Digital protection relay and its maintenance management system

Abstract

To provide a digital protection relay having a continuous monitoring function which enables preventive maintenance.SOLUTION: In a digital protection relay 100, an arithmetic processing unit 30 performs protection relay calculation by using a measurement value of quantity of electricity, which is digitally converted by an analog input unit 20. The arithmetic processing unit 30 performs continuous monitoring processing on at least an input conversion unit 10 and the analog input unit 20 during idle time of protection relay calculation. The arithmetic processing unit 30 determines the input conversion unit 10 or the analog input unit 20 to be malfunctioning when an abnormality determination condition, that a determination value calculated by using the measurement value of the quantity of electricity digitally converted exceeds a threshold, continues for specified time, and records information indicating a deterioration degree of the input conversion unit 10 or the analog input unit 20 when the continuation time of the abnormality determination condition does not reach the specified time in continuous monitoring processing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a digital protection relay and its maintenance management system. [Background technology]

[0002] To ensure high reliability of protective relays, the hardware is equipped with a continuous monitoring function that detects faults through self-diagnosis. The calculations for continuous monitoring are performed during the relay calculation processing gap time within the relay calculation cycle.

[0003] Specifically, as described in paragraph

[0002] of Japanese Patent Laid-Open Publication No. 2008-118747 (Patent Document 1), when an abnormality is confirmed according to abnormality detection conditions defined for each monitoring item, an external alarm is output. The output external alarm is notified to a maintenance base via a remote monitoring control panel or the like. When a maintenance worker at the maintenance base receives the external alarm, he or she rushes to the digital protective relay device where the abnormality occurred, even if it is on a holiday or at night, and after confirming the nature of the abnormality, takes recovery measures.

[0004] Once a fault occurs, as mentioned above, an emergency investigation into the cause and recovery work are required, so measures are needed to prevent excessive fault detection. For this reason, some digital protective relay inspection items are set to notify an abnormality only if the fault symptom continues for a certain period of time (for example, Table 2.14 in Non-Patent Document 1). The duration can be set to, for example, 10 seconds, 15 seconds, 20 seconds, 60 seconds, etc. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-118747 [Non-patent literature]

[0006] [Non-Patent Document 1] "Protection Relay System Basic Technology System," edited by the Basic Technology Research Committee for Protection Relay Systems, Institute of Electrical Engineers of Japan Technical Report No. 641, July 1997 Summary of the Invention [Problem to be solved by the invention]

[0007] In the case of a transient fault where the duration of the problem symptom is less than the set time and the problem disappears immediately, not only is an external alarm not output, but the problem is not recorded either. For this reason, conventional continuous monitoring functions are basically for post-event maintenance and are not intended for preventive maintenance.

[0008] The above-mentioned Patent Document 1 proposes a preventive maintenance method in which a judgment value is set that can be used to judge that an equipment part has deteriorated even if it does not meet the threshold of the abnormality detection condition, and maintenance information is notified when the equipment part reaches the judgment value. However, once deterioration of a part occurs, the threshold of the abnormality detection condition is often exceeded, and it is not easy to set an appropriate deterioration judgment condition between the normal state and the abnormal state.

[0009] The present disclosure has been made in consideration of the above-mentioned problems, and one of its objectives is to provide a digital protective relay having a constant monitoring function that enables preventive maintenance. [Means for solving the problem]

[0010] In one embodiment, the digital protective relay includes an input conversion unit, an analog input unit, and an arithmetic processing unit. The input conversion unit performs level conversion on measured values ​​of electrical quantities of a power system input via a plurality of channels. The analog input unit performs digital conversion on the measured values ​​of the electrical quantities level-converted by the input conversion unit. The arithmetic processing unit performs protective relay calculations using the digitally converted measured values ​​of the electrical quantities. The arithmetic processing unit performs continuous monitoring processing on at least the input conversion unit and the analog input unit during spare time from the protective relay calculations. In the continuous monitoring processing, if an abnormality determination condition, in which a determination value calculated using the digitally converted measured values ​​of the electrical quantities exceeds a threshold, continues for a specified time, the arithmetic processing unit determines that the input conversion unit or the analog input unit has failed, and if the duration of the abnormality determination condition does not reach the specified time, records information indicating a degree of deterioration of the input conversion unit or the analog input unit. [Effects of the Invention]

