Characteristic signal injection method and device suitable for active detection-based protection

Abstract

The present invention relates to the technical field of relay protection, and provides a characteristic signal injection method and device suitable for active detection-based protection, which are applied to a distributed power supply. The distributed power supply is connected to a power distribution grid system. The method comprises the following steps: calculating a first characteristic impedance of the system; determining whether the system has had a malfunction; if so, acquiring a second characteristic impedance of the system; determining whether the malfunction has disappeared on the basis of the relationship between the first characteristic impedance and the second characteristic impedance; if the malfunction has disappeared, injecting a pre-set characteristic voltage within a second pre-set duration; and if the malfunction has not disappeared, injecting a pre-set characteristic current into the system, and determining a characteristic signal injection mode for the power distribution grid system on the basis of whether a third characteristic impedance of the system meets a first set condition. The present invention allows for flexible injection of a distributed power supply characteristic signal, thereby preventing a converter from being locked due to overcurrent when a characteristic signal is injected into a system malfunction.

Description

A characteristic signal injection method and device suitable for active detection protection Technical Field

[0001] The present invention relates to the technical field of relay protection, and in particular to a characteristic signal injection method and device suitable for active detection protection, which is applied to distributed power sources connected to a power distribution network system. Background Art

[0002] With the increasing penetration of distributed power generation (DGs), a large number of flexible and controllable converters have emerged in distribution network systems, leading to a growing research and application of active detection protection. Active detection protection detects characteristic signals injected by DGs and identifies faults based on their changes, enabling fault isolation, self-healing, and reclosing.

[0003] Active detection protection is based on characteristic signals injected into the converter, requiring a signal injection control strategy tailored to its functional requirements. Existing detection signal injection methods, when injected into a fault, can cause the converter to lock due to overcurrent, halting injection and potentially impacting the converter. Some methods address this by limiting the injection time, but excessively short injection times can render fault isolation and self-healing impossible, limiting their scope of application.

[0004] Therefore, it is a problem that needs to be solved at present to construct a reasonable characteristic signal injection method in the process of active detection protection of distributed power sources to support fault isolation, self-healing, reclosing functions and prevent overcurrent locking of the converter. Summary of the Invention

[0005] In order to solve at least one technical problem in the background technology, the present invention provides a characteristic signal injection method and device suitable for active detection protection, which is applied to distributed power sources connected to a power distribution network system.

[0006] To achieve the above object, the present invention provides a characteristic signal injection method suitable for active detection protection, which is applied to a distributed power supply connected to a power distribution network system; the method comprises the following steps:

[0007] Periodically calculating and updating a first characteristic impedance of the system;

[0008] Determining step: determining whether a fault occurs in the system; if a fault occurs, obtaining a second characteristic impedance of the system after a first preset delay; and determining whether the fault disappears based on a relationship between the first characteristic impedance and the second characteristic impedance;

[0009] In the prior art, there are many different ways to determine whether a distribution network system has a fault. The present invention does not specifically limit the specific method adopted, and does not specifically expand on the prior art.

[0010] If the fault disappears, continuously injecting a preset characteristic voltage within a second preset time;

[0011] If the fault persists, a preset characteristic current is injected into the distribution network system, and a third characteristic impedance of the system is obtained. Based on whether the third characteristic impedance satisfies a first set condition, a method of injecting a characteristic signal into the system is determined.

[0012] Preferably, periodically calculating and updating the first characteristic impedance of the system includes: periodically injecting the preset characteristic current into the system, collecting the first characteristic voltage on the system, and calculating and updating the first characteristic impedance based on the preset characteristic current and the first characteristic voltage. ; = |Z1|∠φ1;

[0013] Obtaining a second characteristic impedance of the system, comprising: injecting the preset characteristic current into the system, collecting a second characteristic voltage on the system, and calculating the second characteristic impedance based on the preset characteristic current and the second characteristic voltage ; = |Z2|∠φ2;

[0014] Obtain the third characteristic impedance of the system , including: injecting the preset characteristic current into the system, collecting the third characteristic voltage on the system, and calculating the third characteristic impedance based on the preset characteristic current and the third characteristic voltage.

[0015] Preferably, judging whether the fault disappears based on the relationship between the first characteristic impedance and the second characteristic impedance includes: confirming that the fault disappears when the relationship between the first characteristic impedance and the second characteristic impedance satisfies the following inequality:

[0016]

[0017] Among them, δ set It is the preset phase angle, ranging from 0 to 45 degrees.

