JP2006050732A - Monitoring apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a monitoring apparatus and a monitoring method for detecting an amplitude of a monitoring signal waveform included in signal waveforms at a high frequency resolution and a high time resolution, and accurately monitoring a state of a monitored object. <P>SOLUTION: In a step A, signal waveforms including the monitoring signal waveform for indicating the state of the monitored object are detected. In a step B1, a fast Fourier transform is applied to the detected signal waveforms, and Fourier transform signals are output. In a step B2, the Fourier transform signal in a frequency band including a frequency of the monitoring signal waveform is selected from the Fourier transform signals. In a step B3, an inverse fast Fourier transform is applied to the selected Fourier transform signal, and an inverse Fourier transform signal is output. In a step C, the state of the monitored object is determined on the basis of the amplitude of the inverse Fourier transform signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a monitoring apparatus and a monitoring method for monitoring a state of a monitoring target.

Various proposals have been made as a monitoring device or a monitoring method for monitoring the state of a monitoring target such as a device (for example, whether or not an abnormality has occurred in the monitoring target).
For example, an abnormality diagnosis method described in Patent Document 1 is known as an abnormality diagnosis method for diagnosing the presence / absence of an abnormality in a device.
In the abnormality diagnosis method described in Patent Document 1, first, vibration data indicating vibration generated from the apparatus is measured. Next, a plurality of frequency components (frequency spectra) included in the vibration data are extracted by performing fast Fourier transform (FFT) on the measured vibration data. Then, based on each extracted frequency component or residual frequency component obtained by subtracting each extracted frequency component during normal operation, time domain parameters such as kurtosis, distortion, crest factor and waveform rate are identified. As an index, it is determined whether or not an abnormality has occurred in the apparatus and the location where the abnormality has occurred.
In addition, as an isolated operation detection method for detecting that an inverter connected to a commercial power system is in an isolated operation state, an isolated operation detection method described in Patent Document 2 is known.
The islanding operation detection method described in Patent Document 2 utilizes the fact that a third harmonic voltage is generated due to the excitation characteristics of a pole transformer during a power failure in a commercial power system. In other words, the third harmonic component is extracted from the voltage at the connection point by a band pass filter, the extracted third harmonic component is full-wave rectified by an absolute value circuit, integrated by an integration circuit, and the output of the integration circuit is sampled. It is detected at a constant cycle by a circuit. Then, when the detected value of the third harmonic component increases rapidly, it is determined that the inverter is in the single operation state.
JP 2001-318031 A Japanese Patent Laid-Open No. 7-154920

In the abnormality diagnosis method described in Patent Document 1, the frequency component and the amplitude included in the vibration data are extracted by performing fast Fourier transform on the vibration data. Here, when the frequency component included in the vibration data is extracted using the fast Fourier transform, the frequency component can be extracted from the vibration data in a short time, but only the information on the frequency is obtained and the information on the time is lost. Is called. Therefore, in order to obtain the temporal change of the amplitude of the frequency component included in the vibration data while using the fast Fourier transform, the vibration data is cut out for each short cut-out section, and the vibration data for each cut-out section is converted into the fast Fourier transform. Need to be transformed (referred to as "short-time Fourier transform"). At this time, a window function is usually applied to the vibration data of the cut-out section in order to prevent a frequency component due to the rising portion of the cut-out section rising rapidly from “0”.
In this case, if the cut-out section is short, the time resolution is high (the frequency component extraction time interval is short), but the frequency resolution is low (frequency component extraction accuracy is low). On the other hand, if the cut-out section is long, the frequency resolution is high, but the time resolution is low.
Therefore, in the abnormality diagnosis method described in Patent Document 1, it is difficult to detect temporal changes in the amplitude of the frequency component included in the vibration data with high frequency resolution and high time resolution, and the accuracy of abnormality diagnosis is high. not good.
In addition, since the islanding operation detection method described in Patent Document 2 uses a bandpass filter, an absolute value circuit, an integration circuit, and a sampling circuit, there is a limit in increasing the time resolution of the third harmonic component. Even if a fast Fourier transform circuit is used in place of the bandpass filter, absolute value circuit, integration circuit, and sampling circuit described in Patent Document 2, as described above, the third point included in the interconnection point voltage is used. It is difficult to detect temporal changes in the amplitude of harmonic components with high frequency resolution and high time resolution.
The problem to be solved by the present invention is that it is possible to detect temporal changes in the amplitude of the monitoring signal waveform indicating the state of the monitoring target included in the signal waveform with high frequency resolution and high time resolution. To provide a monitoring device and a monitoring method capable of monitoring a state with high accuracy.

