Single-phase earth fault type intelligent judgment method

Abstract

The invention relates to a method for intelligently judging the type of a single-phase earth fault in a power supply and distribution system, which is suitable for connecting arc extinguishing equipment to a system bus and is parallel to each feeder line connected to the system bus. Wherein the working stage of the arc extinguishing equipment is divided into an arc extinguishing equipment awakening stage, a fault phase selection arc extinguishing stage and a fault type line selection stage. When a single-phase earth fault occurs in the range of a system line where the arc extinction equipment is located, the arc extinction equipment is quickly awakened and enters a fault phase selection arc extinction stage, and the single-phase earth fault occurring in the system line can be quickly processed through three links of phase selection, verification and arc extinction. And the method has the capabilities of fault tolerance, error correction and severe transient process suppression in the processing process. A three-phase split-phase switch driven by eddy current is selected as a phase selection switch in the arc extinction equipment, and the two-phase switch cannot be switched on or switched off at the same time due to disorder switching-on and switching-off programs when the arc extinction equipment performs phase selection action due to the wiring mode of each phase switch coil panel in the three-phase split-phase switch.

Description

Technical Field

[0001] The invention relates to a power supply and distribution system, and in particular to a method for intelligently determining the type of a single-phase grounding fault in the power supply and distribution system. Background Art

[0002] With the widespread use of urban power cable lines, the capacitive current of 10kV non-effectively grounded systems is getting larger and larger. Accordingly, in order for the arc extinguishing coil to achieve effective compensation, the arc extinguishing coil in the power supply and distribution system of urban power cables also needs to be increased in capacity. In this way, the method of using arc extinguishing coils to extinguish arcs makes the following disadvantages increasingly obvious: 1. The large residual current of the arc extinguishing coil compensation is prone to arc overvoltage; Second, the arc suppression coil cannot compensate for high-frequency current; 3. Arc suppression coil capacity limitation; 4. It cannot effectively handle permanent ground fault problems, etc.

[0003] In addition, the single-phase grounding of the domestic 66kV and below non-effective grounding system is allowed to operate for 2 hours. If a permanent grounding fault occurs, the arc grounding is likely to cause cable combustion. In this way, if the single-phase grounding fault cannot be solved in time, the scope of the accident will be expanded, seriously affecting the power supply reliability of the power supply and distribution network and the safety of the power grid operation.

[0004] However, in accordance with Section 5.8.6 of the Technical Guidelines for Distribution Networks (Q / GDW 10370-2016) and the requirements for rapid handling of single-phase grounding faults in some urban distribution cable networks, the handling principles for single-phase grounding faults are clearly defined as "safe arc extinguishing for instantaneous faults and rapid isolation for permanent faults", and the transformation of neutral point grounding methods is steadily promoted, grounding line selection and tripping technology is promoted, low-resistance grounding methods are carefully selected, and distribution automation equipment is used to achieve rapid isolation of single-phase grounding faults nearby.

[0005] Among them, the reason for "carefully selecting a low-resistance grounding method" is that the line tripping rate is high. The increase in ground potential caused by a large ground fault current will bring dangers to low-voltage equipment, electronic equipment and personal safety, and interfere with communication lines, thereby seriously affecting the power supply reliability of the power supply and distribution network and the safety of power grid operation. Summary of the invention

[0006] In order to solve the limitations of using arc suppression coils and low resistance grounding methods to treat single-phase grounding faults in the power supply and distribution system proposed in the above background technology, the present invention provides the following technical solutions: A single-phase grounding fault type intelligent determination method is applicable to connecting arc extinguishing equipment to the system bus, and the arc extinguishing equipment is parallel to each feeder connected to the system bus. The arc extinguishing equipment working stage is divided into arc extinguishing equipment awakening stage, fault phase selection arc extinguishing stage and fault type line selection stage.

[0007] During the arc extinguishing device wake-up phase, a decision is made on whether to wake up the arc extinguishing device by acquiring and analyzing the electrical signals of the system lines.

[0008] During the fault phase selection and arc extinguishing stage, the purpose of arc extinguishing the system line is achieved by acquiring and analyzing the electrical signals of the system line, and going through the three steps of phase selection, verification and arc extinguishing.

[0009] In the fault type line selection stage, the type of single-phase grounding fault is determined by acquiring and analyzing the electrical signals of the system lines, and a decision is made on whether to select the single-phase grounding fault line based on the determination result of the single-phase grounding fault type.

