Protection relay and method for controlling same protection relay

Abstract

The present invention relates to a protection relay comprising: a sampling unit for sampling the amount of electricity of a system sensed by a sensor according to a preset sampling period; a memory for storing a slope factor and offset factors, which are correction values calculated according to the correlation between the magnitude of the amount of electricity actually measured in the protective relay and an estimated value estimated through a mathematical operation on the amount of electricity of the system; a root mean square (RMS) calculation unit for calculating an RMS value according to sampled sample data; a sample correction unit for calculating, on the basis of the calculated RMS value of the sample data and the offset factors, an offset ratio value that is a ratio value of the offset factors to be applied to the sample data, and correcting the sample data on the basis of the calculated offset ratio value and the slope factor; and a control unit for calculating power information related to the power of the system on the basis of current sample data and voltage sample data corrected via the sample correction unit.

Description

Protective relay and control method thereof

[0001] The present invention relates to a protection relay and a control method for the protection relay, and more specifically, to a protection relay capable of correcting errors that may occur in electronic circuits and signal processing.

[0002] Protective relays, typically used for system protection and measurement monitoring in power systems, can calculate various power-related measured values, such as power quantity and power factor, based on basic voltage and current data detected by detection devices. Furthermore, they perform functions such as system protection, monitoring, diagnosis, and measurement based on these calculated measured values. To this end, protective relays can calculate power information, including the power quantity of the system, by signal processing the basic data sensed and amplified by the detection device and converted into digital values ​​according to a preset computational algorithm.

[0003] However, the signal processing process for measuring power from the above basic data may result in errors depending on the circuit hardware or in the calculation process. Such errors may degrade the measurement precision of the protective relay. Therefore, current protective relays calculate a correction value that can compensate for errors that may occur in the process of measuring power based on the above basic data, and reflect the calculated correction value in the measured value after signal processing, thereby compensating for errors that may occur in the hardware or calculation process.

[0004] Meanwhile, in order to measure such power information, signal processing is performed on the current and voltage sample data sampled from the detection device, and the DFT (Discrete Fourier Transform) or RMS (Root Mean Square) algorithm can be used as the signal processing algorithm. In this case, the DFT algorithm decomposes the values ​​of the sample data into frequency components and uses only the components of the fundamental frequency for magnitude calculation, so there is a problem that the precision of the measured value is reduced when components other than the fundamental frequency are included. To prevent this, the magnitude of each frequency component can be calculated through the DFT algorithm, but in this case, the calculation process is very complicated, and there is a problem that complex calculations must be performed, such as adding up all the values ​​calculated for each frequency to measure the amount of power.

[0005] On the other hand, the RMS algorithm, with its simple computational process, allows for rapid calculations. However, the RMS algorithm is limited to simply calculating magnitude and cannot perform phase-related calculations. Therefore, to calculate phase-related power using the RMS algorithm, the values ​​of current and voltage sample data collected at the same time must be multiplied together to calculate the power.

[0006] However, the current and voltage values ​​of the system change over time, and accordingly, the error value also changes over time.

[0007] Referring to Fig. 1, Fig. 1 shows an example of an ideal current value (hereinafter, ideal value) (11) as an estimated value estimated through mathematical operation, that is, a theoretical value, and a current value (hereinafter, actual value) (10) measured in an actual protective relay. Here, the ideal value (11) is an ideal measured value in a state where no hardware error occurs in the signal processing operation process, as the signal processing process is implemented as an algorithm. On the other hand, the actual measured value (10) is a measured value produced in an actual protective relay, and may be a result value produced through a signal processing process of the protective relay. Accordingly, the actual measured value (10) may be a value that includes an error due to the hardware of the protective relay.

[0008] In this case, as shown in the above Fig. 1, a difference value, i.e. an error (12) due to the hardware of the protective relay, may occur between the ideal value (11) and the actual value (10). Meanwhile, since the AC current and AC voltage have the characteristics of a sine wave, the error (12) may continuously vary in size depending on the current size that changes over time, as shown in Fig. 1.

[0009] Meanwhile, the current transformer (CT) and voltmeter (potential transformer) that measure the above basic data have linear characteristics in which the output value changes constantly in response to changes in the input value. Therefore, the actual measured value (10) and the above ideal value (11) can have a linear correlation, i.e., a correlation according to a first-order equation.

[0010] In this case, if the actual measured value is y and the above-mentioned abnormal value is x, if the actual measured value increases or decreases at the same rate as the increase or decrease of the abnormal value of the current or voltage, it can have a correlation of y = ax. However, in reality, the actual measured value does not increase or decrease in the same way according to the rate a at which the abnormal value of the current or voltage increases or decreases, but the actual measured value may increase or decrease by a greater or lesser amount than the increase or decrease of the abnormal value according to the rate a. Here, since the above-mentioned correlation equation is about the size of the result value (actual measured value) for the input value (abnormal value), the value that changes more than the increase or decrease according to the rate (a), that is, the offset value, can be expressed in the form of a first-order equation by reflecting its average value in the correlation according to the change rate of the above-mentioned actual value and the abnormal value.

[0011] In this case, the above-mentioned abnormal value (x) and the actual value (y) can be expressed as having a relationship of y = ax + b. Here, the increase / decrease ratio a of the abnormal value (x) with respect to the actual value (y) may correspond to the slope value in the above-mentioned correlation equation y = ax + b. Accordingly, the increase / decrease ratio a will be referred to as a slope factor hereinafter. In addition, the above-mentioned offset value b is a value corresponding to the y-intercept in the above-mentioned correlation y = ax + b, and the above-mentioned offset value b will be referred to as an offset factor hereinafter.

[0012] However, as examined in the above-described Fig. 1, the current and voltage of the system, i.e., the basic data, change over time, and accordingly, the error value also changes over time. In this case, the slope factor a is a ratio according to the size of the abnormal value and the actual value, and can be applied even when the actual value is a sample. However, the offset factor b has a problem in that it is an average value of the offset values ​​that increase or decrease more or less than the value by which the actual value increases or decreases, identical to the rate at which the abnormal value increases or decreases (slope factor a), and is not a correction value for the sample value.

[0013] That is, as shown in the above Fig. 1, the error (12) has a characteristic that changes over time. If the correlation between the above-mentioned abnormal value and the actual value includes the above-mentioned offset factor b, the offset value of each sample also changes over time according to the error that changes over time. Accordingly, there is a problem that it is difficult to reflect the above-mentioned offset factor b in the sample value.

[0014] Therefore, when calculating power through the RMS algorithm, a typical protection relay compensates the current sample and voltage sample by reflecting only the slope factor a applicable to the sample value, and measures power based on the compensated current sample and voltage sample. Therefore, in the case of a typical protection relay, compensation according to the offset factor b is not performed, and the power is calculated while the error value corresponding to the offset factor b remains. In other words, there is a problem that the measured value is measured incorrectly because the hardware error of the protection relay is partially reflected.