[0018] Preferably, determining a characteristic signal injection mode of the system based on whether the third characteristic impedance satisfies a first set condition includes:

[0019] If it is detected within the second preset time that the third characteristic impedance satisfies the first set condition, stopping injecting the preset characteristic current and injecting the preset characteristic voltage instead;

[0020] Otherwise, the characteristic signal injection is terminated and the cause of the system failure is checked.

[0021] Preferably, the first setting condition is: ;

[0022] in, is the third characteristic impedance, is the characteristic impedance value of the system before 20ms, k4 is the fourth preset coefficient, and its value is 0.2~0.3.

[0023] Preferably, injecting a preset characteristic voltage comprises: injecting the preset characteristic voltage When the initial voltage is , and increase k2 every 20ms| |The amplitude is increased by a step size of |; wherein k2 is the second preset coefficient, and its value is 0.1.

[0024] Preferably, the method further comprises:

[0025] Inject the characteristic voltage When the characteristic current is collected in real time , when | |≥k3| |, stop increasing The amplitude of ; where k3 is 0.95, is the preset characteristic current.

[0026] Preferably, the method further comprises:

[0027] The real-time load impedance of the system is obtained, and when the real-time load impedance meets a second set condition, the determination step is performed.

[0028] Preferably, the second setting condition is: the following formula is continuously established within a time period of t / 2,

[0029]

[0030] in, is the real-time load impedance, is the real-time load impedance value before time t, k1 is the first preset coefficient, which is 0.2~0.3, and t is the preset judgment time, which is 10~20 minutes.

[0031] Preferably, determining whether the system fails specifically includes determining whether the voltage or frequency of the system is abnormal.

[0032] To achieve the above-mentioned objectives, the present invention provides an electronic device, characterized in that it includes a processor, a memory, and a computer program stored in the memory and capable of running on the processor, and when the computer program is executed by the processor, it implements any one of the characteristic signal injection methods suitable for active detection protection as described above.

[0033] The present invention achieves the following beneficial effects: A characteristic signal injection method suitable for active detection protection injects different types of characteristic signals based on the persistence of a fault, providing characteristic electrical quantities for active detection protection. This method enables flexible injection of characteristic signals from distributed power sources, preventing converter lockout due to overcurrent when the signal is injected into a system fault. This supports the construction of active detection protection, achieving rapid fault isolation, self-healing, and safe and reliable reclosing. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG1 schematically shows a typical system diagram of a characteristic signal injection method applicable to active detection protection according to an embodiment of the present invention;

[0035] FIG2 schematically shows a method flow chart of an embodiment of the present invention;

[0036] FIG3 schematically shows a method flow chart of another embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention will now be discussed with reference to exemplary embodiments. It should be understood that the embodiments discussed are only intended to enable those skilled in the art to better understand and implement the present invention, rather than to imply any limitation on the scope of the present invention.

[0038] As used herein, the term "including" and variations thereof are to be interpreted as open-ended terms meaning "including, but not limited to." The term "based on" is to be interpreted as "based, at least in part, on." The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment."

[0039] Figure 1 schematically illustrates a typical system diagram of a characteristic signal injection method suitable for active detection protection according to one embodiment of the present invention. P1-P4 are protection devices, CB1-CB4 are circuit breakers, and F1 is the fault point. P2 and P3 have active detection isolation capabilities, and P4 is an open-loop point with self-healing capabilities. Figure 2 schematically illustrates a method flow chart according to one embodiment of the present invention. Figure 3 schematically illustrates a method flow chart according to another embodiment of the present invention.

[0040] Example 1

[0041] As shown in FIG1 to FIG3, in this embodiment, a characteristic signal injection method suitable for active detection protection is applied to a distributed power supply, and the distributed power supply is connected to the distribution network system; the method includes the following steps:

[0042] Step S102: periodically calculate and update the first characteristic impedance of the system.

[0043] The period is determined according to the variation pattern of the system load. In this embodiment, the period can be 4 to 6 hours.

[0044] Step S104, determine whether the system fails; if not, repeat step S102; if yes, execute step S106.

[0045] In an embodiment of the present invention, whether a system fault occurs can be determined by determining whether the system voltage or frequency is abnormal; for example: the current system voltage exceeds 20% of the rated voltage, or the frequency deviates from the rated frequency (50Hz) by more than 2Hz; this is the prior art and will not be further elaborated.

