Protective relay and system including same

Abstract

This protective relay comprises: a memory; and a control circuit that, when a setting of a setting value is changed, leaves a setting change history of the setting value in the memory. The history includes, for example, a setting value before a setting change. The history includes, for example, a setting value before a plurality of past setting changes. The history includes, for example, a setting value after a setting change. For example, each time the setting of the setting value is changed, the control circuit leaves the setting value before the setting change in the memory. The history includes, for example, time information. The history includes, for example, identification information about a setting changer. The history includes, for example, a character string input at the time of a setting change. The memory is, for example, a nonvolatile memory.

Description

Protective Relay and System Comprising the Same

[0001] The present disclosure relates to a protective relay and a system comprising the same.

[0002] A multifunctional protective relay that cuts off an electric circuit by energizing a trip coil of a circuit breaker when an abnormality in an electric power system such as a ground fault, overvoltage, undervoltage, overload, or short circuit is detected is known (see, for example, Patent Document 1).

[0003] Japanese Unexamined Patent Publication No. 2018-85796

[0004] If a setting value is incorrectly changed, the protective relay may perform an unintended protection operation and cause an unintended power outage. However, with conventional technology, it is difficult to evaluate whether a change in the setting of a setting value is the cause of the protection operation.

[0005] The present disclosure provides a protective relay and a system capable of evaluating the soundness of a setting change of a setting value.

[0006] One aspect of the present disclosure is a protective relay comprising: a memory; and a control circuit that stores a history of setting changes of a setting value in the memory when the setting of the setting value is changed.

[0007] Another aspect of the present disclosure is a system comprising: a protective relay; an external device connected to the protective relay via a wired or wireless connection; and a storage device provided outside the protective relay, wherein when the setting of a setting value of the protective relay is changed, the external device stores a history of the setting change of the setting value in the storage device.

[0008] According to the present disclosure, the soundness of a setting change of a setting value can be evaluated.

[0009] FIG. 1 is a single-line diagram showing one configuration of an electric power system including a protective relay. FIG. 2 is an external perspective view of an example of a protective relay. FIG. 3 is a diagram showing an example of an internal configuration of a protective relay. FIG. 4 is a diagram showing an example of a setting screen. FIG. 5 is a diagram showing an example of a display screen of a history of setting changes of setting values. FIG. 6 is a diagram showing an example of a protective relay and a system. FIG. 7 is a diagram showing an example of a hardware configuration of an external terminal.

[0010] The embodiments of this disclosure will be described below with reference to the drawings.

[0011] Figure 1 is a single-line diagram showing one configuration of a power system including protective relays.

[0012] The high-voltage power receiving equipment 11 includes a zero-phase current transformer 12, a transformer 13, a current transformer 14, a protective relay 15, and a circuit breaker 16.

[0013] The zero-sequence current transformer 12 sends the current (zero-sequence current) flowing to the secondary side due to a ground fault to the protective relay 15.

[0014] The transformer 13 is an instrument transformer that converts the voltage of the high-voltage circuit to a low voltage and supplies the secondary voltage to the protective relay 15 or an instrument (not shown). The rated voltage of the secondary side is, for example, 110 [V]. An instrument transformer is sometimes abbreviated as VT.

[0015] The current transformer 14 converts the current in a high-current circuit to a low-current circuit and sends the current flowing on the secondary side to the protective relay 15 or an instrument (not shown). The rated current on the secondary side is, for example, 5 [A]. The current transformer is sometimes abbreviated as CT.

[0016] The protective relay 15 is a multi-functional relay that operates the circuit breaker 16 in response to the zero-sequence current detected by the zero-sequence current transformer 12, the voltage transformed by the transformer 13, or the current transformed by the current transformer 14. Specifically, when the protective relay 15 detects an abnormality in the power system such as a ground fault, overvoltage, undervoltage, overload, or short circuit, it interrupts the circuit by energizing the trip coil 17 of the circuit breaker 16.

[0017] The circuit breaker 16 interrupts the circuit when the trip coil 17 is energized.

