Impedance Measurement in Real Time, Employing Sine and Cosine Filters Simultaneously, Incorporating Spline Functions for Interpolation.

The aim of the present paper is to show a real time digital system which measures the impedance corresponding to the fundamental frequency of the electrical power system (50 or 60 Hz depending on the country). Considering the frequency contents typical of the signals coming from the electrical system, Sine and cosine filters are used to obtain the voltage and current phasors, respectively. The system proposed can be applied to single-phase systems, and due to the incorporation of an interpolation method using spline functions, it is possible to use data acquisition devices with multiplexing sampling (more economical than those with simultaneous sampling). The system was carried out by means of LabView software and a multifunction data acquisition device with multiplexing sampling.