Patent ID: 6069780
Filing Date: 2000-05-30
Classification: H02H,H03H

Abstract:
An electronic trip device connected to means for measuring the current flowing in a polyphase electrical power system to be protected and comprising means for sampling current signals supplied by the means for measuring, means for calculating connected to the means for sampling and calculating a quantity representative of the thermal state of the power system, and means for comparing said quantity to preset tripping thresholds, the means for calculating comprising first means for filtering, receiving the current signal samples and supplying signals representative of the rms value of the current, a trip device wherein said first means for filtering comprise a finite impulse response filter associated to each phase of the power system, a maximum circuit connected to the output of each finite impulse response filter, and an infinite impulse response filter, having an input connected to the output of the maximum circuit and an output connected to the means for comparing.