JP2001327062A - Monitoring method of analog input circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in the conventional method that wrong judgment is made that an equivalent harmonic is included in the outer input, when the monitoring input of harmonic is superimposed in an analog input circuit and the normality/abnormality is observed, only from the data whether there is a harmonic or not or from the level of harmonic included in the output. SOLUTION: An observation input to be superimposed in an analog input circuit 1 is turned off by a switch 5. If the abnormality is a result of judgment by a judgment part 4, an observation treatment unit 6 cuts off an observation input temporarily, by using the switch. Whether the same harmonic as the observation input is included or the level of harmonic is judged from the output of filter 3 during the cut-off by the observation treatment unit 6, and on the basis of the result, whether the judgment result of the judgment part 4 is good can be judged. The switch 5 is turned off periodically, and whether there is harmonic or the level of harmonic is judged beforehand, and a observed width εand the observed input are adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a monitoring system for monitoring the normal / abnormal operation of an analog input circuit.

[0002]

2. Description of the Related Art For example, a protection relay device for a power system detects a voltage or a current of the system, determines a ground fault or a short circuit accident of a transmission and distribution line based on these signals, and obtains a system protection output. Such a protection relay device includes an analog system and a digital system. In any case, an analog input circuit is required for detecting current and voltage.

[0003] A failure of this type of analog input circuit makes it impossible to detect an accident and causes an accident to propagate. Therefore, monitoring circuits and inspection circuits have conventionally been provided.

FIG. 4 shows a conventional monitoring system, which is applied to a digital protection relay. An external input that becomes a detection signal such as a voltage is a constant frequency f of a power system.
The input signal is converted into an appropriate voltage signal by an analog input circuit (A / I) 1, sampled and held, and converted into a digital value by an A / D converter 2. The digital value is supplied to a protection relay computer as protection data as one detection data.

To monitor the analog input circuit, a higher harmonic (third harmonic f _{3 in} the figure) is superimposed as an input signal for monitoring on an external input having a fundamental frequency f and injected into the analog input circuit 1. , The digital output of the A / D converter 2 is passed through a digital filter 3 composed of a computer software or the like to extract the third harmonic component contained in the digital output of the A / D converter 2, A determination unit 4 having a configuration or the like determines whether or not the absolute value difference between the output f _3OUT of the filter 3 and the injected third harmonic signal f _3IN is smaller than the monitoring width ε.

[0006]

The normality / abnormality of the analog input circuit 1 is monitored from | f _3OUT −f _3IN | ≦ ε.

[0007] In the case of monitoring the protection relay device of the analog type, the third harmonic is extracted from the output of the analog input circuit 1 using an analog filter circuit, and the absolute value difference from the monitoring input signal is obtained. Become.

[0008]

SUMMARY OF THE INVENTION Lightning arrester operation in a power system
And the load state, the third harmonic f
_3IN’May be included. In this case, the injected monitoring
Input f_3INTo the third harmonic f _3IN’Adds at random phase
Will be done. At this time, the output of the filter 3 is also f
_3OUTTo f_3OUT’. The judgment at this time is

[0009]

Normal / abnormal is determined from | f _3OUT − (f _3IN ± f _3IN ') | ≦ ε, and it is determined that the analog input circuit is abnormal even though it is normal. Regardless, there was a problem that it was determined to be normal.

An object of the present invention is to provide a monitoring method capable of reliably determining whether an analog input circuit is normal or abnormal even when a harmonic signal included in an external input and a monitoring input signal have equivalent frequency components. It is in.

[0011]

According to the present invention, a harmonic signal included in an external input is removed by temporarily removing a harmonic signal serving as a monitoring input and extracting a harmonic signal included in an output of the analog input circuit in this state. Find the presence or level of a wave signal,
This harmonic signal enables a true / false judgment or a normal judgment of the judgment result of the judgment unit, and is characterized by the following method.

A monitor input of a harmonic is superimposed on an input of an analog input circuit having an external input having a constant fundamental frequency, and the analog input circuit is determined based on the presence or absence or level of the harmonic contained in the output of the analog input circuit. A monitoring method of an analog input circuit for monitoring whether the analog input circuit is normal or abnormal, wherein the switch means can cut off the monitoring input superimposed on the input of the analog input circuit, and the result of the normal / abnormal determination of the analog input circuit becomes abnormal. The monitor input is temporarily cut off by the switch means, and whether or not the same harmonic as the monitor input is included in the external input from the output of the analog input circuit at the time of the cutoff, or the harmonic level And monitoring processing means for judging whether the judgment result is true or false based on the judgment.

In addition, a monitor input of a harmonic is superimposed on an input of an analog input circuit having an external input having a constant fundamental frequency, and the analog input circuit determines the analog input based on the presence or absence of the harmonic contained in the output of the analog input circuit. Input circuit normal /
A monitoring method of an analog input circuit for monitoring an abnormality,
Switch means for interrupting the monitoring input superimposed on an input of the analog input circuit; and a monitoring input periodically interrupted by the switch means. Whether or not the same harmonic is included, or the level of the harmonic, is determined in advance, and when the result of the normal / abnormal determination of the analog input circuit becomes abnormal, the result of the determination is determined by the presence or absence or the level of the harmonic. And monitoring processing means for judging true / false.

