JPH09304452A - Harmonic monitoring equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it sure to monitor a harmonic having possibility of damage generation, by obtaining and accumulating the content value or the content ratio of a specified order harmonic component of a signal to be measured, at a specified judgment time and interval, and generating an alarm when the judgment level is exceeded. SOLUTION: A signal to be measured is inputted in an input circuit 1. An I/O 5 outputs a timing signal, and delivers input signal data to a CPU 9. A memory card 7 sequentially stores measured each order harmonic data. The CPU 9 executes various kinds of processes on the basis of the program of an ROM 10, the setting condition of a key input part 13, etc. That is, the CPU 9 obtains repeatedly the content value or the content ratio of specific order harmonic component of the signal to be measured, at constant time intervals in a specific judgment time, and accumulates the frequency. When the content value or the content ratio of the previously determined cumulative frequency exceeds a previously determined judgment level, an alarm is generated. Thereby generation of excessive harmonic level in a short time is surely detected without being affected by transient harmonic, and the alarm signal can be outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a harmonic monitoring device for monitoring a harmonic component of a voltage signal or a current signal of a power system or an electric load.

[0002]

2. Description of the Related Art Conventionally, in order to prevent obstacles caused by harmonics to power receiving and transforming equipment and electric loads, harmonic components superimposed on a power system or harmonic components generated by electric equipment existing in the power system A harmonic monitoring device is used to analyze and monitor.

The causes of disturbance due to harmonics can be roughly classified into the following three.

Abnormal noise, vibration, overheating, burnout, etc. due to the inflow of harmonic current to the equipment. Damage such as dielectric breakdown due to the application of harmonic voltage to the equipment. Due to the fluctuation of the zero cross point due to the application of harmonic voltage to the equipment. Erroneous control / malfunction, etc. Among them, is related to the product of the harmonic voltage / current level and its generation time, and is mainly related to the level and waveform of the harmonic voltage.

In order to prevent the above-mentioned troubles, the conventional harmonic monitoring device constantly monitors the level of harmonics and issues an alarm when a certain judgment level is exceeded.

The determination method is as follows.

The n-th harmonic voltage content rate is Vn, the n-th harmonic current content value is In, the total voltage distortion rate is V _THD , and the total current distortion is I _THD . Assuming that the determination levels of the harmonic current content value are Vhn and Ihn, respectively, Vn ≧ Vhn, V _THD ≧ Vh _THD , In ≧ Ihn,
An alarm signal is output when the condition where any or all of I _THD ≧ Ih _THD is satisfied continues for a set time.

[0008]

However, in such a conventional harmonic monitoring device, since the determination is simply made based on the harmonic level and its duration, the following problems occur. There were cases.

It is indistinguishable between the generation state of harmonics that greatly exceed the determination level and the generation state of harmonics that slightly exceed the determination level.

Even when the harmonics exceeding the determination level continue, if the harmonic level falls below the determination level for a short time during the duration and the duration does not reach the set time, the alarm is not output.

[0011] The level of harmonics generally varies greatly depending on the operating state of the source that generates the harmonics, the magnitude of the load, and the configuration of the power system, so that the harmonics are generated only when a specific load is operating for a short time. Although the level may become extremely high, in the conventional harmonic monitoring device, the alarm is not output unless the harmonic exceeding the determination level continues for the set time. In order to detect the increase in the harmonic level in such a short time and output an alarm, it is conceivable to set the above setting time short, but in that case, it does not lead to the above-mentioned obstacles, for example, a motor or a transformer. The alarm level is immediately output upon detection of the transiently increasing harmonic level that occurs when the power supply to the load is turned on, and it is not suitable for the purpose of preventing the above-mentioned harmonic-induced failure.

An object of the present invention is to provide a harmonic monitoring device capable of reliably monitoring the presence or absence of harmonics which may cause troubles such as abnormal noise, vibration, overheating, and burning due to the inflow of harmonic currents into the equipment. To provide.

