Research And Realization Of Dielectric Loss Factor On-line Monitoring

The measurament of dieletric loss in the eletrical equipment is a high vital experiment project, which can show the stituation of insulation. Since long ago, the tradditional eletric-bridged apparatus have still used to measure the dieletric loss factor (tanδ) of eletrical equipment, but it has shortcomings of complex operation and Antijamming ability. In recent years, with the development of computer technology and digital signal processing, the on-line monitoring technology of dieletric loss based on microprocessor is emphasized increasingly.This paper analyzes some research methods and applical situation, and takes the measure of harmonic analysis to solve some difficult problems of dieletric loss monitoring. As for the high harmonic frequency fluctuations in the power grid resulting in spectrum leakage, applies window function(Blackman-Harris window) and uses phase-locked loop frequency multiplication to ensure the complete cycle sampling of two channel signal by tracking the signal frequency to reduce the error and increase precision. According to the principle of practication and reliablity, the paper proposes the software on-line monitoring methods based on virtual instrument, and assembles the virtual instrument system based on personnel computer, programs the procedure of microprocessor and computer respectively.At first, the paper analyzes and compares the tradditional methods with modern measuring methods after introducing the physical meaning of dieletric loss in detail, and carries on simulation analysis due to sampling noncomplete cycle. The hardware circuit of sampling data is designed, and the serial communication Bus is applied to send the signal to personnel computer. Finally, caculates the tanδof dieletric loss after carrying on digital signal processing by virtual instrument which can offer the function, such as indicating, conveying, saving, alarming. And what is more, the on-line detected apparatus can monitor the stiuation of some places in the same time, and has the function of network and broad prospects for development.