JP2021071336A - Excitation inrush current discrimination device and discrimination method - Google Patents

Abstract

To provide a device and method with which it is possible to discriminate an excitation inrush current with higher accuracy than before.SOLUTION: In an excitation inrush current discrimination device 200, a storage unit 202 stores, as first time-series data, the current value of a detection current detected every data sampling cycle T1. A frequency f1 that corresponds to the data sampling cycle T1 is 4n times a rated frequency f0 of fundamental wave of the detection current (n=integer of 1 or greater). A data generation unit 204 successively adds a current value at a time preceding the sampling time by 2n times the data sampling cycle to a current value at each sampling time of the first time-series data, and thereby generates second time-series data. A discrimination unit 206 discriminates an excitation inrush current on the basis of the ratio of the current amplitude of the second time-series data to the current amplitude based on the first time-series data.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to a discriminating device and a discriminating method for an exciting inrush current.

The inventor of the present application uses three consecutive voltage rotation vectors (or current rotation vectors) in time series as a method for measuring the amount of electricity by utilizing the symmetry of the amount of electricity (that is, AC voltage or AC current) in the power system. ) Has been proposed as a method using a gauge voltage group (or gauge current group). Further, the inventor of the present application creates a gauge difference voltage group (or gauge difference current group) composed of a difference vector between adjacent vectors among four voltage rotation vectors (or current rotation vectors) that are continuous in time series. I have proposed a method to use.

Specifically, Japanese Patent No. 5214074 (Patent Document 1) discloses a method of calculating various invariants by calculating the product between the elements constituting the gauge voltage group or the gauge differential voltage group. There is.

The inventor of the present application further discloses a method of detecting an exciting inrush current at high speed by using the gauge current group and the gauge difference current group described above. Specifically, the method disclosed in Japanese Patent No. 6351537 (Patent Document 2) calculates the ratio between the amplitude of the direct current component and the amplitude of the fundamental wave component based on the input alternating current. The fundamental wave amplitude is calculated using the instantaneous value of the gauge difference current group, and the DC amplitude is calculated using the instantaneous value of the gauge current group.

Japanese Patent No. 5214074 Japanese Patent No. 6351537

In the case of the method described in Patent Document 2 above, since the exciting inrush current is determined based on the ratio of the DC amplitude and the fundamental wave amplitude, the exciting inrush current is misjudged due to the influence of the DC current at the time of power system failure. There is a risk of separating. The present disclosure has been made in consideration of the above problems, and an object of the present disclosure is to provide an apparatus and a method capable of discriminating an exciting inrush current with higher accuracy than before.

The excitation inrush current discriminating device according to one embodiment includes a storage unit, a data generation unit, a first amplitude calculation unit, a second amplitude calculation unit, and a discriminating unit. The storage unit stores the instantaneous value of the detected current detected for each data sampling cycle as the first time series data. The data generation unit includes the current instantaneous value of each sampling time of the first time-series data in the detected current by adding the current instantaneous value of the time preceding the sampling time by the first time interval. A second time series data representing the current component to be generated is generated. Here, the first time interval is set to the value closest to the reciprocal of twice the rated frequency of the fundamental wave of the detected current among the integral multiples of the data sampling period. The first amplitude calculation unit calculates the amplitude of the detected current based on the first time series data. The second amplitude calculation unit calculates the amplitude of the current component based on the second time series data. The discriminating unit determines whether or not the ratio of the amplitude of the current component to the amplitude of the detected current exceeds the threshold value.

According to the above embodiment, the exciting inrush current is determined based on the ratio of the current amplitude based on the first time series data and the current amplitude based on the second time series data, so that the excitation inrush current is more accurate than before. It is possible to distinguish.

It is a figure for demonstrating the gauge current group on a complex plane. It is a block diagram which shows an example of the hardware composition of the exciting inrush current discriminating device. It is a block diagram which shows the functional structure of the discriminator of an exciting inrush current. It is a flowchart which shows the procedure of discriminating the excitation inrush current. It is a figure which shows the simulation result of case 1. It is a figure which shows the time change of the even wave amplitude ratio calculated based on the amplitude calculation result of FIG. It is a figure which shows the simulation result of case 2. It is a figure which shows the time change of the even wave amplitude ratio calculated based on the amplitude calculation result of FIG.

