Analysis Of Frequency Characteristics Of Analog Photoelectric Current Transformer

Power transformers,as a key link connecting primary and secondary equipment in the power network,are widely used in power systems,and their transmission and transformation performance has an important impact on the stable and safe operation of power systems.With the continuous development of the power grid,the voltage level and capacity of the power grid continue to increase,and electromagnetic current transformers have been difficult to meet the needs of the new generation of power system automation and digital development.The digital electronic transformer is subject to the sampling rate,and its cut-off frequency is not high,so it cannot adapt to the measurement of high-frequency signals.Analog photoelectric current transformers have the unique advantages of large dynamic range,frequency bandwidth,strong anti-interference ability,and no time synchronization by converting the measured analog electrical signals into analog optical signals for transmission.Due to the lack of systematic research on the frequency characteristics of analog photoelectric current transformers,its broadband advantages have not been fully demonstrated.Therefore,it is of great theoretical significance and practical application value to establish a model for simulating a photoelectric current transformer,and to conduct frequency characteristic analysis and application research on it.Based on the simulation of the composition and realization principle of the photoelectric current transformer,the sensor head and the optical transmission system are modeled separately,and the transfer function of the corresponding unit is derived.Through the simulation circuit model,it is found that the cut-off frequency band of the simulated photoelectric current transformer can reach 1MHz,and it has a rise response time of less than 1?s even for the 1MHz high-frequency traveling wave signal.The transformer has good steady-state and transient signals.Transmittance characteristics,especially in the transmission of high-frequency signals,compared with digital photoelectric current transformers have unique advantages.In order to verify the accuracy of modeling and simulation,a prototype of a simulated photoelectric current transformer was trial-produced,and the steady state signal and transient signal transmission of the prototype were tested separately.Through the analysis of the measured data,it is shown that the analog photoelectric current transformer has a bandwidth of 1MHz,and the amplitude error and phase angle error meet the requirements of the electronic transformer,especially in the high-frequency signal measurement,which proves the accuracy of the modeling.Finally,the transformer is used in the fault line selection of small current single phase to earth fault.According to the measured signal of the transformer,the line selection shows high accuracy,which proves the engineering application value of this type of transformer.