JP7432468B2 - Digital protection control device and monitoring method for digital protection control device - Google Patents

Description

The present invention relates to a digital protection control device and a monitoring method for detecting abnormalities in the digital protection control device.

For example, as described in Patent Document 1, the conventional technology uses a multiplexer to switch a plurality of analog input signals, multiplex the signals, and time-divisionally transmit the multiplexed signals to one analog/digital ( A digital protection control device that converts into a digital quantity through A/D conversion has been proposed, and has been adopted as the mainstream configuration for protection devices for substations.

The above device performs digital calculation processing on A/D converted data using a digital calculation means such as a microcomputer based on a predetermined program, detects the presence or absence of a system fault, and issues a trip command to the circuit breaker. It is something that emanates.

In such a protection control device, harmonics are superimposed on the input stage of an analog low-pass filter that is generally applied as described in Patent Document 2 for circuit monitoring of an analog input section, and a signal of the harmonic component is generated. The size of the filter is detected and fluctuations in the filter's attenuation characteristics are monitored.

Furthermore, as described in Patent Document 3, a method has been adopted in which a highly accurate harmonic signal is superimposed on an analog input, and the amplitude and phase deviation are used to monitor both A/D conversion accuracy and harmonic abnormality. ing.

Patent No. 3186735 Japanese Patent Application Publication No. 2003-37928 Japanese Patent Application Publication No. 2011-160497

According to the conventional technology, a high harmonic signal having an integral multiple of the frequency of the analog input input from the power system is superimposed on the analog input input from the power system to eliminate the amplitude deviation and phase deviation of the harmonic signal. By checking this, it is possible to detect an abnormality in the analog filter or A/D converter. Here, if the harmonic signal is generated using a direct digital synthesizer and a D/A converter, a distortion-free signal will be obtained, but the components will be expensive. On the other hand, harmonic signals generated using inexpensive oscillators and analog filters are distorted, and fixed criteria may result in erroneous detection due to manufacturing variations. Furthermore, if the number of inputs containing high-frequency components increases due to the introduction of distributed power sources, there is a concern that false detections may occur due to the high-frequency components of the inputs.

Therefore, an object of the present invention is to provide a digital protection control device and its monitoring method that can prevent false detection and detect abnormalities with high accuracy even with a low-cost configuration using an inexpensive oscillator and analog filter. do.

In order to solve the above problems, one of the representative digital protection control devices of the present invention includes a harmonic generation circuit that generates a harmonic signal of a higher frequency than the analog input input from the power system, and a plurality of analog filters that superimpose the harmonic signal on the analog input input from the system and perform capture filter processing; and a plurality of analog filters that are provided for each of the plurality of analog filters and convert the output of the analog filter into a digital quantity. The apparatus includes an analog-to-digital converter and a monitoring means for performing abnormality detection processing for the analog filter and/or the analog-to-digital converter using outputs from the plurality of analog-to-digital converters.
Further, one of the representative monitoring methods of a digital protection control device according to the present invention is a monitoring method of a digital protection control device for determining the presence or absence of an accident in an electric power system, in which a digital protection control device is monitored based on an analog input input from the electric power system. a harmonic generation step of generating a harmonic signal of a high frequency; a step of a plurality of analog filters superimposing the harmonic signal on an analog input input from the electric power system to take in the harmonic signal and perform filter processing; A plurality of analog-to-digital converters provided for each of the plurality of analog filters converts the outputs of the plurality of analog filters into digital quantities, respectively, and the outputs of the plurality of analog-to-digital converters are used to convert the outputs of the plurality of analog filters and/or Alternatively, the method includes a step of performing abnormality detection processing of the analog-to-digital converter.

According to the present invention, it is possible to provide a digital protection control device and a monitoring method for a digital protection control device that can detect an abnormality with high accuracy at low cost. Problems, configurations, and effects other than those described above will be made clear by the following description of the embodiments.

