Protection relay system

Abstract

To provide a protective relay system capable of performing a normal data communication by reducing a load in a network switch.SOLUTION: A protective relay system comprises: a plurality of network switches; and a plurality of relay devices that is connected to each network switch connected in a loop like. A first relay device connected to each network switch transmits a first frame containing a first electric amount data to the network switch at a first timing when a first time passes from a sampling timing. A second relay device connected to the network switch transmits a second frame containing a second electric amount data to the network switch at a second timing when a second time passes from the sampling timing. Each network switch transmits the first frame and the second frame that were received to the other network switch.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a protection relay system.

Background Art

[0002] A protection relay system is provided in a power system. The protection relay system is applied to various uses. For example, a transmission line protection relay system is known. The transmission line protection relay system disconnects a fault section when detecting a fault in a transmission line and a bus. In the transmission line protection relay system, relay devices are arranged at each terminal of a transmission line section. Each relay device measures electrical quantity data and transmits and receives a communication frame including the electrical quantity data to and from other relay devices.

[0003] For example, a protection relay system according to Japanese Patent Application Laid-Open No. 2014-138454 (Patent Document 1) includes a plurality of protection relay devices that perform protection of a power system based on electrical quantity data of the power system. Communication is performed between the protection relay devices using a network.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] At each terminal of a protection section, various devices such as a relay device and a monitoring device are provided, and communication is performed using a network. When transmitting and receiving various types of data via the same network, if the transmission timings of the data of the various devices provided at each terminal concentrate, a standby state of the data at a network switch may occur, and there is a possibility that the data may not be normally transmitted and received and may be lost.

[0006] An object in one aspect of the present disclosure is to provide a technology capable of reducing the load on a network switch and enabling normal data communication in a protection relay system including a plurality of relay devices provided at each terminal. **Means for Solving the Problems**

[0007] A protection relay system according to an embodiment includes a plurality of network switches respectively provided at a plurality of terminals, and for each of the plurality of network switches connected in a loop, a plurality of relay devices connected to the network switch. For each of the plurality of network switches, a first relay device connected to the network switch transmits a first frame including first electrical quantity data sampled at a sampling timing to the network switch at a first timing when a first time has elapsed from the sampling timing. For each of the plurality of network switches, a second relay device connected to the network switch transmits a second frame including second electrical quantity data sampled at the sampling timing to the network switch at a second timing when a second time has elapsed from the sampling timing. Each network switch transmits the received first frame and second frame to other network switches. **Advantages of the Invention**

[0008] According to the present disclosure, in a protection relay system including a plurality of relay devices provided at each terminal, the load on the network switch can be reduced and normal data communication can be achieved. **Brief Description of the Drawings**

[0009]

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Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0011] <Overall Configuration> FIG. 1 is an overall configuration diagram of a protection relay system according to the present embodiment. Referring to FIG. 1, the protection relay system 1000 includes network switches 3_1 to 3_5 (hereinafter also collectively referred to as "switch 3"), a plurality of relay devices 2_1 to 2_20 (hereinafter also collectively referred to as "relay device 2"), and a synchronization device 20. In the present embodiment, a configuration in which the synchronization device 20 is connected to the switch 3_1 will be described, but the synchronization device 20 may be connected to any of the other switches 3_2 to 3_5.

[0012] The network NW used in the protection relay system 1000 shown in FIG. 1 is configured by connecting 20 relay devices 2_1 to 2_20 to each other using five switches 3_1 to 3_5. The plurality of switches 3_1 to 3_5 are respectively provided at a plurality of terminals (for example, electrical substations) E1 to E5. The plurality of switches 3_1 to 3_5 are connected in a loop via a communication path R. The network NW is configured by, for example, a high-speed communication network such as Ethernet (registered trademark). Each switch 3 is, for example, an L3 switch.

[0013] A plurality of relay devices 2 (that is, the first to fourth relay devices) are connected to each switch 3. For example, at the terminal E1, there are provided the switch 3_1, the first relay device 2_1, the second relay device 2_2, the third relay device 2_3, and the fourth relay device 2_4 connected to the switch 3_1, and the synchronization device 20. Also, at the terminal E2, there are provided the switch 3_2, the first relay device 2_5, the second relay device 2_6, the third relay device 2_7, and the fourth relay device 2_8 connected to the switch 3_2. The same applies to the other terminals E3 to E5.

[0014] Each relay device 2 is a digital protection relay device. For example, it is a current differential relay device for performing current differential calculation to protect a protection section. In the present embodiment, each first relay device 2_1, 2_5, 2_9, 2_13, 2_17 (hereinafter, also collectively referred to as "first relay device 2") is a current differential relay device for protecting the first transmission line. Similarly, each second relay device 2_2, 2_6, 2_10, 2_14, 2_18 (hereinafter, also collectively referred to as "second relay device 2") protects the second transmission line, each third relay device 2_3, 2_7, 2_11, 2_15, 2_19 (hereinafter, also collectively referred to as "third relay device 2") protects the third transmission line, and each fourth relay device 2_4, 2_8, 2_12, 2_16, 2_20 (hereinafter, also collectively referred to as "fourth relay device 2") protects the fourth transmission line.

