Analysis of traveling wave based fault location method for distribution network with image processing

Laws of traveling wave data related to fault location for medium voltage distribution network are discussed and summarized. Given the tree structure of a distribution network, an image of nodes voltage is created combining the use of real-time traveling wave meters at all nodes of the tree. The novelty of this paper is that travelling wavefront are analyzed based on the dynamic changes of these images. Based on principle of the traditional fault location with traveling wave-based method for transmission networks, traveling wave data of fault location for medium voltage distribution networks are plotted in order to estimate propagation velocity and distance between the fault position and the reference node. The results indicate that taking advantage of the laws of data related to first wave front can improve the reliability of the fault location for medium voltage networks

Modeling and simulation of intermittent arc effects on traveling wave based fault location techniques for distribution network

With rapidly developing of the distribution networks the rate of the earth fault increases sharply. Aiming to fault location for distribution networks, many techniques are proposed and applied in distribution networks throughout the world. However, until now the technology for precise fault point location has not been successfully implemented in engineering practice. Traveling wave based methods as common techniques are widely applied in transmission line protection for locating fault point. However, these methods face severe challenge in fault location for distribution networks. The main reason is that the intermittent arc fault easily results in failure of detecting inceptive travelling wave and this intermittent arc is a common earth fault in distribution networks compared with transmission networks. In this paper, a simplified distribution line is built by making reference to the two parallel lossless transmission lines system. Then, the intermittent arc effects on traveling wave based method are modeled and discussed. Finally, the reason why these travelling wave based methods are hard to locate fault point precisely is illustrated

Test of a simple and flexible S8 model molecule in alpha-s8 crystals

Alpha S8 is the most stable crystalline form, at ambient pressure and temperature (STP), of elemental sulfur. In this paper we analyze the zero pressure low temperature part of the phase diagram of this crystal, in order to test a simple and flexible model molecule. The calculations consist in a series of molecular dynamics (MD) simulations, performed in the constant pressure- constant temperature ensemble. Our calculations show that this model, that gives good results for three crystalline phases at STP and T>~300 K, fails at low temperatures, predicting a structural phase transition at 200 K where there should be none.Comment: 6 pages, 4 figures, submitted to Chem. Phys. Lett, a figure change

The hydrogenation-dependent thermal expansion properties of hydrogenated graphene

Thermal expansion properties of hydrogenated graphene are investigated by performing the first-principles calculations. We find that both fully hydrogenated graphene (graphane) and half hydrogenated graphene (graphone) exhibit negative thermal expansion properties at low temperatures. Their thermal expansion behaviors display the hydrogenation-dependent features: hydrogenated graphene with boat-like structures possess better negative thermal expansion properties than those with chair-like structures. In particular, the graphane with boat-like structure shows giant negative thermal expansion, with thermal expansion coefficient of about −4.1 × 10-5 K-1. Such different thermal behaviors are ascribed to different vibrational features, and the typical modes contributing to the negative thermal properties of the systems are addressed. Our results will be of importance for both fundamental understanding and the application of this family in nanodevices in the future

Simulation of Realistic Core-shell Silicon Nanowires

AbstractWe have developed an efficient scheme for simulating silicon nanowires with crystalline cores and amorphous sheaths, using molecular dynamics. By starting with a crystalline nanowire and performing high temperature anneal an amorphous outer sheath can be grown with controlled thickness on the nanowire. Simulations for [001] nanowires with diameters of 12 nm find low energy facets between the amorphous and crystalline layers. Simulations for [110] nanowires find weak faceting and an inhomogeneous amorphous-crystalline boundary.</jats:p