Fault diagnosis method and device of protection device, computer equipment, computer readable storage medium and computer program product

Abstract

The application relates to a fault diagnosis method and device of a protection device, computer equipment, a computer readable storage medium and a computer program product. The method comprises the following steps: obtaining recording wave signals in the same suspected fault period, wherein the recording wave signals comprise a first recording wave signal of a first protection device to be diagnosed, a second recording wave signal of a second protection device serving as a reference protection device, and a third recording wave signal of a third protection device having the same protection object as the first protection device; judging whether the first protection device is in a zero sequence current loss state and a self-produced zero sequence voltage existing state and whether the second protection device is in a zero sequence current existing state to obtain a first diagnosis result; comparing waveforms of the first recording wave signal and the third recording wave signal to obtain a second diagnosis result; and fusing the first diagnosis result and the second diagnosis result to obtain a target diagnosis result. Thus, the safety and reliability of the secondary circuit operation in important occasions such as pumped storage power stations are improved.

Description

Technical Field

[0001] This application relates to the field of equipment safety technology, and in particular to a fault diagnosis method, apparatus, computer equipment, computer-readable storage medium, and computer program product for a protection device. Background Technology

[0002] Hydropower stations are important peak-shaving, frequency regulation, and emergency backup power sources for power grids. The protection and measurement of their electrical equipment generally rely on current transformers (CTs) to proportionally transform large primary currents into smaller secondary currents.

[0003] Existing CT neutral line break detection mainly relies on monitoring the zero-sequence current of a single protection device to determine whether a fault exists. However, since conclusions are drawn based solely on a single zero-sequence quantity from a single device, it is impossible to distinguish the specific circumstances of the neutral line abnormality, resulting in false alarms or missed alarms. Furthermore, it is difficult to reliably locate the specific break side or break circuit.

[0004] Furthermore, a neutral line breakage in a CT is a hidden fault that is difficult to detect under normal circumstances. If a real ground fault occurs during its existence, the zero-sequence current that should appear cannot be correctly transmitted, which will cause the grounding protection to fail to operate, endangering the safety of the equipment and the power grid. Summary of the Invention

[0005] Therefore, it is necessary to provide a fault diagnosis method, apparatus, computer equipment, computer-readable storage medium, and computer program product for protection devices that can improve the accuracy of fault diagnosis, in order to address the above-mentioned technical problems.

[0006] Firstly, this application provides a fault diagnosis method for a protection device, including:

[0007] Acquire waveform signals during the same suspected fault period; wherein, the waveform signals include the first waveform signal of the first protection device to be diagnosed, the second waveform signal of the second protection device as a reference protection device, and the third waveform signal of the third protection device that has the same protection object as the first protection device;

[0008] Based on the first recorded waveform signal, it is determined whether the first protection device is in a state of zero-sequence current deficiency and self-generated zero-sequence voltage existence, and based on the second recorded waveform signal, it is determined whether the second protection device is in a state of zero-sequence current existence, and the first diagnostic result is obtained.

[0009] Compare the waveforms of the first and third recorded waveforms and determine their consistency to obtain the second diagnostic result;

[0010] The target diagnostic result is obtained by combining the first and second diagnostic results.

[0011] In one embodiment, the step of acquiring waveform signals during the same fault period includes:

[0012] The fault triggering condition is any of the following events: ground fault outside the power grid area, ground fault in other bays within the plant, zero-sequence voltage exceeding the limit on the bus, or zero-sequence current start-up of any protection device within the station.

[0013] In response to the fault triggering condition, the waveform recording signals of the first protection device, the second protection device and the third protection device during the suspected fault period corresponding to the triggering condition are retrieved to obtain the first waveform recording signal, the second waveform recording signal and the third waveform recording signal.

[0014] In one embodiment, after the step of acquiring waveform signals during the same fault period, the method further includes:

[0015] The channels of each recorded waveform signal are mapped to three-phase current channels and three-phase voltage channels to obtain three-phase current and three-phase voltage, and zero-sequence current and zero-sequence voltage are synthesized based on the three-phase current and three-phase voltage respectively;

[0016] Based on the protection start flag, the start point of the sudden change, or the peak value of the cross-correlation of the voltage channel, the fault start time of the aligned waveform signal is used, and the first preset number of cycles before the fault start time is taken as the reference window, and the second preset number of cycles after the fault start time is taken as the diagnostic window.

[0017] In one embodiment, the steps of determining whether the first protection device is in a state of zero-sequence current deficiency and self-generated zero-sequence voltage existence based on the first recorded waveform signal, and determining whether the second protection device is in a state of zero-sequence current existence based on the second recorded waveform signal, to obtain the first diagnostic result include:

[0018] Based on the noise level of the zero-sequence quantity within the reference window, a corresponding zero-sequence quantity threshold is generated; wherein, the zero-sequence quantity threshold includes the first zero-sequence current threshold and the zero-sequence voltage threshold of the first protection device, and the second zero-sequence current threshold of the second protection device;

[0019] Within the diagnostic window, when the zero-sequence current of the first protection device is lower than the first zero-sequence current threshold, the first protection device is determined to be in a state of zero-sequence current deficiency; when the zero-sequence voltage of the first protection device is higher than the zero-sequence voltage threshold, the first protection device is determined to be in a state of self-generated zero-sequence voltage existence.

[0020] Furthermore, when the zero-sequence current of the second protection device is higher than the second zero-sequence current threshold, it is determined that the second protection device has a zero-sequence current.

[0021] When the first protection device has zero-sequence current deficiency and self-generated zero-sequence voltage, and the second protection device has zero-sequence current, a suspected open circuit is determined, and the first diagnostic result is obtained.

[0022] In one embodiment, the step of comparing the waveforms of the first recorded waveform signal and the third recorded waveform signal, and determining the consistency of the waveforms to obtain the second diagnostic result includes:

[0023] By correlating the analog quantity channels representing the same physical quantity in the first and third recorded waveforms, multiple channel pairs are obtained.

[0024] Within the diagnostic window, the difference data between the two analog channels in each channel pair is calculated, and the difference degree of the channel pair is calculated based on the difference data; wherein, the difference data includes at least waveform residual difference, correlation coefficient difference, fundamental phasor difference, and zero-sequence reconstruction difference;

[0025] When the difference between voltage channel pairs is lower than the preset consistency threshold, and the difference between current channel pairs or zero-sequence current channel pairs is higher than the preset inconsistency threshold, a suspected disconnection is determined, and a second diagnostic result is obtained.

[0026] In one embodiment, the step of fusing the first diagnostic result and the second diagnostic result to obtain the target diagnostic result includes:

[0027] Based on the zero-sequence voltage over-limit intensity, the reference zero-sequence current response intensity, and the degree of zero-sequence current missingness in the first diagnostic results, a first confidence level is generated.

[0028] A second confidence level is generated based on the consistency of voltage channels, the intensity of differences in current channels, and the intensity of differences in zero-sequence reconstruction in the second diagnostic results.

[0029] Determine the smaller value between the first confidence level and the second confidence level, and then sum the values ​​of the first confidence level, the second confidence level, and the smaller value to obtain the fusion score.

[0030] When the fusion score is not lower than the first threshold, and the first diagnostic result and the second diagnostic result point to the same current transformer secondary circuit, it is determined that the neutral line of the current transformer is broken, and the target diagnostic result is obtained.

[0031] Secondly, this application also provides a fault diagnosis device for a protection device, the device comprising:

[0032] The data acquisition module is used to acquire waveform signals during the same fault period; wherein, the waveform signals include the first waveform signal of the first protection device to be diagnosed, the second waveform signal of the second protection device as a reference protection device, and the third waveform signal of the third protection device that has the same protection object as the first protection device.

[0033] The first comparison module is used to determine whether the first protection device is in a state of zero-sequence current deficiency and self-generated zero-sequence voltage existence based on the first recorded waveform signal, and to determine whether the second protection device is in a state of zero-sequence current existence based on the second recorded waveform signal, so as to obtain the first diagnostic result.

[0034] The second comparison module is used to compare the waveforms of the first and third recorded waveforms, determine the consistency of the waveforms, and obtain the second diagnostic result.

[0035] The diagnostic fusion module is used to fuse the first diagnostic result and the second diagnostic result to obtain the target diagnostic result.

[0036] Thirdly, this application also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps performed by the fault diagnosis method of the above-mentioned protection device.

[0037] Fourthly, this application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps performed by the fault diagnosis method of the aforementioned protection device.

[0038] Fifthly, this application also provides a computer program product, including a computer program that, when executed by a processor, implements the steps performed by the fault diagnosis method of the aforementioned protection device.

