JP2003037928A - Digital protection and control apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect the existence of abnormality caused by deterioration of characteristics of an analog signal system. SOLUTION: A higher harmonic wave generated from a higher harmonic signal generator 10 is superposed on an analog signal from an electric power system and inputted to a multiplexer 16 through an analog filter 14n. The higher harmonic signal is directly inputted to the multiplexer 16. These signals are sequentially sampled and converted into a digital signal by a sample hold circuit 18 and an A/D converter 20. Only higher harmonic signal component in the digital signal is extracted by a digital filter 24. A phase of digital signal obtained from the extracted digital signal by passing the analog filter 14n is corrected by a phase correcting circuit 26. A gain of the digital signal is corrected by a gain correcting circuit 28. A comparator 30 compares the digital signal whose phase and gain are corrected with the digital signal whose phase and gain are not corrected, and determines whether their deviation is within the normal 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 control device, and more particularly, to a protection control calculation for inputting an analog signal of a power system to convert it into a digital signal and protecting a protection target according to the digital signal. It relates to a digital protection control device suitable for carrying out.

[0002]

2. Description of the Related Art Conventionally, as a device for performing control for protecting a circuit breaker or the like, for example, a digital protection relay (second generation digital relay) described in Vol. Has been. A conventional device of this type is configured to include an analog input unit, a digital arithmetic processing unit, a settling unit, and an output unit. The input unit includes an analog filter for preventing folding error, a sample hold circuit, a multiplexer, An A / D converter and a buffer are provided. This type of device is mainly composed of an input board for digital filter processing using high-speed sampling data and an operation board for protection control operation. The input board samples at an electrical angle of 3.75 degrees. Then, the digital filter calculation is executed, and the calculation result is output to the calculation board once every 30 degrees.

The arithmetic board receives data from the input board and executes arithmetic processing for protecting the circuit breaker and the like based on a protection arithmetic algorithm.

Conventionally, in this type of digital protection control device, in order to detect the consistent characteristic deterioration of the analog input section, a harmonic signal which is an integral multiple of the fundamental wave of the power system, for example, 4 times or 12 times is used. The signal is superposed on the analog signal of the power system and captured by the analog filter, the signal size after passing through the analog filter is detected, and according to the detection result, the presence or absence of an abnormality due to the characteristic deterioration of the analog input section is monitored. It is configured.

[0005]

SUMMARY OF THE INVENTION Using the above conventional technique,
The following problems occur in the method of detecting the consistent characteristic deterioration of the analog input section.

(1) It is difficult to detect the presence or absence of abnormality with high accuracy because only the magnitude of the harmonic signal superimposed on the analog signal of the power system is detected and no consideration is given to the phase characteristics of the signal. Is.

(2) In order to detect the characteristic deterioration of the analog input portion with high accuracy, it is necessary to obtain the effective value of the detected harmonic, and it takes time to calculate the effective value, and it is determined whether or not there is an abnormality. There will be a time delay.

Therefore, in the prior art, when the signal that has passed through the analog filter is processed and an abnormality is detected, it may be after the circuit breaker has erroneously operated, which is effective only for identifying the defective portion. There was no sex. For this reason, in terms of the system, it is impossible to cover malfunctions other than configuring the duplication.

An object of the present invention is to provide a digital protection control device capable of highly accurately detecting the presence / absence of an abnormality due to deterioration of characteristics of an analog signal system.

[0010]

In order to solve the above-mentioned problems, the present invention provides a monitor signal generating means for generating a monitor signal having a frequency different from the analog signal of the power system, and an analog signal from the power system. A plurality of analog filter means for superimposing and inputting the supervisory signal and filtering the input signal, and output signals of the plurality of analog filter means and supervisory signals generated by the supervisory signal generating means are sequentially selected and output. Multiplexing means, analog / digital converting means for sampling the output signal of the multiplexing means at a constant period to convert it into a digital signal, and a digital signal corresponding to the monitoring signal from the output signal of the analog / digital converting means. Of the digital signal extracting means for extracting and the digital signal extracted by the digital signal extracting means, The correction means for correcting the digital signal corresponding to the monitoring signal superimposed on the analog signal, and the monitoring signal directly inputted from the monitoring signal generating means to the multiplexing means among the digital signals extracted by the digital signal extracting means. The digital protection control device comprises a determination means for comparing the corresponding digital signal with the digital signal corrected by the correction means to determine whether or not there is an abnormality in the analog signal system.

