A5045923616- Power Transformer Diagnostics and Insulation
- High voltage insulation and dielectric phenomena
- Lightning and Electromagnetic Phenomena
- Magnetic Properties and Applications
- Non-Destructive Testing Techniques
- Semiconductor materials and devices
- Power System Reliability and Maintenance
- Corrosion Behavior and Inhibition
- Advancements in Semiconductor Devices and Circuit Design
- Integrated Circuits and Semiconductor Failure Analysis
- Power Quality and Harmonics
- Electrochemical Analysis and Applications
- Ferroelectric and Negative Capacitance Devices
- Advanced Memory and Neural Computing
- Electrical and Bioimpedance Tomography
- Reliability and Maintenance Optimization
- Petroleum Processing and Analysis
- Thermal Analysis in Power Transmission
- Spectroscopy and Chemometric Analyses
- Electrohydrodynamics and Fluid Dynamics
- Electrostatic Discharge in Electronics
- Advanced Electrical Measurement Techniques
- MXene and MAX Phase Materials
- Probabilistic and Robust Engineering Design
- Water Quality Monitoring and Analysis
University of Manchester
2005-2024
National Grid (United States)
2007-2022
GlobalFoundries (Germany)
2015-2022
Université d'Artois
2022
Physical Measurement Laboratory
2020
National Institute of Standards and Technology
2020
National Grid (United Kingdom)
2010-2019
Fraunhofer Institute for Photonic Microsystems
2009-2016
GlobalFoundries (United States)
2012
University of Liverpool
2005
With the ability to engineer ferroelectricity in HfO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> thin films, manufacturable and highly scaled MFM capacitors MFIS-FETs can be implemented into a CMOS-environment. NVM properties of resulting devices are discussed contrasted existing perovskite based FRAM.
We successfully implemented a one-transistor (1T) ferroelectric field effect transistor (FeFET) eNVM into 28nm gate-first super low power (28SLP) CMOS technology platform using two additional structural masks. The electrical baseline properties remain the same for FeFET integration and JTAG-controlled 64 kbit memory shows clearly separated states. High temperature retention up to 250 °C is demonstrated endurance 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML"...
We report on the most aggressively scaled ferroelectric field effect transistor so far. These were successfully fabricated using Si:HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> in a 28 nm HKMG stack (TiN/Si:HfO /SiO /Si). For ± 5 V program/erase operation with pulses as short 20 ns, reliable threshold voltage shifts observed resulting memory window of about 0.9 V. further demonstrate endurance characteristics matching demands...
Recent discovery of ferroelectricity in HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> thin films paved the way for demonstration ultra-scaled 28 nm Ferroelectric FETs (FeFET) as non-volatile memory (NVM) cells [1]. However, such small devices are inevitably sensible to granularity polycrystalline gate oxide film. Here we report first time evidence single ferroelectric (FE) domain switching scaled devices. These properties sensed...
A different approach to the study of surface tracking reveals a new view oil-pressboard interface and suggests link between electric double layer boundary layer.
This paper presents experimental research of creepage discharge on insulation barriers in power transformers. Using point-to-plate electrode configurations under AC voltages is studied for both single flashover breakdown and partial induced failure modes. It confirmed that the dielectric strength oil gap will not be reduced with introducing dry new pressboard surface into gap, indeed voltage hardly compromised by aged up to 3% moisture. However, increased moisture content reduces inception...
Analysis of real operating condition revealed that HVDC transformers experience combined effect DC biased AC electric field. The dynamics pressboard particle in contaminated transformer oil under the influence DC, and field has been investigated this paper. Different levels concentrations are tested at different applied voltages. Optical images particles accumulation together with conduction current have recorded during experiments. A complete bridge between electrodes cellulose were...
Frequency response analysis (FRA) is an effective diagnostic tool for detecting transformer winding movements. Various FRA traces can be measured from a set of terminals each which relate to different test connection scheme. Practical considerations and time dictate that only some the connections are used, currently there no standard connection. This paper presents comparison three measurement widely employed in industry today, namely: end-to-end voltage ratio, input admittance transfer...
The paper investigates the effect of age related failure power transformers on identification most critical transformer sites for system reliability. end-of-life model is modified first to integrate loading conditions effect. adopted Arrhenius-Weibull probability distribution, which represents thermal stress transformer's failure, was compared with commonly used Gaussian distribution model. sensitivity results uncertainty in parameters thoroughly assessed, and acceptable level determined....
Knowledge of the condition power transformer winding insulation paper is fundamental to making optimum asset replacement decisions in industry. The ability assess aged Kraft quickly and non-destructively using portable instrumentation would significantly increase opportunities for gaining this knowledge. Insulation degrades over time in-service its degree polymerization (DP) reduces, eventually affecting mechanical strength. At low DP levels may start disintegrate risk electrical breakdown...