Another object of the present invention is to prevent the occurrence of harmonics that may cause malfunctions such as malfunction or erroneous control due to the application of a harmonic voltage to a device without giving a false alarm due to a transiently occurring harmonic. It is an object of the present invention to provide a harmonic monitoring device capable of reliably monitoring the occurrence or non-occurrence of occurrence.

[0014]

The harmonic monitoring device of the present invention is not affected by a very transient harmonic generated by, for example, an inrush current flowing at the start of power supply to a load such as a motor or a transformer, and In order to reliably detect the occurrence of an excessive harmonic level due to the operation of a specific load or the like even for a relatively short time and to output an alarm signal, as described in claim 1, a voltage signal of a power system or The current signal is input as the signal to be measured, and the content value or content rate of the harmonic component of a predetermined order of the signal under measurement is repeatedly obtained at a predetermined time interval at a predetermined determination time, and the frequency of the content value or the content rate is calculated. While accumulating, an alarm is issued when the content value or content rate of a predetermined cumulative frequency exceeds a predetermined determination level.

Because of this, the content value or content rate that is a cumulative frequency slightly lower than the total frequency (expressed as a cumulative probability frequency with 100% as the total frequency, for example, 97%) is set as the maximum value in the above-mentioned fixed time. It will be appreciated and an alarm will be issued when this value exceeds the judgment level.

Here, the histogram showing the frequency distribution data for the nth harmonic obtained by measuring m times is as shown in FIG. 3, for example. In this example, the nth
The content ratio of the second harmonic is distributed in 0 to 9.0%, and the highest content ratio is about 9% (value included in 8.5 to 9.0%).
It is. The present invention has a maximum value of 9 in the measurement of m times.
3 is not compared with the judgment level, but in the example of FIG. 3, the content rate 7.5% at which the cumulative probability frequency is 97% is regarded as the highest value in the measurement of m times, and this value is compared with the judgment level. I do. That is, the content of more than 7.5% (3% of the total frequency) is ignored as a result. As described above, the harmonic component generated at the start of power supply to a load such as a motor or a transformer has a relatively high content rate, but its generation time is relatively short, and its proportion in m measurements is Few. In the example of FIG. 3, the content rate is 7.5%.
Range (98% to 100% in cumulative probability)
%)to go into. Therefore, it is possible to perform monitoring based on the amount that indicates a risk of causing erroneous control or malfunction of the device without issuing an alarm with such a transient harmonic component.

Further, the harmonic monitoring device of the present invention allows the judgment level in the conventional harmonic monitoring device to continue for a set time even if there is a risk of substantial overheating or burning due to the inflow of the harmonic current into the equipment. In order to solve the problem that the judgment level is exceeded or lowered, and the alarm is not output forever, the voltage signal or the current signal of the power system is input as the signal under measurement as described in claim 2, Obtain the content value or content rate of the harmonic component of a predetermined order of the signal under measurement by harmonic analysis, find the content value or the average value of the content rate repeatedly obtained at a fixed time interval at the predetermined judgment time, and then calculate the average value. Alarm is issued when exceeds a predetermined judgment level.

Since the content value or the average value of the content ratios of the harmonic components repeatedly obtained at the predetermined determination time at the predetermined determination time is obtained as described above, an alarm is issued when the average value exceeds the predetermined determination level. , Regardless of the variation pattern of the harmonic level, the alarm can be reliably issued when there is a risk of overheating or burning due to the inflow of the harmonic current into the device.

Further, according to the harmonic monitoring apparatus of the present invention, as described in claim 3, by combining the above-mentioned cumulative frequency and the above-mentioned averaging, the measurement result and the average value by the cumulative frequency are predetermined. An alarm signal is output to the outside when the judgment level is exceeded. With this configuration, its frequency distribution extends to relatively high harmonic levels,
The alarm is issued only when the average value of the harmonic level is high.

