Simulation of switching overvoltages of 400 kV shunt reactor

Bam 400/132 kV substation in Kerman region, Iran, has a 50 MVAR shunt reactor on 400 kV busbar which is grounded through a 128 kVAR neutral reactor. The neutral earthing reactor assists in interrupting line to ground arcing current when switching for clearing a line to ground arcing fault, but the switching of shunt reactor which is grounded through a neutral reactor can impose a more severe duty on the circuit breakers than switching a solidly grounded shunt reactor. While opening shunt reactor, transient phenomena, such as chopping overvoltages and reignition overvoltage/overcurrents can occur. These overvoltages/currents can put circuit breakers, reactors and other equipment in danger. In this paper, the Bam substation’s equipment such as electrical circuits and associated equipment will be modelled in transient mode using EMTDC/PSCAD software. The arc behaviour and excessive voltage caused by the switching will be analysed. Finally, three methods including controlled switching, using surge arrester and a disconnecting switch across the neutral earthing reactor for mitigating these overvoltages will be compared

Simulation of switching overvoltages of 400 kV shunt reactor

Bam 400/132 kV substation in Kerman region, Iran, has a 50 MVAR shunt reactor on 400 kV busbar which is grounded through a 128 kVAR neutral reactor. The neutral earthing reactor assists in interrupting line to ground arcing current when switching for clearing a line to ground arcing fault, but the switching of shunt reactor which is grounded through a neutral reactor can impose a more severe duty on the circuit breakers than switching a solidly grounded shunt reactor. While opening shunt reactor, transient phenomena, such as chopping overvoltages and reignition overvoltage/overcurrents can occur. These overvoltages/currents can put circuit breakers, reactors and other equipment in danger. In this paper, the Bam substation’s equipment such as electrical circuits and associated equipment will be modelled in transient mode using EMTDC/PSCAD software. The arc behaviour and excessive voltage caused by the switching will be analysed. Finally, three methods including controlled switching, using surge arrester and a disconnecting switch across the neutral earthing reactor for mitigating these overvoltages will be compared

Shedding light on LMA-Dark solar neutrino solution by medium baseline reactor experiments: JUNO and RENO-50

In the presence of Non-Standard neutral current Interactions (NSI) a new solution to solar neutrino anomaly with $\cos 2\theta_{12}<0$ appears. We investigate how this solution can be tested by upcoming intermediate baseline reactor experiments, JUNO and RENO-50. We point out a degeneracy between the two solutions when both hierarchy and the $\theta_{12}$ octant are flipped. We then comment on how this degeneracy can be partially lifted by long baseline experiments sensitive to matter effects such as the NOvA experiment.Comment: 9 pages, 2 figure

Simulation of hydrogen production for mobile fuel cell applications via autothermal reforming of methane

This paper presents a simulation of catalytic autothermal reforming (ATR) of methane (CH4) for hydrogen (H2) production. ATR is essentially an oxidative steam reforming, which combines the exothermic partial oxidation (PO) with the endothermic steam reforming (SR) under thermally neutral conditions. A model is developed using HYSYS 2004.1 to simulate the conversion behavior of the reformer. The model covers all aspects of major chemical kinetics and heat and mass transfer phenomena in the reformer. The ATR and preferential oxidation (PrOx) processes is modeled using conversion reactor, while the water gas shift (WGS) process is modeled using equilibrium reactor within HYSYS environment. The conditions used for high CH4 conversion and high H2 yield are at air to fuel ratio of 2.5 and water to fuel ratio of 1.5. Under this condition, CH4 conversion of 100% and H2 yield of 44% on wet basis can be achieved and the system efficiency is about 87.7%

Neutrino-induced deuteron disintegration experiment

Cross sections for the disintegration of the deuteron via neutral-current (NCD) and charged-current (CCD) interactions with reactor antineutrinos are measured to be 6.08 +/- 0.77 x 10^(-45) cm-sq and 9.83 +/- 2.04 x 10^(-45) cm-sq per neutrino, respectively, in excellent agreement with current calculations. Since the experimental NCD value depends upon the CCD value, if we use the theoretical value for the CCD reaction, we obtain the improved value of 5.98 +/- 0.54 x 10^(-45) for the NCD cross section. The neutral-current reaction allows a unique measurement of the isovector-axial vector coupling constant in the hadronic weak interaction (beta). In the standard model, this constant is predicted to be exactly 1, independent of the Weinberg angle. We measure a value of beta^2 = 1.01 +/- 0.16. Using the above improved value for the NCD cross section, beta^2 becomes 0.99 +/- 0.10.Comment: 22pages, 9 figure

Sensitivities of Low Energy Reactor Neutrino Experiments

The low energy part of the reactor neutrino spectra has not been experimentally measured. Its uncertainties limit the sensitivities in certain reactor neutrino experiments. The origin of these uncertainties are discussed, and the effects on measurements of neutrino interactions with electrons and nuclei are studied. Comparisons are made with existing results. In particular, the discrepancies between previous measurements with Standard Model expectations can be explained by an under-estimation of the low energy reactor neutrino spectra. To optimize the experimental sensitivities, measurements for \nuebar-e cross-sections should focus on events with large ($>$1.5 MeV) recoil energy while those for neutrino magnetic moment searches should be based on events $<$100 keV. The merits and attainable accuracies for neutrino-electron scattering experiments using artificial neutrino sources are discussed.Comment: 25 pages, 9 figure

Microbial community assembly, theory and rare functions

Views of community assembly have traditionally been based on the contrasting perspectives of the deterministic niche paradigm and stochastic neutral models. This study sought to determine if we could use empirical interventions conceived from a niche and neutral perspective to change the diversity and evenness of the microbial community within a reactor treating wastewater and to see if there was any associated change in the removal of endocrine disrupting compounds (EDCs). The systematic removal of EDCs and micropollutants from biological treatment systems is a major challenge for environmental engineers. We manipulated pairs of bioreactors in an experiment in which “niche” (temporal variation in resource concentration and resource complexity) and “neutral” (community size and immigration) attributes were changed and the effect on the detectable diversity and the removal of steroidal estrogens was evaluated. The effects of manipulations on diversity suggested that both niche and neutral processes are important in community assembly. We found that temporal variation in environmental conditions increased diversity but resource complexity did not. Larger communities had greater diversity but attempting to increase immigration by adding soil had the opposite effect. The effects of the manipulations on EDC removal efficiency were complex. Decreases in diversity, which were associated with a decrease in evenness, were associated with an increase in EDC removal. A simple generalized neutral model (calibrated with parameters typical of wastewater treatment plants) showed that decreases in diversity should lead to the increase in abundance of some ostensibly taxa rare. We conclude that neither niche and neutral perspectives nor the effect of diversity on putative rare functions can be properly understood by naïve qualitative observations. Instead, the relative importance of the key microbial mechanisms must be determined and, ideally, expressed mathematically

A Pilot Experiment with Reactor Neutrinos in Taiwan

A Collaboration comprising Taiwan and mainland Chinese scientists has been built up since 1996 to pursue a experimental program in neutrino and astro-particle physics in Taiwan. A pilot experiment to be performed at the Nuclear Power Station II in Taiwan is now under intense preparation. It will make use of a 600 kg CsI(Tl) crystal calorimeter to study various neutrino interactions. The feasibility of performing a long baseline reactor neutrino experiment will also be investigated. The conceptual design and the physics to be addressed by the pilot experiment are presented.Comment: 14 pages, 8 figures, 2 table