Method and system for compensating pilot frequency current error of low-voltage current transformer

Abstract

The invention discloses a method and a system for compensating different-frequency current errors of a low-voltage current transformer, and belongs to the technical field of error measurement of electric energy metering equipment. The method comprises the following steps: measuring the magnetic conductivity of a low-voltage current transformer CT iron core under power frequency and different frequency current, and calculating to obtain low-voltage CT equivalent circuit excitation impedance parameters under the magnetic conductivity corresponding to different frequency circuits; measuring to obtain the direct current resistance of the low-voltage CT secondary winding, and calculating to obtain the excitation current value under each frequency calibration range point based on the direct current resistance; and calculating a current error value of the measuring range point under each frequency based on the excitation current value, calculating a pilot frequency error compensation coefficient of the measuring range point under each frequency based on the current error value, and compensating the abnormal current error of the low-voltage CT by using the pilot frequency error compensation coefficient. According to the invention, large-scale and high-efficiency utilization of pilot frequency current is facilitated to carry out low-voltage CT live calibration error verification, and the metering performance of the low-voltage CT in the commissioning process is accurately judged.

Description

Technical Field

[0001] The present invention relates to the technical field of error measurement of electric energy metering equipment, and more specifically, to a method and system for compensating for heterofrequency current errors of low-voltage current transformers. Background Art

[0002] As an important device for electric energy trade settlement, the stability of the measurement performance of low-voltage current transformer (low-voltage CT) is related to the accuracy of trade settlement. Today, when the State Grid Corporation has put forward extremely high requirements for power supply reliability, a method for calibrating low-voltage CT without power outage has emerged, which includes injecting a current with a different frequency from the power frequency into the primary circuit of the low-voltage CT, measuring the error of the current with a different frequency, and determining the accuracy of the low-voltage CT.

[0003] The live calibration method of heterofrequency current can effectively obtain the low-voltage CT error under live conditions. However, due to the different current frequencies, the heterofrequency current error obtained under the same range is inconsistent with the power frequency current error. Summary of the invention

[0004] In view of the above problems, the present invention proposes a method for compensating for the current error of a low-voltage current transformer with different frequencies, comprising:

[0005] Measuring the magnetic permeability of the iron core of the low-voltage current transformer CT under power frequency and heterofrequency current, obtaining the power frequency and heterofrequency current magnetic permeabilities of the iron core of the low-voltage CT based on the magnetic permeability of the iron core, and calculating the excitation impedance parameters of the low-voltage CT equivalent circuit under the corresponding magnetic permeabilities of different frequency circuits based on the power frequency and heterofrequency current magnetic permeabilities;

[0006] The DC resistance of the secondary winding of the low voltage CT is measured, and based on the DC resistance, the excitation current value at each frequency calibration range point is calculated;

[0007] Based on the excitation current value, the current error value of the range point at each frequency is calculated, and based on the current error value, the out-of-frequency error compensation coefficient of the range point at each frequency is calculated. The out-of-frequency error compensation coefficient is used to compensate for the abnormal current error of the low-voltage CT.

[0008] Optionally, measure the magnetic permeability of the low voltage current transformer CT core under power frequency and differential frequency current, including:

[0009] The magnetic induction intensity of the low-voltage CT output voltage and the magnetic induction intensity of the input excitation current are measured; based on the magnetic induction intensity of the output voltage and the magnetic induction intensity of the input excitation current, the magnetic permeability of the low-voltage current transformer CT core under the power frequency and the heterofrequency current is calculated, and the calculation formula is as follows:

[0010]

[0011] in, is the magnetic permeability of the low voltage current transformer CT core, B is the magnetic induction intensity of the output voltage, and H is the magnetic induction intensity of the input excitation current.

[0012] Optionally, the excitation impedance parameters of the low-voltage CT equivalent circuit under the corresponding magnetic permeability of the circuit at different frequencies are calculated, including:

[0013]

[0014] Among them, Z m is the excitation impedance of the low voltage CT equivalent circuit, is the magnetic permeability of the low voltage current transformer CT core, S is the core cross-sectional area, l is the length of the magnetic path inside the core, N1 is the number of turns of the excitation winding, ω is the current frequency, and j is the imaginary unit.

[0015] Optionally, the calculated excitation current value at each frequency calibration range point includes: a primary side working current value, and the calculation formula of the primary side working current value is as follows:

[0016] I1=I0+I′2

[0017] Among them, I1 is the primary side working current value, I′2 is the secondary side working current value, and I0 is the test current of each frequency.

