JP6563286B2 - Protection relay and protection relay program - Google Patents

Description

  Embodiments described herein relate generally to a protection relay and a protection relay program applied to a power system.

  A protection system that protects a power system using a protection relay is applied to a wide variety of uses such as a power transmission line protection system and a system stabilization control system. The protection relay in the power transmission line protection system detects a power transmission line or bus accident and outputs a command to disconnect the fault section to the circuit breaker. The protection relay in the system stabilization control system detects system faults at power plants and substations, predicts system instability events such as frequency step-out, and outputs a signal to disconnect the generator from the system to the circuit breaker . With such a protection system, it is possible to prevent the accident from spreading in the power system and stabilize the power system.

  Electricity data measured by various detection means such as a current value, a voltage value, and contact information in a section monitored by itself is input to the protection relay. In addition, the protection relay exchanges electricity data with the protection relay device or computer at the other end via the communication path, and relay calculations such as current differential calculation and stability calculation are performed by the internal calculation device. doing.

  Such a protection relay is installed in each terminal of a power transmission line or a substation that is a protection section. In the following description, one protection relay may be called a self-end, and the other party's protection relay that the self-end transmits and receives data may be called a counterpart.

  A typical protection relay conventionally used is a PCM (Pulse Code Modulation) current differential relay. The PCM current differential relay samples current data at a predetermined cycle at each of its own end and the other end. Then, the current data sampled by the local end and the other end are communicated with each other via a communication transmission path, so that the differential calculation between the own end and the other end is performed. The presence or absence of is determined.

  The differential operation is performed as follows. First, a difference current is obtained from a vector sum of current data sampled at its own end and the other end. Next, an amplitude value that is the magnitude of the difference current is calculated. Furthermore, the operation is determined by comparing the amplitude value with a predetermined determination value.

Japanese Patent No. 5127482

  As described above, in a protection system in which a plurality of protection relays are connected by a route, it is necessary for each protection relay to perform a differential operation or the like using data measured at the same time. In other words, the protection relay must be synchronized in sampling time between terminals. For this reason, the protection relay communicates between its own end and the other end, and synchronizes. At this time, a terminal serving as a reference for synchronization is referred to as a main end, and a terminal for performing synchronization adjustment processing is referred to as a slave end. Further, the path from the slave end to the master end is called ascending, and the path from the master end to the slave end is called as descending.

  Such synchronization processing is performed on the premise that the transmission times are equal on the upstream and downstream of the path between the main end and the slave end. Here, as a path of the current differential relay, a dedicated communication line has been conventionally used. In the case of a dedicated communication line, since the route is fixed, the coincidence of uplink and downlink transmission times has been ensured.

  However, in recent years, a protection system using IP or Ethernet (registered trademark) as a communication protocol has been put into practical use. In communication using IP, a communication device such as a router autonomously selects an optimum route and performs route control. For this reason, since the upstream and downstream communication paths between the protection relays fluctuate due to changes in the network conditions, the transmission time also fluctuates. As described above, when the uplink and downlink transmission times fluctuate, the synchronization processing is hindered.

  In order to cope with this, when IP is applied, a route can be fixed by using a protocol such as MPLS (Multi-Protocol Label Switching). However, in this case as well, when the communication path is switched and switched back when a transmission failure occurs, a period in which the path is different between upstream and downstream may temporarily occur for several minutes.

  During this period, there is a delay time difference between the upper and lower paths, and therefore when the synchronization control is executed based on this delay time, the sampling timing shifts and the calculation accuracy of the protection relay decreases. When this synchronization deviation exceeds a value allowable for relay calculation, the accuracy required for protection cannot be ensured and the protection function cannot be continued.

  Embodiments of the present invention have been proposed to solve the above-described problems of the prior art. The purpose of the present invention is to prevent a synchronization error by detecting a difference in a transmission / reception route of a protection relay. It is an object of the present invention to provide a protection relay and a protection relay program that make it possible to cope with the problem.

In order to solve the above problems, the protection relays embodiment of the present invention is connected to a communication route including a plurality of communication devices, an acquisition unit that acquires information on the number of communication devices in which data has traversed, The information about the number of communication devices through which the data acquired by the acquisition unit is compared with predetermined information, and is transmitted to the path for receiving data from the protection relay at the other end and to the protection relay at the other end A determination unit that determines a difference from a route of data to be extracted, and an extraction unit that extracts information about the number of communication devices included in the data received from the protection relay at the other end and through which the data transmitted by the protection relay at the other end has passed If, have a, the predetermined information, Ru information der on the number of communication devices extracted by the extracting unit.

