The development of high-voltage direct current gas-insulated switchgear assemblies(DC GIS)of rated voltages up to±550 kV has been completed.DC GIS provide a compact technical solution with a high functional densi...The development of high-voltage direct current gas-insulated switchgear assemblies(DC GIS)of rated voltages up to±550 kV has been completed.DC GIS provide a compact technical solution with a high functional density,optimized for projects with limited space as in offshore HVDC converter platforms,onshore HVDC converter stations and transition stations between different transmission media.Up to now,no standards for testing of gas-insulated DC systems are available,although pre-standardization work is in progress within CIGRE.Some tests can be performed as required in AC GIS standards.Special aspects of DC voltage stress,like the electric field distribution of insulators influenced by the accumulation of electrical charge carriers and the operation-related inhomogeneous temperature distribution,must be considered by additional electric and thermoelectric tests.For DC GIS,the experience of long-term performance is limited today.Although ageing is expected to be of lower importance,tests are recommended.This contribution summarizes the physical and technical background to design and develop compact DC switchgear assemblies using gas-insulated technology.It explains the developed modules of the substation and gives an overview of the performed tests.Furthermore,it provides an insight in the on-going standardization activities and describes applications in converter and transition stations,showing its space-saving characteristics.展开更多
Transient enclosure voltage（TEV）,which is a phenomenon induced by the inner dielectric breakdown of SF_6 during disconnector operations in a gas-insulated switchgear（GIS）,may cause issues relating to shock hazard ...Transient enclosure voltage（TEV）,which is a phenomenon induced by the inner dielectric breakdown of SF_6 during disconnector operations in a gas-insulated switchgear（GIS）,may cause issues relating to shock hazard and electromagnetic interference to secondary equipment.This is a critical factor regarding the electromagnetic compatibility of ultra-high-voltage（UHV）substations.In this paper,the statistical characteristics of TEV at UHV level are collected from field experiments,and are analyzed and compared to those from a repeated strike process.The TEV waveforms during disconnector operations are recorded by a self-developed measurement system first.Then,statistical characteristics,such as the pulse number,duration of pulses,frequency components,magnitude and single pulse duration,are extracted.The transmission line theory is introduced to analyze the TEV and is validated by the experimental results.Finally,the relationship between the TEV and the repeated strike process is analyzed.This proves that the pulse voltage of the TEV is proportional to the corresponding breakdown voltage.The results contribute to the definition of the standard testing waveform of the TEV,and can aid the protection of electronic devices in substations by minimizing the threat of this phenomenon.展开更多
Environment-friendly gas insulating mediums adapted to a DC gas-insulated transmission line(GIL)electric field condition is the key to the next generation of Environment-friendly HVDC GILs.In this paper,we review the ...Environment-friendly gas insulating mediums adapted to a DC gas-insulated transmission line(GIL)electric field condition is the key to the next generation of Environment-friendly HVDC GILs.In this paper,we review the literature on sulfur hexafluoride(SF6)alternatives including the scientific understanding,control,and implementation of gas-solid systems in this type of power transmission.First,the structure-activity relationship between the molecular structure and physico-chemical properties of Environment-friendly insulating gases is presented.Then,the search and prediction of important physicochemical properties of gases are summarized.Subsequently,in view of the potential of environmental friendly insulating gases,the swarm parameters of gas discharge and breakdown properties in a quasi-uniform field,inhomogeneous field,and at the gas-solid interface,that need to be taken into account with industrialized DC GILs are discussed.The latest research progress on insulation characteristics,especially the polarity effect in DC gas-solid insulation systems,the sensitivity to the electrode surface state,and the non-uniformity of the electric field,and the influence of metal particles and their variation with air pressure,is highlighted.In addition,the heat transfer characteristics of insulating gases,related to DC GIL transmission with a large current-carrying capacity and the influence of alternative gases on the heat transfer characteristics are described.Finally,aiming at solving the contradiction of low environmental impact,high dielectric strength and low liquefaction temperatures in the selection of alternative gases,an coordinated regulation model for Environment-friendly gases in DC GILs is established.Considerations for future work on this topic are also presented.展开更多
Heptafluoroisobutyrontrile(C_(3)F_(7)CN)performs well in dielectric properties and environmental protection,which has the potential to replace SF6 gas.The decomposition characteristics of C_(3)F_(7)CN mixture under fa...Heptafluoroisobutyrontrile(C_(3)F_(7)CN)performs well in dielectric properties and environmental protection,which has the potential to replace SF6 gas.The decomposition characteristics of C_(3)F_(7)CN mixture under fault conditions directly affect the possibility of its replacement for SF6 gas.However,the number of studies on the decomposition characteristics of C_(3)F_(7)CN mixture under overheating fault is less.In this paper,the decomposition characteristics of C_(3)F_(7)CN/CO_(2) mixture under an overheating fault are studied by gas chromatography-mass spectrometry(GC/MS)and quantum chemical calculations.Byproducts CO,C_(3)F_(6) and HF are detected at 200℃.At 550℃,the C_(3)F_(7)CN molecule begins to decompose and produces CHF_(3),C_(2)F_(4),CF_(3)CN and CNCN.Moreover,the results of GC/MS show that the insulation medium C_(3)F_(7)CN contains an impurity,which is C3HF7(HFC-227ea).Combined with the results of GC/MS and quantum chemistry calculations,it can be concluded that the decomposition by-product C_(3)F_(6) at 200℃ mainly comes from the decomposition of C_(3)HF_(7).C_(3)HF_(7) reduces the decomposition temperature of the C_(3)F_(7)CN/CO_(2) mixture.Therefore,it is very important to improve the purity of the insulation medium C_(3)F_(7)CN.展开更多
基金supported by the Federal Ministry for Economic Affairs and Energy, Germany (FKZ:03ET7511C)the Bavarian Ministry of Economic Affairs, Regional Development and Energy (FKZ:IET-1208-0018)
文摘The development of high-voltage direct current gas-insulated switchgear assemblies(DC GIS)of rated voltages up to±550 kV has been completed.DC GIS provide a compact technical solution with a high functional density,optimized for projects with limited space as in offshore HVDC converter platforms,onshore HVDC converter stations and transition stations between different transmission media.Up to now,no standards for testing of gas-insulated DC systems are available,although pre-standardization work is in progress within CIGRE.Some tests can be performed as required in AC GIS standards.Special aspects of DC voltage stress,like the electric field distribution of insulators influenced by the accumulation of electrical charge carriers and the operation-related inhomogeneous temperature distribution,must be considered by additional electric and thermoelectric tests.For DC GIS,the experience of long-term performance is limited today.Although ageing is expected to be of lower importance,tests are recommended.This contribution summarizes the physical and technical background to design and develop compact DC switchgear assemblies using gas-insulated technology.It explains the developed modules of the substation and gives an overview of the performed tests.Furthermore,it provides an insight in the on-going standardization activities and describes applications in converter and transition stations,showing its space-saving characteristics.
