Research Of Cable Fault Location System Based On Virtual Instrument

Power cable is used widely in current power system with merits of power cable such as safety, high reliability, beautification of urban layout. But due to influence of all kinds of factors, power cable may go wrong. It is the decisive effect for improving reliability and stability of power supply to remove faults speedily. It is enormously useful to society and economy to renew power supply quickly and to reduce economic loss.Now traveling-waves method is widely used in cable fault location and the merit is that the reliability is not influenced by faults. Further traditional instruments of cable fault location mainly base on microcomputer unit and fault distance can be required directly from the display of instruments with the movement of cursors. It is the shortcoming that assembly language is adopted and the function of calculation and analysis is weak. Therefore, the validity of fault location is low and the error is rather obvious. The validity is mainly depended on experience of operators, and intellectualized degree is not high. The difficulty of fault location is produced by all sorts of disturbs and reverberation of nodes. Besides users can't change the functions. It is the purpose of the research how to improve validity and precision of fault location in this thesis.There was the concept of virtual instrument in traditional instruments with fast development of computers and the introduction of virtual technology in 1980's. Virtual instrument is actually automatic testing instrument based on computers. It integrates common computers and hardware module through applications in order to provide support in various measurements for users. Users can operate the computer through friendly interface so as to accomplish the functions of collection, analysis, display and storage. Users operate instruments at their pleasure. Virtual instrument as the outcome of computer and modern instrument technology realizes revolutionary breakthrough in theory and method of measurement.Intelligent system of cable fault location based on virtual instrument is designed and developed independently through wide reading and thorough research of virtual instrument in this thesis. The main function of the hardware of virtual instrument is obtaining fault signal, and the software is the key to the system. Considering thecharacteristic of cable fault location, the principle of the whole numeric measurement system is designed based on virtual instrument. The software includes initialization module, parameter setting module, data collection module, data display module and data processing module. Wavelet transform and autocorrelation analysis are introduced into the data processing module. Denoising of signal based on mutli-resolution transform is the base of reconstructing real fault signal. The restriction is obtained through autocorrelation analysis. Due to the relationship of singularity and max-module, fault signal can be identified and located in mutli-resolution transform in order to exactly locate fault point.The characteristics of the system including reasonable configuration, reliable capability, high integration and convenient installation fully show the merits of virtual instrument. The system can be connected to notebook PC and exterior power supply, and it can be used in field test. The practicability of this system is validated through local testing.