Current Protective Devices Research Articles

A comparative assessment of interface pressures generated by four surgical theatre heel pressure ulcer prophylactics

Current heel protection devices used in the operating room do not comply with the consensus document of the European and National (North American) Pressure Ulcer Advisory Panels. A complying prototype has been tested. Prospective cohort study comparing interface pressures. While using the prototype device, the heel interface pressure is significantly [mean 0·0 mmHg, standard deviation (SD) 0·0] less than the viscose elastic gel (VEG) mat (mean 174·8 mmHg, SD 64·5), the Action(®) heel block (mean 182·3 mmHg, SD 70·8) and the theatre table (mean 193·2 mmHg, SD 57·1). At the Achilles tendon, the prototype device (mean 16·2 mmHg, SD 19·0) is significantly superior to the Oasis (mean 183·7 mmHg, SD 67·4) and Action(®) heel blocks (mean 112·3 mmHg, SD 64·7). At the lateral malleolus, the prototype device (mean 0·0, SD 0·0) is better than the Action(®) (mean 24·3 mmHg, SD 53·4) and Oasis heel blocks (mean 20·9 mmHg, SD 49·2). At the calf, the prototype (mean 53·7 mmHg, SD 23·0) imposed more pressure than all other devices tested but was not statistically significant compared with the theatre table or the VEG mat. It is possible to design a device that protects the heel, lateral malleolus and Achilles tendon without causing hyperextension of the knee and consequent popliteal vein compression, thereby complying with the above guidelines.

해안지역에서의 저압용 누전차단기 교체주기 연구

??The role of RCDs(Residual Current Protective Device) that are installed before the load is very important for preventing electric shock and electrical fire. However, although fault rate of RCD is increasing due to deterioration and long period usage, the RCD is permanently used without a checking of performance evaluation and it causes the electrical accident. In this paper, the amount of airborne chloride is researched in domestic costal area and the accelerated life test is conducted using a salt water spray tester in order to decide the life time of RCD. As a result of an accelerated life test, the MTTF(Mean Time To Failure) of RCD is 110.81 hours and B10 life time of RCD is 45.81 hours for the all samples. when an accelerated life test result is applied to within 2 km costal area, the life time of RCD is predicted about 5 years.

Renal angioplasty stenting under embolic protection device: first human study with the FiberNet™ 3D filter

Background: Atheroemboli are the rule in any intervention and the leading cause of complications during percutaneous coronary intervention, carotid angioplasty (CAS), and probably after renal angioplasty stenting (RAS), which could explain the renal function deterioration after RAS in 20–30% of the cases. Several series of RAS under protection were reported using current embolic protection devices (EPDs), but these EPD have significant limitations that may be addressed by a new EPD, the FiberNet™ (Lumen Biomedical Inc, MN, USA). Methods: FiberNet is a 3D expandable filter made of fibers, which expands radially to fill the lumen, that is mounted onto a 190-cm long 0.014-inch wire. No delivery sheath is required. The crossing profile (1.7–2.9F) is low. With the retrieval catheter a focal suction can be performed during device removal allowing a meticulous cleaning of the vessel. The filter can fill vessels from 1.75 to 7 mm without requiring a long landing zone, allowing protection in the majority of renal ...

분산전원이 연계된 배전계통의 고장특성을 고려한 방향성 보호계전 방식 적용 연구

Penetration of distributed generator(DG) to power distribution system can cause malfunction of existing protection schemes. Because grid interconnected DG can contribute fault currents and make bidirectional current flows on the system, fault contributions from DG can cause an interference of protection relay operation. Therefore, over current protection device of the distribution system with DGs need directional protection schemes. In this paper, improved directional protection algorithms are proposed for the distribution system with DG considering their fault characteristics. And than, these directional protection algorithms are tested and validated in various fault conditions. From the simulation results, it can be seen that the proposed directional protection algorithms are practically efficient for the radial distribution system with DG.

Shock Hazard in the Presence of Protective Residual-Current Devices

The application of residual-current principle, as carried out by zero-sequence current protective devices, is one of the most efficient ways to reduce the hazard of electric shock in case of a failure of the equipment's basic insulation to ground. Highly sensitive and regularly tested residual-current-operated circuit breakers without integral overcurrent protection (RCCBs) devices are rightfully recognized worldwide by standards and codes as an effective means to protect persons against direct and indirect contact with energized parts by disconnecting the supply in a timely fashion. These devices are also referred to as ground-fault circuit interrupters. The protective action of the RCCBs, however, can be nullified not only due to internal malfunctions of the device but also due to particular ground-fault conditions. In these dangerous situations for persons, for example, accidental direct contact with two parts at different potentials, the residual current flowing through the RCCB is below its residual operating value, and therefore, it cannot trip. This hazardous circumstance exposes persons to dangerous touch voltages despite the presence of an efficient protective device, which cannot be blamed for not intervening. This paper seeks to clarify these particular fault conditions occurring even in the presence of healthy RCCBs.

