Study On Spatial-temporal Characteristic And Flow Transfer Identification Of 500kV Transmission Line Fault

With the enlarging scale of power system and regional interconnection,probability of system chain-fault continuously increases,which severely affects system’s safe and stable operation.Therefore,it is of theory value and application significance to perceive the distribution characteristic of system faults and reveal the causes of system chain-fault.This paper has carried out researches through the following aspects:Firstly,through theory research it is found that system faults show long-term correlation on the level of time series and power-law distribution characteristic on the level of space.Statistical analysis on actual faults of 500 kV transmission lines in H province from 2008 to 2012 is carried out,and it was proved that transmission line faults show power-law distribution.Hurst exponent is calculated via R/S model,and the obtained Hurst exponent is over 0.5.Significance testing is proceeded for the calculated Hurst exponent and the result is prominent,which indicates faults of 500 kV transmission lines in H province show long-term correlation on the level of time series.With every transmission line in the network as classification gist,times of transmission line faults are quantified into each transmission line.Analysis obtains that fault line and its occurrences show power-law distribution.Secondly,based on DC power flow model and topological structure of power system,load rate model of transmission line is proposed.Load rate of every transmission line under circumstance when neighbor line breaks is calculated,and the calculated load rate is compared with the presupposed heavy load threshold.The more load rate is close to the heavy load threshold,the more pivotal the corresponding breaking line is.And this is employed to judge the critical line in the power system.Because operation status and topological structure are together taken into consideration,the proposed model can identify the critical line and search the vulnerable point in power system.Finally,the two common methods to identify power flow transferring – line current estimation based on the method of compensation with add-on current source and line power flow estimation based on the method of branch outage distribution factor– are thoroughly researched.Through derivation and collating about the flow transfer factors obtained by the two methods,it is found that,with line resistance neglected,flow transfer factor formulas acquired by the two methods are the same.By simulation calculation of power flow transfer,estimation errors of the two methods are analyzed,and enhancement to improve judgment reliability is presented.In summary,this paper researches spatial-temporal characteristic of 500 kV transmission line faults in H province through analyzing the fault data,and recognizes the critical line of 500 kV transmission network by the transmission line load rate model.Power flow transferring is identified with the critical line breaking.The research is of significant meaning in monitoring and management of vulnerable part in power system,and maintaining system security.