In addition, a monitor input of a harmonic is superimposed on an input of an analog input circuit having an external input having a constant fundamental frequency, and the analog input circuit determines the analog input based on the presence or absence or the level of the harmonic contained in the output. Input circuit normal /
A monitoring method of an analog input circuit for monitoring an abnormality,
Switch means for interrupting the monitoring input superimposed on the input of the analog input circuit, and the monitoring input is periodically interrupted by the switch means, and the same harmonic as the monitoring input is output from the output of the analog input circuit at the time of the interruption. Monitoring processing means for determining the level of the analog input circuit and including this harmonic level in the monitoring width for determining whether the analog input circuit is normal / abnormal.

Also, a monitor input of a harmonic is superimposed on an input of an analog input circuit having an external input of a constant fundamental frequency, and the analog input circuit is used to determine whether or not the level of the harmonic is contained in the output of the analog input circuit. Input circuit normal /
A monitoring method of an analog input circuit for monitoring an abnormality,
Switch means for interrupting the monitoring input superimposed on the input of the analog input circuit, and the monitoring input is periodically interrupted by the switch means, and the same harmonic as the monitoring input is output from the output of the analog input circuit at the time of the interruption. And monitoring processing means for determining the level of the harmonic and including this harmonic level in the monitoring input.

[0016]

FIG. 1 shows a monitoring circuit according to an embodiment of the present invention, and the same parts as those in FIG. 4 are denoted by the same reference numerals.

In FIG. 1, a switch section 5 is for temporarily cutting off a monitor input f _3IN superimposed on an external signal. The monitoring processing unit 6 configured by software
When the determination result of the determination unit 4 becomes abnormal, the switch unit 5 is temporarily turned off (cut off). At this time, the third harmonic f _3IN ′ included in the external input f from the output of the filter 3
The presence or absence or level of this third harmonic f _3IN ′ is checked, and the true / false judgment result of the judgment unit 4 is judged by this check, that is, the normality / abnormality of the analog input circuit 1 is monitored.

FIG. 2 shows a monitoring processing type by the monitoring processing unit 6.
3 shows a time chart. The monitoring processing unit 6 normally operates the switch.
Switch 5 is turned on, and in this state, the determination
The result is determined to be an abnormality of the analog input circuit 1.
Switch unit 5 is switched from on to off. This state
In the state, the monitoring processing unit 6 outputs the output f of the filter 3._3OUTTake
put out. The output f of the filter 3 at this time_3OUTIs an external input
The third harmonic f contained in _3IN′, And this signal f_3IN’
The monitoring processing unit 6 determines whether the determination result of the determination unit 4 is true /
Determine false.

That is, when the level of the third harmonic f _3IN ′ included in the external input is higher than a certain value, the decision unit 4
Is determined to be "false", the output of the determination unit 4 is returned to "normal", the switch unit 5 is turned on from off, and the monitoring of the analog input circuit 1 is resumed. Conversely, if the level of the third harmonic f _3IN ′ included in the external input is less than a certain value, the determination result of the determination unit 4 is determined to be “true”, and the determination of the analog input circuit 1 is determined to be abnormal. Enable output.

The process of validating / invalidating the output of the judging unit 4 by the monitoring processing unit 6 is realized by, for example, transferring the data to the computer using a flag or providing a suppression circuit in the judgment output of the judging unit 4. You.

The monitoring process is performed each time the determination result of the determination unit 4 becomes abnormal, and the valid / invalid process is performed based on whether or not the “false” determination is continued for a certain number of times. An erroneous determination when the third harmonic is temporarily included can be prevented.

FIG. 3 shows a monitoring processing type according to another embodiment.
FIG. In the figure, the judgment of the judgment unit 4 is
The monitoring process is executed periodically while the
You. The monitoring processor 6 turns off the switch 5 periodically.
In this state, the output f of the filter 3 is_3OUTTake out this
Signal f_3OUTLevel, ie the third harmonic at the external input
f _3IN’Is included and determined
Good.

Thus, when an abnormality occurs in the determination unit 4 in the monitoring state where the switch unit 5 is turned on thereafter,
The third information included in the external input stored immediately before by the monitoring processing unit 6
True / false of the determination result of the determination unit 4 can be determined from the level of the harmonic f _3IN ′. This makes it possible to quickly determine whether the output of the determination unit 4 is true or false.

In the monitoring process based on the time chart shown in FIG. 3, the extracted third harmonic f _3IN ′ may be included in the judgment formula of the judgment unit 4. In other words, the monitoring width ε is

[0025]

| F _3IN + f _3IN '| = ε', and the determination unit 4 makes a determination based on the monitoring width ε '.
As a result, it is possible to quickly determine whether the output of the determination unit 4 is true or false, and to improve the determination accuracy by setting the monitoring width ε strictly.

