Flexible arc extinction method and device based on line voltage injected through non-fault phase

Abstract

The invention discloses a flexible arc extinction method and device based on a line voltage injected through a non-fault phase, the method mainly aims at a neutral point ungrounded system, and the arc extinction method comprises the following steps: comparing neutral point zero sequence voltage # imgabs0 # and # imgabs1 # which are measured in real time at present, and judging whether a single-phase grounding fault occurs at present; if the current single-phase grounding fault occurs, continuing to judge whether the fault is a high-resistance grounding fault or a non-high-resistance grounding fault; if the high-resistance grounding fault occurs at present, judging that the lagging phase of the phase with the maximum voltage to ground is a fault phase, and injecting the line voltage of the phase with the maximum voltage to ground and the fault phase into the phase with the maximum voltage to ground; and if a non-high-resistance grounding fault occurs at present, determining that the phase with the minimum voltage to ground is a fault phase, and injecting line voltage of the leading phase of the fault phase and the fault phase into the leading phase of the fault phase. According to the invention, a fault phase line can be selected timely and active voltage reduction and arc extinction can be realized, thereby eliminating potential safety hazards.

Description

Technical Field

[0001] The invention belongs to the field of arc extinguishing of distribution network faults, and specifically relates to a flexible arc extinguishing method and device based on line voltage injection through a non-fault phase, which is applied to single-phase grounding fault processing of a distribution network or generator with an ungrounded neutral point. Background Art

[0002] At present, most of my country's 6-66kV medium-voltage power grids adopt the neutral point ungrounded operation mode. When a single-phase grounding fault occurs in the system, the line voltage and phase between the phases in the neutral point ungrounded system remain unchanged. Therefore, it can still operate for 1-2 hours after the fault occurs. However, after a long time, it will cause insulation damage, intermittent arc grounding overvoltage, system stability reduction and many other problems.

[0003] In addition, as the capacity of the distribution network system increases year by year, and the proportion of cable lines in the distribution network is also increasing, the ground capacitance current of the distribution network is also increasing, which greatly increases the possibility of further development of the fault. Once the distribution network maintains the abnormal operation state of single-phase fault for a long time, the ground capacitance current will increase rapidly. Since the increase of ground capacitance current will cause the ground voltage to increase, it is easy to cause intermittent arc overvoltage with a large area and long-term existence. This overvoltage will cause irreversible damage to power equipment and its insulation, thereby adversely affecting the reliability of power supply. In addition, due to the high resistance of the grounding point transition resistance and the small distributed capacitance current of the system itself during a single-phase grounding fault, the fault current is the sum of the ground capacitance currents of all lines. Therefore, the fault current is small, and the characteristics of fault detection, fault location, and fault isolation before and after the fault are relatively poor. At the same time, single-phase grounding in the distribution network includes various grounding forms such as metal grounding, arc grounding, and high-resistance grounding. Under various grounding forms, the magnitude of the fault current, the current rise rate, the degree of voltage sag, and the instantaneous resistance at the moment of the fault are very different, making the line selection of the grounding fault in the ungrounded system a complex problem with multiple factors. Due to the existence of the grounding fault, if it is not handled in time, it is easy to further deteriorate, thereby threatening the safe operation of the power grid. Therefore, improving the accuracy and timeliness of the ungrounded line selection and phase selection, timely selecting the faulty line, eliminating safety hazards, and improving the safety and reliability of the power grid from a technical level are of great significance to improving the power supply quality of the power grid. Summary of the invention

[0004] The present invention provides a flexible arc extinguishing method and device based on line voltage injected through a non-fault phase, which improves the accuracy and timeliness of line and phase selection in a neutral point ungrounded system, timely selects the fault phase line and actively reduces the voltage to extinguish the arc, eliminating safety hazards.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0006] A flexible arc extinguishing method based on injecting line voltage through a non-fault phase, comprising:

[0007] The current real-time measured neutral point zero-sequence voltage The preset value of the neutral point zero sequence voltage By comparison, determine whether a single-phase grounding fault currently occurs in the neutral ungrounded system;

[0008] If a single-phase grounding fault occurs currently, continue to determine whether the fault is a high-resistance grounding fault or a non-high-resistance grounding fault;

[0009] If a high-resistance ground fault occurs, the lagging phase of the phase with the maximum voltage to ground is determined to be the fault phase, and the line voltage between the phase with the maximum voltage to ground and the fault phase is injected into the phase with the maximum voltage to ground;

[0010] If a non-high-resistance ground fault occurs at present, the phase with the minimum voltage to ground is determined to be the fault phase, and the line voltage between the leading phase of the fault phase and the fault phase is injected into the leading phase of the fault phase.

