Investigation on the definition and digital algorithm of instantaneous dielectric loss factor

Among the digital algorithms presently available for on-line monitoring of the dielectric loss factor of power apparatus, there are unavoidable limitations that most of them must meet strictly the synchronous sampling criterion, simultaneously with a precondition that the power frequency must be invariable in the sampling periods. This paper presents a unique definition and corresponding digital algorithm of instantaneous dielectric loss factor. In non-stationary signal environment where power frequencies are randomly variable, the algorithm can accurately track the instantaneous frequency of power signals and recursively calculate the parameters of parallel equivalent circuit, and finally figure out the waveform of instantaneous dielectric loss factor.