Hereinafter, embodiments will be described in detail with reference to the drawings. The same or corresponding parts are designated by the same reference numerals, and the description thereof will not be repeated.

Embodiment 1.
[Calculation method of current amplitude]
First, a method for calculating the current amplitude used in the present embodiment will be described. This amplitude calculation method is based on a gauge current group on the complex plane. Basically, the amplitude can be calculated by calculating the sum of the squares of the instantaneous current values, so that the current amplitude can be calculated at high speed and with high accuracy under any conditions.

FIG. 1 is a diagram for explaining a gauge current group on a complex plane. As shown in FIG. 1, the gauge current group on the complex plane is divided by three current rotation vectors i ₁ (t + T), i ₁ (t), and i ₁ (t−T) having different time intervals for each gauge sampling period T. It is composed. In the present disclosure, the current vector on the complex plane is defined as a rotation vector that rotates counterclockwise with the passage of time. Specifically, the gauge current group can be expressed as the following equation (1).

In the above equation (1), I is the current amplitude, T is the gauge sampling period (also referred to as the second time interval), α is the gauge rotation phase angle corresponding to T, and φ ₀ is the central phase angle of the gauge current group. .. FIG. 1 shows the case where α = 90 °. Center phase angle phi ₀ varies periodically with time.

By expanding each current vector of the above equation (1) on the real number axis, the following equation (2) is obtained. In the following equation (2), Re [A] represents the real part of A.

_{Using the instantaneous current values i 01} , i ₊₁ and i _-1 of the above equation (2), the _{gauge current Ig} is defined according to the following equation (3). That is, the three instantaneous current values detected for each gauge sampling period T are set to i _{+ 1} , i ₀₁ , and i _-1 from the newest in time. In this case, the gauge current _{I g is} equal to the square and the square root of the sum obtained by adding the square of the square of averaging the _{i 01} of _{i -1} of _{i +1.}

Substituting the above equation (2) into the above equation (3) gives the following equation (4A). In the following equation (4A), f _C is referred to as a frequency coefficient and is calculated as in the following equation (4B).

The above equation (4A) indicates that the gauge current _Ig oscillates at a frequency twice that of the fundamental wave of the input alternating current. Accordingly, the window length half period of the fundamental wave of the input AC current, by performing moving average processing on the gauge current I _g, the square root of the portion of the equation (4A) approximates to 1. Thereby, the current amplitude I can be calculated.

When α = 90 °, the square root portion of the above equation (4A) is equal to 1, so the gauge current _Ig is equal to the current amplitude I. However, since the actual frequency and the rated frequency are usually different, the gauge sampling period α is not exactly 90 °. In such a case, the fluctuation of the actual frequency can be automatically compensated by performing the moving average processing.

Specifically, the number of sampling points for one period of the fundamental wave and N _0, if the gauge current calculated for each of k = 1 to N ₀ and I _gk, alternating current amplitude following formula (5) Can be calculated as By calculating the moving average value, the frequency can be calculated even if the frequency of the input AC current deviates from the rated frequency.

The geometric interpretation of the above equation (3) will be supplemented below. The gauge rotation phase angle α is 90 °. As shown in FIG. 1, three right triangles ΔODA, ΔBEO, and ΔOFC are configured. These three right triangles are similar. That is, it is expressed as the following equation (6).

By applying the Pythagorean theorem to the right triangles ΔODA and ΔOFC, it can be seen that the following relational expressions (7) hold, respectively.

Substituting OA = OC = _Ig , OD = i _{+ 1} , AD = CF = i ₀₁ , and OF = i _-1 in the above equation (7), the above equation (3) is obtained.

[Configuration of excitation inrush current discrimination device]
Hereinafter, the configuration of the excitation inrush current discriminating device will be described. First, an example of the hardware configuration will be described, and then the functional configuration of the discriminating device will be described.

