关于架空输电线除冰措施的研究
山 霞,舒乃秋
(武汉大学电气工程学院,武汉430072)
摘 要:降低冰灾损失是目前的技术难题,通常的融冰措施可分为热融冰和机械除冰两类,该文简要阐述了利用焦耳效应、短路电流热效应、高频高压激励时介质损耗发热以及双分裂导体间电磁力、短时脉冲引起的电动力除冰的机理,并分析了各方案的利弊及应用范围。此外,介绍了其它国家在此领域取得的科技成果。
关键词:架空线;除冰;融冰;利弊分析;机理
中图分类号:TM726文献标识码:A文章编号:100326520(2006)0420025203
Discussion on Methods of De2icing for Overhead T ransmission Lines
SHAN Xia,SHU Naiqiu
(School of Elect rical Engineering,Wuhan U niversity,Wuhan430072,China)
Abstract:It is an often2seen,natural phenomena that electric wires covered by ice at central china or alpine areas in winter and early2spring.Covering ice poses serious threat to the security of grid operation and costs millions of dollars in repair expenses.Power line icing is complicated phenomena,which involved thermodynamic and hydrome2 chanical matters.Reduction of ice2damage is a difficult problem,there are more than thirty kinds of measures are taken usually for resolve it.In general,they can be classed as two kinds:one is ice2melting by exterior or exterior heating of the overhead line,the other is through mechanical stripping of ice from conductors by equipments such as ice2roll2 ing machines.This paper describes the mechanism of some innovative and practical methods for de2icing transmission lines such as reconfigure distribution network,short circuit,ice dielectric heating at high2frequency excitation and electromagnetic force on twin bundles and analyzed their merits and limitations.Furthermore,this paper introduces the achievement ob2 tained in this field at home and abroad.This paper has been of great value to the security of power system.
K ey w ords:overhead transmission lines;power line icing;de2icing;ice2melting;analysis of merits and limitations; mechanism
0 引 言
2005202207/16,华中电网遭遇了一场罕见冰灾,造成500kV变电站发生设备故障5次,500kV 交直流输电线路共跳闸18条69次。灾害造成500 kV的TA损坏2只,500kV刀闸支柱瓷瓶损坏1只;500kV交流输电线路倒塔4条25基,严重变形4基;地线滑移四处、断线1处,地线支架屈服5处; 220kV线路倒塔25基,严重变形1基;电网解列4次。故障时间跨度之长、频率之高、故障时电网运行方式的恶劣程度,为华中电网建网以来首次。在此期间,华中电网500kV线路因技术条件限制,只能进行进度缓慢且极为艰苦甚至是危险的人工除冰, 220kV线路则被迫多次进行短路融冰。
严冬及初春季节,我国云贵高原、川陕一带及两湖地区,常出现雾凇和雨凇现象,造成架空输电线路覆冰,使线路舞动、闪络、烧伤,甚至断线倒杆,使电网结构遭到破坏,安全运行受到严重威胁。在紧急情况下寻道员用带电操作杆或其它类似的绝缘棒只能为很少的一部分覆冰线路除冰,劳动密集且不经济,因此为减少损失有必要采用更有效的措施和装置。目前国内外除冰方法有30余种,大致可分为热力除冰法和机械除冰法两类[1,2]。通过对当前的几种典型除冰方法的对比分析,指出了今后研究工作的重点。
1 改变潮流分配融冰
工程应用中针对输电线路最方便、有效、适用的除冰方法有增大线路传输负荷电流。相同气候条件下,重负载线路覆冰较轻或不覆冰,轻载线路覆冰较重,而避雷线与架空地线相对于导线覆冰更多,这一现象与导线通过电流时的焦耳效应有关,当负荷电流足够大时,导线自身的温度超过冰点,则落在导体表明的雨雪就不会结冰。通过对导线在通流情况下的覆冰过程进行有效的传热分析可得覆冰气象条件下导线不覆冰的临界负荷电流I c为:
I c=(Q f+Q d)/R t=1,(1)其中R t=1为1°C时单位长度导体交流电阻,计算中可近似取20°C的直流电阻;Q f为单位长度辐射散热;Q d为单位长度对流散热。Q f、Q d的值与外部气候条件和导体本身情况有关[3]。
为防止导线覆冰,对220kV及以上轻载线路,
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第32卷第4期
2006年 4月
高 电 压 技 术
High Voltage Engineering
Vol.32No.4
Apr. 2006
