There is no limit to creativity, and the instrument is invented. Today, we introduce a national invention patent for invention - a method for preventing external electromagnetic field interference based on finite element simulation analysis. The patent was filed by the State Grid Corporation and was issued an authorization announcement on March 29, 2017.
Description
The invention relates to computer-aided engineering analysis, and more particularly to an influence of a simulated interfering electromagnetic field (power frequency magnetic field, DC magnetic field) on a voltage meter internal current transformer, a current transformer and a transformer power source in a finite element software, On this basis, some anti-stealing measures for smart meters are obtained.
Background of the invention
Computer Aided Design (CAE) is widely used in engineering for assisted design and analysis. CAE analysis, especially finite element analysis (FEA), is widely used in structural, thermodynamic and electromagnetic analysis. Finite element analysis solves the problem by finding the approximate solution of partial differential equations. With the rapid development of computer technology, finite element analysis Get more and more applications. The finite element analysis of the electromagnetic field is based on Maxwell's equations, using simple and interacting elements, ie, units, to approximate an infinitely unknown real system with a finite number of unknowns, primarily to calculate magnetic or flux, other concerns. The physical quantities can be derived from these degrees of freedom. Depending on the cell type and cell options, the finite element calculations can be used to make scalar magnetic bits, vector magnetic bits, or edge fluxes.
The inside of the smart meter is mainly composed of hardware circuit and voltage transformer, current transformer and transformer. Among them, the voltage transformer is used to convert the large voltage into a small voltage for measurement, and the current transformer converts the large current into a A small current for measurement, and finally the voltage and current are sent to the metering chip for operation to measure the electrical energy. The transformer is mainly used as a power source to supply power to the entire smart meter. When the transformer, voltage transformer and current transformer are interfered by the external electromagnetic field (power frequency magnetic field, DC magnetic field), the interference electromagnetic field will affect the distribution of the original magnetic field, the power frequency electromagnetic field will be superimposed with the original magnetic field, and the transformer, voltage transformer and The output of the current transformer; the DC magnetic field causes an offset in the original magnetic field, which is manifested by distortion of the output voltage and current, and the waveform is no longer symmetrical. Smart meters are extremely susceptible to interference from external electromagnetic fields, so lawless elements often use the role of electromagnetic fields to achieve the purpose of stealing electricity. In the prior art, a smart meter generally determines whether it is in a power stealing state by detecting current, voltage, and intersection. When it is judged to be a power stealing state, a specific rule is used for measurement, and only when a power stealing occurs, a specific measurement rule is adopted. Metering is performed, but the occurrence of power stealing behavior cannot be prevented, that is, the power meter cannot be prevented from entering the power stealing state.
Summary of the invention
The invention performs three-dimensional electromagnetic field analysis based on finite element analysis, and analyzes the influence of different forms of electromagnetic fields (power frequency magnetic field, DC magnetic field, etc.) on the key components (voltage transformers, current transformers and transformers) inside the smart meter. On the analysis of the smart meter in the production process should ensure how much safety distance (internal power supply, voltage transformer and current transformer and other important components and the distance of the smart meter case) can effectively reduce the impact of external electromagnetic field on smart meter measurement To prevent the meter from measuring errors and entering the state of stealing electricity.
