Calibration system and calibration method for protective relays

Abstract

The input conversion board, analog input board, and arithmetic processing board provided on the protective relay can be removed independently of each other. The analog input board (20) to be calibrated is mounted on the board mounting section (61) of the calibration system (60). The phase reference signal generation circuit (80) generates a phase reference signal (92) in response to the trigger signal (76). The calibration power supply (62) generates a sinusoidal calibration analog signal (64) based on the phase reference signal (92) and the amplitude setpoint (91). The control device (70), which outputs the trigger signal (76) and the amplitude setpoint (91), determines the gain correction value and phase correction value (94) of the analog input board (20) by comparing the amplitude and phase of the first digital conversion signal (93) generated by A / D conversion of the calibration analog signal (64) with the phase of the amplitude setpoint (91) and the phase reference signal (92).

Description

Technical Field

[0001] The present disclosure relates to a correction system and a calibration method for a protective relay.

Background Art

[0002] A protective relay is a device for detecting an accident occurring in a power system or electrical equipment and minimizing the impact of the accident by disconnecting the fault location with a circuit breaker. Specifically, the protective relay determines the occurrence of an accident by performing a relay operation based on analog signals such as current and / or voltage detected in a power system or electrical equipment.

[0003] The protective relay is provided with a circuit (hereinafter referred to as an analog circuit) for receiving the above analog signal. The analog circuit is composed of analog components. Specifically, as analog components, a transformer or an operational amplifier, an analog filter, and an A / D (Analog to Digital) converter are provided. Hereinafter, a transformer or an operational amplifier is also referred to as an input converter.

[0004] The electrical characteristics of analog components include manufacturing variations, and further change due to the influence of temperature and humidity, and also change depending on the magnitude of the input analog signal. Therefore, the actual value of the electrical characteristics of analog components is different from the nominal value (also referred to as the catalog value). As a result, the gain and phase characteristics of the analog circuit are also different from the characteristics calculated from the nominal values of the respective analog components. For the above reasons, calibration of the analog circuit is essential for accurately performing accident determination based on relay operation.

[0005] Japanese Unexamined Patent Application Publication No. 2023-38522 (Patent Document 1) discloses a digital protective relay that can correct the error in the input / output characteristics of an input converter regardless of whether the amplitude value of an analog signal input from a power system is any value from the minimum value to the maximum value of performance guarantee.

[0006] Specifically, the analog circuit of the protective relay in this document includes an analog filter to which a phase reference signal is directly input, and multiple analog filters corresponding to each input converter, to which the analog signal output from the corresponding input converter is input. The output of each analog filter is A / D converted.

[0007] When calculating the gain correction amount and phase correction amount, the amplitude values ​​of the phase reference signal and the analog signal are sequentially changed in multiple steps from the minimum low input amplitude to the rated input amplitude according to the sweep step. The ratio of the resulting amplitude value of the phase reference signal to the amplitude value of the analog signal obtained by the Fourier transform is calculated as the gain correction amount for each sweep step. Furthermore, the difference between the phase of the phase reference signal obtained by the Fourier transform and the phase of the analog signal obtained by the Fourier transform is calculated as the phase correction amount for each sweep step. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2023-38522 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] According to the above-mentioned Japanese Patent Publication No. 2023-38522 (Patent Document 1), errors in the input / output characteristics of the analog circuit from the input converter to the analog filter can be calculated and corrected. However, a problem arises in that the phase correction value of the analog circuit is a relative value between channels. Since the phase correction value is calculated for each protective relay device, if, for example, multiple protective relay devices are used in combination, errors will occur in the phase correction values ​​between different devices.

