JP2017017968A - Current differential relay system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current differential relay system constituted by a plurality of current differential relay devices which manage control commands output from a plurality of protection control devices in a power system.SOLUTION: A current differential relay system 1 is connected through terminals A-D to an external electric power system, to perform the protection of an electric power system E of a protection target. The current differential relay system 1 includes current differential relay devices 21-24 and a cutoff device CB. The current differential relay devices 21-24 are installed corresponding to the terminals A-D. The current differential relay devices 21-24 are annularly disposed with a wired cable 3 which becomes a transmission line. Each current differential relay device 21-24 includes: a transmission line abnormality detection unit 7 which detects the abnormality of the transmission line; and a detection method changeover unit 9 which changes the detection method of an accident in the electric power system E, according to the abnormality of the transmission line.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a current differential relay system including a plurality of current differential relay devices. The current differential relay device manages control commands output from a plurality of protection control devices in the power system.

  In general, current differential relay devices are widely used for power system protection because they have a simple operation principle and can detect accidents with high sensitivity and high speed. However, in the transmission line protection, the current data of each terminal of the transmission line is transmitted to each other, and the current data for all terminals is collected and differential operation is adopted. Since the current data is not prepared, a differential current is generated, which may cause a malfunction. For this reason, if a transmission failure occurs at one location when the transmission path configuration is an open configuration and at two locations when the loop configuration is a system configuration, the system is locked.

  On the other hand, there is a line selection relay (hereinafter referred to as a balance relay) device as a relay that does not require transmission and has a hardware configuration similar to that of a current differential relay device. In the case of an external accident, the balance relay has the same current flowing in the first line and the second line, but in the case of an internal accident, the current flowing in the accident line side is larger than the current in the other line. This relay is used to detect accidents by crossing current between the first line and the second line.

  However, in the case of a balanced relay, in a two-line multi-terminal system, the fault current is diverted to the branch combination terminal. become. Moreover, since it becomes a series strip depending on the accident point, the larger the number of terminals, the longer the accident removal time.

  For the above reasons, the balance relay has no problem regarding transmission, but it is difficult to apply to a system having four terminals or more. To solve this problem, the third and subsequent terminals are connected by a transmission line, and by using the composite value of the zero-phase crossing current, the terminals connected by the transmission line are collectively regarded as one terminal, and the entire system is as if three terminals. Some communication-type balance relays have overcome the problem of the number of terminals by considering them as systems. However, the balance relay and the communication type balance relay are inferior in protection performance as compared with the current differential relay. In addition, the communication type balance relay shuts off at the time of transfer interruption in the case of a short-circuit accident, so that all terminals cannot be tripped simultaneously.

  For this reason, paying attention to hardware similarity, one device software has the function of a loop configuration PCM current differential relay and communication type balance relay, and the function of the device software can be changed by switching the wiring of the terminal block. There is also a current differential relay device that can be switched and the protection function can be switched. However, the current differential relay device that can switch this protection function does not automatically switch the protection function. In each case of operating as a type balance relay, the above-mentioned problems cannot be overcome.

JP 2006-223055 JP 2012-135150 A

  In the above-described current differential relay device in which the protection function can be switched, the switching of the protection method is the terminal block switching. When operating as a current differential relay, a system lock may occur due to a transmission failure. Moreover, when operating as a communication-type balance relay, the accuracy of internal / external accident determination is lower than that of a current differential relay. Therefore, in the case of a short-circuit accident, since the transfer is cut off, it is a problem that all terminals cannot be tripped simultaneously.

  In order to solve this point, the embodiment of the present invention has a protection performance equivalent to that of a current differential relay in a normal transmission line, and can continue protection without locking the system even when transmission is defective. The purpose is to provide.

