JP7390926B2 - Protection systems for multi-terminal power transmission systems - Google Patents

Description

This disclosure relates to protection systems for protecting multi-terminal power transmission systems.

It is desirable that power transmission line protection can continue even if the connection form of power transmission lines is changed. For example, Patent Document 1 (Japanese Unexamined Patent Publication No. 2011-239521) discloses a current differential relay used in a power transmission line in which a line jumper or a line breaker is installed in the middle.

Specifically, in the current differential relay of this document, when the state determination unit determines that the line jumper is in the "on" state, the current differential relay is connected to the power transmission line based on the difference between the current on the own terminal side and the current on the other terminal side. Detect accidents that have occurred. On the other hand, when the state determining section determines that the line jumper is in the "off" state, this current differential relay detects an accident occurring in the power transmission line based only on the current on its own terminal side.

JP2011-239521A

For example, a current differential relay that protects a multi-line, multi-terminal power transmission network where No. 1 and No. 2 transmission lines are installed on one tower is a current differential relay for No. 1 transmission line and a No. 2 transmission line. A current differential relay for electric wires is required. The current differential relay for the No. 1 power transmission line uses the current at each terminal of the No. 1 power transmission line to determine the presence or absence of an internal fault, and the current differential relay for the No. The presence or absence of an internal accident is determined using the terminal current.

By the way, when connecting distributed power sources such as solar power generation and wind power generation, which are expected to increase in the future, to the power transmission grid, or when changing one line to a π lead-in line, it is necessary to reduce the power supply to consumers. It is necessary to avoid stopping as much as possible. For this purpose, it is convenient to provide a plurality of switches for connecting the No. 1 power transmission line and the No. 2 power transmission line. This is because it may not be possible to take a detour route using other power transmission lines.

However, when the No. 1 power transmission line and the No. 2 power transmission line are connected using a switch, or when each power transmission line is separated in the middle, the protection section of the current differential relay ends up being changed. In the prior art, no means have been disclosed to deal with such a case.

The present disclosure has been made in consideration of the above-mentioned problems, and one of its purposes is to provide a multi-terminal power transmission system in which the protection interval is changed by changing the open/close state of a plurality of switches, by controlling the current difference. The purpose of the present invention is to provide a protection system for protection by a dynamic method.

In one aspect, a protection system for a multi-terminal power transmission system is provided. A multi-terminal power transmission system includes multiple power transmission lines that connect three or more substations, multiple switches, and multiple circuit breakers. Each power transmission line connects any one substation among the three or more substations and one or more other substations. The plurality of switches are provided at one or more power transmission lines and between the power transmission lines. A plurality of circuit breakers are individually provided adjacent to the terminals of each power transmission line. The protection system includes a plurality of protection relays that are individually provided corresponding to each terminal of a plurality of power transmission lines and connected to each other via a communication path. Each protection relay includes a protection section identification section and a protection relay calculation section. When the open/close states of multiple switches are changed, the protection zone identification unit detects electricity at the own terminal of the power transmission line equipped with the corresponding circuit breaker based on information on the changed open/close states of the multiple switches. By specifying all other terminals that are connected to each other, the protection interval to be protected is specified using the current differential method. The protective relay calculation unit performs relay calculation using a current differential method based on the current value sampled at its own terminal and the current value sampled at each specified other terminal.

According to one aspect of the protection system described above, when the open/close states of multiple switches are changed, each protection relay determines the changed protection interval based on information about the changed open/close states of the multiple switches. By specifying and performing relay calculation using the current differential method based on the specified protection interval, a multi-terminal power transmission system can be protected.

1 is a diagram illustrating a configuration example of a multi-terminal power transmission system and its protection system. FIG. 2 is a diagram for explaining the operating method and protection zone of the multi-terminal power transmission system in FIG. 1. FIG. FIG. 2 is a diagram illustrating an example of a configuration of a communication path based on Ethernet (registered trademark). FIG. 2 is a diagram showing an example of the hardware configuration of the protection relay in FIG. 1. FIG. FIG. 2 is a diagram showing an example of the hardware configuration of the switch control device shown in FIG. 1. FIG. 2 is a diagram illustrating an example of the hardware configuration of a host computer in FIG. 1. FIG. FIG. 3 is a functional block diagram showing the operation of the arithmetic processing section of the protection relay. 2 is a flowchart illustrating an example of the operation of the protection system for the multi-terminal power transmission system in FIG. 1 (showing a procedure when switching from 3-terminal operation to π pull-in operation of Line 2). 2 is a flowchart illustrating an example of the operation of the protection system for the multi-terminal power transmission system in FIG. 1 (showing the procedure when switching from π pull-in operation to 3-terminal operation of Line 2). FIG. 3 is a functional block diagram showing the operation of an arithmetic processing unit of a host computer according to a second embodiment. FIG. 7 is a diagram showing an example of a configuration of a communication path using Ethernet in the protection system of Embodiment 3; 11 is a flowchart illustrating an example of the operation of the protection system for a multi-terminal power transmission system according to Embodiment 4 (showing the procedure when switching from 3-terminal operation to π pull-in operation of line 2). 12 is a flowchart illustrating an example of the operation of the protection system for a multi-terminal power transmission system according to Embodiment 4 (showing a procedure when switching from π pull-in operation of Line 2 to 3-terminal operation).

Each embodiment will be described in detail below with reference to the drawings. Note that the same reference numerals are given to the same or corresponding parts, and the description thereof may not be repeated.

Embodiment 1.
[Example of overall configuration of multi-terminal power transmission system protection system]
FIG. 1 is a diagram showing a configuration example of a multi-terminal power transmission system and its protection system.

The multi-terminal power transmission system 30 includes a No. 1 power transmission line 1L and a No. 2 power transmission line 2L that connect between a substation 31 (A end), a substation 32 (B end), and a substation 33 (C end). . The No. 1 transmission line 1L has a section A-1L that connects the bus A-1B of the substation 31 and the node N1, a section B-1L that connects the bus B-1B of the substation 32 and the node N1, and a substation It is divided into a section C-1L that connects the bus line C-1B of station 33 and node N1. The No. 2 transmission line 2L has a section A-2L that connects the bus A-2B of the substation 31 and the node N2, a section B-2L that connects the bus B-2B of the substation 32 and the node N2, and a section B-2L that connects the bus A-2B of the substation 31 and the node N2. It is divided into a section C-2L that connects the bus line C-2B of station 33 and node N2.

