JP2000037031A - Digital protective relay device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital protective relay device capable of eliminating misjudge even if a relay input signal includes the frequency component of a monitoring signal. SOLUTION: Focusing attention on the fact that the third harmonic component included in relay input is eliminated by the averaging of effective values, an average value determining circuit 16 obtains the average value |f|ave of the effective value, obtains a failure determination signal when a difference between it and a specified value (k) exceeds a determination level (ε), and obtains monitoring failure output by confirming continuance for a fixed period with an off-delay timer 17. This device is also provided with a means of locking the determination output that the effective value has exceeded a specified range when the average is within a specified range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital protection relay, and more particularly, to a superimposition of a monitor signal having a frequency higher than a fundamental frequency of a relay input signal to an analog input circuit and an output of the analog input circuit. The present invention relates to a monitoring device for monitoring the normal / abnormal of an analog input circuit based on the effective value of a monitoring signal appearing on a monitor.

[0002]

2. Description of the Related Art FIG. 3 shows an analog input circuit of a digital protection relay device to which such a monitoring method is applied.

An analog input circuit 1 removes a harmonic component such as noise by passing a relay input signal, which is a detection signal of a voltage or a current of a system to be protected, through an analog filter 2. Just hold. These analog filter 2 and sample
The hold circuit 3 is provided for each relay input. The multiplexer 4 takes in the hold signal of each relay input in a time-division manner, and sequentially converts the output sequence into a digital signal by the A / D converter 5.

The protection operation unit 11 performs a protection operation using a relay input signal with the microprocessor as a central unit,
Provided digital filter 12 extracts only the fundamental frequency f ₁ component of the relay input signal at its input stage and the input data for the protection operation of this signal.

Here, as means for monitoring whether the analog input circuit 1 is normal or abnormal, the analog filter 2 includes a third harmonic signal having a level of about 5 to 10% of its full scale with respect to the relay input signal. f ₃ (or the fourth harmonic signal f ₄ ) is superimposed.

By superimposing this high frequency monitor signal f ₃ on the relay input signal, the monitor signal f _3
3 appears as an output of the A / D converter 5 through the analog input circuit 1 and is extracted by the digital filter 13 as harmonic component data separated from the relay input signal.
The harmonic monitoring circuit 14 converts the harmonic component data into an effective value, and this effective value is ±
When the deviation is within 30%, it is determined that the analog input circuit 1 is operating normally.

That is, the harmonic monitoring circuit 14 performs the following calculation to determine normal / abnormal.

[0008]

| F ₃ −k | ≧ ε F ₃ : Effective value of harmonic signal f ₃ k: Specified value to be used as reference for comparing F ₃ ε: Judgment level (= 30%) 14, considering that it superimposed line noise to the relay input signal may be included in the effective value F _3, a state in which the effective value F ₃ exceeds 30% ± respect prescribed value k constant When the time has elapsed, it is determined that the analog input circuit is abnormal.

[0009]

[SUMMARY OF THE INVENTION In the conventional monitoring system, relay input signals from the system becomes distorted waveform, the component close to the frequency of the monitoring signal f ₃ to the harmonic component is present, the harmonic component is monitored incorporated into the monitoring circuit as an addition amount of the signal f _3, it may be erroneously determined as abnormal analog input circuit depending on the size of the harmonic components.

That is, the third signal included in the relay input signal
Assuming that the harmonic component is f ₃ ′, the detection amount f detected by the digital filter 13 is

[0011]

## EQU2 ## f = f ₃ + f ₃ ′ (1). Depending on the magnitude of the third harmonic component f ₃ ′, the value exceeds the determination level ε and an erroneous determination is made.

Each signal in the equation (1) is a vector quantity, and the detected quantity f when they are converted to an effective value is a minimum value |
f | _min and the maximum value | f | _max are as follows.

[0013]

[Number 3] _{| f | min = | f 3} | - | f 3 '| ... (2) | f | max = | f 3 | + | f 3' | ... (3) object of the present invention, the relay input It is an object of the present invention to provide a digital protection relay device that eliminates erroneous determination even when a signal contains a frequency component of a monitoring signal.

