CN116482453A - Flexible direct-current transmission line overvoltage interference identification method, system and device - Google Patents
Flexible direct-current transmission line overvoltage interference identification method, system and device Download PDFInfo
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Abstract
The invention belongs to the field of direct current transmission line protection, and particularly relates to a method, a system and a device for identifying overvoltage interference of a flexible direct current transmission line. According to the overvoltage interference identification method, the waveform characteristics of the line mode current fault components under the condition that overvoltage interference occurs to the direct-current transmission line are used for determining the judgment conditions of the time domain energy values of the line mode current fault components in a specific time window under the condition of overvoltage, so that the overvoltage interference and the line faults are separated according to the existence of the fault components of the line mode current before protection starting and the interference and the line faults caused by the overvoltage by distinguishing operation, the quick-break protection misoperation of a normal line is avoided, and the protection reliability is improved. And after the line voltage mutation quantity meets the protection starting criterion, the process of judging the selection criterion is continued, and after the selection criterion is met, the subsequent identification process is started, so that frequent triggering of the identification process can be avoided, and the cost is saved.
Description
Technical Field
The invention belongs to the field of direct current transmission line protection, and particularly relates to a method, a system and a device for identifying overvoltage interference of a flexible direct current transmission line.
Background
As the technical level of the direct current transmission in China is gradually improved, flexible direct current transmission is an important hot spot developed in recent years; as a new generation direct current transmission technology, the method has the characteristics of flexibility, firmness and high efficiency, can fully utilize renewable energy sources in actual use, reduces the loss of social resources, and is a necessary trend of the future development of direct current transmission. More importantly, the method does not have the unavoidable commutation failure of the conventional direct current, so the method is widely applied to direct current power transmission and distribution in recent years.
In the application of the traditional flexible direct current transmission engineering, such as in the flexible direct current engineering A, taking a section of transmission line as an example, when a valve area short circuit or a bus ground fault occurs outside the section, the section of line is blocked, an adjacent direct current breaker is disconnected, power transmission is interrupted, the line voltage is caused to rise suddenly and then suddenly drop, the voltage characteristic can cause line protection action, the line in a fault-free area is interfered by the overvoltage of the adjacent fault line, and the line is mistakenly identified as the quick-break protection misoperation caused by the line fault of the section, so that the transmission efficiency is influenced.
Disclosure of Invention
The invention aims to provide a method, a system and a device for identifying overvoltage interference of a flexible direct current transmission line, which are used for solving the problem that the existing quick-break protection mode in the prior art causes quick-break protection misoperation due to overvoltage interference of adjacent fault lines.
In order to achieve the above purpose, the invention provides a flexible direct current transmission line overvoltage interference identification method, which comprises the following steps:
collecting positive and negative current signals of one end of a flexible direct current transmission line, and respectively calculating positive and negative current fault components of the end line by combining the current signals of the line at steady-state moment; obtaining a line mode current fault component of the end line according to the positive and negative current fault components of the line; obtaining a voltage signal of the line, and calculating a voltage abrupt change;
when the voltage mutation quantity of the line at the end meets a set condition, determining the time domain energy value of the line mode current fault component of the line in a set time window;
judging whether overvoltage interference occurs to the power transmission line according to the time domain energy value: if the time domain energy value is larger than the set energy threshold value, judging that overvoltage interference occurs to the circuit, otherwise, judging that the circuit fails; wherein the energy threshold is set to be greater than 0.
According to the overvoltage interference identification method, the waveform characteristics of the line mode current fault components under the condition that overvoltage interference occurs to the direct-current transmission line are used for determining the judgment conditions of the time domain energy values of the line mode current fault components in a specific time window under the condition of overvoltage, so that the interference and line faults caused by overvoltage operation can be distinguished according to the existence of the fault components of the line mode current before protection starting by setting the time domain energy value characteristics of the line mode current fault components in the time window, overvoltage interference and line faults are separated, quick-break protection misoperation of a normal line section is avoided, and protection reliability is improved.
