DC bus and the acquisition module 20, and a second end of the second resistor R2 is grounded.

[0080] Specifically, refer to Figure 4 The first resistor R1 is connected between the positive end of the DC bus and the ground, and the second resistor R2 is connected between the negative end of the DC bus and the ground. The first resistor R1 and the second resistor R2 act as balanced bridge resistors. It can be understood that the second resistor R2 and the first resistor R1 can both be composed of multiple resistors connected in series and / or in parallel.

[0081] In some optional embodiments, Figure 4 As shown, the DC grounding detection circuit also includes:

[0082] An alarm module 40, which is connected to the processing module 30 and is used to output an alarm signal after receiving an alarm control signal;

[0083] The processing module 30 outputs the alarm control signal when confirming that the feeder to be tested is short-circuited to ground.

[0084] Specifically, refer to Figure 4When the processing module 30 confirms that the feeder to be tested is short-grounded, the alarm module 40 is controlled to output an alarm signal, thereby reminding the user to perform maintenance. The alarm module 40 can be an alarm light or a buzzer, or a sound system for fault voice broadcasting. The test module is connected to the DC bus and the ground terminal respectively, and the acquisition module collects the current signal of the feeder to be tested and the voltage signal of the test module respectively, and calculates the grounding resistance value of the feeder to be tested based on the voltage signal and the current signal. When the grounding resistance value is detected to be within a preset range, it is confirmed that the feeder to be tested is short-grounded. Therefore, compared with the DC grounding troubleshooting through the pull-through method that causes equipment failure, the stability is greatly improved. In addition, by calculating the grounding resistance value, the DC grounding position can be accurately determined without an external injection source. The interference of harmonics on the current signal is also eliminated. At the same time, the harmonics of the current signal are filtered out, eliminating the interference of harmonic currents on the DC grounding search.

[0085] It should be noted that the reference Figure 4 , the first resistor R1, the second resistor R2, the current acquisition unit 22, the processing module 30 and the alarm module 40 are integrated into an insulation monitoring host. The processing module 30 is the CPU of the insulation monitoring host. Therefore, when performing detection, it is only necessary to connect the insulation monitoring host to the negative end of the DC bus, the positive end of the DC bus and the ground end respectively. At the same time, the insulation monitoring host and the current acquisition subunit are connected in communication, and the handheld current clamp A is clamped to the feeder to be tested. Therefore, the processing module 30 of the insulation monitoring host is used to determine whether there is a ground fault on the feeder to be tested based on the current signal. When there is a ground fault, after further calculating the ground resistance value of the ground resistor Rd, the degree of the ground fault is further determined based on the ground resistance value.

[0086] In addition, it should be noted that the DC grounding detection circuit can include multiple handheld current clamps A, so as to respectively collect multiple feeders to be tested. After receiving the current signals of multiple feeders to be tested respectively through the current acquisition subunit B, the multiple current signals are packaged and sent to the insulation monitoring host, and the insulation monitoring host determines whether each insulation monitoring host has a grounding fault in turn. When it is detected that one or more feeders to be tested have a grounding fault, the insulation monitoring host respectively filters out the harmonics of the current signals of the feeders to be tested with grounding faults, and then calculates the grounding resistance value of each feeder to be tested in turn, thereby determining the grounding fault condition of each feeder to be tested in turn.

