JPS61147724A - Automatic monitor system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an automatic monitoring system, particularly an analog signal input section.
The present invention relates to an automatic monitoring system for a digital relay having a filter circuit.

[Technical background of the invention]

In recent years, multiple AC electrical quantities are introduced from the power system via input converters, and the resulting analog AC signals are periodically sampled and converted into digital quantities, which are then protected by digital processing devices such as microcomputers. Digital protection relays that perform calculations are applied to power system protection.

The protection calculation of a digital protection relay uses a digital quantity obtained by sampling an analog AC signal, and this is based on the sampling theorem. As is well known, in order to guarantee equidistantness between the analog AC signal and the digital quantity, when the sampling frequency is f: fllF, the analog AC signal should not contain signals with frequency components of fsP/2 or higher. Therefore, digital relays are configured to remove high frequency components of the input signal by installing an analog filter in the input circuit section. Since there is a concern that the characteristics of this analog circuit may change due to aging of the components, it is essential to check the accuracy through automatic monitoring.

To check the accuracy of the analog circuit of the input section, including the conventional analog filter, a known AC check signal is applied to the all-digital relay, and the amplitude value calculated from the signal converted to a digital quantity and the preset value are used. This method detects the error between the amplitude value of the AC check signal and the configuration thereof is shown in FIG.

In FIG. 5, the input converter 1 is always inputted with the amount of system electricity i, but when inspecting the analog circuit, a known AC inspection signal iT is inputted. This alternating current inspection signal IT is introduced into the digital relay 2 and analog filter 3't-
After passing through, sample and hold circuit (S/) () 4
, is converted into a digital quantity at every predetermined sampling period by an analog-to-digital converter (LVD) 5, and is temporarily stored in a random access memory (RAM) 6.
Further, a digital calculation circuit (CPU) 7 calculates the amplitude value air. 8 is read-only memory (ROM), 2
0 is an input/output circuit (Ilo). Since the read-only memory (ROM) 8 stores in advance the amplitude values of the AC inspection signal iT, the CPU 7 stores the following (1) amplitude values.
) By calculating the equation, it is possible to detect an error with the amplitude value calculation result and detect a characteristic variation of the analog circuit of the input section. An example of the error determination formula is shown in the following formula (1).

1■Uue, 1〉ε7・・・・・・
・(1) However, ■M: Value stored as the true value of the amplitude value of the AC input signal IT IT: Result of amplitude value calculation by the digital relay of the AC input signal i εT: Tolerance error [Problems with the background art ] In the case of the above-described conventional method, since the digital relay performs protection calculation using the inspection signal while the AC inspection signal 1Tfr is being applied, there is a risk of malfunction due to the inspection input. Therefore, since an inspection is performed after the relay lock or trip circuit is locked, the protective function of the relay is impaired during the inspection. As a countermeasure to this problem, there is a method of adding an accident response function during inspection, but in this case, the operating time of the relay will be delayed. Further, since an external control circuit such as a trip circuit lock during inspection is required, it has the disadvantage that the configuration becomes complicated.

[Purpose of the invention]

The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide an automatic monitoring method that can detect characteristic fluctuations of an analog circuit of a digital relay input section with high accuracy without impairing the protection function. It is said that

[Summary of the invention]

In the present invention, a check signal synchronized with a sampling signal is applied, and a sampling value that is digitally converted at that time and a sampling value that is digitally converted when the input circuit is in a normal response state and whose value is stored in a storage circuit in advance are obtained. The aim is to automatically monitor the input circuit by comparing the

[Embodiments of the invention]

Examples will be described below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the automatic monitoring system according to the present invention.

In FIG. 1', the same parts as those in FIG. 5 are designated by the same reference numerals, and the explanation thereof will be omitted. Reference numeral 9 denotes an inspection input application circuit which receives inspection signals 1.9 synchronized with the sampling period applied to the sample/hold circuit 4. f, occurs, and this embodiment shows a case where a check signal is applied to the filter 3. In this case, the inspection signal 1T is converted into a digital signal when the input circuit is in a normal response state, and is stored in a read-only memory (ROM) in advance.
It is stored in 8.

Next, the operation will be explained. The system electrical quantity iL is introduced into a digital relay 2 via an input converter 1 and then input into an analog filter 3. The filter output is sent to a sample/hold circuit (S) 4 and an analog/digital converter (A/
D) 5 is converted into a digital quantity at each sampling period and stored in a random access memory (RAM) 6.

On the other hand, the first inspection signal i is superimposed on the system electrical quantity IL, converted into a digital quantity in the same manner as described above, and then stored in a random access memory (RAM) 6, after which it is read-only by a digital processing unit (CPU) 7. Memo I
It is compared with the data at the time of normal response stored in advance in J (ROM) 8.

FIG. 2 is a waveform diagram illustrating signal processing. In Figure 2, (a) is the sampling signal (8P), (b) is the system electricity quantity (iL), and (c) is the inspection signal (IT). The figure shows an example of a square wave for simplicity. , whose phase is synchronized with the sampling signal. Therefore, the input signal to the analog filter 3 is the system electricity quantity LL superimposed with the inspection signal iT, and becomes IL+IT. Taking the example of a low-pass filter, the output signal iFl of the analog filter 3 is as shown in Figure 2 (d). This is because the principle of superposition holds true for the input signal, so it is indicated by the broken line in (d). Filter response waveform I due to the indicated system electricity quantity LL
The waveform is the sum of L□1 and filter response waveforms iT, X, and J according to the inspection signal family indicated by dotted lines. Here, if the amount of grid electricity is constant before and after the application of the inspection signal, then from the output signal 'sp of the filter converted to the digital amount of (,),
As shown by the broken line in the same figure, by subtracting the system electrical quantity 'LFfL converted into a digital quantity before application of the inspection signal, only the response output signal (shaded area) of the filter due to the inspection signal can be extracted.