[0011] Furthermore, after injecting the line voltage for a certain period of time, it also includes: monitoring the zero-sequence admittance of the current neutral point of the neutral ungrounded system and compare it with the zero-sequence admittance to ground when the system is normal Comparison: If the admittance angles of the two are different, the current fault is judged to be a permanent fault, an early warning is initiated, and arc extinguishing is waited for human intervention; if the admittance angles of the two are consistent, the current fault has been eliminated and flexible arc extinguishing is completed.

[0012] Furthermore, the injected zero-sequence voltage and zero-sequence current are collected and the zero-sequence admittance to ground is calculated accordingly.

[0013] Further, the determination of whether a single-phase grounding fault occurs is specifically as follows: And the three-phase line voltage equal, or And three-phase line power If they are equal, it is determined that a single-phase grounding fault has occurred; otherwise, it is determined that no single-phase grounding fault has occurred. is the real-time change rate of the neutral point zero-sequence voltage, Preset value for the rate of change of neutral point zero-sequence voltage.

[0014] Further, the determination of whether the fault is a high-resistance grounding fault or a non-high-resistance grounding fault is specifically as follows: determining the current zero-sequence voltage With rated phase voltage Whether the conditions are met , when the conditions are met, the current fault is determined to be a high-resistance grounding fault, otherwise the current fault is determined to be a non-high-resistance grounding fault.

[0015] A flexible arc extinguishing device based on line voltage injection through a non-fault phase comprises: a data acquisition module, a fault judgment module, a voltage source module, a step-up transformer module and a circuit breaker module;

[0016] The data acquisition module is used to measure the zero-sequence voltage of the neutral point. , and measure the voltage of each phase to ground;

[0017] The judgment and control module is used to: (1) convert the current real-time measured neutral point zero-sequence voltage The preset value of the neutral point zero sequence voltage Compare and determine whether a single-phase grounding fault currently occurs in the neutral ungrounded system; (2) If a single-phase grounding fault currently occurs, continue to determine whether the fault is a high-resistance grounding fault or a non-high-resistance grounding fault; (3) If a high-resistance grounding fault currently occurs, determine the lagging phase of the phase with the maximum voltage to ground as the fault phase; (4) If a non-high-resistance grounding fault currently occurs, determine the phase with the minimum voltage to ground as the fault phase;

[0018] The voltage source module is used to: generate a voltage which is preset in a small proportion to the voltage difference between the maximum phase of the voltage to ground and the fault phase;

[0019] The step-up transformer module is used to: reversely amplify the voltage generated by the voltage source module according to the preset small ratio to obtain the difference voltage between the phase with the maximum voltage to ground and the fault phase voltage;

[0020] The judgment and control module is also used to: when a high-resistance grounding fault occurs, control the circuit breaker module to inject the difference voltage between the phase with the maximum voltage to the ground and the fault phase voltage into the phase with the maximum voltage to the ground; and when a non-high-resistance grounding fault occurs, control the circuit breaker module to inject the difference voltage between the leading phase of the fault phase and the fault phase voltage into the leading phase of the fault phase.

[0021] Furthermore, the judgment and control module is also used to: monitor the current zero-sequence admittance to ground of the neutral ungrounded system after injecting the line voltage for a certain period of time and compare it with the zero-sequence admittance to ground when the system is normal Comparison: If the admittance angles of the two are different, the current fault is judged to be a permanent fault, an early warning is initiated, and arc extinguishing is waited for human intervention; if the admittance angles of the two are consistent, the current fault has been eliminated and flexible arc extinguishing is completed.

[0022] Furthermore, the data acquisition module is also used to collect the zero-sequence voltage and zero-sequence current injected into the high-voltage side of the transformer; the judgment and control module is also used to calculate the zero-sequence admittance to ground based on the collected zero-sequence voltage and zero-sequence current injected into the high-voltage side of the transformer.

