Condition Monitoring Techniques of Power Transformers: A Review

Power transformers provide a vital link between the generation and distribution of produced energy. Such static equipment is subjected to abuse during operation in generation and distribution stations and leads to catastrophic failures. This paper reviewed the techniques in the field of condition monitoring of power transformers in recent years. Transformer monitoring and diagnosis are the effective techniques for preventing the eventual failures and contributing to ensure the plan’s reliability. This paper provided a survey on the existing techniques for monitoring, diagnosis, condition evaluation, maintenance, life assessment and possibility of extending the life of the existing assets of power transformers with be appropriate classifications. Thus, this survey could help researchers through providing better techniques for condition monitoring of power transformers

Sub-transmission sub-station expansion planning based on bacterial foraging optimization algorithm

In recent years, significant research efforts have been devoted to the optimal planning of power systems. Substation Expansion Planning (SEP) as a sub-system of power system planning consists of finding the most economical solution with the optimal location and size of future substations and/or feeders to meet the future load demand. The large number of design variables and combination of discrete and continuous variables make the substation expansion planning a very challenging problem. So far, various methods have been presented to solve such a complicated problem. Since the Bacterial Foraging Optimization Algorithm (BFOA) yield to proper results in power system studies, and it has not been applied to SEP in sub-transmission voltage level problems yet, this paper develops a new BFO-based method to solve the Sub-Transmission Substation Expansion Planning (STSEP) problem. The technique discussed in this paper uses BFOA to simultaneously optimize the sizes and locations of both the existing and new installed substations and feeders by considering reliability constraints. To clarify the capabilities of the presented method, two test systems (a typical network and a real ones) are considered, and the results of applying GA and BFOA on these networks are compared. The simulation results demonstrate that the BFOA has the potential to find more optimal results than the other algorithm under the same conditions. Also, the fast convergence, consideration of real-world networks limitations as problem constraints, and the simplicity in applying it to real networks are the main features of the proposed method

The COVID-19 Pandemic Affects Seasonality, With Increasing Cases of New-Onset Type 1 Diabetes in Children, From the Worldwide SWEET Registry

Objective: To analyze whether the coronavirus disease 2019 (COVID-19) pandemic increased the number of cases or impacted seasonality of new-onset type 1 diabetes (T1D) in large pediatric diabetes centers globally. Research design and methods: We analyzed data on 17,280 cases of T1D diagnosed during 2018-2021 from 92 worldwide centers participating in the SWEET registry using hierarchic linear regression models. Results: The average number of new-onset T1D cases per center adjusted for the total number of patients treated at the center per year and stratified by age-groups increased from 11.2 (95% CI 10.1-12.2) in 2018 to 21.7 (20.6-22.8) in 2021 for the youngest age-group, <6 years; from 13.1 (12.2-14.0) in 2018 to 26.7 (25.7-27.7) in 2021 for children ages 6 to <12 years; and from 12.2 (11.5-12.9) to 24.7 (24.0-25.5) for adolescents ages 12-18 years (all P < 0.001). These increases remained within the expected increase with the 95% CI of the regression line. However, in Europe and North America following the lockdown early in 2020, the typical seasonality of more cases during winter season was delayed, with a peak during the summer and autumn months. While the seasonal pattern in Europe returned to prepandemic times in 2021, this was not the case in North America. Compared with 2018-2019 (HbA1c 7.7%), higher average HbA1c levels (2020, 8.1%; 2021, 8.6%; P < 0.001) were present within the first year of T1D during the pandemic. Conclusions: The slope of the rise in pediatric new-onset T1D in SWEET centers remained unchanged during the COVID-19 pandemic, but a change in the seasonality at onset became apparent.info:eu-repo/semantics/publishedVersio

Effects of laser beam shapes on depths of penetration in dermatology

For many medical laser applications, a particular beam shape is required. The output beam of a laser can be approximated by a Gaussian, higher-order Gaussian, annular or a flat-top (uniform) distribution. Here, we investigate, analytically and experimentally, the effects of laser beam shapes on the depths of penetration in treatments of any types of vascular malformation. In order to do this, the physical and optical parameters of the skin must be known and measured correctly. Using the Monte-Carlo method for seven layers of skin, a software predicting the beam propagation and intensity distribution inside of tissue has been developed in our centre. In this paper, a 15 watts copper vapour laser producing (511nm and 578 nm) for treatments of patients having PWS (Port Wine Stains) of different sizes is employed. The output beam of this laser was Gaussian. We have designed a beam homogenizer converting a Gaussian beam into flat-top distribution. Therefore, the effects of the laser irradiance beam shape (before and after beam shaping) on the depth of penetration have been investigated before people's treatments. Initially, two laser beams having Gaussian output distribution of the same power are considered. The diameter of one beam is 5mm and the other one is 10 mm. The intensity distribution of these beam inside of similar tissues are predicted and it is concluded that for deep but small size PWS the Gaussian beam having smaller beam diameter is more suitable than the larger spot size. Then, the beam intensity distribution inside of the same tissue (similar parameters) for two flat-top beams of the same power but different diameters (one is 5mm and the other is 10 mm) is calculated. It can be seen that the flat top beam of bigger spot-size has smaller penetration depth but it illuminates a larger area uniformly (suitable for large but not deep area). The depth of penetration of flat-top beam with smaller spot size is deeper but it illuminates a smaller area uniformly and is suitable for treatments of patients with small but deep PWS. Using a low power laser, we have been able to image the PWS area and roughly determine the depths of malformations. Finally, depends on the size, depth and shapes of the area the required beam shape can be chosen. A clinical protocol is developed for 25 patients and it is shown an extreme improvement in related medical procedures.12 page(s