  A current differential relay system in an embodiment of the present invention is a current differential relay system that is connected to an external power system at a terminal and protects a power system to be protected, and is installed with respect to the terminal, A current differential relay device that communicates with another current differential relay device installed in the current differential relay system via a transmission line, and shuts off the power system to be protected from the external power system A transmission line abnormality detection unit that detects an abnormality of the transmission line, and a method of detecting an accident in the power system according to the abnormality of the transmission line. And a detection method switching unit.

It is a block diagram which shows the structure of the current differential relay system of 1st Embodiment. It is a block diagram which shows the structure of the current differential relay apparatus of 1st Embodiment. It is a figure which shows the example of the abnormal pattern of the transmission line in 1st Embodiment. It is a figure which shows the mode of the short circuit accident in 1st Embodiment. It is a flowchart which shows operation | movement of the current differential relay system of 1st Embodiment. It is a figure which shows the example of the abnormal pattern of the transmission line in the modification of 1st Embodiment. It is a block diagram which shows the structure of the current differential relay system of 2nd Embodiment. It is a block diagram which shows the structure of the current differential relay apparatus of 2nd Embodiment. It is a flowchart which shows operation | movement of the current differential relay system of 2nd Embodiment.

  Hereinafter, embodiments of a current differential relay system according to the present invention will be described with reference to the drawings.

[1. First Embodiment]
Below, the current differential relay system which is 1st Embodiment of embodiment is demonstrated using FIGS. The current differential relay device according to the present embodiment is characterized in that system protection can be continued by using the amount of electricity used for differential calculation when a transmission failure between terminals is used as a cross current of each terminal.

FIG. 1 is a block diagram showing the configuration of the current differential relay system of this embodiment. The current differential relay system 1 of the present embodiment will be described in detail with reference to FIG. The current differential relay system 1 of the present embodiment includes the following devices (a) and (b).
(A) Based on the amount of electricity calculated from the current transformer CT installed in the electric power system E, an accident in the electric power system E is detected, and when an accident is detected, an interruption command is issued to the interruption device CB. Current differential relay device 2 to output.
(B) A shut-off device CB that shuts off the power system E from other power systems based on a cut-off command output from the current differential relay device 2.

(Current differential relay device)
The current differential relay device 2 detects an accident in the power system E based on the amount of electricity acquired from the power system E. The electric power system E is an example of parallel 2-line 4-terminal. The electric power system E includes transmission lines 1L and 2L. The power system E is connected to an external power system through terminals A to D. Two power transmission lines 1L and 2L are connected to the four terminals A to D of the power system E.

  The A terminal and the B terminal are connected by power transmission lines 1L and 2L. The power transmission lines 1L and 2L are electrically parallel. Two nodes a and b are provided in the power transmission lines 1L and 2L connecting the A terminal and the B terminal, respectively. From each node a and b, one transmission line branches. In each node a and b, the two power transmission lines 1L and 2L branched from the power transmission lines 1L and 2L are electrically parallel to each other. The two power transmission lines 1L and 2L branched from the node a are connected to the terminal D. The two power transmission lines 1L and 2L branched from the node b are connected to the terminal C.

The current differential relay device 2 is installed in the same number as the number of terminals of the electric power system E. One current differential relay device 2 is installed for one terminal. The current differential relay device 2 is connected to current transformers CT installed at 1L and 2L on the power transmission lines of the terminals A to D. The current transformer CT detects the value and direction of the current flowing through the transmission lines 1L and 2L. In the present embodiment, four current differential relay devices 21 to 24 are arranged for a power system E having four terminals. For example, the current differential relay device 21 installed for the terminal A includes a current transformer CT _AL1 installed in the vicinity of the terminal A of the transmission line L1, and a current transformer installed in the vicinity of the terminal A of the transmission line L2. Connected to CT _AL2 .

  The current differential relay devices 21 to 24 are connected by a wired cable 3. The wired cable 3 serves as a transmission line that connects the current differential relay devices 21 to 24. The current differential relay devices 21 to 24 are connected in a ring shape by a wired cable 3. In FIG. 1, the current differential relay device 21 is connected to the current differential relay device 22. The current differential relay device 22 is connected to the current differential relay device 23. The current differential relay device 24 is connected to the current differential relay device 21. The current differential relay devices 21 to 24 are connected via the wired cable 3 so as to be able to transmit in both directions.