Further, the setting conditions comprise a selection criterion, which is specifically as follows:
wherein: deltau max (k) For the maximum abrupt change of the voltage of the line in N periods, deltau (k) is the abrupt change of the voltage of the direct current line at the current moment, deltau (k-N+1) is the abrupt change of the voltage at the moment before N periods, and Delta2 is the area selection criterion threshold value.
Further, the setting conditions further include a protection starting criterion, which is specifically as follows:
wherein: deltau p (k) U is the voltage abrupt change of the direct current line at the current moment p (k) For the voltage sampling value at the current moment, u p (k-1) is a voltage sampling value at a time before the current time, and delta 1 is a starting criterion threshold value;
the voltage jump of the circuit meets the set condition, including:
when the protection starting criterion and the area selection criterion are met at the same time, the voltage mutation quantity is judged to meet the set condition.
Further, the energy threshold is set to be greater than the maximum value of the line mode current fault component under normal operation current fluctuation.
Further, the area selection criterion threshold value is set according to the maximum value of the direct current line voltage under the condition of avoiding the metal fault outside the area; the maximum value is the maximum abrupt voltage change when the adjacent bus is in metallic fault.
Further, the calculation of the time domain energy value of the line mode current fault component in the set time window is specifically as follows:
wherein: e (E) 1 For the time domain energy value of the line mode current fault component,in order to protect the selection criterion from meeting the time sampling point, N is the sampling point number in the length of the integration window, and delta i 1 (k) For the line mode current fault component, Δt is the sampling period.
Further, the specific calculation formula of the line mode current fault component is as follows:
wherein: Δi 1 (k) Δi, the line mode current fault component P (k)、Δi N (k) The fault components of the positive and negative current of the line are respectively indicated by subscript 1, which indicates a line mode.
Further, the calculation formula of the fault components of the positive and negative current of the line is as follows:
wherein: Δi P (k)、Δi N (k) The current fault components of the positive and negative poles of the line, i P (t)、i N (t) is the collected positive and negative current signals of the circuit, i P (0)、i N (0) Respectively is the steady state of the positive electrode and the negative electrode of the lineA time of day current signal.
The invention also provides a system for identifying the overvoltage interference of the flexible direct current transmission line, which comprises a collector and a processor, wherein the collector is used for collecting the positive and negative current signals and the voltage signals of the transmission line at one end in real time, and the processor is used for executing program instructions so as to realize the method for identifying the overvoltage interference of the flexible direct current transmission line. The system can achieve the same beneficial effects as the overvoltage interference identification method of the flexible direct-current transmission line.
The invention also provides a device for identifying overvoltage interference of the flexible direct current transmission line, which comprises the following components:
and the acquisition module is used for: collecting positive and negative current signals of one end of a flexible direct current transmission line, and respectively calculating positive and negative current fault components of the end line by combining the current signals of the line at steady-state moment; obtaining a line mode current fault component of the end line according to the positive and negative current fault components of the line; the voltage signal of the end line is obtained, and the voltage abrupt change is calculated;
the calculation triggering module: when the voltage mutation quantity of the end line meets the set condition, determining the time domain energy value of the line mode current fault component in a set time window;
and a judging module: judging whether overvoltage interference occurs to the power transmission line according to the time domain energy value: if the time domain energy value is larger than the set energy threshold value, judging that overvoltage interference occurs to the circuit, otherwise, judging that the circuit fails; wherein the energy threshold is set to be greater than 0. The device can realize the same beneficial effects as the overvoltage interference identification method of the flexible direct current transmission line.
Drawings
Fig. 1 is a flow chart of line overvoltage interference recognition in an embodiment of the flexible dc power line overvoltage interference recognition method of the present invention;
fig. 2 is a schematic diagram illustrating comparison of voltage and current waveform changes when a valve area short circuit occurs outside a converter station A1 area or a bus has a ground fault in an embodiment of an overvoltage interference identification method of a flexible dc transmission line according to the present invention;
fig. 3 is a schematic diagram illustrating comparison of voltage and current waveform changes when a valve area short circuit occurs outside a converter station A2 area or a bus has a ground fault in an embodiment of the method for identifying overvoltage interference of a flexible direct current transmission line.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent.