[0010] Furthermore, the arc extinguishing device includes a pre-circuit breaker, a phase selection switch, a current limiting resistor, an arc extinguishing switch, a line selection switch, an impedance grounding transformer and a controller. The pre-circuit breaker serves as the main switch of the feeder where the arc extinguishing device is located, and its outgoing line side is connected to the phase selection branch and the line selection branch, and the phase selection branch and the line selection branch are connected in parallel and then grounded; the phase selection switch is connected to the phase selection branch; the current limiting resistor is connected to the phase selection branch and is located on the outgoing line side of the phase selection switch; the arc extinguishing switch is connected to the phase selection branch and is connected in parallel with the current limiting resistor; the line selection switch is connected to the line selection branch; the impedance grounding transformer is connected to the line selection branch and is located on the outgoing line side of the line selection switch; the controller processes the system line electrical signals, and selects the corresponding closing and opening strategies of the phase selection switch, arc extinguishing switch and line selection switch according to the system line electrical signal processing results.

[0011] Furthermore, the system line electrical signal of the controller comes from the collection of the electrical signal of the line where the CT sensor is located, which is distributed in the system line.

[0012] Furthermore, the phase selection switch is a three-phase split-phase switch.

[0013] Furthermore, the phase selection switch, arc extinguishing switch and line selection switch are all eddy current driven switches, and the power used by the coil disk to establish the magnetic field is stored in advance in a capacitor connected in parallel with the coil disk in a pre-charged manner.

[0014] Furthermore, the closing coil disks of the phase switches in the phase selection switch are connected in parallel with each other and in parallel with the same capacitor; the opening coil disks of the phase switches in the phase selection switch are connected in parallel with each other and in parallel with the same capacitor. The capacitor connected in parallel with the closing coil disk of each phase switch in the phase selection switch is different from the capacitor connected in parallel with the opening coil, and the electric energy released by the same capacitor at the same time can only be used to establish a magnetic field for closing or opening the switch for one coil disk connected in parallel.

[0015] Furthermore, the front circuit breaker in the arc extinguishing device is closed, and the phase selection switch, arc extinguishing switch and line selection switch are opened, and the arc extinguishing device is in a standby state.

[0016] Furthermore, the wake-up condition in the arc extinguishing device wake-up phase is: , In the formula, represents the system neutral point displacement voltage, Represents the fault starting voltage. If the above formula is true, the arc extinguishing device wake-up condition is met, the arc extinguishing device switches from the standby state to the awakened state, and enters the fault phase selection arc extinguishing stage; if the above formula is not true, the arc extinguishing device wake-up condition is not met, and the arc extinguishing device continues to remain in the standby state.

[0017] Furthermore, in the fault phase selection and arc extinguishing stage, in the phase selection link, the phase where the single-phase grounding fault point is located is determined by online analysis of the change of the three-phase current of the system line, and the phase selection switch is made according to the determination result of the phase where the single-phase grounding fault point is located. After the phase selection switch completes the phase separation, closing and opening strategy, it enters the verification link. In the verification link, the determination result of the phase where the single-phase grounding fault point is located in the phase selection link is verified by online analysis of the system ground capacitance current value and the current value flowing through the current limiting resistor; if the system ground capacitance current value is greater than the current value flowing through the current limiting resistor, the determination result of the phase where the single-phase grounding fault point is located in the phase selection link is correct, and the arc extinguishing link is entered; or if the system ground capacitance current value is less than the current value flowing through the current limiting resistor, the determination result of the phase where the single-phase grounding fault point is located in the phase selection link is wrong, the option switch is reset, and the phase selection link is re-entered. In the arc extinguishing link, the arc extinguishing switch is closed to make the current limiting resistor withdraw, the system line fault current is grounded through the arc extinguishing switch, and the arc extinguishing switch is opened after the preset closing time.

[0018] Furthermore, after the arc extinguishing link is completed, the phase selection switch is reset, and the three-phase voltage and zero-sequence voltage of the system line are analyzed online to determine whether the single-phase grounding fault point is arc extinguished. If the arc has been extinguished, the system line returns to normal, and the fault type of the single-phase grounding fault point is determined to be an instantaneous single-phase grounding fault. The arc extinguishing device records the event and reports to the background, and no longer selects the line for the single-phase grounding fault line; or if the arc has not been extinguished, the system line fault is still there, and the fault type of the single-phase grounding fault point is determined to be a permanent single-phase grounding fault. The line selection switch is closed, and the line where the single-phase grounding fault point is located is determined by analyzing the changes in the zero-sequence voltage of the system line online, and the line selection switch is opened after the line selection determination is completed, and the arc extinguishing device records the event and reports to the background.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. In this method, when there is no single-phase grounding fault within the range of the system line where the arc extinguishing device is located, the arc extinguishing device is in a standby state, which not only reduces the power consumption of the arc extinguishing device, but also helps to reduce the impact of the arc extinguishing device on the system line.

