Flexible grounding distribution network single-phase grounding fault direction detection method, device and medium

Abstract

The present application discloses a method, device and medium for detecting the direction of single-phase grounding faults in a flexible grounding distribution network, which relates to the technical field of distribution network fault detection and protection. The method of the present application includes: obtaining and analyzing the distribution characteristics of zero-sequence voltage and zero-sequence current at each detection point when a single-phase grounding fault occurs in the flexible grounding distribution network; constructing a zero-sequence voltage-zero-sequence current distribution area map of healthy lines and upstream and downstream sections of the fault point before and after the parallel small resistor is put into operation; and determining the direction of the grounding fault point relative to the detection point according to the distribution differences of the zero-sequence voltage and zero-sequence current at each detection point in the area map. This method utilizes the fault information throughout the process before and after the parallel small resistor is put into the neutral point, and when the grounding resistance is large, by setting the inflection point voltage and the minimum operating current, it overcomes the problems of weak zero-sequence voltage signal and inaccurate measurement of the mutual inductor, and improves the reliability of the protection discrimination result during high-resistance grounding.

Description

Technical Field

[0001] The present application relates to the technology of distribution network fault detection and protection. More specifically, it relates to a method, device and medium for detecting the direction of single-phase grounding faults in a flexible grounding distribution network. Background Technique

[0002] The basic idea of the flexible grounding method is to rely on the arc suppression coil to compensate for the fault current in the initial stage of the grounding fault to eliminate instantaneous faults; when the fault lasts for a certain period of time and is determined to be a permanent grounding fault, a parallel small resistor is put into operation through a switching device to start the zero-sequence overcurrent protection of the line to cut off the faulty line or faulty section.

[0003] At present, regarding the grounding fault protection and treatment of flexible grounding distribution networks, only relevant regulations give the basic process, and there is still a lack of in-depth systematic analysis of fault characteristics and protection schemes. On-site protection mostly directly uses the traditional zero-sequence overcurrent protection in small-resistor grounded distribution networks. On the one hand, this protection method also faces the problem of protection refusal in the case of high-resistance grounding faults in flexible grounding distribution networks. On the other hand, the single-phase grounding fault characteristics of flexible grounding systems are significantly different from those of resonant grounding systems and small-resistor grounding systems, and the understanding of them is not clear. The traditional zero-sequence overcurrent protection only uses the fault information after the small resistor is put into operation and insufficiently utilizes the fault characteristics under the arc suppression coil grounding method before the small resistor is put into operation. Therefore, there is still great room for improvement in the performance of the detection and protection methods for grounding faults in flexible grounding distribution networks.

[0004] The control method of the arc suppression coil in parallel with a medium resistor is similar to the flexible grounding method. It uses the difference in the zero-sequence current amplitude or active component before and after the medium resistor is put into operation to detect the faulty line, but its fault characteristics are quite different from those when a parallel small resistor is used, and the protection method is not applicable to flexible grounding distribution networks. Therefore, it is urgent to analyze the single-phase grounding fault characteristics of the distribution network under the flexible grounding method, study new protection methods, and improve the sensitivity of protection in the case of high-resistance grounding. Summary of the Invention

[0005] In view of this, in order to solve or improve the problem that the existing protection methods are not applicable to flexible grounding distribution networks, the present application proposes a method, device and medium for detecting the direction of single-phase grounding faults in a flexible grounding distribution network.

[0006] To achieve the above object, the present application provides a method for detecting the direction of single-phase grounding faults in a flexible grounding distribution network, including: acquiring and analyzing the distribution characteristics of zero-sequence voltage and zero-sequence current at each detection point when a single-phase grounding fault occurs in the flexible grounding distribution network; constructing a zero-sequence voltage-zero-sequence current distribution area map of healthy lines and the upstream and downstream sections of the fault point before and after the parallel small resistor is put into operation; and determining the direction of the grounding fault point relative to the detection point according to the distribution difference of the zero-sequence voltage and zero-sequence current at each detection point in the area map.

