Pre-screening device and method based on small resistance grounding instantaneous arc tripping

Abstract

The present application discloses a pre-screening device and method based on instantaneous arc tripping due to low-resistance grounding, and relates to the technical field of grounding fault processing equipment, which includes a pre-screening mechanism and a low-resistance grounding mechanism; the pre-screening mechanism includes a phase circuit breaker and a pre-screening switch, the output end of the pre-screening switch is connected to the input end of the phase circuit breaker, the phase circuit breaker includes a first switch, a second switch and a third switch connected in parallel with each other, the first switch, the second switch and the third switch are arranged one by one corresponding to the three-phase line, a current limiting resistor is installed on the output end line of the phase circuit breaker, and the output end of the current limiting resistor is grounded; the low-resistance grounding mechanism includes a grounding switch and a grounding resistor, the output end of the grounding switch is connected to the input end of the grounding resistor, and the output end of the grounding resistor is grounded. The pre-screening switch and the grounding switch are arranged in parallel with each other. The present application has the effect of reducing the influence of instantaneous single-phase grounding faults on the power supply stability of the low-resistance grounding system.

Description

Technical Field

[0001] The present application relates to the technical field of ground fault processing equipment, and in particular to a pre-screening device and method based on small resistance grounding instantaneous arc tripping. Background Art

[0002] In the power supply line of the power system, different short-circuit faults may occur during operation under the influence of some uncontrollable factors. According to the type of short-circuit fault, it can be divided into single-phase grounding fault, multi-phase grounding fault and intermittent grounding fault. The occurrence of grounding fault will not only cause accidents such as equipment damage and casualties, but also reduce the stability of power supply of the power grid.

[0003] In the prior art, the technical solutions for handling single-phase grounding faults include: arc suppression coil grounding system, low resistance grounding system and active intervention arc suppression system, etc. Among them, the principle of handling single-phase grounding faults through low resistance grounding system is to connect a resistor with a relatively small resistance value to the neutral point line of the power system to achieve grounding. The advantage of low resistance grounding system is that it can quickly cut off the fault and effectively suppress overvoltage phenomenon.

[0004] However, the low-resistance grounding system also has certain application disadvantages. For example, the tripping frequency of the low-resistance grounding system is relatively high, that is, the low-resistance grounding system adopts tripping processing for both instantaneous grounding faults and permanent grounding faults. However, the use of a low-resistance grounding system in a line with a high tripping frequency will cause the stability of the line power supply to be significantly reduced, seriously affecting the production and life of power supply users. Summary of the invention

[0005] In order to reduce the impact of instantaneous single-phase grounding faults on the power supply stability of a low-resistance grounding system, the present application provides a pre-screening device and method based on low-resistance grounding instantaneous arc tripping.

[0006] In the first aspect, the pre-screening device based on small resistance grounding instantaneous arc tripping provided by the present application adopts the following technical solution:

[0007] A pre-screening device based on small resistance grounding instantaneous arc tripping, comprising a pre-screening mechanism and a small resistance grounding mechanism;

[0008] The pre-screening mechanism includes a phase circuit breaker and a pre-screening switch, the output end of the pre-screening switch is connected to the input end of the phase circuit breaker, the phase circuit breaker includes a first switch, a second switch and a third switch connected in parallel, the first switch, the second switch and the third switch are arranged in one-to-one correspondence with the three-phase lines, a current limiting resistor is installed on the output end line of the phase circuit breaker, and the output end of the current limiting resistor is grounded;

[0009] The low-resistance grounding mechanism comprises a grounding switch and a grounding resistor. The output end of the grounding switch is connected to the input end of the grounding resistor, and the output end of the grounding resistor is grounded.

[0010] The pre-screening switch and the grounding switch are arranged in parallel with each other.

[0011] Through the above technical solution, when the power grid system operates normally, the grounding switch in the device is in the open state, that is, the low-resistance grounding mechanism is in the offline state, and the pre-screening switch is in the closed state, that is, the pre-screening mechanism is in the online state.

