JP2013178186A - Voltage monitoring device and voltage monitoring method - Google Patents

Abstract

Provided are a voltage monitoring device and a voltage monitoring method capable of not only detecting an instantaneous voltage drop but also obtaining information on a voltage change before and after the occurrence of the instantaneous voltage drop.
An electric energy sensor has a voltage monitoring function. The electric energy sensor 1 includes a measurement unit 10 that measures an alternating voltage at a measurement location and detects an instantaneous voltage drop that occurs at the measurement location, and a storage unit 19. The measurement unit 10 includes the first history data regarding the transition of the AC voltage at the first time interval and the second time after the detection time of the instantaneous voltage drop in the first period until the detection time of the instantaneous voltage drop. Second history data indicating the transition of the AC voltage at intervals is generated, and the first and second history data are stored in the storage unit 19. Since the second time interval is shorter than the first time interval, detailed information on the voltage of the instantaneous voltage drop can be obtained.
[Selection] Figure 2

Description

  The present invention relates to a voltage monitoring apparatus and a voltage monitoring method for monitoring an instantaneous voltage drop and an instantaneous power failure.

  An instantaneous voltage drop or an instantaneous power failure greatly affects the operation of equipment, devices, etc. that are sensitive to fluctuations in the power supply voltage. For example, in the manufacture of semiconductor devices, since fine processing is required, the manufacturing apparatus is precisely controlled. An instantaneous voltage drop or an instantaneous power failure may have an important influence on the operation of the manufacturing apparatus. For this reason, techniques for monitoring instantaneous voltage drop or instantaneous power failure have been proposed so far.

  For example, Japanese Patent Application Laid-Open No. 11-51985 (Patent Document 1) discloses an arithmetic processing unit for detecting a power failure and power recovery of an AC power supply that supplies driving power to a microcomputer. This device includes an A / D converter that converts an instantaneous voltage of an AC power source into a digital value, a comparator that determines whether the digital value is less than or equal to a set value, and a length of a period in which the digital value is less than or equal to a set value. And a detection processing unit that detects a power failure based on the power. When a power failure is detected, the CPU operating clock frequency is reduced from the normal frequency. When power recovery is detected, the CPU operating clock frequency is returned to the normal frequency.

Japanese Patent Laid-Open No. 11-51985

  The arithmetic processing device disclosed in Patent Document 1 aims to detect the phenomenon of power failure and power recovery. As described above, in the factory, when an instantaneous power failure or an instantaneous voltage drop that does not reach the power failure occurs, the production process is greatly affected. In order to analyze a phenomenon such as a momentary power failure and a momentary voltage drop and determine a countermeasure, it is desirable to obtain as detailed information as possible about the voltage change before and after the occurrence of the phenomenon. However, Patent Document 1 does not describe a specific method for obtaining such information.

  An object of the present invention is to provide a voltage monitoring apparatus and a voltage monitoring method capable of not only detecting an instantaneous voltage drop but also obtaining information on a voltage change before and after the occurrence of the instantaneous voltage drop.

  According to one aspect of the present invention, the voltage monitoring device includes a measurement unit that measures an alternating voltage at a measurement location and detects an instantaneous voltage drop that occurs at the measurement location, and a storage unit. The measurement unit includes first history data related to the transition of the AC voltage at the first time interval in the first period until the moment when the instantaneous voltage drop is detected, and a second time interval after the moment when the momentary voltage drop is detected. The second history data indicating the transition of the AC voltage at is generated, and the first and second history data are stored in the storage unit. The second time interval is shorter than the first time interval.

  According to this configuration, the measurement unit detects an instantaneous voltage drop at the measurement location. A measurement part produces | generates the 1st historical data regarding transition of the alternating voltage during the 1st period until the detection time of the instantaneous voltage drop. Further, the measurement unit generates second history data after the detection time of the instantaneous voltage drop. In the second history data, the transition of the AC voltage at a small time interval is shown, so that detailed data on the voltage fluctuation after the detection of the instantaneous voltage drop can be obtained. The first and second history data are stored in the storage unit. Therefore, it is possible to obtain information regarding voltage fluctuations during the period before and after the detection point of the instantaneous voltage drop.

  An “instantaneous voltage drop” may include both an instantaneous power failure and an instantaneous voltage drop that does not lead to a power failure.

  The timing at which the first history data is stored in the storage unit may be either before the detection of the instantaneous voltage drop or after the detection of the instantaneous voltage drop. The occurrence of instantaneous voltage drop is often unpredictable. For this reason, for example, the first history data may be stored in the storage unit and the data may be updated at regular time intervals. Alternatively, the measurement unit may hold the first history data in advance and write the data to the storage unit when an instantaneous voltage drop is detected.

  Preferably, the measurement unit further generates AC voltage waveform data after the detection of the instantaneous voltage drop and stores the waveform data in the storage unit.

  According to this configuration, more detailed information regarding the transition of the voltage after the detection of the instantaneous voltage drop can be acquired. For example, the voltage waveform after the detection of the instantaneous voltage drop can be reproduced based on the waveform data stored in the storage unit.

  Preferably, the first history data includes the first data acquired for each first cycle of the AC voltage in the first period, and the AC voltage in the second period until the moment when the instantaneous voltage drop is detected. And second data acquired every second period. The second history data includes third data acquired for each third period of the AC voltage in a third period shorter than the first period. The first time interval corresponds to the first period. The second time interval corresponds to the third period. The second period is shorter than the first period.

