Online Detection Method and System for DC Power Supply Grounding Fault

Abstract

The present invention discloses an on-line detection method and system for DC power supply grounding faults. The method includes: S10, collecting detection data of the output end of the measured DC power supply under the condition of AC-to-earth power-on, and judging whether there is a grounding fault at the output end of the measured DC power supply according to the detection data. If so, execute step S20; otherwise, end the detection; S20, collecting the current waveform signal of the previous undetected branch on the output end with a grounding fault; S30, judging whether there is a grounding fault in the branch according to the current waveform signal. If so, execute step S40; otherwise, return to S20; S40, generating a fault location prompt signal according to the phase of the current waveform signal. The present invention can achieve on-line fault detection. The whole detection process will not affect the equipment running normally online, plays a positive role in maintaining the stable operation of nuclear power plants, and has high detection efficiency. It can quickly and accurately lock the grounding fault point, effectively shortening the troubleshooting man-hours for grounding faults.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical equipment maintenance, and particularly to an on-line detection method and system for DC power supply grounding faults. Background Art

[0002] Due to the important position of the DC power supply system in nuclear power plants, the reliability and safety of its system directly affect the safety of the entire power plant. Given the special application of the DC power supply in nuclear power units, especially in control circuits and protection circuits, DC system failures will become one of the key safety hazards for major failures in nuclear power units, especially the hazards of DC system grounding faults.

[0003] There are a large number and various types of on-site equipment involved in the DC system of nuclear power plants. During the long-term operation of the system, due to many reasons such as environmental changes, climate changes, on-site cable loosening, connector aging, and equipment itself problems, DC system grounding faults will inevitably occur on-site. Especially during the construction of power plants, due to various problems such as on-site construction, equipment installation, and cable termination, the probability of power supply failures in the power system will be significantly increased. In addition, the longer the DC system is in operation, the greater the probability of DC system grounding faults.

[0004] Although there is a corresponding DC grounding insulation alarm system in nuclear power plants that can detect DC system grounding faults, the currently commonly used detection method is the power-off troubleshooting method. The power-off process during detection not only seriously affects the daily operation of nuclear power plants but also has a large workload; in related technologies, the on-line detection method cannot accurately locate the grounding fault equipment. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an on-line detection method and system for DC power supply grounding faults in view of at least one defect existing in the prior art.

[0006] The technical solution adopted by the present invention to solve its technical problems is to construct an on-line detection method for DC power supply grounding faults, including the following steps:

[0007] S10. Collect the detection data of the output terminal of the measured DC power supply in the state of AC energized to the ground, and judge whether there is a grounding fault at the output terminal of the measured DC power supply according to the detection data. If so, execute step S20; otherwise, end the detection;

[0008] S20. Collect the current waveform signal of the previous undetected branch on the output terminal with a grounding fault;

[0009] S30. Judge whether there is a grounding fault in the branch according to the current waveform signal. If so, execute step S40; otherwise, return to step S20;

[0010] S40. Generate a fault location prompt signal according to the phase of the current waveform signal.

[0011] Preferably, the detection data includes a positive terminal AC voltage component, a positive terminal AC current component, a negative terminal AC voltage component, and a negative terminal AC current component.

[0012] In the S10, determining whether there is a ground fault at the output terminal of the measured DC power supply according to the detection data includes: respectively calculating the terminal-to-ground impedance of the measured DC voltage according to the AC voltage component and the AC current component of the corresponding output terminal, and determining whether there is at least one case where the terminal-to-ground impedance is less than the fault threshold. If so, it is determined that there is a ground fault at the output terminal of the measured DC power supply; otherwise, it is determined that there is no ground fault at the output terminal of the measured DC power supply; wherein, the terminal-to-ground impedance includes a positive terminal-to-ground impedance and a negative terminal-to-ground impedance.

[0013] Preferably, the S30 includes:

[0014] S301. Perform a similarity analysis on the current waveform signal according to a preset waveform to obtain a similarity coefficient, and determine whether the similarity coefficient is greater than the similarity threshold. If so, execute step S302; otherwise, mark the branch as a dual-power supply branch and execute step S303.