[0007] Preferably, when obtaining and analyzing the distribution characteristics of zero-sequence voltage and zero-sequence current at each detection point during a single-phase grounding fault in a flexible grounded distribution network, it includes: measuring the effective value of zero-sequence voltage and the effective value of zero-sequence current at the detection point in the current cycle; calculating the zero-sequence impedance and saving the zero-sequence impedance.

[0008] Preferably, the calculation formula for the zero-sequence impedance is: zero-sequence impedance = effective value of zero-sequence voltage / effective value of zero-sequence current.

[0009] Preferably, determining the direction of the grounding fault point relative to the detection point according to the distribution differences of zero-sequence voltage and zero-sequence current at each detection point in the regional map includes: if the zero-sequence voltage measured at the detection point is greater than or equal to the starting voltage and the zero-sequence impedance is less than or equal to the setting value; or, the zero-sequence voltage measured at the detection point is less than the starting voltage but greater than or equal to the inflection point voltage and the zero-sequence impedance is less than or equal to the setting value; or, the zero-sequence voltage measured at the detection point is less than the inflection point voltage and three times the zero-sequence current is greater than the minimum operating current; then it is determined that the fault location is downstream of the detection point; if none of the above three conditions are met, it is determined that the detection point is downstream of the fault point on the faulty line or on a sound line.

[0010] Preferably, if it is determined that the fault location is downstream of the detection point, upload the fault information and wait for an action instruction or trip with a time delay to cut off the fault; if it is determined that the detection point is downstream of the fault point on the faulty line or on a sound line, the protection returns.

[0011] Preferably, the starting voltage is set greater than the maximum unbalanced voltage of the resonant grounding system, that is, the starting voltage is not less than 866V.

[0012] Preferably, the minimum operating current is set according to the measurement accuracy of the zero-sequence current transformer and the expected withstand transition resistance value; among them, the minimum operating current is greater than 1 ampere.

[0013] Preferably, the inflection point voltage is set according to the minimum operating current, that is: where U 0g is the inflection point voltage, I act is the minimum operating current, Z is the zero-sequence capacitive reactance of a single line to the ground, and Z is not less than 636.1 ohms.

[0014] This application also provides a device for detecting the direction of a single-phase grounding fault in a flexible grounded distribution network, including: a first unit for obtaining and analyzing the distribution characteristics of zero-sequence voltage and zero-sequence current at each detection point during a single-phase grounding fault in a flexible grounded distribution network; a second unit for constructing a zero-sequence voltage-zero-sequence current distribution regional map of the sound line and the sections upstream and downstream of the fault point before and after the parallel small resistor is put into operation; a third unit for determining the direction of the grounding fault point relative to the detection point according to the distribution differences of zero-sequence voltage and zero-sequence current at each detection point in the regional map.

[0015] The present application also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to execute any one of the above-mentioned single-phase grounding fault direction detections in a flexible grounding distribution network.

[0016] Beneficial effects

[0017] Compared with the prior art, the advantages of the present technical solution are as follows: the method of the present application utilizes the fault information throughout the process before and after the parallel resistor is inserted, as well as the differences in the distribution laws of zero-sequence voltages and zero-sequence currents upstream and downstream of the fault point, and can effectively identify the direction of the detection point relative to the grounding fault point, improving the reliability of the grounding protection in the flexible grounding distribution network; at the same time, by setting the minimum operating current and the inflection point voltage, the problem of insufficient accuracy of the zero-sequence voltage transformer during high-resistance grounding faults is effectively avoided, and the ability to withstand transition resistors is significantly improved compared with the traditional zero-sequence overcurrent protection method; in addition, this method has self-sufficiency, that is, the device can determine whether a fault occurs and the fault direction only by using its own measurement information, and line section protection can be achieved; for lines with a distribution network automation system, the terminal only needs to upload the relative position information between the detection point and the grounding fault point, the communication pressure is small, the cooperation is convenient, and precise synchronous timekeeping is not required between terminals; for distribution lines without communication conditions, the fault can be removed by means of multi-stage protection time delay cooperation or fault indicators can be installed to improve the line patrol efficiency; the present invention is easy to be put into engineering practice and can further improve the safe and stable operation level of the medium-voltage distribution network. Description of the drawings