In the monitoring process according to the time chart shown in FIG. 3, the level of the monitoring input f _3IN can be switched or continuously changed according to the level of the extracted third harmonic f _3IN ′. . That is, the monitoring width ε
To

[0027]

| Δf _3IN + f _3IN '| = ε', and the determination unit 4 makes a determination based on the monitoring width ε '.
Also in this case, it is possible to quickly determine whether the output of the determination unit 4 is true or false, and to improve the determination accuracy by setting the monitoring width ε strictly.

When the monitoring method of the above embodiment is applied to an analog type analog input circuit, a filter for extracting the third harmonic from the output of the analog input circuit 1 is provided, and the third harmonic is extracted from the output. Is realized by determining the level of.

The monitoring input is not limited to the third harmonic.
The fifth harmonic or the like can be used, or the determination can be made by combining a plurality of harmonics.

Further, in the embodiment, the case where the present invention is applied to an analog input circuit of a protection relay device is shown. The same effect can be obtained.

[0031]

As described above, according to the present invention, a harmonic signal serving as a monitoring input is temporarily removed, and in this state, a harmonic signal contained in an output of the analog input circuit is taken out to be included in an external input. The level and the level of the harmonic signal to be detected are determined, and the harmonic signal included in the external input and the monitoring input signal are equivalent because the harmonic signal can be used to make the true / false judgment of the judgment result or the normal judgment. Can be reliably determined whether the analog input circuit is normal or abnormal.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a monitoring circuit according to an embodiment of the present invention.

FIG. 2 is a monitoring processing time chart according to the embodiment.

FIG. 3 is a monitoring processing time chart according to another embodiment.

FIG. 4 is an example of a conventional monitoring method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Analog input circuit 2 ... A / D converter 3 ... Filter 4 ... Judgment part 5 ... Switch part 6 ... Monitoring processing part

Claims (4)

[Claims] 1. A monitor input for harmonics is superimposed on an input of an analog input circuit having an external input of a constant fundamental frequency, and the analog input circuit is used to determine the presence or absence or the level of the harmonic contained in the output of the analog input circuit. A monitoring method of an analog input circuit for monitoring normality / abnormality of an input circuit, comprising: a switch unit capable of cutting off the monitoring input superimposed on an input of the analog input circuit; When an abnormality occurs, the monitoring input is temporarily cut off by the switch means, and whether or not the same harmonic as the monitoring input is included in the external input from the output of the analog input circuit at the time of the cutoff, or Monitoring means for judging a wave level and judging whether the judgment result is true or false based on the judgment. . 2. A monitor input of a harmonic is superimposed on an input of an analog input circuit having an external input having a constant fundamental frequency, and the analog input circuit determines the analog signal based on the presence or absence or the level of the harmonic contained in the output of the analog input circuit. A monitoring method of an analog input circuit for monitoring the normal / abnormal of an input circuit, comprising: a switch means capable of interrupting the monitoring input superimposed on an input of the analog input circuit; and a monitoring input periodically interrupted by the switching means. ,
From the output of the analog input circuit at the time of the cutoff, it is determined whether or not the external input contains the same harmonic as the monitor input, or the harmonic level is determined, and the normal / abnormal determination result of the analog input circuit is determined. A monitoring processing means for determining whether the determination result is true or false based on the presence or absence or level of the harmonic when an error occurs in the analog input circuit. 3. A monitor input of a harmonic is superimposed on an input of an analog input circuit having an external input having a constant fundamental frequency, and the analog input circuit determines the analog input based on the presence or absence or the level of the harmonic contained in the output of the analog input circuit. A monitoring method of an analog input circuit for monitoring the normal / abnormal of an input circuit, comprising: a switch means capable of interrupting the monitoring input superimposed on an input of the analog input circuit; and a monitoring input periodically interrupted by the switching means. ,
A monitor which determines the level of the same harmonic as the monitor input from the output of the analog input circuit at the time of the cutoff, and includes this harmonic level in the monitor width for determining whether the analog input circuit is normal / abnormal. A monitoring method for an analog input circuit, comprising: a processing unit. 4. A monitor input of a harmonic is superimposed on an input of an analog input circuit having an external input having a constant fundamental frequency, and the analog input circuit is determined based on the presence or absence or the level of the harmonic contained in the output of the analog input circuit. A monitoring method of an analog input circuit for monitoring the normal / abnormal of an input circuit, comprising: a switch means capable of interrupting the monitoring input superimposed on an input of the analog input circuit; and a monitoring input periodically interrupted by the switching means. ,
Monitoring means for judging the level of the same harmonic as the monitor input from the output of the analog input circuit at the time of the cutoff, and including the harmonic level in the monitor input. Monitoring method for input circuit.