[0039] The aforementioned fault diagnosis method, apparatus, computer equipment, computer-readable storage medium, and computer program product for protection devices acquire waveform recording signals during the same suspected fault period. These waveform recording signals include a first waveform recording signal of the first protection device to be diagnosed, a second waveform recording signal of a second protection device serving as a reference protection device, and a third waveform recording signal of a third protection device with the same protected object as the first protection device. Based on the first waveform recording signal, it is determined whether the first protection device is in a state of zero-sequence current deficiency and self-generated zero-sequence voltage existence. Based on the second waveform recording signal, it is determined whether the second protection device is in a state of zero-sequence current existence, thus obtaining a first diagnostic result. The waveforms of the first and third waveform recording signals are compared, and their consistency is determined, thus obtaining a second diagnostic result. The first and second diagnostic results are then fused to obtain a target diagnostic result.

[0040] Therefore, the self-generated zero-sequence voltage of the first protection device indicates that the system has indeed experienced a ground fault during the same suspected fault period, while the zero-sequence current of the second protection device indicates that the system has indeed generated a zero-sequence response. These two, together with the zero-sequence current deficiency state of the first protection device, constitute a ternary correlation criterion. This allows the phenomenon of zero-sequence current deficiency to be distinguished from the situation where the system itself does not have a zero-sequence component, overcoming the problem of being unable to identify the cause of deficiency and thus leading to false alarms or missed alarms when judging solely based on the single zero-sequence current quantity of a single protection device. Simultaneously, the third protection device, which has the same protected object as the first protection device... The waveform recording signal of the device serves as a second layer of evidence independent of the zero-sequence electrical quantity judgment. By comparing the waveform consistency of the two waveform recording signals, the first diagnostic result is independently verified, avoiding misjudgments caused by changes in the primary system operation mode, false triggering of waveform recording, sampling errors, or abnormalities of a single protection device. The target diagnostic result is output after the two diagnostic results are fused. The two types of evidence constrain and verify each other within the same suspected fault period, effectively improving the accuracy of the current transformer neutral line breakage diagnosis and reducing the risk of long-term lurking of breakage hazards and failure of grounding protection to operate when a real grounding fault occurs. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 A diagram illustrating the application environment of a fault diagnosis method for a protection device in one embodiment;

[0043] Figure 2 This is a flowchart illustrating a fault diagnosis method for a protection device in one embodiment;

[0044] Figure 3 This is a schematic diagram of the structure of a fault diagnosis device for a protection device in one embodiment;

[0045] Figure 4 This is a schematic diagram of the internal structure of a computer device in one embodiment. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0047] It should be noted that the terms "first," "second," etc., used in this application can be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from the second element. The terms "comprising" and "having," and any variations thereof, used in this application, are intended to cover non-exclusive inclusion. The term "multiple" used in this application refers to two or more. The term "and / or" used in this application refers to one of the embodiments, or any combination of multiple embodiments.

[0048] In traditional CT neutral line breakage detection technology, the fault identification process is based solely on whether the zero-sequence current of a single protection device exceeds the limit or is missing. It lacks correlation analysis to determine whether the system actually has a zero-sequence fault background during the same suspected fault period, resulting in insufficient fault identification accuracy. Furthermore, the ground fault characteristics represented by the zero-sequence voltage generated by the protection device itself, as well as the zero-sequence current response of other protection devices within the substation, are not included in the fault judgment criteria. This makes it impossible to distinguish between the failure of zero-sequence current transmission due to neutral line breakage and the absence of a zero-sequence component in the system itself, leading to frequent false alarms and missed alarms. Moreover, the judgment criteria are based solely on a single electrical quantity from a single protection device, without establishing a waveform consistency verification mechanism with another set of protection devices for the same protected object. This makes it impossible to independently verify the judgment conclusions or pinpoint the anomaly to a specific CT secondary circuit, resulting in a lack of direction in investigating potential grounding breakages and directly affecting the reliability of grounding protection operation.

[0049] For example, during an external grounding fault at a pumped storage power station, the neutral line of the CT (current transformer) of the device under diagnosis is disconnected due to loose terminal block wiring. The zero-sequence current it collects is close to zero, even though the system already exhibits grounding fault characteristics and other bay protection devices within the station have detected significant zero-sequence current. However, existing methods only consider that the zero-sequence current of the device under diagnosis has not reached the over-limit threshold, thus assuming that no zero-sequence component was generated during that period and no disconnection alarm is triggered. Specifically, in this scenario, the zero-sequence current failure caused by the neutral line disconnection and the absence of zero-sequence component in the system present the same numerical characteristics on the protection device side. However, traditional methods do not introduce the self-generated zero-sequence voltage of the protection device or the zero-sequence current response of other protection devices within the station as corroborating evidence, nor do they compare the waveforms with another set of protection devices for the same protected object. As a result, the disconnection state cannot be identified, and it is impossible to determine which set of protection devices' CT secondary circuit the abnormality originates from.

[0050] If the above problems are not resolved, the neutral line breakage of the CT will remain hidden in the secondary circuit for a long time. Due to the lack of an independent chain of evidence, the broken side cannot be located or investigated in a targeted manner. As a result, when a real ground fault occurs during the period of the breakage, the zero-sequence current that should appear cannot be correctly transmitted to the protection device, causing the grounding protection to fail to operate. This leads to accidents such as delayed fault clearing, expansion of the fault range, and damage to primary equipment, which seriously threaten the safe operation of the unit and the reliability of the power grid system.

[0051] To address the aforementioned problems, embodiments of this application provide a fault diagnosis method for a protection device, which can be applied to, for example... Figure 1 In the application environment shown, terminal 102 communicates with server 104 via a network. A data storage system can store the data that server 104 needs to process. The data storage system can be integrated onto server 104, or it can be located in the cloud or on another network server.

[0052] Terminal 102 can be, but is not limited to, various personal computers, laptops, smartphones, tablets, drones, aircraft, low-altitude aircraft, IoT devices, and portable wearable devices. IoT devices can include smart speakers, smart TVs, smart air conditioners, smart in-vehicle devices, projection devices, etc. Portable wearable devices can include smartwatches, smart bracelets, head-mounted devices, etc. Head-mounted devices can include virtual reality (VR) devices, augmented reality (AR) devices, smart glasses, etc.

[0053] Server 104 can be a standalone physical server, a server cluster or distributed system consisting of multiple physical servers, or a cloud server that provides cloud computing services.

[0054] This application provides a fault diagnosis method for a protection device, such as Figure 2 As shown, this method is applied to Figure 1 Taking server 104 as an example, by correlating and comparing the waveforms recorded by multiple protection devices during the same suspected fault period, the potential for a broken neutral wire in the secondary circuit of the current transformer can be detected in a timely manner. This ensures that the protection device can correctly reflect the zero-sequence current and operate reliably when a real ground fault occurs. The fault diagnosis method of this protection device may include steps 21 to 24, wherein:

[0055] Step 21: Obtain waveform signals from the same suspected fault period.

[0056] The waveform recording signals include the first waveform recording signal of the first protection device to be diagnosed, the second waveform recording signal of the second protection device as a reference protection device, and the third waveform recording signal of the third protection device that has the same protection object as the first protection device.

[0057] Here, the waveform recording signal can be an analog sampling sequence recorded by a protection device or a fault waveform recording device during a fault. It can include three-phase current, three-phase voltage, and channel data such as zero-sequence current and zero-sequence voltage, which are used to reflect the electrical response characteristics of the primary system and secondary circuit during this period.

[0058] The suspected fault period can be used to represent a time interval in the system where fault characteristics have appeared, but the nature and location of the fault have not yet been determined. Since a CT neutral line break is a hidden fault in the secondary circuit, it will only be exposed when a zero-sequence component appears in the system. Therefore, the time interval in which the system actually experiences fault disturbance needs to be used as the time reference for diagnosis.

[0059] The first protection device can be the one targeted in this diagnosis, whose neutral wire breakage in the CT secondary circuit is yet to be determined. The second protection device can be a protection device in other bays within the station, whose CT secondary circuit is independent of the first protection device, and is used to provide a reference for whether the system actually generates a zero-sequence response during this period. The third protection device can be another set of protection devices that protects the same object as the first protection device, but uses an independent CT secondary circuit and an independent sampling channel; in important occasions such as pumped storage power stations, the same protected object is usually configured with two sets of protection devices, A and B, and the first protection device and the third protection device can be respectively the A set protection and the B set protection.

[0060] It should be noted that the second and third protection devices play different roles in this scheme: the second protection device and the first protection device are not the same protected object, and its zero-sequence current is only used to characterize whether there is a zero-sequence component at the system level; while the third protection device and the first protection device are the same protected object, and under normal circumstances, the electrical quantities recorded by the two should be consistent with each other. Therefore, its waveform signal can be used to perform channel-by-channel consistency verification of the first waveform signal.

[0061] One approach is to pre-establish an association table for the first, second, and third protection devices in the on-site fault recording management system or protection information substation, based on the correspondence between the protected objects and the intervals. When a fault disturbance occurs, recording files for the same time period can be retrieved in batches according to this association table. Another approach is for the server to send recording request commands to each protection device or recording device via the network to actively read recording signals for a specified time period.

[0062] Step 22: Based on the first recorded waveform signal, determine whether the first protection device is in a state of zero-sequence current deficiency and self-generated zero-sequence voltage existence, and based on the second recorded waveform signal, determine whether the second protection device is in a state of zero-sequence current existence, and obtain the first diagnostic result.

