Power system applications for phasor measurement units

State-of-the-art technology now permits measurement and analysis of power system performance on a scale not previously possible. Synchronized sampling, derived from the GPS (Global Positioning System), and high accuracy sigma-delta analog-to-digital converters form the basis for a system that can measure the state of the power system at a given instant over any area. Samples are acquired 12 times per cycle and are processed by a recursive discrete Fourier transform (DFT) algorithm. This produces the magnitude and angle of the input signal for each sample. The resulting phasors can be combined to produce a positive sequence phasor for a set of three phase inputs. The positive sequence quantities can be used to calculate voltage and current phase and magnitude, real and reactive power, frequency, and impedance. Since the positive sequence parameters are acquired at the same instant (within 1 microsecond), the state of the system at the measured nodes is known at the sample time. Applications to fault recording, disturbance recording, transmission and generation modelling verification, and power system stabiliser testing, are discussed.>