Electrical protective relay apparatus

Claim 1

PROTECTIVE RELAY APPARATUS FOR AN ELECTRICAL SYSTEM COMPRISING, A PLURALITY OF FIRST INPUT CIRCUITS FOR DEVELOPING SIGNALS PROPORTIONAL TO FIRST ELECTRICAL CONDITIONS ASSUMED BY THE PROTECTED SYSTEM, EACH INPUT CIRCUIT INCLUDING A FIST UNDIRECTIONALLY CONDUCTING DEVICE, AND FIRST CONNECTING MEANS FOR CONNECTING TOGETHER LIKE POLES OF EACH DEVICE IN ALL SAID INPUT CIRCUITS TO A FIRST TERMINAL IN A MANNER SUCH THAT ONLY THE LARGEST OF SAID SIGNALS IS DEVELOPED AT SAID TERMINAL, A PLURALITY OF SECOND INPUT CIRCUITS FOR DEVELOPING SIGNALS PROPORTIONAL TO SECOND ELECTRICAL CONDITIONS ASSUMED BY THE PROTECTED SYSTEM, EACH SAID SECOND INPUT CIRCUIT INCLUDING A SECOND UNIDIRECTIONALLY CONDUCTING DEVICE, AND SECOND CONNECTING MEANS FOR CONNECTING TOGETHER LIKE POLES OF EACH SECOND DEVICE IN ALL SAID SECOND INPUT CIRCUITS TO A SECOND TERMINAL, AND SWITCHING MEANS CONNECTED BETWEEN SAID FIRST AND SECOND TERMINALS AND OPERATIVE TO EFFECT AN ALARM OR CONTROL FUNCTION, THE POLARITY OF SAID SECOND UNIDIRECTIONALLY CONDUCTING DEVICES BEING SUCH THAT SAID SWITCHING MEANS IS OPERATIVE TO EFFECT SAID FUNCTION IN RESPONSE TO THE SIGNAL AT THE FIRST TERMINAL EXCEEDING BY A PREDETERMINED AMOUNT THE SMALLEST SIGNAL DEVELOPED BY ANY OF SAID SECOND INPUT CIRCUITS.