[0018] Figure 2 is an external perspective view of an example of a protective relay. The protective relay 15 is equipped with a function to adjust the protection characteristics in order to provide versatility. The adjustment of the protection characteristics is called "setting". The protective relay 15 has a display device 25, an operating unit 21, and a communication terminal 28.

[0019] The display device 25 has a display screen 26 that displays information such as measured values, set values, and a history of changes to the set values. An example of the display screen 26 is a liquid crystal display.

[0020] Examples of measured values ​​include the primary current of the current transformer 14, the primary voltage of the transformer 13, and the zero-sequence current of the zero-sequence current transformer 12.

[0021] Examples of setting values ​​include the rated current on the primary side of the current transformer 14, the rated voltage on the primary side of the transformer 13, the rated voltage on the secondary side of the transformer 13, the rated frequency, the rated current on the primary side of the zero-phase current transformer 12, the operating threshold for protective operation (e.g., current operating value, voltage operating value, etc.), and the time from when the measured current or voltage reaches the operating threshold until protective operation is performed (operating time). Setting values ​​may also be values ​​used to calculate the operating threshold (e.g., a multiplier applied to the rated current or rated voltage, a ratio to the rated current or rated voltage, etc.). Setting values ​​are not limited to numerical values ​​related to setting, but may also include setting information related to setting. Examples of setting information related to setting include setting information for disabling or enabling the protection function, and setting information for whether or not to have a trip output during protective operation.

[0022] The operation unit 21 is an interface that accepts user input. The operation unit 21 includes a directional pad 22, a confirmation button 23, and a reset button 24. The directional pad 22 is an operation button used for switching displays, selecting items, or changing settings. The confirmation button 23 is an operation button used for switching modes or confirming setting changes. The reset button 24 is an operation button used for canceling setting changes or restoring after protective actions.

[0023] User operations are accepted by pressing buttons on the control unit 21, but may also be accepted by touching the display screen 26 or by using a remote control.

[0024] The communication terminal 28 is a connection port for connecting to an external terminal 50 (for example, a personal computer (PC), tablet terminal, etc.) via a communication cable, and one end of the communication cable is connected to it. An example of the communication terminal 28 is a USB connector. The protective relay 15 may be connected to the external terminal 50 wirelessly.

[0025] The protective relay 15 may be equipped with a function to record waveforms before and after protective operation, along with the time of occurrence, to assist in investigating the cause and analyzing factors during protective operation. This function is called the fault waveform recording function. The protective relay 15 displays the recorded waveforms on the display screen 26. The external terminal 50, described later, connected to the communication terminal 28, retrieves data from the protective relay 15 and displays the waveforms recorded in the protective relay 15 on a screen separate from the display screen 26.

[0026] Figure 3 shows an example of the internal configuration of a protective relay. When the measured value of current or voltage exceeds a set operating threshold, the protective relay 15 performs a protective operation by energizing the trip coil 17 of the circuit breaker 16. The circuit breaker 16 interrupts the circuit by energizing the trip coil 17. As a result, power equipment (not shown) installed downstream of the circuit breaker 16 is protected from power system abnormalities such as ground faults, overvoltage, undervoltage, overload, or short circuits.

[0027] The protective relay 15 includes an analog filter 34, a control circuit 30, an output circuit 35, and a non-volatile memory 40. The control circuit 30 includes a processor 31, RAM 32, and a clock 33. The measured current or voltage is input to the control circuit 30 via the analog filter 34. Noise superimposed on the measured current or voltage is attenuated by the analog filter 34. The control circuit 30 compares the measured current or voltage with a currently set operating threshold, and if the measured value exceeds the operating threshold, it outputs a protection detection signal to energize the trip coil 17. When the protection detection signal is input, the output circuit 35 drives the trip coil 17 to energize the trip coil 17 of the circuit breaker 16.

[0028] The non-volatile memory 40 has multiple areas (in this example, areas 41, 42, 43, and 44) ​​where data is stored.

[0029] The control circuit 30 stores the waveform data of the current or voltage measured before and after the protection operation in the memory area 42, along with the time of occurrence. When an instruction is received to display the waveform data before and after the protection operation on the display screen 26, the control circuit 30 reads the waveform data from the memory area 42 and instructs the display device 25 to display the waveform generated based on the read waveform data on the display screen 26. As a result, the waveforms before and after the protection operation are displayed on the display screen 26.

