JP2021136707A - Protection system for multi-terminal power transmission system - Google Patents

Abstract

To provide a protection system which protects a multi-terminal power transmission system, in which a protection section is changed by the change of open/close states of a plurality of switches, using a current differential method.SOLUTION: The protection system includes a plurality of protection relays RY which are connected each other through communication. Each protection relay RY includes: a protection section identification unit 62 which, when the open/close state of the plurality of switch SW is changed, identifies the protection section based on the information of the open/close state after the change of a switch SW; and a protection relay calculation unit 63 which performs protection relay calculation using the current differential method, based on a current value sampled at each terminal of the identified protection section.SELECTED DRAWING: Figure 7

Description

This disclosure relates to a protection system that protects a multi-terminal transmission system.

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

Specifically, the current differential relay of this document is used as a transmission line based on the difference between the current on the own terminal side and the current on the other terminal side when the line jumper is determined to be in the "on" state by the state determination unit. Detect the accident that occurred. On the other hand, when the state determination unit determines that the line jumper is in the "off" state, this current differential relay detects an accident that has occurred in the transmission line based only on the current on the own terminal side.

Japanese Unexamined Patent Publication No. 2011-239521

For example, the current differential relay that protects the multi-terminal transmission line network of multiple lines in which the No. 1 transmission line and the No. 2 transmission line are laid in one steel tower is the current differential relay for the No. 1 transmission line and the No. 2 transmission. A current differential relay for electric wires is required. The current differential relay for the No. 1 transmission line uses the current of each terminal of the No. 1 transmission line to determine the presence or absence of an internal accident, and the current differential relay for the No. 2 transmission line is for each of the No. 2 transmission lines. 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 transmission line network, or when changing one line to a π lead-in line, power supply to consumers is provided. It is necessary not to stop as much as possible. For this reason, it is convenient to provide a plurality of switches for connecting between the No. 1 transmission line and the No. 2 transmission line. This is because there are cases where a detour route using another transmission line cannot be taken.

However, if the No. 1 transmission line and the No. 2 transmission line are connected by using a switch, or if each transmission line is separated in the middle, the protection section of the current differential relay is changed. In the prior art, the means for dealing with such a case has not been clarified.

The present disclosure has been made in consideration of the above-mentioned problems, and one of the purposes thereof is to provide a multi-terminal power transmission system in which the protection section is changed by changing the open / closed state of a plurality of switches. It is to provide a protection system for protection by the dynamic method.

In one aspect, a protection system for multi-terminal transmission systems is provided. The multi-terminal transmission system includes a plurality of transmission lines connecting three or more substations, a plurality of switches, and a plurality of circuit breakers. Each transmission line connects one of three or more substations to one or more other substations. A plurality of switches are provided between one or more transmission lines and transmission lines. A plurality of circuit breakers are individually provided adjacent to the terminals of each transmission line. The protection system includes a plurality of protection relays individually provided corresponding to each terminal of the plurality of transmission lines and connected to each other via a communication path. Each protection relay includes a protection section specifying unit and a protection relay calculation unit. When the open / closed state of a plurality of switches is changed, the protection section identification unit supplies electricity to the own terminal of the transmission line provided with the corresponding circuit breaker based on the information of the opened / closed state after the change of the multiple switches. By identifying all the other terminals that are specifically connected, the protection section to be protected is specified using the current differential method. The protection relay calculation unit performs a relay calculation by the current differential method based on the current value sampled at its own terminal and the current value sampled at each of the other specified terminals.

According to the above-mentioned one-phase protection system, when the open / closed state of a plurality of switches is changed, each protection relay sets the changed protection section based on the information of the changed open / closed state of the plurality of switches. The multi-terminal power transmission system can be protected by specifying and performing relay calculation by the current differential method based on the specified protection section.