[0015] The present invention aims to solve the above-mentioned problems and other problems, and provides a protection relay capable of more accurately calculating the power amount of a system and a control method of the protection relay.

[0016] According to one aspect of the present invention to achieve the above or other purposes, a protection relay according to an embodiment of the present invention is characterized by including a sampling unit that samples the electric quantity of a system sensed by a sensor according to a preset sampling cycle, a memory that stores slope factors and offset factors, which are correction values ​​calculated based on a correlation between the size of the electric quantity actually measured by the protection relay and an estimated value estimated through a mathematical operation on the electric quantity of the system, an RMS calculation unit that calculates an RMS (Root Mean Square) value according to sampled sample data, a sample correction unit that calculates an offset ratio value, which is a ratio value of the offset factor to be applied to the sample data based on the RMS value of the calculated sample data and the offset factor, and corrects the sample data based on the calculated offset ratio value and the slope factor, and a control unit that calculates power information related to the power of the system based on current sample data and voltage sample data corrected through the sample correction unit.

[0017] In one embodiment, the offset ratio value is characterized by being a ratio of the offset factor to the RMS value of the currently sampled sample data.

[0018] In one embodiment, the sample correction unit is characterized in that it calculates a correction factor for the currently sampled electric quantity by adding the offset ratio value to the slope factor, and corrects the sample data of the currently sampled electric quantity according to the calculated correction factor.

[0019] In one embodiment, the sample correction unit corrects current sample data and voltage sample data according to the same sampling order based on a current correction factor calculated for the current of the system and a voltage correction factor calculated for the voltage of the system, respectively, and the control unit calculates the power information based on the corrected current sample data and voltage sample data according to the same sampling order.

[0020] In one embodiment, the control unit is characterized in that it calculates the current amount corresponding to the corrected current sample data and the voltage amount corresponding to the corrected current sample data through an RMS operation on the corrected current sample data and the voltage sample data, and calculates power information of the system according to the calculated current amount and voltage amount.

[0021] In one embodiment, the RMS calculation unit calculates an RMS value according to sample data of a sampling order prior to the currently sampled sample data, and the sample correction unit calculates the offset ratio value based on the RMS value according to sample data of the previous sampling order.

[0022] In one embodiment, the control unit is characterized in that, when the protection relay is initially driven, it estimates a plurality of electric quantities of the system over time through mathematical calculations, calculates a plurality of sizes of electric quantities according to sample data sampled at points in time corresponding to the estimated electric quantities, and calculates a correlation between a first coordinate pair of an estimated value estimated at a first point in time and a calculated value calculated from the sample data sampled at the first point in time, and a second coordinate pair of an estimated value estimated at a second point in time and the sample data sampled at the second point in time, thereby calculating the slope factor and the offset factor.

[0023] In one embodiment, the control unit is characterized in that it calculates a correlation between the first coordinate pair and the second coordinate pair as a linear equation, calculates the slope of the calculated linear equation as the slope factor, and calculates the y-intercept of the linear equation as the offset factor.

[0024] In one embodiment, the control unit is characterized in that it generates the second coordinate pair after a preset time has elapsed from the first point in time.

[0025] In one embodiment, the control unit is characterized in that it calculates a phase difference between the corrected current sample data and the voltage sample data and calculates a power factor according to the calculated phase difference or a reactive power according to a shifted phase of the corrected current sample data and the voltage sample data as the power information.

[0026] According to one aspect of the present invention to achieve the above or other purposes, a method for controlling a protection relay according to an embodiment of the present invention is characterized by including the steps of sampling an electric quantity of a system sensed by a sensor according to a preset sampling cycle, calculating an RMS (Root Mean Square) value according to currently sampled sample data, calculating a correction factor to be applied to the sample data based on a slope factor and an offset factor, which are correction values ​​calculated in advance according to a correlation between a size of an electric quantity actually measured by the protection relay and an estimated value estimated through a mathematical operation on the electric quantity of the system, correcting the currently sampled sample data according to the calculated correction factor, and calculating power information related to the power of the system based on the corrected current sample data and voltage sample data.

[0027] In one embodiment, the step of calculating the correction factor is characterized by including the step of calculating an offset ratio value which is a ratio of the offset factor to an RMS value of the currently sampled sample data, and the step of calculating the correction factor by adding the calculated offset ratio value and the slope factor.

[0028] In one embodiment, the step of calculating the RMS value is a step of calculating the RMS value according to sample data of a sampling order prior to the currently sampled sample data, and the step of calculating the correction factor is characterized by including a step of calculating an offset ratio value which is a ratio of the offset factor to the RMS value of sample data of the previous sampling order, and a step of calculating the correction factor by adding the calculated offset ratio value and the slope factor.

[0029] In one embodiment, the method is characterized by further comprising, before the sampling step, a step of detecting whether there is a pre-stored slope factor and an offset factor, and, if there is no pre-stored slope factor and an offset factor, a step of detecting the slope factor and the offset factor based on the size of the electric quantity actually measured by the protective relay and an estimated value estimated through a mathematical operation on the electric quantity of the system.

[0030] In one embodiment, the step of detecting the slope factor and the offset factor is characterized by including the steps of: estimating the electric quantity of the system at a first point in time through a mathematical operation; generating a first coordinate pair according to the magnitude of the electric quantity calculated from the protective relay and the estimated value at the first point in time based on sample data sampled at the first point in time; estimating the electric quantity of the system at a second point in time through a mathematical operation; generating a second coordinate pair according to the magnitude of the electric quantity calculated from the protective relay and the estimated value at the second point in time based on sample data sampled at the second point in time; calculating a correlation between the first coordinate pair and the second coordinate pair as a linear equation; and calculating the slope factor and the offset factor based on the slope and y-intercept of the calculated linear equation.

[0031] The effects of the protective relay and the control method of the protective relay according to the present invention are described as follows.

[0032] According to at least one of the embodiments of the present invention, the present invention calculates an offset ratio value, which is an offset value that can be applied to sample data, which is an instantaneous value that changes over time from an offset factor, and corrects current and voltage sample data at the sample stage so that both the slope factor and the offset factor are reflected through a correction factor according to the offset ratio value as well as the slope factor. Accordingly, since all hardware errors of the protection relay are reflected and measurement values ​​are performed according to the corrected sample data, there is an effect that more accurate power information of the system can be measured.

[0033] Furthermore, the present invention compensates for hardware errors in a protection relay with respect to current and voltage sample data acquired during the sampling phase, thereby allowing the hardware errors to be reflected in the power information measurement calculated using the current and voltage sample data. Accordingly, the hardware errors are automatically reflected in the power information calculated using the phase of the sample data, thereby facilitating the measurement of power information related to phase.