Overvoltage interference identification method embodiment of flexible direct-current transmission line
The embodiment provides a technical scheme of a method for identifying overvoltage interference of a flexible direct current transmission line, referring to fig. 1, the steps are as follows:
1) Collecting positive and negative current signals of one end of a failed power transmission line in real time, and respectively calculating positive and negative current fault components of the end line by combining the current signals of the line at steady-state moment; obtaining a line mode current fault component of the end line according to the positive and negative current fault components of the line; and obtaining the voltage signal of the end line, and calculating the voltage abrupt change.
The calculation formula of the fault components of the positive and negative current of the line is as follows:
wherein: Δi P (k)、Δi N (k) The current fault components of the positive and negative poles of the line, i P (t)、i N (t) is the collected positive and negative current signals of the circuit, i P (0)、i N (0) The current signals are respectively the steady-state time current signals of the positive electrode and the negative electrode of the line.
For a symmetrical flexible direct current bipolar system, a polar-to-analog conversion method can be utilized to construct a conversion matrix Q to decouple the bipolar line into zero-modes and polar moduli. The line mode current fault components adopted in the embodiment are obtained by positive and negative current fault components through the following polar mode transformation matrix Q:
therefore, in this embodiment, the specific calculation formula of the line mode current fault component is:
wherein: Δi 1 (k) Δi, the line mode current fault component P (k)、Δi N (k) The fault components of the positive and negative current of the line are respectively indicated by subscript 1, which indicates a line mode. The basic goal of the overvoltage identification scheme is to realize the identification of overvoltage interference and line faults caused by operations such as breaker actions and the like, so that when the line suffers from the overvoltage interference such as breaker actions and the like, the protection is not in malfunction, and when the line suffers from short-circuit faults, the protection is not in malfunction; in order to simply and intuitively extract the difference of transient currents under the conditions, and eliminate the influence of electromagnetic coupling between two poles on the waveform of the transient currents of the two poles, the line mode currents related in the embodiment are all analyzed by taking one mode current as a characteristic.
2) And after the voltage abrupt change of the end line meets the set condition, determining the time domain energy value of the line mode current fault component of the end line in the set time window.
In this embodiment, the setting conditions include a line protection start criterion and a selection criterion, and the transient overvoltage setting condition of the line is determined only when the protection start criterion and the selection criterion are satisfied at the same time; under normal conditions, the starting protection criterion is a precondition of protection starting, so that the embodiment starts to start the area selection criterion after the protection starting is firstly judged (namely, after the voltage abrupt quantity can trigger quick-break protection), and judges whether protection misoperation is caused by line transient overvoltage after the area selection criterion is met, thereby achieving the technical effect of accurately avoiding misoperation; in other embodiments, the start criteria and the selection criteria may also be determined in parallel.
The protection start criteria to be satisfied are specifically as follows:
wherein: deltau p (k) U is the voltage abrupt change of the direct current line at the current moment p (k) For the voltage sampling value at the current moment, u p (k-1) is a voltage sampling value at a time before the current time, and delta 1 is a starting criterion threshold value; the moments mentioned in this embodiment are all referred to as sampling moments. Under the normal condition, the starting criterion threshold value is selected to be larger than the maximum value of the voltage gradient under the normal operation voltage fluctuation, and meanwhile, the accurate and quick starting of the internal faults of the direct current power grid is ensured; in this embodiment, the starting criterion threshold Δ1 is 0.02pu; wherein pu is a normalization unit, and the steady-state voltage value of the line is set to 1pu under normal conditions. And after the line voltage abrupt change quantity meets the protection starting criterion, the process of judging the selection criterion is continued, so that the frequent triggering of the identification process is avoided, and the identification cost is saved.