It is a figure which shows the configuration example of a multi-terminal power transmission system and its protection system. It is a figure for demonstrating the operation method and protection section of the multi-terminal power transmission system of FIG. It is a figure which shows the configuration example of the communication path by Ethernet (registered trademark). It is a figure which shows an example of the hardware configuration of the protection relay of FIG. It is a figure which shows an example of the hardware composition of the switch control device of FIG. It is a figure which shows an example of the hardware configuration of the upper computer of FIG. It is a functional block diagram which shows the operation of the arithmetic processing part of a protection relay. It is a flowchart which shows an example of the operation of the protection system of the multi-terminal power transmission system of FIG. It is a flowchart which shows an example of the operation of the protection system of the multi-terminal power transmission system of FIG. It is a functional block diagram which shows the operation of the arithmetic processing part of the high-order computer by Embodiment 2. FIG. It is a figure which shows the configuration example of the communication path by Ethernet in the protection system of Embodiment 3. It is a flowchart which shows an example of the operation of the protection system of the multi-terminal power transmission system according to Embodiment 4 (the procedure when switching from the 3-terminal operation to the π lead-in operation of line 2 is shown). It is a flowchart which shows an example of the operation of the protection system of a multi-terminal power transmission system according to Embodiment 4 (the procedure when switching from the π lead-in operation of line 2 to the 3-terminal operation is shown).

Hereinafter, each embodiment will be described in detail with reference to the drawings. In some cases, the same or corresponding parts are designated by the same reference numerals and the description thereof may not be repeated.

Embodiment 1.
[Overall configuration example of protection system for multi-terminal power transmission system]
FIG. 1 is a diagram showing a configuration example of a multi-terminal power transmission system and a protection system thereof.

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

The multi-terminal transmission system 30 further includes circuit breakers CB1, CB3, CB5 provided adjacent to each terminal of the No. 1 transmission line 1L and a circuit breaker provided adjacent to each terminal of the No. 2 transmission line 2L. Includes CB2, CB4, and CB6. Further, the multi-terminal transmission system 30 includes current transformers CT1, CT3, CT5 and terminals of the No. 2 transmission line 2L, which are individually provided between each terminal of the No. 1 transmission line 1L and the corresponding circuit breaker. Includes current transformers CT2, CT4, CT6, which are individually provided between the circuit breaker and the corresponding circuit breaker. 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 generically or unspecified.

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

In FIG. 1, one transmission line is used for easy illustration, but in the case of a three-phase transmission line, there are actually three transmission lines. Further, each of the circuit breaker CB, the current transformer CT, and the switch SW is actually provided for each phase, but in the present disclosure, the three phases are collectively provided as one breaker CB and the current transformer CT. , And the switch SW.

The protection system for protecting the multi-terminal power transmission system 30 having the above configuration is provided in the protection relays RY1 and RY2 provided in the substation 31, the protection relays RY3 and RY4 provided in the substation 32, and the substation 33. Includes protection relays RY5 and RY6, a switch control device SWCU that controls the opening and closing of switches SW1 to SW3, and a host computer 35 provided at the control station 34. The protection relays RY1 to RY6 are collectively referred to as protection relays RY when they are generically or unspecified.

The protection relay RY1 is connected to the current transformer CT1 and the circuit breaker CB1 provided adjacent to the terminal (A end) on the substation 31 side of the No. 1 transmission line 1L. The protection relay RY1 controls the opening and closing of the circuit breaker CB1. Similarly, the protection relay RY2 is connected to the current transformer CT2 and the circuit breaker CB2 provided adjacent to the terminal (A end) on the substation 31 side of the No. 2 transmission line 2L to control the opening and closing of the circuit breaker CB2. do. The protection relay RY3 is connected to the current transformer CT3 and the circuit breaker CB3 provided adjacent to the terminal (B end) on the substation 32 side of the No. 1 transmission line 1L, and controls the opening and closing of the circuit breaker CB3. The protection relay RY4 is connected to the current transformer CT4 and the circuit breaker CB4 provided adjacent to the terminal (B end) on the substation 32 side of the No. 2 transmission line 2L, and controls the opening and closing of the circuit breaker CB4. The protection relay RY5 is connected to the current transformer CT5 and the circuit breaker CB5 provided adjacent to the terminal (C end) on the substation 33 side of the No. 1 transmission line 1L, and controls the opening and closing of the circuit breaker CB5. The protection relay RY6 is connected to the current transformer CT6 and the circuit breaker CB6 provided adjacent to the terminal (C end) on the substation 33 side of the No. 2 transmission line 2L, and controls the 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 connected to each other via a communication path (not shown) for serial transmission. As a result, each protection relay RY receives the switch opening / closing information of the switches SW1 to SW3 from the switch control device SWCU, and further receives a command from the host computer 35. A specific configuration example of the communication path will be described later.