In constructing the digital protection control device, the following elements can be added.

(1) The correction means, with respect to the digital signal corresponding to the supervisory signal superimposed on the analog signal, at least one of a gain error and a phase error caused by the plurality of analog filter means, The digital signal corresponding to the supervisory signal directly input from the supervisory signal generating means to the multiplexing means is corrected and used as a reference.

(2) The judging means judges whether or not there is an abnormality for each sampling by the analog / digital converting means.

(3) A digital signal corresponding to a harmonic component of the analog signal is removed from the output signal of the analog-digital converting means, and a protection target is controlled based on the digital signal from which the harmonic component is removed. The digital filter arithmetic processing means for performing the protection control arithmetic is provided.

(4) The monitoring signal generating means generates a harmonic signal that is an integral multiple of the fundamental wave of the power system as a monitoring signal.

According to the above means, the digital signal corresponding to the supervisory signal is extracted from the digital signals obtained by sampling the output signal of the multiplexing means, and the analog signal of the power system is extracted from the extracted digital signals. Correct the digital signal corresponding to the supervisory signal superimposed on the signal,
The corrected digital signal and the digital signal corresponding to the supervisory signal directly input from the supervisory signal generating means to the multiplexing means are compared, and if the deviation between the two exceeds, for example, a prescribed range, it is abnormal. When the difference between the two is within the specified range, it can be determined as normal, and the presence or absence of abnormality in the analog signal system including the plurality of analog filter means can be detected with high accuracy.

When an abnormality in the analog signal system is detected,
By outputting the lock signal for invalidating the processing result of the digital filter arithmetic processing means to the digital filter arithmetic processing means, it is possible to prevent the protection target from malfunctioning.

Further, for the digital signal corresponding to the supervisory signal superimposed on the analog signal, at least one of the gain error and the phase error caused by the plurality of analog filter means is transferred from the supervisory signal generating means to the multiplexing means. Since the digital signal corresponding to the directly input monitoring signal is used as the reference for correction, it is not necessary to calculate the effective value of the monitoring signal, and it is possible to instantly determine the presence or absence of an abnormality according to the digital signal obtained from the instantaneous value. can do.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a digital protection control device showing an embodiment of the present invention. Figure 1
In the digital protection control device, the harmonic signal generator 10, the plurality of addition circuits 12a to 12n, the plurality of analog filters 14a to 14n, the multiplexer circuit 16,
Sample-hold circuit 18, analog / digital converter (A / D converter) 20, harmonic removal digital filter 22, harmonic signal extraction digital filter 24,
Phase correction circuit 26, gain correction circuit 28, comparator 30,
The memory circuit 32 is provided.

The harmonic signal generator 10 is an integral multiple of the fundamental wave (50 Hz or 60 Hz) of the power system, for example, 12
It is configured as a monitor signal generation unit that generates a double harmonic signal (600 Hz) and outputs this harmonic signal as a monitor signal to each of the adder circuits 12a to 12n and the multiplexer circuit 16. The adder circuits 12a to 12n take in the analog signals (50 Hz) Ia to In from the power system, add the analog signals and the harmonic signals, that is, superimpose the harmonic signals on the analog signals, and convert the analog signals and the harmonic signals. The signals including the analog filters 14a to 14n are respectively included.
It is designed to output to. Each analog filter 14
a to 14n are configured as analog filter means for removing noise due to a specific frequency component contained in the input signal and preventing aliasing error due to sampling. That is, each of the adder circuits 12a to 12n and the analog filters 14a to 14n are configured as analog filter means for superimposing a harmonic signal on an analog signal and inputting it, and filtering this input signal.

The multiplexer circuit 16 directly inputs the harmonic signal from the harmonic signal generator 10, and sequentially selects and inputs the signals in which the harmonic signals are superimposed on the analog signals from the analog filters 14a to 14n and multiplexes them. The sampled and held circuit 18 sequentially converts the multiplexed and multiplexed signals.
It is configured as a multiplexing means for outputting to. The sample hold circuit 18 sequentially samples and holds the output signal of the multiplexer circuit 16 in accordance with the sampling frequency, and outputs the held signal to the analog / digital converter 20 sequentially. The analog / digital converter 20 is adapted to convert the analog signal output from the sample hold circuit 18 into a digital signal and output the converted digital signal to the digital filters 22 and 24. That is, the sample hold circuit 18 and the analog / digital converter 20 are configured as analog / digital conversion means.

