In modern power transmission systems,AC cables are increasingly integrated with overhead lines,forming hybrid networks.These cables are frequently exposed to repeated impulse voltages from the overhead lines.While sur...In modern power transmission systems,AC cables are increasingly integrated with overhead lines,forming hybrid networks.These cables are frequently exposed to repeated impulse voltages from the overhead lines.While surge arresters offer partial protection,the long-term effects of these impulses on polypropylene(PP)insulation remain unclear.This study systematically investigates the cumulative degradation of the electrical breakdown properties of PP insulation under repeated impulse voltage stress.The 50%impulse breakdown voltage(U_(50))was first determined,and a series of impulse tests were conducted at varying voltage levels to assess the number of impulses required for elec-trical breakdown,leading to the construction of an amplitude of impulse voltage(U)and the number of times required for breakdown(N),which is U-N curve.To evaluate the cumulative degradation,impulse voltage at 0.8 U_(50)was applied for 50,100,and 200 cycles,with the electrical conductivity current measured before and after each series of impulses.The results indicate significant degradation in the insulating properties of PP under repeated impulse stress.Mechanisms of cumulative degradation under impulse stress were further explored using isothermal relaxation current and space charge measurements.These findings provide critical insights into the performance of PP in hybrid transmission systems and offer valuable data to inform improved insulation design and protection strategies.展开更多
As wind power penetration has been gaining in the power grid for decades,a large number of the doubly fed induction generator(DFIG)based wind farms are being established around the globe.The power capacities of these ...As wind power penetration has been gaining in the power grid for decades,a large number of the doubly fed induction generator(DFIG)based wind farms are being established around the globe.The power capacities of these wind farms may vary around hundreds of MW,and most of the wind farms are connected to long transmission cables whose impedances can not be ignored and require careful attention.Several works have investigated the impedance interaction between the DFIG based wind farm and long transmission cables which may unfortunately cause high frequency resonance(HFR).The main contribution of this paper is to investigate the influence of the variable wind farm capacity on the behavior of the HFR when certain transmission cables are provided.It is found out that the potential HFR may happen in certain wind farms,and the larger wind farm capacity causes more severe HFR due to the relatively weaker grid transmission capability.Simulation results based on Matlab/Simulink are given to validate the analysis of HFR.展开更多
With the development of deep-sea wind power and large-scale onshore clean energy,the global demand for higher voltage level DC cable power transmission technology has become increasingly urgent.This paper systematical...With the development of deep-sea wind power and large-scale onshore clean energy,the global demand for higher voltage level DC cable power transmission technology has become increasingly urgent.This paper systematically reviews the technical advancements in high voltage direct current(HVDC)cable accessories,addressing design challenges of terminations and joints,insulation material performance,manufacturing processes for large-scale components,standard frameworks and long-term reliability.The core challenges in HVDC accessories are identified as conductivity matching of insulating materials,interface electric field regulation and multi-field coupling reliability,requiring synergistic optimisation of electrical,thermal and mechanical behaviours through the modification of rubber materials,interfacial compatibility and multi-physics field modelling.Silicon rubber and ethylene propylene diene monomer made in China have achieved electrical properties comparable to international standards,yet breakthroughs in tear resistance,process consistency and environmental sustainability remain critical.The injection moulding defect control and uniform moulding process of large rubber and epoxy parts demand further improvement.The standard system in China needs to be strengthened in terms of systematic certification and long-term reliability evaluation.Future research should prioritise eco-friendly material development,intelligent monitoring technologies and multi-field coupling ageing life prediction to enhance the reliability of HVDC cable systems under extreme voltages and complex operational scenarios.展开更多
基金China Southern Power Grid Company Limited,Grant/Award Number:ZBKJXM20220101National Natural Science Foundation of China,Grant/Award Number:52107019。
文摘In modern power transmission systems,AC cables are increasingly integrated with overhead lines,forming hybrid networks.These cables are frequently exposed to repeated impulse voltages from the overhead lines.While surge arresters offer partial protection,the long-term effects of these impulses on polypropylene(PP)insulation remain unclear.This study systematically investigates the cumulative degradation of the electrical breakdown properties of PP insulation under repeated impulse voltage stress.The 50%impulse breakdown voltage(U_(50))was first determined,and a series of impulse tests were conducted at varying voltage levels to assess the number of impulses required for elec-trical breakdown,leading to the construction of an amplitude of impulse voltage(U)and the number of times required for breakdown(N),which is U-N curve.To evaluate the cumulative degradation,impulse voltage at 0.8 U_(50)was applied for 50,100,and 200 cycles,with the electrical conductivity current measured before and after each series of impulses.The results indicate significant degradation in the insulating properties of PP under repeated impulse stress.Mechanisms of cumulative degradation under impulse stress were further explored using isothermal relaxation current and space charge measurements.These findings provide critical insights into the performance of PP in hybrid transmission systems and offer valuable data to inform improved insulation design and protection strategies.
文摘As wind power penetration has been gaining in the power grid for decades,a large number of the doubly fed induction generator(DFIG)based wind farms are being established around the globe.The power capacities of these wind farms may vary around hundreds of MW,and most of the wind farms are connected to long transmission cables whose impedances can not be ignored and require careful attention.Several works have investigated the impedance interaction between the DFIG based wind farm and long transmission cables which may unfortunately cause high frequency resonance(HFR).The main contribution of this paper is to investigate the influence of the variable wind farm capacity on the behavior of the HFR when certain transmission cables are provided.It is found out that the potential HFR may happen in certain wind farms,and the larger wind farm capacity causes more severe HFR due to the relatively weaker grid transmission capability.Simulation results based on Matlab/Simulink are given to validate the analysis of HFR.
基金supported by the Science and Technology Project of SGCC(521001250033-246-YYGG).
文摘With the development of deep-sea wind power and large-scale onshore clean energy,the global demand for higher voltage level DC cable power transmission technology has become increasingly urgent.This paper systematically reviews the technical advancements in high voltage direct current(HVDC)cable accessories,addressing design challenges of terminations and joints,insulation material performance,manufacturing processes for large-scale components,standard frameworks and long-term reliability.The core challenges in HVDC accessories are identified as conductivity matching of insulating materials,interface electric field regulation and multi-field coupling reliability,requiring synergistic optimisation of electrical,thermal and mechanical behaviours through the modification of rubber materials,interfacial compatibility and multi-physics field modelling.Silicon rubber and ethylene propylene diene monomer made in China have achieved electrical properties comparable to international standards,yet breakthroughs in tear resistance,process consistency and environmental sustainability remain critical.The injection moulding defect control and uniform moulding process of large rubber and epoxy parts demand further improvement.The standard system in China needs to be strengthened in terms of systematic certification and long-term reliability evaluation.Future research should prioritise eco-friendly material development,intelligent monitoring technologies and multi-field coupling ageing life prediction to enhance the reliability of HVDC cable systems under extreme voltages and complex operational scenarios.