The configuration of the multi-terminal power transmission system 30 described above is an example, and is not intended to be limited to this. More generally, a multi-terminal transmission system includes a plurality of transmission lines that electrically connect three or more substations. Each transmission line connects one of three or more substations to one or more other substations. The multi-terminal transmission system further includes a plurality of switches provided between one or more transmission lines and transmission lines, and a plurality of circuit breakers individually provided adjacent to the terminals of each transmission line, and each transmission. Includes multiple current transformers that are individually provided between the terminals of the wire and the corresponding circuit breakers. By changing the open / closed state 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 transmission lines.

[How to operate transmission lines]
By switching the open / closed state of the switches SW1 to SW3 in FIG. 1, the electrical connection form between the substations 31 to 33 can be changed. Hereinafter, the operation of 3 terminals and the operation of π lead-in of the No. 2 transmission line will be described.

FIG. 2 is a diagram for explaining an operation method and a protection section of the multi-terminal power transmission system of FIG. By changing the electrical connection form between the substations 31 to 33, the protection section by the current differential method is also changed.

First, referring to FIG. 2A, when the switches SW1 and SW2 are turned on and the switches SW3 are disconnected, the No. 1 transmission line 1L connects the A end, the B end, and the C end. It is configured as a terminal transmission line, and the No. 2 transmission line 2L is also configured as a 3-terminal transmission line connecting the A end, the B end, and the C end. Hereinafter, this operation method will be referred to as 3-terminal operation. On the other hand, when the switches SW1 and SW2 are disconnected and the switch SW3 is turned on, the No. 1 transmission line 1L is configured as a two-terminal transmission line connecting the A end and the B end, and the No. 2 transmission line 2L is It is configured as a two-terminal transmission line connecting the A end and the C end and a two-terminal transmission line connecting the B end and the C end. This operation method is called the π pull-in operation of Line 2.

Next, with reference to FIG. 2B, the protection section of the current differential system in the case of 3-terminal operation will be described. In this case, there are two protected sections.

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

The second protected section is composed of the section A-2L, the section B-2L, and the section C-2L of FIG. In this case, the protection relay calculation by the current differential method is executed by the protection relays RY2, RY4, and RY6 provided corresponding to the terminals of the protection section. Assuming that the instantaneous values of the currents detected by the current transformers CT2, CT4, and CT6 are i2, i4, and i6, respectively, the sum of these currents (that is, i2 + i4 + i6) exceeds the threshold value in each of the protection relays RY2, RY4, and RY6. If so, it is determined that the accident is inside the protected section.

Next, with reference to FIG. 2C, the 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 protected sections.

The first protected section is composed of the section A-1L and the section B-1L of FIG. In this case, the protection relay calculation by 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 the current transformers CT1 and CT3 are i1 and i3, respectively, each of the protection relays RY1 and RY3 has a protection section when the sum of these currents (that is, i1 + i3) exceeds the threshold value. Judged as an internal accident.

The second protected section is composed of the section A-2L and the section C-1L of FIG. In this case, the protection relay calculation by 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 the current transformers CT2 and CT5 are i2 and i5, respectively, each of the protection relays RY2 and RY5 has a protection section when the sum of these currents (that is, i2 + i5) exceeds the threshold value. Judged as an internal accident.

The third protected section is composed of the section B-2L and the section C-2L of FIG. In this case, the protection relay calculation by the current differential method is executed by the protection relays RY4 and RY6 provided corresponding to the terminals of the protection section. Assuming that the instantaneous values of the currents detected by the current transformers CT4 and CT6 are i4 and i6, respectively, each of the protection relays RY4 and RY6 has a protection section when the sum of these currents (that is, i4 + i6) exceeds the threshold value. Judged as an internal accident.

As described above, the configuration of the protection section by the current differential method and the open / closed state 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 section based on the information on the open / closed state of the switches SW1 to SW3 received from the switch control device SWCU via the communication path. There is.

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

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

By connecting the network switches 40 to 47 via the optical fiber 39, a first communication path 49 for connecting the host computer 35, the protection relays RY1 to RY6, and the switch control device SWCU is configured. By connecting the network switches 50 to 57 via the optical fiber 39, a second communication path 59 for connecting the host computer 35, the protection relays RY1 to RY6, and the switch control device SWCU is configured. 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 enhanced.