[0015] S302. Calculate the branch-to-ground impedance according to the current waveform signal and the AC voltage component of the corresponding output terminal, and determine whether the branch-to-ground impedance is less than the fault threshold. If so, it is determined that there is a ground fault in the branch and execute the S40; otherwise, it is determined that there is no ground fault in the branch and execute S303.

[0016] S303. Determine whether there is still an undetected branch at the output terminal. If so, return to the S20; otherwise, perform a fault round-robin check on the dual-power supply branch to determine the branch where the ground fault occurs.

[0017] Preferably, after the S30, it further includes:

[0018] S31. Generate different alarm signals according to the branch-to-ground impedance; wherein, the alarm signals include an insulation low alarm signal and a ground alarm signal.

[0019] Preferably, in the S31, generating different alarm signals according to the branch-to-ground impedance includes: if the branch-to-ground impedance is less than the first alarm threshold, generating the insulation low alarm signal; if the branch-to-ground impedance is less than the second alarm threshold, generating the ground alarm signal.

[0020] Preferably, after the step S20, the method further includes: S21, denoising the current waveform signal according to the pre-collected background noise.

[0021] Preferably, after the step S40, the method further includes:

[0022] S50, after disconnecting the connection between the branch with a ground fault and the measured DC power supply, returning to the step S10.

[0023] The present invention also provides a DC power supply ground fault online detection system, including an AC signal source, a first judgment unit, a signal acquisition unit, a second judgment unit, a main control unit, and a fault location prompt unit;

[0024] The AC signal source is used to set the output end of the measured DC power supply to an AC power-on state with respect to the ground;

[0025] The first judgment unit is used to collect detection data of the output end of the measured DC power supply according to a first acquisition instruction, judge whether there is a ground fault at the output end of the measured DC power supply according to the detection data, and send the judgment result to the main control unit;

[0026] The signal acquisition unit is used to collect the current waveform signal of an undetected branch on the output end with a ground fault when receiving a second acquisition instruction;

[0027] The second judgment unit is used to judge whether there is a ground fault in the branch according to the current waveform signal, and send the judgment result to the main control unit;

[0028] The main control unit is used to generate the first acquisition instruction according to the input instruction of the user, and also generate the second acquisition instruction when there is a ground fault at the output end of the measured DC power supply, and generate a fault location detection instruction when there is a ground fault in the branch;

[0029] The fault location prompt unit is used to generate a fault location prompt signal according to the phase of the current waveform signal when receiving the location detection instruction.

[0030] Preferably, the DC power supply ground fault online detection system further includes: a denoising unit, which is used to denoise the current waveform signal according to the pre-collected background noise.

[0031] Preferably, the system further includes: an alarm unit, which is used to generate different alarm signals according to the impedance of the branch to the ground; wherein, the alarm signals include an insulation low alarm signal and a ground alarm signal.

[0032] The present invention has at least the following beneficial effects: It provides an online detection method for DC power supply grounding faults. The method includes: S10. Collect the detection data at the output end of the DC power supply to be measured under the condition of AC-to-earth power-on, and determine whether there is a grounding fault at the output end of the DC power supply to be measured according to the detection data. If so, execute step S20; otherwise, end the detection. S20. Collect the current waveform signal of the previous undetected branch on the output end with a grounding fault. S30. Determine whether there is a grounding fault in the branch according to the current waveform signal. If so, execute step S40; otherwise, return to S20. S40. Generate a fault location prompt signal according to the phase of the current waveform signal. The present invention can achieve online fault detection. The entire detection process will not affect the equipment operating normally online, plays a positive role in maintaining the stable operation of nuclear power plants, and has high detection efficiency. It can quickly and accurately lock the grounding fault point, effectively shortening the troubleshooting man-hours for grounding faults. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be further described below in conjunction with the drawings and embodiments. In the drawings:

[0034] Figure 1 is a flowchart of the online detection method for DC power supply grounding faults provided by the present invention;

[0035] Figure 2 is an equivalent schematic diagram of collecting detection data in some embodiments provided by the present invention;

[0036] Figure 3 is a flowchart of step S30 in the online detection method for DC power supply grounding faults provided by the present invention;

[0037] Figure 4 is a power distribution structure diagram of a dual-power supply branch in some embodiments;

[0038] Figure 5 is a structure diagram of the online detection system for DC power supply grounding faults provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] In order to have a clearer understanding of the technical features, objectives, and effects of the present invention, the specific embodiments of the present invention will now be described in detail with reference to the drawings.