[0011] According to the above embodiment, in the continuous monitoring process, if the duration of the abnormality determination condition does not reach the specified time, preventive maintenance becomes possible by recording information representing the degree of deterioration of the input conversion unit or analog input unit being monitored. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a digital protection relay. [Figure 2] FIG. 10 is a diagram showing examples of continuous monitoring items in a table format. [Figure 3] 4 is a flowchart showing a continuous monitoring procedure in the digital protection relay of the first embodiment. [Figure 4] 10A and 10B are diagrams conceptually showing an example of a change in a determination value over time and a failure determination result based on the change in a determination value; [Figure 5] 10 is a flowchart showing a continuous monitoring procedure in the protection relay device of the second embodiment. [Figure 6] FIG. 6 is a diagram showing an example of data stored in step S70A of FIG. 5 in the case of zero-phase monitoring. [Figure 7] 11 is a flowchart for explaining a monitoring procedure that is periodically executed in the digital protection relay of the third embodiment. [Figure 8] FIG. 2 is a diagram showing, in a table format, information stored in a nonvolatile memory of the arithmetic processing unit. [Figure 9] FIG. 9 is a graph showing the information in FIG. 8. DETAILED DESCRIPTION OF THE INVENTION

[0013] Each embodiment will be described in detail below with reference to the drawings. The same or corresponding parts will be denoted by the same reference characters and description thereof will not be repeated.

[0014] Embodiment 1 [Outline of digital protection relay configuration] Fig. 1 is a block diagram showing an example of the configuration of a digital protective relay. Referring to Fig. 1, the digital protective relay 100 includes an input conversion unit 10, an analog input unit 20, an arithmetic processing unit 30, an IO (Input and Output) unit 40, a bus 50, a power supply device 51, a power supply monitoring device 52, and a communication device 53. The configuration and operation of each element will be briefly described below.

[0015] The input converter 10 includes input converters 11 (11A, 11B) provided for each of a plurality of channels. Only two channels are shown in FIG.

[0016] Each of the input converters 11 converts a voltage signal detected by a voltage transformer (VT) 2 provided on the electric line 1 or a current signal detected by a current transformer (CT) 3 provided on the electric line 1 into a signal level suitable for signal processing inside the digital protection relay 100. As the input converter 11, for example, an auxiliary transformer (auxiliary voltage transformer, auxiliary current transformer) is used.

[0017] Although the power line 1 is configured as a three-phase AC power line (i.e., a transmission line or a distribution line), it is shown as a single line in Fig. 1 for ease of illustration. Therefore, each of the voltage transformer 2 and the current transformer 3 is actually provided for each phase, and correspondingly, the input converter 11 is also provided with three channels for each phase.

[0018] The analog input unit 20 includes analog filters 21 (21A, 21B) provided for each channel, sample and hold circuits (S / H) 22 (22A, 22B) provided for each channel, a multiplexer (MUX) 23, an analog to digital converter (ADC) 24, and a reference voltage source 25.

[0019] The analog filter 21 is provided to avoid aliasing errors due to sampling in the analog-to-digital converter 24. Ideally, the analog filter 21 may be a low-pass filter that attenuates half or more of the sampling frequency, or in practice, may be a filter that provides large attenuation between the rated frequency of the power system and the sampling frequency.

[0020] The sample-and-hold circuit 22 samples and holds the voltage signal or current signal for each channel. The sample-and-hold circuit 22 is not necessarily provided. The multiplexer 23 sequentially selects the values ​​held in the sample-and-hold circuit 22 for each channel. The analog-to-digital converter 24 converts the values ​​selected by the multiplexer 23 into analog data.

[0021] The arithmetic processing unit 30 includes a central processing unit (CPU) 31 and a memory 32. The memory 32 includes a read-only memory (ROM) and a random access memory (RAM) used as main memory, as well as an electrically rewritable non-volatile memory used as auxiliary memory.

[0022] The arithmetic processing unit 30 executes relay arithmetic processing and also executes continuous monitoring processing during the idle time of the relay arithmetic processing. These functions of the arithmetic processing unit 30 are realized by the central processing unit 31 executing a program stored in the memory 32.

