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This paper presents a method that allows observability analysis and restoration, identification of critical measurements and critical sets as well as the updating of these measurement set qualitative characteristics in real time, based only on the network topology. The identification of critical measurements and sets is carried out in a beforehand basis, that is, they are identified using the network topology properties before running any state estimation. Making a mapping of the system states, and using information concepts, a new state space is obtained where, in a straightforward manner, the desired relationship (information) between measurements and states is obtained. The mentioned mapping and the state information are easily found via triangular factorization of the Jacobian matrix, characterizing the method as numerical. Starting from a Base Case Measurement Set, every time a snapshot of measurements has to be analyzed, only re-factorization corresponding to the lost measurements has to be made. The sparse structure of such matrix allows the use of sparse techniques speeding up the process.The method was tested in the IEEE-14-bus system, IEEE-30-bus system as well as in one Brazilian real system (the 383-bus system by CHESF-Companhia Hidroelétrica do São Francisco). The results proved to be reliable, easy to implement and fast, showing the proposition is a useful tool for power systems realtime operation.

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SUMMARY This paper proposes an index, called Undetectability Index (UI), to classify the measurements according to their characteristics of not reflecting their errors into the residuals of the weighted least squares state estimator (WLS) from a geometric analysis of this estimator. Gross errors in measurements with high UIs are very difficult to be detected by methods based on residual analysis, because the errors in those measurements are “masked”, i.e. they are not reflected in their residuals. The paper also presents a very simple algorithm to compute the UI of all available measurements in a metering system. This algorithm is very simple and uses routines already available in the existing WLS Estimator software. Two UI applications are investigated (i) to design more reliable metering systems for bad data processing, i.e. metering systems formed by measurements with UI lower than a pre‐specified value and (ii) to estimate the measurement errors. Several simulation results (with IEEE‐14 and 30 bus systems) have validated the propositions. Copyright © 2013 John Wiley & Sons, Ltd.

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