The multi-terminal power transmission system 30 further includes circuit breakers CB1, CB3, and CB5 provided adjacent to each terminal of the No. 1 power transmission line 1L, and circuit breakers provided adjacent to each terminal of the No. 2 power transmission line 2L. It includes CB2, CB4, and CB6. In addition, the multi-terminal power transmission system 30 includes current transformers CT1, CT3, CT5 individually provided between each terminal of the No. 1 power transmission line 1L and the corresponding circuit breaker, and each terminal of the No. 2 power transmission line 2L. It includes current transformers CT2, CT4, and CT6 individually provided between the corresponding circuit breakers. In the following description, the circuit breakers CB1 to CB6 and the current transformers CT1 to CT6 will be referred to as a circuit breaker CB and a current transformer CT, respectively, when they are referred to generically or unspecified.

Multi-terminal power transmission system 30 further includes switches SW1 to SW3. Switch SW1 is provided in section C-1L of No. 1 power transmission line 1L. Switch SW2 is provided in section B-2L of No. 2 power transmission line 2L. Switch SW3 connects to node N3 between switch SW2 and circuit breaker CB2 in section A-2L of No. 2 transmission line 2L, and switch SW1 and circuit breaker CB5 in section C-1L of No. 1 power transmission line 1L. and a node N4 between the two. In the following description, the switches SW1 to SW3 will be referred to as switches SW when they are referred to generically or when an unspecified item is indicated.

Although FIG. 1 shows one power transmission line for ease of illustration, there are actually three power transmission lines in the case of a three-phase power transmission line. Further, although the circuit breaker CB, current transformer CT, and switch SW are actually provided for each phase, in the present disclosure, three phases are combined into one circuit breaker CB, current transformer CT, and switch SW. , and switch SW.

The protection system that protects the multi-terminal power transmission system 30 configured as described above includes protection relays RY1 and RY2 provided in the substation 31, protection relays RY3 and RY4 provided in the substation 32, and protection relays RY3 and RY4 provided in the substation 33. protection relays RY5 and RY6, a switch control device SWCU that controls opening and closing of switches SW1 to SW3, and a host computer 35 provided in a control center 34. The protection relays RY1 to RY6 will be referred to as protection relays RY when used collectively or when referring to an unspecified item.

The protective relay RY1 is connected to a current transformer CT1 and a circuit breaker CB1 that are provided adjacent to a terminal (A end) on the substation 31 side of the No. 1 power transmission line 1L. Protection relay RY1 controls opening and closing of circuit breaker CB1. Similarly, the protective relay RY2 is connected to the current transformer CT2 and the circuit breaker CB2, which are provided adjacent to the terminal (A terminal) on the substation 31 side of the No. 2 power transmission line 2L, and controls the opening and closing of the circuit breaker CB2. do. The protective relay RY3 is connected to a current transformer CT3 and a circuit breaker CB3 that are provided adjacent to a terminal (B end) on the substation 32 side of the No. 1 power transmission line 1L, and controls opening and closing of the circuit breaker CB3. The protective relay RY4 is connected to a current transformer CT4 and a circuit breaker CB4 that are provided adjacent to a terminal (B end) on the substation 32 side of the No. 2 power transmission line 2L, and controls opening and closing of the circuit breaker CB4. Protective relay RY5 is connected to current transformer CT5 and circuit breaker CB5, which are provided adjacent to the substation 33 side terminal (C end) of No. 1 power transmission line 1L, and controls opening and closing of circuit breaker CB5. The protective relay RY6 is connected to a current transformer CT6 and a circuit breaker CB6 that are provided adjacent to a terminal (C end) on the substation 33 side of the No. 2 power transmission line 2L, and controls opening and closing of the circuit breaker CB6.

The protection relays RY1 to RY6, the switch control device SWCU, and the host computer 35 are interconnected via a communication path (not shown) that performs serial transmission. As a result, each protection relay RY receives switching information for the switches SW1 to SW3 from the switch control device SWCU, and further receives instructions from the host computer 35. A specific example of the configuration of the communication path will be described later.

In addition, the structure of the said multiterminal power transmission system 30 is an example, Comprising: It is not intended to be limited to this. More generally, a multiterminal power transmission system includes a plurality of power transmission lines that electrically connect three or more substations. Each power transmission line connects any one substation among the three or more substations and one or more other substations. A multi-terminal power transmission system further includes one or more transmission lines, a plurality of switches provided between the transmission lines, a plurality of circuit breakers individually provided adjacent to the terminals of each transmission line, and a plurality of circuit breakers provided individually adjacent to the terminals of each transmission line. and multiple current transformers individually provided between the wire terminals and the corresponding circuit breakers. By changing the open/close states of the plurality of switches, the electrical connection form between the three or more substations described above is changed. The plurality of protection relays are individually provided corresponding to each terminal of the plurality of power transmission lines.

[How to operate power transmission lines]
By switching the open/close states of the switches SW1 to SW3 in FIG. 1, the electrical connection form between the substations 31 to 33 can be changed. The three-terminal operation and the π pull-in operation of the No. 2 transmission line will be explained below.

FIG. 2 is a diagram for explaining the operating method and protection zone of the multi-terminal power transmission system in FIG. 1. By changing the electrical connection form between the substations 31 to 33, the protection zone based on the current differential method is also changed.

First, referring to FIG. 2(A), when switches SW1 and SW2 are turned on and switch SW3 is disconnected, No. 1 power transmission line 1L connects end A, end B, and end C. It is configured as a terminal power transmission line, and the No. 2 power transmission line 2L is also configured as a three-terminal power transmission line that connects the A end, B end, and C end. Hereinafter, this operating method will be referred to as three-terminal operation. On the other hand, when switches SW1 and SW2 are disconnected and switch SW3 is closed, the No. 1 power transmission line 1L is configured as a two-terminal power transmission line connecting the A end and the B end, and the No. 2 power transmission line 2L is It is configured as a two-terminal power transmission line that connects the A end and the C end, and a two-terminal power transmission line that connects the B end and the C end. This operation method is referred to as Line 2 π pull-in operation.