[0015] Each relay device 2 measures electrical quantity data (for example, current data, voltage data), and transmits and receives frames including the electrical quantity data to and from other relay devices 2 connected to each switch 3 on the communication path R. Thereby, each relay device 2 shares the electrical quantity data measured by other relay devices 2 that protect the same transmission line. Specifically, each first relay device shares the electrical quantity data measured by other first relay devices that protect the first transmission line. Similarly, each second relay device shares the electrical quantity data measured by other second relay devices, each third relay device shares the electrical quantity data measured by other third relay devices, and each fourth relay device shares the electrical quantity data measured by other fourth relay devices.

[0016] Each relay device 2 generates a frame including the electrical quantity data measured at its own terminal, and transmits the generated frame to the switch 3 connected to the relay device 2. Specifically, each first relay device transmits a frame F1 including the electrical quantity data M1 measured at its own terminal to the switch 3. Each second relay device transmits a frame F2 including the electrical quantity data M2 measured at its own terminal to the switch 3. Each third relay device transmits a frame F3 including the electrical quantity data M3 measured at its own terminal to the switch 3. Each fourth relay device transmits a frame F4 including the electrical quantity data M4 measured at its own terminal to the switch 3.

[0017] Each switch 3 sequentially transmits the received frames F1 to F4 to other switches 3 via the communication path R. Specifically, switch 3_1 transmits each of the frames F1 to F4 to switch 3_2. Switch 3_2 transmits each of the frames F1 to F4 to switch 3_1 and switch 3_3. The same applies to switches 3_3 to 3_5.

[0018] Details will be described later, but in this embodiment, the timing of transmitting frames from each relay device 2 to the switch 3 is managed. Therefore, data can be normally transmitted and received via the communication path R without imposing a load exceeding the specifications of each switch 3.

[0019] The synchronization device 20 transmits and receives synchronization messages for synchronizing the time of each relay device 2 with its own time to each relay device 2. As a result, the times of all the relay devices 2 in the protection relay system 1000 are synchronized. Each relay device 2 performs operations such as accident detection determination using the electrical quantity data measured at the same time (i.e., sampling timing). The timing for measuring the electrical quantity data is determined based on a sampling pulse signal generated by dividing the hardware clock. For example, the sampling period is set to an electrical angle of 30° of the system frequency (for example, 1.67 ms in the case of a 50 Hz system).

[0020] Typically, each relay device 2 performs a current differential operation using the electrical quantity data (in this case, current data) sampled at each terminal. The first relay device protects the first transmission line by performing a current differential operation using the electrical quantity data M1 sampled at its own terminal and the electrical quantity data M1 sampled at one or more other terminals. The second relay device protects the second transmission line by performing a current differential operation using the electrical quantity data M2 sampled at its own terminal and the electrical quantity data M2 sampled at one or more other terminals. The same applies to the third to fourth relay devices.

[0021] As an example, the current differential method by each first relay device 2 for protecting the first transmission line will be described. Let the current data measured by the first relay devices 2_1, 2_5, 2_9, 2_13, 2_17 be current data I1, I5, I9, I13, I17, respectively. In this case, each first relay device calculates the vector sum of the respective current data I1, I5, I9, I13, I17, and calculates the magnitude of the calculated vector sum as the differential current IDL. Each first relay device determines whether the differential current IDL is greater than the threshold value K (that is, whether IDL1>K holds). When IDL>K holds, each first relay device determines that an accident has occurred in the protection section (that is, the first transmission line), and outputs a trip command TR.

[0022] A standby communication path is prepared between switch 3_1 and switch 3_5. For example, when the communication path R between switch 3_4 and switch 3_5 becomes incommunicable due to a failure, the communication path R between switch 3_4 and switch 3_5 is used as a new standby communication path. Then, each switch 3 is communicatively connected in a loop using the original standby communication path or the like.

[0023] <Hardware Configuration> An example in which each relay device 2 is configured based on a microcomputer will be described. Different from the following example, each relay device 2 may be configured based on an electronic circuit such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). Alternatively, each relay device 2 may be configured by combining an electronic circuit such as an FPGA or an ASIC with a microcomputer.

[0024] FIG. 2 is a block diagram showing an example of the hardware configuration of the relay device 2. Referring to FIG. 2, the relay device 2 includes an auxiliary transformer 32, an A / D conversion unit 35, an arithmetic processing unit 40, a sampling pulse generation circuit 45, a communication circuit 50, a digital output circuit (D / O: Digital Output) 55, and a digital input circuit (D / I: Digital Input) 56.

