JP7724685B2 - Protection Relay System - Google Patents

Description

This disclosure relates to a protective relay system.

Power systems are equipped with protective relay systems. Protective relay systems are used for a variety of purposes; for example, transmission line protective relay systems are well known. A transmission line protective relay system isolates the faulted section when it detects a fault on a transmission line or bus. In a transmission line protective relay system, a relay device is installed at each terminal of the transmission line section. Each relay device measures electrical quantity data and sends and receives communication frames containing the electrical quantity data to and from other relay devices.

For example, Japanese Patent Application Laid-Open Publication No. 2011-200100 (Patent Document 1) discloses a protective relay system that performs relay calculations to detect faults in a power system from system current information transmitted between multiple units. The multiple units divide the electrical angle period into multiple slots for each piece of data to be transmitted. The multiple slots include a first slot in which system current information is transmitted between the multiple units, and a second slot in which a sampling time synchronization signal is transmitted.

JP 2011-200100 A

In a protective relay system like the one described above, the relay devices located at each terminal function as either a master that sends out a time signal, or a slave that receives the time signal and adjusts the time. If, for some reason, the master function needs to be switched from one relay device to another, the system operation must be temporarily stopped. Patent Document 1 does not teach or suggest a solution to this problem.

An object of one aspect of the present disclosure is to provide technology that enables proper continuation of operation of a protection relay system when switching the master function from one relay device to another.

According to one embodiment, a protection relay system is provided that includes multiple relay devices. The multiple relay devices include a master, a sub-master, and one or more slaves. The master includes a first electrical quantity communication unit that transmits first electrical quantity data sampled at the master's sampling timing to the sub-master and one or more slaves, and a first synchronization data communication unit that transmits first time synchronization data to the sub-master and one or more slaves. The sub-master includes a second electrical quantity communication unit that transmits second electrical quantity data sampled at the sub-master's sampling timing to the master and one or more slaves, and a second synchronization data communication unit that transmits the second time synchronization data to the one or more slaves. Each of the one or more slaves includes a third electrical quantity communication unit that transmits third electrical quantity data sampled at the slave's sampling timing to the master and the sub-master, and a time synchronization unit that performs a first synchronization calculation based on the first time synchronization data and a second synchronization calculation based on the second time synchronization data. If the master has not left the group including the master, sub-master, and one or more slaves, the time synchronization unit of each of the one or more slaves executes a first synchronization process to synchronize the sampling timing of the slave with the sampling timing of the master based on the result of the first synchronization calculation, and if the master has left the group, executes a second synchronization process to synchronize the sampling timing of the slave with the sampling timing of the sub-master based on the result of the second synchronization calculation.

A protection relay system according to another embodiment includes multiple relay devices, a first synchronizer, and a second synchronizer. The first synchronizer transmits first time synchronization data to the second synchronizer and the multiple relay devices. The second synchronizer transmits second time synchronization data to the multiple relay devices. Each of the multiple relay devices includes an electrical quantity communication unit that transmits electrical quantity data sampled at the sampling timing of the relay device to other relay devices, and a time synchronization unit that performs a first synchronization calculation based on the first time synchronization data and a second synchronization calculation based on the second time synchronization data. If the first synchronization device has not left a group including the multiple relay devices, the first synchronization device, and the second synchronization device, the time synchronization unit of each of the multiple relay devices performs a first synchronization process to synchronize the sampling timing of the relay device with the time of the first synchronizer based on the result of the first synchronization calculation. If the first synchronization device has left the group, the time synchronization unit performs a second synchronization process to synchronize the sampling timing of the relay device with the time of the second synchronizer based on the result of the second synchronization calculation.

According to the present disclosure, when the master function is switched from one relay device to another, the operation of the protection relay system can be continued.

FIG. 1 is an overall configuration diagram of a protective relay system. FIG. 2 is a block diagram illustrating an example of a hardware configuration of a relay device. FIG. 1 is a diagram for explaining a data communication method relating to an amount of electricity. FIG. 1 is a diagram illustrating a data communication method related to time synchronization. FIG. 10 is a sequence diagram illustrating an example of a time synchronization method. FIG. 10 is a sequence diagram illustrating a switching method for time synchronization processing. FIG. 10 is a sequence diagram illustrating an example of communication of a synchronization message between a master and a slave. FIG. 10 is a sequence diagram illustrating an example of communication of a synchronization message between a sub-master and a slave. FIG. 2 is a block diagram showing an example of a functional configuration of a protection relay system. FIG. 10 is a diagram showing the overall configuration of a protection relay system according to another embodiment.