[0040] Refer to Figure 1 , an online detection method for DC power supply grounding faults, which is used to perform online grounding fault detection on a target DC power supply after an alarm signal is issued by a safety-class or non-safety-class DC grounding insulation alarm system to determine the specific grounding fault point. The method includes step S10, step S20, step S30, and step S40.

[0041] Step S10 includes: collecting detection data of the output terminal of the DC power supply under test in the state of AC-to-ground power-on, and judging whether there is a grounding fault at the output terminal of the DC power supply under test according to the detection data. If so, execute step S20; otherwise, end the detection.

[0042] Figure 2 FIG. 4 is an equivalent schematic diagram of collecting detection data in some embodiments provided by the present invention. The load is equivalent to a resistor RX. The first output terminal of the AC signal source S is connected to the positive terminal of the DC power supply under test through a first balancing resistor R1. The first output terminal of the AC signal source S is also connected to the negative terminal of the DC power supply under test through a second balancing resistor R2. The second output terminal of the AC signal source S is grounded. The AC signal output by the AC signal source S makes the output terminal of the DC power supply under test enter the state of ground power-on. At this time, for the positive terminal, the AC signal source S forms a loop through the first balancing resistor R1 and the equivalent-to-ground resistor R3 at the positive terminal. Therefore, the resistance value can be calculated through the AC voltage component and the AC current component at both ends of the equivalent-to-ground resistor R3 at the positive terminal. For the negative terminal, the AC signal source S forms a loop through the second balancing resistor R2 and the equivalent-to-ground resistor R4 at the negative terminal. The resistance value can also be calculated through the AC voltage component and the AC current component at both ends of the equivalent-to-ground resistor R4 at the negative terminal. Therefore, in some embodiments, the detection data includes the positive-terminal AC voltage component, the positive-terminal AC current component, the negative-terminal AC voltage component, and the negative-terminal AC current component.

[0043] Further, in some embodiments, judging whether there is a grounding fault at the output terminal of the DC power supply under test according to the detection data in step S10 includes: respectively calculating the terminal-to-ground impedance of the DC voltage under test according to the AC voltage component and the AC current component of the corresponding output terminal, and judging whether there is a situation where at least one terminal-to-ground impedance is less than the fault threshold. If so, it is determined that there is a grounding fault at the output terminal of the DC power supply under test; otherwise, it is determined that there is no grounding fault at the output terminal of the DC power supply under test. Among them, the terminal-to-ground impedance includes the positive-terminal-to-ground impedance and the negative-terminal-to-ground impedance.

[0044] Specifically, based on Ohm's law, the positive-terminal-to-ground impedance of the DC voltage under test is calculated according to the positive-terminal AC voltage component and the positive-terminal AC current component, and the negative-terminal-to-ground impedance of the DC voltage under test is calculated according to the negative-terminal AC voltage component and the negative-terminal AC current component. As long as the positive-terminal-to-ground impedance and / or the negative-terminal-to-ground impedance is less than the fault threshold, it is determined that there is a grounding fault at the output terminal of the DC power supply under test. If both the positive-terminal-to-ground impedance and the negative-terminal-to-ground impedance are not less than the fault threshold, it is determined that there is no grounding fault at the output terminal of the DC power supply under test. Among them, the fault threshold can be set according to the detection environment (such as environmental humidity, temperature, etc.). Further, the fault threshold can be 50 kΩ.