A first aspect of the present invention for solving the above-described problem is a monitoring apparatus having the configuration according to claim 1.
The present invention relates to a signal waveform detecting means for detecting a signal waveform including a monitor signal waveform, a Fourier transform means for Fourier transforming the signal waveform to output a Fourier transform signal, and a frequency of the monitor signal waveform from the Fourier transform signal. Including a bandpass filter that passes a Fourier transform signal in a frequency band including, a Fourier inverse transform unit that performs Fourier inverse transform on the Fourier transform signal that has passed through the bandpass filter, and outputs a Fourier inverse transform signal, and an output from the Fourier inverse transform unit Determination means for determining the state of the monitoring target based on the amplitude of the inverse Fourier transform signal is provided.
The “monitoring signal waveform” referred to in the present invention is a waveform component indicating the state of the monitoring target, and is included in the signal waveform in the monitoring target.
The “signal waveform detection means” is a signal waveform including a monitoring signal waveform indicating the state of the monitoring target, for example, a voltage or current waveform of an electrical device connected to the power system, a voltage at a predetermined point of the power system. A continuous waveform such as a current waveform, a vibration of a device to be monitored, or a generated sound is cut out and detected. The type and number of signal waveforms detected by the signal waveform detection means are appropriately selected according to the monitoring target, the monitored state, and the like. For example, a mode of detecting signal waveforms at one or a plurality of locations and a mode of detecting different types of signal waveforms are used. As the “signal waveform detection means”, a signal waveform detection means for detecting a signal waveform at one place or a signal waveform detection means capable of detecting a signal waveform at a plurality of places can be used.
The “Fourier transform unit” cuts out a signal waveform in a predetermined cut-out section, and Fourier-transforms the cut-out signal waveform. The length of this cut-out section is set to a time interval at which Fourier transform can be performed with a desired frequency resolution. As the “Fourier transforming means”, it is preferable to use fast Fourier transforming means (FFT) that performs fast Fourier transform and that has a high processing speed.
As the frequency band of the band filter, it is preferable to use a narrow band whose center frequency is the frequency of the monitoring signal waveform. The frequency of the monitoring signal waveform is determined according to the monitoring target, the state to be monitored, and the like. The number of frequency bands is appropriately set according to the number of monitoring signal waveforms necessary for determining the state of the monitoring target. As the band filter, a band filter that allows only a Fourier transform signal of one frequency band to pass may be used, or a band filter that can pass a Fourier transform signal of a plurality of frequency bands may be used.
The “inverse Fourier transform means” performs inverse Fourier transform for each Fourier transform signal obtained by performing Fourier transform on the extracted signal waveform by the Fourier transform means. As the “Fourier inverse transforming means”, it is preferable to use fast Fourier inverse transforming means (IFFT) that performs fast Fourier inverse transform processing and has a high processing speed.
Various states including abnormal states can be selected as the state of the monitoring target determined by the determining unit.
The method of determining the state of the monitoring target based on the amplitude of the inverse Fourier transform signal includes a method of determining the state of the monitoring target based on the time change state of the amplitude of the Fourier inverse transform signal.
As a method for determining the state of the monitoring target based on the amplitude of the inverse Fourier transform signal, an appropriate method is used according to the monitoring target, the monitoring state, and the like. For example, the method of judging when the amplitude of the inverse Fourier transform signal or the rate of change of the amplitude satisfies the judgment condition, the ratio of the amplitude of the inverse Fourier transform signal and the amplitude of the signal waveform or the rate of change of the ratio satisfies the judgment condition Can be used. Alternatively, a method of determining based on a comparison result (for example, a coincidence rate) between the time variation state of the amplitude of the inverse Fourier transform signal and the time variation state of the amplitude of the Fourier inverse transform signal obtained in advance in a predetermined state of the monitoring target. Can be used. When it is determined that the monitoring target is in an abnormal state, the Fourier of a characteristic portion (a characteristic portion that can be determined to be in an abnormal state) in a predetermined period before and after the time when the monitoring target has shifted to the abnormal state. It is preferable to obtain in advance the time variation state of the amplitude of the inverse transform signal. Further, it is possible to use a determination method based on the amplitude of each of a plurality of inverse Fourier transform signals obtained from one signal waveform or the time-varying state of the amplitude. Furthermore, it is possible to use a method of determining based on the amplitude of each of the plurality of inverse Fourier transform signals obtained from the plurality of signal waveforms or the time variation state of the amplitude.
Various output methods can be used as a method for outputting the determination result by the determination means. For example, when it is determined that the monitoring target is in an abnormal state, the time change state of the amplitude of the inverse Fourier transform signal in a predetermined period before and after the time of the abnormal state is output to the display unit or the printing unit in the form of a graph or a table Can be used. Also, a method of outputting an abnormal state determination signal to a control device that controls a monitoring target or a device related to the monitoring target and executing a predetermined control can be used.
According to a second aspect of the present invention, there is provided a monitoring device having the configuration according to claim 2.
The present invention monitors a state of a monitoring target in a power system having a power line and an electric device connected to the power line.
The present invention provides a signal waveform detection means for detecting a voltage waveform or a current waveform including a monitoring signal waveform indicating a state of a monitoring target in a power system as a signal waveform, and Fourier-transforms the detected signal waveform to output a Fourier transform signal. A Fourier transform unit, a bandpass filter that passes a Fourier transform signal in a frequency band including the frequency of the monitoring signal waveform from the Fourier transform signal output from the Fourier transform unit, and a Fourier transform of the Fourier transform signal that has passed through the bandpass filter. A Fourier inverse transform unit that converts and outputs an inverse Fourier transform signal and a determination unit that determines the state of the monitoring target based on the amplitude of the Fourier inverse transform signal output from the Fourier inverse transform unit are provided.
The “signal waveform detection means” is a signal waveform including a monitoring signal waveform indicating a state of a monitoring target in the power system, for example, an electric device (for example, a generator, a load, a circuit breaker, etc.) connected to the power system. ) Voltage and current waveforms, and voltage and current waveforms at predetermined points in the power system are detected. You may detect waveforms, such as a vibration waveform and generated sound, of the electric equipment etc. in an electric power system.
The type and number of signal waveforms detected by the signal waveform detection means are appropriately selected according to the monitoring target, the monitored state, and the like. For example, a mode of detecting signal waveforms at one or a plurality of locations and a mode of detecting different types of signal waveforms are used. As the “signal waveform detection means”, a signal waveform detection means for detecting a signal waveform at one place or a signal waveform detection means capable of detecting a signal waveform at a plurality of places can be used.
Various determination methods and output methods can be used as the method for determining the state of the monitoring target and the method for outputting the determination result based on the amplitude of the inverse Fourier transform signal, as in the first invention.
According to a third aspect of the present invention, there is provided a monitoring device having the configuration according to the third aspect.
In the present invention, the bandpass filter passes a Fourier transform signal in a frequency band including a frequency that is an integral multiple of the fundamental frequency of the power system from the Fourier transform signal.
“The basic frequency of the power system” means the power frequency of the power system (50 Hz or 60 Hz in a general commercial power system). In addition, as a “frequency band including a frequency that is an integral multiple of the fundamental frequency”, a frequency band that includes an arbitrary single multiple of the frequency may be used, or any continuous or discrete multiple of multiple integral multiples. You may use the frequency band containing a frequency.
According to a fourth aspect of the present invention, there is provided a monitoring device having the configuration according to the fourth aspect.
In the present invention, the signal waveform detection means detects a signal waveform including a plurality of monitoring signal waveforms, and the bandpass filter includes Fouriers in a plurality of frequency bands including the frequencies of the plurality of monitoring signal waveforms from the Fourier transform signal. The transform signal is passed, and the Fourier inverse transform means performs Fourier inverse transform on the Fourier transform signals of the plurality of frequency bands that have passed through the bandpass filter, and outputs a plurality of Fourier inverse transform signals. The monitoring state is determined based on the amplitude of each of the plurality of inverse Fourier transform signals output.
The plurality of monitoring signal waveforms are appropriately selected according to the monitoring target, the monitored state, and the like. For example, when monitoring that the monitoring target of the power system having a power supply frequency of 50 Hz or 60 Hz is in an abnormal state, a plurality of monitoring signal waveforms having a frequency that is an integral multiple of 50 Hz or 60 Hz can be selected.
According to a fifth aspect of the present invention, there is provided a monitoring device having the configuration according to the fifth aspect.
The present invention monitors a state of a monitoring target in a power system having a power line and an electric device connected to the power line.
The present invention includes a plurality of detection devices and processing devices provided corresponding to a plurality of monitoring targets of an electric power system.
The plurality of detection devices detect and detect a voltage waveform or a current waveform including a monitoring signal waveform as a signal waveform from a receiving unit that receives the reference time signal transmitted from the reference time signal transmitting unit and a corresponding monitoring target. Signal waveform detecting means for outputting a signal waveform together with a time signal corresponding to the reference time signal received by the receiving means.
The processing device Fourier-transforms each signal waveform output together with the time signal from the plurality of detection devices, and outputs a set of Fourier transform signals corresponding to each of the signal waveforms, and corresponds to each of the signal waveforms. From the set of Fourier transform signals, the bandpass filter that passes the Fourier transform signal in the frequency band including the frequency of the monitoring signal waveform, and the Fourier transform signal corresponding to each signal waveform that has passed through the bandpass filter is Fourier transformed. The inverse Fourier transform means for outputting the inverse Fourier transform signal corresponding to each signal waveform, and monitoring based on the amplitude of the inverse Fourier transform signal corresponding to each of the signal waveforms detected by each of the plurality of detection devices at the same time Judgment means for judging the state of the object is provided.
The plurality of detection devices are arranged so as to detect a signal waveform including a monitoring signal waveform necessary for determining the state of the monitoring target.
As the receiving means, a receiving means capable of receiving the reference time signal transmitted from the reference time signal transmitting means is used. For example, a GPS receiving unit that can receive a reference time signal transmitted from a GPS (Global Positioning System) can be used.
The “time signal corresponding to the reference time signal” includes the reference time signal itself and a time signal that is timed in each detection device and corrected by the reference time signal.
As a mode of “outputting the waveform signal together with the time signal”, it is only necessary that the processing device can determine the detection time of the waveform signal detected by each detection device.
The “Fourier inverse transform signal corresponding to each signal waveform detected by each of the plurality of signal waveform detection means at the same time” means that the Fourier transform means, the bandpass filter, and the Fourier transform signal from the signal waveforms detected by the respective detection devices at the same time. It means the Fourier inverse transform signal acquired by the inverse transform means.
As a method of “determining the state of the monitoring target based on the amplitude of the inverse Fourier transform signal corresponding to each of the signal waveforms detected by each of the plurality of signal waveform detection means at the same time”, the monitoring target and the monitoring state Various determination methods can be used according to the above. For example, the method of comparing the amplitude of each Fourier inverse transform signal corresponding to each of the signal waveforms detected at the same time and the time-varying state of the amplitudes and determining based on the comparison result, the signal waveform detected at the same time A method for determining each of the inverse Fourier transform signals corresponding to each of them and a time change state of the amplitude by satisfying a determination condition corresponding to the monitored state, and a Fourier inverse corresponding to each of the signal waveforms detected at the same time A method of judging by the comparison result (coincidence rate) between the amplitude of each converted signal and the time variation state of the amplitude and the time converted state of each Fourier inverse transformed signal obtained in advance corresponding to the monitored state. Can be used.
According to a sixth aspect of the present invention, there is provided a monitoring method comprising the configuration according to the sixth aspect.
The present invention includes a step (a) for detecting a signal waveform including a monitoring signal waveform, a step (b) for Fourier-transforming the detected signal waveform to output a Fourier transformed signal, and a monitoring signal from among the Fourier transformed signals. A step (c) of selecting a Fourier transform signal in a frequency band including the frequency of the waveform, a step (d) of performing a Fourier inverse transform on the selected Fourier transform signal and outputting a Fourier inverse transform signal, and an output inverse Fourier transform There is provided a step (e) of determining the state of the monitoring target based on the comparison result between the amplitude of the signal and the amplitude of the inverse Fourier transform signal obtained in advance in the predetermined state of the monitoring target.
The type and number of signal waveforms to be detected and the frequency to be selected are appropriately selected according to the monitoring target, the state to be monitored, and the like.
The frequency band is preferably set to a narrow band whose center frequency is the frequency of the monitoring signal waveform.
The method of comparing the amplitude of the output inverse Fourier transform signal with the amplitude of the Fourier inverse transform signal obtained in advance in a predetermined state to be monitored includes a method of comparing the time-varying state of the amplitude.
A seventh aspect of the present invention is a monitoring method having the configuration according to the seventh aspect.
In the present invention, after step (d), steps (c) and (d) are performed on a plurality of frequency bands including the frequencies of the plurality of monitoring signal waveforms included in the signal waveform, Step (f) for outputting a Fourier inverse transform signal corresponding to each frequency band is provided, and in step (e), the amplitude of the Fourier inverse transform signal corresponding to each of the plurality of frequency bands output in step (f) is provided. The state of the monitoring target is determined based on the comparison result obtained in advance with the amplitude of the inverse Fourier transform signal corresponding to each of the plurality of frequency bands when the monitoring target is in the predetermined state.