  The current differential relay devices 21 to 24 detect an accident in the electric power system E based on the amount of electricity calculated from the current transformer CT installed in the electric power system E. A shutoff command is output to CB. FIG. 2 is a block diagram showing a configuration of the current differential relay device 2 in the present embodiment. As shown in FIG. 2, the electric quantity acquisition unit 4, the electric quantity storage unit 5, the transmission unit 6, the transmission line abnormality detection unit 7, the transmission line abnormality determination unit 8, the detection method switching unit 9, the differential current calculation unit 10, the internal An accident detection unit 11, a protection command output unit 12, a cross current calculation unit 13, and a short circuit detection unit 14 are provided.

The electric quantity acquisition unit 4 is connected to a current transformer CT installed in the power transmission lines 1L and 2L near the terminals. The electrical quantity acquisition unit 4 receives the current values I _1L and I _2L measured by the connected current transformer CT. The electrical quantity acquisition unit 4 transfers the received current values I _1L and I _2L to the electrical quantity storage unit 5. For example, the electrical quantity acquisition unit 4 of the current differential relay device 21 installed with respect to the terminal A acquires the current values I _1L and I _2L at the terminal A.

The transmission means 6 is connected to the transmission means 6 of another current differential relay device via the wired cable 3. The transmission means 6 receives the amount of electricity transmitted by the transmission means 6 of another current differential relay device. On the other hand, the transmission means 6 transmits the electrical quantity stored in the electrical quantity storage unit 5 to other current differential relay devices. For example, the transmission means 6 of the current differential relay device 21 installed with respect to the terminal A receives the current values I _1L and I _2L at the terminals B to D. In addition, current values I _1L and I _2L are transmitted to the current differential relay devices 22 to 24 installed for the terminals B to D. In this case, the current differential relay device 21 installed for the terminal A and the current differential relay device 24 installed for the terminal C are not directly connected by the wired cable 3. Therefore, communication between the current differential relay device 21 and the current differential relay device 23 is performed via the current differential relay device 22 installed at the terminal B or the current differential relay device 24 installed at the terminal D. Done.

The electric quantity storage unit 5 stores an electric quantity necessary for calculating the differential current and the crossing current. As will be described later, the differential current is calculated for each of the power transmission lines 1L and 2L. The amount of electricity required for calculating the differential current is the current value and direction at each terminal. In the electric quantity storage unit, the current values I _1L and I _{2L of} the power transmission lines 1L and 2L acquired by the self-current differential relay device 2 and the power transmission lines 1L and 2L transferred from other current differential relay devices 2 are stored. The current values I _1L and I _2L are stored.

  The transmission line abnormality detection unit 7 monitors the state between the current differential relay devices 21 to 24 and detects a transmission abnormality between the current differential relay devices 21 to 24. For example, a monitoring frame is transmitted between the current differential relay devices 21 to 24, and a response is detected by monitoring the response. When the transmission line abnormality detection unit 7 detects a transmission abnormality in two or more sections, the transmission line abnormality detection unit 7 of the current differential relay device 21 is connected to the transmission line abnormality detection unit 7 of the current differential relay devices 22 to 24. A monitoring frame is transmitted. The transmission line abnormality detection unit 7 of the current differential relay devices 22 to 24 that has received the monitoring frame transmits the reception result to the current differential relay device 21 that is the transmission source of the monitoring frame. When there is no response to the monitoring frame transmitted from the transmission abnormality detection unit 7 of the current differential relay device 21 to the current differential relay device 22, the current differential relay device 21 and the current differential relay device 22 are not connected. In this case, it is determined that a transmission abnormality has occurred in two or more sections.