[0034] Figure 1 is an example diagram showing the error between the measured value and the calculated value that changes over time.

[0035] FIG. 2 is a block diagram illustrating the configuration of a protection relay according to an embodiment of the present invention.

[0036] FIG. 3 is a flowchart illustrating an operation process for measuring power information from collected current and voltage sample data in a protection relay according to an embodiment of the present invention.

[0037] FIG. 4 is a conceptual diagram illustrating an example of calculating a slope factor and an offset factor during initial operation in a protection relay according to an embodiment of the present invention.

[0038] Figure 5 is a flowchart illustrating the operation process for performing compensation to measure power in a conventional protective relay.

[0039] FIG. 6 is a flowchart illustrating an operation process in which power is measured after correction for samples of current and voltage in a protection relay according to an embodiment of the present invention.

[0040] Figures 7 (a) and (b) are exemplary diagrams showing the difference in power amount according to the actual power amount of a system, and the measured and corrected power measurement values ​​in a conventional protection relay and a protection relay according to an embodiment of the present invention.

[0041] It should be noted that the technical terms used herein are used merely to describe specific embodiments and are not intended to limit the present invention. Furthermore, singular expressions used herein include plural expressions unless the context clearly dictates otherwise. The suffixes "module" and "part" used in the following description for components are assigned or used interchangeably solely for the convenience of writing the specification, and do not in themselves have distinct meanings or roles.

[0042] In this specification, the terms “comprises” or “includes” should not be construed to necessarily include all of the components or steps described in the specification, and some of the components or steps may not be included, or additional components or steps may be included.

[0043] In addition, when describing the technology disclosed in this specification, if it is determined that a detailed description of a related known technology may obscure the gist of the technology disclosed in this specification, the detailed description is omitted.

[0044] In addition, the attached drawings are only intended to facilitate easy understanding of the embodiments disclosed in this specification, and the technical ideas disclosed in this specification are not limited by the attached drawings, and should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention. In addition, not only each embodiment described below, but also a combination of embodiments may correspond to the spirit and technical scope of the present invention as modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

[0045] Meanwhile, as mentioned above, signal processing algorithms that derive power information from sample values ​​include not only the RMS algorithm but also the DFT algorithm. However, due to the complex computational process and large computational load of the DFT algorithm, the RMS algorithm is currently widely used.

[0046] However, as described above, since the RMS algorithm can simply calculate the average size of the power amount, it has been mentioned that when using the RMS algorithm, power information can be calculated by calculating the sample values ​​of the current and voltage of the system obtained through sampling.

[0047] However, when calculating power information based on sample values ​​of current and voltage in this way, there is a problem in that it is difficult to correct each sample value using the conventional correction method, that is, the correction method using the slope factor and offset factor that correct the average size of the power amount. In particular, in the case of the offset factor, it is difficult to calculate the correction value for each sample, so current protective relays usually correct using only the slope factor excluding the offset factor, or correct the value after signal processing for calculating the power amount, such as the RMS algorithm, is completed, thereby compensating for hardware errors, etc.

[0048] In order to solve these problems, the present invention allows a protection relay to calculate a ratio correction factor that reflects not only a slope factor but also an offset factor for each sample, and to reflect the calculated ratio correction factor on currently collected sample data, thereby obtaining sample data in which hardware errors, etc. are corrected in the sample data collection stage.

[0049] Accordingly, the present invention can not only perform the hardware correction at the sampling stage, but also increase the precision of measurement through correction according to the offset factor that was not reflected in the conventional sampling stage. In addition, since the current sample and voltage sample with the hardware error corrected are processed by the signal according to the RMS algorithm to produce power information, the present invention can have the effect of easily calculating power information related to the phase, such as reactive power and power factor, while maintaining the advantages of the RMS algorithm, such as fast calculation speed and reduced calculation load.

[0050] Figure 2 is a block diagram showing the configuration of a protection relay (20) according to an embodiment of the present invention.

[0051] Referring to FIG. 2, a protection relay (20) according to an embodiment of the present invention may be configured to include a control unit (100), a sampling unit (110), a sample correction unit (120), an RMS calculation unit (130), a measurement unit (140), and a memory (150). The components illustrated in FIG. 2 are not essential for implementing the protection relay (20), and thus, the protection relay (20) described in this specification may have more or fewer components than the components listed above.

[0052] In more detail, the sampling unit (110) can sample the electric quantity converted into a digital value from a detection device that senses basic data of the electric quantity in the system according to a preset sampling cycle. Here, the electric quantity of the system may refer to the current or voltage of the system. Hereinafter, the electric quantity refers to the current or voltage.

[0053] To this end, the detection device may be equipped with a sensor capable of measuring an electric quantity from the system, i.e., a current transformer (CT) and a voltmeter (potential transformer (PT)). The current and voltage of the system, i.e., the electric quantity, may be sensed through the sensor, and a filter and amplifier may be provided to filter out noise from the sensed electric quantity and amplify it. The device may be equipped with an analog-to-digital converter (ADC), and may convert the amplified analog-type electric quantity into a digital value. The sampling unit may sample the current and voltage of the system converted into digital values ​​through the ADC according to a preset sampling cycle to obtain a current sample and a voltage sample.

[0054] And the sample correction unit (120) can calculate correction factors for the current sample and voltage sample according to the control of the control unit (100). Here, the correction factors can include a slope factor and an offset factor according to the correlation between the actual measured value and the ideal value of the electric quantity of the system, which are calculated based on the linear characteristics of the ammeter (CT) and the voltmeter (PT).

[0055] In this case, the sample correction unit (120) can calculate a slope factor and an offset factor based on the correlation between the estimated value estimated through mathematical operation, that is, the ideal measured value in a state where no error occurs in the hardware and signal processing operation, and the actual measured value of the protection relay (20) that has not been corrected, that is, the actual measured value, by implementing the amplification and digital conversion and the signal processing process for the basic data as an algorithm. To this end, the sample correction unit (120) can convert the actual measured value into a coordinate on the y-axis and the ideal value into a coordinate on the x-axis, thereby generating at least two coordinate pairs having the ideal value and the actual measured value as the x-coordinate and the y-coordinate, respectively.

[0056] In this case, if there are two coordinate pairs, a first coordinate (x1, y1) and a second coordinate (x2, y2) can be generated, respectively. Then, the sample correction unit (120) can generate a linear equation based on the at least two coordinates. Then, a slope factor and an offset factor can be calculated from the generated linear equation. In this case, in the sample correction unit (120), the correlation equation y = ax + b of the ideal value (x) to the actual value (y) can be calculated as follows.

[0057]

[0058] Here, a is the slope factor, and b is the offset factor.

[0059] In addition, the sample correction unit (120) can calculate a correction factor that can be applied to the sample obtained from the sampling unit (110) based on the calculated offset factor (b).