In this embodiment, after the start criterion is satisfied, the maximum mutation amount Deltau in N periods is calculated max (k) The method comprises the steps of carrying out a first treatment on the surface of the The selection criterion is specifically as follows:
wherein: deltau max (k) For the maximum abrupt change of the voltage of the line in N periods, deltau (k) is the abrupt change of the voltage of the direct current line at the current moment, deltau (k-N+1) is the abrupt change of the voltage at the moment before N periods, and Delta2 is the area selection criterion threshold value.
In the flexible direct current engineering A, when a line fails, the voltage of the line suddenly drops, and the line falls to an extreme point within 200 us; if the execution period is 50us, N is preferably 5. Threshold value delta of selection criterion 2 Setting is carried out according to the maximum value of the direct current line voltage under the condition of avoiding the metallic fault outside the zone, and simulation verification proves that the maximum value is the maximum mutation delta u when the metallic fault occurs on the adjacent bus max 0.1pu, wherein pu is a normalization unit, and the steady-state voltage value of the line is set to be 1pu under normal conditions; consider a certain reliabilityCoefficient k 1 Take 1.2 and Δ2 take 0.12pu.
The time domain energy value of the line mode current fault component in the set time window is calculated as follows:
wherein: e (E) 1 For the time domain energy value of the line mode current fault component,in order to protect the selection criterion from meeting the time sampling point, N is the sampling point number in the length of the integration window, and delta i 1 (k) For the line mode current fault component, Δt is the sampling period.
In the traditional direct current line protection, the requirement on the line protection mobility is not high, a time window of about 2ms is generally taken, and if the sampling rate is 10KHz, N is 20; in flexible dc line protection, the requirement for line protection mobility is generally high, for example, flexible dc transmission project a requires a protection action outlet within 3ms, and if Δt is 50us, a time window of 0.5ms is generally taken, and N is taken to be 10.
4) Judging whether overvoltage interference occurs to the power transmission line according to the time domain energy value of the line mode current fault component; the judging conditions are as follows:
if the conditions are satisfied: e (E) 1 ＞Δ 3 Judging that overvoltage interference occurs on the circuit, and locking a circuit protection action outlet; otherwise, judging that the line fails; wherein delta is 3 To set an energy threshold.
According to simulation analysis of the direct current engineering A, reference is made to fig. 2 and 3, wherein fig. 2 is a voltage-to-current waveform comparison schematic diagram when a valve area short circuit occurs outside a region of the converter station A1 or a bus is grounded, and fig. 3 is a voltage-to-current waveform comparison schematic diagram when a valve area short circuit occurs outside a region of the converter station A2 or a bus is grounded, so that when the converter station fails (about 5 ms), the electric quantity starts to change immediately, and when a direct current breaker acts and line protection adjacent to the non-failure converter station starts (about 10 ms), a line mode current has accumulated a significant failure component. When the line is failed, the change of the line mode current is almost synchronous with the line protection when the line protection is started, and no failure component is accumulated before. Therefore, based on the presence or absence of a fault component (how much a fault component accumulates) of the line mode current before the protection start, it is possible to distinguish between a disturbance caused by an operation overvoltage and a line fault.
Setting an energy threshold delta 3 Is selected to be greater than the maximum value of the line mode current fault component under normal operation current fluctuation. Under the disturbance condition, the current change amplitude is very small, usually much smaller than 0.1 times of rated current, and the current during disturbance appears to fluctuate around a steady-state operation value, positive and negative cancellation is carried out after the integration of the current fault components, and the calculated result is smaller. Taking the DC engineering A as an example, the set energy threshold can be conservatively set to the fluctuation amount of 0.1 times rated current (0.3 kA) within the integral time (0.5 ms), and a certain reliability coefficient k is considered 2 Taking 1.5, in this embodiment, an energy threshold DeltaV is set 3 The method comprises the following steps:
in order to meet the reliability of protection, the starting criterion threshold value is larger than the maximum value of the voltage gradient under the fluctuation of normal operation voltage; the area selection criterion threshold value is set according to the maximum value of the direct current line voltage under the condition of avoiding the metallic fault outside the area, and in the embodiment, the maximum value is determined through simulation and is the maximum abrupt change of the voltage when the metallic fault occurs on the adjacent bus.