[0025] The auxiliary transformer 32 takes in the electrical quantity from a current transformer or a voltage transformer, and converts and outputs it to a voltage suitable for signal processing in the relay internal circuit. The A / D conversion unit 35 takes in the voltage output from the auxiliary transformer 32 and converts it into digital data. Specifically, the A / D conversion unit 35 includes an analog filter, a sample hold circuit, a multiplexer, and an A / D converter.

[0026] The analog filter removes high-frequency noise components from the waveform signal of the current output from the auxiliary transformer 32. The sample hold circuit samples the waveform signal of the current output from the analog filter at the period of the sampling pulse (i.e., the sampling period) generated by the sampling pulse generation circuit 45. The multiplexer sequentially switches the waveform signal input from the sample hold circuit in time series based on the timing signal input from the arithmetic processing unit 40 and inputs it to the A / D converter. The A / D converter converts the waveform signal input from the multiplexer from analog data to digital data. The A / D converter outputs the digitally converted waveform signal (i.e., digital data) to the arithmetic processing unit 40.

[0027] The arithmetic processing unit 40 includes a CPU (Central Processing Unit) 41, a RAM (Random Access Memory) 42, and a ROM (Read Only Memory) 43. These elements are interconnected via a bus 44. The arithmetic processing unit 40 may include an electrically rewritable non-volatile memory such as a flash memory. The RAM 42 and the ROM 43 are used as the main memory of the CPU 41. The CPU 41 controls the operation of the entire relay device 2 according to a program stored in the ROM 43 or the non-volatile memory. Typically, each process of the relay device 2 described below is executed by the arithmetic processing unit 40.

[0028] The sampling pulse generation circuit 45 includes an oscillator and a frequency division circuit. The oscillator outputs a reference frequency signal of a reference frequency for generating a sampling pulse. The frequency division circuit divides the reference frequency signal input from the oscillator by a division ratio n to generate a sampling pulse. Note that the division ratio n of the frequency divider is controlled by the CPU 41. Thereby, the frequency of the sampling pulse (i.e., the sampling frequency) is controlled.

[0029] The communication circuit 50 communicates with the switch 3. The communication circuit 50 performs communication with the switch 3 according to a specified protocol.

[0030] The digital output circuit 55 is an interface circuit for outputting a signal to an external device. For example, the digital output circuit 55 outputs a trip command TR to a circuit breaker provided in a power transmission line according to a command from the CPU 41. The digital input circuit 56 receives, for example, opening / closing information indicating the open / closed state of the circuit breaker from the circuit breaker.

[0031] <Time synchronization method> FIG. 3 is a sequence diagram showing an example of a time synchronization method. The process shown in FIG. 3 is a time synchronization method according to IEEE1588. The synchronization device 20 executes the process shown in FIG. 3 with each relay device 2.

[0032] Referring to FIG. 3, the synchronization device 20 transmits a Sync message, which is a synchronization frame for time synchronization control, to the relay device 2 (sequence SQ2). The synchronization device 20 stores the time k1 when the Sync message is transmitted in the internal memory. The relay device 2 receives the Sync message and stores the received time k2 in the internal memory.

[0033] The synchronization device 20 reads out the time k1 when the Sync message is transmitted from the internal memory and transmits a Follow_Up message storing the time k1 to the relay device 2 (sequence SQ4). The relay device 2 stores the time k1 stored in the received Follow_Up message in the internal memory. Note that the synchronization device 20 may be configured to transmit the Sync message storing the time k1 to the relay device 2.

[0034] The relay device 2 transmits a Delay_Req message to the synchronization device 20 (sequence SQ6). The relay device 2 stores the time k3 when the Delay_Req message is transmitted in the internal memory. The synchronization device 20 receives the Delay_Req message and stores the received time k4.

[0035] The synchronization device 20 transmits a Delay_Resp message storing the time k4 to the relay device 2 (sequence SQ8). The relay device 2 stores the time k4 stored in the received Delay_Resp message in the internal memory.

[0036] Through the above sequence, the times k1, k2, k3, and k4 are stored in the internal memory of the relay device 2.

[0037] The relay device 2 calculates the difference between time k1 and time k2 (i.e., "k2 - k1") to obtain the sum of the time deviations of the synchronization device 20 and the relay device 2 at each time and the transmission line delay for the transmission line from the synchronization device 20 to the relay device 2. Further, the relay device 2 calculates the difference between time k3 and time k4 (i.e., "k4 - k3") to obtain the sum of the time deviations of the synchronization device 20 and the relay device 2 at each time and the transmission line delay for the transmission line from the relay device 2 to the synchronization device 20.

[0038] Also, the sum of the time difference "k4 - k3" and the time difference "k2 - k1" corresponds to twice the time of the transmission line delay. The difference between the time difference "k4 - k3" and the time difference "k2 - k1" corresponds to twice the time of the deviation between the time of the synchronization device 20 and the time of the relay device 2. Here, it is assumed that the transmission delay between the synchronization device 20 and the relay device 2 is equivalent for the forward and return paths. In this case, the delay time tx of a single - direction transmission line is expressed as in the following formula (1).

