Epoxy rubber-impregnated paper sleeve has the advantages of stable electrical performance,explosion-proof function,small volume,lightweight,etc.,and is widely used in transformer casing and through-wall casing.However,its manufacturing process is complex,which makes it easy to produce defects in the production process,and it is difficult to detect certain defects in the test at room temperature.To study the partial discharge and dielectric loss characteristics of typical defects of rubber-im-pregnated paper sleeve after temperature rise,defective bushings with moisture,metal particles,and core cracks are designed and prepared.After heating the sleeves to a certain temperature,the partial discharge pattern and dielectric loss factor of the sleeves are measured.The results show that the discharge of core crack defective sleeve and the moisture defective sleeve increa-ses more after heating after the temperature rise,while the metal particles defective sleeve has the smallest impact,which indi-cates that the temperature rise test has a better detection effect on the core crack and moisture defective sleeves in the thermal state.The results of the study can provide certain references and guidance for the factory inspection and troubleshooting of rub-ber-impregnated paper sleeve.
Under the continuous promotion of the "double carbon" strategic goal, the "oil to electricity" development momentum of heavy trucks is strong, and the pure electric heavy truck has become the main mode of logistics and transportation. Overall scheme design of aggregation regulation and control for friendly interaction between pure electric heavy truck cluster and power grid is proposed in this paper. Firstly, the aggregation regulation and control system are expounded from four dimensions of the problem solved, the technological innovation point, the deployment framework and the functional framework. Secondly, based on the perspective of power grid side, the comprehensive function and application scenario of the upper-level interactive control platform of pure electric heavy truck cluster is designed. Then, based on the perspective of aggregator side, the six functions of the middle-level aggregation management and control platform for pure electric heavy truck charging and changing station are constructed. Finally, based on the perspective of load side, the lower-level intelligent edge terminal of pure electric heavy truck charging and changing station is summarized, and the functional module is constructed from the three aspects of data processing, resource management and optimization control. The overall scheme of aggregation regulation and control designed in this paper is helpful to realize the friendly interaction between the pure electric heavy truck cluster and the power grid, and further improve the safe and stable operation of power grid.
High-resistance faults in direct current (DC) microgrids are small and thus difficult to detect. Such faults may be "invisible" in that grid operation continues for a considerable time, which damages the grid. It is essential to detect and remove high-resistance faults; we present a detection method herein. First, the transient DC current during the fault is subjected to hierarchical wavelet decomposition to identify high-resistance faults accurately and sensitively; the wavelet coefficients are detected using the singular value decomposition (SVD) method. The SVD valve can denoise the dc microgrid fault current, which eliminates the influence of converter switching frequency and background noise effectively. Power system computer-aided design (PSCAD)/electromagnetic transients including direct current (EMTDC)-based simulations showed that our method successfully identified high-resistance faults.
针对多分支配电网拓扑结构复杂,单一行波故障测距无法普适的问题,构建多分支配电网模型、改进行波提取装置为分支点处间隔配置、定义配电网中三类故障位置,同时对无行波提取装置的分支故障定位提出双端模量波速差测距方法,结合双端行波故障测距与单端模量波速差故障测距方法组合测距,实现了配电网内单相接地故障定位全覆盖.并采用PSCAD/EMPDC仿真平台搭建故障测距模型,结果表明该方法测距精度较高且稳定性强,满足了工程实际需求.
随着我国新能源发电占比不断提高,仅靠传统手段已难以维持电网安全平稳运转和动态平衡,亟需通过调整灵活负荷资源积极参与电网调节.本文以电动汽车、空调、储能等柔性负荷作为参与电网平衡的主体,研究通过负荷聚合的形式参与多级电网平衡.首先,建立各个参与平衡主体的优化模型;其次,基于电价型需求响应与主从博弈,提出以配电网运营商经济效益最大、电动汽车与空调各自用电成本最低为目标的优化模型.最后,建立上层为配电网运营商,下层为电动汽车聚合商和空调聚合商的主从博弈模型.算例分析表明,所提出的优化模型在提高各主体经济性的同时能有效降低峰谷差.
