Typical Characteristic Quantity Analysis And Propagation Characteristics Study Of Voltage Sag

As a large number of sensitive load puts into use,the effect of voltage sag problems is more and more serious and noticed by the people.This thesis focuses on the study of typical characteristics and propagation characteristics of voltage sag.In the study of typical characteristics,this thesis analyzes two aspects of the cause of voltage sag and actual data:(1)In this thesis,the various causes of voltage sag are summarized into two categories: short circuit fault and impact load.Detailed mechanism analysis is carried out,and the short circuit fault with the highest probability of occurrence is simulated.The simulation results verify the correctness of the theoretical analysis and reflect the difference of voltage sag caused by different short circuit faults.(2)The voltage sag events of a large city in Henan are comprehensively analyzed from three angles: voltage waveform,typical feature quantity and different voltage levels based on the actual data of all events in 2018.And the severity of voltage sag is analyzed by using four evaluation indicators.Finally,the relevant conclusions are given about the characteristics and laws of the voltage sag events.In the study of propagation characteristics,this thesis analyzes two aspects.On the one hand,voltage sag is transmitted by transformer;On the other hand,voltage sag is transmitted by line.(1)The simulation model with different types of transformers is built by MATLAB/Simulink.By setting different short circuit faults to simulate the voltage sag on the primary side of the transformer,changes of the valtage RMS and phase of the transformer’s primary and secondary sides are compared to obtain the characteristics of voltage sag passing through transformers(2)Two kinds of simulation models of radiation network and dual power supply network under the same voltage level are built by MATLAB/Simulink.This thesis sets the short circuit fault to analog generation process of voltage sag.Changes of voltage are compared to obtain the characteristic of voltage sag passing through the line.