A fast arc extinguishing method for fast switching parallel gap switch

Abstract

The present invention belongs to the field of power technology and discloses a method for rapidly extinguishing arcs using a fast-acting switch in parallel with a gap switch. This method utilizes the fast-acting nature of the gap switch to eliminate arc grounding faults within milliseconds. The fast switch handles the long-term current flow. The fast-acting switch in parallel with the gap switch can significantly accelerate arc extinguishing while requiring less cost and space. The method provided by the present invention is of great significance and practicality for rapidly extinguishing grounding arcs and reducing the cost of arc extinguishing equipment.

Description

Technical Field

[0001] The present invention belongs to the field of electric power technology, and more particularly, relates to a fast arc extinguishing method for a fast switch parallel to a gap switch. Background Art

[0002] The increasing use of solid-insulated cross-linked polyethylene cables in distribution networks presents the challenge of handling irreversible single-phase ground faults caused by solid insulation. When a single-phase ground fault occurs in the system, the steady-state current flowing through the grounding point is the system's capacitive current to ground. The high-frequency current amplitude and duration of the ground arc in the cable grid are significantly increased compared to overhead lines. Consequently, the arc-flash grounding overvoltage in the non-fault phase can exceed four times the phase voltage, posing a serious threat to cable insulation. Therefore, quickly and accurately identifying the faulty line and extinguishing the ground arc as soon as possible are crucial to preventing cable insulation damage and fault expansion. Summary of the Invention

[0003] The object of the present invention is to provide a fast arc extinguishing method for a fast switch parallel to a gap switch, so as to achieve fast extinguishing of a grounding arc.

[0004] The present invention provides a method for quickly extinguishing arcs by connecting a fast switch in parallel with a gap switch. The fast switch and the gap switch are connected in parallel. The method comprises the following steps:

[0005] Step 1: Determine whether a single-phase grounding fault occurs in the distribution network; if a single-phase grounding fault occurs, proceed to step 2;

[0006] Step 2: Select the fault phase according to the three-phase voltage;

[0007] Step 3: The microcomputer integrated controller controls the parallel fault phase gap switch and the fault phase fast switch to perform the closing action;

[0008] Wherein, when the fault phase gap switch is turned on and the fault phase fast switch has not yet completed the closing action, the microcomputer integrated controller monitors the current of the fault phase gap switch and triggers the fault phase gap switch when the current passes through zero, so that the fault phase gap switch remains turned on; after the fault phase fast switch completes the closing action, the microcomputer integrated controller no longer sends a pulse trigger signal to the fault phase gap switch, and the fault phase gap switch automatically opens when the current passes through zero next time;

[0009] Step 4: Select the fault line based on the zero-sequence current and determine whether the fault line is a cable line;

[0010] If the fault line is a cable line, the fast switch of the fault phase is kept in the closed state;

[0011] If the fault line is not a cable line, then immediately after the fault phase fast switch is closed, the fault phase fast switch is controlled to be opened by the microcomputer integrated controller, and the microcomputer integrated controller is used to determine whether the fault has disappeared. If the fault still exists, step 3 is executed again.

[0012] Preferably, the gap switch adopts a three-electrode controllable gap switch, the trigger level of the gap switch is connected to the pulse trigger, and the two ends of the gap switch are connected to an external power supply, and the external power supply is in a non-working state under normal circumstances; the microcomputer integrated controller is connected to the pulse trigger and the external power supply respectively; when the gap switch needs to be turned on, the microcomputer integrated controller sends a signal to the pulse trigger and the external power supply, the external power supply starts working, and the pulse trigger sends a pulse signal to the trigger level of the gap switch to turn on the gap switch.

[0013] Preferably, the closing action time of the fast switch is less than 7ms, and the opening action time is less than 3ms.

[0014] Preferably, in step 1, the specific implementation method of determining whether a single-phase grounding fault occurs in the distribution network is: real-time online monitoring of the open triangle voltage on the secondary side of the voltage transformer through the microcomputer integrated controller; if the open triangle voltage exceeds a preset voltage threshold, it is determined that a single-phase grounding fault occurs.