Embodiments of the present invention will now be described with reference to the drawings. In the following description, identical components are designated by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions of them will not be repeated.

<Overall structure>
Fig. 1 is a diagram showing the overall configuration of a protective relay system. The example of Fig. 1 shows the overall configuration when a protective relay system 1000 is applied to a four-terminal power transmission system.

The protective relay system 1000 includes relay devices 10a to 10d (hereinafter also collectively referred to as "relay devices 10"). Relay devices 10a to 10d are provided at terminals A to D, respectively. Each relay device 10 is a digital protective relay device, for example, a current differential relay device that performs current differential calculations using current data sampled in each relay device 10.

Relay device 10a functions as the master, relay device 10b functions as a sub-master, and relay devices 10c and 10d function as slaves. In this embodiment, if the master's operation is stopped, the slave that functions as the next master is called the "sub-master." The method for selecting a sub-master is determined appropriately by the operator, such as in order of the address numbers of multiple slaves or according to predetermined rules. Below, relay device 10a will also be called "master 10a," relay device 10b will be called "sub-master 10b," and relay devices 10c and 10d will be called "slaves 10c and 10d."

The power transmission system includes three power transmission lines L1, L2, and L3 connected between four terminals A, B, C, and D. Terminal A is equipped with a circuit breaker 7a and a current transformer (CT) 5a, terminal B is equipped with a circuit breaker 7b and a CT 5b, terminal C is equipped with a circuit breaker 7c and a CT 5c, and terminal D is equipped with a circuit breaker 7d and a CT 5d. Current data measured by CTs 5a, 5b, 5c, and 5d is input to master 10a, sub-master 10b, and slaves 10c and 10d, respectively. A voltage transformer (VT) may also be connected to each of terminals A through D. In this case, voltage data measured by each VT is input to each relay device 10.

Each relay device 10 is configured to be able to communicate with each other via a network 70. Each relay device 10 transmits electrical quantity data (e.g., current data, voltage data, etc.) measured at its own end and time synchronization data for synchronizing the time of each relay device 10 via the network 70. The network 70 is configured, for example, by a high-speed communication network such as Ethernet (registered trademark).

<Hardware configuration>
An example will be described in which each relay device 10 of the master 10a, sub-master 10b, and slaves 10c and 10d is configured based on a microcomputer. Unlike the following example, each relay device 10 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 10 may be configured by combining an electronic circuit such as an FPGA or ASIC with a microcomputer.

Figure 2 is a block diagram showing an example of the hardware configuration of the relay device 10. Referring to Figure 2, the relay device 10 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 55 (D/O: Digital Output), and a digital input circuit 56 (D/I: Digital Input).

The auxiliary transformer 32 takes in electrical quantities from the current transformer, voltage transformer, etc., converts them into voltages suitable for signal processing in the relay's internal circuitry, and outputs them. 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-and-hold circuit, a multiplexer, and an A/D converter.

The analog filter removes high-frequency noise components from the current waveform signal output from the auxiliary transformer 32. The sample-and-hold circuit samples the current waveform signal output from the analog filter at the period of the sampling pulse generated by the sampling pulse generating circuit 45 (i.e., the sampling period). Based on the timing signal input from the calculation processing unit 40, the multiplexer sequentially switches the waveform signals input from the sample-and-hold circuit in time series and inputs them to the A/D converter. The A/D converter converts the waveform signals 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 calculation processing unit 40.

The calculation 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 calculation processing unit 40 may also include electrically rewritable non-volatile memory such as flash memory. The RAM 42 and ROM 43 are used as the main memory for the CPU 41. The CPU 41 controls the operation of the entire relay device 10 in accordance with programs stored in the ROM 43 and non-volatile memory.

The sampling pulse generating circuit 45 includes an oscillator and a frequency divider circuit. The oscillator outputs a reference frequency signal with a reference frequency for generating sampling pulses. The frequency divider circuit divides the reference frequency signal input from the oscillator by a frequency division ratio to generate sampling pulses. The frequency division ratio of the frequency divider is controlled by the CPU 41. This controls the frequency of the sampling pulses (i.e., the sampling frequency).