FIG. 1 is a configuration diagram of a digital protection control device according to an embodiment. FIG. 2 is a functional block diagram of a digital protection control device according to an embodiment. An explanatory diagram of a signal processing block. 5 is a flowchart showing the processing procedure of monitoring processing. 5 is a flowchart showing the processing procedure of abnormality type determination processing.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of a digital protection control device according to an embodiment. As shown in FIG. 1, the digital protection control device has a plurality of input converters (VT/CT) 1a. The plurality of input converters 1a each convert voltage and current signals from different power systems into voltage signals within a range of ±10V that can be handled by analog electronic circuits. The digital protection control device also includes a harmonic generation circuit 1b that generates an n-times harmonic signal (n is a natural number) of the frequency of the power system.

Each input converter 1a is provided with two analog filters (AF) 1c. That is, the output of one input converter 1a is input to two AF1c. Furthermore, harmonics generated by the harmonic generation circuit 1b are further input to each AF 1c, and the harmonics are superimposed on the output of the input converter 1a. This AF1c is for preventing aliasing errors due to digital sampling.

The plurality of AFs 1c are provided with A/D converters 1d in one-to-one correspondence. The analog voltage signal output by the AF 1c is converted into a digital quantity by the corresponding A/D converter 1d. The output of the A/D converter 1d is input to a CPU (Central Processing Unit) 1f.

Further, the output of the harmonic generation circuit 1b is input to a plurality of AFs 1c and also to one A/D converter 1d. This A/D converter 1d converts the harmonics generated by the harmonic generation circuit 1b and not passed through the AF 1c into digital quantities, and inputs the digital quantities to the CPU 1f. For convenience, this harmonic is referred to as an AF non-pass harmonic.

Further connected to the CPU 1f are a RAM 1g that is a work memory, a Flash 1h that is a nonvolatile memory for recording initial values, and an I/O 1i that is an input/output interface.

FIG. 2 is a functional block diagram of the digital protection control device according to the embodiment. As shown in FIG. 2, the digital protection control device includes a digital filter (DF) 2a, a Fourier transform calculation unit 2b, a protection It has a calculation section 2c and an analog monitoring section 2d. Among these, the harmonic generation circuit 1b, AF1c, A/D converter 1d, and Flash1h are hardware, but the digital filter 2a, Fourier transform calculation section 2b, protection calculation section 2c, and analog monitoring section 2d are software, That is, it is a functional unit realized by the arithmetic processing of the CPU 1.

The digital filter 2a filters the outputs of the plurality of A/D converters 1d and passes them to the Fourier transform calculation section 2b. The Fourier transform calculation unit 2b performs a discrete Fourier transform process on the signal input through the digital filter 2a.

The protection calculation unit 2c performs protection calculation based on the Fourier-transformed signal and determines whether there is an accident in the power system. For example, if it is determined that there is an accident in the power system, the protection calculation unit 2c will output an instruction to disconnect the power supply.

The analog monitoring unit 2d determines whether there is an abnormality in various analog elements or the harmonic generation circuit 1b based on the Fourier-transformed signal. Here, the analog elements include AF1c and A/D converter 1d.

FIG. 3 is an explanatory diagram of signal processing. The harmonic superimposed signal S1 and the harmonic superimposed signal S2 in FIG. 3 indicate signals input from the same input converter 1a via different AF1c and A/D converter 1d.

In FIG. 3, as a result of processing the harmonic signal S1 by the Fourier transform calculation section 2b, an amplitude A1 and a phase θ1 in the frequency domain are obtained. Similarly, the amplitude A2 and the phase θ2 are obtained as a result of processing the harmonic signal S2 by the Fourier transform calculation section 2b.

