Intelligent determination method for single-phase grounding fault type

Abstract

The present invention relates to an intelligent determination method for single-phase grounding fault types in a power supply and distribution system, which is applicable to a system where an arc suppression device is connected to the system bus, and the arc suppression device is parallel to each feeder connected to the system bus. Among them, the working stages of the arc suppression device are divided into the arc suppression device wake-up stage, the fault phase selection and arc suppression stage, and the fault type selection and line selection stage. When a single-phase grounding fault occurs within the range of the system line where the arc suppression device is located, the arc suppression device quickly wakes up and enters the fault phase selection and arc suppression stage. Through three links of phase selection - verification - arc suppression, the single-phase grounding fault occurring in the system line can be quickly processed, and during the processing process, it has the ability of fault tolerance and error correction and the ability to suppress violent transient processes. The phase selection switch in the arc suppression device is selected as a three-phase split-phase switch driven by eddy current. The wiring method of the switch coils of each phase in it makes it not close or open the switches of two phases simultaneously due to the disorder of the closing and opening procedures during the phase selection operation.

Description

Technical Field

[0001] The present invention relates to a power supply and distribution system, and in particular to an intelligent determination method for single-phase grounding fault types in a power supply and distribution system. Background Art

[0002] With the wide use of urban power cable lines, the capacitive current to the ground in a 10 kV non-effectively grounded system is increasing. Correspondingly, in order to enable the arc suppression coil to achieve an effective compensation effect, the arc suppression coil in the power supply and distribution system of urban power cables also needs to be appropriately increased in capacity. Thus, the disadvantages of using the arc suppression coil for arc extinction are becoming increasingly obvious:

[0003] First, the residual current compensated by the arc suppression coil is large, which is likely to generate arc overvoltage;

[0004] Second, the arc suppression coil cannot compensate for high-frequency current;

[0005] Third, there is a limit to the capacity of the arc suppression coil;

[0006] Fourth, it cannot effectively handle permanent grounding fault problems, etc.

[0007] In addition, in domestic non-effectively grounded systems of 66 kV and below, single-phase grounding is allowed to operate for 2 hours. If a permanent grounding fault occurs, arc grounding is likely to cause cable combustion. Thus, if the single-phase grounding fault cannot be resolved in time, the accident scope will be expanded, seriously affecting the power supply reliability of the power supply and distribution network and the safety of the power grid operation.

[0008] However, in accordance with Section 5.8.6 of the "Technical Guidelines for Distribution Networks" (Q / GDW 10370-2016) and the requirements for rapid disposal of single-phase grounding faults in some urban distribution cable networks, the treatment principle of "safe arc extinction for instantaneous faults and rapid isolation for permanent faults" is clearly defined for single-phase grounding faults. The transformation of the neutral point grounding method is steadily promoted, the grounding line selection and tripping technology is popularized, the small-resistance grounding method is carefully selected, and the distribution automation equipment is used to achieve the nearby and rapid isolation of single-phase grounding faults.

[0009] Among them, for the "careful selection of the small-resistance grounding method", it is because the line tripping rate is high, and the increase in the ground potential caused by a large grounding fault current will pose a danger to low-voltage equipment, electronic equipment, and personal safety, and will interfere with communication lines, thus seriously affecting the power supply reliability of the power supply and distribution network and the safety of the power grid operation. Summary of the Invention

[0010] In order to solve the limitations existing in the treatment of single-phase grounding faults by using an arc suppression coil and a small-resistance grounding method in the power supply and distribution system as mentioned in the above background art, the present invention provides the following technical solutions:

[0011] An intelligent determination method for single-phase grounding fault types is applicable to a system where an arc suppression device is connected to the system bus, and the arc suppression device is parallel to each feeder connected to the system bus. Among them, the working stages of the arc suppression device are divided into the arc suppression device wake-up stage, the fault phase selection and arc suppression stage, and the fault type line selection stage.

[0012] In the arc suppression device wake-up stage, a decision on whether to wake up the arc suppression device is made by acquiring and analyzing the electrical signals of the system lines.