[0010] This disclosure has been made in consideration of the above-mentioned problems, and one of its objectives is to provide a calibration system for protective relays that can easily evaluate the absolute error of the input / output characteristics of analog components provided in an analog circuit. Other issues and features of this application will be described in the following embodiments. [Means for solving the problem]

[0011] In one embodiment, a calibration system for a protective relay is provided. The protective relay comprises an input conversion board, an analog input board, and an arithmetic processing board. The input conversion board is equipped with a plurality of input converters provided for each channel, and a first memory for storing correction values ​​for the plurality of input converters. The analog input board is equipped with a plurality of analog filters provided for each channel, one or more A / D converters, and a second memory for storing correction values ​​for the plurality of analog filters. The arithmetic processing board is equipped with a circuit for performing protective relay calculations. The input conversion board, analog input board, and arithmetic processing board can be removed from the protective relay independently of each other. The calibration system comprises a board mounting section, a phase reference signal generation circuit, a calibration power supply, a channel switch, and a control device. The analog input board to be calibrated is mounted on the board mounting section. The phase reference signal generation circuit generates a phase reference signal in response to a trigger signal. The calibration power supply generates a sinusoidal calibration analog signal based on the phase reference signal and amplitude setpoints. The channel switch inputs the calibration analog signal to the channel selected according to the channel switching request. The control unit outputs the trigger signal, amplitude setpoint, and channel switching request described above. The control unit acquires a first digital conversion signal generated by A / D conversion of the calibration analog signal that has passed through the analog filter of the selected channel. The control unit determines the gain correction value and phase correction value of the analog input board for the selected channel by comparing the amplitude and phase of the acquired first digital conversion signal with the amplitude setpoint and the phase of the phase reference signal. The control unit stores the determined gain correction value and phase correction value of the analog input board in a second memory. [Effects of the Invention]

[0012] According to the above embodiment, since the gain correction value and phase correction value are determined based on the amplitude set value and the phase of the phase reference signal, the absolute error of the input / output characteristics of the analog components provided in the analog circuit of the protective relay can be easily evaluated. [Brief explanation of the drawing]

[0013] [Figure 1] This block diagram shows an example configuration of a protective relay to which the calibration system of this disclosure is applied. [Figure 2] This is a block diagram showing an example configuration of a calibration system. [Figure 3] Figure 2 is a flowchart showing the operation of the calibration system. [Figure 4] This is a diagram illustrating the effects of Embodiment 1. [Figure 5] This is a block diagram showing an example configuration of the calibration system according to Embodiment 2. [Figure 6] Figure 5 is a flowchart showing the operation of the calibration system. [Modes for carrying out the invention]

[0014] Each embodiment will be described in detail below with reference to the drawings. Note that the same or corresponding parts will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0015] Embodiment 1. Embodiment 1 describes a method for evaluating the error of the input / output characteristics of each analog filter provided in the analog circuit of a protective relay. Below, we will first describe the configuration of a protective relay to which the calibration system of this disclosure is applied, and then describe the configuration and operation of the calibration system.

[0016] [Example of protective relay configuration] FIG. 1 is a block diagram showing a configuration example of a protection relay 1 to which the calibration system of the present disclosure is applied. As shown in FIG. 1, the protection relay 1 includes an input conversion board 10, an analog input board 20, and a CPU board 40. The input conversion board 10, the analog input board 20, and the CPU board 40 are independent of each other and can be individually taken out from the housing (not shown) of the protection relay 1.

[0017] The input conversion board 10 includes n input converters 11_1 to 11_n, a data bus 12, a ROM (Read Only Memory) 13, an input connector 14, an output connector 15, and a bus line connector 16. These components are mounted on a common printed board. The input converter 11 is provided for each of the n channels. In the present disclosure, the ROM 13 is also referred to as the first memory.

[0018] The input connector 14 is connected to an external connection terminal group (not shown) provided on the housing of the protection relay 1 via a wiring group (not shown) such as a harness. The external connection terminal group is connected to a plurality of voltage transformers and a plurality of current transformers provided in a power system or electrical equipment.

[0019] The input converter 11 attenuates or amplifies the signal level of the voltage signal detected by the voltage transformer or the current signal detected by the current transformer to a level suitable for signal processing on the analog input board 20. When insulation is required between the input section of the input conversion board 10 and the subsequent analog input board 20, an auxiliary transformer (that is, an auxiliary voltage transformer and an auxiliary current transformer) or a Hall element can be used as the input converter 11. When insulation is not required, a voltage dividing circuit using a resistor, a current-voltage conversion circuit using a shunt resistor, an operational amplifier, or the like can be used as the input converter 11.