The transmission line abnormality determination unit 8 determines the state of the transmission line based on the detection result in the transmission line abnormality detection unit 7. The transmission line abnormality determination unit 8 determines the state of the transmission line as follows.
(I) No transmission line abnormality (ii) Any of the current differential relay devices cannot transmit to other current differential relay devices

  3A to 3D are diagrams illustrating transmission states between the current differential relay devices 21 to 24 of the present embodiment.

(I) No transmission line abnormality The state without transmission abnormality indicates a state in which transmission between the current differential relay devices 21 to 24 is possible. That is, as shown in FIG. 3 (a), a transmission failure does not occur in any section, or as shown in FIG. 3 (b), transmission failure occurs at one place between the current differential relay devices 21-24. Indicates the state where has occurred. The current differential relay devices 21 to 24 are connected in a ring shape. Therefore, even if a transmission failure occurs at one place, the current differential relay devices 21 to 24 are connected through a normal transmission path.

(Ii) Any of the current differential relay devices cannot transmit to other current differential relay devices Any of the current differential relay devices 2 cannot transmit to other current differential relay devices Indicates a state in which there is an abnormality in the transmission path. Therefore, one of the current differential relay devices 21 to 24 in the power system indicates a state in which transmission with other current differential relay devices is impossible. For example, in FIG.3 (d), the current differential relay apparatus 21 is a state which cannot transmit with the other current differential relay apparatuses 22-24.

  The detection method switching unit 9 switches an accident detection method in the power system based on the detection result of the transmission abnormality in the transmission line abnormality detection unit 7. The detection method switching unit 9 switches between detection of an internal accident due to a differential current and detection of a short circuit in the power system due to a cross current. In the detection method switching unit 9, when the transmission line abnormality determination unit 8 determines “(i) No transmission abnormality”, it selects detection of an internal accident due to a differential current. On the other hand, when the transmission line abnormality determination unit 8 determines that “(ii) any of the current differential relay devices cannot transmit to other current differential relay devices”, the cross-current differential current Select short-circuit detection by.

The differential current calculation unit 10 calculates a differential current from the amount of electricity acquired by the self-current differential relay device 2 stored in the amount-of-electricity storage unit 5 and the amount of electricity acquired by the other current differential relay device 2. . The differential current is the sum of the current flowing into the power system E and the current flowing out from the power system E. The differential current calculation unit 10 calculates the differential currents ΣI _1L and ΣI _2L in the respective transmission lines in the transmission line L1 and the transmission line L2. The differential currents ΣI _1L and ΣI _2L are calculated from the following equation (1).

[Formula 1]
Differential current ΣI _1L = I _1L (terminal A) + I _1L (terminal B) + I _1L (terminal C) + I _1L (terminal D)
Differential current ΣI _2L = I _2L (terminal A) + I _2L (terminal B) + I _2L (terminal C) + I _2L (terminal D)
(1)

The internal accident detection unit 11 detects an accident in the electric power system E. The detection of the accident is based on the calculation result in the differential current calculation unit 10. The internal accident detection unit 11 detects an internal accident depending on whether the differential current ΣI _1L or the differential current ΣI _2L is zero. That is, if the differential current .SIGMA.I _1L or differential current .SIGMA.I _2L is _{0, (ΣI 1L = 0orΣI 2L} = 0), the accident in the power system E does not occur. On the other hand, when the differential current ΣI _1L or the differential current ΣI _2L is not 0 (ΣI _1L ≠ 0 or ΣI _2L ≠ 0), it is assumed that an accident has occurred in the power system E. However, in general, it is assumed that an accident occurs when a predetermined size is exceeded.

The cross current calculation unit 13 calculates the cross current from the amount of electricity stored in the electricity amount storage unit 5. The crossing current is calculated from the difference between the current _I1L flowing through the power transmission line L1 connected to the terminal and the current _I2L flowing through the power transmission line L2. The cross currents of the terminals A to D are defined as cross currents I _{AR to} I _DR . The cross currents I _{AR to} I _DR are calculated from the following equation (2).