The protection calculation unit 2c and the analog monitoring unit 2d perform processing using these signals (amplitude A1, phase θ1, amplitude A2, phase θ2). Further, the analog monitoring unit 2d stores, for example, the signal (amplitude A1, phase θ1, amplitude A2, phase θ2) obtained when the digital protection control device starts to be used as an initial value in the Flash 1h, and stores the signal (amplitude A1, phase θ1, amplitude A2, phase θ2) as an initial value, and Abnormalities can be detected by changes.

FIG. 4 is a flowchart showing the processing procedure of monitoring processing by the analog monitoring section 2d. The analog monitoring unit 2d first calculates the deviation ε1 of the analog input and the deviation ε2 of the initial value of the analog input (step S101). Here, the analog input deviation ε1 is the difference between the outputs of two analog-to-digital converters provided for the same power system, that is, the difference between the harmonic signal S1 and the harmonic signal S2. Further, the deviation ε2 of the initial value of the analog input is the difference between the initial values of the harmonic signal S1 and the harmonic signal S2 stored in Flash1h.

After step S101, the analog monitoring unit 2d determines whether the analog input deviation ε1 is greater than or equal to the first threshold α1. If ε1 is less than α1 (step S101; No), the analog monitoring unit 2d determines whether ε1−ε2 is greater than or equal to the second threshold α2. ε1-ε2 is obtained by subtracting ε2, which is the difference in initial values, from ε1, which is the difference between the outputs of two analog-to-digital converters provided for the same power system. For example, abnormalities caused by aging may occur in the same way in two analog-to-digital converters installed in the power system, and in this case, ε1 will be less than α1, but ε1 - ε2 It can be detected by comparing it with the second threshold value α2. If ε1−ε2 is less than α2, the process is immediately terminated.

If ε1 is greater than or equal to α1 (step S102), or if ε1−ε2 is greater than or equal to α2, the analog monitoring unit 2d outputs a determination result that an abnormality has been detected (step S104). After that, the analog monitoring unit 2d executes an abnormality type determination process (step S105), and ends the process.

FIG. 5 is a flowchart showing the processing procedure of the abnormality type determination process. When the abnormality type determination process is started, the analog monitoring unit 2d compares the AF passing harmonics and the AF non-passing harmonics with their corresponding threshold values. AF passing harmonics are harmonics that have passed through an analog filter. That is, it indicates the high frequency component of the harmonic superimposed signal S1 or the harmonic superimposed signal S2. Moreover, the threshold value corresponding to the AF passing harmonic and the threshold value corresponding to the AF non-passing harmonic may be different values.

If the AF passing harmonic is greater than or equal to the corresponding threshold value, and the AF non-passing harmonic is greater than or equal to the corresponding threshold value (step S201; Yes), the analog monitoring unit 2d determines that an abnormality has occurred in the harmonic generation circuit. It is determined that there is one (step S202), and the process ends.

If at least one of the AF passing harmonic or the AF not passing harmonic is less than the threshold (step S201; No), the analog monitoring unit 2d sets the deviation of the AF passing harmonic of the analog input to ε3 (step S203). . The deviation of the AF passing harmonics of the analog input is the difference between the harmonic components of the outputs of two analog-to-digital converters provided for the same power system, that is, the harmonic components of the harmonic signal S1 and the harmonic signal. This is the difference from the harmonic component of S2.

After step S203, the analog monitoring unit 2d determines whether the deviation ε3 of the AF passing harmonic of the analog input is equal to or greater than the third threshold value α3 (step S204).

If ε3 is greater than or equal to α3 (step S204; Yes), the analog monitoring unit 2d determines that an abnormality has occurred in the analog element (analog filter or analog-to-digital converter) (step S205), and ends the process.

If ε3 is less than α3 (step S204; No), the analog monitoring unit 2d determines that the abnormality is due to disturbance (step S206), and ends the process. The abnormality due to disturbance is, for example, a determination result that an abnormality is obtained due to a high frequency component included in the power supply system, and does not indicate an abnormality in the digital protection control device. When introducing distributed power sources such as solar power generation, which have been increasing in number in recent years, there is a possibility that the input from the power supply system also contains high frequency components. It is preferable to make it distinguishable as an abnormality.