[0063] Among them, the zero-sequence current missing state can be used to indicate that the first protection device did not collect a valid zero-sequence current during the suspected fault period, that is, the value of its zero-sequence current is lower than the threshold used to determine whether the zero-sequence current is valid.

[0064] The presence of self-generated zero-sequence voltage can be used to indicate that the zero-sequence voltage synthesized from the three-phase voltage of the first protection device itself is clearly present during the suspected fault period, that is, its value is higher than the threshold used to determine the presence of zero-sequence voltage. Here, "self-generated" can be used to indicate that the zero-sequence quantity is not taken from a dedicated zero-sequence channel, but is directly synthesized from the three-phase quantities collected by the same protection device.

[0065] The presence of zero-sequence current can be used to indicate that the second protection device has collected a valid zero-sequence current during the same suspected fault period.

[0066] Understandably, the three judgments mentioned above serve different purposes: the absence of zero-sequence current in the first protection device indicates an abnormal phenomenon to be verified; the presence of zero-sequence voltage generated by the first protection device indicates that the system has indeed exhibited ground fault characteristics during this period, meaning that zero-sequence current should have appeared under normal circumstances; and the presence of zero-sequence current in the second protection device further corroborates from the independent secondary circuit that the system has indeed generated a zero-sequence response, thus ruling out the possibility that the system itself does not have a zero-sequence component. These three together constitute a correlated criterion, enabling the determination of the cause of the absence of zero-sequence current.

[0067] The first diagnostic result can be used to represent the diagnostic conclusion obtained based on the zero-sequence electrical quantity correlation verification. As one implementation, when the first protection device is in a state of zero-sequence current absence and a state of self-generated zero-sequence voltage existence, and the second protection device is in a state of zero-sequence current existence, the first diagnostic result can be determined as a suspected open circuit; when any of the above conditions are not met, the first diagnostic result can be determined as no suspected open circuit existence.

[0068] For example, if the zero-sequence current of the first protection device is close to zero, while its self-generated zero-sequence voltage increases significantly, and the second protection device detects a significant zero-sequence current, it indicates that a ground fault has indeed occurred in the system and a zero-sequence component has been generated. However, the first protection device has failed to correctly reflect the zero-sequence current. In this case, the first diagnostic result can be determined to be that there is a suspected open circuit. Conversely, if the zero-sequence current of the first protection device is close to zero, and its self-generated zero-sequence voltage does not exceed the limit, and the second protection device does not detect a zero-sequence current, it indicates that there is no zero-sequence component in the system during this period, which is a normal situation. In this case, the first diagnostic result can be determined to be that there is no suspected open circuit.

[0069] Step 23: Compare the waveforms of the first and third recorded waveforms and determine their consistency to obtain the second diagnostic result.

[0070] Among them, waveform consistency can be used to indicate the degree of similarity in amplitude, shape and phase of the sampled waveforms of the first and third recorded waveforms representing the same physical quantity within the same time period.

[0071] Understandably, the first and third protection devices protect the same object, and the electrical processes experienced on their primary side are exactly the same. Under normal conditions, the waveforms of the same physical quantity recorded by the two devices should be highly consistent. If there is a significant difference between the two devices, it indicates that there is an abnormality in the secondary circuit or sampling link of one of the protection devices.

[0072] It should be noted that the distribution characteristics of the waveform differences have diagnostic significance: if the voltage channel waveforms are consistent but the current channel or zero-sequence current channel waveforms are inconsistent, it indicates that the two recorded signals have been reliably aligned in time and the electrical response at the primary system level is the same. The difference should originate from the current loop itself, and thus correspond to the abnormality of the CT secondary circuit. If the voltage channel waveforms are also inconsistent, it may be that the recorded signals have not been reliably aligned or there are other common abnormalities. In this case, the difference should not be attributed to the CT neutral line being broken.

[0073] The second diagnostic result can be used to represent the diagnostic conclusion obtained based on the waveform consistency comparison of the dual protection devices. As one implementation, when the waveforms of the voltage channel are consistent, but the waveforms of the current channel or zero-sequence current channel are inconsistent, the second diagnostic result can be determined as a suspected open circuit; otherwise, the second diagnostic result can be determined as no suspected open circuit.

[0074] Furthermore, if the second diagnostic result indicates a suspected open circuit, the zero-sequence current of the first protection device and the third protection device can be compared. The secondary circuit of the CT corresponding to the one with a significantly smaller zero-sequence current can be identified as the suspected open circuit side, thereby pinpointing the anomaly to a specific circuit and providing direction for on-site troubleshooting.

[0075] Step 24: Combine the first diagnostic result and the second diagnostic result to obtain the target diagnostic result.

[0076] In this context, "fusion" can be used to represent the process of mutually verifying and comprehensively deciding on the two diagnostic results mentioned above, rather than simply adding the two together logically.

[0077] Understandably, the first diagnostic result answers whether the system truly has a zero-sequence fault background during that period and whether the zero-sequence current of the first protection device is abnormally missing. The second diagnostic result answers whether there is a difference in current between two protection devices with the same protected object under the same fault, and whether this difference points to the same CT secondary circuit. The information sources on which the two are based are independent of each other, so when both point to the same conclusion, the credibility of that conclusion is significantly improved.

[0078] The target diagnostic results can be used to represent the final output diagnostic conclusion. One implementation method is to generate corresponding confidence levels based on the strength of each of the two diagnostic results, then weight and fuse these confidence levels to obtain a fusion score. Finally, based on the comparison between the fusion score and a preset threshold, and whether the two diagnostic results point to the same CT secondary circuit, the target diagnostic results are output in a graded manner.

[0079] For example, when both diagnostic results indicate a suspected open circuit and point to the same CT secondary circuit, the target diagnostic result can be determined as an open circuit in the neutral line of the current transformer, and the suspected open circuit side can be output. When the two diagnostic results are only partially consistent, the target diagnostic result can be determined as a high-risk open circuit in the neutral line of the current transformer, and a verification prompt can be output. When neither diagnostic result supports the conclusion of an open circuit, or the voltage channels of the two recorded waveforms cannot be reliably aligned, the conclusion of an open circuit can be left unoutput, and only this event can be recorded.

[0080] In traditional CT neutral line breakage detection schemes, the judgment and alarm are usually based solely on whether the zero-sequence current of a single protection device exceeds the limit or is missing. However, this method of judging by a single electrical quantity has problems such as low recognition accuracy and susceptibility to false alarms or missed alarms: because the manifestation of a missing zero-sequence current on the protection device side is exactly the same as the absence of a zero-sequence component in the system itself, the real breakage fault often cannot be detected; and when the system operating mode changes or there are sampling errors, the normal state may be misjudged as a breakage.

[0081] In the above implementation, the limitations mentioned above are overcome by introducing a correlation verification between the self-generated zero-sequence voltage and the zero-sequence current of the reference protection device. Although the absence of zero-sequence current itself cannot explain the cause, the self-generated zero-sequence voltage of the first protection device indicates that the system has indeed experienced ground fault characteristics during this period, and the zero-sequence current detected by the second protection device confirms from an independent loop that the system has indeed generated a zero-sequence response. The two, together with the absence of zero-sequence current, constitute a correlation criterion, enabling the accurate identification of this anomaly that should have been present but was not. In addition, by comparing the waveform consistency with a third protection device that has the same protected object, a second layer of evidence independent of the zero-sequence electrical quantity is introduced. Based on the distribution characteristics of consistent voltage channels but inconsistent current channels, the anomaly can be attributed to the current loop and located to the specific CT secondary circuit, avoiding the problems of single judgment criteria, unverifiable conclusions, and inability to locate anomalies in traditional methods.

[0082] Compared to existing technologies where the criteria are singular and hidden faults are difficult to detect, this embodiment can detect potential neutral line breakage in the CT before a real grounding fault occurs and provide troubleshooting directions. This effectively reduces the probability of grounding protection failing to operate due to the incorrect transmission of zero-sequence current, and improves the safety and reliability of secondary circuit operation in important situations such as pumped storage power stations.

[0083] Based on this, this application proposes a fault diagnosis method for a protection device, in which the real-time rotational speed of the unit where the valve is located is added to the real-time data. In an exemplary embodiment, the fault diagnosis method for the protection device may include steps 301 to 310, wherein:

[0084] Step 301: Use any of the following events as the fault triggering conditions: ground fault outside the power grid area, ground fault in other bays within the substation, zero-sequence voltage exceeding the limit on the bus, or zero-sequence current start-up of any protection device within the substation.

[0085] Among them, the fault triggering condition can be used to indicate the basis for determining whether to start this diagnostic process.

[0086] Understandably, a neutral line break in a CT (Cyclic Transmission Unit) will only be exposed as a zero-sequence current that should have appeared but did not, when the system actually generates a zero-sequence component. Therefore, the above four types of events are all indicators that the system has or may have a zero-sequence component: grounding faults outside the power grid area and grounding faults in other bays within the substation indicate that the system has been grounded; exceeding the limit of the bus zero-sequence voltage indicates that a zero-sequence voltage component has appeared in the system; and the activation of zero-sequence current in any protection device within the substation indicates that a device has detected a zero-sequence current response. Using the above events as triggering conditions allows for diagnosis to be carried out during the period when the potential for a break is most likely to be exposed, avoiding invalid diagnosis when there is no zero-sequence component in the system.