Further, the harmonic monitoring apparatus of the present invention, as set forth in claim 4, enables a plurality of sets of the judgment time and the judgment level to be set. As a result, for example, an alarm is not issued even if a high-level harmonic is detected for a relatively short time, and an alarm is issued if it continues for a long time even if the harmonic level is relatively low. Setting is also easy.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The configuration of a harmonic monitoring apparatus according to a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a block diagram showing the configuration of the harmonic monitoring device. In FIG. 1, the CPU 9 executes a program written in advance in the ROM 10 to monitor harmonics by various processes described later. The RAM 11 is used as a calculation working area for analyzing harmonic components when the program is executed. The input circuit 1 inputs the voltage signal or the current signal at the measured point of the power system as the measured signal, and the low-pass filter (LPF) 2 has a predetermined frequency band of the input signal or more so as not to be affected by the folding error due to sampling. To remove. The sample hold circuit 3 samples the output signal of the low pass filter 2 in accordance with the sampling pulse and holds it. A /
The D converter 4 converts the voltage signal into digital data. The I / O port 5 outputs a timing signal to the sample and hold circuit 3 and the A / D converter 4, and inputs the data resulting from the A / D conversion. C
The PU 9 reads the digital data of the signal under measurement via the I / O port 5. The clock circuit (RTC) 6 measures the current date and time, and the CPU 9 reads the current date and time from the RTC 6. The memory card 7 sequentially stores the data of each harmonic component obtained by each measurement. CP
U9 controls the writing / reading via the interface 8. This memory card 7 uses the harmonic monitoring device shown in FIG. 1 simply as a harmonic measuring device, and uses it as a data medium when another device outputs an alarm signal according to the determination. The key input unit 13 is used as an input device for setting various conditions such as the monitoring target order, the measurement interval, the number of data, the designated cumulative probability frequency, and the determination level. The CPU 9 reads the key operation content via the interface 12. The display unit 15 displays the input data from the key input unit 13. The CPU 9 controls the display via the interface 14. CO16 is a contact signal output circuit, C
As a result of the harmonic measurement, the PU 9 outputs an alarm contact signal by this contact signal output circuit when an alarm signal should be output.

FIG. 2 is a flowchart showing the processing procedure of the CPU. First, the monitoring target order n, the measurement interval t, the number of data m, the designated cumulative probability frequency x, and the determination level Vhn
Set various parameters such as (x) and Vh _THD (x). When the measurement timing corresponds to the measurement interval t, the signal under measurement (voltage signal in this case) is sampled and its digital data is read. For example, a fixed number of points are sampled for a period corresponding to one cycle of the fundamental wave frequency. Then, the content value of each harmonic is calculated by FFT based on the sampling data of this fixed point, and the ratio of the fundamental frequency to the content value is calculated as the content of each harmonic. After that, the frequencies of the harmonic content of each order are added. For example, the frequency of the content rate is counted in 0.5% steps, and if the content rate of the nth harmonic calculated this time is 5.35, the content rate of the nth harmonic is 5.35. Increment the frequency from 0 to 5.5. M above processing
Repeated times to obtain frequency distribution data with cumulative frequency m. Nth
The frequency distribution data of the next harmonic is represented by a histogram as shown in FIG. After the measurement is performed m times, the cumulative probability frequency data of each order is created, and the content rate Vn corresponding to the designated cumulative probability frequency x% is obtained.
(X) is extracted. In the example shown in FIG. 3, the content rate Vn (97%) corresponding to the designated cumulative probability frequency of 97% is 7.5%.
It is. The content rate corresponding to the specified cumulative probability frequency is not limited to the monitored order, but is similarly calculated for all orders obtained by measurement, and the content rates are added to add the total voltage distortion rate V _THD at the specified cumulative probability frequency. Extract (x). Then, when Vn (x) or V _THD (x) is equal to or higher than a predetermined determination level Vhn (x) or Vh _THD (x), an alarm signal is output. If this condition is not met, no warning signal will be output. The harmonics are monitored by repeating the above processing.

