Impact ofincreasing levels ofDERonthedip frequency intransmission systems

* Three phase faults -5% Abstract--This paperdescribes astudy toestimate theincrease involtage-dip frequency whenanincreasing amountoflarge An increase indistributed energy resources (DER)was power stations isreplaced bysmall units connected todistribution assumed, equally spread overthesystem. Thiswasmodelled systems. asa reduction intheloadasseenfrom thetransmission IndexTerms--power transmission anddistribution, distributed system. Thisrepresentation doesnotinclude thecontribution, (embedded) generation, power quality, voltage dips (sags) ifany,fromtheDER units totheshort-circuit capacity. Forthe penetration levels assumed inthis paper(upto400/O), this ~~~~~~~~~~~~voltage dipfrequency duetofaults attransmission level. The corresponding nodes. Thezerosequence impedance ofthese g o q y feeders~~~~~~ wase.qa otepstv euneipdne h methodoffault positions wasfirst usedbyConrad(3)and zero sequencesimpedancelof.the linesiwasssetneq