[0012] When a single-phase grounding fault occurs in the power grid system, the switch of the phase where the fault occurs (i.e., one of the first switch, the second switch, and the third switch of the phase-splitting circuit breaker) is closed. After closing, observe whether the single-phase grounding fault disappears. If the single-phase grounding fault disappears, the fault is a transient fault and the device can be directly exited; if the fault still exists, the fault is a permanent fault. At this time, the pre-screening switch is opened, and the grounding switch is opened and closed, and the low-resistance grounding mechanism is put into use to continuously transfer the fault current, so that the operator can handle the permanent single-phase grounding fault.

[0013] Based on the principle of low-resistance grounding, this device adds a pre-screening mechanism for pre-screening instantaneous single-phase grounding faults. When a single-phase grounding fault occurs, the possibility of the low-resistance grounding mechanism being affected by the instantaneous single-phase grounding fault and started is effectively reduced by eliminating the instantaneous single-phase grounding fault. Therefore, the instantaneous single-phase grounding fault will no longer trigger the low-resistance grounding mechanism, thereby effectively reducing the impact of the instantaneous single-phase grounding fault on the power supply stability of the low-resistance grounding system.

[0014] In addition, the device can determine the specific phase of the single-phase grounding fault by closing the three switches of the phase-splitting circuit breaker in sequence, thereby providing more accurate maintenance positioning for the faulty phase and improving the work efficiency of grounding fault maintenance.

[0015] In a preferred example, the present application may be further configured as follows: a first current transformer is installed on the grounding line of the current limiting resistor, and a second current transformer is installed on the output line of the grounding resistor.

[0016] Through the above technical solution, by setting the first current transformer on the grounding line of the current limiting resistor, it is possible to know whether a short-circuit current passes after a switch of the phase circuit breaker is closed, so as to judge whether the closing phase of the phase circuit breaker is correct (that is, whether the closing switch corresponds to the fault phase).

[0017] Similarly, a second current transformer is installed on the output line of the grounding resistor to monitor the current flowing through the grounding resistor.

[0018] In a preferred example, the present application may be further configured as follows: further comprising a pre-circuit breaker, wherein the pre-circuit breaker is installed on a common input terminal line of the pre-screening switch and the grounding switch.

[0019] Through the above technical solution, a pre-circuit breaker is installed on the common input end line of the grounding switch and the pre-screening switch to facilitate the installation and maintenance of the device.

[0020] In the second aspect, based on the above-mentioned pre-screening device based on small resistance grounding instantaneous arc tripping, the present application also provides a pre-screening method based on small resistance grounding instantaneous arc tripping, adopting the following technical solution:

[0021] A pre-screening method based on small resistance grounding instantaneous arc tripping, the method comprising:

[0022] When the power supply line operates normally, the pre-screening switch is closed and the grounding switch is opened;

[0023] When a single-phase grounding fault occurs, a switch of one phase of the phase-splitting circuit breaker is controlled to close;

[0024] If the single-phase grounding fault disappears, the device exits; if the single-phase grounding fault still exists, the phase circuit breaker and the pre-screening switch are disconnected, and the grounding switch is closed.

[0025] Through the above technical scheme, instantaneous single-phase grounding faults are screened out based on the above method, that is, before the low-resistance grounding mechanism is put into use, the instantaneous single-phase grounding faults are eliminated, and the low-resistance grounding mechanism is put into use only when a permanent single-phase grounding fault occurs, which effectively reduces the impact of instantaneous single-phase grounding faults on the power supply stability of the low-resistance grounding system, and also improves the power supply stability of the power supply line where the low-resistance grounding system is located.

[0026] In a preferred example, the present application may be further configured as follows: controlling a certain phase switch of the phase-splitting circuit breaker to close includes:

[0027] If there is no abnormality in the first current transformer after the switch that is first closed in the phase circuit breaker is closed, the switch that is first closed in the phase circuit breaker is opened, and other switches that have not been closed in the phase circuit breaker are closed in sequence.

[0028] Through the above technical solution, when the switch in the phase-splitting circuit breaker is closed incorrectly (that is, the closed switch and the phase where the fault is located do not correspond), at this time, the wrongly closed switch is opened, and the switches in the phase-splitting circuit breaker that are not closed during this fault processing are closed in sequence, thereby fully ensuring the closing accuracy of the phase-splitting circuit breaker, and making the device have the functions of fault tolerance and error correction.

