Probabilistic Assessment of Voltage Sag in radial distribution networks

The main aim of this paper is to develop a stochastic model for carrying out a predictive assessment of voltage sag (PAVS) in radial distribution systems. The PAVS estimates the voltage sag characteristics (magnitude, duration and frequency) and evaluates probabilistic indices of power quality in a distribution system. The proposed model is based on the combination of the Monte Carlo simulation method (MCSM) and the admittance summation method in phase coordinates. The MCSM is used to model uncertainties associated with fault scenarios and the admittance summation method (ASM) is used to evaluate the fault currents. The duration of the voltage sag has been estimated using the currentxtime curves of the protection devices (fuses, breakers and reclosers). The proposed methodology has been tested in a feeder belonging to the Maranhao electricity utility (CEMAR), Brazil, and the results indicate that the proposed methodology is a good tool for studies of sags in distribution systems.