[0087] As one implementation method, the server can receive protection start signals, alarm signals and bus zero-sequence voltage measurement values ​​sent by the protection information substation within the station. When any one of them meets the above event characteristics, the fault triggering condition is determined to be met.

[0088] As another implementation method, the fault recording device can send a start message to the server when it starts recording waveforms, and the server uses the message as the trigger.

[0089] Step 302: In response to the fault triggering condition, retrieve the waveform recording signals of the first protection device, the second protection device and the third protection device during the suspected fault period corresponding to the triggering condition, and obtain the first waveform recording signal, the second waveform recording signal and the third waveform recording signal.

[0090] Here, the suspected fault period corresponding to the triggering condition can be a time interval determined based on the time when the triggering condition occurs. It can include a period of time before the triggering time and a period of time after the triggering time, so as to obtain normal operation data before the fault and response data during the fault at the same time.

[0091] As one implementation method, after the fault triggering condition is met, the server can automatically retrieve the waveform recording files within that time period from the waveform recording devices corresponding to the first protection device, the second protection device, and the third protection device according to the pre-established device association relationship, without the need for manual retrieval one by one.

[0092] It should be noted that when the same protected object is equipped with both A and B protection devices, the synchronous waveform recording signals of both protection devices under the same fault should be acquired simultaneously. At the same time, the waveform recording signals of other bay protection devices within the station should also be acquired as reference data. When multiple other bay protection devices exist within the station, the waveform recording signals of multiple devices can be acquired, and the maximum value of their zero-sequence current can be used as a reference to improve the reliability of the reference results.

[0093] Step 303: Map the channels of each recorded signal to three-phase current channels and three-phase voltage channels to obtain three-phase current and three-phase voltage, and synthesize zero-sequence current and zero-sequence voltage based on the three-phase current and three-phase voltage respectively.

[0094] Channel mapping can be used to represent the process of uniformly classifying channels with different naming methods and arrangement orders in different waveform signals into a standard channel category.

[0095] Understandably, different manufacturers have different naming conventions for channels of the same physical quantity in their waveform recordings. The same phase current may be recorded with different names, and the channel's arrangement in the file may also differ. If channel mapping is not performed and channels are directly used according to their serial numbers, channels of different physical quantities may be matched with each other, rendering subsequent calculations meaningless.

[0096] As one implementation method, the channels of each recorded signal can be uniformly mapped to standard channels such as Ia, Ib, Ic, Ua, Ub, and Uc. In the case where there is no dedicated zero-sequence channel in the recorded signal, the zero-sequence current can be synthesized from the three-phase current and the zero-sequence voltage can be synthesized from the three-phase voltage, that is, the corresponding zero-sequence quantity is obtained by adding the instantaneous values ​​of the three phases point by point. In the case where there is a dedicated zero-sequence channel, the dedicated channel can be included in the subsequent comparison range.

[0097] It should be noted that the zero-sequence quantity obtained by synthesizing three-phase quantities is called the self-generated zero-sequence quantity. It has the same physical meaning as the zero-sequence quantity collected by the dedicated channel, but its transmission path does not pass through the secondary neutral line of the CT. Therefore, it can still reflect the zero-sequence voltage characteristics of the system normally when the neutral line is broken. This is why this scheme uses the self-generated zero-sequence voltage as one of the criteria.

[0098] Step 304: Based on the protection start flag, the start point of the sudden change, or the peak value of the cross-correlation of the voltage channel, the fault start time of the aligned waveform signal is used, and the first preset number of cycles before the fault start time is taken as the reference window, and the second preset number of cycles after the fault start time is taken as the diagnostic window.

[0099] The fault initiation time can be used to indicate the time when the fault disturbance begins to appear in each recorded waveform signal, and can be denoted as t0.

[0100] Understandably, the start time and recording length of each waveform recording device are not the same. If time alignment is not performed, the sampling points with the same sequence number in different waveform recording signals do not correspond to the same physical time. Based on this, waveform comparison will yield meaningless difference results.

[0101] One approach is to use the protection start flag as the alignment reference, i.e., the protection start time stamp recorded in the waveform file is t0; another approach is to use the abrupt change start point as the alignment reference, i.e., the moment when the electrical quantity undergoes a significant abrupt change is t0; yet another approach is to use the peak value of the voltage channel cross-correlation as the alignment reference, i.e., the time shift corresponding to the maximum value of the cross-correlation function of the two waveform signals is used as the relative offset between them, and alignment is completed accordingly. Any of these methods can be chosen, or they can be cross-checked before being used.

[0102] The baseline window, denoted as W0, represents a normal operating range before a fault occurs and is used to statistically analyze the noise levels of various electrical quantities under fault-free conditions. The diagnostic window, denoted as Wf, represents the range used for diagnostic calculations after a fault occurs.

[0103] As one implementation method, the first preset number of cycles can be 3 to 5 cycles before the fault, and the second preset number of cycles can be 2 to 6 cycles after the fault. It should be noted that the diagnostic window should avoid the transient spikes in the initial stage of the fault. This is because when the fault just occurs, the electrical quantities contain large non-periodic and high-frequency components. Directly using them for calculation will amplify the waveform differences, thereby affecting the accuracy of the diagnostic results.

[0104] Furthermore, after completing time alignment and window division, each recorded signal can be normalized according to the transformer ratio, rated current, rated voltage, and polarity configuration, converting it into primary or per-unit values. The first and third recorded signals are then resampled to the same sampling rate to ensure a one-to-one correspondence between sampling points at the same time. It should be noted that if the phases of all three phase voltage channels of a recorded signal are reversed, it indicates an abnormal polarity configuration. In this case, it should be marked as an abnormal configuration, rather than directly using the resulting difference as evidence of a broken neutral line in the CT, thus ruling out misjudgments caused by incorrect wiring polarity.

[0105] Step 305: Generate the corresponding zero-sequence threshold based on the noise level of the zero-sequence quantity within the reference window; wherein, the zero-sequence threshold includes the first zero-sequence current threshold and the zero-sequence voltage threshold of the first protection device, and the second zero-sequence current threshold of the second protection device.

[0106] Among them, the noise level can be used to represent the inherent fluctuation amplitude of the zero-sequence quantity due to three-phase imbalance, sampling error and background interference under normal system conditions without faults.

[0107] Understandably, different protection devices have different CT characteristics, secondary circuit conditions, and sampling accuracy, resulting in different inherent fluctuations in their zero-sequence quantities. If a uniform fixed threshold is applied to all devices, misjudgments are likely to occur for devices with high noise levels, while sensitivity may be lost for devices with low noise levels. Therefore, this embodiment generates a specific threshold for each device based on its measured noise level within a reference window.

[0108] It should be noted that although the first zero-sequence current threshold and the second zero-sequence current threshold are both zero-sequence current thresholds, their functions are opposite: the former is used to determine whether the zero-sequence current of the first protection device is low enough to be considered absent, while the latter is used to determine whether the zero-sequence current of the second protection device is high enough to be considered present. Both are generated based on the noise level of their respective devices and should not use the same value.

[0109] One approach is to first calculate the mean and standard deviation of the effective values ​​of each zero-sequence quantity within the baseline window. Then, take the larger of the sum of the mean and several times the standard deviation, and a certain proportion of the rated value, as the corresponding zero-sequence quantity threshold. Taking the larger of the two allows for necessary margins even at low noise levels, preventing frequent misjudgments due to an excessively small threshold.

[0110] Step 306: In the diagnostic window, when the zero-sequence current of the first protection device is lower than the first zero-sequence current threshold, the first protection device is determined to be in a state of zero-sequence current deficiency; when the zero-sequence voltage of the first protection device is higher than the zero-sequence voltage threshold, the first protection device is determined to be in a state of self-generated zero-sequence voltage presence; and when the zero-sequence current of the second protection device is higher than the second zero-sequence current threshold, the second protection device is determined to have zero-sequence current presence; when the first protection device is in a state of zero-sequence current deficiency and self-generated zero-sequence voltage presence, and the second protection device has zero-sequence current presence, a suspected open circuit is determined, and a first diagnostic result is obtained.

[0111] The above comparison can be based on the effective values ​​of each electrical quantity within the diagnostic window. That is, first calculate the effective values ​​of zero-sequence current and zero-sequence voltage within the diagnostic window, and then compare them with the corresponding thresholds.

[0112] Furthermore, to avoid misjudgments caused by instantaneous glitches and transient interference, the above states can be further subject to duration and time overlap requirements: the duration for which the zero-sequence current of the first protection device is lower than the first zero-sequence current threshold is at least one cycle, in order to determine a zero-sequence current deficiency state; the time period for which the self-generated zero-sequence voltage of the first protection device is higher than the zero-sequence voltage threshold should overlap with the diagnostic window, in order to determine a self-generated zero-sequence voltage presence state. This ensures that the deficiency of zero-sequence current and the appearance of ground fault characteristics occur within the same time period, and that the two have a corresponding relationship.