[0020] The signals level-converted by the input converters 11_1 to 11_n are output to the subsequent analog input board 20 via the output connector 15. [[ID=十八]]

[0021] ROM13 is an electrically rewritable non-volatile memory. Examples of ROM13 include EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable and Programmable Read Only Memory), flash memory, MRAM (Magnetoresistive Random Access Memory), and FeRAM (Ferroelectric Random Access Memory). ROM13 stores the gain correction value and phase correction value for each input converter 11. The gain correction value and phase correction value are determined via the data bus 12 by the control device 70 of the calibration system 60 (Figure 2, described later) and written to ROM13.

[0022] The analog input board 20 includes n analog filters 21_1 to 21_n, n A / D (Analog to Digital) converters 22_1 to 22_n, a data bus 28, a ROM 29, an input / output interface (I / F) circuit 30, an input connector 31, a bus line connector 32, and connection connectors 33 and 34. These components are mounted on a common printed circuit board. The analog filters 21 and A / D converters 22 are provided for each of the n channels.

[0023] The input connector 31 is connected to the output connector 15 of the input conversion board 10 via a harness-like wiring harness. The analog input board 20 receives the output signals of the input converters 11_1 to 11_n via the input connector 31.

[0024] The analog filter 21 is provided to avoid aliasing errors caused by sampling in the A / D converter 22. Ideally, the analog filter 21 may be a low-pass filter that attenuates more than half of the sampling frequency, or practically, it may be one that provides significant attenuation between the rated frequency of the power system and the sampling frequency.

[0025] The A / D converter 22 converts the analog input signals of the corresponding channels, which have passed through the input converter 11 and the analog filter 21, into digital signals. Instead of n A / D converters 22, one or more A / D converters may be provided, and the output signals of the n analog filters 21 may be sequentially selected by a multiplexer and input to one or more A / D converters.

[0026] ROM29 is an electrically rewritable non-volatile memory. For ROM13, for example, EPROM, EEPROM, flash memory, MRAM, FeRAM, etc., can be used. ROM29 stores the gain correction value and phase correction value of each analog filter 21. The gain correction value and phase correction value are determined by the control device 70 of the calibration system 60 (Figure 2, described later) via the data bus 28 and written to ROM29.

[0027] The bus line connector 32 of the analog input board 20 is connected to the bus line connector 16 of the input conversion board 10. This makes the data bus 28 of the analog input board 20 and the data bus 12 of the input conversion board 10 common.

[0028] The input / output interface circuit 30 temporarily stores the digital data generated by each A / D converter 22 and transfers this digital data to the CPU board 40 and the control device 70 of the calibration system 60. Furthermore, the input / output interface circuit 30 writes the gain correction value and phase correction value of each input converter 11, generated by the control device 70 of the calibration system 60, to the ROM 13 of the input conversion board 10. In addition, the input / output interface circuit 30 writes the gain correction value and phase correction value of each analog filter 21, generated by the control device 70 of the calibration system 60, to the ROM 29 of the analog input board 20. The input / output interface circuit 30 can also read the gain correction value and phase correction value from ROMs 13 and 29 and transfer them to the control device 70 of the calibration system 60.

[0029] More specifically, the input / output I / F circuit 30 includes n control circuits 23_1 to 23_n, n buffer memories 24_1 to 24_n, a bus interface (I / F) circuit 25, a write / read circuit 26, and a control device interface (I / F) circuit 27, as shown in Figure 1. In Figure 1, these components are implemented by an FPGA (Field Programmable Gate Array), but they may also be constructed using dedicated digital circuits.

[0030] n control circuits 23_1 to 23_n are provided, each corresponding to one of the n A / D converters 22_1 to 22_n. Each control circuit 23 controls the operation of the corresponding A / D converter 22.

[0031] n buffer memories 24_1 to 24_n are provided, each corresponding to one of the n A / D converters 22_1 to 22_n. Each buffer memory 24 stores the digital data output from the corresponding A / D converter 22.

[0032] The bus I / F circuit 25 is connected to the bus 46 of the CPU board 40 via connection connectors 33 and 47. The control device I / F circuit 27 is connected to the I / F circuit 71 of the control device 70 via connection connector 34 and the connection connector 75 of the control device 70. The write / read circuit 26 reads data from ROMs 13 and 29 and writes data to ROMs 13 and 29.

