隧道内电缆集群敷设对载流量的影响研究

Influence of Cluster Laying on Permitted Current Rating of Power Cables in Tunnels

不断增加的城市用电负荷和经济环保的电力发展需求决定了大中型城市中电缆隧道的广泛应用,而邻近磁热效应是影响隧道中集群敷设的电缆线路载流量的重要因素。为了获得隧道内集群敷设对电缆线路允许载流量影响的定量规律,文中主要以110、220 kV高压电缆为研究对象,在水平排列和品字形排列两种典型敷设方式下,探讨了隧道内空气温度、电缆相间距、回路间距和回路数量对载流量的影响。结果表明,通风效果对隧道内温度影响大,对电缆允许载流量的作用最为显著;相比于水平排列,三相电缆品字形排列时受其他各种因素的影响小,应优先选用;品字形分离式放置的电缆载流量比接触式高,但空间占用大;隧道内多回路集群敷设时,应严格按照规程要求的间距进行设计,并且对中、低压电缆需要考虑约15%的载流量降低因数。

Cable tunnels are widely used in large and medium-sized cities along with the continuous increase of urban power load and the economic and environmental development demand of power system.The adjacent magneticthermal effect is one of the most important factors affecting the permitted current rating of power cable lines.In order to investigate the influence of cluster laying on cable current rating quantitatively,this paper presents case studies of110 kV and 220 kV cable lines,which are laid in two typical arrangements of flat and trefoil formations.The permitted current ratings of cable clusters are calculated under different tunnel temperature,cable phase spacing,circuit spacing and circuit number.It is shown that ventilation affects the temperature distribution in the tunnel remarkably,and it is the most influential factor for cable’s permitted current rating.Three single-core cables in trefoil formation will be less influenced by other factors than those in flat formation,so the trefoil formation is preferred.Three phases of single-core cables in untouching trefoil formation will have a higher permitted current rating than those in touching trefoil formation,but the untouching trefoil formation occupies more space.For installation of a multi-circuit cluster in tunnel,the spacing design must strictly obey the regulations,and about 15 percent current rating reduction should be considered for the low or medium voltage power cables in cluster laying.