[0113] Furthermore, in addition to the three conditions mentioned above, a zero-sequence current ratio condition can be added. That is, a suspected open circuit is determined only when the ratio of the effective value of the zero-sequence current of the first protection device to the effective value of the zero-sequence current of the second protection device is lower than a preset ratio. It should be noted that the aforementioned three conditions are all absolute limit-exceeding criteria, and their thresholds are generated based on the noise level of each device, reflecting the inherent fluctuation level of the device and failing to reflect the zero-sequence intensity of the current fault. Therefore, when the ground fault is relatively minor, even if the first protection device has some transmission loss, its residual zero-sequence current may still be higher than the absolute threshold and not be detected. Conversely, when the fault is more severe, the opposite occurs, causing the sensitivity of the criteria to drift with the fault intensity. Introducing the ratio condition, using the zero-sequence current of the second protection device as the denominator, is equivalent to automatically normalizing the criteria according to the actual zero-sequence intensity of the current fault, ensuring that the first-level diagnosis maintains consistent sensitivity under different fault intensities.

[0114] The first diagnostic result can include two scenarios: suspected open circuit and no suspected open circuit. When all the above conditions are met simultaneously, the first diagnostic result is determined to be a suspected open circuit; when any one of the conditions is not met, the first diagnostic result is determined to be no suspected open circuit. For example, if the zero-sequence current of the first protection device is below the threshold, but its self-generated zero-sequence voltage does not exceed the limit and the second protection device does not detect zero-sequence current, it indicates that the system itself does not have a zero-sequence component during that period, which is a normal situation and should be determined as no suspected open circuit.

[0115] Step 307: Correlate the analog quantity channels representing the same physical quantity in the first and third recorded waveform signals to obtain multiple channel pairs.

[0116] The channel pair can be used to represent the correspondence between an analog channel in the first recorded waveform signal and an analog channel in the third recorded waveform signal that represents the same physical quantity.

[0117] Understandably, this step addresses the question of which waveform to compare with which other waveform. The channel mapping in the previous step solved the problem of channel classification, that is, classifying the channels of each recorded signal into a standard category; while this step, based on this, links the channels of the same category in the two recorded signals in pairs, thereby determining the calculation objects for subsequent channel-by-channel difference calculations.

[0118] As one approach, the association can be established based on two dimensions: phase and electrical quantity type. That is, the A-phase current channels and A-phase voltage channels in the two recorded signals are associated with each other, and the other phases are associated in the same way. If both recorded signals have a dedicated zero-sequence current channel, then the dedicated channel is associated together and included in the comparison range. If one of the recorded signals lacks a dedicated zero-sequence channel, then the zero-sequence current can be synthesized from its three-phase currents and then associated.

[0119] Step 308: Within the diagnostic window, calculate the difference data between the two analog channels in each channel pair, and calculate the difference degree of the channel pair based on the difference data; wherein, the difference data includes at least waveform residual difference, correlation coefficient difference, fundamental phasor difference, and zero-sequence reconstruction difference; when the difference degree of the voltage channel pair is lower than the preset consistency threshold, and the difference degree of the current channel pair or the zero-sequence current channel pair is higher than the preset inconsistency threshold, it is determined that there is a suspected disconnection, and a second diagnostic result is obtained.

[0120] Among them, waveform residual difference can be used to reflect the overall amplitude deviation of the sampled waveforms of the two channels; correlation coefficient difference can be used to reflect whether the waveform shapes of the two channels are consistent, and can identify waveform distortion, phase loss and phase drift; fundamental phasor difference can be used to reflect the amplitude difference and phase angle difference of the fundamental component at the same time, which is suitable for comparison of power frequency fault recordings; zero sequence reconstruction difference can be used to reflect the consistency of the zero sequence quantity obtained by the synthesis of the three-phase currents of the two protection devices.

[0121] It should be noted that the above four types of difference data describe waveform differences from four perspectives: amplitude, shape, phasor, and zero-sequence synthesis results. Each type has a different focus, but together they constitute a complete characterization of waveform consistency. In actual implementation, three or more types of difference data can be selected based on the device's recording accuracy, and the difference degree of the channel pair can be obtained through weighted synthesis. For voltage channel pairs, since they do not involve the synthesis of zero-sequence current, the zero-sequence reconstruction difference term can be excluded, and the weights of the remaining terms can be normalized.

[0122] Among them, the preset consistency threshold can be used to determine whether the waveform of the voltage channel pair is sufficient to be considered consistent, and the preset inconsistency threshold can be used to determine whether the waveform of the current channel pair or the zero-sequence current channel pair is sufficient to be considered inconsistent.

[0123] Understandably, the reason why this step requires the voltage channels to be consistent while the current channels are inconsistent is because: a small difference in the voltage channels indicates that the two recorded signals have been reliably aligned within the diagnostic window and that the voltage response at the primary system level is the same, thus eliminating the two types of interference factors: alignment error and common anomaly; under this premise, a significant difference in the current channel or the zero-sequence current channel can only be caused by the current loop itself, and therefore corresponds to an abnormality in the CT secondary circuit.

[0124] Furthermore, to improve the reliability of the conclusion, the following conditions can be added: only one of the first and third protection devices shows an abnormally small zero-sequence current, while the other protection device and the second protection device both have normal zero-sequence current responses; and the duration of the difference is not less than one cycle, with the difference period overlapping with the diagnostic window.

[0125] The second diagnostic result can include two scenarios: suspected disconnection and no suspected disconnection. When the above conditions are met, the second diagnostic result is determined to be suspected disconnection. When the difference between the voltage channels is not lower than the preset consistency threshold, it indicates that the two recorded waveforms have not been reliably aligned or that there are other common anomalies. In this case, the difference should not be attributed to a CT neutral line disconnection, and it should be determined that there is no suspected disconnection.

[0126] Furthermore, if the second diagnostic result indicates a suspected open circuit, the zero-sequence currents of the first and third protection devices can be compared. The CT secondary circuit corresponding to the device with the significantly smaller zero-sequence current can be identified as the suspected open circuit side. For example, if the zero-sequence current of the first protection device is significantly smaller than that of the third protection device, and the zero-sequence responses of the third and second protection devices are consistent, then the CT neutral circuit corresponding to the first protection device is identified as the suspected open circuit side; conversely, the CT neutral circuit corresponding to the third protection device is identified as the suspected open circuit side.

[0127] Step 309: Generate a first confidence level based on the zero-sequence voltage over-limit intensity, reference zero-sequence current response intensity, and zero-sequence current missing degree in the first diagnostic result; generate a second confidence level based on the voltage channel consistency, current channel difference intensity, and zero-sequence reconstruction difference intensity in the second diagnostic result; determine the smaller value between the first confidence level and the second confidence level, and obtain a fusion score by weighted summation of the first confidence level, the second confidence level, and the smaller value.

[0128] Among them, the zero-sequence voltage over-limit intensity can be used to indicate the degree to which the self-generated zero-sequence voltage of the first protection device exceeds its threshold; the reference zero-sequence current response intensity can be used to indicate the degree to which the zero-sequence current of the second protection device exceeds its threshold; and the zero-sequence current missing degree can be used to indicate the degree to which the zero-sequence current of the first protection device is smaller than the reference zero-sequence current. All of the above quantities can be normalized to the interval between 0 and 1 and then weighted and summed to obtain the first confidence level.

[0129] Among them, voltage path consistency can be used to indicate the degree to which the difference between voltage path pairs is below the consistency threshold; current path difference intensity can be used to indicate the degree to which the difference between current path pairs exceeds the inconsistency threshold; and zero-sequence reconstruction difference intensity can be used to indicate the significance of the difference between the synthesized zero-sequence quantities of the two protection devices. All of the above quantities are also normalized and then weighted and summed to obtain the second confidence level.

[0130] Furthermore, when generating the second confidence level, the factor of whether the difference direction can be located to the same set of protection devices or the same CT secondary circuit can also be taken into account: when the first diagnostic result and the second diagnostic result point to the same suspected broken wire side, this factor takes a larger value; otherwise, it takes a smaller value.

[0131] It's important to note that the smaller of the first and second confidence levels is included in the weighted summation. This serves to reflect the degree of mutual corroboration between the two diagnostic results. Understandably, if only one diagnosis provides a high confidence level while the other has a low confidence level, this smaller value will also be low, suppressing the fusion score. Only when both diagnoses provide high confidence levels will this smaller value be high, significantly improving the fusion score. Thus, the two diagnoses form a mutually constraining relationship in the fusion process, rather than being a simple logical addition, thereby suppressing misjudgments caused by occasional anomalies in a single diagnostic chain.

[0132] Step 310: When the fusion score is not lower than the first threshold and the first diagnostic result and the second diagnostic result point to the same current transformer secondary circuit, it is determined that the neutral line of the current transformer is broken, and the target diagnostic result is obtained.