[0015] Preferably, in step 2, the specific implementation method of selecting the fault phase according to the three-phase voltage is: monitoring the three-phase voltage output by the voltage transformer through the microcomputer integrated controller, if one phase voltage is close to 0 and the other two phase voltages are close to the line voltage, it is determined to be a metallic grounding fault, and the phase with voltage close to 0 is determined to be the fault phase; if one phase voltage amplitude is the largest and the other two phase voltage amplitudes are close, it is determined to be a small resistance grounding fault, and the phase with the smallest voltage amplitude is determined to be the fault phase; if the three-phase voltage amplitudes are all greater than the preset voltage amplitude, it is determined to be a large resistance grounding fault, and the phase after the phase with the largest voltage amplitude is determined to be the fault phase.

[0016] Preferably, in step 4, the fault line is selected by analyzing the zero-sequence current measured by the current recorder installed at the head end of each feeder, and the basis for selecting the fault line according to the zero-sequence current is: before the fault phase gap switch is turned on, if the zero-sequence current on one of the lines is opposite to the zero-sequence current of all other lines and the amplitude is greater than that of other lines, and the direction of the zero-sequence current on one of the lines changes before and after the fault phase gap switch is operated, then it can be determined that the line is a fault line.

[0017] One or more technical solutions provided in the present invention have at least the following technical effects or advantages:

[0018] The present invention utilizes the fast-action characteristics of the gap switch to eliminate arc grounding faults within a few milliseconds. At the same time, considering that the gap switch cannot stably pass current for a long time, the present invention connects the fast switch and the gap switch in parallel, using the fast switch to handle the long-term current flow. The fast switch connected in parallel with the gap switch can greatly accelerate the arc extinguishing speed, while requiring less cost and space. The method provided by the present invention is of great significance and practicality for quickly extinguishing the grounding arc and reducing the cost of arc extinguishing devices. The present invention is suitable for rapid arc extinguishing in distribution networks and is of great significance for suppressing arc grounding overvoltage in distribution networks and preventing personal electric shock casualties. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A primary system wiring diagram of a device used in a rapid arc extinguishing method for a rapid switch parallel gap switch provided by an embodiment of the present invention;

[0020] Figure 2 A flow chart of a method for rapidly extinguishing arcs by connecting a fast switch in parallel with a gap switch provided by an embodiment of the present invention;

[0021] Figure 3 Flowchart for phase selection for faults;

[0022] Figure 4 Flowchart for fault line selection;

[0023] Figure 5 This is the structural diagram of the fast switch;

[0024] Figure 6 is the conversion characteristic diagram of the gap switch;

[0025] Figure 7 Schematic diagram of the gap switch trigger system. DETAILED DESCRIPTION

[0026] In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0027] This embodiment provides a method for quickly extinguishing arcs by connecting a fast switch in parallel with a gap switch. The fast switch and the gap switch are connected in parallel. The method mainly includes the following steps:

[0028] (1) Determine whether a single-phase grounding fault occurs in the distribution network; if a single-phase grounding fault occurs, proceed to step (2);

[0029] (2) Select the fault phase according to the three-phase voltage;

[0030] (3) The microcomputer integrated controller controls the parallel fault phase gap switch and the fault phase fast switch to perform the closing action;

[0031] Wherein, when the fault phase gap switch is turned on and the fault phase fast switch has not yet completed the closing action, the microcomputer integrated controller monitors the current of the fault phase gap switch and triggers the fault phase gap switch when the current passes through zero, so that the fault phase gap switch remains turned on; after the fault phase fast switch completes the closing action, the microcomputer integrated controller no longer sends a pulse trigger signal to the fault phase gap switch, and the fault phase gap switch automatically opens when the current passes through zero next time;

[0032] (4) Select the fault line based on the zero-sequence current and determine whether the fault line is a cable line;

[0033] If the fault line is a cable line, the fast switch of the fault phase is kept in the closed state;

[0034] If the fault line is not a cable line, then immediately after the fault phase fast switch is closed, the fault phase fast switch is controlled to be disconnected by the microcomputer integrated controller, and the microcomputer integrated controller is used to determine whether the fault has disappeared. If the fault still exists, step (3) is executed again.

[0035] The primary system wiring diagram of the device used in the above method is as follows: Figure 1 As shown, the specific method process can be found in Figure 2 , including the following steps:

[0036] Step 1: Determine whether a single-phase grounding fault occurs in the distribution network.