In the monitoring device according to claim 1, a Fourier transform signal in a frequency band including the frequency of the monitor signal waveform is selected from Fourier transform signals obtained by performing Fourier transform on the signal waveform cut (detected) in the cut section, The selected Fourier transform signal is inversely Fourier transformed. That is, the frequency component of the frequency band including the frequency of the monitoring signal waveform among the frequency components included in the signal waveform can be acquired in a state including the time change information of the amplitude in the cut-out section. This makes it possible to increase the frequency resolution by lengthening the cut-out section while maintaining a high time resolution, so that the amplitude of the monitoring signal waveform can be detected with a high frequency resolution and a high time resolution. The state can be monitored with high accuracy.
Further, according to the present invention, only the Fourier transform signal in the frequency band including the frequency of the monitoring signal waveform is subjected to inverse Fourier transform, so that the processing speed can be increased.
The processing time can be further increased by using fast Fourier transform means or fast Fourier inverse transform means as Fourier transform means or inverse Fourier transform means.
If the monitoring device according to claim 2 is used, the amplitude of the monitoring signal waveform can be detected with high frequency resolution and high time resolution as in the monitoring device according to claim 1, so that the monitoring target in the power system can be detected. Can be monitored with high accuracy.
If the monitoring device according to claim 3 is used, only the Fourier transform signal in the frequency band including a frequency that is an integral multiple of the fundamental frequency of the power system is subjected to Fourier inverse transform, so that the processing of the band filter is simple. You can speed up the time.
If the monitoring apparatus of Claim 4 is used, the state of monitoring object can be monitored more correctly.
If the monitoring apparatus of Claim 5 is used, the state (for example, the state of the harmonic in a power system) of the various monitoring object of a power system can be determined correctly.
If the monitoring method of Claim 6 is used, since the amplitude of the monitoring signal waveform can be detected with high frequency resolution and high time resolution, the state of the monitoring target can be monitored with high accuracy.
If the monitoring method of Claim 7 is used, the state of monitoring object can be determined more correctly.

Embodiments of the present invention will be described below with reference to the drawings.
First, the outline of the present invention will be described.
The present invention monitors the state of the monitoring target based on the amplitude of the monitoring signal waveform indicating the state of the monitoring target or the time-varying state of the amplitude included in the signal waveform.
Here, in order to quickly determine the state of the monitoring target (especially that the monitoring target is in an abnormal state), the time varying state of the amplitude of the monitoring signal waveform, that is, the unsteady spectrum of the monitoring signal waveform is analyzed. There is a need to.
In the present invention, an unsteady spectrum analysis method capable of detecting the amplitude of the monitoring signal waveform with high frequency resolution and high time resolution is used.

The concept of one embodiment of the unsteady spectrum analysis method used in the present invention is shown in FIG. In the embodiment shown in FIG. 1, the unsteady spectrum analysis method using a multi-filter is used as the unsteady spectrum analysis method.
First, in step A, a signal waveform including a monitoring signal waveform is detected. The signal waveform to be detected only needs to include a monitoring signal indicating the state of the monitoring target, such as a voltage or current waveform of an electric device or power line, or a vibration or sound waveform generated from the monitoring target.
Next, in step B, a process of analyzing the time change state of the amplitude of the monitoring signal waveform included in the signal waveform, that is, an unsteady spectrum analysis process is executed. The unsteady spectrum analysis process is configured by the processes of steps B1 to B3.
In step B1, the signal waveform detected in step A is cut out for each predetermined cut-out section, and the cut-out signal waveform is fast Fourier transformed (FFT) to obtain a Fourier transform signal.
In Step B2, the Fourier transform signal in the frequency band including the frequency of the monitoring signal waveform is passed from the Fourier transform signal obtained in Step B1 by the band filter, and the Fourier transform signal excluding the frequency in the frequency band is removed (Step B2). Select a Fourier transform signal in the frequency band that includes the frequency of the monitoring signal waveform).
In step B3, the Fourier transform signal selected in step B2 is subjected to fast Fourier inverse transform (IFFT) to obtain an inverse Fourier transform signal. As a result, a monitoring signal waveform having an amplitude that changes with time is extracted from the signal waveform cut out in the cut-out section.
Next, in step C, the state of the monitoring target is determined based on the amplitude of the monitoring signal waveform extracted in step B. As a method for determining the state of the monitoring target based on the amplitude of the monitoring signal waveform, an appropriate determination method is used according to the type and number of signal waveforms, the frequency band of the band filter, the monitoring target, the monitoring state, and the like. The determination method will be described later.