[0046] Step S106, after a first preset time delay, obtaining a second characteristic impedance of the system;

[0047] Since the system has a reclosing function, the first preset time T1 needs to take into account the arc extinction time of the transient fault, that is, the value of the first preset time T1 is not less than the disappearance time of the transient fault to ensure that the second characteristic impedance is calculated. When T1 is set, the transient fault has reliably disappeared, thus preventing misjudgment. In this embodiment, T1 is set to 1s~1.5s.

[0048] Step S108, based on the relationship between the first characteristic impedance and the second characteristic impedance, determine whether the fault disappears; if yes, execute step S112; if not, execute step S110;

[0049] Step S110 , injecting a preset characteristic current into the system, obtaining a third characteristic impedance of the system, and determining a method of injecting a characteristic signal into the system based on whether the third characteristic impedance meets a first set condition.

[0050] Step S112: injecting a preset characteristic voltage, the injection duration being a second preset time.

[0051] In this embodiment, the preset characteristic current Take the maximum output current designed for the converter to prevent the inverter from overcurrent lockout; in order to accurately obtain the characteristic impedance of the system, inject a preset characteristic current into the system The method is to inject a preset characteristic current for a short time In this embodiment, a preset characteristic current is injected into the system for a short time The injection time can be 20ms.

[0052] The present invention, under the condition of judging that a system fault exists, judges whether the system fault disappears by using the first characteristic impedance of the normal operating state and the second characteristic impedance of the fault state; when it is confirmed that the system fault disappears, the reclosing function of the active detection protection is realized by injecting a preset characteristic voltage; when it is confirmed that the system fault has not disappeared, a preset specific signal is injected to realize the fault isolation function of the active detection protection, and a third characteristic impedance is obtained. Based on the third characteristic impedance, the characteristic signal injection method of the system is determined; when the third characteristic impedance meets the first set condition, the active detection self-healing function is realized by injecting the preset characteristic voltage, and at the same time, the converter is prevented from being locked due to overcurrent during the period when the fault persists.

[0053] Optionally, in another implementation of this embodiment, the converter of the distributed power supply periodically injects a preset characteristic current into the system , the first characteristic voltage on the acquisition system , based on the preset characteristic current and the first characteristic voltage Calculate and update the first characteristic impedance ;in,

[0054] = |Z1|∠φ1;

[0055] After determining that the system has failed, stop updating the first characteristic impedance After the first preset time T1, the preset characteristic current is injected into the system , the second characteristic voltage on the acquisition system , based on the preset characteristic current With the second characteristic voltage The second characteristic impedance is calculated ;in,

[0056] = |Z2|∠φ2;

[0057] If the system fault is judged to have not disappeared, a preset characteristic current is injected into the distribution network system for a short time. , the third characteristic voltage on the acquisition system, based on the preset characteristic current Calculate the third characteristic impedance with the third characteristic voltage , based on the third characteristic impedance Whether the first set condition is met determines the characteristic signal injection method of the distribution network system.

[0058] In this embodiment, the preset characteristic current Take the maximum output current designed for the converter to prevent the inverter from overcurrent lockout; in order to accurately obtain the characteristic impedance of the system, inject a preset characteristic current into the system The method is to inject a preset characteristic current for a short time In this embodiment, a preset characteristic current is injected into the system for a short time The injection time can be 20ms.

[0059] The present invention takes the maximum output current designed for the converter by presetting the characteristic current, which can effectively prevent the inverter from overcurrent lockout. At the same time, the converter injects the same preset characteristic current into the system to obtain the first characteristic impedance, the second characteristic impedance and the third characteristic impedance respectively. The characteristic impedances obtained based on the same injection signal have better consistency, which can improve the accuracy of the judgment.

[0060] Optionally, in another implementation of this embodiment, in step S110, based on the third characteristic impedance Whether the first set condition is met determines the method of injecting the characteristic signal into the system, specifically:

[0061] At the second preset time T cur Internally detecting whether the third characteristic impedance meets the first setting condition, if yes, executing step S1102; if no, executing step S1104;

[0062] In order to prevent the protection devices at different levels from operating at the same time, it is necessary to set different action delays for the protection devices, which results in the longest action delay for the last level. cur Setting it to be greater than the maximum inter-stage delay of the system can protect the reliability of the active detection isolation function of the protection device and reduce the probability of system misjudgment. For a typical distribution network line, it generally does not exceed 5 segments and is considered as 0.2s. Therefore, in this embodiment, T cur The value is 1s.