[0039] tx = {(k4 - k3)+(k2 - k1)} / 2 …(1) Also, the time difference td between the time of the synchronization device 20 and the time of the relay device 2 is expressed as in the following formula (2).

[0040] td = {(k4 - k3)-(k2 - k1)} / 2 …(2) The relay device 2 performs time synchronization with the synchronization device 20 by correcting its own time using the time difference td as the correction amount for time synchronization. As a result, the time of the synchronization device 20 and the time of the relay device 2 are synchronized (i.e., coincide).

[0041] As described above, each relay device 2 synchronizes the time of the relay device 2 with the time of the synchronization device 20 based on the time - synchronization data received from the synchronization device 20 via the corresponding switch 3. As a result, each relay device 2 can synchronize its own sampling timing with the sampling timing of other relay devices 2. Consequently, the sampling timings of all of the relay devices 2_1 to 2_20 are synchronized.

[0042] <Frame transmission method> (Transmission method according to the comparative example) FIG. 4 is a timing chart for explaining the frame transmission timing according to the comparative example. Referring to FIG. 4, the arrows in the figure indicate the sampling timing. The period Ta from the current sampling timing at time t0 to the next sampling timing at time t0x indicates the sampling period.

[0043] In the relay device according to the comparative example, it is configured to transmit a frame after a certain period from the sampling timing. Therefore, in a configuration where a plurality of relay devices are connected to the switch 3, when the sampling timings of the respective relay devices coincide, each relay device transmits a frame including the electrical quantity data sampled at the same time to the switch 3 simultaneously. That is, the transmission periods of the frames transmitted from each relay device 2 overlap. In the example of FIG. 4, the first to fourth relay devices transmit frames F1 to F4 to the switch 3 at time t1 when a time T1 has elapsed from the sampling timing at time t0, respectively.

[0044] Each switch 3 stores the frames F1 to F4 received simultaneously from the first to fourth relay devices in an internal buffer, and sequentially reads out the stored frames F1 to F4 and transmits them to another switch 3. For example, each switch 3 transmits the frames F1, F2, F3, and F4 in this order. In the buffer of each switch 3, the remaining frames are stored until the transmission of the previous frame is completed. Furthermore, frames transmitted from other switches 3 are also stored in the buffer of each switch 3. Therefore, when frames from each relay device 2 arrive at the switch 3 at the same timing, a large load is applied to the buffer. In this case, a data waiting state may occur exceeding the memory capacity of the buffer of the switch 3, and there is a possibility that the data may disappear without being normally transmitted and received.

[0045] FIG. 5 is a diagram for explaining the frame arrival timing at the switch according to the comparative example. The horizontal axis of FIG. 5 indicates the relay numbers of each relay device 2. Specifically, the relay numbers of relay devices 2_1 to 2_20 are indicated by 1 to 20, respectively. The vertical axis of FIG. 5 indicates the arrival time from the sampling timing until the frame of each relay device 2 arrives at the switch 3. Specifically, FIG. 5(a) shows the arrival time at switch 3_1, and FIG. 5(b) shows the arrival time at switch 3_3. For ease of explanation, it is assumed that the distances between the switches 3 shown in FIG. 1 are the same.

[0046] Referring to FIG. 5(a), since each relay device 2_1 to 2_4 is connected to switch 3_1, the frames of each relay device 2_1 to 2_4 arrive at switch 3_1 simultaneously. At an arrival time in the vicinity of 35 μs to 40 μs, the frames of each relay device 2_5 to 2_8 connected to switch 3_2 adjacent to switch 3_1 arrive at switch 3_1 sequentially. At an arrival time in the vicinity of 65 μs to 70 μs, the frames of each relay device 2_9 to 2_12 connected to switch 3_3 arrive at switch 3_1 sequentially via switch 3_2. The same applies to the frames of each relay device 2_13 to 2_20 as shown in FIG. 5(a).

[0047] Referring to FIG. 5(b), since each relay device 2_9 to 2_12 is connected to switch 3_3, the frames of each relay device 2_9 to 2_12 arrive at switch 3_3 simultaneously. Switch 3_3 is adjacent to switch 3_2 and switch 3_4. Therefore, at an arrival time in the vicinity of 35 μs to 40 μs, the frames of each relay device 2_5 to 2_8 and the frames of each relay device 2_13 to 2_16 arrive at switch 3_1 sequentially. Also, at an arrival time in the vicinity of 65 μs to 70 μs, the frames of each relay device 2_1 to 2_4 and the frames of each relay device 2_17 to 2_20 arrive at switch 3_3 sequentially.

[0048] Referring to FIG. 5, it can be understood that the arrival timings of each frame at switch 3 are concentrated within a short period. In particular, in the case of switch 3_3 to which other switches 3 are connected on both sides, the number of frames received by the switch 3_3 in a short period is larger. Therefore, it is considered that the load on the buffer increases.

