Ground fault detection device and processing system

Abstract

The invention provides a ground fault detection device and a processing system. The detection device comprises a filtering module, an amplifying module, an extracting module and a judging module. The input end of the filtering module is used for receiving an initial signal and filtering the initial signal; the input end of the amplification module is electrically connected with the output end of the filtering module, and the amplification module is used for amplifying the filtered initial signal; the input end of the extraction module is electrically connected with the output end of the amplification module, and the extraction module is used for extracting a transient characteristic signal in the amplified initial signal; the input end of the judgment module is electrically connected with the output end of the extraction module, the judgment module is used for determining a target judgment result of the ground fault according to the transient characteristic signal, the output end of the judgment module is used for outputting the target judgment result, the target judgment result is used for driving circuit processing, and the accuracy of ground fault recognition is improved.

Description

Technical Field

[0001] The present invention relates to the field of electric power, and in particular to a ground fault detection device and a processing system. Background Art

[0002] Ground fault is the most likely fault type in power system. It will pose a serious threat to equipment safety and personnel. If it is not discovered and handled in time, it will cause adverse consequences. Therefore, the judgment and protection technology of ground fault has always been the focus of research in the field of power protection.

[0003] In the current ground fault identification, the accuracy of ground fault identification is low because the grounding system of the ground fault has weak recognition of transient characteristic signals. Summary of the invention

[0004] The present invention aims at the problem of low accuracy in identifying ground faults in the prior art and proposes a ground fault detection device and a processing system.

[0005] In a first aspect, an embodiment of the present invention provides a ground fault detection device, the detection device comprising a filtering module, an amplifying module, an extracting module and a judging module;

[0006] The input end of the filter module is used to receive the initial signal and filter the initial signal;

[0007] The input end of the amplification module is electrically connected to the output end of the filtering module, and the amplification module is used to amplify the filtered initial signal;

[0008] The input end of the extraction module is electrically connected to the output end of the amplification module, and the extraction module is used to extract the transient characteristic signal from the amplified initial signal;

[0009] The input end of the judgment module is electrically connected to the output end of the extraction module. The judgment module is used to determine the target judgment result of the ground fault according to the transient characteristic signal. The output end of the judgment module is used to output the target judgment result, and the target judgment result is used for driving circuit processing.

[0010] In one embodiment, the filtering module includes a notch filter circuit, and the limiting frequency is a first preset frequency.

[0011] In one embodiment, the trap circuit includes a low-pass filter subcircuit and a high-pass filter subcircuit, and the low-pass filter subcircuit and the high-pass filter subcircuit are connected in parallel.

[0012] In one embodiment, the amplification module includes a second-order active low-pass filter circuit, the cutoff frequency of the second-order active low-pass filter circuit is a second preset frequency, and the amplification factor of the second-order active low-pass filter circuit is a preset amplification factor.

[0013] In one embodiment, the transient characteristic signal includes a first characteristic signal and a second characteristic signal;

[0014] The extraction module includes a first characteristic signal extraction circuit and a second characteristic signal extraction circuit, and the first characteristic signal extraction circuit and the second characteristic signal extraction circuit are connected in series with each other;

[0015] The first characteristic signal extraction circuit is used to extract the first characteristic signal from the amplified initial signal, and the second characteristic signal extraction circuit is used to extract the second characteristic signal from the amplified initial signal.

[0016] In one embodiment, the judgment module includes a first characteristic signal judgment circuit, a second characteristic signal judgment circuit and a result output circuit, and the first characteristic signal judgment circuit and the second characteristic signal judgment circuit are connected in series to the input end of the result output circuit;

[0017] The first characteristic signal judgment circuit is used to receive the first characteristic signal and output a first judgment result; the second characteristic signal judgment circuit is used to receive the second characteristic signal and output a second judgment result; the result output circuit is used to determine the target judgment result based on the first judgment result and the second judgment result.

