Largest Normalized Residual Test Analysis for Measurements Gross Errors Processing in the WLS Estimator

Breno E.B. Carvalho and Newton G. Bretas


Power systems, WLS state estimator, gross errors, normalized residual


This paper purpose is to implement a computational program to estimate the states of a power system and showing that the largest normalized residual test fails many times. The chosen solution method was the Weighted Least Squares State Estimator. Once the states are estimated a gross error analysis is made with the purpose to detect and identify the measurements that may contain gross errors (GEs), which can interfere in the estimated states, leading the process to an erroneous state estimation. If a measurement is identified as having error, it is discarded from the measurements set and the whole process is remade until all measurements are within an acceptable error threshold. To validate the implemented software, there have been performed several computer simulations in the IEEEĀ“s systems of 6 and 14 buses. Another purpose is to show that even a widespread and used method as the largest normalized residual test is subjected to serious conceptual flaws, probably due to a lack of mathematical foundation attendance in the methodology. The paper highlights the need for continuous improvement of the employed techniques and a critical view, on the part of the researchers, to see those types of failures.

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