  According to this configuration, it is possible to obtain detailed information on the voltage immediately before and immediately after the detection of the instantaneous voltage drop by the second and third data. Furthermore, information about a rough tendency of the voltage before the detection of the instantaneous voltage drop can be obtained from the first data.

Preferably, the period during which the measurement unit acquires waveform data is shorter than the third period.
According to this configuration, the size of the waveform data can be suppressed. Thereby, for example, the storage capacity of the storage unit can be saved. Furthermore, the time for writing data to the storage unit can be shortened. The power supply voltage of the voltage monitoring device may be affected by the instantaneous voltage drop. By shortening the writing time, it is possible to increase the probability that the waveform data can remain in the storage unit.

  Preferably, the first period corresponds to a plurality of periods of AC voltage. The second and third periods correspond to one period of the AC voltage. The first data indicates the sum of squares of the instantaneous voltage value over a plurality of periods. The second and third data indicate the sum of squares of the instantaneous voltage value during one cycle of the AC voltage.

  According to this configuration, it is possible to shorten the time required for the measurement unit to generate data related to the voltage effective value. Generally, in order to obtain an effective value, an average value of square sums of voltage instantaneous values in a predetermined period (for example, one cycle) is calculated, and a square root of the average value is calculated. However, it may take time to calculate the square root. According to the above configuration, since the calculation of the square root is omitted, the data generation time can be shortened.

  Preferably, the measurement unit generates monitoring data by generating a square sum of instantaneous voltage values during a half cycle of the AC voltage, and compares the transition of the monitoring data with a set pattern to reduce the instantaneous voltage drop. To detect.

  According to this configuration, the time required for generating the monitoring data can be shortened. Thereby, the instantaneous voltage drop can be detected quickly.

  Preferably, the set pattern is selected from a plurality of patterns. The voltage monitoring device further includes an alarm output unit that outputs an alarm corresponding to a set pattern among a plurality of alarms respectively corresponding to the plurality of patterns when an instantaneous voltage drop is detected.

According to this configuration, the alarm can be varied according to the instantaneous voltage drop pattern.
Preferably, the storage unit stores the first and second history data in a nonvolatile manner.

  According to this configuration, it is possible to prevent the generated first and second history data from being lost.

  According to another aspect of the present invention, a voltage monitoring method measures an alternating voltage at a measurement location, detects an instantaneous voltage drop that occurs at the measurement location, and a first time until a detection time point of the instantaneous voltage drop is detected. The storage unit stores the first history data relating to the transition of the AC voltage at the first time interval in the period, the step of generating data after the detection point of the instantaneous voltage drop, and the generated data. And a step of performing. The data generated after the detection time point includes second history data indicating the transition of the AC voltage at the second time interval. The second time interval is shorter than the first time interval. In the storing step, the storage unit stores the first and second history data.

  According to this configuration, it is possible to obtain information relating to voltage fluctuations during a period before and after the instantaneous voltage drop is detected. The storage unit may store both the first and second history data after the instantaneous voltage drop is detected. Alternatively, the storage unit may store the first history data before the instantaneous voltage drop detection time and store the second history data after the instantaneous voltage drop detection time.

  Preferably, the data generated after the detection time point includes waveform data of the alternating voltage after the instantaneous voltage drop is detected. In the storing step, the storage unit further stores the waveform data.

  According to this configuration, more detailed information regarding the transition of the voltage after the detection of the instantaneous voltage drop can be acquired.

  Preferably, the first history data includes the first data acquired for each first cycle of the AC voltage in the first period, and the AC voltage in the second period until the moment when the instantaneous voltage drop is detected. And second data acquired every second period. The second history data includes third data acquired for each third period of the AC voltage in a third period shorter than the first period. The first time interval corresponds to the first period. The second time interval corresponds to the third period. The second period is shorter than the first period.

  According to this configuration, it is possible to obtain detailed information on the voltage immediately before and immediately after the detection of the instantaneous voltage drop by the second and third data. Furthermore, information about a rough tendency of the voltage before the detection of the instantaneous voltage drop can be obtained from the first data.

Preferably, the period for generating the waveform data is shorter than the third period.
According to this configuration, the size of the waveform data can be suppressed.

  Preferably, the first period corresponds to a plurality of periods of AC voltage. The second and third periods correspond to one period of the AC voltage. The first data indicates the sum of squares of the instantaneous voltage value over a plurality of periods. The second and third data indicate the sum of squares of the instantaneous voltage value during one cycle of the AC voltage.

  According to this configuration, it is possible to shorten the time required for the measurement unit to generate data related to the voltage effective value.

  Preferably, in the detecting step, monitoring data is generated by generating a square sum of instantaneous voltage values during a half cycle of the AC voltage, and the instantaneous voltage drop is compared with the transition of the monitoring data and the set pattern. Is detected.

  According to this configuration, the time required for generating the monitoring data can be shortened. Thereby, the instantaneous voltage drop can be detected quickly.

  Preferably, the set pattern is selected from a plurality of patterns. The voltage monitoring method further includes a step of outputting an alarm corresponding to the set pattern among the plurality of alarms respectively corresponding to the plurality of patterns when the instantaneous voltage drop is detected.

According to this configuration, the alarm can be varied according to the instantaneous voltage drop pattern.
Preferably, the storage unit stores the first and second history data in a nonvolatile manner.

  According to this configuration, it is possible to prevent the generated first and second history data from being lost.

