摘要:
高压直流塑料交联聚乙烯电缆的研发难点是消除其中的空间电荷效应.目前,国内外学者普遍通过添加纳米粒了在聚乙烯体内形成深陷阱捕获电荷的机理来抑制电荷积聚,但此抑制机理违背了电场的基本理论.以能带理论全面削述聚合物介质中空间电荷的形成和抑制机理,从一级陷阱模型出发,应用电荷入陷和脱陷动力方程,推导了聚合物介质中空间电荷的形成过程.在聚合物介质中引入深陷阱后,介质Fermi能级位移,电极与介质之间界面接触由Ohm接触转变为阻塞接触.考虑到无定形相中大量的陷阱密度,电荷耗尽区宽度小于100 A,电极与介质之间的界面对电子变得透明,形成中性接触,在电压作用下,这种聚乙烯介质中不再可能形成空间电荷.最后,在纯聚乙烯和纳米改性后含有深陷阱的聚乙烯两种试样上,分别测量了电导与电场强度的关系和空间电荷分布曲线,实验结果符合理论推导.
Abstract:
The key factor for developing cable plastic cross-linked polyethylene cable is to eliminate space charge in the bulk.Nowadays,it is universally received that the suppression mechanism of charge accumulation in polyethylene/nano-particle composite is the formation of deep traps for trapping charges,which,in fact,is contrary to the principles of electrical field.So in this paper,the formation and the suppression mechanisms of space charge are elaborated by the energy band theory of polymeric dielectric.Then based on the first order trap model,the formation of space charge in polymeric dielectric is deduced by dynamical equation of the trapped and detraped charges.When the deep traps are introduced into polymeric dielectric,a displacement of Fermi energy level in dielectric occurs and the electric contact of interface between electrode and dielectric changes from ohmic contact to blocking contact.The width of the depletion region associated with blocking contact is less than 100 A,due to huge density of traps existing in amorphous polyethylene （PE）.The tunnel effect of electron makes the electrical contact of interface a neutral contact.The space charges cannot be formed in PE dielectric under electrical stress.Finally,the conductive current as a function of electrical stress and the space charge distribution are measured respectively on both PE samples,one is pure PE and the other is the nano-particle modified PE filled with deep traps.The test results are consistent with the theoretical results.
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