Techniques fortheSteady State Representation ofUnbalanced PowerSystems, PARTI:A Systematic Building BlockApproach

The effects ofinterphase coupling inmultiphase powersystems becomeimportant inthepresence ofnetwork topology imbalance andunbalanced phase loadings. Currents thatflowintheearth can havesignificant effects on the system's behavior. Bothoftheseeffects ofimbalance must be accounted forinan accuratemodelofa multiphase system. A step-by-step procedure forunbalanced powersystem modeling ispresented. Theprocedure relies uponlinear graph theory andproduces amultiport modelwhichisageneraliza¬ tionofthewell-known busadmittance model.Thispaper reviews some important results oflinear graph theory and gives sufficient detail thattheprocedure can befollowed without extensive use ofthereferences (whose nomencla¬ turesdiffer). Mutualcoupling effects, theeffects ofneutral andstatic conductors, thefinite conductivity ofearth, and various component modelsare considered. A companion paperdescribes a procedure forreducing theorderofthe powersystem model. Abstract.A powersystem modelthataccountsformutual coupling effects, theeffects ofneutral andstatic conductors, andthefinite conductivity ofearthisgenerally large and explicitly represents manyuninteresting currentsandvolt¬ ages.A systematic procedure ispresented togreatly reduce theorderofsucha modelwithoutlossofinformation regarding suppressed variables. A convenient methodis presented forrepresenting theeffects ofpassive control devices suchastap-changing-under-load transformers, and an example multiphase loadflowsolution isgiven fora small unbalanced powersystem.