Supplying the power for medicine.

The specification of power supplies for medical applications needs to be approached with care. The check list here, which is designed to help the selection process, includes a look at the performance benefits of switch-mode circuitry.

Optimal Operation of an Urban Microgrid Using Model Predictive Control Considering Power Quality Improvements

Abstract Microgrids have been widely applied to improve the energy quality parameters of a distribution system locally, in addition to ensuring the operation of the system in an isolated manner. The Model Predictive Control (MPC) is a great solution to guarantee the operation of the system considering forecasting models and also physical restrictions of the system, which ensure the optimal operation of the Microgrid. However, the construction of a control scheme following the objectives established in order to meet the connected and isolated operation of a Microgrid is still a challenge. This paper proposes the development of an MPC control scheme that assures optimal system operation in connected and islanded mode, improving power quality indexes, ensuring network requirements, and extending battery life cycle. The proposed control operation in the connected mode can attend to the needs of the Microgrid, reducing the impacts of peak demand and the intermittent variations in renewable generation, where a linear objective function is developed for this purpose. In the islanded mode, grid requirements are guaranteed through load shedding, considering improvements in continuity indicators. Forecasting models are implemented considering the MPC approach and a detailed network model is developed. Simulation results highlight the effectiveness of the proposed control strategy.

Improved Active Harmonic Current Elimination Based on Voltage Detection.

With the increasing penetration of power electronic equipment in modern residential distribution systems, harmonics mitigation through the distributed generation (DG) interfacing converters has received significant attention. Among recently proposed methods, the so-called active resonance damper (ARD) and harmonic voltage compensator (HVC) based on voltage detection can effectively reduce the harmonic distortions in selected areas of distribution systems. However, it is found out that when traditional ARD algorithm is used to eliminate harmonic current injected by non-linear loads, its performance is constrained by stability problems and can at most eliminate half of the load harmonic currents. Thus, inspired by the duality between ARD and HVC, this paper presents a novel improved resistive active power filter (R-APF) algorithm based on integral-decoupling control. The design guideline for its parameters is then investigated through carefully analyzing the closed-loop poles' trajectory. Computer studies demonstrate that the proposed algorithm can effectively mitigate the load harmonic currents and its performance is much better than traditional ARD based on proportional control.

Analysis of thermal characteristics of electrical wiring for load groups in cattle barns.

The purpose of the current study is to analyze the thermal characteristics of electrical wirings depending on the number of operating load by connecting four types of electrical wirings that are selected by surveying the conditions for the electric fans, automatic waterers and halogen warm lamps that were installed in cattle barns in different years. The conditions of 64 cattle barns were surveyed and an experimental test was conducted at a cattle barn. The condition-survey covered inappropriate design, construction and misuse of electrical facility, including electrical wiring mostly used, and the mode of load current was evaluated. The survey showed that the mode of load current increased as the installation year of the fans, waterers and halogen lamps became older. Accordingly, the cattle barn manager needed to increase the capacity of the circuit breaker, which promoted the degradation of insulation of the electrical wires' sheath and increased possibility for electrical fires in the long-run. The test showed that the saturation temperature of the wire insulated sheath increased depending on the installation year of the load groups, in case of VCTFK and VFF electric wires, therefore, requiring their careful usage in the cattle barns.

Electricity-related deaths on lakes--Oklahoma, 1989-1993.

Drowning accounts for approximately 4200 deaths each year in the United States. Although electricity is documented infrequently as a cause of such fatalities, contact with electricity can result in death through temporary paralysis and drowning of persons who are swimming or wading, or through electrocution. From June 1989 through September 1993, five persons died on lakes in Oklahoma following contact or suspected contact with electrical currents. Four deaths occurred at two adjoining lakes in northeastern Oklahoma (lake A), and one at a lake in the southern part of the state (lake B). The five deaths occurred among males aged 13-50 years who were either swimming, working on or near docks, or working with electricity when they sustained fatal injuries. This report summarizes the investigation of these deaths by medical examiners (MEs) and the Oklahoma State Department of Health (OSDH).

Health risks of electric and magnetic fields caused by high-voltage systems in Finland.

Health risks of power-frequency electric and magnetic fields (EMF) in the generation and transmission of electric power were investigated in a program comprising nine separate projects. The central objectives were to assess the practical importance of electric and magnetic field exposure as a health risk, to produce data applicable to field management measures at a major power company, and to support and spur research activities on electric and magnetic fields as environmental agents. Electric and magnetic fields seemed to be weak environmental factors, but the findings were uncertain and controversial as to the health risks except that, electric field strengths (about 1.5 kV.m-1) found even in the vicinity of 110 kV power lines may cause interference with cardiac pacemakers. There is still a need, however, for further basic research focused on the interaction mechanisms of electric and magnetic fields and biological tissue.