基金supported by the National Basic Research Program of China(973 Program) under grant 2011CB209405
文摘Transient enclosure voltage（TEV）,which is a phenomenon induced by the inner dielectric breakdown of SF_6 during disconnector operations in a gas-insulated switchgear（GIS）,may cause issues relating to shock hazard and electromagnetic interference to secondary equipment.This is a critical factor regarding the electromagnetic compatibility of ultra-high-voltage（UHV）substations.In this paper,the statistical characteristics of TEV at UHV level are collected from field experiments,and are analyzed and compared to those from a repeated strike process.The TEV waveforms during disconnector operations are recorded by a self-developed measurement system first.Then,statistical characteristics,such as the pulse number,duration of pulses,frequency components,magnitude and single pulse duration,are extracted.The transmission line theory is introduced to analyze the TEV and is validated by the experimental results.Finally,the relationship between the TEV and the repeated strike process is analyzed.This proves that the pulse voltage of the TEV is proportional to the corresponding breakdown voltage.The results contribute to the definition of the standard testing waveform of the TEV,and can aid the protection of electronic devices in substations by minimizing the threat of this phenomenon.
基金This work was supported in part by the National Basic Research Program of China(973 Program)(2014CB239500).
文摘Environment-friendly gas insulating mediums adapted to a DC gas-insulated transmission line(GIL)electric field condition is the key to the next generation of Environment-friendly HVDC GILs.In this paper,we review the literature on sulfur hexafluoride(SF6)alternatives including the scientific understanding,control,and implementation of gas-solid systems in this type of power transmission.First,the structure-activity relationship between the molecular structure and physico-chemical properties of Environment-friendly insulating gases is presented.Then,the search and prediction of important physicochemical properties of gases are summarized.Subsequently,in view of the potential of environmental friendly insulating gases,the swarm parameters of gas discharge and breakdown properties in a quasi-uniform field,inhomogeneous field,and at the gas-solid interface,that need to be taken into account with industrialized DC GILs are discussed.The latest research progress on insulation characteristics,especially the polarity effect in DC gas-solid insulation systems,the sensitivity to the electrode surface state,and the non-uniformity of the electric field,and the influence of metal particles and their variation with air pressure,is highlighted.In addition,the heat transfer characteristics of insulating gases,related to DC GIL transmission with a large current-carrying capacity and the influence of alternative gases on the heat transfer characteristics are described.Finally,aiming at solving the contradiction of low environmental impact,high dielectric strength and low liquefaction temperatures in the selection of alternative gases,an coordinated regulation model for Environment-friendly gases in DC GILs is established.Considerations for future work on this topic are also presented.
基金supported by the National Key R&D Program of China(2017YFB0902500)Science&Technology Project of State Corporation of China:The Environment-Friendly Gas-Insulated Transmission Line(GIL)and National Natural Science Foundation of China(51877203)。
文摘Heptafluoroisobutyrontrile(C_(3)F_(7)CN)performs well in dielectric properties and environmental protection,which has the potential to replace SF6 gas.The decomposition characteristics of C_(3)F_(7)CN mixture under fault conditions directly affect the possibility of its replacement for SF6 gas.However,the number of studies on the decomposition characteristics of C_(3)F_(7)CN mixture under overheating fault is less.In this paper,the decomposition characteristics of C_(3)F_(7)CN/CO_(2) mixture under an overheating fault are studied by gas chromatography-mass spectrometry(GC/MS)and quantum chemical calculations.Byproducts CO,C_(3)F_(6) and HF are detected at 200℃.At 550℃,the C_(3)F_(7)CN molecule begins to decompose and produces CHF_(3),C_(2)F_(4),CF_(3)CN and CNCN.Moreover,the results of GC/MS show that the insulation medium C_(3)F_(7)CN contains an impurity,which is C3HF7(HFC-227ea).Combined with the results of GC/MS and quantum chemistry calculations,it can be concluded that the decomposition by-product C_(3)F_(6) at 200℃ mainly comes from the decomposition of C_(3)HF_(7).C_(3)HF_(7) reduces the decomposition temperature of the C_(3)F_(7)CN/CO_(2) mixture.Therefore,it is very important to improve the purity of the insulation medium C_(3)F_(7)CN.
