(1) due to the joint box or terminal box structure is not sealed or poor installation caused by water;
(2) cable manufacturing defects, metal sheath with small holes or cracks;
(3) cable transport, construction or operation, the cable sheath due to external damage;
(4) cable test or run, the cable insulation breakdown damage cable sheath;
(5) the operating environment is corrosive, guiding the cable sheath corrosion damage.
(1) to buy the cable, you must choose a good quality of the manufacturers, the manufacturers of samples submitted to be rigorous testing;
(2) to ensure that the cable head seal is good, for the sawing of the cable end, whether it is stacked or laying, are required to use a special cover to prevent moisture infiltration;
(3) after the laying of the cable to the timely production of the cable head, because the conditions can not be immediately made of restrictions, the cable head sealed after the shelves placed;