[0049] (Transmission method according to this embodiment) FIG. 6 is a timing chart for explaining the frame transmission timing of the relay device according to this embodiment. Referring to FIG. 6, the first to fourth relay devices according to this embodiment transmit frames including the electrical quantity data sampled at the same time at different timings to switch 3. That is, the transmission periods of frames F1 to F4 do not overlap with each other.

[0050] In the example of FIG. 6, the first relay device transmits frame F1 sampled at the sampling timing at the timing (i.e., time t1) when a time T1 has elapsed from the sampling timing at time t0. The second relay device transmits frame F2 sampled at the sampling timing at the timing (i.e., time t2) when a time T2 has elapsed from the sampling timing. According to FIG. 6, it can be understood that after the transmission of frame F1 is completed, frame F2 is being transmitted. That is, the period during which the first relay device transmits frame F1 does not overlap with the period during which the second relay device transmits frame F2. Similarly, the third relay device transmits frame F3 at time t3 when a time T3 has elapsed from the sampling timing, and the fourth relay device transmits frame F4 at time t4 when a time T4 has elapsed from the sampling timing.

[0051] The time difference in the frame transmission timings of each relay device 2 is constant. That is, the time from time t1 to time t2, the time from time t2 to time t3, and the time from time t3 to time t4 are all Ts and are the same.

[0052] According to the above transmission method, the timings at which the switch 3 receives the frames F1 to F4 from the first to fourth relay devices are different. The switch 3 stores the received frames in a buffer and immediately transmits the frames to other switches 3.

[0053] Therefore, the timings at which the switch 3 transmits the frames F1 to F4 to other switches 3 are substantially synchronized with the timings (for example, times t1 to t4) at which the first to fourth relay devices transmit the frames F1 to F4 to the switch 3. For example, after the switch 3 transmits the frame F1 received from the first relay device to other switches 3, the switch 3 receives the frame F2 from the second relay device and transmits the frame F2 to other switches 3.

[0054] Compared with the case where the frames F1 to F4 are received simultaneously as in the transmission method of FIG. 4, in the transmission method of FIG. 6, the number of frames (that is, the data amount) stored in the buffer simultaneously is small. Therefore, in the present embodiment, the load on the buffer of each switch 3 can be reduced.

[0055] FIG. 7 is a diagram for explaining the frame arrival timings at the switch according to the present embodiment. The horizontal axis and the vertical axis in FIG. 7 are the same as those in FIG. 5. Also, it is assumed that the distances between the switches 3 are the same. FIG. 7(a) shows the arrival time at the switch 3_1, and FIG. 7(b) shows the arrival time at the switch 3_3.

[0056] Referring to FIG. 7(a), the frames of the relay devices 2_1 to 2_4 arrive at the switch 3_1 sequentially at regular intervals (corresponding to the time Ts in FIG. 6, for example, 10 μs). The frames of the relay devices 2_5 to 2_8 connected to the switch 3_2 adjacent to the switch 3_1 arrive at the switch 3_1 sequentially every 10 μs. After the frame of the relay device 2_4 arrives, the frames of the relay devices 2_5 to 2_8 arrive. The arrival timings of the frames of the relay devices 2_13 to 2_20 are also as shown in FIG. 7(a). Thus, it is understood that the arrival timings of the frames at the switch 3_1 are not concentrated in a short period.

[0057] Referring to FIG. 7(b), the frames of each relay device 2_9 to 2_12 arrive at the switch 3_3 sequentially every 10 μs. The frames of each relay device 2_5 to 2_8 connected to the switch 3_2 and the frames of each relay device 2_13 to 2_16 arrive at the switch 3_3 sequentially every 10 μs. After the frame of the relay device 2_12 arrives, the frames of each relay device 2_5 to 2_8 and the frames of each relay device 2_13 to 2_16 arrive.

[0058] According to FIG. 7(b), for example, the frames F1 of the first relay devices 2_5, 2_13 arrive at the switch 3_3 at substantially the same timing. This is the same for the frames F2 of the second relay devices 2_6, 2_14, the frames F3 of the third relay devices 2_7, 2_15, and the frames F4 of the fourth relay devices 2_8, 2_16. However, the arrival timings of the respective frames do not concentrate in a short period. Comparing with FIG. 5(b), it is understood that the number of frames received by the switch 3_3 in a short period is clearly less. From this, the load on the buffer of each switch 3 can be reduced, and the situation where data (that is, frames) overflows from the buffer can be prevented.

[0059] (Modification example) In FIGS. 6 and 7, the case where the intervals of the frame transmission timings of the first to fourth relay devices are constant (for example, time Ts) has been described. In the modification example, a configuration will be described in which each of the frames F1 to F4 is divided into two groups, and a relatively long delay time is provided between the transmission timing of the frames belonging to the first group and the transmission timing of the frames belonging to the later group.