[0023] Further, the determination of whether a single-phase grounding fault occurs is specifically as follows: And the three-phase line voltage equal, or And three-phase line power If they are equal, it is determined that a single-phase grounding fault has occurred; otherwise, it is determined that no single-phase grounding fault has occurred. is the real-time change rate of the neutral point zero-sequence voltage, Preset value for the rate of change of neutral point zero-sequence voltage.

[0024] Further, the determination of whether the fault is a high-resistance grounding fault or a non-high-resistance grounding fault is specifically as follows: determining the current zero-sequence voltage With rated phase voltage Whether the conditions are met , when the conditions are met, the current fault is determined to be a high-resistance grounding fault, otherwise the current fault is determined to be a non-high-resistance grounding fault.

[0025] Beneficial Effects

[0026] The present invention is based on a flexible arc extinguishing method and device for injecting line voltage through a non-fault phase. After a single-phase grounding fault occurs in the system, the relationship between the zero-sequence voltage and the rated phase voltage is used to determine whether it is a high-resistance grounding fault. If it is determined to be a high-resistance grounding fault, the line voltage is injected into the phase with the maximum voltage to ground; if it is determined to be a low-resistance grounding fault, the line voltage is injected into the leading phase with the minimum voltage to ground; by fine-tuning the amplitude and phase angle of the injected line voltage, the voltage at the fault point can be reduced to below the preset voltage, and the residual current is mA level, forcing the cable arc fault to be extinguished quickly, thereby ensuring the safe operation of the power grid. The present invention injects line voltage through a step-up transformer and a single-phase switch that selects one from three. The power electronics uses open-loop control, does not require high-speed current acquisition control logic, can effectively prevent the system from back-injecting current into the power electronics, and ensures the reliability and feasibility of flexible arc extinguishing of single-phase grounding faults. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a flow chart of a flexible arc extinguishing method based on line voltage injection through a non-fault phase according to an embodiment of the present application;

[0028] Figure 2 It is a schematic diagram of a case where a phase C grounding fault occurs in the distribution network according to an embodiment of the present application;

[0029] Figure 3It is the zero-sequence equivalent circuit of the distribution network after the line voltage is injected through the non-fault phase as described in the embodiment of the present application. DETAILED DESCRIPTION

[0030] The following is a detailed description of an embodiment of the present invention. This embodiment is based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process to further explain the technical solution of the present invention.

[0031] Example 1

[0032] This embodiment provides a flexible arc extinguishing method based on injecting line voltage through a non-fault phase, referring to Figure 1 As shown, including:

[0033] S1, measures the zero-sequence admittance of the distribution network to ground when the system is normal .

[0034] Among them, the zero-sequence voltage and zero-sequence current injected into the high-voltage side of the step-up transformer are collected, and the zero-sequence admittance to ground is calculated accordingly. , and use this as a reference value for monitoring in subsequent steps.

[0035] S2, the current real-time measurement of the neutral point zero-sequence voltage The preset value of the neutral point zero sequence voltage Compare and determine whether a single-phase grounding fault currently occurs in the neutral ungrounded system.

[0036] like And the three-phase line voltage equal, or And the three-phase line voltage If they are equal, it is determined that a single-phase grounding fault has occurred; otherwise, it is determined that no single-phase grounding fault has occurred. is the real-time change rate of the neutral point zero-sequence voltage, Preset value for the rate of change of neutral point zero-sequence voltage.

[0037] S3: If a single-phase grounding fault occurs currently, continue to determine whether the fault is a high-resistance grounding fault or a non-high-resistance grounding fault.

[0038] Specific judgment of the current zero-sequence voltage With rated phase voltage Whether the conditions are met , when the conditions are met, the current fault is determined to be a high-resistance grounding fault, otherwise the current fault is determined to be a non-high-resistance grounding fault.

[0039] S4, if a high-resistance ground fault occurs currently, the lagging phase of the phase with the maximum voltage to ground is determined to be the fault phase, and the line voltage between the phase with the maximum voltage to ground and the fault phase is injected into the phase with the maximum voltage to ground.

[0040] Assume that a phase C ground fault occurs in the distribution network, as shown in the schematic diagram Figure 2 As shown, the ground fault resistance , the neutral point zero sequence voltage is , the three-phase voltage to ground is shown in formula 1.