  According to the present invention, not only the instantaneous voltage drop can be detected, but also information regarding the voltage change before and after the occurrence of the instantaneous voltage drop can be obtained.

1 is a diagram showing one embodiment of a voltage monitoring device according to the present invention. It is the functional block diagram which showed the structure of the principal part of the electric energy sensor which concerns on embodiment of this invention. It is the flowchart which showed the voltage monitoring process performed by the electric energy sensor 1 shown by FIG. 1 and FIG. It is a figure for demonstrating an example of a detection pattern. It is a figure for demonstrating the production | generation method of monitoring data. It is a figure for demonstrating the procedure of the production | generation and holding | maintenance of data before the detection of an instantaneous voltage drop. It is a figure for demonstrating the procedure of the production | generation and holding | maintenance of data after the detection of an instantaneous voltage drop.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a diagram showing one embodiment of a voltage monitoring device according to the present invention. Referring to FIG. 1, in this embodiment, the voltage monitoring device according to the present invention is realized as an electric energy sensor 1. The electric energy sensor 1 measures the voltage and current at the measurement location of the AC circuit 5.

  The premises electrical equipment 2 outputs the power supplied via the power transmission line 2 a to the AC circuits 5 and 9. The on-premises electrical equipment 2 includes a receiving / transforming equipment, a distribution board, a distribution board, and a on-site trunk line.

  The AC circuit 5 supplies AC power to the load device 6. The load device 6 is, for example, a device or equipment in a factory. An auxiliary power supply 8 is connected to the AC circuit 5. The auxiliary power supply 8 is a backup power supply for the load device 6. For example, UPS (Uninterruptible Power Supply) is applied.

  AC circuit 5 includes power lines 5a, 5b, 5c. FIG. 1 shows a three-phase three-wire system as an example of a distribution system of the AC circuit 5. The distribution system of the AC circuit 5 is not limited to the three-phase three-wire system, and may be, for example, a single-phase two-wire system, a single-phase three-wire system, or a three-phase four-wire system.

  The electric energy sensor 1 receives a power supply voltage via an AC circuit 9. An auxiliary power source 3 is connected to the AC circuit 9. The auxiliary power source 3 is a backup power source for the electric energy sensor 1 and is, for example, a UPS. However, the auxiliary power source 3 is not essential.

  The measurement location of the electric energy sensor 1 corresponds to a portion where AC power is transmitted between the AC circuit 5 and the load device 6. Specifically, the electric energy sensor 1 is connected to the power lines 5a, 5b, 5c and measures the voltage of the AC circuit 5. Furthermore, current transformers 1 a and 1 b are connected to the electric energy sensor 1. Current transformers 1a and 1b detect currents flowing through power lines 5a and 5b, respectively. The electric energy sensor 1 measures the current at the measurement location based on the signals output from the current transformers 1a and 1b.

  The electric energy sensor 1 calculates the electric energy at the measurement location based on the measured voltage and the measured current. The amount of power obtained by calculation is not limited to the amount of power consumed by the load device 6. For example, when the load device 6 includes a motor and the motor performs a regenerative operation, the amount of power generated by the motor may be obtained.

  For example, when an accident occurs in a power facility of a power supplier (such as a power company) due to a lightning strike, the accident facility is disconnected from the power system. In such a case, the voltage of the local electrical equipment 2 and the AC circuits 5 and 9 may decrease for a short period. Such a voltage drop is called “instantaneous voltage drop”. Alternatively, it is conceivable that an instantaneous power failure occurs in the above case. Such a power outage is called “instantaneous power outage”. In this embodiment, the term “instantaneous voltage drop” includes both an instantaneous power failure and an instantaneous voltage drop that does not lead to a power failure.

  The electric energy sensor 1 monitors the AC voltage at the measurement location and detects an instantaneous voltage drop that occurs at the measurement location. The electric energy sensor 1 detects an instantaneous voltage drop by comparing the measured voltage transition pattern with a preset pattern. In this case, the electric energy sensor 1 outputs a signal (alarm output) for generating an alarm to the alarm device 4. The alarm device 4 issues an alarm according to the alarm output from the electric energy sensor 1. The alarm device 4 is, for example, a lamp or a buzzer, but is not limited thereto.

  The electric energy sensor 1 further generates history data regarding the transition of the AC voltage of the AC circuit 5 and holds the history data. When the electric energy sensor 1 detects an instantaneous voltage drop, the history data is stored in the electric energy sensor 1. At an appropriate timing, the history data stored in the electric energy sensor 1 is sent to the data processing device 7. The electric energy sensor 1 transfers data to the data processing device 7 via a communication device and a communication line (not shown), for example. The data processing device 7 is realized by, for example, a personal computer that executes a predetermined program.

  The electric energy sensor 1 may store not only data relating to voltage transition but also other data such as data relating to electric energy. The electric energy sensor 1 may record data on a recording medium such as a memory card. The recording medium is taken out from the electric energy sensor 1 and inserted into the data processing device 7. The data processing device 7 reads power amount data stored in the recording medium. Also by such a method, data can be transferred from the electric energy sensor 1 to the data processing device 7.

  FIG. 2 is a functional block diagram showing the configuration of the main part of the electric energy sensor according to the embodiment of the present invention. Referring to FIG. 2, the electric energy sensor 1 includes a measurement unit 10, a communication control unit 13, a connection unit 14, a signal path 15 including an isolator 15 a, a power supply circuit 16, a storage unit 19, and a capacitor 20. And the semiconductor relay 21.