Figure is a flow chart of the method for preventing external electromagnetic field interference of smart meter based on finite element simulation analysis The technical scheme of the present invention is as follows: a method for preventing external electromagnetic field interference of a smart meter based on finite element simulation analysis, comprising the following steps: S01, parameter determination of an electric meter simulation model, establishing a meter simulation model: combining an actual smart meter internal voltage transformer, a current transformer and the size of the transformer, core simulation model to determine meter parameters, parameters of transformer coil, the coil parameters of the voltage transformer and current transformer coil parameters, based on finite element analysis simulation model established meter; i.e., the meter software to establish the simulation model by finite element analysis, the meter During the establishment of the simulation model, it is necessary to monitor whether the voltage and current of the output of the voltage transformer, current transformer and transformer in the meter simulation model are proportional to the number of turns of the coil. If it is not proportional, the model needs to be modified and adjusted until the output voltage Whether the current is proportional to the number of turns of the coil; S02: calculating the voltage transformer, current transformer and transformer output without external electromagnetic interference: calculating the voltage mutual inductance of the electric meter simulation model in step S01 by harmonic analysis in the finite element analysis Current
S03, calculating a voltage transformer, a current transformer and a transformer output when there is a power frequency magnetic field interference: adding a simulated electromagnet (for providing an interference magnetic field) on a coil side of the electric meter simulation model, and changing the electromagnet coil Simultaneously calculate the magnitude, direction and frequency of the excitation voltage, calculate the output of the voltage transformer, current transformer and transformer of the electric meter simulation model, and obtain the output data of the voltage transformer, current transformer and transformer under the condition of external power frequency magnetic field with different strengths. Obtaining a function relationship between the power frequency magnetic field and the output of the voltage transformer, the current transformer and the transformer through the mathematical software; S04, analyzing the change of the distance between the electromagnet and the electric energy meter to the voltage transformer, the current transformer and the transformer output The effect: change the distance between the electromagnet and the voltage transformer, current transformer and transformer, record the voltage transformer, current transformer and transformer output data when the distance changes, and obtain the distance when the voltage on the electromagnet remains unchanged. Changes, electromagnets to voltage transformers, current transformers and transformer output data
S05, analyze the influence of DC magnetic field on transformer power supply: electromagnet plus DC voltage, in order to visually observe the output voltage waveform of transformer, use transient method to simulate DC magnetic field, change DC field strength by changing DC voltage value, record different DC Under the condition of magnetic field strength, the output data of voltage transformer and current transformer obtains the relationship function between DC field strength and voltage transformer and current transformer output; S06, analyzes the shielding effect of different magnetic materials on interference electromagnetic field: A magnetic conductive plate is added between the electromagnet and the electric meter simulation model, and the magnetic conductive plate is used for electromagnetic shielding, and the output data of the voltage transformer and the current transformer of the electric meter simulation model are recorded under different magnetic permeability materials, and different guides are obtained. The shielding effect of magnetic materials on interfering electromagnetic fields.
S07, in conjunction with the electromagnet actual experience stealing used, according to step S03, S04, S05 respectively acquired frequency magnetic field, the electromagnet and the voltage transformer, the current transformer and from the transformer, a DC magnetic field of the voltage transformer, different magnetically permeable material corresponding relation of the current transformer and the output data transformer, combined with step S06 to obtain the electromagnetic interference shielding effect, acquired at different shield of magnetically permeable material, the smart meter internal power supply, voltage transformer, current transformers and transformer and a safe distance from the case of smart meters.
Advantageous effects of the technical solution of the present invention comprises: (1), three-dimensional electromagnetic field analysis based on finite element analysis, a comprehensive analysis of the current transformer and the electromagnetic fields of different forms and different intensities of electromagnetic fields on internal smart metering voltage transformer, the transformer, acquired at different shields of magnetically permeable material, the smart meter internal power supply, voltage transformers, current transformers, and the safety transformer case smart meter distance, to prevent the influence of external electromagnetic energy meter, to prevent the occurrence of stealing power meter . (2) The field path coupling method is used to analyze the electromagnetic field, and the coil is applied with excitation through the circuit. (3) Optimize the model of the voltage transformer (current transformer and transformer), and place the primary coil and the secondary coil on the same side of the iron core to reduce the influence of magnetic flux leakage. (4) Harmonic analysis and transient analysis are used respectively to simulate. The calculation time of harmonic analysis is short, and the data of calculation result is small, but the change of voltage and magnetic field in the whole cycle cannot be observed. Transient analysis On the contrary, the transient analysis requires a lot of calculations and therefore a long calculation time and a large amount of data, but the transient analysis can observe the changes of voltage and magnetic field in the whole cycle in the calculation result, which is very intuitive. (5) Add different materials between the voltage transformer (current transformer and transformer) and the electromagnet to analyze the shielding effect of different materials on the external electromagnetic field interference. (6) The research results of the present invention can guide the optimization design of the smart meter. The internal voltage transformer, current transformer and transformer of the smart meter should be placed in the inner center of the meter and the meter case should be above a certain safe distance to reduce Magnetic field interference, to prevent electricity theft, can also be coated with a layer of magnetically permeable material on important components and smart meter case to isolate the interference of external electromagnetic fields.
