FAQ

GENERAL

How accurate is the FOCS?
The accuracy is 0.1% of the reading in the range from 1...120% of the rated current.

Is an analysis of magnetic field distribution required to assist in selecting and placing the sensor head?
No. The system is immune to electromagnetic interference and also requires no magnetic centring.

What is the minimal current resolution?
Minimal dc current resolution depends on the FOCS configuration, i.e. for a 500kAdc type the smallest value is below 100A.
Lower rated FOCS have lower current resolutions.


MECHANICAL

Do parallel busbars or busbar corners influence on the accuracy of the FOCS?
No.

How close or far from the bus must the fiber optic cable be installed?
The sensor head housing is mounted around the bus bar (without an civil bus bar work). The size of the housing thus determines the distance of the fiber cable from the bus. The sensor performance does not depend on this distance.

How difficult is it to install the Fiber-Optic Current Sensor?
Easy, since the sensing fiber is packaged in a single-ended flexible cable by a proprietary ABB technique. This cable is accommodated in a modular sensor head housing of fiber re-enforced epoxy.
The installation is done by assembling the sensor head housing (delivered in parts) around the bus bar and inserting a single loop of the current-sensitive cable section into the housing. There is no possibility and also no need to touch and or manipulate the optical sensing fiber itself.
Preferably, installation is performed when all supplies are de-energized.

What is the mounting position of the measuring head?
Preferable the plane of the sensing head should be perpendicular to the bus bar. However, no negative effects occur from non-perpendicular orientation.

Is a special structure needed for installation?
No. The sensor is small in size and weight. It can easily be attached around the bus bar and can also easily be moved to another location if required.

What is the usual timescale for installation?
Around half a day.


ELECTRONIC

What is the FOCS power consumption?
The FOCS is supplied with 24Vdc and the power consumption is about 20W, therefore the heat dissipation is negligible small. Other supply voltages on request.

What measuring outputs does the FOCS provide?
The FOCS provides today's state of the art Industrial IT standard outputs.
Please refer to the ABB FOCS Data Sheet


CALIBRATION

How easy is calibration performed?
Each ABB FOCS is tested & calibrated in our works before shipment.
During the calibration measurements the sensor will be subjected to temperature cycles and varying load current.

Can an electrician do the calibration or will we need ABB support?
Upon delivery, the Fiber-Optic Current Sensor is completely tested and calibrated. There is no need for calibration after initial installation. Re-calibration can only be done by ABB.

Is on-site calibration required?
No. The Fiber-Optic Current Sensor is pre-calibrated and there is no need for recalibration during its lifetime.

Will it be necessary / possible to re- calibrate the FOCS after some time on site?
Yes, it is possible to re-calibrate the FOCS on site after some years of operation. Installing temporarily reference equipment performs this task. Preferably re-calibration is performed when all supplies are de-energized.
The re-calibration period depends on various environmental influences. ABB recommends to re-calibrate essential measuring equipment every 3...5 years.

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