Compare the advantages and disadvantages of prefabricated cable accessories and cold-shrinkable cable accessories
Prefabricated and cold-shrinkable cable accessories are made of silicon rubber with good material properties such as high elasticity, high volume resistivity, good hydrophobicity and good aging resistance. These two kinds of accessories use the same raw materials, but the production and installation technology and design of the different make the two kinds of cable accessories reflect different characteristics.
First, prefabrication:
Advantages: Due to no pre-expansion, the production process is relatively simple and the productivity is high. Small volume, simple installation technology, simple installation and operation, and no fire, save time and effort, greatly reduce the quality accidents caused by improper operation, low possibility of installation error;
Disadvantages: due to the limitations of precast technology brings a series of problems, the inner diameter of the prefabricated type terminal is only slightly less than the outer diameter of cable insulation layer makes the terminal to the smaller radial pressure produced by the cable to cable respiration is not obvious, sealing is relatively weak, it's easy to have a gap which can lead to happen because of the possibility of creepage flashover greatly increase (of course this does not mean that unsafe prefabricated cable accessories, please don't be taken out of context, is only relative to the cold type it in this lower safety coefficient). The radial pressure of the terminal on the cable is low, and the terminal positioning is not stable, which is easy to occur due to the dislocation in the process of moving the cable (such as holding the pole on the cable). As a result, the stress cone deviates from the copper shielding section and fails to work, resulting in the breakdown accident.
The cold type:
Advantages: applicable surface width, one specification suitable for three square cable; After installation, the proper radial pressure is always maintained for the cable body, so that the internal interface is tightly bound and the electrical breakdown will not occur due to the breathing action during the cable operation. The installation operation is simple, no fire, save time and effort, solve the prefabricated cable accessories shrink or install not in the phenomenon. The sealing performance is good in the high humidity and high salt fog environment.
Disadvantages: due to an additional expansion process in the production process and the need for expansion and contraction characteristics, the silicone used in the cold-shrinkable cable accessories has a much higher performance than the prefabricated ones (such as tensile ratio and tear resistance, etc.), so the production cost is higher than the prefabricated accessories; The storage period is short, generally half a year to two years, because the cold-shrink cable accessories are pre-expanded, under the condition of a long time of storage, the internal brace may appear scattered or the silica gel material fatigue shrinkage is not in place. (so cold cable accessories are generally using high performance liquid silicone production, now there are some cheaper cold cable accessories use solid silica gel production performance is much worse, aging fast prone to cracking, the phenomenon of contraction is not tight, the advantages of using solid silica gel production cold type attachments will soon disappear. Suggest that we don't keen on gaining petty advantages when cold cable accessories of choose and buy, try to choose those imported liquid silicone production cable accessories manufacturers products, such as the United States dow corning liquid silicone should be regarded as the best) relative to prefabricated type, installed the cold cable accessories for workers of some higher requirements, installation is relatively complex.
To the city for a cold type prefabricated cable accessories, shrinkage cable accessories based design based on prefabricated type attachment evolved thanks to the progress of silicone materials (because of the cold type attachment using silicone material performance requirements is very high, prefabricated type attachment arises silicone material performance can not meet the requirements of current cold attachment). The design concept of cold-shrinkable cable accessories is more advanced, and there is a tendency to replace prefabricated cable accessories.