Research On High-precision Measurement And Modeling Of High Voltage Electric Transformers

Protective high voltage electrical current transformers (CT) play an important role in the field of power system's protection. The air gap current transformer, especially TPY current transformer which has transient protection features is more and more widely used. However, the traditional measurement of TPY current transformer often requires high voltage and high current environment, which brings complexity and noise interference of the measurement. Therefore, the achievement of rapid and effective measurement of TPY current transformer has a significant meaning to the production and improvement of current transformers. To solve these problems, this thesis did the work as follow:(1) This thesis discussed the intelligent testing technology, about its characteristics, development and key technologies. According to the requirement of testing the transient performance of TPY-level electrical current transformers, and combined with the intelligent testing technology, this thesis introduced the design method of the automatic test system for testing the TPY-level electrical current transformer. Additionally, according to the transformer transient saturation characteristics, the thesis analyzed the advantages and disadvantages of the commonly used testing methods and designed a simple method to improve the testing of the current transformers, and then this thesis introduced the design process of the system, mainly in terms of hardware and software. In order to improve the reliability of the test system, this thesis added the maintainability of the instruments to the system, and added a remote diagnostic system to help the operation of the system.(2) Under the factory environment, due to the the zero drift of the Hall sensor and noise, there exists the problem that the flux measurement is inaccurate during the transient testing process of the TPY-level electrical current transformers. By analyzing the internal flux relationship of TPY-level current transformer during the internal excitation process, and according to the TPY-level current transformer excitation characteristics, through applying Kalman filter for data integration, this thesis presented an multi-phased measurement method to eliminate the influnce of the measurement error on the precision of the measurement results. After Kalman filter process, the problem of error accumulation caused by sensor's zero drift errors were eliminated, and the curves from the test were more accurate and smooth.(3) Finally, this thesis studied how to build the simulation models and current transformer excitation curve. According to the excitation curve and transformer parameters gotten from the test, least squares support vector machine was used to build the model, and made some improvement for the traditional simulation model, as a result, more accurate mathematical expressions were generated to describe the transformer characteristics.