Synthesis of a base-stock for electrical insulating fluid based on palm kernel oil

This report presents a method for synthesizing base-stock for green industrial product from a vegetable oil with a high composition of unsaturated fatty acids. Epoxy methyl ester of palm kernel oil was synthesized from laboratory purified palm kernel oil using a two-step reaction and the products were used as a base-stock for green electrical insulation fluid. Epoxidized palm kernel oil was first prepared through epoxidation reaction involving purified palm kernel oil, acetic acid and hydrogen peroxide in the presence of amberlite as catalyst which lasted for 4 h. It was then followed by transesterification reaction involving the epoxidized product and methanol in the presence of sodium hydroxide as catalyst to synthesize the corresponding epoxy methyl ester. The thermal and electrical breakdown properties of the epoxy methyl ester demonstrated significantly improved properties for its use as raw material for bio-based industrial products such as electrical insulation fluids

Exposure Path Perceptions and Protective Actions in Biological Water Contamination Emergencies

This study extends the Protective Action Decision Model, developed to address disaster warning responses in the context of natural hazards, to “boil water” advisories. The study examined 110 Boston residents’ and 203 Texas students’ expectations of getting sick through different exposure paths for contact with contaminated water. In addition, the study assessed respondents’ actual implementation (for residents) or behavioral expectations (for students) of three different protective actions – bottled water, boiled water, and personally chlorinated water – as well as their demo-graphic characteristics and previous experience with water contamination. The results indicate that people distinguish among the exposure paths, but the differences are small (one-third to one-half of the response scale). Nonetheless, the perceived risk from the exposure paths helps to explain why people are expected to consume (or actually consumed) bottled water rather than boiled or personally chlorinated water. Overall, these results indicate that local authorities should take care to communicate the relative risks of different exposure paths and should expect that people will respond to a boil water order primarily by consuming bottled water. Thus, they should make special efforts to increase supplies of bottled water in their communities during water contamination emergencies

The Cholecystectomy As A Day Case (CAAD) Score: A Validated Score of Preoperative Predictors of Successful Day-Case Cholecystectomy Using the CholeS Data Set

Background Day-case surgery is associated with significant patient and cost benefits. However, only 43% of cholecystectomy patients are discharged home the same day. One hypothesis is day-case cholecystectomy rates, defined as patients discharged the same day as their operation, may be improved by better assessment of patients using standard preoperative variables. Methods Data were extracted from a prospectively collected data set of cholecystectomy patients from 166 UK and Irish hospitals (CholeS). Cholecystectomies performed as elective procedures were divided into main (75%) and validation (25%) data sets. Preoperative predictors were identified, and a risk score of failed day case was devised using multivariate logistic regression. Receiver operating curve analysis was used to validate the score in the validation data set. Results Of the 7426 elective cholecystectomies performed, 49% of these were discharged home the same day. Same-day discharge following cholecystectomy was less likely with older patients (OR 0.18, 95% CI 0.15–0.23), higher ASA scores (OR 0.19, 95% CI 0.15–0.23), complicated cholelithiasis (OR 0.38, 95% CI 0.31 to 0.48), male gender (OR 0.66, 95% CI 0.58–0.74), previous acute gallstone-related admissions (OR 0.54, 95% CI 0.48–0.60) and preoperative endoscopic intervention (OR 0.40, 95% CI 0.34–0.47). The CAAD score was developed using these variables. When applied to the validation subgroup, a CAAD score of ≤5 was associated with 80.8% successful day-case cholecystectomy compared with 19.2% associated with a CAAD score >5 (p < 0.001). Conclusions The CAAD score which utilises data readily available from clinic letters and electronic sources can predict same-day discharges following cholecystectomy

Space Charge Formation and its Modified Electric Field under Applied Voltage Reversal and Temperature Gradient in XLPE Cable

The results of space charge evolution in cross-linked polyethylene power cables under dc electrical field at a uniform temperature and during external voltage polarity reversal are presented in the paper. A mirror image charge distribution was observed in the steady state, but the pre-existing field altered the way in which the steady state charge distribution was formed from that obtaining when the cable was first polarized. Polarity reversing charge was generated in the middle of the insulation and moved towards the appropriate electrodes under the influence of a field in excess of the maximum applied field. Our results show that the mirror effect is a steady state effect that is due to crossinterface currents that depend only on the interface field and not its polarity. Measurements on cable sections with an elevated mean temperature and temperature gradient show that the interface currents are temperature dependent, and that differences between the activation energies of the interface and bulk currents can eliminate and possibly even invert the polarity of the space charge distributio

Electro-chemical degradation of thin film X2 safety capacitors

There is some field evidence that certain manufactured batches of thin film X2 capacitors are more susceptible to electro-chemical corrosion than others. Studies undertaken at the University of Leicester, City University London and the University of Southampton have investigated this degradation mechanism, developed underlying theory for this behaviour and validated the theory using data from damp heat testing. This paper details the anatomy of thin film X2 capacitors, details the principal mechanisms of degradation and breakdown before explaining the electrochemical corrosion mechanism and associated loss of capacitance. The effects of this degradation mechanism on other properties of the capacitor are shown to be minimal as evidenced by dielectric spectroscopy and other measurements. The ultimate conclusion is that unlike other types of capacitor, a pre-defined drop in initial capacitance does not signify end of useful life and for specific applications end of life of an X2 capacitor should be defined as the minimum value of X2 capacitance that will ensure reliable operation of a given circuit

Identifying Electrical Ageing in Polymeric Insulation

A brief review of the random nature of the processes involved in producing a breakdown path through an insulator suggests that breakdown may occur spontaneously, i.e. without any physical ageing/degradation, especially at high electric fields. This can be supported by considering the distribution function of the times-to-breakdown and, in particular, the shape parameter of the Weibull distribution. The work is supported by data from tests on PET and XLPE and from a preliminary computer simulation

Aging mechanisms of X2 metallized film capacitors in a high temperature and humidity environment

Safety capacitors (usually denoted as X1, X2 or Y) are metallized film capacitors (MFC). Two kinds of capacitance loss mechanism typically occur in this metallized film structure: (1) caused by self-healing resulting in a very small electrode area loss; (2) caused by electrode oxidation by electrochemical corrosion under ac stress in a humid environment. This study focuses on the aging mechanism of X2 film capacitors working in high temperature and high humidity environments. Two types of X2 film capacitors have been stressed under an applied voltage of 270Vac at 85 ¼C, 78.68%RH. Capacitance and equivalent series resistance (ESR) were monitored during the experiment as parametric parameters that reflect the aging process. The aging mechanism including moisture ingress time were calculated and comprehensively analyzed with the capacitance change characteristics. It was found that capacitors with lower aluminum metallization has a better capacitance stability, the mean corrosion rate of Type2 (9.7% aluminum metallization) is more than 3 times of the Type1(6.9% aluminum metallization).The ingress time calculated by capacitance change and normalized ESR show reasonable agreement