METHOD IMPLEMENTED IN ELECTRICITY METER AND ELECTRICITY METER - Patent application

Abstract

To detect the waveform distortion of a signal based on signals obtained from a watt-hour meter.SOLUTION: Provided is a method which is executed by a watt-hour meter and includes the steps of: acquiring a set of sampling data obtained by sampling an AC signal measured by the watt-hour meter; calculating the harmonic data related to harmonics included in the AC signal based on the set of the acquired sampling data; and recording the event indicative of the waveform distortion in the AC signal when the harmonic data satisfies a first predetermined condition.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a method executed by a watt-hour meter and a watt-hour meter.

Background Art

[0002] A watt-hour meter that measures and displays the amount of electric power used by power consumers such as ordinary households, buildings, and factories is known. An electronic watt-hour meter calculates the amount of electric power used by an electronic circuit built into the device by measuring the input current and input voltage. Generally, the harmonic components included in the input current and input voltage measured by the watt-hour meter are not of one type, but include various frequency components.

[0003] When an alternating voltage is applied to an incandescent lamp or a heater, etc., it is known that current is consumed in proportion to the power supply voltage, resulting in a clean sine wave and no harmonics being generated. On the other hand, inverter devices such as air conditioners and refrigerators convert alternating current to direct current once and perform frequency control. Since most electronic devices are structured to convert alternating current to direct current and store power in a capacitor, a pulsed current flows only when the voltage of the capacitor drops. That is, although the power supply voltage is a sine wave, the current flowing through the electronic device has a distorted waveform. This distorted waveform includes harmonic components that are frequency components that are integer multiples of the commercial frequency.

Summary of the Invention

Problems to be Solved by the Invention

[0004] A large harmonic current may cause heating and burnout of the capacitors that make up the electronic device. Also, if the harmonic generation source is near the electronic device, harmonics may flow directly into the capacitors that make up the electronic device, and harmonic failures such as overcurrent and overheating may occur locally. For this reason, it has been necessary to detect harmonic currents generated from electronic devices, etc.

[0005] An object of the present disclosure is to detect waveform distortion of an alternating current signal based on harmonic data obtained from the alternating current signal measured by a watt-hour meter.

Means for Solving the Problem

[0006] The present technology has been made in view of the above-described problems. One aspect of the present disclosure is a method executed by a watt-hour meter, the method including: obtaining a set of sampling data obtained by sampling an AC signal measured by the watt-hour meter; calculating harmonic data regarding harmonics included in the AC signal based on the obtained set of sampling data; and recording an event indicating that there is waveform distortion in the AC signal when the harmonic data satisfies a first predetermined condition.

[0007] The present technology has been made in view of the above-described problems. Another aspect of the present disclosure is a watt-hour meter including at least one processor, which, when executed by the at least one processor, causes the watt-hour meter to perform: obtaining a set of sampling data obtained by sampling an AC signal measured by the watt-hour meter; calculating harmonic data regarding harmonics included in the AC signal based on the obtained set of sampling data; and recording an event indicating that there is waveform distortion in the AC signal when the harmonic data satisfies a first predetermined condition.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0009] [Description of Embodiments of the Present Disclosure] First, the content of the embodiments of the present disclosure will be listed and described. An embodiment of the present disclosure has the following configuration.

[0010] (Item 1) According to Item 1, a method executed by an electricity meter, comprising: acquiring a set of sampling data obtained by sampling an AC signal measured by the electricity meter; calculating harmonic data regarding harmonics included in the AC signal based on the acquired set of sampling data; when the harmonic data satisfies a first predetermined condition, recording an event indicating that there is waveform distortion in the AC signal; A method is provided that includes this.

[0011] (Item 2) According to Item 2 The method according to Item 1 is further provided, which further includes recording an event indicating that there is no waveform distortion in the AC signal when the harmonic data satisfies a second predetermined condition.

[0012] (Item 3) According to Item 3 The harmonic data includes at least one of the total harmonic distortion rate and the harmonic content rate of a predetermined order for the AC signal, and the method according to any one of items 1 or 2 is provided.

[0013] (Item 4) According to item 4 The first predetermined condition is that at least one of the total harmonic distortion rate and the harmonic content rate of a predetermined order for the AC signal is equal to or greater than a predetermined threshold value, and the method according to any one of items 1 to 3 is provided.

[0014] (Item 5) According to item 5 The first predetermined condition is that at least one of the total harmonic distortion rate and the harmonic content rate of a predetermined order for the AC signal is equal to or greater than a predetermined threshold value over a predetermined period, and the method according to any one of items 1 to 3 is provided.

[0015] (Item 6) According to item 6 The second predetermined condition is that at least one of the total harmonic distortion rate and the harmonic content rate of a predetermined order for the AC signal is less than a predetermined threshold value over a predetermined period, and the method according to item 2 is provided.

[0016] (Item 7) According to item 7 The harmonic content rate of the predetermined order includes at least one harmonic content rate among the harmonic content rates of the components at frequencies of 5 times, 7 times, 11 times, 13 times, 17 times, 19 times, 23 times, and 25 times the fundamental frequency of the AC signal, and the method according to any one of items 3 to 6 is provided.

[0017] (Item 8) According to item 8 The predetermined threshold value for the harmonic content rate is settable for each predetermined order, and the method according to any one of items 4 to 6 is provided.

[0018] (Item 9) According to item 9 The set of the sampling data is a set of transition data shifted by a predetermined time from the sampling time so as to be synchronized with the timing at which the AC signal becomes an offset value, and the method according to any one of items 1 to 8 is provided.

[0019] (Item 10) According to item 10 The set of the sampling data is a data set including an additional data set in addition to the set of the transition data, and the sampling interval of the additional data set is shorter than the sampling interval of the set of the transition data, and the method according to item 9 is provided.

[0020] (Item 11) According to item 11 An electric energy meter including at least one processor, which, when executed by the at least one processor, causes the electric energy meter to acquire a set of sampling data obtained by sampling an AC signal measured by the electric energy meter; calculate harmonic data regarding harmonics included in the AC signal based on the acquired set of sampling data; when the harmonic data satisfies a first predetermined condition, record an event indicating that there is waveform distortion in the AC signal; and execute. An electric energy meter is provided.