Next, with reference to FIG. 2(B), the protection interval of the current differential method in the case of three-terminal operation will be described. In this case, there are two protection intervals.

The first protection zone is constituted by zone A-1L, zone B-1L, and zone C-1L in FIG. In this case, protection relay calculation using the current differential method is executed by the protection relays RY1, RY3, and RY5 provided corresponding to the terminals of the protection section. If the instantaneous values of the currents detected by current transformers CT1, CT3, and CT5 are i1, i3, and i5, respectively, each of the protective relays RY1, RY3, and RY5 detects when the sum of these currents (i1+i3+i5) exceeds the threshold value. If the accident occurs within the protected area, it is determined that the accident occurred within the protected area.

The second protection zone is constituted by zone A-2L, zone B-2L, and zone C-2L in FIG. In this case, protection relay calculation using the current differential method is executed by the protection relays RY2, RY4, and RY6 provided corresponding to the terminals of the protection section. If the instantaneous values of the currents detected by current transformers CT2, CT4, and CT6 are i2, i4, and i6, respectively, then each of the protective relays RY2, RY4, and RY6 detects when the sum of these currents (i.e., i2+i4+i6) exceeds the threshold value. If the accident occurs within the protected area, it is determined that the accident occurred within the protected area.

Next, with reference to FIG. 2(C), a protection section of the current differential method in the case of the π pull-in operation of Line 2 will be described. In this case, there are three protection intervals.

The first protection zone is constituted by zone A-1L and zone B-1L in FIG. In this case, protection relay calculation using the current differential method is executed by the protection relays RY1 and RY3 provided corresponding to the terminals of the protection section. Assuming that the instantaneous values of the currents detected by current transformers CT1 and CT3 are i1 and i3, respectively, each of protection relays RY1 and RY3 changes the protection interval when the sum of these currents (i1+i3) exceeds the threshold value. It was determined that the accident occurred inside the building.

The second protection zone is constituted by zone A-2L and zone C-1L in FIG. In this case, protection relay calculation using the current differential method is executed by the protection relays RY2 and RY5 provided corresponding to the terminals of the protection section. Assuming that the instantaneous values of the currents detected by current transformers CT2 and CT5 are i2 and i5, respectively, each of protection relays RY2 and RY5 changes the protection interval when the sum of these currents (i2+i5) exceeds the threshold value. It was determined that the accident occurred inside the building.

The third protection zone is constituted by zone B-2L and zone C-2L in FIG. In this case, protection relay calculation using the current differential method is executed by protection relays RY4 and RY6 provided corresponding to the terminals of the protection section. Assuming that the instantaneous values of the currents detected by current transformers CT4 and CT6 are i4 and i6, respectively, each of protection relays RY4 and RY6 changes the protection interval when the sum of these currents (i4+i6) exceeds the threshold value. It was determined that the accident occurred inside the building.

As described above, the configuration of the protection zone based on the current differential method and the open/close states of the switches SW1 to SW3 are associated with each other. Each protection relay RY of the present embodiment is configured to automatically switch the protection interval based on information on the open/close states of the switches SW1 to SW3 received from the switch control device SWCU via a communication path. There is.

[Example of communication channel configuration]
FIG. 3 is a diagram showing an example of a configuration of a communication path using Ethernet. As shown in FIG. 3, network switches 40 and 50 are arranged in the control center 34. In the substation 31, network switches 41, 42, 51, and 52 are arranged. Network switches 43, 44, 53, and 54 are arranged in the substation 33. Network switches 45, 46, 51, and 52 are arranged in the substation 32. Network switches 47 and 57 are arranged near the switch control device SWCU.

The host computer 35 is connected to each of the network switches 40 and 50. Protection relay RY1 is connected to each of network switches 41 and 51. Protection relay RY2 is connected to each of network switches 42 and 52. Protection relay RY5 is connected to each of network switches 43 and 53. Protection relay RY6 is connected to each of network switches 44 and 54. Protection relay RY3 is connected to each of network switches 45 and 55. Protection relay RY4 is connected to each of network switches 46 and 56. The switch control device SWCU is connected to each of the network switches 47 and 57.

By connecting network switches 40 to 47 via optical fiber 39, a first communication path 49 is configured that connects host computer 35, protection relays RY1 to RY6, and switch control device SWCU. By connecting network switches 50 to 57 via optical fiber 39, a second communication path 59 is configured that connects host computer 35, protection relays RY1 to RY6, and switch control device SWCU. By providing the first communication path 49 and the second communication path 59 in this way to provide redundancy, the reliability of the protection system can be improved.

[Example of hardware configuration of protection relay]
FIG. 4 is a diagram showing an example of the hardware configuration of the protection relay in FIG. 1. Since the protection relays RY1 to RY6 in FIG. 1 have the same configuration, the protection relay RY1 will be described below as a representative example.

Referring to FIG. 4, protection relay RY1 includes an input conversion section 100, an A/D conversion section 110, an arithmetic processing section 120, and an input/output section (I/O section) 130.

The input conversion section 100 is an input section into which current signals of each phase output from the current transformer CT1 in FIG. 1 are input. The input converter 100 is provided with input converters 101a, 101b, . . . for each channel. Current signals of each phase are input to each channel (only two channels are typically shown in FIG. 4). Each input converter 101a, 101b is configured, for example, by an auxiliary transformer, and converts the current signal from the current transformer CT1 into a signal at a voltage level suitable for signal processing in the A/D converter 110 and the arithmetic processing unit 120. Convert.

The A/D conversion unit 110 includes an analog filter (AF) 111, a sample and hold circuit (S/H) 112, a multiplexer (MPX) 113, and an analog/digital (A/D) circuit. ) converter 114. Each of the analog filters 111 (111a, 111b, . . . ) and sample-and-hold circuits 112 (112a, 112b, . . . ) is provided for each channel corresponding to the plurality of input converters 101 (101a, 101b, .

Each analog filter 111 is a filter provided to remove aliasing errors during A/D conversion. Each sample and hold circuit 112 samples and holds the signal that has passed through the corresponding analog filter 111 at a specified sample rate (also referred to as sampling frequency). Multiplexer 113 sequentially selects the voltage signals held in each sample and hold circuit 112. A/D converter 114 converts the signal selected by the multiplexer into a digital value.

