Power system stabilization system

Abstract

To provide a power system stabilization system capable of responding to an accident involving a plurality of power transmission routes.SOLUTION: A power system stabilization system includes: an accident determination part; an accident type determination part; a multiple route accident determination part; and a comprehensive accident type determination part. The accident determination part determines, for each power transmission route provided in the power system, whether an accident is occurring in the power transmission route. The accident type determination part determines an accident type in the power transmission route determined to be in the event of an accident. The multiple route accident determination part determines that a multiple route accident is occurring during a period in which accidents are occurring in a plurality of the power transmission routes. The comprehensive accident type determination part determines a comprehensive accident type according to a degree of influence of each accident of the plurality of power transmission routes on the power system, based on a combination of accident types of each of the plurality of power transmission routes determined to be in the event of an accident during the period in which it is determined that the multiple route accident is occurring.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to a power system stabilization system. [Background technology]

[0002] There are power system stabilization systems that control the power grid to ensure a stable supply of power even when an accident such as a lightning strike occurs in the power grid. Most power system stabilization systems are capable of handling accidents up to N-2, in which two pieces of equipment in the power grid are lost simultaneously.

[0003] Here, most transmission lines are configured with one route and two circuits. A transmission line consisting of one route and two circuits is called a transmission route. An accident equivalent to an N-2 fault is assumed to be an accident in which both circuits of a single transmission route are lost. In response to the loss of both circuits of a single transmission route due to an accident, power source restriction (shunting) may be implemented to parallel off controlled objects (shunting generators) within the power system in order to suppress abnormal phenomena that occur within the power system.

[0004] In recent years, the occurrence of large-scale blackouts has led to calls for further improvements in the resilience of power grids. Power grids are being required to respond to N-3 or higher accidents, in which three or more pieces of equipment are lost simultaneously, i.e., accidents involving multiple power transmission routes, such as the loss of three or more circuits out of a total of four circuits on two transmission routes. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Yoshifumi Oura, editor, "Protective Relay System Engineering", Institute of Electrical Engineers, 2002, pp.258-270 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide a power system stabilization system that can deal with accidents involving multiple power transmission routes. [Means for solving the problem]

[0007] An embodiment of the power system stabilization system includes a power transmission route fault determination unit and a comprehensive fault determination unit. The power transmission route fault determination unit includes a fault determination unit and a fault type determination unit. The comprehensive fault determination unit includes a multiple route fault determination unit, a comprehensive fault type determination unit, a control target selection unit, and a control target determination unit. The fault determination unit determines, in chronological order, whether a single route fault is occurring on each power transmission route provided in the power system. The fault type determination unit determines the fault type according to the degree of impact the fault has on the power system in relation to the number of operating circuits on the power transmission route determined by the fault determination unit to be experiencing the single route fault. The multiple route fault determination unit determines, based on the determination result by the fault determination unit, that a multiple route fault is occurring during a period in which the single route fault is occurring on multiple power transmission routes. The comprehensive fault type determination unit determines a comprehensive fault type according to the degree of overall impact that each fault on the power transmission route has on the power grid, based on a combination of fault types on each of the power transmission routes determined to be causing the single-route fault during the period determined to be causing the multiple-route fault by the multiple-route fault determination unit. The control object selection unit selects a control object according to the comprehensive fault type determined by the comprehensive fault type determination unit. The control object determination unit determines a control object based on the determination result determined by the comprehensive fault type determination unit and the selection result selected by the control object selection unit. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a configuration diagram of a power system stabilization system 1 according to an embodiment. [Figure 2] FIG. 10 is a diagram showing the configuration of an accident type determination table 180. [Figure 3]FIG. 10 is a diagram showing the configuration of a comprehensive accident type determination table 280. [Figure 4] FIG. 10 is a diagram showing the configuration of a control target selection table 282. [Figure 5] FIG. 10 is a diagram showing an example of a conventional control target selection table Tb1. [Figure 6] FIG. 10 is a diagram showing an example of a conventional control target selection table Tb2. [Figure 7] FIG. 3 is a diagram for explaining the processing performed by the multiple route accident determination unit 22. [Figure 8] 4 is a flowchart showing the flow of processing performed by the comprehensive accident determination unit 20. [Figure 9] FIG. 10 is a diagram showing the configuration of an accident type determination table 180 according to a first modified example of the embodiment. [Figure 10] FIG. 10 is a diagram showing an example of a table for determining whether high-speed reclosing can be performed. [Figure 11] FIG. 10 is a diagram showing the configuration of an accident type determination table 180 according to a second modification of the embodiment. [Figure 12] FIG. 11 is a diagram showing the configuration of an accident type determination table 180 according to a third modified example of the embodiment. [Figure 13] 10 is a diagram for explaining the processing performed by the accident determination unit 14 in the fourth modified example of the embodiment. FIG. [Figure 14] FIG. 3 is a diagram for explaining the processing performed by the multiple route accident determination unit 22. [Figure 15] 13 is a diagram for explaining the processing performed by the accident determination unit 14 in the fifth modified example of the embodiment. FIG. [Figure 16] FIG. 10 is a diagram showing the relationship between accident type and accident impact time. [Figure 17] FIG. 3 is a diagram for explaining the processing performed by the multiple route accident determination unit 22. [Figure 18] 3 is a diagram for explaining the processing performed by the comprehensive accident determination unit 20. FIG. [Figure 19] FIG. 13 is a diagram for explaining the processing performed by the multiple route accident determination unit 22 in the sixth modified example of the embodiment. [Figure 20] FIG. 3 is a diagram for explaining the processing performed by the multiple route accident determination unit 22. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a power system stabilization system according to an embodiment will be described with reference to the drawings.

[0010] 1 is a diagram showing the configuration of a power system stabilization system 1 according to an embodiment. The power system stabilization system 1 acquires system information from a power system E. The system information is information relating to the power system, and particularly includes information indicating the state of a power transmission line detected by a protective relay device (to be described later), such as operation information such as circuit breaker disconnection and reclosing.

[0011] The power system E is a collection of equipment for generating power and transmitting the generated power to consumer loads. The power system E includes, for example, power equipment such as generators, buses, transformers or transmission lines, loads, phase modifying equipment, circuit breakers, and disconnecting switches. The power system E includes a voltage measuring transformer and a current measuring transformer for measuring the power supplied to the power equipment.

[0012] The generators in the power system E include, for example, synchronous generators and asynchronous generators other than synchronous generators. A synchronous generator is a generator that has a rotating body such as a turbine, and its rotation is synchronized with the frequency of the power system E, and includes, for example, a thermal power generator and a nuclear power generator. An asynchronous generator includes, for example, a renewable energy generator such as a solar power generator or a wind power generator. The generators in the power system E are subject to control by power source limitation (power control) implemented by the power system stabilization system when a system fault occurs.