[0023] The IO unit 40 includes a plurality of digital output circuits (D / O: Digital Output) 41 and a plurality of digital input circuits (D / I: Digital Input) 42. In Fig. 1, one digital output circuit 41 and one digital input circuit 42 are shown as representatives.

[0024] The digital output circuit 41 outputs a digital signal (i.e., a logic value having a high level and a low level) to the outside of the digital protection relay 100. For example, the digital output circuit 41 outputs a trip signal to a trip circuit 43 for opening a circuit breaker (CB) 4 provided on the electric power line 1. The arithmetic processing unit 30 can detect an open circuit of the trip circuit 43 via the bus 50 and the digital output circuit 41.

[0025] The digital input circuit 42 receives a digital signal (i.e., a logic value having a high level and a low level) from outside the digital protection relay 100. For example, the digital input circuit 42 receives contact information representing the open / closed state of the circuit breaker 4 and the switch (not shown) provided on the electric power line 1.

[0026] The power supply device 51 supplies power to each component of the digital protection relay 100. The power supply monitoring device 52 monitors whether the voltage and current output from the power supply device 51 are within specified ranges.

[0027] The communication device 53 exchanges information with a monitoring server 54 installed at a maintenance base. For example, the arithmetic processing unit 30 outputs the results of continuous monitoring processing to the monitoring server 54 via the communication device 53. A maintenance management system is constructed by the digital protection relay 100 and the monitoring server 54.

[0028] [Overview of continuous monitoring function] The calculation processing unit 30 constantly monitors the entire digital protection relay 100, from the input section to the output section, in hardware block units. The constant monitoring calculation is performed during the relay calculation cycle, utilizing the idle time other than relay calculation. For example, if the rated frequency of the power system is 50 Hz and relay calculation is performed every 30 electrical degrees, the relay calculation cycle is approximately 1.67 milliseconds. Therefore, the constant monitoring cycle is also approximately 1.67 milliseconds.

[0029] Fig. 2 is a diagram showing an example of items to be constantly monitored in the form of a table. The table in Fig. 2 is based on, for example, Table 2.14 in Non-Patent Document 1 ("Basic Technology System for Protective Relay Systems," Institute of Electrical Engineers Technical Report No. 641, July 1997). In the example of items to be constantly monitored shown in Fig. 2, the calculation processing unit 30 determines that an abnormality has occurred when the abnormality detection conditions continue for a certain period of time.

[0030] Specifically, in the negative-phase sequence monitoring, the arithmetic processing unit 30 takes in the three-phase voltages and three-phase currents of the power system as measurements, calculates the magnitudes of the negative-phase sequence voltages and currents as determination values ​​using the symmetric coordinate method, and determines whether the magnitudes of the negative-phase sequence voltages and currents calculated as the determination values ​​exceed threshold values, that is, whether the abnormality determination condition continues for a certain period of time.

[0031] In the zero-phase monitoring, the calculation processing unit 30 takes in the three-phase voltages and three-phase currents of the power system as measurements, and calculates the magnitudes of the zero-phase voltages and currents as judgment values ​​using the symmetric coordinate method. The calculation processing unit 30 determines whether the magnitudes of the zero-phase voltages and currents calculated as the judgment values ​​exceed the thresholds, which is an anomaly judgment condition, continues for a certain period of time.

[0032] In checking the accuracy of the AD conversion, the arithmetic processing unit 30 selects the output voltage of the reference voltage source 25 using the multiplexer 23, and takes in the value AD converted by the analog-to-digital converter 24 as a measurement value. The arithmetic processing unit 30 calculates the error between the AD-converted value of the output voltage of the reference voltage source 25 and the expected value as a judgment value. The arithmetic processing unit 30 determines whether the abnormality judgment condition, that the magnitude of the AD conversion error calculated as the judgment value exceeds a threshold, continues for a certain period of time.

[0033] In D / I input monitoring, the arithmetic processing unit 30 detects information on the open / closed state of the same contact (circuit breaker, switch) via different digital input circuits 42. The arithmetic processing unit 30 determines whether the abnormality determination condition, that the contact information of the detected same contact does not match, continues for a certain period of time.