[0033] The CPU board 40 includes a CPU (Central Processing Unit) 41, RAM (Random Access Memory) 42, ROM 43, communication circuit 44, I / F circuit 45, bus 46, and connection connectors 47, 48, 49. These components are mounted on a common printed circuit board. In the example in Figure 1, the CPU board 40 is configured as a microcomputer, but at least a portion of the CPU board 40 may be composed of at least one of an FPGA or an ASIC (Application Specific Integrated Circuit). In this disclosure, the CPU board 40 is also referred to as an arithmetic processing board.

[0034] The CPU 41 controls the entire protection relay 1 and performs various protection relay calculations using the time-series digital data output from each A / D converter 22. The RAM 42 and ROM 43 are used as the work memory of the CPU 41. The ROM 43 is an electrically rewritable non-volatile memory. For example, EPROM, EEPROM, flash memory, MRAM, FeRAM, etc. can be used as the ROM 43. The ROM 43 stores the operating program and various data.

[0035] The communication circuit 44 is connected to an external computer or other protective relay via a connection connector 48 and a communication line (not shown). The I / F circuit 45 is connected to external power equipment (circuit breakers, switches, etc.) via a connection connector 49 and a communication line (not shown).

[0036] Bus 46 connects each of the above components to each other. Furthermore, bus 46 is connected to the bus I / F circuit 25 of the analog input board 20 via connection connectors 47 and 33.

[0037] [Example of a calibration system configuration] Figure 2 is a block diagram showing an example configuration of the calibration system 60. As shown in Figure 2, the calibration system 60 includes a substrate mounting section 61, a calibration power supply 62, a channel switch 63, a control device 70, and a phase reference signal generation circuit 80.

[0038] The board mounting section 61 is where the board to be calibrated, among the boards that make up the protective relay 1 in Figure 1, is mounted. In the example in Figure 2, the analog input board 20 to be calibrated is mounted on the board mounting section 61. In this case, the input connector 31 of the analog input board 20 is connected to multiple output terminals of the channel switch 63 via a wiring harness. The connection connector 34 of the analog input board 20 is connected to the connection connector 75 of the control device 70 via wiring.

[0039] The calibration power supply 62 outputs a calibration analog signal 64, which is a sinusoidal signal for input to the circuit board to be calibrated. The calibration power supply 62 generates the calibration analog signal 64 based on the phase reference signal 92 output from the phase reference signal generation circuit 80 and the amplitude setting value 91 output from the control device 70.

[0040] The channel switch 63 selects a channel to input the calibration analog signal 64 generated by the calibration power supply 62, in accordance with the channel switching request 90 output from the control device 70.

[0041] The phase reference signal generation circuit 80 comprises a control circuit 81, a phase reference signal generation table 82, and a D / A (Digital to Analog) converter 83. The phase reference signal generation table 82 stores the digital data that will be the basis of the phase reference signal 92. The D / A converter 83 generates a sinusoidal phase reference signal 92 by performing D / A conversion on the digital data output from the phase reference signal generation table 82. The control circuit 81 controls the phase reference signal generation table 82 and the D / A converter 83. The control circuit 81 controls the timing of outputting the phase reference signal 92 based on a trigger signal 76 output from the control device 70.

[0042] The control device 70 controls the entire calibration system 60. The control device 70 is based on a computer, including a CPU and memory. At least a portion of the control device 70 may be composed of at least one of an FPGA or an ASIC.

[0043] Functionally, the control device 70 includes an interface (I / F) circuit 71, a buffer memory 72, a gain / phase calculation unit 73, a correction control unit 74, and a connection connector 75. The functions of the gain / phase calculation unit 73 and the correction control unit 74 are realized, for example, by the CPU constituting the control device 70 operating according to a program.

[0044] The I / F circuit 71 is connected to the control device I / F circuit 27 of the analog input board 20 via connection connectors 75 and 34. The buffer memory 72 stores time-series digital data corresponding to the calibration analog signal 64 generated by each A / D converter 22 of the analog input board 20. Hereinafter, the time-series digital data, which is the A / D conversion result of the calibration analog signal 64, will be referred to as the digital conversion signal.