The arithmetic processing unit 120 includes a CPU (Central Processing Unit) 121, a RAM (Random Access Memory) 122, a ROM (Read Only Memory) 123, and an electrically rewritable nonvolatile memory 124 such as a flash memory. Each of these elements is interconnected via a bus 125. RAM122 and ROM123 are used as main memory of CPU121. CPU 121 controls the overall operation of protection relay RY1 according to programs stored in ROM 123 and nonvolatile memory 124.

The input/output unit 130 includes a communication circuit (TX/RX) 131 connected to the network switch 41 in FIG. 3, and a communication circuit 132 connected to the network switch 51 in FIG. Furthermore, the input/output unit 130 includes a digital input (D/I) circuit 133 and a digital output (D/O) circuit 134. The digital input circuit 133 is an interface circuit for receiving a signal output from an external device, and the digital output circuit 134 is an interface circuit for outputting a signal to the external device. For example, the digital output circuit 134 outputs a trip signal to the corresponding circuit breaker CB1, and the digital input circuit 133 acquires information on the open/closed state of the corresponding circuit breaker CB1.

[Example of hardware configuration of switch control device]
FIG. 5 is a diagram showing an example of the hardware configuration of the switch control device shown in FIG. 1. Referring to FIG. 5, the switch control device SWCU includes an arithmetic processing section 200 and an input/output section (I/O section) 210.

The arithmetic processing unit 200 includes a CPU 201, a RAM 202, a ROM 203, and an electrically rewritable nonvolatile memory 204 such as a flash memory. Each of these elements is interconnected via a bus 205. RAM202 and ROM203 are used as main memory of CPU201. CPU 201 controls the overall operation of switch control device SWCU according to programs stored in ROM 203 and nonvolatile memory 204.

The input/output unit 210 includes a communication circuit (TX/RX) 211 connected to the network switch 47 in FIG. 3, and a communication circuit 212 connected to the network switch 57 in FIG. Further, the input/output section 210 includes a digital input (D/I) circuit 213 and a digital output (D/O) circuit 214. The digital input circuit 213 is an interface circuit for receiving a signal output from an external device, and the digital output circuit 214 is an interface circuit for outputting a signal to the external device. Specifically, the digital output circuit 214 outputs a closing command or an opening command to the switches SW1 to SW3 based on a command from the host computer 35. The digital input circuit 213 acquires information on the open/close states of the switches SW1 to SW3.

[Example of hardware configuration of host computer]
FIG. 6 is a diagram showing an example of the hardware configuration of the host computer in FIG. 1. Referring to FIG. 5, host computer 35 includes an arithmetic processing section 300 and an input/output section (I/O section) 310.

The arithmetic processing unit 300 includes a CPU 301, a RAM 302, a ROM 303, and an electrically rewritable nonvolatile memory 304 such as a flash memory. Each of these elements is interconnected via a bus 305. RAM302 and ROM303 are used as main memory of CPU301. CPU 301 controls the overall operation of host computer 35 according to programs stored in ROM 303 and nonvolatile memory 304 .

The input/output unit 310 includes a communication circuit (TX/RX) 311 connected to the network switch 40 in FIG. 3, and a communication circuit 312 connected to the network switch 50 in FIG.

[Protection relay operation]
Next, the protection operation of the multi-terminal power transmission system 30 by each protection relay RY will be explained. Since each of protection relays RY1 to RY6 performs similar protection operations, the operation of protection relay RY1 will be described below.

FIG. 7 is a functional block diagram showing the operation of the arithmetic processing section of the protection relay RY1. In FIG. 7, current transformer CT1, circuit breaker CB1, and network switches 41, 51 connected to protective relay RY1, sample and hold circuit 112, A/D converter 114, communication circuit 131, and 132 and digital input/output circuits 133 and 134 are also shown.

Referring to FIG. 7, from a functional perspective, the arithmetic processing unit 120 includes a protection interval identification unit 62, a sampling synchronization control unit 61, a protection relay calculation unit 63, and a logic calculation unit 64. Each of these functions is realized by the CPU 121 executing a program.

The protection zone specifying unit 62 receives information on the open/closed states of the switches SW1 to SW3 from the switch control device SWCU via the communication path 49 or 59. The protection zone identifying unit 62 identifies all other terminals that are electrically connected to the own terminal of the power transmission line provided with the corresponding circuit breaker CB1 when the open/close states of the switches SW1 to SW3 are changed. By this, the protection section including the own terminal to be protected is specified using the current differential method. For example, information representing the correspondence between the open/close state patterns of the switches SW1 to SW3 and the protection intervals corresponding to each pattern is stored in advance in the memory (ROM 123, nonvolatile memory 124). The protection section specifying unit 62 specifies the protection section corresponding to the received open/close states of the switches SW1 to SW3 based on the information representing this correspondence.

The sampling synchronization control unit 61 communicates with the sampling synchronization control unit 61 of the protection relay RY associated with the other terminal specified by the protection interval identification unit 62 via the communication path 49 or 59. The sampling timing of the current at the terminal and the sampling timing of the current at each of the specified other terminals are synchronized.

Various methods can be adopted as the sampling synchronization method. In this embodiment, PTP (Precision Time Protocol) of the IEEE1588 standard using Ethernet is used. As another method, the clocks provided in each protection relay RY may be synchronized by using GPS (Global Positioning System) signals. Alternatively, the protection relay RY of the own terminal and the protection relay RY of the other terminal transmit the timing flag to each other via a dedicated line, and the time difference between the transmission time and reception time of the timing flag at both the own terminal and the other terminal is determined. Based on this, sampling timing can be synchronized.

Note that if it is possible to synchronize the sampling timings of currents at all terminals of all power transmission lines, the sampling synchronization control unit 61 may first establish synchronization of sampling timings at all terminals. In this case, even if the protection interval is changed due to a change in the open/closed state of the switch SW, there is no need to re-establish the synchronization of the sampling timing. For example, by connecting each protection relay RY via an optical fiber or a plurality of communication devices, it is possible to achieve the same sampling synchronization among all protection relays. Alternatively, sampling synchronization at all terminals may be performed by synchronizing the built-in clock of each protection relay RY using a GPS signal. Details will be explained in Embodiment 4.