[0060] FIG. 8 is a timing chart for explaining the frame transmission timing of the relay device according to a modification of the present embodiment. Referring to FIG. 8, frames F1 and F2 belong to group G1, and frames F3 and F4 belong to group G2. The first relay device belonging to group G1 transmits frame F1 at time t1 when a time T1 has elapsed from the sampling timing at time t0, and the second relay device belonging to group G1 transmits frame F2 at time t2 when a time T2 has elapsed from the sampling timing. The time difference between the transmission timing of frame F1 (for example, time t1) and the transmission timing of frame F2 (for example, time t2) is "Ts".

[0061] The third relay device transmits frame F3 at time t3 when a time T3 has elapsed from the sampling timing, and the fourth relay device transmits frame F4 at time t4 when a time T4 has elapsed from the sampling timing. The time difference between the transmission timing of frame F3 (for example, time t3) and the transmission timing of frame F4 (for example, time t4) is "Ts". On the other hand, the time difference between the transmission timing of frame F2 and the transmission timing of frame F3 is "Ts1". The time Ts1 is sufficiently longer than the time Ts. That is, the interval between the frame transmission timings of each relay device 2 belonging to different groups (for example, time Ts1) is sufficiently longer than the interval between the frame transmission timings of each relay device 2 belonging to the same group (for example, time Ts).

[0062] Switch 3 sequentially transmits the received frames F1 to F4 to other switches 3. Therefore, the timing at which switch 3 transmits frames F1 to F4 to other switches 3 is substantially synchronized with the timing (for example, times t1 to t4) at which the first to fourth relay devices transmit frames F1 to F4 to switch 3. After a relatively long time has elapsed since switch 3 transmits frames FM1 and FM2 belonging to group G1, switch 3 transmits frame FM3 belonging to group G2. Therefore, the timing at which each of frames F1 and F2 arrives at switch 3 from other switches 3 is significantly different from the timing at which each of frames F3 and F4 arrives at switch 3 from other switches 3.

[0063] Therefore, since the frames F1 and F2 corresponding to the group G1 and the frames F3 and F4 corresponding to the group G2 arrive at each switch 3 in a dispersed manner, the number of frames received by each switch 3 in a short period is reduced.

[0064] FIG. 9 is a diagram for explaining the arrival timing of frames at a switch according to a modification of the present embodiment. The horizontal axis and the vertical axis in FIG. 9 are as described in FIG. 5. Also, it is assumed that the distances between the switches 3 are the same. FIG. 9(a) shows the arrival time at the switch 3_1, and FIG. 9(b) shows the arrival time at the switch 3_3.

[0065] Referring to FIG. 9(a), the frames of each relay device 2_1 and 2_2 arrive at the switch 3_1 sequentially every 10 μs. Subsequently, the frames of each relay device 2_5 and 2_6, the frames of each relay device 2_9 and 2_10, the frames of each relay device 2_13 and 2_14, and the frames of each relay device 2_17 and 2_18 arrive at the switch 3_1 sequentially.

[0066] Approximately 200 μs after the sampling timing, the frames of each relay device 2_3 and 2_4 arrive at the switch 3_1 sequentially every 10 μs. Subsequently, the frames of each relay device 2_7 and 2_8, the frames of each relay device 2_10 and 2_11, the frames of each relay device 2_15 and 2_16, and the frames of each relay device 2_19 and 2_20 arrive at the switch 3_1 sequentially.

[0067] Referring to FIG. 9(b), the frames of each relay device 2_9 and 2_10 arrive at the switch 3_3 sequentially every 10 μs. Subsequently, the frames of each relay device 2_5 and 2_6 and the frames of each relay device 2_13 and 2_14 arrive at the switch 3_3 sequentially, and the frames of each relay device 2_1 and 2_2 and the frames of each relay device 2_17 and 2_18 arrive at the switch 3_3 sequentially.

[0068] Approximately 200 μs after the sampling timing, the frames of each relay device 2_9, 2_10 arrive at the switch 3_3 sequentially every 10 μs. Subsequently, the frames of each relay device 2_7, 2_8 and the frames of each relay device 2_14, 2_15 arrive at the switch 3_3 sequentially, and the frames of each relay device 2_3, 2_4 and the frames of each relay device 2_19, 2_20 arrive at the switch 3_3 sequentially.

[0069] From the above, in the transmission method according to the modified example, after the frames F1, F2 corresponding to the first relay device and the second relay device respectively arrive at the switch 3, the frames F3, F4 corresponding to the third relay device and the fourth relay device respectively arrive at the switch 3. Thus, it is understood that each frame arrives at the switch 3_1 more dispersedly.

