Research On Fault Diagnosis Of Fast Line Selection And Location Algorithms In Intelligent Distribution Network

Realizing distribution automation is the requirement of smart grid development.Distribution feeder automation is an important part of distribution automation system.Its operation directly affects the implementation effect of distribution automation system.Improving the operation level of feeder automation is of great significance for improving the reliability of power supply and ensuring the safe and economic operation of distribution network.Starting from the concept of distribution automation,this paper introduces and expounds the concept,significance and main functions of feeder automation,introduces the main problems faced by feeder automation in distribution network,and expounds the necessity and urgency of realizing feeder automation in smart grid construction.On this basis,the key technical issues such as feeder automation mode,feeder fault line selection method and the influence of distributed generation on feeder automation are studied emphatically.The steady-state and transient characteristics of feeder single-phase grounding fault in small current grounding system are analyzed.A zero-sequence current difference wavelet energy method for feeder grounding fault line selection is proposed.This method calculates the difference of zero-sequence current between feeders by two or two ways.Using the frequency-division characteristic of wavelet transform,the difference of zero-sequence current between the first half cycle of fault and the last 1.5 cycle of fault is decomposed by wavelet transform,and the wavelet energy of the coefficients of each layer in the main fault frequency band is obtained.Then,the wavelet decomposition layer with the most concentrated energy is selected and the transient zero-sequence current difference energy of each feeder occupies all feeders is utilized.The simulation results show that the algorithm can automatically adapt to the operation mode of the system,and is not affected by grounding resistance,fault distance and fault closing angle.It has high sensitivity and reliability.The hardware and software systems of the line selection device are designed.The new line selection device has been applied in more than one substation.The switchoperation of dispatching personnel and substation operators is convenient when the system is single-phase grounded,shortening the time of troubleshooting and reducing the accident risk caused by operation.The requirements of distribution automation construction for primary grid structure,main station and sub-station system,distribution terminal and other aspects are analyzed.Based on the distribution automation system,the principle of fault identification and location in distribution network is studied,and the corresponding algorithm is given.The algorithm can identify fault points quickly and effectively.The relay protection hierarchical cooperation scheme for fault isolation in distribution network is studied.For overhead lines and cable lines,the scheme of fault isolation by relay protection and distribution automation system is proposed respectively.The scheme of distribution network automation in the power supply company is discussed.The feasibility of the fault identification,location and isolation scheme of distribution network under the framework is demonstrated through a case study.