Near isolation method applied to earth fault of 6kV power supply system in mining area

Abstract

The invention discloses a nearby isolation method applied to a mining area 6kV power supply system ground fault, and belongs to the technical field of mining area power supply system ground fault protection. The method is characterized by comprising the following steps: step a, collecting data in a line and performing fault judgment, and executing step b when a grounding fault occurs in the line; b, judging the fault direction by using the transient direction; c, starting a tripping delay strategy which is increased step by step; step d, judging whether the fault disappears after tripping; step e, starting reclosing time delay; and step f, judging whether the fault is not detected again when the reclosing delay is executed. According to the nearby isolation method applied to the earth fault of the 6kV power supply system in the mining area, the directionality of transient zero-sequence voltage and current and a step-by-step increasing action time limit strategy are utilized, so that rapid positioning and accurate isolation of the earth fault and rapid power supply recovery of a non-fault section can be realized, and the accuracy and efficiency of fault processing are remarkably improved; and the safety and stability of the power supply system are enhanced.

Description

Technical Field

[0001] The invention discloses a local isolation method for grounding faults of a 6kV power supply system in a mining area, belonging to the technical field of grounding fault protection of power supply systems in mining areas. Background Art

[0002] At present, the 6kV high-voltage power supply system in the mining area plays a key role, providing the necessary power support for the production and life of the mine. However, these systems often face the problem of single-phase grounding faults, which account for about 70% of the faults in the high-voltage power supply system in the mining area. This fault not only affects the stability of the power supply, but also may pose a potential threat to the safety of the mining area.

[0003] In the working environment of the mining area, single-phase grounding faults are usually identified by monitoring the indications on the current grounding signal device. Typical fault manifestations include: the voltage of the fault phase decreases, the voltage of the non-fault phase increases, and the "zero-sequence voltage", "inductance current", and "excitation current" instrument pointers on the current grounding signal device display abnormalities. These indicator changes can help operators quickly determine the occurrence and location of the fault, so as to take appropriate countermeasures.

[0004] Although the existing technology can detect single-phase grounding faults, it is still difficult to accurately and quickly locate these faults. Some methods using transient zero-sequence current direction protection devices have been proposed, attempting to quickly locate the fault point by monitoring the transient zero-sequence current direction in the power system and taking corresponding measures to isolate it. However, these methods still have some limitations. Especially in special working environments such as coal mines, it is very important to quickly isolate faults and restore power supply to avoid production interruptions and safety accidents. Therefore, developing an effective method for isolating ground faults nearby in order to improve the reliability and safety of the 6kV power supply system in the mining area has become a problem to be solved in this field. Summary of the invention

[0005] The technical problem to be solved by the present invention is: to overcome the shortcomings of the prior art and provide a method for isolating ground faults in a 6kV power supply system in a mining area, which utilizes the directionality of transient zero-sequence voltage and current and a step-by-step increasing action time limit strategy, and can achieve rapid positioning and precise isolation of ground faults and rapid restoration of power supply to non-fault sections, significantly improve the accuracy and efficiency of fault handling, reduce operation and maintenance costs, enhance the safety and stability of the power supply system, and provide reliable power guarantee for mining production.

[0006] The technical solution adopted by the present invention to solve the technical problem is: the local isolation method for grounding faults in a 6kV power supply system in a mining area is characterized by comprising the following steps:

[0007] Step a, collecting data in the line and performing fault judgment. When a ground fault occurs in the line, executing step b;

[0008] Step b, using the transient direction to determine the fault direction; when the fault direction is positive, executing step c, when the fault direction is positive, continuously detecting the fault state until the fault completely disappears;

[0009] Step c, starting a step-by-step increasing tripping delay strategy;

[0010] Step d, determine whether the fault disappears after tripping. If the fault disappears, execute step e. If the fault still exists after tripping, report the abnormality and execute reclosing after the delay time expires;

[0011] Step e, start reclosing delay;

[0012] Step f, determining whether the fault is not detected again during the reclosing delay. If the fault is detected again, re-isolate the faulty section. If the fault disappears, it means that the protection group is restored and the fault handling is completed.

[0013] Preferably, in step c, the step-by-step increasing tripping delay strategy is: according to the fault direction, the step-by-step increasing tripping delay strategy is started, the initial delay is set from the end of the line, and the delay is increased step by step along the line toward the substation, and the tripping operation is performed after the set delay is reached to isolate the fault.