[0020] 2. In this method, when a single-phase grounding fault occurs within the range of the system line where the arc extinguishing device is located, the arc extinguishing device quickly wakes up and enters the fault phase selection and arc extinguishing stage. Through the three links of phase selection-verification-arc extinguishing, the single-phase grounding fault occurring in the system line can be quickly processed, and the processing process has the ability of fault tolerance, error correction and suppression of severe transient processes.

[0021] 3. In this method, the phase selection switch in the arc extinguishing device selects a three-phase split-phase switch driven by eddy current, and the wiring method of the coil disk of each phase switch in it makes it possible to close or open the switches of two phases at the same time due to disorder of the closing and opening procedures when performing phase selection. That is, the arc extinguishing device has the ability to prevent errors when quickly handling single-phase grounding faults in the system line.

[0022] 4. In this method, the arc extinguishing equipment is put into use for a short time with impedance grounding transformer to stabilize the system zero-sequence voltage and protect the busbar voltage transformer and its fuse from damage.

[0023] 5. In this method, the arc extinguishing device can quickly determine the phase where the single-phase grounding fault point is located through the application of phase selection branches, so as to quickly take arc extinguishing measures for the phase to avoid the expansion of the fault range.

[0024] 6. In this method, the arc extinguishing device can quickly determine the line where the single-phase grounding fault point is located through the application of line selection branches, and then report it to the background so that the staff can take corresponding measures as needed.

[0025] 7. In this method, the arc extinguishing device identifies whether the arc extinguishing effect is achieved by analyzing the three-phase voltage and zero-sequence voltage of the system after the arc extinguishing link is completed during the fault type selection stage, thereby determining the type of single-phase grounding fault.

[0026] 8. In this method, by operating the arc extinguishing equipment in three working stages, it overcomes the limitations of using arc extinguishing coils and low-resistance grounding methods to treat single-phase grounding faults. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A primary structural principle diagram of the arc extinguishing device involved in the present invention connected to the power grid system; Figure 2 A wiring diagram of the arc extinguishing device involved in the present invention; Figure 3 A control logic diagram of the arc extinguishing device involved in the present invention; Figure 4 A single-phase grounding fault processing flow chart of the arc extinguishing device involved in the present invention; Figure 5 The present invention provides a wiring diagram of a closing coil disk or an opening coil disk in a phase-selective switch in the arc extinguishing device involved in the present invention. DETAILED DESCRIPTION

[0028] The preferred specific embodiments for implementing the present invention are described in detail below, and a clear and complete description is made in conjunction with the accompanying drawings.

[0029] See also Figure 1-Figure 5 The present invention provides a single-phase grounding fault type intelligent determination method. The method is applicable to arc extinguishing equipment connected to the system bus, and the arc extinguishing equipment is parallel to each feeder connected to the system bus.

[0030] In the figure: K1 represents the front circuit breaker; K2 represents the line selection switch; K represents the phase selection switch, Ka represents the switch installed in the A-phase line of the phase selection switch, Kb represents the switch installed in the B-phase line of the phase selection switch, and Kc represents the switch installed in the C-phase line of the phase selection switch; K0 represents the arc suppression switch; R represents the current limiting resistor; T represents the impedance grounding transformer; CT represents the CT sensor; La represents the closing coil disk or the opening coil disk of the switch installed in the A-phase line of the phase selection switch, Lb represents the closing coil disk or the opening coil disk of the switch installed in the B-phase line of the phase selection switch, and Lc represents the closing coil disk or the opening coil disk of the switch installed in the C-phase line of the phase selection switch; C represents the capacitor that provides power to establish a magnetic field for the coil disk.