[0018] Optionally, the current error value of the range point at each frequency is calculated, including: composite error, ratio difference and angle difference. The calculation formulas of the composite error, ratio difference and angle difference are as follows:

[0019]

[0020] f=Asinθ

[0021] δ=Acosθ

[0022] Among them, Δ is the composite error, f is the ratio difference, δ is the angle difference, I1 is the primary side working current value, I0 is the test current of each frequency, A is the real part value of I0 / I1, and θ is the angle of I0 / I1.

[0023] On the other hand, the present invention also provides a system for compensating for the current error of a low-voltage current transformer with different frequencies, comprising:

[0024] The first calculation unit is used to measure the magnetic permeability of the low-voltage current transformer CT core under power frequency and heterofrequency current, obtain the power frequency and heterofrequency current magnetic permeability of the iron core of the low-voltage CT based on the magnetic permeability of the iron core, and calculate the low-voltage CT equivalent circuit excitation impedance parameters under the corresponding magnetic permeabilities of different frequency circuits based on the power frequency and heterofrequency current magnetic permeabilities;

[0025] The second calculation unit is used to measure the DC resistance of the secondary winding of the low-voltage CT, and calculate the excitation current value at each frequency calibration range point based on the DC resistance;

[0026] The third calculation unit is used to calculate the current error value of the range point at each frequency based on the excitation current value, calculate the different-frequency error compensation coefficient of the range point at each frequency based on the current error value, and use the different-frequency error compensation coefficient to compensate for the abnormal current error of the low-voltage CT.

[0027] Optionally, measure the magnetic permeability of the low voltage current transformer CT core under power frequency and differential frequency current, including:

[0028] The magnetic induction intensity of the low-voltage CT output voltage and the magnetic induction intensity of the input excitation current are measured; based on the magnetic induction intensity of the output voltage and the magnetic induction intensity of the input excitation current, the magnetic permeability of the low-voltage current transformer CT core under the power frequency and the heterofrequency current is calculated, and the calculation formula is as follows:

[0029]

[0030] in, is the magnetic permeability of the low voltage current transformer CT core, B is the magnetic induction intensity of the output voltage, and H is the magnetic induction intensity of the input excitation current.

[0031] Optionally, the excitation impedance parameters of the low-voltage CT equivalent circuit under the corresponding magnetic permeability of the circuit at different frequencies are calculated, including:

[0032]

[0033] Among them, Z m is the excitation impedance of the low voltage CT equivalent circuit, is the magnetic permeability of the low voltage current transformer CT core, S is the core cross-sectional area, l is the length of the magnetic path inside the core, N1 is the number of turns of the excitation winding, ω is the current frequency, and j is the imaginary unit.

[0034] Optionally, the calculated excitation current value at each frequency calibration range point includes: a primary side working current value, and the calculation formula of the primary side working current value is as follows:

[0035] I1=I0+I′2

[0036] Among them, I1 is the primary side working current value, I′2 is the secondary side working current value, and I0 is the test current of each frequency.

[0037] Optionally, the current error value of the range point at each frequency is calculated, including: composite error, ratio difference and angle difference. The calculation formulas of the composite error, ratio difference and angle difference are as follows:

[0038]

[0039] f=A sinθ

[0040] δ=Acosθ

[0041] Among them, Δ is the composite error, f is the ratio difference, δ is the angle difference, I1 is the primary side working current value, I0 is the test current of each frequency, A is the real part value of I0 / I1, and θ is the angle of I0 / I1.

[0042] In yet another aspect, the present invention further provides a computing device, comprising: one or more processors;

[0043] a processor for executing one or more programs;

[0044] When the one or more programs are executed by the one or more processors, the above-described method is implemented.