The communication circuit 50 communicates with other relay devices 10 via the network 70. The communication circuit 50 communicates with other relay devices 10 in accordance with a specified protocol.

The digital output circuit 55 (corresponding to "D/O" in the diagram) is an interface circuit for outputting signals to external devices. For example, the digital output circuit 55 outputs a trip command TS to a circuit breaker installed on the transmission line in accordance with instructions from the CPU 41. The digital input circuit 56 receives open/close information from the circuit breaker indicating the open/close state of the circuit breaker.

<Data communication method>
3 is a diagram illustrating a data communication method related to electrical quantities. Referring to FIG. 3, each relay device 10 transmits a frame including electrical quantity data measured at its own end to the other relay devices 10. Specifically, the master 10a transmits current data measured by the CT 5a to the sub-master 10b and the slaves 10c and 10d. The sub-master 10b transmits current data measured by the CT 5b to the master 10a and the slaves 10c and 10d. The same applies to the slaves 10c and 10d. As a result, each relay device 10 shares the current data measured by all the relay devices 10.

In the protective relay system 1000, each relay device 10 performs calculations such as fault detection and determination using electrical quantity data measured at the same time. 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 (e.g., 1.67 ms for a 50 Hz system).

Typically, each relay device 10 performs a current differential calculation using each electrical quantity data (current data in this case). Each relay device 10 calculates the vector sum of each current data and calculates the magnitude of the calculated vector sum as the differential current IDL. Each relay device 10 determines whether the differential current IDL is greater than a threshold K (i.e., whether IDL1 > K holds). If IDL > K holds, each relay device 10 determines that a fault has occurred in the protection section and outputs a trip command TS.

Figure 4 is a diagram illustrating a data communication method related to time synchronization. Referring to Figure 4, the master 10a transmits and receives synchronization messages to and from the sub-master 10b and the slaves 10c and 10d, which are used to synchronize the time of the other relay devices 10 with the time of the master 10a.

Submaster 10b transmits and receives synchronization messages with master 10a and slaves 10c and 10d, which are used to synchronize the time of other relay devices 10 with the time of submaster 10b. Synchronization messages are not transmitted and received between slave 10c and slave 10d.

<Time synchronization method>
Fig. 5 is a sequence diagram showing an example of a time synchronization method. The process shown in Fig. 5 is a time synchronization method conforming to IEEE 1588. Fig. 5 shows a representative time synchronization method between a master 10a and a slave 10c. Note that the time synchronization method between the master 10a and other relay devices 10 (e.g., a sub-master 10b, a slave 10d) is also similar to the method shown in Fig. 5.

Referring to Figure 5, master 10a transmits a Sync message, which is a synchronization frame for time synchronization control, to slave 10c (sequence SQ2). At this time, master 10a stores the time t1 at which the Sync message was transmitted in internal memory (e.g., RAM 42 or ROM 43). Slave 10c receives the Sync message and stores the time t2 at which it was received in its internal memory.

The master 10a reads the time t1 at which the Sync message was sent from its internal memory and sends a Follow_Up message storing the time t1 to the slave 10c (sequence SQ4). The slave 10c stores the time t1 stored in the received Follow_Up message in its internal memory. Note that the master 10a may also be configured to send a Sync message storing the time t1 to the slave 10c.

Slave 10c sends a Delay_Req message to master 10a (sequence SQ6). Slave 10c stores the time t3 when it sent the Delay_Req message in its internal memory. Master 10a receives the Delay_Req message and stores the time t4 when it was received.

The master 10a sends a Delay_Resp message containing time t4 to the slave 10c (sequence SQ8). The slave 10c stores the time t4 contained in the received Delay_Resp message in its internal memory.

As a result of the above sequence, times t1, t2, t3, and t4 are stored in the internal memory of slave 10c.

By calculating the difference between time t1 and time t2 (i.e., "t2 - t1"), slave 10c obtains the sum of the time difference between master 10a and slave 10c and the transmission path delay for the transmission path from master 10a to slave 10c. Furthermore, by calculating the difference between time t3 and time t4 (i.e., "t4 - t3"), slave 10c obtains the sum of the time difference between master 10a and slave 10c and the transmission path delay for the transmission path from slave 10c to master 10a.