[0031] That is, the arc extinguishing equipment targeted by this method includes a pre-circuit breaker K1, a phase selection switch K, a current limiting resistor R, an arc extinguishing switch K0, a line selection switch K2, an impedance grounding transformer T and a controller. These components are connected by the following method: The front circuit breaker K1 serves as the main switch of the feeder where the arc extinguishing equipment is located. The outgoing line side of the circuit breaker K1 is connected to the phase selection branch and the line selection branch, and the phase selection branch and the line selection branch are connected in parallel and then grounded.

[0032] The phase selection switch K is connected to the phase selection branch. The current limiting resistor R is connected to the phase selection branch and is located at the outgoing line side of the phase selection switch K. The arc extinguishing switch K is connected to the phase selection branch and is connected in parallel with the current limiting resistor R.

[0033] The line selection switch K2 is connected to the line selection branch. The impedance grounding transformer T is connected to the line selection branch and is located at the outgoing line side of the line selection switch K2.

[0034] The controller processes the system line electrical signals and selects the closing and opening strategies of the phase selection switch K, arc suppression switch K0 and line selection switch K2 according to the system line electrical signal processing results. The system line electrical signals of the controller are derived from the collection of the line electrical signals by the CT sensors distributed in the system lines.

[0035] Preferably, the phase selection switch K is a three-phase split-phase switch, and it adopts an eddy current drive mode. The closing coil disks of each phase switch (Ka, Kb, Kc) in the phase selection switch K are connected in parallel to form three parallel branches, and each of the three branches is equipped with a thyristor to control the circuit on and off of the branch in which it is located. In addition, the closing coil disks of the three switches are connected in parallel with a capacitor C.

[0036] The opening coils of each phase switch (Ka, Kb, Kc) in the phase selection switch K are connected in parallel to form three parallel branches, and each of the three branches is equipped with a thyristor to control the circuit on and off of the branch. In addition, the opening coils of the three switches are connected in parallel with a capacitor C.

[0037] The capacitor C connected in parallel to the closing coil disk of each phase switch (Ka, Kb, Kc) in the phase selection switch K is different from the capacitor C connected in parallel to the opening coil, and the electric energy released by the same capacitor C at the same time can only be used to establish a magnetic field for closing or opening for one coil disk connected in parallel. In this way, the phase selection switch K is prevented from closing or opening two phases of the switch at the same time due to the disorder of closing and opening. That is, when the arc extinguishing device quickly handles the single-phase grounding fault in the system line, it has the ability to prevent closing and opening errors.

[0038] In this method, if the single-phase grounding fault point is in phase A, when closing is required, the controller turns on the thyristor in series with the closing coil disk of phase A switch Ka in the phase selection switch K, so that the closing coil disk is energized to drive the A phase switch Ka to complete the closing action; when opening is required, the controller turns on the thyristor in series with the opening coil disk of phase A switch Ka in the phase selection switch K, so that the opening coil disk is energized to drive the A phase switch Ka to complete the opening action.

[0039] In this method, if the single-phase grounding fault point is in phase B, when closing is required, the controller turns on the thyristor in series with the closing coil disk of phase B switch Kb in the phase selection switch K, so that the closing coil disk is energized to drive the phase B switch Kb to complete the closing action; when opening is required, the controller turns on the thyristor in series with the opening coil disk of phase B switch Kb in the phase selection switch K, so that the opening coil disk is energized to drive the phase B switch Kb to complete the opening action.

[0040] In this method, if the single-phase grounding fault point is in the C phase, when closing is required, the controller turns on the thyristor in series with the closing coil disk of the C phase switch Kc in the phase selection switch K, so that the closing coil disk is energized to drive the C phase switch Kc to complete the closing action; when opening is required, the controller turns on the thyristor in series with the opening coil disk of the C phase switch Kc in the phase selection switch K, so that the opening coil disk is energized to drive the C phase switch Kc to complete the opening action.

[0041] In this method, the power used by the coil disk to establish the magnetic field is stored in advance in the capacitor C connected in parallel with the coil disk by pre-charging. In this way, if the thyristor connected in series with the closing coil disk of two phase switches in the phase selection switch K is turned on due to the disorder of the controller program, or the thyristor connected in series with the opening coil disk of two phase switches is turned on, because the electric energy of the capacitor C is shared among the two coil disks, the two coil disks cannot obtain enough current to establish a magnetic field that can complete the closing or opening. In this case, after the power supply action of the capacitor C is completed, the capacitor C is recharged by the power supply, and after the charging is completed, the switch (Ka, Kb or Kc) of the other phase where the single-phase grounding fault point is located is re-controlled to perform the closing and opening operations.

