Research On Transient Signal Feature Extraction Of Medium Voltage Overhead Distribution Network

With the increase of electricity demand and the development of electricity market reform,the requirement of power quality and power supply reliability from consumers becomes higher and higher.However,the probability of distribution line failure is very high,especially for the medium voltage overhead lines.In China,the medium voltage distribution network widely uses small current grounding system,which continues to work for 1-2 hours after the single-phase grounding fault to improve the reliability of electricity supply.However,when the single-phase grounding fault occurs,the non fault relative voltage rises and the system insulation is still under threat.Hence the fault must be found and eliminated as soon as possible.When the small single-phase grounding fault occurs,the small fault current,the complex distribution network structure and varied operation mode influences the fault judgment accuracy.The existing fault detection,line selection and location methods mainly use theoretical analysis,model establishment and simulation to make judgement.Especially for the fault location methods,most of the theory,the application results of most theory,algorithm and model are not satisfactory.The existing fault location methods lack the necessary fault waveform data to meet the current distribution automation requirements.To solve the fault diagnosis and location problem in medium voltage distribution network,this dissertation investigates the research and application status and focuses on the following aspects:1)This dissertation designs a feature exaction algorithm based on wavelet entropy,and evaluates it on the simulation and field data.2)This dissertation develops a feature gene library based on the feature exaction algorithm,whicn is used to represent different running and fault states and improve the accuracy of fault location.The field data experiment shows that the feature exaction algorithm and the feature gene library effectively identy the three-phase short-circuit fault,two-phase short-circuit fault,single-phase grounding fault and abnormal operation fault.The application data provided by Power Grid Corp shows that the feature extraction algorithm and the feature gene library have good economic and social benefits.