Tools for Assessing the Robustness of Electrical System against Voltage Dips in terms of Amplitude, Duration and Frequency

Abstract

The method of fault position is useful for characterizing power-system performance in the presence of voltage dips due to faults. It is based on short-circuit simulations repeated for all the system nodes and for many points along the system lines: fault voltages that are below a preset threshold are the required voltage dips. These dips are stored in so-called dip matrices, which contain only the dips in all the system nodes when faults occur at points along the lines. Graphical presentation of dip matrices has been proposed as a valuable tool to ascertain the critical area for system performance; this graphical visualization immediately correlates dip severity in terms of amplitude with colours defined by a proper scale. This paper proposes a new graphical representation of the During Fault Voltage matrices that allow accounting for also the dip frequency that is a very important aspect for assessing the voltage dip severity. New robustness indices are also proposed to synthesize bus performance in terms of affected and exposed areas able to account for not only the amplitude of the residual voltage but also the frequency. All the concepts are introduced and illustrated with reference to a real distribution systems.