Rotor earth protection arrangement for sync. generator - uses phase angle between measuring voltage and current through series through series protection circuit as response criteria

摘要

The protection arrangement comprises a series circuit between the motor circuit and earth, contg. a coupling capacitor (Cv) an inductance (Lv) and a measuring AC voltage source. Response criteriaa are provided by the phase angle between the measuring AC voltage aand the current through the series circuit and the insulation resistance. The coupling capacitance and inductance values and the frequency of the AC measuring voltage are selected so that the series resonance frequency is for enough from the measuring voltage frequency to obtain a purely capacitive current with a high insulation resistancee and is purely inductive when the earth connection has no resistance. ADVANTAGE - Response value is adjustable in range between 100 and 1,000 Ohm.