Next, FIG. 4 is a flowchart showing a processing procedure of the CPU in the harmonic monitoring apparatus according to the second embodiment of the present invention. First, various parameters such as the monitored order n, the measurement interval t, the number of data m, and the determination level Ih are set. When the measurement timing corresponds to the measurement interval t, the signal under measurement (current signal in this case) is sampled at a certain number of points for a period corresponding to one cycle of the fundamental frequency, and the data is read. Then, the content value of each harmonic is calculated by FFT based on the sampling data of a certain number of points. After that, the square root of the value obtained by squaring the content values for all orders is the total current distortion I
_THD is obtained, and the content value In of the nth harmonic current and the total current distortion _ITHD are arithmetically added. After repeating the above processing m times, ΣIn is divided by m to obtain the average value In ′ of the nth harmonic current, and ΣI
_By dividing _THD by m, the average value of total current distortion I
Calculate _THD '. Then, it outputs a warning signal when In 'or I _THD' is a predetermined judgment level Ihn or Ih _THD more. If this condition is not met, no warning signal will be output. The harmonics are monitored by repeating the above processing.

Next, FIG. 5 is a flowchart showing a processing procedure of the CPU in the harmonic monitoring apparatus according to the third embodiment of the present invention. First, various parameters such as the monitored order n, the measurement interval t, the data number m, the designated cumulative probability frequency x, and the determination levels Vhn (x) and Vhn are set. When the measurement timing corresponds to the measurement interval t, the signal to be measured (voltage signal in this case) is sampled at a fixed number of points and its digital data is read. Then, the content value of each harmonic is calculated by FFT based on the sampling data of this fixed point, and the ratio of the fundamental frequency to the content value is calculated as the content of each harmonic. After that, add the frequencies for the harmonic content of each order,
Further, the content rate Vn of the nth harmonic voltage is arithmetically added.
After repeating the above process m times, the nth-order cumulative probability frequency data is created and the content rate Vn (x) corresponding to the designated cumulative probability frequency x% is extracted. Further, by dividing ΣVn by m, the average value V of the nth harmonic voltage is
Find n '. Then, Vn (x) is the determination level Vhn
When (x) or more and Vn 'is the determination level Vhn or more, an alarm signal is output. If this condition is not met, no warning signal will be output. The harmonics are monitored by repeating the above processing.

Next, FIG. 6 is a flowchart showing a processing procedure of the CPU in the harmonic monitoring apparatus according to the fourth embodiment of the present invention. First, the monitoring target order n, the measurement interval t, the number of data m1 and m2, and the determination levels Ihn1 and I2.
Set various parameters such as hn2. At the measurement timing corresponding to the measurement interval t, the current signal, which is the signal to be measured, is sampled at a fixed point and the data is read.
Then, based on this fixed number of sampling data, FFT
Then, the content value of the nth harmonic is calculated, and the ratio of the fundamental frequency to the content value is calculated as the content rate. Then, the content value of the nth harmonic current is Σ in this example.
In1 and ΣIn2 are arithmetically added in two systems. When the above measurement is repeated m1 times, ΣIn1 is divided by m1 to obtain an average value In1 ′ of the m1 times measurement of the nth harmonic current. Then, when In1 'is equal to or higher than the predetermined determination level Ihn1, an alarm signal is output. When the above measurement is repeated m2 times, ΣIn2 is divided by m2 to obtain an average value In2 ′ of the m2 times measurement of the nth harmonic current. And In
When 2'is equal to or higher than the predetermined determination level Ihn2, an alarm signal is output. The harmonics are monitored by repeating the above processing.

The fourth embodiment has shown an example in which a method of setting and monitoring a plurality of sets of judgment time and judgment level is applied to the averaging process, but it is also applied to the case of obtaining the cumulative probability frequency. it can. That is, the content rate of the harmonic component corresponding to the designated cumulative probability frequency is obtained for each of a plurality of different determination times, that is, a plurality of different data numbers, and the content rate of the harmonic component corresponding to the designated cumulative probability frequency is calculated for each. The determination may be made at the determination level set for each determination time.

In each of the above-described embodiments, only the voltage signal or the current signal is monitored, but both the voltage and the current are monitored depending on the characteristics of the power system to be monitored or the monitoring purpose. As an object to be monitored, determination levels may be set for each of voltage and current, and an alarm signal may be output when both exceed the determination level or when either one exceeds the determination level.

