Intermittent grounding fault protection method and computer equipment

Abstract

The invention relates to an intermittent grounding fault protection method and computer equipment, and belongs to the technical field of power equipment protection. When it is detected that the grounding fault occurs at the current moment, the number of times that the grounding fault occurs in the power distribution network in a first time window and a second time window before the current moment is determined respectively; if the number of times of occurrence of the grounding faults in the first time window exceeds a grounding fault number fixed value corresponding to the first time window, or the number of times of occurrence of the grounding faults in the second time window exceeds a grounding fault number fixed value corresponding to the second time window, triggering a protection action; otherwise, the protection action is not triggered; the time length of the first time window is smaller than that of the second time window. According to the method, double guarantees are provided for timely and accurately identifying and removing the intermittent grounding fault, fault expansion caused by the fact that the intermittent instantaneous grounding fault is not identified or the intermittent instantaneous fault cannot be removed in time is avoided, and the safety of a power distribution network running under the protection method is higher.

Description

Technical Field

[0001] The invention relates to a protection method for intermittent grounding faults and computer equipment, belonging to the technical field of power equipment protection. Background Art

[0002] my country's medium-voltage distribution network mostly uses overhead wiring under the low-current grounding method. Single-phase grounding faults caused by various reasons are the main faults. Intermittent grounding faults occurring in the same section are instantaneous, and the grounding current is usually not large. The traditional low-current grounding fault handling solution cannot remove the intermittent grounding faults that occur repeatedly in the same section before they develop into permanent faults. There is even a defect that the accident is expanded because the traditional zero-sequence overcurrent protection and conventional low-current grounding line selection cannot remove the intermittent grounding faults in time; intermittent grounding of the power grid will bring a series of safety hazards, seriously affecting the safety and stability of the power grid operation.

[0003] In response to intermittent grounding faults in the power grid, a Chinese invention patent with application publication number CN110601157A proposes a technical solution for an intermittent single-phase grounding fault protection method and device. This technical solution determines whether an intermittent single-phase grounding fault occurs in the distribution network line and outputs an alarm signal or trips based on whether the cumulative number of grounding faults occurring within the intermittent overcurrent protection action time setting is greater than a threshold value, thereby solving the problem that the current traditional zero-sequence overcurrent protection cannot promptly remove intermittent grounding faults, leading to the expansion of accidents. However, the intermittent overcurrent protection action time setting in this technical solution is not easy to set, and may be too long or too short. When the intermittent overcurrent protection action time setting is too short, although the fault is guaranteed to be quickly cut off, when the number of grounding faults within the time setting is less than one time, the threshold value can be reached. After the time setting is passed, another grounding fault occurs immediately. At this time, the intermittent grounding fault cannot be identified, resulting in the failure to identify and cut off the fault, which may develop into a permanent fault, bringing a series of safety hazards; when the intermittent overcurrent protection action time setting is too long, the above-mentioned problem of not identifying and cutting off the fault in time can be solved. However, when the time setting has not been reached and the cumulative number of grounding faults is greater than the threshold value, it is necessary to wait until the time setting is reached before the intermittent grounding fault is identified and cut off. At this time, the intermittent grounding fault cannot be cut off in time, and there are a series of safety hazards. Therefore, the intermittent overcurrent protection action time setting of this technical solution is not easy to set, and there is a situation where the intermittent grounding fault cannot be identified or the intermittent grounding fault cannot be cut off in time, which poses a great safety hazard. Summary of the invention

[0004] The purpose of the present invention is to provide a protection method and computer equipment for intermittent grounding faults, so as to solve the problem that the intermittent overcurrent protection action time constant is difficult to set and the safety hazard is great in the current intermittent grounding fault processing method.

[0005] In order to solve the above technical problems, the present invention provides a protection method for intermittent ground faults, the method comprising: when a ground fault is detected at the current moment, the number of ground faults occurring in the power distribution network in a first time window and a second time window before the current moment is determined respectively; if the number of ground faults occurring in the first time window exceeds the fixed number of ground faults corresponding to the first time window, or the number of ground faults occurring in the second time window exceeds the fixed number of ground faults corresponding to the second time window, a protection action is triggered; otherwise, the protection action is not triggered;

[0006] The time length of the first time window is shorter than the time length of the second time window.

[0007] Further, the protection action triggered includes at least one of triggering tripping and triggering alarm.

[0008] Furthermore, the fixed value of the number of ground faults corresponding to the first time window is smaller than the fixed value of the number of ground faults corresponding to the second time window.

[0009] Furthermore, the method further includes: whenever the power distribution network meets an instantaneous ground fault condition, recording the number of times the ground fault occurs.