[0070] <Advantages> According to the present embodiment, the arrival timing of each frame transmitted from each relay device 2 at the switch 3 can be dispersed. Therefore, the load on the switch 3 is reduced, and data can be normally transmitted and received without data loss. As a result, the continuity of data transmitted at a high-speed period used for the protection operation of the current differential relay is ensured, and the interruption of the current differential operation due to data dropout (i.e., the interruption of protection) can be prevented.

[0071] Other embodiments. (1) In the above-described embodiment, a configuration in which other devices other than the relay device 2 are connected to each switch 3 may be adopted.

[0072] FIG. 10 is an overall configuration diagram of a protection relay system 1000A according to another embodiment. Referring to FIG. 10, the protection relay system 1000A corresponds to a configuration in which, in the protection relay system 1000 of FIG. 1, monitoring devices 5_1 to 5_5 (hereinafter also collectively referred to as "monitoring device 5") are connected to a plurality of switches 3_1 to 3_5 respectively, and an analysis device is connected to the switch 3_5.

[0073] The monitoring device 5 stores in the internal memory the electrical quantity data measured at its own terminal and the calculation data based on the electrical quantity data. The calculation data is, for example, power data calculated based on voltage data and current data measured at its own terminal, frequency data calculated based on voltage data for a specified period, and the like. The monitoring device 5 may have the same hardware configuration as the relay device 2. In this case, various processes by the monitoring device 5 are executed by an arithmetic processing unit included in the monitoring device 5. Note that the configuration may be such that the functions of the monitoring device 5 are provided in each relay device 2.

[0074] The synchronization device 20 transmits and receives synchronization messages to and from each monitoring device 5 for synchronizing the time of each monitoring device 5 with its own time. As described above, the synchronization device 20 also exchanges synchronization messages with each relay device 2. Therefore, the times of all relay devices 2 and monitoring devices 5 in the protection relay system 1000A are synchronized. Thereby, the sampling timings of each relay device 2_1 to 2_20 and each monitoring device 5_1 to 5_5 are synchronized.

[0075] The monitoring device 5 sequentially stores the electrical quantity data measured at the synchronized sampling timing. Further, the monitoring device 5 executes necessary calculations on the electrical quantity data and sequentially stores the calculation data. Typically, the monitoring device 5 measures electrical quantity data corresponding to the electrical quantity data measured by the first to fourth relay devices. The monitoring device 5 stores these electrical quantity data and calculation data as monitoring data. The monitoring device 5 transmits a frame FX including the monitoring data (for example, at least one of the electrical quantity data of the first to fourth transmission lines and the calculation data based on each electrical quantity data) to another monitoring device 5 via the corresponding switch 3.

[0076] Each monitoring device 5 has a function of displaying monitoring data including electrical quantity data (for example, current data, voltage data), calculation data based on the electrical quantity data (for example, active power data, reactive power data, frequency data), and the like on a display. Thereby, the user (for example, a grid operator) of each monitoring device 5 can check the monitoring data of its own device and other monitoring devices 5.

[0077] When an accident occurs in a protection section (for example, any one of the first to fourth transmission lines), the analysis device 60 performs accident analysis. Specifically, when the analysis device 60 receives a notification from at least one of each relay device 2 that an accident has occurred, it requests data related to the accident from each monitoring device 5. For example, assume that an accident has occurred on the first transmission line. In this case, the analysis device 60 requests each monitoring device 5 to transmit the electrical quantity data and calculation data related to the first transmission line during a certain period before and after the accident. Each monitoring device 5 transmits a frame FY including these data to the analysis device 60 via the corresponding switch 3.

[0078] FIG. 11 is a diagram for explaining the frame transmission timing according to other embodiments. Each of the frames F1 to F4, FX, FY is divided into four groups. The frames F1, F2 belong to the group G1, the frames F3, F4 belong to the group G2, the frame FX belongs to the group G3, and the frame FY belongs to the group G4.

[0079] Referring to FIG. 11, the first relay device transmits the frame F1 at the time t1 when a time T1 has elapsed from the sampling timing at time t0, and the second relay device transmits the frame F2 at the time t2 when a time T2 has elapsed from the sampling timing. The third relay device transmits the frame F3 at the time t3 when a time T3 has elapsed from the sampling timing, and the fourth relay device transmits the frame F4 at the time t4 when a time T4 has elapsed from the sampling timing. The monitoring device 5 transmits the frame FX at the timing (for example, time t5) when a time T5 has elapsed from the sampling timing, and transmits the frame FY at the timing (for example, time t6) when a time T6 has elapsed from the sampling timing.

[0080] Switch 3 sequentially transmits the received frames F1 to F4, FX, and FY to other switches 3. Therefore, the timing at which switch 3 transmits frames F1 to F4, FX, and FY to other switches 3 is almost synchronized with the timing (e.g., times t1 to t6) at which each device transmits frames F1 to F4, FX, and FY to switch 3.