Overvoltage interference identification system embodiment of flexible direct-current transmission line
The embodiment provides a technical scheme of a flexible direct-current transmission line overvoltage interference identification system, which comprises a collector and a processor; the collector is used for collecting positive and negative current signals and voltage signals of the power transmission line at one end in real time, and the processor is used for executing program instructions so as to realize the overvoltage interference identification method in the embodiment of the overvoltage interference identification method of the flexible direct current power transmission line. Because the processing principle, the content and the corresponding beneficial effects of the system processor are described in detail in the embodiment of the method for identifying overvoltage interference of the flexible direct current transmission line, the details are not repeated here.
Overvoltage interference recognition device embodiment of flexible direct-current transmission line
The embodiment provides a technical scheme of a flexible direct current transmission line overvoltage interference identification device, which comprises:
and the acquisition module is used for: collecting positive and negative current signals of one end of a flexible direct current transmission line, and respectively calculating positive and negative current fault components of the end line by combining the current signals of the line at steady-state moment; obtaining a line mode current fault component of the end line according to the positive and negative current fault components of the line; the voltage signal of the end line is obtained, and the voltage abrupt change is calculated;
the calculation triggering module: when the voltage mutation quantity of the end line meets the set condition, determining the time domain energy value of the line mode current fault component in a set time window;
and a judging module: judging whether overvoltage interference occurs to the power transmission line according to the time domain energy value: if the time domain energy value is larger than the set energy threshold value, judging that overvoltage interference occurs to the circuit, otherwise, judging that the circuit fails; wherein the energy threshold is set to be greater than 0.
The functional principle, specific operation mode and corresponding beneficial effects of the device module are described in detail in the above embodiment of the method for identifying overvoltage interference of the flexible direct current transmission line, so that the description is omitted here.
The invention is characterized in that: the waveform characteristics of the line mode current fault components under the condition of overvoltage interference to the direct current transmission line are utilized to determine the judgment conditions of the time domain energy values of the line mode current fault components in a specific time window under the condition of overvoltage interference caused by the fault outside the area, so that the interference and the line faults caused by the overvoltage operation can be distinguished according to the existence of the fault components of the line mode current before the protection start by setting the time domain energy value characteristics of the line mode current fault components in the time window, the overvoltage interference and the line faults are separated, the quick-break protection misoperation of a normal line section is avoided, and the protection reliability is improved. And after the line voltage mutation quantity meets the protection starting criterion, the process of judging the selection criterion is continued, and after the selection criterion is met, the subsequent identification process is started, so that frequent triggering of the identification process can be avoided, and the identification cost is saved.
Finally, it should be noted that: the above embodiments are only for illustrating the technical aspects of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those of ordinary skill in the art that: modifications and equivalents may be made to the specific embodiments of the invention without departing from the spirit and scope of the invention, which is intended to be covered by the claims. It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein. The solutions in the embodiments of the present application may be implemented in various computer languages, for example, object-oriented programming language Java, and an transliterated scripting language JavaScript, etc.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks. These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (10)
1. The method for identifying the overvoltage interference of the flexible direct-current transmission line is characterized by comprising the following steps:
collecting positive and negative current signals of one end of a flexible direct current transmission line, and respectively calculating positive and negative current fault components of the end line by combining the current signals of the line at steady-state moment; obtaining a line mode current fault component of the end line according to the positive and negative current fault components of the line; the voltage signal of the end line is obtained, and the voltage abrupt change is calculated;
when the voltage mutation quantity of the end line meets the set condition, determining the time domain energy value of the line mode current fault component in a set time window;
judging whether overvoltage interference occurs to the power transmission line according to the time domain energy value: if the time domain energy value is larger than the set energy threshold value, judging that overvoltage interference occurs to the circuit, otherwise, judging that the circuit fails; wherein the energy threshold is set to be greater than 0.
