A STUDY OF ESTIMATION TECHNIQUES FOR FREQUENCY-RELAYING APPLICATIONS

This paper presents an evaluation and performance comparison of two es timating algorithms used for frequency-relaying applications. The firs t algorithm is based on least squares (LS) error estimation, while the second is based on the least absolute value (LAV) approximations. Two models for frequency estimation, namely the constant-frequency model (CFM) and the variable-frequency model (VFM), are used. CFM is used to measure the steady-state frequency deviation, while VFM is used to me asure the transient frequency and its rate of change. For the constant -frequency model, which is suitable for use in microprocessor-based re lays, the algorithms are tested using two data sets. The first involve s a pure sine waveform, and the second is a wave generated from the el ectromagnetic transients program (EMTP) simulating a study system. The EMTP is used to generate the corresponding voltage samples at a relay location. Fault conditions applied on the study system to generate di storted waves with and without frequency deviations are considered. Fo r the variable-frequency model, the algorithms are tested using a data set generated from a pure sine waveform. The effects of sampling rate , sample window size and bad data on the performance of each algorithm are studied. A comparison of the results is offered to evaluate the t wo techniques.