[0045] In yet another aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed, the method described above is implemented.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] The present invention provides a method for compensating the error of low-voltage current transformer at different frequencies, including: measuring the magnetic permeability of the iron core of the low-voltage current transformer CT under power frequency and different frequency current, obtaining the power frequency and different frequency current magnetic permeability of the iron core of the low-voltage CT based on the magnetic permeability of the iron core, and calculating the excitation impedance parameters of the low-voltage CT equivalent circuit under the corresponding magnetic permeability of different frequency circuits based on the power frequency and different frequency current magnetic permeabilities; measuring the DC resistance of the secondary winding of the low-voltage CT, and calculating the excitation current value at each frequency calibration range point based on the DC resistance; calculating the current error value at each frequency range point based on the excitation current value, calculating the different frequency error compensation coefficient at each frequency range point based on the current error value, and using the different frequency error compensation coefficient to compensate for the abnormal current error of the low-voltage CT. The application of the present invention is helpful to carry out the calibration error verification of low-voltage CT on-line using different frequency current on a large scale and with high efficiency, and accurately judge the metering performance of low-voltage CT during the commissioning process. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a flow chart of the method of the present invention;

[0049] Figure 2 A low voltage CT current error calculation flow chart of an embodiment of the method of the present invention;

[0050] Figure 3It is a T-type equivalent circuit diagram of a current transformer in an embodiment of the method of the present invention;

[0051] Figure 4 A diagram of a device for measuring the magnetic permeability of a low-voltage CT core according to an embodiment of the method of the present invention;

[0052] Figure 5 A circuit diagram for measuring the secondary winding impedance of a low voltage CT according to an embodiment of the method of the present invention;

[0053] Figure 6 It is a structural diagram of the system of the present invention. DETAILED DESCRIPTION

[0054] Now, exemplary embodiments of the present invention are described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely and to fully convey the scope of the present invention to those skilled in the art. The terms used in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present invention. In the accompanying drawings, the same units / elements are marked with the same reference numerals.

[0055] Unless otherwise specified, the terms (including technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0056] Embodiment 1:

[0057] The present invention proposes a method for compensating the frequency error of low voltage current transformer. Figure 1 As shown, including:

[0058] Step 1, measuring the magnetic permeability of the low-voltage current transformer CT core under power frequency and heterofrequency current, obtaining the power frequency and heterofrequency current magnetic permeabilities of the iron core of the low-voltage CT based on the magnetic permeability of the iron core, and calculating the low-voltage CT equivalent circuit excitation impedance parameters under the corresponding magnetic permeabilities of different frequency circuits based on the power frequency and heterofrequency current magnetic permeabilities;

[0059] Step 2: Measure the DC resistance of the secondary winding of the low voltage CT, and calculate the excitation current value at each frequency calibration range point based on the DC resistance;

[0060] Step 3: Based on the excitation current value, calculate the current error value of the range point at each frequency; based on the current error value, calculate the out-of-frequency error compensation coefficient of the range point at each frequency; use the out-of-frequency error compensation coefficient to compensate for the abnormal current error of the low-voltage CT.

[0061] Among them, the magnetic permeability of the low-voltage current transformer CT core under power frequency and heterofrequency current is measured, including:

[0062] The magnetic induction intensity of the low-voltage CT output voltage and the magnetic induction intensity of the input excitation current are measured; based on the magnetic induction intensity of the output voltage and the magnetic induction intensity of the input excitation current, the magnetic permeability of the low-voltage current transformer CT core under the power frequency and the heterofrequency current is calculated, and the calculation formula is as follows:

[0063]

[0064] in, is the magnetic permeability of the low voltage current transformer CT core, B is the magnetic induction intensity of the output voltage, and H is the magnetic induction intensity of the input excitation current.

[0065] Among them, the excitation impedance parameters of the low-voltage CT equivalent circuit under the corresponding magnetic permeability of the circuit at different frequencies are calculated, including:

[0066]

[0067] Among them, Z m is the excitation impedance of the low voltage CT equivalent circuit, is the magnetic permeability of the low voltage current transformer CT core, S is the core cross-sectional area, l is the length of the magnetic path inside the core, N1 is the number of turns of the excitation winding, ω is the current frequency, and j is the imaginary unit.

[0068] The excitation current value calculated at each frequency calibration range point includes: a primary side working current value, and the calculation formula of the primary side working current value is as follows:

[0069] I1=I0+I′2

[0070] Among them, I1 is the primary side working current value, I′2 is the secondary side working current value, and I0 is the test current of each frequency.

[0071] The current error values ​​of the range points at each frequency are calculated, including composite error, ratio error and angle error. The calculation formulas of composite error, ratio error and angle error are as follows:

[0072]

[0073] f=Asinθ

[0074] δ=Acosθ

[0075] Among them, Δ is the composite error, f is the ratio difference, δ is the angle difference, I1 is the primary side working current value, I0 is the test current of each frequency, A is the real part value of I0 / I1, and θ is the angle of I0 / I1.