The block diagram which shows the electric power system to which the protection relay of embodiment is applied Block diagram showing the network configuration of the protection system Explanatory drawing showing the procedure of sampling synchronization control Frame format used by protection relay for data communication The flowchart which shows the process sequence of 1st Embodiment. Explanatory drawing which shows the detection process by 1st Embodiment. Explanatory diagram showing the case where route switching cannot be detected Explanatory drawing which shows the detection process of 2nd Embodiment. Explanatory drawing which shows the detection process of 3rd Embodiment. The flowchart which shows the process sequence of 5th Embodiment. Explanatory drawing which shows the detection process of 5th Embodiment. Explanatory drawing which shows the detection process of 6th Embodiment

[First Embodiment]
[Basic configuration]
The configuration of the present embodiment will be described with reference to the drawings. The protection relay of this embodiment is applied to the protection system S and the network NW as shown in FIG. The protection relays 4a, 4b, and 4c included in the protection system S are connected to the power system E to be protected. The power system E includes a transmission line 1, a current transformer 2, and a circuit breaker 3.

  The power transmission line 1 is an electric line that transmits electric power. In addition, although the power transmission line 1 in this embodiment is a three-phase alternating current, it is simplified and illustrated in a single phase. The current transformer 2 is a detector that detects current. The circuit breaker 3 is a device that interrupts the current during an accident. The current transformer 2 and the circuit breaker 3 are installed at each terminal of the power transmission line 1.

  The protection relays 4a, 4b, and 4c are devices that protect the power system E by detecting an accident and outputting a break command to the breaker 3. For example, PCM current differential relays can be used as the protection relays 4a, 4b, and 4c. The circuit breaker 3 performs a breaking operation in response to a breaking command from the protection relays 4a, 4b, and 4c.

  FIG. 1 shows details of the configuration of the protection relay 4a. However, the other protection relays 4b and 4c have the same configuration. In the following description, when the protection relays 4a, 4b, and 4c are not distinguished, the protection relay 4 is assumed.

  The protection relay 4 includes an input converter 6, an analog filter 7, an A / D conversion unit 8, a calculation unit 9, an output unit 10, a communication unit 11, a synchronization control unit 12, and a storage unit 13. The input converter 6 insulates the analog signal from the current transformer 2 from the system side and converts it to an appropriate size. The analog filter 7 performs band limitation for sampling. The A / D converter 8 converts an analog signal into a digital signal.

  The calculation unit 9 performs a differential calculation based on the input signal. That is, the arithmetic unit 9 determines an accident current and generates a cutoff command. The output unit 10 outputs a cutoff command to the circuit breaker 3. The communication unit 11 performs communication with the protection relay 4 at the other end. Details of the configuration of the communication unit 11 will be described later.

  The synchronization control unit 12 performs synchronization control to synchronize synchronization timing by performing communication via the network NW. Details of this synchronization control will be described later. The storage unit 13 stores various types of information necessary for the processing of this embodiment. The information to be stored includes TTL value, network distance, communication device address information, time for which self-running can be continued, various setting values, received data, and the like.

  As shown in FIG. 2, the network NW connects the protection relays 4a, 4b, and 4c to each other to transmit and receive data. The network NW is an L2 / L3 network in which the L2 switch 14 and the L3 switch 15 are connected via a communication path R. Information transmitted and received in the network NW is collectively referred to as data. Data relayed in layer 2 which is the data link layer is called a frame. Data relayed in layer 3 which is a network layer is called a packet. An area including actual data such as current data included in the packet is referred to as a data portion.

  The L2 switch 14 is a relay device that relays frames at layer 2. The destination of the frame is determined based on the MAC address. The L3 switch 15 is a relay device that relays packets in layer 3. The destination of the packet is determined based on the IP address.

  Each L3 switch 15 is connected in a ring shape via a path R. Each protection relay 4a, 4b, 4c is connected to the L3 switch 15 via the L2 switch 14. A router can be used instead of the L3 switch 15.

  Although not shown, the protection relay 4 is connected to a backup network. The backup network may be a separate network independent of the network NW, or may be any one of the multiplexed networks NW.

[Communication Department]
As illustrated in FIG. 1, the communication unit 11 includes a transmission / reception unit 110, a setting unit 111, an acquisition unit 112, an extraction unit 113, a determination unit 114, a self-propelled unit 115, a switching unit 116, a return unit 117, and a notification unit 118. .

  The transmission / reception unit 110 transmits / receives a frame to / from the protection relay 4 at the other end. The setting unit 111 sets a value related to the number of communication devices that pass between the protection relays 4 during frame transmission. The value related to the number of communication devices is, for example, a TTL value or a network distance. The TTL value is a value that is decremented every time it passes through the L3 switch 15 that is a communication device. The network distance is the number of 15 L3 switches through which data measured based on the TTL value passes. The setting unit 111 sets a TTL value for the IP header of the packet, adds a network distance to the data portion of the packet, and the like.

  The acquisition unit 112 acquires information related to the number of communication devices through which data passes. That is, the acquisition unit 112 acquires the network distance from the data received by the transmission / reception unit 110. The network distance is acquired by subtracting the TTL value included in the IP header of the packet received by the transmission / reception unit 110 from a fixed TTL value set in advance.

  The extraction unit 113 extracts information related to the number of communication devices included in the data received from the protection relay 4 at the other end and through which the data transmitted by the protection relay 4 at the other end has passed. Here, the information regarding the number of communication devices included in the data portion is a network distance. This network distance is the network distance acquired by the acquisition unit 112 at the other end when the data transmitted from the protection relay 4 at the other end is received by the protection relay 4 at the other end.