[0021] <Configuration of Electric Energy Meter 10> FIG. 1 shows a schematic configuration diagram of an electric energy meter 10 according to an embodiment of the present disclosure. The electric energy meter 10 includes at least a control unit 12 that controls the operation of the electric energy meter 10 and a terminal unit 14 that is connected to a load. The load can be a monitoring target device 30 that uses the power passing through the electric energy meter 10. The electric energy meter 10 measures the amount of power passing through the electric energy meter 10 and supplied to the monitoring target device 30, and acquires usage information. The electric energy meter 10 may be for single-phase use or for three-phase use.

[0022] The usage information may include the instantaneous values of the voltage input to the device 30 to be monitored at a plurality of time points within a certain period. Further, the usage information may include the instantaneous values of the current flowing through the device 30 to be monitored at a plurality of time points within a certain period.

[0023] The control unit 12 controls the operation of the watt-hour meter 10 and is composed of at least a processor (not shown), a memory (not shown), and a storage (not shown). These components included in the control unit 12 are electrically connected to each other by a bus. The cooperation of the processor, the memory, the storage, etc. functions as the control unit 12. For example, the control unit 12 performs digital sampling processing on the current and voltage measured by the watt-hour meter 10 and acquires a set of sampling data of the current and voltage at a plurality of time points. Further, the control unit 12 acquires a set of transition data obtained at a timing based on the offset value from the set of sampling data. Details of the transition data will be described later.

[0024] The processor expands and executes the read program in the memory. As an example, the processor executes a series of instructions included in the program expanded in the memory based on the signal acquired by the watt-hour meter 10.

[0025] The memory is a main storage device and is composed of storage devices such as a ROM (Read Only Memory) and a RAM (Random Access Memory). As an example, the memory provides a working area for the processor by temporarily storing the program and various data read by the processor from the storage described later.

[0026] The storage is an auxiliary storage device. The storage permanently holds programs and data. The storage is realized, for example, as a non-volatile storage device such as a hard disk device or a flash memory.

[0027] The power meter 10 may be a smart meter. In this case, as shown in FIG. 1, the power meter 10 may further include a communication control unit 16 communicably connected to the power meter 10. The communication control unit 16 periodically transmits information (such as usage data) to the power company. The communication control unit 16 may be configured separately from the power meter 10.

[0028] The monitored device 30 is composed of one or more electrical and electronic devices, for example, an air conditioner, a television, a personal computer (PC), a refrigerator, a microwave oven, or a combination thereof. The monitored device 30 may be an IoT device.

[0029] (First Embodiment) FIG. 2 is a diagram showing the time change of an AC signal, which is usage information measured by the power meter 10 in an embodiment of the present disclosure, at a plurality of time points. In the following example, the case where the AC signal is voltage will be described as an example, but the same applies to current. In this figure, the vertical axis represents voltage and the horizontal axis represents time. Each individual point is the voltage value (sampling data) measured at each time point, and a set of voltage values (a set of sampling data) for approximately one cycle is shown. In the example of FIG. 2, the time change of the set of sampling data depicts a curve that is approximately sinusoidal, but the set of sampling data only needs to have periodicity and does not necessarily depict a sinusoidal shape.

[0030] In one example, the power meter 10 measures the voltage at an interval of 1 cycle / second, i.e., every 1 second. If the sampling frequency of the power meter 10 is 8 kHz, the sampling interval by the power meter 10 is 125 μS. When the commercial power supply frequency is 50 Hz, in the example of FIG. 2, due to the influence of the commercial power supply frequency, one cycle of the measured voltage is about 0.02 seconds, and about 160 sampling data are obtained in one cycle.

[0031] Due to the influence of fluctuations in the commercial power frequency, etc., there may be a deviation between the time when the waveform of the voltage measured by the watt-hour meter 10 (the time change of the set of sampling data) intersects the offset value and the sampling time by the watt-hour meter 10. Therefore, necessarily, the commercial power supply cycle and the cycle of the measured voltage do not necessarily match. For example, when the commercial power frequency is 50 Hz, one cycle of the commercial power supply is 0.02 seconds, but one cycle of the measured voltage does not necessarily become 0.02 seconds. According to the present disclosure, by calculating the offset period at which the time change of the measured set of sampling data intersects the offset value, a new interval (first interval) for acquiring a desired number of data based on the offset value is calculated. Further, the control unit 12 calculates a set of data of voltage values based on the new interval (first interval) based on the offset period. Note that in this specification, the case where the commercial power frequency is a 50 Hz system is described as an example, but the same applies to a 60 Hz system.

[0032] FIG. 3 is an enlarged view of a part 300 of the time change of the voltage measured by the watt-hour meter 10 shown in FIG. 2. FIG. 3 shows the sampling time t immediately before the first time T1 when the time change of the measured voltage intersects the offset value. 0 from, and the subsequent sampling time t 1 to t 4 and shows the voltage sampling data up to. V 0 is the voltage value at the sampling time t 0 , V 1 is the voltage value at the sampling time t1. In FIG. 3, two adjacent voltage values are approximated by a linear line (for example, line segment L1) having these as both ends. As shown in FIG. 3, the first time T1 when the time change (linear line) of the measured voltage becomes the offset value does not necessarily coincide with the sampling times t 0 , t 1 .

[0033] FIG. 4 is an enlarged view of a part 400 of the time change of the voltage measured by the watt-hour meter 10 shown in FIG. 2. FIG. 4 shows the sampling time t N-3from the sampling time t immediately after the second time T2 when the time change of the measured voltage intersects the offset value N+1 to the sampling data is shown. V N is the voltage value at the sampling time t N and V N+1 is the voltage value at the sampling time t N+1 In FIG. 4, two adjacent voltage values are approximated by a linear line (for example, line segment L2) having these as both ends. As shown in FIG. 4, the second time T2 when the time change (linear line) of the measured voltage becomes the offset value does not necessarily coincide with the sampling times t N , t N+1 .

[0034] FIG. 5 shows an example of processing executed in the control unit 12 of the wattmeter 10 according to an embodiment of the present disclosure. The control unit 12 executes various processes shown in FIG. 5 according to the description of the program. Although FIG. 5 illustrates an example of processing of voltage values, the same processing shown in FIG. 5 can be applied to current values as well.

[0035] Steps S502 to S508 relate to a process of calculating an offset period in which the measured voltage becomes an offset value and acquiring a set of transition data of the voltage synchronized with the timing based on the calculated offset period.

