Research Institutes of Sweden

Safety and TransportMeasurement Science and Technology – Electricity

Practical experience with optical currentsensor design

Alf-Peter Elg

19 April 2017

Research Institutes of Sweden

Safety and TransportMeasurement Science and Technology – Electricity

Optical current sensor design

• Targets and strategy

• System designs• Interferometry / Network Independent Modulation

• Phase / Birefringence modulation

• Free space propagation

• All fibre version

• Fibre development – University of Southampton• New materials

• Reference measurements at LNE

• Programming of API

• Theoretical dissemination

Research Institutes of Sweden

Safety and TransportMeasurement Science and Technology – Electricity

Targets and strategy

• Targets

• 1 – 10 kA dynamic range.

• 100 ppm measurement uncertainty

• Strategy

• Selection of system working principle

• Interferometric, birefringence and phase modulationin Sagnac and Reflective mode have been studied

• Use of 633 with 4 x higher response than @ 1300 nm

• Not available on the market – Development needed

• Investigate Tb doping of fibres for higher response

• HiBi Spun fibre – avoid effects of birefringence

Research Institutes of Sweden

Safety and TransportMeasurement Science and Technology – Electricity

System designs – Interferometric detection• Interferometer – Renishaw

• Network independent modulation - Arteche

Research Institutes of Sweden

Safety and TransportMeasurement Science and Technology – Electricity

System design – Interferometer• Built around system interferometer developed for length

measurements (Renishaw)

• Results

• 10 turns of undoped spun LoBi fibre

• High noise level

• Sensitive to acoustics and temperature

Research Institutes of Sweden

Safety and TransportMeasurement Science and Technology – Electricity

System design – Phase modulation

• System overview – reflective mode

Research Institutes of Sweden

Safety and TransportMeasurement Science and Technology – Electricity

System design - Phase modulation• Free space propagation

Research Institutes of Sweden

Safety and TransportMeasurement Science and Technology – Electricity

System design - Phase modulation

• Free space propagation

• Parameter space and modulation techniques

• Lock-in amplifier core system

• Modulation frequency and phase

• Modulation amplitude

• Polarisation state of source and at fibre entrance

• PID regulator for closed loop phase detection (NIM)

• Zero-Flux reference system for calibration at 53 Hz

• Full system control programming with LabVIEW

• Parameter space optimization performed in thissystem and then implemented in an all fibre system

Research Institutes of Sweden

Safety and TransportMeasurement Science and Technology – Electricity

System design - Phase modulation

• Insensitive to nearby currents

Research Institutes of Sweden

Safety and TransportMeasurement Science and Technology – Electricity

System design - Phase modulation

• All fibre version instead of free space propagation

• Components not available on the market

• Fibre welding needed

• SP purchased a Fujikura in 2016

• Components

• SLED Source at 650 nm, EOM

• 50/50 Splitters ordered (delivery May 5)

• Splicing – Fujikura FSM-100P

• Sensing fibre – HiBi spun undoped fibre

• Calibration and final results in May 2017.

Research Institutes of Sweden

Safety and TransportMeasurement Science and Technology – Electricity

Fibre development - University of Southampton

• Tb doping of glasses

• Possible Tb-doping in Al2O3-P2O5-SiO2, Al2O3-SiO2 orP2O5-SiO2 – A preform shown

• Spinning of fibres – pitch 3 – 7 mm

• HiBi fibres for optimum performance to counterinherent birefringence and induced by bending.

Research Institutes of Sweden

Safety and TransportMeasurement Science and Technology – Electricity

Fibre characterization - LNE

• Verdet constant

• Temperature coefficient

Research Institutes of Sweden

Safety and TransportMeasurement Science and Technology – Electricity

Fibre characterization - LNE

MeasurementsType of optical

fiberV (22.5 °C,632.8 nm)

[rad/(T∙m)]

V (SDEV)[rad/(T∙m)]

Comments

Sept – Oct2015

Spun LoBiundoped 5 mm

spin pitch3.97 0.38

1= 1.2 10 (1 °⁄ )

Nov. 2015Spun LoBi

undoped 7 mmspin pitch

4.50 0.09

June 2016 Unspun, TbAldoped HiBi 2.0* -

Very thin fibres. Cut-offwavelength 430 nm

*Birefringence obscure theFaraday Effect

Nov – Dec2016

Spun TbAl doped5 mm spin pitch 4.10 0.08

.

Spun TbAl doped7 mm spin pitch 3.94 0.55

Research Institutes of Sweden

Safety and TransportMeasurement Science and Technology – Electricity

Conclusions and outlook

• The interferometer design offer highly sensitive detection, but isaffected by perturbations as acoustics and temperature

• The phase modulation design has given a robust and sensitivesolution but need further development to be used for metrologyand possible future on-site calibration

• A concept has been developed for producing doped and/or HiBi PMspun fibre at University of Southampton

• Doping of fibre material gave no increase of the Verdet constant

• A theoretical model of the complete system has been developed – isadaptable to any configuration and allow for advanced perturbationmodelling

Future work• To further develop the all fibre system for on-site calibrations

Research Institutes of Sweden

Safety and TransportMeasurement Science and Technology – Electricity

Thank you for your attention!

The TeamFibre characterization LNE D. Istrate, et.al.System development SP - RISE G. Bideberg, S.C. Ebenhag, A.P. Elg,

A. Nilsson, M. Lindgren, P.O. HedekvistVTT J. Hällström

Theory Univ. of Chalmers P. JohannissonFibre development Univ. of Southampton Prof. J. Sahu

nLIGHT Corporation P. KiiveriSystem selection LNE, SP-RISE, VTT, Univ. of Chalmers

Univ. of Strathclyde G. Fusiek, P. Niewczas