Description
The invention relates to computer-aided engineering analysis, and more particularly to an influence of a simulated interfering electromagnetic field (power frequency magnetic field, DC magnetic field) on a voltage meter internal current transformer, a current transformer and a transformer power source in a finite element software, On this basis, some anti-stealing measures for smart meters are obtained.
Background of the invention
Computer Aided Design (CAE) is widely used in engineering for assisted design and analysis. CAE analysis, especially finite element analysis (FEA), is widely used in structural, thermodynamic and electromagnetic analysis. Finite element analysis solves the problem by finding the approximate solution of partial differential equations. With the rapid development of computer technology, finite element analysis Get more and more applications. The finite element analysis of the electromagnetic field is based on Maxwell's equations, using simple and interacting elements, ie, units, to approximate an infinitely unknown real system with a finite number of unknowns, primarily to calculate magnetic or flux, other concerns. The physical quantities can be derived from these degrees of freedom. Depending on the cell type and cell options, the finite element calculations can be used to make scalar magnetic bits, vector magnetic bits, or edge fluxes.
The inside of the smart meter is mainly composed of hardware circuit and voltage transformer, current transformer and transformer. Among them, the voltage transformer is used to convert the large voltage into a small voltage for measurement, and the current transformer converts the large current into a A small current for measurement, and finally the voltage and current are sent to the metering chip for operation to measure the electrical energy. The transformer is mainly used as a power source to supply power to the entire smart meter. When the transformer, voltage transformer and current transformer are interfered by the external electromagnetic field (power frequency magnetic field, DC magnetic field), the interference electromagnetic field will affect the distribution of the original magnetic field, the power frequency electromagnetic field will be superimposed with the original magnetic field, and the transformer, voltage transformer and The output of the current transformer; the DC magnetic field causes an offset in the original magnetic field, which is manifested by distortion of the output voltage and current, and the waveform is no longer symmetrical. Smart meters are extremely susceptible to interference from external electromagnetic fields, so lawless elements often use the role of electromagnetic fields to achieve the purpose of stealing electricity. In the prior art, a smart meter generally determines whether it is in a power stealing state by detecting current, voltage, and intersection. When it is judged to be a power stealing state, a specific rule is used for measurement, and only when a power stealing occurs, a specific measurement rule is adopted. Metering is performed, but the occurrence of power stealing behavior cannot be prevented, that is, the power meter cannot be prevented from entering the power stealing state.
Summary of the invention
The invention performs three-dimensional electromagnetic field analysis based on finite element analysis, and analyzes the influence of different forms of electromagnetic fields (power frequency magnetic field, DC magnetic field, etc.) on the key components (voltage transformers, current transformers and transformers) inside the smart meter. On the analysis of the smart meter in the production process should ensure how much safety distance (internal power supply, voltage transformer and current transformer and other important components and the distance of the smart meter case) can effectively reduce the impact of external electromagnetic field on smart meter measurement To prevent the meter from measuring errors and entering the state of stealing electricity.