[0030] The currently set setting value is stored in area 43. The control circuit 30 uses the current setting value read from area 43 into RAM 32 for various controls. For example, the control circuit 30 compares a measured value of current or voltage with the current operating threshold read from area 43 into RAM 32, and outputs a protection detection signal to energize the trip coil 17 if the measured value exceeds the operating threshold.

[0031] Figure 4 shows an example of the setting screen. In Figure 4, "ENTER" represents the confirmation button 23, and "RESET" represents the reset button 24.

[0032] When "Change Setting" is selected by the operation unit 21 on the top screen of the setting mode, the control circuit 30 displays the setting list on the display screen 26. When "Basic Settings" is selected from the setting list by the operation unit 21, the control circuit 30 displays the setting items, which are element items within "Basic Settings," and the current setting value (setting value on RAM 32) of that setting item on the display screen 26. When one setting value is selected from among multiple setting values ​​by the operation unit 21, the control circuit 30 displays the setting change screen for the selected setting value on the display screen 26.

[0033] When the control circuit 30 receives input from the operation unit 21 and selects a change value for the setting on the setting change screen, it stores the change value in RAM 32 as the setting change value (current setting value) in area 43 of the non-volatile memory 40. The setting change is completed when the setting change value is stored in area 43.

[0034] When a change in the setting value is input and selected by the operation unit 21 on the setting change screen, the control circuit 30 returns to the setting item screen display. After returning to the setting item screen display, the control circuit 30 may store one or more change values ​​of the setting values ​​on RAM 32 as the setting value after the setting change (current setting value) in area 43 of the non-volatile memory 40. When the reset button 24 is operated on the setting item screen display, the control circuit 30 returns to the selection list display screen.

[0035] Thus, the protective relay 15 has the function of accepting changes to the setting value. However, if the setting value of the protective relay 15 is changed incorrectly, it may perform an unintended protective action, potentially causing an unintended power outage.

[0036] In digital multi-function protective relays that utilize digital technology, multiple protective elements are mounted in a single unit, resulting in a large number of setting values ​​and complex operation and management. Therefore, support tools using external terminals 50 such as PCs are provided. However, setting value changes can be made not only by operation from the external terminal 50, but also by direct operation (main unit operation) on the protective relay 15 itself. To prevent errors in setting value changes, the protective relay 15 is equipped with a function to lock setting value changes made via main unit operation. However, this lock can be easily released via main unit operation.

[0037] During the period from equipment delivery to operation and maintenance, external contractors other than the business owner often have opportunities to handle protective relays. It is not uncommon for the setting values ​​to change during the period leading up to operation. Furthermore, during maintenance, there are opportunities to check or change the setting values, which presents a potential risk of human error.

[0038] Thus, there is a possibility that the setting value may be incorrectly changed, leading to unintended protective actions, or that the setting value may be changed maliciously. With conventional technology, it is difficult to evaluate whether a change in the setting value caused the protective action to be triggered.

[0039] In the protective relay 15 according to the first embodiment shown in Figure 3, the control circuit 30 has a function (setting change history saving function) that stores a history of setting value changes in memory when the setting value is changed. By storing a history of setting value changes in memory, the protective relay 15 can retrospectively check the history of setting value changes, or it can allow a user or external device to retrospectively check the history of setting value changes. Examples of external devices include the external terminal 50 or external system 80 described later. As a result, the protective relay 15, the user, or the external device can determine, based on the checked history, whether the setting value change was a simple human error, intentional, or within the scope of known operations. This makes it possible to evaluate the soundness of setting value changes.

[0040] The memory where the history of setting value changes is stored may be RAM 32, but non-volatile memory 40 is preferred. By storing the history of setting value changes in non-volatile memory 40, the history of setting value changes is not lost even if the control power supply of the protective relay 15 itself is lost. Therefore, the history can be read after power is restored, allowing for tracking and verification of the history. The control circuit 30 stores the history of setting value changes in area 44.

[0041] The control circuit 30, for example, stores the setting value before the change in area 44 as a history of setting value changes. This makes it possible to check not only the fact that the setting value has been changed, but also the setting value before the change, thereby allowing the soundness of the setting value before the change to be evaluated.

