地下排管多电缆线路分流对运行寿命的影响

Influence of Redistribution Circuit Current in an Underground Cable Trench on Cable Service Life

地下排管中聚集电缆线路数较多,散热困难,导致运行温度高。而过高的温度会加速电缆的老化,降低电缆的寿命。为延长电缆寿命,基于有限元法计算了地下排管中电缆群运行温度场,依据电缆老化理论建立地下排管电缆群寿命评估模型,并以延长电缆群平均寿命为目标函数,电缆群中总载流量不变且排管中各电缆运行温度不超过90℃为约束条件,提出了地下排管多电缆线路分流优化方法。实际工程应用结果表明:与未分流情况相比,采用优化方法后排管中电缆群的平均寿命延长了14.9 a,夏季排管中最高温电缆的导体芯温度降低了29.7℃,优化效果显著;与现行分流方案相比,采用优化方法后排管中电缆群平均寿命延长了3.0 a,夏季排管中最高温电缆的导体芯温度降低了2.7℃,验证了该方法的有效性。利用优化方法来指导未来电缆线路运行问题,能较大程度地保留排管中电缆的原始运行负荷,降低排管中电缆的温度,延长排管中电缆的平均寿命。

There are a large number of concentrated cable lines in the underground exhaust pipe,and it is difficult to dissipate the heat,which results in the high operation temperature of cable.Excessive temperature will accelerate the aging of the cable insulation and reduce the service life of the cable.In order to extend the average service life of cables in an underground cable trench,the temperature field in an underground trench was simulated based on the finite element method;the average service life of cables in the trench was quantitatively assessed according to cable aging theory.The temperature of the highest temperature cable in the cable group was not allowed to exceed 90℃,and the total current of all the circuits in the trench should remain unchanged,so that an optimization model of reallocating the current in the cable group was established to extend average service life of cables.The results of practical applications reveal that,compared with the results without redistribution at all,the average service life of the cables in the redistribution optimization program is increased by 14.9 years and the conductor core temperature of cable with the highest temperature in summer is reduced by almost 29.7℃;compared with the results of the current distribution program,the average service life of the cables in the redistribution optimization program is increased by 3.0 years and the conductor core temperature of cable with the highest temperature in summer is reduced by almost 2.7℃,which verify the effectiveness of the method.The proposed optimization method can be used to guide maintenance engineers when plans and designs are required to redistribute currents among cables in an underground trench,which can limit the operating temperature and extend average service life of cables.