[0063] Step S1102: Stop injecting the preset characteristic current , instead inject a preset characteristic voltage ;

[0064] Step S1104, end the characteristic signal injection and check the cause of the system failure.

[0065] In this embodiment, if the system maximum inter-stage delay T cur If the fault is not detected to have disappeared within a certain period of time, the system is judged to be unable to isolate the fault and recover on its own, and the input of characteristic signals is stopped. The cause of the system fault is checked through other technical means.

[0066] When the fault has not disappeared, the present invention identifies whether the system fault has disappeared based on the change of the system characteristic impedance. When the system fault disappears, it is determined that the instantaneous fault has been resolved. While the fault persists, a preset characteristic current is continuously injected within a second preset time, and protection action is continuously performed to realize the isolation function of active detection protection and cut off the fault. The present invention sets the second preset time to be no less than the maximum inter-stage delay of the system, which can reduce the probability of misjudgment and realize rapid isolation and self-healing of the fault.

[0067] Optionally, in another implementation of this embodiment, in step S110, the first setting condition is:

[0068] ;

[0069] in, is the third characteristic impedance, is the characteristic impedance value of the system before 20ms, k4 is the fourth preset coefficient, and its value ranges from 0.2 to 0.3.

[0070] When the fault has not disappeared, the present invention identifies whether the system fault has disappeared based on the change of the system characteristic impedance, and has the advantages of a simple judgment method and a fast identification speed.

[0071] Optionally, in another implementation of this embodiment, a preset characteristic voltage is injected When the preset characteristic voltage initial voltage is , and increase k2 every 20ms| | increases the amplitude by a step size of |; wherein k2 is a second preset coefficient, which is 0.1;

[0072] When presetting characteristic voltage When injecting, it is necessary to avoid injecting excessive voltage when the system fault is not resolved. Therefore, in this embodiment, | |Take 5% of the rated voltage,| |Take| 0.1 times of |

[0073] The present invention uses a technical means of gradually increasing the value of a preset characteristic voltage during the characteristic voltage injection process to avoid the converter being locked due to overcurrent when a signal is injected into a system fault, thereby improving the safety of detection.

[0074] Optionally, in another implementation of this embodiment, a characteristic signal injection method applicable to active detection protection further includes:

[0075] Injection characteristic voltage When the characteristic current is collected in real time , when | |≥k3| |, stop increasing The amplitude of; wherein k3 is the third preset coefficient, the value is 0.95, is the preset characteristic current.

[0076] The present invention collects the characteristic current in the system in real time during the characteristic voltage injection process, ensures that the characteristic current does not exceed the maximum current of the converter, and prevents the converter from overcurrent locking.

[0077] Optionally, in another implementation of this embodiment, a characteristic signal injection method applicable to active detection protection further includes:

[0078] Step S101: Obtaining the real-time load impedance of the system , when the real-time load impedance When the second setting condition is met, step S104 is executed;

[0079] In this embodiment, the second setting condition is: the following formula is continuously established within a time period of t / 2,

[0080]

[0081] in, is the real-time load impedance, is the real-time load impedance value before time t, k1 is the first preset coefficient, which is 0.2~0.3, and t is the preset judgment time, which is 10~20 minutes.

[0082] The present invention performs real-time detection on the system load impedance when the system is in working state, and triggers the step of performing fault detection on the system when the real-time load impedance changes significantly, thereby further improving the safety of system operation.

[0083] Example 2

[0084] As shown in Figures 1 to 3, a characteristic signal injection method suitable for active detection and protection includes the following steps:

[0085] Step S202: When the distribution network system is operating normally, the distributed power supply side periodically injects a preset characteristic current into the system for a short period of time. , the first characteristic voltage on the acquisition system , based on the preset characteristic current and the first characteristic voltage Calculate and update the first characteristic impedance ;

[0086] in, = |Z1|∠φ1;

[0087] In this embodiment, the cycle can be 4 to 6 hours, and the preset characteristic current The amplitude is the maximum output current designed by the converter, and the preset characteristic current is injected into the system for a short time. The injection time is 20ms;

[0088] Step S204, determine whether the system fails. If not, repeat step S202; if yes, execute step S206;

[0089] In this embodiment, the distributed power supply side determines whether a system fault has occurred by determining whether the system voltage or frequency is abnormal; for example, if the current system voltage exceeds 20% of the rated voltage, or if the frequency deviates from the rated frequency (50 Hz) by more than 2 Hz;

