Effect of transformer on stochastic estimation of voltage sag due to faults in the power system: a PSCAD/EMTDC simulation

摘要

Voltage sags in the electric power system are mostly due tofaults in the power system. Voltage sag is characterized by itsmagnitude (the retained voltage), phase-angle jump, unbalance in thesag in the three phases, and duration. Type of transformers in theelectrical system is the important parameter influencing thecharacteristic of sag at the node where sensitive loads are connected.For sensitive loads it is necessary to estimate how many times in ayear the voltage at their terminal will experience sag to avoidtripping of operation. In this paper the effect of transformer onstochastic estimation of voltage sag is studied. Several stochasticmethods for the estimation of number of sags have been developed inrecent years. Various methods of sag prediction require lengthyprogramming or calculations. In the present work the PSCAD/EMTDCsoftware package is used to estimate number of sags assuming uniformdistribution of faults along the lines.