[0013] In the fault phase selection and arc suppression stage, through the acquisition and analysis of the electrical signals of the system lines, the purpose of arc suppression for the system lines is completed through three links: phase selection - verification - arc suppression.

[0014] In the fault type line selection stage, through the acquisition and analysis of the electrical signals of the system lines, the type of single-phase grounding fault is determined, and a decision on whether to select the line of the single-phase grounding fault is made according to the determination result of the single-phase grounding fault type.

[0015] Furthermore, the arc suppression device includes a pre-circuit breaker, a phase selection switch, a current-limiting resistor, an arc suppression switch, a line selection switch, an impedance grounding transformer, and a controller. Among them, the pre-circuit breaker serves as the main switch of the feeder where the arc suppression 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 grounded in parallel; the phase selection switch is connected to the phase selection branch; the current-limiting resistor is connected to the phase selection branch and is on the outgoing line side of the phase selection switch; the arc suppression switch is connected to the phase selection branch and is 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 on the outgoing line side of the line selection switch; the controller processes the electrical signals of the system lines and selects the closing and opening strategies of the corresponding phase selection switch, arc suppression switch, and line selection switch according to the processing results of the electrical signals of the system lines.

[0016] Furthermore, the electrical signals of the system lines of the controller are sourced from the acquisition of the electrical signals of the lines where the CT sensors distributed in the system lines are located.

[0017] Furthermore, the phase selection switch is a three-phase split-phase switch.

[0018] Furthermore, the phase selection switch, the arc suppression switch, and the line selection switch are all eddy current-driven switches, and the power for establishing the magnetic field of their coil discs is stored in advance in the capacitor connected in parallel with the coil disc in a pre-charged manner.

[0019] Further, the closing coil discs of each phase switch in the phase selection switch are connected in parallel with each other and in parallel with the same capacitor; the opening coil discs of each phase switch in the phase selection switch are connected in parallel with each other and in parallel with the same capacitor. The capacitor to which the closing coil discs of each phase switch in the phase selection switch are connected is different from the capacitor to which the opening coils are connected, and the electric energy released by the same capacitor at the same moment can only supply the magnetic field for closing or opening established by one coil disc connected in parallel with it.

[0020] Further, when the pre - circuit breaker in the arc suppression device closes, and the phase selection switch, the arc suppression switch, and the line selection switch open, the arc suppression device is in the standby state.

[0021] Further, the wake - up condition in the wake - up stage of the arc suppression device is:

[0022] ,

[0023] wherein, represents the neutral - point displacement voltage of the system, represents the fault starting voltage. If the above formula holds, the wake - up condition of the arc suppression device is satisfied, and the arc suppression device switches from the standby state to the wake - up state and enters the fault phase - selection arc suppression stage; if the above formula does not hold, the wake - up condition of the arc suppression device is not satisfied, and the arc suppression device continues to maintain the standby state.

[0024] Further, in the fault phase - selection arc suppression stage, in the phase - selection link, the single - phase grounding fault point's phase is determined by online analyzing the changes in the three - phase currents of the system line, and the closing and opening strategy of the phase selection switch is made based on the determination result of the single - phase grounding fault point's phase. After the phase selection switch completes the closing and opening strategy, it enters the verification link. In the verification link, the determination result of the single - phase grounding fault point's phase in the phase - selection link is verified by online analyzing the system's capacitive current to ground value and the current value flowing through the current - limiting resistor; if the system's capacitive current to ground value is greater than the current value flowing through the current - limiting resistor, the determination result of the single - phase grounding fault point's phase in the phase - selection link is correct, and it enters the arc suppression link; or if the system's capacitive current to ground value is less than the current value flowing through the current - limiting resistor, the determination result of the single - phase grounding fault point's phase in the phase - selection link is incorrect, the option switch is reset, and it re - enters the phase - selection link. In the arc suppression link, the arc suppression switch is closed, the current - limiting resistor is disconnected, the system line fault current is grounded through the arc suppression switch, and the arc suppression switch opens after a preset closing duration.