[0045] The gain / phase calculation unit 73 applies a Discrete Fourier Transform (DFT) to the digital conversion signal. This allows the gain / phase calculation unit 73 to obtain the amplitude and phase of the digital conversion signal.

[0046] The correction control unit 74 outputs a channel switching request 90 to the channel switch 63, outputs an amplitude setting value 91 to the calibration power supply 62, and outputs a trigger signal 76 to the phase reference signal generation circuit 80 to determine the output timing of the phase reference signal 92. Furthermore, the correction control unit 74 calculates the gain correction value and phase correction value of each analog filter 21 of the analog input board 20 to be calibrated by comparing the phase of the amplitude setting value 91 and the phase reference signal 92 with the amplitude and phase of the above-mentioned digital conversion signal. The correction control unit 74 outputs the calculated gain correction value and phase correction value of each analog filter 21 to the write / read circuit 26 of the analog input board 20 via the I / F circuit 71.

[0047] [Operation of the calibration system] Figure 3 is a flowchart showing the operation of the calibration system 60 in Figure 2. The flowchart in Figure 3 shows the procedure for calibrating the analog input board 20, which is the object of calibration.

[0048] In step S10 of Figure 3, the analog input board 20 to be calibrated is mounted on the board mounting section 61 of the calibration system 60. In this case, the input connector 31 of the analog input board 20 is connected to multiple output terminals of the channel switch 63 via a wiring harness. The connection connector 34 of the analog input board 20 is connected to the connection connector 75 of the control device 70 via wiring.

[0049] In the next step S20, the correction control unit 74 of the control device 70 outputs a channel switching request 90 to the channel switcher 63. As a result, the calibration power supply 62 is connected to the analog filter 21 of the channel selected for calibration.

[0050] In the next step, S30, the correction control unit 74 of the control device 70 outputs the amplitude setting value 91 of the calibration analog signal 64 to the calibration power supply 62. Note that steps S20 and S30 may be performed in either order or simultaneously.

[0051] In the next step S40, the correction control unit 74 of the control device 70 outputs a trigger signal 76 to the phase reference signal generation circuit 80. Using this trigger signal 76 as a reference, the phase reference signal generation circuit 80 outputs a phase reference signal 92 to the calibration power supply 62. The calibration power supply 62 generates a calibration analog signal 64 based on the phase reference signal 92 and the amplitude setting value 91. The generated calibration analog signal 64 is input to the analog filter 21 of the selected channel. The calibration analog signal 64 that has passed through the analog filter 21 is A / D converted by the corresponding A / D converter 22, and the A / D conversion result is stored in the buffer memory 24 of the corresponding channel.

[0052] In the next step S50, the control device 70 acquires A / D conversion data 93 for the calibration analog signal 64 from the buffer memory 24 of the analog input board 20 and stores it in the buffer memory 72 of the control device 70.

[0053] In the next step, S60, the control device 70 calculates the gain and the phase difference with respect to the phase reference signal 92 based on the acquired A / D conversion data 93. More specifically, the gain / phase calculation unit 73 of the control device 70 calculates the amplitude and phase of the digital conversion signal by applying a discrete Fourier transform to the digital conversion signal, which is the A / D conversion data 93 corresponding to the calibration analog signal 64. Then, the correction control unit 74 calculates the gain and phase difference by comparing the amplitude setting value 91 and the phase of the phase reference signal 92 with the amplitude and phase of the digital conversion signal. Note that the phase difference can also be calculated by comparing the zero-crossing point of the phase reference signal 92 with the zero-crossing point of the digital conversion signal without using a discrete Fourier transform.

[0054] Based on this calculation result, the correction control unit 74 determines the gain correction value and phase correction value of the analog filter 21 of the analog input board 20, and outputs the determined gain correction value and phase correction value to the analog input board 20 via the I / F circuit 71.

[0055] In the next step S70, the write / read circuit 26 of the analog input board 20 stores the gain correction value and phase correction value obtained from the control device 70 as the correction value 94 for the analog input board 20 for the selected channel in the ROM 29 of the analog input board 20.