[0029] In a preferred example, the present application may be further configured such that after the phase circuit breaker is closed correctly, the following steps are further included:

[0030] Obtaining the closing times of three switches in the phase circuit breaker to generate a total closing times;

[0031] Obtaining the closing upper limit number of times of the phase circuit breaker and a preset balance trigger value, and calculating and generating a balance comparison value based on the total closing number of times, the closing upper limit number of times, and the balance trigger value;

[0032] comparing the balance trigger value with the balance comparison value;

[0033] If the balance comparison value is less than the balance trigger value, there is no need to set the priority closing object; if the balance comparison value is greater than or equal to the balance trigger value, the priority closing object is set in ascending order according to the number of closing times of multiple switches in the phase circuit breaker.

[0034] During the development and performance testing of the phase-splitting circuit breaker equipment, the mechanical characteristics of different switches in the phase-splitting circuit breaker will be tested, including the test of the number of closing and opening times, to obtain the upper limit of the number of closing and opening times of the equipment, so as to estimate the aging time of the equipment. Then, through the above technical solution, after the instantaneous fault pre-screening of a single-phase grounding fault is completed (that is, after the phase-splitting circuit breaker is closed correctly), based on the total closing times of the phase-splitting circuit breaker (that is, the sum of the closing times of the three switches), the upper limit of closing times (the sum of the maximum closing times of the three switches of the phase-splitting circuit breaker obtained in the test) and the balance trigger value (the difference between the upper limit of closing times and the closing times that need to be balanced when the phase-splitting circuit breaker leaves the factory), the balance comparison value is calculated and the balance comparison value and the balance trigger value are compared.

[0035] If the balance comparison value does not reach the balance trigger value, it means that the phase circuit breaker still has relatively good mechanical properties and there is no need to set a priority closing object. If the balance comparison value has reached the balance trigger value, it means that the remaining effective closing times of the phase circuit breaker are few, and it is necessary to set a priority closing object for the closing of multiple switches in the phase circuit breaker to balance the number of times each switch is used, so that the mechanical performance of the equipment can be fully utilized before the phase circuit breaker reaches the upper limit of the number of closing times of the phase circuit breaker.

[0036] In a preferred example, the present application may be further configured as follows: according to the closing times of multiple switches in the phase circuit breaker, setting the priority closing objects in ascending order, including the following steps:

[0037] If there are two switches with the same number of closing times in the phase-splitting circuit breaker, the priority closing object is set according to the order of the most recent closing time.

[0038] Through the above technical solution, during the actual use of the phase circuit breaker, it is possible that multiple switches inside it have the same number of closing times. Therefore, when switches with the same number of closing times occur, priority closing objects are set in the order of the most recent closing time, thereby reducing the possibility of equipment operation errors and improving the stability of the operation of the equipment.

[0039] In a preferred example, the present application may be further configured as follows: after the phase-splitting circuit breaker is closed correctly, the following steps are further included:

[0040] Obtaining the closing times of three switches in the phase circuit breaker to generate a total closing times;

[0041] Obtaining the closing upper limit number of times of the phase circuit breaker and a preset balance trigger value, and calculating and generating a balance comparison value based on the total closing number of times, the closing upper limit number of times, and the balance trigger value;

[0042] If the balance comparison value is less than the balance trigger value, there is no need to adjust the closing priority of the multiple switches in the phase circuit breaker; if the balance comparison value is greater than or equal to the balance trigger value, based on the balance comparison value, the closing upper limit number and the total closing number, the priority closing reference value of the switch in the phase circuit breaker is calculated and generated;

[0043] Based on the priority closing reference value, the closing priority of multiple switches in the phase circuit breaker is adjusted.

[0044] Through the above technical scheme, if the balance comparison value has reached the balance trigger value, it means that the remaining effective closing times of the phase circuit breaker are few. At this time, the closing limited closing reference value is calculated, and the closing priority of multiple switches in the phase circuit breaker is adjusted according to the closing priority reference value, so as to balance the number of times each switch is used, which will give full play to the mechanical performance of the equipment.

[0045] In a preferred example, the present application may be further configured such that, the larger the priority closing reference value is, the higher the planned closing frequency of the switch with fewer closing times in the phase circuit breaker is.