[0036] Steps 510 and S512 relate to a process of calculating a set of additional data obtained by further shifting the transition data of the voltage by one fraction of the first interval.

[0037] Steps S502 to S508 in FIG. 5 will be described.

[0038] First, in step S502, the control unit 12 acquires a set of sampling data when sampling the voltage measured by the watt-hour meter 10 at the sampling interval set in the watt-hour meter 10. As described above, the times (the first time T1 and the second time T2) when the measured voltage becomes the offset value do not necessarily coincide with the sampling times. Therefore, according to the processes from step S504 to step S508, the control unit 12 obtains transition data obtained at the timing based on the offset value from the sampling data acquired in step S502.

[0039] In step S504, the control unit 12 selects an arbitrary one cycle from the set of sampling data acquired in step S502, and extracts a set of sampling data of approximately one cycle centered on this one cycle. The set of sampling data of approximately one cycle to be extracted includes (i) a set of sampling data in which the voltage centered on the selected one cycle is included between the first time T1 when passing through the first offset value and the second time T2 when passing through the next second offset value, (ii) the sampling data immediately before the first time T1, and (iii) the sampling data immediately after the second time T2. Details of the first time T1 and the second time T2 will be described in detail below with reference to FIGS. 3 and 4.

[0040] As shown in FIG. 3, the first time T1 is the time corresponding to the first intersection point CP1 where the first approximate straight line L1 connecting two adjacent sampling data having an increasing trend across the first offset value among the set of sampling data obtained centered on the selected one cycle intersects the first offset value.

[0041] Also, as shown in FIG. 4, the second time T2 is the time corresponding to the second intersection point CP2 which is the next intersection point of the intersection point CP1 where the second approximate straight line L2 connecting two adjacent sampling data having an increasing trend across the second offset value among the set of sampling data obtained centered on the selected one cycle intersects the second offset value. Hereinafter, the first offset value and the second offset value may be collectively referred to as the offset value.

[0042] Returning to FIG. 5, in step S506, the control unit 12 calculates an offset period (T in FIG. 2) based on the times (the first time T1 and the second time T2) when the voltage measured by the watt-hour meter 10 crosses the offset value. The offset value varies depending on the settings, situation, model, etc. of the watt-hour meter 10. When the offset value is zero volts, the offset period becomes the zero-crossing period. cycle ) The offset period is the period from the first time T1 when the measured voltage passes through the first offset value to the second time T2 when the measured voltage passes through the next second offset value. The offset period does not have to match the commercial power supply period. The offset period is calculated based on the set of sampling data extracted in step S504. More specifically, the offset period is calculated according to the process shown below.

[0043] First, the control unit 12 calculates a first time difference Δts, which is the difference from the first time T1 to the sampling time t immediately after the first time T1, from the set of sampling data extracted in step S504 (FIG. 3).

[0044] Specifically, based on the linearly approximated voltage waveform shown in FIG. 3, the first time difference Δts is calculated by the following equation (1). 1 to the first time difference Δts which is the difference up to the sampling time t immediately after the first time T1 (FIG. 3).

[0045] Specifically, based on the linearly approximated voltage waveform shown in FIG. 3, the first time difference Δts is calculated by the following equation (1).

[0046]

Equation

[0047] Here, T sample is the sampling interval by the watt-hour meter 10, and Offset is the offset value of the voltage. V 0 is the voltage value obtained at the sampling time t 0 immediately before the first time T1. V 1 is the voltage value obtained at the sampling time t 1 immediately after the first time T1, that is, V 0It is sampling data that follows.

[0048] Similarly, the sampling time t immediately before the second time T2 N A second time difference Δte, which is the difference from the second time T2, is calculated (Fig. 4). Based on the waveform of the linearly approximated voltage shown in Fig. 4, the second time difference Δte is calculated by the following equation (2).

[0049]

Equation

[0050] Here, V N is the voltage value obtained at the sampling time t immediately before the second time T2 N , V N+1 is the voltage value obtained at the sampling time t immediately after the second time T2 N+1 , that is, the voltage value sampled following V N is.

[0051] Next, based on the first time difference Δts, the second time difference Δte, and the number N of sampling data for approximately one cycle centered on the selected one cycle, the offset period T cycle is obtained. The offset period T cycle can be calculated from the following equation (3).

Equation

[0052] Here, N is the number of sampling data from the sampling time t 1 immediately after the first time T1 to the sampling time t N immediately before the second time T2. That is, N is the number of sampling data corresponding to the offset period T 0 excluding the sampling data at the sampling time t N+1 and the sampling time t cycle .

[0053] Returning to FIG. 5, the control unit 12 obtains a set of transition data from the set of sampling data at a plurality of time points in a substantially one-cycle period extracted in step S504 (step S508). The transition data is a set of voltage values obtained when the sampling start time of the sampling data in the extracted substantially one-cycle period is shifted to the first time T1.

[0054] In calculating the set of transition data, first, the sampling time t immediately before the first time T1 0 to the sampling time t immediately after the second time T2 N+1 In the set of sampling data over the period, for a certain sampling time t n The sampling data V at n and the sampling time t n The next sampling time t of n+1 The sampling data V at n+1 An approximate expression for linearly approximating the line segment with both ends is obtained. n is an integer from 0 to N inclusive.

[0055] Next, based on the obtained approximate expression, the transition data is calculated with reference to the timing when the voltage becomes the offset value. Specifically, the control unit 12, based on the approximate expression, calculates the transition data V shifted by a predetermined time based on the offset period from a certain sampling time. sft The predetermined time to shift is obtained by subtracting the sampling time from the time for each first interval T sft For calculating the transition data V int1 The first interval T int1 Is the interval for calculating the transition data V sft Based on the offset period T cycle Based on. The sampling time t 0 From the sampling time t N+1 To the sampling time t int1 For each first interval T

[0056] Specifically, the set of transition data can be calculated from the following equation (4).

Equation

[0057] Here, t n is the n-th sampling time within a selected one cycle. V n is the voltage value measured at the sampling time t n . V n+1 is the voltage value measured at the next sampling time t n after t n+1 .

[0058] Also, V sft is transition data. The transition data is data obtained when the sampled voltage value is shifted by a predetermined shift time (T sft -t n ). V sft (m) is the m-th transition data among the transition data obtained every first interval T int1 (m is an integer from 1 to M). The first transition data V sft(1) is the voltage value at the first time T1 and serves as an offset value. By incrementing m from 1 to M one by one, a set of transition data including the transition data for each first interval T int1 over the offset period Tcycle can be calculated.