Furthermore, the sum of the time difference "t4 - t3" and the time difference "t2 - t1" corresponds to twice the transmission path delay. The difference between the time difference "t4 - t3" and the time difference "t2 - t1" corresponds to twice the time difference between the time of the master 10a (hereinafter also referred to as "master time") and the time of the slave 10c (hereinafter also referred to as "slave time"). Here, the transmission delay between the master 10a and the slave 10c is assumed to be equivalent on the outbound and inbound paths. In this case, the delay time tx on a unidirectional transmission path is expressed as in the following equation (1):

tx={(t4-t3)+(t2-t1)}/2...(1)
The time difference td between the master time and the slave time is expressed by the following equation (2).

td={(t4-t3)-(t2-t1)}/2...(2)
The slave 10c performs time synchronization with the master 10a by correcting its own time using the time difference td as the correction amount for time synchronization. As a result, the master time and the slave time are synchronized (i.e., match), and the sampling timing of the master 10a and the sampling timing of the slave 10c can be synchronized. Similarly, the sub-master 10b and the slave 10d each perform time synchronization with the master 10a, thereby synchronizing their own sampling timing with the sampling timing of the master 10a.

The time synchronization method between submaster 10b and other relay devices 10 is the same as the time synchronization method shown in Figure 5. For example, the time synchronization process between submaster 10b and slave 10c calculates the delay time tx1 of the transmission path between submaster 10b and slave 10c, and the time difference td1 between the time of submaster 10b (hereinafter referred to as "submaster time") and the slave time. Slave 10c stores the delay time tx1 and the time difference td1 in its internal memory.

Here, if master 10a is present in group G1, which includes master 10a, sub-master 10b, and slaves 10c and 10d (i.e., master 10a has not left group G1), master 10a functions as the master of group G1. Therefore, sub-master 10b and slaves 10c and 10d each synchronize their own sampling timing with the sampling timing of master 10a through time synchronization processing with master 10a.

On the other hand, if master 10a does not exist in group G1 (i.e., if master 10a leaves group G1), sub-master 10b functions as the master of group G1. Therefore, each of slaves 10c and 10d synchronizes its own sampling timing with the sampling timing of sub-master 10b through time synchronization processing with sub-master 10b.

<Time synchronization processing switching method>
As described above, when the master 10a leaves the group G1, the sub-master 10b functions as the new master of the group G1. Here, we will explain the procedure when the slave 10c switches from the process of synchronizing the slave time with the master time to the process of synchronizing the slave time with the sub-master time. The same applies to the slave 10d.

Figure 6 is a sequence diagram illustrating the switching method for time synchronization processing. Referring to Figure 6, master 10a and slave 10c send and receive synchronization messages as described in Figure 5 (sequence SQ50). Slave 10c synchronizes its time with the master time using the time difference td as the time synchronization correction amount (sequence SQ52). As a result, the sampling timing of slave 10c is synchronized with the sampling timing of master 10a. Slave 10c also stores the delay time tx and time difference td, which are the results of the synchronization calculation, in its internal memory.

Sub-master 10b and slave 10c send and receive synchronization messages (sequence SQ54). Slave 10c stores the synchronization calculation results, delay time tx1 and time difference td1, in its internal memory (sequence SQ56). Slave 10c calculates the difference value Δtd (= |td - td1|) between the time difference td and the time difference td1 (sequence SQ58). Slave 10c transmits the difference value Δtd to master 10a (sequence SQ60).

Master 10a confirms that the difference value Δtd is less than threshold value K (sequence SQ62). Threshold value K is determined arbitrarily by the operator. Master 10a then transmits withdrawal information indicating withdrawal from group G1 to submaster 10b and slave 10c (sequence SQ64).

When submaster 10b receives the withdrawal information, it sends a notification to slave 10c that it will begin operating as the new master (sequence SQ66). Upon receiving this notification, slave 10c synchronizes its time with the submaster time (sequence SQ68). That is, slave 10c synchronizes its time with the submaster time using the time difference td1 stored in its internal memory as the time synchronization correction amount.

With the above configuration, if the difference value Δtd between the time difference td and the time difference td1 is less than the threshold value K, the master 10a withdraws and the sub-master 10b functions as the new master. Furthermore, because the difference value Δtd is less than the threshold value K, even if the slave 10c switches from synchronizing the slave time with the master time to synchronizing the slave time with the sub-master time, the slave time does not fluctuate significantly. Therefore, the system can continue to operate with the sub-master 10b as the new master without locking the system (for example, locking the protection function of the protection relay system 1000).