[0041] Formula 1

[0042] Where U A Represents the voltage of phase A to ground, U B Represents the voltage of phase B to ground, U C represents the voltage of phase C to ground, E A Represents the power supply potential of phase A, E B Represents the power supply potential of phase B, E C Represents the power supply potential of phase C.

[0043] Assume that the three-phase equivalent capacitance to ground is , , then the three-phase equivalent ground current and fault point current are shown in Formula 2.

[0044] Formula 2

[0045] Where I A It represents the current flowing through the capacitance and conductivity branch of phase A. B It represents the current flowing through the capacitance and the conductivity branch of phase B to ground, I C It represents the current flowing through the capacitance and the conductivity branch of phase C to ground, I f is the fault current.

[0046] After the C phase ground fault occurs and it is a high-resistance ground fault, the voltage of phase B is the largest at this time, so the high-voltage contactor KM2 in the circuit breaker module of phase B (i.e. the leading phase of the faulty phase C) is closed, and the voltage source injects the BC line voltage U into phase B through the step-up transformer. IN (i.e., the line voltage between phase B (the phase with the maximum voltage to ground) and phase C (the fault phase)), resulting in changes in the three-phase to ground voltage, three-phase to ground current, neutral point zero-sequence voltage, fault point voltage and current, as shown in Equation 3.

[0047] Formula 3

[0048] Where U ’ A , U ’ B , U ’ C The arc extinguishing voltage U is injected into phase B. IN The relative voltages to ground are then obtained, U’ 0 is the neutral point voltage after the arc extinguishing voltage is injected.

[0049] As for why phase A is not selected, it is mainly because of the fear that the system will backflow current to the power electronics, causing overcurrent protection, and ensuring the reliability and feasibility of flexible arc extinguishing of single-phase grounding faults.

[0050] In command 3 If it is forced to 0, the current at the fault point will also be 0, and the neutral point zero-sequence voltage is equal to the reverse potential of the fault direction, as shown in Equation 4.

[0051] Formula 4

[0052] Substituting equation 4 into equation 3 and rearranging it, we obtain equation 5.

[0053] Formula 5

[0054] The voltage source injected current is as shown in Formula 6. When the voltage and current at the fault point are adjusted to 0, the voltage source injected current is related to the three-phase equivalent capacitance to ground and the leakage conductance to ground, and has nothing to do with the resistance at the fault point.

[0055] Formula 6

[0056] Combining the voltage injection equation 5 and the current injection equation 6, the equivalent circuit can be used to obtain the zero-sequence equivalent circuit of the distribution network after the non-fault phase voltage is injected: Figure 3 As shown, the control injection voltage U IN =E BC , the fault phase voltage is below 100V, the fault point current is 0, and the single-phase grounding fault is extinguished.

[0057] S5, if a non-high-resistance ground fault occurs currently, the phase with the minimum voltage to ground is determined to be the fault phase, and the line voltage between the leading phase of the fault phase and the fault phase is injected into the leading phase of the fault phase.

[0058] S6, after injecting the line voltage for a certain period of time, also includes: monitoring the current zero-sequence admittance to ground of the neutral ungrounded system and compare it with the zero-sequence admittance to ground when the system is normal Comparison: If the admittance angles of the two are different, the current fault is judged to be a permanent fault, an early warning is initiated, and arc extinguishing is waited for human intervention; if the admittance angles of the two are consistent, the current fault has been eliminated and flexible arc extinguishing is completed.

[0059] Fault Equivalent Circuit Figure 3 The zero-sequence admittance phase angle of the fault line can be obtained, as shown in Equation 7.

[0060] Formula 7

[0061] From formula 7, we can see that when a high-resistance or low-resistance grounding fault occurs, , which makes the system zero-sequence admittance angle θ smaller, and based on this, the zero-sequence admittance of the line when it is working normally By comparison, it can be determined whether the line fault still exists, and thus whether the fault is a permanent fault. When the fault is determined to be a permanent fault, the early warning system is activated to continue to maintain the injection line voltage while waiting for manual intervention.

