Transcription of Protection Basics - IEEE
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Protection Basics - IEEE
Copyright SEL 2013 Protection Basics Protection Review Fault types Electrical equipment damage Time versus current plot Protection requirements Protection system elements Power System Faults Short circuits Contacts with ground Isolated neutral systems High-impedance grounded systems Open phases Typical Short-Circuit-Type Distribution Single-phase-to-ground 70 80% Phase-to-phase-to-ground 10 17% Phase-to-phase 8 10% Three-phase 2 3% abcDistribution SubstationFaults in Electrical Systems Produce current Increments I I Wire teeiT(t) (T T )eT =+2dWIRdt=Temperature Rise From current tTEquilibriumTiTeI T Constant current Factors Influence Wire Heating d current Magnitude Wire Material Properties Ambient Temperature and Other Environmental Factors I Wire Size tTtdInsulation DamageTiTdTeInsulated Conductor (Cable) Thermal Damage I Insulation Insulated Conductor Thermal Damage I T Damage CurveI1 ImdItI2I3t1t2t3t2t3tTt1 TdTiI = ImdI = I1I = I2 > I1I = I3 > I2 Damage CurveRatingInImdItElectrical Equipment Component Thermal Damage Curve Mechanical Damage Mechanical forces (f1 and f2) produced by short-circuit currents cause instantaneous damage to busbars, insulators, supports, transformers, and machines i1 i2 f1 f2
Protection Review • Fault types • Electrical equipment damage • Time versus current plot • Protection requirements • Protection system elements
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