  The measurement unit 10 includes a voltage measurement unit 11, a current measurement unit 12, and an arithmetic circuit 18. The voltage measuring unit 11 includes a voltage dividing circuit 11a and an A / D conversion circuit 11b. The current measurement unit 12 includes current transformers 1a and 1b, a current / voltage conversion circuit 12a, and an A / D conversion circuit 12b. The A / D conversion circuits 11b and 12b may be integrated into one circuit. Alternatively, the A / D conversion circuits 11b and 12b and the arithmetic circuit 18 may be integrated into one processing device (for example, a CPU). The communication control unit 13 is also realized by a CPU, for example.

  The voltage measuring unit 11 measures the voltages Va, Vb, Vc of the power lines 5a, 5b, 5c. The voltage dividing circuit 11a divides the input voltage (voltages Va, Vb, Vc) to generate a voltage having a strength suitable for measurement. The A / D conversion circuit 11b performs sampling and A / D conversion on the voltage output from the voltage dividing circuit 11a. Thereby, digital data indicating each value of the voltages Va, Vb, and Vc is generated.

  The current measuring unit 12 measures the currents I1 and I3 of the power lines 5a and 5b. The current transformer 1a outputs a current I1a that is proportional to the current I1. The current transformer 1b outputs a current I3a that is proportional to the current I3. The current / voltage conversion circuit 12a converts the currents I1a and I3a into voltages, and further amplifies the voltages. As a result, the current / voltage conversion circuit 12a generates a voltage having a strength suitable for measurement. The A / D conversion circuit 12b performs sampling and A / D conversion on the voltage output from the current / voltage conversion circuit 12a. Thereby, digital data indicating the values of the currents I1 and I3 is generated.

  The arithmetic circuit 18 generates digital data indicating the value of the current I2 flowing through the power line 5c based on the digital data indicating the values of the currents I1 and I3 from the current measuring unit 12. Since the sum of the currents I1, I2, and I3 is 0, the value of the current I2 can be calculated based on the values of the currents I1 and I3. The arithmetic circuit 18 calculates the electric energy at the measurement location using the digital data of the voltages Va, Vb, and Vc output from the voltage measuring unit 11 and the digital data of the currents I1 to I3. The arithmetic circuit 18 stores power amount data as a calculation result in the storage unit 19.

  Further, the arithmetic circuit 18 generates history data (first history data) regarding each transition of the voltages Va, Vb, and Vc, and stores the history data in the storage unit 19. As will be described in detail later, the arithmetic circuit 18 causes the storage unit 19 to store history data for a certain period. The arithmetic circuit 18 updates the first history data stored in the storage unit 19 with the latest data regarding the voltage. Note that the first history data may be held inside the arithmetic circuit 18 (for example, a cache) until an instantaneous voltage drop is detected.

  Furthermore, the arithmetic circuit 18 generates monitoring data for monitoring each of the voltages Va, Vb, and Vc. The arithmetic circuit 18 detects the instantaneous voltage drop by comparing the transition of the monitoring data with the set pattern. When the instantaneous voltage drop is detected, the arithmetic circuit 18 generates second history data regarding the transition of the voltages Va, Vb, and Vc after the detection of the instantaneous voltage drop, and stores the second history data in the storage unit 19. Let

  The first history data indicates the transition of the AC voltage at the first time interval. On the other hand, 2nd historical data shows transition of the alternating voltage in a 2nd time interval. The second time interval is shorter than the first time interval. That is, after an instantaneous voltage drop is detected, data indicating a fine transition of the AC voltage is generated. The arithmetic circuit stores the second history data in the storage unit 19.

  The data stored in the storage unit 19 is read out by the arithmetic circuit 18 when necessary and sent to the communication control unit 13. The communication control unit 13 outputs the data to the outside via the connection unit 14.

  When the arithmetic circuit 18 detects an instantaneous voltage drop, the arithmetic circuit 18 outputs a detection signal. This signal is sent to the communication control unit 13 via the signal path 15. The communication control unit 13 operates the semiconductor relay 21 in response to the detection signal. In this case, the semiconductor relay 21 outputs a signal (alarm output) for generating an alarm to the alarm device 4.

  The signal path 15 is provided between the arithmetic circuit 18 and the communication control unit 13. An isolator 15 a is provided in the signal path 15. The isolator 15 a insulates the arithmetic circuit 18 from the communication control unit 13. When the voltage value and current value of the AC circuit 5 are high, the voltage measuring unit 11 and the current measuring unit 12 can be a high voltage circuit. An isolator 15a as a signal insulating portion is provided to enable signal transmission while ensuring electrical insulation with respect to the high voltage portion. The isolator 15a is, for example, a capacitor type digital isolator. However, the signal insulating part may be realized by a photocoupler, for example.

  The connection unit 14 is used for data communication between the electric energy sensor 1 and another device. Although not shown, the connection unit 14 is configured by a connector for connecting a bus and a communication line, for example. For example, the electric energy sensor 1 receives the electric energy data calculated by another electric energy sensor (not shown) via the connection unit. The electric energy sensor 1 may output the electric energy data obtained by the calculation of the electric energy sensor 1 through the connection unit 14.

  The power supply circuit 16 converts an external power supply voltage (AC voltage) into a DC voltage and supplies the DC voltage to each block of the electric energy sensor 1. Capacitor 20 is charged by a DC voltage from power supply circuit 16. The capacitor 20 is used as a backup power source when an instantaneous voltage drop occurs. Capacitor 20 is, for example, an electric double layer capacitor. Instead of the capacitor, for example, a secondary battery may be used as a backup power source.