[0090] Step S206: After determining that a system failure occurs, stop updating the first characteristic impedance. After the first preset time T1, the inverter injects the preset characteristic current into the system , the second characteristic voltage on the acquisition system , based on the preset characteristic current With the second characteristic voltage The second characteristic impedance is calculated ;

[0091] in, = |Z2|∠φ2;

[0092] When the system has a fault point F1, the circuit breaker CB1 trips based on the traditional protection configured on P1; the distributed power supply detects an abnormal system voltage or frequency and determines that the system has a fault;

[0093] In this embodiment, T1 can be 1s~1.5s;

[0094] Step S208: Based on the first characteristic impedance and the second characteristic impedance , determine whether the fault disappears; if yes, execute step S212; if not, execute step S210;

[0095] Specifically, when the first characteristic impedance and the second characteristic impedance When the relationship satisfies the following inequality, it is determined that the fault disappears:

[0096] ;

[0097] Among them, δ set It is the preset phase angle, ranging from 0 to 45 degrees;

[0098] Otherwise, make sure the fault has not disappeared.

[0099] Step S210: When it is determined that the fault at point F1 has not disappeared, a preset characteristic current is injected into the system. , and obtain the third characteristic impedance of the system , at the second preset time T cur Internal detection of the third characteristic impedance Whether the first setting condition is met, the first setting condition is ;

[0100] Among them, T cur Not less than the maximum inter-stage delay of the system. In this embodiment, T cur The value is 1s; is the characteristic impedance value of the system before 20ms, k4 is the fourth preset coefficient, and its value ranges from 0.2 to 0.3;

[0101] At this time, the preset characteristic current is injected It is mainly used for the active detection isolation function of P2 and P3 to isolate faults. After a certain injection time, the active detection isolation function of P2 is satisfied and the CB2 circuit breaker is tripped. At this time, the characteristic impedance changes from fault impedance to load impedance.

[0102] At the second preset time T cur Detected within When the first setting condition is met, determine If there is a sudden increase, it means that the fault has been isolated by the active detection isolation function of P2, and step S2102 is executed; otherwise, step S2104 is executed;

[0103] Step S2102: Stop injecting the preset characteristic current , instead inject a preset characteristic voltage ;

[0104] Since the protection device P4 with self-healing function is located at the open-loop point, the characteristic impedance cannot be obtained. Therefore, it is necessary to inject characteristic voltage instead of characteristic current, and control the circuit breaker CB4 to close through the protection device P4 to realize the self-healing function of the system.

[0105] Step S2104, end the characteristic signal injection and check the cause of the system failure.

[0106] Not detected within the second preset time If the first precondition is met and it is determined that the current system failure cannot be self-healed, use other technical means to check the cause of the system failure.

[0107] Step S212: injecting a preset characteristic voltage , the injection duration is the second preset time T vol .

[0108] At this time, it is determined that the fault at the fault point F1 is a transient fault. The fault has been eliminated, P1 is closed, and the system resumes normal operation.

[0109] The present invention injects different types of characteristic signals based on the fault persistence, which can realize the flexible injection of distributed power supply characteristic signals, avoid the converter from being locked due to overcurrent when the signal is injected into the system fault, support the construction of active detection protection, and realize rapid isolation and self-healing of the fault, as well as safe and reliable reclosing.

[0110] Optionally, in another implementation of this embodiment, a characteristic signal injection method applicable to active detection protection further includes:

[0111] Step S201: In the distributed power supply working state, the real-time load impedance of the system is obtained based on the real-time working voltage and working current of the system. , when the real-time load impedance When the second setting condition is met, step S204 is executed;

[0112] In this embodiment, the second setting condition is: the following formula is continuously established within a time period of t / 2,

[0113]

[0114] in, is the real-time load impedance, is the real-time load impedance value before time t, k1 is the first preset coefficient, which is 0.2~0.3, and t is the preset judgment time, which is 10~20 minutes.

[0115] The present invention detects the system load impedance in real time when the system is in working state, and triggers the step of calculating the characteristic impedance of the system when the real-time load impedance changes significantly, thereby further improving the safety of the system operation.

[0116] To achieve the above objectives, the present invention also provides an electronic device, including a processor, a memory, and a computer program stored in the memory and runnable on the processor. When the computer program is executed by the processor, the characteristic signal injection method suitable for active detection protection as described above is implemented.

[0117] The present invention injects different types of characteristic signals based on the persistence of the fault, providing a reasonable characteristic model for active detection protection. It can avoid the inverter from being locked due to overcurrent when the signal is injected into the system fault, support the construction of active detection protection, and realize rapid isolation and self-healing of the fault, as well as safe and reliable reclosing.

