Research On Distribution Network Fault Diagnosis Method Considering Electrical Quantity And Timing Information

Due to natural disasters,complicated load equipment,man-made operations and other reasons,resulting in an increasingly frequent fault in power grid,especially the distribution network.Therefore,how to detect and restore the fault quickly and accurately has become the focus of many scholars in modern power system.Generally,traditional fault diagnosis methods only consider the operation information of relay protection and circuit breaker to diagnose faults,and neglect the information of electrical quantities and timing information in power system.However,if there is malfunction in relay protection and circuit breaker,using switch information only cannot achieve distribution network fault diagnosis accurately,meanwhile it's easy to field dispatchers work to bring a certain degree of risk.In addition,in the real power generation process,the electrical quantities information and the timing information contain a large number of fault information,an effective use of these information will make the fault diagnosis results much more accurate and rapid,thus seeking a method that combined with a variety of information for fault diagnosis in distribution network is very necessary.As an effective fault diagnosis method,Petri net method has been widely used in fault diagnosis.It is mainly based on fault analysis and reasoning of relay protection and circuit breaker action information.Many experts and scholars have applied fuzzy and probabilistic methods to fault diagnosis.However,there are still some problems,such as the lack of a common analytical model,and the lack of analysis accuracy when malfunction appears.Therefore,this thesis makes full use of the information of electrical quantities and time series in the distribution network,and realizes the accurate fault diagnosis of the distribution network by combining with the physical characteristics of the Petri net method.The main work of this thesis is as follows:(1)The information that can be obtained when the power grid breaks down is divided according to its importance,and then the priority of the information is uploaded to the dispatching center and sub-station,and according to the fault features of the grid element and information accuracy of protection and circuit breaker,it analyzes and clearly confirms reasons of switch action when component failure and failure occurs.The causes of inaccurate operation of the relay protection device and the circuit breaker are analyzed,and the blind spot problem in the process of fault diagnosis is analyzed.(2)Through the improved input information of Petri net,the control relationship between the input fault information is tighter,and the judgment result reasoning process of Petri net is improved after combined the information of timing and electrical quantities.In Petri net,the main fault information for the initial judgments may be mistaken,refused to move the case,this time need to combine continuous electrical information,through the sub-case processing to make the results more convincing.(3)Through the establishment of the fault hypothesis,this thesis judges the fault situation,and through solving the objective function to determine the credibility of the hypothesis.In the process of solving the objective function,the problem of refusal,malfunction,information loss,information distortion and timing conflict is fully considered,and the penalty function is added to solve the problem of electrical quantities.This analysis method can effectively combine various electrical quantities information,making the diagnosis of failure to draw a more comprehensive and authoritative.