[0018] Figure 1 is a schematic diagram of the single-phase grounding fault direction detection method for a flexible grounding distribution network of the present application;

[0019] Figure 2 is a flow chart for discriminating the grounding fault direction of a flexible grounding distribution network in an embodiment of the present application;

[0020] Figure 3 is a schematic diagram of a simulation model in an embodiment of the present application;

[0021] Figure 4 is the simulated waveforms of zero-sequence voltage and zero-sequence current at the detection point in an embodiment of the present application Figure 1 ;

[0022] Figure 5 is the second set of simulated waveforms of zero-sequence voltage and zero-sequence current at the detection point in an embodiment of the present application;

[0023] Figure 6 is a schematic diagram of the single-phase grounding fault direction detection device for a flexible grounding distribution network of the present application.

[0024] Main reference signs in the figures; 1, the first unit; 2, the second unit; 3, the third unit. Detailed implementation manners

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0026] It should be understood that when used in this specification and the appended claims, the terms "comprises" and "comprising" indicate the presence of the described features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or their groups.

[0027] It should also be understood that the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0028] It should be further understood that the term " / and / " used in the specification of the present invention and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0029] As Figure 1 shown, in view of the problems of the lack of a dedicated protection scheme for the current flexible grounding (arc suppression coil shunted with a small resistor grounding) distribution network and the low level of fault detection and protection, the embodiments of the present application provide a method for detecting the direction of a single-phase grounding fault in a flexible grounding distribution network, including:

[0030] S110. Obtain and analyze the distribution characteristics of zero-sequence voltage and zero-sequence current at each detection point when a single-phase grounding fault occurs in the flexible grounding distribution network;

[0031] S120. Construct a zero-sequence voltage-zero-sequence current distribution area map for the healthy lines and the upstream and downstream sections of the fault point before and after the shunted small resistor is put into operation;

[0032] S130. Determine the direction of the grounding fault point relative to the detection point according to the distribution differences of the zero-sequence voltage and zero-sequence current at each detection point in the area map.

[0033] Among them, as Figure 2 shown, the implementation steps of the partial discrimination process for the direction of the grounding fault in the flexible grounding distribution network of this method are:

[0034] The device starts up, measures and records the zero-sequence voltage and the effective values of zero-sequence current U0 and I0 at each detection point of the line in the current cycle;

[0035] Calculate the zero-sequence impedance U0 / I0 at each detection point and store it in Z0;

[0036] If the zero-sequence voltage U0 measured at a certain detection point is greater than or equal to the starting voltage U st and the zero-sequence impedance Z0 is less than or equal to K., it is determined that the fault location is downstream of the detection point, upload the fault information and wait for the action instruction or trip with a time delay to cut off the fault. If U0≥U st but Z0>K, the protection returns and proceeds to the next step;

[0037] Or the zero-sequence voltage U0 measured at this detection point is less than the starting voltage U st but greater than or equal to the inflection point voltage U 0g and the zero-sequence impedance Z0 is less than or equal to K, it is determined that the fault location is downstream of the detection point, upload the fault information and wait for the action instruction or trip with a time delay to cut off the fault. If U 0g ≤U0<U st but Z0>K, the protection returns and proceeds to the next step;

[0038] Or the zero-sequence voltage measured at this detection point is less than the inflection point voltage U 0g and 3 times the zero-sequence current 3I0 is greater than the minimum operating current I act , it is determined that the fault location is downstream of the detection point, upload the fault information and wait for the action instruction or trip with a time delay to cut off the fault. If U0<U 0g but 3I0<I act , the protection returns and the process ends;

[0039] If none of the above conditions are met, it is determined that this detection point is located downstream of the fault point on the faulty line or on a sound line, and the protection returns.

