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Cigré 2005, SC B5 Colloquium in Calgary Preferential Subject 1 Question 7. Zoran Gaji ć ABB Sweden. SC B5: PS1, Q7 Transformer Inrush Currents. EFFECT OF TRANSFORMER INRUSH CURRENTS ON PROTECTION FUNCTIONS. Where to Look, Security, Dependability.
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Cigré 2005, SC B5 Colloquium in Calgary Preferential Subject 1 Question 7 Zoran GajićABBSweden
SC B5: PS1, Q7 Transformer Inrush Currents EFFECT OF TRANSFORMER INRUSH CURRENTS ON PROTECTION FUNCTIONS Where to Look, Security, Dependability
Transformer Inrush Currents – Where to look? • Measured in Phase Currents or in Differential Currents? • 2nd harmonic • 4th harmonic • 5th harmonic • DC offset • Wave shape recognition • etc. • Set block level depends on position where measurement is taken
Transformer Inrush Currents – Security? • Security? • Block for all inrush cases • Not good practice to put burden on the end user to completely set this logic • 15% or 7%? • Adaptive 2nd harmonic + WaveBlock good results • Correct and easy to use design is manufacturer responsibility
Transformer Inrush Currents – Dependability? • Dependability? • Trip for all internal faults • Insure that restraint level will trip in spite of CT saturation • Use of adaptive second harmonic blocking insures that • Paper in IEE DPSP 2001