Digital protection relay device

Abstract

To provide a digital protective relay device which corrects errors of input / output characteristics of an input converter.SOLUTION: A device includes: a plurality of input converters 1a which converts levels of an analog signal; a plurality of A / D converters 1c which converts an analog signal or a phase reference signal by an output of each input converter to a digital signal; a plurality of Fourier transformation computation units which calculates an amplitude value and a phase of each analog signal; a correction arithmetic unit which corrects the amplitude value obtained through calculation by each Fourier transformation computation unit by a first correction amount and corrects the phase obtained through calculation by each Fourier transformation computation unit by a second correction amount; and a protection computation unit which performs a protection computation upon a protection object based on each arithmetic result of the correction arithmetic unit. When an adjustment input signal, an amplitude value of which sequentially varies from the minimum value to the rated value according to the amount of sweep increment, is inputted to a specified input converter, the correction arithmetic unit calculates a first correction amount based on an amplitude value and a second correction amount based on a phase through calculation by a specific Fourier transformation computation unit corresponding to the specific input converter.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a digital protective relay device for protecting a protected object connected to an electric power system. [Background technology]

[0002] As a conventional technique, for example, there is a digital protection control device that takes in an analog signal input from a power system via an input converter, converts the taken-in analog signal into a digital signal with an A / D (Analog / Digital) converter, calculates an amplitude value from the converted digital signal, calculates the ratio between the calculated amplitude value and a preset reference amplitude value as a gain correction coefficient, and corrects the gain with the calculated gain correction coefficient (see Patent Document 1). There is also a digital protection control device that calculates the excitation impedance of an input converter that affects the input / output characteristics, and corrects the input / output characteristics from the calculated excitation impedance and a theoretical formula for the input / output characteristics (see Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-149536 [Patent Document 2] JP 2013-106359 A Summary of the Invention [Problem to be solved by the invention]

[0004] Conventionally, analog signals input from a power system are input to a protective relay device via an input converter in order to insulate the signal from the power system and convert it to an appropriate input level. The input / output characteristics of the transformer used in the input converter differ depending on the full-scale specification, which is the specification of the maximum amplitude of the analog signal input from the power system. Therefore, even if the input / output characteristics of the transformer differ depending on the full-scale specification, in order to ensure the relay accuracy in the digital protective relay device, the error in the input / output characteristics of the transformer is corrected by digital calculation. For example, the error in the input / output characteristics of the transformer when a rated analog signal is applied to the input converter is corrected by gain correction and phase correction.

[0005] However, when the input amplitude of the analog signal is smaller than the rated input amplitude and is the minimum input amplitude for which performance is guaranteed, the magnetic flux density of the transformer is low, and the excitation current of the transformer decreases, which reduces the excitation impedance of the transformer and increases the current flowing to the excitation coil of the transformer, while the current transmitted from the input side of the transformer to the output side of the transformer decreases, resulting in a large input / output error of the transformer. Furthermore, since the input / output characteristics of the input converter vary due to individual differences in each transformer, in order to eliminate the characteristic variation, it is necessary to measure the input / output characteristics of the transformer alone at the minimum input amplitude for which performance is guaranteed, and select and use those that are within the judgment criteria. However, in this case, there is a problem that unnecessary costs are incurred for the parts cost of the transformer that falls outside the judgment criteria range during selection, and the selection measurement work cost.

[0006] An object of the present invention is to correct errors in the input / output characteristics of an input converter regardless of whether the amplitude value of an analog signal input from a power system is anywhere from the minimum value to the maximum value of performance guarantee. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a protection system including a plurality of input converters which receive an analog signal indicating an analog amount of an electric signal from a protected object connected to a power system and convert and output a level of the input analog signal, a plurality of analog-to-digital converters which convert an analog signal output from each of the input converters into a digital signal, a plurality of Fourier transform calculation units which perform Fourier transform processing on the digital signal output from each of the analog-to-digital converters to calculate an amplitude value and a phase of each of the analog signals, a correction calculation unit which executes a calculation to correct the amplitude value calculated by each of the Fourier transform calculation units with a first correction amount and a calculation to correct the phase calculated by each of the Fourier transform calculation units with a second correction amount, a protection calculation unit which executes a protection calculation process for the protected object based on the calculation results of the correction calculation units, a phase reference signal analog-digital converter which converts a phase reference signal into a digital signal, and and a phase reference signal Fourier transform calculation unit that performs the Fourier transform process on the digital signal output from the phase reference signal analog-digital converter to calculate an amplitude value and a phase of the phase reference signal and outputs each calculation result to the correction calculation unit, wherein the correction calculation unit calculates the first correction amount based on the amplitude value of the adjustment input signal among the calculation results of a specific Fourier transform calculation unit corresponding to the specific input converter among the multiple Fourier transform calculation units, and calculates the second correction amount based on the phase of the adjustment input signal among the calculation results of the specific Fourier transform calculation unit, on condition that an adjustment input signal, which is an AC signal corresponding to the analog signal and is a known input signal for adjustment whose amplitude value changes sequentially in multiple steps from a low input amplitude minimum value to a rated input amplitude value of the analog signal in accordance with a sweep increment, is input to a specific input converter among the multiple input converters. Effect of the Invention