[0040] In this embodiment, the starting voltage U st , the minimum operating current value I act , the inflection point voltage U 0g , and the setting value K are set as follows:

[0041] The starting voltage U st (primary side) is set to avoid the maximum unbalanced voltage (15% of the rated phase voltage) in the resonant grounding stage, that is, not less than 866V. Let U st =866V to ensure the starting sensitivity;

[0042] The minimum operating current value I actIt is set according to the measurement accuracy of the zero-sequence current transformer and the expected withstand transition resistance value. The smaller the protection operating current, the higher its ability to withstand the transition resistance. Taking the ability to reflect a 3 kΩ withstand transition resistance as an example, the minimum operating current value is calculated using the following formula:

[0043]

[0044] In the formula, U f takes the phase voltage of the ground during normal system operation, Z0 is the zero-sequence impedance of the system after the parallel small resistor is inserted, which is approximately equal to 3 times the neutral grounding resistance R n (In this paper, R n = 15 Ω), R f is the grounding resistance, taking 3 kΩ, so it is assumed that

[0045] I act = 3I0 = 1.9 A,

[0046] which is greater than the minimum measured current (1 A) of the zero-sequence current transformer in the 10 kV distribution system and meets the on-site measurement requirements;

[0047] The inflection point voltage U 0g (primary side) is set according to the minimum operating current I act , that is Z is the zero-sequence capacitive reactance of a single line to the ground, and its value is not less than 636.1 Ω, so it is assumed that U 0g = 402 V;

[0048] The setting value K is set to be greater than the maximum zero-sequence measured impedance of the upstream line of the fault point after the parallel small resistor is inserted and less than the minimum zero-sequence measured impedance of the non-fault section before the parallel small resistor is inserted, between 45 Ω and 476.2 Ω. Considering factors such as the leakage conductance of the line to the ground, the zero-sequence measured impedance of the non-fault section in actual engineering applications is slightly less than 476.2 Ω, so K takes a smaller value, and it is assumed that K = 100 Ω.

[0049] The following is a specific implementation demonstration of this method:

[0050] Based on the MATLAB simulation platform, a 10 kV flexible grounding system simulation model is built as Figure 3 shown. The system operates in an over-compensation mode, the detuning degree is -10%, the arc suppression coil inductance is 0.1309 H, and the end of each line is a 1 MW constant impedance load. At 0.02 s, a single-phase (phase A) grounding fault occurs in the system, and the fault location is at P1 or P2 or P3, 6 km, 11 km, and 3 km away from the bus respectively. There is a detection device M0 and M0' at 1 km before and after the fault point. The parallel small resistor is inserted 1 s after the fault occurs.

[0051] Figure 4When the P2 point is grounded through a 110 Ω resistor, the simulated waveforms of zero-sequence voltage and zero-sequence current at the outlets and detection points of each healthy line are as follows. Figure 5 When the P3 point is grounded through a 1500 Ω resistor, the simulated waveforms of zero-sequence voltage and zero-sequence current at the outlets and detection points of each healthy line are as follows. From Figure 4 , Figure 5 it can be seen that after the parallel small resistor is put into operation, the zero-sequence voltage decreases significantly, and the zero-sequence current upstream of the fault point is significantly greater than the zero-sequence current in the healthy section.

[0052] Table 1 shows the simulation results at the outlets of each healthy line and at each detection point of the faulty line after single-phase grounding faults of different situations occur in the system. The difference between the zero-sequence voltage at each detection point and the zero-sequence voltage of the bus is not large. In the table, "*" indicates that the judgment result is in the waiting area, "×" indicates that the judgment result is in the return area, and "√" indicates that the judgment result is in the action area.

