Things have two sides, Magnesia cable is no exception, with many advantages, there are some shortcomings, should be in the selection and construction attention.
1. High investment cost
As a result of magnesium oxide cable sheath is made up of seamless copper tube, the overall copper content far more than ordinary cable, and Magnesia cable construction technology for equipment requirements higher than ordinary cable, resulting in magnesium oxide cable prices and ordinary cable than 30% higher.
2. Easy to damp at joints Insulating layer is composed of mineral magnesia, it is very easy to react with moisture in air, and generate conductive magnesium hydroxide. In the construction of cable head, when the cable end is stripped of the bare conductor, the insulation resistance of the cable is generally above 10mω, but if the cable head is not finished within 1 hours, the insulation resistance can descend to the 10mω below,
May even appear below the 0.5mω condition, if does not pay attention to cut the outer layer, also did not discover in time and seals the damp-proof treatment, the insulating value will descend quickly and will descend gradually to 0, thus will cause this cable to be unable to use.
3, the construction difficulty is big
Magnesia cable hardness compared with the general cable is relatively high, weight of about twice times the general cable, the installation is not easy to achieve a parallel neat impression effect, and the line long, many joints, find fault points difficult, so the construction is more difficult, in and out of the wiring box and the bridge frame bending forming difficulties.
4. Large construction work Magnesia cable where the specifications of more than 35mm are single core cable, such as 1 70mm of cable, ordinary cable only 3x70+2x35 five conductor in the same outer sheath can, and magnesia to achieve the same specification must be 3 70mm plus 1 35mm of single core cable. Single-core cable delivery length is shorter, such as 240mm cable delivery length of 69 meters, if the laying distance will increase the production of a large number of intermediate joints, so that the construction workload doubled.