[0062] Example 2

[0063] This embodiment provides a flexible arc extinguishing device based on line voltage injection through a non-fault phase, comprising: a data acquisition module, a fault judgment module, a voltage source module, a step-up transformer module and a circuit breaker module;

[0064] The data acquisition module is used to measure the zero-sequence voltage of the neutral point. , and measure the voltage of each phase to ground;

[0065] The judgment and control module is used to: (1) convert the current real-time measured neutral point zero-sequence voltage and Compare and determine whether a single-phase grounding fault has occurred; (2) If a single-phase grounding fault has occurred, continue to determine whether the fault is a high-resistance grounding fault or a non-high-resistance grounding fault; (3) If a high-resistance grounding fault has occurred, determine that the lagging phase of the phase with the maximum voltage to ground is the fault phase; (4) If a non-high-resistance grounding fault has occurred, determine that the phase with the minimum voltage to ground is the fault phase;

[0066] The voltage source module is used to: generate a voltage which is preset in a small proportion to the voltage difference between the maximum phase of the voltage to ground and the fault phase;

[0067] The step-up transformer module is used to: reversely amplify the voltage generated by the voltage source module according to the preset small ratio to obtain the difference voltage between the phase with the maximum voltage to ground and the fault phase voltage;

[0068] The judgment and control module is also used to: when a high-resistance grounding fault occurs, control the circuit breaker module to inject the difference voltage between the phase with the maximum voltage to the ground and the fault phase voltage into the phase with the maximum voltage to the ground; and when a non-high-resistance grounding fault occurs, control the circuit breaker module to inject the difference voltage between the leading phase of the fault phase and the fault phase voltage into the leading phase of the fault phase.

[0069] In a more preferred embodiment, the judgment and control module is further used to: after injecting the line voltage for a certain period of time, monitor the current zero-sequence admittance of the system to ground and compare it with the zero-sequence admittance to ground when the system is normal Comparison: If the admittance angles of the two are different, the current fault is judged to be a permanent fault, an early warning is initiated, and arc extinguishing is waited for human intervention; if the admittance angles of the two are consistent, the current fault has been eliminated and flexible arc extinguishing is completed.

[0070] In a more preferred embodiment, the data acquisition module is also used to: collect the zero-sequence voltage and zero-sequence current injected into the high-voltage side of the transformer; the judgment and control module is also used to: calculate the zero-sequence admittance to ground based on the collected zero-sequence voltage and zero-sequence current injected into the high-voltage side of the transformer.

[0071] In a more preferred embodiment, the judgment and control module judges whether a single-phase grounding fault currently occurs, and judges whether the fault is a high-resistance grounding fault or a non-high-resistance grounding fault, which is the same as described in Embodiment 1.

[0072] The above embodiments are preferred embodiments of the present application. Ordinary technicians in this field can also make various changes or improvements on this basis. Without departing from the overall concept of the present application, these changes or improvements should fall within the scope of protection required by the present application.

Claims

1. A flexible arc extinguishing method based on line voltage injection via a non-fault phase, characterized in that: include: The current real-time measured neutral point zero-sequence voltage The preset value of the neutral point zero sequence voltage By comparison, determine whether a single-phase grounding fault currently occurs in the neutral ungrounded system; If a single-phase grounding fault occurs currently, continue to determine whether the fault is a high-resistance grounding fault or a non-high-resistance grounding fault; If a high-resistance ground fault occurs, the lagging phase of the phase with the maximum voltage to ground is determined to be the fault phase, and the line voltage between the phase with the maximum voltage to ground and the fault phase is injected into the phase with the maximum voltage to ground; If a non-high-resistance ground fault occurs at present, the phase with the minimum voltage to ground is determined to be the fault phase, and the line voltage between the leading phase of the fault phase and the fault phase is injected into the leading phase of the fault phase.

2. The flexible arc extinguishing method based on line voltage injection via non-fault phase according to claim 1, characterized in that: After injecting line voltage for a certain period of time, it also includes: monitoring the zero-sequence admittance of the current neutral point of the neutral ungrounded system and compare it with the zero-sequence admittance to ground when the system is normal Comparison: If the admittance angles of the two are different, the current fault is judged to be a permanent fault, an early warning is initiated, and arc extinguishing is waited for human intervention; if the admittance angles of the two are consistent, the current fault has been eliminated and flexible arc extinguishing is completed.

3. The flexible arc extinguishing method based on line voltage injection via non-fault phase according to claim 2 is characterized in that: The injected zero-sequence voltage and zero-sequence current are collected and the zero-sequence admittance to ground is calculated accordingly.