2. The method for identifying overvoltage interference of flexible direct current transmission line according to claim 1, wherein the set condition comprises a selection criterion, specifically:
wherein: deltau max (k) For the maximum abrupt change of the voltage of the line in N periods, deltau (k) is the abrupt change of the voltage of the direct current line at the current moment, deltau (k-N+1) is the abrupt change of the voltage at the moment before N periods, and Delta2 is the area selection criterion threshold value.
3. The method for identifying overvoltage interference of flexible direct current transmission line according to claim 2, wherein the set condition further comprises a protection start criterion, specifically:
wherein: deltau p (k) U is the voltage abrupt change of the direct current line at the current moment p (k) For the voltage sampling value at the current moment, u p (k-1) is a voltage sampling value at a time before the current time, and delta 1 is a starting criterion threshold value;
the voltage jump of the circuit meets the set condition, including:
when the protection starting criterion and the area selection criterion are met at the same time, the voltage mutation quantity is judged to meet the set condition.
4. The method for identifying overvoltage disturbances on a flexible dc transmission line according to claim 1 where the energy threshold is set to be greater than the maximum value of the line mode current fault component under normal operating current ripple.
5. The method for identifying overvoltage interference of the flexible direct current transmission line according to claim 2, wherein the area selection criterion threshold value is set according to the maximum value of the direct current line voltage under the condition of avoiding an out-of-area metallic fault; the maximum value is the maximum abrupt voltage change when the adjacent bus is in metallic fault.
6. The method for identifying overvoltage disturbance of flexible direct current transmission line according to any one of claims 1 to 5, wherein the calculation of the time domain energy value of the line mode current fault component within a set time window is specifically as follows:
wherein: e (E) 1 For the time domain energy value of the line mode current fault component,in order to protect the selection criterion from meeting the time sampling point, N is the sampling point number in the length of the integration window, and delta i 1 (k) For the line mode current fault component, Δt is the sampling period.
7. The method for identifying overvoltage interference of flexible direct current transmission line according to any one of claims 1 to 5, wherein the specific calculation formula of the line mode current fault component is:
wherein: Δi 1 (k) Δi, the line mode current fault component P (k)、Δi N (k) The fault components of the positive and negative current of the line are respectively indicated by subscript 1, which indicates a line mode.
8. The method for identifying overvoltage interference of flexible direct current transmission line according to any one of claims 1 to 5, wherein the calculation formula of the positive and negative current fault components of the line is:
wherein: Δi P (k)、Δi N (k) The current fault components of the positive and negative poles of the line, i P (t)、i N (t) is the collected positive and negative current signals of the circuit, i P (0)、i N (0) The current signals are respectively the steady-state time current signals of the positive electrode and the negative electrode of the line.
9. The overvoltage interference identification system of the flexible direct current transmission line comprises a collector and a processor, wherein the collector is used for collecting positive and negative current signals and voltage signals of the transmission line at one end in real time, and the processor is used for executing program instructions to realize the overvoltage interference identification method of the flexible direct current transmission line according to any one of claims 1-8.
10. The utility model provides a flexible direct current transmission line overvoltage interference recognition device which characterized in that includes:
and the acquisition module is used for: collecting positive and negative current signals of one end of a flexible direct current transmission line, and respectively calculating positive and negative current fault components of the end line by combining the current signals of the line at steady-state moment; obtaining a line mode current fault component of the end line according to the positive and negative current fault components of the line; the voltage signal of the end line is obtained, and the voltage abrupt change is calculated;
the calculation triggering module: when the voltage mutation quantity of the end line meets the set condition, determining the time domain energy value of the line mode current fault component in a set time window;
and a judging module: judging whether overvoltage interference occurs to the power transmission line according to the time domain energy value: if the time domain energy value is larger than the set energy threshold value, judging that overvoltage interference occurs to the circuit, otherwise, judging that the circuit fails; wherein the energy threshold is set to be greater than 0.
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