EPECentre: Journal Articles

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  • ItemOpen Access
    Optimization of Supercapacitor Assisted Surge Absorber (SCASA) Technique: A New Approach to Improve Surge Endurance Using Air-Gapped Ferrite Cores
    (MDPI AG, 2021) Kularatna N; Steyn-Ross DA; Silva Thotabaddadurage, Dr. Sadeeshvara
    SCASA is a patented technique commercialized as a surge protector device (SPD) that adheres to UL-1449 test standards. Apart from the novel use of supercapacitors, SCASA design incorporates a coupled-inductor wound to a specially selected magnetic material of powdered-iron. In this study, we investigate the limitations of the present design under transient operation and elucidate ways to eliminate them with the use of air-gapped ferrite cores. In modelling the operation under 50 Hz AC and transient conditions, a permeance-based approach is used; in addition, non-ideal characteristics of the transformer core are emphasized and discussed with empirical validations. The experimental work was facilitated using a lightning surge simulator coupled with the 230 V AC utility mains; combinational surge-waveforms (6 kV/3 kA) defined by IEEE C62.41 standards were continuously injected into SPD prototypes during destructive testing. Such procedures substantiate the overall surge-endurance capabilities of the different core types under testing. With regard to optimizations, we validated a 95% depletion of a negative-surge effect that would otherwise pass to the load-end, and another 13–16% reduction of the clamping voltage verified the effectiveness of the methods undertaken. In conclusion, SCASA prototypes that utilized air-gapped cores revealed a greater surge endurance with improved load-end characteristics.
  • ItemOpen Access
    Do investors respond to changes in the composition of sustainability indices?
    (2021) Sławik A; Bialkowski, Jedrzej
    This paper investigates the price effects associated with changes in the composition of the first sustainability index in Central and Eastern Europe – the RESPECT Index – over its lifetime, i.e. 2009–2019, using an event study technique and the advanced market model for the calculation of abnormal returns. The results show a strong negative reaction by the stock prices of companies that are either included in or excluded from a sustainability index. The effect is short-lived but statistically significant in some asymmetric event windows. The study contributes to the discussion of how the emerging capital markets perceive the value of socially responsible activities undertaken by firms. The research indicates that events such as addition to and removal from a sustainability index (as well as announcements thereof) create a trading opportunity. Additionally, it suggests that investors at the Warsaw Stock Exchange – at least in the short run – tend to sell stocks of companies formally recognised as socially responsible.