| The capacitor voltage transformer (CVT) is widely applied in power systems of 110kV or more. It can be used for the measurement of voltage relay protection. Its capacitor divider can replace the coupling capacitor for carrier communication of the power transmission line, and it can be used for the transmission thoroughfare of the signal for high frequency of relay protection as well. Proper design and tuning of CVT components guarantee that its output is the required replica of the input (system voltage) under steady-state conditions. Due to the circuit inherent characteristics of CVT, its transients response is poor. The problem of CVT transient characteristic and solution are studied. This thesis researches and achievements are stated in following paragraph.(1) This paper established the transient equivalent circuit of CVT. Illustrate that the initial capacitor voltage values influence the model of CVT in theory.(2) Through the application of Power System Block-Set and Simulink based on MATLAB software, to achieve digital calculation and simulation of the CVT transient process. Lastly the experiments were performed with a sample CVT, and validate the model furthermore.(3) Presents the use of MATLAB neural network toolboxes to correct capacitor voltage transformer secondary waveform distortions. Performance studies results that the propose method is accurate. Presents the method can be incorporated within the digital protective relaying algorithm.(4) Using the CVT transient models, Through the application of Powerlib we can conveniently change different parameters and study the initial capacitor voltage values, damper resistence influence the ferroresonances process, by which we are able to determine the conditions for the occurrence of the most serious ferroresonances. Supply a relative credibility and accuracy system simulation model for the futurity design and study of CVT. |
PDF Full Text Request