Equipotential earthing study: equipotential wiring is unnecessary.

This study was undertaken to determine the ongoing need for Equipotential (EP) earthing as required in AS/NZS 3003, section 4.4.2. A total of 2279 earth points were tested in four clinical institutions in Body Protected areas (as defined in AS/NZS 3003). Each earth point was tested for potentials existing in the earthing in order to assess whether any potentials exceeded the 100 mV requirement of AS/NZS 3003 for EP earthing. The voltage measured was 1.21 mV +/- 3.59 mV, (mean +/- standard deviation (SD)), with a of 99 % confidence interval between 1.0 mV and 1.4 mV. This study suggests that the requirements for EP earthing in section 4.4.2 of AS/NZS 3003 are unnecessary. It is further suggested that Standards Australia review these requirements with the view of withdrawing them from the Standard.

NFPA 99 Health Care Facilities--changes and controversy.

Overall, the 1990 edition of NFPA 99 represents a refinement of the 1987 edition. Health care professionals need to be aware of several significant changes.

[Dampness in an electric plug as a cause of electricity failure in an operation theatre]. / Fugt i el-stik medfører el-udfald på operationsstue.

Two cases of electricity failure in an operation theatre during open heart surgery are discussed. The fuse for the patient monitor, ventilator, surgery instruments and heart lung machine was blown. Short-circuit was established because of humidity in the plug of the heater for fluid and blood. We recommend sealed or founded plugs and that anaesthesia equipment should not be used as an electrical supply for other electronic apparatus.

Standards: what's new in NFPA 99-1993?

Another revision cycle for the National Fire Protection Association's (NFPA) Standard for Health Care Facilities (ANSI/NFPA 99, An American National Standard, February 12, 1993) was recently completed. The 1993 edition incorporates numerous changes. Below, we present a summary of the changes that relate to electrical systems and electrical safety. Extensive changes have also been made to the chapters dealing with medical gas systems; we will be commenting on these revisions in an upcoming Health Devices article on medical gas systems, and we will discuss other changes in future issues as the need arises.

Fiberoptic phototherapy systems.

According to the American Academy of Pediatrics (AAP), about 60% of all newborns in the United States each year are diagnosed with jaundice, a major symptom of hyperbilirubinemia. Even though only a small percentage of these infants will have bilirubin levels that, according to the current AAP practice parameters, are high enough to require treatment, many of these infants will be treated with phototherapy (past research has associated very high bilirubin levels with brain damage). Because jaundice is unlikely to be noticed within the typical 24-hour period before discharge from the hospital, a phototherapy device that is convenient and safe for use in the home, as well as in the hospital, is desirable. In the following study, we address the performance, safety, and convenience of three fiberoptic phototherapy systems (which consist of pads and light sources), from three manufacturers, that can be used in either a hospital or the home. We also assess the advantages and disadvantages of this technology compared with those of the conventional overhead phototherapy lamps that are still commonly used. Two systems are rated Acceptable based on their light performance and are ranked equally; one system is rated Acceptable--Not Recommended because it does not provide the typical power levels obtainable with either of the other two evaluated fiberoptic systems or conventional overhead lamps. Readers are cautioned not to base purchasing or use decisions on our ratings alone, but on a thorough understanding of the issues surrounding fiberoptic phototherapy systems, which can be gained by reading this issue in its entirety. Also see the Clinical Perspective, "Hyperbilirubinemia--When and How to Treat?," for pertinent clinical background information; the supplementary articles "Uses and Limitations of Radiometers" and "Uniformity of Light" for additional technical background information; and the supplementary article "Operating Costs of Phototherapy Devices" for additional purchasing information.

[Sanitary-protective and limitation areas for antennae of the decameter range]. / Sanitarno-zashchitnye zony i zony ogranicheniia zastroiki antenn dekametrovogo diapazona.

A detailed overview of a transmitting antenna of the decameter range is provided. It is shown that the field near such antennas has rather a complex structure. A comparative analysis of the existing design techniques for the determination of electromagnetic field intensity has been undertaken. On the basis of numerical design techniques the procedure of automated prediction of the electromagnetic situation is proposed. The basic components of the procedure are set forth. As illustrated by some antennas the dependence of sanitary and limitation zones on the wavelength, radiated power and the type of soil has been studied.