  The storage unit 19 can write data, and stores the written data in a nonvolatile manner. For example, FeRAM (Ferroelectric Random Access Memory) is used for the storage unit 19. In addition to the non-volatile characteristics, the FeRAM has characteristics such as no erasing time and no waiting time for writing, characteristics of a large number of reading and rewriting, characteristics of low power consumption, and the like. By applying FeRAM to the storage unit 19, a large amount of data can be written to the storage unit 19 in a short time. A storage unit for storing power amount data may be provided independently of the storage unit 19.

  FIG. 3 is a flowchart showing a voltage monitoring process executed by the electric energy sensor 1 shown in FIGS. 1 and 2. 2 and 3, in step S1, arithmetic circuit 18 sets a detection pattern, for example, according to a user instruction. The number of patterns to be set may be plural or one.

  The detection pattern includes a voltage level (reference value) for detecting a voltage drop and a duration of the voltage level. For example, a plurality of detection patterns may be stored in the storage unit 19 in advance, and the arithmetic circuit 18 may read at least one of the plurality of detection patterns.

  In step S2, information relating to the presence or absence of the auxiliary power source 3 (see FIG. 1) is set in the arithmetic circuit 18 by, for example, a user instruction.

  In step S3, the arithmetic circuit 18 uses the instantaneous voltage value (A / D value) obtained by sampling and A / D conversion by the A / D conversion circuit 11b to generate data relating to the instantaneous voltage, and the data Is temporarily stored in the storage unit 19. This data includes first history data and monitoring data. The first history data is stored in the storage unit 19.

  The first history data includes first data and second data. The first data is data acquired for each first cycle of the AC voltage in the first period. The second data is second data acquired for each second period of the AC voltage in the second period until the moment when the instantaneous voltage drop is detected.

  For example, the first data is a sum of squares of instantaneous voltage values acquired every 10 AC cycles for 10 seconds. This sum of squares is an average value in 10 cycles of the sum of squares of instantaneous voltage values obtained every AC cycle. Therefore, the “first period” is 10 seconds, and the “first period” is 10 periods of the AC waveform. The “first period” corresponds to the “first time interval” in the first history data.

  For example, the second data is a sum of squares of instantaneous voltage values obtained every second AC cycle per second. Therefore, the “second period” is one second, and the “second period” is one period of the AC waveform.

  Note that the first period and the second period are updated until an instantaneous voltage drop is detected. The end point of the first period and the end point of the second period are the time points when the latest first and second data are acquired. The starting point of the first period is a time point that goes back 10 seconds from the time when the latest first data is acquired, and the starting point of the second period is from the time point when the latest second data is acquired. It is a point that goes back one second.

  In step S4, the arithmetic circuit 18 generates a sum of squares using an A / D value within a period corresponding to 0.5 period of the AC waveform until the latest A / D value is obtained. The value of the sum of squares is used as monitoring data for detecting an instantaneous voltage drop. The arithmetic circuit 18 compares the monitoring data with the set pattern.

  In step S5, the arithmetic circuit 18 determines whether the voltage transition pattern represented by the monitoring data corresponds to the setting pattern. If the voltage transition pattern represented by the monitoring data does not correspond to the setting pattern, the arithmetic circuit 18 determines that no instantaneous voltage drop has occurred. In this case (NO in step S5), the process returns to step S3. On the other hand, when the voltage transition pattern represented by the monitoring data corresponds to the setting pattern, the arithmetic circuit 18 determines that an instantaneous voltage drop has occurred. In this case (YES in step S5), the process proceeds to step S6.

  When a plurality of detection patterns are set in step S1, the monitoring data is compared with each of the plurality of setting patterns in step S4. If the monitoring data transition pattern corresponds to at least one of the plurality of setting patterns in step S5, the process proceeds to step S6.

  In step S6, the arithmetic circuit 18 outputs a detection signal indicating that an instantaneous voltage drop has been detected. This detection signal is different for each set detection pattern. For example, the frequency of the detection signal may be varied according to the detection pattern. When the detection signal is a pulse signal, the duty of the signal may be varied depending on the detection pattern. The communication control unit 13 receives the detection signal and controls the semiconductor relay 21 in response to the detection signal. Thereby, the semiconductor relay 21 generates an alarm output. Since the detection signal is different for each set detection pattern, the alarm output is also different for each set detection pattern.

  In step S7, the arithmetic circuit 18 determines whether or not the auxiliary power source 3 is present. This determination is based on the setting of the arithmetic circuit 18 in step S2. If auxiliary power supply 3 is present (YES in step S7), the process proceeds to step S8. On the other hand, when auxiliary power supply 3 is not present (NO in step S7), the process proceeds to step S10.

  In step S8, the arithmetic circuit 18 generates second history data and waveform data indicating an AC waveform. In step S <b> 9, the arithmetic circuit 18 stores the second history data and waveform data in the storage unit 19.

  The second history data includes third data acquired for each third period of the AC voltage in a third period shorter than the first period. For example, the “third period” is one second, and the “third period” is one period of alternating current. Specifically, the arithmetic circuit 18 generates a square sum of instantaneous voltage values for each period of the AC waveform. The third data is a value of this sum of squares. The “third period” corresponds to the “second time interval” in the second history data.

