A new digital filter for phasor computation. II. Evaluation [power system protection]

The results of the evaluation of a new type of digital filter are presented in this paper. The filter theory is outlined in Part I of the paper. The new filter results from the application of a special window to the coefficients of the traditional Fourier, Cosine and Sine algorithms. It is compared in the paper with the Fourier, Cosine and Sine filters in terms of steady-state and transient responses. Extensive time-domain simulations are performed to evaluate the filter transient behavior. The new filter is shown to be more accurate than the Fourier filter for window lengths equal or greater than 3 cycles of the fundamental frequency. It retains its accuracy even for window lengths being different from multiples of one cycle. The new filter is suitable for phasor computation for the fault location and measuring functions required in digital distance relays and fault recorders