To deal with the problem of low computational precision at the nodes near the source and satisfy the requirements for computational efficiency in inversion imaging and finite-element numerical simulations of the direc...To deal with the problem of low computational precision at the nodes near the source and satisfy the requirements for computational efficiency in inversion imaging and finite-element numerical simulations of the direct current method, we propose a new mesh refinement and recoarsement method for a two-dimensional point source. We introduce the mesh refinement and mesh recoarsement into the traditional structured mesh subdivision. By refining the horizontal grids, the singularity owing to the point source is minimized and the topography is simulated. By recoarsening the horizontal grids, the number of grid cells is reduced significantly and computational efficiency is improved. Model tests show that the proposed method solves the singularity problem and reduces the number of grid cells by 80% compared to the uniform grid refinement.展开更多
To achieve the current study, geoelectrical surveys along six (06) profiles of 4 km long in a 100 m × 200 m grid defined according to the triangulation principle in the Tindikala-Boutou (Eastern-Cameroon) area al...To achieve the current study, geoelectrical surveys along six (06) profiles of 4 km long in a 100 m × 200 m grid defined according to the triangulation principle in the Tindikala-Boutou (Eastern-Cameroon) area along the Kadey River have been made through electrical sounding and profiling following Schlumberger array. The instrument is the resistive meter Syscal Junior 48 (IRIS Instrument). The data have been processed and modelled with Res2Dinv and Winsev softwares, and then interpolated with Surfer software. Investigation method used is the Direct Current (DC) method. Interpretations and analyses of results from the investigation method highlight weak zones or conductive discontinuities. The latter has been identified as shear zones within granitic structures of the Precambrian basement, according to the geologic and tectonic background of the area. The structural trend of these shear zones is E-W approximately. The mineralization characterized by conductive zones proves the presence of clay minerals disseminated in weathered quartz vein, which cross the shear zones. The intense activities of gold washers encountered in the studied area are able to attest the presence of clay minerals concentrations.展开更多
针对换相失败恢复过程中直流电流预测难度大的问题,首先对直流线路的等效模型进行分析,建立整流侧直流电压与逆变侧各电气量之间的定量关系,结合直流控制分析提出一种可准确预测直流电流变化量的方法。其次,基于最小关断面积判别与直流...针对换相失败恢复过程中直流电流预测难度大的问题,首先对直流线路的等效模型进行分析,建立整流侧直流电压与逆变侧各电气量之间的定量关系,结合直流控制分析提出一种可准确预测直流电流变化量的方法。其次,基于最小关断面积判别与直流电流变化量的预测方法,构建后续换相失败风险评估模型,并根据风险评估结果实现对触发角的定量控制,从而抑制后续换相失败的发生。以PSCAD/EMTDC平台中的国际大电网会议(conseil interna-tional des grands reseaux elecctriques,CIGRE)标准模型为测试系统,不同故障类型、严重程度及故障持续时间下的仿真结果验证了所提直流电流预测、后续换相失败风险评估的准确性和后续换相失败抑制策略的有效性。展开更多
基金financially supported by the National Natural Science Foundation of China(No.41574127 and 41174104)the National Key Technology R&D Program for the 13th five-year plan(No.2016ZX05018006-006)
文摘To deal with the problem of low computational precision at the nodes near the source and satisfy the requirements for computational efficiency in inversion imaging and finite-element numerical simulations of the direct current method, we propose a new mesh refinement and recoarsement method for a two-dimensional point source. We introduce the mesh refinement and mesh recoarsement into the traditional structured mesh subdivision. By refining the horizontal grids, the singularity owing to the point source is minimized and the topography is simulated. By recoarsening the horizontal grids, the number of grid cells is reduced significantly and computational efficiency is improved. Model tests show that the proposed method solves the singularity problem and reduces the number of grid cells by 80% compared to the uniform grid refinement.
文摘To achieve the current study, geoelectrical surveys along six (06) profiles of 4 km long in a 100 m × 200 m grid defined according to the triangulation principle in the Tindikala-Boutou (Eastern-Cameroon) area along the Kadey River have been made through electrical sounding and profiling following Schlumberger array. The instrument is the resistive meter Syscal Junior 48 (IRIS Instrument). The data have been processed and modelled with Res2Dinv and Winsev softwares, and then interpolated with Surfer software. Investigation method used is the Direct Current (DC) method. Interpretations and analyses of results from the investigation method highlight weak zones or conductive discontinuities. The latter has been identified as shear zones within granitic structures of the Precambrian basement, according to the geologic and tectonic background of the area. The structural trend of these shear zones is E-W approximately. The mineralization characterized by conductive zones proves the presence of clay minerals disseminated in weathered quartz vein, which cross the shear zones. The intense activities of gold washers encountered in the studied area are able to attest the presence of clay minerals concentrations.
文摘针对换相失败恢复过程中直流电流预测难度大的问题,首先对直流线路的等效模型进行分析,建立整流侧直流电压与逆变侧各电气量之间的定量关系,结合直流控制分析提出一种可准确预测直流电流变化量的方法。其次,基于最小关断面积判别与直流电流变化量的预测方法,构建后续换相失败风险评估模型,并根据风险评估结果实现对触发角的定量控制,从而抑制后续换相失败的发生。以PSCAD/EMTDC平台中的国际大电网会议(conseil interna-tional des grands reseaux elecctriques,CIGRE)标准模型为测试系统,不同故障类型、严重程度及故障持续时间下的仿真结果验证了所提直流电流预测、后续换相失败风险评估的准确性和后续换相失败抑制策略的有效性。