The digital filter 22 is configured as a harmonic-removing digital filter for removing a harmonic unnecessary for protection control calculation, for example, a harmonic (600 Hz) that is 12 times higher than the fundamental wave (50 Hz). The digital filter 22 is, for example, as shown in FIG. 2A, as a biquad-type second-order delay digital filter, a multiplication circuit 22a, 22c, 22d, 22e, 22f, and a delay circuit for delaying the signal by one sample. 22g, 22
h, adder circuits 22i, 22j, 22 for adding input signals
k and 22l. The digital filter 22 has coefficients H0, AI, A of each circuit.
2, B1, and B2 are configured so that the type of filter, for example, bandpass, lowpass, lowpass notch, allpass, cutoff frequency, center frequency, and selectivity Q of the filter can be arbitrarily set.

When the digital filter 22 is used as a low pass notch, as shown in FIG. 2 (b), a gain-frequency characteristic that can sufficiently attenuate the harmonic 600 Hz, which is 12 times the fundamental wave 50 Hz, is obtained. be able to. This characteristic is an example in which the fundamental wave F1 is 50 Hz and the transmission zero is 12 times the fundamental wave, that is, 600 Hz. By using the digital filter 22 having this filter characteristic, the harmonics 12 times the fundamental wave can be completely eliminated. Can be shut off. The analog signal from which the harmonics have been removed by the digital filter 22 is input to a control circuit for controlling the object to be protected, for example, a control circuit composed of a CPU, and in this control circuit, the digital signal from which the harmonic components have been removed. Based on the above, the protection control calculation for controlling the protection target is performed. That is, the digital filter 22 is configured as a digital filter arithmetic processing means together with the control circuit.

The digital filter 24 is constructed as a digital signal extracting means for extracting with high precision only the signal component of the harmonic signal superimposed on the analog signal. That is, the digital filter 24 extracts the digital signal corresponding to the harmonic signal (600 Hz) from the digital signal output from the analog / digital converter 20,
The extracted digital signal is used for the comparator 30 and the phase correction circuit 2
It is designed to output to 6. This digital filter 24 can be configured by using a digital filter having the same elements as the digital filter 22 as a bandpass, and the gain-frequency characteristic at that time is shown in FIG. Are shown in FIG. 3 (b), respectively.

As shown in FIG. 3, the characteristic of the digital filter 24 is that the fundamental wave is 50 Hz and the harmonic wave is 600 Hz.
The gain of is set to be extremely large, and other frequency components are attenuated. Regarding the phase of the digital filter 24, since the center frequency is set to F12 (600 Hz) due to the characteristics of the bandpass filter, the phase delay is 0 degree.

The digital filters 22 and 24 have the configuration shown in FIG.
As shown in (a), the digital signal corresponding to the signal component in which the harmonic component is superimposed on the analog signal is input, but the digital filter 24 outputs the harmonic component as shown in FIG. 4C, the digital filter 22 outputs a digital signal corresponding to the signal component from which the harmonic components have been removed, as shown in FIG. 4C.

The phase correction circuit 26 inputs the digital signal obtained by passing through the analog filters 14a to 14n among the digital signals output from the digital filter 24 from the harmonic signal generator 10 directly to the multiplexer circuit 16. Based on the digital signal obtained based on the obtained signal, the filter coefficient 34 stored in the storage circuit 32 is configured as one element of a correction unit that corrects the phase error caused by the analog filters 14a to 14n. .

As shown in FIG. 5A, this phase correction circuit 26 has the same elements as the digital filters 22 and 24 such that multiplication circuits 26a, 26c, 26d, 26e,
26f, delay circuit 2 for delaying data by one sample
6g, 26h, 26i, 26j, 2 for adding input signals
It is configured with 6k and 26l and has a filter coefficient of 3
4 is selected so that arbitrary phase-frequency characteristics such as characteristics 1 to 3 can be realized as shown in FIG. 5B.