[0025] Further, after the arc suppression link is completed, the phase selection switch is reset, and whether the single-phase grounding fault point is arc-suppressed is determined by online analyzing the three-phase voltage and zero-sequence voltage of the system line. If the arc has been suppressed, 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 suppression device records this event and reports it to the background, and no longer selects the line of the single-phase grounding fault line; or if the arc has not been suppressed, the system line fault still exists, and the fault type of the single-phase grounding fault point is determined to be a permanent single-phase grounding fault. The phase selection switch is closed, and the line where the single-phase grounding fault point is located is determined by online analyzing the change of the zero-sequence voltage of the system line. After the line selection determination is completed, the phase selection switch is opened, and the arc suppression device records this event and reports it to the background.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] First, in this method, when there is no single-phase grounding fault within the range of the system line where the arc suppression device is located, the arc suppression device is in a standby state, which is beneficial to reducing the power consumption of the arc suppression device and reducing the impact of the arc suppression device on the system line.

[0028] Second, in this method, when a single-phase grounding fault occurs within the range of the system line where the arc suppression device is located, the arc suppression device is quickly awakened and enters the fault phase selection and arc suppression stage. The single-phase grounding fault that occurs in the system line can be quickly processed through three links of phase selection - verification - arc suppression, and has the ability of fault tolerance and error correction and suppressing violent transient processes during the processing.

[0029] Third, in this method, the phase selection switch in the arc suppression device selects a three-phase split-phase switch driven by eddy current. The wiring method of each phase switch coil disc in it makes it not close or open the switches of two phases simultaneously due to the disorder of the closing and opening procedures during the phase selection operation. That is, when the arc suppression device quickly processes the single-phase grounding fault in the system line, it has the ability to prevent errors.

[0030] Fourth, in this method, the arc suppression device short-term inputs a grounding transformer with impedance to stabilize the zero-sequence voltage of the system and protect the bus voltage transformer and its fuse from damage.

[0031] Fifth, in this method, through the application of the phase selection branch in the arc suppression device, the phase where the single-phase grounding fault point is located can be quickly determined, so as to quickly take arc suppression measures for this phase and avoid the expansion of the fault range.

[0032] Sixth, in this method, through the application of the line selection branch in the arc suppression device, the line where the single-phase grounding fault point is located can be quickly determined, and then reported to the background so that the staff can take corresponding measures as needed.

[0033] VII. In this method, during the fault type line selection stage, the arc suppression device analyzes the three-phase voltage and zero-sequence voltage of the system after the arc suppression link to identify whether the arc suppression effect is achieved, thereby determining the type of single-phase grounding fault.

[0034] VIII. In this method, through the operations in the three working stages of the arc suppression device, in the treatment of single-phase grounding faults, it overcomes the limitations existing in the treatment of single-phase grounding faults by using arc suppression coils and small resistance grounding methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is the primary structural schematic diagram of the arc suppression device involved in the present invention connected to the power grid system;

[0036] Figure 2 is the wiring diagram of the arc suppression device involved in the present invention;

[0037] Figure 3 is the control logic diagram of the arc suppression device involved in the present invention;

[0038] Figure 4 is the flow chart of the single-phase grounding fault treatment of the arc suppression device involved in the present invention;

[0039] Figure 5 is the wiring diagram of the closing coil disk or opening coil disk in the phase selection switch of the arc suppression device involved in the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] 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 drawings.

[0041] Please refer to Figures 1 - 5 , the present invention provides an intelligent determination method for single-phase grounding fault types. This method is applicable to the arc suppression device connected to the system bus, and this arc suppression device is parallel to each feeder connected to the system bus.

[0042] In the figure: K1 represents the pre-breaker; K2 represents the line selection switch; K represents the phase selection switch, Ka represents the switch installed in the A-phase line in the phase selection switch, Kb represents the switch installed in the B-phase line in the phase selection switch, Kc represents the switch installed in the C-phase line in 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 opening coil disk of the switch installed in the A-phase line in the phase selection switch, Lb represents the closing coil disk or opening coil disk of the switch installed in the B-phase line in the phase selection switch, Lc represents the closing coil disk or opening coil disk of the switch installed in the C-phase line in the phase selection switch; C represents the capacitor that provides power to establish a magnetic field for the coil disk.