[0060] For example, if N sample data of current or voltage converted to digital values ​​are x0, x1, x2, ... x n In this case, the RMS (Root Mean Square) value (X) for the N sample data can be calculated as shown in Equation 2 below.

[0061]

[0062] Here, N is the number of sample data, and X is the RMS value.

[0063] In this case, as seen in the correlation equation between the above ideal value and the actual value, the actual value has an error value, so assuming that the corrected RMS value is Y, the corrected RMS value (Y) can be expressed as a correlation equation according to the slope factor a and the offset factor b, as in Equation 3 below.

[0064]

[0065] Here, Y is the corrected RMS value, X is the RMS value of N sample data, a is the slope factor, and b is the offset factor.

[0066] Then, if X is reflected in Equation 3 according to Equation 2 and organized, it can be organized as Equation 4 below.

[0067]

[0068] Here, Y is the corrected RMS value, N is the number of sample data, a is the slope factor, and b is the offset factor.

[0069] Meanwhile, since RMS is an average value and current or voltage value is a sine wave, only the ratio correction value applied at the same ratio according to the size of the actual value can be applied to apply the slope factor and offset factor on a sample basis. Accordingly, if the ratio correction value (hereinafter referred to as correction factor) is C, the corrected RMS value Y of the nth sample data can be expressed as the product of the RMS value X of the nth sample data and the correction factor C, as in Equation 5 below.

[0070]

[0071] Here, Y is the corrected RMS value of the nth sample data, X is the RMS value of the nth sample data, a is the slope factor, b is the offset factor, and C is the correction factor applied to the nth sample data.

[0072] Therefore, as shown in the above equation 5, the correction factor C can be expressed as the sum of the offset factor b divided by the RMS value (X) of the nth sample data, i.e., the ratio value of the offset value to be applied to the current sample (hereinafter, the offset ratio value) b / X and the slope factor a.

[0073] In this case, when the correction factor C is calculated, the nth acquired sample data x is calculated by reflecting the correction factor C. n Correction value for y ncan be expressed as in Equation 6 below.

[0074]

[0075] Here, y n is the correction value of the nth acquired sample data, C is the correction factor applied to the nth sample data, x n is the nth acquired sample data, X n is the RMS value of the nth acquired sample data, a is the slope factor, and b is the offset factor.

[0076] Through the above-described formula 6, the sample correction unit (120) uses the correction factor calculated according to the RMS value of the uncorrected sample data to calculate the currently collected sample data (x n ) for which hardware errors, etc. have been corrected for sample data (y n ) can be obtained. In this case, if the collected sample data is current sample data, the sample correction unit (120) can obtain current sample data corrected according to the above equation 6.

[0077] Likewise, the sample correction unit (120) can calculate a correction factor for the voltage sample data, i.e., a voltage correction factor, based on the RMS value of the sample data and the previously calculated slope factor and offset factor for the voltage sample data collected at the same time as the current sample data. Then, based on the calculated voltage correction factor, voltage sample data with hardware errors, etc. corrected can be obtained.

[0078] In this case, the current and voltage sample data collected from the sampling unit (110) at the same time may be sample data having the same sampling order. In addition, the current and voltage samples collected at the same time, i.e., the corrected current sample data and the corrected voltage sample data having the same sampling order, may be input to the control unit (100).

[0079] And the RMS (Root Mean Square) calculation unit (130) can calculate an operation value, i.e., an RMS value, according to the RMS algorithm for the sample data input by the control unit (100). The RMS calculation unit (130) calculates the sample data sampled by the sampling unit (110), i.e., the uncorrected sample data (x) according to the control of the control unit (100). n ) to calculate the RMS value for the sample data (y) corrected in the sample correction unit (120). n ) can be calculated. In this case, the RMS value for the uncorrected sample data can be used to calculate a correction factor for correcting the current sample data or the voltage sample data in the sample correction unit (120). In addition, the RMS value for the sample data corrected in the sample correction unit (120) can be used to measure power information according to the current and voltage of the system.

[0080] Meanwhile, the sample correction unit (120) is configured to enhance robustness against sudden noise, etc. by using the currently sampled sample data x n Alternatively, correction of sample data may be performed based on the RMS value of previously acquired sample data. For example, the sample correction unit (120) may calculate the offset ratio value based on the RMS value of sample data of a previous order by one sample.

[0081] The following equation 7 illustrates an example of a correction factor calculated based on the RMS value of the sample data one sample prior to the previous order.

[0082]

[0083] Here, C is the correction factor applied to the nth sample, X n-1 is the RMS value of the n-1th sample, a is the slope factor, and b is the offset factor.

[0084] In this case, the sample correction unit (120) can calculate a correction factor based on the RMS value of the previous sampling order (n-1) for the collected sample, and the previously calculated slope factor and offset factor. Then, based on the calculated correction factor, the currently collected sample data x n Correction data for y n can be produced.

[0085] To this end, the RMS calculation unit (130) can calculate an RMS value according to not only the currently sampled current sample data and voltage sample data but also at least one of the previously provided current sample data and voltage sample data under the control of the control unit (100).

[0086] Meanwhile, in the above description, the RMS value of the sample data (n-1th sample data) collected immediately before the sampling order of the currently collected sample data (nth sample data) was used as the sample data of the previous sampling order, but it is obvious that the present invention is not limited thereto. Accordingly, it is obvious that the correction factor according to the previous order, i.e., the n-2th or n-3rd sample data, can be calculated. In addition, when sampling is performed for each period of the current signal and voltage signal, the sample correction unit (120) may use the RMS value according to the sample data of the previous period sampling order corresponding to the current sampling order under the control of the control unit (100).

[0087] And, the measuring unit (140) can measure power information of the system according to the current sample data and voltage sample data corrected by the sample correction unit (120) under the control of the control unit (100). In this case, the power information can include active power, reactive power, and power factor.

[0088] For example, the measuring unit (140) can calculate active power by multiplying the value of current sample data and the value of voltage sample data sampled at the same time, i.e., having the same sampling order, as the power information, and can calculate reactive power by shifting the phase of the calculated active power by 90 degrees. In addition, the measuring unit (140) can also calculate power factor based on the value of the current sample data and the value of the voltage sample data and the phase difference between the current sample data and the voltage sample data.

[0089] Meanwhile, the memory (150) can store data supporting various functions of the protection relay (20). The memory (150) can store data and commands to support functions according to a number of algorithms driven by the protection relay (20).

[0090] For example, the memory (150) may include data and commands to support an algorithm (e.g., RMS algorithm) for calculating the RMS value of the sample values ​​calculated from the RMS calculation unit (130), and may store power information calculated from the measurement unit (140), that is, algorithms for calculating active power, reactive power, and power factor, and data and commands to support the algorithms.