The space charge accumulation can affect the dielectric performance of oil-impregnated pressboard in convertor transformers. In this paper, behaviour 1mm thick impregnated pressboards is investigated by means pulsed electroacoustic method. dried are separately fresh oil and service aged as comparison. distributions under ±15 kV/mm ±25 at room temperature. homocharge injection be observed for all samples, which much more significant samples. amount injected charges depth bulk closely related...
IEC 60897 (determination of lightning impulse breakdown voltage, LIBV) and 61294 partial discharge inception PDIV) are designed with the purpose evaluating insulating liquids' electrical property in a divergent field, their current versions have existed for about two decades without revision. In view interest use natural synthetic esters transformers, suitability to evaluate new liquids potential revisions discussed here. Through comparative tests mineral oil esters, it is proposed that...
Statistical lifetime modeling is of importance for replacement management aged power transformers. Survival data are recognized as important failure in improving the accuracy level models since transformer failures rare events and most units still operating condition. This paper argues that differentiating random aging-related also important. Different requisites analyzed compared through Monte Carlo simulations. The life-cycle model can be built by combining models. A case study presented...
Contaminated transformer oil has been tested under non uniform electric fields and the effect of different electrode systems presented in this paper. Three were examined i.e. DC, AC DC biased AC. These experiments revealed that with all electrodes arrangements, contaminated particles always formed bridges between field. The thicker more attracted field (spherical electrode) than a divergent (needle-plane).
The reliability of oil-pressboard insulation system used in high voltage direct current (HVDC) convertor transformers can be affected by the presence space charge. In this paper, charge behaviors a 0.5 mm thick oil film combined with 1mm impregnated pressboard have been investigated pulsed electroacoustic (PEA) technique under 12 kV/mm and 20 at room temperature for both short term long time tests. Two types different aging status were comparison. results show that peak is quickly formed...
The thermal design of a power transformer determines its lifetime and loading capability, so correct modelling liquid flow temperature distributions in the winding is vital importance. Existing standards widely used simple calculation models can seriously under/overestimate hotspot temperatures under certain circumstances. In this paper, physical model representing disc-type forced directed cooling mode are investigated experimentally using Particle Image Velocimetry (PIV) measurement system...
In the context of thermal performance and lifetime, it is greatly important to predict magnitude location 'hot-spot' temperature inside a transformer. Various calculation approaches have been developed in attempt accurately hot-spot, including so-called 'network models'. terms methodology used network modelling, complex pattern oil ducts passes winding reduced matrix simple hydraulic channel approximations, where empirical analytical expressions are employed hydraulically thermally describe...
The effect of cellulose particles contamination on transformer oil has been investigated. Different sizes and concentration levels fibres were used to contaminate the for experiments. conduction current was measured using electrodes 10 mm diameter with a gap optical microscopic images bridge creation between also recorded. thickened increasing level bridging time shortened as voltage increased. increased voltage. Smaller size had stronger bond while creating higher current.
We report the fabrication of highly scaled sub-0.3 μm ferroelectric field-effect transistors on basis HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . The electrical properties 9 nm thick Si-doped films depending silicon content and annealing temperature were investigated. most suitable conditions for emergence ferroelectricity identified. verified up to temperatures 170°C. N-channel MFIS-FETs...
The ultimate life of a power transformer is critically governed by the condition its insulation paper which undergoes thermal degradation during operation. A model has been published in IEC loading guide 60076-7 and can be used to calculate windings' hot-spot temperature based on operating conditions parameters, assess insulating paper's aging rate. However, accuracy greatly affected generally unknown factor. In this paper, utilizing samples scrapped transformers degree polymerization (DP)...
This work studies the sensitivity of frequency response analysis (FRA) method in detecting different types deformations on a 6.6 kV plain disc type transformer winding. Winding such as axial displacements and inter-turn faults are experimentally simulated measured FRA results presented. A high transformer-winding model is developed to investigate for these winding deformations. comparison carried out good agreement shown between calculated results.
A portable fiber-optic spectroscopic system (TRANSPEC) has been developed for nondestructive measurement of aged transformer insulating paper. Following successful degree polymerization (DP) a range transformer-aged paper samples, the now shown to separate oil and information DP in oil-wetted samples. In addition, be capable prediction both water content high accuracy, is also identifying quantifying different species. Spectroscopic measurements have used together with gravimetric adsorption...
Two important factors affecting the characteristics of 'hot-spot' inside an oil cooled transformer winding are total amount being supplied into and its flow distribution across discs arrangement. The latter is unavoidably related to hydraulic network ducts where combining or dividing at duct junctions. expressions describing junction pressure loss often contain a significant number empirical parameters obtained by limited experimental tests. Applicability these should therefore be carefully...