[0037] Specifically, the microcomputer integrated controller (ZK) 109 monitors the open-delta voltage on the secondary side of the voltage transformer (PT) 104 in real time. If the voltage is normal, the monitoring state is maintained. During normal system operation, the system operating voltage, open-delta voltage, and arc suppression device operating status are displayed. If the open-delta voltage exceeds the voltage threshold, a single-phase grounding fault has occurred, and the process proceeds to step 2. If other faults are detected, a fault alarm signal is issued.

[0038] When the open delta voltage ΔU changes from a low level to a high level, it indicates that a system fault occurs, and the microcomputer integrated controller 109 immediately starts an interrupt and enters the fault type identification and line zero-sequence current data acquisition program.

[0039] The microcomputer integrated controller 109 monitors the voltage waveform of the secondary side triangle interface of the electromagnetic voltage transformer 104 in real time online, sets a threshold for the open triangle voltage, and the threshold needs to avoid the three-phase unbalanced voltage. As long as the voltage rises above the threshold, it is judged that a system fault occurs, that is, it is judged that a single-phase grounding fault occurs in the system, and the program is started to determine the type of fault; if the voltage rise does not exceed the threshold, the monitoring is continued.

[0040] Step 2: Select the fault phase based on the three-phase voltage.

[0041] The microcomputer integrated controller 109 starts to run the fault phase selection program. Figure 3 , the phase selection program quickly selects the fault phase according to the three-phase fault voltage.

[0042] Specifically, the microcomputer integrated controller 109 determines the fault type and phase difference such as single-phase grounding and disconnection according to the PT secondary output signals Ua, Ub, and Uc.

[0043] Since different fault transition resistances correspond to different three-phase voltage magnitude relationships, different fault phase selection schemes need to be formulated according to different fault conditions.

[0044] The three-phase voltage output by the voltage transformer is monitored by the microcomputer integrated controller 109. If one phase voltage is close to 0 and the other two phase voltages are close to the line voltage, it is determined to be a metallic ground fault, and the phase with the voltage close to 0 is determined to be the fault phase; if one phase voltage amplitude is the largest and the other two phase voltage amplitudes are close, it is determined to be a small resistance ground fault, and the phase with the smallest voltage amplitude is determined to be the fault phase; if the three-phase voltage amplitudes are all greater than the preset voltage amplitude, it is determined to be a large resistance ground fault, and the phase subsequent to the phase with the largest voltage amplitude is determined to be the fault phase.

[0045] The following is a detailed description of different fault phase selection schemes.

[0046] a. Metallic grounding fault.

[0047] When a single-phase metallic ground fault occurs in a system with an ungrounded neutral point, the voltage of the faulted phase approaches 0, while the voltage of the unfaulted phase approaches the line voltage. Based on this, the phase with the voltage close to 0 is identified as the faulty phase. For a 10kV distribution system, for example, the three-phase voltage threshold is set to: if one phase voltage is less than 1kV and the other two phase voltages are greater than 9kV, a single-phase metallic ground fault is considered to have occurred, and the phase with the voltage less than 1kV is identified as the faulty phase. Because the three-phase voltages vary significantly when a metallic fault occurs, if faster fault phase selection is needed, transient voltage signals can be used to make the determination and shorten the phase selection time.

[0048] b. Low resistance grounding fault.

[0049] The critical condition for a low-resistance ground fault is defined as the voltage of the faulted phase reaching the same amplitude as the voltage of a non-faulted phase. When a low-resistance ground fault occurs, the voltage of the faulted phase has the smallest amplitude among the three-phase voltages, so the phase with the smallest amplitude can be identified as the faulted phase. For a 10kV distribution system, in the critical condition for a low-resistance ground fault, the voltages of the faulted phase and the phase following it are both 5kV, and the voltage of the phase preceding the faulted phase is 8.66kV. Considering the three-phase imbalance in actual systems, the three-phase voltage threshold can be set as follows: when the voltage of a phase is less than 4kV and the voltage of the phase preceding it is greater than 8kV, the phase with a voltage less than 4kV is identified as the faulted phase.

[0050] c. High resistance ground fault.