[0045] In some embodiments, the on-line detection method for DC power supply grounding faults further includes: Step S11, when the output terminal of the measured DC power supply is in a state of AC-to-earth power-on, keep the current waveform signal detection device in a stationary state, collect the ground wire noise of the measured DC power supply, perform waveform analysis on the ground wire noise, and generate a device calibration signal according to the analysis result. Specifically, the waveform analysis includes: comparing and analyzing the ground wire noise waveform with the output signal of the AC signal source. If the amplitude or frequency ratio of the two exceeds the relevant threshold, it is determined that the sensitivity of the detection device does not meet the requirements, and a device calibration signal needs to be generated to prompt the user to calibrate the current waveform signal detection device. For the case where the current waveform signal detection device is a detection device composed of current transformers, the calibration process includes cleaning the interface of the iron core in the current transformer. If the current waveform signal detection device is a mobile device, the sensitivity may decrease due to insufficient power. Correspondingly, the calibration process also includes replacing the battery.

[0046] Generally, the output terminal of each DC power supply serves as a busbar and supplies power to multiple loads in parallel. The power supply circuit of one load is equivalent to a branch. When there is a grounding fault in a certain branch, the output terminal impedance of the DC power supply will be pulled down. It is impossible to determine which branch has a grounding fault based solely on this impedance. For the branches without grounding faults, since their impedance to the ground is large, the AC current flowing through these branches is small; while for the branches with grounding faults, since their impedance to the ground is small, the AC current flowing through these branches is large. Therefore, in order to further determine the branch where the grounding fault occurs, in this embodiment, Step S20 includes: collecting the current waveform signal of an undetected branch on the output terminal with a grounding fault.

[0047] In some embodiments, the on-line detection method for DC power supply grounding faults further includes: Step S21, perform denoising processing on the current waveform signal according to the pre-collected background noise. Specifically, place the current waveform signal detection device in the environment where the measured DC power supply is located. Without detecting the current waveform signals of any branches, keep it in a stationary state, use the detection signal obtained by the current waveform signal detection device as the background noise, and then perform algorithm operations (such as subtraction operations) on the current waveform signal according to the background noise to eliminate the background noise component in the current waveform signal.

[0048] Step S30 includes: judging whether there is a grounding fault in the branch according to the current waveform signal. If so, execute Step S40; otherwise, collect the current waveform signal of the next undetected branch on the output terminal and return to S30.

[0049] Further, in some embodiments, such as Figure 3As shown, determining whether there is a ground fault in the branch according to the current waveform signal in step S30 includes step S301, step S302, and step S303.

[0050] Step S301 includes: performing similarity analysis on the current waveform signal according to a preset waveform to obtain a similarity coefficient, and determining whether the similarity coefficient is greater than a similarity threshold. If so, execute step S302; otherwise, mark the branch as a dual-power-supply branch and execute step S303.

[0051] Specifically, for a single-power-supply branch, the amplitudes and frequencies of the positive and negative half-cycles of the detected current waveform signal are basically the same, and its waveform shape is basically similar to the shape of the AC signal input by the AC signal source. Specifically, the peak-to-peak value may be reduced proportionally due to the shunt effect, while the frequency is basically the same.

[0052] Figure 4 is the power distribution structure diagram of a dual-power-supply branch in some embodiments. IN1 is connected to the positive terminal bus of the first power supply, and IN2 is connected to the positive terminal bus of the second power supply; combined Figure 2 Analysis shows that only a single-direction signal output by the AC signal source can pass through the diode. When the ground fault point and the acquisition position of the current waveform signal are on both sides of the diode respectively, the detected current waveform signal will be an "irregular waveform". The specific reasons are as follows: Refer to Figure 4 , assuming that the ground fault point is A. Since point A is on the anode side of diode D1, and the acquisition position of the current waveform signal is point B, which is also on the anode side of diode D1, the AC signal can still flow through the positive terminal equivalent resistance R3 as normal. Then, the detected current waveform signal will still be similar to the shape of the AC signal input by the AC signal source. In this case, this loop will not be marked as a "dual-power-supply branch", but will participate in the detection process of the single-power-supply branch and can also complete the detection process; if the ground fault point is C, since point C is on the cathode side of diode D1, and the acquisition position of the current waveform signal is point B, the current signal of the negative half-cycle AC signal input by the AC signal source flowing through the positive terminal equivalent resistance R3 cannot pass through diode D1, ultimately resulting in the detected current waveform signal showing an "irregular waveform". And because the current waveform signal at this time lacks some AC components, the ground impedance calculated according to this current waveform signal is inaccurate, and it is impossible to determine whether there is a ground fault in the dual-loop power supply branch.

