KR101089458B1 - Method for controlling of Analog input signal in Digital Protection Relay and Apparatus thereof - Google Patents

Abstract

The present invention relates to an analog input signal processing method and apparatus for a digital protective relay. When the present invention receives an analog signal from a plurality of sensors installed for the protection operation and measurement of the relay, the redundancy unit 104 duplicates the band above the rated band and the band below the rated band. Then, the first execution unit 106 and the second execution unit 108 perform calibration for each of the bands. When the calibration is completed, the generation unit 114 combines the data of the two duplicated bands into one, and the operation unit 116 performs a calculation operation by applying the DFT algorithm. The RMS extractor 118 extracts an RMS value that is a result of the calculation. Thereafter, the verification unit 120 verifies the linearity of the input signal using the extracted value. In this case, when the data cannot maintain linearity, the linearity is maintained by reducing the width of the reference value for each band. According to the present invention, since the redundant channel for the actual precision processing is calculated as one channel, even if an expensive A / D converter is not used, there is an advantage that no loss of computation throughput and computation processing time occurs. .

Protection relay, DFT, RMS, calibration, redundancy

Description

Method for controlling analog input signal and device of digital protection relay {Method for controlling of Analog input signal in Digital Protection Relay and Apparatus

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective relay. In particular, when extracting a root-mean-square (RMS) value of an externally input analog signal using an A / D converter, a redundant channel for actual precision processing The present invention relates to a method and apparatus for processing an analog input signal of a digital protective relay capable of operating like a channel.

The stable and continuous supply of high quality power in the power system is a very important problem in modern society. As a result, the importance of protection of power systems is increasing day by day, and the ability to detect faults quickly and accurately in the event of failure can be called a key to protection of power systems.

Therefore, a protection relay is used to detect and protect failures and accidents of various power devices and facilities constituting the power system.

The protective relay should operate correctly by detecting the voltage and current of the system without distortion even in the low current of 1A or less and the low voltage of 10V or less to several hundred A and several hundred V. In other words, the protection relay is a device for quickly detecting a short circuit or ground fault in the protected power system or equipment, and for securing power supply and supply through separation and interruption from the normal system.

In recent years, the configuration and features of the protected equipment have become complicated and diverse, and the protection requirements thereof have not only increased more severely, but also digital protection relays have become more practical than the analog type due to the development of digital technology.

The digital protection relay is characterized in that the monitoring and control of the power quality is periodically performed as a preventive diagnosis function, not just a protection function for the power system.

To this end, the digital protection relay essentially consists of an A / D converter for converting an AC signal of an external type into a digital signal through a series of calculation processes.

The A / D converter basically performs a plurality of channels and a fast channel switching operation. Thus, the digital protective relay should be configured with the A / D converter, but can accurately perform the basic functions of the digital protective relay, such as monitoring and control of abnormality of the system.

However, when the A / D converter converts an analog signal into a digital signal, an unintended error occurs due to the performance of the A / D converter. As such, most digital protective relays involve initial calibration, or during operation, precision processing (referred to as "calibration") to remove the error. The calibration is an operation for fitting the digital signal converted by the A / D converter to an analog signal reference as an original signal. Therefore, the calibration is to improve the precision of the digital protective relay.

1 is a flowchart of processing an analog input signal of a general digital protection relay.

First, the digital protective relay receives an AC signal, that is, a voltage and a current signal, which are analog signals detected by various sensors installed in the system (s10).

When the AC signal is input, a filtering operation for removing noise included in the AC signal is performed (S12).

The A / D converter performs a conversion operation of converting an analog signal into a digital signal with respect to the filtered AC signal (S14). In this case, since the A / D converter is composed of multiple channels, the operation of converting a corresponding analog signal into a digital signal is repeatedly performed while sequentially changing channels within a channel range provided.

The Discrete Fourier Transformation (DFT) algorithm is applied to the digital signal converted by the A / D converter to extract an RMS value which is converted into a fixed amount of a fixed value such as DC (s16).

A calibration process is performed such that the RMS value has an error within an allowable range with a reference value preset to the input of the digital protection relay (S18).