[0042] Preferably, the arc extinguishing switch and the line selection switch also adopt eddy current driving mode.

[0043] More preferably, the eddy current drive mode means that the lower pull rod of the vacuum interrupter is equipped with two coil disks (one for closing is called the closing coil disk, and the other for opening is called the opening coil disk), an eddy current disk is arranged between the two coil disks, and a through hole is opened in the middle of the eddy current disk for the lower pull rod to pass through. After the coil disk is energized, a repulsive magnetic field is established between the energized coil disk and the eddy current disk, and the repulsive force in the magnetic field can drive the vacuum interrupter to perform closing and opening actions.

[0044] The working stages of the arc extinguishing equipment are divided into the arc extinguishing equipment wake-up stage, the fault phase selection arc extinguishing stage and the fault type line selection stage.

[0045] During the arc extinguishing device wake-up phase, a decision is made on whether to wake up the arc extinguishing device by acquiring and analyzing the electrical signals of the system lines.

[0046] During the fault phase selection and arc extinguishing stage, the purpose of arc extinguishing the system line is achieved by acquiring and analyzing the electrical signals of the system line, and going through the three steps of phase selection-verification-arc extinguishing.

[0047] In the fault type line selection stage, the type of single-phase grounding fault is determined by acquiring and analyzing the electrical signals of the system lines, and a decision is made on whether to select the single-phase grounding fault line based on the determination result of the single-phase grounding fault type.

[0048] Specifically: The front circuit breaker K in the arc extinguishing device is closed, while the phase selection switch K, arc extinguishing switch K0 and line selection switch K2 are opened. At this time, the arc extinguishing device is in standby state, in which the arc extinguishing device does not operate, which not only reduces the power consumption of the arc extinguishing device, but also reduces the load burden of the arc extinguishing device on the system line.

[0049] The wake-up conditions in the arc extinguishing device wake-up phase are:

[0050] In the formula, represents the system neutral point displacement voltage, Represents the fault starting voltage. The fault starting voltage is set by the user as required. For example, in a 35KV neutral point ungrounded system, the fault starting voltage is set to 15% of the system phase voltage.

[0051] If the above equation is true, the arc extinguishing device wake-up condition is met, the arc extinguishing device switches from the standby state to the awakened state, and enters the fault phase selection arc extinguishing stage. If the above equation is not true, the arc extinguishing device wake-up condition is not met, and the arc extinguishing device continues to remain in the standby state.

[0052] The specific methods of the three links in the fault phase selection arc extinguishing stage are: The phase selection link determines the phase where the single-phase grounding fault point is located by analyzing the changes in the three-phase current of the system line online, and makes the phase separation, closing and opening strategy of the phase selection switch K based on the determination result of the phase separation, closing and opening strategy. After that, the phase selection switch enters the verification link after completing the phase separation, closing and opening strategy.

[0053] The verification phase verifies the determination result of the phase where the single-phase grounding fault point is located in the phase selection phase by online analyzing the system ground capacitance current value and the current value flowing through the current limiting resistor R. If the system ground capacitance current value is greater than the current value flowing through the current limiting resistor R, the determination result of the phase where the single-phase grounding fault point is located in the phase selection phase is correct, and the arc extinguishing phase is entered; if the system ground capacitance current value is less than the current value flowing through the current limiting resistor R, the determination result of the phase where the single-phase grounding fault point is located in the phase selection phase is wrong, the option switch K is reset, and the phase selection phase is re-entered; After entering the arc extinguishing stage, the arc extinguishing switch K0 is closed first to withdraw the current limiting resistor R, and the system line fault current is grounded through the arc extinguishing switch K0, and the arc extinguishing switch K0 is opened after the preset closing time.

[0054] In this method, when performing the phase selection link, the controller obtains and analyzes the changes in the three-phase current of the system line. When the system current of a phase increases, the phase is the phase where the single-phase grounding fault point is located. The controller controls the corresponding phase switch (Ka, Kb or Kc) in the phase selection switch K to close accordingly.

[0055] In this method, during the verification phase, the controller obtains and analyzes the system ground capacitance current value and the current value flowing through the current limiting resistor R. By verifying the phase selection result, the accuracy of phase selection arc extinguishing is improved, and the power supply reliability of the system line is guaranteed.

