Digital algorithm based on orthogonal decomposition for measurement of dielectric loss factor

As one of the most important technical indexes for the evaluation of insulation condition, the dielectric loss factor is necessary in preventive experiments and online monitoring of insulation of high-voltage apparatuses in an electric power system. First, the definition of the dielectric loss factor and the impact of the harmonic voltage on that was discussed. Secondly, the voltage and the leakage current were defined as vectors in normed linear space. By using the characteristic of an orthogonal vector in the inner product space, the leakage current signal was decomposed to active and reactive components that were orthogonal. Subsequently, a novel digital algorithm of the dielectric loss factor measurement, which was defined as the ratio of norms of the active current to the reactive current, was proposed. At last, the proposed algorithm was simulated under several conditions such as harmonic voltage and voltage frequency fluctuation. In addition, the proposed algorithm was tested on two electric power capacitors. Both simulation and experiment results were provided and show that the proposed algorithm is simpler and less sensitive to influence factors than the Fourier analysis method.