[0014] Preferably, when executing step b, firstly, a bandpass filter is used to obtain transient information of ground fault, and then a line current direction parameter D is defined. k , by defining the line current direction parameter D k Determine whether it is a faulty line or a sound line.

[0015] Preferably, the high frequency of the bandpass filter is 2 kHz, and the low frequency is 150 Hz.

[0016] Preferably, the line current direction parameter D k The calculation formula is:

[0017]

[0018] Where, T is the duration of the transient process; u0(t) is the transient component of the zero-sequence voltage, i 0k (t) is the transient component of zero-sequence current of line k;

[0019] For the fault line: Line current direction parameter D k <0; for a sound line: line current direction parameter D k >0.

[0020] Preferably, in step a, the data collected in the line include three-phase current, three-phase voltage, zero-sequence current and zero-sequence voltage. When any one of the three-phase current, three-phase voltage, zero-sequence current and zero-sequence voltage exceeds its set threshold, it indicates that a line fault has occurred.

[0021] Preferably, in step f, the judgment condition for the disappearance of the fault is: the three-phase electricity, three-phase current, zero-sequence voltage and zero-sequence current are all less than 0.8 times of their respective thresholds.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] By using the directionality of transient zero-sequence voltage and current and the step-by-step action time limit strategy for the local isolation method applied to the grounding fault of the 6kV power supply system in the mining area, the grounding fault can be quickly located, accurately isolated and the power supply of the non-fault section can be quickly restored, which significantly improves the accuracy and efficiency of fault handling, reduces operation and maintenance costs, enhances the safety and stability of the power supply system, and provides reliable power guarantee for mining production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The figure is a flow chart of the local isolation method for ground faults in the 6kV power supply system in mining areas.

[0025] Figure 2 This is a schematic diagram of the action time limit configuration of the local isolation method for grounding faults in the 6kV power supply system in mining areas. DETAILED DESCRIPTION

[0026] Figures 1-2 The best embodiment of the present invention is shown below in conjunction with the attached Figures 1-2 The present invention is further described.

[0027] like Figure 1 As shown, a local isolation method for ground faults in a 6 kV power supply system in a mining area (hereinafter referred to as the isolation method) includes the following steps:

[0028] Step 1001, start;

[0029] The local isolation method for ground faults in the 6kV power supply system in the mining area has begun to be implemented.

[0030] Step 1002, data collection and fault diagnosis;

[0031] The three-phase voltage, three-phase current, zero-sequence voltage and zero-sequence current of the line are monitored in real time, and a judgment is made. When the line data is monitored to exceed the threshold, a ground fault is determined to have occurred. The judgment conditions for judging that a ground fault has occurred in the line are: the three-phase voltage Ua+Ub+Uc is greater than the voltage threshold, or the zero-sequence voltage is greater than the voltage threshold; the three-phase current Ia+Ib+Ic is greater than the current threshold, or the zero-sequence current is greater than the current threshold. In this isolation method, the voltage threshold is set to 15V; and the current threshold is set to 1A.

[0032] Step 1003, using the transient direction to determine the fault direction;

[0033] First, a passband filter is set, and the transient quantity information of the ground fault is obtained by using the passband filter. The high frequency of the passband filter is 2kHz, and the low frequency is 150Hz, so as to obtain the transient quantity.

[0034] Select the line where the transient component of zero-sequence current flows from the line to the bus as the fault line, and define the line current direction parameter D k :

[0035]

[0036] Where, T is the duration of the transient process; u0(t) is the transient component of the zero-sequence voltage, i 0k (t) is the transient component of zero-sequence current of line k. For the fault line: the line current direction parameter D k <0; for a sound line: line current direction parameter D k >0.

[0037] Step 1004, the fault direction is forward;

[0038] Determine whether the fault direction is positive. If the fault direction is positive, execute step 1005. If the fault direction is negative, execute step 1009. k When <0, it indicates that the fault direction is positive.

[0039] Step 1005, start the delay and perform tripping after the delay reaches the setting;

[0040] According to the fault direction, the step-by-step tripping delay strategy is started. The initial delay is set from the end of the line, and the delay is gradually increased along the line toward the substation. After the set delay is reached, the tripping operation is performed to isolate the fault. When isolating the fault, the tripping delay time is set to 2s at the end of the line, and the time from the end of the line to the substation is gradually increased by a time difference of 1s. Figure 2As shown, the user grounding fault Q321 at k1 is cleared after 10s; the branch fault Q31 at k2 is cleared after 13s; and the trunk line fault Q2 at k4 is cleared after 15s.