  That is, the protection relay 4 at the other end includes the network distance obtained by the obtaining unit 112 based on the TTL value of the IP header of the received packet in the data portion of the packet transmitted by the setting unit 111. The protection relay 4 at the other end transmits this packet to the protection relay 4 at its own end.

  The determination unit 114 compares the information acquired by the acquisition unit 112 with predetermined information, thereby comparing the route R of data received from the protection relay 4 at the other end and the data transmitted to the protection relay 4 at the other end. The difference from the route R is determined. The predetermined information is the network distance included in the data part of the packet received from the protection relay 4 at the other end and extracted by the extraction unit 113 as described above.

  When the determination unit 114 determines that the route R is different, the self-running unit 115 stops the synchronization by the synchronization control unit 12 and causes the self-running unit to perform self-running. Self-run means to align the timing with the protection relay at the other end by controlling according to the accuracy of its own internal clock.

  The switching unit 116 switches to the backup route when the self-running by the self-running unit 115 has passed a preset time. The preset time is a time during which the self-running period can maintain a predetermined synchronization accuracy. The restoration unit 117 restores synchronization by the synchronization control unit 12 when sampling synchronization is possible. The notification unit 118 includes information for notifying the difference in the path R in a frame transmitted by the transmission / reception unit 110 and notifies the other protection relay 4.

[Action]
[Synchronous control]
As described above, in order for the protection relay 4 to perform a differential operation, the sampling timing needs to be synchronized. This synchronization is performed by the synchronization control unit 12. This synchronization control process will be described with reference to FIG. FIG. 3 shows the control between two terminals for transmitting and receiving with the main end and the slave end determined.

  First, the slave end and the main end transmit data Td1 and Td2 including the transmission timing which is the sampling timing of its own end. At both terminals, the time intervals tm and ts between the sampling timing of the local end and the reception time of the data Td1 and Td2 from the counterpart end are measured. Then, the simultaneity is ensured by correcting the sampling timing so that ts−tm = 0.

  However, in order to perform such synchronization control, it is necessary to maintain that the upstream and downstream routes R of the slave and main ends are the same and the transmission delay times are equal. That is, the transmission delay times of Td1 and Td2 must be the same. If there is a difference in transmission delay time, a synchronization error of 1/2 of the difference, that is, Δt = (Td1−Td2) / 2 occurs. When the time of the synchronization error exceeds a value allowable for the relay calculation by the calculation unit 9, correct calculation cannot be performed. This allowable value is, for example, about several tens to several hundreds μs.

  As described above, in the network NW configured in a ring shape, when connected communication apparatuses communicate with each other, one route can be used or the opposite route can be used. Hereinafter, for the sake of convenience, one route is called clockwise and the opposite route is called counterclockwise.

  Whether the clockwise or counterclockwise route is used is different for each packet transmitted by the communication apparatus. However, for the above sampling synchronization, in order to make the transmission delay time between the protection relays 4 the same, it is necessary to fix the route. For example, by using a protocol such as MPLS, the route can be fixed either clockwise or counterclockwise. However, as described above, even when these protocols are used, a period during which sampling synchronization cannot be performed temporarily may occur.

[Frame structure]
An example of a frame structure of data transmitted and received by the protection relay 4 is shown in FIG.
The contents of each item are as follows.
Preamble: Bit string indicating frame delimiter Destination MAC: Frame destination MAC address Source MAC: Frame source MAC address Type: Ethernet frame type IP packet: IP header, data part FCS: Frame check sequence code IP header: Destination IP Address, source IP address, TTL value, etc. Data section: actual data such as electricity data and synchronization data

  This frame is an Ethernet frame configured by adding an Ethernet header to a packet. The frame transmitted from the protection relay 4 passes through the L2 network configured by the L2 switch 14 and the route R.

  In the L3 network, only the IP packet is transmitted, and the Ethernet header is added again by the L3 switch 15 on the other side. As a result, the frame passes through the partner L2 switch 14 and is transmitted to the protection relay 4 at the partner end.

  The synchronization data included in the data part is data used for synchronization control. The synchronization data includes a synchronization master / slave terminal number, synchronization frame transmission / reception timing (time) information, synchronization command / response type information, and the like. Further, as will be described later, a network distance obtained from a TTL value may be added to the data portion.

  The TTL value included in the IP header is decremented by 1 each time it passes through the L3 switch 15. When the TTL value becomes 0, the packet is discarded by the L3 switch 15. This prevents packets from continuing to flow through the network NW even when a loop occurs in the path R.

[Route switching detection]
The path switching detection process according to the present embodiment will be described with reference to the flowchart of FIG. 5 and the explanatory diagram of FIG. This processing is an aspect in which the slave protection relay 4b detects the network distance and notifies the primary protection relay 4a. In FIG. 6, the illustration of the L2 switch 14 in which the TTL value does not decrement is omitted.