FIG. 2 is a block diagram showing an example of the hardware configuration of the exciting inrush current discriminating device. With reference to FIG. 2, the exciting inrush current discriminating device 100 includes an analog input circuit 101, an arithmetic circuit 110, and an I / O (Input and Output) circuit 120.

The analog input circuit 101 includes an input transformer 102, an analog filter (AF: Analog Filter) 103, a sample hold circuit (S / H: Sample Hold Circuit) 104, a multiplexer (MPX: Multiplexer) 105, and A / D conversion. A device 106 and a DMA (Direct Memory Access) controller 107 are included.

The input transformer 102 includes an auxiliary transformer for each of the input channels CH1 and CH2. A current signal is input to the input transformer 102 from the current transformer of the power system. Each auxiliary transformer converts the current signal into a voltage level signal suitable for signal processing in the analog input circuit 101 and the arithmetic circuit 110. The analog filter 103 and the sample hold circuit 104 are provided for each of the input signal channels CH1 to CHn.

Each analog filter 103 is a low-pass filter provided for removing a folding error during A / D conversion. Each sample hold circuit 104 samples and holds a signal that has passed through the corresponding analog filter 103 at a predetermined sampling frequency. The sampling frequency is, for example, 4800 Hz. Normally, the sampling frequency of the sample hold circuit 104 is higher than the data sampling frequency.

The multiplexer 105 sequentially selects the voltage signals held in each sample hold circuit 104. The A / D converter 106 converts the signal selected by the multiplexer 105 into a digital value.

The DMA controller 107 transfers the digital data output from the A / D converter 106 to the RAM 113.

The arithmetic circuit 110 includes a CPU (Central Processing Unit) 111, a RAM (Random Access Memory) 113, a ROM (Read Only Memory) 114, a memory 112, and a bus 115 connecting them. The CPU 111 controls the overall operation of the excitation inrush current discriminating device 100 by operating according to the program. The RAM 113 and ROM 114 are used as the main memory of the CPU 111. By using a non-volatile memory such as a flash memory, the memory 112 can store a program, a set value for signal processing, and the like.

The arithmetic circuit 110 may be configured by some kind of electronic circuit, and is not limited to the example of FIG. For example, the arithmetic circuit 110 may include a plurality of CPUs. Further, the arithmetic circuit 110 may be composed of at least one ASIC (Application Specific Integrated Circuit) or at least one FPGA (Field Programmable Gate Array) instead of a processor such as a CPU. Good. Alternatively, the arithmetic circuit 110 may be composed of any combination of a processor, an ASIC, and an FPGA.

The I / O circuit 120 includes a communication circuit 121, a digital input (D / I: Digital Input) circuit 122, and a digital output (D / O: Digital Output) circuit 123. The communication circuit 121, the digital input circuit 122, and the digital output circuit 123 are interface circuits for communicating between the CPU 111 and the external device.

FIG. 3 is a block diagram showing a functional configuration of an exciting inrush current discriminating device. As shown in FIG. 3, the exciting inrush current discriminating device 200 includes an input unit 201 for instantaneous current value data, a storage unit 202, an arithmetic processing unit 210, and a signal output unit 207.

The input unit 201 receives a current detection signal from a current transformer (CT: Current Transformer) installed on the line 11 of the power system 10. A transformer 12 is connected to the line 11. When a current is applied to the transformer 12, a significantly large exciting current may flow. This large current is called the excitation inrush current.

The input unit 201 converts the time-series instantaneous current value data obtained by sampling the current detection signal into digital current instantaneous value data. The storage unit 202 stores the current instantaneous value data after digital conversion. The arithmetic processing unit 210 determines the exciting inrush current based on the digital instantaneous current value data. The signal output unit 207 outputs a signal based on the determination result of the exciting inrush current to the outside.

More specifically, the arithmetic processing unit 210 includes a total current amplitude calculation unit 203, an even-wave pair current generation data generation unit 204, an even-wave pair current amplitude calculation unit 205, and an excitation inrush current discrimination unit. Includes 206 and. The functions of these components will be described later with reference to the flowchart of FIG.

