1.The selection of cable insulation type shall meet the following requirements:
- Under the operating voltage, operating current and its characteristics and environmental conditions, the cable insulation characteristics should not be less than the conventional expected service life.
- The selection should be based on factors such as operational reliability, ease of construction and maintenance, and comprehensive economy of allowable maximum operating temperature and cost.
- It shall meet the requirements of fire prevention places and shall be conducive to safety.
- When it is clear that it is necessary to coordinate with environmental protection, an environmentally-friendly cable insulation type should be selected.
2.The selection of insulation type of commonly used cables shall meet the following requirements:
- In addition to the selection of insulation type for medium and low voltage cables, it should comply with the provisions of 3.4.3～3.4.7 of this code. Low voltage cables should use polyvinyl chloride or cross-linked polyethylene extruded insulation type, and medium voltage cables should use cross-linked insulation. Polyethylene insulation type.
When it is clearly necessary to coordinate with environmental protection, PVC insulated cables shall not be used.
- For cable lines in high-voltage AC systems, cross-linked polyethylene insulation should be used. In areas with more operating experience, self-contained oil-filled can be used cable.
- For high voltage DC transmission cables, non-drip impregnated paper insulation and self-contained oil-filled types can be selected. When it is necessary to increase the power transmission capacity, the type constructed with semi-synthetic paper materials should be selected.
Ordinary XLPE cables should not be used for DC transmission systems.
3.For circuits that frequently bend and move or have higher flexibility requirements, such as mobile electrical equipment, cables such as rubber insulation should be used.
4.According to the requirements of the insulation type, cables with radiation resistance strength such as cross-linked polyethylene or ethylene-propylene rubber insulation should be selected for the radiation site.
5.For high temperature places above 60℃, heat-resistant polyvinyl chloride and cross-linked polyethylene should be selected according to the requirements of high temperature and duration and insulation type.
Heat-resistant cables such as ethylene or ethylene-propylene rubber insulation; mineral insulated cables should be used in high temperature environments above 100°C.
Ordinary PVC insulated cables should not be used in high temperature locations.
6.For low-temperature environments below -15℃, cross-linked polyethylene, polyethylene insulation, and cold-resistant rubber insulation should be selected according to low-temperature conditions and insulation type requirements.
PVC insulated cables are not suitable for low temperature environments.
7.In crowded public facilities, and places with low-toxicity, flame retardancy and fire protection requirements, cross-linked polyethylene or ethylene-propylene rubber can be selected.
Halogen insulated cables.
When fire protection has low toxicity requirements, PVC cables should not be used.
8.In addition to the conditions specified in Article 3.4.5~3.4.7 of this code, PVC insulated cables can be used for circuits below 6kV.
For 6kV critical circuits or XLPE cables above 6kV, the three-layer co-extrusion process characteristics of inner and outer semi-conductive and insulating layers should be used.