[0013] In the power system E, protective relay devices that protect and control power facilities are installed in substations, power plants, etc. The protective relay devices detect the occurrence of accidents such as lightning strikes and disconnect the transmission line where the detected accident occurred from the power system. For example, the protective relay devices measure the currents at both ends of a transmission line and determine whether an accident has occurred on that transmission line based on whether the difference between the currents is equal to or greater than a predetermined threshold. In this case, if the difference between the currents is equal to or greater than the predetermined threshold, it is determined that an accident has occurred.

[0014] In power system E, most of the transmission lines are configured with one route and two circuits. A transmission line configured with one route and two circuits is called a transmission route. Conventional power system stabilization systems can handle up to an N-2 fault, where faults occur on both circuits of a single transmission route. When a fault occurs on a transmission route, the system stabilizes the power system by sending control commands to control targets (also called shearing generators) that are predetermined for each fault pattern (fault type) according to the degree of impact that the fault will have on power system E (severity of the fault), thereby implementing shearing control.

[0015] Here, in power system E, it is believed that faults rarely occur simultaneously (within a few milliseconds) on multiple transmission routes. However, there is a possibility that faults may occur on multiple transmission routes consecutively with a certain interval between them. In the following, faults that occur consecutively on multiple transmission routes with a certain interval between them will be referred to as a "multiple route fault." Also, a fault that occurs on a single route, which is one transmission route, will be referred to as a "single route fault." In a multi-route fault, multiple single route faults occur consecutively, and the combined impact of each of the single route faults interacting with each other will affect the power system. For this reason, it is better to be able to respond to a multi-route fault separately from an event in which a single route fault occurs intermittently.

[0016] As a countermeasure against this, the power system stabilization system 1 of this embodiment is configured to manage the accident situation using two statuses: whether or not an accident is occurring. Specifically, for a single-route accident corresponding to an N-2 accident (or an N-1 accident), whether or not an accident is occurring is determined periodically (or irregularly) along a time series. Then, if a single-route accident is occurring during a period in which another single-route accident is occurring, it is determined that a multi-route accident is occurring. In other words, it is possible to detect the occurrence of a multi-route accident by determining that a multi-route accident is occurring during a period in which multiple single-route accidents overlap.

[0017] Furthermore, in this embodiment, the fault type of the multiple-route fault is determined based on a combination of the fault types of the multiple power transmission routes determined to be single-route faults during a period in which it is determined that a multiple-route fault is occurring. This makes it possible to determine a comprehensive fault type according to the overall degree of impact that each fault on the power transmission route has on the power grid. Then, a control command is sent to a predetermined control target for each comprehensive fault type to implement power control. This makes it possible to implement a response to the multiple-route fault that is different from the response to the intermittent occurrence of single-route faults.

[0018] As shown in FIG. 1, the power system stabilization system 1 includes, for example, a plurality of power transmission route fault determination units 10 (power transmission route fault determination unit 10-1, ..., power transmission route fault determination unit 10-K) and a comprehensive fault determination unit 20. K is an integer equal to or greater than 2. The plurality of power transmission route fault determination units 10 determine faults on different power transmission routes. The power transmission route fault determination unit 10-1 determines a fault that occurs on power transmission route 1. The power transmission route fault determination unit 10-K determines a fault that occurs on power transmission route K. In the following description, when there is no need to distinguish between the power transmission route fault determination unit 10-1 and the power transmission route fault determination unit 10-K, the explanation of the symbols following the hyphen will be omitted.

[0019] Each of the power transmission route fault determination units 10 is communicably connected to a protective relay device that monitors the power transmission route that is the target of the determination. The power transmission route fault determination unit 10 receives, as system information, information indicating the state of the power transmission line, such as operation information such as circuit breaker disconnection and reclosing, from the connected protective relay device.

[0020] The power transmission route fault determination unit 10 includes a system information acquisition unit 12, a fault determination unit 14, a fault type determination unit 16, and a storage unit 18. The system information acquisition unit 12 acquires system information from a protective relay device, and outputs the acquired system information to the fault determination unit 14 and the fault type determination unit 16.

[0021] The fault determination unit 14 determines whether a single route fault is occurring based on the system information. For example, when the system information received from the protective relay device indicates that a fault has been detected on a power transmission route, the fault determination unit 14 uses the time when the fault was detected as a reference point and determines that the single route fault is "not occurring" before that point, and determines that the single route fault is "occurring" after that point.

[0022] Furthermore, after determining that "an accident is occurring," the fault determination unit 14 determines that "an accident is not occurring" when a predetermined termination condition is satisfied. The termination condition may be set arbitrarily. For example, if the termination condition is that a circuit breaker is opened by a tripping command from a protective relay device and the power transmission route is cut off, the fault determination unit 14 determines that the single route fault is "occurring an accident" before the circuit breaker is opened, and determines that the single route fault is "not occurring" after the circuit breaker is opened. The fault determination unit 14 transmits a determination result indicating whether or not a single route fault is occurring on the target power transmission route to the comprehensive fault determination unit 20.

[0023] The storage unit 18 stores an accident type determination table 180. The accident type determination table 180 is a table in which the accident type of a single route accident is associated with an accident type number. The accident type of a single route accident is determined in advance according to the degree of impact that the accident will have on the power system E (the severity of the accident). For example, the accident type of a single route accident is a type that indicates whether an accident has occurred on one line of the power transmission route or on both lines. An accident occurring on both lines has a greater impact on the power system E than an accident occurring on only one line. In this way, the accident type determination table 180 associates an accident type according to the severity of the accident with its accident type number.

[0024] When it is determined that a single-route accident has occurred based on the system information, the accident type determination unit 16 determines the accident type of the single-route accident. The accident type determination unit 16 determines the accident type using, for example, an accident type determination table 180. The accident type determination unit 16 transmits an accident type number corresponding to the determined accident type to the comprehensive accident determination unit 20.

[0025] The fault type determination table 180 may be stored in an external database server or the like that is different from the power transmission route fault determination unit 10. In this case, the fault type determination unit 16 accesses the external database server and refers to the fault type determination table 180 to determine the fault type.

[0026] The comprehensive accident determination unit 20 includes a multiple route accident determination unit 22, a comprehensive accident type determination unit 24, a control target determination unit 26, a control target selection unit 27, a storage unit 28, and a control output unit 29. The comprehensive accident determination unit 20 receives the determination result (determination result indicating whether or not a single route accident is occurring) and the accident type number of the single route accident from each of the multiple power transmission route accident determination units 10.

