(1) When the cable is to be laid through a protective tube, the inner diameter of the pipe shall not be less than 1.5 times the outer diameter of the cable, and the inner diameter of the concrete pipe, clay pipe, asbestos, cement pipe shall not be less than 100mm;

(2)The bending radius of the cable tube shall comply with the requirements for the bending radius of the cable to be penetrated;

(3) Each pipe should not have more than three elbows and no more than two right angle bends.