Next, a non-stationary spectrum analysis method using a multifilter will be specifically described.
As shown in FIG. 2, consider a case where input signals [f (t)] (t is time) are simultaneously input to band filters (band pass filters) having different system functions [H _n (ω)]. As the system function [H _n (ω)], as shown in FIG. 3, a system function indicating a symmetric frequency band at the center frequency [ω _n ] is used. Further, an output signal output from a band-pass filter having a system function [H _n (ω)] is assumed to be [g _n (t)].
In this case, the time variation of the amplitude envelope of the output signal [g _n (t)] is the frequency component of the frequency band corresponding to the center frequency [ω _n ] included in the input signal [f (t)]. The time change of the amplitude is shown. That is, when the center frequency [ω _n ] of the system function [H _n (ω)] of the band filter is matched with the frequency of the monitoring signal waveform, the monitoring included in the input signal [f (t)] of the band filter The time change of the amplitude of the component having the frequency equal to the frequency of the signal waveform can be obtained from the amplitude envelope of the output signal [g _n (t)] of the bandpass filter.

（式１）
したがって、出力信号［ｇｎ（ｔ）］は、（式１）をフーリエ逆変換した（式２）によって得ることができる。

（式２）
なお、帯域フィルタの時間分解能及び周波数分解能はシステム関数［Ｈｎ（ω）］によって決定されるが、帯域フィルタの時間分解能と周波数分解能は互いに相反している。例えば、通過帯域を狭帯域とするシステム関数［Ｈｎ（ω）］を用いて帯域フィルタの周波数分解能を高めると、帯域フィルタの応答速度が遅くなる。したがって、帯域フィルタのシステム関数［Ｈｎ（ω）］は、必要とする時間分解能や周波数分解能、解析を行う周波数帯域、解析の目的等に応じて適宜設定される。
以下に示す本発明の実施の形態では、システム関数［Ｈｎ（ω）］を、（３式）のように設定している。

（式３）
なお、α、βは定数である。βは、計算時間を有利にするために導入されたものである。（式３）のシステム関数では、帯域フィルタの周波数帯域幅は、周波数帯によって変化しない。 Here, the Fourier transform signals obtained by Fourier transforming the input signal [f (t)] and the output signal [g _n (t)] of the bandpass filter having the system function [H _n (ω)] are respectively [F ₀ (ω). ], [H _n (ω)], (Equation 1) is established.

(Formula 1)
Therefore, the output signal [gn (t)] can be obtained by (Equation 2) obtained by inversely transforming (Equation 1).

(Formula 2)
Note that the time resolution and frequency resolution of the bandpass filter are determined by the system function [Hn (ω)], but the time resolution and frequency resolution of the bandpass filter are mutually contradictory. For example, if the frequency resolution of the band-pass filter is increased using a system function [Hn (ω)] that narrows the pass band, the response speed of the band-pass filter becomes slow. Therefore, the system function [Hn (ω)] of the band filter is appropriately set according to the required time resolution and frequency resolution, the frequency band for analysis, the purpose of analysis, and the like.
In the following embodiment of the present invention, the system function [Hn (ω)] is set as shown in (Expression 3).

(Formula 3)
Α and β are constants. β is introduced to make calculation time advantageous. In the system function of (Expression 3), the frequency bandwidth of the bandpass filter does not change depending on the frequency band.

Next, a monitoring device according to an embodiment of the present invention, which monitors whether the generator has changed from the interconnected operation state to the single operation state, using the above-described unsteady spectrum analysis method using a multi-filter will be described. . Below, the electric power system shown in FIG. 4 is demonstrated.
The power system shown in FIG. 4 includes a power line and electric devices (generators G, Gn, load L, circuit breakers CB1, CBn, etc.) connected to the power line. Here, the generator G connected to the power line via the circuit breaker CB1 is a monitoring target for monitoring that the power generator G is in an independent operation state. A load L is connected to the power line, and another generator Gn is connected via a circuit breaker CBn. That is, the generator G is in a connected operation state with the other generators Gn.
In the present embodiment, for example, the circuit breaker CBn is interrupted and the connection between the generator G and the other generator Gn is interrupted, thereby monitoring that the generator G is in the single operation state.

Here, in the power system, the frequency components included in the voltage and current waveforms at each point include the waveform of the basic frequency of the power system (50 Hz or 60 Hz in a general commercial power system) and the basics of the power system. A waveform of a frequency component having a frequency that is an integral multiple of the frequency (hereinafter referred to as “harmonic waveform”) occupies most of the frequency.
In addition, each order of the harmonic waveform included in the waveform of the generator voltage (terminal voltage on the generator G side from the circuit breaker CB1) when the generator G changes from the connected operation state to the single operation state. FIG. 6 shows an example of the time variation state of the ratio (content ratio) between another amplitude and the amplitude of the waveform of the fundamental frequency of the generator voltage. In addition, FIG. 6 is a thing when a generator transfers to an independent operation state at the time [1.1 second].
As shown in FIG. 6, before and after the time [1.1 seconds] when the generator is in a single operation state, among the harmonic waveforms, the fifth harmonic waveform, the seventh harmonic waveform, and the eleventh harmonic waveform. The contents of each of the thirteenth harmonic waveform and the total harmonic waveform are rapidly decreased.
As described above, when the generator is in the single operation state, when the waveform of the harmonic waveform fluctuates with time as shown in FIG. 6, the fifth of the harmonic waveforms included in the voltage of the generator. The time variation state of the amplitude of the harmonic waveform, the seventh harmonic waveform, the eleventh harmonic waveform, the thirteenth harmonic waveform, the plurality or all of the waveforms, and the amplitude of the fundamental frequency waveform of the generator voltage By determining the ratio (content ratio) of the fluctuating state, it can be monitored that the generator is in a single operation state.
Normally, the average value of the amplitude of the voltage waveform of the power system is controlled to be substantially constant. For this reason, when detecting the voltage waveform as a signal waveform and monitoring that the generator is in a single operation state, the time variation state of the amplitude content of the harmonic waveform included in the voltage waveform Instead of the method for determining the above, it is also possible to use a method for determining the temporal change state of the amplitude of the harmonic waveform included in the voltage waveform.

FIG. 5 shows a schematic configuration diagram of the monitoring apparatus according to the present embodiment.
The monitoring device according to the present embodiment includes a waveform detection device 10, a processing device 20, a storage device 30, and an output device 40.
The waveform detection device 10 detects a signal waveform including a monitoring signal waveform indicating the state of the monitoring target. In the present embodiment, the waveform detection device 10 detects the waveform of the terminal voltage of the generator G.
The processing device 20 includes a waveform analysis unit 21 and a determination unit 22. Moreover, the waveform analysis means 21 has a fast Fourier transform means 21a, a bandpass filter 21b, and a fast Fourier inverse transform means 21c. The fast Fourier transform unit 21a, the band filter 21b, the fast Fourier inverse transform unit 21c, and the determination unit 22 can be configured by software or can be configured by hardware. For example, the processing of each means may be executed by one processing device (CPU), or the processing of each means may be executed by each of a plurality of processing devices (CPU).
In the storage device 30, the program executed by each means, the time change state (reference time change state) of the amplitude of the Fourier inverse transform signal obtained in advance to determine the state of the monitoring target, or the Fourier inverse transform acquired as needed Signals and the like are stored.
As the output device 40, a display device, a printing device, a terminal device, or the like that outputs the determination result of the determination means 22 in the form of a graph or a table is used. In addition, as the output device 40, a control device that performs predetermined control when the monitoring target (in this embodiment, the generator G) is in the single operation state can be used.