[0046] Through the above technical solution, the larger the priority closing reference value is, the higher the planned closing frequency of the switch with fewer closing times in the phase circuit breaker (that is, the closing frequency of each switch in the phase circuit breaker during some subsequent pre-screening processes, for example, for switches with more closing times, the closing frequency is reduced, and for switches with fewer closing times, the closing frequency is increased), that is, the time for the closing times between multiple switches in the phase circuit breaker to reach a relatively balanced state is shortened, so that the mechanical properties of the phase circuit breaker can be more fully utilized, the frequency of equipment replacement is reduced, and the operation and maintenance cost of the equipment is reduced.

[0047] In a preferred example, the present application may be further configured as follows: the formula for calculating and generating the priority closing reference value of the switch in the phase circuit breaker is as follows:

[0048] ,

[0049] in, is the priority closing reference value, is the total closing times, i.e. the sum of the closing times of the three switches in the phase circuit breaker, is the upper limit of closing times, The trigger value for balance.

[0050] Through the above technical solution, the priority closing reference value is calculated by the above formula, and according to its value, the planned closing frequency of multiple switches in the phase circuit breaker is adjusted in the next pre-screening process.

[0051] In summary, this application includes the following beneficial technical effects:

[0052] 1. Based on the principle of low-resistance grounding, this device adds a pre-screening mechanism for instantaneous single-phase grounding faults. When a single-phase grounding fault occurs, the instantaneous single-phase grounding fault will no longer trigger the low-resistance grounding mechanism by eliminating the instantaneous single-phase grounding fault, thereby effectively reducing the impact of the instantaneous single-phase grounding fault on the power supply stability of the low-resistance grounding system;

[0053] 2. This method can correct the wrongly closed switch of the phase-splitting circuit breaker until the closing phase corresponds to the phase where the fault is located, thereby improving the accuracy of single-phase grounding pre-screening and providing maintenance personnel with more accurate fault phase information;

[0054] 3. This method monitors the closing times of each switch of the phase circuit breaker and balances the closing times of each switch, thereby giving full play to the mechanical properties of the phase circuit breaker and reducing the equipment operation and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 Schematic diagram of the circuit of the device in the embodiment of the present application.

[0056] Figure 2 It is a schematic diagram of the process of the pre-screening method in the embodiment of the present application.

[0057] Figure 3 It is a schematic diagram of the process of setting the priority closing object in the embodiment of the present application.

[0058] Figure 4 It is a flow chart of closing priority adjustment in an embodiment of the present application.

[0059] Description of reference numerals:

[0060] 1. Phase circuit breaker; 11. First switch; 12. Second switch; 13. Third switch; 2. Pre-screening switch; 3. Current limiting resistor; 4. Grounding switch; 5. Grounding resistor; 6. First current transformer; 7. Second current transformer; 8. Pre-circuit breaker. DETAILED DESCRIPTION

[0061] The following is combined with Figure 1 -Attached Figure 4 This application is described in further detail.

[0062] The embodiments of the present application disclose a pre-screening device based on instantaneous arc tripping caused by a small resistance grounding and a pre-screening method based on instantaneous arc tripping caused by a small resistance grounding.

[0063] See attached Figure 1 As shown, the pre-screening device based on small resistance grounding instantaneous arc tripping includes a pre-screening mechanism, a small resistance grounding mechanism and a pre-circuit breaker 8. The pre-screening mechanism is used to screen out instantaneous single-phase grounding faults for the small resistance grounding mechanism, so that the small resistance grounding mechanism can process permanent single-phase grounding faults to improve the stability of the power supply system.

[0064] See attached Figure 1 As shown, the pre-screening mechanism includes a phase circuit breaker 1 and a pre-screening switch 2, the output end of the pre-screening switch 2 is connected to the input end of the phase circuit breaker 1, the phase circuit breaker 1 includes a first switch 11, a second switch 12 and a third switch 13 connected in parallel, the first switch 11, the second switch 12 and the third switch 13 are arranged in one-to-one correspondence with the three-phase lines, a current limiting resistor 3 is installed on the output end line of the phase circuit breaker 1, the output end of the current limiting resistor 3 is grounded, and a first current transformer 6 is installed on the grounding line of the current limiting resistor 3;

[0065] See attached Figure 1 As shown, the low-resistance grounding mechanism includes a grounding switch 4 and a grounding resistor 5, the output end of the grounding switch 4 is connected to the input end of the grounding resistor 5, the pre-screening switch 2 and the grounding switch 4 are arranged in parallel with each other, the output end of the grounding resistor 5 is grounded, and a second current transformer 7 is installed on the output line of the grounding resistor 5.