[0091] As such data, the memory (150) can store digitized sample data sampled by the sampling unit (110). And, it can store RMS values ​​calculated by the RMS calculation unit (130). In addition, it can store values ​​calculated for correction of each sample data in the sample correction unit (120), for example, an offset ratio value, and store sample data corrected by the sample correction unit (120). In addition, the memory (150) can store information on a slope factor and an offset factor for calculating a correction factor.

[0092] The control unit (100) controls each connected component and can control the overall operation of the protective relay (20). In addition, the control unit (100) can control at least some of the components described in FIG. 2 to drive an application program stored in the memory (150). Furthermore, at least two or more of the components can be combined and operated.

[0093] In more detail, the control unit (100) can control the sampling unit (110) to collect sample data for each of the current and voltage sensed from the system. In this case, the sample data collected may be data obtained by sampling the current and voltage of the system converted into digital values ​​at a preset sampling period, and may be current data and voltage data of the system measured at each sampling period.

[0094] And the control unit (100) can control the RMS calculation unit (130) to calculate the RMS value for each of the currently collected current sample data and voltage sample data. And the sample correction unit (120) can be controlled to calculate the current correction factor to be applied to the currently collected current sample data and the voltage correction factor to be applied to the voltage sample data according to the calculated RMS values ​​of each of the current and sample data and the slope factor and the offset factor stored in the memory (150). And the sample correction unit (120) can be controlled to calculate the correction sample data for each of the currently collected current sample data and voltage sample data based on the calculated current correction factor and voltage correction factor.

[0095] And the control unit (100) can control the measuring unit (140) to calculate power information related to the power amount of the system based on the corrected samples, i.e., the corrected current sample data and the corrected voltage sample data. In this case, the control unit (100) can further control the RMS calculating unit (130) to calculate an RMS value according to the corrected current sample data and the corrected voltage sample data, and can apply the result value calculated by the RMS calculating unit (130) again to the measuring unit (140) to calculate power information related to the RMS value.

[0096] Accordingly, the protection relay (20) according to an embodiment of the present invention can perform correction for hardware errors, etc., on samples obtained through sampling at the stage where the current data and voltage data of the system are sampled. That is, by generating current sample data and voltage sample data in which hardware errors, etc. are corrected through correction at the sampling stage, power information in which the hardware errors, etc. are corrected can be produced only by power calculation using the sample data. Therefore, the present invention has the advantage that there is no need for additional correction according to the measured power amount, and since the error has already been corrected at the sampling stage, various power calculations, such as phase calculations, can be easily performed using the sample data without having to consider subsequent corrections.

[0097] Furthermore, the present invention allows for different offset values ​​to be applied to each sample data by reflecting not only the slope factor but also the ratio of the offset factor to the RMS value of the sample data, thereby allowing for errors due to the offset factor to be reflected. Accordingly, there is an advantage in that power information of the system can be calculated more precisely.

[0098] FIG. 3 is a flowchart illustrating an operation process for measuring power information from collected current and voltage sample data in a protective relay (20) according to an embodiment of the present invention. FIG. 4 is a conceptual diagram illustrating an example of calculating a slope factor and an offset factor during initial operation in a protective relay (20) according to an embodiment of the present invention.

[0099] Referring to FIG. 3, the control unit (100) of the protection relay (20) according to an embodiment of the present invention can first calculate a slope factor and an offset factor for the current and voltage measurement values ​​of the system (S300).

[0100] In order to calculate these slope factors and offset factors, the control unit (100) can generate coordinate values ​​by matching the theoretical current and voltage values ​​(hereinafter, ideal values) of the system with the current and voltage values ​​(hereinafter, actual values) measured by the protection relay (20).

[0101] In this case, the current value and voltage value (actual value) actually measured in the protective relay (20) may be the result of amplifying and filtering the detection value sensed from the system through a sensor (an ammeter and a voltmeter), and digitally converting the sample data into a signal, for example, calculating the RMS value by the RMS calculation unit (130). That is, it may be the RMS value of the current sample of the system and the RMS value of the voltage sample actually measured in the protective relay (20). In this case, the RMS values ​​of the actually measured current samples, that is, the actual values, may be values ​​that include the hardware error of the protective relay (20).

[0102] On the other hand, the current and voltage values ​​(ideal values) of the theoretical system may be calculated values ​​obtained by estimating the current and voltage values ​​of the system over time through mathematical operations, as the current and voltage values ​​of an ideal system. In this case, the estimated values ​​may have a size calculated according to the RMS algorithm. Therefore, the estimated values ​​calculated through the mathematical operations may be ideal measured values, i.e., ideal values, that do not include hardware errors of the protective relay (20).

[0103] In this case, the control unit (100) can calculate the actual value and the ideal value for at least two samples obtained from the sampling unit (110). Then, coordinates having the calculated actual value and the ideal value as the y-axis value and the x-axis value, respectively, can be generated. Therefore, when calculating the actual value and the ideal value for two samples, the control unit (100) can generate a first coordinate (x1, y1) corresponding to the first sample and a second coordinate (x1, y1) corresponding to the second sample.

[0104] Meanwhile, as described above, since the ammeter and voltmeter have linear characteristics in which the output value changes constantly in response to changes in the input value, the control unit (100) can generate a straight line component connecting the first coordinate and the second coordinate, and analyze the linear correlation between the measured value and the ideal value, i.e., the correlation according to the first-order equation, based on the generated straight line component. Then, the slope factor and the offset factor can be calculated from the analyzed first-order correlation, i.e., the first-order equation.

[0105] FIG. 4 is a conceptual diagram for explaining an example of calculating a slope factor and an offset factor in a protective relay (20) according to an embodiment of the present invention.

[0106] First, if the actual value changes at the same rate as the abnormal value changes, the actual value and the abnormal value may have a proportional relationship according to a specific slope value. In this case, as shown in (a) of Fig. 4, a straight line (410) connecting the first sample (411) and the second sample (412) may pass through the origin (0,0) on the coordinates, and the actual value (y) and the abnormal value (x) may have a correlation of y = ax, which is proportional to a specific slope value (a). In this case, the control unit (100) may calculate the specific slope value a according to the above equation 1, and may calculate the calculated slope value a as a slope factor.

[0107] However, as shown in (b) of FIG. 4, the actual measured value may change more or less than the amount of change according to the rate at which the abnormal value changes. In this case, the straight line (420) connecting the first sample (421) and the second sample (422) may be a straight line that does not pass through the origin (0,0) on the coordinates. In this case, the actual measured value (y) and the abnormal value (x) may have a correlation that further includes the amount of change (a*x) of the abnormal value (x) according to the specific slope value (a) and the offset value (b) according to the difference from the actual measured value (y), that is, a correlation of y = ax + b. In this case, the control unit (100) may calculate the specific slope value a and the offset value b according to the above equation 1, and may calculate the calculated slope value a as a slope factor, and the offset value b as an offset factor.