[0008] According to the present invention, errors in the input / output characteristics of an input converter can be corrected regardless of the amplitude value of an analog signal input from a power system, from the minimum value to the maximum value of performance guarantee. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a configuration diagram showing a configuration example of a digital protection relay device according to a first embodiment of the present invention. [Diagram 2] FIG. 1 is a configuration diagram showing an example of the hardware and software configuration of a digital protection relay device according to a first embodiment of the present invention. [Diagram 3] 11 is a flowchart for explaining a correction process when a rated input is applied in the digital protective relay device used in the comparative example. [Figure 4] FIG. 13 is an input / output characteristic diagram of the digital protective relay device used in the comparative example, obtained by correction processing when a rated input is applied. [Diagram 5] 4 is a flowchart for explaining a first correction process at the time of a low input amplitude in the digital protection relay device according to the first embodiment of the present invention. [Figure 6A] 11 is a flowchart for explaining a second correction process at the time of a low input amplitude in the digital protection relay device according to the second embodiment of the present invention. [Figure 6B] 11 is a flowchart for explaining a process to which a second correction process result is applied when an input amplitude is low in the digital protection relay device according to the second embodiment of the present invention. [Figure 7] FIG. 11 is an input / output characteristic diagram of the digital protection relay device according to the second embodiment of the present invention when the input amplitude is low, according to the second correction process. [Figure 8A] 13 is a flowchart for explaining a third correction process of the digital protection relay device according to the third embodiment of the present invention. [Figure 8B] 13 is a flowchart for explaining a process to which a third correction process result is applied in the digital protection relay device according to the third embodiment of the present invention. [Figure 9] FIG. 11 is an input / output characteristic diagram of a third correction process of the digital protection relay device according to the third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. EXAMPLES

[0011] Fig. 1 is a configuration diagram showing a configuration example of a digital protection relay device according to a first embodiment of the present invention. In Fig. 1, the digital protection relay device 1 includes a plurality of input converters 1a, a plurality of analog filters 1b, a plurality of A / D converters 1c, a plurality of digital filters 1d, a CPU (Central Processing Unit) 1e, a work memory 1f, a non-volatile memory for recording correction values ​​1g, and an input / output interface (I / O interface) 1h, and the digital filters 1d, the CPU 1e, the work memory 1f, the non-volatile memory for recording correction values ​​1g, and the input / output interface 1h are connected to each other via a bus 1i.

[0012] Each input converter 1a is divided into a plurality of channels, for example, 16 channels consisting of (three-phase / zero-phase) x (input side + output side) x (voltage + current) channels, and is connected to the power system 10, and is composed of a transformer (VT) or current transformer (CT) that converts a voltage signal or current signal, which is an analog signal (50 Hz or 60 Hz) from the power system 10, into a voltage or current level that can be handled by an analog electronic circuit, and outputs the converted voltage or current signal to each analog filter 1b. When the input converter 1a is composed of a transformer, the input converter 1a converts the voltage signal from the power system 10 into a voltage signal within the range of, for example, ±10V.

[0013] One of the multiple analog filters 1b (analog filter for phase reference signal) 1b receives a phase reference signal 20, passes only signals in the frequency band of the input phase reference signal 20, and outputs them to an A / D converter (A / D converter for phase reference signal) 1c, while the remaining analog filters 1b receive analog signals from each input converter 1a, passes only signals in the frequency band of the input analog signal, and outputs them to each A / D converter 1c. In this case, an analog filter for preventing aliasing errors due to digital sampling can be used as each analog filter 1b.

[0014] Each A / D converter 1c converts an analog signal into a digital signal and transfers the converted digital signal to the CPU 1e. The CPU 1e is composed of a processor that functions as a control unit that controls the entire digital protection relay device 1, and receives output signals from each digital filter 1b via the bus 1i, as well as correction values ​​recorded in the non-volatile memory 1g, and executes various protection calculation processes based on control programs stored in the work memory 1f or a storage device. The work memory 1f can be a RAM (Random Access Memory), and the non-volatile memory 1g can be a conductive memory such as a flash memory.

[0015] At this time, for example, if the voltage from any one of the multiple channels changes from 100 V to 0 V, the current changes from 5 A to 20 A, and a zero-phase current is detected, the CPU 1e determines that a ground fault has occurred on that channel and executes a protection calculation process to operate a protection relay to protect the transformer to be protected.

[0016] Fig. 2 is a configuration diagram showing an example of the configuration of hardware and software of a digital protection relay device according to the first embodiment of the present invention. In Fig. 2, hardware 2a of the digital protection relay device 1 is composed of an input converter 1a, a plurality of analog filters 1b, a plurality of A / D converters 1c, and a non-volatile memory 1g for recording correction values. The software 2b of the digital protection relay device 1 includes a specific Fourier transform calculation unit 2c that performs Fourier transform processing on the digital signal output from the A / D converter 1c that converts the phase reference signal 20 into a digital signal, a phase reference signal Fourier transform calculation unit 2c that performs Fourier transform processing on the digital signal output from the A / D converter 1c that converts the analog signal from the power system 10 into a digital signal, a correction calculation unit 2d that performs calculation to correct the amplitudes A0, A1 and phases θ0, θ1 of the signals Fourier transformed by each Fourier transform calculation unit 2c with each correction value (first correction amount and second correction amount) recorded in the correction value recording nonvolatile memory 1g, and generates a correction processing signal of amplitude Ac1 and phase θc1, and a protection calculation unit 2e that performs a protection calculation based on the correction processing signal based on the calculation result of the correction calculation unit 2d and judges the presence or absence of an accident (ground fault, etc.) in the power system by this protection calculation. Each calculation unit is configured by a control program. At this time, the correction calculation unit 2d executes a calculation to correct the amplitude value calculated by each Fourier transform calculation unit 2c with a first correction amount, and a calculation to correct the phase calculated by each Fourier transform calculation unit 2c with a second correction amount. Furthermore, the protection calculation unit 2e executes a calculation to detect earth faults and short circuit faults in each channel based on the calculation results of the correction calculation unit 2d. Note that Fig. 2 shows only the input converter 1a, analog filter 1b, and A / D converter 1c, which are used for the correction calculation, among the hardware 2a of the digital protective relay device 1.