  In the present embodiment, the generator G corresponds to the “electric equipment connected to the power line” of the present invention, is the “monitoring target in the power system” of the present invention, and the waveform detection device 10 is the “signal waveform” of the present invention. The fast Fourier transform means 21a corresponds to the "Fourier transform means" of the present invention, the band filter 21b corresponds to the "band filter" of the present invention, and the fast Fourier inverse transform means 21c corresponds to the "detection means". Corresponding to the “Fourier inverse transforming means”, the judging means 22 corresponds to the “determining means” of the present invention, and the single operation state or the interconnected operation state of the generator G corresponds to the “monitored state” of the present invention. .

The fast Fourier transform means 21a performs fast Fourier transform on the signal waveform detected by the waveform detector 10 and outputs a Fourier transform signal. In the present embodiment, the fast Fourier transform means 21a cuts out the waveform of the terminal voltage of the generator G detected by the waveform detection device 10 for each cut section, performs fast Fourier transform on the cut-out voltage waveform, and generates a Fourier transform signal. Is output. This Fourier transform signal is stored in the storage device 30, for example.
The band filter 21b passes (selects) a Fourier transform signal in a frequency band including the frequency of the monitoring signal waveform from the Fourier transform signal that has been fast Fourier transformed by the fast Fourier transform means 21a. The frequency of the monitoring signal waveform is determined according to the monitoring target, the state to be monitored, and the like. In this embodiment, the frequency of the monitoring signal waveform is determined by knowing in advance the state of the harmonics indicating that the generator is in a single operation state with respect to the state of the harmonics during grid connection. can do. Further, in the present embodiment, the band filter 21b passes the Fourier transform signal in the frequency band including the frequency of the harmonic waveform included in the voltage waveform of the generator G.
The frequency band of the band-pass filter 21b is preferably set to a narrow band with the frequency of the harmonic waveform as the center frequency.
In the present embodiment, the frequency band of the band filter 21b is set to a frequency band including a frequency (harmonic waveform frequency) that is an integral multiple of the fundamental frequency (for example, 50 Hz or 60 Hz) of the power system. Further, the frequency band of the band filter 21b is appropriately set according to the monitoring target or the monitoring state. For example, when the generator enters a single operation state, when the content of the harmonic waveform varies with time as shown in FIG. 6, the fifth harmonic waveform, the seventh harmonic waveform, the eleventh harmonic waveform, Any, plural, or all of the frequency bands including the frequencies of the 13 harmonic waveforms are set.
The fast Fourier inverse transform unit 21c performs fast Fourier inverse transform on the Fourier transform signal (Fourier transform signal in the frequency band set in the band filter 21b) that has passed through the band filter 21b, and outputs an inverse Fourier transform signal. In this case, as described above, the time variation of the amplitude of the Fourier transform signal corresponding to the frequency band of the bandpass filter 21b output from the fast Fourier transform unit is the amplitude of the monitoring signal waveform included in the signal waveform. The time fluctuation state of is shown. In the present embodiment, the time variation of the Fourier transform signal passing through the frequency band corresponding to the frequency of the harmonic waveform set in the band filter 21c is the time variation of the harmonic waveform corresponding to the frequency in the frequency band. Is shown.

  In addition, when passing the Fourier-transform signal of a several frequency band by the band filter 21b, you may use the band filter in which each frequency band is set, respectively, and the band filter which can set a some frequency band is used. It may be used. When a band-pass filter capable of setting a plurality of frequency bands is used, a Fourier transform signal selection process of the frequency band set in the band filter and a Fourier inverse transform process of the selected Fourier transform signal (step of FIG. 1). By repeating the processing of B2 and B3 for each frequency band, an inverse Fourier transform signal corresponding to each frequency band is obtained.

The determination unit 22 determines the state of the monitoring target based on the amplitude of the Fourier inverse transform signal output from the fast Fourier inverse transform unit 21c.
The mode of determining the state of the monitoring target based on the amplitude of the inverse Fourier transform signal in the determination unit 22 includes a mode of determining the state of the monitoring target based on the time change state of the amplitude of the Fourier inverse transform signal. .
In addition, the status of the monitoring target determined by the determination means includes not only the status related to the abnormality such as the monitoring target being in an abnormal state, the monitoring target being in an abnormal state, the deterioration state of the monitoring target, the connection of the system A state that occurs when the state is normal is included.

As the determination method for determining the state of the monitoring target based on the inverse Fourier transform amplitude by the determination means 22, various determination methods are used depending on the monitoring target, the monitoring state, and the like.
When determining the determination method, a signal waveform (for example, a normal signal waveform) indicating the monitoring state of the monitoring target is selected for the monitoring target and the monitoring state (hereinafter referred to as “monitoring state”). The time variation state of the amplitude of the inverse Fourier transform signal extracted from the signal waveform in the monitoring state of the monitoring target is obtained in advance.
Then, the time change state of the amplitude of the obtained Fourier inverse transform signal is set as the reference time change state, and the first determination is made based on whether or not the extracted time change state of the amplitude of the Fourier inverse transform matches the reference time change state. A determination method is determined based on a method or a time variation state of the amplitude of the obtained inverse Fourier transform signal, and a second determination is made based on whether the amplitude of the extracted inverse Fourier transform signal or the rate of change of the amplitude satisfies the determination condition. Decide whether to use the judgment method.
Note that the first determination method has a large amount of processing but high determination accuracy. On the other hand, the second determination method has a small processing amount, but the determination accuracy is lower than that of the first determination method. Whether to use the first determination method or the second determination method is selected according to the monitoring target, the monitoring state, the processing time, the monitoring accuracy, and the like.

In the first determination method, the time variation state of the characteristic portion that allows easy determination of the state of the monitoring target is stored in the storage device 30 as the reference time variation state from the time variation state of the amplitude of the obtained inverse Fourier transform signal. . In this case, the reference time variation state of the inverse Fourier transform signal to be stored in the storage device 30 may store only the reference time variation state corresponding to one monitoring state to be monitored, or a plurality of monitoring states to be monitored. A plurality of reference time fluctuation states corresponding to each may be stored.
Then, the time variation state of the amplitude of the inverse Fourier transform signal extracted from the signal waveform to be monitored is compared with the reference time variation state of the inverse Fourier transform signal stored in the storage device 30, and based on the comparison result ( For example, based on the coincidence rate of the time variation state of the amplitude of the inverse Fourier transform signal), the state of the monitoring target is determined. In the case where a plurality of reference time fluctuation states corresponding to each of a plurality of monitoring states to be monitored are stored in the storage device 30, which of the reference time fluctuation states stored in the storage device 30 is the same? Determine.
For example, when monitoring that the generator is in the single operation state, when the generator is in the single operation state, when the content rate of the amplitude of the harmonic waveform varies with time as shown in FIG. Time-varying state of one or more or all of the amplitudes of the fifth harmonic waveform, the seventh harmonic waveform, the eleventh harmonic waveform, and the thirteenth harmonic waveform of the characteristic portion that can be identified as being in the operating state Is stored in the storage device 30 as the reference time change state. And the time change state of the amplitude of the Fourier transform signal corresponding to the frequency band of the harmonic waveform set in the band filter 21b and extracted from the waveform of the generator voltage is stored in the storage device 30. By determining that the amplitude of the inverse Fourier transform signal matches the reference time fluctuation state, it is determined that the generator has shifted to the single operation state. Of course, it is also possible to use a method for determining that the time fluctuation state of the ratio (content ratio) of the harmonic waveform amplitude and the signal waveform matches.