The protection relay calculation unit 63 receives the current sampling value at each other terminal from the protection relay RY at each other terminal via the communication path 49 or 59. The protective relay calculation unit 63 executes relay calculation using a current differential method based on the current sampling value at its own terminal and the current sampling value at each other terminal at the same time.

The logic calculation unit 64 outputs a trip signal to the corresponding circuit breaker CB1, or outputs a signal for re-closing the corresponding circuit breaker CB1, based on the relay calculation result in the protection relay calculation unit 63. do. Further, the logic calculation unit 64 outputs a control signal for performing an opening operation and a closing operation on the corresponding circuit breaker CB1 according to a command from the host computer 35. Further, when changing the open/close states of the switches SW1 to SW3, the logic calculation unit 64 determines whether the order of opening and closing of each switch SW and related circuit breaker CB follows a predetermined procedure.

[Protection system operation]
Next, the operation of the entire protection system including the host computer 35, switch control device SWCU, and each protection relay RY will be explained.

8 and 9 are flowcharts illustrating an example of the operation of the multi-terminal power transmission system protection system of FIG. 1. As shown below, the flowchart in Figure 8 shows the procedure when switching from 3-terminal operation to π-pulling operation on Line 2, and the flowchart in Figure 9 shows the procedure when switching from π-pulling operation on Line 2 to 3-terminal operation. Show the steps. By automatically switching the protection interval according to the operation method, protection of the multi-terminal power transmission system 30 by the protection relay RY is realized in any operation.

Referring to FIG. 8, in step S100, multi-terminal power transmission system 30 of FIG. 1 is in three-terminal operation under the control of host computer 35. That is, switches SW1 and SW2 are in a closed state, and switch SW3 is in an open state.

In the next step S105, the host computer 35 first outputs a command to disconnect the circuit breaker CB5 to the protection relay RY5 in order to switch from the three-terminal operation to the π pull-in operation of line 2. In step S300, protection relay RY5, which has received the command to disconnect circuit breaker CB5 via communication path 49 or 59, outputs a control signal for disconnecting circuit breaker CB5 to circuit breaker CB5.

In the next step S110, the host computer 35 outputs a command to disconnect the switch SW1 to the switch control device SWCU. In step S200, the switch control device SWCU, which has received the command to disconnect the switch SW1 via the communication path 49 or 59, outputs a control signal for disconnecting the switch SW1 to the switch SW1.

In the next step S115, the host computer 35 outputs a command to disconnect the circuit breaker CB2 to the protection relay RY2. In step S305, protection relay RY2, which has received the command to disconnect circuit breaker CB2 via communication path 49 or 59, outputs a control signal for disconnecting circuit breaker CB2 to circuit breaker CB2.

In the next step S120, the host computer 35 outputs a command to disconnect the switch SW2 to the switch control device SWCU. In step S205, the switch control device SWCU, which has received the command to disconnect the switch SW2 via the communication path 49 or 59, outputs a control signal for disconnecting the switch SW2 to the switch SW2.

In the next step S125, the host computer 35 outputs a closing command for the switch SW3 to the switch control device SWCU. In step S210, the switch control device SWCU, which has received the command to close the switch SW3 via the communication path 49 or 59, outputs a control signal for closing the switch SW3 to the switch SW3.

In the next step S310, each protection relay RY determines whether the order of closing or disconnecting the circuit breakers CB2, CB5 and switches SW1 to SW3 is in accordance with a predetermined order. This verifies whether the switching of the operation method is valid. Each protective relay RY notifies the host computer 35 of an abnormality if the order of closing or disconnecting the circuit breaker CB and the switch SW does not follow the predetermined order (NO in step S310). Interrupt processing. On the other hand, in each protection relay RY, when the order of closing or disconnecting the circuit breaker CB and the switch SW follows a predetermined order (YES in step S310), the process proceeds to the next step S315.

In step S315, the protection section specifying unit 62 (see FIG. 7) of each protection relay RY specifies the protection section corresponding to the π pull-in operation of Line 2. In the next step S320, each protection relay RY locks its relay operation. In the next step S325, the sampling synchronization control unit 61 of each protection relay RY communicates with other protection relays RY constituting the specified protection interval to adjust the current sampling timing between its own terminal and other terminals. synchronize.

In the next step S330, each protection relay RY changes the calculation formula for differential relay calculation to one corresponding to the protection section of the π pull-in operation. In the next step S335, each protection relay RY unlocks its relay operation. With the above steps, switching of protection sections by each protection relay RY is completed.

In the next step S130, host computer 35 outputs a closing command for circuit breaker CB5 to protection relay RY5. In step S340, protection relay RY5, which has received the closing command for circuit breaker CB5 via communication path 49 or 59, outputs a control signal for closing circuit breaker CB5 to circuit breaker CB5.

In the next step S135, the host computer 35 outputs a closing command for the circuit breaker CB2 to the protective relay RY2. In step S345, protection relay RY2, which has received the closing command for circuit breaker CB2 via communication path 49 or 59, outputs a control signal for closing circuit breaker CB2 to circuit breaker CB2. With the above steps, the switch from the 3-terminal operation to the π pull-in operation of Line 2 is completed.

Referring to FIG. 9, in step S150, under the control of host computer 35, multi-terminal power transmission system 30 of FIG. That is, switches SW1 and SW2 are in an open state, and switch SW3 is in a closed state.

In the next step S155, the host computer 35 first outputs a command to disconnect the circuit breaker CB2 to the protection relay RY2 in order to switch from the π pull-in operation to the 3-terminal operation of line 2. In step S350, protection relay RY2, which has received the command to disconnect circuit breaker CB2 via communication path 49 or 59, outputs a control signal for disconnecting circuit breaker CB2 to circuit breaker CB2.

In the next step S160, host computer 35 outputs a command to disconnect circuit breaker CB5 to protection relay RY5. In step S355, protection relay RY5, which has received the command to disconnect circuit breaker CB5 via communication path 49 or 59, outputs a control signal for disconnecting circuit breaker CB5 to circuit breaker CB5.

In the next step S165, the host computer 35 outputs a command to disconnect the switch SW3 to the switch control device SWCU. In step S250, the switch control device SWCU, which has received the command to disconnect the switch SW3 via the communication path 49 or 59, outputs a control signal for disconnecting the switch SW3 to the switch SW3.