Here, before master 10a leaves, the sub-master time and slave time are synchronized with the master time. Therefore, it is typically considered that the slave time is also synchronized with the sub-master time, so the difference value Δtd should be less than the threshold value K.

However, the transmission path between master 10a and sub-master 10b is different from the transmission path between sub-master 10b and slave 10c. Furthermore, in transmission between sub-master 10b and slave 10c, the hardware circuits used on the outbound path are different from the hardware circuits used on the inbound path. Therefore, it is conceivable that the difference value Δtd may exceed the threshold value K. An example in which the difference value Δtd exceeds the threshold value K will be described using Figures 7 and 8.

Figure 7 is a sequence diagram showing an example of communication of synchronization messages between a master and a slave. The communication method for time synchronization messages is the same as the communication method described in Figure 5, so a detailed description will not be provided.

Referring to Figure 7, the time t1 when the Sync message is sent from master 10a to slave 10c is "0". The time t2 when slave 10c receives the Sync message is "3t" (where t is a positive number). The time t3 when slave 10c sends the Delay_Req message is "10t". The time t4 when master 10a receives the Delay_Req message is "13t". Therefore, from equations (1) and (2), the delay time tx is calculated to be "3t" and the time difference td is calculated to be "0".

Figure 8 is a sequence diagram showing an example of synchronization message communication between a sub-master and a slave. Referring to Figure 8, the time t1 when the Sync message is sent from the sub-master 10b to the slave 10c is "0". The time t2 when the slave 10c receives the Sync message is "3.5t". The time t3 when the slave 10c sends the Delay_Req message is "10t". The time t4 when the master 10a receives the Delay_Req message is "13t". Therefore, from equations (1) and (2), the delay time tx1 is calculated to be "3.25t", and the time difference td1 is calculated to be "0.25t".

In the example of Figure 7, time t2 is "3t", and in the example of Figure 8, time t2 is "3.5t". This difference occurs, for example, because the transmission path between master 10a and sub-master 10b is different from the transmission path between sub-master 10b and slave 10c. Furthermore, the transmission delay time on the outbound path from sub-master 10b to slave 10c is "t2 - t1 = 3.5t", and the transmission delay time on the return path from slave 10c to sub-master 10b is "t4 - t3 = 3t". This difference occurs, for example, because the hardware circuits used on the outbound path and the hardware circuits used on the return path are different.

Here, let's assume that the threshold value K is set to 0.2t, and that when the difference value Δtd exceeds the threshold value K, the master 10a leaves and the sub-master 10b functions as the new master. In this case, the slave 10c switches from synchronizing the slave time with the master time to synchronizing the slave time with the sub-master time. However, because the slave time fluctuates significantly, continued system operation could affect the accuracy of the protection function. Therefore, when the difference value Δtd exceeds the threshold value K, the master 10a does not send the departure information to the other relay devices 10. In this case, the system is temporarily locked, the slave time is synchronized with the sub-master time, and then system operation is resumed.

<Functional configuration>
Fig. 9 is a block diagram showing an example of the functional configuration of the protection relay system 1000. For ease of explanation, Fig. 9 will explain a case where there is one slave (here, only the slave 10c).

Referring to FIG. 9, the master 10a includes a first electrical quantity communication unit 110, a first synchronous data communication unit 120, and a withdrawal information transmission unit 130. The sub-master 10b includes a second electrical quantity communication unit 210 and a second synchronous data communication unit 220. The slave 10c includes a third electrical quantity communication unit 310, a third synchronous data communication unit 320, and a time synchronization unit 330. Each of these functions is realized by a processing circuit. The processing circuit may be dedicated hardware, or may be a CPU 41 that executes a program stored in the internal memory of the relay device 10. If the processing circuit is dedicated hardware, the processing circuit may be configured, for example, by an FPGA, an ASIC, or a combination of these.

The first electrical quantity communication unit 110 transmits electrical quantity data sampled at the sampling timing of the master 10a to the submaster 10b and slave 10c. The first synchronization data communication unit 120 transmits time synchronization data (e.g., Sync messages, Follow_Up messages, Delay_Resp messages) to the submaster 10b and slave 10c. The withdrawal information transmission unit 130 transmits withdrawal information indicating that the master 10a will be leaving group G1 to the submaster 10b and slave 10c.