[0118] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the electronic device described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0119] The above description is merely a preferred embodiment of the present invention and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of the invention is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the inventive concept. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in the present invention.

[0120] It should be understood that the size of the serial numbers of each step in the content of the invention and the embodiments of the present invention does not absolutely mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

Claims

1. A characteristic signal injection method suitable for active detection protection, applied to distributed power sources, wherein the distributed power sources are connected to a distribution network system; characterized in that: The method comprises the following steps: Periodically calculating and updating a first characteristic impedance of the system; Determining step: determining whether the system has a fault; if so, obtaining a second characteristic impedance of the system after a first preset delay time; determining whether the fault disappears based on the relationship between the first characteristic impedance and the second characteristic impedance; If it disappears, then a preset characteristic voltage is injected, and the injection duration is a second preset time; If it has not disappeared, a preset characteristic current is injected into the system, and a third characteristic impedance of the system is obtained at the same time. Based on whether the third characteristic impedance meets the first set condition, a method of injecting a characteristic signal into the system is determined.

2. The characteristic signal injection method applicable to active detection protection according to claim 1, characterized in that: The first characteristic impedance of the system is periodically calculated and updated, including: periodically injecting the preset characteristic current into the system, collecting the first characteristic voltage on the system, and calculating and updating the first characteristic impedance based on the preset characteristic current and the first characteristic voltage. ； = |Z1|∠φ1; Acquiring a second characteristic impedance of the system, comprising: injecting the preset characteristic current into the system, collecting a second characteristic voltage on the system, and calculating the second characteristic impedance based on the preset characteristic current and the second characteristic voltage ； = |Z2|∠φ2; Get the third characteristic impedance of the system , including: injecting the preset characteristic current into the system, collecting a third characteristic voltage on the system, and calculating the third characteristic impedance based on the preset characteristic current and the third characteristic voltage.

3. The characteristic signal injection method applicable to active detection protection according to claim 2, characterized in that: Based on the relationship between the first characteristic impedance and the second characteristic impedance, judging whether the fault disappears, comprising: when the relationship between the first characteristic impedance and the second characteristic impedance satisfies the following inequality, determining that the fault disappears, ； Among them, δ set It is the preset phase angle, and its value ranges from 0 to 45 degrees.

4. The characteristic signal injection method applicable to active detection protection according to claim 1, characterized in that: Determining a method of injecting a characteristic signal into the system based on whether the third characteristic impedance satisfies a first setting condition includes: If it is detected within the second preset time that the third characteristic impedance satisfies the first setting condition, stopping injecting the preset characteristic current and injecting the preset characteristic voltage instead; Otherwise, the characteristic signal injection is terminated and the cause of the system failure is checked.

5. The characteristic signal injection method applicable to active detection protection according to claim 1, characterized in that: The first setting condition is: ; in, is the third characteristic impedance, is the characteristic impedance value of the system before 20 ms, k4 is the fourth preset coefficient, and its value is 0.2-0.

3.

6. The characteristic signal injection method applicable to active detection protection according to claim 1, characterized in that: Injecting a preset characteristic voltage, comprising: injecting the preset characteristic voltage When the initial voltage is , and increase k2 every 20ms| |The amplitude is increased by a step size of |; wherein k2 is the second preset coefficient, and its value is 0.

1.

7. The characteristic signal injection method applicable to active detection protection according to claim 6, characterized in that: The method further comprises: Inject the characteristic voltage When the characteristic current is collected in real time , when | |≥k3| |, stop increasing The amplitude of; wherein k3 is the third preset coefficient, the value is 0.95, is the preset characteristic current.

8. The characteristic signal injection method applicable to active detection protection according to claim 1, characterized in that: The method further comprises: The real-time load impedance of the system is obtained, and when the real-time load impedance meets a second set condition, the determination step is performed.

9. The characteristic signal injection method applicable to active detection protection according to claim 8, characterized in that: The second setting condition is: the following formula is valid for a period of time t / 2, ； in, is the real-time load impedance, is the real-time load impedance value before time t, k1 is the first preset coefficient, which is 0.2~0.3, and t is the preset judgment time, which is 10~20mins.

10. An electronic device, characterized in that: The invention comprises a processor, a memory and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, the characteristic signal injection method suitable for active detection protection as described in any one of claims 1 to 9 is implemented.

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