[0018] In one embodiment, the first characteristic signal determination circuit is composed of a first NOR gate subcircuit and a second NOR gate subcircuit connected in series;

[0019] And / or, the second characteristic signal determination circuit includes a third NOR gate circuit and a fourth NOR gate circuit connected in series;

[0020] And / or, the result output circuit includes an OR gate circuit.

[0021] In one embodiment, the number of filtering modules includes at least one; and / or, the number of amplification modules includes at least one; and / or, the number of extraction modules includes at least one; and / or, the number of judgment modules includes at least one.

[0022] In a second aspect, an embodiment of the present invention provides a ground fault processing system, the ground fault processing system comprising a ground fault detection device as described in any one of the first aspects, and a control device, wherein the detection device and the control device are electrically connected;

[0023] The control device is used to receive the target judgment result and perform circuit processing based on the target judgment result.

[0024] In one embodiment, the control device includes a review module and a processing module, the review module is electrically connected to the processing module, and the review module is electrically connected to the detection device;

[0025] The grounding algorithm is loaded into the review module, and the review module is used to receive the target judgment result, and review based on the target judgment result to obtain the review result;

[0026] The processing module is used to receive the review result and perform circuit processing based on the review result.

[0027] The present invention provides a ground fault detection device and processing system with the following technical effects:

[0028] The initial signal is pre-processed by the filtering module and the amplifying module, which can filter out the clutter signal and amplify the transient characteristic signal separately; then the transient characteristic signal is separated from the initial signal by the extraction module and converted into a signal that is convenient for grounding fault judgment; finally, the judgment module is used to judge the grounding fault and obtain the target judgment result, which can effectively avoid the influence of the power frequency signal and improve the efficiency and accuracy of grounding judgment.

[0029] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0031] Figure 1 A schematic structural diagram of a ground fault detection device provided by an exemplary embodiment of the present invention;

[0032] Figure 2 A circuit diagram of a filter module provided by an exemplary embodiment of the present invention;

[0033] Figure 3 A circuit diagram of an amplification module provided by an exemplary embodiment of the present invention;

[0034] Figure 4 A circuit diagram of an extraction module provided by an exemplary embodiment of the present invention;

[0035] Figure 5 A circuit diagram of a judgment module provided by an exemplary embodiment of the present invention;

[0036] Figure 6 A schematic structural diagram of a ground fault processing system provided by an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0038] The following detailed description is an exemplary description, which is intended to provide further detailed description of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the present invention belongs. The terms used in the present invention are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present invention.

[0039] In the case of grounding faults, the classification of grounding faults includes but is not limited to metal grounding faults, low-resistance grounding faults, and high-resistance grounding faults. The grounding characteristics of metallic grounding faults and low-resistance grounding faults are relatively obvious, so the recognition rate is relatively high. However, the recognition rate of high-resistance grounding faults in neutral point grounding systems and arc suppression coil grounding systems is still relatively low. The main reason is that in this case, the characteristics of single-phase grounding faults are weak and the fault development process is complex, making it difficult to effectively identify and quickly remove them.

[0040] Based on this, an embodiment of the present invention provides a ground fault detection device, which preferably detects high-resistance ground faults in a neutral point grounding system and a grounding system through an arc suppression coil, and can also detect attribute ground faults and low-resistance ground faults. It is not limited to this and can be selected according to actual conditions.

[0041] The ground fault detection provided in this embodiment can be applied to power system substation comprehensive protection devices, distribution station terminals, feeder terminals and other distribution protection devices to provide reliable and accurate ground fault judgment signals for power system protection and measurement and control devices, but is not limited to this.

[0042] See also Figure 1 The detection device includes a filtering module 1, an amplifying module 2, an extracting module 3 and a judging module 4.

[0043] Among them, the input end of the filtering module 1 is used to receive the initial signal, the input end of the amplifying module 2 is electrically connected to the output end of the filtering module 1, the input end of the extraction module 3 is electrically connected to the output end of the amplifying module 2, the input end of the judgment module 4 is electrically connected to the output end of the extraction module 3, and the output end of the judgment module 4 is used to output the target judgment result.