Analysis of transfer touch voltages in low-voltage electrical installations

Protection against electric shock in our homes and work places is one of the most important priorities for electrical services engineers who are now designing electrical installations to conform to the requirements of the 17th edition IEE Wiring Regulations (BS7671: 2008). Now Chapter 41 of BS7671: 2008 requires that additional protection by means of a 30 mA 40 ms residual current protection device be provided for final circuits supplying general purpose socket outlets that are intended for use by ‘Ordinary persons’. However, there are few publications and little information available on the theory describing how touch voltage of a dangerous magnitude could be transferred from a faulty circuit onto the exposed-conductive-parts of Class 1 equipment of another healthy circuit. This paper summarises the theory of transfer touch voltage calculations and expands on it to show how to carry out a sensitivity analysis in relation to the design parameters that are being used by designers and installers. Based on the results of a real case study, it appears that there is sufficient evidence to show that it may not be sufficiently safe to use the nominal external earth fault loop impedance quoted by the electricity utility companies for adopting a low touch voltage design. Practical application: The touch voltage sensitivity equation derived in this paper is a powerful tool for designers and installers of electrical installations to investigate and identify the sensitivity of resulting touch voltages of any electrical circuits.

Electrical conduction of graphite filled high density polyethylene composites; experiment and theory

IntroductionDisorderedconductor–insulatorcompositesexhibitavarietyof phenomena, some of which have important commercialapplications. Among large number of composite materials,conductive polymer composites have been extensively usedin resistors, self regulating heaters, over current and overtemperature circuit protection devices, antistatic materials,and materials for electromagnetic interference shielding. Inorder to analyze the conducting behavior in such systems onmicroscopic scale, several models have been proposed, suchaspercolationtheory[1],effectivemediatheoryasprojectedby Bruggeman [2], aggregate structure model which over-come the disadvantage of effective media theory [3], andMcLachlan’s general effective medial (GEM) theory whichcombines most of the features of both percolation andeffective mediatheory[4].GEM equationis aninterpolationbetween Bruggeman’s symmetric and asymmetric theories.The format of equation is in the same mathematical form asof the percolation equation of conductivity when the ratio ofconductivities of the two components is infinitely large.Whileintroducingthisequationithasbeen supposedthatthebinary system is microscopically homogeneous, the particlesize distributions are infinitely wide and the particles are incontact with each other with no voids. This equation isapplicable to all volume fractions and not only near theinsulator–conductor transition as in percolation theory.In the past few decades, some works on effective mediatheory on polymer composites filled with carbon blackparticles have been reported [3, 5], but the use of graphite asfiller is almost unavailable in literature. The experimentalstudies in which the critical behavior of polymer compositeshave been investigated using effective media theory are sofar concerned with system of sphere-like conducting parti-cles embedded in an insulating matrix. A reasonableagreement between the experimental results and theoreti-callypredictedcriticalbehaviorofconductivitywasfound[5].This work presents the study of decisive behavior ofpercolation process using general effective media theory ina composite in which the conducting particles localized inan insulating matrix are better described as flakes, thanspheres. Previous experimental studies reported by thisgroup for graphite/polymer composites are concerned withthe qualitative features of conductivity [6] and the theo-retical studies are confined only to the percolation theory[7]. No attempt has been made to explain the conductivitybehavior using GEM theory. In the present work, con-ducting behavior of a series of graphite/HDPE compositeshas been studied experimentally. A comparative analysis ofapplicability of GEM equation for expressing of conduc-tivity behavior of HDPE composites filled with differentfillers has been made. The effect of processing methodsbesides shape and size of filler particles has been discussed.ExperimentalCommercial grade of high density polyethylene used in thiswork was procured from Reliance industry, India. Flakeshaped graphite powder [7] supplied by Graphite India wasselected as filler. The particle size was ranging from 10 to20 lm with a resistivity of 7.5 9 10

Applying acoustic ray tracing from the full wave equation solution to determine the nonair conduction pathways into the human head.