[0043] That is, the arc suppression device targeted by this method includes a pre - circuit breaker K1, a phase - selection switch K, a current - limiting resistor R, an arc suppression switch K0, a line - selection switch K2, an impedance - grounded transformer T, and a controller. Among them, these components are wired in the following way:

[0044] The pre - circuit breaker K1 serves as the main switch of the feeder where the arc suppression device is located. Its outgoing line side leads out 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.

[0045] The phase - selection switch K is wired in the phase - selection branch. The current - limiting resistor R is wired in the phase - selection branch and is on the outgoing line side of the phase - selection switch K. The arc suppression switch K is wired in the phase - selection branch and is connected in parallel with the current - limiting resistor R.

[0046] The line - selection switch K2 is wired in the line - selection branch. The impedance - grounded transformer T is wired in the line - selection branch and is on the outgoing line side of the line - selection switch K2.

[0047] The controller processes the electrical signals of the system line and selects the closing and opening strategies of the corresponding phase - selection switch K, arc suppression switch K0, and line - selection switch K2 according to the processing results of the electrical signals of the system line. Among them, the electrical signals of the system line of the controller come from the acquisition of the electrical signals of the line where it is located by CT sensors distributed in the system line.

[0048] Preferably, the phase - selection switch K is a three - phase split - phase switch and adopts an eddy - current drive method. Among them:

[0049] 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 these three branches is equipped with a thyristor to control the on - off of the circuit in its branch. In addition, the closing coil disks of these three switches are commonly connected in parallel with a capacitor C.

[0050] The opening 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 these three branches is equipped with a thyristor to control the on - off of the circuit in its branch. In addition, the opening coil disks of these three switches are commonly connected in parallel with a capacitor C.

[0051] The capacitor C connected in parallel with the closing coil disks of each phase switch (Ka, Kb, Kc) in the phase - selection switch K is different from the capacitor C connected in parallel with its opening coil. And the electrical energy released by the same capacitor C at the same moment can only supply the magnetic field for establishing closing or opening for one coil disk it is connected in parallel with. In this way, it is prevented that the phase - selection switch K closes or opens the switches of two phases simultaneously due to closing and opening disorders. That is, when the arc suppression device quickly processes the single - phase grounding fault in the system line, it has the ability to prevent errors in closing and opening.

[0052] In this method, when a single-phase grounding fault occurs at phase A and closing is required, the thyristor connected in series with the closing coil disk of phase A switch Ka in the phase selection switch K is turned on by the controller, so that the closing coil disk is energized to drive the phase A switch Ka to complete the closing operation; when opening is required, the thyristor connected in series with the opening coil disk of phase A switch Ka in the phase selection switch K is turned on by the controller, so that the opening coil disk is energized to drive the phase A switch Ka to complete the opening operation.

[0053] In this method, when a single-phase grounding fault occurs at phase B and closing is required, the thyristor connected in series with the closing coil disk of phase B switch Kb in the phase selection switch K is turned on by the controller, so that the closing coil disk is energized to drive the phase B switch Kb to complete the closing operation; when opening is required, the thyristor connected in series with the opening coil disk of phase B switch Kb in the phase selection switch K is turned on by the controller, so that the opening coil disk is energized to drive the phase B switch Kb to complete the opening operation.

[0054] In this method, when a single-phase grounding fault occurs at phase C and closing is required, the thyristor connected in series with the closing coil disk of phase C switch Kc in the phase selection switch K is turned on by the controller, so that the closing coil disk is energized to drive the phase C switch Kc to complete the closing operation; when opening is required, the thyristor connected in series with the opening coil disk of phase C switch Kc in the phase selection switch K is turned on by the controller, so that the opening coil disk is energized to drive the phase C switch Kc to complete the opening operation.

