The Research On The Voltage Sag Online Monitoring System Based On The Virtual Instrument

With the rapid development of industrial technology and national economics, power quality has attracted more and more attentions in the field of power apartments and users. Voltage sag has been the most serious problem in power quality and cost a lot of money. So, the voltage sag online monitoring system based on the virtual instrument is developed using LabVIEW in this thesis, which is of benefit to improve the power quality.This thesis first introduced the basic concept of the voltage sag and the virtual instrument, and analyzed the actuality of the research on the voltage sag monitoring both domestic and abroad. Then compared all kinds of present methods to detect voltage sag, designed the program of the arithmetic which is appropriate to the monitoring system in the project background, and simulated this measuring arithmetic using LabVIEW. This arithmetic was checked for its veracity and real-time nature by the simulation. Then, combined with the technology of virtual instrument, network communication and database management, combined with the hardware and software, with the help of data-acquiring card, a voltage sag online monitoring system based on the virtual instrument is developed, the real-time collection and monitoring of the voltage in power system is completed. It is suitable for three-phase voltage online monitoring. The functions of the automatic long-term operation, the real-time measurement and analysis, and management of historic data are realized. The hardware composition and software programming are expounded, the plans of the client computer and the host computer are particularly introduced, and the main functions of the system are described. The main modules and the key technical measures of the system are explained.At last, considering the flexible expansibility of the virtual instrument, the function of the system is expanded on the fault recording. Combined with the voltage sag online monitoring and fault recording, the problem that there is no expert fault recording in the medium and low power system is solved.Compared with the traditional monitoring instruments, it not only has the advantages of short development cycle, easy control, enhanced processing ability and flexible expansibility, but also can meet the needs of modern power system fault study in sampling rate and precision and recording capacity.