Patent ID: 7869170

Claim:
A time-synchronized method of self-protecting a circuit breaker having a current transformer coupled to a power source, the method comprising: charging, in a first time interval, a stored energy circuit via a secondary current coupled from the current transformer; after expiration of the first time interval, first measuring a voltage across at least a burden resistor to produce a burden resistor voltage and determining whether the burden resistor voltage exceeds a predetermined trip threshold indicative of a high instantaneous fault current; multiplexing charging the stored energy circuit toward a stored energy voltage sufficient to power a solenoid of the circuit breaker and determining whether the burden resistor voltage exceeds the predetermined trip threshold; responsive to the stored energy circuit being charged to the stored energy voltage, second measuring the voltage across the burden resistor and determining whether the voltage across the burden resistor exceeds at least one trip threshold indicative of a fault current; and tripping the circuit breaker in response to the burden resistor voltage exceeding the predetermined trip threshold or the voltage across the burden resistor exceeding the at least one trip threshold.