[0044] The filtering module 1 is used to filter the initial signal. The amplifying module 2 is used to amplify the filtered initial signal. The extracting module 3 is used to extract the transient characteristic signal from the amplified initial signal. The judging module is used to determine the target judgment result of the ground fault according to the transient characteristic signal.

[0045] Among them, the initial signal is sent by the device to be detected, and the initial signal specifically includes the voltage signal and the current signal output by the transformer. In addition to the required transient characteristic signal, the initial signal is also mixed with many other types of signals, such as industrial frequency signals, etc. These types of signals will affect the ground fault judgment. Therefore, in this embodiment, most of the clutter signals are filtered out by the filtering module 1 to improve the purity of the transient characteristic signal detection.

[0046] In order to facilitate the extraction of transient characteristic signals, before the extraction of transient characteristic signals, the initial signal is amplified by the amplification module 2. Then, the extraction module 3 extracts the transient characteristic signal from the amplified initial signal.

[0047] The transient characteristic signal refers to the transient behavior and characteristics of the system response when a ground fault occurs in the power system or electrical equipment. The transient characteristic signal is mainly characterized by the instantaneous voltage and current fluctuations of the system in response to the ground fault, and how these fluctuations change over time. Specifically, the transient characteristic signal in this embodiment includes a positive transient characteristic signal and a negative transient characteristic signal. The positive transient characteristic signal includes a positive transient voltage signal and a positive transient current signal. The negative transient characteristic signal includes a negative transient voltage signal and a negative transient current signal.

[0048] The transient current signal is the moment of ground fault, and a very large current impact may occur in the system. The characteristics of the transient current signal include the peak value, attenuation process and the impact on the system. The transient voltage signal is the instantaneous change of the system voltage caused by the ground fault. The transient characteristics of voltage include voltage mutation, oscillation and stability process.

[0049] In some application scenarios, the transient characteristic signal also includes system response and / or frequency characteristics.

[0050] The system response is the reaction of the power system to the ground fault, including the action of the protection device, the automatic adjustment of the system and the fault isolation process. The frequency characteristic is that the ground fault will also have a transient impact on the frequency of the system, which may cause instantaneous frequency fluctuations.

[0051] Transient characteristic signals are crucial for designing and optimizing power system protection measures because they help engineers evaluate and predict system performance after a fault occurs and take appropriate protection and control strategies accordingly to ensure system stability and safety.

[0052] After the extraction module 3 extracts the transient characteristic signal, the judgment module makes a judgment based on the transient characteristic signal and obtains a judgment result. The extraction module 3 in this embodiment adopts a transient grounding characteristic recognition method, and makes a judgment based on the transient polarity of the transient current signal and the transient voltage signal. When a grounding occurs, the transient current signal and the transient voltage signal will have opposite polarities. By performing a logical operation on the transient current signal and the transient voltage signal, the grounding target judgment result is output.

[0053] The target judgment result is used for driving circuit processing. Specifically, the control device can be driven to review the target judgment result of ground fault detection, the control device can be driven to perform ground fault protection, and it can also be sent to the management device for ground fault warning.

[0054] In this embodiment, the initial signal is pre-processed by the filtering module and the amplification module, so that the clutter signal can be filtered out and the transient characteristic signal can be amplified separately; then the transient characteristic signal is separated from the initial signal by the extraction module, and converted into a signal that is convenient for ground fault judgment; finally, the judgment module is used to judge the ground fault and obtain the result of the target judgment, which can effectively avoid the influence of the power frequency signal and improve the efficiency and accuracy of the ground judgment.

[0055] The specific structure of the above detection device is described below:

[0056] For filter module 1, see Figure 2 The filter module 1 includes a notch filter circuit. The notch filter circuit is a double-T notch filter circuit, and the notch filter circuit includes a low-pass filter subcircuit and a high-pass filter subcircuit, and the low-pass filter subcircuit and the high-pass filter subcircuit are connected in parallel.

[0057] Specifically, R1, R3 and C2 form a low-pass filter subcircuit, C1, C3 and R2 form a high-pass filter subcircuit, and the input end of the filter module 1 is Uin.