[0014]

The frequency component of the monitoring signal and the harmonic component contained in the relay input do not completely match in frequency, and the harmonic component contained in the relay input varies periodically. I do. Therefore, the frequency difference between the two frequency components is accompanied by a so-called periodic slip that changes periodically.

Therefore, the detected value f converted into an effective value by the harmonic monitoring circuit 14 has a minimum value | f |
It varies between _min and the maximum value | f | _max . When the minimum value and the maximum value are detected for a sufficiently long time compared to the slip period, and the average value | f | _ave is obtained,

[0016]

_Ave = (| f | _min + | f | _max ) / 2 (4) This equation (4) is obtained from the above equations (2) and (3).
The following equation (5) is obtained.

[0017]

_{│f│ ave} = _{│f 3} │ (5) In this equation (5), the average value _{│f│ ave} is the effective value │f ₃ │ of the monitoring input signal f ₃ , and the relay input signal if it contains harmonic components to obtain the effective value of the signal monitoring input signal f _3, excluding the effect of the harmonic component of the relay input signals to the average value of the minimum and maximum values of the effective value of the monitoring signal Can be.

[0018] From the above, in place of a conventional method of monitoring the difference between the effective value F ₃ of the harmonic signal f ₃ a specified value k,
By monitoring whether the difference between the average value | f | _ave and the specified value k exceeds the determination level ε, it is possible to eliminate erroneous determination due to harmonic components included in the relay input signal.

Further, the average value excluding the effect of the harmonic components included in the relay input signal | f | for _ave is the effective value itself of the monitoring signal f _3, average value | f | _ave and the prescribed value k When the difference is lower than the determination level ε, that is, when the effective value of the monitoring signal f ₃ is within the specified range, the monitoring signal f exceeds the specified value due to the harmonic f ₃ ′ included in the relay input signal. In addition, the erroneous determination can be eliminated by locking the abnormality determination output.

Based on the above principle, the present invention has the following features.

(First Invention) A monitor signal having a frequency higher than a fundamental frequency of a relay input signal to an analog input circuit is superimposed on the relay input signal, and the effective monitor signal extracted from the output of the analog input circuit is used as an effective signal. In a digital protection relay device that determines whether an analog input circuit is normal or abnormal based on whether a value exceeds a specified range, a frequency slip between a high-frequency signal included in the relay input signal and the monitor signal is provided. Monitoring means for obtaining an average value of the minimum value and the maximum value of the effective value of the monitor signal generated by the above, and obtaining an abnormality determination of the analog input circuit when the average value exceeds a specified range. I do.

(Second Invention) A monitor signal having a frequency higher than the fundamental frequency of the relay input signal to the analog input circuit is superimposed on the relay input signal, and the effective monitor signal extracted from the output of the analog input circuit is used. In the digital protection relay device which determines whether the analog input circuit is normal or abnormal based on whether the value exceeds a specified range, when the effective value of the monitoring signal exceeds the specified range, the analog input circuit is determined to be abnormal. First monitoring processing means for calculating an average value of a minimum value and a maximum value of an effective value of the monitor signal caused by a frequency slip between a high-frequency signal included in the relay input signal and the monitor signal; And second monitoring processing means for locking the output of the first monitoring processing means when the average value is within a specified range.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an apparatus configuration diagram showing an embodiment of the present invention. The harmonic monitoring circuit 14 obtains the effective value | f | from the third harmonic f ₃ extracted by the digital filter 13 by the effective value calculation circuit 15, and this effective value | f
|, An average value | f | _ave is obtained by the average value judgment circuit 16, and it is detected whether or not the difference between the average value and the specified value k exceeds the judgment level ε. After a predetermined time is continued by the delay timer 17, a monitoring abnormality determination output is obtained.

In the determination by the average value determination circuit 16, the maximum value and the minimum value within a time sufficiently longer than the slip period are stored, and the average value is calculated by the above equation (4). It is determined whether the difference is within a specified range by comparing the difference between the specified value k and the judgment level ε.