[0076] The present invention is further described below with reference to specific examples of the present invention:

[0077] Specific case flow: Figure 2 As shown, including:

[0078] Step 1: Measure the magnetic permeability of the low-voltage CT core under power frequency and differential frequency current.

[0079] Step 2: Calculate the excitation impedance parameters of the low-voltage CT equivalent circuit under the corresponding magnetic permeability of the circuit at different frequencies.

[0080] Step 3: Measure the DC resistance of the transformer secondary winding and improve the low-voltage CT equivalent circuit parameters.

[0081] Step 4: Determine the excitation current value at each frequency calibration range point.

[0082] Step 5: Calculate the current error value at each range point at each frequency.

[0083] Step 6: Compare the calculated error values ​​at the same range points under each frequency current to determine the error proportional coefficient.

[0084] The transformer converts the large current on the primary side into a small current on the secondary side. A part of the current on the primary side is used to generate the electromotive force of the secondary winding, driving the secondary winding to generate current. This part of the current is called the excitation current. The excitation current is the root cause of the error. The equivalent circuit diagram of the current transformer T is as follows: Figure 3 shown.

[0085] I1 is the primary current, N1 is the number of turns of the primary winding; I0 is the excitation current, Z m is the excitation impedance; Z 20 ′ is the total impedance of the secondary circuit referred to the primary side.

[0086] Z m =2πjωL m +R m , L m , R m are the equivalent inductance and equivalent resistance components of the excitation impedance respectively; Z 20 ′=Z2′+Z′, where the secondary winding impedance referred to the primary side is Z2′=R2′+2πjωL2′, and the load impedance referred to the primary side is Z′=R′+2πjωL′.

[0087] Total impedance of secondary circuit Z 20 ' is formula (1):

[0088] Z 20 ′=R2′+2πjωL2′+R′+2πjωL′ (1)

[0089] According to the principle of current error generation, the specific method and process of heterodyne current error compensation is as follows.

[0090] Step 1: The method for measuring the core excitation impedance is as follows:

[0091] pass Figure 4 The circuit shown measures the magnetic permeability of the low voltage CT core The system consists of a different-frequency current signal generator, a power amplifier, a current and voltage measurement unit, a high-precision voltage measurement circuit, an oscilloscope, and a low-voltage current transformer to be tested. The entire device generates excitation currents of different frequencies by setting the frequency of the different-frequency current signal generator. The excitation signal increases the output power through the power amplifier. Its output end is connected to the excitation winding to generate test currents I0 of various frequencies until the low-voltage CT to be tested reaches the saturation of the core. The output end measures the open-circuit voltage e of the secondary winding. The measurement and display unit generally includes an effective value voltmeter V and an ammeter A, which can visually monitor the test data and facilitate real-time adjustment of the output signal. The precision voltage measurement circuit is responsible for collecting the output voltage and calculating the magnetic induction intensity B according to formula (2), where S is the cross-sectional area of ​​the core and N1 is the number of turns of the excitation current coil. The signal acquisition system simultaneously collects the input excitation current and calculates the magnetic field intensity H according to formula (3), where l is the length of the magnetic path of the core. The signal acquisition system can calculate the corresponding relationship between BH, and substitute formula (3) into (4) to calculate I0 and The corresponding relationship.

[0092]

[0093] Hl=NI0 (3)

[0094]

[0095] Step 2: Calculate the low voltage CT core excitation impedance parameters at the corresponding frequency and permeability.

[0096] Low voltage current transformer excitation impedance Z m According to the magnetic permeability of the transformer core As well as the core cross-sectional area S and the core internal magnetic path length l are obtained.

[0097] From the law of electromagnetic induction we know that:

[0098]

[0099] Where N1 is the number of turns of the excitation winding; φ is the core magnetic flux, and e is the secondary winding excitation voltage.

[0100] The magnetic flux of the core cross section can be expressed as formula (6):

[0101] φ=N1BS (6)

[0102] Substituting equations (3) and (4) into the above equation, we obtain equation (7).

[0103]

[0104] Substituting formula (7) into formula (5) yields:

[0105]

[0106] At the same time, the excitation voltage generated by the excitation current can be expressed by the excitation impedance, that is:

[0107] -e=Z m I0 (6)

[0108] Combining equations (5) and (6), we get:

[0109]

[0110] Will Substitute into formula (7);

[0111] Get the excitation impedance Z m Expression (8), where the number of primary turns N1=1.