[0027] The multiple route accident determination unit 22 determines whether a multiple route accident is occurring based on the determination results (determination results indicating whether a single route accident is occurring or not) notified from each of the multiple power transmission route accident determination units 10. The multiple route accident determination unit 22 determines that a multiple route accident is occurring when a single route accident is occurring on multiple power transmission routes. On the other hand, the multiple route accident determination unit 22 determines that a multiple route accident is not occurring when a single route accident is not occurring on any power transmission route or when a single route accident is occurring on only one power transmission route. The multiple route accident determination unit 22 outputs the determination result (determination result indicating whether a multiple route accident is occurring or not) to the comprehensive accident type determination unit 24.

[0028] When the multiple route accident determination unit 22 determines that a multiple route accident is occurring, the comprehensive accident type determination unit 24 determines the accident type (comprehensive accident type) of the multiple route accident. The comprehensive accident type determination unit 24 acquires a determination result (a determination result indicating whether a multiple route accident is occurring) from the multiple route accident determination unit 22. When the acquired determination result indicates that a multiple route accident is occurring, the comprehensive accident type determination unit 24 acquires the accident type numbers of each of the multiple single route accidents corresponding to the multiple route accident from the accident type numbers notified from each of the multiple power transmission route accident determination units 10. The comprehensive accident type determination unit 24 determines the accident type of the multiple route accident based on a combination of the respective accident type numbers of the acquired multiple single route accidents. The comprehensive accident type determination unit 24 determines the accident type using, for example, a comprehensive accident type determination table 280. The comprehensive accident type determination table 280 is a table in which the accident types of the multiple route accidents are associated with the accident type numbers. The fault type of a multi-route fault is determined in advance according to the degree of overall impact (severity of the fault) that each of the single-route faults that make up the multi-route fault will have on the power system E. The overall fault type determination unit 24 outputs an fault type number corresponding to the determined fault type to the control target determination unit 26.

[0029] The control object selection unit 27 selects a control object according to the fault type number of a multi-route fault at a regular interval. The control object selection unit 27 constantly performs a system simulation using the latest system information for pre-assumed multi-route faults and their fault types at a regular interval. Then, the control object selection unit 27 selects a control object according to the fault type number of the assumed multi-route fault. In this way, preparations are made so that power control can be immediately carried out when a multi-route fault occurs. The control object selection unit 27 selects a control object using, for example, a control object selection table 282. The control object selection table 282 is a table in which fault type numbers of multi-route faults are associated with control objects. The control object selection unit 27 outputs the selection result to the control object determination unit 26.

[0030] The control target determination unit 26 compares the determination result (fault type number of the multi-route fault) by the comprehensive fault type determination unit 24 with the selection result (generators selected as targets for shear control) by the control target selection unit 27, and determines the generators that will actually be subjected to shear control. The control target determination unit 26 outputs the determined control targets (generators that will actually be subjected to shear control) to the control output unit 29.

[0031] The control output unit 29 transmits a control command to instruct a circuit breaker provided in the controlled object (electrically controlled generator) determined by the controlled object determination unit 26 to shut off the power. This shuts off the power supply from the controlled object, thereby stabilizing the power system E.

[0032] The storage unit 28 stores a comprehensive accident type determination table 280 and a control target selection table 282. The comprehensive accident type determination table 280 is a table in which the accident type of a multi-route accident is associated with the accident type number. The control target selection table 282 is a table in which the accident type number of a multi-route accident is associated with the control target.

[0033] The comprehensive accident type determination table 280 may be stored in an external database server or the like different from the comprehensive accident determination unit 20. In this case, the comprehensive accident type determination unit 24 accesses the external database server and determines the accident type by referring to the comprehensive accident type determination table 280. Furthermore, the control object selection table 282 may be stored in an external database server or the like different from the comprehensive accident determination unit 20. In this case, the control object selection unit 27 accesses the external database server and refers to the control object selection table 282 to select the control object (electrically controlled generator).

[0034] The functional units (including the system information acquisition unit 12, the fault determination unit 14, the multi-route fault determination unit 22, the comprehensive fault type determination unit 24, the control target determination unit 26, the control target selection unit 27, and the control output unit 29) of the power system stabilization system 1 are realized by, for example, a hardware processor such as a CPU (Central Processing Unit) executing a program (software). Some or all of the functional units of the power system stabilization system 1 may be realized by hardware (including circuitry) such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a GPU (Graphics Processing Unit), or may be realized by a combination of software and hardware. Some or all of the functional units of the power system stabilization system 1 may be realized by a dedicated LSI. The program may be stored in advance in a storage device (storage device with a non-transitory storage medium) such as an HDD (Hard Disk Drive) or flash memory provided in the power system stabilization system 1, or may be stored in a removable storage medium (non-transitory storage medium) such as a DVD or CD-ROM, and installed in the storage device provided in the power system stabilization system 1 by inserting the storage medium into a drive device provided in the power system stabilization system 1 or the power supply system.

[0035] FIG. 2 is a diagram showing the configuration of the fault type determination table 180. The fault type determination table 180 is a table in which the fault type of a single route fault is associated with the fault type number. In this figure, two fault types are shown: a single-line fault and a double-line fault. A single-line fault is an fault in which an fault occurs on only one line of the power transmission route. A double-line fault is an fault in which an fault occurs on both lines of the power transmission route. In addition, in the example of this figure, the fault type number "1" is associated with the single-line fault. The fault type number "2" is associated with the double-line fault. In the example of this figure, the larger the fault type number, the greater the impact that the fault will have on the power system E.

[0036] FIG. 3 is a diagram showing the configuration of the comprehensive accident type determination table 280. The comprehensive accident type determination table 280 is a table in which the accident type of a multi-route accident is associated with the accident type number. This figure shows the accident type of a multi-route accident in which two power transmission routes (power transmission route 1 and power transmission route 2) are simultaneously experiencing accidents. The comprehensive accident type determination table 280 shows the accident type number of power transmission route 1 horizontally and the accident type number of power transmission route 2 vertically, and the accident type number of the multi-route accident is shown in the cell corresponding to each combination of the accident type numbers. When the accident type number of power transmission route 1 is "1" and the accident type number of power transmission route 2 is "1", the accident type number of the multi-route accident is "A1". When the accident type number of power transmission route 1 is "1" and the accident type number of power transmission route 2 is "2", the accident type number of the multi-route accident is "B1". When the fault type number of transmission route 1 is "2" and the fault type number of transmission route 2 is "1", the fault type number of the multi-route fault is "A2". When the fault type number of transmission route 1 is "2" and the fault type number of transmission route 2 is "2", the fault type number of the multi-route fault is "B2".

