Charge dynamics at interfaces in high voltage direct current(HVDC)cable joints consisting of cable,joint insulation and lubricant may have an impact on the overall joint reliability.Although interactions between diffe...Charge dynamics at interfaces in high voltage direct current(HVDC)cable joints consisting of cable,joint insulation and lubricant may have an impact on the overall joint reliability.Although interactions between different lubricants and the joint insulation have been studied in recent years,the effect of lubricant diffusion on the electrical properties and charge dynamics at interfaces remains unclear and is therefore investigated in this paper.Different lubricants were applied at the interface of crosslinked polyethylene(XLPE)and silicone rubber(SIR)samples,and mass,electrical conductivity,and space charge were measured over a 96 h ageing period.The mass of the samples was found to exhibit nonmonotonic behaviour,indicating complex interactions between the lubricant and material.XLPE experiences a decrease in conductivity while there is an increase in conductivity for SIR,which is linked to the migration of lubricant and therefore changes in trap distribution.Space charge measurements indicate changes in trap characteristics,which depend strongly on the used type of lubricant.The findings highlight that lubricant diffusion affects both the bulk properties and charge accumulation at the interface,and underline the large effect of the type of lubricant.These results are crucial for understanding the long-term performance of cable joints and insulating materials in HVDC cable systems.展开更多
High-voltage direct current(HVDC)cables are growing rapidly all over the world due to the development of offshore wind power interconnections,cross-island power interconnections,etc.Extensive research has been conduct...High-voltage direct current(HVDC)cables are growing rapidly all over the world due to the development of offshore wind power interconnections,cross-island power interconnections,etc.Extensive research has been conducted and many achievements have been made in the study of theoretical issues of HVDC insulation,structural design and manufacture of HVDC cables with the corresponding accessories,as well as in condition monitoring technology.展开更多
Today's power systems are seeing a paradigm shift under the energy transition,sparkled by the electrification of demand,digitalisation of systems,and an increasing share of decarbonated power generation.Most of th...Today's power systems are seeing a paradigm shift under the energy transition,sparkled by the electrification of demand,digitalisation of systems,and an increasing share of decarbonated power generation.Most of these changes have a direct impact on their control centers,forcing them to handle weather-based energy resources,new interconnections with neighbouring transmission networks,more markets,active distribution networks,micro-grids,and greater amounts of available data.Unfortunately,these changes have translated during the past decade to small,incremental changes,mostly centered on hardware,software,and human factors.We assert that more transformative changes are needed,especially regarding human-centered design approaches,to enable control room operators to manage the future power system.This paper discusses the evolution of operators towards continuous operation planners,monitoring complex time horizons thanks to adequate real-time automation.Reviewing upcoming challenges as well as emerging technologies for power systems,we present our vision of a new evolutionary architecture for control centers,both at backend and frontend levels.We propose a unified hypervision scheme based on structured decision-making concepts,providing operators with proactive,collaborative,and effective decision support.展开更多
This study presents an investigation of the impact of the quasi-stationary voltage support provided by a voltage source converter(VSC)connected to a single point of a power system.Based on the directional derivative c...This study presents an investigation of the impact of the quasi-stationary voltage support provided by a voltage source converter(VSC)connected to a single point of a power system.Based on the directional derivative concept,an analytical method is developed to quantify the sensitivities of the AC bus voltage with respect to the VSC reactive power control modes.Based on a real case study,it is shown that the method applies to VSC units that are part of VSC-HVDC systems,which can operate in a point-to-point or multi-terminal configuration.Time-domain simulations are performed to verify the findings from the application of the analytical method on a reduced size power system.展开更多
The operation of electricity grids has become increasingly complex due to the current upheaval and the increase in renewable energy production.As a consequence,active grid management is reaching its limits with conven...The operation of electricity grids has become increasingly complex due to the current upheaval and the increase in renewable energy production.As a consequence,active grid management is reaching its limits with conventional approaches.In the context of the Learning to Run a Power Network(L2RPN)challenge,it has been shown that Reinforcement Learning(RL)is an efficient and reliable approach with considerable potential for automatic grid operation.In this article,we analyse the submitted agent from Binbinchen and provide novel strategies to improve the agent,both for the RL and the rule-based approach.The main improvement is a N-1 strategy,where we consider topology actions that keep the grid stable,even if one line is disconnected.More,we also propose a topology reversion to the original grid,which proved to be beneficial.The improvements are tested against reference approaches on the challenge test sets and are able to increase the performance of the rule-based agent by 27%.In direct comparison between rule-based and RL agent we find similar performance.However,the RL agent has a clear computational advantage.We also analyse the behaviour in an exemplary case in more detail to provide additional insights.Here,we observe that through the N-1 strategy,the actions of both the rule-based and the RL agent become more diversified.展开更多