[0017] 3 is a flowchart for explaining the correction process when the rated input is applied in the digital protective relay device used in the comparative example. In FIG. 3, the digital protective relay device used in the comparative example has a rated input amplitude A R1 , Rated input amplitude theoretical value A T1 , Gain correction amount G CR1 , rated input phase of analog signal θ R1, reference signal phase θ REF , phase correction amount θ CR1 Each of these is taken in as input information (S1), and the gain correction amount G at the rated input is calculated based on the input information. CR1 and the phase correction amount θ CR1 (S2) At this time, the gain correction amount G CR1 is the gain correction amount G CR1 = Theoretical value of rated input amplitude A T1 / Rated input amplitude A R1か The phase correction amount θ CR1 is the phase correction amount θ CR1 =phase correction amount θ CR1 -Reference signal phase θ REF It is calculated from:

[0018] FIG. 4 shows the input / output characteristics of the digital protective relay device used in the comparative example after correction processing when the rated input is applied. As shown in FIG. 4, in the comparative example, the gain correction amount G CR1 and the phase correction amount θ CR1 Since the above calculation is performed, it can be seen that the error in the input / output characteristics becomes large when the input amplitude is low.

[0019] 5 is a flowchart for explaining a first correction process at the time of low input amplitude in the digital protection relay device according to the first embodiment of the present invention. This process is a process for averaging correction errors as a correction process at the time of low input amplitude at the time of shipment from the factory.

[0020] In FIG. 5, for example, the specific input converter 1a shown in FIG. 2 is connected to a power system, and the input converter 1a is connected to a power system. The ... LAn adjustment input signal is input, which is a known input signal for adjustment that changes sequentially in multiple stages from the low input amplitude minimum value of the analog signal (minimum value for guaranteed performance, for example, tens of mV or tens of mA) to the rated input amplitude value (maximum value for guaranteed performance, for example, 110 V or 5 A) in accordance with a predetermined threshold voltage (for example, 0.1 V). The adjustment input signal is a signal that changes sequentially in multiple stages, for example, from tens of mV to 110 V, in increments of 0.1 V. Note that performance guarantee means guaranteeing the performance of the digital protection relay device 1.

[0021] The correction calculation unit 2d is a low input amplitude A L [i], low input amplitude theoretical value A LT [i], Low input gain compensation amount G CL [i], low input phase θ L [i], reference signal phase θ REF [i], low input phase correction amount θ CL [i], Low input gain average correction amount G AVL , low input phase average correction amount θ AVL , Low input amplitude sweep step size ΔA L , rated input amplitude A R1 The process starts with the information related to (A R1 -A L ) / ΔA L =N (N is a natural number), A L [i]=A R1 , i = 0, A L [0] = Treat low input amplitude as minimum value.

[0022] When the adjustment input signal is input to the specific input converter 1a, the correction calculation unit 2d receives the calculation results of the specific Fourier transform calculation unit 2c corresponding to the specific input converter 1a and the calculation results of the phase reference signal Fourier transform calculation unit 2c, and calculates a low input gain correction amount G CL [i] and the amount of low-input phase correction θ for the phase of the adjustment input signal CL [i] is the sweep step (low input amplitude sweep step ΔA L At this time, the correction calculation unit 2d calculates the low input gain correction amount G CL[i] = theoretical low input amplitude value A defined for phase reference signal 20 LT [i] / Low input amplitude A of adjustment input signal L [i] and the low input phase correction amount θ CL [i] = low input phase θ of the adjustment input signal L [i]-Reference signal phase θ REF It is calculated as follows.

[0023] Next, the correction calculation unit 2d calculates the low input gain average correction amount G AVL and low input phase average correction amount θ AVL is the sweep step size (low input amplitude sweep step size ΔA L At this time, the correction calculation unit 2d calculates the low input gain average correction amount G AVL = Average low input gain correction amount G AVL (Initial value) + Low input gain compensation amount G CL [i] / N, and the low input phase average correction amount θ AVL =Low input phase average correction amount θ AVL (Initial value) + low input phase correction amount θ CL Calculated as [i] / N.

[0024] Next, the correction calculation unit 2d executes a process of setting i=i+1 (S14), and then determines whether i is smaller than N or equal to N (S15). If i is smaller than N or equal to N, the process proceeds to step S12 and the processes of steps S12 to S15 are repeated. If i becomes larger than N, the process result of step S13 is stored in the non-volatile memory 1g for recording correction values ​​(S16), and then the process of this routine is terminated.