[0051] When the ground transition resistance is large, the fault phase voltage will no longer have the smallest amplitude among the three phases. However, the phase preceding the fault phase will always have the largest voltage amplitude during the transition resistance change process. Based on this, the phase following the phase with the largest voltage amplitude can be identified as the fault phase. For a 10kV distribution system, when all three phases are greater than 4kV, the phase with the largest voltage amplitude is first compared and selected, and then the phase following it is identified as the fault phase.

[0052] Step 3: The microcomputer integrated controller controls the parallel fault phase gap switch and the fault phase fast switch to perform the closing action.

[0053] The microcomputer integrated controller 109 executes the operating procedures for the fast switch (JD) 106 and the gap switch (GS) 107 based on the fault phase, sending trigger signals to the phase gap switch 107 and the fast switch 106 of the fault phase busbar. The gap switch 107 quickly turns on, directing the fault current to ground, extinguishing the ground arc, and limiting the arc-fault overvoltage to the line voltage level. In the few milliseconds before the fast switch 106 completes its operation, at the moment when the current in the gap switch 107 passes through zero, the microcomputer integrated controller 109 sends a turn-on signal to the gap switch 107 to maintain its conduction. After the fast switch 106 completes its operation, no trigger signals are sent to the gap switch 107. The gap switch 107 opens at the next current zero crossing, and the ground current is transferred to the fast switch 106.

[0054] Step 4: Select the fault line by analyzing the zero-sequence current measured by the current recorder installed at the head end of each feeder. The basis for selecting the fault line based on the zero-sequence current is: before the fault phase gap switch is turned on, if the zero-sequence current on one of the lines is opposite to the zero-sequence current of all other lines and has a larger amplitude than that of other lines, and the direction of the zero-sequence current on one of the lines changes before and after the fault phase gap switch is turned on, then it can be determined that the line is the fault line.

[0055] Specifically, the fault line selection program is started and the fault line is selected based on the zero sequence current measured at the line head end. The flow chart of the fault line selection program is shown in Figure 4 , determine whether the line is a cable line. If it is a cable line, keep the fast switch 106 in the closed state, and then open the gap switch 107; if the fault line is an overhead line, go to step 5.

[0056] After a ground fault occurs in a cable line, the insulation cannot be restored, and the cable line must remain grounded to transfer the grounding current at the fault point to the metallic grounded phase of the busbar. However, transient faults caused by ground faults in overhead lines can be restored due to the restorative nature of air insulation.

[0057] The basis for fault line selection is the variation characteristics of the zero-sequence current of each feeder line during a single-phase grounding fault in the distribution network, and the difference in direction and amplitude between the zero-sequence current of the fault line and the zero-sequence current of the non-fault line before and after the gap switch is closed 107 is combined to determine the fault line.

[0058] a. Zero-sequence current characteristics before the gap switch is turned on.

[0059] The zero-sequence current amplitude at the head end of the line where the fault point is located is the largest. Due to the existence of the branch line, the steady-state effective value is larger than the sum of the zero-sequence currents of other feeders, and the direction is opposite to the direction of the zero-sequence currents of other feeders; the zero-sequence current of the overhead line is relatively small; the zero-sequence current of the cable line is larger than that of the overhead line, but still smaller than that of the fault line.

[0060] b. Zero-sequence current characteristics after the gap switch is turned on.

[0061] When gap switch 107 is activated, the zero-sequence current of the faulty feeder undergoes a significant phase reversal, but the amplitude change is not noticeable compared to before the switch was activated. The zero-sequence current of the non-faulty line remains unchanged in both direction and magnitude, exhibiting only a brief, small oscillation. After gap switch 107 is activated, the zero-sequence currents of the faulty and non-faulty lines no longer have opposite directions, but instead differ by a certain angle.

[0062] Step 5: The microcomputer integrated controller sends an opening action signal to the fast switch immediately after sending the closing action signal, and the fast switch is disconnected, and the process goes to step 6.

[0063] Specifically, 5 seconds after the fast switch 106 is closed, the fault point of the instantaneous ground fault is insulated from the ground. At this time, the system returns to normal after the fast switch 106 is opened. If a permanent ground fault occurs, the system cannot resume normal operation in this way.

[0064] Step 6: The microcomputer integrated controller determines the fault signal again. If the fault disappears, the controller enters the standby state of step 1; if the fault is still found, execute step 3 again.

