Automatic protection device with ground fault annunciation
AssigneeGeneral Electric Company
InventorMorris J. Kornblit
Life of this patent
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Abstract
A trip unit, such as one comprising a current sensor generating a current signal indicative of current in a power circuit, an analog to digital converter converting said signal into digital form, and a controller monitoring the current signal and sensing whether an over current condition exists and whether a ground fault condition exists. In case of an over-current condition, the controller causes a trip signal to be output resulting in the power circuit being opened. In the case of a ground fault condition, the controller causes an annunciation output signal but does not generate a trip signal in the case of a ground fault condition and therefore does not cause the power circuit to be opened.
Claims25
A method of protecting a power circuit having a circuit breaker thereon, said method comprising:
- sensing for a fault condition in said power circuit, said fault condition comprising an over-current condition and a ground fault condition;
- annunciating the fault condition at a remote location if said fault condition is sensed;
- tripping the circuit breaker if the fault condition is an over-current condition;
- and
- if the fault condition is a ground-fault condition:
- checking whether it is safe to shut down the power circuit, and
- sending a trip signal to a trip unit in said circuit breaker from the remote location after determining that it is safe to shut down the power circuit.
A trip unit comprising:
- an input for receiving a selection between a first option and a second option;
- an input for inputting signals from a current sensor;
- an analog to digital converter converting said signals into digital form;
- and
- a controller monitoring said signals and determining whether an over current condition exists and whether a ground fault condition exists, said controller is configured to:
- cause a trip signal to be output when said over-current condition exists,
- cause a trip signal to be output when said ground-fault condition exists and said first option is selected, and
- cause an annunciation signal to be output and no trip signal to be output when said ground-fault condition exists and said second option is selected.
A circuit breaker comprising:
- a pair of separable contacts;
- a trip unit;
- a trip module adapted to separate said separable contacts in response to a trip signal from said trip unit;
- and
- sensing means for sensing current levels in said power circuit;
- said trip unit comprising:
- an input for receiving a selection between a first option and a second option,
- an input for inputting signals from said sensing means,
- an analog to digital converter converting said signals into digital form, and
- a controller monitoring said signal and determining whether an over current condition exists and whether a ground fault condition exists, said controller is configured to:
- cause a trip signal to be output in the when said over-current condition exists,
- cause a trip signal to be output when said ground-fault condition exists and said first option is selected, and
- cause an annunciation signal to be output and no trip signal to be generated when said ground-fault condition exists and said second option is selected.
A system for protecting critical equipment from electrical fault conditions, the system comprising:
- a circuit breaker comprising:
- separable contacts for connecting in a power distribution circuit providing electrical power to said critical equipment,
- sensing means for sensing current in said power distribution circuit and for generating signal indicative of said current,
- circuitry for generating a trip signal when an over-current condition is detected and for generating an annunciation signal and not a trip signal when a ground fault condition is detected, and
- tripping means for separating said separable contacts in response to a trip signal from said circuitry;
- and a remote monitoring computer, said remote monitoring computer comprising:
- an input/output for receiving said annunciation signal, and
- a processor for processing computer language instructions stored on non-volatile memory accessible by said processor, said instructions causing said remote monitoring computer to implement:
- annunciating the ground fault condition,
- checking whether it is safe to shut down the power circuit when said annunciation is made at said remote location, and
- sending a trip signal to said circuit breaker after determining that it is safe to shut down the power circuit.
Dependencies are inferred from the claim text.