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

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

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

The A / D converter 110 includes an analog filter (AF: Analog Filter) 111, a sample hold circuit (S / H: Sample and Hold Circuit) 112, a multiplexer (MPX: Multiplexer) 113, and an analog digital (A / D). ) Includes a converter 114. Each of the analog filter 111 (111a, 111b, ...) And the sample hold circuit 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 for removing a folding error at the time of A / D conversion. Each sample hold circuit 112 samples and holds a signal that has passed through the corresponding analog filter 111 at a specified sample rate (also referred to as a sampling frequency). The multiplexer 113 sequentially selects the voltage signals held in each sample hold circuit 112. The 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 non-volatile memory 124 such as a flash memory. Each of these elements is connected to each other via a bus 125. The RAM 122 and the ROM 123 are used as the main memory of the CPU 121. The CPU 121 controls the overall operation of the protection relay RY1 according to the programs stored in the ROM 123 and the non-volatile memory 124.

The input / output unit 130 includes a communication circuit (TX / RX) 131 connected to the network switch 41 of FIG. 3 and a communication circuit 132 connected to the network switch 51 of FIG. Further, the input / output unit 130 includes a digital input (D / I: Digital Input) circuit 133 and a digital output (D / O: Digital Output) 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 controller]
FIG. 5 is a diagram showing an example of the hardware configuration of the switch control device of FIG. With reference to FIG. 5, the switch control device SWCU includes an arithmetic processing unit 200 and an input / output unit (I / O unit) 210.

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

The input / output unit 210 includes a communication circuit (TX / RX) 211 connected to the network switch 47 of FIG. 3 and a communication circuit 212 connected to the network switch 57 of FIG. Further, the input / output unit 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 / closed state of the switches SW1 to SW3.

[Example of hardware configuration of higher-level calculator]
FIG. 6 is a diagram showing an example of the hardware configuration of the higher-level calculator of FIG. With reference to FIG. 5, the high-level computer 35 includes an arithmetic processing unit 300 and an input / output unit (I / O unit) 310.

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

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

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

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

From a functional point of view with reference to FIG. 7, the arithmetic processing unit 120 includes a protection section specifying unit 62, a sampling synchronization control unit 61, a protection relay arithmetic unit 63, and a logic arithmetic unit 64. Each of these functions is realized by the CPU 121 executing a program.

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

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 section identification unit 62 via the communication path 49 or 59. Synchronize the current sampling timing at the terminals with the current sampling timing at each of the other specified terminals.

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 clock provided in each protection relay RY may be synchronized by using the GPS (Global Positioning System) signal. Alternatively, the timing flag is transmitted to each other from the protection relay RY of the own terminal and the protection relay RY of the other terminal via the dedicated line, and the time difference between the transmission time and the reception time of the timing flag at both the own terminal and the other terminal. The sampling timing can be synchronized based on the above.

If it is possible to synchronize the sampling timing of the currents at all the terminals of all the transmission lines, the sampling synchronization control unit 61 may first establish the synchronization of the sampling timings at all the terminals. In this case, even if the protection section is changed due to the change in the open / closed state of the switch SW, it is not necessary to reestablish the synchronization of the sampling timing. For example, by connecting each protection relay RY via an optical fiber or a plurality of communication devices, the same sampling synchronization can be realized among all protection relays. Further, sampling synchronization may be performed at all terminals by synchronizing the built-in clock for each protection relay RY using GPS signals. Details will be described in the fourth embodiment.

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

The logic calculation unit 64 outputs a trip signal to the corresponding circuit breaker CB1 or outputs a signal for reclosing 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 to the corresponding circuit breaker CB1 in accordance with a command from the host computer 35. Further, the logic calculation unit 64 determines whether the opening / closing order of each switch SW and the related circuit breaker CB follows a predetermined procedure when changing the open / closed state of the switches SW1 to SW3.

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

8 and 9 are flowcharts showing an example of the operation of the protection system of the multi-terminal power transmission system of FIG. As shown below, the flowchart of FIG. 8 shows the procedure for switching from the 3-terminal operation to the π-drawing operation of Line 2, and the flowchart of FIG. 9 shows the procedure for switching from the π-drawing operation of Line 2 to the 3-terminal operation. The procedure is shown. By automatically switching the protection section according to the operation method, the protection of the multi-terminal power transmission system 30 by the protection relay RY is realized in any operation.