[0053] Table 1 Fault direction discrimination results at each detection point under different fault conditions

[0054]

[0055] It can be seen that after a single-phase grounding fault occurs in a flexible grounding distribution network, if the fault can disappear by itself, that is, the parallel small resistor is not put into operation, this method can ensure that the protection will not malfunction, so as to ensure the power supply reliability of the system; if the fault persists and is judged as a permanent grounding fault, and the parallel small resistor is put into operation, the protection will act accurately and cut off the fault. Taking the first group of data (metallic grounding fault) in Table 1 as an example, at the initial stage of the fault occurrence, the parallel small resistor is not put into operation, and the detected values of the zero-sequence impedance of the three healthy lines are 1593 Ω, 1017 Ω, and 1286 Ω respectively. The detected values of the zero-sequence impedance upstream and downstream of the fault point are 2950 Ω and 72000 Ω respectively, both of which are greater than 100 Ω, and each protection does not act, meeting the requirements; after the fault persists for a period of time and does not disappear, the parallel small resistor is put into operation. At this time, the detected values of the zero-sequence impedance of the three healthy lines are 1679 Ω, 1014 Ω, and 1282 Ω respectively. The detected values of the zero-sequence impedance upstream and downstream of the fault point are 30 Ω (<100 Ω) and 68181 Ω respectively. The protection at the detection point upstream of the fault point acts and cuts off the fault nearby.

[0056] The embodiments of the present application also provide a computer-readable storage medium. The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the processor is caused to execute some or all of the instructions of the above-mentioned flexible grounded distribution network single-phase grounding fault direction detection method. If the flexible grounded distribution network single-phase grounding fault direction detection method is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, to implement all or part of the processes in the above-mentioned embodiment methods of the present application, a computer program can be used to instruct relevant hardware to complete. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, the functions of the above-mentioned flexible grounded distribution network single-phase grounding fault direction detection method can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file or some intermediate form, etc. The computer-readable medium can at least include: any entity or device that can carry the computer program code to the photographing device / terminal device, recording medium, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electrical carrier signal, telecommunication signal, and software distribution medium. For example, a USB flash drive, a mobile hard disk, a magnetic disk or an optical disc, etc. In some jurisdictions, according to legislation and patent practice, the computer-readable medium cannot be an electrical carrier signal and a telecommunication signal.

[0057] As Figure 6 shown, the present application also provides a flexible grounded distribution network single-phase grounding fault direction detection device, including: a first unit 1, configured to obtain and analyze the distribution characteristics of zero-sequence voltage and zero-sequence current at each detection point when a single-phase grounding fault occurs in the flexible grounded distribution network; a second unit 2, configured to construct a zero-sequence voltage-zero-sequence current distribution region map of healthy lines and upstream and downstream sections of the fault point before and after the parallel small resistor is inserted; a third unit 3, configured to determine the direction of the grounding fault point relative to the detection point according to the distribution differences of the zero-sequence voltage and zero-sequence current at each detection point in the region map.

[0058] Those of ordinary skill in the art can realize that the units of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the components of each example have been generally described according to their functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. A professional technician can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0059] In the embodiments provided in this application, it should be understood that the division of units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units can be combined into one unit, one unit can be split into multiple units, or some features can be ignored, etc.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features. And these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered by the scope of the claims and the description of the present invention.

Claims

1. A method for detecting the direction of single-phase grounding faults in a flexible grounding distribution network, characterized in that Including: Obtaining and analyzing the distribution characteristics of zero-sequence voltage and zero-sequence current at each detection point when a single-phase grounding fault occurs in a flexible grounding distribution network; Constructing a zero-sequence voltage-zero-sequence current distribution area map of healthy lines and the upstream and downstream sections of the fault point before and after the parallel small resistor is put into operation; Judging the direction of the grounding fault point relative to the detection point according to the distribution difference of zero-sequence voltage and zero-sequence current at each detection point in the area map, including: If the zero-sequence voltage measured at the detection point is greater than or equal to the starting voltage and the zero-sequence impedance is less than or equal to the setting value; or, the zero-sequence voltage measured at the detection point is less than the starting voltage but greater than or equal to the inflection point voltage and the zero-sequence impedance is less than or equal to the setting value; or, the zero-sequence voltage measured at the detection point is less than the inflection point voltage and 3 times the zero-sequence current is greater than the minimum operating current; Then it is determined that the fault location is downstream of the detection point; If the above three conditions are not all met, it is determined that the detection point is downstream of the fault point of the faulty line or on a healthy line.

