A novel multi-slice electromagnetic field-circuit coupling method for transient computation of long-distance gas-insulated transmission lines

Accurate calculation of short-circuit electromagnetic force is crucial for both mechanical strength check and the optimal design of gas-insulated transmission lines(GIL).Since the full 3D numerical simulation method is highly time-consuming,a novel lightweight 2D multi-slice electromagnetic field-circuit coupled method for computing transient electromagnetic force is proposed,where appropriate port voltage degrees of freedom(DoFs)are introduced for the solid GIL conductor terminals.When the transient magnetic field equations are combined with the constraint equations of circuit part,including nodal voltage and loop current DoFs,a direct field-circuit coupling scheme is thus derived.The proposed method can simultaneously consider the effect of interphaseshunts and ground wires,as well as the skin effect and proximity effect.It can accurately capture the transient electromagnetic characteristics of GIL spanning from several to tens of kilometers under different short-circuit conditions.The transient electromagnetic forces,as well as the induced voltages and currents of the enclosure,are analysed by the proposed method for both single-phase and three-phase enclosed GIL under various short-circuit conditions.The proposed method has the advantages of high accuracy and lightweight computational cost,and thus it is also suitable for conducting important simulation tasks such as mechanical strength checks during the design optimisation phase of long-distance GIL.

Spatio-temporal variation in rock exhumation linked to large-scale shear zones in the southeastern Tibetan Plateau

Crustal-scale shear zones are believed to have played an important role in the tectonic and landscape evolution of orogens. However, the variation of long-term rock exhumation between the interior of shear zones and adjacent regions has not been documented in detail. In this study, we obtained new zircon U-Pb, biotite ^(40)Ar/^(39)Ar, zircon and apatite(U-Th)/He data, and conducted inverse thermal history modeling from two age-elevation profiles(the Pianma and Tu'er profiles) in the southeastern Tibetan Plateau. Our goal is to constrain the exhumation history of the Gaoligong and Chongshan shear zones and adjacent regions, so as to explore the effect of the shear zones on exhumation and their thermal effect on cooling that should not be ignored. Our results suggest that during the interval of 18–11 Ma the exhumation rates of rocks within the Gaoligong shear zone are anomalously high compared with those outside of. The rapid cooling during 18–11 Ma appears to be restricted to the shear zone, likely due to localized thermal effects of shearing and exhumation. After 11 Ma, both the areas within and outside of the shear zones experienced a similar two-stage exhumation history: slower cooling until the early Pliocene, and then a rapid increase in cooling rate since the early Pliocene. Our results indicate a synchronized exhumation but with spatially varied exhumation rates. Our study also highlights the important role of large-scale shear zones in exposing rocks, and thus the importance of the structural context when interpreting thermochronological data in the southeastern margin of the Tibetan Plateau.