[0053] In some examples, the similarity analysis includes: amplifying the current waveform signal based on the peak-to-peak ratio of the preset waveform and the current waveform signal, performing coincidence analysis on the amplified current waveform signal, and using the obtained coincidence as the similarity coefficient. Additionally, the preset waveform should be determined based on the type of AC signal input by the AC signal source, and the signal types include sine wave, triangular wave, etc.

[0054] Step S302 includes: calculating the branch-to-ground impedance based on the current waveform signal and the AC voltage component at the corresponding output terminal, determining whether the branch-to-ground impedance is less than the fault threshold. If so, it is determined that there is a ground fault in the branch, and S40 is executed; otherwise, it is determined that there is no ground fault in the branch, and S303 is executed. Among them, the fault threshold can be 50 kΩ.

[0055] Step S303 includes: determining whether there are still undetected branches at the output terminal. If so, return to S20; otherwise, perform fault round-robin detection on the branches powered by dual power supplies to determine the branch with the ground fault.

[0056] Since there may be multiple branches powered by dual power supplies at the output terminal of the DC power supply, and there may also be a situation where multiple branches powered by dual power supplies have ground faults. Further, in some embodiments, the fault round-robin detection includes: sequentially collecting the feeder current signals on the other side of the diode of all branches powered by dual power supplies, and determining whether there is a ground fault in the corresponding branch based on the feeder current signals. Specifically, taking a branch powered by dual power supplies as an example, if the first collection position is on the anode side of the diode, then the current waveform signal on the cathode side of the diode should be collected as the feeder current signal this time. Then, calculate the branch-to-ground impedance based on the feeder current signal and the AC voltage signal at the collection position, and determine whether the branch-to-ground impedance is less than the fault threshold. If so, it is determined that there is a ground fault in the branch; otherwise, it is determined that there is no ground fault in the corresponding branch. It can be understood that after determining that there is a ground fault in the branch powered by dual power supplies, a fault location prompt signal can also be generated based on the feeder current signal. It can be understood that when performing the fault round-robin detection, the fault detection of all branches powered by single power supplies has been completed. Therefore, the detection task can be ended after the fault round-robin detection is completed.

[0057] In some embodiments, after S30, there is also step S31 of generating different alarm signals based on the branch-to-ground impedance. Among them, the alarm signals include an insulation low alarm signal and a ground alarm signal. The insulation low alarm signal is used to prompt the user that there may be situations such as slight damage to the cable or chemical corrosion of components on the load of this branch; the insulation low alarm signal is used to prompt the user that there has been a serious ground fault on the load of this branch and immediate troubleshooting measures need to be taken.

[0058] Further, in some examples, generating different alarm signals according to the branch-to-ground impedance in step S31 includes: if the branch-to-ground impedance is less than the first alarm threshold, generating an insulation-low alarm signal; if the branch-to-ground impedance is less than the second alarm threshold, generating a grounding alarm signal. Wherein, the first alarm threshold can be 50 kΩ, and the second alarm threshold can be 6.25 kΩ.

[0059] Step S40 includes: generating a fault location prompt signal according to the phase of the current waveform signal. Specifically, the process of generating a fault location prompt signal according to the phase of the current waveform signal is as follows: As Figure 2 shown, taking a branch at the positive terminal of the DC power supply under test as an example, when collecting the current waveform signal of the branch, if the current direction in the positive half-cycle of the current waveform signal is flowing towards the positive terminal of the load, it indicates that the current waveform signal acquisition point is located between the positive terminal of the DC power supply under test and the grounding fault point, that is, the generated fault location prompt signal should point to the grounding fault point; if the current direction in the positive half-cycle of the current waveform signal is flowing towards the positive terminal of the DC power supply under test, it indicates that the current waveform signal acquisition point is located between the grounding fault point and the positive terminal of the load, that is, the generated fault location prompt signal points to the grounding fault point. Similarly, when collecting the current waveform signal of a branch at the negative terminal, the generated fault location prompt signal also points to the grounding fault point.