As an example, the input unit 201 corresponds to the analog input circuit 101 of FIG. The storage unit 202 corresponds to the non-volatile memory 112 or RAM 113 of FIG. The arithmetic processing unit 210 corresponds to the CPU 111 of FIG. The function of the arithmetic processing unit 210 is realized by the CPU 111 executing an instruction according to a program. The signal output unit 207 corresponds to the communication circuit 121 or the digital output circuit 123 of FIG.

[Operation of excitation inrush current discriminator]
FIG. 4 is a flowchart showing a procedure for determining the exciting inrush current. Hereinafter, the operation of the exciting inrush current discriminating device 200 will be described with reference to FIGS. 3 and 4.

In step S101 of FIG. 4, the input unit 201 acquires the instantaneous current value data by sampling the current signal detected by the current transformer CT. The input unit 201 converts the acquired analog current instantaneous value data into digital current instantaneous value data. By this digital conversion, time-series instantaneous current value data (first time-series data) as shown in the following (8) can be obtained.

Current instantaneous values _{i 1, i 2, i 3} , ... from more temporally subsequent (i.e., from more new time) aligned and, of the alternating current detected for each data sampling period T ₁ It is composed of instantaneous current values. The digitally converted instantaneous current value data is stored in the storage unit 202.

Here, the reciprocal of the data sampling period T ₁ is referred to as the data sampling frequency f ₁ . _{Let f 0 be} the rated frequency of the detected alternating current fundamental wave, and let _{T 0} be the period of the fundamental wave, which is the reciprocal of the rated frequency. In the following, for the sake of simplicity, a case where the data sampling frequency f ₁ is 12 times the rated frequency f _{0 (f 1} = 12 × f ₀ ) will be described as an example. Therefore, if the actual frequency of the fundamental wave is equal to the rated frequency, the phase angle corresponding to the data sampling period T ₁ is 30 degrees. In general, the data sampling frequency f ₁ does not have to be an integral multiple of the rated frequency f _0.

In the next step S102, the amplitude calculation unit 203 calculates the amplitude of the detected current based on the above-mentioned instantaneous current value data. Here, the detected instantaneous current value data includes all current components such as a DC component and a harmonic component in addition to the fundamental wave component. The alternating current detected in this sense is called the total current.

For the calculation of the amplitude of the total current, the formula _{for calculating the gauge current Ig in} the above formula (3) is used. The gauge sampling period T (also referred to as the second time interval) is an integral multiple of _{the data sampling period T 1 and is the reciprocal of 4 times the rated frequency f 0} of the fundamental wave (that is, _{1 of the period T 0} of the fundamental wave). It is desirable to set the value closest to (4 times). Therefore, when the actual frequency of the fundamental wave is equal to the rated frequency, it is desirable that the gauge rotation phase angle α is set to a value equal to or as close to 90 degrees as possible. However, as explained with reference to the equation (4A), since the vibration component of the gauge current Ig is removed by the moving average processing, the gauge rotation phase angle α does not necessarily have to be set to a value close to 90 degrees. ..

_{Specifically, the amplitude calculation unit 203 extracts three current instantaneous values i + 1} , i ₀₁ , and i _-1 separated from each other by the gauge sampling period T from the current instantaneous value data, and extracts the three current instantaneous values. Is used to calculate the amplitude of the alternating current according to equation (3). In the case of the instantaneous current value data shown in (8) above, for example, the instantaneous current values i ₁ , i ₄ , and i ₇ are extracted. Then, the amplitude calculation unit 203 calculates the gauge current I _mg according to the following equation (9).

Furthermore, the amplitude calculating unit 203 calculates the amplitude I _m of the total current by performing a moving average process on the gauge current I _mg. Specifically, the number of sampling points for one period of the fundamental wave and N _0, a gauge current calculated for each of k = 1 to N ₀ if I _mk, amplitude I _m of the total current, the following equation It is represented by (10).