4. The flexible arc extinguishing method based on line voltage injection via non-fault phase according to claim 1, characterized in that: The determination of whether a single-phase grounding fault occurs is specifically as follows: And the three-phase line voltage equal, or And the three-phase line voltage If they are equal, it is determined that a single-phase grounding fault has occurred; Otherwise, it is determined that no single-phase grounding fault has occurred at present; wherein, is the real-time change rate of the neutral point zero-sequence voltage, Preset value for the rate of change of neutral point zero-sequence voltage.

5. The flexible arc extinguishing method based on line voltage injection via non-fault phase according to claim 1, characterized in that: The method of determining whether the fault is a high-resistance grounding fault or a non-high-resistance grounding fault is specifically as follows: determining the current zero-sequence voltage With rated phase voltage Whether the conditions are met , when the conditions are met, the current fault is determined to be a high-resistance grounding fault, otherwise the current fault is determined to be a non-high-resistance grounding fault.

6. A flexible arc extinguishing device based on line voltage injection via a non-fault phase, characterized in that: include: Data acquisition module, fault judgment module, voltage source module, step-up transformer module and circuit breaker module; The data acquisition module is used to measure the zero-sequence voltage of the neutral point. , and measure the voltage of each phase to ground; The judgment and control module is used to: (1) convert the current real-time measured neutral point zero-sequence voltage The preset value of the neutral point zero sequence voltage By comparison, determine whether a single-phase grounding fault currently occurs in the neutral ungrounded system; (2) If a single-phase ground fault occurs, continue to determine whether the fault is a high-resistance ground fault or a non-high-resistance ground fault; (3) If a high-resistance ground fault occurs, determine that the lagging phase of the phase with the maximum voltage to ground is the fault phase; (4) If a non-high-resistance ground fault occurs, the phase with the minimum voltage to ground is determined to be the fault phase; The voltage source module is used to: generate a voltage which is preset in a small proportion to the voltage difference between the maximum phase of the voltage to ground and the fault phase; The step-up transformer module is used to: reversely amplify the voltage generated by the voltage source module according to the preset small ratio to obtain the difference voltage between the phase with the maximum voltage to ground and the fault phase voltage; The judgment and control module is also used to: when a high-resistance ground fault occurs, control the circuit breaker module to inject the difference voltage between the phase with the maximum voltage to ground and the fault phase voltage into the phase with the maximum voltage to ground; And, when a non-high-resistance ground fault occurs, the circuit breaker module is controlled to inject a voltage difference between the leading phase of the fault phase and the fault phase voltage into the leading phase of the fault phase.

7. The flexible arc extinguishing device based on line voltage injection via non-fault phase according to claim 6, characterized in that: The judgment and control module is also used to: monitor the current zero-sequence admittance to ground of the neutral ungrounded system after injecting the line voltage for a certain period of time and compare it with the zero-sequence admittance to ground when the system is normal Comparison: If the admittance angles of the two are different, the current fault is judged to be a permanent fault, an early warning is initiated, and arc extinguishing is waited for human intervention; if the admittance angles of the two are consistent, the current fault has been eliminated and flexible arc extinguishing is completed.

8. The flexible arc extinguishing device based on line voltage injection via non-fault phase according to claim 7, characterized in that: The data acquisition module is also used to collect the zero-sequence voltage and zero-sequence current injected into the high-voltage side of the transformer; the judgment and control module is also used to calculate the zero-sequence admittance to ground based on the collected zero-sequence voltage and zero-sequence current injected into the high-voltage side of the transformer.

9. The flexible arc extinguishing device based on line voltage injection via non-fault phase according to claim 6, characterized in that: The determination of whether a single-phase grounding fault occurs is specifically as follows: And the three-phase line voltage equal, or And the three-phase line voltage If they are equal, it is determined that a single-phase grounding fault has occurred; Otherwise, it is determined that no single-phase grounding fault has occurred at present; wherein, is the real-time change rate of the neutral point zero-sequence voltage, Preset value for the rate of change of neutral point zero-sequence voltage.

10. The flexible arc extinguishing device based on line voltage injection via non-fault phase according to claim 6, characterized in that: The method of determining whether the fault is a high-resistance grounding fault or a non-high-resistance grounding fault is specifically as follows: determining the current zero-sequence voltage With rated phase voltage Whether the conditions are met , when the conditions are met, the current fault is determined to be a high-resistance grounding fault, otherwise the current fault is determined to be a non-high-resistance grounding fault.

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