In the next step S170, the host computer 35 outputs a command to close the switch SW2 to the switch control device SWCU. In step S255, the switch control device SWCU, which has received the command to close the switch SW2 via the communication path 49 or 59, outputs a control signal for closing the switch SW2 to the switch SW2.

In the next step S175, the host computer 35 outputs a command to close the switch SW1 to the switch control device SWCU. In step S260, the switch control device SWCU, which has received the command to close the switch SW1 via the communication path 49 or 59, outputs a control signal for closing the switch SW1 to the switch SW1.

In the next step S360, each protection relay RY determines whether the order of closing or disconnecting the circuit breakers CB2, CB5 and switches SW1 to SW3 is in accordance with a predetermined order. This verifies whether the switching of the operation method is valid. Each protective relay RY notifies the host computer 35 of an abnormality if the order of closing or disconnecting the circuit breaker CB and the switch SW does not follow the predetermined order (NO in step S360). Interrupt processing. On the other hand, in each protection relay RY, when the order of closing or disconnecting the circuit breaker CB and the switch SW follows a predetermined order (YES in step S360), the process proceeds to the next step S365.

In step S365, the protection section specifying unit 62 (see FIG. 7) of each protection relay RY specifies a protection section corresponding to three-terminal operation. In the next step S370, each protection relay RY locks relay operation. In the next step S375, the sampling synchronization control unit 61 of each protection relay RY communicates with other protection relays RY constituting the specified protection interval to adjust the current sampling timing between its own terminal and other terminals. synchronize.

In the next step S380, each protection relay RY changes the calculation formula for differential relay calculation to one corresponding to the protection section of three-terminal operation. In the next step S385, each protection relay RY unlocks its relay operation. With the above steps, switching of protection sections by each protection relay RY is completed.

In the next step S180, host computer 35 outputs a closing command for circuit breaker CB2 to protection relay RY2. In step S390, protection relay RY2, which has received the command to close circuit breaker CB2 via communication path 49 or 59, outputs a control signal for closing circuit breaker CB2 to circuit breaker CB2.

In the next step S185, host computer 35 outputs a closing command for circuit breaker CB5 to protection relay RY5. In step S395, protection relay RY5, which has received the closing command for circuit breaker CB5 via communication path 49 or 59, outputs a control signal for closing circuit breaker CB5 to circuit breaker CB5. With the above steps, the switching from the π lead-in operation to the 3-terminal operation of Line 2 is completed.

[Effects of Embodiment 1]
As described above, in the protection system that protects the multi-terminal power transmission system 30, each protection relay RY acquires information on the open/close states of multiple switches, and when the open/close states of multiple switches are changed, Automatically identify the protection zone corresponding to the subsequent opening/closing state. Then, each protection relay RY synchronizes the sampling timing of the current at each terminal of the changed protection section. Further, each protection relay RY automatically changes the current value to be calculated by the current differential method so as to correspond to the changed protection interval. Thereby, protection by the current differential method can be continued even for the multi-terminal power transmission system 30 after changing the open/close state of the switch.

In addition, after outputting a command to open the corresponding circuit breaker CB to at least one protective relay RY in order to change the open/close states of the multiple switches, the host computer 35 closes each of the multiple switches SW. Output command or open command. Thereafter, the host computer 35 outputs a closing command for the corresponding circuit breaker CB to the at least one protection relay RY that has output the opening command. Each protection relay RY determines whether the output order of the above-mentioned opening command for circuit breaker CB and closing command and opening command for each switch SW outputted from host computer 35 follows a predetermined order. When the output order of each command follows a predetermined order, each protection relay RY provides protection using the current differential method for the protection section corresponding to the changed open/close state of the multiple switches SW. Execute. Thereby, the multi-terminal power transmission system 30 can be protected more reliably.

Embodiment 2.
In the second embodiment, a case will be described in which each protection relay RY does not execute protection relay calculations, but the host computer 35 collectively executes protection relay calculations for each protection section. In this case, the protection relay calculation unit 63 is not provided in the calculation processing unit 120 in FIG. Each protection relay RY transmits the current data after A/D conversion to the host computer 35 via the communication path 49 or 59.

FIG. 10 is a functional block diagram showing the operation of the arithmetic processing section of the host computer according to the second embodiment. In FIG. 10, network switches 40 and 50 connected to the host computer 35 and communication circuits 311 and 312 forming the host computer 35 are also shown.

Referring to FIG. 10, when viewed functionally, the arithmetic processing section 300 includes a protection section specifying section 66, a protection relay arithmetic section 67, and a logic arithmetic section 68. Each of these functions is realized by the CPU 301 executing a program.

When the operation mode is switched by changing the open/closed state of the switches SW1 to SW3, the protection zone specifying unit 66 specifies all the protection zones corresponding to the switched operation mode. For example, information representing the correspondence between the open/close state patterns of the switches SW1 to SW3 and all the protection intervals corresponding to each pattern is stored in advance in the memory (ROM 303, nonvolatile memory 304). The protection section specifying unit 66 specifies all the protection sections corresponding to the open/closed states of the switches SW1 to SW3 based on the information representing this correspondence.

Protection relay calculation unit 67 receives current data sampled by each of protection relays RY1 to RY6. The protection relay calculation unit 67 performs relay calculation using a current differential method for each protection section based on the received current data.

If there is a protection section in which an internal accident has occurred based on the protection relay calculation result for each protection section, the logic calculation unit 68 is configured to detect the accident in order to separate the fault section from the multi-terminal power transmission system 30. A circuit breaker CB opening command is output to each protective relay RY corresponding to the section.

[Modification of Embodiment 2]
Any one of protection relays RY1 to RY6 may be configured to execute all protection relay calculations at once. For example, when protection relay RY1 executes all protection relay calculations at once, protection relay calculation unit 63 is not provided in calculation processing unit 120 of each of protection relays RY2 to RY6. Each of protection relays RY2 to RY6 transmits the current data after A/D conversion to protection relay RY1 via communication path 49 or 59.

When the open/close states of the switches SW1 to SW3 are changed, the protection section specifying unit 62 of the protection relay RY1 specifies all the protection sections corresponding to the changed open/close states of the switches SW1 to SW3. Information representing the correspondence between the open/close state patterns of the switches SW1 to SW3 and all the protection intervals corresponding to each pattern is stored in advance in the memory (ROM 123, nonvolatile memory 124). The protection section specifying unit 62 specifies all the protection sections corresponding to the open/closed states of the switches SW1 to SW3 based on the information representing this correspondence relationship.