  Further, the arithmetic circuit 18 uses the instantaneous voltage value to generate waveform data after the detection of the instantaneous voltage drop. Waveform data is generated for five alternating cycles. The arithmetic circuit 18 stores the third data and the waveform data in the storage unit 19.

  The length of the third period is not particularly limited. For example, the third period may be a certain period from when the instantaneous voltage drop is detected. Alternatively, the third period may be a period from when the instantaneous voltage drop is detected until the voltage recovers. Alternatively, the third period is set to the shorter of the certain period and the voltage recovery period.

  If there is no auxiliary power (NO in step S7), the process proceeds to step S10. In step S10, the arithmetic circuit 18 shifts to the energy saving mode. In the energy saving mode, for example, power supplied to blocks other than the measurement unit 10 and the storage unit 19 is reduced as much as possible. Preferably, the supply of power to the blocks other than the measurement unit 10 and the storage unit 19 is stopped.

  Next, in step S11, the arithmetic circuit 18 generates second history data and waveform data indicating an AC waveform. In step S <b> 12, the arithmetic circuit 18 stores the second history data and waveform data in the storage unit 19. Since the processes in steps S11 and S12 are the same as those in steps S8 and S9, the following description will not be repeated. In this case, the third period is, for example, a certain period from the moment when the instantaneous voltage drop is detected, or a period until the voltage recovers from the moment when the momentary voltage drop is detected, or the shorter of both. It may be a period.

  FIG. 4 is a diagram for explaining an example of the detection pattern. Referring to FIG. 4, each pattern includes a voltage level and a duration. Pattern 1 corresponds to the case where a voltage equal to or lower than VL1 (%) of the original voltage level continues for t1 (seconds). In pattern 2, the voltage level is defined as VL2 (%) of the original voltage, and the duration is defined as t2 (seconds). In pattern 3, the voltage level is defined as VL3 (%) of the original voltage, and the duration is defined as t3 (seconds). VL1> VL2> VL3 and t1> t2> t3. That is, the longer the voltage drops, the shorter the duration for which the drop is detected as an instantaneous voltage drop.

  The pattern shown in FIG. 4 may be set according to a specific standard, or may be set arbitrarily. As an example, a pattern can be set according to the SEMI F47 standard.

FIG. 5 is a diagram for explaining a monitoring data generation method. Referring to FIG. 5, first, the arithmetic circuit 18 determines the A / D values V ₁ , V ₂ , V ₃ , V _{4 ,.} And the sum of squares (V ₁ ² + V ₂ ² + V ₃ ² + V ₄ ² +... + V _n1 ² ) is calculated. Since the sampling frequency is constant, the number n1 of A / D values in the half cycle of the AC voltage is obtained in advance.

  The arithmetic circuit 18 determines the voltage level using the above sum of squares and the reference value. This reference value is obtained in advance by multiplying the sum of squares when the voltage is normal by the voltage level shown in FIG.

The arithmetic circuit 18 compares the reference value with the square sum (V ₁ ² + V ₂ ² + V ₃ ² + V ₄ ² +... + V _n1 ² ). Next, the arithmetic circuit 18 compares the reference value with the sum of squares every time an A / D value is acquired from the A / D conversion circuit 11b. At this time, the arithmetic circuit 18 discards the oldest square value (= V ₁ ² ) of the original sum of squares and adds the latest square value. Accordingly, the next sum of squares is (V ₂ ² + V ₃ ² + V ₄ ² +... + V _n1 ² + V _n2 ² ). The arithmetic circuit 18 compares the square sum (V ₂ ² + V ₃ ² + V ₄ ² +... + V _n1 ² + V _n2 ² ) with the reference value.

Thereafter, similarly, the arithmetic circuit 18 compares the square sum (x ₃ ² + x ₄ ² +... + X _n1 ² + x _n2 ² + x _n3 ² ) with the reference value, and then compares the square sum (x ₄ ² +... • + x _n1 ² + x _n2 ² + x _n3 ² + x _n4 ² ) and the reference value are compared. In this way, the arithmetic circuit 18 always compares the sum of the squares of ½ period up to the latest time point with the reference value. The time interval for monitoring the instantaneous voltage drop is approximately equal to the sampling interval of the A / D value.

  The effective value is the square root of the average value of the sum of squares. However, it may be time-consuming to calculate the square root. Therefore, when the arithmetic circuit 18 calculates the effective value and detects the instantaneous voltage drop using the effective value, the detection of the instantaneous voltage decrease may be delayed. In this embodiment, the calculation of the square root is omitted by comparing the sum of squares with a reference value. Thereby, it is possible to prevent delay in detection of instantaneous voltage drop.

  Furthermore, in this embodiment, the instantaneous voltage drop is calculated based on the sum of squares of the instantaneous values acquired during the AC half cycle (T / 2). Usually, the effective value is calculated based on the instantaneous value acquired during one AC cycle. In the case of an AC waveform, the positive waveform and the negative waveform are basically the same. By utilizing this fact, the sum of squares of instantaneous values acquired during a half period (T / 2) of alternating current is used as monitoring data. Accordingly, it is possible to prevent the calculation time of the monitoring data from becoming long, so that it is possible to prevent a delay in detection of an instantaneous voltage drop.

  FIG. 6 is a diagram for explaining a procedure for generating and holding data before detecting an instantaneous voltage drop. Referring to FIG. 6, based on the instantaneous value of the voltage acquired by sampling and A / D conversion of AC voltage 30 during one period T, arithmetic circuit 18 generates square sum 41 for each period. . The one-period square sum 41 is stored in the buffer 40 of the storage unit 19. When the square sum 41 for 10 cycles is generated, the arithmetic circuit 18 calculates an average value of 10 cycles of the square sum 41.