As described above, the digital protection control device according to the present embodiment includes a harmonic generation circuit that generates a harmonic signal with a higher frequency than the analog input input from the power system, and a harmonic signal generating circuit that generates a harmonic signal with a higher frequency than the analog input input from the power system. a plurality of analog filters that superimpose the harmonic signals on their inputs and perform capture filter processing; and a plurality of analog-digital converters provided for each of the plurality of analog filters and converting the outputs of the analog filters into digital quantities; and monitoring means for detecting an abnormality in the analog filter and/or the analog-to-digital converter using the outputs of the plurality of analog-to-digital converters.
With this configuration, one power system can be captured and evaluated through multiple analog paths, so even if a low-cost harmonic generation circuit is used, false detections due to manufacturing variations in elements on the analog path can be prevented. It is possible to detect abnormalities with high precision at low cost.
Specifically, the monitoring means determines the difference between the outputs of two analog-to-digital converters provided for the same power system, and determines that an abnormality has occurred when the difference is equal to or greater than a first threshold. Judging.

Further, the digital protection control device according to the present embodiment further includes a storage means for storing initial values of the outputs of the plurality of analog-to-digital converters, and the monitoring means further uses the initial values to perform abnormality detection processing. Therefore, abnormalities caused by aging can be detected.
Specifically, the storage means stores the initial values of the outputs of two analog-to-digital converters provided for the same power system, and the monitoring means stores the initial values of the outputs of the two analog-to-digital converters provided for the same power system, and the monitoring means stores the initial values of the outputs of two analog-digital converters provided for the same power system. The difference between the initial values is subtracted from the difference between the outputs of the analog-to-digital converter, and when the result of the subtraction is equal to or greater than a second threshold, it is determined that an abnormality has occurred.

Further, as disclosed in the embodiment, if the harmonics that have passed through the analog filter are above the corresponding threshold, and the harmonics that have not passed through the analog filter are above the corresponding threshold, the monitoring means It is determined that an abnormality has occurred in the wave generation circuit.
Then, the monitoring means determines that an abnormality due to disturbance has occurred on the condition that the difference between the plurality of harmonics that have passed through the plurality of analog filters is less than the third threshold.
Furthermore, the monitoring means determines that an abnormality has occurred in the analog filter and/or the analog-to-digital converter on the condition that the difference between the plurality of harmonics that have passed through the plurality of analog filters is equal to or greater than a third threshold value.
As described above, according to the present invention, it is possible to identify abnormalities in the harmonic generation circuit, abnormalities in the analog elements on the analog path, and abnormalities caused by disturbances.

In addition, although the above-mentioned embodiment was explained by taking as an example a configuration in which the function of the digital filter is realized by software, the digital filter may be provided as hardware. Further, each of the disclosed processes related to abnormality detection is merely an example, and can be modified as appropriate.

Thus, the present invention is not limited to the above-described embodiments, but includes various modifications. For example, the embodiments described above are described in detail to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to having all the configurations described. Furthermore, it is possible not only to delete such a configuration but also to replace or add a configuration.

1a: input converter, 1b: harmonic generation circuit, 1c: analog filter, 1d: A/D converter, 1f: CPU 1g: RAM, 1h, Flash, 2a: digital filter, 2b: Fourier transform calculation section, 2c: Protection calculation section, 2d: Analog monitoring section