The second electrical quantity communication unit 210 transmits electrical quantity data sampled at the sampling timing of the sub-master 10b to the master 10a and slave 10c. The second synchronization data communication unit 220 transmits time synchronization data (e.g., Sync messages, Follow_Up messages, Delay_Resp messages) to the master 10a and slave 10c.

The third electrical quantity communication unit 310 transmits electrical quantity data sampled at the sampling timing of the slave 10c to the master 10a and the sub-master 10b. The third synchronization data communication unit 320 transmits response data (e.g., a Delay_Req message) in response to the time synchronization data from the master 10a to the master 10a, and transmits response data in response to the time synchronization data from the sub-master 10b to the sub-master 10b.

The time synchronization unit 330 performs a first synchronization calculation based on the time synchronization data from the master 10a, and a second synchronization calculation based on the time synchronization data from the sub-master 10b. The first synchronization calculation is a calculation that uses equations (1) and (2) to determine the delay time tx and the time difference td. The second synchronization calculation is a calculation that determines the delay time tx1 and the time difference td1. Therefore, the result of the first synchronization calculation includes the time difference td indicating the difference between the time of the master 10a and the time of the slave 10c, and the result of the second synchronization calculation includes the time difference td1 indicating the difference between the time of the sub-master 10b and the time of the slave 10c.

If master 10a has not left group G1, the time synchronization unit 330 executes synchronization processing P1, which synchronizes the sampling timing of slave 10c with the sampling timing of master 10a, based on the result of the first synchronization calculation. Synchronization processing P1 synchronizes the sampling timing of master 10a with the sampling timing of slave 10c by matching the master time and slave time using the time difference td as the time synchronization correction amount.

On the other hand, when master 10a leaves group G1, the time synchronization unit 330 executes synchronization process P2, which synchronizes the sampling timing of slave 10c with the sampling timing of sub-master 10b based on the second synchronization calculation result. Synchronization process P2 synchronizes the sampling timing of sub-master 10b with the sampling timing of slave 10c by matching the sub-master time and slave time using the time difference td1 as the time synchronization correction amount. Note that when the time synchronization unit 330 receives departure information from master 10a, it determines that master 10a has left group G1.

The time synchronization unit 330 switches from synchronization process P1 to synchronization process P2 based on the difference value Δtd between the time difference td and the time difference td1. Specifically, if master 10a leaves group G1 and the difference value Δtd is less than threshold value K, the time synchronization unit 330 switches from synchronization process P1 to synchronization process P2. Therefore, even if master 10a leaves group G1, if the difference value Δtd is equal to or greater than threshold value K, the time synchronization unit 330 does not switch from synchronization process P1 to synchronization process P2.

<Advantages>
According to this embodiment, each of the slaves 10c and 10d executes a first synchronization calculation based on the time synchronization data from the master 10a and a second synchronization calculation based on the time synchronization data from the sub-master 10b. Therefore, when the master 10a leaves the group G1, the slaves 10c and 10d can smoothly shift from synchronizing their own sampling timing with that of the master 10a to synchronizing their own sampling timing with that of the sub-master 10b. Therefore, when the master function is switched from the master 10a to the sub-master 10b, it is possible to continue operation of the protection relay system 1000.

Other embodiments.
(1) In the above-described embodiment, one of the relay devices 10 functions as a master and another relay device functions as a sub-master. Here, a configuration will be described in which two external synchronization devices each have the time synchronization functions of the master 10a and the sub-master 10b.

Figure 10 is a diagram showing the overall configuration of a protection relay system according to another embodiment. Referring to Figure 10, protection relay system 1100 includes relay devices 10a1, 10b1, 10c, and 10d, and external synchronization devices 20a and 20b. Relay devices 10a1, 10b1, 10c, and 10d are provided at terminals A, B, C, and D in Figure 1, respectively. Relay device 10a1 corresponds to relay device 10a in Figure 1, which does not have master functionality. Relay device 10b1 corresponds to relay device 10b in Figure 1, which does not have sub-master functionality. Relay devices 10a1 to 10d all function as slaves. In the following description, relay devices 10a1 to 10d are also referred to as "slaves 10a1 to 10d."

The external synchronization device 20a has functions related to time synchronization in the master 10a. Specifically, the external synchronization device 20a has the functions of the first synchronization data communication unit 120 in Figure 9. The external synchronization device 20a transmits time synchronization data (e.g., Sync messages, Follow_Up messages, Delay_Resp messages) to the external synchronization device 20b and each of the slaves 10a1 to 10d.

