FIBER OPTIC SENSOR SYSTEM FOR STRESS MONITORING IN POWER CABLES

FIBER OPTIC SENSOR SYSTEM FOR STRESS MONITORING IN POWER CABLES:

FIBER OPTIC SENSOR SYSTEM FOR STRESS MONITORING IN POWER CABLES Presented by Shambhu.C S7 A R.No.39 COLLEGE OF ENGINEERING CHENGANNUR

Contents:

Contents What is OFS Basics of Optical fiber Raman Backscattering Fiber Bragg grating Stress monitoring by OFS Advantages Conclusion COLLEGE OF ENGINEERING CHENGANNUR 2

FIBER OPTIC SENSORS:

FIBER OPTIC SENSORS Optical fiber sensor : A sensor that measures a physical quantity based on its modulation on the intensity , spectrum , phase , or polarization of light traveling through an optical fiber. To measure physical parameters such as strain, temperature, pressure, velocity, and acceleration Optical fibers : strands of glass that transmit light over long distances (wire in electrical systems) Light : transmitted by continuous internal reflections in optical fibers (electron in electrical systems) 3 COLLEGE OF ENGINEERING CHENGANNUR

OPTICAL FIBRE:

OPTICAL FIBRE COLLEGE OF ENGINEERING CHENGANNUR 4

Total Internal Reflection:

Total Internal Reflection COLLEGE OF ENGINEERING CHENGANNUR 5

Singlemode and multimode optical fibers:

Singlemode and multimode optical fibers COLLEGE OF ENGINEERING CHENGANNUR 6

PRINCIPLE:

PRINCIPLE Procedure in Fiber optic sensor systems : Transmit light from a light source along an optical fiber to a sensor , which sense only the change of a desired environmental parameter . The sensor modulates the characteristics (intensity, wave length, amplitude, phase) of the light. The modulated light is transmitted from the sensor to the signal processor and converted into a signal that is processed in the control system. The properties of light involved in fiber optic sensors: reflection, refraction and interference 7 COLLEGE OF ENGINEERING CHENGANNUR

TYPE OF FIBER OPTIC SENSORS:

TYPE OF FIBER OPTIC SENSORS Fiber optic sensors can be divided by: Places where sensing happens Extrinsic or Hybrid fiber optic sensors Intrinsic or All-Fiber fiber optic sensors 8 COLLEGE OF ENGINEERING CHENGANNUR

Extrinsic or Hybrid Fiber Optic Sensors:

Extrinsic or Hybrid Fiber Optic Sensors Consist of optical fibers that lead up to and out of a “ black box ” that modulates the light beam passing through it in response to an environmental effect. Sensing takes place in a region outside the fiber. 9 COLLEGE OF ENGINEERING CHENGANNUR

Intrinsic or All-Fiber Optic Sensors:

Intrinsic or All-Fiber Optic Sensors Sensing takes place within the fiber itself. The sensors rely on the properties of the optical fiber itself to convert an environmental action into a modulation of the light beam passing through it. 10 COLLEGE OF ENGINEERING CHENGANNUR

Raman Backscattering:

Raman Backscattering Inelastic scattering (whereas Rayleigh scattering is elastic and is predominant) Occur with a change in vibrational, rotational or electronic energy of a molecule Stokes scattering :the atom or molecule absorbs energy; the emitted photon has less energy than the absorbed photon . Anti-Stokes scattering :the atom or molecule loses energy; the emitted photon has more energy than the absorbed photon. COLLEGE OF ENGINEERING CHENGANNUR 11

Comparison of Rayleigh, Stokes and anti-Stokes scattering:

Comparison of Rayleigh, Stokes and anti-Stokes scattering COLLEGE OF ENGINEERING CHENGANNUR 12

Fiber Bragg grating :

Fiber Bragg grating wavelength-specific reflector constructed in a short segment of optical fiber reflects particular wavelengths of light and transmits all others periodic variation to the refractive index of the fiber core COLLEGE OF ENGINEERING CHENGANNUR 13

Schematic of the fiber stress sensor system :

Schematic of the fiber stress sensor system COLLEGE OF ENGINEERING CHENGANNUR 14

Working:

Working Supercontinuum(range:400-1600nm) obtained by pumping a PCF by a nanosecond microchip laser( λ =1064nm,t=1ns, E pulse =10 µ J ). Supercontinuum illuminates FBG. Part of laser radiation(1064 or 532nm) is coupled to standard single mode fiber for measuring time resolved raman backscattering signals. COLLEGE OF ENGINEERING CHENGANNUR 15

Temperature measurement:

Temperature measurement Time resolved Raman backscatttering used. anti-Stoke photons temp dependent(unlike Stoke photons) Ratio of anti-Stoke and Stoke intensity gives temp Both detected by 2 photomultiplier tubes combined with a bandpass filter. Time resolved single photon counting. Spatial resolution:5cm COLLEGE OF ENGINEERING CHENGANNUR 16

Squeezing measurement:

Squeezing measurement Increased pressure on power cable(therefore also on the fiber) results in loss of Backscattered Raman light. By measuring time resolved Raman intensities gives spatially resolved information on squeezing. Spatial resolution is 5cm. COLLEGE OF ENGINEERING CHENGANNUR 17

Backscattered stokes light of an 18m long fiber squeezed at position 16m. :

Backscattered stokes light of an 18m long fiber squeezed at position 16m. COLLEGE OF ENGINEERING CHENGANNUR 18

Bending and Torsion(by FBG):

Bending and Torsion(by FBG) Supercontinuum provides the broadband source. FBG provided by point to point femtosecond laser inscription. The FBG reflects a defined wavelength which is given by the grating period Δ & the effective index n eff of refraction: λ bragg =2.n eff . Δ In this case, a FBG for the wavelength = 1550.8nm was written by the femtosecond laser( λ =800nm, f=1kHz, t =130fs, E pulse =1µJ ) COLLEGE OF ENGINEERING CHENGANNUR 19

Bending and Torsion(by FBG) cont.:

Bending and Torsion(by FBG) cont. Bending the fiber which is integrated into the power cable, results in a change of the grating period and thus different wavelengths from the broadband source will be reflected and can easily monitored . Bragg wavelength is given as: λ bragg =2.n eff . Δ n eff - effective index of refraction Δ - grating period COLLEGE OF ENGINEERING CHENGANNUR 20

A FBG sensor was glued on the jacket of a power cable and the reflected light was measured for different cable positions:

A FBG sensor was glued on the jacket of a power cable and the reflected light was measured for different cable positions COLLEGE OF ENGINEERING CHENGANNUR 21

What Does F.O.S. Look Like?:

What Does F.O.S. Look Like? Strain Gage Embeddable Strain Gage Pressure Transducer Displacement Transducer Temperature Transducer 22 COLLEGE OF ENGINEERING CHENGANNUR

ADVANTAGES:

A DVANTAGES Immunity to electromagnetic interference (EMI) and radio frequency interference (RFI) All- passive dielectric characteristic: elimination of conductive paths in high-voltage environments Inherent safety and suitability for extreme vibration and explosive environments Tolerant of high temperatures (>1450 C) and corrosive environments Light weight, and small size High sensitivity 23 COLLEGE OF ENGINEERING CHENGANNUR

GENERAL USES:

G ENERAL U SES Measurement of physical properties such as strain, displacement, temperature, pressure, velocity, and acceleration in structures of any shape or size Monitoring the physical health of structures in real time Damage detection Used in multifunctional structures , in which a combination of smart materials, actuators and sensors work together to produce specific action 24 COLLEGE OF ENGINEERING CHENGANNUR

Conclusion:

Conclusion The sensor system described in this paper will be installed into a 6 MW wind power plant for monitoring stress in power cables. Optical fiber sensors are superior to electric sensors in terms of sensitivity, immunity to EM radiation.. They can work at very high temperatures. Constantly evolving technology. It has got numerous applications. COLLEGE OF ENGINEERING CHENGANNUR 25

References:

References Fiber Optic Sensor System for Stress Monitoring in Power Cables by J. Burgmeier, W. Schippers, and W. Schade Clausthal University of Technology, LaserAnwendungsCentrum, Energy Campus, Am Stollen 19, 38640 Goslar, Germany Optical Fiber Communications : John M.Senior www.bluerr.com/images/Overview_of_FOS2.pdf COLLEGE OF ENGINEERING CHENGANNUR 26

THANK YOU:

THANK YOU COLLEGE OF ENGINEERING CHENGANNUR 27

Questions…:

Questions… COLLEGE OF ENGINEERING CHENGANNUR 28