[0042] The control circuit 30 may retain the setting values ​​prior to multiple past setting changes in area 44 as a history of setting value changes. If one or more setting values ​​have been changed multiple times in the past, the setting values ​​prior to those multiple past setting changes can be checked retrospectively, making it possible to evaluate the soundness of those setting values ​​prior to those multiple past setting changes.

[0043] The control circuit 30 may leave the setting value before the setting change in the area 44 and leave the setting value after the setting change in the area 43. This enables confirmation of the setting values before and after the setting change, so that the soundness of the setting values before and after the setting change can be evaluated.

[0044] The control circuit 30 may leave the setting value before the setting change in a memory every time the setting of the setting value is changed. Accordingly, even if the setting change of the setting value is repeated, the setting value immediately before the setting change can be confirmed, so that the soundness of the setting value immediately before the setting change can be evaluated.

[0045] The control circuit 30 may leave the time information acquired from the clock 33 in the area 44 as a history of setting changes of setting values. This enables confirmation of the timing of the setting change of the setting value, so that the setting change can be tracked with higher accuracy. Examples of the time information include date and time information. For example, the control circuit 30 stores, in the area 44, the date and time when the setting value after the setting change is stored in the area 43.

[0046] The control circuit 30 may leave identification information of a person who made the setting change as a history of setting changes of setting values. This makes it possible to retrospectively determine who made the setting change to the setting value. The identification information is input to the protective relay 15, for example, when a setting value is changed. When the setting change of the setting value is performed by an external device such as the external terminal 50, the identification information may be an IP address of the external device, or the like.

[0047] The control circuit 30 may use a character string input when changing the setting of a setting value as the history of the setting change of the setting value. When any unique character string is input to the protective relay 15 at the time of changing the setting of the setting value, it is possible to retrospectively determine who made the setting change of the setting value by collating the unique character string.

[0048] The protective relay 15 includes a display device 25 that displays a history of setting changes of setting values. By displaying the history of setting changes of setting values on the display screen 26, a user can visually confirm the history. Therefore, the user can visually evaluate the soundness of the setting change of the setting value.

[0049] Figure 5 shows an example of a display screen for the history of setting changes. The control circuit 30 displays the history of setting changes on the display screen 26. The control circuit 30 displays the history of each setting change (date and time of setting change, setting item, setting value before setting change, setting value after setting change, input string).

[0050] Figure 6 shows an example of a system comprising a protective relay and an external device. System 100 comprises a protective relay 15 and an external terminal 50. The external terminal 50 is connected to the communication terminal 28 of the protective relay 15 via a communication cable 51. The external terminal 50 has a display screen 52. The external terminal 50 may acquire the history of setting value changes from the protective relay 15 via the communication cable 51 and display it on the display screen 52. The external terminal 50 may acquire the history of setting value changes from the protective relay 15 via wireless communication and display it on the display screen 52. The display screen 52 may be a screen provided on the external terminal 50, or a screen provided on a display device connected to the external terminal 50 by wire or wireless. The external terminal 50 may store the history of setting value changes in a storage device built into or connected to it.

[0051] The external terminal 50 is an example of an external device connected to the protective relay 15 by wire or wireless. The storage device built into or connected to the external terminal 50 is an example of a storage device provided outside the protective relay 15.

[0052] The external terminal 50 may verify the integrity of the setting value change by comparing the history obtained from the protective relay 15 via the communication cable 51 or wireless communication with the history previously obtained from the protective relay 15 via the communication cable 51 or wireless communication.

[0053] System 100 may include an external system 80, such as a power monitoring system. The external system 80 is, for example, a server. The data acquisition device 70 collects the measured amount of power from the protective relay 15 and a plurality of power monitoring devices 60, 61, 62 via a communication line 71. The external system 80 acquires the collected amount of power from the data acquisition device 70 via a communication line 72.

[0054] The external system 80 has a display screen 82. The display screen 82 may be a screen provided on the external system 80, or a screen provided on a display device connected to the external system 80 by wire or wireless. The external system 80 may acquire a history of setting changes of the setting values ​​via a communication line 72 or a wireless or wired communication line 81 and display it on the display screen 82. The external system 80 may also store a history of setting changes of the setting values ​​in a storage device built into or connected to it.

