A lightning arrester is used for electrical equipment protection against damage due to lightning strikes.One example of protected electrical equipment is electrical power transformer.If there is no lightning arrester ...A lightning arrester is used for electrical equipment protection against damage due to lightning strikes.One example of protected electrical equipment is electrical power transformer.If there is no lightning arrester installed to the transformer,when a lightning strike happens,it may receive a very high lightning overvoltage,which is certainly resulted in the transformer damage at its insulation.Usually,a lightning arrester specification data attached to a lightning arrester contains the rating data of the lightning arrester current and voltage.In the use of lightning arrester,the possibility of receiving multiple lightning strikes is not taken into account sometimes.In fact,in some places,the number of multiple strikes in short duration is quiet high in number.This condition makes the lightning arrester being stroked by multiple lightning strikes.Therefore,it may change the lightning arrester's properties,and then the arrester may not be able to provide good electrical equipment protection against lightning strike anymore.This condition will result in great loss to electrical companies and electrical consumers.Therefore,this research studied the effect of applying multiple lightning strikes to ZnO lightning arrester block.Every time a group of lightning impulse current is applied to the ZnO lightning arrester block,it is followed by the measuring of its 50 Hz voltage and current characteristic. The changing in the ZnO lightning arrester block 50 Hz characteristic then can be analyzed.It was found that by applying more numbers of lightning strikes which made the arrester becoming worse,even though,actually,the lightning impulse peak current was still under the rating of the lightning arrester current.In this case for a 5 kA,24 kV lightning arrester,even though the lightning impulse peak current flowing through the ZnO lightning arrester block was still 2500 A,the lightning arrester ZnO block had already been damaged.Having been damaged,an alternating current flowing through the damaged ZnO block was about 10000 times as much current flowing to the good one.The maximum of impulse energy absorbed by a ZnO block recorded was 334.7 J/cm^3.The damaged ZnO block should be replaced by a good one.展开更多
In this work,the results of an experimental study of the impulse characteristic of practical ground electrodes consisting of horizontal conductors of various lengths and full-scale tower footings were reported.These e...In this work,the results of an experimental study of the impulse characteristic of practical ground electrodes consisting of horizontal conductors of various lengths and full-scale tower footings were reported.These electrodes were installed at an outdoor test site having nonuniform soil,with equipment facilities for generating low-and high-magnitude impulse currents.The tests on the horizontal electrode were used to determine the effective length,the voltage and current distribution along the electrode length and the effect of the injection point along the electrode.The tests on the tower footings were used to determine impulse resistance and demonstrate its non-linear variation with current magnitude.Computer simulations of the test electrodes using the electromagnetic field method showed good agreement with the measured result.展开更多
文摘A lightning arrester is used for electrical equipment protection against damage due to lightning strikes.One example of protected electrical equipment is electrical power transformer.If there is no lightning arrester installed to the transformer,when a lightning strike happens,it may receive a very high lightning overvoltage,which is certainly resulted in the transformer damage at its insulation.Usually,a lightning arrester specification data attached to a lightning arrester contains the rating data of the lightning arrester current and voltage.In the use of lightning arrester,the possibility of receiving multiple lightning strikes is not taken into account sometimes.In fact,in some places,the number of multiple strikes in short duration is quiet high in number.This condition makes the lightning arrester being stroked by multiple lightning strikes.Therefore,it may change the lightning arrester's properties,and then the arrester may not be able to provide good electrical equipment protection against lightning strike anymore.This condition will result in great loss to electrical companies and electrical consumers.Therefore,this research studied the effect of applying multiple lightning strikes to ZnO lightning arrester block.Every time a group of lightning impulse current is applied to the ZnO lightning arrester block,it is followed by the measuring of its 50 Hz voltage and current characteristic. The changing in the ZnO lightning arrester block 50 Hz characteristic then can be analyzed.It was found that by applying more numbers of lightning strikes which made the arrester becoming worse,even though,actually,the lightning impulse peak current was still under the rating of the lightning arrester current.In this case for a 5 kA,24 kV lightning arrester,even though the lightning impulse peak current flowing through the ZnO lightning arrester block was still 2500 A,the lightning arrester ZnO block had already been damaged.Having been damaged,an alternating current flowing through the damaged ZnO block was about 10000 times as much current flowing to the good one.The maximum of impulse energy absorbed by a ZnO block recorded was 334.7 J/cm^3.The damaged ZnO block should be replaced by a good one.
文摘In this work,the results of an experimental study of the impulse characteristic of practical ground electrodes consisting of horizontal conductors of various lengths and full-scale tower footings were reported.These electrodes were installed at an outdoor test site having nonuniform soil,with equipment facilities for generating low-and high-magnitude impulse currents.The tests on the horizontal electrode were used to determine the effective length,the voltage and current distribution along the electrode length and the effect of the injection point along the electrode.The tests on the tower footings were used to determine impulse resistance and demonstrate its non-linear variation with current magnitude.Computer simulations of the test electrodes using the electromagnetic field method showed good agreement with the measured result.