[0055] In this method, the power for the coil disk to establish a magnetic field is stored in advance in the capacitor C connected in parallel with the coil disk in a pre-charged manner. Thus, if the thyristors connected in series with the closing coil disks of two-phase switches in the phase selection switch K are turned on due to a disorder in the controller program, or the thyristors connected in series with the opening coil disks of two-phase switches are turned on, since the electric energy of the capacitor C is shared by the two coil disks, neither of these two coil disks can obtain enough current to establish a magnetic field capable of completing closing or opening. In this case, after the power supply operation of the capacitor C ends, the capacitor C is recharged through the power supply. After the charging is completed, the switches (Ka, Kb, or Kc) of the phase where the single-phase grounding fault point is located are re-controlled for closing and opening operations.

[0056] Preferably, the arc extinguishing switch and the line selection switch also adopt the eddy current drive method.

[0057] More preferably, the eddy current drive method means that two coil disks are installed on the lower pull rod of the vacuum interrupter (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 provided between these two coil disks, and a through hole for the lower pull rod to pass through is provided in the middle of the eddy current disk. 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 this magnetic field can drive the vacuum interrupter to perform closing and opening operations.

[0058] The working stages of the arc suppression device are divided into the arc suppression device wake-up stage, the fault phase selection and arc suppression stage, and the fault type line selection stage.

[0059] In the arc suppression device wake-up stage, a decision on whether to wake up the arc suppression device is made by acquiring and analyzing the electrical signals of the system line.

[0060] In the fault phase selection and arc suppression stage, through the acquisition and analysis of the electrical signals of the system line, the purpose of arc suppression for the system line is completed through three links: phase selection - verification - arc suppression.

[0061] In the fault type line selection stage, by acquiring and analyzing the electrical signals of the system line, the type of single-phase grounding fault is determined, and a decision on whether to select the line of the single-phase grounding fault line is made according to the determination result of the single-phase grounding fault type.

[0062] Specifically:

[0063] The pre-breaker K in the arc suppression device closes, while the phase selection switch K, the arc suppression switch K0, and the line selection switch K2 open. At this time, the arc suppression device is in the standby state. In this state, the arc suppression device does not operate, which not only reduces the power consumption of the arc suppression device but also reduces the load burden of the arc suppression device on the system line.

[0064] The wake-up condition in the arc suppression device wake-up stage is:

[0065]

[0066] In the formula, represents the neutral point displacement voltage of the system, represents the fault starting voltage. Among them, the fault starting voltage is set by the user as needed. For example, in a 35KV neutral non-grounding system, the fault starting voltage is set to 15% of the system phase voltage.

[0067] If the above formula holds, the arc suppression device wake-up condition is satisfied. The arc suppression device switches from the standby state to the wake-up state and enters the fault phase selection and arc suppression stage. If the above formula does not hold, the arc suppression device wake-up condition is not satisfied, and the arc suppression device continues to maintain the standby state.

[0068] The specific methods of the three links in the fault phase selection and arc suppression stage are as follows:

[0069] In the phase selection link, by analyzing the changes in the three-phase current of the system line online, the phase where the single-phase grounding fault point is located is determined, and a switching strategy for the phase selection switch K is made according to the determination result of the phase where the single-phase grounding fault point is located. Subsequently, after the phase selection switch completes the switching strategy, it enters the verification link.

[0070] In the verification process, the online analysis system verifies the determination result of the phase where the single-phase grounding fault point is located in the phase selection process by comparing the value of the line-to-ground capacitance current of the system with the value of the current flowing through the current-limiting resistor R. If the value of the line-to-ground capacitance current of the system is greater than the value of the current 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 process is correct, and the arc suppression process is entered; if the value of the line-to-ground capacitance current of the system is less than the value of the current 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 process is incorrect, the option switch K is reset, and the phase selection process is re-entered;

[0071] After entering the arc suppression process, the arc suppression switch K0 is first closed to disconnect the current-limiting resistor R. The fault current of the system line is grounded through the arc suppression switch K0, and the arc suppression switch K0 opens after a preset closing duration.

[0072] In this method, during the phase selection process, the controller obtains and analyzes the changes in the three-phase currents of the system line. When the current of a certain phase of the system increases, that phase is the phase where the single-phase grounding fault point is located. The controller controls the closing of the corresponding switch (Ka, Kb, or Kc) in the phase selection switch K accordingly.