[0058] The limiting frequency of the notch filter is The wave limiting frequency in this embodiment can be set to a first preset frequency. Therefore, the low-pass filter circuit is used to filter the clutter signals of the first preset frequency and above the power frequency, and the high-pass filter circuit is used to filter the clutter signals of the first preset frequency and above the power frequency. As an example, the first preset frequency can be 50 Hz, but is not limited thereto.

[0059] For enlargement module 2, see Figure 3The amplification module 2 includes a second-order active low-pass filter circuit. The second-order active low-pass filter circuit is composed of resistors R4, R5, R6, R7, capacitors C4, C5 and an amplifier. The input end of the second-order active low-pass filter circuit is at the resistor R4, and the output end of the second-order active low-pass filter circuit is Uout.

[0060] To simplify the calculation, in general, the resistance is set to R4=R6=R and the capacitance is set to C4=C5=C.

[0061] The cut-off frequency of the second-order active low-pass filter circuit is The cutoff frequency in this embodiment can be set to a second preset frequency, and the second-order active low-pass filter circuit can be used to filter out interference signals and improve driving capability. As an example, the second preset frequency can be 2kHz, but is not limited to this.

[0062] Amplification of the second-order active low-pass filter circuit In this circuit, the gain A is determined according to the amplitude of the input signal and the input range of the operational amplifier. To ensure signal quality, the gain A can be set to a preset gain. As an example, the preset gain should be less than 10.

[0063] The second-order active low-pass filter circuit provided in this embodiment can amplify the initial signal after filtering by the filter module 1, and further, can filter out high-frequency interference signals in the initial signal, improve the driving capability, and meet the needs of transient characteristic signal extraction in the extraction module 3. In addition, the initial signal output by the second-order active low-pass filter circuit can also be used for AD (analog-to-digital conversion) signal collection.

[0064] Regarding the extraction module 3, the transient characteristic signal includes a first characteristic signal and a second characteristic signal. In this embodiment, the first characteristic signal may refer to a positive polarity transient characteristic signal, and the second characteristic signal may refer to a negative polarity transient characteristic signal. This is only an example but not limited to this.

[0065] See also Figure 4 The extraction module 3 includes a first characteristic signal extraction circuit and a second characteristic signal extraction circuit, which are connected in series. The first characteristic signal extraction circuit is composed of resistors R12, R13, R14, R15, capacitors C9, C10, C11 and transistor Q2, and the second characteristic signal extraction circuit is composed of resistors R8, R9, R10, R11, capacitors C6, C7, C8 and transistor Q1.

[0066] The first characteristic signal extraction circuit is used to extract the first characteristic signal from the amplified initial signal, and the second characteristic signal extraction circuit is used to extract the second characteristic signal from the amplified initial signal.

[0067] Taking the first characteristic signal extraction circuit as an example, R12 and R13 are bias resistors that provide bias current for transistor Q2, R15 and C11 are a DC negative feedback loop for stabilizing the DC operating point; R14 and C10 are load loops, and C9 is a DC blocking capacitor.

[0068] The positive polarity transient characteristic signal first passes through the C9 DC blocking capacitor, converting the voltage transient into a current signal to drive the transistor Q2. When the threshold is exceeded, the transistor is turned on, generating a voltage drop on R14. At this time, the first characteristic signal becomes a low level, and the output terminal Up of the first characteristic signal extraction circuit outputs a low level pulse signal.

[0069] The principle of the second characteristic signal extraction circuit can be referred to the first characteristic signal extraction circuit and will not be repeated here. When the negative polarity transient characteristic signal passes through the second characteristic signal extraction circuit, the output terminal Un of the second characteristic signal extraction circuit outputs a high level pulse signal.

[0070] Regarding the judgment module 4, the judgment module 4 includes a first characteristic signal judgment circuit, a second characteristic signal judgment circuit and a result output circuit, and the first characteristic signal judgment circuit and the second characteristic signal judgment circuit are connected in series to the input end of the result output circuit. The first characteristic signal judgment circuit is used to receive the first characteristic signal and output the first judgment result; the second characteristic signal judgment circuit is used to receive the second characteristic signal and output the second judgment result; the result output circuit is used to determine the target judgment result according to the first judgment result and the second judgment result.

