多次雷电冲击对氧化锌避雷器阀片性能的影响(英文)

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.

硅橡胶环氧树脂复合材料电痕的实验研究(英文)

The use of polymer materials as electrical insulators on transmission and distribution lines has been increasing such as epoxy resin.Several advantages of using epoxy resin as an insulating material are its low density,better dielectric properties,and epoxy resin has higher volume resistivity than that of the glass and porcelain.However,epoxy resin has some disadvantages when it is used in tropical areas concerning with the humidity,high ultraviolet radiation, acid rain and effects of contaminants.Consequently,insulator surface will be easily damaged due to electrical tracking,which is indicated by the surface tracking.In this paper,the surface tracking on epoxy resin compound with silicon rubber has been investigated.The test was done based on the method of Inclined-Planed Tracking(IPT) IEC 587:1984 with NH_4C1 as contaminant.The test materials used were epoxy resins based on Diglycidyl Ether of Bisphenol A(DGEBA) and Methaphenylene Diamine(MPDA) compound with silicon rubber(SiR) with the dimensions of 50 mm×120 mm and the thickness of 6 mm.The flow rate of contaminant was 0.3 mL/min.The 3.5 kV AC high voltage 50 Hz was applied to the top electrodes.The experimental results show that the contact angle of hydrophobic was affected by compound of silicon rubber.The surface tracking,time to tracking and discharge current were affected by applied voltage,contamination and contact angle.By using micro-cameras,the surface damage was detected. The severest damaged sample surface on a sample had small contact angle.On the other hand,samples with the greatest contact angle needed longer time to have surface damage in the surface discharge.This shows that it is more difficult for large contact angle samples or more hydrophobic to have surface discharge.Epoxy resin compound with silicon rubber has contact angle of hydrophobic greater than epoxy resin without silicon rubber.

The Design of a 10 000 Ampere Impulse Current Generator Using Low Voltage Components

More and more applications of ZnO arrester in electrical system experienced more problems.One thing,that is still under some investigation,is the effect of multiple lightning strike to the performance of ZnO arrester.As we know,the design of ZnO arrester for transmission system and for distribution system differs in the point of view of the number of ZnO blocks.Transmission system,due to its higher nominal voltage than distribution system,has more numbers of ZnO blocks inside an arrester tube.In term of the current rating of an arrester,it is found that there is some different value of the current rating.The current rating of an arrester installed closer to electrical substation is higher than that of some further away from the substation.To the respond of a lightning impulse strike,the arrester will let a high value of impulse current flowing.It tends to heat the ZnO material of the arrester.If the number of impulse strike is quite high then it may give the effect to the change of the arrester performance.This condition will endanger the equipment that is protected by the arrester from lightning strikes.During this research,the scope of work is limited to making an impulse current generator toward to one having 8/20 μs wave-shape.This kind of impulse current wave-shape is the one that is used for studying the performance of ZnO block.The effect of the inductance and capacitance of the impulse current generator were also studied.A 10 fused cut out was blown by an impulse having 10321 A of 17.8/37.8 μs.A ZnO arrester block brokendown/allowed large value of current :10982 A flowing under the voltage of 10.5