When the calibration process is completed, after performing the measurement process for the measurement and the relay element by the digital protection relay substantially, it is determined whether or not the abnormality (s20).

As a result of the determination, the calibrated value is compared with the preset reference value, and when the comparison result is abnormal (s22), a series of operations for cutting off the system by driving the breaker is performed (s24).

However, since the DFT algorithm performs internal multiplication, sum, and division operations during a calculation operation, the DFT algorithm itself has a large amount of calculation. Therefore, it is necessary to determine the abnormality of the system by performing a calculation process on the measurement and relay elements within a relatively fast time, but due to the characteristics of the DFT algorithm, which has a large amount of its own calculation, it is difficult to properly perform in time.

Of course, A / D converters can be used that provide high speed and high resolution characteristics. In this case, however, A / D converters are expensive and the price of the product itself increases.

In order to solve this problem, conventionally, the input channel of each phase with respect to the voltage and the current of the AC signal is duplicated, and the scale of the A / D converter is controlled while taking a value matching the input signal.

However, the above method also has the following problems.

That is, the method should read two pieces of information per channel. Therefore, the algorithm for converting an AC signal input to the digital protection relay into a DC signal should also be performed twice for each channel. The algorithm is executed twice, which means that the processing time becomes longer, which leads to the disadvantage that the operation takes a long time.

Of course, in order to improve the accuracy of the analog input signal, high precision measurement function can be realized by increasing the number of single period sample data. In this case, however, the computation time and the throughput are increased, resulting in a problem that the measurement itself becomes impossible.

Accordingly, an object of the present invention is to solve the above problems, and the computational processing time for the analog input signal is less and the processing time for the analog input signal is less than that of processing the input of each phase without using an expensive A / D converter. The present invention provides a method and apparatus for processing an analog input signal of a digital protective relay that enables a shorter operation.

According to a feature of the present invention for achieving the above object, the step of receiving an analog signal from a plurality of sensors installed for the protective operation and measurement of the relay; Duplicating the input analog signal into a band above a rating and a band below the rating; Setting a reference value for each band; Performing each of the band-specific calibrations; And combining the duplicated two band data into one after completing the calibration, and applying a DFT algorithm to calculate the data.

The method may further include verifying linearity of data according to the calculation result.

In the linearity verification step, when the data does not maintain linearity, the width of the reference value for each band may be reduced to maintain linearity.

If the data do not maintain linearity, the calibrated value may be programmatically corrected.

According to another feature of the invention, the redundancy unit for dualizing the analog signal for each channel into two bands; A first performer and a second performer for performing calibration for each of the redundant bands; A first extractor extracting a calibration value performed by the first performer and a second extractor extracting a calibration value performed by the second performer; A generation unit generating a calibration value extracted by the first extraction unit and the second extraction unit as one signal; An arithmetic unit for calculating a DFT algorithm with respect to one signal generated by the generator and an RMS extracting unit for extracting the calculated value; And a verifying unit verifying linearity of data for each channel based on the value extracted by the RMS extracting unit.

A setting unit for setting a reference value for each band; And a mode selector for selecting a mode to perform the calibration, wherein the calibration is performed in an initial setting mode of the digital protection relay.

If the linearity of the data is not maintained after the calibration is completed, a correction unit for correcting the calibration value by a program is further included.

According to the analog input signal processing method and apparatus of the digital protective relay of the present invention having such a configuration has the following effects.

That is, calibration is performed using the data divided by channel duplication of the A / D converter, and the DFT algorithm is applied to only one signal generated by combining the data of two duplicated bands. We are calculating a duplicated channel for a single channel.

Therefore, even in comparison with the conventional arithmetic processing method, even without using an expensive A / D converter, it is possible to precisely process the input signal of the digital protection relay without any loss of arithmetic throughput and arithmetic processing time.

In addition, since the linearity determination routine for self calibration is performed, the calibration value can be corrected by an internal determination program when the linearity is not maintained.

