SERIESCOMPENSATION OPERATINGLIMITS- A NEW CONCEPTFOR SUBSYNCHRONOUS RESONANCESTABILITYANALYSI'-S

A new concept is presentedfor analyzingthe stabilityof turbine-generatortorsional modes of oscillationin the presence of series compensated transmissionlines. A method is described for obtaininga locus representingconstant damping of a torsionalmode of oscillationas a function of series compensation levels in two transmission lines. A digitalcomputer program named SCOL which performsthe computationsand plots the results in a directlyusableformhas been developedand validated againstthe MANSTABprogram, used to establishthe IEEE benchmarkeigenvaluecalculations.The paper includesan examplewhichdemonstratesthe utilityof this analyticaltool for studying subsynchronous resonance on a majortransmissionsystem in the southwestern UnitedStates. This method providesthe system plannerwith a directmeans of calculatingmaximumallowablecompensationlevelsin two lines at a time. Currentlyused methods,such as eigenvalueanalysis,are indirectand requiremany calculationsand engineeringinterpretation to achievethe equivalentinformation.Utilization of the methoddescribedin thispaper can result in considerable savingsin both computerand engineering time. It is felt that the developmentof this concept and digitalcomputer program representsa valuableadvancementin the state of the art for analyzingthe problem of subsynchronousresonance stabilityon large ac -transmission systems requiring theuse of severalseriescompensated lines.