Protection relay calculation unit 63 receives current data sampled by each of protection relays RY2 to RY6. The protection relay calculation section 63 performs relay calculation using a current differential method for each protection section based on the current data of the own end sampled by itself and the received current data.

If there is a protection section in which an internal accident has occurred based on the protection relay calculation result for each protection section, the logic calculation unit 64 is configured to detect the accident in order to separate the fault section from the multi-terminal power transmission system 30. A circuit breaker CB opening command is output to each protective relay RY corresponding to the section. When the own terminal is included in the fault section, the logic calculation unit 64 outputs a trip signal to the corresponding circuit breaker CB1.

Embodiment 3.
In Embodiment 3, a network configuration between protection relay units will be described in a case where protection relays RY provided in the same substation are configured as a common unit.

FIG. 11 is a diagram showing a configuration example of a communication path using Ethernet in the protection system of the third embodiment. As shown in FIG. 11, in the substation 31, the protection relay elements RY1 and RY2 are provided as a common protection relay unit RY1 & RY2. In the substation 32, the protection relay elements RY3, RY4 are provided as a common protection relay unit RY3&RY4. In the substation 33, the protection relay elements RY5, RY6 are provided as a common protection relay unit RY5&RY6.

Protection relay units RY1 & RY2 are connected to each of network switches 41 and 51. That is, the protection relay elements RY1 and RY2 share the communication circuits 131 and 132 in FIG. 4. Similarly, protection relay units RY3 & RY4 are connected to each of network switches 45, 55, and protection relay units RY5 & RY6 are connected to network switches 43, 53.

By connecting network switches 40, 41, 43, 45, and 47 via optical fiber 39, host computer 35, protection relay units RY1 & RY2, protection relay units RY5 & RY6, protection relay units RY3 & RY4, and switch control device SWCU are connected. A first communication path 49 to be connected is configured. Similarly, network switches 50, 51, 53, 55, and 57 are connected via optical fiber 39, thereby controlling host computer 35, protection relay units RY1 & RY2, protection relay units RY5 & RY6, protection relay units RY3 & RY4, and switch control. A second communication path 59 is configured to connect the devices SWCU.

According to the above configuration, the number of network switches can be reduced. Note that Embodiment 3 can be combined with Embodiment 2 and its modifications.

Embodiment 4.
In Embodiment 4, a case will be described in which sampling timing synchronization is first established at all terminals of all power transmission lines. By connecting each protection relay RY via an optical fiber or a plurality of communication devices, it is possible to achieve the same sampling synchronization among all protection relays. Alternatively, sampling synchronization at all terminals may be performed by synchronizing the built-in clock of each protection relay RY using a GPS signal.

12 and 13 are flowcharts illustrating an example of the operation of the multi-terminal power transmission system protection system according to the fourth embodiment. The flowchart in FIG. 12 shows the procedure when switching from 3-terminal operation to π-pulling operation of Line 2, and the flowchart in FIG. 13 shows the procedure when switching from π-pulling operation of Line 2 to 3-terminal operation. The flowcharts in FIGS. 12 and 13 correspond to the flowcharts in FIGS. 8 and 9, respectively. Hereinafter, steps common to those in the flowcharts of FIGS. 8 and 9 will be given the same reference numerals and the description will not be repeated.

Referring to FIG. 12, all-protection relay RY has established sampling synchronization (step S3000). In this method, each protection relay RY can always calculate the differential current relay calculation required for each protection section, regardless of changes in protection sections due to switch switching. As a result, even if the protection interval is changed, it is only necessary to switch the protection relay calculation result to be output, so there is no need to lock and unlock the relay operation.

The subsequent steps S100 to S125, steps S200 to S210, and steps S300 to S310 are the same procedures as in the flowchart of FIG. 8, so the description will not be repeated.

In the next step S315, the protection section specifying unit 62 (see FIG. 7) of each protection relay RY specifies the protection section corresponding to the π pull-in operation of Line 2. In the next step S330, each protection relay RY changes the calculation formula for differential relay calculation to one corresponding to the protection section of the π pull-in operation.

In the case of FIG. 8, step S320 locks the relay operation of each protection relay RY, step S325 establishes sampling synchronization at each terminal within the specified protection interval, and step S335 unlocks the relay operation. It was necessary. However, in the case of FIG. 12, these steps S320, S325, and S335 are not necessary. Sampling synchronization for all terminals has been established, and furthermore, with the opening of the circuit breaker CB, no current flows through the current transformer CT involved in changing the protection zone, so there is no need to stop the relay operation. No matter what protection interval is changed, calculations according to the current differential relay system can be executed immediately and the calculation results can be output.

Thereafter, based on the closing command from the host computer 35 (steps S130, S135), circuit breaker CB5 and circuit breaker CB2 are closed (steps S340, S345), thereby changing the 3-terminal operation to the π pull-in operation of Line 2. The switching is completed.

Referring to FIG. 13, all protection relays have established sampling synchronization (step S3500). The subsequent steps S150 to S175, steps S250 to S260, and steps S350 to S360 are the same procedures as in the flowchart of FIG. 9, so the description will not be repeated.

In the next step S365, the protection section specifying unit 62 (see FIG. 7) of each protection relay RY specifies a protection section corresponding to three-terminal operation. In the next step S380, each protection relay RY changes the calculation formula for differential relay calculation to one corresponding to the protection section of three-terminal operation.

In the case of FIG. 13, unlike the case of FIG. 9, there are a step S370 of locking the relay operation of each protection relay RY, a step S375 of establishing sampling synchronization at each terminal within the specified protection interval, and a step S375 of locking the relay operation. Step S385 for canceling is not necessary. As explained in Fig. 12, sampling synchronization for all terminals has been established, and furthermore, due to the opening of circuit breaker CB, no current flows through the current transformer CT related to the protection interval change, so the relay This is because there is no need to stop the operation.

Thereafter, based on the closing command from the host computer 35 (steps S180, S185), circuit breaker CB2 and circuit breaker CB5 are closed (steps S390, S395), thereby changing the line 2 from π pull-in operation to 3-terminal operation. The switching is completed.

