Increase of static electrification in an aged oil‐immersed transformer

Abstract

Background We investigated the potential for selection bias due to non‐participation in the follow‐up of a large prospective cohort study. Methods Licensed pesticide applicators (52,395 private; 4,916 commercial) in the Agricultural Health Study provided demographic, health, and pesticide exposure information at enrollment (1993–1997) and in a 5‐year follow‐up telephone interview. Factors associated with non‐participation in the follow‐up were identified using multiple logistic regression. Potential for selection bias was evaluated by comparing exposure–disease associations between the entire cohort and the follow‐up subset. Results Sixty‐six percent of private and 60% of commercial applicators completed the follow‐up interview. Private and commercial applicators who did not complete the follow‐up reported at enrollment younger age, less education, lower body mass index, poorer health behaviors but fewer health conditions, and lower pesticide use. Estimates of exposure–disease associations calculated with and without non‐participants did not indicate strong selection bias. Conclusions Differences between non‐participants and participants in the follow‐up interview were generally small, and we did not find significant evidence of selection bias. However, the extent of bias may depend on the specific exposure and outcome under study. Am. J. Ind. Med. 53:486–496, 2010. © 2009 Wiley‐Liss, Inc.

Electrical-Based Diagnostic Techniques for Assessing Insulation Condition in Aged Transformers

“…The insulator edges are rounded and duct structures are designed so as to suppress turbulence and direct blow up of oil flow into the coils. In addition, flow speeds are limited [35]. In Japan, a method of suppressing charging tendency by using benzotriazole (BTA) as an insulating oil additive was developed [36,37].…”

Numerical Study on the Charge Transport in a Space between Concentric Circular Cylinders

“…El-Adawy et al [27] conducted numerical simulation for the foundation of EDL without the convection effect and calculated ECT in the presence of fluid flow with source terms representing the ion dissociation and recombination in the bulk. Kobayashi et al [28] paid attention to the competitive role of oil and pressboard in the electrification process. Okabe et al [29] investigated the effect of the compounds in oil on ECT and showed that increase of ECT was mostly caused by the oxidation of sulfides.…”