[0059] M is the number of transition data to be calculated and is an arbitrary integer. M can be determined by the value of the sampling frequency with respect to the power supply frequency, and it is ideal that at least one or more data are sampled between the transition data to be obtained. For this reason, "sampling frequency of the power supply frequency × offset period Tcycle" can be set as the upper limit. M is, for example, 80 in the case of a power supply frequency of 50 Hz and a sampling frequency of 8 kHz, which is 8 kHz × 20 ms / 2.

[0060] T sft is obtained by the following formula (5).

Equation

[0061] T cycle / M is the value obtained by dividing the offset period T cycle by M, and is the interval (the first interval T int1 ) for calculating the transition data Vsft. The first interval T int1 is based on the offset period T cycle . m is an integer from 1 to M inclusive.

[0062] T sft is the time at which the transition data V sft is calculated. That is, T sft is the time that is separated by the first interval T int1 from the starting point of the first time T1 corresponding to the intersection point CP1 where the voltage waveform obtained by linearly approximating two adjacent sampling data intersects the offset value. T sft (m) is the time of the m-th transition data. For example, the time T sft (1) corresponding to the first transition data is the first time T1 at which the line segment L1 (Figure 3) with the voltage values V 0 and V 1 at both ends intersects the offset value among the set of sampled data for approximately one period that has been extracted.

[0063] From the above, from equations (4) and (5), the transition data can be calculated for each first interval T int1 of the offset period starting from the first time T1 at which the voltage passes through the offset value, and a set of transition data can be calculated.

[0064] Alternatively, in another example, a set of transition data of the voltage may be calculated from the following equation (6).

Equation

[0065] Note that the transition data is for one or more offset periods T cycleIt can be calculated over. When calculating over j offset periods, since there are M transition data in one offset period, the number of transition data included in the set of transition data is M×j. At this time, m is an integer of 1 or more and M×j or less.

[0066] As described above, the voltage measured by the watt-hour meter 10 has been used as an example. Similarly to the voltage, for the current as well, a set of transition data can be calculated from the following formula (7) or formula (8).

Number

[0067]

Number

[0068] According to the present disclosure, a set of transition data can be obtained by calculation from the sampling data acquired in step S504. Therefore, without performing a change process of the sampling interval by the watt-hour meter 10 or an additional sampling process, a set of transition data synchronized with the offset period of the commercial power supply can be obtained from the sampling data of the voltage measured by the watt-hour meter 10.

[0069] Also, according to the present disclosure, a set of transition data based on the offset period can be obtained without considering the influence of fluctuations due to the commercial power supply frequency. Therefore, even in regions where the commercial power supply frequencies are different, any number of transition data synchronized with the offset period can be obtained without changing the hardware structure related to the sampling frequency of the watt-hour meter 10. That is, a frequency-free watt-hour meter 10 can be configured without changing the hardware structure.

[0070] Returning to FIG. 5, the process of calculating a set of additional data based on step S510 and step S512 will be described. The additional data is data obtained at a timing based on the offset period, and the first interval T int1 (Tcycle a second interval T shorter than (T int2 It is a set of data of voltage values for each. The additional data is the voltage value data in the first interval T int1 interpolated with the data in the second interval T int2 .

[0071] In step S510, the control unit 12 calculates a data set consisting of additional data based on the sampling data in a predetermined period. The data set consisting of additional data is, based on the offset value, a set of data of voltage values obtained every 1 / M of the first interval T int1 a second interval T int2 . The second interval T int2 is the value obtained by dividing the first interval T int1 (T cycle / M) by an integer i. i is an integer of 1 or more, for example, 3.

[0072] Note that the process shown in FIG. 5 is merely exemplary, and the order thereof may be changed, and processes may be added or deleted. For example, the data set consisting of additional data may be calculated from the set of transition data after calculating the transition data. That is, as shown in FIG. 5, after performing the transition data calculation process of step S508, the additional data calculation process of step S510 may be performed. Alternatively, the data set consisting of additional data may be directly calculated from the set of sampling data based on Expression (4) and the following Expression (9). That is, following step S506, the processes of step S508 and step 510 may be performed simultaneously.

[0073] The additional data is obtained by obtaining the time T int2 for each second interval T sft and introducing this into the above Expression (4).

[0074] [Number]

[0075] In Equation (9), by incrementing m by 1 from 1 to iM, the offset period T cycle for the second interval T int2 across can calculate a set of additional data at each interval. For example, when i is 3, additional data can be calculated at every one-third interval of the first interval T int1 , and thereby obtain a set of data that is three times the set of transition data calculated in step S508. That is, the set of transition data can be doubled. According to the present disclosure, doubling means increasing by an integer multiple.

[0076] Note that when an integer multiple of the second interval T int2 equals the first interval T int1 , the additional data will overlap with the transition data V sft . Therefore, the data obtained for each first interval T int1 can be excluded from the additional data. For example, in step S508, when the transition data V int1 (=T cycle / M) is obtained for each first interval T sft , it is not necessary to calculate the data for each first interval T int1 as additional data in step S510.

[0077] FIG. 6A illustrates a set of transition data obtained for each first interval T int1 according to an embodiment of the present disclosure. FIG. 6B shows an example of a set of transition data including a set of additional data obtained for each second interval T int2 where the set of transition data is doubled. The set of additional data shown in FIG. 6B exists at the midpoint of the first interval T int1 for each first interval T int1 . In this example, by including a set of data consisting of additional data in the set of data consisting of transition data, the set of transition data can be approximately doubled.

[0078] In one example, the sampling data of a predetermined period used to calculate the additional data in step S510 is the sampling data of the first period of the voltage corresponding to the set of transition data calculated in step S508. That is, the set of transition data and the set of additional data are calculated based on the sampling data of the same period.

[0079] In another example, the sampling data of a predetermined period used to calculate the additional data in step S510 is a second period different from the first period of the voltage corresponding to the set of transition data calculated in step S508. The control unit 12 calculates a set of transition data based on the sampling data of a certain predetermined first period, and calculates a set of additional data based on the sampling data of a period different from the first period. In this case, it is preferable that the shapes of the voltage waveforms (waveforms based on sampling data) of one period of the voltage corresponding to the set of transition data and the second period are substantially the same.