[0108] [Formula 1]

[0109]

[0110] Here, a is the slope factor, and b is the offset factor.

[0111] The process of calculating the slope factor and the offset factor in the above step S300 can be performed for each of the current sample and the voltage sample, and accordingly, the slope factor and the offset factor for the current (hereinafter referred to as the current slope factor and the current offset factor) and the slope factor and the offset factor for the voltage (hereinafter referred to as the voltage slope factor and the voltage offset factor) can be calculated, respectively.

[0112] Meanwhile, in the above step S300, the closer the two samples used to calculate the slope factor and offset factor are to each other, the smaller the size difference between the samples may be. In addition, the smaller the size difference between the samples, the more difficult it may be to calculate the slope factor and offset factor.

[0113] Accordingly, the control unit (100) can acquire two samples used for calculating the slope factor and offset factor at a certain time interval between each other. In this case, the time interval between the two samples may be a time corresponding to one or more cycles of the current or voltage. That is, the control unit (100) can acquire samples acquired at a time difference of one or more cycles, and calculate the slope factor and offset factor from the actual values ​​and abnormal values ​​according to the acquired samples.

[0114] However, as the time required in the above S300 step increases, the initial measurement of the current and voltage of the system may be delayed, so the time interval between samples used to calculate the slope factor and offset factor may be limited to a time within at least one cycle.

[0115] Meanwhile, when the slope factor and offset factor are calculated in step S300, the control unit (100) can control the sampling unit (110) to collect current and voltage sample data (S302). In this case, the collected current sample data and voltage sample data may have the same sampling order. In other words, they may be sample data acquired at the same point in time.

[0116] When current and voltage sample data are acquired in the above step S302, the control unit (100) can first control the RMS calculation unit (130) to calculate RMS values ​​for each of the currently acquired current sample data and voltage sample data (S304). As seen in the above equation 2, the RMS value may be a value corresponding to the square root of the average value of the squares of the sample values ​​of n sample data collected in the current period when the currently collected sample data is the nth sample data. Accordingly, in the above step S304, the RMS value for the currently acquired current sample data and the RMS value for the voltage sample data can be calculated.

[0117] In the step S304, when the RMS values ​​for each of the current and voltage sample data are calculated, the control unit (100) can calculate the ratio value of the offset value to be applied to the currently acquired sample, i.e., the offset ratio value, based on the calculated RMS values ​​(S306). Here, the offset ratio value can be calculated according to the ratio of the offset factor b to the RMS value of the currently acquired sample, i.e., the n-th sample data, i.e., the offset ratio value (b / X), as described in the above equation 5. In this case, the control unit (100) can calculate the offset ratio value of the current sample data based on the RMS value of the n-th current sample data calculated in the step S304, and can calculate the offset ratio value of the voltage sample data based on the RMS value of the n-th voltage sample data.

[0118] Then, the control unit (100) can calculate correction factors for correcting the voltage and current sample data based on the current and voltage offset ratio values ​​calculated in step S306 and the previously calculated current and voltage slope factors (S308).

[0119] In this case, the correction factor (C) can be calculated as the sum of the slope factor (a) and the offset ratio value (b / X), as seen in the above equation 5. Here, the control unit (100) can calculate the correction factor for the current sample data (hereinafter, the current correction factor) according to the sum of the slope factor for the current and the offset ratio value, and can calculate the correction factor for the voltage sample data (hereinafter, the voltage correction factor) according to the sum of the slope factor for the voltage and the offset ratio value.

[0120] Meanwhile, in step S308, when the current correction factor and the voltage correction factor are calculated, the control unit (100) can correct the sample data by multiplying the currently sampled sample data, i.e., the nth sample data, by the calculated correction factor (S310). Accordingly, the control unit (100) can correct the nth current sample data by multiplying the value of the nth current sample data by the current correction factor. In addition, the control unit (100) can correct the nth voltage sample data by multiplying the value of the nth voltage sample data by the voltage correction factor.

[0121] Then, the control unit (100) can control the measurement unit (140) to measure power information according to the nth current sample data and voltage sample data corrected in step S310 (S312). For example, the control unit (100) can calculate active power according to the product of the corrected nth current sample data and voltage sample data, and can calculate reactive power corresponding to the nth current and voltage sample data by delaying the phase of the corrected nth current sample data and voltage sample data by 90 degrees. In addition, the power factor can also be calculated based on the corrected nth current sample data and voltage sample data and the phase difference.

[0122] Meanwhile, when the power information measurement in step S312 is completed, the control unit (100) can proceed to step S302 again to acquire the current sample data and voltage sample data of the next sampling order. In this case, if the sample for which power information was calculated in the previous step is the nth sample, the n+1th current sample data and voltage sample data can be acquired in step S302 that is performed again. Then, the control unit (100) can perform the operation processes after step S302 again to correct the currently obtained n+1th current sample data and voltage sample data, and measure the power information according to the values ​​of the corrected current sample data and voltage sample data.

[0123] As described in FIG. 3, the calculation of the slope factor and offset factor performed in step S300 is performed only during the initial operation of the protection relay (20) according to the embodiment of the present invention, and thereafter, the processes from step S302 to step S312, in which current and voltage sample data are acquired, are repeated, so that power information can be measured each time sample data is acquired.

[0124] Meanwhile, in the above-described Fig. 3, it was explained that the slope factor and offset factor are calculated at the time of initial operation of the protection relay (20), and the subsequent steps are repeated while the values ​​are stored in the memory (150). However, it is of course possible to omit the S300 step if the values ​​of the slope factor and offset factor are calculated in advance.

[0125] For example, when the protection relay (20) is turned on again after being turned off, before performing the operation process of FIG. 3, it can check whether there are slope factors and offset factors pre-stored in the memory (150). And if there are slope factors and offset factors pre-stored in the memory (150), that is, if there are slope factors and offset factors pre-calculated before the protection relay (20) is turned off, the control unit (100) can of course omit the step S300. In this case, only the operation process from step S302 to step S312 of FIG. 3 can be repeatedly performed.

[0126] Similarly, the slope factor and offset factor may be values ​​stored in advance in the memory (150) during the manufacturing of the protection relay (20). That is, the slope factor and offset factor may be calculated based on the difference between the ideal measurement value that does not reflect the hardware error of the protection relay (20) as described above and the average size of the measurement value actually measured according to the hardware equipped in the protection relay (20), i.e., the RMS value.

[0127] Accordingly, the manufacturer of the protection relay (20) can, of course, calculate the slope factor and offset factor based on at least two samples with a certain time interval during the manufacturing of the protection relay (20). In addition, the calculated slope factor and offset factor can be input in advance into the memory of a protection relay of the same model equipped with the same hardware.