[0025] Through the above processing, the correction calculation unit 2d calculates a gain correction amount as a first correction amount from the ratio between the average value of the amplitude theoretical values ​​for each sweep increment specified for the phase reference signal and the amplitude value of the adjustment input signal among the calculation results of the specific Fourier transform calculation unit 2c, which is the average value of the amplitude values ​​for each sweep increment, and calculates a phase correction amount as a second correction amount from the difference between the phase of the phase reference signal and the average value of the phase of the adjustment input signal among the calculation results of the specific Fourier transform calculation unit 2c, which is the phase of the adjustment input signal.

[0026] According to this embodiment, regardless of whether the amplitude value of the analog signal input from the power system is anywhere between the minimum value and the maximum value of the performance guarantee, the error in the input / output characteristics of the input converter can be averaged and corrected over the signal range from the minimum value to the maximum value. As a result, it is possible to obtain a gain correction amount and a phase correction amount in which the error in the input / output characteristics of the input converter is averaged and corrected over the signal range from the minimum value to the maximum value. EXAMPLES

[0027] 6A is a flowchart for explaining a second correction process at low input amplitude in a digital protection relay device according to a second embodiment of the present invention. This process is a correction process at low input amplitude at the time of shipment from the factory, in which a correction error is calculated by linear approximation using the least squares method. Note that the hardware and software configurations of the digital protection relay device in the second embodiment are the same as those in the first embodiment.

[0028] In FIG. 6A, for example, an adjustment input signal that changes sequentially in multiple steps of 0.1 V from several tens of mV to 110 V, similar to the first embodiment, is input to a specific input converter 1a shown in FIG.

[0029] The correction calculation unit 2d is a low input amplitude A L [i], low input amplitude theoretical value A LT [i], Low input gain compensation amount G CL [i], low input phase θ L [i], reference signal phase θ REF [i], low input phase correction amount θ CL[i], Calculated low input gain correction value G Lcalc , low input phase correction amount calculation value θ Lcalc , Low input amplitude sweep step size ΔA L , rated input amplitude A R1 The process starts with the information related to (A R1 -A L ) / ΔA L =N (N is a natural number), A L [i]=A R1 , i = 0, A L [0] = Process as low input amplitude minimum value (S21).

[0030] Next, the correction calculation unit 2d calculates the low input amplitude theoretical value A LT [i] and the low input amplitude A of the adjustment input signal L [i] and the low input gain correction amount G CL [i] is calculated, and the low input phase θ L [i] and the reference signal phase θ of the phase reference signal 20 REF Therefore, the low input phase correction amount θ CL At this time, the correction calculation unit 2d calculates the low input gain correction amount G CL [i] = Low input amplitude theoretical value A LT [i] / Low input amplitude A L [i] and the low input phase correction amount θ CL [i] = low input phase θ L [i]-Reference signal phase θ REF It is calculated as follows.

[0031] Next, the correction calculation unit 2d executes a process of setting i=i+1 (S23), and then judges whether i is smaller than N or equal to N (S24). If i is smaller than N or equal to N, the process proceeds to step S22, and the processes of steps S22 to S24 are repeated. If i becomes larger than N, the process sets i=0 and reinitializes the loop count i (S25).

[0032] By the processing from step S22 to step S24, the correction calculation unit 2d calculates the low input amplitude theoretical value A LT [i] and the low input amplitude A of the adjustment input signal L [i] and the low input gain correction amount G CL [i] is the sweep step (low input amplitude sweep step ΔA L ) and the low input phase θ L [i] and the reference signal phase θ of the phase reference signal 20 REF Therefore, the low input phase correction amount θ CL [i] is the sweep step (low input amplitude sweep step ΔA L ) is calculated.

[0033] Next, the correction calculation unit 2d calculates the gain correction approximate line calculation coefficients Yg, Xg based on the calculation results of steps S22 to S24, using the approximate lines of the gain correction and phase correction as coefficients of linear approximation by the least squares method. 、 Xgsq, XYg, and phase correction approximate straight line coefficients Yp, Xp, Xpsq, and XYp are calculated (S26). At this time, the correction calculation unit 2d calculates the gain correction approximate straight line calculation coefficient Xg=Xg (initial value)+low input amplitude A L [i], and the gain correction approximate straight line calculation coefficient Yg = Yg (initial value) + low input gain correction amount G CL [i], the gain correction approximate straight line calculation coefficient Xgsq = Xgsq (initial value) + low input amplitude A L [i] × low input amplitude A L [i] is calculated, and the gain correction approximate straight line calculation coefficient XYg = XYg (initial value) + low input amplitude A L [i] × Low input gain compensation amount G CL [i]. The correction calculation unit 2d calculates the phase correction approximate straight line coefficient Xp=Xp (initial value)+low input amplitude A L [i], and calculate the phase correction approximation linear coefficient Yp = Yp (initial value) + low input phase correction amount θ CL [i] is calculated as the phase correction approximate linear coefficient Xpsq = Xpsq (initial value) + low input amplitude A L [i] × low input amplitude A L [i] is calculated as the phase correction approximate linear coefficient XYp = XYp (initial value) + low input amplitude A L[i] × Low input gain compensation amount G CL Calculate as [i].