The external synchronization device 20b has functions related to time synchronization in the sub-master 10b. Specifically, the external synchronization device 20b has the functions of the second synchronization data communication unit 220 in FIG. 9. The external synchronization device 20b transmits time synchronization data (e.g., Sync messages, Follow_Up messages, Delay_Resp messages) to each of the slaves 10a1 to 10d. Note that the external synchronization device 20b may also transmit time synchronization data to the external synchronization device 20a.

Each of the slaves 10a1-10d has the same functions as slave 10c. Each of the slaves 10a1-10d executes the same time synchronization process shown in FIG. 5 with the external synchronization device 20a. For example, the time synchronization process between the external synchronization device 20a and slave 10a1 corresponds to the process when "master 10a" in FIG. 5 is replaced with the external synchronization device 20a, and "slave 10c" in FIG. 5 is replaced with "slave 10a1." By executing this process, each of the slaves 10a1-10d calculates the delay time tx2 of the transmission path between the external synchronization device 20a and the slave, and the time difference td2 between the time of the external synchronization device 20a and the slave time.

Each slave 10a1-10d corrects its own time using the time difference td2 as the time synchronization correction amount. This synchronizes the time of the external synchronization device 20a with the time of each slave. In other words, the time of each slave is synchronized. This allows the sampling timing of each slave 10a1-10d to be synchronized. Note that the external synchronization device 20b synchronizes its own time with the time of the external synchronization device 20a by performing the same time synchronization process as the external synchronization device 20a.

Furthermore, each slave 10a1-10d performs time synchronization processing with the external synchronization device 20b. By performing this processing, each slave 10a1-10d calculates the delay time tx3 of the transmission path between the external synchronization device 20b and the slave, and the time difference td3 between the time of the external synchronization device 20b and the slave time.

Here, group G2 includes slaves 10a1-10d, external synchronization device 20a, and external synchronization device 20b. If external synchronization device 20a has not left group G2, the time synchronization unit of each slave 10a1-10d executes synchronization process Q1 to synchronize the sampling timing of that slave with the time of external synchronization device 20a based on the first synchronization calculation result (e.g., time difference td2). On the other hand, if external synchronization device 20a has left group G2, the time synchronization unit of each slave 10a1-10d executes synchronization process Q2 to synchronize the sampling timing of that slave with the time of external synchronization device 20b based on the second synchronization calculation result (e.g., time difference td3).

The time synchronization unit of each slave 10a1-10d switches from synchronization process Q1 to synchronization process Q2 based on the difference between time difference td2 and time difference td3. Specifically, if external synchronization device 20a leaves group G2 and the difference is less than threshold K, the time synchronization unit switches from synchronization process Q1 to synchronization process Q2.

The external synchronization device 20a may transmit to the external synchronization device 20b and each slave withdrawal information indicating that the external synchronization device 20a is withdrawing from group G2. The time synchronization unit of each slave 10a1-10d may be configured to determine that the external synchronization device 20a has withdrawn from group G2 upon receiving the withdrawal information.

(2) In the above-described embodiment, a configuration has been described in which each relay device 10 transmits electrical quantity data and time synchronization data for synchronizing the time of each relay device 10 via the same network 70. For example, the first electrical quantity communication unit of the master 10a transmits sampled electrical quantity data to the sub-master 10b and slaves 10c and 10d via the network 70. The first synchronization data communication unit 120 of the master 10a transmits time synchronization data to the sub-master 10b and slaves 10c and 10d via the network 70. However, the network for communicating electrical quantity data and the network for communicating time synchronization data may be different. For example, the first electrical quantity communication unit 110 transmits sampled electrical quantity data to the sub-master 10b and slaves 10c and 10d via the first network (e.g., a cyclic transmission network). The first synchronization data communication unit 120 transmits time synchronization data to the sub-master 10b and slaves 10c and 10d via a second network (e.g., an Ethernet network) different from the first network.

(3) The configurations exemplified as the above-described embodiments are examples of the configurations of the present disclosure, and may be combined with other known technologies. They may also be modified, such as by omitting some parts, without departing from the spirit of the present disclosure. Furthermore, the above-described embodiments may also be implemented by appropriately adopting the processes and configurations described in other embodiments.