With reference to FIG. 8, in step S100, the multi-terminal power transmission system 30 of FIG. 1 is operating at three terminals under the control of the host computer 35. That is, the switches SW1 and SW2 are in the closed state, and the switches SW3 are in the open state.

In the next step S105, the host computer 35 first outputs a disconnection command for the circuit breaker CB5 to the protection relay RY5 in order to switch from the 3-terminal operation to the π pull-in operation of the line 2. In step S300, the protection relay RY5 that has received the disconnection command of the circuit breaker CB5 via the communication path 49 or 59 outputs a control signal for disconnecting the circuit breaker CB5 to the circuit breaker CB5.

In the next step S110, the host computer 35 outputs a disconnection command for the switch SW1 to the switch control device SWCU. In step S200, the switch control device SWCU that has received the switch SW1 disconnection command 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 disconnection command for the circuit breaker CB2 to the protection relay RY2. In step S305, the protection relay RY2 that has received the disconnection command of the circuit breaker CB2 via the communication path 49 or 59 outputs a control signal for disconnecting the circuit breaker CB2 to the circuit breaker CB2.

In the next step S120, the host computer 35 outputs a disconnection command for the switch SW2 to the switch control device SWCU. In step S205, the switch control device SWCU that has received the switch SW2 disconnection command 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 switch SW3 closing command to the switch control device SWCU. In step S210, the switch control device SWCU that has received the switch SW3 closing command via the communication path 49 or 59 outputs a control signal for turning on the switch SW3 to the switch SW3.

In the next step S310, each protection relay RY determines whether or not each of the circuit breakers CB2, CB5 and the switches SW1 to SW3 is turned on or off in a predetermined order. This verifies whether or not the switching of the operation method is legitimate. If the circuit breaker CB and the switch SW are turned on or off in a predetermined order (NO in step S310), each protection relay RY notifies the host computer 35 of an abnormality. Suspend processing. On the other hand, if each protection relay RY follows a predetermined order of turning on or off the circuit breaker CB and the switch SW (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 lead-in operation of the line 2. In the next step S320, each protection relay RY locks the relay operation. In the next step S325, the sampling synchronization control unit 61 of each protection relay RY communicates with another protection relay RY constituting the specified protection section to perform current sampling timing between its own terminal and the other terminal. To synchronize.

In the next step S330, each protection relay RY changes the calculation formula of the 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 the relay operation. As described above, the switching of the protection section by each protection relay RY is completed.

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

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

With reference to FIG. 9, in step S150, the multi-terminal power transmission system 30 of FIG. 1 is in the π pull-in operation of line 2 under the control of the host computer 35. That is, the switches SW1 and SW2 are in the open state, and the switches SW3 are in the closed state.

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

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

In the next step S165, the host computer 35 outputs a disconnection command for the switch SW3 to the switch control device SWCU. In step S250, the switch control device SWCU that has received the switch SW3 disconnection command 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 switch SW2 closing command to the switch control device SWCU. In step S255, the switch control device SWCU that has received the switch SW2 closing command via the communication path 49 or 59 outputs a control signal for turning on the switch SW2 to the switch SW2.

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

In the next step S360, each protection relay RY determines whether or not each of the circuit breakers CB2, CB5 and the switches SW1 to SW3 is turned on or off in a predetermined order. This verifies whether or not the switching of the operation method is legitimate. If the circuit breaker CB and the switch SW are turned on or off in a predetermined order (NO in step S360), each protection relay RY notifies the host computer 35 of an abnormality. Suspend processing. On the other hand, if each protection relay RY follows a predetermined order of turning on or off the circuit breaker CB and the switch SW (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 the protection section corresponding to the 3-terminal operation. In the next step S370, each protection relay RY locks the relay operation. In the next step S375, the sampling synchronization control unit 61 of each protection relay RY communicates with another protection relay RY constituting the specified protection section, so that the sampling timing of the current between its own terminal and the other terminal To synchronize.

In the next step S380, each protection relay RY changes the calculation formula of the differential relay calculation to one corresponding to the protection section of the 3-terminal operation. In the next step S385, each protection relay RY unlocks the relay operation. As described above, the switching of the protection section by each protection relay RY is completed.

