A novel overcurrent protection method based on wide area measurement in smart grid

PowerTech is the anchor conference of the IEEE Power & Energy Society in EuropeConventional overcurrent protection settings are fixed to detect faults. Power system operation mode varies while the settings of protection devices remain constant. As a result, overcurrent protection has a small protection range and a long operating time because it is incapable of adjusting its setting online. Wide Area Measurements System (WAMS) provides synchronized and real time data which can be utilized in new protection devices. This paper proposes a novel online setting scheme which utilizes online system data to calculate real-time system operation mode. Based on the real-time operation mode, real-time fault current is calculated before fault occurring. Settings of the protection devices are by this means adjusted in real time to expand the protection area and shorten the operating time. The calculation is expanded from single source model to multi-source with Π model. In addition, interval time of settings adjustment Tchange is proposed and calculated by using hyperbolic function model. Based on this method, power system real-time operation condition can be better monitored and the real-time short circuit current can be obtained to improve protection performance. © 2013 IEEE.published_or_final_versio

HTS transformer and its related loss measurement and quench protection techniques

Recently research and development concerning applications of high temperature superconducting (HTS) transformers have been progressed actively in the world. Besides the HTS rated current capability, it is also essential to develop the relevant and precise performance test and protection systems for HTS transformers. This paper mainly presents elementary test and protection methods of HTS transformers including AC loss measurement, and quench detection and protection. A new integrated measurement system for HTS transformers is also proposed by using the Labview virtual instrument software

A new strategy to enhance polysialic acid production by controlling sorbitol concentration in cultivation of Escherichia coli K235

Polysialic acid (PSA) is a new pharmaceutical material used in control release of protein drugs and as scaffold material in biomedical applications. It is also a vital source of sialic acid and its derivatives. In this paper, we demonstrated that the substrate sorbitol has significant effect on bacterial growth and PSA formation in cultivation of Escherichia coli K235. Lower sorbitol concentration favored bacterial growth but retards PSA formation in the fed-batch fermentation. Higher sorbitol concentration stimulated PSA formation but inhibited bacterial growth in the batch fermentation. Sorbitol concentration gradient experiment revealed that PSA formation was seriously limited as sorbitol concentration was lower than 20 g/L, while bacterial growth was obviously inhibited as the sorbitol concentration higher than 40 g/L. A new strategy of controling sorbitol concentration in a range of 20 - 40 g/L in the broth during the fermentation process increased PSA yield by 20%

A new metric for rotating charged Gauss-Bonnet black holes in AdS spaces

This paper presents a new metric for slowly rotating charged Gauss-Bonnet black holes in higher dimensional anti-de Sitter spaces. Taking the angular momentum parameter $a$ up to second order, the slowly rotating charged black hole solutions are obtained by working directly in the action.Comment: 11 pages and accepted by Chin. Phys.

Optical generation of hybrid entangled state via entangling single-photon-added coherent state

We propose a feasible scheme to realize the optical entanglement of single-photon-added coherent state (SPACS) and show that, besides the Sanders entangled coherent state, the entangled SPACS also leads to new forms of hybrid entanglement of quantum Fock state and classical coherent state. We probe the essential difference of two types of hybrid entangled state (HES). This HES provides a novel link between the discrete- and the continuous-variable entanglement in a natural way.Comment: 6 pages, 2 figure

Rationale of internationalization of China's national oil companies: seeking natural resources, strategic assets or sectoral specialization?

The bulk of the existing literature emphasized that China's companies sought strategic assets (technology, brands and access to markets) through internationalization in order to overcome latecomers' comparative disadvantage, while some studies suggested that these firms went after natural resources to address China's rising oil imports. The third argument (which we coin the ‘sectoral strength’ hypothesis) suggested that the upstream firms in extractive business would seek natural resources, whereas downstream ones would seek strategic assets. In this study, we examine the rationale of main overseas investment deals (‘going out’) of China's two largest national oil companies during 2002–2010 which were also China's top two non-financial firms with the largest outward investment stocks during 2004–2010. We conclude that these deals can be best explained by the ‘sectoral specialisation’ hypothesis supplemented with a consideration for strategic assets