[0128] Then, the control unit (100) of the protection relay (20) can detect the slope factor and offset factor that have been previously stored during the initial operation as described above. Accordingly, the control unit (100) can proceed directly to step S302, correct the collected samples using the slope factor and offset factor that have been previously stored in the memory (150), and measure the power information corresponding to each sample data according to the value of the corrected sample data. In other words, the step S300 can be omitted.

[0129] Figures 5 and 6 illustrate the operational processes for performing correction for measuring power quantity in a conventional protection relay and a protection relay according to an embodiment of the present invention.

[0130] First, Fig. 5 illustrates the operation processes for performing correction for measuring power quantity in a conventional protective relay (510).

[0131] Referring to FIG. 5, a detection device (500) capable of detecting an electric quantity from a system can sense the current and voltage of the system, i.e., the electric quantity, through a sensor capable of detecting an electric quantity from the system, i.e., an ammeter (CT, Current Transformer) and a voltmeter (PT, Potential Transformer) (501). In addition, noise can be removed from the sensed electric quantity through filtering and amplified (502), and the amplified analog electric quantity can be converted into a digital value through an ADC (Analog Digital Convertor) (503).

[0132] Meanwhile, a conventional protection relay (510) can sample the digital measurement value converted from the detection device (500) according to a preset sampling cycle (511). Then, the magnitude of the electric quantity, i.e., the magnitude of the current or voltage, for the sample data collected during the sampling process can be calculated through signal processing according to the RMS algorithm (512). Then, correction can be performed according to a slope factor and an offset factor for the magnitude of the current and voltage calculated through the signal processing process (512) (513). Then, power information can be measured based on the magnitude of the corrected current value and voltage value (514).

[0133] Meanwhile, as described above, since the slope factor and offset factor are correction values ​​according to the size of the RMS value, a conventional protection relay (510) can only perform correction for the RMS size of the current and voltage calculated through the signal processing process (512) as shown in Fig. 5. Accordingly, a conventional protection relay (510) can only measure the size of the current and voltage, and it is difficult to calculate power information related to the phase due to the phase difference between samples, etc., so there is a problem that it is difficult to obtain power information related to the phase.

[0134] Meanwhile, FIG. 6 is a flowchart illustrating an operation process in which power is measured after correction for samples of current and voltage in a protection relay (600) according to an embodiment of the present invention.

[0135] Referring to FIG. 6, the protective relay (600) according to an embodiment of the present invention can sample the amount of electricity detected and converted into a digital value from the detection device (500).

[0136] And for the sampled sample data, the offset factor for the currently sampled sample data, which is calculated based on the calculated slope factor and the RMS value and the calculated offset factor for the currently collected sample data, is calculated as a ratio value, that is, an offset ratio value, and a correction factor for the currently sampled sample data can be calculated based on the calculated offset ratio value and the slope factor. And, based on the calculated correction factor, the currently sampled sample data can be corrected to correct the sample data (610). In this case, the correction factor can be calculated for current and voltage, respectively, and accordingly, the protection relay (600) according to the embodiment of the present invention can correct the current sample data and the voltage sample data according to the respective correction factors.

[0137] And the protection relay (600) can calculate the magnitude of current and voltage through signal processing (e.g., RMS calculation) based on the corrected current sample data and the corrected voltage sample data (611). And, based on the calculated magnitude of current and voltage, the power information of the system can be measured (612). In this case, the protection relay (600) can calculate phase information based on the corrected current sample data and the corrected voltage sample data for measuring the power information.

[0138] For example, the protection relay (600) can calculate the phase difference between current and voltage based on the sizes of the corrected current sample data and voltage sample data, and can calculate power information reflecting the calculated phase difference. In this case, the protection relay (600) can calculate the power factor of the current system using the corrected current sample data, the corrected voltage sample data, and the phase difference.

[0139] In this way, the protection relay (600) according to the embodiment of the present invention performs correction according to the slope factor and the offset factor in the sample data stage, so that correction for hardware errors is made in the sample data stage, and thus it is possible to calculate power information (e.g., reactive power or power factor, etc.) using the sample data as it is. In addition, since the hardware error is corrected in the sample data stage, the hardware error unique to the protection relay (600) can be corrected in all calculation processes using the sample data, such as phase calculation. Accordingly, there is no need to separately correct the power amount after signal processing, and since the power amount, etc. can be calculated only with the calculation of the sample data itself without the need to consider the hardware error, there is an advantage in that power information can be calculated in an easier and more diverse way.

[0140] In addition, the present invention compensates for sample data by reflecting not only the slope factor but also the offset factor ratio value for the currently sampled sample data, i.e., the offset ratio value. Therefore, even hardware errors due to the offset factor can be reflected in the sample data. Therefore, there is an advantage in that more precise power information can be produced based on the actual electricity amount of the system.

[0141] Meanwhile, (a) and (b) of FIG. 7 are exemplary diagrams showing the difference between the measured and corrected power measurement values ​​and the amount of power according to the amount of electricity in the actual system in a conventional protection relay and a protection relay according to an embodiment of the present invention.

[0142] According to the above explanation, in the case of a conventional protection relay, it has been explained that in order to perform correction at the sample stage, it is possible to reflect only the slope factor, which is the ratio of the actual value to the abnormal value. Accordingly, since the hardware error according to the offset factor is not reflected, a conventional protection relay that corrects the slope factor at the sample stage can produce a measurement result (710) in which the error according to the offset factor, which is a constant value and the actual power amount (700) calculated from the power amount of the system, is included in the power amount, as shown in (a) of FIG. 7.

[0143] In contrast, the protective relay (20) according to an embodiment of the present invention corrects the sample data according to a correction factor based on the ratio value (offset ratio value) of the offset factor reflected in each sample data at the sample data stage as described above, so that not only the slope factor but also the offset factor can be reflected. Accordingly, the hardware error of the protective relay (20) can be corrected, so that a measurement result that matches the actual power amount (700) calculated from the electric amount of the system can be produced.

[0144] Meanwhile, according to the above description, it has been mentioned that the protective relay (20) according to the embodiment of the present invention can use the RMS value according to the sample data of the sampling order prior to the currently sampled sample data in calculating the correction factor in order to enhance the robustness. In this case, a response delay for a predetermined period of time may occur depending on the difference between the current sampling order and the sampling order of the sample data using the RMS value.

[0145] For example, if the sampling order of sample data corresponding to the RMS value for calculating the offset ratio value is sample data sampled one sampling order prior to the currently sampled sample data, the protection relay (20) according to the embodiment of the present invention can reflect the offset ratio value according to the RMS value of the sample data prior to the time at which one sample data is sampled to the currently sampled sample data. Accordingly, a response delay may occur during the time at which the one sample data is sampled, i.e., the time corresponding to one sampling cycle.