[0037] 4 is a diagram showing the configuration of the control target selection table 282. The control target selection table 282 is a table in which the fault type numbers of multi-route faults are associated with control targets. This diagram shows that the control target (electrically controlled generator) corresponding to the combination of the fault type number of power transmission route 1 being "1" and the fault type number of power transmission route 2 being "2", that is, the fault type number of the multi-route fault being "B1", is generator G3 (2000 MW).

[0038] Here, as a comparative example, control by a conventional power system stabilization system will be described. The conventional power system stabilization system does not deal with multiple route faults. Therefore, in the case of multiple route faults in this embodiment, that is, when faults occur on multiple power transmission routes consecutively at a certain interval, respective controls are implemented for each single route fault. In each control, the control target is determined on the assumption that no faults have occurred on other power transmission routes, so appropriate control cannot always be implemented, and there is a possibility of insufficient control.

[0039] 5 and 6 are diagrams showing examples of conventional control object selection tables Tb1 and Tb2. In FIG. 5, the control object associated with fault type number "1" on power transmission route 1 is generator G1 (1000 MW). The control object associated with fault type number "2" on power transmission route 2 is also generator G1 (1000 MW). In conventional power system stabilization systems, the control object is determined for each of the faults on power transmission route 1 and the faults on power transmission route 2 without considering the relationship between them. For this reason, when the control object is selected according to control object selection table Tb1, there is a possibility that the same generator G1 will be selected. Therefore, when multiple route faults occur on power transmission route 1 and power transmission route 2, only generator G1 will be subject to power control, which may result in insufficient control.

[0040] In Figure 6, the control object associated with fault type number "2" on power transmission route 2 is generator G2 (750 [MW]). The control objects associated with each of the two faults are different generators. In this case, power control is implemented for generator G1 in response to the fault on power transmission route 1, and power control is implemented for generator G2 in response to the fault on power transmission route 2. However, even when different control objects are selected for each fault in this way, there is a possibility that insufficient control may occur if the impact on power system E is greater due to the successive occurrence of two single-route faults than if each fault occurs individually.

[0041] In contrast to this, the power system stabilization system 1 of this embodiment can select a control target corresponding to the fault type number of the multi-route fault. Therefore, it is possible to select a control target according to the magnitude of the impact on the power system E caused by the occurrence of two consecutive single-route faults.

[0042] FIG. 7 is a diagram for explaining the processing performed by the multiple route accident determination unit 22. The horizontal axis in FIG. 7 represents time. As described above, the multiple route accident determination unit 22 determines whether a multiple route accident is occurring based on the determination results (determination results indicating whether a single route accident is occurring) notified from each of the multiple power transmission route accident determination units 10. In this diagram, a single route accident is occurring on power transmission route 1 from time t0 to t2. A single route accident is occurring on power transmission route 2 from time t1 to t3. In this case, the multiple route accident determination unit 22 determines that a multiple route accident is occurring on power transmission route 1 and power transmission route 2 during the period when time t0 to t2 and time t1 to t3 overlap, that is, during time t2 to t3.

[0043] 8 is a flowchart showing the flow of processing performed by the comprehensive accident determination unit 20. The multiple route accident determination unit 22 of the comprehensive accident determination unit 20 acquires the determination result for each power transmission route notified from the power transmission route accident determination unit 10 (determination result as to whether or not a single route accident is occurring) (step S10). The multiple route accident determination unit 22 of the comprehensive accident determination unit 20 determines whether or not it has been determined that a single route accident is occurring on two or more power transmission routes based on the acquired determination result (step S11). If it has been determined that a single route accident is occurring on two or more power transmission routes, the multiple route accident determination unit 22 determines that a multiple route accident is occurring (step S12). The comprehensive accident type determination unit 24 of the comprehensive accident determination unit 20 determines the accident type of the multiple route accident (comprehensive accident type) (step S13). The control object determination unit 26 of the comprehensive accident determination unit 20 determines the control object as a generator to be actually controlled based on the fault type of the multi-route fault determined in step S13 and the control object selected by the control object selection unit 27 (step S14). The control output unit 29 of the comprehensive accident determination unit 20 transmits a control signal to the control object determined in step S14 to implement the control (step S15).

[0044] On the other hand, if it is determined in step S11 that a single route accident is not occurring in two or more power transmission routes, the comprehensive accident determination unit 20 determines whether it is determined that a single route accident is occurring in one power transmission route (step S16). If it is determined that a single route accident is occurring in one power transmission route, the control object determination unit 26 of the comprehensive accident determination unit 20 determines a control object according to the accident type of the single route accident (step S17). The comprehensive accident determination unit 20 determines a control object associated with the accident type of the single route accident using a conventional control object selection table (for example, control object selection table Tb1). Note that if it is not determined that a single route accident is occurring in one power transmission route in step S16, that is, if no accident has occurred, the comprehensive accident determination unit 20 ends the processing.

[0045] With the above configuration, in the power system stabilization system 1 according to the embodiment, the multiple route fault determination unit 22 determines that a period during which a single route fault occurs on multiple power transmission routes is a multiple route fault, based on the determination results of the respective fault determination units 14 in the multiple power transmission route fault determination units 10. Furthermore, in the power system stabilization system 1 according to the embodiment, the fault type (overall fault type) of the multiple route fault is determined based on the combination of the fault types of the multiple power transmission routes determined to be experiencing single route faults during the period during which a multiple route fault is determined to be occurring. This makes it possible to distinguish a multiple route fault in which multiple single route faults occur consecutively from a case in which each single route fault occurs individually, and to implement control according to the magnitude of the overall impact on the power system E caused by the mutual influence of the single route faults that constitute the multiple route fault. Therefore, it is possible to appropriately respond to faults involving multiple power transmission routes.

[0046] (Modification 1 of the embodiment) Here, a first modification of the embodiment will be described. In this modification, the power system stabilization system 1 determines the fault type of a single route fault depending on whether the single route fault is an fault that allows fast reclosing.

[0047] After a power line is shut down due to a fault, high-speed reclosing may be performed depending on the condition of the shut down power line. High-speed reclosing is a control that quickly (within approximately one second after the fault) recloses the power line after it has been shut down, and is performed by a protective relay device. If the cause of the fault can be immediately resolved, such as a temporary insulation breakdown due to a lightning strike, high-speed reclosing can be performed to quickly restore the power line to its original state, allowing power transmission to continue with little disruption and stabilizing the power system. Each power line contains three phases corresponding to each phase of three-phase AC. When a power line is shut down, the protective relay device determines whether to perform high-speed reclosing based on the condition of the remaining phases (healthy phases) that are not affected by the fault among the transmission lines (two circuits for each of the three phases) that make up the power transmission route corresponding to the shut down power line. For example, the protective relay device will perform high-speed reclosing if two or more of the three phases in two circuits are healthy. The conditions for performing high speed reclosing are determined in advance by the operator (electric power company) that manages the power system E.