[Modifications of Embodiments 1 to 4]
In FIGS. 4 to 6, examples of the hardware configuration of the protection relay RY, the switch control device SWCU, and the host computer 35 are shown, but other configurations may be used. For example, a plurality of CPUs may be provided. The arithmetic processing units 120, 200, and 300 may be configured as a dedicated circuit such as an ASIC (Application Specific Integrated Circuit), or may be configured using an FPGA (Field Programmable Gate Array). Alternatively, the arithmetic processing units 120, 200, and 300 may be configured by appropriately combining at least two of a CPU, an ASIC, and an FPGA. Further, the host computer 35 may be configured by a plurality of server devices.

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of this application is indicated by the claims rather than the above description, and it is intended that all changes within the meaning and range equivalent to the claims are included.

1L, 2L power transmission line, 30 multi-terminal power transmission system, 31-33 substation, 34 control center, 35 host computer, 40-47, 50-57 network switch, 49, 59 communication path, 61 sampling synchronization control unit, 62, 66 protection zone identification unit, 63, 67 protection relay calculation unit, 64, 68 logic calculation unit, 120, 200, 300 calculation processing unit, CB circuit breaker, CT current transformer, RY protection relay, SW switch, SWCU switch Control device.

Claims (9)

A protection system for a multi-terminal power transmission system, comprising:
The multi-terminal power transmission system includes a plurality of power transmission lines connecting three or more substations,
Each of the plurality of power transmission lines connects any one substation among the three or more substations and one or more other substations,
The multi-terminal power transmission system further includes:
one or more power transmission lines and a plurality of switches provided between the power transmission lines;
a plurality of circuit breakers individually provided adjacent to the terminals of each of the power transmission lines;
The protection system includes a plurality of protection relays provided individually corresponding to each terminal of the plurality of power transmission lines and connected to each other via a communication path,
Each of the plurality of protection relays includes:
When the open/close states of the plurality of switches are changed, all other terminals electrically connected to the own terminal of the corresponding power transmission line are connected based on information on the changed open/close states of the plurality of switches. a protection area identification unit that identifies a protection area to be protected using a current differential method by specifying the protection area;
Protection of a multi-terminal power transmission system, comprising a protective relay calculation unit that performs relay calculation using a current differential method based on a current value sampled at the own terminal and a current value sampled at each of the specified other terminals. system. Each of the plurality of protection relays includes:
The present invention further comprises a sampling synchronization control unit that synchronizes the sampling timing of the current at the own terminal and the sampling timing of the current at each of the specified other terminals when the open/close states of the plurality of switches are changed. A protection system for a multi-terminal power transmission system according to item 1. Each of the plurality of protection relays includes:
The multi-terminal power transmission according to claim 1, further comprising a sampling synchronization control unit that synchronizes sampling timing of current at the own terminal and sampling timing of current at all terminals of the plurality of power transmission lines except the own terminal. Grid protection system. Each of the plurality of protection relays includes a memory that stores information representing a correspondence relationship between open/closed state patterns of the plurality of switches and protection intervals corresponding to each pattern,
4. The protection area specifying unit identifies a protection area corresponding to a changed open/closed state of the plurality of switches based on information representing the correspondence relationship. Protection systems for multi-terminal power transmission systems. The protection system further comprises:
a switch control device connected to the communication path and controlling the open/close states of the plurality of switches;
a host computer connected to the communication path and outputting a closing command or opening command for each of the plurality of switches to the switch control device;
The host computer outputs a command to open a circuit breaker provided adjacent to a corresponding terminal to at least one protection relay in order to change the open/close state of the plurality of switches, and then Claims 1 to 4, wherein a closing command or opening command for each of the switches is output, and then a closing command for the corresponding circuit breaker is output to the at least one protection relay to which the opening command is output. A protection system for a multi-terminal power transmission system according to any one of the above. Each of the plurality of protection relays has a predetermined output order of the opening command of the corresponding circuit breaker outputted to the at least one protection relay and the closing command or opening command of each of the plurality of switches. The protection system for a multi-terminal power transmission system according to claim 5, which determines whether or not the order is followed. Each of the plurality of protection relays performs protection using a current differential method for a protection section corresponding to a changed open/closed state of the plurality of switches when the output order follows a predetermined order. The protection system for a multi-terminal power transmission system according to claim 6. A protection system for a multi-terminal power transmission system, comprising:
The multi-terminal power transmission system includes a plurality of power transmission lines connecting three or more substations,
Each of the plurality of power transmission lines connects any one substation among the three or more substations and one or more other substations,
The multi-terminal power transmission system further includes:
one or more power transmission lines and a plurality of switches provided between the power transmission lines;
a plurality of circuit breakers individually provided adjacent to the terminals of each of the power transmission lines;
The protection system includes:
a plurality of protection relays provided individually corresponding to each terminal of the plurality of power transmission lines and connected to each other via a communication path;
and a host computer connected to the plurality of protection relays via the communication path,
The upper level computer is
A protection interval that identifies all protection intervals to be protected using a current differential method based on information on the changed open/close states of the plurality of switches when the open/close states of the plurality of switches are changed. A specific part,
A protection system for a multi-terminal power transmission system, comprising: a protection relay calculation unit that performs relay calculation using a current differential method based on current values sampled at each terminal for each of all of the protection intervals. A protection system for a multi-terminal power transmission system, comprising:
The multi-terminal power transmission system includes a plurality of power transmission lines connecting three or more substations,
Each of the plurality of power transmission lines connects any one substation among the three or more substations and one or more other substations,
The multi-terminal power transmission system further includes:
one or more power transmission lines and a plurality of switches provided between the power transmission lines;
a plurality of circuit breakers individually provided adjacent to the terminals of each of the power transmission lines;
The protection system includes:
comprising a plurality of protection relays individually provided corresponding to each terminal of the plurality of power transmission lines and connected to each other via a communication path,
The first protection relay among the plurality of protection relays is
A protection interval that identifies all protection intervals to be protected using a current differential method based on information on the changed open/close states of the plurality of switches when the open/close states of the plurality of switches are changed. A specific part,
A protection system for a multi-terminal power transmission system, comprising: a protection relay calculation unit that performs relay calculation using a current differential method based on current values sampled at each terminal for each of all of the protection intervals.

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