[0146] Fig. 7 (b) shows an example in which a response time delay occurs for a time corresponding to one sampling cycle by using the RMS value of sample data one sampling cycle ago. In this case, as shown in Fig. 7 (b), the protective relay (20) according to the embodiment of the present invention can calculate a power measurement value (720) that is almost identical to the actual power amount (700) of the system after a time corresponding to one sampling cycle.

[0147] The present invention described above can be implemented as computer-readable code on a medium in which a program is recorded. Computer-readable media include all types of recording devices that store data that can be read by a computer system. Examples of computer-readable media include hard disk drives (HDDs), solid-state disk drives (SSDs), silicon disk drives (SDDs), ROMs, RAMs, CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, etc., and also include media implemented in the form of carrier waves (e.g., transmission via the Internet). In addition, the computer may include a control unit (100) of a protection relay. Therefore, the above detailed description should not be construed as limiting in all respects, but should be considered as illustrative. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are intended to be included in the scope of the present invention.

Claims

1. In protective relays, A sampling unit that samples the electrical quantity of a system sensed by a sensor according to a preset sampling cycle; A memory storing the slope factor and offset factors, which are correction values ​​calculated based on the correlation between the size of the electric quantity actually measured in the above protection relay and the estimated value estimated through mathematical calculation for the electric quantity of the above system; An RMS calculation unit that calculates the RMS (Root Mean Square) value according to sampled sample data; A sample correction unit that calculates an offset ratio value, which is a ratio value of the offset factor to be applied to the sample data, based on the RMS value of the generated sample data and the offset factor, and corrects the sample data based on the calculated offset ratio value and the slope factor; and A protection relay characterized by including a control unit that calculates power information related to the power of the system based on current sample data and voltage sample data corrected through the sample correction unit.

2. In the first paragraph, the offset ratio value is A protection relay characterized by the ratio of the above offset factor to the RMS value of the currently sampled sample data.

3. In the second paragraph, the sample correction unit, A protection relay characterized in that a correction factor for the currently sampled electric quantity is calculated by adding the offset ratio value to the above slope factor, and sample data of the currently sampled electric quantity is corrected according to the calculated correction factor.

4. In paragraph 3, The above sample correction unit, Current sample data and voltage sample data according to the same sampling order are respectively corrected based on a current correction factor calculated for the current of the system and a voltage correction factor calculated for the voltage of the system, The above control unit, A protection relay characterized in that the power information is calculated based on the corrected current sample data and voltage sample data according to the same sampling order.

5. In the first paragraph, the control unit, A protection relay characterized in that it calculates the current amount corresponding to the corrected current sample data and the voltage amount corresponding to the corrected current sample data through RMS calculation on the corrected current sample data and the voltage sample data, and calculates power information of the system according to the calculated current amount and voltage amount.

6. In paragraph 1, The above RMS calculation unit is, Calculate the RMS value according to the sample data of the previous sampling order compared to the currently sampled sample data, The above sample correction unit, A protection relay characterized in that the offset ratio value is calculated based on the RMS value according to the sample data of the previous sampling order.

7. In the first paragraph, the control unit, When the above protection relay is initially operated, it estimates multiple electric quantities of the system over time through mathematical operations, and calculates multiple sizes of electric quantities according to sample data sampled at a time corresponding to the estimated electric quantities. A protection relay characterized in that the slope factor and the offset factor are calculated by calculating the correlation between a first coordinate pair of an estimated value estimated at a first point in time and an output value calculated from sample data sampled at the first point in time, and a second coordinate pair of an estimated value estimated at a second point in time and sample data sampled at the second point in time.

8. In paragraph 7, the control unit, A protection relay characterized in that the correlation between the first coordinate pair and the second coordinate pair is calculated as a first-order equation, the slope of the calculated first-order equation is calculated as the slope factor, and the y-intercept of the first-order equation is calculated as the offset factor.

9. In paragraph 7, the control unit, A protection relay characterized in that the second coordinate pair is generated after a preset time has elapsed from the first point in time.

10. In the first paragraph, the control unit, A protection relay characterized in that it calculates the phase difference between the corrected current sample data and the voltage sample data and calculates the power factor according to the calculated phase difference or the reactive power according to the shifted phase of the corrected current sample data and the voltage sample data as the power information.

11. In the control method of the protective relay, A step of sampling the amount of electricity in a system sensed by a sensor according to a preset sampling cycle; A step of calculating the RMS (Root Mean Square) value according to the currently sampled sample data; A step of calculating a correction factor to be applied to sample data based on a slope factor and an offset factor, which are correction values ​​calculated based on a correlation between the size of the electric quantity actually measured by the protective relay and the estimated value estimated through mathematical calculation for the electric quantity of the system; A step of correcting the currently sampled sample data according to the calculated correction factor; and, A control method for a protection relay, characterized in that it comprises a step of calculating power information related to the power of the system based on corrected current sample data and voltage sample data.

12. In the 11th paragraph, the step of calculating the correction factor is: A step of calculating an offset ratio value which is a ratio of the offset factor to the RMS value of the currently sampled sample data; and, A control method for a protection relay, characterized in that it includes a step of calculating the correction factor by adding the calculated offset ratio value and the slope factor.

13. In paragraph 11, The steps for calculating the above RMS value are: This is a step of calculating the RMS value according to the sample data of the previous sampling order of the currently sampled sample data. The step of calculating the above correction factor is: A step of calculating an offset ratio value, which is a ratio of the offset factor to the RMS value of the sample data of the previous sampling order; and, A control method for a protection relay, characterized in that it includes a step of calculating the correction factor by adding the calculated offset ratio value and the slope factor.

14. In paragraph 11, Before the sampling step, a step of detecting whether there are pre-stored slope factors and offset factors; and, A control method for a protection relay, characterized in that it further includes a step of detecting the slope factor and offset factor based on the size of the electric quantity actually measured by the protection relay and an estimated value estimated through mathematical calculation for the electric quantity of the system, when the above-mentioned pre-stored slope factor and offset factor do not exist.

15. In paragraph 14, The step of detecting the above slope factor and offset factor is: A step of estimating the electric quantity of the above system at the first point in time through mathematical calculation; A step of generating a first coordinate pair according to the magnitude of the electric quantity produced by the protective relay and the estimated value at the first time point based on the sample data sampled at the first time point; A step of estimating the amount of electricity in the system at the second point in time through mathematical calculation; A step of generating a second coordinate pair according to the magnitude of the electric quantity produced by the protective relay and the estimated value at the second time point based on the sample data sampled at the second time point; A step of calculating the correlation between the first coordinate pair and the second coordinate pair as a first-order equation; and, A control method for a protection relay, characterized in that it includes a step of calculating the slope factor and the offset factor based on the slope and y-intercept of the calculated first-order equation.

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