[Formula 2]
Cross current I _AR = I _1L (terminal A) −I _2L (terminal A)
Cross current I _BR = I _1L (terminal B) −I _2L (terminal B)
Cross current I _CR = I _1L (terminal C) −I _2L (terminal C)
Cross current I _DR = I _1L (terminal D) −I _2L (terminal D)
(2)

The short circuit detection unit 14 detects a short circuit in the power system E. As a short-circuit detection method, it is assumed that an accident occurs when the cross currents I _{AR to} I _DR exceed a predetermined magnitude.

  The protection command output unit 12 outputs a cutoff command to the cutoff device CB when the internal fault detection unit 11 detects an internal fault or when the short-circuit detection unit 14 detects the occurrence of a short circuit.

(Blocking device)
The cutoff device CB receives the cutoff command and disconnects the power system E from the other power systems. The breaking device CB is a mechanical contact. The breaker CB normally closes the contacts. On the other hand, when the interruption command is received, the contact is opened.

  The blocking device CB is installed in the vicinity of the terminals A to D of the power transmission line L1 and the power transmission line L2. The breaking device CB is connected to the current differential relay devices 21 to 24 through a network (not shown). The cutoff command output by the cutoff command output unit 12 of the current differential relay devices 21 to 24 is transferred to the cutoff device CB.

[1-2. Action]
The operation in the current differential relay system 1 of the present embodiment having the above configuration will be described. FIG. 5 is a flowchart showing the operation of the current differential relay system 1 of the present embodiment.

  In the following flowchart, transmission is performed between the current differential relay device 21 and the current differential relay device 24 and between the current differential relay device 22 and the current differential relay device 23 as illustrated in FIG. Assume that a defect has occurred. In this state, it is assumed that a short circuit accident has occurred between the terminal A and the terminal B of the power transmission line L1.

When the current differential relay system 1 starts operation, each of the current differential relay devices 21 to 24 acquires the current values I _1L and I _2L from the current transformer CT installed at its own terminal. The current values I _1L and I _2L acquired here are stored in the electric quantity storage unit 5 as electric quantities (STEP 101).

  Next, the amount of electricity is shared between the current differential relay devices 21 to 24 (STEP 102). Sharing of the amount of electricity is performed via a wired cable 3 that connects the current differential relay devices 21 to 24. The transmission means 6 of each current differential relay device 21 to 24 transmits the amount of electricity acquired by the self-current differential relay device 2 to the other current differential relay device 2. On the other hand, the electric quantity transmitted from the other current differential relay device 2 is received and stored in the electric quantity storage unit 5.

  In parallel with STEP 101 and STEP 102, the transmission line abnormality is detected (STEP 103). Transmission line abnormality detection is performed by transmitting a monitoring frame from each of the current differential relay devices 21 to 24.

  The transmission line abnormality determination unit 8 determines the abnormality of the transmission line based on the detection result of the transmission line abnormality. In the transmission line abnormality determination, it is determined whether or not there are two or more abnormalities in the transmission line (S104).

When there are no two or more abnormalities in the transmission line (STEP 104: NO), the ΣI _1L and ΣI _2L of the differential current for each of the transmission lines L1 and L2 are calculated with reference to the electrical quantity storage unit 5 (STEP 105). . Then, an internal accident is detected from the differential currents ΣI _1L and ΣI _2L (STEP 106). When an internal accident is detected, a cutoff command is output to the cutoff device CB (STEP 107). In the interruption | blocking apparatus CB, based on reception of interruption | blocking instruction | command, a contact is open | released so that the electric power grid | system E may be cut off from another electric power grid | system.

  On the other hand, when there is an abnormality in two or more transmission paths (STEP 104: YES), the crossover current at the other terminal that can transmit with the own terminal is calculated with reference to the electric quantity storage unit 5 (STEP 108). Then, a short circuit is detected from the calculated crossing current (S109). If a short circuit is detected, a cutoff command is output to the cutoff device CB (STEP 107). In the interruption | blocking apparatus CB, based on reception of interruption | blocking instruction | command, a contact is open | released so that the electric power grid | system E may be cut off from another electric power grid | system.