2. The single-phase grounding fault direction detection method for a flexible grounding distribution network according to claim 1, wherein The obtaining and analyzing the distribution characteristics of zero-sequence voltage and zero-sequence current at each detection point when a single-phase grounding fault occurs in a flexible grounding distribution network includes: Measuring the effective value of zero-sequence voltage and the effective value of zero-sequence current at the detection point in the current cycle; Calculating the zero-sequence impedance and saving the zero-sequence impedance.

3. The single-phase grounding fault direction detection method for a flexible grounding distribution network according to claim 1, characterized in that, The calculation formula of the zero-sequence impedance is: Zero-sequence impedance = effective value of zero-sequence voltage / effective value of zero-sequence current.

4. The single-phase grounding fault direction detection method for a flexible grounding distribution network according to claim 1, characterized in that If it is determined that the fault location is downstream of the detection point, upload the fault information and wait for the action instruction or trip with a time delay to cut off the fault; if it is determined that the detection point is downstream of the fault point of the faulty line or on a healthy line, the protection returns.

5. The single-phase grounding fault direction detection method for a flexible grounding distribution network according to claim 1, wherein The starting voltage is set to be greater than the maximum unbalanced voltage of the resonant grounding system; wherein, the maximum unbalanced voltage is 15% of the rated phase voltage.

6. The single-phase grounding fault direction detection method for a flexible grounding distribution network according to claim 1, characterized in that, The minimum operating current is set according to the measurement accuracy of the zero-sequence current transformer and the expected withstand transition resistance value; wherein, the minimum operating current is greater than 1 ampere.

7. The single-phase grounding fault direction detection method for a flexible grounding distribution network according to claim 1, wherein The inflection point voltage is set according to the minimum operating current, that is: ; where is the inflection point voltage, is the minimum operating current, Z is the zero-sequence capacitance of a single line to the ground, and Z is not less than 636.1 ohms.

8. A single-phase grounding fault direction detection device for a flexible grounding distribution network, characterized in that, Including: The first unit is used to obtain and analyze the distribution characteristics of zero-sequence voltage and zero-sequence current at each detection point when a single-phase grounding fault occurs in a flexible grounding distribution network; The second unit is used to construct a zero-sequence voltage-zero-sequence current distribution area map of healthy lines and the upstream and downstream sections of the fault point before and after the parallel small resistor is put into operation; The third unit is used to judge the direction of the grounding fault point relative to the detection point according to the distribution difference of zero-sequence voltage and zero-sequence current at each detection point in the area map, wherein, the judging the direction of the grounding fault point relative to the detection point according to the distribution difference of zero-sequence voltage and zero-sequence current at each detection point in the area map includes: If the zero-sequence voltage measured at the detection point is greater than or equal to the starting voltage and the zero-sequence impedance is less than or equal to the setting value; or, the zero-sequence voltage measured at the detection point is less than the starting voltage but greater than or equal to the inflection point voltage and the zero-sequence impedance is less than or equal to the setting value; or, the zero-sequence voltage measured at the detection point is less than the inflection point voltage and 3 times the zero-sequence current is greater than the minimum operating current; Then it is determined that the fault location is downstream of the detection point; If the above three conditions are not all met, it is determined that the detection point is downstream of the fault point of the faulty line or on a healthy line.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, which, when executed by a processor, causes the processor to execute the method according to any one of claims 1 to 7.

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