[0034] Next, the correction calculation unit 2d executes a process of setting i=i+1 (S27), and then determines whether i is smaller than N or equal to N (S28). If i is smaller than N or equal to N, the process proceeds to step S26 and repeats the processes of steps S26 to S28. If i is greater than N, the process proceeds to step S29.

[0035] Next, the correction calculation unit 2d calculates the low input amplitude A L The slope of the gain correction approximation line in G and intercept b G , and the slope of the phase correction approximation line a θ and intercept b θ Calculate the low input gain correction amount G from the calculation result (gain correction approximate linear equation). Lcalc Calculate the low input phase correction amount θ from the calculation result (phase correction approximation formula). Lcalc is calculated (S29), and then the processing in this routine ends.

[0036] At this time, the correction calculation unit 2d calculates the slope a of the gain correction approximation line. G = (N × XYg-Xg × Yg) / (N × Xgsq-Xg × Xg), and the intercept of the gain correction approximation line b G = (Yg × Xgsq - Xg × XYg) / (N × Xgsq - Xg × Xg). The correction calculation unit 2d calculates the slope a θ= Calculate (N×XYp-Xp×Yp) / (N×Xgsq-Xg×Xp), and the intercept of the phase correction approximation line b θ= Calculated as (Yp×Xpsq-Xp×XYp) / (N×Xpsq-Xg×Xp).

[0037] Furthermore, the correction calculation unit 2d calculates the low input gain correction amount G Lcalc = Slope of the gain correction approximation line a G ×Low input amplitude A L + Gain correction approximation line intercept bG The low input phase correction amount is calculated as θ Lcalc = Slope of the phase correction approximation line a θ ×Low input amplitude A L + Intercept of the phase correction approximation line b θ The calculated low input gain correction amount G Lcalc is the first correction amount, and the low input phase correction amount calculation value θ Lcalc are stored as second correction amounts in the correction value recording non-volatile memory 1g.

[0038] FIG. 6B is a flowchart for explaining a process to which a result of the second correction process is applied in the digital protection relay device according to the second embodiment of the present invention when the input amplitude is low.

[0039] In FIG. 6B, for example, an analog signal is input to each input converter 1a. The correction calculation unit 2d calculates the input amplitude A in , the input phase of the analog signal θ in , the rated amplitude of the analog signal A R , low input amplitude A of analog signal L , the rated gain correction amount of the analog signal G CR1 , rated phase correction amount of analog signal θ CR1 The information on the low input gain correction amount G calculated in step S29 is input. Lcalc and the low input phase correction amount calculation value θ Lcalc Based on the information entered, the rated input amplitude A R and low input amplitude A L Intermediate amplitude value A MID =(A R +A L ) / 2, Amplitude after correction A out , corrected phase θ out The process of calculating is started (S31).

[0040] Next, the correction calculation unit 2d calculates the rated input amplitude A of the analog signal. R and low input amplitude A of analog signal L Intermediate amplitude value A MID =(A R +A L) / 2, the input amplitude A in is the intermediate amplitude value A MID (S32) to determine whether the input amplitude A in is the intermediate amplitude value A MID If it is determined that the amplitude is greater than out and the corrected phase θ out (S33), and then the process in this routine is terminated. At this time, the correction calculation unit 2d calculates the corrected amplitude A out= Input amplitude A in × Rated gain correction amount G CR1 The corrected phase θ out = Input phase θ in × Rated phase correction amount θ CR1 It is calculated as follows.

[0041] The correction calculation unit 2d calculates the input amplitude A in is the intermediate amplitude value A MID The analog signal input amplitude A must be greater than in and the rated gain correction amount G CR1 and the corrected amplitude A out (first correction amplitude) and the input phase θ of the analog signal in and the rated phase correction amount θ CR1 Then, the corrected phase θ out (first corrected phase), and corrects the amplitude value of the analog signal calculated by the Fourier transform calculation unit 2c based on the calculated first corrected amplitude, and corrects the phase of the analog signal calculated by the Fourier transform calculation unit 2c based on the calculated first corrected phase.

[0042] On the other hand, in step S32, the input amplitude A in is the intermediate amplitude value A MID If it is determined that the input amplitude A in However, 0≦A in MID It is determined whether the condition is satisfied (S34). in However, between 0 and the intermediate amplitude value A MID If it is determined that the amplitude is between out and the corrected phase θ out ​(S35), and then the process in this routine ends. At this time, the correction calculation unit 2d calculates the corrected amplitude A out= Input amplitude A in × Calculated low input gain correction amount G Lcalc The corrected phase θ out= Input phase θ in × Calculated value of low input phase correction θ Lcalc It is calculated as follows.

[0043] The correction calculation unit 2d calculates the input amplitude A in However, 0≦A in MID The analog signal input amplitude A is within the range in and the calculated low input gain correction amount G Lcalc and the corrected amplitude A out (amplitude after second correction) and the input phase θ of the analog signal in and the calculated low input phase correction value θ Lcalc Then, the corrected phase θ out (second corrected phase), and corrects the amplitude value of the analog signal calculated by the Fourier transform calculation unit 2c based on the calculated second corrected amplitude, and corrects the phase of the analog signal calculated by the Fourier transform calculation unit 2c based on the calculated second corrected phase.