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

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

[Effect 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 / closed state of the plurality of switches, and changes the open / closed state of the plurality of switches when the open / closed state is changed. The protection section corresponding to the later open / closed state is automatically specified. 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 of the calculation target by the current differential method so as to correspond to the changed protection section. As a result, protection by the current differential method can be continued even for the multi-terminal power transmission system 30 after the open / closed state of the switch has been changed.

Further, the host computer 35 outputs a release command of the corresponding circuit breaker CB to at least one protection relay RY in order to change the open / closed state of the plurality of switches, and then turns on each of the plurality of switches SW. Output a command or open command. After that, the host computer 35 outputs a closing command of 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 or not the output order of the circuit breaker CB opening command, the switch SW closing command, and the opening command output from the host computer 35 follows a predetermined order. Then, when the output order of each command follows a predetermined order, each protection relay RY protects the protection section corresponding to the changed open / closed state of the plurality of switches SW by the current differential method. Run. Thereby, the multi-terminal power transmission system 30 can be protected more reliably.

Embodiment 2.
In the second embodiment, a case where the host computer 35 collectively executes the protection relay calculation for each protection section without executing the protection relay calculation for each protection relay RY will be described. In this case, the arithmetic processing unit 120 of FIG. 7 is not provided with the protection relay arithmetic unit 63. 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 unit 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, 312 constituting the host computer 35 are also shown.

From a functional point of view with reference to FIG. 10, the arithmetic processing unit 300 includes a protection section specifying unit 66, a protection relay arithmetic unit 67, and a logic arithmetic unit 68. Each of these functions is realized by the CPU 301 executing a program.

When the operation method is switched by changing the open / closed state of the switches SW1 to SW3, the protection section specifying unit 66 specifies all the protection sections corresponding to the operation method after the switch. For example, information representing the correspondence between the open / closed pattern of the switches SW1 to SW3 and all the protection sections corresponding to each pattern is stored in the memory (ROM 303, non-volatile memory 304) in advance. The protection section specifying unit 66 identifies all the protection sections corresponding to the open / closed states of the switches SW1 to SW3 based on the information representing this correspondence relationship.

The protection relay calculation unit 67 receives the current data sampled by each of the protection relays RY1 to RY6. The protection relay calculation unit 67 executes a relay calculation by the 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 will separate the accident section from the multi-terminal power transmission system 30. An release command for the circuit breaker CB is output to each protection relay RY corresponding to the section.

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

When the open / closed state of the switches SW1 to SW3 is changed, the protection section specifying unit 62 of the protection relay RY1 specifies all the protected sections corresponding to the changed open / closed state of the switches SW1 to SW3. Information indicating the correspondence relationship between the open / closed state patterns of the switches SW1 to SW3 and all the protection sections corresponding to each pattern is stored in advance in the memory (ROM 123, non-volatile 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.

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

When 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 separates the accident section from the multi-terminal power transmission system 30. An release command for the circuit breaker CB is output to each protection relay RY corresponding to the section. When the own terminal is included in the accident section, the logic calculation unit 64 outputs a trip signal to the corresponding circuit breaker CB1.

Embodiment 3.
In the third embodiment, when the protection relay RY provided in the same substation is configured as a common unit, the network configuration between the protection relay units will be described.

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 common protection relay units RY1 & RY2. In the substation 32, the protection relay elements RY3 and RY4 are provided as common protection relay units RY3 & RY4. In the substation 33, the protection relay elements RY5 and RY6 are provided as common protection relay units RY5 & RY6.

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

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

According to the above configuration, the number of network switches can be reduced. In addition, the third embodiment can be combined with the second embodiment and a modification thereof.

Embodiment 4.
In the fourth embodiment, the case where the sampling timing synchronization is first established at all the terminals of all the transmission lines will be described. By connecting each protection relay RY via an optical fiber or a plurality of communication devices, the same sampling synchronization can be realized among all protection relays. Further, sampling synchronization may be performed at all terminals by synchronizing the built-in clock for each protection relay RY using GPS signals.