In the next step S103, the data generation unit 204 has a time interval (also referred to as a first time interval) in which the current instantaneous value at each sampling time of the current instantaneous value data is substantially equal to the half period of the fundamental wave from the sampling time. The second current instantaneous value data (second time series data) is generated by adding the current instantaneous values of the previous time respectively. The first time interval described above is the _{reciprocal of twice the rated frequency f 0} of the fundamental wave (that is, 1/2 times _{the period T 0} of the fundamental wave) among the integer multiples of _{the data sampling cycle T 1.} Set to a close value. Specifically, in the case of the time-series instantaneous current value data shown in (8) above, the second instantaneous current value data i _e1 , i _e2 , ... Are generated by the arithmetic operation shown in the following equation (11). ..

When the actual frequency of the fundamental wave is equal to the rated frequency, the above arithmetic operation is the same as adding the instantaneous current values that are approximately 180 ° out of phase with each other. Therefore, the odd-numbered harmonic component is removed by the above arithmetic operation, and the DC component and the even-numbered harmonic component are extracted from the alternating current. In this disclosure, the extracted current component is referred to as an even wave pair current.

In the next step S104, the amplitude calculation unit 205 calculates the amplitude of the even-wave pair current based on the above-mentioned second instantaneous current value data. This amplitude calculation method is the same as that described with reference to Eqs. (9) and (10). Specifically, the amplitude calculating unit 205, the second current instantaneous values _{i e1, i e2,} ... from extracts gauge sampling period T only separated three current instantaneous value _{i e1, i e4, i e7} each other _{, The gauge current Ieg} is calculated according to the following equation (12).

Further, the amplitude calculation unit 205 _{obtains the amplitude Ie} of the even-wave pair current by _{performing a moving average process on the gauge current Ieg.} Specifically, the number of sampling points for one period of the fundamental wave and N _0, a gauge current calculated for each of k = 1 to N ₀ if I _ek, amplitude I _e of the even waves pair currents, It is expressed by the following equation (13).

In the next step S105, determination unit 206, as shown in the following equation (14), calculating the ratio _{k Inrush} of even waves pair current _{I e} of the total current to the amplitude _{I m.} In this disclosure, the ratio _kinrush may be referred to as an even wave amplitude ratio.

The discriminating unit 206 determines whether or not the even-wave amplitude ratio k _inrush is larger than the threshold value. When the even wave amplitude ratio k _inrush is larger than the threshold value, the discriminating unit 206 determines that the detected current is an exciting inrush current. The discriminating unit 206 determines that the detected current is not an exciting inrush current when the even-wave amplitude ratio k _{inrush is equal to or less than the threshold value.} For example, 1.4 is selected as the threshold value.

In the next step S106, the signal output unit 207 outputs a trip signal to, for example, a circuit breaker in order to disconnect the transformer 12 from the power system 10 when the exciting inrush current is determined.

In the next step S107, if the discriminator 200 has not received the end command (NO in step S107), the process returns to step S101. When the discriminator 200 receives the end command (YES in step S107), the discriminating device 200 ends the frequency measurement process.

[Technical effect]
Hereinafter, the merits of the above-mentioned excitation inrush current determination method will be described. In the transformer protection relay, a second wave-tuning lock method is generally adopted in which it is determined that an exciting inrush current is generated when the second wave-tuning content is equal to or higher than the threshold value and the operation of the transformer is locked. However, as the energization angles of the exciting inrush current increase to 60 °, 90 °, and 120 °, the second wave-tuning content decreases to 27.5%, 21%, and 9%, respectively. Therefore, for example, when the second wave control content of 10% is set as the determination threshold value, the exciting inrush current with an energization angle of 120 ° cannot be detected. As a countermeasure, a method of lowering the determination threshold value can be considered, but if this is done, it becomes difficult to distinguish between the fault current and the inrush current because the fault current also includes a certain amount of the second wave tuning current. The energization angle represents the time zone width in which the current is flowing in one cycle of the excitation inrush current waveform by the electric angle.