[0071] See also Figure 5 The first characteristic signal judgment circuit is composed of a first NOR gate subcircuit U1 and a second NOR gate subcircuit U3 connected in series, a positive polarity transient voltage signal is input from the input terminal Up of the first NOR gate subcircuit U1, and a positive polarity transient current signal is input from the input terminal Ip of the second NOR gate U3. The second characteristic signal judgment circuit includes a third NOR gate circuit U2 and a fourth NOR gate circuit U4 connected in series, a negative polarity transient voltage signal is input from the input terminal Un of the fourth NOR gate subcircuit U4, and a negative polarity transient current signal is input from the input terminal In of the third NOR gate U2. The result output circuit includes an OR gate circuit U5.

[0072] The logical relationship of the judgment module is: Pout is the output terminal, which outputs the target judgment result. When the target judgment result is high level, it indicates that a ground fault occurs; otherwise, there is no ground fault.

[0073] Specifically, when the input voltage and current pulse signals meet the grounding judgment logic, that is, the positive polarity transient voltage signal Up is at a low level and the negative polarity transient current signal In is at a high level at the same time, or the negative polarity transient voltage signal Un is at a high level and the positive polarity transient current signal Ip is at a low level at the same time, the output terminal Pout of the judgment module 4 outputs the target judgment result as a high level.

[0074] In addition, in order to improve the accuracy of the detection module, the number of each module in the detection device can be multiple, and multiple identical modules are incorporated into the device in series. Specifically, the number of filtering modules includes at least one, the number of amplification modules includes at least one, the number of extraction modules includes at least one, and the number of judgment modules includes at least one.

[0075] An exemplary embodiment of the present invention provides a ground fault processing system, see Figure 6 The ground fault processing system comprises a ground fault detection device as described in any one of the first aspects, and a control device 5, wherein the detection device is electrically connected to the control device 5. The control device 5 is used to receive a target judgment result and perform circuit processing based on the target judgment result.

[0076] Specifically, the control device includes a review module 51 and a processing module 52 . The review module 51 is electrically connected to the processing module 52 , and the review module 51 is electrically connected to the detection device.

[0077] The review module 51 can be electrically connected to the determination module 4 in the detection device to receive the target determination result. The review module is loaded with a grounding algorithm and performs a review based on the target determination result to obtain a review result.

[0078] Regarding the grounding algorithm, the first half-wave algorithm is preferably used in this embodiment. The first half-wave algorithm (Half-Wave Method) is a calculation method for analyzing transient characteristics in power systems, especially under ground fault or electrical fault conditions. It is mainly used to estimate and analyze the waveforms and changes of current and voltage under fault conditions. The core idea of ​​the algorithm is to predict the behavior of the system under fault conditions by simulating the first half-wave of the current waveform in the power system. The first half-wave algorithm usually focuses on the first half-wave of the current or voltage after the fault occurs. That is, only the positive half-wave (from zero to the peak) of the current or voltage waveform is considered to simplify calculation and analysis. In power system analysis, current and voltage waveforms can be simplified to periodic sine waves or pulse waveforms. The first half-wave algorithm analyzes the impact of the fault by modeling the first half-wave of these waveforms. Under ground fault or other electrical fault conditions, the first half-wave algorithm helps engineers calculate and predict the transient behavior of current and voltage in the system. This includes calculating the instantaneous current, instantaneous voltage and their changing characteristics after the fault occurs. The first half-wave algorithm reduces the complexity of analysis by simplifying the calculation of current and voltage waveforms. For some fault conditions, the first half-wave algorithm can provide sufficiently accurate analysis results to help make quick decisions.

[0079] The processing module 52 is used to receive the review result and perform circuit processing based on the review result. The processing method includes but is not limited to driving the control device to perform ground fault protection, and can also be sent to the management device for ground fault warning, etc.

