Determination oftheOptimumRoutine TestandSelf-Checking Intervals inProtective Relaying UsingaReliability Model

M.;Sidhu, T.S. Author Affiliation: University ofSaskatchewan, Saskatoon, Canada Abstract: Relaying reliability isgenerally separated into thetwodif- ferent aspects ofdependability andsecurity. Thereliability ofaprotec- tion relay canbeimproved bycanying outroutine maintenance orby including built-in monitoring andself-checking facilities during thede- sign stages. AMarkov model isdescribed inthis paper that canbeused to examine these features. Themodel also recognizes common-cause fail- ures, temporary andpermanent faults andtheassociated clearing times, operation ofback-up protection, andrelay mal-trips. Studies havebeen conducted toillustrate theexpected reliability benefits byinclusion of monitoring andself-checking facilities within therelay. Abstract: Aprobabilistic powersystem stabilizer (PSS) design con- sidering multi-operating conditions isproposed inthis paper. Underthe assumption ofnormal distribution, theconventional eigenvalue sensitiv- ityanalysis isextended toprobabilistic environment bydescribing the statistical nature ofelgenvalues asexpectations andvariances. Two probabilistic indices derived fromthesensitivities ofelgenvalue expecta- tions andvariances areintroduced tothePSSsite andparameter selec- tion. Therobustness ofthesystem canbeguaranteed because awide range oftheloadvariation hasbeentaken into account inprobabilistic representation. Theeffectiveness oftheproposed PSSisdemonstrated onathree-machine system byprobabilistic eigenvalue analysis andtran- sient response simulation.