Therefore, when the input circuit such as a filter is normal, the data IDATA(f) after digital conversion of the response waveform by the check signal is stored in read-only memory (ROM).
8, but since the inspection signal is synchronized with the sampling signal, the sampling time of this data is
This always coincides with the sampling time of the filter response waveform by the inspection signal. Therefore, 1□TA and the above (
The accuracy of the input section can be checked by comparing the response waveforms of the actual inspection signals in the shaded area shown in e). An example of the determination formula for accuracy check according to the above embodiment is shown in the following (2) 2.

(('sP(m)''''''8P(m-n) )-'DA
Tmu(m))/'Dmu! M (m) ('・・・・・・(
2) However, (m) is the time series data at time m (,) is the system electrical quantity data n cycles ago. Furthermore, the electrical quantity I By used for the protection calculation of the digital relay when the inspection signal is applied is the input When the circuit is normal, the following (3 ), the application of the inspection signal does not affect the protection calculation.

”)'(m) = 18P(rl) −'DATm(m
) --------(3) FIG. 3 is a book showing a block diagram of the functions of the CPU 7 in order to obtain the automatic monitoring system according to the present invention.

10 is the filter output that is converted into a digital quantity at time m after the application of the inspection signal, and 11 is the filter output value n cycles before the period of the system electricity amount from time m, and is the filter output value before the application of the entire inspection signal. This is the data.

Then, the latter is subtracted from the former by the subtractor 12 to calculate a filter output signal based only on the inspection signal, and this signal is compared with the pre-stored data 13 when the input circuit responds normally, and is inputted by the comparator 15. Check the accuracy of the circuit section. The comparator output is configured to confirm the continuation of the failure using the counter 16, and then issue an alarm output. on the other hand,
The amount of electricity introduced into the protection calculation is determined by the subtractor 14 as described above (3).
) Calculate all the operations in the formula. It should be noted that the alarm output may end with a mere alarm, or may be configured to prevent protection calculations.

According to the above embodiment, since the method is to check the transient response of the input circuit including the filter using the inspection signal, there is an advantage that the signal transfer characteristics of the filter etc. can be directly monitored.
Since it does not affect the amount of electricity introduced for protection calculation, the protection function of the relay is not restricted.

FIG. 4 is a block diagram of still another embodiment for explaining the automatic monitoring system according to the present invention.

In FIG. 4, the same parts as in FIG. 5 are given the same reference numerals, and the explanation thereof will be omitted. In this embodiment, the output signal of the inspection input application circuit 9 is applied to the secondary side of the input converter 10. The other configurations are the same as in FIG. 1.

As a result, it is possible to monitor including the mechanical connection between the input converter 1 and the digital relay 2, thereby expanding the monitoring range.

In the above embodiment, the inspection signal has been described as a square wave, but it is not limited to this.

That is, since the present invention is a method of comparing data with normal response data, the inspection signal may have an arbitrary waveform. Furthermore, it goes without saying that analog filters can be applied not only to low-pass filters but also to all filters.

〔Effect of the invention〕

As explained above, according to the present invention, a check signal synchronized with a sampling signal is applied, and a digitally converted sampling value of this check signal and a check signal in a normal state of the input circuit, which is stored in advance in a storage circuit, are used. The accuracy of the input circuit is checked by comparing the digitally converted sampling values, and when a check signal is applied, the sampling value during normal response is subtracted from the digitally converted filter output value, so the protection calculation It is possible to introduce only the amount of system electricity excluding the inspection signal into the circuit, without impairing the protection function, and to provide an automatic monitoring system that can monitor the analog circuit of the digital relay input section with high precision.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the automatic monitoring system according to the present invention, Fig. 2 is a waveform diagram illustrating signal processing, Fig. 3 is a block circuit diagram of the automatic monitoring system, and Fig. 4 is a block diagram of the present invention. FIG. 5 is a block diagram of another embodiment of the automatic monitoring system according to the invention. FIG. 5 is a block diagram of a conventional automatic monitoring system. 1... Input converter 2... Digital relay 3... Analog filter 4... Sample and hold circuit 5... Analog-digital converter 6... RAM 7... Digital calculation circuit 8 ...ROM 9...Inspection input application circuit 10.11...Filter output

Claims (1)

[Claims] A check input is applied together with the system electricity amount to the digital relay via an input converter, and the input check input value and the pre-stored check input value are compared, and the error is determined by the input circuit of the digital relay. In the automatic monitoring method for checking the accuracy of the digital relay, a first
a second means for pre-memorizing the digitally converted sampling value in the normal response state of the input circuit when the inspection signal is applied; a digitally converted sampling value when a check signal is applied by the first means;
An automatic monitoring system characterized in that the input circuit is checked by comparing the digitally converted sampling value during normal response stored by the second means.