InfluenceofHVDC Ground Electrode Current onAC TransmissionSystemand ItsRestraining

HVDC powersystems operating inground- return modeproduce DC voltages aroundtheelectrodes. During Monopolar operations oftheHVDC electrode, DC biases ofthe transformers causedbytheDC current through neutral points maydamagethetransformers andthewholenetwork. Thenoises andtheneutral point DC currents ofthemaintransformers with earthed neutral points inYihesubstation andLN powerplant weremeasuredandrecorded during thecommissioning ofthe HVDC systemfromThreeGorgespowerstation toGuangdong powernetwork. Comparedtoinjecting reverse direct current andinserting inseries withtheneutral point anappropriate resistance, thestrategy ofinstalling capacitors tothemain transformer neutral point ismoreeffective. According totheDC currentvaluesmeasuredatthetransformer neutrals ofLN power station, thismethodwas studied basedon its corresponding moduleofpowersystemwithgroundgrid proposed. Simulations havebeencarried outandsomemain technology parameters wereputforwardaccording tothe research results. IndexTerms-- DCbias; HVDC;transformer neutral point ~~~~AC LineII