[0034] In D / O output monitoring, the arithmetic processing unit 30 detects the result of the opening and closing command output via the digital output circuit 41 using the digital input circuit 42. The arithmetic processing unit 30 determines whether the abnormality determination condition, that the output opening and closing command does not match the result, continues for a certain period of time.

[0035] In trip circuit monitoring, the calculation processing unit 30 determines whether a disconnection state (abnormality determination condition) in which a current sufficiently smaller than the minimum operating current flows through the trip coil and the current becomes high resistance and cannot be detected continues for a certain period of time.

[0036] In power supply monitoring, it is determined whether or not the abnormality determination condition, that the magnitude of the error between the measurement result of the output voltage of the power supply device 51 and the expected value exceeds a threshold, continues for a certain period of time.

[0037] In this way, in the above-mentioned continuous monitoring function, the arithmetic processing unit 30 measures an electrical quantity or logical value related to the monitored object, and determines whether the abnormality determination condition based on the measured electrical quantity or logical value has continued for a certain period of time. If the abnormality determination condition has continued for a certain period of time, the arithmetic processing unit 30 determines that the monitored part or unit has failed.

[0038] [Deterioration detection function] Next, a preventive maintenance method for detecting the degree of deterioration of a monitored part or unit before it reaches a breakdown will be described.

[0039] 3 is a flowchart showing a continuous monitoring procedure in the digital protection relay of embodiment 1. The continuous monitoring function is executed during idle time of the protection relay calculation for each calculation cycle of the protection relay calculation.

[0040] In step S10, the arithmetic processing unit 30 in FIG. 1 measures an electrical quantity (i.e., voltage or current) or a logical value related to the unit being monitored and captures the measured value. For example, in the case of negative-phase sequence monitoring and zero-phase sequence monitoring in FIG. 2, the three-phase voltage or three-phase current of the power system is captured as the measured value, and in the case of checking the accuracy of AD conversion, the output voltage of the reference voltage source 25 is captured as the measured value. In the case of D / I input monitoring and D / O output monitoring, a logical value of "1" or "0" is captured as the measured value via the digital input circuit 42. In the case of trip circuit monitoring, the current flowing through the trip coil being monitored is captured as the measured value, and in the case of power supply monitoring, the output voltage of the power supply device 51 is captured as the measured value.

[0041] In the next step S20, the calculation processing unit 30 calculates a judgment value based on the acquired measured values. For example, in the case of negative-phase-sequence monitoring shown in FIG. 2, the magnitudes of the negative-phase-sequence voltage and negative-phase-sequence current are calculated as the judgment value, and in the case of zero-phase-sequence monitoring, the magnitudes of the zero-phase-sequence voltage and zero-phase-sequence current are calculated as the judgment value. In the case of checking the accuracy of A / D conversion, the magnitude of the error between the measured value and the expected value is calculated as the judgment value. In the case of D / I input monitoring, the difference between the logical values ​​acquired via the first and second digital input circuits 42 is calculated as the judgment value. In the case of D / O output monitoring, the difference between the logical value output via the digital output circuit 41 and the logical value acquired via the digital input circuit 42 is calculated as the judgment value. In the case of trip circuit monitoring, the measured current value is used as the judgment value. In the case of power supply monitoring, the magnitude of the error between the measured value and the expected value is calculated as the judgment value.

[0042] In the next step S30, the calculation processing unit 30 determines whether the determination value calculated in step S20 exceeds the threshold value, i.e., whether the abnormality determination condition is satisfied. If the determination value is equal to or less than the threshold value, i.e., if the abnormality determination condition is not satisfied (NO in step S30), the calculation processing unit 30 ends the continuous monitoring process.

[0043] On the other hand, if the determination value exceeds the threshold value (YES in step S30), in the next step S40, the calculation processing unit 30 determines whether the state in which the determination value exceeds the threshold value continues for a certain period of time, i.e., whether the state in which the abnormality determination condition is satisfied continues for a certain period of time. In the case of Fig. 3, a specified time of, for example, 20 seconds is selected as the certain period of time.

[0044] If the state in which the judgment value exceeds the threshold continues for a certain period of time (YES in step S40), in step S50, the arithmetic processing unit 30 judges that the monitored unit is faulty, and stores fault information such as the monitored item judged to be faulty and the date and time of the fault occurrence in non-volatile memory. Furthermore, in the next step S60, the arithmetic processing unit 30 outputs an alarm to the outside of the digital protection relay 100. Specifically, the arithmetic processing unit 30 notifies the alarm to a monitoring control panel or the like via the digital output circuit 41. Furthermore, an abnormality alarm is notified from the monitoring control panel or the like to a maintenance base.