[0044] In addition, in step S34, the correction calculation unit 2d in However, 0≦A in MID If it is determined that the above condition is not satisfied, an abnormality in the amplitude value is detected (S36), and then the processing in this routine is terminated.

[0045] Fig. 7 shows an input / output characteristic diagram of the digital protection relay device according to the second correction process at low input amplitude. In this embodiment, at low input amplitude, the correction error is corrected by a linear approximation calculated by the least squares method, so as shown in Fig. 7, it can be seen that the error at low input amplitude shows a smaller characteristic than that of the comparative example shown in Fig. 4.

[0046] ​​According to this embodiment, even if the amplitude value of the analog signal input from the power system is anywhere from the minimum value to the maximum value of the performance guarantee, the error of the input / output characteristics of the input converter can be corrected by the calculation of the linear approximation by the least squares method over the signal range from the minimum value to the maximum value, and as a result, the gain correction amount and the phase correction amount corrected by the linear approximation by the least squares method can be obtained. in However, between 0 and the intermediate amplitude value A MID When there is an input amplitude A in is the intermediate amplitude value A MID In this case, the amplitude value of the analog signal input from the power grid can be corrected by dividing the case into two cases: when the amplitude value is greater than 0.01 and when the amplitude value is greater than 0.01. EXAMPLES

[0047] 8A is a flowchart for explaining a third correction process of the digital protection relay device according to the third embodiment of the present invention. This process involves sweeping and inputting a known input signal for adjustment (adjustment input signal) that varies from the minimum input amplitude to the full-scale input amplitude, which is the maximum amplitude, that guarantees the performance of the digital protection relay device according to the present invention, and creating a look-up table of gain correction values ​​and phase correction values ​​corresponding to the input amplitude of the input adjustment input signal. Note that the hardware and software configurations of the digital protection relay device in the third embodiment are similar to those in the first embodiment.

[0048] In FIG. 8A, for example, an adjustment input signal that changes sequentially in multiple steps of 0.1 V from several tens of mV to 110 V, similar to the first embodiment, is input to a specific input converter 1a shown in FIG.

[0049] The correction calculation unit 2d calculates the input amplitude A[i] of the adjustment input signal and the theoretical input amplitude A[i] defined in the phase reference signal 20. T [i], Input gain correction amount G C [i], the input phase θ[i] of the adjustment input signal, and the reference signal phase θ of the phase reference signal 20. REF [i], input phase correction amount θ C [i], full-scale input amplitude A of the adjustment input signalFS The processing starts with the information on the input amplitude sweep step ΔA, (A FS -A[0]) / ΔA=N (N is a natural number), A[N]=A FS , i=0, and A[0]=low input amplitude minimum value (S41).

[0050] Next, the correction calculation unit 2d calculates the input gain correction amount G of the adjustment input signal based on the calculation results of each of the Fourier transform calculation units 2c. C [i] and the input phase correction amount θ of the adjustment input signal C At this time, the correction calculation unit 2d calculates the input gain correction amount G C [i] = theoretical input amplitude A defined by the phase reference signal 20 T [i] / input amplitude A[i] of the adjustment input signal, and the input phase correction amount θ C [i] = input phase θ[i] of adjustment input signal - reference signal phase θ of phase reference signal 20 REF It is calculated as follows.

[0051] Next, the correction calculation unit 2d calculates the input gain correction amount G corresponding to the input amplitude A[i]. C The gain correction lookup table that outputs [i] and the input phase correction amount θ corresponding to the input amplitude A[i] C As a process of recording the phase correction lookup table that outputs the phase correction amount G corresponding to the input amplitude A[i] C [i] is recorded in the gain correction lookup table GLLUT as the first correction amount, and the input phase correction amount θ corresponding to the input amplitude A[i] is calculated. C [i] is recorded in the phase lookup table PLUT as the second correction amount (S44). Note that the gain correction lookup table GLLUT and the phase lookup table PLUT are stored in the correction value recording nonvolatile memory 1g.

[0052] Next, the correction calculation unit 2d executes a process of setting i=i+1 (S44), and then judges whether i is smaller than N or equal to N (S45). If i is smaller than N or equal to N, the process proceeds to step S42, and the processes of steps S42 to S45 are repeated. If i becomes larger than N, the process in this routine ends.

[0053] Through the processing of steps S42 to S45, the correction calculation unit 2d calculates an input gain correction amount corresponding to each sweep increment as a gain correction amount from the ratio between the amplitude theoretical value for each sweep increment specified for the phase reference signal 20 and the amplitude value of the adjustment input signal among each calculation result of the Fourier transform calculation unit 2c, which is the amplitude value for each sweep increment (input amplitude sweep increment ΔA), and records the calculated input gain correction amount corresponding to each sweep increment as a first correction amount in the gain correction lookup table GLUT, and calculates an input phase correction amount corresponding to each sweep increment as a phase correction amount from the phase of the adjustment input signal among each calculation result of the Fourier transform calculation unit 2c, which is the difference between the phase for each sweep increment and the phase of the phase reference signal, and records the calculated input phase correction amount corresponding to each sweep increment as a second correction amount in the phase lookup table PLUT.

[0054] FIG. 8B is a flowchart for explaining a process for applying a result of the third correction process in the digital protection relay device according to the third embodiment of the present invention.