[0065] Specifically, after the fast switch 106 is opened, if the microcomputer integrated controller 109 determines that the fault disappears, it means that the grounding fault is a transient fault, and the system resumes normal operation; if the microcomputer integrated controller 109 determines that the fault has not disappeared, it means that the grounding fault is a permanent fault, and it is necessary to reclose the switch to transfer the grounding current at the fault point to the metallic grounding current at the bus position.

[0066] The present invention realizes the transfer of fault current within milliseconds through the cooperation of fast switches and gap switches, while requiring less cost and space. It is of great significance and practicality for quickly extinguishing grounding arcs and reducing the cost of arc extinguishing devices.

[0067] Specifically, the primary system wiring diagram of the device used in the method provided by the present invention can be found in Figure 1 , including a front circuit breaker (DL) 101, a current transformer (TA) 102, a PT high-voltage fuse (RD) 103, a voltage transformer (PT) 104, a primary harmonic eliminator (DR) 105, a fast switch (JD) 106, a gap switch (GS) 107, a zero-sequence current transformer (TZ) 108, and a microcomputer integrated controller (ZK) 109. Among them, the PT high-voltage fuse 103 and the primary harmonic eliminator 105 can avoid possible ferromagnetic resonance. After the device is activated, the zero-sequence current transformer 108 reads the grounding capacitance current of the system. During the closing period of the fault phase of the device, if a ground fault occurs again when the device is not in fault state, the zero-sequence CT secondary provides a current mutation for the microcomputer integrated controller 109 to sample. The microcomputer integrated controller 109 issues a tripping command, and the closed phase of the circuit breaker is opened.

[0068] See also Figure 1 The parallel operation logic of the fast switch 106 and the gap switch 107 is as follows: when the parallel switches need to be turned on, the microcomputer integrated controller 109 simultaneously sends an activation signal to the gap switch 107 and the fast switch 106. The gap switch 107 quickly turns on, but the fast switch 106 takes several milliseconds to close. During the period when the gap switch 107 is turned on but the fast switch 106 has not yet completed its operation, the current flowing through the gap switch 107 is monitored. If the current in the gap switch 107 passes through zero, a trigger signal is applied to the gap switch 107 to maintain the conductive state. After the fast switch 106 completes its operation, the current flows through the fast switch 106, and the gap switch 107 extinguishes the arc and opens after the current passes through zero.

[0069] The fast switch 106 used in the present invention is an improved fast switch based on an electromagnetic repulsion mechanism, which can achieve closing within 7ms and opening within 3ms, with a breaking current of 40kA. It can meet the requirements of fast opening and closing and quickly disconnecting the short-circuit current when single-phase grounding occurs.

[0070] Specifically, the improved fast switch used in the present invention is a new type of fast operating mechanism based on the eddy current principle. Figure 5 The fast switch includes a vacuum interrupter 501, a static conductive rod 502, a static contact 503, a moving contact 504, a moving conductive rod 505, an insulating pull rod 506, an opening holding magnet 507, an opening coil 508, an electromagnet armature 509, a closing coil 510, a closing holding magnet 511, an opening control 512, an opening energy storage capacitor 513, a closing control 514, a closing energy storage capacitor 515, and a charging power supply 516.

[0071] The operating mechanism of the moving contact 504 within the vacuum interrupter 501 is driven by an electromagnetic repulsion mechanism. The electromagnetic repulsion mechanism operates as follows: When the switch receives a closing (or opening) command, a pulse current lasting several milliseconds is generated in the opening coil 508 (or closing coil 510). This pulse current generates an alternating magnetic field in the excitation coil, while the electromagnetic armature 509 generates electromagnetic force due to induced eddy currents. The electromagnetic armature 509 rapidly moves under the influence of the Lorentz repulsion force, driving the moving contact 504 of the vacuum interrupter 501 through the insulating pull rod 506, thereby achieving rapid opening and closing of the switch branch.

[0072] The fast switch charges the opening energy storage capacitor 513 and the closing energy storage capacitor 515 through the charging power supply 516, and controls the opening of the fast switch through the opening control 512 and the opening coil 508, and controls the closing of the fast switch through the closing control 514 and the closing coil 510, and maintains the opening state and the closing state respectively through the opening holding magnet 507 and the closing holding magnet 511.