[0133] The first threshold can be used to represent the fusion score level required to confirm the disconnection conclusion.

[0134] It should be noted that, in addition to the fusion score, this step also requires that the two diagnostic results point to the same current transformer secondary circuit. This is because: the fusion score reflects the strength of each of the two diagnoses, while the consistency of the points of reference reflects the correspondence between the two in spatial location; only when the two types of evidence are both strong enough and point to the same circuit can it be determined that there is indeed a neutral wire break in the circuit.

[0135] Furthermore, in addition to the aforementioned confirmed disconnection scenario, other branches can be set to cover different judgment results: when the fusion score is between the second and first thresholds, or when the first and second diagnostic results are only partially consistent, the target diagnostic result can be determined as a high risk of neutral line disconnection in the current transformer, and a verification prompt can be output; when the fusion score is below the second threshold, or when the voltage channels of the first and third waveform signals are inconsistent and cannot be reliably aligned, a disconnection conclusion can be left unoutput, only the current event can be recorded, and a prompt indicating insufficient waveform quality can be given if necessary. The second threshold is less than the first threshold.

[0136] Furthermore, if the target diagnostic result is determined to be a broken neutral line of the current transformer, a clear alarm can be generated, along with the suspected broken side, the waveform signal number on which it is based, and key difference indicators, so that maintenance personnel can trace the basis for diagnosis. If it is determined to be a high-risk case, a verification alarm can be generated, prompting on-site confirmation in conjunction with terminal block inspection, secondary circuit insulation inspection, and protection sampling inspection.

[0137] In the above technical solution, by determining the fault triggering conditions before acquiring the waveform signal, the diagnosis is carried out during the period when the system is most likely to generate zero-sequence components and expose potential open circuit hazards. Through preprocessing such as channel mapping, time alignment, window division, value normalization, and sampling rate unification, waveform signals from devices from different manufacturers and models are made comparable in the same coordinate system, laying the foundation for subsequent zero-sequence quantity calculation and waveform comparison. By adaptively generating thresholds based on the noise level of the reference window, the criteria can adapt to the inherent fluctuation levels of different devices, avoiding the problem of difficulty in balancing sensitivity and reliability with fixed thresholds. By decomposing waveform differences into four dimensions—amplitude, shape, phasor, and zero-sequence synthesis—and weighting them to form a difference degree, waveform consistency can be quantitatively expressed, and anomalies can be attributed to the current loop based on the distribution characteristics of voltage and current channel differences. By introducing the smaller value of two confidence levels into the fusion score, the two diagnoses form a mutually corroborating and mutually constraining relationship, suppressing misjudgments caused by accidental anomalies in a single diagnostic chain. Thus, while improving the accuracy of CT neutral line breakage identification, it also enables the hierarchical output of location and diagnostic conclusions for suspected breakage sides, providing a clear direction for on-site investigation and further enhancing the safety and reliability of secondary circuit operation.

[0138] To better illustrate the technical solution of this embodiment, an exemplary description is provided below. In an exemplary embodiment, a fault diagnosis method for a protection device is provided, which can be applied to the diagnosis of potential neutral line breakage in the secondary circuit of the CT of the protected objects such as the main transformer and generator motor in a pumped storage power station.

[0139] First, triggering conditions include ground faults outside the power grid area, ground faults in other bays within the substation, or bus grounding disturbances. This automatically retrieves fault waveform files from the protection device to be diagnosed and from dual protection devices protecting the same object. At least the waveform file of the protection device to be diagnosed is retrieved; when dual protection devices (A and B) exist, synchronous waveform files of both devices under the same fault are retrieved simultaneously; and waveform files from other bay protection devices within the substation are retrieved as reference data. After channel naming normalization, sampling rate unification, time alignment, rated value normalization, and fundamental phasor extraction, the waveform files are respectively entered into the zero-sequence electrical quantity characteristic diagnosis stage and the dual-protection waveform consistency diagnosis stage.

[0140] Secondly, data preprocessing is performed. Different manufacturers' recording channels are uniformly mapped to standard channels such as Ia, Ib, Ic, Ua, Ub, Uc, 3I0, and 3U0. Missing 3I0 or 3U0 channels are calculated by self-generated three-phase quantities. The protection start-up flag, the starting point of the sudden change, or the cross-correlation peak value of the voltage channel are used as the alignment benchmark, and the fault start time of different recording files is unified as t0. The 3 to 5 cycles before the fault are taken as the reference window W0, and the 2 to 6 cycles after the fault, avoiding the initial transient peak, are taken as the diagnostic window Wf. The primary value or per-unit value is converted according to the CT / PT ratio, rated current In, rated voltage Un, polarity configuration, and sampling rate. The mapping relationship between Ia, Ib, Ic, Ua, Ub, and Uc of protection set A and protection set B is established one by one. If a dedicated 3I0 channel exists, it is included in the comparison. The recordings of the two sets of protection are resampled to the same sampling rate to ensure that the samples correspond one-to-one at the same time. If the phase of the three-phase voltage channel is reversed as a whole, it is marked as an abnormal configuration and is not directly used as evidence of CT neutral line breakage.

[0141] The first level of diagnosis is used to confirm whether an external or other interval fault has generated a zero-sequence component, but the protection device under diagnosis is not correctly reflecting the zero-sequence current. The self-generated zero-sequence current and self-generated zero-sequence voltage of the protection device under diagnosis are calculated:

[0142] 3I0_self(t)=Ia(t)+Ib(t)+Ic(t);

[0143] 3U0_self(t)=Ua(t)+Ub(t)+Uc(t);

[0144] Calculate the self-generated zero-sequence current of other reference protection devices k within the station:

[0145] 3I0_ref,k(t)=Ia,k(t)+Ib,k(t)+Ic,k(t).

[0146] The effective values ​​of each electrical quantity are calculated within the diagnostic window Wf, and a threshold is adaptively generated based on the noise level of the pre-fault reference window W0.

[0147] I0_self = RMS(3I0_self, Wf);

[0148] U0_self = RMS(3U0_self, Wf);

[0149] I0_ref=max_kRMS(3I0_ref,k,Wf);

[0150] Ith_self=max(0.02In,mean(RMS(3I0_self,W0))+4σI);

[0151] Uth_self=max(0.02Un,mean(RMS(3U0_self,W0))+4σU);

[0152] where In is the rated current, Un is the rated voltage, and σI and σU are respectively the standard deviations of the zero-sequence current RMS value and the zero-sequence voltage RMS value within the reference window.

[0153] When the following four conditions are satisfied simultaneously, the first diagnosis result R1 is set to: suspected CT neutral line disconnection:

[0154] (1) I0_self<Ith_self, and the duration is no less than 1 cycle, indicating that the protection device to be diagnosed has not detected a valid zero-sequence current;

[0155] (2) U0_self>Uth_self, and it overlaps with the fault period Wf, indicating that self-generated zero-sequence voltage exists in the same fault period, which shows that the system has the characteristics of a ground fault;

[0156] (3) I0_ref>max(0.05In,Ith_ref), indicating that other protection devices in the station have detected zero-sequence current, which excludes the case where there is no zero-sequence component in the system;

[0157] (4) I0_self / (I0_ref+ε)<0.15, indicating that the zero-sequence current of the protection device to be diagnosed is abnormally small relative to the reference value in the station; where ε is a small quantity for preventing division by zero.

[0158] The above criterion completes cross verification through the ternary relationship of zero-sequence missing of this protection, existence of self-generated zero-sequence voltage, and existence of zero-sequence response of other bays, which can be distinguished from the traditional judgment made only based on the over-limit or missing of a single 3I0.

[0159] The second-level diagnosis is used to confirm whether the analog quantity responses of the two sets of protections A and B for the same protected object under the same fault are consistent. Its core is to comprehensively quantify the waveform residual, correlation, fundamental phasor and zero-sequence reconstruction result of each analog channel within the same diagnosis window. For each analog channel c, at least the following four types of indicators are calculated in the diagnosis window Wf. In actual implementation, more than three of the indicators can be selected according to the recording accuracy of the device to form a comprehensive difference degree:

[0160] Waveform residual difference DE: DE(c)=RMS(xA,c−xB,c) / (RMS(xA,c)+RMS(xB,c)+ε), which reflects the overall amplitude deviation of the sampled waveforms of the same channel of the two sets of protections;

[0161] Correlation coefficient difference DC: DC(c)=1−corr(xA,c,xB,c), which reflects whether the waveform shapes are consistent, and can identify distortion, phase loss and phase drift;

[0162] Fundamental phasor difference DP: DP(c) = α × ||XA,c| − |XB,c|| / max(|XA,c|,|XB,c|,ε) + β × |∠XA,c − ∠XB,c| / π, which considers both the fundamental amplitude difference and the phase angle difference, and is suitable for recording power frequency faults; where α and β are the weights of the amplitude difference and the phase angle difference, and it is recommended to take α = 0.6 and β = 0.4;

[0163] The formula for calculating the zero-order reconstruction difference D0 is as follows:

[0164] D0=|RMS(3I0_A)−RMS(3I0_B)| / max(RMS(3I0_A),RMS(3I0_B),ε), can be used to reflect the consistency of the combined zero-sequence quantity of the three-phase current of the two sets of protection.

