A fiber-optic current sensor (FOCS) is a

current sensor In electrical engineering, current sensing is any one of several techniques used to measure electric current. The measurement of current ranges from picoamps to tens of thousands of amperes. The selection of a current sensing method depends on ...

for measuring

direct current Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or even ...

. By using a single-ended optical fiber around the current conductor that utilizes the magneto-optic effect (

Faraday effect The Faraday effect or Faraday rotation, sometimes referred to as the magneto-optic Faraday effect (MOFE), is a physical magneto-optical phenomenon. The Faraday effect causes a polarization rotation which is proportional to the projection of the ...

), FOCS measures uni- or bidirectional DC currents of up to 600 kA within ±0.1% of the measured value. Because it does not need a magnetic yoke, an FOCS is smaller and lighter than

Hall effect The Hall effect is the production of a voltage difference (the Hall voltage) across an electrical conductor that is transverse to an electric current in the conductor and to an applied magnetic field perpendicular to the current. It was disco ...

current sensors, and suffers no reduction in accuracy due to saturation effects. Because magnetic field sensing is distributed around circumference, it is unaffected by stray magnetic fields, and there is no need for magnetic centering. It also does not need recalibration after installation or during its service life. Because the optical fiber is inherently insulating, electrical isolation is easier to maintain. The optical phase detection circuit, light source and digital signal processor are contained within the sensor electronics; this technology has been proven in highly demanding applications such as navigation systems in the air, on land and at sea.

Applications

In 2013,

ABB ABB Ltd. is a Swedish- Swiss multinational corporation headquartered in Zürich, Switzerland. The company was formed in 1988 when Sweden's Allmänna Svenska Elektriska Aktiebolaget (ASEA) and Switzerland's Brown, Boveri & Cie merged to crea ...

launched a 420 kV Disconnecting Circuit Breaker (DCB) with integrated FOCS. Since one FOCS replaces many conventional

current transformer A current transformer (CT) is a type of transformer that is used to reduce or multiply an alternating current (AC). It produces a current in its secondary which is proportional to the current in its primary. Current transformers, along with volt ...

s, engineering and design of the substation is simplified. By reducing the material needed, including insulation, a 420 kV DCB with integrated FOCS can reduce a substation's

footprint Footprints are the impressions or images left behind by a person walking or running. Hoofprints and pawprints are those left by animals with hooves or paws rather than feet, while "shoeprints" is the specific term for prints made by shoes. The ...

by over 50% compared to the conventional solution of live tank breakers with

disconnector In electrical engineering, a disconnector, disconnect switch or isolator switch is used to ensure that an electrical circuit is completely de-energized for service or maintenance. They are often found in electrical distribution and industrial ap ...

s and

References

{{Reflist Sensors Electrical components Electric power distribution Electric power systems components de:FOCS