Differential relay with restraining means responsive to transformer bank voltage

Claim 1

IN A PROTECTING DEVICE, A SWITCHING APPARATUS COMPRISING OPERATE AND RESTRAINT ENERGIZABLE CONTROL ELEMENTS AND CIRCUIT CONTROLLING MEANS ACTUATED BY SAID ELEMENTS TO A FIRST CONDITION IN RESPONSE TO RATIOS OF ENERGIZATION OF SAID OPERATE ELEMENT TO THE ENERGIZATION OF SAID RESTRAINT ELEMENT BELOW A CRITICAL MAGNITUDE AND TO A SECOND CONDITION IN RESPONSE TO THE RATIOS OF SAID ENERGIZATION ABOVE SAID CRITICAL MAGNITUDE, FIRST AND SECOND PAIRS OF INPUT TERMINALS, A NETWORK CONNECTED TO BOTH OF SAID PAIRS OF TERMINALS AND INCLUDING A PAIR OF OUTPUT TERMINALS ENERGIZED WITH A FIRST ELECTRICAL QUANTITY HAVING A MAGNITUDE WHICH IS A FUNCTION OF THE DIFFERENCE IN MAGNITUDE OF A PAIR OF ELECTRICAL INPUT QUANTITIES SUPPLIED TO SAID PAIRS OF INPUT TERMINALS, A FIRST CIRCUIT CONNECTING SAID OPERATE ELEMENT TO SAID OUTPUT TERMINALS FOR ENERGIZING SAID OPERATE ELEMENT AS A FUNCTION OF THE MAGNITUDE OF THE SAID FIRST ELECTRICAL QUANTITY, A THIRD PAIR OF INPUT TERMINALS, AND A SECOND CIRCUIT CONNECTING SAID RESTRAINT ELEMENT TO SAID THIRD PAIR OF INPUT TERMINALS FOR ENERGIZING SAID RESTRAINT ELEMENT BY A CONTROL ELECTRICAL QUANTITY SUPPLIED TO SAID THIRD PAIR OF INPUT TERMINALS, SAID SECOND CIRCUIT INCLUDING A MAGITUDE SENSING DEVICE, SAID MAGNITUDE SENSING DEVICE BEING EFFECTIVE TO PREVENT ENERGIZATION OF SAID