[0165] A comprehensive degree of difference is established for each current channel or zero-sequence channel:

[0166] D(c)=0.35×DE(c)+0.25×DC(c)+0.25×DP(c)+0.15×D0.

[0167] When the channel is a three-phase voltage channel, the D0 term can be excluded and the remaining weights can be normalized.

[0168] The second diagnostic result R2 is set to: suspected CT neutral line breakage when the following conditions are met:

[0169] (1) The average comprehensive difference of voltage channels D_U_avg<0.05 indicates that the recording times of the two sets of protection are aligned and the voltage response is consistent;

[0170] (2) If the comprehensive difference degree D_I0 or D_I_avg of the three-phase current channel or the zero-sequence current channel is greater than 0.30, it indicates that there is an abnormal inconsistency in the current quantity;

[0171] (3) Of the two sets of protection, A and B, only one set satisfies the abnormally small 3I0, while the other set of protection and the reference protection in the station have a normal zero-sequence current response;

[0172] (4) The duration of the difference is not less than one cycle, and the difference period overlaps with the fault diagnosis window Wf.

[0173] If the I0_A of protection set A is significantly smaller than the I0_B of protection set B, and the zero-sequence response of protection set B is consistent with that of the reference protection within the station, then the neutral line circuit of the CT corresponding to protection set A will be positioned as the suspected open circuit side; the opposite is also true.

[0174] In this embodiment, the first and second diagnostics are designed as a mutually constrained fusion algorithm. The first diagnostic answers whether the system has a zero-sequence fault background and whether the zero-sequence current of this protection is abnormally missing. The second diagnostic answers whether there is a difference in current between the two sets of protections under the same fault and whether the difference points to the same suspected circuit.

[0175] Define the first diagnostic confidence level S1:

[0176] S1=0.35×A_U0+0.35×A_ref+0.30×A_loss.

[0177] Where A_U0 represents the self-generated zero-sequence voltage over-limit intensity, A_ref represents the substation reference zero-sequence current response intensity, and A_loss represents the degree of zero-sequence current loss of the protection device to be diagnosed. All three are normalized to 0 to 1.

[0178] A_U0=min(1,U0_self / (2×Uth_self));

[0179] A_ref=min(1,I0_ref / (2×Ith_ref));

[0180] A_loss=min(1,1−I0_self / (I0_ref+ε)).

[0181] Define the second diagnostic confidence level S2:

[0182] S2=0.40×A_D0+0.30×A_DI+0.20×A_Ucons+0.10×A_side.

[0183] Where A_D0 represents the zero-sequence reconfiguration difference intensity, A_DI represents the comprehensive difference intensity of the current path, A_Ucons represents the voltage path consistency, and A_side represents whether the difference direction can be located to the same set of protection or the same CT secondary circuit:

[0184] A_D0=min(1,D0 / 0.30);

[0185] A_DI=min(1,D_I_avg / 0.30);

[0186] A_Ucons=max(0,1−D_U_avg / 0.05);

[0187] A_side=1 when R1 and R2 point to the same suspected broken side; otherwise A_side=0.

[0188] The final fusion score S is:

[0189] S=0.45×S1+0.45×S2+0.10×min(S1,S2).

[0190] Among them, min(S1,S2) is used to reflect the degree of mutual corroboration between the two types of diagnostic results.

[0191] The final determination rules are as follows:

[0192] When S≥0.80, and R1 and R2 point to the same protection device or the same CT secondary circuit, it is determined that the CT neutral line is broken, a clear alarm is generated, and the suspected broken side, fault waveform number and key difference indicators are output.

[0193] When 0.60≤S<0.80, or R1 and R2 are only partially consistent, it is judged as a high risk of CT neutral line disconnection, and a verification alarm is generated. It is recommended to confirm by combining terminal block inspection, secondary circuit insulation inspection and protection sampling inspection.

[0194] When S < 0.60, or when the voltage channels are inconsistent and cannot be reliably aligned, the CT neutral line is not considered to be broken. The event is recorded but no breakage conclusion is output. If necessary, the recording quality is indicated as insufficient.

[0195] Following an external grounding fault at a pumped storage power station, multiple protection devices within the station generated fault recordings. The system read the recordings of protection device A (to be diagnosed), protection device B (for the same protected object), and other reference protection recordings for other bays, and performed time alignment and channel normalization. Calculations showed that protection device A's I0_self was below the adaptive threshold Ith_self for more than one cycle within the fault window, and its self-generated zero-sequence voltage U0_self exceeded Uth_self. Simultaneously, the I0_ref of other protection bays within the station significantly exceeded the reference threshold, thus meeting the first diagnostic condition.

[0196] Further consistency comparison was performed on the synchronous waveforms of protection systems A and B. The average comprehensive difference of voltage channels Ua, Ub, and Uc was less than 0.05, indicating that the two waveforms were aligned and had consistent voltage responses during the fault period. However, the difference D0 between the three-phase current composite zero-sequence quantity of system A and system B was greater than 0.30, and the 3I0 of system A was significantly smaller than that of system B. Combining the conclusion of missing zero-sequence current in system A in the first diagnosis, the fusion score S reached above 0.80, and the final diagnostic result of suspected open circuit in the neutral line circuit of the CT corresponding to protection system A was output.

[0197] In this example, the first diagnosis provides evidence of the system's zero-sequence fault background and the lack of zero-sequence in this protection, while the second diagnosis provides evidence of the differences between the two sets of protection waveforms and the location of the suspected disconnection side. The two are cross-verified by the same fault time period and the same disconnection side, thereby achieving accurate diagnosis of the potential CT neutral line disconnection.

[0198] It should be understood that although the steps in the flowcharts of the above embodiments are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the above embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages in other steps. It is understood that the steps in different embodiments can be freely combined as needed, and all non-contradictory solutions formed by such combinations are within the scope of protection of this application.

[0199] In other embodiments, this application proposes a fault diagnosis device for a protection device, please refer to... Figure 3 The fault diagnosis device for the protection device includes:

[0200] The data acquisition module is used to acquire waveform signals during the same suspected fault period; wherein, the waveform signals include the first waveform signal of the first protection device to be diagnosed, the second waveform signal of the second protection device as a reference protection device, and the third waveform signal of the third protection device that has the same protection object as the first protection device.

[0201] The first comparison module is used to determine whether the first protection device is in a state of zero-sequence current deficiency and self-generated zero-sequence voltage existence based on the first recorded waveform signal, and to determine whether the second protection device is in a state of zero-sequence current existence based on the second recorded waveform signal, so as to obtain the first diagnostic result.

[0202] The second comparison module is used to compare the waveforms of the first and third recorded waveforms, determine the consistency of the waveforms, and obtain the second diagnostic result.

[0203] The diagnostic fusion module is used to fuse the first diagnostic result and the second diagnostic result to obtain the target diagnostic result.

[0204] In one exemplary embodiment, the fault diagnosis device for the protection device further includes a preprocessing module, wherein:

[0205] The preprocessing module is used to map the channels of each recorded signal into three-phase current channels and three-phase voltage channels to obtain three-phase current and three-phase voltage, and to synthesize zero-sequence current and zero-sequence voltage according to the three-phase current and three-phase voltage respectively; and to align the fault start time of the recorded signal with the protection start flag, the start point of the sudden change or the cross-correlation peak value of the voltage channel as a reference, and take the first preset number of cycles before the fault start time as the reference window and the second preset number of cycles after the fault start time as the diagnostic window.

[0206] In one exemplary embodiment, the data acquisition module includes a trigger determination unit and a waveform retrieval unit, wherein:

[0207] The trigger determination unit is used to determine any event as the fault triggering condition, including grounding fault outside the power grid area, grounding fault in other intervals within the plant, zero-sequence voltage exceeding the limit of the bus, or zero-sequence current start of any protection device within the station.

[0208] The waveform retrieval unit is used to retrieve the waveform signals of the first protection device, the second protection device and the third protection device during the suspected fault period corresponding to the triggering condition in response to the fault triggering condition, and obtain the first waveform signal, the second waveform signal and the third waveform signal.

[0209] In one exemplary embodiment, the first comparison module includes a threshold generation unit, a state determination unit, and a first result determination unit, wherein:

[0210] The threshold generation unit is used to generate a corresponding zero-sequence threshold based on the noise level of the zero-sequence quantity within the reference window; wherein, the zero-sequence threshold includes the first zero-sequence current threshold and the zero-sequence voltage threshold of the first protection device, and the second zero-sequence current threshold of the second protection device.

[0211] The status determination unit is used to determine, within the diagnostic window, that the first protection device is in a state of zero-sequence current deficiency when the zero-sequence current of the first protection device is lower than the first zero-sequence current threshold; to determine that the first protection device is in a state of self-generated zero-sequence voltage existence when the zero-sequence voltage of the first protection device is higher than the zero-sequence voltage threshold; and to determine that the second protection device has zero-sequence current when the zero-sequence current of the second protection device is higher than the second zero-sequence current threshold.