[1-3. effect]
According to the present embodiment having the configuration and operation as described above, the following effects can be obtained.

(1) Depending on the state of the transmission path of the current differential relay devices 21 to 24 in the current differential relay system 1, protection of the power system suitable for that state can be implemented. That is, in the normal state, an internal accident is detected based on the differential currents ΣI _1L and ΣI _2L . On the other hand, when two or more abnormalities are detected in the transmission line and the current values of all the terminals are not uniform, the presence / absence of a short circuit is detected based on the cross currents I _{AR to} I _DR .

In the detection of an internal accident based on the differential currents ΣI _1L and ΣI _2L , current information is generated if current information of all terminals cannot be detected. As a result, the system cannot be normally protected. However, the system protection can be continued by switching the calculation method when an abnormality occurs in the transmission path. As a result, system lock can be prevented.

(2) Moreover, although this embodiment demonstrated the current relay system which consists of the four current differential relay apparatuses 21-24, if the number of current differential relay apparatuses is two or more, it will not restrict to this. For example, it can also be comprised from six current differential relay apparatuses 21-26. In that case, even when three transmission abnormalities occur in the transmission line, the current differential relay devices 21 to 26 can detect the occurrence of a short circuit based on the cross current as shown in FIG.

(3) In addition, other methods can be used as a method for detecting an internal accident due to a differential current and a method for detecting a short circuit due to a cross current. For example, in the present embodiment, the cross current is calculated from the difference between the current I _1L flowing through the power transmission line L1 connected to the terminal stored in the electrical quantity storage unit 5 and the current I _2L flowing through the power transmission line L2, but the cross current A current transformer CT for measuring the current may be installed in the electric power system E.

(4) In the present embodiment, when a transmission line abnormality occurs, the detection method of the accident in the power system E is switched from the detection of the internal fault by the differential current to the detection of the short circuit by the differential of the cross current. . However, the switching of the accident detection method is not limited to this. For example, at the normal time, detection of an internal accident by a differential current and detection of a short circuit by a cross current are used in combination. And when two or more abnormalities of the transmission line occur, it may be switched only to the detection of the short circuit due to the cross current.

The internal accident detection unit 11 detects an internal accident based on whether the differential current ΣI _1L or the differential current ΣI _2L is 0, but is not limited thereto. For example, a predetermined value may be set and an internal accident may be detected when the differential current ΣI _1L or the differential current ΣI _2L exceeds a predetermined value.

[2. Second Embodiment]
In the current differential relay system of the present embodiment, in normal times when two or more abnormalities have not occurred in the transmission line, the first zero-phase differential current calculated from the zero-phase current of the own terminal and the other terminal, A ground fault is detected by direction determination using zero-phase voltage. On the other hand, when two or more abnormalities occur in the transmission line, a ground fault is detected by direction determination using the second zero-phase differential current calculated from the zero-phase crossing current and the zero-phase voltage of its own terminal. I do.

[2-1. Constitution]
FIG. 7 is a block diagram showing the configuration of the current differential relay system of this embodiment. That is, the current differential relay system of this embodiment includes a voltmeter VT that detects a voltage applied between the power transmission line L1 and the power transmission line L2 at each of the terminals A to D, as shown in FIG. In addition, the same code | symbol is attached | subjected to the structure same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

  FIG. 8 is a block diagram showing the configuration of the current differential relay device of this embodiment. In the current differential relay device of the present embodiment, a first zero-phase differential current calculation unit 15 is arranged instead of the differential current calculation unit 10 of the current differential relay device 2 of the above-described embodiment, and the cross current calculation unit 13 is arranged. Instead of this, the second zero-phase differential current calculation unit 16 is arranged, and the ground fault detection unit 17 is arranged instead of the internal fault detection unit 11 and the short circuit detection unit 14.