[0048] If a fault that occurs on a power transmission route is one for which high-speed reclosing can be performed, high-speed reclosing is performed. If high-speed reclosing is successful, the transmission line quickly returns to its original state, and therefore the degree of impact of this fault on the power grid E is smaller than that of a fault for which high-speed reclosing is not performed. In other words, whether or not a fault is one for which high-speed reclosing can be performed correlates with the degree of impact the fault has on the power grid E. From this perspective, in this modification, the fault type of a single route fault is determined depending on whether or not the single route fault is one for which high-speed reclosing can be performed. This makes it possible to determine the fault type according to the degree of impact the fault has on the power grid E.

[0049] FIG. 9 is a diagram showing the configuration of the fault type determination table 180 in the first modified example of the embodiment. In this diagram, the fault type includes the fields for the number of operating lines, the number of faulted lines, and the number of lines on which high-speed reclosing is possible. The number of operating lines is set to the number of lines operating on the power transmission route. When a power transmission route consisting of two lines on one route is in operation, the number of operating lines is set to "2." Even in a power transmission route consisting of two lines on one route, there are cases where only one line is operated due to maintenance or the like. In such cases, the number of operating lines is set to "1." The number of faulted lines is set to the number of lines on which a fault occurred on the power transmission route. The number of lines on which high-speed reclosing is possible is set to the number of lines on which high-speed reclosing is possible among the lines on which a fault occurred. In the example shown in this diagram, if there are two operating lines, faults have occurred on both lines, and high-speed reclosing is possible for both of these faults, the fault type determination unit 16 determines the fault type of this fault to be "A." On the other hand, if there is one operating line, a fault occurs on that line, and high-speed reclosing is not performed for this fault, the fault type determination unit 16 determines the fault type of this fault as "C." If a fault occurs on one of the two lines, and high-speed reclosing is not performed for this fault, the fault type determination unit 16 determines the fault type of this fault as "E."

[0050] FIG. 10 shows an example of a table for determining whether high-speed reclosing can be performed. In FIG. 10, the number of operating circuits, the number of faulted phases, the fault state, and reclosing are associated with each other. The number of operating circuits is the number of circuits operating in the transmission route. The number of faulted phases is the number of phases where the fault occurred. The fault state is a breakdown of the three phases in the transmission line (or transmission route) where the fault occurred. The three circles shown in the fault state correspond to the three phases of the three-phase AC in the transmission line. The black circles indicate faulted phases. The white circles indicate healthy phases. The reclosing state indicates whether reclosing can be performed, and if reclosing is possible, the reclosing method (high-speed reclosing or medium-speed reclosing) is indicated. Medium-speed reclosing is a control that performs reclosing within approximately 1 to 15 seconds after the fault. In Figure 10, when there is one operating circuit, high-speed reclosing is possible if there is one faulty phase, but if there are two or more faulty phases, reclosing is not performed as a final cutoff. Also, when there are two operating circuits, high-speed reclosing is possible if there is one faulty phase. When there are two operating circuits and two faulty phases, high-speed reclosing is possible if, for example, two or more of the two circuits are sound.

[0051] With the above configuration, in the power system stabilization system 1 according to the first modification of the embodiment, the fault type determination unit 16 determines the fault type of the single route fault depending on whether the single route fault is an fault for which high-speed reclosure can be performed. This makes it possible to determine the fault type depending on the degree of influence that the single route fault has on the power system E.

[0052] (Modification 2 of the embodiment) Here, a second modification of the embodiment will be described. In this modification, the power system stabilization system 1 determines the fault type of the single route fault depending on whether or not the fast reclosing performed in the single route fault was successful.

[0053] High-speed reclosing is a control with a high success rate, but there are cases where reclosing fails. For example, if an accident occurs due to a tree coming into contact with a power line (tree contact), the ground fault state will continue until the tree is removed, and high-speed reclosing will not be successful. Also, with some circuit breakers, repeated closing and opening control can require a certain amount of time before the next control. In this case, the circuit breaker will not be able to respond to the control command corresponding to high-speed reclosing, and high-speed reclosing will not be successful even if it is attempted.

[0054] Fig. 11 is a diagram showing the configuration of the fault type determination table 180 in Modification 2 of the embodiment. In this figure, the fault type has items for before and after high-speed reclosure. The item before high-speed reclosure has items for the number of operating lines, the number of faulted lines, and the number of lines on which high-speed reclosure can be performed. These items are the same as those in Fig. 9. The item after high-speed reclosure has an item for the number of lines after reclosure.

[0055] Before high-speed reclosing is performed, the fault type determination unit 16 determines the fault type on the assumption that all high-speed reclosing attempts will be successful. In this case, the number of circuits on which high-speed reclosing can be performed is equal to the number of circuits after reclosing.

[0056] When high-speed reclosure is performed, the fault type determination unit 16 re-determines the fault type depending on the number of circuits after the reclosure. For example, suppose that a fault occurs on both circuits of a power transmission route with two operating circuits, resulting in a single-route fault in which high-speed reclosure is possible on both circuits. In this case, the fault type determination unit 16 determines the fault type of the fault as "0" when the fault occurs. High-speed reclosure is then performed. If the number of circuits after high-speed reclosure is two, this indicates that reclosure of both circuits was successful, and the fault type determination unit 16 sets the fault type of the fault to "0." On the other hand, if the number of circuits after high-speed reclosure is one, the fault type determination unit 16 determines that reclosure of one of the two circuits failed, and sets the fault type of the fault to "1." Furthermore, if the number of circuits after high-speed reclosure is zero, it indicates that reclosure of both of the two circuits failed, and sets the fault type of the fault to "2." The accident types "0" to "2" shown in FIG. 11 are unrelated to the numbering system of the accident type numbers "1" and "2" in FIG.

[0057] With the above configuration, in the power system stabilization system 1 according to the second modification of the embodiment, when high-speed reclosing is performed in the event of a single route fault, the fault type of the single route fault is determined according to the number of circuits after the high-speed reclosing is performed. This makes it possible to assign different fault types to cases where reclosing is successful and cases where reclosing is unsuccessful, and to determine the fault type according to the degree of impact of the single route fault on the power system E.

[0058] (Modification 3 of the embodiment) Here, a third modification of the embodiment will be described. In this modification, the power system stabilizing system 1 combines the first and second modifications to determine the fault type of a single route fault.

[0059] 12 is a diagram showing the configuration of the accident type determination table 180 of the embodiment of the modified example 3. In this figure, the accident type is indicated by a two-digit type that combines the accident types "A" to "E" in FIG. 9 of the modified example 1 and the accident types "0" to "2" in FIG. 11 of the modified example 2.

