Protective relay

Claim 1

MEANS FOR INITIATING A PREDETERMINED CONTROL FUNCTION IN DELAYED RESPONSE TO THE OCCURRENCE OF AN ABNORMAL CONDITION IN AN ELECTRIC CURRENT CIRCUIT, THE AMOUNT OF DELAY BEING INVERSELY RELATED TO THE SEVERITY OF THE ABNORMAL CONDITION, COMPRISING: CONDITION RESPONSIVE MEANS ADAPTED TO BE COUPLED TO THE CIRCUIT FOR DERIVING THEREFROM A D.C. SIGNAL HAVING A MAGNITUDE WHICH IS DEPENDENT UPON THE VALUE OF A CHARACTERISTIC ELECTRIC QUANTITY OF THE CIRCUIT; A PULSATING SIGNAL SOURCE FOR SUPPLYING A REGULAR SUCCESSION OF TRIANGULAR-WAVEFORM SIGNAL PULSES; ADDING MEANS CONNECTED TO SAID CONDITION RESPONSIVE MEANS AND TO SAID PULSATING SIGNAL SOURCE FOR PROVIDING A RESULTANT SIGNAL CORRESPONDING TO THE SUM OF THE D.C. AND PULSATING SIGNALS; IMPEDANCE MEANS ASSOCIATED WITH SAID ADDING MEANS FOR INTRODUCING, IN SUBTRACTIVE RELATIONSHIP WITH THE RESULTANT SIGNAL, A UNIPOLARITY REFERENCE SIGNAL LEVEL EQUIVALENT TO THE PEAK MAGNITUDE OF SAID SIGNAL PULSES; ELECTRIC ENERGY STORING MEAN, INCLUDING A REACTANCE ELEMENT, CONNECTED TO SAID ADDITING MEANS FOR ENERGIZATION IN ACCORDANCE WITH THE DIFFERENCE BETWEEN THE RESULTANT SIGNAL MAGNITUDE AND THE REFERENCE SIGNAL LEVEL WHENEVER THE FORMER EXCEEDS THE LATTER, WHEREBY THE TIME REQUIRED FOR THE ENERGY BEING ACCUMULATED IN SAID REACTANCE ELEMENT TO BUILD UP TO A PREDETERMINED CRITICAL LEVEL FOLLOWING THE OCCURRENCE OF AN ABNORMAL CIRCUIT CONDITION IS INVERSELY RELATED TO THE VALUE OF SAID CHARACTERISTIC ELECTRIC QUANTITY; AND LEVEL DETECTING MEANS, CONNECTED TO SAID REACTANCE ELEMENT, ADAPTED TO INITIATE THE PREDETERMINED CONTROL FUNCTION IN RESPONSE TO THE ATTAINMENT IN SAID ELEMENT OF AN ENERGY LEVEL WHICH IS GREATER THAN SAID PREDETERMINED CRITICAL LEVEL, SAID LEVEL DETECTING MEANS HAVING ASSOCIATED THEREWITH PERIODICALLY ACTIVE SAMPLING MEANS FOR EFFECTING A SUFFICIENT INCREASE IN THE SENSITIVITY OF THE LEVEL DETECTING MEANS TO ENABLE THE LEVEL DETECTING MEANS TO RESPOND, AT PREDETERMINED TIME INTERVALS, TO THE ACCUMMULATION IN SAID REACTANCE ELEMENT OF SAID PREDETERMINED CRITICAL LEVEL OF ENERGY.