[0056] In this method, when the arc extinguishing link is performed, the current limiting resistor R is removed by closing the arc extinguishing switch K0, and the fault phase current is grounded through the arc extinguishing switch KO. That is, the unstable grounding of the fault point in the system line is converted into a stable metal grounding in the substation, and the voltage of the fault phase to the ground drops to zero, thereby making it difficult to maintain the arc at the fault point and extinguishing it. This fast phase selection arc extinguishing method is conducive to avoiding the expansion of the single-phase grounding fault range and the escalation of power grid events.

[0057] The fault type determination method and line selection decision in the fault type line selection stage are as follows: After completing the arc extinguishing link, the phase selection switch K is reset, and the three-phase voltage and zero-sequence voltage of the system line are analyzed online to determine whether the single-phase grounding fault point is arc extinguished.

[0058] If the arc has been extinguished, the system line returns to normal, and the fault type of the single-phase grounding fault point is determined to be an instantaneous single-phase grounding fault. The arc extinguishing device records the event and reports it to the background, and no line selection is performed on the single-phase grounding fault line.

[0059] If the arc is not extinguished, the system line fault is still there, and the fault type of the single-phase grounding fault point is determined to be a permanent single-phase grounding fault. Close the line selection switch K2, and determine the line where the single-phase grounding fault point is located by online analysis of the changes in the zero-sequence voltage of the system line. After completing the line selection determination, open the line selection switch K2, and the arc extinguishing equipment records the event and reports it to the background.

[0060] In this method, by switching on and off the impedance grounding transformer T and the arc suppression switch K0 and the phase selection switch K, the system zero-sequence voltage changes concavely during this period, so that the zero-sequence current waveform characteristics of the fault branch and the normal branch show obvious differences. That is, the amplitude of the system zero-sequence voltage drops significantly during this period, the zero-sequence current of the fault branch changes from small to large, and the zero-sequence current of the normal branch changes from large to small. According to this feature, the fault line and the non-fault line can be clearly distinguished, so that the fault line can be accurately selected, and the accuracy of line selection is improved.

[0061] In this method, when the arc extinguishing device determines that the single-phase grounding fault point is a permanent single-phase grounding fault and reports it to the background, the staff can choose whether to convert the single-phase grounding fault into a metal grounding fault in the substation for continuous arc extinguishing, or to trip the main switch of the feeder where the single-phase grounding fault point is located. In addition, the staff can also set the priority of the two processing methods in the background, and the background will make a decision based on the set priority.

[0062] Based on the above content and the accompanying drawings, those skilled in the art can understand and implement the present invention. In addition, any non-creative modifications made to the present invention by those skilled in the art without creative work still fall within the protection scope of the present invention.

Claims

1. A single-phase grounding fault type intelligent determination method, suitable for connecting arc extinguishing equipment to the system bus, and the arc extinguishing equipment is parallel to each feeder connected to the system bus, characterized in that: The arc extinguishing equipment working stages are divided into: During the arc extinguishing device wake-up phase, a decision is made on whether to wake up the arc extinguishing device by acquiring and analyzing the electrical signals of the system lines; In the fault phase selection and arc extinguishing stage, the purpose of arc extinguishing the system line is achieved through the acquisition and analysis of the system line electrical signal through the three links of phase selection, verification and arc extinguishing. In the fault type line selection stage, the type of single-phase grounding fault is determined by acquiring and analyzing the electrical signals of the system lines, and a decision is made on whether to select the single-phase grounding fault line based on the determination result of the single-phase grounding fault type.

2. The single-phase grounding fault type intelligent determination method according to claim 1 is characterized in that: The arc extinguishing equipment includes a pre-circuit breaker, a phase selection switch, a current limiting resistor, an arc extinguishing switch, a line selection switch, an impedance grounding transformer and a controller, and is wired in the following way: The front circuit breaker serves as the main switch of the feeder where the arc extinguishing device is located, and its outgoing line side is connected to a phase selection branch and a line selection branch, and the phase selection branch and the line selection branch are connected in parallel and then grounded; The phase selection switch is connected to the phase selection branch; The current limiting resistor is connected to the phase selection branch and is located at the outgoing line side of the phase selection switch; The arc extinguishing switch is connected to the phase selection branch and is connected in parallel with the current limiting resistor; The line selection switch is connected to the line selection branch; The impedance grounding transformer is connected to the line selection branch and is located on the outgoing line side of the line selection switch; The controller processes the system line electrical signals and selects the closing and opening strategies of the corresponding phase selection switches, arc extinguishing switches and line selection switches according to the system line electrical signal processing results.