[0056] In the next step, S80, the correction control unit 74 of the control device 70 determines whether there are any channels for which the correction value has not been calculated. If there are channels for which the correction value has not been calculated (YES in step S80), the correction control unit 74 returns to step S20. If there are no channels for which the correction value has not been calculated (NO in step S80), the correction control unit 74 terminates the calibration process of the analog input board 20.

[0057] [Effects of Embodiment 1] As described above, the calibration system 60 for the protective relay of Embodiment 1 can absolutely determine the gain correction value and phase correction value for each channel based on the amplitude set value of the calibration analog signal and the phase of the phase reference signal. Furthermore, since the control device 70 for calculating the gain correction value and phase correction value is provided separately from the CPU board 40 of the protective relay 1, the configuration of the CPU board 40 can be simplified and costs can be reduced.

[0058] Figure 4 is a diagram illustrating the effects of Embodiment 1. Referring to Figure 4, the phase correction value of the A / D conversion data for channel 1 (CH1) is determined based on the phase difference between the A / D conversion data for channel 1 (CH1) and the phase reference signal. The phase correction value of the A / D conversion data for channel 2 (CH2) is determined based on the phase difference between the A / D conversion data for channel 2 (CH2) and the phase reference signal. In this way, the phase correction value for each channel can be absolutely determined based on the phase of the phase reference signal.

[0059] Furthermore, among the components of the calibration system 60, the phase reference signal generation circuit 80 may be mounted on the analog input board 20.

[0060] Embodiment 2. Embodiment 2 describes the case where the input conversion board 10 is the target of correction.

[0061] [Example of a calibration system configuration] Figure 5 is a block diagram showing an example configuration of the calibration system 60 of Embodiment 2. The configuration of the calibration system 60 in Figure 5 is the same as in Embodiment 1 in Figure 2. The difference in Figure 5 from Figure 2 is that both the calibrated analog input board 20 and the input conversion board 10 to be calibrated are mounted on the board mounting section 61 of the calibration system 60.

[0062] Specifically, the input connector 14 of the input conversion board 10 is connected to multiple output terminals of the channel switch 63 via a harness-like wiring harness. The output connector 15 of the input conversion board 10 is connected to the input connector 31 of the analog input board 20 via a harness-like wiring harness. The bus line connector 16 of the input conversion board 10 is connected to the bus line connector 32 of the analog input board 20. The connection connector 34 of the analog input board 20 is connected to the connection connector 75 of the control device 70 via wiring. The ROM 29 of the calibrated analog input board 20 stores channel-specific correction values ​​94 (gain correction value and phase correction value).

[0063] [Operation of the calibration system] Figure 6 is a flowchart showing the operation of the calibration system 60 in Figure 5. The flowchart in Figure 6 shows the procedure for calibrating the analog input board 20, which is the object of calibration.

[0064] In step S110 of Figure 6, the calibrated analog input board 20 and the input conversion board 10 to be calibrated are mounted on the board mounting section 61 of the calibration system 60. The connection between the input conversion board 10 and the analog input board 20 and the calibration system 60 is as described with reference to Figure 5.

[0065] In the next step S120, the correction control unit 74 of the control device 70 outputs a channel switching request 90 to the channel switcher 63. As a result, the calibration power supply 62 is connected to the input converter 11 of the channel selected for calibration.

[0066] In the next step, S130, the correction control unit 74 of the control device 70 outputs the amplitude setting value 91 of the calibration analog signal 64 to the calibration power supply 62. Note that steps S120 and S130 may be executed in either order or simultaneously.

[0067] In the next step S140, the correction control unit 74 of the control device 70 outputs a trigger signal 76 to the phase reference signal generation circuit 80. Using this trigger signal 76 as a reference, the phase reference signal generation circuit 80 outputs a phase reference signal 92 to the calibration power supply 62. The calibration power supply 62 generates a calibration analog signal 64 based on the phase reference signal 92 and the amplitude setting value 91. The generated calibration analog signal 64 is input to the input converter 11 of the selected channel. The calibration analog signal 64, which has been level-converted by the input converter 11 and has passed through the analog filter 21, is then A / D converted by the corresponding A / D converter 22. The A / D conversion result is stored in the buffer memory 24 of the corresponding channel.

