About
19
Publications
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Introduction
Current institution
Additional affiliations
February 2018 - June 2018
Position
- PostDoc Position
Description
- Development of a novel concept for fiber optic hotspot/ quench detection in high temperature superconductors.
July 2015 - February 2018
Position
- PhD Student
Description
- My PhD research concentrates on the development of a monitoring system for distribution and power transformers. In detail, I develop fiber optic sensors measuring dissolved hydrogen in transformer oil.
January 2014 - November 2014
Publications
Publications (19)
The recent adoption of high-T c superconductor (HTS) wires for ultra-high field magnet windings provide great promise for future applications, such as high-power generators and Tokamak fusion reactors. However, an open issue with the use of HTS is the challenge of rapidly detecting a hot spot which could lead to a quench. Optical fiber sensors have...
This paper reports on a method for strain calibration of fiber optic sensors which have been adhesively bonded to a structural member. Generally, the coefficient of strain transfer (kST) can be used to calibrate the strain sensitivity of the surface bonded FBG. Here we propose an alternative method to determine kST which is based solely on observin...
The energy stored in a 2 MW motor coil, or a generator field winding, may be as high as 25 kJ (for a 5 H field windings with 100 A current) and this energy release would be catastrophic if rapidly released. Therefore quench detection and protection in large machine coils is a significant concern. In this work, the feasibility of uncoated Fiber Brag...
This paper reports on the characterization of a palladium (Pd)-based fiber-optic hydrogen (H
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) sensor for health monitoring of distribution and power transformers in the electrical grid. The sensor consists of a Pd foil, which expands due to H
<su...
We developed and optimized a new fiber optic sensor using palladium foils attached to optical fiber Bragg gratings (FBG) for hydrogen measurements. Fifteen in parallel processed sensors were characterized and qualified in two custom tailored experimental set ups and their response to a 5% hydrogen/nitrogen gas mixture and the same gas bubbled troug...
Online diagnostics of distribution transformers have traditionally not been performed due to the lack of financial benefit. The current cost of the systems used make it infeasible for distribution transformers. However, with NZ's aging distribution network and introduction of new technologies such as photovoltaic systems and electric vehicle chargi...
This paper reports on the sensitivity improvement of palladium (Pd) based fiber optic hydrogen sensors. The expansion of Pd undergoing hydrogen absorption transduces strain in a suitable sensing element. The sensors reported here are based on fiber Bragg grating (FBG) strain sensors with a Pd foil hydrogen sensing element. The hydrogen sensitivity...
We propose a distributed hydrogen sensing system based on ϕ-OTDR and a novel coating configuration with fiber adhesively bonding to palladium foils. An ultra-high sensitive distributed hydrogen sensing with 5 cm spatial resolution is demonstrated.
This paper reports on the sensitivity optimization of palladium based hydrogen sensors. The transduction mechanism is the volumetric expansion of palladium, leading to induced strain in a strain sensing element. Absorption of hydrogen in the palladium lattice causes expansion, which can be measured using strain sensors attached to the palladium. Th...
This paper presents a palladium foil based hydrogen sensor using a fiber Bragg grating and recent advances in its manufacturing methods and their influence on the sensitivity.
This paper presents a palladium foil based hydrogen sensor using a fiber Bragg grating and recent advances in its manufacturing methods and their influence on the sensitivity.
Hydrogen evolution, identified by dissolved gas analysis (DGA), is commonly used for fault detection in oil immersed electrical power equipment. Palladium (Pd) is often used as a sensing material due to its high hydrogen absorption capacity and related change in physical properties. Hydrogen is absorbed by Pd causing an expansion of the lattice. Th...
Hydrogen evolution, identified by dissolved gas analysis (DGA), is commonly used for fault detection in oil immersed electrical power equipment. Palladium (Pd) is often used as a sensing material due to its high hydrogen absorption capacity and related change in physical properties. Hydrogen is absorbed by Pd causing an expansion of the lattice. Th...
This paper reports on the development and evaluation of fiber optic hydrogen sensors based on fiber Bragg gratings. The sensors were tested in a newly developed measurement system for long term experiments of fiber optic gas sensors. Two types of palladium metal sensors were manufactured; sputter coated and a new concept using palladium foil. The s...
This paper reports on the development, and evaluation, of fiber optic hydrogen sensors based on fiber Bragg gratings (FBG) and an experimental measurement system for long term experiments of fiber optic gas sensors. Two types of palladium metal sensors were manufactured; sputter coated and modified palladium foil with 20 and 100 μm thickness. The r...
We report on the development of optical fiber sensors (OFS) based on palladium and fiber Bragg gratings. Furthermore, we introduce a newly developed measurement setup for long term experiments of OFS gas sensors. We present two different types of palladium sensors; (a) with sputter coated palladium, (b) with palladium foil adhesively bonded to the...
Selective laser melting is a promising additive manufacturing technology for the production of complex metal components. The technique uses metallic powder as a starting material and a laser for melting and building-up parts layer by layer. One crucial factor influencing the process stability and therefore the part quality is the shielding gas flow...
Questions
Questions (2)
Hi,
I want to calculate the diffusion of a gas into a solid.
The problem/model:
the solid is a (compared to the thickness) long plate. The thickness is 2*l. The diffusion will happen from both sides, it is not a membrane. To simplify the model I halfed the solid and added a diffusion barrier at x=l. The concentration of the gas is constant c=c_0. In the beginning (t_0) the gas concentration in the solid is 0. at t_1(infinity) the gas concentration should be at an equilibrium with its surrounding.
What I want to calculate:
I would need to calculate the time t at which the concentration at x=l reacheas certain limits.
My approach was using the heat function (du/dt=D*d^2u/dx^2).
I tried to solve with the greens function and seperation of variables, but it takes me quite a while and I am still far from the solution. I set my boundary conditions as: with u(x,t): u(0,t)=c_0, u(l,0)=0, u(l,t→inf)=c_0 .
Does have an example on how to solve that issue?
Kind reagrds,
Max
I am doing long term measurements of fiber bragg gratings with an Anritsu MS9740A. The device is calibrated (optical alignment with DFB laser, wavelength calibration with internal light source). The room temperature is stable at 20±0.5°C. This room temperature fluctuation causes fluctuations/ drifts in the detected peak wavelength of ±30 pm. The peak is detected with a algorithm using a quadratic fit over the 300nm. and is highly accurate. Slides 1-4 show the results of a temperature controlled DFB laser (S3FC1550 from thorlabs) and a temperature controlled FBG.
I contacted Anritsu Australia with that issue and they say the equipment is not made for long term measurements and the fluctuation are in spec.
I then compared my MS9740A to another unit of the same model from another group. Both calibrated before measurements. Slide5 shows the results recorded over the last day. The loan OSA has a significantly smaller drift then my OSA. The drift of the loaner is about 10-15pm and similar to the temperature drift, whereas the drift of my OSA is 40 pm and inverse to the temperature drift.
So the questions I have are:
Have you experienced similar stability problems with Anritsu optical spectrum analysers or Anritsu equipment in general? Is that fluctuation normal and acceptable? Is the difference in drift/fluctuation (comparing two identical OSA) normal and acceptable?