[0041] Step 1006, whether the fault disappears;

[0042] Determine whether the fault disappears. If the fault disappears after tripping, execute step 1007. If the fault still exists after tripping, execute step 1010.

[0043] Step 1007, start reclosing delay;

[0044] After tripping, the fault disappears and the reclosing delay is started. The delay time is set to 1s. When the delay time is up, the reclosing is executed.

[0045] Step 1008, determining whether no fault is detected;

[0046] Determine whether the fault is not detected again within 0.5s after the reclosing is performed. If the fault is not detected again, execute step 1012. If the fault is detected again, execute step 1011.

[0047] The judgment conditions for the disappearance of the fault are: the three-phase voltage Ua+Ub+Uc, the three-phase current Ia+Ib+Ic, the zero-sequence voltage and the zero-sequence current are all less than 0.8 times of their respective thresholds.

[0048] Step 1009: Continue to detect the fault until the fault ends;

[0049] The fault status is continuously detected until the fault completely disappears, and step 1012 is executed.

[0050] Step 1010, reporting an abnormality, and executing reclosing after the delay time expires;

[0051] If the fault does not disappear after tripping, an abnormal alarm is reported and the reclosing delay is started. When the delay time is up, reclosing is performed;

[0052] Step 1011, re-isolate the faulty section.

[0053] Step 1012: the fault completely disappears, the protection of the entire group is restored, and the fault handling is completed.

[0054] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A local isolation method for ground faults in a 6kV power supply system in a mining area, characterized in that: The steps include: Step a, collecting data in the line and performing fault judgment. When a ground fault occurs in the line, executing step b; Step b, using the transient direction to determine the fault direction; When the fault direction is positive, execute step c; when the fault direction is negative, continue to detect the fault state until the fault disappears completely; Step c, starting a step-by-step increasing tripping delay strategy; Step d, determine whether the fault disappears after tripping. If the fault disappears, execute step e. If the fault still exists after tripping, report the abnormality and execute reclosing after the delay time expires; Step e, start reclosing delay; Step f, determining whether the fault is not detected again after the reclosing delay is executed, and if the fault is detected again, re-isolating the faulty section; If the fault disappears, it means that the entire protection group has been restored and the fault handling is completed.

2. The local isolation method for ground fault in a 6kV power supply system in a mining area according to claim 1 is characterized in that: In step c, the step-by-step increasing tripping delay strategy is: according to the fault direction, the step-by-step increasing tripping delay strategy is started, the initial delay is set from the end of the line, and the delay is increased step by step along the line toward the substation. After reaching the set delay, the tripping operation is performed to isolate the fault.

3. The local isolation method for ground fault in a 6kV power supply system in a mining area according to claim 1 is characterized in that: When executing step b, first use the bandpass filter to obtain the transient information of the ground fault, and then define the line current direction parameter D k , by defining the line current direction parameter D k Determine whether it is a faulty line or a sound line.

4. The local isolation method for ground fault of 6kV power supply system in mining area according to claim 3 is characterized in that: The bandpass filter has an upper frequency of 2kHz and a lower frequency of 150Hz.

5. The local isolation method for ground fault in a 6kV power supply system in a mining area according to claim 3 is characterized in that: Line current direction parameter D k The calculation formula is: Where, T is the duration of the transient process; u0(t) is the transient component of the zero-sequence voltage, i 0k (t) is the transient component of zero-sequence current of line k; For the fault line: Line current direction parameter D k <0; for a sound line: line current direction parameter D k >0.

6. The local isolation method for ground fault of 6kV power supply system in mining area according to claim 1 is characterized in that: In step a, the data collected in the line include three-phase current, three-phase voltage, zero-sequence current and zero-sequence voltage. When any one of the three-phase current, three-phase voltage, zero-sequence current and zero-sequence voltage exceeds the set threshold, it indicates that the line has a fault.

7. The local isolation method for ground fault in a 6kV power supply system in a mining area according to claim 1 is characterized in that: In step f, the judgment condition for the disappearance of the fault is that the three-phase power, three-phase current, zero-sequence voltage and zero-sequence current are all less than 0.8 times of their respective thresholds.

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