A novel fault current limiter topology design based on liquid metal current limiter

The liquid metal current limiter(LMCL)is regarded as a viable solution for reducing the fault current in a power grid.But demonstrating the liquid metal arc plasma self-pinching process of the resistive wall,and reducing the erosion of the LMCL are challenging,not only theoretically,but also practically.In this work,a novel LMCL is designed with a resistive wall that can be connected to the current-limiting circuit inside the cavity.Specifically,a novel fault current limiter(FCL)topology is put forward where the novel LMCL is combined with a fast switch and current-limiting reactor.Further,the liquid metal self-pinch effect is modeled mathematically in three dimensions,and the gas-liquid two-phase dynamic diagrams under different short-circuit currents are obtained by simulation.The simulation results indicate that with the increase of current,the time for the liquid metal-free surface to begin depressing is reduced,and the position of the depression also changes.Different kinds of bubbles formed by the depressions gradually extend,squeeze,and break.With the increase of current,the liquid metal takes less time to break,but breaks still occur at the edge of the channel,forming arc plasma.Finally,relevant experiments are conducted for the novel FCL topology.The arcing process and current transfer process are analyzed in particular.Comparisons of the peak arc voltage,arcing time,current limiting efficiency,and electrode erosion are presented.The results demonstrate that the arc voltage of the novel FCL topology is reduced by more than 4.5times and the arcing time is reduced by more than 12%.The erosions of the liquid metal and electrodes are reduced.Moreover,the current limiting efficiency of the novel FCL topology is improved by 1%–5%.This work lays a foundation for the topology and optimal design of the LMCL.

Multiple-Stage Mineralization in the Huayangchuan U-REE-Mo-Cu-Fe Ore Belt of the Qinling Orogen,Central China:Geological and Re-Os Geochronological Constraints

The Huayangchuan ore belt is located in the western segment of Xiaoqinling Orogen in the southern margin of the North China Craton(NCC),and hosts voluminous magmatism and significant U-REE-Mo-Cu-Fe polymetallic mineralization.However,geochronological framework of the various mineralization phases in this region is poorly understood.Here,we present new Re-Os isochron ages on magnetite from the Caotan Fe deposit(2 675 ± 410 Ma,MSWD = 0.55),and on pyrite from the Jialu REE deposit(2 127 ± 280 Ma,MSWD = 1.9) and Yuejiawa Cu deposit(418 ± 23 Ma,MSWD =11.5),and Re-Os weighted average model age on pyrite from the Taoyuan Mo-U deposit(235 ± 14 Ma,MSWD = 0.17).These ages,combined with regional geology and mineralization ages from other deposits,suggest that mineralization in the Huayangchuan ore belt lasted from the Neoarchean to the Late Mesozoic.The mineralization corresponds to regional tectono-magmatic events,including the Neoarchean alkali magmatism(REE mineralization),Paleoproterozoic plagioclase-amphibolite emplacement(Fe mineralization),Paleoproterozoic pegmatite magmatism(U mineralization),Paleozoic Shangdan oceanic slab subduction-related arc magmatism(Cu mineralization),Early Mesozoic Paleo-Tethys Ocean subduction-related arc magmatism(Mo-U mineralization),and Late Mesozoic Paleo-Pacific oceanic plate subduction direction change-related Mo(-Pb) mineralization.We proposed that the Huayangchuan ore belt has undergone prolonged metallogenic evolution,and the magmatism and associated mineralization were controlled by regional geodynamic events.

Dating of monazite-apatite-allanite-epidote corona from the Bayan Obo Group in the northern margin of the North China Craton:implications for the time of regional Au and REE mineralization

The Mesoproterozoic Bayan Obo Group located along the northern margin of the North China Craton(NMNCC)hosts a world’s largest known rare-earth element(REE)deposit(Bayan Obo Fe-REE-Nb deposit)[1,2]and a number of large gold deposits(eg.,Haoyaoerhugong and Zhulazhaga gold deposits;Fig.1a)[3],and has a long and protracted thermal history spanning from1.3 Ga to 250 Ma[1].The tectonic history was associated with Proterozoic rifting with carbonatite magmatism at1.3 Ga[4]and subsequent subduction-accretion processes of the Paleo-Asian Ocean[5,6].The Paleo-Asian oceanic subduction beneath the North China Craton(NCC)initiated in the Middle Silurian[7,8]and the ocean was closed in the Permian to induce the accretion of arcs and terranes with the NCC[2].This long and protracted tectonic history increases the difficulties both in dating and understanding the genesis of the Bayan Obo REE deposit and black shale-hosted gold deposits(e.g.,Haoyaoerhudong deposit).Thus,it is important to understand the thermal history of the hosting strata in order to constrain the tectonic drive and timing of polymetallic mineraliza-tion.There have been few attempts to date the multistage thermal events which the Bayan Obo Group has witnessed,predominantly because of greenschist facies overprint of the host rocks and lack of reliable geochronometers[9,10].