[0029]

According to the invention as set forth in claim 1, the content value or content rate at which the cumulative value of the content value or content rate of the harmonic component reaches a predetermined value is obtained, and the value and the determination level are determined. Since the alarm is issued by comparing the above, for example, the content value or content rate of the harmonic component having a relatively high cumulative probability frequency of less than 100% is obtained, and the content value or content rate is treated as a determination target. The influence of a transient harmonic component that occurs in a very short time at the time of starting the power supply to a load such as is removed, and the monitoring can be performed based on the amount indicating the risk of being substantially erroneously controlled or erroneously operated.

According to the second aspect of the present invention, the content value or the average value of the content rates of the harmonic components repeatedly obtained at a predetermined time interval at a predetermined determination time is obtained, and this is a predetermined determination level. Since the alarm signal is output when the temperature exceeds the limit, it is possible to reliably issue an alarm when there is a risk of overheating or burning due to the inflow of the harmonic current into the equipment, regardless of the variation pattern of the harmonic level. Like

According to the third aspect of the invention, the alarm can be issued only when the frequency distribution is widened to a relatively high harmonic level and the average value of the harmonic levels is high. Become.

According to the fourth aspect of the present invention, for example, even if a high level harmonic is detected for a relatively short period of time, an alarm is not issued, and even if the harmonic level is relatively low, it does not occur. It becomes easy to set an alarm to be issued when the alarm continues for a long time, and the alarm generation condition can be finely set according to the characteristics of the power system to be monitored or the monitoring purpose.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a harmonic monitoring device according to a first embodiment.

FIG. 2 is a flowchart showing a processing procedure of a CPU in the harmonic monitoring device according to the first embodiment.

FIG. 3 is a diagram showing an example of a harmonic content rate, its frequency distribution, and a cumulative probability frequency.

FIG. 4 is a flowchart showing a processing procedure of a CPU in the harmonic monitoring device according to the second embodiment.

FIG. 5 is a flowchart showing a processing procedure of a CPU in the harmonic monitoring device according to the third embodiment.

FIG. 6 is a flowchart showing a processing procedure of a CPU in the harmonic monitoring device according to the fourth embodiment.

Claims (4)

[Claims] 1. Harmonic analysis means for inputting a voltage signal or a current signal of a power system as a signal under measurement to obtain a content value or content rate of a harmonic component of a predetermined order of the signal under measurement, and the harmonic analysis. The content value or content rate is repeatedly obtained at a certain time interval at a predetermined determination time by means, and the frequency of the content value or content rate is accumulated, and the content value or content rate of a predetermined cumulative frequency is a predetermined determination level. And a means for issuing an alarm when the frequency exceeds the limit. 2. A measured signal input circuit for inputting a voltage signal or a current signal of a power system as a measured signal, and a harmonic analysis means for obtaining a content value or a content rate of a harmonic component of a predetermined order of the measured signal. A means for obtaining an average value of the content value or content rate repeatedly obtained at a predetermined time interval at a predetermined determination time by the harmonic analysis means, and an alarm is issued when the average value exceeds a predetermined determination level. And a harmonics monitoring device. 3. A measured signal input circuit for inputting a voltage signal or a current signal of an electric power system as a measured signal, and a harmonic analysis means for obtaining a content value or a content rate of a harmonic component of a predetermined order of the measured signal. And, by repeatedly obtaining the content value or the content rate at a predetermined time interval at a predetermined determination time by the harmonic analysis means, and accumulating the frequency of the content value or the content rate, and the content value or the content rate of a predetermined cumulative frequency. A means for obtaining as a measurement result, a means for obtaining an average value of the content value or the content rate at the determination time obtained by the harmonic analysis means, when the measurement result and the average value exceed a predetermined determination level , A harmonic monitoring device provided with means for issuing an alarm. 4. The harmonic monitoring device according to claim 1, wherein a plurality of sets of the judgment time and the judgment level can be set.