[0060] For example, suppose a fault occurs on both circuits of a power transmission route with two operating circuits, and both circuits are single-route faults for which high-speed reclosure is possible. In this case, if reclosure is successful on both circuits before and after high-speed reclosure, the fault type determination unit 16 determines the fault type of the fault as "A0." On the other hand, if reclosure fails on one of the two circuits, the fault type of the fault is determined as "A1." If reclosure fails on both of the two circuits, the fault type of the fault is determined as "A2."

[0061] Also, suppose that a power transmission route has two operating circuits, and faults occur on both circuits, one of which is a single-route fault where high-speed reclosing is possible. In this case, the fault type determination unit 16 determines the fault type as "B1" if the reclosing was successful before high-speed reclosing was performed and in the high-speed reclosing performed on one circuit. On the other hand, if the reclosing failed, the fault type determination unit 16 determines the fault type as "B2."

[0062] With the above configuration, in the power system stabilization system 1 according to the third modification of the embodiment, when high-speed reclosing is performed in the event of a single route fault, the fault type of the single route fault is determined depending on the number of circuits after the high-speed reclosing is performed. This makes it possible to assign a fault type depending on whether high-speed reclosing is possible or not and whether the high-speed reclosing was successful or not, and to determine the fault type depending on the degree of impact that the single route fault has on the power system E.

[0063] For example, in the above-described embodiment, if whether high-speed reclosing is possible and whether the reclosing is successful are individually considered, the number of fault types will increase. For example, suppose that power system E has K transmission routes, and the number of fault types into which single-route faults involving one route and two circuits are classified is L. In this case, the total number of fault types determined by the comprehensive fault type determination unit 24 is L to the Kth power, which becomes an enormous number. In contrast, in Modifications 1, 2, and 3 of the embodiment, faults that have a similar magnitude of impact on power system E can be grouped together. Therefore, the processing load when determining the fault type of a multi-route fault can be reduced.

[0064] (Fourth Modification of the Embodiment) Here, a fourth modification of the embodiment will be described. In this modification, the power system stabilization system 1 determines that the single route fault is not occurring when the state of the power transmission route in which the single route fault occurred returns to the state before the single route fault occurred.

[0065] In the above-described embodiment, the fault determination unit 14 determines that a single route fault is occurring from the time when a fault is detected on the power transmission route, and determines that "an fault is not occurring" when the power transmission route is blocked by a control command. In contrast, in this modified example, the fault determination unit 14 determines that a single route fault is not occurring when the state of the power transmission route in which it was determined that a single route fault is occurring returns to the state before the fault occurred.

[0066] For example, in the case of a single-route fault where high-speed reclosure is possible, the fault determination unit 14 determines that a single-route fault is not occurring when high-speed reclosure is performed and successful closure is detected. On the other hand, if high-speed reclosure is performed but the closure fails, medium-speed reclosure or low-speed reclosure is performed, ultimately returning to the state before the fault occurred. Low-speed reclosure is a control that performs reclosure within approximately 15 seconds to 1 minute after the fault. If high-speed reclosure is performed but the closure fails, the fault determination unit 14 determines that a single-route fault is not occurring when successful closure is detected by performing medium-speed reclosure or low-speed reclosure.

[0067] FIG. 13 is a diagram for explaining the processing performed by the fault determination unit 14 in the fourth modification of the embodiment. In this diagram, the fault determination unit 14 acquires system information from the system information acquisition unit 12. Based on the system information acquired from the system information acquisition unit 12, the fault determination unit 14 determines whether a state has changed from one in which a single-route fault has not occurred to one in which one has occurred (reference numeral 140), and inputs the determination result to a terminal S (set) of a sequential circuit (reference numeral 141). The fault determination unit 14 also acquires a CB condition (reference numeral JK). This CB condition is information indicating the state of a circuit breaker (CB), for example, information indicating a closed circuit or an open circuit. Based on the CB condition, the fault determination unit 14 determines whether the state of the power transmission route in which the single-route fault occurred has returned to the state before the fault occurred (reference numeral 143), and inputs the determination result to a terminal R (reset) of the sequential circuit (reference numeral 141). The sequential circuit (reference numeral 141) outputs a signal (a signal indicating that an accident is occurring) that is input to terminal S (set) and held internally while the state of the power transmission route has not returned to the state before the accident (i.e., reset has not been applied). On the other hand, the sequential circuit (reference numeral 141) clears the signal held internally and outputs a signal indicating that an accident is not occurring when the state of the power transmission route returns to the state before the accident (i.e., reset has been applied). The accident determination unit 14 outputs whether or not an accident is occurring (reference numeral 142) according to the output of the sequential circuit (reference numeral 141).

[0068] FIG. 14 is a diagram illustrating the processing performed by the multiple route fault determination unit 22 in the fourth modified example of the embodiment. The horizontal axis of FIG. 14 represents time. In this diagram, a single route fault occurs on the power transmission route 1 at time t0, the circuit breaker-controlled fault is cleared at time t3, and the circuit closing is successful at time t6. On the power transmission route 2, a single route fault occurs on the power transmission route 2 at time t1, the circuit breaker-controlled fault is cleared at time t4, and the circuit closing is successful at time t8. On the power transmission route 3, a single route fault occurs on the power transmission route 3 at time t2, the circuit breaker-controlled fault is cleared at time t5, and the circuit closing is successful at time t7. The multiple route fault determination unit 22 determines that a multiple route fault is not occurring from time t0 to t1. From time t1 to t2, the multiple route fault determination unit 22 determines that a multiple route fault is occurring on the power transmission route 1 and the power transmission route 2. From time t2 to t6, the multiple route fault determination unit 22 determines that a multiple route fault is occurring among the power transmission route 1, the power transmission route 2, and the power transmission route 3. From time t6 to t7, the multiple route fault determination unit 22 determines that a multiple route fault is occurring among the power transmission route 2 and the power transmission route 3. After time t7, the multiple route fault determination unit 22 determines that a multiple route fault is not occurring.

[0069] With the above configuration, in the power system stabilization system 1 according to the fourth modification of the embodiment, the fault determination unit 14 determines that a single-route fault is not occurring when the state of the power transmission route returns to the state before the fault. When a single-route fault occurs in the power system E, the power system E may experience an open phase and a reduced number of circuits compared to before the fault during the period from the occurrence of the single-route fault until successful reclosure. By determining that a single-route fault is occurring during this period of reduced stability in the power system E, it is possible to determine that a multiple-route fault has occurred if a fault occurs on another power transmission route before successful reclosure. Therefore, power control can be implemented according to the degree of overall impact of a series of faults on the power system E, thereby suppressing shortage control.

[0070] (Fifth Modification of the Embodiment) Here, a fifth modification of the embodiment will be described. In this modification, the power system stabilization system 1 determines that a single route fault is occurring during a period from the time when a single route fault occurs until a time (fault impact time) preset according to the fault type of the multiple route fault has elapsed.