[0060] Further, in some embodiments, step S40 further includes: adjusting the acquisition point according to the fault location prompt signal. When the prompt direction of the fault location prompt signal is reversed compared with the prompt direction of the fault location prompt signal generated in the previous detection, it indicates that the acquisition point is close to the grounding fault point, thereby determining the grounding fault point.

[0061] In some cases, there may be a situation where multiple branches of the DC power supply under test have grounding faults. After detecting that one of the branches of the DC power supply under test has a grounding fault, in order to further determine whether there are still grounding faults in other branches, in some embodiments, after S40, it further includes: step S50, after disconnecting the connection between the branch with the grounding fault and the DC power supply under test, returning to S10.

[0062] Reference Figure 5 In addition, the present invention also provides a DC power supply grounding fault online detection system, including an AC signal source, a first judgment unit, a signal acquisition unit, a second judgment unit, a main control unit, and a fault location prompt unit.

[0063] The AC signal source is used to set the output terminal of the DC power supply under test to an AC-to-ground energized state.

[0064] The first judgment unit is used to collect the detection data of the output terminal of the DC power supply under test according to the first collection instruction, judge whether there is a grounding fault at the output terminal of the DC power supply under test according to the detection data, and send the judgment result to the main control unit.

[0065] In some embodiments, the detection data includes the positive terminal AC voltage component, the positive terminal AC current component, the negative terminal AC voltage component, and the negative terminal AC current component.

[0066] Further, in some embodiments, the first judgment unit is used to calculate the terminal-to-ground impedance of the DC voltage under test respectively according to the AC voltage component and the AC current component of the corresponding output terminal. When at least one terminal-to-ground impedance is less than the fault threshold, it is determined that there is a grounding fault at the output terminal of the DC power supply under test. When both output terminals are greater than the fault threshold, it is determined that there is no grounding fault at the output terminal of the DC power supply under test; wherein, the terminal-to-ground impedance includes the positive terminal-to-ground impedance and the negative terminal-to-ground impedance.

[0067] The signal acquisition unit is used to collect the current waveform signal of the untested branch on the output terminal with a grounding fault when receiving the second collection instruction.

[0068] The second judgment unit is used to judge whether there is a grounding fault in the branch according to the current waveform signal, and send the judgment result to the main control unit.

[0069] Further, in some embodiments, the second judgment unit is used to perform similarity analysis on the current waveform signal according to the preset waveform to obtain a similarity coefficient. When the similarity coefficient is greater than the similarity threshold, calculate the branch-to-ground impedance according to the current waveform signal and the AC voltage component of the corresponding output terminal, and when the branch-to-ground impedance is less than the fault threshold, determine that there is a grounding fault in the branch. When the branch-to-ground impedance is not less than the fault threshold, it is determined that there is no grounding fault in the branch; when the similarity coefficient is not greater than the similarity threshold, the branch is marked as a dual-power supply branch.

[0070] The main control unit is used to generate the first collection instruction according to the user's input instruction, and also generate the second collection instruction when there is a grounding fault at the output terminal of the DC power supply under test, and generate a fault location detection instruction when there is a grounding fault in the branch.

[0071] In some embodiments, the main control unit is further used to generate the second collection instruction when there are still untested branches at the output terminal, and perform fault round-robin detection on the dual-power supply branches when there are no untested branches at the output terminal.

[0072] The fault location prompt unit is used to generate a fault location prompt signal according to the phase of the current waveform signal when receiving the location detection instruction.