[0087] In this embodiment, the present invention also provides a DC grounding detector, which is connected to the DC bus and the ground terminal respectively, and is arranged close to the feeder to be tested. Thus, the grounding resistance value of the grounding resistor Rd is calculated by the current signal and the voltage signal, and when the grounding resistance value is detected to be within a preset range, it is confirmed that the feeder to be tested is short-grounded. The test module is connected to the DC bus and the ground terminal respectively, and the acquisition module respectively acquires the current signal of the feeder to be tested and the voltage signal of the test module, and calculates the grounding resistance value of the feeder to be tested based on the voltage signal and the current signal. When the grounding resistance value is detected to be within a preset range, it is confirmed that the feeder to be tested is short-grounded. Thus, compared with the DC grounding troubleshooting by the pull-road method that causes equipment failure, the stability is greatly improved. In addition, by calculating the grounding resistance value, the DC grounding position can be accurately determined without an external injection source. It should be noted that whether a DC grounding fault exists is inferred by the size of the current of the feeder to be tested. Then the size of the grounding resistance value of the grounding resistor Rd is specifically calculated, and the grounding condition of the grounding fault is specifically obtained. Specifically, if the current flowing through the feeder to be tested is larger, the grounding resistance value of the grounding resistor Rd is smaller, and the DC grounding fault is deeper. If the current flowing through the feeder to be tested is smaller, the grounding resistance value of the grounding resistor Rd is larger, and the DC grounding fault is shallower. The preset range can be less than the preset resistance value. When the grounding resistance value is monitored to be within the preset range, it is confirmed that the feeder to be tested is short-grounded.

[0088] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A DC grounding detection circuit, characterized in that: The DC grounding detection circuit comprises: A test module, wherein the test module is connected to the DC bus and the ground terminal respectively, so as to be connected to the feeder to be tested based on the ground terminal; A collection module, the collection module is connected to the test module and the feeder to be tested respectively, and is used to collect the voltage signal of the test module and the current signal of the feeder to be tested and send them; A processing module receives the voltage signal and the current signal, calculates the grounding resistance value of the feeder to be tested based on the voltage signal and the current signal, and confirms that the feeder to be tested is short-grounded when the grounding resistance value is detected to be within a preset range.

2. The DC grounding detection circuit according to claim 1, characterized in that: The processing module is further used to perform harmonic filtering processing on the current signal to obtain a filtered current signal, and calculate the grounding resistance value of the feeder to be tested based on the voltage signal and the filtered current signal.

3. The DC grounding detection circuit according to claim 2, characterized in that: The processing module performs Fourier forward transform on the current signal to obtain a Fourier forward transformed current signal, and then performs inverse transform on the Fourier forward transformed current signal to obtain an inverse Fourier transformed current signal to filter out the harmonics of the current signal, and uses the inverse Fourier transformed current signal as a filtered current signal.

4. The DC grounding detection circuit according to claim 1, characterized in that: The acquisition module comprises: A current acquisition unit, which is arranged close to the feeder to be tested, connected to the processing module, and is used to acquire a current signal of the feeder to be tested and then output it to the processing module; A voltage acquisition unit is connected to the test module and the processing module respectively, and is used for acquiring the voltage signal of the test module and then outputting it to the processing module.

5. The DC grounding detection circuit according to claim 4, characterized in that: The current collection unit comprises: A handheld current clamp, which is arranged close to the feeder to be tested and is used to collect the current signal of the feeder to be tested and then output it; A current collection subunit, wherein the current collection subunit is connected to the handheld current clamp and the processing module respectively, and is used to receive the current signal and transmit it to the processing module.

6. The DC grounding detection circuit according to claim 5, characterized in that: The current collection subunit and the processing module are connected based on a communication line.

7. The DC grounding detection circuit according to claim 4, characterized in that: The voltage acquisition unit comprises: An analog-to-digital converter, wherein the analog-to-digital converter is connected to the test module and the processing module respectively, and is used for collecting the voltage signal of the test module and then outputting it to the processing module.

8. The DC grounding detection circuit according to claim 1, characterized in that: The DC bus includes: a DC bus negative terminal and a DC bus positive terminal, and the test module includes: A first resistor, wherein a first end of the first resistor is respectively connected to the positive end of the DC bus and the acquisition module, and a second end of the first resistor is grounded; A second resistor, wherein a first end of the second resistor is respectively connected to the negative end of the DC bus and the acquisition module, and a second end of the second resistor is grounded.

9. The DC grounding detection circuit according to claim 1, characterized in that: The DC grounding detection circuit also includes: An alarm module, which is connected to the processing module and is used to output an alarm signal after receiving an alarm control signal; The processing module outputs the alarm control signal when confirming that the feeder to be tested is short-grounded. 10 . A DC grounding detector, comprising the DC grounding detection circuit according to claim 1 .

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