  The setting unit 111 in the communication unit 11 of the slave protection relay 4b always sets M, which is a fixed TTL value, in the IP header of the frame to be transmitted. The TTL value is, for example, 255. The slave transmission / reception unit 110 transmits the synchronization frame in which the TTL value is set as described above, with the main end as the destination (step S01).

  The TTL value is decremented every time it passes through the L3 switch 15. That is, the calculation of M = M−1 is performed. For this reason, for example, when there are two L3 switches 15 in the path R, the TTL value of the data reaching the main end is M−2. When the fixed TTL value is 255, it becomes 253.

  The storage unit 13 of the protection relay 4a at the main end stores in advance M, which is a TTL value transmitted by the slave end. For example, 255 is stored. The main end acquisition unit 112 subtracts the TTL value included in the received IP header from the previously stored TTL value. As a result, the network distance, which is the number of L3 switches 15 through which data is transmitted from the slave end to the master end, is acquired. In the above example, since 255−253 = 2, it can be seen that the network distance is 2, that is, there are two L3 switches passed through.

  The main end setting unit 111 adds the acquired network distance value to the data portion of the packet transmitted to the slave end. The transmitting / receiving unit 110 notifies the slave end of the network distance from the slave end to the master end by transmitting a frame including this packet with the slave end as the destination.

  The slave transmitting / receiving unit 110 receives this frame (step S02). Similarly to the above, the slave acquisition unit 112 obtains the network distance from the TTL value of the packet received from the master terminal and the preset TTL value (step S03). This network distance is the number of L3 switches 15 through which the packet actually passes from the main end to the subordinate end.

  Further, the extraction unit 113 extracts the network distance included in the data part of the packet (step S04). This network distance is a network distance from the slave end to the master end, and the master end is included in the data portion.

  Then, the determination unit 114 compares the network distance of the route R through which the packet has actually passed with the network distance included in the data unit to determine the difference of the route R (step S05).

  As a result of the comparison, when the network distances match between the upstream and downstream routes R (YES in step S06), the determination unit 114 assumes that there is no route mismatch in the vertical direction of the route R, and performs synchronization control. continue. If the network distances do not match (NO in step S06), it is determined that there is a route mismatch in the vertical direction of the route R.

  When the determination unit 114 determines that there is a path mismatch in the vertical direction of the path R, the free-running unit 115 stops the synchronous pull-in process by the sampling synchronization control unit 12 and performs free-running by the internal clock (step) S07). This prevents the pull-in due to the apparent synchronization error. This self-running continues until a time when the preset synchronization accuracy can be maintained (NO in step S08).

  When it is determined that the self-running period has exceeded the time during which the synchronization accuracy can be maintained (YES in step S08), the switching unit 116 switches the route R used for synchronization to the backup network (step S09).

  When the path R is restored and sampling synchronization is possible, the restoration unit 117 restores synchronization by the synchronization control unit 12. Further, the notification unit 118 may notify the other protection relay 4 of the switching of the route R.

[effect]
In the present embodiment as described above, the acquisition unit 112 that is connected to the communication path R including the plurality of L3 switches 15 and acquires the network distance that is the number of the L3 switches 15 through which the data passes is acquired by the acquisition unit 112. The determination to determine the difference between the route R for receiving data from the protection relay 4 at the other end and the route R for data to be transmitted to the protection relay 4 at the other end by comparing the determined network distance with predetermined information Part 114.

  For this reason, the difference in the transmission / reception route R of the protection relay 4 is detected, and the countermeasure for preventing the synchronization shift is enabled. That is, while the upstream and downstream routes R are different, it is possible to prevent the occurrence of synchronization shift by setting a self-running state without performing synchronization control or switching the network used for synchronization to another network.

  In addition, the present embodiment includes an extraction unit 113 that extracts information related to the number of communication devices that are included in the data received from the protection relay 4 at the other end and through which the data transmitted by the protection relay 4 at the other end has passed, The predetermined information compared by the determination unit 114 is the network distance extracted by the extraction unit 113.

  For this reason, it is possible to easily and accurately determine the difference between the network distance through which the upstream data passes and the network distance through which the downstream data passes from only the received data.

  Further, in this embodiment, when the synchronization control unit 12 that synchronizes the sampling timing with the protection relay 4 at the other end and the determination unit 114 determine that the path R is different, the synchronization control unit 12 performs synchronization. And a self-running unit 115 that stops and performs control by an internal clock. For this reason, it is possible to detect the switching of the route R at an early stage and promptly enter the self-running state.

  Furthermore, the present embodiment includes a switching unit 116 that switches to a backup route when a backup route is connected and the self-running by the free-running unit 115 has passed a predetermined time. For this reason, when the self-running state continues for a certain time or longer, the synchronization control can be continued by switching the network used for synchronization to the network on the backup side.