In the second determination method, a determination condition for determining that the monitoring target is in the monitoring state is determined based on the obtained temporal variation state of the amplitude of the inverse Fourier transform signal, and is stored in the storage device 30.
As the determination condition, a determination condition that can determine that the monitoring target may be in a monitoring state or that the monitoring target is in a monitoring state is set. As the determination condition, for example, a determination condition related to the amplitude of the inverse Fourier transform signal or a determination condition related to the temporal change state of the amplitude of the inverse Fourier transform signal can be set.
For example, the upper limit determination value and the lower limit determination value of the amplitude of the inverse Fourier transform signal can be set in correspondence with the monitoring state of the monitoring target. In this case, the monitoring target is monitored by determining that the amplitude of the inverse Fourier transform signal extracted from the signal waveform of the monitoring target is greater than or equal to the upper limit determination value or less than or equal to the lower limit determination value. It is determined that there is a possibility that the monitoring target is in a state or that the monitoring target is in a monitoring state.
Alternatively, an increase rate determination value or a decrease rate determination value of the amplitude of the inverse Fourier transform signal can be set in correspondence with the monitoring state of the monitoring target. In this case, the rate of change in the amplitude of the inverse Fourier transform signal extracted from the signal waveform to be monitored increased at an increase rate equal to or greater than the increase rate determination value, or decreased at a decrease rate equal to or greater than the decrease rate determination value. Thus, it is determined that there is a possibility that the monitoring target is in the monitoring state, or that the monitoring target is in the monitoring state.
Alternatively, the upper limit determination value, lower limit determination value, increase rate determination value, and decrease rate determination value of the ratio (content ratio) of the amplitude of the inverse Fourier transform signal and the amplitude of the signal waveform are set according to the monitoring state of the monitoring target. can do. In this case, the ratio (content ratio) between the amplitude of the inverse Fourier transform signal extracted from the monitored signal waveform and the amplitude of the signal waveform is equal to or higher than the upper limit determination value or equal to or lower than the lower limit determination value. The rate of change in the ratio (content ratio) of the amplitude of the inverse Fourier transform signal extracted from the monitored signal waveform to the amplitude of the signal waveform increased or decreased at an increase rate greater than the increase rate judgment value. It is determined that there is a possibility that the monitoring target is in a monitoring state due to a decrease at a reduction rate equal to or greater than the rate determination value, or that the monitoring target is in a monitoring state.
Alternatively, it is possible to set an upper limit determination value or a lower limit determination value and an increase rate determination value or a decrease rate determination value for the amplitude or content of the inverse Fourier transform signal.
Further, as a determination method for determining that the monitoring target is in the monitoring state, a method for determining whether or not the amplitude of the inverse Fourier transform signal corresponding to one predetermined frequency band satisfies the determination condition is used. It is also possible to use a method of determining whether or not the amplitudes of a plurality of inverse Fourier transform signals corresponding to a plurality of frequency bands satisfy the respective determination conditions.
Furthermore, it is possible to use a method for determining whether or not the amplitude of the inverse Fourier transform signal extracted from each of the plurality of signal waveforms satisfies the determination condition.

The determination unit 22 can output the determination result determined based on the amplitude of the inverse Fourier transform signal to the output device 40.
For example, when it is determined that the monitoring target is in an abnormal state, the time change state of the amplitude of the inverse Fourier transform signal for a predetermined period before and after the time when the monitoring target is in the abnormal state is used as the output device 40. Output to a display device, a printing device, or a terminal device, and output in the form of a graph or a table.
Alternatively, the time change state of the amplitude of the inverse Fourier transform signal extracted from the signal waveform to be monitored is stored in the storage device 30 together with the time signal, and if necessary, the amplitude of the inverse Fourier transform signal of the instructed period is stored. The time change state is read from the storage device 30 and output to a display device, a printing device, or a terminal device used as an output device.
Alternatively, a status signal such as an abnormality occurrence signal is output to a notification device used as the output device 40, and notification information by light or sound is output. Alternatively, a status signal such as an abnormality occurrence signal is output to the control device to control the monitoring target and the equipment related to the monitoring target.

As described above, in the monitoring apparatus according to the present embodiment, the signal waveform including the monitoring signal waveform is subjected to the fast Fourier transform and the Fourier transform signal is output, and the frequency band including the frequency of the monitoring signal waveform from the Fourier transform signal. The Fourier transform signal is selected, a fast Fourier inverse transform is performed on the selected Fourier transform signal, an inverse Fourier transform signal is output, and the state of the monitoring target is monitored based on the amplitude of the Fourier inverse transform signal.
Thereby, even if the cut-out section is long, a high time resolution can be obtained, so that the amplitude of the monitoring signal waveform can be detected with a high frequency resolution and a high time resolution. Therefore, the state of the monitoring target can be monitored accurately and quickly.
Also, only the Fourier transform signal in the frequency band having the frequency of the monitoring signal waveform is subjected to fast Fourier inverse transform, so that the processing load is reduced and the processing time is increased.
Also, the status of the monitoring target can be determined online.

In the above, the waveform of the generator voltage is detected as the signal waveform, but the waveform of the generator current can also be detected. When the current waveform is detected as a signal waveform, the amplitude of the current waveform varies due to load fluctuations, etc., so the monitoring status of the monitoring target is determined based on the amplitude of the harmonic waveform included in the current waveform. The determination method needs to be set in consideration of fluctuations in the amplitude of the current waveform.
For example, the judgment condition for the amplitude of the harmonic waveform and the judgment condition for the ratio (content ratio) between the amplitude of the harmonic waveform and the amplitude of the voltage waveform are set. Is used.
Depending on the monitoring target and the monitoring state, it may be easier to monitor the state of the monitoring target if the current waveform is detected as a signal waveform than the voltage waveform.

In the above embodiment, the state of the monitoring target is monitored based on the amplitude of the inverse Fourier transform signal extracted from the signal waveform detected at one location, but the inverse Fourier transform signal extracted from each of the signal waveforms detected at multiple locations. It is also possible to monitor the state of the monitoring target based on the amplitude of.
Another embodiment in which the present invention is configured as a monitoring device that monitors the state of a monitoring target based on signal waveforms detected at a plurality of locations will be described.
Below, the electric power system shown in FIG. 7 is demonstrated.
The power system shown in FIG. 7 includes a power line and electric devices (generators G1, G2, load L, circuit breakers CB1, CB2, etc.) connected to the power line. In the present embodiment, detection devices 111, 112, and 113 are provided corresponding to the points X1, X2, and X3 of the electric power system. From the voltages at the points X1, X2, and X3 detected by the detection devices 111, 112, and 113, respectively. The state of the monitoring target of the power system can be monitored based on the extracted amplitude of the inverse Fourier transform signal corresponding to the frequency of the harmonic waveform. For example, when harmonics are generated at the time of startup of a device that generates harmonics, and harmonics are flowing into a power factor adjustment capacitor, etc. at another point, the power is detected by simultaneously detecting at multiple points. It is possible to monitor from which device the harmonics flowing into the rate adjusting capacitor or the like are mainly generated. Alternatively, the power line short-circuit failure or ground fault between the points X1, X2, and X3 can be monitored.
Here, in order to monitor the state of the monitoring target based on the inverse Fourier transform signals extracted from the signal waveforms at a plurality of points, the inverse Fourier transform signals extracted from the signal waveforms detected from the plurality of points at the same time are discriminated. There is a need. Therefore, in this embodiment, a receiving device capable of receiving the reference time signal transmitted from the reference time signal transmitting device is provided, and the voltage waveforms at a plurality of points are managed by the reference time signal.

