A novel accelerated criterion for loss of field protection

Traditional loss of field protection can not measure exciting voltage easily and causes long time delay,thus a new accelerated criterion based on the synchronous electromotive force Eq is proposed.It adopts synchronous electromotive force instead of traditional exciting voltage,dispenses with the excitation side electrical quantity,performs reliably and can distinguish the loss of field from the oscillation,short circuit fault and other abnormal conditions,which improves the rapidity and selectivity greatly,and solves the long term problem that loss of field protection can not meet the requirements of rapidity and selectivity at the same time.PSCAD/EMTDC simulation verifies the correctness of the above conclusion.