Direct current arc fault detector and circuit interrupter, and method of detecting an arc in a direct current power circuit

摘要

A direct current arc fault detector includes a first current sensor sensing an alternating current component of current flowing in a DC power circuit; a second current sensor sensing a DC component of the current; and a bandpass filter filtering the sensed AC component. A demodulating logarithmic amplifier includes an input of the filtered AC component, and an output. An integrator or minimum detector includes an input connected to the amplifier output, and an output. A processor repetitively inputs and then resets the integrator or minimum detector output, and determines an arc when, for a predetermined time: the sensed DC component being greater than a first predetermined value, and a present value of the integrator or minimum detector output being greater than or different from a previous value of such output by more than a second predetermined value, or the present value being greater than a third predetermined value.

主权项

1. A direct current arc fault detector for a direct current power circuit having a current flowing therein, said direct current arc fault detector comprising:
a first current sensor structured to sense an alternating current component of the current flowing in said direct current power circuit; a second current sensor structured to sense a direct current component of the current flowing in said direct current power circuit; a bandpass filter structured to filter the sensed alternating current component of the current flowing in said direct current power circuit; a demodulating logarithmic amplifier including an input of the filtered alternating current component of the current flowing in said direct current power circuit, and an output; an integrator or minimum detector circuit including an input electrically connected to the output of said demodulating logarithmic amplifier, and an output; and a processor structured to repetitively input and then reset the output of said integrator or minimum detector circuit, and:
(a) to increment a first arc fault accumulator when the sensed direct current component of the current flowing in said direct current power circuit is greater than a first predetermined value and a present value of the output of said integrator or minimum detector circuit is different from a previous value of the output of said integrator or minimum detector circuit by more than a second predetermined value with a first predetermined time being between the present value of the output of said integrator or minimum detector circuit and the previous value of the output of said integrator or minimum detector circuit, or otherwise to decrement the first arc fault accumulator, and to determine an arc in said direct current power circuit when the first arc fault accumulator is greater than a third predetermined value; and(b) to increment a second arc fault accumulator when the sensed direct current component of the current flowing in said direct current power circuit is greater than the first predetermined value and the present value of the output of said integrator or minimum detector circuit is greater than another previous value of the output of said integrator or minimum detector circuit by more than a fourth predetermined value with a second predetermined time, which is longer than the first predetermined time, being between the present value of the output of said integrator or minimum detector circuit and said another previous value of the output of said integrator or minimum detector circuit, or otherwise to decrement the second arc fault accumulator, and to determine the arc in said direct current power circuit when the second arc fault accumulator is greater than a fifth predetermined value.