[0112]

[0113] Step 3: Measure the secondary winding impedance as follows:

[0114] Secondary winding impedance measurement circuit Figure 5 As shown in the figure, since the inductance of the secondary winding is very small, the inductance of the secondary winding can be ignored, and only the resistance of the winding is measured. The impedance value R' is measured using a DC power supply, and the current I at both ends of the winding is obtained. R , voltage across the terminals U R , the calculation formula is (9).

[0115]

[0116] Step 4: Determine the excitation current value under each frequency calibration range current:

[0117] According to step 3, calculate the excitation impedance value Z corresponding to the excitation current m Calculate the secondary side working current I′2 using formula (10).

[0118]

[0119] The total current I1 is calculated as shown in formula (11), and the total current value is the primary side working current value of the current transformer.

[0120] I1=I0+I′2 (11)

[0121] At this time, the corresponding relationship between I0 and I1 at each frequency is obtained.

[0122] Step 5: Calculate the current error value at each range point.

[0123] According to the primary current and excitation current values ​​calculated in step 4, the error values ​​corresponding to each range point are calculated. The formula of composite error Δ is as shown in formula (12):

[0124]

[0125] The calculation formula of the ratio difference f is (13), and the calculation formula of the angle difference δ is (14).

[0126] f=A sinθ (13)

[0127] δ=AcoSθ (14)

[0128] This step can obtain the ratio difference and angle difference at the same range at each frequency.

[0129] Step 6: Compare the calculated error values ​​at the same range points under each frequency current to determine the error proportional coefficient.

[0130] The ratio difference f at 50Hz calculated in step 5 50 , angle difference δ 50 The ratio difference f with the frequency difference 异频 , angle difference δ 异频 , calculate the frequency ratio difference proportional coefficient x1 and the angle difference proportional coefficient x2 through equations (15) and (16).

[0131]

[0132] The error value of the heterofrequency current measurement can be corrected according to the error proportional coefficients x1 and x2.

[0133] The low-voltage current transformer power frequency and heterodyne current magnetic permeability measurement system calculates the relationship between the input power frequency and heterodyne excitation current and the output induced voltage, obtains the BH characteristic curve of the low-voltage current transformer core, and calculates the excitation impedance value of the transformer T-type equivalent circuit corresponding to each frequency excitation current according to the corresponding BH characteristic;

[0134] The transformer secondary winding impedance measurement system utilizes a DC excitation source to effectively measure the secondary winding resistance value;

[0135] The transformer working current and error calculation module effectively calculates the primary current value corresponding to the transformer under the excitation current value according to the theoretical method proposed by the method, and calculates the error corresponding to the primary current value according to the current value.

[0136] The out-of-frequency current error compensation module compares the error result obtained by the error calculation module with the power frequency current error at the corresponding range point to obtain an error compensation coefficient.

[0137] Compared with the prior art, the present invention has the following beneficial effects:

[0138] The method of the invention builds a low-voltage CT core magnetic permeability measurement system, combines theoretical calculations to accurately obtain the excitation impedance parameters of the equivalent circuit under various frequency currents, proposes a calculation method corresponding to the excitation current and the working current, and clarifies the error correspondence under different frequencies and the same working current.

[0139] The method proposed in the present invention can compensate the measurement error of the heterofrequency current into the measurement error of the power frequency current, which is helpful to carry out the calibration error verification of the low-voltage CT on-line using the heterofrequency current on a large scale and with high efficiency, and accurately judge the metering performance of the low-voltage CT during the commissioning process.

[0140] Embodiment 2:

[0141] The present invention also proposes a system 200 for compensating for the frequency-different current error of a low-voltage current transformer, such as Figure 6 As shown, including:

[0142] The first calculation unit 201 is used to measure the magnetic permeability of the low-voltage current transformer CT core under power frequency and heterofrequency current, obtain the power frequency and heterofrequency current magnetic permeability of the iron core of the low-voltage CT based on the magnetic permeability of the iron core, and calculate the low-voltage CT equivalent circuit excitation impedance parameters under the corresponding magnetic permeabilities of different frequency circuits based on the power frequency and heterofrequency current magnetic permeabilities;

[0143] The second calculation unit 202 is used to measure the DC resistance of the secondary winding of the low voltage CT, and calculate the excitation current value at each frequency calibration range point based on the DC resistance;

[0144] The third calculation unit 203 is used to calculate the current error value of the range point at each frequency based on the excitation current value, calculate the different-frequency error compensation coefficient of the range point at each frequency based on the current error value, and use the different-frequency error compensation coefficient to compensate for the abnormal current error of the low-voltage CT.