[0055] The external system 80 is an example of an external device connected to the protective relay 15 by wire or wireless. The storage device built into or connected to the external system 80 is an example of a storage device provided outside the protective relay 15.

[0056] Figure 7 shows an example of the hardware configuration of the external terminal 50. The configuration shown in Figure 7 is also applicable to the external system 80, so the following explanation will be applied to the external system 80. As shown in Figure 7, the external terminal 50 has a control unit 53 (processor 401 and memory 402), an auxiliary storage device 403, an I / F (interface) device 404, a communication device 405, and a drive device 406. Each piece of hardware of the external terminal 50 is interconnected via a bus 407.

[0057] The processor 401 has various computing devices such as a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). The processor 401 reads various programs (for example, a program that acquires and displays the history of setting changes from the protective relay 15) into the memory 402 and executes them.

[0058] The memory 402 has main memory devices such as ROM (Read Only Memory) and RAM (Random Access Memory). The control unit 53 is hardware including the processor 401 and the memory 402. The processor 401 executes various programs read from the memory 402, and the control unit 53 realizes various functions.

[0059] The auxiliary storage device 403 stores various programs and various information used when these programs are executed by the processor 401.

[0060] The I / F device 404 connects an external terminal 50 to an operating device 411 for inputting user instructions and a display device 412 for displaying processing results to the user.

[0061] The communication device 405 sends and receives signals with the protective relay 15.

[0062] The drive device 406 is a device for setting the recording medium 413. The recording medium 413 includes media for recording information optically, electrically, or magnetically, such as CD-ROMs, flexible disks, and magneto-optical disks. The recording medium 413 may also include semiconductor memory for recording information electrically, such as ROMs and flash memory.

[0063] The various programs to be installed on the auxiliary storage device 403 are installed, for example, when the distributed recording medium 413 is set in the drive device 406 and the various programs recorded on the recording medium 413 are read by the drive device 406. Alternatively, the various programs to be installed on the auxiliary storage device 403 may be installed by downloading them from an external network via the communication device 405.

[0064] The present invention is not limited by the embodiments described above. The embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, and modifications are possible without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

[0065] This international application claims priority based on Japanese Patent Application No. 2025-047633, filed on 24 March 2025, and the entire contents of Japanese Patent Application No. 2025-047633 are incorporated herein by reference.

[0066] 11 High-voltage power receiving equipment 12 Zero-phase current transformer 13 Transformer 14 Current transformer 15 Protective relay 16 Circuit breaker 17 Trip coil 21 Control panel 22 Cross buttons 23 Confirm button 24 Reset button 25 Display device 26 Display screen 28 Communication terminal 40 Non-volatile memory 41, 42, 43, 44 Area 50 External terminal 100 System

Claims

1. A protective relay comprising a memory and a control circuit that, when the setting of a setting value is changed, records a history of the setting change in the memory.

2. The protective relay according to claim 1, wherein the history includes the set value before the setting change.

3. The protective relay according to claim 2, wherein the history includes the set values ​​before multiple setting changes in the past.

4. The protective relay according to claim 2, wherein the history includes the set value after the setting change.

5. The protective relay according to claim 2, wherein the control circuit retains the setting value before the setting change in the memory each time the setting value is changed.

6. The protective relay according to any one of claims 1 to 5, wherein the history includes time information.

7. The protective relay according to any one of claims 1 to 5, wherein the history includes identification information of the person who changed the settings.

8. The protective relay according to any one of claims 1 to 5, wherein the history includes a string entered when the settings are changed.

9. The protective relay according to any one of claims 1 to 5, wherein the memory is a non-volatile memory.

10. A protective relay according to any one of claims 1 to 5, comprising a display device for displaying the history.

11. A system comprising: a protective relay; an external device connected to the protective relay by wire or wireless means; and a storage device provided outside the protective relay, wherein the external device records a history of the setting change in the storage device when the setting value of the protective relay is changed.

12. The system according to claim 11, further comprising a display device for displaying the history.

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