[0073] In some embodiments, the on-line detection system for DC power supply grounding faults further includes: an alarm unit, configured to generate different alarm signals according to the branch-to-ground impedance; wherein, the alarm signals include an insulation low alarm signal and a grounding alarm signal.

[0074] In some embodiments, the on-line detection system for DC power supply grounding faults further includes: a denoising unit, configured to perform denoising processing on the current waveform signal according to the pre-collected background noise.

[0075] In some embodiments, the on-line detection system for DC power supply grounding faults further includes: a calibration unit, configured to collect the ground wire noise of the measured DC power supply when the current waveform signal detection device is in a predetermined condition, and generate a device calibration signal according to the ground wire noise.

[0076] The present invention has at least the following beneficial effects: providing an on-line detection method for DC power supply grounding faults, the method includes: S10, collecting the detection data of the output end of the measured DC power supply in the state of AC-to-ground power-on, and judging whether there is a grounding fault at the output end of the measured DC power supply according to the detection data. If so, execute step S20, otherwise end the detection; S20, collecting the current waveform signal of the previous undetected branch on the output end with a grounding fault; S30, judging whether there is a grounding fault in the branch according to the current waveform signal. If so, execute step S40, otherwise return to S20; S40, generating a fault location prompt signal according to the phase of the current waveform signal. The present invention can realize on-line fault detection, and the whole detection process will not affect the equipment operating normally online, which plays a positive role in maintaining the stable operation of nuclear power plants. Moreover, the detection efficiency is high, the grounding fault point can be quickly and accurately locked, and the troubleshooting working hours of the grounding fault are effectively shortened.

[0077] It can be understood that the above embodiments only represent the preferred embodiments of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent of the present invention; it should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can also be made, which all belong to the protection scope of the present invention; therefore, all equivalent transformations and modifications made to the scope of the claims of the present invention should belong to the scope covered by the claims of the present invention.

Claims

1. An on-line detection method for DC power supply grounding faults, characterized in that, it includes the following steps: S10. Collect the detection data of the output terminal of the DC power supply to be measured under the condition of AC-to-ground power-on, and judge whether there is a grounding fault at the output terminal of the DC power supply to be measured according to the detection data. If so, execute step S20; otherwise, end the detection; S20. Collect the current waveform signal of the previous undetected branch on the output terminal with a grounding fault; S30. Judge whether there is a grounding fault in the branch according to the current waveform signal. If so, execute step S40; otherwise, return to S20; S40. Generate a fault location prompt signal according to the phase of the current waveform signal; The detection data includes the positive terminal AC voltage component, the positive terminal AC current component, the negative terminal AC voltage component and the negative terminal AC current component; In S10, judging whether there is a grounding fault at the output terminal of the DC power supply to be measured according to the detection data includes: calculating the terminal-to-ground impedance of the DC voltage to be measured respectively according to the AC voltage component and the AC current component of the corresponding output terminal, and judging whether there is at least one case where the terminal-to-ground impedance is less than the fault threshold. If so, it is determined that there is a grounding fault at the output terminal of the DC power supply to be measured; otherwise, it is determined that there is no grounding fault at the output terminal of the DC power supply to be measured; wherein, the terminal-to-ground impedance includes the positive terminal-to-ground impedance and the negative terminal-to-ground impedance; S30 includes: S301. Perform similarity analysis on the current waveform signal according to a preset waveform to obtain a similarity coefficient, and judge whether the similarity coefficient is greater than the similarity threshold. If so, execute step S302; otherwise, mark the branch as a dual-power supply branch and execute step S303; S302. Calculate the branch-to-ground impedance according to the current waveform signal and the AC voltage component of the corresponding output terminal, and judge whether the branch-to-ground impedance is less than the fault threshold. If so, it is determined that there is a grounding fault in the branch, and execute S40; otherwise, it is determined that there is no grounding fault in the branch, and execute S303; S303. Judge whether there is still an undetected branch at the output terminal. If so, return to S20; otherwise, perform a fault round-robin check on the dual-power supply branch to determine the branch where the grounding fault occurs.