[0045] On the other hand, if the state in which the judgment value exceeds the threshold value does not continue for a certain period of time (NO in step S40), in step S70, the calculation processing unit 30 records the duration of the abnormality judgment condition in non-volatile memory together with information such as the monitored item and date and time as information representing the deterioration state of the monitored object.

[0046] In the next step S80, the arithmetic processing unit 30 transmits the information stored in the nonvolatile memory to the monitoring server 54 provided at the maintenance base. This completes the continuous monitoring procedure.

[0047] 4 is a diagram conceptually showing an example of a change in the judgment value over time and the fault judgment result based on that change. Referring to FIG. 4, it is assumed that the judgment value exceeds the threshold value TH at time t1. At this point, the fault judgment result is low (L) level, and a fault has not yet been confirmed.

[0048] At time t2, the state in which the determination value exceeds the threshold value TH exceeds the specified time (20 seconds in this case), causing the failure determination result to become high (H) level, resulting in a confirmed failure.

[0049] On the other hand, if the judgment value returns to the threshold value (TH) or less at time t3 (19 seconds have passed since time t1) before time t2 is reached, the failure is not confirmed. In this case, the calculation processing unit 30 records the duration of the state in which the judgment value exceeds the threshold value TH as information for preventive maintenance that indicates the deterioration state of the monitored object.

[0050] [Effects of the First Embodiment] According to the continuous monitoring procedure described above, even if the condition for determining an abnormality does not continue for the specified time and a failure is not determined, information indicating the deterioration state of the monitored object is recorded. Therefore, the progress of deterioration of a part can be identified and the degree of deterioration can be diagnosed. For example, the monitoring server 54 at the maintenance base may predict the replacement time of a part based on the accumulated records of the duration of multiple abnormalities. This prediction may be made using artificial intelligence (AI). This enables preventive maintenance before a failure of the equipment is confirmed, preventing unexpected part replacement and enabling planned equipment upgrades.

[0051] Furthermore, in comparison with the above-mentioned Patent Document 1 (JP 2008-118747 A), this embodiment has the advantage that it is not necessary to use a criterion for determining deterioration in addition to a threshold value for determining a failure, because it is practically difficult to set such a criterion.

[0052] In the above, the failure information or information for preventive maintenance stored in the non-volatile memory is transmitted to the monitoring server 54 installed at the maintenance base, but transmitting the information is not necessarily required. For example, a maintenance person at the maintenance base may periodically visit the installation location of the digital protection relay 100 and retrieve the information from the non-volatile memory, or the owner of the digital protection relay 100 may periodically retrieve the information from the non-volatile memory.

[0053] Furthermore, in the case of monitoring items that utilize the electrical quantities (voltage and current) of the power system (for example, the negative-phase and zero-phase monitoring in Figure 2), the measured values ​​also include influences from the power system (flicker, equipment harmonics, voltage fluctuations, frequency fluctuations, etc.). Therefore, not only can the deterioration of the digital protective relay be diagnosed, but unnecessary alarms or relay malfunctions caused by the power system can also be prevented.

[0054] Embodiment 2 In the second embodiment, the information indicating the degree of deterioration of the monitored object that is recorded when the state in which the abnormality determination condition is satisfied does not continue for a specified time and it is not determined to be a failure is different from that in the first embodiment. Hereinafter, a specific description will be given with reference to the drawings.

[0055] Fig. 5 is a flowchart showing a continuous monitoring procedure in the protective relay device of embodiment 2. The continuous monitoring procedure in Fig. 5 differs from the flowchart in Fig. 3 in that step S70A is provided instead of step S70.