Flight deck crews are subject to high intensity sounds for prolonged periods of time. Even while using current hearing protection devices such as ear plugs, ear muffs, and helmets, hearing loss is still possible. It is likely that this hearing loss is due to the cochlear stimulation through pathways other than the usual air conduction pathways. In order to develop new hearing protection devices to prevent hearing loss due to these nonair conduction pathways, ray tracing from the full wave equation solution is being used to determine and visualize these dominant pathways. Numerical techniques for performing ray tracing are presented along with the validation of the method by comparing with Snell's law. For small changes in sound speed, angle of transmission errors are less than 20%. As the frequency of the incident pulse is increased, these errors are reduced as would be expected. Results of ray tracing performed on simulation data from two concentric fluid spheres as an approximation to the human head are...

Flame Spread and Damaged Properties of RCD Cases by Tracking

In this paper, the flame spread and damaged properties of residual current protective devices (RCDs) by tracking were analyzed. Pictures of tracking process were taken by High Speed Imaging System (HSIS), and fire progression was observed by timeframe. During the tracking process of RCD, it seemed to explode just once in appearance, but in the results of HSIS analysis, a small fire broke out and disappeared repeatedly 35 times and a flash of light repeated 15 times. Finally, an explosion with a flash of light occurred and lots of particles were scattered. Electric muffle furnace was used for heat treatment of RCD cases. The surface characteristics of specimens due to heat treatment and tracking deterioration were taken by Scanning Electron Microscope (SEM). Chemical and thermal properties of these deteriorated specimens were analyzed by Fourier Transform Infrared Spectrometer (FT-IR) and Differential Thermal Analyzer (DTA). The carbonization characteristics showed different chemical properties due to energy sources, and the results could be applicable to judge the accident causes.

고조파가 누전차단기에 미치는 영향

고조파에 의한 누전차단기 동작이 계속적으로 보고되어 왔으나 누전차단기 동작을 설명할 수 있는 자료가 없는 실정이다. 본 논문에서는 누전차단기에 대한 고조파 영향을 규명하기 위해 누전차단기 오동작 현황에 대한 조사 및 누전차단기 원인불명 동작이 자주 발생하는 건물에서 고조파를 측정 및 분석하였다. 또한 왜곡된 파형을 발생시킬 수 있는 고조파 합성장치를 이용하여 누전차단기 동작 특성을 시험하였다. 시험결과 3차 고조파가 기본파에 합성되었을 때 가장 작은 값의 누설전류에 누전 차단기가 동작되었고 기본파에 더해진 고조파 차수가 증가할 수 록 누전 차단기 동작전류는 증가하였다.

Embolic protection devices.

The limiting factor in coronary artery bypass surgery is the relatively rapid progression of atheromatous disease in the saphenous vein grafts. Greater than one-half of these vein grafts will fail by 10 years, and the risks associated with repeat coronary artery bypass surgery are significantly greater than that of the initial surgery. Yet, catheter-based interventional treatment of saphenous vein grafts is hindered by distal embolization of friable lipidrich plaque. This is one mechanism responsible for reduced antegrade flow (i.e., "no-reflow" phenomenon), including spasm of the distal microcirculation and platelet clumping. This complication increases the risk of a major adverse clinical event (i.e., myocardial infarction or late mortality). Distal protection devices are designed to provide protection of the distal microcirculation during percutaneous intervention. One device type is a balloon occlusive system that temporarily occludes the distal vessel during the intervention followed by the aspiration of liberated atheromatous and thrombotic material before it reaches the arteriolar and capillary bed. The other device type is a nonocclusive, filter-based system that preserves coronary blood flow through tiny pores, as low as 100 microns. Atheromatous and thrombotic material is trapped in the filter-based systems and then removed with the retrieval of the device through a retrieval catheter. This article discusses the current distal protective devices.

A current self-limited protective device studied by LF-noise measurements

Electrical properties of composite carbon-epoxy material may lead to many applications in electronics systems, in particular as protective devices. Conduction mechanisms in such components are investigated on the basis of first order characteristics (I–V curves) and of excess low frequency noise measurements. The great influence of thermal effects on the electrical characteristics are highlighted by complementary studies using IR thermography. A first attempt is made to test the reliability of these devices and to determine the failure modes by the comparison of the excess noise before and after high stress cycles.

Selecting A-C overcurrent protective device settings for industrial plants

FAULT current (also designated overcurrent or short-circuit current) protective devices, fuses, circuit breakers, and relays are the watchmen of a power system, whose job it is to detect trouble and get rid of it as expeditiously as possible. The design of such a protective system involves two separate although interrelated steps.

On the Test of Carrier Current Line Protective Device at 154kV Line of Mansyu Dengyo K. K.

On the Test of Carrier Current Line Protective Device at 154kV Line of Mansyu Dengyo K. K.

On the Test of Carrier Current Line Protective Device at 154kV Line of Mansyu Dengyo K. K.

On the Test of Carrier Current Line Protective Device at 154kV Line of Mansyu Dengyo K. K.