Estimation of Pst indicator value for a simultaneous influence of two disturbing loads

The analytical model of an IEC flickermeter has been proposed in this paper. It has been assumed that the flickermeter's input voltage contains voltage fluctuation caused by the influence of two independent loads. Equations have been obtained that represent the signal at consecutive points of the flickermeter's signal chain. The Pst indicator value obtained at the model's output depends on the parameters describing the voltage fluctuation in a power grid. On the basis of the determined model, the dependencies of Pst indicator on the amplitude, the frequency as well as the times of activity and delay of the two rectangular modulating signals have been presented. Also, a comparison of the Pst indicator values determined with the use of an analytical model, the results of numerical simulations, and the results of laboratory measurements have been provided.