Common construction failure causes and preventive measures of cold shrinkable straight through joint

Field construction of cold shrinkable straight through joint is simple and convenient, overcomes the shortcomings of heat shrinkage materials, and is widely welcomed by power system. Because of the short stripping length of the cold shrinkable straight through joint, the construction environment and operation technology are more demanding and more strict. Because its application time is not long, the operation of this new technology is very insufficient, so it is necessary to analyze the construction failure of cold shrinkage intermediate joint. Its common construction failure causes and preventive measures are:

1. The cut marks are too deep when peeling the cable semiconductor shielding layer. Make the surface of the main insulation layer scarred, easy to accumulate air gaps.

Preventive measures: After the cable insulation layer is stripped, polish the surface of the main insulation layer carefully with fine sandpaper to make it smooth and free of cut marks and semiconductor residue.

2. After the cable semiconductor shield layer is stripped, the semiconductor remains on the main insulation layer. Or do not follow the process requirements in cleaning, scrubbing back and forth, leaving hidden dangers, flashover discharge.

Preventive measures: Special attention should be paid to keeping the cable joint clean during the production process, because whether it is clean or not is one of the important factors affecting the construction quality of the joint. Cleaning the insulation layer must be carried out with cleaning solvent from the core to the direction of the semiconductor shield layer. Do not use the cleaning paper that has been in contact with the semiconductor shield layer to clean the surface of the main insulation layer. At the same time, shorten the production time as far as possible. The longer the cable is exposed in the air after stripping, the greater the possibility of the intrusion of impurities, water, gas, dust, etc., thus affecting the quality of the joint. Therefore, it is required to fully do the preparatory work before construction to ensure uninterrupted production.

3. After the cable core is crimped, the connecting pipe is deformed with tips and edges, resulting in local field concentration, electric field distortion and tip discharge.

Preventive measures: After crimping the wire core, polish carefully with file and sandpaper to eliminate the edges and tips, and pay attention to the metal dust shall not remain on the surface of the insulation layer.

4. The cold shrinkable straight through joint is a prefabricated accessory, which must be matched with the cable section. Do not check carefully before the joint, is bound to cause the contraction is not tight and can not ensure the interface pressure, resulting in the formation of air gap or damp.

Preventive measures: Before making cold shrink joint, carefully check the cable accessories, and cable matching. In this way, the interference amount of cold shrink silicone rubber insulated sleeve can be strictly controlled to ensure that it has enough grip force, so that the interface contact is close and there is no air gap.

5.In the manufacturing process of cold shrinkage joint, the two ports are not sealed after the shrinkage of the silicone rubber insulating sleeve, which is easy to cause moisture invasion.

Preventive measures: The semiconductor self-adhesive tape is wrapped around the two ports of each phase silicone rubber composite insulating sleeve after contraction, which can not only make the outer semiconductor layer of silicone rubber sleeve and the outer semiconductor shield layer of XLPE cable good connection, but also play an axial role in preventing water from being damp.

6.When the cold shrinkable joint is made, because the three-phase cold shrinkage insulation sleeve is in the same central position, there will be wrinkles when wrapping the waterproof belt due to the uneven, resulting in not tight wrapping, which is also one of the important reasons for easy to lead to the joint water and damp.

Preventive measures: Wrap the self-adhesive waterproof belt, is the key link of the moisture-proof sealing of the cold joint, to the semi-overlapping method from one end of the joint wrap around to the other end, and then the opposite direction wrap around to the beginning of the end, wrap two layers. After each layer is wrapped, it is necessary to grip it with both hands in turn to make it better glued. When wrapping, we must pull properly, so as to wrap tightly without gaps.