[0073] The breakdown mechanism of gap switches is streamer theory. The advantages of gap switches include simplicity, ruggedness, voltage resistance, high current capacity, and high switching speed. Gap switches are generally classified into three categories based on their triggering method: self-breakdown, electrically triggered, and optically triggered. Compared to two-electrode self-breakdown switches, three-electrode gap switches with a trigger electrode enable controlled triggering and offer better performance in terms of switch jitter, spark path inductance, and spark path resistance, making them suitable for high-power single-shot or repetitive-rate operation.

[0074] The present invention utilizes the high action speed of the gap switch to quickly eliminate the arc grounding fault of the system. Specifically, the gap switch of the present invention adopts a three-electrode controllable gap switch, and the conversion characteristics of the gap switch are as follows: Figure 6 As shown, the meaning of each symbol is:

[0075] V T (min)—Minimum trigger voltage. To obtain reliable triggering, the applied trigger voltage must not be lower than this voltage.

[0076] EE(co)—cut-off operating voltage across the main electrodes.

[0077] EE(min)—To obtain reliable operation, the minimum operating voltage of the main electrode is about 1 / 3 of the maximum operating voltage of the main electrode.

[0078] EE(max)—maximum operating voltage. It is the maximum operating voltage allowed to be loaded between the main electrodes of the switch to ensure that there is no self-flashover during the operation of the switch. It is about 80% of the static self-breakdown voltage.

[0079] SBV—static self-breakdown voltage. The maximum operating voltage of the main electrode is the highest DC voltage that the switch gap can withstand when no triggering measures are taken.

[0080] Operating range—The range between the maximum and minimum operating voltages of the main electrode.

[0081] In order for the gap switch to work properly, the voltage across the gap switch must not be lower than the minimum operating voltage, and a pulse trigger signal must be applied to control the gap switch to be turned on.

[0082] The working principle of the trigger system of the gap switch in the present invention is as follows Figure 7 As shown, the trigger stage of gap switch 703 is connected to a pulse trigger 702; both ends of gap switch 703 are connected to an external power supply 704. External power supply 704 is normally inactive. When gap switch 703 needs to be turned on, microcomputer integrated controller 701 sends a signal to pulse trigger 702 and external power supply 704 via optical fiber 705, causing external power supply 704 to start operating. The voltage across gap switch 703 remains above the minimum operating voltage. Then, pulse trigger 702 sends a pulse signal to the trigger stage of gap switch 703 via wire 706, turning gap switch 703 on. External power supply 704 automatically stops operating after operating for a few seconds.

[0083] The embodiment of the present invention provides a method for rapidly extinguishing arcs in parallel with a gap switch, which has at least the following technical effects:

[0084] (1) The present invention adopts a gap switch in the arc extinguishing system. Since the gap switch has a fast conduction speed, it can quickly transfer the fault current at the fault point to the metallic grounding current of the busbar. The arc extinguishing system using this method has excellent fast-acting performance, thereby quickly eliminating arc grounding faults and suppressing arc grounding overvoltage. And by applying a trigger signal at the moment when the gap switch current passes through zero, the problem of the gap switch being extinguished at the moment when the current passes through zero is solved. At the same time, since the gap switch is connected in parallel with the fast switch, after the gap switch is turned on, the closing fast switch bears the steady-state current, thereby converting the arc grounding fault at the fault point into metallic single-phase grounding at the busbar position. According to regulations, in a distribution system with an ungrounded neutral point, the overhead line can operate with the fault for 1-2 hours after a single-phase grounding fault occurs, thereby reducing the power outage time of the distribution network.

[0085] (2) The present invention adopts an active intervention arc suppression method, which is applicable to systems with any capacitive current, and is particularly effective for distribution networks with large capacitive currents and a large number of cable lines. This method is applicable to distribution networks with different capacitive currents at the same voltage level, and does not require the design of different arc suppression coil capacities for different systems, as is required with arc suppression coils.

[0086] (3) The present invention considers the three-phase voltage characteristics under fault conditions, thereby accurately determining the fault type and phase. In particular, it considers the three-phase voltage characteristics under different ground transition resistances. In the case of high-resistance grounding, the fault phase is selected in conjunction with the zero-sequence voltage, effectively improving the accuracy of high-resistance grounding fault determination.