[0066] See attached Figure 1 As shown, the pre-circuit breaker 8 is installed on the common input end line of the pre-screening switch 2 and the grounding switch 4, and is used to control the switching on and off of the device.

[0067] When the power grid system operates normally, the grounding switch 4 is open and the low-resistance grounding system is in an offline state; the pre-screening switch 2 is closed and the pre-screening system is in an online state.

[0068] After a single-phase grounding fault occurs, the switch of the phase where the fault occurs (i.e., one of the first switch 11, the second switch 12, and the third switch 13 of the phase circuit breaker 1) is closed, and then it is observed whether the single-phase grounding fault disappears. If it disappears, the fault is a transient single-phase grounding fault, and the device can be directly exited.

[0069] If it does not disappear, the fault is a permanent single-phase grounding fault. At this time, the pre-screening switch 2 is opened, the grounding switch 4 is closed, the grounding is performed by the low-resistance grounding mechanism, and the fault line is powered off to facilitate the permanent single-phase grounding fault processing.

[0070] Based on the low-resistance grounding mechanism, this device adds a pre-screening mechanism for pre-screening instantaneous single-phase grounding faults. By eliminating the instantaneous single-phase grounding faults, the instantaneous single-phase grounding faults will no longer trigger the low-resistance grounding mechanism, thereby effectively reducing the impact of the instantaneous single-phase grounding faults on the power supply stability of the low-resistance grounding system.

[0071] In addition, during the process of closing the switch in the phase-splitting circuit breaker 1, if the first current transformer 6 does not detect an obvious current change after the first closing, it means that the closing switch is wrong, that is, the closing switch and the phase where the fault is located do not correspond. At this time, the switch that is closed for the first time (such as the first switch 11) is opened, and the second switch 12 or the third switch 13 is closed until the first current transformer 6 detects an obvious current change. It means that the closing is correct, that is, the closing switch and the phase where the fault is located correspond to each other, which improves the accuracy of single-phase grounding pre-screening and can also provide maintenance personnel with more accurate fault phase information.

[0072] See attached Figure 2 As shown, based on the above-mentioned pre-screening device based on small resistance grounding instantaneous arc tripping, the present application also discloses a pre-screening method based on small resistance grounding instantaneous arc tripping.

[0073] See attached Figure 2 As shown, the pre-screening method based on small resistance grounding instantaneous arc tripping includes the following processing steps.

[0074] S101. When the power supply line operates normally, the pre-screening switch 2 is closed and the grounding switch 4 is opened.

[0075] In implementation, when the power supply line operates normally, the pre-screening mechanism is online and the low-resistance grounding mechanism is offline, so that the pre-screening mechanism can preferentially screen single-phase grounding faults.

[0076] S102: When a single-phase grounding fault occurs, a switch of a certain phase of the phase-splitting circuit breaker 1 is controlled to be closed.

[0077] In implementation, the phase where the fault is located is determined according to the fault information, and the corresponding switch is closed according to the phase.

[0078] S103. If the single-phase grounding fault disappears, the device exits; if the single-phase grounding fault still exists, the phase circuit breaker 1 and the pre-screening switch 2 are disconnected, and the grounding switch 4 is closed.

[0079] In practice, after the corresponding switch of a phase circuit breaker 1 is closed, if the single-phase grounding fault disappears, it means that the fault is a transient fault and does not need to be processed by a small resistance grounding mechanism. If the single-phase grounding fault still exists, it means that the fault is a permanent fault and needs to be processed by a small resistance grounding mechanism, which means that the phase circuit breaker 1 and the pre-screening switch 2 need to be opened, and the grounding switch 4 needs to be closed, that is, the pre-screening mechanism is exited and the small resistance grounding mechanism is put into operation.

[0080] In step S102 of the above method, when a single-phase grounding fault occurs, a switch of a certain phase of the phase circuit breaker 1 is controlled to be closed, and the following processing steps may be specifically performed.

[0081] If the first current transformer 6 has no abnormality after the first switch of the phase circuit breaker 1 is closed, the first switch in the phase circuit breaker 1 is opened, and other switches in the phase circuit breaker 1 that have not been closed are closed in turn.