[0080] According to the present disclosure, without changing the sampling frequency, it is possible to increase the set of transition data representing the voltage values synchronized with the commercial power frequency. As a result, it is possible to obtain data that is a multiple (for example, three times) of the transition data obtained in the first interval T. int1 Thereby, from the digital data of the AC signal measured by the watt-hour meter 10, the time change of the AC signal can be expressed in more detail, and detailed analysis such as FFT analysis using the set of additional data becomes possible.

[0081] Furthermore, by analyzing the time change (signal waveform) of the AC signal based on the set of transition data including the set of additional data, detailed FFT analysis becomes possible, and thus it is possible to analyze which monitoring target device 30 is connected to the watt-hour meter 10.

[0082] <Modification Example> Modification examples of the embodiments described above are listed below.

[0083] 〔Configuration 1〕 The characteristic configuration of the method for achieving the above object is A method for obtaining a dataset of an AC signal measured by a wattmeter synchronized with the timing of the offset value, the AC signal measured by the wattmeter being sampled at the sampling interval (T sample ) of the wattmeter to obtain a set of sampling data (voltage value, current value), and calculating transition data (V sft , I sft ), the transition data being calculated from each sampling time (t 0 ~t n ) of the sampling data by shifting by a predetermined time respectively, and obtaining a transition dataset including the transition data, the predetermined time being based on the timing when the AC signal becomes the offset value.

[0084] According to the above characteristic configuration, based on the signal obtained from the wattmeter, a set of data synchronized with the timing when the input voltage or current becomes the offset value can be obtained.

[0085] 〔Configuration 2〕 Another characteristic configuration of the method according to the present invention is The step of calculating the transition data further includes extracting from the set of sampling data a set of sampling data included between a first time when an AC signal centered on a selected one cycle passes through the offset value and a second time when the next offset value is passed, sampling data immediately before the first time (T1), and sampling data immediately after the second time (T2).

[0086] 〔Configuration 3〕 Another characteristic configuration of the method according to the present invention is The step of calculating the transition data further includes: obtaining a first approximate straight line (L1) that connects two adjacent sampling data points that are increasing and sandwich the first time among the set of the sampled data that has been further extracted; obtaining a second approximate straight line (L2) that connects two adjacent sampling data points that are increasing and sandwich the second time among the set of the sampled data that has been extracted; calculating a first time difference (Δt 1 ) which is the difference between the first time and the sampling time (t s ) immediately after the first time; calculating a second time difference (Δt N ) which is the difference between the sampling time (t e ) immediately before the second time and the second time (T2); and calculating an offset period from the first time to the second time from the first time difference (Δt s ), the second time difference (Δt e ), and the sampling interval (T sample ).

[0087] 〔Configuration 4〕 Another characteristic configuration of the method according to the present invention is that the step of calculating the transition data further includes: obtaining an approximation formula for linearly approximating a line segment having, at both ends, the sampling data (V n ) at a first sampling time (t n ) and the sampling data (V n+1 ) at a second sampling time (t n+1 ) that is the next sampling time after the first sampling time in the set of the sampling data included between the first time and the second time; and calculating the transition data of the AC signal when shifted by the predetermined time from the first sampling time or the second sampling time from the approximation formula.

[0088] 〔Configuration 5〕 Another characteristic configuration of the method according to the present invention is that The transition data set includes transition data of a first interval based on an offset period from the first time to the second time, and further, at a predetermined offset period, from the transition data set, the first interval (T int1 ) shorter than the second interval (T int2 ) of additional data is calculated, and an additional data set including the additional data is obtained, and the additional data set is further included in the transition data set.

[0089] According to the above characteristic configuration, from the value of the signal obtained from the watt-hour meter, without changing the sampling frequency of the watt-hour meter, a signal with a frequency higher than the sampling frequency of the watt-hour meter can be obtained, and the number of signal data can be increased.

[0090] 〔Configuration 6〕 Another characteristic configuration of the method according to the present invention is In the step of calculating the additional data, further, at the predetermined offset period, in a set of sampling data included between a first time when the AC signal passes through an offset value and a second time when the next offset value is passed, an approximate formula for linearly approximating a line segment having sampling data at a first sampling time and sampling data at a second sampling time next to the first sampling time as both ends is obtained, and from the approximate formula, the additional data for each predetermined second interval (T int2 ) is calculated starting from the first sampling time or the second sampling time.

[0091] 〔Configuration 7〕 The characteristic configuration of the watt-hour meter for achieving the above object is An electricity meter for obtaining a dataset of an AC signal measured by an electricity meter synchronized with the timing of an offset value, including at least one processor, and when executed by the at least one processor, sampling the AC signal measured by the electricity meter at the sampling interval of the electricity meter to obtain a set of sampling data; calculating transition data, where the transition data is shifted by a predetermined time from each sampling time of the sampling data; and obtaining a transition dataset including the transition data, and the predetermined time is based on the timing when the AC signal becomes the offset value.

[0092] (Second Embodiment) FIG. 7 is a flowchart 700 showing an example of a process flow implemented in the electricity meter 10 according to the second embodiment of the present disclosure. The electricity meter 10 is configured as a low-voltage instrument installed in a general household or the like. Here, the low voltage is one of the power transmission voltage standards in the electrical equipment standards, referring to a voltage of 750 V or less in DC and 600 V or less in AC.

[0093] In the second embodiment, the electricity meter 10 measures the AC signal of each phase, which is the usage information of the monitoring target device 30 (FIG. 1), and samples each measured AC signal to generate sampling data. The electricity meter 10 performs a fast Fourier transform (FFT) on the generated sampling data to analyze the harmonics and calculates harmonic data from the analysis result. The electricity meter 10 records an event when the harmonic data satisfies a predetermined condition. Note that the sampling data for the fast Fourier transform may be transition data synchronized with the timing of the offset value described in the first embodiment. By using the transition data synchronized with the timing of the offset value, the harmonics can be analyzed more accurately.