[0071] FIG. 15 is a diagram for explaining the processing performed by the fault determination unit 14 in the fourth modification of the embodiment. In this diagram, the fault determination unit 14 acquires system information from the system information acquisition unit 12. Based on the system information acquired from the system information acquisition unit 12, the fault determination unit 14 determines whether a state has changed from one in which a single-route fault has not occurred to one in which one has occurred (reference numeral 145), and outputs the determination result to a timer setting circuit (reference numeral 146). The fault determination unit 14 also acquires the fault type of the single-route fault from the fault type determination unit 16. The fault determination unit 14 determines the fault influence time corresponding to the fault type based on the acquired fault type and Table H (see FIG. 16) (reference numeral 148), and outputs the determined fault influence time to the timer setting circuit (reference numeral 146). The timer setting circuit (reference numeral 146) counts the fault influence time using a timer, starting from the time when the single-route fault occurred. The fault determination unit 14 determines that a single route fault is occurring during the period from when the timer count by the timer setting circuit (reference numeral 146) starts to when it ends (reference numeral 147).

[0072] Fig. 16 is a diagram showing the relationship between the type of fault and the fault impact time as an example of Table H. For example, the fault impact time is a time including the time required for reclosing, which is performed depending on the type of fault, and the time during which the stability of power system E remains reduced after reclosing is performed.

[0073] FIG. 17 is a diagram for explaining the processing performed by the multiple route accident determination unit 22 in the fifth modified example of the embodiment. The horizontal axis of FIG. 17 represents time. In this diagram, a single route accident occurred on the power transmission route 1 at time t0, causing the timer for the accident influence time T2 to start, and the timer for the accident influence time T2 to finish (count up) at time t4. On the power transmission route 2, a single route accident occurred on the power transmission route 2 at time t1, causing the timer for the accident influence time T0 to start, and the timer for the accident influence time T0 to finish (count up) at time t3. On the power transmission route 3, a single route accident occurred on the power transmission route 3 at time t2, causing the timer for the accident influence time T1 to start, and the timer for the accident influence time T1 to finish (count up) at time t5. The multiple route accident determination unit 22 determines that a multiple route accident is not occurring from time t0 to t1. From time t1 to t2, the multiple route accident determination unit 22 determines that a multiple route accident is occurring on the power transmission route 1 and the power transmission route 2. From time t2 to t3, the multiple route fault determination unit 22 determines that a multiple route fault is occurring among the power transmission route 1, the power transmission route 2, and the power transmission route 3. From time t3 to t4, the multiple route fault determination unit 22 determines that a multiple route fault is occurring among the power transmission route 1 and the power transmission route 3. After time t4, the multiple route fault determination unit 22 determines that a multiple route fault is not occurring.

[0074] FIG. 18 is a diagram for explaining the processing performed by the comprehensive fault judgment unit 20. The horizontal axis of FIG. 18 represents time. FIG. 18 chronologically shows the relationship between the selection of a control object by the control object selection unit 27 and faults that occur in the power system E. In this diagram, at time t0, selection result 1 as the control object was selected by the control object selection unit 27. At time t1, a single route fault occurred and the timer for the fault impact time T3 was started. At time t2, selection result 2 as the control object was selected by the control object selection unit 27. At time t3, the timer for the fault impact time T3 ended (counted up). At time t4, selection result 3 as the control object was selected by the control object selection unit 27. At time t5, selection result 4 as the control object was selected by the control object selection unit 27.

[0075] In the power system stabilization system 1 according to the embodiment, faults occur regardless of the fixed cycle in which the control object is selected, and reclosing is performed to address the fault. For example, assume that high-speed reclosing is performed between times t1 and t2 in response to a single-route fault that occurred at time t1. In this case, after reclosing, the faulted transmission route is closed, but the stability of the power system E remains reduced for a while. More specifically, the state of the circuit breaker changes every few hundred milliseconds due to the occurrence of a fault, fault removal, reclosing, etc. At time t2, when the state changes in this way, it is difficult to accurately grasp the state of the power system E (system state), and it is not always possible to select the correct control object. For example, in this figure, selection result 1 selected at time t0 is highly reliable because it was selected when the system state was stable. On the other hand, selection result 2 selected at time t2 is unreliable because it was selected when the system state was unstable. If shedding control is performed based on a selection result with low reliability, there is a possibility that the amount of control achieved by shedding control will be insufficient.

[0076] Therefore, in this modification, the fault impact time is set according to the fault type as shown in Table H, and the period during which the grid state becomes unstable due to the occurrence of a route fault is determined to be a fault occurrence. This makes it possible to determine whether the selection result selected by the control target selection unit 27 was selected at a time when the grid state was stable or at a time when the grid state was unstable. For example, in this figure, when power control is performed during the period ST from time t2 to t3, the most recent selection result is selection result 2, which was selected at a time when the grid state was unstable. In this case, the control target determination unit 26 of the comprehensive fault determination unit 20 determines the control target based on the most recent selection result among the selection results selected at a time when the grid state was stable. In other words, when power control is performed during the period ST from time t2 to t3, the control target determination unit 26 determines the control target based on selection result 1 to avoid insufficient control.

[0077] With the above configuration, in the power system stabilization system 1 according to the fifth modification of the embodiment, the fault determination unit 14 determines that a single route fault is not occurring when the fault influence time corresponding to the fault type of the single route fault has elapsed. This makes it possible to avoid determining a control target based on a selection result selected at a time when the grid state is unstable, thereby avoiding insufficient control.

[0078] (Modification 6 of the embodiment) Here, a sixth modification of the embodiment will be described. In this modification, the power system stabilization system 1 determines that a multi-route fault is not occurring when it is determined that a single-route fault is not occurring in all of the power transmission routes in which a single-route fault was determined to be occurring within a period in which it was determined that a multi-route fault was occurring.