[0087] (4) The present invention determines the fault line by analyzing the changing characteristics of the zero-sequence current of each feeder line during a single-phase grounding fault in the distribution network, and combining the differences in direction and amplitude between the zero-sequence current of the fault line and the zero-sequence current of the non-fault line before and after the gap switch is turned on. The fault line can be effectively determined, so that different action strategies can be adopted for cables and overhead lines.

[0088] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A fast arc extinguishing method for a fast switching parallel gap switch, characterized in that: Connecting a fast switch in parallel with a gap switch comprises the following steps: Step 1: Determine whether a single-phase grounding fault occurs in the distribution network; if a single-phase grounding fault occurs, proceed to step 2; Step 2: Select the fault phase according to the three-phase voltage; Step 3: The microcomputer integrated controller controls the parallel fault phase gap switch and the fault phase fast switch to perform the closing action; Wherein, when the fault phase gap switch is turned on and the fault phase fast switch has not yet completed the closing action, the microcomputer integrated controller monitors the current of the fault phase gap switch and triggers the fault phase gap switch when the current passes through zero, so that the fault phase gap switch remains turned on; after the fault phase fast switch completes the closing action, the microcomputer integrated controller no longer sends a pulse trigger signal to the fault phase gap switch, and the fault phase gap switch automatically opens when the current passes through zero next time; Step 4: Select the fault line based on the zero-sequence current and determine whether the fault line is a cable line; The fault line is selected by analyzing the zero-sequence current measured by the current recorder installed at the head end of each feeder. The basis for selecting the fault line based on the zero-sequence current is: before the fault phase gap switch is turned on, if the zero-sequence current on one line is opposite to the zero-sequence current of all other lines and has a larger amplitude than that of other lines, and the direction of the zero-sequence current on one line changes before and after the fault phase gap switch is turned on, then the line can be determined to be the fault line; If the fault line is a cable line, keep the fast switch of the fault phase closed; If the fault line is not a cable line, immediately after the fault phase fast switch is closed, the microcomputer integrated controller controls the fault phase fast switch to be opened, and the microcomputer integrated controller determines whether the fault disappears. If the fault still exists, step 3 is executed again. The gap switch adopts a three-electrode controllable gap switch, the trigger stage of the gap switch is connected to a pulse trigger, and both ends of the gap switch are connected to an external power supply, which is in a non-working state under normal conditions; the microcomputer integrated controller is respectively connected to the pulse trigger and the external power supply; When the gap switch needs to be turned on, the microcomputer integrated controller sends a signal to the pulse trigger and the external power supply, the external power supply starts working, and the pulse trigger sends a pulse signal to the trigger level of the gap switch to turn on the gap switch.

2. The rapid arc extinguishing method of the fast switch parallel gap switch according to claim 1, characterized in that: The fast switch has a closing action time of less than 7ms and an opening action time of less than 3ms.

3. The rapid arc extinguishing method of a fast switch parallel gap switch according to claim 1, characterized in that: In step 1, the specific implementation method of determining whether a single-phase grounding fault occurs in the distribution network is: real-time online monitoring of the open triangle voltage on the secondary side of the voltage transformer by the microcomputer integrated controller; if the open triangle voltage exceeds a preset voltage threshold, it is determined that a single-phase grounding fault occurs.

4. The rapid arc extinguishing method of a fast switch parallel gap switch according to claim 1, characterized in that: In step 2, the specific implementation method of selecting the fault phase according to the three-phase voltage is as follows: the three-phase voltage output by the voltage transformer is monitored by the microcomputer integrated controller. If one phase voltage is close to 0 and the other two phase voltages are close to the line voltage, it is determined to be a metallic ground fault, and the phase with the voltage close to 0 is determined to be the fault phase; If one phase voltage has the largest amplitude and the other two phase voltages have similar amplitudes, it is determined to be a low-resistance ground fault, and the phase with the smallest voltage amplitude is determined to be the fault phase; If the three-phase voltage amplitudes are all greater than the preset voltage amplitudes, it is determined to be a large resistance grounding fault, and the phase following the phase with the largest voltage amplitude is determined to be the fault phase.

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