12 and 13 are flowcharts showing an example of the operation of the protection system of the multi-terminal power transmission system according to the fourth embodiment. The flowchart of FIG. 12 shows the procedure for switching from the 3-terminal operation to the π-drawing operation of Line 2, and the low chart of FIG. 13 shows the procedure for switching from the π-drawing operation of Line 2 to the 3-terminal operation. The flowcharts of FIGS. 12 and 13 correspond to the flowcharts of FIGS. 8 and 9, respectively. In the following, the steps common to the flowcharts of FIGS. 8 and 9 are basically not repeated by adding the same reference numerals.

With reference to FIG. 12, the full 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 in each protection section regardless of the change in the protection section due to the switching of the switch. As a result, even if the protection section is changed, it is only necessary to switch the protection relay calculation result to be output, so that it is not necessary to lock and unlock the relay operation.

Subsequent steps S100 to S125, steps S200 to S210, and steps S300 to S310 are the same procedures as the flowchart of FIG. 8, and thus 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 the line 2. In the next step S330, each protection relay RY changes the calculation formula of the differential relay calculation to one corresponding to the protection section of the π pull-in operation.

In the case of FIG. 8, a step S320 for locking the relay operation of each protection relay RY, a step S325 for establishing sampling synchronization at each terminal in the specified protection section, and a step S335 for releasing the lock for the relay operation are performed. It was necessary. However, in the case of FIG. 12, these steps S320, S325 and S335 are not necessary. Sampling synchronization has been established for all terminals, and since no current is flowing through the current transformer CT related to the change of the protection section due to the opening of the circuit breaker CB, it is not necessary to stop the relay operation. No matter what protection section is changed, the calculation according to the current differential relay method can be executed immediately and the calculation result can be output.

After that, the circuit breaker CB5 and the circuit breaker CB2 are turned on (steps S340 and S345) based on the closing command (steps S130 and S135) from the host computer 35, so that the operation from the 3-terminal operation to the π pull-in operation of the line 2 is performed. Switching is completed.

With reference to FIG. 13, all protection relays have established sampling synchronization (step S3500). Subsequent steps S150 to S175, steps S250 to S260, and steps S350 to S360 are the same procedures as the flowchart of FIG. 9, and thus 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 the protection section corresponding to the 3-terminal operation. In the next step S380, each protection relay RY changes the calculation formula of the differential relay calculation to one corresponding to the protection section of the 3-terminal operation.

In the case of FIG. 13, unlike the case of FIG. 9, step S370 for locking the relay operation of each protection relay RY, step S375 for establishing sampling synchronization at each terminal in the specified protection section, and locking of the relay operation. Step S385 and the like are not required. As described with reference to FIG. 12, sampling synchronization has been established for all terminals, and further, due to the opening of the circuit breaker CB, no current is flowing through the current transformer CT related to the change of the protection section, so that the relay This is because there is no need to stop the operation.

After that, the circuit breaker CB2 and the circuit breaker CB5 are turned on based on the closing command (steps S180 and S185) from the host computer 35 (steps S390 and S395), so that the π pull-in operation of the line 2 is changed to the 3-terminal operation. Switching is completed.

[Modifications of Embodiments 1 to 4]
Although the hardware configuration example of the protection relay RY, the switch control device SWCU, and the host computer 35 is shown in FIGS. 4 to 6, 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 by 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 the CPU, ASIC, and FPGA. Further, the host computer 35 may be composed of a plurality of server devices.

The embodiments disclosed this time should be considered as exemplary in all respects and not restrictive. The scope of this application is indicated by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1L, 2L transmission line, 30 multi-terminal transmission system, 31-33 substation, 34 control station, 35 high-level computer, 40-47, 50-57 network switch, 49,59 communication path, 61 sampling synchronization control unit, 62, 66 Protected section identification unit, 63, 67 Protected 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)