The electric quantity acquisition unit 4 acquires the voltage value V of the own terminal in addition to the current values I _1L and I _2L in the transmission lines 1L and 2L of the own terminal as the electric quantity. The voltage value V of the own terminal is obtained from a voltmeter V arranged at each terminal. The obtained voltage value V of the own terminal is stored in the electrical quantity storage unit 5 in the same manner as the current values in the transmission lines 1L and 2L.

  The first zero-phase differential current calculation unit 15 includes the zero-phase current of the own terminal acquired by the own-current differential relay device 2 stored in the electric quantity storage unit 5 and the other acquired by the other-current differential relay device 2. The differential current of the first zero-phase current of the terminal is calculated.

  The second zero-phase differential current calculation unit 16 calculates a second zero-phase differential current from the zero-phase cross current of its own terminal and the zero-phase cross current of the other terminal.

  The ground fault detection unit 17 detects a ground fault from the zero phase differential current calculated by the first and second zero phase differential current calculation units and the zero phase voltage at its own end.

[2-2. Action]
The operation in the current differential relay system 1 of the present embodiment having the above configuration will be described. FIG. 9 is a flowchart showing the operation of the current differential relay system 1 of the present embodiment. The flowchart of FIG. 9 is obtained by changing STEPs 105, 106, 108, and 109 of FIG.

When the operation of the current differential relay system 1 is started and there are no two or more abnormalities in the transmission line (STEP 204: NO), the zero-phase for each of the transmission lines L1 and L2 is referred to by referring to the electric quantity storage unit 5. ΣI _1L and ΣI _2L of the differential current are calculated (STEP 205). Then, the direction determination using the zero-phase differential currents ΣI _1L and ΣI _2L and the zero-phase voltage at its own end is performed to detect a ground fault (STEP 206). When a ground fault is detected, a cutoff command is output to the cutoff device CB (STEP 207). In the interruption | blocking apparatus CB, based on reception of interruption | blocking instruction | command, a contact is open | released so that the electric power grid | system E may be cut off from another electric power grid | system.

  On the other hand, when there are two or more abnormalities in the transmission line (STEP 204: YES), the current differential relay devices 21 to 24 calculate a zero-phase crossing current at the own terminal and other terminals that can be transmitted. Then, a zero-phase differential current is calculated from the calculated crossing current. This differential current becomes the second differential current (STEP 208). Then, the direction determination using the second differential current and the zero-phase voltage at its own end is performed to detect a ground fault (STEP 206). When a ground fault is detected, a cutoff command is output to the cutoff device CB (STEP 207). In the interruption | blocking apparatus CB, based on reception of interruption | blocking instruction | command, a contact is open | released so that the electric power grid | system E may be cut off from another electric power grid | system.

[2-3. effect]
According to the present embodiment having the configuration and operation as described above, the following effects can be obtained. Similarly to the first embodiment, according to the state of the transmission path of the current differential relay device 2 in the current differential relay system 1, protection of the electric power system E suitable for the state can be performed.

[3. Other Embodiments]
In the present specification, a plurality of embodiments according to the present invention have been described. However, these embodiments are presented as examples and are not intended to limit the scope of the invention. Specifically, in a current differential relay that protects a parallel two-line system, when the current values of all terminals are aligned, current differential is performed for each line unit, and the current values of all terminals are not aligned. Is to perform cross current differential, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and gist of the invention.

