The author has been in business for some years, and most of them are aluminum wires, so what I am talking about here is mainly aluminum wires and low-voltage wires and cables. The so-called low pressure is relative to the medium and high pressure. Looking through the Technical Specification for Safety of Temporary Electricity Use in Construction Site, the definition of low voltage is the voltage with AC rated voltage of 1KV and below. Therefore, we usually use aluminum sleeve or wire nose crimping to deal with cable joints, and the wires are treated in the conventional way. What about the high-voltage cable? Let me use a case to illustrate.
situation
Considering that the road surface at the entrance of the project is uneven, the general contractor of the project wants to deal with it and modify the road surface again. Who knows that the excavator only watched the sparks and lightning cut off the high-voltage cable leading to the project all the way down, because the project was in a busy section of the city, surrounded by many transformers and projects under construction, which directly gave a jump. And it is in the open and closed positions. The fault is very difficult. In this process, the most talked about by relevant construction workers are "dry filling" and "thermal shrinkage", which I think is the so-called middle joint treatment.
Through on-the-spot observation and study, it is known that after the wires are connected by stress tubes (namely aluminum sleeves), they are wound with high-voltage self-adhesive tapes in multiple layers, which is called "dry winding". According to the master of the site construction, if thermal shrinkage is used, the working space will be very large, and there is no thermal shrinkage sleeve at the site. In order to meet the urgent time, the "dry packing" process is adopted.
The manufacturing process of thermoplastic cable head is more complicated than that of "dry-wrapped" cable head. In addition, with the development of science and technology, cold shrinkage technology is widely used now, without hot work and special tools. As long as the core rope is gently pulled out, it will rely on its own elastic retraction. Attached to the cable. In addition, silicone rubber has good insulation, good sealing and convenient installation. Electrical test 5min power frequency withstand voltage test 39KV without flashover breakdown.
Summary: Although water and electricity are not divided, the risk factor of electricity being invisible and intangible is too high, so it must be done in accordance with the norms and not sloppy. After the cable head is made, in addition to the experiment according to the requirements of the specification, it is also necessary to send electricity without load for 24 hours without abnormal phenomena, and go through the acceptance procedures and hand it over to the construction unit.