Detection of voltage sag sources based on instantaneous voltage and current vectors and orthogonal Clarke´s transformation

Different methods for voltage sag source detection are discussed. They are based either on disturbance energy, voltage-current characteristic or active (real) current component. It is shown that, in the cases of asymmetrical voltage sags, both current-based methods known from literature do not work well. These two methods are therefore generalised using a vector-space approach. Furthermore, three new methods are introduced using orthogonal Clarke´s transformation, which can be used to detect the sources of those voltage sags provoked by earth faults. All the discussed methods for voltage sag source detection have been tested by applying extensive simulations, laboratory tests and field testing. The results obtained show the very high effectiveness of the proposed methods, which are superior to the methods known from literature, especially for detecting sources of asymmetrical voltage sags.