Research On The Advanced Applications In Fault Information Management System Of Power Systems

With the rapid development of computer and communication technology,the academicand the engineering community began the exploration on fault information managementsystem of power systems(FIMS).In recent years,the number of trial systems is on agradual rise.The function of FIMS lies in the advanced applications based on data acquiredfrom the secondary equipments in power systems.However,the main role of FIMS now isserving raw data for dispatchers to analyze faults in power systems.There are not enoughadvanced applications to raise the value of the system,which prevents the system fromfurther development.Thus,this paper makes a detailed study on the advanced applicationsof FIMS,such as fault section estimation in power systems,fault location in distributionnetworks,analysis on the operational characteristics of protections,as well as the reliabilityanalysis of protections.Currently,the construction of FIMS is still in the process of exploration and therelevant concepts are vague.According to the theoretical studies,the operationalexperiences and the related standards,this paper makes a discussion on the concepts indetails.First the definition of FIMS is given,and it is followed by the analysis of some keytechnical problems for its further advancement.A gradual-optimization based approach for fault section estimation in power systemsunder aberrant information is proposed.First,methods to search for outage areas under bothaccurate and aberrant alarm of breaker-position change are presented respectively.For thetraditional optimization-based methods,the diagnostic methods based on similarityprinciple may omit some faulty sections whereas the parsimonious covering principle basedmethods may regard normal sections as faulty ones.To improve the correctness of thediagnostic methods,a gradual-optimization based diagnostic method is proposed,whichcombines the features of the above two types of methods.Case studies show that themethod proposed can quickly locate the correct multiple faulty sections in theabove-mentioned scenarios,and can make an evaluation of protection operations by simplecalculation of some state vectors.Furthermore,a new diagnostic method grounded on elementary net theory is presented.First,the maximum likelihood decoding theory is adopted to correct the aberrated alarm.Toovercome the drawbacks of traditional models based on Petri nets,a new diagnostic modelbased on the elementary net is built.Then correct alarms are fed into the new model tocarry out the diagnosis process.Logical analysis and case studies show that the model built can accurately simulate the practical fault clearing process,and can make a quick andaccurate estimation of the faulty sections,misoperated protections and breakers as well asthe aberrant alarm.To locate the faults in complex multi-source distribution networks,a new methodbased on over-heated area searching is proposed.By defining the load on the vertices withmultiple branches and locating the minimum distribution area in the over-heated arcmethod,the method can be easily used in the multi-source distribution networks withspecial switches.Then,measures are given for its use under aberrant alarms.Based on thenew method,a concise unified criterion for fault location in complex multi-sourcedistribution networks for its simple version,matrix algorithm,is proposed,followed by themeasures when alarms become aberrant.Borrowing methods to analyze operational characteristics of AC protections,those ofvalve short-circuit protections and unbalance protections for high-voltage(HV)capacitorsin high voltage direct current(HVDC)transmission systems are studied.There are somedifferences between the two types of valve short-circuit protections which are commonlyadopted in HVDC systems.By analyzing the variational rules of the relational currents ofthe protections,the performances of the two operational equations are compared.Then,oneof them is revised so that it can locate the faulty bridge.To coordinate the contradictionrequirements of selectivity and sensitivity in protection settings,a setting function isproposed according to the analysis of existent setting functions.High voltage capacitors inHVDC projects are H-connected or branch-connected.The ratio of the unbalance current tothe filter current and the over voltage are calculated during the evolution of the inner faultboth in a single capacitor branch and in multiple capacitor branches.Based on the study,operational characteristics of HV capacitor unbalance protections are studied.Finally,take the valve short-circuit protection in HVDC projects as an example,reliability of the whole protection system under different redundant configurations isanalyzed with Goal Oriented methodology.Some rules on HVDC protections are obtainedby observing the waveforms which depict the rate of unwanted trip and the rate of failure totrip of the whole protection system changes with those of the protection equipments and themeasurement equipments,respectively.