The arithmetic circuit 18 stores the average value in, for example, the buffer 42 of the storage unit 19. The buffer 42 has a ring buffer structure composed of _x buffers B ₁ , B ₂ ,..., B _x-2 , B _x−1 , B _x . Buffer B _1, B _2, ···, each _{B x-2, B x-} 1, B x, the average value _{A 1, A 2, ···,} A x-2, A x-1, A x Is stored. Count value _{C 1, C 2, ···,} C x-2, C x-1, C x buffer _{B 1, B 2, ···,} B x-2, B x-1, respectively B _x Assigned. These count values specify the buffer in which the latest average value is stored. For example, when the latest average value is stored in the buffer B ₁ , the average values are arranged in order from the oldest average value A _2, and the average values are newly added in the order of A _x-2 , A _x-1 , A _x , A _1. Become.

Thereafter, similarly, the arithmetic circuit 18 calculates a sum of squares for each period and stores the sum of squares in the buffer 40. When the sum of squares for the next 10 cycles is stored in the buffer 40, the arithmetic circuit 18 calculates an average value of the sum of squares for the 10 cycles and stores the average value in the buffer 42. In the above example, the oldest average value A ₂ is stored in the buffer B ₂ . Accordingly, the arithmetic circuit 18 stores the latest average value in the buffer B _2.

  The buffer 40 is configured to store, for example, the sum of squares per period for at least one second (that is, the same number as the frequency of the AC voltage 30). As a result, the sum of squares per cycle for one second until the latest time point is stored in the buffer 40.

  When the arithmetic circuit 18 detects an instantaneous voltage drop, the arithmetic circuit 18 calculates the mean value of the sum of squares for one cycle (1 second) stored in the buffer 40 and the sum of the squares of ten cycles stored in the buffer 42 ( 10 seconds) is stored in another storage area of the storage unit 19.

  The buffers 40 and 42 are not limited to those provided in the storage unit 19. For example, the buffers 40 and 42 may be buffers inside the arithmetic circuit 18.

  FIG. 7 is a diagram for explaining a procedure for generating and holding data after detection of an instantaneous voltage drop. Referring to FIG. 7, the arithmetic circuit 18 stores the instantaneous value of the voltage acquired by sampling and A / D conversion during one period T of the AC voltage 30 in the storage unit 19 as waveform data. Further, the arithmetic circuit 18 calculates the sum of squares of these instantaneous values and stores the sum of squares in the storage unit 19.

  The arithmetic circuit 18 causes the storage unit 19 to store waveform data for five cycles from the detection of the instantaneous voltage drop. The waveform data and the sum of squares corresponding to the waveform data are stored in the storage unit 19 until five cycles have elapsed since the detection of the instantaneous voltage drop. After the sixth period from the detection of the instantaneous voltage drop, the arithmetic circuit 18 calculates the sum of squares for each period based on the A / D value, and stores the sum of the squares in the storage unit 19. For example, the arithmetic circuit 18 stores the sum of squares for each period in the storage unit 19 until 1 second has elapsed since the detection of the instantaneous voltage drop.

  In this way, a sum of squares is generated for each cycle for 1 second before detection of the instantaneous voltage drop and for 1 second after detection, and the sum of squares is stored in the storage unit 19. Furthermore, after detecting the instantaneous voltage drop, waveform data for five cycles of the AC voltage is stored in the storage unit 19. As a result, it is possible to store in the storage unit 19 data relating to fine voltage transitions immediately before and immediately after the occurrence of the instantaneous voltage drop. Furthermore, after detecting the instantaneous voltage drop, the sum of squares for each cycle is acquired for one second, whereas the waveform data is acquired for only five cycles. That is, the period in which the waveform data is acquired is shorter than the period in which the sum of squares for each cycle is acquired. Thereby, the data size memorize | stored in the memory | storage part 19 can be suppressed.

  Due to the instantaneous voltage drop, the power supply voltage of the electric energy sensor 1 may temporarily drop. As a result, the writing of data to the storage unit 19 may be terminated halfway. Therefore, the shorter the writing time to the storage unit 19, the better. According to the above configuration, the data writing time to the storage unit 19 can be shortened by saving the data size. Thereby, the possibility that waveform data can be left in the storage unit 19 can be increased.

  Further, the average value of the sum of squares (every 10 cycles) for 10 seconds before the occurrence of the instantaneous voltage drop is stored in the storage unit 19. Thereby, it is possible to grasp a rough transition of the voltage before the occurrence of the instantaneous voltage drop.

  In the above embodiment, the electric energy sensor is shown as an embodiment of the voltage monitoring device of the present invention. However, the configuration and other functions of the device are not particularly limited as long as the device has the voltage monitoring function described in the above embodiment.

  Moreover, in said embodiment, it showed that the electric power supplied to the block around the measurement part 10 was reduced as an example of energy saving mode. For example, in the energy saving mode, the operation clock frequency of the arithmetic circuit 18 (for example, CPU) may be lowered in addition to the above control or instead of the above control.

  In the above embodiment, the sum of squares is calculated as a method for calculating data related to the effective value. However, the effective value may be calculated by converting an AC voltage into a DC voltage.

