New,more stringent environmental requirements for electrical insulation liquids have led to the development of novel,more environment‐friendly liquid dielectrics.Ester fluids,introduced several decades ago,provide a ...New,more stringent environmental requirements for electrical insulation liquids have led to the development of novel,more environment‐friendly liquid dielectrics.Ester fluids,introduced several decades ago,provide a viable alternative to traditional mineral insu-lating liquids.In order to expand the practical applications of these novel dielectric fluids,their dielectric and electrical parameters should be established.One of the critical pa-rameters that affects and governs the development of pre‐breakdown processes in insulating liquids is the mobility of charge carriers.In the present paper,the mobility of charge carriers in commercially available synthetic and natural insulating ester fluids and in a mineral insulating oil were obtained using two methods,the time of flight and the space charge saturation current methods.The mobility was obtained for a wide range of electrical field magnitudes.It was found that the mobility of charge carriers is greater in the mineral oil than in both,the natural and synthetic,ester fluids.It was also established that the mobility is higher for higher applied electric field.The results of this work will help in characterizing liquid dielectrics and in optimizing high‐voltage systems in which liquid dielectrics,including natural and synthetic ester fluids,are used.展开更多
Polymeric insulation is a critical component of high voltage systems.However,exposure to high electric stress can cause partial discharges(PDs)to occur and may result in the deterioration of insulation and lead to die...Polymeric insulation is a critical component of high voltage systems.However,exposure to high electric stress can cause partial discharges(PDs)to occur and may result in the deterioration of insulation and lead to dielectric failure.These PD events are accompanied by the production of acoustic pressure impulses in the polymer.Detection of these acoustic pressure impulses can reveal the presence of PDs and locate their source.However,analysing the detected acoustic emission(AE)signal is challenging.The acoustic pressure source's nature and the propagating medium's properties,such as density,viscosity,and elasticity,significantly affect the propagating AE signal.The effects of the hardness of the polyurethane(PU)on the propagating AE signal are reported by the authors based on results obtained from laboratory experiments.It was observed that the decay rate in the magnitude of the acoustic impulse was high in PU at all hardness levels following an exponential behaviour.The analysis of the frequency spectra indicates that the higher frequency components attenuate more strongly with distance.These laboratory results can be valuable for engineers and industries as they provide valuable insight into how the physical characteristics of a material affect the propagation characteristics of AE signals during the detection and location of PD source using the AE detection technique.展开更多
文摘New,more stringent environmental requirements for electrical insulation liquids have led to the development of novel,more environment‐friendly liquid dielectrics.Ester fluids,introduced several decades ago,provide a viable alternative to traditional mineral insu-lating liquids.In order to expand the practical applications of these novel dielectric fluids,their dielectric and electrical parameters should be established.One of the critical pa-rameters that affects and governs the development of pre‐breakdown processes in insulating liquids is the mobility of charge carriers.In the present paper,the mobility of charge carriers in commercially available synthetic and natural insulating ester fluids and in a mineral insulating oil were obtained using two methods,the time of flight and the space charge saturation current methods.The mobility was obtained for a wide range of electrical field magnitudes.It was found that the mobility of charge carriers is greater in the mineral oil than in both,the natural and synthetic,ester fluids.It was also established that the mobility is higher for higher applied electric field.The results of this work will help in characterizing liquid dielectrics and in optimizing high‐voltage systems in which liquid dielectrics,including natural and synthetic ester fluids,are used.
文摘Polymeric insulation is a critical component of high voltage systems.However,exposure to high electric stress can cause partial discharges(PDs)to occur and may result in the deterioration of insulation and lead to dielectric failure.These PD events are accompanied by the production of acoustic pressure impulses in the polymer.Detection of these acoustic pressure impulses can reveal the presence of PDs and locate their source.However,analysing the detected acoustic emission(AE)signal is challenging.The acoustic pressure source's nature and the propagating medium's properties,such as density,viscosity,and elasticity,significantly affect the propagating AE signal.The effects of the hardness of the polyurethane(PU)on the propagating AE signal are reported by the authors based on results obtained from laboratory experiments.It was observed that the decay rate in the magnitude of the acoustic impulse was high in PU at all hardness levels following an exponential behaviour.The analysis of the frequency spectra indicates that the higher frequency components attenuate more strongly with distance.These laboratory results can be valuable for engineers and industries as they provide valuable insight into how the physical characteristics of a material affect the propagation characteristics of AE signals during the detection and location of PD source using the AE detection technique.