[0094] The monitored device 30 can include electronic devices that consume current in proportion to the power supply voltage (such as incandescent lamps and heaters), and electronic devices that require a rectifier circuit (such as refrigerators and air conditioners). When an AC voltage is applied to an incandescent lamp, a heater, etc., the current flowing on the system side does not contain harmonics. On the other hand, digital devices that require a rectifier circuit, etc., generate harmonics in the current flowing on the system side. For this reason, the harmonic components included in the AC signal measured by the watt-hour meter 10 are not of one type, but can include various frequency components. As a result, although the power supply voltage waveform is a sine wave, the AC signals (voltage, current) measured by the watt-hour meter 10 include waveform distortion. According to the present disclosure, excessive waveform distortion can be detected from the AC signal measured by the watt-hour meter 10 and recorded as an event.

[0095] Hereinafter, with reference to FIG. 7, a flowchart 700 implemented in the system according to the second embodiment of the present disclosure will be described. The processes from the following step S702 to step S714 are repeatedly performed at each measurement interval (for example, 1 second).

[0096] In step S702, the watt-hour meter 10 acquires sampling data at a plurality of time points of the AC signal, which is the measured usage information. The AC signal may be a voltage or a current.

[0097] Next, in step S704, the watt-hour meter 10 performs a fast Fourier transform on the sampling data of each phase of the acquired AC signal, extracts the harmonic components included in each phase of the AC signal, and stores them in the storage device. The storage device is at least one of the memory or the storage of the watt-hour meter 10. A harmonic is a sine wave having a frequency that is an integer multiple of the fundamental frequency. When the fundamental wave is a commercial power supply frequency of 60 Hz, the frequency of the third harmonic is 180 Hz, and the frequency of the fifth harmonic is 300 Hz.

[0098] Alternatively, instead of sampling data, the power meter 10 may perform a fast Fourier transform on a data set consisting of transition data synchronized with the timing at which the AC signal becomes an offset value, or a data set including an additional data set in the transition data set. By using a data set including an additional data set in the transition data set, the number of samples can be increased, and harmonic analysis can be performed more accurately. When performing a fast Fourier transform on a data set consisting of transition data or a data set including an additional data set in the transition data set, the power meter 10 executes a series of processes shown in FIG. 7 (after step S704) after executing a series of processes for obtaining the transition data set shown in FIG. 5.

[0099] Next, in step S706, the power meter 10 calculates harmonic data from the harmonic components extracted from the measured AC signal. The harmonic data includes at least one of the total harmonic distortion rate of the AC signal or the harmonic content rate of a predetermined order. The configuration of the harmonic data can be arbitrarily determined.

[0100] The total harmonic distortion (THD) is also referred to as total harmonic distortion and is the ratio of the sum of the effective values of all harmonic components included in the AC signal to the effective value of the fundamental wave component, and can be calculated by the following formula (10).

[0101]

Equation

[0102] The harmonic content rate is the ratio of the effective value of harmonics of a predetermined order to the effective value of the fundamental wave, and the harmonic voltage content rate can be calculated by the following formula (11). The harmonic content rate of each order indicates the degree to which harmonic components are contained in the measured AC signal waveform. Although there is no upper limit to the order of the harmonic content rate, for the sake of simplifying the calculation, the upper limit can be set to the 25th order.

[0103] Harmonic voltage content rate = (Effective value of each harmonic voltage) / (Effective value of fundamental wave voltage) × 100 [%] (11)

[0104] Note that although formulas (10) and (11) are the calculation formulas for the total harmonic distortion rate and the harmonic content rate related to "voltage" respectively, they can be calculated in the same way for "current".

[0105] The watt-hour meter 10 stores the calculated harmonic data (total harmonic distortion rate, harmonic content rate) in the storage device. Regarding the harmonic content rate, the harmonic content rate of a predetermined order is stored in the storage device.

[0106] Next, the process proceeds to step S708. In step S708, the watt-hour meter 10 determines whether the harmonic data of the AC signal satisfies the first predetermined condition at predetermined intervals (for example, the measurement interval). The first predetermined condition is a condition for assigning an alert flag to the harmonic data. When the first predetermined condition is satisfied, the watt-hour meter 10 determines that excessive waveform distortion has been detected in the measured AC signal (current signal, voltage signal).

[0107] Here, the first predetermined condition regarding the total harmonic distortion rate is that the total harmonic distortion rate of the measured AC signal is equal to or higher than a threshold value Tha1. Alternatively, the first predetermined condition may be that the total harmonic distortion rate is equal to or higher than the threshold value Tha1 over a predetermined regulation period Tda1. By determining the regulation period Tda1, it is possible to detect the presence of continuous waveform distortion that is highly likely to cause harmonic interference. Also, by determining the regulation period Tda1, the power meter 10 can be prevented from frequently notifying the occurrence of an event indicating that waveform distortion has been detected. The threshold value Tha1 regarding the total harmonic distortion rate and the regulation period Tda1 of this threshold value can each be set independently. That is, regarding the total harmonic distortion rate, a total of four parameters (the threshold value and regulation period regarding current, and the threshold value and regulation period regarding voltage) can be set.

[0108] Furthermore, in step S708, the power meter 10 may determine whether the harmonic content satisfies the first predetermined condition in addition to or instead of the total harmonic distortion rate.

[0109] The first predetermined condition regarding the harmonic content is that the harmonic content of the measured AC signal is equal to or higher than a threshold value Tha2. Alternatively, the first predetermined condition may be that the harmonic content of the measured AC signal is equal to or higher than the threshold value Tha2 over a predetermined regulation period Tda2. By determining the regulation period Tda2, it is possible to detect the presence of continuous waveform distortion that is highly likely to cause harmonic interference. Also, by determining the regulation period Tda2, the power meter 10 can be prevented from frequently notifying the occurrence of an event indicating that waveform distortion has been detected. The threshold value Tha2 regarding the harmonic content and the regulation period Tda2 can each be set independently. That is, regarding the harmonic content, a total of four parameters (the threshold value and regulation period regarding current, and the threshold value and regulation period regarding voltage) can be set for each order.

[0110] Hereinafter, the combination of the threshold Tha1 of the total distortion rate and the specified period Tda1 (Table 1) and the combination of the threshold Tha2 of the harmonic distortion rate and the specified period Tda2 (Table 2) are exemplified.

[0111]

Table 1

[0112] As exemplified in Table 1, the first predetermined condition regarding the total harmonic distortion rate is that the total harmonic distortion rate of the measured AC signal (current, voltage) is 5% or more of the threshold value over a specified period of 10 seconds. The threshold Tha1 of the total harmonic distortion rate and the specified period Tda1 can be set in advance in the watt-hour meter 10 during the manufacture of the watt-hour meter 10, or the setting can be changed after the installation of the watt-hour meter 10.

