1. Cable technical requirements: basically in accordance with the technical conditions of the order (according to

According to the standard IEC840-1998, GB11017-89, etc.), according to the problems encountered in our construction, we specifically require the following items:

Main insulation eccentricity <8% (new regulation of IEC840-1998)

The outer sheath is made of flame-retardant red PVC. The sheath should be firmly wrapped on the metal, and the cable will not loosen or slip during construction and operation.

The outer sheath should be coated with a graphite conductive layer, the coating should be smooth and firm, and will not fall off under laying and long-term operation.

The traction head and the lead sheath (aluminum flux for aluminum sheath) should be welded firmly to ensure sealing and prevent water from entering. The overlapping length of the heat shrinkable sleeve of the pulling head to the pulling head and the cable shall not be less than 200mm respectively.

The flame retardant test is based on the provisions of IEC-332-C, and tested according to IEC754-1 or IEC745-2. The halogen content is <330mg/g (reference value), and the smoke density is provided according to ASTME662-83. The smoke density and its light transmittance> 20% (reference value), and provide a test report.

For cables with lead metal sheath and semiconducting resistance water tape as inner lining, the carbonization and adhesion of the water blocking tape caused by the carbonization temperature (>230 degrees) of the water blocking tape being lower than the pressing lead temperature (290 degrees) should be avoided. on the cable insulation shield. The semi-conductive resistance hose is easy to absorb moisture. The cable manufacturer should pay attention to the short exposure time when wrapping the semi-conductive resistor hose to prevent moisture absorption in the manufacturer. When the cable is broken on site, be sure to check whether the semi-conductive resistor hose is dry. We once found that there seems to be a gelatinous substance on the semi-conductive resistor hose of a manufacturer, and finally confirmed that it was seriously water in the manufacturer.

2. Cable joint installation

1. Domestic construction units generally pay little attention to the environmental humidity and dust conditions at the joints. In fact, for the long-term operation of the cable, moisture and small impurities are very harmful, and it is easy to cause the occurrence of water trees and partial discharge. Therefore, we must pay attention to the environmental humidity and dust during the joint construction, and pay attention to cleaning the environment before construction. , In summer, the construction joint personnel should wear gloves. If the ambient humidity is too high, dehumidification treatment should be performed (increase the ambient temperature or use a dehumidifier), and the insulating surface should be dried with a hair dryer before inserting the stress cone.

2. The cable should be heated and straightened before the cable joint. Sometimes the construction workers think that the cable can not be heated without bending. In fact, this view is incorrect. There are two reasons why the cable should be heated and straightened: one is to eliminate the mechanical stress in the cable caused by twisting when the cable is unloaded; the other is to eliminate the dimensional change caused by the thermal shrinkage of the insulation after the cable is put into operation. Therefore, the cable must be heated and straightened before the cable joint.

3. Insulation shielding end treatment

Insulation shielding end treatment is an extremely important step in the work of cable joints. This step has the highest technical and technological requirements and must not be sloppy. If the process is not mastered, it is easy to grind the end of the insulating shield with pits, steps or semi-conductive tips, which are very dangerous.

The methods generally used by cable accessory manufacturers include brushing semiconducting paint (ELASTIMOLD in the United States, C.C in Switzerland, etc.), molding semiconducting layers (Japanese manufacturers), sheathing semiconducting tubes (G&W in the United States), and only scraping the ends of the semiconducting shielding together. To form a smooth and excessive slope (Switzerland BRUGG, Germany K.P company), in comparison, the method of molding a semiconducting layer is safer.

4. Insulation surface treatment

Since the wrap-around cable joints are basically out of operation now, the main two types of cable accessories are assembled cable joints (Japanese manufacturers, Korean manufacturers, Changsha Cable Accessories Factory terminals, Shenyang Furukawa intermediate joints), prefabricated cable joints ( European manufacturers, American manufacturers, Shenyang outdoor terminals). Assembled cable joints The cable joints have higher requirements on the outer diameter of the insulation (the error of the outer diameter is within 0.5 mm), the flatness of the insulation surface (the sandpaper used is generally not less than 600#), and the size requirements are also strict (the error of the size requirements is in Within 1 mm), in a project in Beijing area, after the joints were completed, the Japanese construction workers felt that the size of one of the joints was not well controlled, and they were not sure, so they disassembled and rejoined. In comparison, the prefabricated cable joint technology is more advanced, and the outer diameter of the insulation (the allowable range of the outer diameter of the EPDM type stress cone is within 4.5 mm, and the allowable range of the outer diameter of the silicone rubber type stress cone is within 8-16 mm), insulation The surface flatness requirements are not high (the sandpaper used is generally required to be up to 400#), and the size requirements are also relatively loose (the size requirement error is within 15 mm).

After grinding, clean it with lint-free cleaning paper, and dry it with a hair dryer. Some manufacturers use a high-heat hair dryer to heat the insulating surface for a short time to ensure a smooth surface. Dehumidify the stress cone and cable insulation surface with a hair dryer before installing the stress cone.