隧道施工中，沿隧道敷设的动力和照明电缆由于线路过长造成功率因数低，电压损失大，导致设备和照明无法正常工作。为改善这种情况，结合工程实例通过功率补偿,并以最低的成本实现了减少电压损失的目的。尤其在长距离低压供电时电压损失严重的工况下，具有较好的实施效果。同时也对功率因素与电压损耗之间的关系进行了探讨，可供借鉴参考。

During tunnel construction, the equipment and lighting can not work due to great voltage loss and low power factor caused by the fact the line of the power cable and lighting cable laid along the tunnel is too long. To improve this situation, power compensation is adopted to reduce voltage loss with the lowest cost based on the engineering practice. This method has a better effect, especially on the improvement of sever voltage loss upon long distance low voltage power supply. A discussion has also been made on the relationship between power factor and voltage loss, which can be use for reference.