| Under the background of the State Grid Corporation of China's efforts to promote the construction of a strong smart grid,electronic transformers have the advantages of simple insulation structure,large dynamic range,small size,light weight,and the ability to output signals directly into microcomputerized metering and protection equipment interfaces.It is widely used in smart substations.Electronic transformer as an electrical measuring device,the main characteristics of the demand for two points: First,the accuracy of the measurement;Second,the stability of the operation.At present,the technology and theory of the air-core coil are relatively complete,and the digital quantity also becomes the technical characteristic of the smart grid.Therefore,the accuracy of the digital integrator is a key link in the overall accuracy of the transformer.With the continuous improvement of the voltage level of substations,the electromagnetic environment of substations has become increasingly complex,and the isolation switch has been opened and closed,lightning strikes,and equipment operation and faults have caused a series of electromagnetic interference problems in the actual operation of electronic transformers.Therefore,this article has conducted in-depth research on these two core characteristics of electronic transformers.The main research content is as follows:1.The digital integral principle of electronic current transformer is introduced and analyzed in detail,which provides a theoretical basis for the improvement of the proposed algorithm.In view of the electromagnetic interference problem existing in the operation process of electronic current transformers,combined with its working principle and structural characteristics,it conducts research from the electromagnetic interference mechanism and proposes feasible anti-jamming measures.2.An improved high-precision digital integration algorithm based on variable step length principle is proposed.According to the principle of variable step length quadrature algorithm,in the integration process,each time the integration is integrated,the integration step is based on the last integration.In half processing,the integral formula is used repeatedly until the absolute value of the adjacent two integration results is less than the allowable error,and the integration is stopped.In this way,an improved algorithm with high accuracy and low computational complexity is proposed.The simulation experiment and field operation prove that under the conditions of noise,harmonics,and other conditions,the algorithm has good characteristics,compared to some improved transfer functions.Better frequency characteristics.3.Set up the isolation switch to open and combine capacitive low-current test,and carry out modeling in the ATP-EMTP according to the test results.The results after modeling and simulation are compared with the test results to see whether it meets the actual conditions of the project site operation.On this basis,the air-core coil is modeled,the parameters of the air-core coil are calculated,and the air-core coil is replaced by an equivalent circuit.Then the output of the isolation switch is used as an excitation to analyze the inductive output of the air-core coil under the opening and closing of the isolating switch.Finally,the influence of the inductive output on the subsequent acquisition unit is analyzed.4.Propose anti-jamming measures and optimization,add RC passive filter circuit in the interference circuit,add to low-pass filter circuit can effectively reduce the amplitude of the high-frequency inductive output of the air-core coil,but with the increase of the upper cut-off frequency of the RC filter circuit Large,the effect of filtering high frequencies also deteriorates.Therefore,it is proposed to add a TVS tube in the circuit to clamp the transient overvoltage,but the simulation results still cannot achieve the desired results.Finally,a combination of RC filtering and TVS tube was used to achieve the desired results. |
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