2. The on-line detection method for DC power supply grounding faults according to claim 1, characterized in that, after S30, it further includes: S31. Generate different alarm signals according to the branch-to-ground impedance; wherein, the alarm signals include an insulation low alarm signal and a grounding alarm signal.

3. The on-line detection method for DC power supply grounding faults according to claim 2, characterized in that, in S31, generating different alarm signals according to the branch-to-ground impedance includes: if the branch-to-ground impedance is less than the first alarm threshold, generate the insulation low alarm signal; if the branch-to-ground impedance is less than the second alarm threshold, generate the grounding alarm signal.

4. The on-line detection method for DC power supply grounding faults according to claim 3, characterized in that, After the S20, it further includes: S21, denoising the current waveform signal according to the pre-collected background noise.

5. The on-line detection method for DC power supply grounding fault according to any one of claims 1 to 4, characterized in that, after the S40, it further includes: S50, after disconnecting the connection between the branch with the grounding fault and the measured DC power supply, returning to the S10.

6. An on-line detection system for DC power supply grounding fault, characterized in that, it includes an AC signal source, a first judgment unit, a signal acquisition unit, a second judgment unit, a main control unit and a fault location prompt unit; The AC signal source is used to set the output end of the measured DC power supply to an AC power-on state to the ground; The first judgment unit is used to collect the detection data of the output end of the measured DC power supply according to the first acquisition instruction, and judge whether there is a grounding fault at the output end of the measured DC power supply according to the detection data, and send the judgment result to the main control unit; the detection data includes the positive terminal AC voltage component, the positive terminal AC current component, the negative terminal AC voltage component and the negative terminal AC current component; Judging whether there is a grounding fault at the output end of the measured DC power supply according to the detection data includes: calculating the terminal-to-ground impedance of the measured DC voltage according to the AC voltage component and the AC current component of the corresponding output end respectively, and when there is at least one terminal-to-ground impedance less than the fault threshold, it is determined that there is a grounding fault at the output end of the measured DC power supply, and when both output ends are greater than the fault threshold, it is determined that there is no grounding fault at the output end of the measured DC power supply; wherein, the terminal-to-ground impedance includes the positive terminal-to-ground impedance and the negative terminal-to-ground impedance; The signal acquisition unit is used to collect the current waveform signal of an undetected branch on the output end with a grounding fault when receiving the second acquisition instruction; The second judgment unit is used to judge whether there is a grounding fault in the branch according to the current waveform signal, and send the judgment result to the main control unit. Judging whether there is a grounding fault in the branch according to the current waveform signal includes: performing similarity analysis on the current waveform signal according to a preset waveform to obtain a similarity coefficient. When the similarity coefficient is greater than the similarity threshold, calculating the branch-to-ground impedance according to the current waveform signal and the AC voltage component of the corresponding output end, and when the branch-to-ground impedance is less than the fault threshold, it is determined that there is a grounding fault in the branch, and when the branch-to-ground impedance is not less than the fault threshold, it is determined that there is no grounding fault in the branch; when the similarity coefficient is not greater than the similarity threshold, the branch is marked as a dual-power supply branch; The main control unit is configured to generate the first acquisition instruction according to the input instruction of the user, and also generate the second acquisition instruction when there is a ground fault at the output terminal of the DC power supply under test, and generate a fault location detection instruction when there is a ground fault in the branch; the main control unit is further configured to generate a second acquisition instruction when there are still undetected branches at the output terminal, and perform fault round-robin detection on the dual-power supply branch when there are no undetected branches at the output terminal; The fault location prompting unit is configured to generate a fault location prompting signal according to the phase of the current waveform signal when receiving the location detection instruction.

7. The on-line DC power supply ground fault detection system according to claim 6, characterized in that the on-line DC power supply ground fault detection system further includes: a denoising unit, configured to perform denoising processing on the current waveform signal according to the pre-collected background noise.

8. The on-line DC power supply ground fault detection system according to claim 7, characterized in that the system further includes: an alarm unit, configured to generate different alarm signals according to the impedance of the branch to the ground; wherein, the alarm signals include an insulation low alarm signal and a ground alarm signal.

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