The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present disclosure is indicated by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

7a, 7b, 7c, 7d: circuit breaker, 10: relay device, 20a, 20b: external synchronization device, 32: auxiliary transformer, 35: A/D conversion unit, 40: calculation processing unit, 42: RAM, 43: ROM, 44: bus, 45: sampling pulse generation circuit, 50: communication circuit, 55: digital output circuit, 56: digital input circuit, 70: network, 110: first electrical quantity communication unit, 120: first synchronization data communication unit, 130: departure information transmission unit, 210: second electrical quantity communication unit, 220: second synchronization data communication unit, 310: third electrical quantity communication unit, 320: third synchronization data communication unit, 330: time synchronization unit, 1000, 1100: protection relay system.

Claims (7)

A protection relay system including a plurality of relay devices,
the plurality of relay devices include a master, a sub-master, and one or more slaves;
The master
a first electrical quantity communication unit that transmits first electrical quantity data sampled at the sampling timing of the master to the sub-master and the one or more slaves;
a first synchronization data communication unit that transmits first time synchronization data to the sub-master and the one or more slaves;
The sub-master:
a second electric quantity communication unit that transmits second electric quantity data sampled at the sampling timing of the sub-master to the master and the one or more slaves;
a second synchronization data communication unit that transmits second time synchronization data to the one or more slaves;
Each of the one or more slaves
a third electric quantity communication unit that transmits third electric quantity data sampled at the sampling timing of the slave to the master and the sub-master;
a time synchronization unit that executes a first synchronization calculation based on the first time synchronization data and a second synchronization calculation based on the second time synchronization data;
The time synchronization unit of each of the one or more slaves
if the master has not left the group including the master, the sub-master, and the one or more slaves, executes a first synchronization process for synchronizing the sampling timing of the slave with the sampling timing of the master based on the result of the first synchronization calculation;
a protection relay system that, when the master leaves the group, executes a second synchronization process to synchronize the sampling timing of the slave with the sampling timing of the sub-master based on the result of the second synchronization calculation. the master further includes a withdrawal information transmitter that transmits withdrawal information indicating that the master will withdraw from the group to the sub-master and the one or more slaves;
The protection relay system according to claim 1 , wherein the time synchronization unit determines that the master has left the group when the time synchronization unit receives the leaving information from the master. the result of the first synchronization calculation includes a first time difference indicating a difference between the time of the master and the time of the slave, and the result of the second synchronization calculation includes a second time difference indicating a difference between the time of the sub-master and the time of the slave,
3. The protection relay system according to claim 1, wherein the time synchronizer switches from the first synchronization process to the second synchronization process based on a difference value between the first time difference and the second time difference. The protective relay system according to any one of claims 1 to 3 , wherein each of the plurality of relay devices is a current differential relay device that performs a current differential calculation using current data sampled in each relay device. the first electrical quantity communication unit transmits the first electrical quantity data to the sub-master and the one or more slaves via a first network;
The protection relay system according to any one of claims 1 to 4 , wherein the first synchronization data communication unit transmits the first time synchronization data to the sub-master and the one or more slaves via the first network. the first electrical quantity communication unit transmits the first electrical quantity data to the sub-master and the one or more slaves via a first network;
The protection relay system according to any one of claims 1 to 4 , wherein the first synchronization data communication unit transmits the first time synchronization data to the sub-master and the one or more slaves via a second network different from the first network. a plurality of relay devices;
a first synchronizing device and a second synchronizing device;
the first synchronization device transmits first time synchronization data to the second synchronization device and the plurality of relay devices;
the second synchronization device transmits second time synchronization data to the plurality of relay devices;
Each of the plurality of relay devices
an electric quantity communication unit that transmits electric quantity data sampled at the sampling timing of the relay device to another relay device;
a time synchronization unit that executes a first synchronization calculation based on the first time synchronization data and a second synchronization calculation based on the second time synchronization data;
The time synchronization unit of each of the plurality of relay devices
If the first synchronization device has not left the group including the plurality of relay devices, the first synchronization device, and the second synchronization device, a first synchronization process is executed to synchronize a sampling timing of the relay device with a time of the first synchronization device based on a result of the first synchronization calculation;
When the first synchronization device leaves the group, a second synchronization process is executed to synchronize the sampling timing of the relay device with the time of the second synchronization device based on the result of the second synchronization calculation.