Instantaneous arc fault light detector with resistance to false tripping

An improved switchgear comprising:

• a light detector for generating a light detector signal in response to light emitted by an arcing fault;
• a differentiator circuit for receiving the light detector signal and creating a differentiated light detector signal;
• a comparator circuit for comparing the differentiated light detector signal and a reference signal and generating a comparator output signal when the differentiated light detector signal exceeds the reference signal, thereby indicating a detected arc fault;
• and
• an electrical switch responsive to the comparator circuit output signal for disconnecting an arc fault source voltage.

An improved switchgear comprising:

• a light detector for generating a light detector signal in response to light emitted by an arcing fault;
• a differentiator circuit for receiving the light detector signal and creating a differentiated light detector signal;
• a comparator circuit for comparing the differentiated light detector signal and a reference signal and generating a comparator output signal when the differentiated light detector signal exceeds the reference signal;
• a second comparator circuit for comparing the light detector signal to a second reference signal and generating a second comparator output signal when the light detector signal exceeds the second reference signal;
• a logic circuit for receiving the comparator output signal and the second comparator output signal and generating a logic circuit output signal when the comparator output signal and the second comparator output signal each exceed their respective reference signal value, thereby indicating a detected arc fault;
• and
• an electrical switch responsive to the logic circuit output signal for disconnecting an arc fault source voltage.

An arc fault detection circuit for distinguishing light emitted by an arcing fault from light emitted by other sources, the arc fault detection circuit comprising:

• a light detector set to high sensitivity for generating a light detector signal in response to detected light including light emitted by an arcing fault;
• a differentiator circuit for receiving the light detector signal and creating a differentiated lift detector signal;
• and
• a comparator circuit for comparing the differentiated light detector signal and a reference signal, and generating a comparator output signal when the differentiated light detector signal exceeds the reference signal, thereby indicating a detected arc fault.

An arc fault detection circuit for distinguishing light emitted by an arcing fault from light emitted by other sources, the arc fault detection circuit comprising:

• a light detector set to high sensitivity for generating a light detector signal;
• a differentiator circuit for receiving the light detector signal, differentiating the light detector signal with respect to a particular characteristic of light emitted by an arcing fault and creating a differentiated light detector signal;
• and
• a comparator circuit for comparing the differentiated light detector signal and a reference signal, and generating a comparator output signal when the differentiated light detector signal exceeds the reference signal, thereby indicating a detected arc fault.