[Second Embodiment]
[Constitution]
This embodiment is basically the same configuration as the first embodiment. However, in the present embodiment, in the protection relay 4 in which the notification unit 118 has a different network distance in one route R and a network distance in the route R in the opposite direction in the ring-shaped network NW, the determination unit 114. Thus, when the difference between the routes R is determined, the difference between the routes R is notified to the protection relay 4 that is different from the protection relays 4.

[Function and effect]
The operational effects of the present embodiment as described above will be described with reference to the explanatory diagrams of FIGS. First, in the ring-shaped network NW, there are two routes R of the pair of protection relays 4 clockwise and counterclockwise. In this case, in the first embodiment, when the network distance is different between the clockwise route R and the counterclockwise route R, it is possible to detect the mismatch of the route R.

  However, the pair of protection relays 4 may have the same clockwise and counterclockwise network distances in the ring-shaped network NW. In this case, even if the clockwise route R and the counterclockwise route R are switched, the network distance does not change. For this reason, the mismatch of the route R cannot be detected.

  FIG. 7 shows an example where the number of counterclockwise and clockwise L3 switches 15 is the same. In this example, in the network NW having four terminals, the protection relay 4a and the protection relay 4c have three L3 switches 15 that pass therethrough regardless of whether the route R is clockwise or counterclockwise. Same on the table. For this reason, regardless of which route R is switched to, it is not possible to detect a vertical route mismatch due to the network distance.

  However, if the number of terminals is three or more, the corresponding L3 switch 15 is also three or more, and there is always a relationship in which the network distance between the terminals is different when the vertical path mismatch occurs. Such terminals can detect a mismatch in the path R.

  An example of this aspect is shown in FIG. That is, in the network NW having four L3 switches 15, when the protection relay 4a and the protection relay 4b are clockwise, there are two L3 switches 15 to be routed. In the case of counterclockwise rotation, the number of L3 switches 15 to be routed is four. The protection relay 4a and the protection relay 4c are clockwise and counterclockwise, and the number of L3 switches 15 is equal to three.

  Therefore, the determination unit 114 in the protection relay 4b can determine the mismatch of the path R with the protection relay 4a, as in the first embodiment. Therefore, when the determination unit 114 of the protection relay 4b determines the mismatch of the route R, the notification unit 118 notifies the protection relay 4c that the mismatch of the route R is detected.

  In the protection relay 4c that has received this notification, the self-propelled unit 115 self-propels. Alternatively, the synchronization control unit 12 of the protection relay 4a at the main end stops the synchronization process. As a result, the self-running portions 115 of all the slave protection relays 4b and 4c are brought into a self-running state. As a result, synchronization is not pulled in due to an apparent synchronization error. Furthermore, the switching unit 116 switches the communication path used for synchronization to another network for backup when the self-running period exceeds the time during which a certain synchronization accuracy can be maintained.

  According to the present embodiment as described above, even when the network distance between the protection relays 4a and 4c in the ring-shaped network NW is the same in the counterclockwise direction and the clockwise direction, the vertical distance from the other protection relay 4b is increased. By notifying the direction route mismatch, it is possible to prevent the occurrence of a synchronization error as in the above-described embodiment.

  As described above, when the network distance is the same in the counterclockwise direction and the clockwise direction, this cannot be detected when a different route occurs. However, depending on conditions such as the network configuration and communication path length, it may be known in advance that the transmission delay time difference is within the allowable range if the network distances match. Therefore, in such a case, since an apparent synchronization error does not occur, there is no problem even if the synchronization process is continuously executed without stopping when a path mismatch in the vertical direction of the path R is detected. .

[Third Embodiment]
[Constitution]
This embodiment is basically the same configuration as the first or second embodiment described above. However, in the present embodiment, the information regarding the number of communication devices through which the data to be compared by the determination unit 114 is different from the predetermined information. First, information on the number of communication devices through which data passes is obtained by setting the communication device as an initial value by adding a predetermined value to the network distance between the protection relay 4 at the other end and the protection relay 4 at the other end. It is the value subtracted every time it passes. The predetermined information is a value added in the initial value.

[Function and effect]
The operational effects of the present embodiment as described above will be described. First, as in the first embodiment, the acquisition unit 112 at its own end obtains the network distance N from the other end from the TTL value of the packet received from the other end.

  Then, the end setting unit 111 sets the number obtained by adding the predetermined value x to the network distance N as the initial value of the TTL value. x is an integer of 1 or more, and the value of TTL is set to 255 or less. The transmission / reception unit 110 transmits the packet in which the TTL value is set in this way to the other end.

  At the other end, the storage unit 13 stores a predetermined value x in advance. Then, when the other end receives the packet, the acquisition unit 112 acquires a TTL value. Here, when the route R from the other end to the other end and the route R from the other end to the other end coincide, the TTL value is x. If the routes R do not match, the TTL value of the packet received by the other end is a value larger than x or a value smaller than x. That is, the TTL value is a value other than x.

  When the TTL value of the packet is larger than x, the network distance from the other end to the other end is smaller than the network distance from the other end to the own end. When the value is smaller than x, the network distance from the other end to the other end is larger than the network distance from the other end to the own end.