[0145] Among them, the magnetic permeability of the low-voltage current transformer CT core under power frequency and heterofrequency current is measured, including:

[0146] The magnetic induction intensity of the low-voltage CT output voltage and the magnetic induction intensity of the input excitation current are measured; based on the magnetic induction intensity of the output voltage and the magnetic induction intensity of the input excitation current, the magnetic permeability of the low-voltage current transformer CT core under the power frequency and the heterofrequency current is calculated, and the calculation formula is as follows:

[0147]

[0148] in, is the magnetic permeability of the low voltage current transformer CT core, B is the magnetic induction intensity of the output voltage, and H is the magnetic induction intensity of the input excitation current.

[0149] Among them, the excitation impedance parameters of the low-voltage CT equivalent circuit under the corresponding magnetic permeability of the circuit at different frequencies are calculated, including:

[0150]

[0151] Among them, Z m is the excitation impedance of the low voltage CT equivalent circuit, is the magnetic permeability of the low voltage current transformer CT core, S is the core cross-sectional area, l is the length of the magnetic path inside the core, N1 is the number of turns of the excitation winding, ω is the current frequency, and j is the imaginary unit.

[0152] The excitation current value calculated at each frequency calibration range point includes: a primary side working current value, and the calculation formula of the primary side working current value is as follows:

[0153] I1=I0+I′2

[0154] Among them, I1 is the primary side working current value, I′2 is the secondary side working current value, and I0 is the test current of each frequency.

[0155] The current error values ​​of the range points at each frequency are calculated, including composite error, ratio error and angle error. The calculation formulas of composite error, ratio error and angle error are as follows:

[0156]

[0157] f=A sinθ

[0158] δ=A cosθ

[0159] Among them, Δ is the composite error, f is the ratio difference, δ is the angle difference, I1 is the primary side working current value, I0 is the test current of each frequency, A is the real part value of I0 / I1, and θ is the angle of I0 / I1.

[0160] The application of the present invention is helpful to carry out the calibration error verification of low-voltage CT on-line using the heterofrequency current on a large scale and with high efficiency, and to accurately judge the metering performance of the low-voltage CT during operation.

[0161] Embodiment 3:

[0162] Based on the same inventive concept, the present invention also provides a computer device, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding functions, so as to implement the steps of the method in the above embodiment.

[0163] Embodiment 4:

[0164] Based on the same inventive concept, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It is understandable that the computer-readable storage medium here can include both a built-in storage medium in a computer device and an extended storage medium supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by a processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the method in the above embodiment.

[0165] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The schemes in the embodiments of the present invention may be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0166] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0167] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0168] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0169] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0170] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for compensating for the frequency-different current error of a low-voltage current transformer, characterized in that: include: Measuring the magnetic permeability of the iron core of the low-voltage current transformer CT under power frequency and heterofrequency current, obtaining the power frequency and heterofrequency current magnetic permeabilities of the iron core of the low-voltage CT based on the magnetic permeability of the iron core, and calculating the excitation impedance parameters of the low-voltage CT equivalent circuit under the corresponding magnetic permeabilities of different frequency circuits based on the power frequency and heterofrequency current magnetic permeabilities; The DC resistance of the secondary winding of the low voltage CT is measured, and based on the DC resistance, the excitation current value at each frequency calibration range point is calculated; Based on the excitation current value, the current error value of the range point at each frequency is calculated, and based on the current error value, the out-of-frequency error compensation coefficient of the range point at each frequency is calculated. The out-of-frequency error compensation coefficient is used to compensate for the abnormal current error of the low-voltage CT.

2. The method according to claim 1, characterized in that: The method for measuring the magnetic permeability of the low voltage current transformer CT core under power frequency and heterofrequency current includes: The magnetic induction intensity of the low-voltage CT output voltage and the magnetic induction intensity of the input excitation current are measured; based on the magnetic induction intensity of the output voltage and the magnetic induction intensity of the input excitation current, the magnetic permeability of the low-voltage current transformer CT core under the power frequency and the heterofrequency current is calculated, and the calculation formula is as follows: in, is the magnetic permeability of the low voltage current transformer CT core, B is the magnetic induction intensity of the output voltage, and H is the magnetic induction intensity of the input excitation current.