[0010] Furthermore, whenever the distribution network meets the conditions for an instantaneous ground fault, the moment of each instantaneous ground fault is also obtained; the method for determining the number of ground faults that occur within the first time window before the current moment includes: each time a ground fault occurs, taking the moment when the ground fault occurs this time as the starting point, judging whether the moment of each instantaneous ground fault is within the first time window starting from the current moment when the ground fault occurs this time, and obtaining the number of ground faults that occur within the first time window before the moment when the ground fault occurs this time.

[0011] Furthermore, whenever the distribution network meets the conditions for an instantaneous ground fault, the moment of each instantaneous ground fault is also obtained; the method for determining the number of ground faults that occur within the second time window before the current moment includes: for each ground fault, taking the moment when the ground fault occurs this time as the starting point, judging whether the moment of each instantaneous ground fault is within the second time window with the current moment when the ground fault occurs this time as the starting point, and obtaining the number of ground faults that occur within the second time window before the moment when the ground fault occurs this time.

[0012] Beneficial effects: As a pioneering invention, the present invention sets two time windows. When a ground fault is detected at the current moment, the number of ground faults in the distribution network in the first time window and the second time window before the current moment is determined respectively; and whether an intermittent ground fault occurs is determined based on whether the number of ground faults in the distribution network in each time window exceeds the corresponding ground fault number constant of the corresponding time window, thereby realizing protection against intermittent ground faults; the judgment logic in the two time windows adopted by the present invention, in which the short time window (the time window with a smaller time length) is set because the time for judging whether an intermittent ground fault occurs is shorter (the time for judging whether an intermittent ground fault occurs is the time window with a smaller time length). The long time window (the window length of the time window) is set, so the fault can be identified as quickly as possible and the fault protection can be triggered to remove the fault as soon as possible to protect the safety of the system; and the long time window (the time window with a longer time length) is set, so the chance and probability of finding the grounding fault in the window are greater due to the larger window, so it can avoid the time interval length of each intermittent grounding fault exceeding the short time window and causing it to not be identified and removed in time; it is equivalent to providing double protection for timely and accurate identification and removal of intermittent grounding faults, and can take into account the optimization of the expansion of faults caused by unidentified intermittent instantaneous grounding faults or the inability to remove intermittent instantaneous faults in time, so that the distribution network running under this protection method is more secure.

[0013] The present invention also provides a computer device, comprising a processor, wherein the processor is used to execute a computer program to implement the steps of the above-mentioned intermittent ground fault protection method.

[0014] The computer device can achieve the beneficial effects consistent with the above-mentioned intermittent ground fault protection method. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a flow chart for implementing the intermittent grounding fault protection method in the embodiment of the intermittent grounding fault protection method of the present invention. DETAILED DESCRIPTION

[0016] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0017] Intermittent ground fault protection method embodiment

[0018] This embodiment provides a technical solution of a protection method for intermittent ground faults, the method comprising:

[0019] When a ground fault is detected at the current moment, the number of ground faults occurring in the power distribution network in the first time window and the second time window before the current moment is determined respectively; if the number of ground faults occurring in the first time window exceeds the fixed number of ground faults corresponding to the first time window, or the number of ground faults occurring in the second time window exceeds the fixed number of ground faults corresponding to the second time window, a protection action is triggered; otherwise, the protection action is not triggered;

[0020] The time length of the first time window is shorter than the time length of the second time window.

[0021] The implementation process of the intermittent ground fault protection method is as follows: Figure 1 As shown, the following is a specific description:

[0022] When a ground fault is detected at the current moment, the number of ground faults occurring in the distribution network in the first time window and the second time window before the current moment are determined respectively; if the number N1 of ground faults occurring in the first time window exceeds the fixed number of ground faults corresponding to the first time window (i.e., the number of short-delay grounding occurrences), or the number N2 of ground faults occurring in the second time window exceeds the fixed number of ground faults corresponding to the second time window (i.e., the number of long-delay grounding occurrences), the protection action is triggered; otherwise, the protection action is not triggered; the time length of the first time window is less than the time length of the second time window, i.e., the first time window is a short-delay window, and the second time window is a long-delay window.

[0023] The above steps are performed only when intermittent grounding protection is activated. When intermittent grounding protection is not activated, the above steps are returned directly without executing the above steps. Intermittent grounding protection can be activated and deactivated independently, and is independent of conventional grounding protection. It can be activated and deactivated by setting a fixed value; the triggered protection action (i.e., intermittent grounding protection action) includes at least one of triggering a trip and triggering an alarm.

