Study Of Fault Diagnosis In Uncertain Power System On Information Fusion

Along with the development of society,our nation had been set up strategic objectives of "national grid,power transmission from west to East, North South mutual supply".Electric power users have been increasingly strict on electric power reliability,but the faults of electric power system especially transmission systems couldn’t be inevitable. It is important to finf out fault accurally.The emergence and development of various information systems provide technical conditions for obtained the fault information,which makes transmission net fault diagnosis based on realtime information come true. Therefore diagnosing the fault component accurately and real-time can enhance the reliability of power supply,reduce the power restored time and improve the stability,which has great significance.The traditional researches of fault diagnosis are mostly based on digital information(the status of protection and circuit breaker). The location,region, type, error actions and refused actions of fault component could be judged by the states of protections and breakers obtained and the experience of dispatching personnals.It is really important to distinguish fault components. But only digital informations are used in those diagnosis methods above,the procedure of fault occurring could be recorded by the analogue information(the waveforms of current and voltage). As is known to all,there are uncertain factors in digital informations,however,the analogue infonnation has the enormous advantages. Consequently, analogue information is introduced into fault diagnosis.Diffirent data sources of information could be combimed with information fusion technolyg by which branch fault degrees would be got.Finally, power grid fault components would be diagnosed. The major work of this paper Ⅰ have done is as follows:(1) Fuzzy petri nets will be used in power system fault diagnosis which based on digital information. A power system fault diagnosis universal model based on weighted fuzzy petri net is builted. According to time sequence, the time sequence weighted fuzzy petri nets is set up.Fuzzy fault degrees before and after the time sequence are compared by different faults.The diagnosis within time sequence would be proved more effective.(2) The recorded fault data can be analyzed with the multi-resolution analysis wavelet theory. According to the fault current distribution characteristics of the grid, the total fault current waveform of both ends is considerd to wavelet analysis’ inputs. Set up IEEE14simulation model,and the wavelet fault degrees can be found out by compiled MATLAB diagnosis program.(3) We put forward a hierarchical fault diagnosis with information fusion based on multi-data resources.Two types of fault degrees above are decision-level information fusion by improved D-S evidence theory. Set up IEEE39simulation model, and obtain the wavelet fault degrees by compiled MATLAB diagnosis program.Appled D-S evidence theory to diagnosis,then the method used in paper is more effective.