Common low-voltage electrical materials
(A) the power cable representation method
1. Representation method of cable model
In order to accurately indicate the use, structural type and name of cables, the national standard "Cable Outer Sheath" GB/T 2952-1989 stipulates that the combination of pinyin letters and numbers should be used to indicate the types and models of cables. The model is usually represented by capital Chinese pinyin letters, and the cable insulation and internal and external protective layers are represented by the combination of pinyin letters and numbers, which can not only completely reflect the types and uses of cables, but also clearly show the main structure, materials and laying occasions of cables.
Note: The pinyin letter ZR- stands for flame retardant series and NH- stands for fire retardant series before the cable model.
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(2) Classification of power cables
Power cables are generally divided into PVC insulated (plastic) power cables, XLPE insulated power cables, rubber insulated power cables, oil-filled and oil-impregnated paper insulated power cables according to their insulation types, and can be divided into general power cables, overhead power cables, underground power cables, submarine power cables, fire-resistant and flame-retardant power cables according to their work types and properties.
(3) Several common cables and their characteristics
1. Copper conductor power cable
At present, domestic low-voltage power cables are all twisted together by each core. The cable with this structure has poor anti-interference ability and lightning resistance, and the three-phase impedance of the cable is unbalanced and the zero-sequence impedance is large, which makes it difficult for line protection appliances to operate reliably. The copper and aluminum PVC copper conductor power cable with rated voltage of 0.6kv～1kv ~ 1 kV and below developed by Jiangsu Baosheng Cable Factory has solved the above problems.
2. XLPE insulated power cable
XLPE cable for short, it uses chemical or physical methods to change the molecules of polyethylene plastic, the insulating material of cable, from linear structure to three-dimensional network structure, that is, to change thermoplastic polyethylene into thermosetting crosslinked polyethylene plastic, thus greatly improving the heat resistance and service life of cable and still maintaining its excellent electrical properties.
3. PVC insulated PVC sheathed power cable
The long-term working temperature of PVC insulated PVC sheathed power cable shall not exceed 70℃, and the maximum temperature of cable conductor shall not exceed 160℃. The longest duration of short circuit shall not exceed 5s, and the lowest temperature of construction laying shall not be lower than 0℃.