[0068] In the next step S150, the control device 70 controls the write / read circuit 26 of the analog input board 20 to read the correction value 94 stored in the ROM 29 of the analog input board 20. Furthermore, the control device 70 obtains A / D conversion data 93 for the calibration analog signal 64 from the buffer memory 24 of the analog input board 20 and stores it in the buffer memory 72 of the control device 70.

[0069] In the next step, S160, the control device 70 calculates the gain and the phase difference with respect to the phase reference signal 92 based on the acquired A / D conversion data 93. More specifically, the gain / phase calculation unit 73 of the control device 70 calculates the amplitude and phase of the digital conversion signal by applying a discrete Fourier transform to the digital conversion signal, which is the A / D conversion data 93 corresponding to the calibration analog signal 64. Then, the correction control unit 74 calculates the gain and phase difference by comparing the amplitude set value 91 and the phase of the phase reference signal 92 with the amplitude and phase of the digital conversion signal. Note that the phase difference can also be calculated by comparing the zero-crossing point of the phase reference signal 92 with the zero-crossing point of the digital conversion signal without using a discrete Fourier transform.

[0070] Based on the calculation result and the acquired correction values ​​94 (gain correction value and phase correction value) of the analog input board 20, the correction control unit 74 determines the gain correction value and phase correction value of the input converter 11 of the input conversion board 10. The correction control unit 74 outputs the determined gain correction value and phase correction value to the analog input board 20 via the I / F circuit 71.

[0071] In the next step S170, the write / read circuit 26 of the analog input board 20 stores the gain correction value and phase correction value obtained from the control device 70 as the correction value 95 for the input conversion board 10 for the selected channel in the ROM 13 of the input conversion board 10.

[0072] In the next step, S180, the correction control unit 74 of the control device 70 determines whether there are any channels for which the correction value has not been calculated. If there are channels for which the correction value has not been calculated (YES in step S180), the correction control unit 74 returns to step S120. If there are no channels for which the correction value has not been calculated (NO in step S180), the correction control unit 74 terminates the calibration process of the input conversion board 10.

[0073] [Effects of Embodiment 2] As described above, according to the calibration system 60 for the protective relay of Embodiment 2, by combining a calibrated analog input board 20 with an input conversion board 10 to be calibrated, the gain correction value and phase correction value of only the input conversion board 10 to be calibrated can be easily calculated. Furthermore, by providing a ROM 13 for storing the gain correction value and phase correction value of the input conversion board 10 inside the input conversion board 10, and a ROM 29 for storing the gain correction value and phase correction value of the analog input board 20 inside the analog input board 20, the protective relay 1 can be configured by combining any input conversion board 10 and any analog input board 20.

[0074] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this application is indicated by the claims and not by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0075] 1 Protection relay, 10 Input conversion board, 11 Input converter, 12, 28 Data bus, 13, 29, 43 ROM, 14, 31 Input connector, 15 Output connector, 16, 32 Bus line connector, 20 Analog input board, 21 Analog filter, 22 A / D converter, 23, 81 Control circuit, 24, 72 Buffer memory, 25 Bus I / F circuit, 26 Write / read circuit, 27 Control device I / F circuit, 30 Input / output I / F circuit, 33, 34, 47, 48, 49, 75 Connection connector, 40 CPU board (arithmetic processing board), 42 RAM, 44 Communication circuit, 45 I / F circuit, 46 Bus, 60 Calibration system, 61 Board mounting section, 62 Calibration power supply, 63 Channel switch, 64 Calibration analog signal, 70 Control device, 71 I / F circuit, 73 Gain / phase calculation unit, 74 Correction control unit, 76 Trigger signal, 80 Phase reference signal generation circuit, 82 Phase reference signal generation table, 83 D / A converter, 90 Channel switching request, 91 Amplitude setting value, 92 Phase reference signal, 93 A / D conversion data, 94, 95 Correction value.