Hereinafter, an analog input signal processing method and apparatus for a digital protection relay according to a preferred embodiment of the present invention will be described in detail with reference to the preferred embodiment shown in the accompanying drawings.

The voltage range measured by the digital protection relay according to this embodiment is 0.1V to 330.0V (rated 63.5V or 110.0V), and the current range is 0.1A to 110.0A (rated 5.0A).

2 is a block diagram illustrating an apparatus for processing an analog input signal in a digital protection relay according to an exemplary embodiment of the present invention.

Referring to FIG. 2, a digital protection relay (hereinafter, abbreviated as 'relay') 100 is connected to a power line L of a power system.

The relay 100 includes an analog input unit 102 for processing voltage / current values of analog signals detected from a plurality of sensors CT and PT for protection operation and measurement of the relay 100.

The redundancy unit 104 is provided to duplicate each channel for the analog signal for each band. The channel band duplexed by the redundancy section 104 is divided into a first band section (low band section) where a relatively large error occurs and a second band section (band having a rating or higher) with less error occurrence.

A first performer 106 and a second performer 108 are provided to perform calibration for each of the redundant bands. The first performer 106 is preferably performed at a voltage of about 3A, which is about 50% of the rated voltage (63.5V) and about 1.0A, which is about 20% of the power (5.0A). The second performer 108 uses the instantaneous signal data of the first performer 106.

The first extractor 110 extracts the calibration value performed by the first performer 106 and the second extractor 112 extracts the calibration value performed by the second performer 108. Is provided.

A generator 114 for generating each calibration value extracted by the first extractor 110 and the second extractor 112 as a single signal is provided. That is, the generator 114 combines data of two channels extracted by the first extractor 110 and the second extractor 112 into one window.

An operation unit 116 for calculating a DFT algorithm with respect to one signal generated by the generation unit 114 and an RMS extraction unit 118 for extracting the calculated value are provided. The extracted arithmetic value is a direct current value.

A verification unit 120 is provided to verify linearity of data for each channel based on the extracted DC value.

The relay 100 is provided with a mode selector 122 for performing calibration of the relay 100. The mode selector 122 is divided into a normal mode and a calibration mode. If the mode selector 122 is selected, the calibration mode is executed, and if not selected, the calibration mode is performed. The calibration mode is performed at initial system setting.

In addition, a setting unit 124 is provided to set reference values of voltage and current of each phase for each channel for precise adjustment of the AC voltage / current by the calibration mode. In the present embodiment, the reference value is set to an appropriate value so that the voltage can be performed at about 3A, which is about 50% of the rated voltage (63.5V), and about 1.0A, which is about 20% of the power (5.0A).

On the other hand, the control unit 126 for controlling the overall operation of the digital protective relay is provided. The controller 126 may control the above-described components, or may control the operation for each mode selected by the mode selector 122. In addition, the controller 126 may perform a predetermined operation according to the verification result of the verification unit 120. For example, if the linearity of the data is not maintained after the calibration is completed, a function of controlling the correction unit 128 that corrects the calibration value by a program is also performed.

An analog input signal processing method of the digital protective relay configured as described above will be described with reference to FIG. 3.

3 is a flowchart illustrating an analog input signal processing method of a digital protective relay according to an exemplary embodiment of the present invention.

Once the power is applied to the digital protection relay 100, an analog input signal is applied from the outside (s100).

At this time, in order to process the analog input signal, the user selects the mode selector 122 to be in the calibration mode to perform calibration on the analog input signal. When the calibration mode is selected, the determination function of all relay elements is stopped and the digital protection relay 100 is initialized. The calibration mode is encrypted using a password or the like so that it cannot be operated by the general consumer. In addition, by operating the setting unit 124 to set the reference value for the analog voltage / current channel of each phase (s102).

In this state, the calibration mode is performed (s104). The calibration mode is performed only when input information such as a password is correct.

Then, the duplication unit 104 duplicates each phase signal for each channel for each band (s106). The band is divided into a first band section and a second band section.

In this state, the first performing unit 106 performs calibration on the first band unit. According to the calibration, voltage / current of three phases and N phases is precisely adjusted (s108).