  For this reason, the determination unit 114 compares x stored in advance with the TTL value of the received packet, and determines that the route R is different if it is determined that the values do not match. In the middle of the route R, when the TTL value becomes 0 or less, the packet is discarded, so that data does not reach the other end. If the packet cannot be received even after a predetermined time has elapsed, the self-running unit 115 is set in the free-running state without performing the synchronization process.

  A specific example of this embodiment will be described with reference to the explanatory diagram of FIG. First, the acquisition unit 112 obtains 2 which is the network distance N between the own end and the other end from the TTL value of the packet transmitted by the other end protection relay 4b and received by the own end protection relay 4a.

  The local setting unit 111 sets 3 as the TTL value, which is a value obtained by adding the predetermined value 1 to the value 2 of the network distance N. The transmission / reception unit 110 transmits data in which the TTL value is set to 3 in this way to the other end.

  Then, when the upstream and downstream network distances are equal, the TTL value of the data reaching the other end is 1. When the downstream network distance is small, the TTL value of the data reaching the other end is a value larger than 1. The partner end determination unit 114 determines a difference in the route R when the TTL value is larger than 1 as compared with 1, which is a predetermined value. In response to this, self-running by the self-running unit 115, switching to backup by the switching unit 116, and the like are performed as described above.

  Also, when the downstream network distance is large, the TTL value received by the other end is 0 or less in the middle of the route R. For this reason, the packet is discarded and data does not reach the other end. In this case, since synchronization cannot be performed, switching to self-running by the self-running unit 115 and backup by the switching unit 116 is performed as described above. For this reason, it is possible to prevent a pull-in process for an erroneous synchronization error.

  In the present embodiment as described above, there is no need for the setting unit 111 to add the network distance value acquired by the acquisition unit 112 to the data portion of the packet. Further, the extraction unit 113 that extracts the network distance from the data part is not necessary.

[Fourth Embodiment]
[Constitution]
The configuration of this embodiment is basically the same as that of the first embodiment. However, in the present embodiment, the storage unit 13 stores information regarding the number of communication devices acquired by the acquisition unit 112. This information is a TTL value in the IP header. This is predetermined information that the determination unit 114 compares.

  Moreover, the notification part 118 notifies this mutually, when the path | route R is switched by both the self-end and the other party's protection relays 4. Furthermore, when the protection relays 4 perform control by the self-propelling unit 115, the return unit 117 is stopped when the determination unit 114 of both protection relays 4 detects a difference in the path R. The control by the control unit 12 is returned.

[Function and effect]
In the present embodiment as described above, the storage unit 13 at the main end and the slave end stores the TTL value of the data received from the counterpart terminal. Each time data is received, the determination unit 114 compares the TTL value of the received data with the TTL value of the stored data to monitor whether there is a change. If the determination unit 114 determines that the TTL value has changed, it is assumed that route switching has occurred, and the self-running unit 115 stops the synchronous pull-in and enters the self-running state.

  When the determination unit 114 determines the path switching, the notification unit 118 adds information indicating that the path switching is detected to the data, and the transmission / reception unit 110 transmits the data to the other end. When the ring network NW is used, the route R from one protection relay 4 has only two directions. For this reason, when path switching is detected at both terminals from the state where the path R matches, the path R after switching also matches vertically.

  Therefore, when the return unit 117 in the protection relay 4 that is in a self-running state confirms that the path switching has occurred also at the other end by the data notified from the notification unit 118 at the other end, the synchronization control unit 12 Resume synchronization pull-in by.

  Further, even if a route change is detected at one terminal, if a route change is not detected at the other terminal, it is determined that a vertical route mismatch has occurred, and the self-running state is continued. The switching of the backup network is the same as described above.

  In the present embodiment as described above, the switching of the route R can be detected only by monitoring the TTL value of the data received by the protection relay 4. For this reason, a special setting as a TTL value becomes unnecessary. In addition, when both are switched, there is no problem in synchronization, so that synchronization can be resumed promptly.

[Fifth Embodiment]
[Constitution]
The basic configuration of this embodiment is the same as that of the first embodiment. However, the acquisition unit 112 of the present embodiment acquires information for identifying the communication device through which the data has passed. This information is, for example, the MAC address and IP address of the L3 switch 15, unique identification information assigned in the network, and the like. Hereinafter, this information is referred to as address information.

  The storage unit 13 stores the address information of the L3 switch 15 acquired by the acquisition unit 112. Furthermore, the determination unit 114 determines a change in the path R by comparing the address information of the L3 switch 15 stored in the storage unit 13 with the address information of the L3 switch 15 of the received data.

  Here, the address information of the L3 switch 15 is the address information of the L3 switch 15 that has discarded the data. That is, the communication device such as the L3 switch 15 has a function of discarding data when the TTL value becomes 0, and returning an ICMP (Internet Control Message Protocol) time-over response to the packet transmission source. In the present embodiment, the address information of the L3 switch 15 included in this time excess response is used.

