Markov-Based Reliability Assessment for Distribution Systems Considering Failure Rates

Switches (SWs) and renewable distributed generations (RDG) are subject to failure as well as other components of a system that are usually presumed fully reliable in the literature. It can lead to an overestimation of their contribution to reliability enhancement disregarding their dysfunction. This study considers the failure rate of SWs and RDGs to assess their impact on the reliability cost of the system and their effect on the optimal placement using a Markov-based approach. The optimal placement of SWs and RDGs in radial distribution systems is carried out simultaneously aim at minimizing the overall cost including investment, maintenance of SWs, and RDGs alongside the interruption cost. The performance of the model is verified through different scenarios and tested on RBTS bus 2. The results show that high values of the failure rates lead to fewer allocations to prevent plummeting the reliability of the system and increasing the capacity of the RDG results in fewer SWs allocation.©2023 Authors. Published by IEEE. This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/fi=vertaisarvioitu|en=peerReviewed

Effect of Load Priority Modeling on the Size of Fuel Cell as an Emergency Power Unit in a More-Electric Aircraft

The proton exchange membrane fuel cell as a green power source is a suitable replacement of the engine mounted generators in the emergency power unit of a more-electric aircraft. Most existing energy management methods for operation of fuel cells in the more-electric aircraft refer to the hydrogen consumption minimization. But due to the increasing number of electrical components and hence electrical demand in the aircraft, demand-side management should be considered in these methods. In order to determine the effect of demand-side management on the fuel cell operation and size, an efficient load priority model is presented and integrated into an optimization framework. The proposed optimization framework is formulated as mixed-integer quadratic programming using Karush–Kuhn–Tucker optimality condition and is solved by CPLEX optimization tool. The Boeing 787 electrical distribution system is considered as a single-bus case study to evaluate the performance of the proposed optimization framework. Numerical results show that the size of fuel cell as an emergency power unit resource depends on the type and importance of the system’s loads in different emergency conditions. Also, with an efficient priority model, both hydrogen consumption and load shedding can be decreased

Assessment of the effectiveness of ventilation types for reducing the occupational exposure to bioaerosols in health care staffs

Background & Objectives : Hospital indoor air contains a wide range of airborne pathogenic bioaerosols which have a significant impact on health care staff’ health and welfare. The aim of this study was to assess the effects of ventilation system types on occupational exposure of the health care staffs to airborne bioaerosols in the isolation room based on the patient bed arrangements and the standing locations of the health care staff. Methods: Personal exposures were measured based on five given types of ventilation system, 2 patient bed arrangements (at a corner and in the middle of the room), and two different standing locations for the health care staff (standing close to the patient’s bed, and down a side section of the bed). For personal sampling, filtration method recommended by th e American conference of governmental industrial hygienists(ACGIH) was used. Result: The highest exposure to airborne bioaerosols was observed when the ventilation system was switched off. There were significant decreases in the bioaerosols concentration after using all types of ventilation system (P value 0.05). Conclusions : The most effective ventilation system for decreasing health care staff’ exposures in the isolation room was associated with supplying of air from a circular grill located on the northern wall and exhausting it through a linear slot located on the southern wall (type 1) with the ventilation rate of 12 air changes per hour