In addition, the second performing unit 108 performs calibration on the second band unit (S110). Since the calibration by the second band part is already performed after the calibration of the first band part by the first performer 106 has been completed, the calibration is performed by configuring the entire data of the calibrated signal.

When the calibration is performed by the first execution unit 106 and the second execution unit 108, the first extraction unit 110 and the second extraction unit 112 extract the calibrated result to generate the calibration result. Transfer to section 114 (s112).

The generation unit 114 combines the extracted results and generates one signal in operation S114.

The calculation unit 116 calculates the signal generated by the generation unit 114 by applying a DFT algorithm (S116). The operation is substantially a duplicated channel, but the operation is performed by considering it as one channel. This can be compensated for the computational throughput and computational processing time.

The RMS extracting unit 118 extracts a value calculated by the DFT algorithm (s118). The extracted value is a direct current value.

The verification unit 120 verifies the linearity of the instantaneous data of each channel by the value of the DC value calculated by the DFT algorithm (S120). If the linearity of the data is not maintained as a result of the verification of the linearity, the linearity is maintained while reducing the interval between the set reference values of the first band portion and the second band portion.

In addition, if the linearity of the data is not maintained after the calibration is completed, the controller 126 controls the correction unit 128 to allow the calibration value to be corrected by a program.

According to the exemplary embodiment of the present invention, after performing a DFT operation on a conventional duplicated channel, a calibration procedure is performed on an instantaneous data by applying a separate calibration routine without performing direct calibration of RMS value extraction and phase. It can be seen that.

Although described with reference to the illustrated embodiment of the present invention as described above, this is merely exemplary, those skilled in the art to which the present invention pertains various modifications without departing from the spirit and scope of the present invention. It will be apparent that other embodiments may be modified and equivalent. Therefore, the true scope of the present invention should be determined by the technical idea of the appended claims.

In other words, the present embodiment describes a digital protective relay installed in a system for performing functions such as protection and monitoring, for example, but the present invention can be applied to a digital measuring instrument using all A / D converters.

1 is a flowchart for processing an analog input signal of a general digital protective relay

2 is a block diagram of an apparatus for processing an analog input signal in a digital protection relay according to an exemplary embodiment of the present invention.

3 is a flowchart illustrating an analog input signal processing method of a digital protective relay according to an exemplary embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

102: analog input unit 104: redundancy unit

106: first execution unit 108: second execution unit

110: first extraction unit 112: second extraction unit

114: generator 116: calculator

118: RMS extraction unit 120: verification unit

122: mode selection unit 124: setting unit

Claims (6)

Receiving analog signals from a plurality of sensors installed for protection operation and measurement of the relay; Duplicating the input analog signal into a band above a rating and a band below the rating; Setting a reference value for each band; Performing each of the band-specific calibrations; After the calibration is completed, combining the data of the two redundant bands into one and applying a DFT algorithm to calculate the data; And And verifying the linearity of the data according to the calculation result. delete The method of claim 1, In the linearity verification step, if the data does not maintain the linearity, the analog input signal processing method of the digital protective relay, characterized in that to maintain the linearity by reducing the width of the reference value for each band. A redundancy unit which duplicates analog signals for each channel into two bands; A first performer and a second performer for performing calibration for each of the redundant bands; A first extractor extracting a calibration value performed by the first performer and a second extractor extracting a calibration value performed by the second performer; A generation unit generating a calibration value extracted by the first extraction unit and the second extraction unit as one signal; An arithmetic unit for calculating a DFT algorithm with respect to one signal generated by the generator and an RMS extracting unit for extracting the calculated value; And And an verifying unit for verifying linearity of data for each channel based on the value extracted by the RMS extracting unit. The method of claim 4, wherein A setting unit for setting a reference value for each band; And And a mode selector for selecting a mode to perform the calibration, wherein the calibration is performed in an initial setting mode of the digital protective relay. The method of claim 5, And a correction unit for correcting the calibration value by a program when the linearity of the data is not maintained after the calibration is completed.

Images