[0079] FIG. 19 is a diagram for explaining the processing performed by the multiple route accident determination unit 22 in the sixth modified example of the embodiment. In this diagram, the multiple route accident determination unit 22 acquires a determination result indicating whether or not a single route accident is occurring from each of the multiple power transmission route accident determination units 10 (power transmission route accident determination units 10-1, 10-2, and 10-3). Based on the determination results acquired from each of the multiple power transmission route accident determination units 10, the multiple route accident determination unit 22 outputs a determination signal indicating "1" if an accident is occurring and "0 (zero)" if an accident is not occurring (reference signs 220-1 to 220-3). The multiple route accident determination unit 22 outputs "1" if two or more of the three determination signals are "1" (reference signs K1 to K3, K6). More specifically, the multiple route accident determination unit 22 outputs a logical product KV1 of two of the three determination signals, that is, the power transmission route 1 and the power transmission route 2 (reference sign K1). The multiple route fault determination unit 22 outputs a logical product KV2 of two of the three determination signals, that is, power transmission route 2 and power transmission route 3 (symbol K2). The multiple route fault determination unit 22 outputs a logical product KV3 of two of the three determination signals, that is, power transmission route 3 and power transmission route 1 (symbol K3). The multiple route fault determination unit 22 outputs "1" when at least one of the three logical products KV1 to KV3 is 1 or greater, and outputs "0" when all of them are less than 1 (i.e., 0) (symbol K6), and inputs the output result to a terminal S (set) of a sequential circuit (symbol 222). The multiple route fault determination unit 22 also outputs "1" when at least one of the three determination signals is 1 or greater, and outputs "0" when all of them are less than 1 (i.e., 0) (symbol K4), and inputs an inverted signal obtained by inverting the output signal to a terminal R (reset) of the sequential circuit (symbol 222). The sequential circuit (symbol 222) outputs a signal (a signal indicating that multiple multi-route faults are occurring) that is input to terminal S (set) and held internally during a period when at least one of the single-route faults that have occurred on the power transmission route is currently occurring (i.e., when reset is not applied).On the other hand, the sequential circuit (reference numeral 141) clears the signals stored therein when all single-route faults occurring on the power transmission routes are no longer occurring (i.e., reset is applied).The multi-route fault determination unit 22 outputs whether or not a multi-route fault is occurring (reference numeral 224) according to the output of the sequential circuit (reference numeral 222).

[0080] FIG. 20 is a diagram illustrating the processing performed by the multiple route fault determination unit 22 in the sixth modified example of the embodiment. The horizontal axis of FIG. 20 represents time. In this diagram, a single route fault occurs on power transmission route 1 at time t0 and the fault ceases to occur at time t2. A single route fault occurs on power transmission route 2 at time t1 and the fault ceases to occur at time t4. A single route fault occurs on power transmission route 3 at time t3 and the fault ceases to occur at time t5. In this case, the multiple route fault determination unit 22 determines that a multiple route fault is not occurring from time t0 to t1. From time t1 to t3, the multiple route fault determination unit 22 determines that a multiple route fault is occurring on power transmission route 1 and power transmission route 2. From time t3 to t5, the multiple route fault determination unit 22 determines that a multiple route fault is occurring on power transmission route 1, power transmission route 2, and power transmission route 3. After time t5, the multiple route accident determination unit 22 determines that no multiple route accident is occurring.

[0081] That is, the multiple route fault determination unit 22 assumes that single route faults occur in the order of power transmission route 1, power transmission route 2, and power transmission route 3, as shown in this figure. More specifically, assume that a fault occurs on power transmission route 2 while a fault occurs on power transmission route 1, and a fault occurs on power transmission route 3 while a fault occurs on power transmission route 2. In this case, it is determined that a multiple route fault is occurring at the time the single route fault occurs on power transmission route 2. In this figure, a fault occurs on power transmission route 3 after the fault on power transmission route 1 is no longer occurring, but the fault on power transmission route 2 is occurring at the time the fault occurs on power transmission route 3. Therefore, the multiple route fault determination unit 22 determines that a multiple route fault is occurring on the three power transmission routes, power transmission route 1, power transmission route 2, and power transmission route 3, at the time the fault occurs on power transmission route 3. As a result, even if the fault on power transmission route 1 is no longer occurring, it can be determined that a multiple route fault is occurring during the period during which the effects of the fault remain. Then, power control can be implemented based on the overall type of accident determined as a multiple route accident occurring on the three power transmission routes, power transmission route 1, power transmission route 2, and power transmission route 3, thereby reducing the possibility of insufficient control amount due to power control.

[0082] According to at least one of the embodiments described above, by having a multiple route accident determination unit 22 that determines that a period in which a single route accident is occurring on multiple power transmission routes is a multiple route accident occurring, and a comprehensive accident type determination unit 24 that determines the accident type (comprehensive accident type) of a multiple route accident based on a combination of the respective accident types of multiple power transmission routes that are determined to be single route accidents during the period in which it is determined that a multiple route accident is occurring, it is possible to respond to accidents involving multiple power transmission routes.

[0083] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents. [Explanation of symbols]

[0084] 1... power system stabilization system, 10... power transmission route fault determination unit, 14... fault condition determination unit, 16... fault type determination unit, 20... comprehensive fault determination unit, 22... multiple route fault determination unit, 24... comprehensive fault type determination unit

Claims

1. a power transmission route fault determination unit including: a fault determination unit that determines, in chronological order, for each power transmission route provided in the power system, whether a single route fault is occurring on the power transmission route; and a fault type determination unit that determines a fault type according to the degree of influence that the fault has on the power system in relation to the number of operating lines on the power transmission route determined by the fault determination unit to be the occurrence of the single route fault; a multiple route accident determination unit that determines, based on a determination result by the accident determination unit, that a period during which the single route accident is occurring on a plurality of the power transmission routes is a multiple route accident; a comprehensive accident type determination unit that determines, based on a combination of the respective accident types of the plurality of power transmission routes that are determined to be the single route accidents occurring during the period during which the multiple route accident determination unit determines that the multiple route accident is occurring, a comprehensive accident type according to the overall degree of impact that each accident on the power transmission route has on the power system; a control object selection unit that selects a control object according to the comprehensive accident type determined by the comprehensive accident type determination unit; and a control object determination unit that determines a control object based on the determination result determined by the comprehensive accident type determination unit and the selection result selected by the control object selection unit. A power system stabilization system comprising:

2. the fault type determination unit determines a fault type according to whether the fault on the power transmission route determined to be the single route fault is an fault for which high-speed reclosure can be performed. The power system stabilization system according to claim 1 .

3. the fault type determination unit determines a fault type according to the number of circuits of the power transmission route after high-speed reclosing is performed on the power transmission route determined to be experiencing the single route fault. The power system stabilization system according to claim 1 .

4. the fault determination unit determines that the single route fault is not occurring when the state of the power transmission route, which has been determined to be the single route fault, returns to the state before it was determined that the single route fault is occurring. The power system stabilization system according to claim 1 .

5. the fault determination unit determines that the single route fault is not occurring when a time period set according to the fault type of the fault on the power transmission route on which the single route fault has been determined to be occurring has elapsed. The power system stabilization system according to claim 1 .

6. the multiple route fault determination unit determines that the multiple route fault is not occurring when it is determined that the single route fault is not occurring for all of the power transmission routes that were determined to be experiencing the single route fault within the period in which it was determined that the multiple route fault is occurring. The power system stabilization system according to claim 1 .

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