A Computationally Efficient Method to Place Critical Measurements

This paper investigates a very practical and commonly encountered problem in state estimation. It is related to the placement of measurements in order to make an otherwise unobservable system observable. Typically, this is a situation that is frequently encountered during the daily operation as one or more of the measurements become unavailable due to various unexpected reasons. Under such circumstances, the state estimator resorts to the use of pseudo-measurements in order to recover observability and solve the state estimation problem. Pseudo-measurements that will make the system observable can be selected by applying one of the well-developed network observability analysis techniques in a repetitive fashion adding one candidate measurement at a time until the system is no longer unobservable. As the system size increases, this approach may prove computationally expensive. A nonrepetitive solution has also been proposed. However, its computational requirements grow rapidly with increasing number of observable islands that may exist in large scale systems. This paper presents an alternative approach which will be shown to be suitable for large scale power systems providing a compromise between the two existing techniques. Examples are given to highlight the main benefits of the proposed method.