[0056] Specifically, if the state in which the abnormality determination condition is satisfied does not continue for a specified time (20 seconds in the case of FIG. 5 ) (NO in step S40), the calculation processing unit 30 proceeds to step S70A. In step S70A, the calculation processing unit 30 records the data of the determination value within the specified time after the determination value exceeds the threshold (i.e., after the abnormality determination condition is satisfied) together with the monitoring item and date and time in non-volatile memory. Here, since the amount of data to be recorded would be too large if the determination value were recorded every continuous monitoring period (e.g., 1.67 milliseconds), the calculation processing unit 30 records the data of the determination value by thinning it out, for example, every second. Since the rest of FIG. 5 is the same as in FIG. 3 , the same or corresponding steps are designated with the same reference numerals and description thereof will not be repeated.

[0057] 6 is a diagram showing an example of data stored in step S70A of FIG. 5 in the case of zero-phase monitoring. The judgment value (zero-phase current) exceeds the threshold value of 0.2 A for only the first 5 seconds of the specified 20-second time period. For the remaining 15 seconds, the judgment value does not exceed the threshold value. In the case of FIG. 6, the judgment value data is recorded by thinning out every second.

[0058] As described above, according to the continuous monitoring in the protective relay device of the second embodiment, as in the first embodiment, even if the state in which the abnormality determination condition is satisfied does not continue for the specified time and a failure is not determined, information indicating the deterioration state of the monitored object is recorded. Therefore, it is possible to grasp the progress of deterioration of the parts and diagnose the degree of deterioration.

[0059] In particular, in the case of the first embodiment, only the duration of the state in which the judgment value exceeded the threshold was recorded, so in order to diagnose the degree of deterioration of the monitored object, it was necessary to repeatedly collect a large amount of information. On the other hand, in the case of the second embodiment, a single piece of information includes the change in the judgment value over time within a specified period of time. Therefore, the degree of deterioration can be diagnosed based on multiple pieces of information obtained over a shorter period of time than in the case of the first embodiment.

[0060] Note that the first and second embodiments may be combined and implemented. That is, if the state in which the abnormality determination condition is satisfied does not continue for a specified time, the calculation processing unit 30 records information representing the degree of deterioration of the monitoring target. Here, the information representing the degree of deterioration may be the duration of the abnormality determination condition, or may be a plurality of measurement values ​​or a plurality of determination values ​​related to the monitoring target acquired within a specified time after the abnormality determination condition is satisfied, or may be both of these.

[0061] Embodiment 3 In the digital protective relay of the third embodiment, even if the judgment value does not exceed the threshold, the measured value or judgment value of the electrical quantity related to the monitored object is recorded at predetermined intervals. The monitoring procedure of the third embodiment is executed in combination with the continuous monitoring procedures of the first and second embodiments. A specific description will be given below with reference to the drawings.

[0062] FIG. 7 is a flowchart for explaining a monitoring procedure that is periodically executed in the digital protection relay according to the third embodiment.

[0063] In step S100, the calculation processing unit 30 determines whether it is a regular measurement date for the monitored object. The measurement date is determined according to the standard lifespan of the monitored object, such as once a year.

[0064] If it is a regular measurement day for the monitored object (YES in step S100), in step S110, the calculation processing unit 30 measures an electrical quantity (i.e., voltage or current) or a logical value related to the monitored object and captures the measurement value. In the next step S120, the calculation processing unit 30 calculates a judgment value based on the captured measurement value. Here, steps S110 and S120 are the same as steps S10 and S20 in FIGS. 3 and 5. That is, the monitoring procedure in FIG. 7 is executed in combination with the continuous monitoring procedure in FIGS. 3 and 5.

[0065] In the next step S130, the calculation processing unit 30 stores the measurement value or judgment value together with the monitoring item and measurement date in non-volatile memory. In the next step S140, the calculation processing unit 30 transmits the information stored in the non-volatile memory to the monitoring server 54 provided at the maintenance base.

[0066] In the next step S150, the monitoring server 54 at the maintenance base outputs the measured or determined values ​​of the monitored object that have been periodically received. The monitoring server 54 can grasp the progress of deterioration of the part based on the change in the measured or determined values ​​over time and diagnose the degree of deterioration.

[0067] 8 is a table showing information stored in the nonvolatile memory of the arithmetic processing unit. The nonvolatile memory stores monitoring items, measurement dates, and judgment values ​​(zero-phase currents).

[0068] Figure 9 is a graph showing the information in Figure 8. In this way, by periodically capturing the measured values ​​or judgment values ​​of the monitored object and displaying them as changes over time, it becomes possible to determine the degree of deterioration over time even if the judgment value has not reached the threshold value.