  Further, in the above embodiment, the sum of squares in a half cycle of the AC voltage is calculated in order to detect an instantaneous voltage drop. The unit of time may be, for example, one cycle or a plurality of cycles of AC voltage. However, in order to detect the instantaneous voltage drop earlier, it is preferable that the unit of time is shorter.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

DESCRIPTION OF SYMBOLS 1 Electric energy sensor, 1a, 1b Current transformer, 2 premise electric equipment, 2a Power transmission line, 3 Auxiliary power supply, 4 Alarm device, 5,9 AC circuit, 5a-5c Power line, 6 Load device, 7 Data processing device, 10 Measurement unit, 11 voltage measurement unit, 11a voltage dividing circuit, 11b, 12b A / D conversion circuit, 12 current measurement unit, 12a current / voltage conversion circuit, 13 communication control unit, 14 connection unit, 15 signal path, 15a isolator, 16 power supply circuit, 18 arithmetic circuit, 19 storage unit, 20 capacitor, 21 semiconductor relay, 30 AC voltage, 40, 42, B _{1 to} B _x buffer.

Claims (16)

A measurement unit for measuring an alternating voltage at a measurement location and detecting an instantaneous voltage drop generated at the measurement location;
A storage unit,
The measurement unit includes first history data related to the transition of the AC voltage at a first time interval in a first period until a detection time of the instantaneous voltage drop, and a first history data after the detection time of the instantaneous voltage drop. Second history data indicating the transition of the AC voltage at two time intervals, and storing the first and second history data in the storage unit,
The voltage monitoring device, wherein the second time interval is shorter than the first time interval.   The voltage monitoring apparatus according to claim 1, wherein the measurement unit further generates waveform data of the AC voltage after the detection of the instantaneous voltage drop and stores the waveform data in the storage unit. The first history data is
First data acquired for each first period of the AC voltage in the first period;
Second data acquired for each second period of the AC voltage in a second period until the moment of detection of the instantaneous voltage drop,
The second history data is
Including third data acquired for each third period of the AC voltage in a third period shorter than the first period;
The first time interval corresponds to the first period;
The second time interval corresponds to the third period;
The voltage monitoring apparatus according to claim 2, wherein the second period is shorter than the first period.   The voltage monitoring apparatus according to claim 3, wherein a period during which the measurement unit acquires the waveform data is shorter than the third period. The first period corresponds to a plurality of periods of the AC voltage,
The second and third periods correspond to one period of the alternating voltage,
The first data indicates a sum of squares of instantaneous voltage values over the plurality of periods,
The voltage monitoring apparatus according to claim 3, wherein the second and third data indicate a sum of squares of instantaneous voltage values during the one period of the AC voltage.   The measuring unit generates monitoring data by generating a square sum of instantaneous voltage values during a half cycle of the AC voltage, and compares the transition of the monitoring data with a set pattern to reduce the instantaneous voltage drop. The voltage monitoring device according to any one of claims 1 to 5, wherein the voltage monitoring device is detected. The set pattern is selected from a plurality of patterns,
The voltage monitoring device includes:
The voltage monitoring device according to claim 6, further comprising: an alarm output unit that outputs an alarm corresponding to the set pattern among a plurality of alarms respectively corresponding to the plurality of patterns when the instantaneous voltage drop is detected. .   The voltage monitoring apparatus according to claim 1, wherein the storage unit stores the first and second history data in a nonvolatile manner. A step of measuring an alternating voltage at a measurement location and detecting an instantaneous voltage drop generated at the measurement location;
Generating first history data relating to the transition of the AC voltage at a first time interval in a first period up to the time of detection of the instantaneous voltage drop;
Generating data after detection of the instantaneous voltage drop;
A storage unit storing the generated data, and
The data generated after the detection time point includes second history data indicating a transition of the AC voltage at a second time interval,
The second time interval is shorter than the first time interval;
In the storing step, the storage unit stores the first and second history data. The data generated after the detection time point includes waveform data of the AC voltage after detection of the instantaneous voltage drop,
The voltage monitoring method according to claim 9, wherein in the storing step, the storage unit further stores the waveform data. The first history data is
First data acquired for each first period of the AC voltage in the first period;
Second data acquired for each second period of the AC voltage in a second period until the moment of detection of the instantaneous voltage drop,
The second history data is
Including third data acquired for each third period of the AC voltage in a third period shorter than the first period;
The first time interval corresponds to the first period;
The second time interval corresponds to the third period;
The voltage monitoring method according to claim 10, wherein the second period is shorter than the first period.   The voltage monitoring method according to claim 11, wherein a period for generating the waveform data is shorter than the third period. The first period corresponds to a plurality of periods of the AC voltage,
The second and third periods correspond to one period of the alternating voltage,
The first data indicates a sum of squares of instantaneous voltage values over the plurality of periods,
The voltage monitoring method according to claim 11, wherein the second and third data indicate a sum of squares of instantaneous voltage values during the one period of the AC voltage.   In the detecting step, monitoring data generated by generating a square sum of instantaneous voltage values during a half cycle of the AC voltage is generated, and the transition of the monitoring data is compared with a set pattern. The voltage monitoring method according to claim 9, wherein the instantaneous voltage drop is detected. The set pattern is selected from a plurality of patterns,
The voltage monitoring method includes:
The voltage monitoring method according to claim 14, further comprising a step of outputting an alarm corresponding to the set pattern among a plurality of alarms respectively corresponding to the plurality of patterns when the instantaneous voltage drop is detected.   The voltage monitoring method according to claim 9, wherein the storage unit stores the first and second history data in a nonvolatile manner.

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