According to the method for determining the exciting inrush current of the present embodiment, the even wave pair current including the DC component and the even wave tuning component is extracted, and the exciting inrush current is excited based on the ratio of the amplitude of the even wave pair current to the total current amplitude. The current is determined. Therefore, the discrimination method of the present disclosure can discriminate the excitation inrush current with higher accuracy than the second wave-tuning lock method using the content rate of the second wave-tuning current as a determination standard.

In addition, the method described in Patent Document 2 described above has the following problems. First, when the actual frequency of the power system deviates from the rated frequency, an error occurs in the amplitude calculation result. Secondly, the amplitude calculation may become impossible due to the influence of voltage flicker and harmonic noise. Thirdly, there is a risk of erroneous determination due to the influence of the fault current when the power system fails.

Regarding the first and second problems described above, in the case of the present embodiment, the gauge currents (equations (3), (9), (12)) used for the amplitude calculation are instantaneous current values (or two). It is calculated by adding the square of the sum of the instantaneous current values of). Therefore, the calculation is possible even when the alternating current contains voltage flicker and harmonic noise. Furthermore, since the final current amplitude is calculated by applying mobile averaging processing to the gauge current, even if the actual frequency of the fundamental wave of the alternating current deviates from the rated frequency, the frequency will automatically fluctuate. Will be compensated.

Regarding the third problem described above, in the case of the present embodiment, the exciting inrush current is determined in consideration of the even-numbered wave-tuning component in addition to the DC component. Therefore, the technique of the present embodiment can discriminate the exciting inrush current with higher accuracy than the conventional technique.

[simulation result]
Hereinafter, the effectiveness of the above-mentioned excitation inrush current discrimination method will be demonstrated by showing the numerical simulation results.

(Case 1)
When a failure occurs in the power system, the failure current flowing in the power system includes an attenuated DC component and an even wave tuning component. In Case 1, it was confirmed that the exciting inrush current was not discriminated by these fault currents. Table 1 shows the parameters of the exciting inrush current discriminating device 200.

It is assumed that the time when the failure occurs is t = 0 [S: sec], and the total current after the failure occurs is the sum of the decaying DC current component and the fundamental wave component as shown in the following equation (15A). In the initial state of t = 0, the total current i is 0 as shown in the following equation (15B).

FIG. 5 is a diagram showing a simulation result of Case 1. In FIG. 5, the waveform of the total current, which is the sum of the attenuated DC current and the fundamental wave current, and the calculation results of the amplitude of the total current and the amplitude of the even wave pair current are shown. The vertical axis shows the current indicated by the arbitrary unit [PU]. The horizontal axis shows time (unit: seconds).

Calculation of the amplitude of the total current requires instantaneous value data at three points in the time range corresponding to 180 degrees in the electric angle, and calculation of the even-wave pair current requires 5 in the time range corresponding to 360 degrees in the electric angle. Instantaneous point data is needed. Therefore, the calculation result of the amplitude of the total current is shown from the time when 180 degrees elapses in the electric angle, and the calculation result of the amplitude of the even wave pair current is shown from the time when 360 degrees elapses in the electric angle.

FIG. 6 is a diagram showing a time change of the even wave amplitude ratio calculated based on the amplitude calculation result of FIG. Since the DC component generated by the failure of the power system is attenuated, the even wave amplitude ratio _kinrush is also attenuated. _{As shown in FIG. 6, it was demonstrated that the maximum value of the even-wave amplitude ratio kinrush} did not exceed the discrimination threshold even in the state before the DC component was attenuated, and the excitation inrush current was not erroneously discriminated.

(Case 2)
In Case 2, a simulation result using an instantaneous value current waveform of an exciting inrush current at an energization angle of 120 degrees shown in FIG. 15 of Japanese Patent No. 6351537 (Patent Document 2) will be described.

FIG. 7 is a diagram showing a simulation result of Case 2. FIG. 7 shows the instantaneous value current waveform of the excitation inrush current having an energization angle of 120 degrees, and the calculation results of the amplitude of the total current and the amplitude of the even wave pair current. The vertical axis shows the current indicated by the arbitrary unit [PU]. The horizontal axis shows time (unit: seconds).