[0073] In this method, during the verification process, the controller obtains and analyzes the value of the line-to-ground capacitance current of the system and the value of the current flowing through the current-limiting resistor R. By verifying the phase selection result, the accuracy of phase selection and arc suppression is improved, and the power supply reliability of the system line is ensured.

[0074] In this method, during the arc suppression process, by closing the arc suppression switch K0, the current-limiting resistor R is disconnected, and the fault-phase current is grounded through the arc suppression switch KO. That is, the unstable grounding of the fault point in the system line is converted into stable metal grounding in the substation, and the line-to-ground voltage of the fault phase drops to zero, thereby making it difficult to maintain the arc at the fault point and causing it to extinguish. Through this fast phase selection and arc suppression method, it is beneficial to avoid the expansion of the single-phase grounding fault range and cause the escalation of grid events.

[0075] The determination method and line selection decision for the fault type in the fault type line selection stage are as follows:

[0076] After completing the arc suppression process, the phase selection switch K is reset, and the online analysis system is used to determine whether the single-phase grounding fault point has been arc-suppressed by analyzing the three-phase voltage and zero-sequence voltage of the system line.

[0077] If the arc has been suppressed, the system line returns to normal, and the fault type of the determined single-phase grounding fault point is an instantaneous single-phase grounding fault. The arc suppression device records this event and reports it to the background, and no further line selection for the single-phase grounding fault line is performed.

[0078] If the arc suppression is not carried out, the system line fault still exists, and it is determined that the fault type of the single-phase grounding fault point is a permanent single-phase grounding fault. The line selection switch K2 is closed, and the line where the single-phase grounding fault point is located is determined by analyzing the change of the zero-sequence voltage of the system line online. After the line selection determination is completed, the line selection switch K2 is tripped, and the arc suppression device records this event and reports it to the background.

[0079] In this method, by switching on and off the impedance grounding transformer T, the disconnection of the arc suppression switch K0 and the phase selection switch K, the zero-sequence voltage of the system shows a depression change during this period, so that the zero-sequence current waveform characteristics of the fault branch and the normal branch show obvious differences. That is, during this period, the amplitude of the zero-sequence voltage of the system decreases significantly, the zero-sequence current of the fault branch changes from small to large, while the zero-sequence current of the normal branch changes from large to small. According to this characteristic, the fault line and the non-fault line can be clearly distinguished, and the fault line selection can be accurately carried out, improving the line selection accuracy.

[0080] In this method, after the arc suppression 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 suppression as needed, or 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 these two processing methods in the background, and the background makes a decision according to the set priority.

[0081] Based on the above content and the drawings, those skilled in the art can understand and implement the present invention. In addition, any non-creative modification made to the present invention by those skilled in the art without creative labor still falls 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; The arc extinguishing equipment includes an eddy current driven phase selection switch, and the coil disk wiring method of each phase switch is as follows: The closing coil disks of the switches of each phase are connected in parallel with each other, and a thyristor is connected in series in each parallel branch to control the on and off of the branch, and each parallel branch is connected in parallel to the same capacitor; the opening coil disks of the switches of each phase are connected in parallel with each other, and a thyristor is connected in series in each parallel branch to control the on and off of the branch, and each parallel branch is connected in parallel to the same capacitor; the capacitor connected in parallel to the closing coil disk 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 for one coil disk connected in parallel to establish a magnetic field for closing or opening.

2. The single-phase grounding fault type intelligent determination method according to claim 1 is characterized in that: The arc extinguishing equipment also includes a front circuit breaker, 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 in that: 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 by: 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 arc extinguishing switch and the line selection switch are both eddy current driven switches, and the power used by the coil disk to establish the magnetic field is pre-charged and stored in the capacitor connected in parallel with the coil disk in advance; The power used by the coil disk of the phase selection switch to establish a magnetic field is stored in advance in a 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 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.

7. The single-phase grounding fault type intelligent determination method according to claim 6 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.

8. The single-phase grounding fault type intelligent determination method according to claim 2 or 6, 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.

9. The single-phase grounding fault type intelligent determination method according to claim 2 or 6, 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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