[Function and effect]
The above-described path switching detection process of the present embodiment will be described with reference to the flowchart of FIG. 10 and the explanatory diagram of FIG. First, the setting unit 111 at its own end sets a predetermined value shorter than the network distance to the other end as the TTL value of the packet in the monitoring data to be transmitted (step S11). The transmission / reception unit 110 transmits a frame including this packet to the other end (step S12). The own end waits for an overtime response (NO in step S13).

  In the L3 switch 15 in the middle of the route R, since the TTL value is 0, the packet is discarded. At this time, the L3 switch 15 that has discarded the packet returns an ICMP time exceeded response to the packet transmission source. When the self-transmission / reception unit 110 receives the overtime response (YES in step S13), the acquisition unit 112 acquires the address information of the L3 switch 15 as the reply source from the overtime response (step S14).

  The determination unit 114 compares the address information stored in the storage unit 13 with the address information of the received overtime response (step S15). The address information stored in the storage unit 13 is address information acquired in advance by the acquisition unit 112 and stored in the storage unit 13 in the above-described procedure. If the address information matches (YES in step S16), the synchronous control is continued assuming that there is no change in the route R. If the address information does not match (NO in step S16), the determination unit 114 determines that the route R has been switched.

  As described above, the transmission / reception unit 110 of the protection relay 4 periodically transmits monitoring data in which a TTL value is set in which a packet is discarded along the route R. The determination unit 114 monitors the L3 switch 15 in which the packet is discarded based on the time excess response received by the transmission / reception unit 110.

  That is, when the determination unit 114 determines that the packet is discarded in the same L3 switch 15, there is no path change. If the determination unit 114 determines that the packet has been discarded by a different L3 switch 15, the path R has changed. Processing after the determination unit 114 determines that the route R has changed in this manner is the same as that in the first embodiment (steps S17 to S19).

A specific example of this embodiment will be described with reference to the explanatory diagram of FIG.
(1) The setting unit 111 of the own-end protection relay 4a sets a value of 2 smaller than the network distance 3 to the other-end protection relay 4c as the TTL value in the monitoring data. The transmission / reception unit 110 transmits the monitoring data to the protection relay 4c.

(2) Since the TTL value = 0 in the L3 switch 15 in the middle of the route R, the L3 switch 15 discards the packet and returns an ICMP time excess response to the transmission source protection relay 4a.

(3) The transmission / reception unit 110 of the local protection relay 4a receives the ICMP time excess response, and the acquisition unit 112 acquires the address information of the source L3 switch 15. The determination unit 114 continues the synchronization control when there is no change as compared with the address information stored in the storage unit 13.

(1) 'to (3)' Similarly to the above, when monitoring data is transmitted, if there is a path change, a different L3 switch 15 returns an ICMP time excess response. For this reason, the determination unit 114 determines that the route is switched because there is a change compared to the address information stored in the storage unit 13.

(5) When the route is changed, the notification unit 118 notifies the partner end.

(6) Also in the protection relay 4c at the other end, as described above, the determination unit 114 determines the presence / absence of path switching by transmitting monitoring data and receiving an ICMP time excess response.

(7) When the route is changed, the notification unit 118 at the other end notifies the end of the change. If there is a path change at both the other end and the own end, the synchronization control is continued as described above. If there is a route change on either side, it switches between self-running and backup.

(8) Even at the own end, if there is a route change at both the other end and the own end, the synchronization control is continued as described above. If there is a route change on either side, it switches between self-running and backup.

  According to the present embodiment as described above, a change in the path R is detected based on whether or not the L3 switch 15 that is a communication device through which data passes has changed. For this reason, even if the network distances of the clockwise route R and the counterclockwise route R are different or coincide, the change of the route R can be easily detected.

[Sixth Embodiment]
This embodiment is basically the same as the fifth embodiment described above. However, in the present embodiment, the determination unit 114 acquires the address information acquired by the acquisition unit 112 of the counterpart protection relay 4 in the same manner as in the fifth embodiment, and the own protection relay 4 In the same manner as in the embodiment, the address information monitored is compared to determine route switching. That is, in this embodiment, it is confirmed by exchanging address information whether the monitored L3 switch 15 is the same at the local end and the counterpart end.

[Function and effect]
In the present embodiment as described above, as described above, the acquisition unit 112 acquires the address information of the L3 switch 15 to be monitored by using the ICMP time excess response at the own end and the other end, The storage unit 13 stores it.

  Then, the notification unit 118 of the protection relay 4 at its own end and the other end notifies each other of the address information of the L3 switch 15 to be monitored by data transmission. Thereby, the determination unit 114 determines whether or not the L3 switch 15 monitored by the own end and the other end is the same, and can detect that a different path is generated in the vertical direction when the L3 switch 15 is not the same.

  An example of a specific process of this embodiment will be described with reference to the explanatory diagram of FIG. First, in the ring-shaped network NW, the network distance between the local end and the other end is N. When the same route R is used in the vertical direction, the L3 switch 15 at the i-th network distance from its own end and the L3 switch 15 at the (N + 1-i) -th end from the other end are the same. However, when the path R is switched in the vertical direction, the L3 switch 15 becomes a different L3 switch 15. However, the L3 switch 15 with i = 1 and i = N is excluded.

