When a single-phase to ground fault(SPGF)occurs near the main power source in an active distribution network,distance protection sectionⅡ(DPS-Ⅱ)lo-cated at the distributed generator(DG)side operates with a delay.In ...When a single-phase to ground fault(SPGF)occurs near the main power source in an active distribution network,distance protection sectionⅡ(DPS-Ⅱ)lo-cated at the distributed generator(DG)side operates with a delay.In gap-grounded transformers,this delay can lead to gap breakdown due to neutral-point overvoltage,which adversely affects the operation of DPS-Ⅱon the DG side.To address this issue,this paper proposes an improved DPS designed for active distribution networks with gap-grounded transformers.First,the factors influencing the additional impedance are analyzed after gap breakdown.To mitigate the effects of the additional impedance on DPS performance,an improved DPS based on real short-circuit impedances is introduced for active distribution networks.This scheme utilizes the negative-sequence current distribution factor on the DG side to accurately calculate the additional impedance angle,ensuring reliable protection.Simulation results demonstrate that the proposed scheme effectively operates under forward faults across various DG capacities,fault locations,local loads,and fault transition resistances.In addition,it avoids tripping under reverse faults,thereby confirming its reliability and superiority.展开更多
The protection of classical or significant reference stratigraphic sections of the nation’s valuable geoheritage has become a priority by the Chinese government and national stratigraphic commission.The process for t...The protection of classical or significant reference stratigraphic sections of the nation’s valuable geoheritage has become a priority by the Chinese government and national stratigraphic commission.The process for the protection and documentation of stratigraphic sections includes:(1)marked tablets showing the standardized bed,member and formation divisions and,where applicable,standardized meter intervals for future investigations;(2)a monument or other on-site interpretive information;and(3)field guides for different audiences summarizing its importance with maps and detailed descriptions.In particular,the ten Global Stratotype Sections and Points(GSSPs)established in southern China are well preserved and managed;and some are now within tourist-friendly educational national geoparks.We suggest that other national stratigraphic commissions might incorporate some of the experiences from China’s current efforts to preserve and standardize important reference sections for Earth history research.展开更多
基金supported by the Science and Technology Project of China Southern Power Grid(No.030108KK52222003).
文摘When a single-phase to ground fault(SPGF)occurs near the main power source in an active distribution network,distance protection sectionⅡ(DPS-Ⅱ)lo-cated at the distributed generator(DG)side operates with a delay.In gap-grounded transformers,this delay can lead to gap breakdown due to neutral-point overvoltage,which adversely affects the operation of DPS-Ⅱon the DG side.To address this issue,this paper proposes an improved DPS designed for active distribution networks with gap-grounded transformers.First,the factors influencing the additional impedance are analyzed after gap breakdown.To mitigate the effects of the additional impedance on DPS performance,an improved DPS based on real short-circuit impedances is introduced for active distribution networks.This scheme utilizes the negative-sequence current distribution factor on the DG side to accurately calculate the additional impedance angle,ensuring reliable protection.Simulation results demonstrate that the proposed scheme effectively operates under forward faults across various DG capacities,fault locations,local loads,and fault transition resistances.In addition,it avoids tripping under reverse faults,thereby confirming its reliability and superiority.
文摘The protection of classical or significant reference stratigraphic sections of the nation’s valuable geoheritage has become a priority by the Chinese government and national stratigraphic commission.The process for the protection and documentation of stratigraphic sections includes:(1)marked tablets showing the standardized bed,member and formation divisions and,where applicable,standardized meter intervals for future investigations;(2)a monument or other on-site interpretive information;and(3)field guides for different audiences summarizing its importance with maps and detailed descriptions.In particular,the ten Global Stratotype Sections and Points(GSSPs)established in southern China are well preserved and managed;and some are now within tourist-friendly educational national geoparks.We suggest that other national stratigraphic commissions might incorporate some of the experiences from China’s current efforts to preserve and standardize important reference sections for Earth history research.