As described with reference to FIG. 5, the calculation result of the amplitude of the total current is shown from the time when 180 degrees elapses in the electric angle, and the calculation result of the amplitude of the even wave pair current is the time when 360 degrees elapses in the electric angle. Is shown from.

FIG. 8 is a diagram showing a time change of the even wave amplitude ratio calculated based on the amplitude calculation result of FIG. 7. Even when the energization angle is 120 degrees, the even-wave amplitude ratio k _inrush exceeds the discrimination threshold, demonstrating that the excitation inrush current can be reliably discriminated.

The embodiments disclosed this time should be considered to be exemplary and not restrictive in all respects. The scope of the present invention is shown by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the claims.

10 power system, 11 lines, 12 transformers, 100, 200 excitation inrush current discriminator, 201 input unit, 202 storage unit, 203,205 amplitude calculation unit, 204 data generation unit, 206 discriminator unit, 207 signal output unit, 210 processing unit, the amplitude of _{I m} the total current, the amplitude of _{I e} even-wave paired _{current, I eg, I mg, I} g gauge current, T gauge sampling period, _{T 1} data sampling period, _{f 0} rated frequency, _{f 1} Data sampling frequency, _kinrush even-wave amplitude ratio.

Claims (6)

It is a device for discriminating the excitation inrush current and
A storage unit that stores the instantaneous value of the detected current detected for each data sampling cycle as the first time-series data,
The current component included in the detected current is obtained by adding the instantaneous current values of the times prior to the sampling time by the first time interval to the instantaneous current values of each sampling time of the first time series data. It is provided with a data generation unit that generates a second time series data representing
The first time interval is set to the value closest to the reciprocal of twice the rated frequency of the fundamental wave of the detected current among the integral multiples of the data sampling period.
The discriminating device further
A first amplitude calculation unit that calculates the amplitude of the detected current based on the first time series data, and
A second amplitude calculation unit that calculates the amplitude of the current component based on the second time series data, and
An exciting inrush current discriminating device including a discriminating unit for discriminating whether or not the ratio of the amplitude of the current component to the amplitude of the detected current exceeds a threshold value. Each of the first amplitude calculation unit and the second amplitude calculation unit extracts three data values separated from each other by the second time interval from the plurality of data values constituting the time series data. The excitation inrush current discriminating device according to claim 1, wherein the current amplitude is calculated based on the extracted data values of the three points. The data values of the above three points are set to i ₁ , i ₂ , and i ₃ from the later in time.
Each of the first amplitude calculation unit and the second amplitude calculation unit calculates the current amplitude based on the value calculated according to the following equation (A1).

The exciting inrush current discriminating device according to claim 2. The third aspect of claim 3, wherein each of the first amplitude calculation unit and the second amplitude calculation unit calculates the current amplitude by performing a moving averaging process on the value calculated according to the equation (A1). Excitation inrush current discriminator. The second time interval is set to a value closest to the reciprocal of four times the rated frequency of the fundamental wave of the detected current among the integral multiples of the data sampling period, any of claims 2 to 4. The exciting inrush current discriminating device according to item 1. It is a method of determining the exciting inrush current,
The step in which the computer receives the instantaneous value of the detected current detected for each data sampling cycle as the first time series data,
The computer adds the instantaneous current value of the time preceding the sampling time by the first time interval to the instantaneous current value of each sampling time of the first time series data, thereby adding the instantaneous current value of the time before the sampling time to the detected current. It includes a step to generate a second time series data representing the included current components.
The first time interval is set to the value closest to the reciprocal of twice the rated frequency of the fundamental wave of the detected current among the integral multiples of the data sampling period.
The discrimination method further
A step in which the computer calculates the amplitude of the detected current based on the first time series data.
A step in which the computer calculates the amplitude of the current component based on the second time series data.
A method for determining an exciting inrush current, wherein the computer includes a step of determining whether or not the ratio of the amplitude of the current component to the amplitude of the detected current exceeds a threshold value.

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