Circuit protection device with half cycle self test
DCFirst Claim
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1. A self testing protection device including a plurality of line terminals configured to be connected to an alternating current (AC) electrical distribution system, and a plurality of load terminals configured to be connected to at least one load, the device comprising:
- a ground fault simulation circuit for producing a simulated ground fault during a first predetermined half-cycle of AC power;
a detector coupled to the ground fault simulation circuit, the detector configured to detect the simulated ground fault during the first predetermined half-cycle of AC power, and transmit a detection signal in response thereto; and
an alarm circuit coupled to the detector, the alarm circuit being configured to generate an alarm signal if the detection signal is not generated within a predetermined period of time.
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Abstract
A circuit protection device connected between two lines of an AC power source self checks for an introduced simulated ground fault every half cycle during a period when a trip SCR cannot conduct. If the self check fails, the device is tripped on the next half cycle of different phase. Possible responses to the self check failure include lighting an indicator lamp and locking out the device reset mechanism.
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Citations
38 Claims
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1. A self testing protection device including a plurality of line terminals configured to be connected to an alternating current (AC) electrical distribution system, and a plurality of load terminals configured to be connected to at least one load, the device comprising:
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a ground fault simulation circuit for producing a simulated ground fault during a first predetermined half-cycle of AC power;
a detector coupled to the ground fault simulation circuit, the detector configured to detect the simulated ground fault during the first predetermined half-cycle of AC power, and transmit a detection signal in response thereto; and
an alarm circuit coupled to the detector, the alarm circuit being configured to generate an alarm signal if the detection signal is not generated within a predetermined period of time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A self testing protection device including a plurality of line terminals configured to be connected to an alternating current (AC) electrical distribution system, and a plurality of load terminals configured to be connected to at least one load, the device comprising:
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a ground fault sensor coupled to the electrical distribution system, the ground fault sensor being energized by a first polarity of AC power provided by the AC electrical distribution system;
a first detector coupled to the ground fault sensor, the first detector being configured to generate a first detection signal, the first detection signal indicating that each ground fault detection component in the self testing protection device is operational;
a resonant talk circuit coupled to the first detector, the resonant tank circuit being configured to generate a resonant oscillating signal in response to receiving the first detection signal; and
a second detector coupled to the resonant tank circuit, the second detector generating all alarm signal if the resonant oscillating signal is not received within a predetermined period of time. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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36. A method for self-testing a protection device connected between two lines of an AC power line, comprising the steps of
introducing a simulated ground fault during a first predetermined half cycle of AC power; -
detecting said introduced simulated ground fault during said first predetermined half cycle; and
responding to an absence of detecting said introduced simulated ground fault.
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37. A method for self-testing a protection device connected between two lines of an AC power line, comprising the steps of
introducing a simulated ground fault during a negative half cycle of AC power; -
attempting to detect the simulated ground fault during the negative predetermined half cycle; and
generating an alarm signal if the step of attempting is a failure. - View Dependent Claims (38)
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Specification