It is a protection system for multi-terminal power transmission systems.
The multi-terminal transmission system includes a plurality of transmission lines connecting three or more substations.
Each of the plurality of transmission lines connects between any one of the three or more substations and the other one or more substations.
The multi-terminal power transmission system further
With one or more transmission lines and multiple switches between the transmission lines,
Including a plurality of circuit breakers individually provided adjacent to the terminals of each said transmission line.
The protection system includes a plurality of protection relays individually provided corresponding to each terminal of the plurality of transmission lines and connected to each other via a communication path.
Each of the plurality of protection relays
When the open / closed state of the plurality of switches is changed, all other terminals electrically connected to the own terminal of the corresponding transmission line based on the information of the changed open / closed state of the plurality of switches are connected. By specifying, the protection section identification part that specifies the protection section to be protected using the current differential method, and the protection section identification part,
Protection of a multi-terminal power transmission system including a protection relay calculation unit that performs relay calculation by a current differential method based on the current value sampled at its own terminal and the current value sampled at each of the other specified terminals. system. Each of the plurality of protection relays
A claim that further includes a sampling synchronization control unit that synchronizes the current sampling timing at the own terminal with the current sampling timing at each of the specified other terminals when the open / closed state of the plurality of switches is changed. Item 1. The protection system for a multi-terminal power transmission system according to Item 1. Each of the plurality of protection relays
The multi-terminal power transmission according to claim 1, further comprising a sampling synchronization control unit that synchronizes the sampling timing of the current at the own terminal with the sampling timing of the current at all the terminals of the plurality of transmission lines except the own terminal. System protection system. Each of the plurality of protection relays includes a memory for storing information indicating a correspondence relationship between the open / closed state pattern of the plurality of switches and the protection section corresponding to each pattern.
The protection section specifying unit according to any one of claims 1 to 3, wherein the protection section specifying a protection section corresponding to a changed open / closed state of the plurality of switches based on the information representing the correspondence relationship. Multi-terminal transmission system protection system. The protection system further
A switch control device connected to the communication path and controlling the open / closed state of the plurality of switches,
It is provided with a high-level computer connected to the communication path and outputting each turn-in command or open command of the plurality of switches to the switch control device.
The host computer outputs an opening command of a circuit breaker provided adjacent to the corresponding terminal to at least one protection relay in order to change the open / closed state of the plurality of switches, and then the plurality of switches. Claims 1 to 4 output each of the switch closing commands or opening commands, and then output the corresponding circuit breaker closing commands to at least one protection relay to which the opening commands are output. The protection system for a multi-terminal power transmission system according to any one of the above. For each of the plurality of protection relays, the output order of the corresponding circuit breaker opening command output to the at least one protection relay and the closing command or opening command of each of the plurality of switches is predetermined. The protection system for a multi-terminal power transmission system according to claim 5, which determines whether or not the order is followed. When each of the plurality of protection relays follows a predetermined order of output, each of the plurality of protection relays executes protection by a current differential method for a protection section corresponding to the changed opening / closing state of the plurality of switches. The protection system for a multi-terminal power transmission system according to claim 6. It is a protection system for multi-terminal power transmission systems.
The multi-terminal transmission system includes a plurality of transmission lines connecting three or more substations.
Each of the plurality of transmission lines connects between any one of the three or more substations and the other one or more substations.
The multi-terminal power transmission system further
With one or more transmission lines and multiple switches between the transmission lines,
Including a plurality of circuit breakers individually provided adjacent to the terminals of each said transmission line.
The protection system
A plurality of protection relays individually provided corresponding to each terminal of the plurality of transmission lines and connected to each other via a communication path, and a plurality of protection relays.
A high-level computer connected to the plurality of protection relays via the communication path is provided.
The higher-level computer
When the open / closed state of the plurality of switches is changed, a protection section that specifies all the protection sections to be protected by using the current differential method based on the information of the open / closed state after the change of the plurality of switches. With a specific part
A protection system for a multi-terminal power transmission system, which includes a protection relay calculation unit that performs a relay calculation by a current differential method based on a current value sampled at each terminal for each of the protection sections. It is a protection system for multi-terminal power transmission systems.
The multi-terminal transmission system includes a plurality of transmission lines connecting three or more substations.
Each of the plurality of transmission lines connects between any one of the three or more substations and the other one or more substations.
The multi-terminal power transmission system further
With one or more transmission lines and multiple switches between the transmission lines,
Including a plurality of circuit breakers individually provided adjacent to the terminals of each said transmission line.
The protection system
It is provided with a plurality of protection relays individually provided corresponding to each terminal of the plurality of transmission lines and connected to each other via a communication path.
The first protection relay among the plurality of protection relays is
When the open / closed state of the plurality of switches is changed, a protection section that specifies all the protection sections to be protected by using the current differential method based on the information of the open / closed state after the change of the plurality of switches. With a specific part
A protection system for a multi-terminal power transmission system, which includes a protection relay calculation unit that performs a relay calculation by a current differential method based on a current value sampled at each terminal for each of the protection sections.

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