When the phase error of the digital signal is corrected by using the phase correction circuit 26, as shown in FIG. 6A, the harmonic signal generator 10 of the output signal of the digital filter 24 is directly fed to the multiplexer 16. The digital signal obtained based on the input signal has characteristics 10
The digital signal represented by 0 and obtained by passing through the analog filter 14i is represented by the characteristic 102. It can be seen that the gain of the latter digital signal is attenuated by the analog filter 14i and a phase delay occurs.

Therefore, in the present embodiment, the phase of the digital signal obtained by passing through the analog filter 14i is corrected by using the phase correction circuit 26, and as shown in FIG. The phase difference between the digital signal obtained based on the harmonic signal directly input from the generator 10 to the multiplexer circuit 16 and the digital signal obtained through the analog filter 14i is eliminated.

Further, the gain correction circuit 28 is one of correction means for correcting the gain error caused by the analog filter 14i by using the gain correction 36 stored in the storage circuit 32.
It is organized as an element. That is, the gain correction circuit 28 is provided between the digital signal obtained from the harmonic signal input from the harmonic signal generator 10 directly to the multiplexer circuit 16 and the digital signal obtained by passing through the analog filter 14i. Is, as shown in FIG.
Since there is a difference in gain, the gain correction 36 is used to increase the gain of the digital signal obtained by passing through the analog filter 14i so that the amplitude difference between the two becomes zero as shown in FIG. 6 (c). It has become. The phase-corrected and gain-corrected digital signal is input to the comparator 30.

The phase correction circuit 26 corrects the phase delay by the analog filter 14i and the phase shift by successive sampling. If the characteristics and sampling frequency of the analog filter 14i are determined, This value can be obtained in advance.

The comparator 30 is a harmonic signal generator 10 of the digital signal output from the digital filter 24.
Digital signal and analog filter 1 obtained from the harmonic signal directly input from the multiplexer circuit 16
The digital signal obtained by passing through 4i is compared with the digital signal which is phase-corrected and gain-corrected,
It is configured as a determination unit that determines whether or not there is an abnormality in the analog signal system, for example, the analog filter 14i according to the comparison result. In this case, when the deviation between the two signals is within a certain range, for example, when the deviation 104 between the two signals is within a normal range as shown in FIG. A signal indicating that the analog signal system is normal is output assuming that there is no characteristic deterioration due to secular change or abnormality due to element failure.

Although the difference between the two is theoretically 0, a deviation 104 occurs as shown in FIG. 6 (d) due to variations in the initial values of the elements. However, it is possible to detect the presence or absence of abnormality with high accuracy by setting the deviation 104 to be abnormal except for the range in which variations in the initial values of the elements and theoretically generated A / D conversion errors are taken into consideration.

On the other hand, as shown in FIG. 7, when the phase error and the gain error also cause a gain error and the deviation 104 due to the gain error is out of the normal range, it is determined that the analog signal system is abnormal.

Further, as shown in FIG. 8, a phase shift also occurs due to the phase correction and the gain correction.
When 4 exceeds the normal range, it is determined that the analog signal system is abnormal.

As described above, in the present embodiment, it is possible to instantaneously detect the abnormality not only in the gain error but also in the phase shift. Further, since the preset detection range can be determined in consideration of the variation due to the deterioration of the element, it is possible to have flexibility that can be determined according to the importance of the device to be operated.

When an abnormality in the analog signal system is detected, the operation for controlling the circuit breaker or the like to be controlled is stopped, so that a malfunction due to a defective element can be instantaneously stopped. The reliability of can be greatly increased.

In this embodiment, the gain correction is performed on the signals input to a plurality of channels, but since this gain correction is common to all the channels, only one type of correction coefficient is required. Moreover, when the phase-corrected and gain-corrected signals are compared with the digital signal obtained based on the signal directly input to the multiplexer circuit 16, both signals can be set to the same value on the time axis. Therefore, it is possible to detect the presence / absence of an abnormality in the analog signal system by simply comparing the two signals.

