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.