利用短路电流热效应的OPGW分流地线选型

在光纤复合架空地线(OPGW)设计中,通常需考虑送电线路发生单相短路故障时短路电流在OPGW和另一根地线中的分流关系,并需计算出相应的电流分量。为此,首先从OPGW短路电流热效应入手,探讨了短路电流持续时间的取值并推导出OPGW短路电流瞬时温升的公式,同时提出了分流地线在电力系统中的意义,然后对比计算OPGW和分流地线的分流关系后得出了分流地线选型的基本原则:即分流地线应有足够低的阻抗以使得OPGW的电流分量降到允许值以下;分流地线本身要有足够大的热容量;在满足防雷各项要求后应有足够的强度安全系数。最后针对广东省2005年IT项目中OPGW和良导体分流地线的短路电流热效应进行的计算分析验证了OPGW分流地线选型的方法和原则。

Selection of the Shunt Ground Wire of OPGW Using Thermal Effect of Short Circuit Current

In design of Optical-fiber Composite Overhead Ground Wire(OPGW),the shunt ratio of short circuit current between OPGW and the other ground wire should be considered when single-phase short-circuit fault occurs on the transmission line,and corresponding current component should be figured out.By analyzing the thermal effect of short circuit current of OPGW,this paper introduces elements of short circuit current result in the temperature rise of the OPGW,discusses the duration of short-circuit current,and deduces the formula of instantaneous warming-up when the OPGW is in short circuit,meanwhile,this paper explains the significance of the shunt ground wire in the electric power system.The principle of type selection of shunt ground wire by contrasting and calculating the shunt relation of the OPGW and the shunt ground wire are as follows:sufficient low impedance makes the current components OPGW dropped below the allowable value;the shunt ground wire should have sufficient large heat capacity;it should have enough safety factors in addition to meeting the requirements of lightning,etc.Finally,The paper analyzes the thermal effect caused by short-circuit current in OPGW and shunt ground wire based on 2005 IT items in Guangdong province.A conclusion that how to select the OPGW and the shunt ground wire by the software of thermal effect of short circuit current is drawn,and the most appropriate structure of OPGW and the shunt ground wire is established,also the means and principles of selecting shunt ground wire types are presented in resolving the difficult problems about temperature rise and short-circuit current when the grounding fault takes place.