文摘Charge dynamics at interfaces in high voltage direct current(HVDC)cable joints consisting of cable,joint insulation and lubricant may have an impact on the overall joint reliability.Although interactions between different lubricants and the joint insulation have been studied in recent years,the effect of lubricant diffusion on the electrical properties and charge dynamics at interfaces remains unclear and is therefore investigated in this paper.Different lubricants were applied at the interface of crosslinked polyethylene(XLPE)and silicone rubber(SIR)samples,and mass,electrical conductivity,and space charge were measured over a 96 h ageing period.The mass of the samples was found to exhibit nonmonotonic behaviour,indicating complex interactions between the lubricant and material.XLPE experiences a decrease in conductivity while there is an increase in conductivity for SIR,which is linked to the migration of lubricant and therefore changes in trap distribution.Space charge measurements indicate changes in trap characteristics,which depend strongly on the used type of lubricant.The findings highlight that lubricant diffusion affects both the bulk properties and charge accumulation at the interface,and underline the large effect of the type of lubricant.These results are crucial for understanding the long-term performance of cable joints and insulating materials in HVDC cable systems.
文摘High-voltage direct current(HVDC)cables are growing rapidly all over the world due to the development of offshore wind power interconnections,cross-island power interconnections,etc.Extensive research has been conducted and many achievements have been made in the study of theoretical issues of HVDC insulation,structural design and manufacture of HVDC cables with the corresponding accessories,as well as in condition monitoring technology.
文摘Today's power systems are seeing a paradigm shift under the energy transition,sparkled by the electrification of demand,digitalisation of systems,and an increasing share of decarbonated power generation.Most of these changes have a direct impact on their control centers,forcing them to handle weather-based energy resources,new interconnections with neighbouring transmission networks,more markets,active distribution networks,micro-grids,and greater amounts of available data.Unfortunately,these changes have translated during the past decade to small,incremental changes,mostly centered on hardware,software,and human factors.We assert that more transformative changes are needed,especially regarding human-centered design approaches,to enable control room operators to manage the future power system.This paper discusses the evolution of operators towards continuous operation planners,monitoring complex time horizons thanks to adequate real-time automation.Reviewing upcoming challenges as well as emerging technologies for power systems,we present our vision of a new evolutionary architecture for control centers,both at backend and frontend levels.We propose a unified hypervision scheme based on structured decision-making concepts,providing operators with proactive,collaborative,and effective decision support.
文摘This study presents an investigation of the impact of the quasi-stationary voltage support provided by a voltage source converter(VSC)connected to a single point of a power system.Based on the directional derivative concept,an analytical method is developed to quantify the sensitivities of the AC bus voltage with respect to the VSC reactive power control modes.Based on a real case study,it is shown that the method applies to VSC units that are part of VSC-HVDC systems,which can operate in a point-to-point or multi-terminal configuration.Time-domain simulations are performed to verify the findings from the application of the analytical method on a reduced size power system.
基金This work was supported by the Competence Centre for Cognitive Energy Systems of the Fraunhofer IEE and the research group Rein-forcement Learning for cognitive energy systems(RL4CES)from the Intelligent Embedded Systems of the University Kassel.
文摘The operation of electricity grids has become increasingly complex due to the current upheaval and the increase in renewable energy production.As a consequence,active grid management is reaching its limits with conventional approaches.In the context of the Learning to Run a Power Network(L2RPN)challenge,it has been shown that Reinforcement Learning(RL)is an efficient and reliable approach with considerable potential for automatic grid operation.In this article,we analyse the submitted agent from Binbinchen and provide novel strategies to improve the agent,both for the RL and the rule-based approach.The main improvement is a N-1 strategy,where we consider topology actions that keep the grid stable,even if one line is disconnected.More,we also propose a topology reversion to the original grid,which proved to be beneficial.The improvements are tested against reference approaches on the challenge test sets and are able to increase the performance of the rule-based agent by 27%.In direct comparison between rule-based and RL agent we find similar performance.However,the RL agent has a clear computational advantage.We also analyse the behaviour in an exemplary case in more detail to provide additional insights.Here,we observe that through the N-1 strategy,the actions of both the rule-based and the RL agent become more diversified.