[0212] The first result determination unit is used to determine the existence of a suspected open circuit and obtain the first diagnostic result when the first protection device has a zero-sequence current deficiency and a self-generated zero-sequence voltage exists, and the second protection device has a zero-sequence current.

[0213] In one exemplary embodiment, the second comparison module includes a channel association unit, a difference calculation unit, and a second result determination unit, wherein:

[0214] The channel association unit is used to associate the analog quantity channels representing the same physical quantity in the first and third recorded waveform signals to obtain multiple channel pairs.

[0215] The difference calculation unit is used to calculate the difference data between the two analog channels in each channel pair within the diagnostic window, and to calculate the difference degree of the channel pair based on the difference data; wherein, the difference data includes at least waveform residual difference, correlation coefficient difference, fundamental phasor difference and zero-sequence reconstruction difference;

[0216] The second result determination unit is used to determine the existence of a suspected disconnection and obtain a second diagnostic result when the difference between voltage channel pairs is lower than a preset consistency threshold and the difference between current channel pairs or zero-sequence current channel pairs is higher than a preset inconsistency threshold.

[0217] In one exemplary embodiment, the diagnostic fusion module includes a first confidence unit, a second confidence unit, a fusion scoring unit, and a disconnection determination unit, wherein:

[0218] The first confidence unit is used to generate a first confidence level based on the zero-sequence voltage over-limit strength, the reference zero-sequence current response strength, and the degree of zero-sequence current missingness in the first diagnostic result.

[0219] The second confidence unit is used to generate a second confidence level based on the voltage channel consistency, current channel difference intensity, and zero-sequence reconstruction difference intensity in the second diagnostic results.

[0220] The fusion scoring unit is used to determine the smaller value between the first confidence level and the second confidence level, and to obtain the fusion score by weighted summation based on the first confidence level, the second confidence level, and the smaller value;

[0221] The disconnection determination unit is used to determine that the neutral line of the current transformer is disconnected when the fusion score is not lower than the first threshold and the first diagnostic result and the second diagnostic result point to the same secondary circuit of the current transformer, and obtain the target diagnostic result.

[0222] In one exemplary embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 4As shown, the computer device includes a processor, memory, input / output interface, communication interface, display unit, and input device. The processor, memory, and input / output interface are connected via a system bus, and the communication interface, display unit, and input device are also connected to the system bus via the input / output interface. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The input / output interface is used for exchanging information between the processor and external devices. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, Near Field Communication (NFC), or other technologies. When the computer program is executed by the processor, it implements a fault diagnosis method for a protection device. The display unit is used to form a visually visible image and can be a display screen, projection device, or virtual reality imaging device. The display screen can be an LCD screen or an e-ink screen. The input device of the computer device can be a touch layer covering the display screen, or buttons, trackballs, or touchpads set on the casing of the computer device, or external keyboards, touchpads, or mice, etc.

[0223] Those skilled in the art will understand that Figure 4 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0224] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, artificial intelligence (AI) processors, etc., and are not limited to these.

[0225] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0226] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A fault diagnosis method for a protection device, characterized in that, The method includes: Acquire waveform signals during the same suspected fault period; wherein, the waveform signals include the first waveform signal of the first protection device to be diagnosed, the second waveform signal of the second protection device as a reference protection device, and the third waveform signal of the third protection device that has the same protection object as the first protection device; Based on the first recorded waveform signal, it is determined whether the first protection device is in a state of zero-sequence current deficiency and self-generated zero-sequence voltage existence, and based on the second recorded waveform signal, it is determined whether the second protection device is in a state of zero-sequence current existence, and a first diagnostic result is obtained. Compare the waveforms of the first recorded waveform signal and the third recorded waveform signal, and determine the consistency of the waveforms to obtain a second diagnostic result; The target diagnostic result is obtained by combining the first diagnostic result and the second diagnostic result.

2. The method according to claim 1, characterized in that, The step of acquiring waveform signals during the same fault period includes: The fault triggering condition is any of the following events: ground fault outside the power grid area, ground fault in other bays within the plant, zero-sequence voltage exceeding the limit on the bus, or zero-sequence current start-up of any protection device within the station. In response to the fault triggering condition, the waveform recording signals of the first protection device, the second protection device, and the third protection device during the suspected fault period corresponding to the triggering condition are retrieved to obtain the first waveform recording signal, the second waveform recording signal, and the third waveform recording signal.

3. The method according to claim 1, characterized in that, After the step of acquiring waveform signals during the same fault period, the method further includes: The channels of each recorded waveform signal are mapped to three-phase current channels and three-phase voltage channels to obtain three-phase current and three-phase voltage, and zero-sequence current and zero-sequence voltage are synthesized according to the three-phase current and the three-phase voltage respectively. Based on the protection start flag, the start point of the sudden change, or the peak value of the cross-correlation of the voltage channel, the fault start time of the recorded waveform signal is aligned, and the first preset number of cycles before the fault start time is taken as the reference window, and the second preset number of cycles after the fault start time is taken as the diagnostic window.

4. The method according to claim 1, characterized in that, The steps of determining whether the first protection device is in a state of zero-sequence current deficiency and self-generated zero-sequence voltage existence based on the first recorded waveform signal, and determining whether the second protection device is in a state of zero-sequence current existence based on the second recorded waveform signal, to obtain the first diagnostic result, include: Based on the noise level of the zero-sequence quantity within the reference window, a corresponding zero-sequence quantity threshold is generated; wherein, the zero-sequence quantity threshold includes the first zero-sequence current threshold and the zero-sequence voltage threshold of the first protection device, and the second zero-sequence current threshold of the second protection device; Within the diagnostic window, when the zero-sequence current of the first protection device is lower than the first zero-sequence current threshold, the first protection device is determined to be in a state of zero-sequence current deficiency; when the zero-sequence voltage of the first protection device is higher than the zero-sequence voltage threshold, the first protection device is determined to be in a state of self-generated zero-sequence voltage presence. And, when the zero-sequence current of the second protection device is higher than the second zero-sequence current threshold, it is determined that the second protection device has the zero-sequence current; When the first protection device has zero-sequence current deficiency and self-generated zero-sequence voltage exists, and the second protection device has zero-sequence current, it is determined that there is a suspected open circuit, and the first diagnostic result is obtained.

5. The method according to claim 1, characterized in that, The step of comparing the waveforms of the first recorded waveform signal and the third recorded waveform signal, and determining the consistency of the waveforms to obtain the second diagnostic result includes: By associating the analog quantity channels representing the same physical quantity in the first and third recorded waveform signals, multiple channel pairs are obtained. Within the diagnostic window, the difference data between the two analog channels in each channel pair is calculated, and the difference degree of the channel pair is calculated based on the difference data; wherein, the difference data includes at least waveform residual difference, correlation coefficient difference, fundamental phasor difference, and zero-sequence reconstruction difference; When the difference between voltage channel pairs is lower than the preset consistency threshold, and the difference between current channel pairs or zero-sequence current channel pairs is higher than the preset inconsistency threshold, a suspected disconnection is determined, and a second diagnostic result is obtained.

6. The method according to claim 1, characterized in that, The step of fusing the first diagnostic result and the second diagnostic result to obtain the target diagnostic result includes: Based on the zero-sequence voltage over-limit strength, the reference zero-sequence current response strength, and the degree of zero-sequence current missingness in the first diagnostic result, a first confidence level is generated. A second confidence level is generated based on the voltage channel consistency, current channel difference intensity, and zero-sequence reconstruction difference intensity in the second diagnostic results. The smaller of the first confidence level and the second confidence level is determined, and a weighted sum is obtained based on the first confidence level, the second confidence level, and the smaller value to obtain the fusion score; When the fusion score is not lower than the first threshold, and the first diagnostic result and the second diagnostic result point to the same current transformer secondary circuit, it is determined that the neutral line of the current transformer is broken, and the target diagnostic result is obtained.

7. A fault diagnosis device for a protection device, characterized in that, The device includes: The data acquisition module is used to acquire waveform signals during the same fault period; wherein, the waveform signals include the first waveform signal of the first protection device to be diagnosed, the second waveform signal of the second protection device as a reference protection device, and the third waveform signal of the third protection device that has the same protection object as the first protection device. The first comparison module is used to determine whether the first protection device is in a state of zero-sequence current deficiency and self-generated zero-sequence voltage existence based on the first recorded waveform signal, and to determine whether the second protection device is in a state of zero-sequence current existence based on the second recorded waveform signal, so as to obtain a first diagnostic result. The second comparison module is used to compare the waveforms of the first recorded waveform signal and the third recorded waveform signal, and to determine the consistency of the waveforms to obtain a second diagnostic result. The diagnostic fusion module is used to fuse the first diagnostic result and the second diagnostic result to obtain the target diagnostic result.

8. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the fault diagnosis method for the protection device according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

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