[0055] In FIG. 8B, for example, an analog signal is input to each input converter 1a. The correction calculation unit 2d calculates the input amplitude A in , the input phase of the analog signal θ in , gain correction lookup table GLUT, phase lookup table PLUT, lookup table input A[i], input gain correction amount G C [i], input phase correction amount θ C [i], Amplitude after correction A out , corrected phase θ out Processing is started for information related to (S51).

[0056] The correction calculation unit 2d receives information indicating the calculation results of each of the Fourier transform calculation units 2c, and among the received information, the input amplitude A in Based on this, the lookup table input A[i] is calculated (S52).

[0057] Next, the correction calculation unit 2d calculates the input gain correction amount G from the gain correction lookup table GLUT. C [i] is output, and the input phase correction amount θ C [i] is output (S53).

[0058] Next, the correction calculation unit 2d calculates the corrected amplitude A based on the information input in step S51 and the information output in step S53. out and the corrected phase θ out Then, the processing in this routine is terminated. At this time, the correction calculation unit 2d calculates the corrected amplitude A out = Input amplitude A in × Input gain correction amount G C [i] and the corrected phase θ out = Input phase θ in - Input phase correction amount θ C Calculate as [i].

[0059] When an analog signal whose amplitude value includes one of the sweep increments (input amplitude sweep increment ΔA) is input to each input converter 1a, the correction calculation unit 2d extracts an input gain correction amount corresponding to the sweep increment specified by the amplitude value of the analog signal from the gain correction lookup table GLUT, corrects the amplitude value of the analog signal calculated by the Fourier transform calculation unit 2c based on the extracted input gain correction amount, extracts an input phase correction amount corresponding to the sweep increment specified by the amplitude value of the analog signal from the phase lookup table PLUT, and corrects the phase of the analog signal calculated by the Fourier transform calculation unit 2c based on the extracted input phase correction amount.

[0060] Fig. 9 shows an input / output characteristic diagram after the third correction process of the digital protective relay device according to the third embodiment of the present invention. In this embodiment, the adjustment input signal that changes from the minimum input amplitude that guarantees the performance of the digital protective relay device to the full-scale input amplitude that is the maximum amplitude is swept, and the error of the input / output characteristic of the input converter is corrected over the signal range from the minimum value to the maximum value. As a result, as shown in Fig. 9, the input / output characteristic shows a characteristic in which the error in the entire range from the time of low input amplitude (minimum input) to the time of rated input amplitude (full-scale input) is smaller than that of the comparative example shown in Fig. 4.

[0061] According to this embodiment, even if the amplitude value of the analog signal input from the power system is anywhere from the minimum value to the maximum value of the performance guarantee, it is possible to obtain a gain correction amount and an input phase correction amount in which the error of the input / output characteristics of the input converter is corrected over the signal range from the minimum value to the maximum value. For example, even if an analog signal ranging from a low input signal range of tens of mA and tens of mV to a high input signal range of full scale is input to the input converter, it is possible to obtain an input gain correction amount and an input phase correction amount in which the error of the input / output characteristics of the input converter is corrected over the low input signal range to the high input signal range. As a result, it is possible to realize a digital protective relay device that ensures a dynamic range for the analog signal from the power system.

[0062] It should be noted that the present invention is not limited to the above-described embodiments, but includes various modifications and equivalent configurations within the spirit of the appended claims. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations.

[0063] In addition, each of the configurations, functions, etc. described above may be realized in hardware, for example by designing some or all of them as an integrated circuit, or may be realized in software by a processor interpreting and executing a program that realizes each function.

[0064] Information such as programs, tables, files, etc. that realize each function can be stored in a storage device such as a memory, a hard disk, or an SSD (Solid State Drive), or in a recording medium such as an IC (Integrated Circuit) card, an SD card, or a DVD (Digital Versatile Disc). [Explanation of symbols]

[0065] 1 Digital protection relay device, 1a Input converter, 1b Analog filter, 1c A / D converter, 1d Digital filter, 1e CPU, 1f Work memory, 1g Non-volatile memory, 1h Input / output interface, 1i Bus, 2a Hardware, 2b Software, 2c Fourier transform calculation unit, 2d Correction calculation unit, 2e Protection calculation unit

Claims

1. A plurality of input converters that receive analog signals representing analog amounts of electrical signals from objects to be protected that are connected to the power grid, convert the levels of the received analog signals, and output the converted levels; a plurality of analog-to-digital converters for converting analog signals output from the respective input converters into digital signals; a plurality of Fourier transform calculation units that perform Fourier transform processing on the digital signals output from the respective analog-to-digital converters to calculate the amplitude and phase of each of the analog signals; a correction calculation unit that executes a calculation to correct the amplitude value calculated by each of the Fourier transform calculation units with a first correction amount and a calculation to correct the phase calculated by each of the Fourier transform calculation units with a second correction amount; a protection calculation unit that executes a protection calculation process for the protection target based on each calculation result of the correction calculation unit; an analog-to-digital converter for a phase reference signal for converting the phase reference signal into a digital signal; a phase reference signal Fourier transform calculation unit that performs the Fourier transform process on the digital signal output from the phase reference signal analog-digital converter to calculate an amplitude value and a phase of the phase reference signal and outputs each calculation result to the correction calculation unit; The correction calculation unit is a first correction amount calculated based on the amplitude value of the adjustment input signal among the calculation results of a specific Fourier transform calculation unit corresponding to the specific input converter among the multiple Fourier transform calculation units, and a second correction amount calculated based on the phase of the adjustment input signal among the calculation results of the specific Fourier transform calculation unit, on the condition that an adjustment input signal, which is an AC signal corresponding to the analog signal and has an amplitude value that changes sequentially in multiple steps from a low input amplitude minimum value to a rated input amplitude value of the analog signal in accordance with a sweep increment, is input to a specific input converter among the multiple input converters.

