Multi-function DC protection scheme for an LVDC smart distribution network

Low voltage direct current (LVDC) distribution systems have the potential to support future realisation of smart grids functionality. They do however present significant protection challenges that existing schemes based on DC fuses and conventional circuit breakers cannot manage due to slow device performance. Therefore, this research introduces an advanced protection scheme that addresses the outstanding challenges facing realisation of last mile DC distribution

Validation of fast and selective protection scheme for an LVDC distribution network

Low Voltage Direct Current (LVDC) distribution systems are one of the emerging technologies to recently attract attention for more efficient use of energy, and wider uptake of distributed renewables and energy storage. They do however present significant fault protection and safety challenges, which are not possible to address without using advanced protection techniques. Therefore, this paper considerably reviews these key challenges, and presents experimental results of prototyping an advanced protection scheme developed to help enable LVDC distribution networks for utility applications. The developed scheme is a DC current direction-based using multiple intelligent electronic devices (IEDs) relays in combination with controllable solid-state circuit breakers to detect and locate DC faults, and provide selective protection tripping within sub-millisecond timescales. A scaled laboratory demonstrator that emulates an LVDC distribution network is used as a test platform. It allows the characterisation of the transient behaviour for various fault conditions and locations. The developed protection algorithm is implemented in LabVIEW, and its performance against such fault conditions is tested within this environment

Pyrofuse modeling for eVTOL aircraft DC protection

Contemporary trends are leading towards the electrification of aircraft for urban mobility applications. Accordingly, there is a high demand for advancements in light-weight, high voltage technologies to realize these new aircraft types. Driven by recent developments in the automotive industry, hybrid Pyrofuse protection devices have emerged as one such new candidate technology. Pyrofuses offer rapid clearance of fault currents, reduced cost and weight when compared to conventional mechanical breakers. In addition, Pyrofuses have the ability to tune the time-current curve to fit the application's fault response characteristics. However, Pyrofuses are non-resettable devices whose exclusive use for electrical protection could present potential operational hazards and certification challenges in aerospace applications. Model-based analysis will be critical in supporting this evaluation. Accordingly, this paper offers the first complete design methodology to transiently model Pyrofuse operation in MATLAB/Simulink, drawing characteristics from commercially available datasheets. This model is then utilized to undertake an initial protection coordination feasibility study for a candidate eVTOL electrical system architecture, exploring the associated device and system level operational capabilities and limitations. In particular, the results show that the Pyrofuse can offer a good degree of nuisance-tripping resilience against transient events whilst providing quick clearance of short circuit faults

Flight-critical load failure analysis in HVDC More-Electric Aircraft applications

The electrification of aircraft is a key and proven means of realising decarbonisation. A key pillar of this, the More-Electric Aircraft (MEA), has been shown to be a viable alternative to conventional aircraft where traditionally pneumatic and hydraulic systems are replaced with electrical equivalent systems such that efficiency gains, noise, carbon emission and mass reductions are achieved. With electrical systems performing new flight-critical roles on-board MEA, and the Power Electronic Converter (PEC) being a core technology in these systems, there has been increased interest in recent years in better characterising and improving the reliability of PECs. Using Fault-Tree Analysis (FTA) and Reliability Block Diagram (RBD) methods, this paper presents a study of the contribution of the PEC failure rates to the reliability of flight-critical loads in a concept High Voltage Direct Current (HVDC) aircraft application. It is shown that whilst the failure rate of PECs will typically shape the overall failure rate of electrical systems and subsystems, the installed redundancy in aircraft Electrical Power System (EPS) mitigates the risk of unacceptably high rates of failure in flight critical loads, even if the aircraft is dispatched in a non-full-up configuration. Moreover, the paper illustrates how the greatest gains in these load systems’ reliability can be realised through improvements in the reliability of the PEC interfaces to these load subsystems, where there is naturally less system redundancy

Mothers' beliefs about children's learning in Hong Kong and the United States: Implications for mothers' child-based worth

Chinese and American mothers’ beliefs about children’s learning and parents’ role in it were examined using notions salient in Chinese culture. Mothers from Hong Kong (n = 66) and the United States (n = 69) indicated their endorsement of the ideas that children’s learning reflects children’s morality, and parents’ support of children’s learning reflects parents’ love and duty. Mothers also reported on the extent to which their worth is based on children’s performance. Chinese (vs. American) mothers believed more that children’s learning reflects morality and parents’ support of children’s learning reflects love; these differences accounted for their feelings of worth being more dependent on children’s performance. Chinese (vs. American) mothers believed less that parents’ support is a duty.postprin

A hybrid radiation detector for simultaneous spatial and temporal dosimetry

In this feasibility study an organic plastic scintillator is calibrated against ionisation chamber measurements and then embedded in a polymer gel dosimeter to obtain a quasi-4D experimental measurement of a radiation field. This hybrid dosimeter was irradiated with a linear accelerator, with temporal measurements of the dose rate being acquired by the scintillator and spatial measurements acquired with the gel dosimeter. The detectors employed in this work are radiologically equivalent; and we show that neither detector perturbs the intensity of the radiation field of the other. By employing these detectors in concert, spatial and temporal variations in the radiation intensity can now be detected and gel dosimeters can be calibrated for absolute dose from a single irradiation

Screening of Streptococcus suis in swine workers of selected states in Peninsular Malaysia

Background and Aim: Streptococcus suis is a zoonotic pathogen that is highly associated with contact between live pigs and raw pig material. In view of the recent reports of human infections in Malaysia, epidemiological data on the status of S. suis in the human population, especially among people working closely with pigs and/or raw pork, should be provided. The aim of this study was to detect S. suis among individuals working in the swine industry in several major pig production areas in Peninsular Malaysia. Materials and Methods: Demographic information, exposure determinants, and oral swabs were collected from swine personnel, including farmers, butchers, and veterinarians. Oral swabs were subjected to bacterial isolation and conventional polymerase chain reaction (PCR) assays for S. suis detection. Results: The study included 40 participants working in the swine industry, with a predominant representation of males (62.5%) and Malaysian Chinese individuals (60.0%) who consumed pork (92.5%). Notably, none of the participants reported consuming raw or partially cooked pork. In spite of their occupational exposure risk, none of the oral swabs showed positive results for S. suis infection. Conclusion: To the best of our knowledge, this is the first report and detection study of S. suis using oral swabs obtained from swine personnel in Peninsular Malaysia