Patent ID: 7035068

Claim:
Apparatus for detecting an arcing fault at a component of an electric power system, said arcing fault generating light at a first predetermined wavelength in the presence of light at a second wavelength from another source which may include said first predetermined wavelength, said second wavelength being different from said first predetermined wavelength, said apparatus comprising: a light source providing modulated light at the second wavelength and at a first frequency; an optical fiber including a first end, a gathering portion and a second end, the first end of said optical fiber receiving the modulated light from said light source, the gathering portion being proximate said component and receiving gathered light including some of said light at a first predetermined wavelength and some of said light at a second wavelength from another source, the second end of said optical fiber including said modulated light and said gathered light; a splitter receiving said modulated light and said gathered light from the second end of said optical fiber and splitting said modulated light and said gathered light into a first light beam and a second light beam; a first filter extracting from said first light beam a first filtered light beam including a first wavelength bandwidth having said first predetermined wavelength; a first detector generating a first sensed light electrical signal from said first filtered light beam; a second filter extracting from said second light beam a second filtered light beam including a second wavelength bandwidth not having said first predetermined wavelength; a second detector generating a second sensed light electrical signal from said second filtered light beam; a third filter extracting from said second sensed light electrical signal a third electrical signal representative of said some of said light at a second wavelength from another source and not including said modulated light; and means for generating an arcing signal in response to a predetermined relationship between said first sensed light electrical signal and said third electrical signal.