2. 2. The digital protection relay device according to claim 1, The correction calculation unit is a gain correction amount indicating a ratio between an amplitude theoretical value defined in the phase reference signal and an amplitude value of the adjustment input signal calculated by the specific Fourier transform calculation unit is calculated as the first correction amount for each sweep increment, and a phase correction amount indicating a difference between the phase of the adjustment input signal calculated by the specific Fourier transform calculation unit and the phase of the phase reference signal calculated by the phase reference signal Fourier transform calculation unit is calculated as the second correction amount for each sweep increment.

3. 2. The digital protection relay device according to claim 1, The correction calculation unit is a gain correction amount indicating a ratio between an average value of an amplitude theoretical value defined for the phase reference signal and an average value of the amplitude value of the adjustment input signal among the calculation results of the specific Fourier transform calculation unit is calculated as the first correction amount for each sweep increment, and a phase correction amount indicating a difference between an average value of the phase of the adjustment input signal among the calculation results of the specific Fourier transform calculation unit and a phase of the phase reference signal among the calculation results of the phase reference signal Fourier transform calculation unit is calculated as the second correction amount for each sweep increment.

4. 2. The digital protection relay device according to claim 1, The correction calculation unit is calculating, for each sweep increment, a gain correction amount indicating a ratio between an amplitude theoretical value for each sweep increment defined in the phase reference signal and an amplitude value of the adjustment input signal among the calculation results of the specific Fourier transform calculation unit, and calculating, as the first correction amount, a gain correction amount calculated value by linear approximation using a least squares method based on the calculated gain correction amount for each sweep increment and the amplitude value of the adjustment input signal for each sweep increment; a phase correction amount indicating a difference between a phase of the adjustment input signal among the calculation results of the specific Fourier transform calculation unit for each sweep increment and a phase of the phase reference signal among the calculation results of the phase reference signal Fourier transform calculation unit, and a phase correction amount calculated by linear approximation using the least squares method is calculated as the second correction amount based on the calculated phase correction amount for each sweep increment and an amplitude value of the adjustment input signal for each sweep increment.

5. 5. The digital protection relay device according to claim 4, The correction calculation unit is When the analog signal is input to the input converter, on condition that the input amplitude of the analog signal is greater than an intermediate amplitude value that is intermediate between the low input amplitude minimum value and the rated input amplitude value, a first post-correction amplitude is calculated from the input amplitude of the analog signal and a rated gain correction amount, and a first post-correction phase is calculated from the input phase of the analog signal and a rated phase correction amount, correcting the amplitude value of the analog signal calculated by the Fourier transform calculation unit based on the calculated first post-correction amplitude, and correcting the phase of the analog signal calculated by the Fourier transform calculation unit based on the calculated first post-correction phase, a second corrected amplitude is calculated from the input amplitude of the analog signal and the calculated gain correction amount value, and a second corrected phase is calculated from the input phase of the analog signal and the calculated phase correction amount value, on the condition that the input amplitude of the analog signal is between 0 and the intermediate amplitude value, correcting the amplitude value of the analog signal calculated by the Fourier transform calculation unit based on the calculated second corrected amplitude, and correcting the phase of the analog signal calculated by the Fourier transform calculation unit based on the calculated second corrected phase.

6. 2. The digital protection relay device according to claim 1, The correction calculation unit is calculating, for each of the sweep increments, an input gain correction amount indicating a ratio between an amplitude theoretical value for each of the sweep increments defined in the phase reference signal and an amplitude value for each of the sweep increments which is an amplitude value of the adjustment input signal among the calculation results of the Fourier transform calculation unit, and recording the calculated input gain correction amount corresponding to each of the sweep increments in a gain correction lookup table as a first correction amount; a phase lookup table for recording the calculated input phase correction amount corresponding to each sweep increment as the second correction amount, the phase correction amount being a phase of the adjustment input signal among the calculation results of the Fourier transform calculation unit, the phase correction amount indicating a difference between the phase of the adjustment input signal for each sweep increment and the phase of the phase reference signal among the calculation results of the phase reference signal Fourier transform calculation unit, and

7. 7. The digital protection relay device according to claim 6, The correction calculation unit is when the analog signal whose amplitude value includes any one of the sweep increments is input to the input converter, an input gain correction amount corresponding to the sweep increment specified by the amplitude value of the analog signal is extracted from the gain correction lookup table, and the amplitude value of the analog signal calculated by the Fourier transform calculation unit is corrected based on the extracted input gain correction amount; an input phase correction amount corresponding to the sweep increment specified by the amplitude value of the analog signal is extracted from the phase lookup table, and the phase of the analog signal calculated by the Fourier transform calculation unit is corrected based on the extracted input phase correction amount.

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