[0040]

As described above, according to the present invention,
A digital signal corresponding to the monitor signal is extracted from the digital signals obtained by sampling the output signal of the multiplexing means, and corresponds to the monitor signal superposed on the analog signal of the power system among the extracted digital signals. The digital signal is corrected, the corrected digital signal is compared with the digital signal corresponding to the supervisory signal directly input from the supervisory signal generating means to the multiplexing means, and the presence or absence of abnormality in the analog signal system is judged based on the comparison result. Therefore, the presence or absence of abnormality in the analog signal system including the plurality of analog filter means can be detected with high accuracy.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a digital protection control device showing an embodiment of the present invention.

2A is a block diagram of a digital filter, FIG.
(B) is a characteristic diagram showing the relationship between the frequency and the gain of the digital filter.

FIG. 3A is a characteristic diagram showing a relationship between a frequency and a gain of a digital filter, and FIG. 3B is a characteristic diagram showing a relationship between a frequency and a phase of the digital filter.

FIG. 4 is a diagram for explaining an output waveform of a digital filter.

5A is a block configuration diagram of a phase correction circuit, and FIG.
FIG. 4 is a characteristic diagram for explaining the relationship between the frequency and the phase of the phase correction circuit.

FIG. 6 is a waveform diagram for explaining gain correction and phase correction in a normal state.

FIG. 7 is a waveform diagram for explaining gain correction and phase correction when a gain error occurs.

FIG. 8 is a waveform diagram for explaining gain correction and phase correction when a phase shift occurs.

[Explanation of symbols] 10 High frequency signal generator 12a ... 12n adder circuit 14a ... 14n Analog filter 16 multiplexer 18 Sample and hold circuit 20 analog / digital converter 22 Digital filter for removing harmonics 24 Digital Filter for Harmonic Extraction 26 Phase correction circuit 28 Gain correction circuit 30 comparator 32 memory circuits

Continued front page    (72) Inventor Shinji Saito             1-1-1 Kokubuncho, Hitachi-shi, Ibaraki Stock             Hitachi, Ltd. Electric Systems Division (72) Inventor Mitsuo Sato             1-1-1 Kokubuncho, Hitachi-shi, Ibaraki Stock             Hitachi, Ltd. Electric Systems Division F-term (reference) 5G042 GG02 GG08

Claims (5)

[Claims] 1. A monitor signal generating means for generating a monitor signal having a frequency different from that of an analog signal of a power system, and an analog signal from the power system by superimposing and inputting the monitor signal, and filtering the input signal. A plurality of analog filter means, a multiplexing means for sequentially selecting and outputting the output signals of the plurality of analog filter means and the supervisory signal generated by the supervisory signal generating means, and the output signal of the multiplexer means in a constant cycle. By analog / digital conversion means for sampling and converting into a digital signal, digital signal extraction means for extracting a digital signal corresponding to the monitoring signal from the output signal of the analog / digital conversion means, and extraction by the digital signal extraction means. Digit corresponding to the supervisory signal superposed on the analog signal among digital signals Correction means for correcting the digital signal, and among the digital signals extracted by the digital signal extraction means, a digital signal corresponding to the monitoring signal directly input from the monitoring signal generation means to the multiplexing means and corrected by the correction means. A digital protection control device comprising: a judgment means for judging whether or not there is an abnormality in an analog signal system by comparing with a digital signal. 2. The digital protection control device according to claim 1, wherein the correction means applies a gain caused by the plurality of analog filter means to a digital signal corresponding to a supervisory signal superimposed on the analog signal. At least one of an error and a phase error is corrected with reference to a digital signal corresponding to a supervisory signal directly input from the supervisory signal generating means to the multiplexing means, as a reference. 3. The digital protection control device according to claim 1, wherein the determination unit is the analog
A digital protection control device characterized in that the presence or absence of an abnormality is determined for each sampling by the digital conversion means. 4. Any one of claims 1, 2 and 3
In the digital protection control device described in the paragraph (3), a digital signal corresponding to a harmonic component of the analog signal is removed from the output signal of the analog-digital conversion means, and protection is performed based on the digital signal from which the harmonic component is removed. A digital protection control device comprising digital filter arithmetic processing means for performing a protection control calculation for controlling an object. 5. The digital protection control device according to claim 1, wherein the supervisory signal generation unit generates a harmonic signal that is an integral multiple of a fundamental wave of the power system. A digital protection control device characterized by being generated as a monitoring signal.