[0082] In implementation, when a single-phase grounding fault occurs, if the phase where the fault is located can be analyzed based on the fault information, the corresponding switch is closed (i.e., one of the three switches of the phase circuit breaker 1) according to the analyzed phase where the fault is located; if the phase where the fault is located cannot be analyzed based on the fault information, a switch is randomly selected to be closed; if there is no abnormality in the first current transformer 6 after the switch of the phase circuit breaker 1 is closed for the first time, it means that the closing error occurs, i.e., the closed switch does not correspond to the phase where the fault is located. At this time, the switch that is closed for the first time in the phase circuit breaker 1 is opened, and the remaining switches that have not been closed are closed in turn until the closing is correct, i.e., the closed switch corresponds to the phase where the fault is located.

[0083] See attached Figure 2 As shown, during a single-phase grounding fault process of the device, after the phase circuit breaker 1 is closed correctly, the following processing steps may also be included.

[0084] S201. Obtain the closing times of three switches in the phase-splitting circuit breaker 1 and generate a total closing time.

[0085] In implementation, the closing times of each switch in the phase-splitting circuit breaker 1 are recorded, and the closing times of the first switch 11 , the second switch 12 , and the third switch 13 are accumulated to generate a total closing time.

[0086] S202, obtaining the closing upper limit number and the preset balance trigger value of the phase circuit breaker 1, and calculating and generating a balance comparison value based on the total closing number, the closing upper limit number and the balance trigger value.

[0087] In practice, "number of closing and online times" refers to the sum of the maximum number of closing times of the three switches of the phase circuit breaker 1 obtained through testing of the same batch and model products before the equipment leaves the factory.

[0088] "Balance trigger value" refers to the difference between the upper limit of closing times and the closing times that need to be balanced. For example, the closing times of a phase circuit breaker 1 are 3000 times. When the total closing times reach 2000 times, the closing times need to be balanced. Then the balance trigger value is 1000, which is obtained by subtracting 2000 from 3000.

[0089] "Balance comparison value" refers to the value compared with the balance trigger value. For example, in the above example in this paragraph, phase circuit breaker 1 has been closed 2500 times, so the balance comparison value is 500, which is obtained by subtracting 2000 from 2500.

[0090] S203: Compare the balance trigger value and the balance comparison value.

[0091] In practice, the comparison here refers to the comparison of numerical values.

[0092] S204. If the balance comparison value is less than the balance trigger value, there is no need to set the priority closing object; if the balance comparison value is greater than or equal to the balance trigger value, the priority closing object is set in ascending order according to the closing times of multiple switches in the phase circuit breaker 1.

[0093] In implementation, if the balance comparison value is less than the balance trigger value, it means that the standard for balancing the number of closing times has not been reached, and the phase circuit breaker 1 still has relatively good mechanical properties, and there is no need to set a priority closing object.

[0094] If the balance comparison value is greater than or equal to the balance trigger value, it means that the standard for balancing the number of closing times has been reached, and the service life of the phase circuit breaker 1 has reached the second half or the end. It is necessary to set a limited closing object, that is, set the switch with a fewer closing times as the priority closing object, so that the mechanical performance of the equipment can be fully utilized before the phase circuit breaker 1 reaches the upper limit of the number of closing times of the phase circuit breaker 1.

[0095] In step S204, priority closing objects are set in ascending order according to the closing times of multiple switches in the phase circuit breaker 1. If there are two switches with equal closing times in the phase circuit breaker 1, the priority closing objects are set in order of the most recent closing time.

[0096] In practice, this can reduce the possibility of equipment operation errors, thereby improving the stability of the equipment operation.

[0097] See attached Figure 4 As shown, during a single-phase grounding fault process of the device, after the phase circuit breaker 1 is closed correctly, the following processing steps may also be included.

[0098] S301. Obtain the closing times of three switches in the phase-splitting circuit breaker 1 and generate a total closing time.

[0099] S302, obtaining the closing upper limit number and the preset balance trigger value of the phase circuit breaker 1, and calculating and generating a balance comparison value based on the total closing number, the closing upper limit number and the balance trigger value.

[0100] The explanation of the above two steps can be found in the above text and will not be repeated here.