[0069] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of this application is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0070] Various aspects of the present disclosure are summarized below as appendices. (Appendix 1) an input conversion unit that converts the levels of measured values ​​of electrical quantities of the power system input via a plurality of channels; an analog input unit that digitally converts the measured value of the electrical quantity that has been level-converted by the input conversion unit; a calculation processing unit that performs a protective relay calculation using the measured value of the electric quantity converted into digital data, the calculation processing unit performs a constant monitoring process on at least the input conversion unit and the analog input unit during a time when the protection relay calculation is not performed, The calculation processing unit determines that the input conversion unit or the analog input unit has failed if an abnormality determination condition, in which a determination value calculated using the measurement value of the digitally converted electrical quantity exceeds a threshold, continues for a specified time during the continuous monitoring process, and records information representing the degree of deterioration of the input conversion unit or the analog input unit if the duration of the abnormality determination condition does not reach the specified time. (Appendix 2) 2. The digital protective relay according to claim 1, wherein the information representing the degree of deterioration includes a duration of the abnormality determination condition. (Appendix 3) 3. The digital protective relay according to claim 1, wherein the information representing the degree of deterioration includes a plurality of the judgment values ​​obtained between the time when the abnormality judgment condition is satisfied and the time when the specified time has elapsed. (Appendix 4) The digital protective relay according to any one of appendices 1 to 3, wherein the calculation processing unit periodically records the judgment value as information representing the degree of deterioration, regardless of whether the judgment value has reached the threshold value. (Appendix 5) The digital protective relay according to any one of Supplementary notes 1 to 4, further comprising a communication device for transmitting information indicating the degree of deterioration. (Appendix 6) a digital protective relay as described in Appendix 5; A maintenance management system for digital protection relays, comprising: a monitoring server provided at a maintenance base and configured to receive information indicating the degree of deterioration from the digital protection relays. [Explanation of symbols]

[0071] 1 power line, 2 voltage transformer, 3 current transformer, 4 circuit breaker, 10 input conversion section, 11 input converter, 20 analog input section, 21 analog filter, 22 sample and hold circuit, 23 multiplexer, 24 analog-to-digital converter, 25 reference voltage source, 30 arithmetic processing section, 31 central processing unit, 32 memory, 40 section, 41 digital output circuit, 42 digital input circuit, 43 trip circuit, 50 bus, 51 power supply unit, 52 power supply monitoring unit, 53 communication unit, 54 monitoring server, 100 digital protection relay.

Claims

1. an input conversion unit that converts the levels of measured values ​​of electrical quantities of the power system input via a plurality of channels; an analog input unit that digitally converts the measured value of the electrical quantity that has been level-converted by the input conversion unit; a calculation processing unit that performs a protective relay calculation using the measured value of the electric quantity converted into digital data, the calculation processing unit performs a constant monitoring process on at least the input conversion unit and the analog input unit during a time when the protection relay calculation is not performed, The calculation processing unit determines that the input conversion unit or the analog input unit has failed if an abnormality determination condition, in which a determination value calculated using the measurement value of the digitally converted electrical quantity exceeds a threshold, continues for a specified time during the continuous monitoring process, and records information indicating the degree of deterioration of the input conversion unit or the analog input unit as a transient failure without erasing it, for preventive maintenance purposes to determine the progression of component deterioration if the duration of the abnormality determination condition does not reach the specified time.

2. The digital protective relay according to claim 1 , wherein the information representing the degree of deterioration is a duration of the abnormality determination condition.

3. The digital protective relay according to claim 1 , wherein the information representing the degree of deterioration is a plurality of the judgment values ​​obtained during the period from when the abnormality judgment condition is satisfied until when the specified time has elapsed.

4. The digital protective relay according to claim 1 , wherein the calculation processing unit periodically records the determination value as information representing the degree of deterioration, regardless of whether the determination value reaches the threshold value.

5. The digital protection relay according to any one of claims 1 to 4, further comprising a communication device for transmitting information representing the degree of deterioration.

6. The digital protection relay according to claim 5; A maintenance management system for digital protection relays, comprising: a monitoring server provided at a maintenance base and configured to receive information indicating the degree of deterioration from the digital protection relays.

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