Figure is a flow chart of the method for preventing external electromagnetic field interference of smart meter based on finite element simulation analysis
S03, calculating a voltage transformer, a current transformer and a transformer output when there is a power frequency magnetic field interference: adding a simulated electromagnet (for providing an interference magnetic field) on a coil side of the electric meter simulation model, and changing the electromagnet coil Simultaneously calculate the magnitude, direction and frequency of the excitation voltage, calculate the output of the voltage transformer, current transformer and transformer of the electric meter simulation model, and obtain the output data of the voltage transformer, current transformer and transformer under the condition of external power frequency magnetic field with different strengths. Obtaining a function relationship between the power frequency magnetic field and the output of the voltage transformer, the current transformer and the transformer through the mathematical software; S04, analyzing the change of the distance between the electromagnet and the electric energy meter to the voltage transformer, the current transformer and the transformer output The effect: change the distance between the electromagnet and the voltage transformer, current transformer and transformer, record the voltage transformer, current transformer and transformer output data when the distance changes, and obtain the distance when the voltage on the electromagnet remains unchanged. Changes, electromagnets to voltage transformers, current transformers and transformer output data
S05, analyze the influence of DC magnetic field on transformer power supply: electromagnet plus DC voltage, in order to visually observe the output voltage waveform of transformer, use transient method to simulate DC magnetic field, change DC field strength by changing DC voltage value, record different DC Under the condition of magnetic field strength, the output data of voltage transformer and current transformer obtains the relationship function between DC field strength and voltage transformer and current transformer output; S06, analyzes the shielding effect of different magnetic materials on interference electromagnetic field: A magnetic conductive plate is added between the electromagnet and the electric meter simulation model, and the magnetic conductive plate is used for electromagnetic shielding, and the output data of the voltage transformer and the current transformer of the electric meter simulation model are recorded under different magnetic permeability materials, and different guides are obtained. The shielding effect of magnetic materials on interfering electromagnetic fields.
S07, in conjunction with the electromagnet actual experience stealing used, according to step S03, S04, S05 respectively acquired frequency magnetic field, the electromagnet and the voltage transformer, the current transformer and from the transformer, a DC magnetic field of the voltage transformer, different magnetically permeable material corresponding relation of the current transformer and the output data transformer, combined with step S06 to obtain the electromagnetic interference shielding effect, acquired at different shield of magnetically permeable material, the smart meter internal power supply, voltage transformer, current transformers and transformer and a safe distance from the case of smart meters.
Advantageous effects of the technical solution of the present invention comprises: (1), three-dimensional electromagnetic field analysis based on finite element analysis, a comprehensive analysis of the current transformer and the electromagnetic fields of different forms and different intensities of electromagnetic fields on internal smart metering voltage transformer, the transformer, acquired at different shields of magnetically permeable material, the smart meter internal power supply, voltage transformers, current transformers, and the safety transformer case smart meter distance, to prevent the influence of external electromagnetic energy meter, to prevent the occurrence of stealing power meter . (2) The field path coupling method is used to analyze the electromagnetic field, and the coil is applied with excitation through the circuit. (3) Optimize the model of the voltage transformer (current transformer and transformer), and place the primary coil and the secondary coil on the same side of the iron core to reduce the influence of magnetic flux leakage. (4) Harmonic analysis and transient analysis are used respectively to simulate. The calculation time of harmonic analysis is short, and the data of calculation result is small, but the change of voltage and magnetic field in the whole cycle cannot be observed. Transient analysis On the contrary, the transient analysis requires a lot of calculations and therefore a long calculation time and a large amount of data, but the transient analysis can observe the changes of voltage and magnetic field in the whole cycle in the calculation result, which is very intuitive. (5) Add different materials between the voltage transformer (current transformer and transformer) and the electromagnet to analyze the shielding effect of different materials on the external electromagnetic field interference. (6) The research results of the present invention can guide the optimization design of the smart meter. The internal voltage transformer, current transformer and transformer of the smart meter should be placed in the inner center of the meter and the meter case should be above a certain safe distance to reduce Magnetic field interference, to prevent electricity theft, can also be coated with a layer of magnetically permeable material on important components and smart meter case to isolate the interference of external electromagnetic fields.
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