Voltage Dips and Short Supply Interruptions – Case Study

Themainpart of the110kVdistribution systemoperatedby thePDCisa ring-operatednetwork. The whole 110 kV distribution system is operated as a system with a solidly grounded neutral (Figure C4.1). The PDC-operated 110 kV distribution system is connected with neighboring operators’ distribution systems and with the 220 kV transmission system by means of three autotransformers, 160 MVA each, installed at three substations: (a) LUB – industrial and household customers; (b) WAN – predominantly industrial customers; (c) SKA – near to a heat and power generating plant.1 At these points instruments have been installed to measurer the power quality factors. The measurements were carried out over seven months, at three measurement points. The effect of these measurements is recorded in the database which contains, among other things, the recorded voltage dips.