The microstructure and electrical properties of ZnO-Bi2O3-Yb2O3 based varistor ceramics were investigated with various temperature effects from 900°C to 1050°C.From the results,it was observed that the incre...The microstructure and electrical properties of ZnO-Bi2O3-Yb2O3 based varistor ceramics were investigated with various temperature effects from 900°C to 1050°C.From the results,it was observed that the increase of sintering temperature offers a reduced capacitive effect from 0.460 nF to 0.321 nF.Furthermore,the grain sizes of varistors were varied from 6.8μm to 9.8μm.The consequence of such smaller grain sizes provided a better voltage gradient of about 895 V/mm for the disc sintered at 900°C and fallen drastically to 410 V/mm for the sample sintered at 1050°C.In addition,there was an increase of non-linearity index to a maximum value of 36.0 and reduced leakage current of 0.026 mA/cm2.However,the density of the varistor decreased with an increase of temperature from 5.41 g/cm3 to 5.24 g/cm3.With this base,the influence of varistor capacitance and high voltage gradient were scrutinized and it led an improved transition speed of the varistor assembly from non-conduction to conduction mode during intruding nanosecond transients.展开更多
Metal oxide surge arrester models that are currently on rounds suffer from certain deficiencies and as a consequence,they are not in position to portray accurately the arrester residual voltages.This drawback is mainl...Metal oxide surge arrester models that are currently on rounds suffer from certain deficiencies and as a consequence,they are not in position to portray accurately the arrester residual voltages.This drawback is mainly attributed to their inherent features.The prevailing pressing need demands accurate performance assessment of zinc oxide arrester under all types of overvoltages including very fast transient overvoltages(VFTOs).So immediate corrective measures like the formation of a new arrester model or rejig of the existing one are urgently warranted.This issue constitutes the centre piece/core of this study.In consideration of its various merits,which includes its capacity to bring out the virtual representation of arrester activities,electromagnetic transient programme software has been chosen for this study.With its aid,the arrester model recommended by IEEE Working Group has been aptly reshaped to suit the needs of VFTOs studies.The end results of the simulations thus carried out have clearly established its suitability for the studies involving nanosecond waves;additionally,it got its validation and endorsement from the test data obtained from different arrester manufacturers.The commendable endorsements got from these studies shed clear light on it.All these aspects are dealt with this work.展开更多
文摘The microstructure and electrical properties of ZnO-Bi2O3-Yb2O3 based varistor ceramics were investigated with various temperature effects from 900°C to 1050°C.From the results,it was observed that the increase of sintering temperature offers a reduced capacitive effect from 0.460 nF to 0.321 nF.Furthermore,the grain sizes of varistors were varied from 6.8μm to 9.8μm.The consequence of such smaller grain sizes provided a better voltage gradient of about 895 V/mm for the disc sintered at 900°C and fallen drastically to 410 V/mm for the sample sintered at 1050°C.In addition,there was an increase of non-linearity index to a maximum value of 36.0 and reduced leakage current of 0.026 mA/cm2.However,the density of the varistor decreased with an increase of temperature from 5.41 g/cm3 to 5.24 g/cm3.With this base,the influence of varistor capacitance and high voltage gradient were scrutinized and it led an improved transition speed of the varistor assembly from non-conduction to conduction mode during intruding nanosecond transients.
文摘Metal oxide surge arrester models that are currently on rounds suffer from certain deficiencies and as a consequence,they are not in position to portray accurately the arrester residual voltages.This drawback is mainly attributed to their inherent features.The prevailing pressing need demands accurate performance assessment of zinc oxide arrester under all types of overvoltages including very fast transient overvoltages(VFTOs).So immediate corrective measures like the formation of a new arrester model or rejig of the existing one are urgently warranted.This issue constitutes the centre piece/core of this study.In consideration of its various merits,which includes its capacity to bring out the virtual representation of arrester activities,electromagnetic transient programme software has been chosen for this study.With its aid,the arrester model recommended by IEEE Working Group has been aptly reshaped to suit the needs of VFTOs studies.The end results of the simulations thus carried out have clearly established its suitability for the studies involving nanosecond waves;additionally,it got its validation and endorsement from the test data obtained from different arrester manufacturers.The commendable endorsements got from these studies shed clear light on it.All these aspects are dealt with this work.
