Application of RVM technique to study the polarisation and depolarisation characteristics associated with thermal ageing of epoxy mica composite
The Recovery voltage measurement technique was used to investigate the polarization processes in the dielectric to assess the insulation ageing. Two different types of insulation systems are evaluated, resin poor and resin rich mica composites. This paper presents and discusses the data on polarization and depolarization characteristics of thermally degraded epoxy mica composites. Beyond polarization spectrum, additional spectra slope spectrum and peak time spectrum of Recovery voltage measurement technique were used. The combined spectrum: a plot of initial slope (V/s) against Max. Recovered voltage, Vr(V) showed a clear peak in the form of “bun” and “nose” distinctly which probably could give more information on the bigger polar species and the polarization phenomena. Multiple peaks are seen in case of thermally aged samples which clearly exhibit the degradation phenomena.
Polarization and depolarization current of linear low density polyethylene-natural rubber nanocomposite subjected to electrical tracking and moisture
Polymeric nanocomposites are widely used for high voltage outdoor 
insulating application due to their efficient electrical performance. Recently, SiO2, 
TiO2 and MMT nanofillers are used as fillers because there are listed as the main 
nanofiller commonly used in electrical engineering due to the increases of effective 
activation energy. Natural rubber (NR) is used because the nature of the interphase is 
found to affect viscoelasticity and it develops several interphases with the Linear 
Low-Density Polyethylene (LLDPE) matrix. This thesis presents the outcome of an 
experimental study which has been carried out to determine the conductivity level 
and dielectric response function of the LLDPE-NR compound, filled with different 
amount of SiO2, TiO2 and MMT nanofillers using Polarization and Depolarization 
Current (PDC) measurement technique. LLDPE and NR with the ratio composition 
of 80:20 were selected as a base polymer. The PDC testing was done on samples at 
various conditions: without any defect (normal condition), wet condition (moisture 
absorption) and after electrical tracking effect condition based on BS EN 
60587:2007 standards. One of the problems associated with outdoor polymeric 
insulators is the tracking of the surface which can directly influence the reliability of 
the insulator. The amount of water content can be used to monitor the dielectric 
quality of insulation and as an indicator of possible deterioration for outdoor 
degradation. Besides PDC, surface morphology analysis using FESEM was also 
conducted to study the changes in physical structure which can explain the 
conductivity and response function. This research found that an addition of certain 
weight percentage of nanofiller and NR into the LLDPE improved conductivity level 
of the insulator. LLDPE-NR/TiO2 at 5 wt% has become the best sample in terms of 
the lowest conductivity in normal and under electrical tracking effect. Besides, this 
sample has the fastest time response under electrical tracking and moisture 
condition. This investigation has successfully identified the PDC pattern, 
conductivity and dielectric response function of LLDPE-NR nanocomposite. Results 
show that different compositions as well as the surface physical conditions affect the 
PDC measurement results.
Physical Ageing of the Research Reactor Core Structural Materials Due to Neutron Irradiation Exposure: a Review
A research reactor (RR) is a  nuclear reactor that has function to generate and utilize neutron flux and radiation ionization for  research purposes and industrial applications. More than 60% of current operating RRs have  been operated for 30 years or more. As the time passes, the functional capabilities of structures,  systems and components (SSCs) of those RRs deteriorate by physical ageing, which can be  caused by neutron irradiation exposure such as irradiation induced dislocation and  microstructural changes. To extend the lifetime and/or to avoid unplanned outages, ageing on  the safety related SSCs of RRs need to be properly managed. An ageing management is a  strategy to engineer, operate, maintenance, and control SSC degradation within acceptable limits. The purpose of this study is to review physical ageing of the core structural materials of  the RRs caused by neutron irradiation exposure. In order to achieve this objective, a wide range  of literatures are reviewed. Comprehensive discussions on irradiation behaviors are limited only  on reactor vessel and core support structure materials made from zirconium and beryllium as  well as their alloys, which are widely used in RRs. It is found that the stability of the mechanical  properties of zirconium and beryllium as well as their alloys was mostly affected by the neutron  fluences and temperatures.