Thus, the monitoring signal f is added to the relay input signal.
If _{the 3} same harmonic component is included, it is determined that by extracting only components of the monitoring input signal f _3, to eliminate also erroneous determination if it contains a frequency component of the monitoring signal to the relay input signal Can be.

FIG. 2 is a block diagram of the apparatus showing another embodiment of the present invention. The determination circuit 18 of the harmonic monitoring circuit 14
As in the case of the conventional harmonic monitoring circuit, it is determined whether or not the difference between the harmonic component | f | When it exceeds, the on-delay timer 17 confirms the continuation for a certain period of time, and then an abnormality determination signal is obtained.

In addition, in this embodiment, the average value judging circuit 19, the off-delay timer 20, and the suppressing circuit 21
Is provided. The average value judging circuit 19 includes an effective value calculating circuit 15
_Ave is determined, and it is detected whether or not the difference between the average value and the specified value k is within the determination level ε. The off-delay timer 20 generates a suppression signal to the suppression circuit 21 when the average value judgment circuit 19 detects that the average value judgment circuit 19 is within the specified range, and this suppression means that the detection of the average value judgment circuit 19 exceeds the specified range. Sometimes it continues for a certain time.

With this configuration, the determination circuit 18 determines the effective value |
When the average value | f | _ave is within the specified range before the determination output is output to the on-delay timer 17 when the abnormality of f | is determined, the determination circuit 18 as long as the average value determination circuit 19 continues the determination result. Can be locked, and erroneous determination can be eliminated.

The determination circuit and the like in the embodiments described above are not limited to the hardware configuration, but may be a software configuration using a microprocessor mounted on the protection operation unit 11 as a processing unit.

[0030]

As described above, according to the present invention, in order to monitor the abnormality of the analog input circuit based on the magnitude of the effective value of the frequency component of the monitor signal extracted by the digital filter, the average value of the effective value is within a specified range. Since the monitoring is performed using the determination signal as to whether the monitoring signal is present or not, the erroneous determination can be eliminated even when the frequency component of the monitoring signal is included in the relay input signal.

[Brief description of the drawings]

FIG. 1 is an apparatus configuration diagram showing an embodiment of the present invention.

FIG. 2 is an apparatus configuration diagram showing another embodiment of the present invention.

FIG. 3 is a configuration diagram of a conventional analog input circuit and a monitoring circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Analog input circuit 11 ... Protection calculation part 12, 13 ... Digital filter 14 ... High frequency monitoring circuit 15 ... Effective value calculation circuit 16, 19 ... Average value judgment circuit 17 ... On-delay timer 18 ... Judgment circuit 20 ... Off-delay timer 21 ... Suppression circuit

Claims (2)

[Claims] 1. A monitoring signal having a frequency higher than a fundamental frequency of a relay input signal to an analog input circuit is superimposed on the relay input signal, and an effective value of the monitoring signal extracted from an output of the analog input circuit is within a specified range. A digital protection relay device that determines whether the analog input circuit is normal or abnormal based on whether or not the monitoring signal is exceeded, wherein the monitoring caused by a frequency slip between a high-frequency signal included in the relay input signal and the monitoring signal. Digital protection characterized by comprising monitoring processing means for obtaining an average value of the minimum value and the maximum value of the effective value of the signal and obtaining an abnormality judgment of the analog input circuit when the average value exceeds a specified range. Relay device. 2. A monitoring signal having a frequency higher than a fundamental frequency of a relay input signal to an analog input circuit is superimposed on the relay input signal, and an effective value of the monitoring signal extracted from an output of the analog input circuit is within a specified range. A digital protection relay device that determines whether the analog input circuit is normal / abnormal based on whether the analog input circuit has exceeded a predetermined range. Processing means for determining an average value of a minimum value and a maximum value of an effective value of the monitor signal generated by a frequency slip between a high-frequency signal included in the relay input signal and the monitor signal; A second monitoring processing means for locking the output of the first monitoring processing means when is within a prescribed range.