Claims (8)

a harmonic generation circuit that generates a harmonic signal with a higher frequency than the analog input input from the power system;
a plurality of analog filters that superimpose the harmonic signal on an analog input input from the power system and perform a capture filtering process;
a plurality of analog-digital converters provided for each of the plurality of analog filters and converting the output of the analog filter into a digital quantity;
Monitoring means that uses the outputs of the plurality of analog-to-digital converters to perform abnormality detection processing for the analog filter and/or the analog-to-digital converter ;
and storage means for storing initial values of the outputs of the plurality of analog-to-digital converters,
The storage means stores initial values of outputs of two analog-to-digital converters provided for the same power system,
The monitoring means subtracts the difference between the initial values from the difference between the outputs of two analog-to-digital converters provided for the same power system, and when the result of the subtraction is equal to or higher than a second threshold, Determine that an abnormality has occurred
A digital protection control device characterized by: a harmonic generation circuit that generates a harmonic signal with a higher frequency than the analog input input from the power system;
a plurality of analog filters that superimpose the harmonic signal on an analog input input from the power system and perform capture filter processing;
a plurality of analog-digital converters provided for each of the plurality of analog filters and converting the output of the analog filter into a digital quantity;
monitoring means for detecting an abnormality in the analog filter and/or the analog-to-digital converter using the outputs of the plurality of analog-to-digital converters;
Equipped with
The digital protection control device is characterized in that the monitoring means determines that an abnormality due to disturbance has occurred on the condition that the difference between the plurality of harmonics that have passed through the plurality of analog filters is less than a third threshold. . In claim 1 or 2 ,
The monitoring means determines a difference between the outputs of two analog-to-digital converters provided for the same power system, and determines that an abnormality has occurred when the difference is equal to or greater than a first threshold. Features a digital protection control device. In claim 1 or 2 ,
The monitoring means determines that there is an abnormality in the harmonic generation circuit if the harmonics that have passed through the analog filter are above the corresponding threshold and the harmonics that have not passed through the analog filter are above the corresponding threshold. A digital protection control device characterized by determining that an occurrence has occurred. In claim 1 or 2 ,
The monitoring means determines that an abnormality has occurred in the analog filter and/or the analog-to-digital converter on the condition that the difference between the plurality of harmonics that have passed through the plurality of analog filters is equal to or higher than a third threshold value. A digital protection control device characterized by: In claim 1 or 2 ,
A digital protection control device, further comprising protection calculation means for determining whether or not an accident has occurred in the power system using at least one of the outputs of the plurality of analog-digital converters. A monitoring method using a digital protection control device for determining the presence or absence of an accident in a power system, the method comprising:
a harmonic generation step of generating a harmonic signal having a higher frequency than the analog input input from the power system;
a plurality of analog filters superimposing the harmonic signal on an analog input input from the power system to perform capture filter processing;
A step in which a plurality of analog-digital converters provided for each of the plurality of analog filters converts the outputs of the plurality of analog filters into digital quantities, respectively;
using the outputs of the plurality of analog-to-digital converters to perform abnormality detection processing for the analog filter and/or the analog-to-digital converter ;
The step of performing the abnormality detection process subtracts the difference between the initial values of the outputs of the two analog-to-digital converters from the difference between the outputs of the two analog-to-digital converters provided for the same power system, A method for monitoring a digital protection control device, characterized in that it is determined that an abnormality has occurred when the result of the subtraction is equal to or greater than a second threshold value . A monitoring method using a digital protection control device for determining the presence or absence of an accident in a power system, the method comprising:
a harmonic generation step of generating a harmonic signal with a higher frequency than the analog input input from the power system;
a plurality of analog filters superimposing the harmonic signal on an analog input input from the power system to perform capture filter processing;
A step in which a plurality of analog-digital converters provided for each of the plurality of analog filters converts the outputs of the plurality of analog filters into digital quantities, respectively;
performing abnormality detection processing for the analog filter and/or analog-to-digital converter using the outputs of the plurality of analog-to-digital converters;
including;
The step of performing the abnormality detection process is characterized in that it is determined that an abnormality due to disturbance has occurred on the condition that the difference between the plurality of harmonics that have passed through the plurality of analog filters is less than a third threshold. How to monitor digital protection control equipment.

Images