[0113]

Table 2

[0114] As exemplified in Table 2, the first predetermined condition regarding the harmonic content rate is that the 5th harmonic content rate of the measured AC signal (current, voltage) is 5% or more of the threshold value over a specified period of 5 seconds. The threshold Tha2 of the harmonic content rate and the specified period Tda2 can be determined separately for each harmonic order. The plurality of thresholds Tha2 and specified periods Tda2 corresponding to the harmonic content rates of a plurality of orders may be different values or the same values. In the example of Table 2, the threshold of the harmonic content rate is set with 5% as the upper limit, with the harmonic content rate of a lower order being higher and the harmonic content rate of a higher order being lower. These thresholds Tha2 of the harmonic content rate and the specified period Tda2 can be set in advance in the watt-hour meter 10 during the manufacture of the watt-hour meter 10, or the setting can be changed after the installation of the watt-hour meter 10.

[0115] When the harmonic data regarding the harmonics included in the measured AC signal satisfies a first predetermined condition set based on various parameters exemplified in Table 1 and Table 2, that is, when the answer is "Yes" in step S708, the process proceeds to the next step S710. In one example, when at least one of the conditions that the total harmonic distortion rate of the measured AC signal (current, voltage) is equal to or higher than the threshold Tha1 over the specified period Tda1 shown in Table 1, or that the harmonic content rate is equal to or higher than the threshold Tha2 over the specified period Tda2 shown in Table 2 is satisfied, the process proceeds to step S710. Also, when the harmonic content rate of a certain order is equal to or higher than the threshold Tha2, or when the harmonic content rates of a plurality of orders are each equal to or higher than the threshold Tha2, the process may proceed to step S710.

[0116] Next, in step S710, the watt-hour meter 10 records various flags in the history file 800 at each measurement interval. Also, based on this history file 800, the watt-hour meter 10 records an event (occurrence event) indicating that there is excessive waveform distortion in the measured AC signal in the event file 900. The event file 900 can record the state changes (occurrence events, recovery events) of the measured AC signal. The details of the history file 800 will be described with reference to FIG. 8, and the details of the event file 900 will be described with reference to FIG. 9. Further, in step S710, the watt-hour meter 10 may display the occurrence of the event on a display (not shown) or transmit the detection state of the event to the upper system via the communication control unit 16. The upper system is a remote monitoring center system that monitors watt-hour data and the like when the watt-hour meter 10 is a smart meter.

[0117] On the other hand, when the harmonic data does not satisfy the first predetermined condition, that is, when the answer is "No" in step S708, the process proceeds to step S712.

[0118] FIG. 8 shows an example of a part of a history file 800 stored in the storage device of the watt-hour meter 10 according to an embodiment of the present disclosure. The watt-hour meter 10 assigns an alert flag for each order of the total harmonic distortion rate or the harmonic content rate when at least one of the total harmonic distortion rate of the measured AC signal and the harmonic content rate satisfies a first predetermined condition. Further, the watt-hour meter 10 sequentially records the alert flag in the history file 800 together with the measurement date and time over the measurement period.

[0119] In the history file 800, when the total harmonic distortion rate is equal to or higher than a threshold Tha1 at a certain date and time, or when the harmonic content rate of each order is equal to or higher than a threshold Tha2, the first alert flag "Y" is recorded. On the other hand, when the total harmonic distortion rate or the harmonic content rate of each order is less than the threshold value, "N" is recorded respectively. In FIG. 8, THD(V) is the total harmonic distortion rate of the voltage, and THD(I) is the total harmonic distortion rate of the current.

[0120] Further, in the history file 800, when the total harmonic distortion rate is equal to or higher than the threshold Tha1 over a specified period Tda1, or when the harmonic content rate of each order is equal to or higher than the threshold Tha2 over a specified period Tda2, the second alert flag "1" is recorded. On the other hand, when the period during which the harmonic content rate exceeds the threshold is less than the specified period, "0" is recorded.

[0121] In the example of the history file 800 in FIG. 8, since the fifth-order harmonic current content rate is equal to or higher than the threshold Tha2 for 5 seconds or more (from 10:20:01 to 10:20:07) of the specified period Tda2, the second alert flag "1" is assigned when the specified period Tda2 elapses (10:20:05). On the other hand, since the fifth-order harmonic voltage content rate exceeds the threshold for less than the specified period Tda2 (only at 10:20:02), the second alert flag is not assigned.

[0122] The history file 800 can record when and which harmonic data has been above the thresholds (Tha1, Tha2) for what period of time by recording various alert flags together with the date and time. Note that the composition of the harmonic data can be arbitrarily determined, and alert flags regarding desired types of harmonic data can be recorded in the history file 800.

[0123] FIG. 9 shows an example of a part of an event file 900 stored in the storage device of the watt-hour meter 10 according to an embodiment of the present disclosure. The event file 900 is generated based on the history file 800 as described above. In the event file 900, it is possible to record the time when the second alert flag changes and the type of harmonic data for which the second alert flag has changed.

[0124] In step S710, further, the watt-hour meter 10 refers to the history file 800 and records an event (occurrence event) indicating that there is continuous excessive waveform distortion in the measured AC signal in the event file 900. The change of the second alert flag from "0" to "1" in FIG. 8 indicates that continuous excessive distortion has been detected in the measured AC signal. In the example of the history file 800 in FIG. 8, from 10:20:04 to 10:20:05, the second alert flag for the total harmonic distortion rate (voltage) changes from "0" to "1", the second alert flag for the total harmonic distortion rate (current) changes from "0" to "1", and the second alert flag for the 5th harmonic current content rate changes from "0" to "1". Therefore, the watt-hour meter 10 records the time point of 10:20:05 when the second alert flag changes to "1" as occurrence event "1" in the event file 900 (FIG. 9) respectively.

[0125] When the power meter 10 is a smart meter, it can notify the server of the upper system of the occurrence event specified based on the second alert flag via a communication network (not shown). This occurrence event includes at least one of the types of each harmonic data for which there has been a state change in the second alert flag, the date and time when the state change was detected, and an alert indicating the occurrence of the event. The power meter 10 may transmit the event file 900 itself that records the event history to the upper system. The power meter 10 can notify the server of the upper system of the occurrence event actively, periodically, or in response to a request from the upper system every time a state change in the second alert flag is detected.

