Importance

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Abstract

Ground fault trip units for circuit breakers are tested by a passive test circuit which includes a test conductor passing through the current transformer sensing coil(s), and a test switch which selectively connects the test conductor in a loop which simulates a neutral-to-ground fault. In a dormant oscillator ground fault test circuit, the test conductor loop passes through both sensing coils. When the neutral-to-ground detector is combined with a sputtering are fault detector sharing a common sensing coil, testing of all the components is accomplished by adding an additional test circuit which injects pulses derived from the line conductor into the sensing coil secondary, or which alternatively, connects a capacitor charged from a DC supply across the sensing coil secondary. Either of these alternative test circuits generates the successive events needed to produce a sputtering arc trip.

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First Claim