[0024] Since the time length of the first time window is shorter than that of the second time window, the first time window is also called the short time window, and the second time window is also called the long time window. The time length of the first time window and the time length of the second time window can be set according to actual needs, but it is necessary to satisfy that the time length of the first time window is shorter than that of the second time window. The short time window is set to identify and remove the fault as quickly as possible, and the long time window is set to avoid the intermittent grounding fault from occurring for a period exceeding the time length of the short time window and thus failing to be identified and removed in time. Setting two sliding time windows provides double protection for timely and accurate identification of intermittent grounding faults and removal of intermittent grounding faults.

[0025] The instantaneous ground fault number constant value of the first time window and the instantaneous ground fault number constant value of the second time window can be set according to actual needs. Among them, the ground fault number constant value corresponding to the first time window is less than the ground fault number constant value corresponding to the second time window. For example: the length of the first time window can be set to 10s, and the ground fault number constant value corresponding to the first time window can be set to 3 times; the length of the second time window can be set to 30s, and the ground fault number corresponding to the second time window can be set to 5 times.

[0026] The intermittent ground fault protection method further includes: whenever the power distribution network meets an instantaneous ground fault condition, recording the number of times the ground fault occurs.

[0027] Whenever the power distribution network meets the condition of an instantaneous ground fault, the moment of each instantaneous ground fault is also obtained; the time of each instantaneous ground fault is obtained to determine whether the fault is within the first time window and the second time window. The method of determining the number of ground faults that occurred in the first time window before the current moment includes: for each slip when a ground fault occurs, starting from the start time corresponding to the slip of the ground fault that occurs this time, judging whether the moment of each instantaneous ground fault is within the first time window starting from the current time of the ground fault, and obtaining the number of ground faults that occurred in the first time window before the moment of the ground fault that occurs this time.

[0028] Whenever the power distribution network meets the conditions for an instantaneous ground fault, the moment of each instantaneous ground fault is also obtained; the method for determining the number of ground faults occurring within a second time window before the current moment includes: for each ground fault occurring, taking the moment of the current ground fault occurring as the starting point, judging whether the moment of each instantaneous ground fault is within the second time window starting from the current moment of the current ground fault occurring, and obtaining the number of ground faults occurring within the second time window before the moment of the current ground fault occurring.

[0029] Computer device embodiment

[0030] This embodiment provides a technical solution for a computer device, which includes a processor, and the processor is used to execute a computer program to implement the steps of the intermittent grounding fault protection method in the above intermittent grounding fault protection method embodiment.

[0031] Since the specific implementation process and principle of the computer device of this embodiment have been described in detail in the embodiment of the protection method for intermittent grounding faults, they will not be described in detail here.

Claims

1. A protection method for intermittent ground faults, characterized in that: include: When a ground fault is detected at the current moment, the number of times the ground fault occurs in the power distribution network in a first time window and a second time window before the current moment is determined respectively; If the number of ground faults occurring in the first time window exceeds the set value of the number of ground faults corresponding to the first time window, or the number of ground faults occurring in the second time window exceeds the set value of the number of ground faults corresponding to the second time window, the protection action is triggered; otherwise, the protection action is not triggered; The time length of the first time window is shorter than the time length of the second time window.

2. The intermittent ground fault protection method according to claim 1, characterized in that: The protection action triggered includes at least one of triggering a trip and triggering an alarm.

3. The intermittent ground fault protection method according to claim 1, characterized in that: The fixed value of the number of ground faults corresponding to the first time window is smaller than the fixed value of the number of ground faults corresponding to the second time window.

4. The intermittent ground fault protection method according to claim 1 or 3, characterized in that: Also includes: Whenever the distribution network meets the conditions for an instantaneous ground fault, the number of ground faults occurring is recorded.

5. The intermittent ground fault protection method according to claim 4, characterized in that: Whenever the power distribution network meets a transient ground fault condition, the time of each transient ground fault is also obtained; The method for determining the number of ground faults occurring within the first time window before the current moment includes: each time a ground fault occurs, taking the moment when the ground fault occurs this time as the starting point, judging whether the moment of each instantaneous ground fault is within the first time window starting from the current moment when the ground fault occurs this time, and obtaining the number of ground faults occurring within the first time window before the moment when the ground fault occurs this time.

6. The intermittent ground fault protection method according to claim 4, characterized in that: Whenever the power distribution network meets a transient ground fault condition, the time of each transient ground fault is also obtained; The method for determining the number of ground faults occurring within a second time window before a current moment includes: for each ground fault occurring, taking the moment of the current ground fault occurrence as a starting point, judging whether the moment of each instantaneous ground fault is within the second time window taking the current moment of the current ground fault occurrence as a starting point, and obtaining the number of ground faults occurring within the second time window before the moment of the current ground fault occurrence.

7. A computer device comprising a processor, characterized in that: The processor is used to execute a computer program to implement the steps of the intermittent ground fault protection method according to any one of claims 1 to 6.

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