[0081] Frame FX contains data obtained by dividing monitoring data (e.g., each electrical quantity data and each calculation data). The monitoring device 5 transmits all necessary monitoring data by transmitting frame FX every time the time t5 after the sampling timing arrives. Further, frame FY contains data obtained by dividing accident analysis data (e.g., electrical quantity data and calculation data over a certain period) requested from the analysis device 60. The monitoring device 5 transmits all necessary accident analysis data by transmitting frame FY every time the time t6 after the sampling timing arrives.

[0082] As shown in FIG. 11, the interval (e.g., time Ts2) of the frame transmission timing of devices belonging to different groups is sufficiently longer than the interval (e.g., time Ts) of the frame transmission timing of devices belonging to the same group. Thereby, the arrival timing of each frame at switch 3 can be dispersed.

[0083] According to the above, during the sampling period, each relay device 2 transmits the electrical quantity data measured at the latest sampling timing, while the monitoring device 5 transmits the monitoring data and the divided data of the accident analysis data. Thereby, other data (e.g., monitoring data and accident analysis data) other than the data used for the relay operation that needs to be transmitted at a high speed cycle can also be transmitted and received using the same network without affecting the relay operation. In this way, by using the network to the maximum extent, there is no need to construct a new network for other data, so that a reduction in the total cost can also be achieved.

[0084] (2) The configurations exemplified as the above-described embodiments are merely examples of the configuration of the present invention, and it is possible to combine them with other known techniques, or to change the configuration by omitting a part thereof without departing from the gist of the present invention. Further, in the above-described embodiments, it may be the case where the processes and configurations described in other embodiments are appropriately adopted and implemented.

[0085] The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Description of Reference Numerals

[0086] 2 Relay device, 3 Switch, 5 Monitoring device, 20 Synchronization device, 32 Auxiliary transformer, 35 A / D conversion unit, 40 Arithmetic processing unit, 42 RAM, 43 ROM, 44 Bus, 45 Sampling pulse generation circuit, 50 Communication circuit, 55 Digital output circuit, 56 Digital input circuit, 60 Analysis device, 1000, 1000A Protection relay system.

Claims

1. A plurality of network switches respectively provided on a plurality of terminals, For each of the plurality of network switches connected in a loop, each of the plurality of relay devices connected to the network switch is provided, For each of the plurality of network switches, the first relay device connected to the network switch transmits a first frame including first electrical quantity data sampled at the sampling timing to the network switch at a first timing when a first time has elapsed from the sampling timing, For each of the plurality of network switches, the second relay device connected to the network switch transmits a second frame including second electrical quantity data sampled at the sampling timing to the network switch at a second timing when a second time has elapsed from the sampling timing, Each of the network switches is a protection relay system that transmits the received first frame and second frame to other network switches.

2. Further comprising a synchronization device connected to any one of the plurality of network switches, For each of the plurality of network switches, each of the plurality of relay devices connected to the network switch synchronizes the time of the relay device with the time of the synchronization device based on the time synchronization data received from the synchronization device via the network switch, thereby synchronizing the sampling timing of the relay device with the sampling timing of other relay devices. The protection relay system according to claim 1.

3. The first timing is earlier than the second timing, Each of the plurality of network switches transmits the first frame received from the first relay device connected to the network switch to other network switches, and then transmits the second frame received from the second relay device connected to the network switch to other network switches. The protection relay system according to claim 1 or claim 2.

4. For each of the plurality of network switches, a third relay device connected to the network switch transmits a third frame including third electrical quantity data sampled at the sampling timing at a third timing after a third time has elapsed from the sampling timing to the network switch. When the first and second relay devices belong to a first group and the third relay device belongs to a second group, the time difference between the second timing and the third timing is longer than the time difference between the first timing and the second timing. The protection relay system according to any one of claims 1 to 3.

5. Each network switch transmits the third frame belonging to the second group after transmitting the first frame and the second frame belonging to the first group. The protection relay system according to claim 4.

6. Further provided is a monitoring device that is connected to each of the plurality of network switches and stores monitoring data including at least one of electrical quantity data sampled at its own terminal and calculation data calculated based on the electrical quantity data. The monitoring device transmits a fourth frame including the monitoring data to the network switch at a fourth timing after a fourth time has elapsed from the sampling timing. The protection relay system according to claim 4 or claim 5.

7. When the fourth frame belongs to the third group, the time difference between the third timing and the fourth timing is longer than the time difference between the first timing and the second timing. The protection relay system according to claim 6.

8. The first relay device connected to the network switch provided at each of the terminals performs a current differential operation using the first electrical quantity data sampled at its own terminal and the first electrical quantity data sampled at one or more other terminals. The second relay device connected to the network switch provided at each of the terminals performs a current differential operation using the second electrical quantity data sampled at its own terminal and the second electrical quantity data sampled at the one or more other terminals. The protection relay system according to any one of claims 1 to 7.

9. The period during which the first relay device transmits the first frame does not overlap with the period during which the second relay device transmits the second frame. The protection relay system according to any one of claims 1 to 8.

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