[0101] S303. If the balance comparison value is less than the balance trigger value, there is no need to adjust the closing priority of multiple switches in the phase circuit breaker 1; if the balance comparison value is greater than or equal to the balance trigger value, the priority closing reference value of the switch in the phase circuit breaker 1 is calculated and generated based on the balance comparison value, the upper limit of closing times and the total closing times.

[0102] In implementation, a priority closing reference value is calculated and generated so as to adjust the closing priority of the three switches in the phase circuit breaker 1 .

[0103] S304. Based on the priority closing reference value, adjust the closing priority of multiple switches in the phase circuit breaker 1.

[0104] In implementation, if the phase where the fault is located can be analyzed, in order to shorten the fault handling time, the corresponding switch is directly closed; if the phase where the fault is located cannot be analyzed, or in order to correct the error, the priority of the remaining unclosed switches is adjusted.

[0105] In the above step S304, based on the priority closing reference value, the closing priority of multiple switches in the phase circuit breaker 1 is adjusted. The larger the priority closing reference value, the higher the planned closing frequency of the switch with less closing times in the phase circuit breaker 1.

[0106] In implementation, the larger the calculated priority closing reference value is, the more urgent it is for the phase circuit breaker 1 to balance the closing times. Then, the switch with fewer closing times needs to increase the closing times. Relatively speaking, the difference in closing times between the two switches is decreasing. Then, before the switch with more closing times reaches the closing times threshold, the time for the switch with more closing times to reach the closing times threshold can be delayed, thereby giving full play to the mechanical properties of the phase circuit breaker 1.

[0107] The formula for calculating the priority closing reference value of the switch in phase circuit breaker 1 is as follows:

[0108] ,

[0109] in, is the priority closing reference value, is the total closing times, i.e. the sum of the closing times of the three switches in the phase-splitting circuit breaker 1. is the upper limit of closing times, The priority closing reference value is calculated based on the above formula to provide data reference for the setting of closing priority.

[0110] Here, the above formula is explained and further described by taking the example in the above step S202. The upper limit of the closing times of a certain phase circuit breaker 1 is 3000 times. When the total closing times reaches 2000 times, the closing times need to be balanced. Then, the balance trigger value is 1000, which is obtained by subtracting 2000 from 3000. If the current actual total closing times is 2500 times, the balance comparison value is 500, which is obtained by subtracting 2000 from 2500.

[0111] The denominator of the above formula represents the balance trigger value, and the numerator represents the difference between the current total number of closing times (2500) and 2000. Here, the difference is set to a. The ratio between a and represents the urgency of balancing the number of closing times. The larger the value of the priority closing reference value, the more necessary it is to increase the closing frequency of switches with fewer closing times in the subsequent pre-screening process, that is, to increase the planned closing frequency of switches with fewer closing times.

[0112] In addition, the reason why the urgency of balancing the number of closing times is reflected through rather than balancing the number of closing times by exceeding a certain number of closing times is that in some environments, the upper limit of the number of closing times will change with the environment and specific application equipment. Therefore, reflecting it through a ratio is not only more intuitive, but also more in line with environmental requirements and equipment requirements.