3. The single-phase grounding fault type intelligent determination method according to claim 2 is characterized by: The controller's system line electrical signals come from the collection of the line electrical signals by the CT sensors distributed in the system lines.

4. The single-phase grounding fault type intelligent determination method according to claim 2 is characterized in that: The phase selection switch is a three-phase split-phase switch.

5. The single-phase grounding fault type intelligent determination method according to claim 4 is characterized in that: The phase selection switch, arc extinguishing switch and line selection switch are all eddy current driven switches, and the power used by the coil disk to establish the magnetic field is stored in advance in the capacitor connected in parallel with the coil disk in a pre-charged manner.

6. The single-phase grounding fault type intelligent determination method according to claim 5 is characterized in that: The wiring method of the coil disk in the phase selection switch is: The closing coil disks of the switches of each phase in the phase selection switch are connected in parallel with each other and are connected in parallel to the same capacitor; The opening coil disks of the switches of each phase in the phase selection switch are connected in parallel with each other and in parallel with the same capacitor; The capacitor connected in parallel to the closing coil disk of each phase switch in the phase selection switch is different from the capacitor connected in parallel to the opening coil, and the electric energy released by the same capacitor at the same time can only be used to establish a magnetic field for closing or opening the switch for one coil disk connected in parallel.

7. The single-phase grounding fault type intelligent determination method according to claim 2 is characterized in that: The front circuit breaker in the arc extinguishing device is closed, while the phase selection switch, arc extinguishing switch and line selection switch are opened, and the arc extinguishing device is in standby state.

8. The single-phase grounding fault type intelligent determination method according to claim 7 is characterized in that: The wake-up conditions in the arc extinguishing device wake-up phase are: ， In the formula, represents the system neutral point displacement voltage, Represents the fault starting voltage; If the above formula is established, the arc extinguishing device wake-up condition is met, the arc extinguishing device switches from the standby state to the awakened state, and enters the fault phase selection arc extinguishing stage; If the above formula is not true, the arc extinguishing device wake-up condition is not met, and the arc extinguishing device continues to remain in standby mode.

9. The single-phase grounding fault type intelligent determination method according to claim 2 or 7, characterized in that: The specific methods of the three links in the fault phase selection arc extinguishing stage are: In the phase selection phase, the change of the three-phase current of the system line is analyzed online to determine the phase where the single-phase grounding fault point is located, and the phase selection switch's phase separation, closing and opening strategies are made according to the determination result of the phase where the single-phase grounding fault point is located. After the phase selection switch completes the phase separation, closing and opening strategies, it enters the verification phase; In the verification phase, the determination result of the phase where the single-phase grounding fault point is located in the phase selection phase is verified by online analysis of the system ground capacitance current value and the current value flowing through the current limiting resistor; if the system ground capacitance current value is greater than the current value flowing through the current limiting resistor, the determination result of the phase where the single-phase grounding fault point is located in the phase selection phase is correct, and the arc extinguishing phase is entered; or if the system ground capacitance current value is less than the current value flowing through the current limiting resistor, the determination result of the phase where the single-phase grounding fault point is located in the phase selection phase is wrong, the option switch is reset, and the phase selection phase is re-entered; In the arc extinguishing stage, the arc extinguishing switch is closed to make the current limiting resistor withdraw, and the system line fault current is grounded through the arc extinguishing switch, and the arc extinguishing switch is opened after the preset closing time.

10. The single-phase grounding fault type intelligent determination method according to claim 2 or 7, characterized in that: The fault type determination method and line selection decision in the fault type line selection stage are as follows: After the arc extinguishing link is completed, the phase selection switch is reset, and the three-phase voltage and zero-sequence voltage of the system line are analyzed online to determine whether the single-phase grounding fault point is arc extinguished; If the arc has been extinguished, the system line returns to normal, and the fault type of the single-phase grounding fault point is determined to be an instantaneous single-phase grounding fault. The arc extinguishing device records the event and reports it to the background, and no line selection is performed for the single-phase grounding fault line; Or the arc is not extinguished, the system line fault is still there, and the fault type of the single-phase grounding fault point is determined to be a permanent single-phase grounding fault. Close the line selection switch, and determine the line where the single-phase grounding fault point is located by online analysis of the change in the zero-sequence voltage of the system line. After completing the line selection determination, open the line selection switch, and the arc extinguishing device records the event and reports it to the background.

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