Claims

1. A calibration system for protective relays, The aforementioned protective relay, An input conversion board is provided with multiple input converters for each channel, and a first memory for storing the correction values ​​of the multiple input converters is mounted on it. An analog input board is provided with a plurality of analog filters for each channel, one or more A / D (Analog to Digital) converters, and a second memory for storing the correction values ​​of the plurality of analog filters. It comprises a processing board on which circuits for performing protective relay calculations are implemented, The input conversion board, the analog input board, and the arithmetic processing board can be removed from the protective relay independently of each other. The aforementioned calibration system A board mounting section for mounting the analog input board to be calibrated, A phase reference signal generation circuit that generates a phase reference signal in response to a trigger signal, A calibration power supply that generates a sinusoidal calibration analog signal based on the phase reference signal and amplitude setting value, A channel switch for inputting the calibration analog signal to the channel selected in accordance with a channel switching request, The system includes a control device that outputs the trigger signal, the amplitude set value, and the channel switching request, A calibration system for a protective relay, wherein the control device acquires a first digital conversion signal generated by A / D conversion of the calibration analog signal that has passed through the analog filter of the selected channel, determines the gain correction value and phase correction value of the analog input board in the selected channel by comparing the amplitude and phase of the acquired first digital conversion signal with the amplitude set value and the phase of the phase reference signal, and stores the determined gain correction value and phase correction value of the analog input board in the second memory.

2. The aforementioned board mounting section can mount both the input conversion board to be calibrated and the calibrated analog input board. The control device acquires a second digital conversion signal generated by A / D conversion of the calibration analog signal that has passed through the analog filter of the selected channel after being level-converted by the input converter of the selected channel, determines the gain correction value and phase correction value of the input conversion board of the selected channel based on the amplitude and phase of the acquired second digital conversion signal, the amplitude set value and the phase of the phase reference signal, and the gain correction value and the phase correction value of the analog input board, and stores the determined gain correction value and phase correction value of the input conversion board in the first memory, the calibration system for a protective relay according to claim 1.

3. The calibration system for a protective relay according to claim 2, wherein the control device calculates the amplitude and phase of the first digital conversion signal and the amplitude and phase of the second digital conversion signal using a discrete Fourier transform.

4. A method for calibrating a protective relay, The aforementioned protective relay, An input conversion board is provided with multiple input converters for each channel, and a first memory for storing the correction values ​​of the multiple input converters is mounted on it. An analog input board is provided with a plurality of analog filters for each channel, one or more A / D (Analog to Digital) converters, and a second memory for storing the correction values ​​of the plurality of analog filters. It comprises a processing board on which circuits for performing protective relay calculations are implemented, The input conversion board, the analog input board, and the arithmetic processing board can be removed from the protective relay independently of each other. The aforementioned calibration method is: The steps include preparing the analog input board to be calibrated, A step of generating a phase reference signal in response to a trigger signal, The steps include generating a sinusoidal calibration analog signal based on the phase reference signal and amplitude setting value, The steps include: inputting the calibration analog signal to the channel selected in accordance with the channel switching request; The control device outputs the trigger signal, the amplitude set value, and the channel switching request, and includes the step of acquiring a first digital conversion signal, wherein the first digital conversion signal is a signal generated by A / D conversion of the calibration analog signal that has passed through the analog filter of the selected channel. The aforementioned calibration method further, The control device determines the gain correction value and phase correction value of the analog input board in the selected channel by comparing the amplitude and phase of the acquired first digital conversion signal with the amplitude set value and the phase of the phase reference signal. A method for calibrating a protective relay, comprising the steps of the control device storing the determined gain correction value and phase correction value of the analog input board in the second memory.

5. The steps include preparing both the input conversion board to be calibrated and the calibrated analog input board, The control device further comprises the step of acquiring a second digital conversion signal, the second digital conversion signal being a signal generated by A / D conversion of the calibration analog signal which has been level-converted by the input converter of the selected channel and then passed through the analog filter of the selected channel. The aforementioned calibration method further, The control device determines the gain correction value and phase correction value of the input conversion board for the selected channel based on the amplitude and phase of the acquired second digital conversion signal, the amplitude setting value and the phase of the phase reference signal, and the gain correction value and phase correction value of the analog input board. The method for calibrating a protective relay according to claim 4, further comprising the step of the control device storing the determined gain correction value and phase correction value of the input conversion board in a first memory.

6. The method for calibrating a protective relay according to claim 5, wherein the control device calculates the amplitude and phase of the first digital conversion signal and the amplitude and phase of the second digital conversion signal using a discrete Fourier transform.

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