FIG. 8 shows a schematic configuration diagram of the monitoring apparatus according to the present embodiment.
The present embodiment includes detection devices 111, 112, 113, a processing device 120, a storage device 130, and an output device 140 that are provided corresponding to the points X1, X2, and X3.
The detection devices 111 to 113 include waveform detection devices 111a to 113a and GPS reception devices 111b to 113b.
The GPS receivers 111b to 113b receive a reference time signal transmitted from the GPS. Note that the reference time signal receiving device is not limited to the GPS receiving device as long as it can receive the reference time signal transmitted from the reference time signal transmitting device.
The waveform detectors 111a to 113a detect voltage waveforms at the points X1 to X3. The waveform of the voltage at the points X1 to X3 includes a waveform (harmonic waveform) having a frequency that is an integral multiple of the fundamental frequency of the power system as a monitoring signal waveform. Depending on the monitoring target and the monitoring state, it may be easier to monitor the state of the monitoring target by detecting the current waveform as a signal waveform than the voltage waveform. And the waveform of the voltage of the detected points X1-X3 is output to the processing apparatus 120 with the time signal corresponding to the reference | standard time signal received by GPS receiver 111b-113b.
As the time signal corresponding to the reference time signal, the reference time signal itself may be used, or the time signal provided in each of the detection devices 111 to 113 and corrected by the reference time signal transmitted from the reference time signal transmitting means. May be used. Thereby, the waveform of the voltage detected by the waveform detection devices 111a to 113a of the detection devices 111 to 113 can be managed based on the common reference time.
As a method of transmitting the voltage waveform together with the time signal, any method can be used as long as the processing device 120 can determine the time at which the waveform of the voltage output from the waveform detection devices 111a to 113a is detected. Can be used.

The processing device 120 includes a waveform analysis unit 121 and a determination unit 122, like the processing device 20 shown in FIG. The waveform analysis unit 121 includes a fast Fourier transform unit 121a, a bandpass filter 121b, and a fast Fourier inverse transform unit 121c. Each of the units 121a to 121c and 122 can be configured by software or can be configured by hardware.
The storage device 130 stores a program executed by each unit, a time change state (reference time change state) of an amplitude of a Fourier inverse transform signal obtained in advance, a Fourier inverse transform signal acquired as needed, and the like.
As the output device 140, a display device, a printing device, a terminal device, or a control device that performs predetermined control in the event of an abnormality can be used.

  In the present embodiment, the detection devices 111 to 113 correspond to the “detection device” of the present invention, the waveform detection devices 111a to 113a correspond to the “signal waveform detection means” of the present invention, and the GPS reception devices 111b to 113b Corresponding to the “receiving means” of the present invention, the fast Fourier transform means 121a corresponds to the “Fourier transform means” of the present invention, the band filter 121b corresponds to the “band filter” of the present invention, and the fast Fourier inverse transform means 121c. Corresponds to the “inverse Fourier transform unit” of the present invention, and the determination unit 122 corresponds to the “determination unit” of the present invention.

The fast Fourier transform unit 121a uses, for example, the same method as the fast Fourier transform unit 21a shown in FIG. 5 to detect the voltages at the points X1 to X3 detected by the waveform detection devices 111a to 113a of the detection devices 111 to 113, respectively. Are cut out for each cut-out section, the waveform of the cut-out voltage is fast Fourier transformed, and a set of Fourier transform signals corresponding to the waveform of the voltage at each point (corresponding to each signal waveform) is output. At this time, the detection time of the voltage waveform of the cut-out section is managed based on the time signal output from the detection devices 111 to 113 together with the detected voltage waveform.
In addition, the method of outputting the waveform of the voltage for every cut-out section with a time signal from the detection apparatuses 111-113 can also be used. In this case, it becomes easy to manage the detection time of the voltage waveform for each cut-out section.
The band-pass filter 121b uses, for example, a method similar to that of the band-pass filter 21b shown in FIG. 5, and is output from the set of Fourier transform signals corresponding to the waveform of the voltage at each point output from the fast Fourier transform unit 121a. The Fourier transform signal in the frequency band including the frequency of the harmonic waveform that is the monitoring signal waveform is passed (selected). The frequency band of the band filter 121b is appropriately set according to the monitoring target, the monitoring state, and the like.
The fast Fourier inverse transform unit 121c uses the same method as the fast Fourier inverse transform unit 21c shown in FIG. 5 and corresponds to the voltage waveform at each point that has passed through the band-pass filter 121b (corresponding to each signal waveform). ) Fast Fourier inverse transform the Fourier transform signal and output the Fourier inverse transform signal.
In the case where the inverse Fourier transform signal is stored in the storage device 130, the time information (time information when the waveform of the extracted voltage is detected) at which the voltage waveform from which the Fourier inverse transform signal is extracted is detected together with the Fourier inverse transform signal. Remember. Thereby, the inverse Fourier transform signal corresponding to the signal waveform detected at the same time can be easily determined.

The determination means 122 is the monitoring target based on the amplitude of the inverse Fourier transform signal corresponding to each of the voltage waveforms at the points X1 to X3 detected by the waveform detection devices 111a to 113a of the detection devices 111 to 113 at the same time. Determine the state.
As a method of determining the state of the monitoring target based on the amplitude of the inverse Fourier transform signal corresponding to each of the voltage waveforms detected at the same time, various determination methods may be used depending on the monitoring target, the monitoring state, and the like. it can.
For example, a method of comparing each of the inverse Fourier transform signals corresponding to each of the voltage waveforms detected at the same time with each other and the time variation state of the amplitude, and determining by comparing the comparison result with a predetermined comparison result Can be used. Alternatively, a method can be used in which the amplitude of each Fourier inverse transform signal corresponding to each voltage waveform detected at the same time and the time-varying state of the amplitude satisfy a predetermined determination condition (for example, , When determining the state of harmonics). Alternatively, the amplitude and time variation state of each Fourier inverse transform signal corresponding to each voltage or current waveform detected at the same time is the amplitude or time variation state of each Fourier inverse transform signal obtained in advance when the monitoring target is in a predetermined state. A method of determining by matching with the time-varying state of the amplitude can be used (for example, in the case of determination of a power line short circuit fault or a ground fault). Alternatively, the time change states of the amplitudes of the Fourier inverse transform signals corresponding to the current waveforms detected at the same time are compared with each other, and the time change states of the amplitudes coincide with each other, so that the monitoring state of one of the monitoring targets And the monitoring status of the other monitoring target can be determined (for example, in the case of determining the harmonic state).

As described above, in the monitoring apparatus according to the present embodiment, the amplitude of the monitoring signal waveform can be acquired with high time resolution even if the cut-out section is long. Therefore, the amplitude of the monitoring signal waveform is set to high frequency resolution and high time resolution. Can be detected. Therefore, it is possible to accurately monitor the state of the monitoring target.
Moreover, since the state of the monitoring target is monitored based on the amplitude of the inverse Fourier transform signal extracted from the plurality of signal waveforms detected at the same time, the various states of the monitoring target can be monitored more accurately.
Moreover, the detection time of the voltage waveform in each detection device can be managed by the common time only by providing each detection device with reception means for receiving the reference time signal transmitted from the reference time signal transmission means. . Furthermore, by using a receiving unit that receives a reference time signal transmitted from an existing reference time signal transmitting unit, the detection device can be configured at low cost.