3. The method according to claim 1, characterized in that The calculation obtains the low-voltage CT equivalent circuit excitation impedance parameters under the corresponding magnetic permeability of the circuit at different frequencies, including: Among them, Z m is the excitation impedance of the low voltage CT equivalent circuit, is the magnetic permeability of the low voltage current transformer CT core, S is the core cross-sectional area, l is the length of the magnetic path inside the core, N1 is the number of turns of the excitation winding, ω is the current frequency, and j is the imaginary unit.

4. The method according to claim 1, characterized in that: The excitation current value at each frequency calibration range point calculated includes: the primary side working current value, and the calculation formula of the primary side working current value is as follows: I1=I0+I2 ′ Among them, I1 is the primary side working current value, I2 ′ is the secondary side working current value, I0 is the test current at each frequency.

5. The method according to claim 1, characterized in that The current error values ​​of the range points at each frequency are calculated, including: composite error, ratio error and angle error. The calculation formulas of the composite error, ratio error and angle error are as follows: f=A sinθ δ=A cosθ Among them, Δ is the composite error, f is the ratio difference, δ is the angle difference, I1 is the primary side working current value, I0 is the test current of each frequency, A is the real part value of I0 / I1, and θ is the angle of I0 / I1.

6. A system for compensating for the frequency-different current error of a low-voltage current transformer, characterized in that: include: The first calculation unit is used to measure the magnetic permeability of the low-voltage current transformer CT core under power frequency and heterofrequency current, obtain the power frequency and heterofrequency current magnetic permeability of the iron core of the low-voltage CT based on the magnetic permeability of the iron core, and calculate the low-voltage CT equivalent circuit excitation impedance parameters under the corresponding magnetic permeabilities of different frequency circuits based on the power frequency and heterofrequency current magnetic permeabilities; The second calculation unit is used to measure the DC resistance of the secondary winding of the low-voltage CT, and calculate the excitation current value at each frequency calibration range point based on the DC resistance; The third calculation unit is used to calculate the current error value of the range point at each frequency based on the excitation current value, calculate the different-frequency error compensation coefficient of the range point at each frequency based on the current error value, and use the different-frequency error compensation coefficient to compensate for the abnormal current error of the low-voltage CT.

7. The system according to claim 6, characterized in that The method for measuring the magnetic permeability of the low voltage current transformer CT core under power frequency and heterofrequency current includes: The magnetic induction intensity of the low-voltage CT output voltage and the magnetic induction intensity of the input excitation current are measured; based on the magnetic induction intensity of the output voltage and the magnetic induction intensity of the input excitation current, the magnetic permeability of the low-voltage current transformer CT core under the power frequency and the heterofrequency current is calculated, and the calculation formula is as follows: in, is the magnetic permeability of the low voltage current transformer CT core, B is the magnetic induction intensity of the output voltage, and H is the magnetic induction intensity of the input excitation current.

8. The system according to claim 6, characterized in that The calculation obtains the low-voltage CT equivalent circuit excitation impedance parameters under the corresponding magnetic permeability of the circuit at different frequencies, including: Among them, Z m is the excitation impedance of the low voltage CT equivalent circuit, is the magnetic permeability of the low voltage current transformer CT core, S is the core cross-sectional area, l is the length of the magnetic path inside the core, N1 is the number of turns of the excitation winding, ω is the current frequency, and j is the imaginary unit.

9. The system according to claim 6, characterized in that The excitation current value at each frequency calibration range point calculated includes: the primary side working current value, and the calculation formula of the primary side working current value is as follows: I1=I0+I′2 Among them, I1 is the primary side working current value, I′2 is the secondary side working current value, and I0 is the test current of each frequency.

10. The system according to claim 6, characterized in that The current error values ​​of the range points at each frequency are calculated, including: composite error, ratio error and angle error. The calculation formulas of the composite error, ratio error and angle error are as follows: f=A sinθ δ=A cos θ Among them, Δ is the composite error, f is the ratio difference, δ is the angle difference, I1 is the primary side working current value, I0 is the test current of each frequency, A is the real part value of I0 / I1, and θ is the angle of I0 / I1.

11. A computer device, characterized in that: include: one or more processors; a processor for executing one or more programs; When the one or more programs are executed by the one or more processors, the method according to any one of claims 1 to 5 is implemented.

12. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed, the method according to any one of claims 1 to 5 is implemented.

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