[0080] In one embodiment, in order to facilitate the synchronization of the processing system, the processing system also includes an AD acquisition module, the input end of the AD acquisition module is electrically connected to the amplification module 2, and the output end of the AD acquisition module is electrically connected to the review module 51 to collect AD signals and achieve synchronization of the processing system.

[0081] It is known from common technical knowledge that the present invention can be implemented by other embodiments that do not deviate from its spirit or essential features. Therefore, the above disclosed embodiments are only illustrative in all respects and are not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are included in the present invention.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A ground fault detection device, characterized in that: The detection device includes a filtering module, an amplification module, an extraction module and a judgment module; The input end of the filtering module is used to receive an initial signal and filter the initial signal; The input end of the amplification module is electrically connected to the output end of the filtering module, and the amplification module is used to amplify the filtered initial signal; The input end of the extraction module is electrically connected to the output end of the amplification module, and the extraction module is used to extract the transient characteristic signal from the amplified initial signal; The input end of the judgment module is electrically connected to the output end of the extraction module. The judgment module is used to determine a target judgment result of a ground fault according to the transient characteristic signal. The output end of the judgment module is used to output the target judgment result. The target judgment result is used for driving circuit processing.

2. The detection device according to claim 1, characterized in that The filtering module comprises a notch filter circuit, and the limiting frequency of the notch filter circuit is a first preset frequency.

3. The detection device according to claim 2, characterized in that: The trap circuit includes a low-pass filter subcircuit and a high-pass filter subcircuit, and the low-pass filter subcircuit and the high-pass filter subcircuit are connected in parallel with each other.

4. The detection device according to claim 1, characterized in that: The amplification module comprises a second-order active low-pass filter circuit, the cut-off frequency of the second-order active low-pass filter circuit is a second preset frequency, and the amplification factor of the second-order active low-pass filter circuit is a preset amplification factor.

5. The detection device according to claim 1, characterized in that: The transient characteristic signal includes a first characteristic signal and a second characteristic signal; The extraction module includes a first characteristic signal extraction circuit and a second characteristic signal extraction circuit, wherein the first characteristic signal extraction circuit and the second characteristic signal extraction circuit are connected in series; The first characteristic signal extraction circuit is used to extract a first characteristic signal from the amplified initial signal, and the second characteristic signal extraction circuit is used to extract a second characteristic signal from the amplified initial signal.

6. The detection device according to claim 5, characterized in that: The judgment module comprises a first characteristic signal judgment circuit, a second characteristic signal judgment circuit and a result output circuit, wherein the first characteristic signal judgment circuit and the second characteristic signal judgment circuit are connected in series to an input end of the result output circuit; The first characteristic signal judgment circuit is used to receive the first characteristic signal and output a first judgment result; the second characteristic signal judgment circuit is used to receive the second characteristic signal and output a second judgment result; the result output circuit is used to determine a target judgment result based on the first judgment result and the second judgment result.

7. The detection device according to claim 6, characterized in that: The first characteristic signal determination circuit is composed of a first NOR gate subcircuit and a second NOR gate subcircuit connected in series; And / or, the second characteristic signal determination circuit comprises a third NOR gate circuit and a fourth NOR gate circuit connected in series; And / or, the result output circuit includes an OR gate circuit.

8. The detection device according to claim 1, characterized in that: The number of the filtering modules includes at least one; and / or, the number of the amplification modules includes at least one; and / or, the number of the extraction modules includes at least one; and / or, the number of the judgment modules includes at least one.

9. A ground fault processing system, characterized in that: The processing system comprises a ground fault detection device as claimed in any one of claims 1 to 8, and a control device, wherein the detection device and the control device are electrically connected; The control device is used to receive a target judgment result and perform circuit processing based on the target judgment result.

10. The ground fault processing system according to claim 9, characterized in that: The control device comprises a review module and a processing module, wherein the review module is electrically connected to the processing module, and the review module is electrically connected to the detection device; The grounding algorithm is loaded in the review module, and the review module is used to receive the target judgment result and review based on the target judgment result to obtain a review result; The processing module is used to receive the review result and perform circuit processing based on the review result.

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