The present invention is not limited to the configuration described in the embodiment, and various changes, additions, and deletions are possible.
For example, although the case where the state of the monitoring target of the power system is monitored has been described, the present invention is not limited to the state of the monitoring target of the power system, and can be used to monitor the state of various monitoring targets.
In addition, the voltage waveform or current waveform of the power system was used as the signal waveform, but it is sufficient that the signal waveform includes a monitoring signal waveform indicating the state of the monitoring target, other than the voltage waveform or current waveform. Various signal waveforms can be used.
In addition, although receiving means for receiving the reference time signal is provided for each of the plurality of detecting devices, when each detecting device is provided with time detecting means having such an accuracy that does not affect the monitoring of the monitoring target. This receiving means can be omitted.
Moreover, although the case where it monitored that the generator was in the single operation state was demonstrated, this invention can monitor the various states of various other monitoring objects.
Moreover, although the fast Fourier transform means and the fast Fourier inverse transform means are used as the Fourier transform means and the Fourier inverse transform means, other Fourier transform means and Fourier inverse transform means can also be used.
As a determination method, various determination methods according to the monitoring target, the monitoring state, and the like can be used.

It is a figure explaining the outline | summary of one embodiment of this invention. It is a figure which shows the structure of a multi filter. It is a figure which shows the characteristic of a band filter. It is the schematic in the case of monitoring that the generator was in the independent operation state. It is a schematic block diagram of one embodiment of a monitoring device of the present invention. It is a figure which shows the time change state of the harmonic component before and behind the generator set to the single operation state. It is the schematic in the case of monitoring the state of an electric power grid | system. It is a schematic block diagram of other embodiment of the monitoring apparatus of this invention.

Explanation of symbols

10, 11a, 112a, 113a Waveform detection device (signal waveform detection means)
20, 120 Monitoring device (monitoring means)
21, 121 Waveform analysis means 21a, 121a Fast Fourier transform means 21b, 121b Bandpass filter 21c, 121c Fast Fourier inverse transform means 22, 122 Determination means 30, 130 Storage device 40, 140 Output device 111b, 112b, 113b GPS receiver

Claims (7)

A monitoring device that monitors the status of a monitoring target,
Signal waveform detection means for detecting a signal waveform including a monitoring signal waveform indicating the state of the monitoring target;
Fourier transform means for Fourier transforming the signal waveform detected by the signal waveform detection means to output a Fourier transform signal;
A bandpass filter that passes a Fourier transform signal in a frequency band including the frequency of the monitoring signal waveform from the Fourier transform signal output from the Fourier transform means;
Fourier inverse transform means for inversely transforming a Fourier transform signal of the frequency band that has passed through the bandpass filter to output an inverse Fourier transform signal;
Determination means for determining the state of the monitoring target based on the amplitude of the Fourier inverse transform signal output from the Fourier inverse transform means;
A monitoring device comprising: A monitoring device for monitoring a state of a monitoring target in a power system having a power line and an electric device connected to the power line,
Signal waveform detection means for detecting a voltage waveform or a current waveform including a monitoring signal waveform indicating the state of the monitoring target in the power system as a signal waveform;
Fourier transform means for Fourier transforming the signal waveform detected by the signal waveform detection means to output a Fourier transform signal;
A bandpass filter that passes a Fourier transform signal in a frequency band including the frequency of the monitoring signal waveform from the Fourier transform signal output from the Fourier transform means;
Fourier inverse transform means for inversely transforming a Fourier transform signal of the frequency band that has passed through the bandpass filter to output an inverse Fourier transform signal;
Determination means for determining the state of the monitoring target based on the amplitude of the Fourier inverse transform signal output from the Fourier inverse transform means;
A monitoring device comprising: The monitoring device according to claim 2,
The bandpass filter passes a Fourier transform signal in a frequency band including a frequency that is an integral multiple of the fundamental frequency of the power system from the Fourier transform signal output from the Fourier transform means.
A monitoring device characterized by that. The monitoring device according to any one of claims 1 to 3,
The signal waveform detection means detects a signal waveform including a plurality of monitoring signal waveforms indicating the state of the monitoring target,
The bandpass filter passes the Fourier transform signals of a plurality of frequency bands including the frequencies of the plurality of monitoring signal waveforms from the Fourier transform signals output from the Fourier transform means,
The Fourier inverse transform means performs Fourier inverse transform on the Fourier transform signals of the plurality of frequency bands that have passed through the band filter, and outputs a plurality of Fourier inverse transform signals,
The determination means determines the state of the monitoring target based on the amplitude of each of the plurality of Fourier inverse transform signals output from the Fourier inverse transform means.
A monitoring device characterized by that. A monitoring device for monitoring a state of a monitoring target in a power system having a power line and an electric device connected to the power line,
A plurality of detection devices provided corresponding to each of a plurality of monitoring targets of the power system, and a processing device,
The plurality of detection devices include:
Receiving means for receiving a reference time signal transmitted from the reference time signal transmitter;
A voltage waveform or a current waveform including a monitoring signal waveform indicating the state of the monitoring target corresponding to each is detected as a signal waveform, and the detected signal waveform is output together with a time signal corresponding to the reference time signal received by the receiving means. Having signal waveform detection means;
The processor is
Fourier transform means for Fourier transforming each signal waveform output together with the time signal from the plurality of detection devices, and outputting a set of Fourier transform signals corresponding to each signal waveform, and
A bandpass filter that passes a Fourier transform signal in a frequency band including the frequency of the monitoring signal waveform from a set of Fourier transform signals corresponding to each signal waveform output from the Fourier transform means;
Fourier inverse transform means for performing Fourier inverse transform on the Fourier transform signal of the frequency band corresponding to each signal waveform that has passed through the bandpass filter and outputting a Fourier inverse transform signal corresponding to each signal waveform;
At the same time, it has determination means for determining the state of the plurality of monitoring targets based on the amplitude of the inverse Fourier transform signal corresponding to each of the signal waveforms detected by the plurality of signal waveform detection means,
A monitoring device characterized by that. A monitoring method for monitoring the status of a monitoring target,
Detecting a signal waveform including a monitoring signal waveform indicating the state of the monitoring target;
(B) outputting the Fourier transform signal by Fourier transforming the signal waveform detected in the step (a);
Selecting a Fourier transform signal in a frequency band including the frequency of the monitoring signal waveform from the Fourier transform signals output in the step (b);
(D) outputting a Fourier inverse transform signal by performing a Fourier inverse transform on the Fourier transform signal of the frequency band selected in the step (c);
The Fourier inverse transform signal of the frequency band output in the step (d) is compared with the amplitude of the Fourier inverse transform signal of the frequency band obtained in advance in the predetermined state of the monitoring target, and based on the comparison result A step (e) of determining a state of the monitoring target;
A monitoring method comprising: The monitoring method according to claim 6, comprising:
After the step (d), the steps (c) and (d) are performed on a plurality of frequency bands including the frequencies of the plurality of monitoring signal waveforms included in the signal waveform, and the plurality of frequencies Providing a step (f) of outputting an inverse Fourier transform signal of each band;
In step (e), the inverse Fourier transform signal corresponding to each of the plurality of frequency bands output in step (f), and each of the plurality of frequency bands in the predetermined state of the monitoring target obtained in advance. Comparing the amplitude of the corresponding inverse Fourier transform signal, and determining the state of the monitoring object based on the comparison result;
A monitoring method characterized by that.

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