[0126] According to the present disclosure, the server of the upper system can receive an alert based on the occurrence event actively notified from the power meter 10 side without inquiring each individual power meter 10 in the pipeline. Thereby, the upper system can periodically or at any time refer to the alert transmitted from the power meter 10 and identify the power meter 10 with a high possibility of a harmonic failure.

[0127] Returning to FIG. 7, in step S712, the power meter 10 determines whether the harmonic data of the AC signal satisfies a second predetermined condition. If the second predetermined condition is satisfied, the power meter 10 determines that no waveform distortion has been detected from the measured AC signal (current signal, voltage signal). The second predetermined condition is a condition for releasing the second alert flag assigned to the harmonic data.

[0128] Here, the second predetermined condition regarding the total harmonic distortion rate is that the total harmonic distortion rate is less than the threshold value Thr1 over a predetermined regulation period Tdr1. Also, the second predetermined condition regarding the harmonic content rate is that the harmonic content rate is less than the threshold value Thr2 over a predetermined regulation period Tdr2. In step S710, once the second alert flag is given, the total harmonic distortion rate or the harmonic content rate will not have the second alert flag removed unless they are less than the threshold values (Thr1, Thr2) over the predetermined regulation periods (Tdr1, Tdr2), respectively.

[0129] Note that the various parameters (Tha1, Tda1, Tha2, Tda2) based on the first predetermined condition may be the same as or different from the various parameters (Thr1, Tdr1, Thr2, Tdr2) based on the second predetermined condition, respectively.

[0130] In step S712, when it is determined that the harmonic data satisfies the second predetermined condition, that is, when the answer is "Yes" in step S712, the process proceeds to step S714. On the other hand, when the answer is "No" in step S712, the process ends.

[0131] In step S714, the wattmeter 10 records various flags in the history file 800 at each measurement interval. Also, based on this history file 800, the wattmeter 10 records an event (recovery event) indicating that the waveform distortion has disappeared in the event file 900 for an AC signal that has once been determined to have waveform distortion.

[0132] First, when the total harmonic distortion rate is less than the threshold value Thr1 over the regulation period Tdr1, the wattmeter 10 records a recovery flag "0" indicating a recovery state in the history file 800. In the non-recovery state, the second alert flag "1" is maintained. Also, when the harmonic content rate is less than the threshold value Thr2 over the regulation period Tdr2, the wattmeter 10 records a recovery flag "0" indicating a recovery state in the history file 800. In the non-recovery state, the second alert flag "1" is maintained.

[0133] In the example of FIG. 8, since the seventh harmonic voltage content rate is less than the threshold value over 5 seconds or more (from 10:20:01 to 10:20:06) of the specified period Tdr2, when the specified period Tdr2 elapses (10:20:05), a return flag "0" is assigned. On the other hand, since the seventh harmonic current content rate becomes less than the threshold value in less than the specified period Tdr2 (10:20:02 - 10:20:05), the return flag is not assigned and the second alert flag remains "1".

[0134] In step S714, further, the watt-hour meter 10 refers to the history file 800 and records an event (return event) indicating that no continuous excessive waveform distortion has been detected in the measured AC signal in the event file 900. The change of the second alert flag from "1" to "0" in FIG. 8 indicates that no continuous excessive distortion has been detected in the measured AC signal. In the example of the history file 800 in FIG. 8, from 10:20:04 to 10:20:05, the second alert flag of the seventh harmonic voltage content rate changes from "1" to "0". Therefore, the watt-hour meter 10 records the time point of 10:20:05 when the second alert flag changes to "0" in the event file 900 (FIG. 9) as the return event "0".

[0135] When the watt-hour meter 10 is a smart meter, it can notify the server of the upper system of the return event specified based on the second alert flag via a communication network (not shown). This return event includes at least one of the type of harmonic data with a state change in the second alert flag, the date and time when the state change is detected, and an alert indicating the occurrence of the return event. The watt-hour meter 10 can notify the server of the upper system of the return event actively, periodically, or in response to a request from the upper system every time a state change of the second alert flag is detected.

[0136] According to the present disclosure, when the AC signal measured by the watt-hour meter 10 includes excessive waveform distortion, the occurrence event is recorded in the event file 900. On the other hand, when the AC signal does not include excessive waveform distortion over a specified period even after the alert flag is once given, the recovery event is recorded in the event file 900.

[0137] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

Description of Reference Numerals

[0138] T cycle … offset period T1… first time T2… second time t n … sampling time 10… watt-hour meter 12… control unit 14… terminal unit 16… communication control unit 30… monitored device Tha1… threshold of total harmonic distortion rate associated with alert flag assignment Tha2… threshold of harmonic content rate associated with alert flag assignment Tda1… specified period during which the total harmonic distortion rate becomes equal to or higher than the threshold Tha1 Tda2… specified period during which the harmonic content rate becomes equal to or higher than the threshold Tha2 Thr1… threshold of total harmonic distortion rate associated with alert flag cancellation Thr2… threshold of harmonic content rate associated with alert flag cancellation Tdr1… specified period during which the total harmonic distortion rate becomes less than the threshold Thr1 Tdr2… specified period during which the harmonic content rate becomes less than the threshold Thr2 800… history file 900… event file

Claims

1. 1. A method performed in an energy meter, comprising: obtaining a set of sampling data obtained by sampling the AC signal measured by the watthour meter; Calculating harmonic data relating to harmonics contained in the AC signal based on the acquired set of sampling data; recording an event indicating that there is a waveform distortion in the AC signal when the harmonic data satisfies a first condition; when it is determined that the AC signal has a waveform distortion and the harmonic data satisfies a second condition, recording an event indicating that the AC signal does not have the waveform distortion; A method comprising:

2. 1. An energy meter including at least one processor, the energy meter comprising: obtaining a set of sampling data obtained by sampling the AC signal measured by the watthour meter; Calculating harmonic data relating to harmonics contained in the AC signal based on the acquired set of sampling data; recording an event indicating that there is a waveform distortion in the AC signal when the harmonic data satisfies a first condition; when it is determined that the AC signal has a waveform distortion and the harmonic data satisfies a second condition, recording an event indicating that the AC signal does not have the waveform distortion; An electricity meter that performs the following:

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