GE 469 Instruction Manual

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Additional Functional Testing 469Motor Management RelayTestinghttp://www.GEindustrial.com/multilin 7–9GE MultilinUnbalance Test The 469 measures the ratio of negative sequence current (I2 ) to positive sequencecurrent (I1 ). This value as a percent is used as the unbalance level when motor loadexceeds FLA. When the average phase current is below FLA, the unbalance value isde-rated to prevent nuisance tripping as positive sequence current is much smallerand negative sequence current remains relatively constant. The derating formula is:(EQ 7.1)FIGURE 7–2: Three Phase Example for Unbalance CalculationSymmetrical component analysis of vectors using the mathematical vectorconvention yields a ratio of negative sequence current to positive sequence currentas shown:(EQ 7.2)Given the values in the figure above, we have:(EQ 7.3)If FLA = 1000, then:(EQ 7.4)INJECTEDCURRENT 1A UNIT,APPLIED VOLTAGE(Ia is thereference vector)INJECTEDCURRENT 5A UNIT,APPLIED VOLTAGE(Ia is thereference vector)EXPECTEDLEVEL OFPOWERQUANTITYTOLERANCERANGE OFPOWERQUANTITYMEASUREDPOWERQUANTITYEXPECTEDPOWERFACTORMEASUREDPOWERFACTORIa = 1 A ∠0°Ib = 1 A ∠120°Ic = 1 A ∠240°Va = 120 V ∠342°Vb = 120 V ∠102°Vc = 120 V ∠222°Ia = 5 A ∠0°Ib = 5 A ∠120°Ic = 5 A ∠240°Ia = 120 V ∠342°Vb = 120 V ∠102°Vc = 120 V ∠222°+ 3424 kW 3329to3519kW0.95 lagIa = 1 A ∠0°Ib = 1 A ∠120°Ic = 1 A ∠240°Va = 120 V ∠288°Vb = 120 V ∠48°Vc = 120 V ∠168°Ia = 5 A ∠0°Ib = 5 A ∠120°Ic = 5 A ∠240°Va = 120 V ∠288°Vb = 120 V ∠48°Vc = 120 V ∠168°+ 3424kvar3329to3519kvar0.31 lagI2I1----- I avgFLA----------- 100%××Ia=780A@ 0°Ib=1000A@ 113°Ic=1000A@ 247°Ia=780A@ 0°Ib=1000A@ -113°Ic=1000A@ 113°POWER SYSTEMVECTORCONVENTIONMATHEMATICALVECTORCONVENTIONI2I1-----13--- I a a2 I b aI c+ +( )13--- I a aI b a2 I c+ +( )-------------------------------------------------= where a 1 120°∠ 0.5– j0.886+= =I2I1----- 780 0°∠ 1 120°∠( )2 1000 113°–∠( ) 1 120°∠( ) 1000 133°∠( )+ +780 0°∠ 1 120°∠( ) 1000 113°–∠( ) 1 120°∠( )2 1000 133°∠( )+ +----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------=780 0°∠ 1000 127°∠ 1000 233°∠+ +780 0°∠ 1000 7°∠ 1000 353°∠+ +---------------------------------------------------------------------------------------------------------=780 601.8– j798.6 601.8– j798.6–+780 992.5 j121.9 992.5 j121.9+ + + +--------------------------------------------------------------------------------------------------------------- 423.6–2765--------------------== 0.1532=I avg780 1000 1000+ +3------------------------------------------------------ A 926.7 A= =