  The value of the network distance N can be obtained by the acquisition unit 112 as in the first embodiment. The value of i is a value according to a predetermined condition, for example, 2 / N (rounded up). Then, the i-th and (N + 1-i) -th L3 switches 15 are monitored using the ICMP overtime response (1) to (3), as in the fifth embodiment. In FIG. 12, the network distance is 3 and i = 2.

  The address information of the L3 switch 15 monitored by the local protection relay 4a and the remote protection relay 4b is notified by the notification unit 118 (4) and (5). In FIG. 12, since the L3 switch 15 monitored by the own end and the other end is different, the determination unit 114 determines that a path change has occurred and performs the same processing as described above.

  According to the present embodiment as described above, both protection relays 4 exchange the address information of the L3 switch 15 being monitored, and determine path switching. For this reason, it is possible to share information at an early stage and respond at high speed as compared with the case where notifications are sent to each other only when there is a route change.

[Other Embodiments]
(1) In the above embodiment, a different route in the vertical direction is detected by monitoring a change in the route of the network using a TTL value included in data received by the relay device. However, there is a function similar to TTL depending on the protocol used for communication. Therefore, these functions may be used in place of TTL or in combination with TTL.

A typical TTL and similar functions are as follows.
IPv4: TTL
IPv6: Hop Limit
MPLS: TTL

  The MPLS TTL has the same name as the IP TTL. However, this TTL is stored in the MPLS header and is a value independent of the IP TTL. MPLS Propagation, which is a function of the L3 switch, can take over the TTL values of MPLS and IP.

(2) The protection relay and the communication device can be realized by controlling a computer including a CPU with a predetermined program. The program in this case realizes the above-described processing by physically utilizing computer hardware. For this reason, the method, program, and recording medium on which the program is executed are also an aspect of the embodiment. Moreover, how to set the range processed by hardware and the range processed by software including a program is not limited to a specific mode. For example, any one of the above-described units can be configured as a circuit that realizes each process.

(3) The number of protection relays, the number of communication devices, and the like are not limited to the numbers exemplified in the above embodiment. The communication device may be an L3 switch or a router.

(4) Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Transmission line 2 Current transformer 3 Circuit breaker 4, 4a, 4b, 4c Protection relay 6 Input converter 7 Analog filter 8 A / D conversion part 9 Calculation part 10 Output part 11 Communication part 12 Synchronization control part 13 Storage part 110 Transmission / reception Unit 111 setting unit 112 acquisition unit 113 extraction unit 114 determination unit 115 self-propelled unit 116 switching unit 117 restoration unit 118 notification unit E power system NW network R route S protection system

Claims (6)

Connected to a communication path including a plurality of communication devices,
An acquisition unit that acquires information on the number of communication devices in which data has traversed,
The information about the number of communication devices through which the data acquired by the acquisition unit is compared with predetermined information, and is transmitted to the path for receiving data from the protection relay at the other end and to the protection relay at the other end A determination unit for determining a difference from a data path to be performed;
An extraction unit that extracts information about the number of communication devices that are included in the data received from the protection relay at the other end and that the data transmitted by the protection relay at the other end has passed;
I have a,
It said predetermined information, protection relay characterized by information der Rukoto about number of communication device extracted by the extracting unit. The path is ring-shaped;
When at least one of the protection relays in which the number of communication devices in one route differs from the number of communication devices in the opposite direction route, when the difference in the route is determined by the determination unit, the protection relays different protection relay according to claim 1 Symbol placement of the protection relay, characterized in that it has a notification unit for notifying the difference pathways and. A synchronization control unit that synchronizes the sampling timing with the protection relay at the other end,
When the determination unit determines that the path is different, a self-running unit that stops synchronization by the synchronization control unit and performs control by an internal clock; and
Claim 1 or 2 protective relay in accordance characterized by having a. The communication path is ring-shaped;
When the protection relays are performing control by the self-propelled parts, when the determination part of both protection relays detects a difference in the route, the protection relay has a return part for returning the control by the synchronous control part that has been stopped. The protection relay according to claim 3 . The backup route is connected,
The self-propelled by the self-propelled unit, when the lapse of a predetermined time, according to claim 3 or claim 4 protection relay according to, characterized in that a switching unit for switching the path for the backup. A computer having a protection relay connected to a communication path including a plurality of communication devices;
An acquisition process of acquiring information on the number of communication devices in which data has traversed,
By comparing information related to the number of communication devices through which the data acquired by the acquisition process has passed and predetermined information, a route for receiving data from the protection relay at the other end and transmission to the protection relay at the other end A determination process for determining a difference from a data path to be performed;
Extraction processing for extracting information on the number of communication devices that are included in the data received from the protection relay at the other end and the data transmitted by the protection relay at the other end has passed,
Was executed,
The predetermined information, a program for protection relay, wherein information der Rukoto on the number of the extracted communication apparatus in the extraction process.

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