DESCRIPTION OF SYMBOLS 1 ... Current differential relay system 2 ... Current differential relay apparatus 3 ... Wire cable 4 ... Electric quantity acquisition part 5 ... Electric quantity storage part 6 ... Transmission means 7 ... Transmission path abnormality detection part 8 ... Transmission path abnormality determination part 9 ... Detection method switching unit 10 ... differential current calculation unit 11 ... internal accident detection unit 12 ... protection command output unit 13 ... cross current calculation unit 14 ... short circuit detection unit 15 ... first zero-phase differential current calculation unit 16 ... second Zero phase differential current calculation unit 17 ... Ground fault detection unit CT ... Current transformer CV ... Voltmeter CB ... Breaking devices AD ... Terminals a, b ... Section

Claims (9)

A current differential relay system that connects to an external power system at a terminal and protects the power system to be protected.
A current differential relay device that is installed with respect to the terminal and that communicates with other current differential relay devices installed in the current differential relay system via a transmission line;
A shut-off device that shuts off the power system to be protected from the external power system;
With
The current differential relay device is:
A transmission line abnormality detection unit for detecting abnormality of the transmission line;
A detection method switching unit that switches a detection method of an accident in the power system according to an abnormality in the transmission path;
A current differential relay system comprising: The transmission line abnormality detection unit identifies the detected abnormality of the transmission line,
The current differential relay device is:
A transmission line abnormality determination unit that determines whether the abnormality of the transmission line is less than 2 or the abnormality part of the transmission line is 2 or more;
The current differential relay system according to claim 1, further comprising: The transmission line abnormality determination unit, when the number of abnormalities in the transmission line is 2 or more,
3. The current differential relay according to claim 1, wherein a self-current differential relay device determines whether transmission with another current differential relay device is possible due to an abnormality in the transmission path. 4. system. The current differential relay device is:
An electric quantity acquisition unit that acquires the electric quantity of the installed own terminal;
Transmission means for receiving the electric quantity of the other terminal acquired by the other current differential relay device via the transmission line;
The current differential relay system according to any one of claims 1 to 3, further comprising: The electrical quantity acquisition unit acquires the current value of the terminal as an electrical quantity,
The current differential relay device is:
A differential current calculation unit that calculates a differential current from a current value flowing through each terminal in the power system to be protected;
From the differential current, an internal accident detection unit for detecting an internal accident in the power system,
Further comprising
The detection method switching unit switches the fault detection method in the power system from the differential current to the detection of an internal fault in the electric system when the number of abnormal points in the transmission path is less than 2 in the transmission path. The current differential relay system according to claim 4. The electrical quantity acquisition unit acquires the current value of the terminal as an electrical quantity,
The current differential relay device is:
A cross current calculation unit for calculating a cross current at its own terminal and a cross current of another terminal capable of transmission;
A short-circuit detector for detecting a short circuit from the cross current;
Further comprising
When the detection method switching unit has two or more abnormalities in the transmission path in the transmission path,
6. The current differential relay system according to claim 4, wherein a method for detecting an accident in the power system is switched to detection of a short circuit in the electric system due to the cross current. The electricity quantity acquisition unit obtains the current value and voltage value of its own terminal as the electricity quantity,
The current differential relay device is:
A first zero-phase differential current calculation unit that calculates a first zero-phase differential current from the zero-phase current of the own terminal and the zero-phase current of the other terminal;
A ground fault detection unit for detecting a ground fault in the electrical system from the first differential current;
Further comprising
The detection method switching unit is configured to change the detection method of an accident in the power system from the first differential current in the case of a ground fault in the electrical system when the number of abnormal locations in the transmission path is less than 2. The current differential relay system according to claim 4, wherein the current differential relay system is switched to detection. The electrical quantity acquisition unit acquires the current value of the terminal as an electrical quantity,
The current differential relay device is:
A second zero-phase differential current calculation unit that calculates a second zero-phase differential current from the cross-current of the own terminal and the cross-current of another terminal that can be transmitted;
A ground fault detector for detecting a ground fault in the electrical system from the second zero-phase differential current;
Further comprising
When the detection method switching unit has two or more abnormalities in the transmission path in the transmission path,
The current differential relay system according to claim 4 or 7, wherein the fault detection method in the electric power system is switched from the second zero-phase differential current to the detection of a ground fault in the electric system. .   The current differential relay system according to any one of claims 1 to 8, wherein the power system is a parallel 2-line 2-terminal system.

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