[0113] The embodiments of this specific implementation method are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application in turn. Therefore, all equivalent changes made based on the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A pre-screening device based on small resistance grounding instantaneous arc tripping, characterized in that: Including pre-screening mechanism and low resistance grounding mechanism; The pre-screening mechanism comprises a phase circuit breaker (1) and a pre-screening switch (2), the output end of the pre-screening switch (2) is connected to the input end of the phase circuit breaker (1), the phase circuit breaker (1) comprises a first switch (11), a second switch (12) and a third switch (13) connected in parallel with each other, the first switch (11), the second switch (12) and the third switch (13) are arranged in one-to-one correspondence with the three-phase lines, a current limiting resistor (3) is installed on the output end line of the phase circuit breaker (1), and the output end of the current limiting resistor (3) is grounded; The low-resistance grounding mechanism comprises a grounding switch (4) and a grounding resistor (5), the output end of the grounding switch (4) is connected to the input end of the grounding resistor (5), and the output end of the grounding resistor (5) is grounded; The pre-screening switch (2) and the grounding switch (4) are arranged in parallel with each other; The method of using the pre-screening device includes: When the power supply line operates normally, the pre-screening switch (2) is closed and the grounding switch (4) is opened; When a single-phase grounding fault occurs, a switch of a certain phase of the phase-splitting circuit breaker (1) is controlled to close; If the single-phase grounding fault disappears, the device exits; if the single-phase grounding fault still exists, the phase circuit breaker (1) and the pre-screening switch (2) are disconnected, and the grounding switch (4) is closed; The controlling of closing a phase switch of the phase-splitting circuit breaker (1) comprises: If, after the switch that is first closed in the phase-splitting circuit breaker (1) is closed, a first current transformer (6) is installed on the grounding line of the current-limiting resistor (3), and the first current transformer (6) has no abnormality, the switch that is first closed in the phase-splitting circuit breaker (1) is opened, and the other switches that have not been closed in the phase-splitting circuit breaker (1) are closed in sequence; After the phase-splitting circuit breaker (1) is closed correctly, the following steps are also included: Obtaining the closing times of three switches in the phase-splitting circuit breaker (1) to generate a total closing time; Obtaining the closing upper limit number of times and a preset balance trigger value of the phase-splitting circuit breaker (1), and calculating and generating a balance comparison value based on the total closing number, the closing upper limit number and the balance trigger value; comparing the balance trigger value with the balance comparison value; If the balance comparison value is less than the balance trigger value, there is no need to set the priority closing object; if the balance comparison value is greater than or equal to the balance trigger value, the priority closing object is set in ascending order according to the closing times of multiple switches in the phase circuit breaker (1); The balance trigger value refers to the difference between the upper limit of closing times and the closing times required to balance the closing times; the balance comparison value refers to the value compared with the balance trigger value.

2. The pre-screening device based on small resistance grounding instantaneous arc tripping according to claim 1 is characterized in that: A first current transformer (6) is installed on the grounding line of the current-limiting resistor (3), and a second current transformer (7) is installed on the output line of the grounding resistor (5).

3. The pre-screening device based on small resistance grounding instantaneous arc tripping according to claim 2 is characterized in that: It also includes a pre-circuit breaker (8), which is installed on the common input end line of the pre-screening switch (2) and the grounding switch (4).

4. A pre-screening method based on instantaneous arc tripping caused by low-resistance grounding, based on a pre-screening device based on instantaneous arc tripping caused by low-resistance grounding according to any one of claims 1 to 3, characterized in that: The method of setting the priority closing objects in ascending order according to the closing times of the multiple switches in the phase-splitting circuit breaker (1) comprises the following steps: If there are two switches with the same number of closing times in the phase-splitting circuit breaker (1), the priority closing object is set according to the order of the most recent closing time.

5. The pre-screening method based on small resistance grounding instantaneous arc tripping according to claim 4, characterized in that: After the phase-splitting circuit breaker (1) is correctly closed, the method further comprises: Obtaining the closing times of three switches in the phase-splitting circuit breaker (1) to generate a total closing time; Obtaining the closing upper limit number of times and a preset balance trigger value of the phase-splitting circuit breaker (1), and calculating and generating a balance comparison value based on the total closing number, the closing upper limit number and the balance trigger value; If the balance comparison value is less than the balance trigger value, there is no need to adjust the closing priority of the multiple switches in the phase circuit breaker (1); if the balance comparison value is greater than or equal to the balance trigger value, based on the balance comparison value, the closing upper limit number of times and the total closing number of times, the priority closing reference value of the switch in the phase circuit breaker (1) is calculated and generated; Based on the priority closing reference value, the closing priority of multiple switches in the phase circuit breaker (1) is adjusted.

6. The pre-screening method based on small resistance grounding instantaneous arc tripping according to claim 5 is characterized in that: The larger the priority closing reference value is, the higher the planned closing frequency of the switch with a smaller closing frequency in the phase-splitting circuit breaker (1) is.

7. The pre-screening method based on small resistance grounding instantaneous arc tripping according to claim 5, characterized in that: The formula for calculating and generating the priority closing reference value of the switch in the phase-splitting circuit breaker (1) is as follows: ， in, is the priority closing reference value, is the total number of closing times, i.e. the sum of the number of closing times of the three switches in the phase-splitting circuit breaker (1), is the upper limit of closing times, The trigger value for balance.

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