长距离隧道敷设电缆载流量仿真计算方法研究

Study on Simulation Calculation Method of Ampacity for the Cables Laid in Long Distance Tunnel

电网负荷的日益增大使得电缆隧道中敷设电缆回路数逐渐增加,导致电缆隧道温度不断升高,从而限制电缆载流量。对长距离电缆隧道进行强制通风是提高电缆载流量的一个有效措施,但通风状态下的隧道电缆载流量的计算方法还不完善。基于等效热路模型提出多层电缆结构简化计算方法,先求出等效热源Q_(eq)和等效热阻率ρ_(eq),进而建立双层仿真计算模型。为对长距离通风长度的隧道中敷设电缆载流量进行仿真计算,提出分段仿真计算方法,将上一段隧道出口的温度和速度分布作为下一段进口的温度和速度边界条件。进一步地,针对110 kV、220 kV和500 kV电缆,仿真分析得到了不同风速和通风长度对电缆载流量的影响机制。仿真结果表明,对于通风长度为1 km的电缆隧道,10 m/s风速工况下相比静止状态下的110 kV、220 kV和500 kV电缆载流量分别提升了467.05 A、549.18 A和573.4 A;当通风长度从100 m增加到1000 m时,各电缆载流量分别降低了95.34 A、117.54 A和130.6 A。研究成果可为电缆隧道通风设计、在线监测提供参考。

The increasing load of the power grid has gradually increased the number of cable circuits laid in the cable tunnel,resulting in a continuous increase in the temperature of the cable tunnel,thereby limiting the ampacity of the cable.Forced ventilation for long-distance cable tunnels is an effective measure to increase the ampacity of cables,but the calculation method for the ampacity of tunnel cables under ventilated conditions is not perfect.Based on the equivalent thermal circuit model,a simplified calculation method for the multilayer cable structure is proposed.The equivalent heat source Q_(eq) and the equivalent thermal resistance rate ρ_(eq) are firstly obtained,and then a double-layer simulation calculation model is established.In order to simulate and calculate the ampacity of cables laid in long-distance ventilated tunnels,a segmented simulation calculation method is proposed.The temperature and velocity distribution at the exit of the previous section of the tunnel are used as the boundary conditions of the temperature and velocity at the entrance of the next section.Furthermore,for 110 kV,220 kV and 500 kV cables,the influence mechanism of different wind speed and ventilation length on cable ampacity is obtained by simulation analysis.The simulation results show that for a cable tunnel with a ventilation length of 1 km,the current carrying capacity of the 110 kV,220 kV,and 500 kV cables under the static state is increased by 467.05 A,549.18 A and 573.4 A,respectively at a wind speed of 10 m/s.When the ventilation length is increased from 100 m to 1000 m,the ampacity of each cable is reduced by 95.34 A,117.54 A and 130.6 A respectively.The results can provide reference for ventilation design and on-line monitoring of cable tunnel.