Investigation of effects of short duration voltage sags on industrial distribution systems

INVESTIGATION OF EFFECTS OF SHORT DURATION VOLTAGE SAGS ON INDUSTRIAL DISTRIBUTION SYSTEMS SUMMARY Keywords : Short duration voltage sags. Embedded generators. Power quality. Distribution systems. This thesis consists of six chapters. There are three main sections that include investigations. In first chapter, it is given a literature study after a short introduction and then investigated phenomena are presented. In second chapter, a detailed theoretical background, mathematical equations and methods used in the analysis are given. In chapter three, influences of short duration voltage sags on a sample industrial system that include mostly induction motors are investigated. In this chapter, it is presented that the behavior of induction motors during the different operating conditions and simulations are realized in an industrial system without any embedded generation system. Inductions motors are modeled by using suitable equivalent circuits and effects of fault location, fault types and mechanical load torque are investigated. In chapter four, an embedded generation plant is added in the sample system used in previous chapter and it is investigated that effects of embedded generators on voltage sags. In the simulations, different loading condition between generators and networks are considered. Effects of fault location, fault types and mechanical load torque are investigated. Also effects of embedded generators on voltage sag due to voltage starting of large induction motors are investigated. In final chapter, effects of voltage sags caused by faults occurred both in external network and internal networks and starting of large motors on behavior of embedded generators. It is investigated that behavior of embedded generators during and after the sag conditions in previous chapters. In the computer simulations, Simpow package are used. XIX