Estimation of voltage sag using transient stability analysis and automation of power factor correction using PLC in a petrochemical industry

The power quality, mainly voltage sag performance and power factor of a distribution system have been evaluated. The analysis of voltage sag uses the Monte-Carlo procedure carried out in the Electrical Transient Analysis Program (ETAP) to construct the sag density table and to estimate the probable number of critical voltage sags per annum at a given node. These calculations have taken into account the entire system comprising the transmission, sub transmission and distribution subsystems. Also, the various improvement methods for sag performance have been suggested. To improve power factor, a scheme for automation of power factor correction using Programmable Logic Controller (PLC) based on actual installations has been developed. For automation, Boolean logic circuit has been developed and ladder diagram has been drawn. From the ladder diagram, program for the PLC has been written.