OVERVOLTAGESDUE TO OPEN-PHASEOCCURRENCE INREACTOR COMPENSATEDEHV LINES F.ILICETO, Senior memberIEEE University ofRome.Consultant toTurkish Electricity Authority andVolta River Authority

Theresults arereported ofadigital computer study forthecalculation oftheovervoltages induced inopen-phase condition inHV lines equipped withshuntreactors connected totheir terminals, asmay occurinconjunction withsingle-pole reclosure andstuckbreaker poles. Theimportance isemphasized ofthecorrect simulation ofline coronalosses, thatareshowntoreduce theopen-phase overvoltages drastically whentheonsetvisible corona voltage isexceeded. Itis alsoshownthatshuntreactor saturation mayincrease theopen-phase overvoltage ,ifferroresonance occurs. A physical explanation ofthephenomenon isgiven first. Thena modelisproposed forcoronasimulation, whichleads toresults in agreement withreported field measurements. Theresults arepresentedofa parametric study, concerning 380kV lines withtwinand triplet bundle conductors andshuntcompensation from15%to100%. And inconclusion several considerations areputforward onthe possible damages toshuntreactors, lightning arresters andcircuit brea kers.