The design and manufacturing technology of self-supporting insulated wires (SIPs) was developed more than half a century ago by engineers of Finnish network companies with the assistance of power equipment manufacturers as an alternative to bare aluminum wires and cable rope systems. Installation of such lines does not require special skills from the performer. Various technological operations have been greatly simplified: laying on supports, connecting SIP to SIP, to existing power lines, to consumers.
Types and specifications
Today, various options for self-supporting wires are presented on the electrical materials market: from SIP-1 - a four-wire version with a carrier zero core for 380 V networks - to complex systems that include control conductors, and SIP-3, designed for rated voltage 35 kV. Insulation, as a rule, is made of cross-linked stabilized polyethylene resistant to ultraviolet radiation, current-carrying conductors with a cross section of 16 to 150 mm2 are made of aluminum alloy. SIP for specialized purposes is produced: sealed (SIPg), notsupporting combustion (SIPn) and others.
Materials for connecting SIP
Each brand of wires has its own characteristics and, accordingly, the fittings used for installation have some differences. By functional purpose, all materials can be divided into several groups:
- Intermediate suspensions, hooks and brackets, anchor clamps, fasteners designed for fastening wires to supports, structural elements, building facades, distribution and input devices.
- Piercing clamps. Serve to create connections and branch lines, connect SIP to wires and consumers.
- Earthing kits, safety devices, insulating materials.
- Installation tools and accessories.
Materials are made using high-quality anti-corrosion coated steel and weather and UV resistant polymers.
All right
The requirements and norms for laying insulated overhead lines (VLI) are set out in the regulatory document "PU VLI up to 1kV", compiled on the basis of the PUE (Electrical Installation Rules) taking into account the standards of current SNiPs and GOSTs. The PU specifies the minimum allowable distances of VLI wires to the surface of the earth, highways, shipping routes, walls and roofs of buildings, windows and balconies. Clear instructions are given on the methods of installation and fastening of the power supply line, the rules for connecting SIP,surge protection devices and grounding elements.
The minimum service life of the SIP, according to manufacturers, is 25 years, and the declared one is about 40. The main advantage of such an overhead line is the minimization of labor costs during installation, operation and maintenance.
Main Highway
In preparation for the main work, the area is cleared of large branches of trees, shrubs, freeing up space for the installation of supports, rolling and pulling SIP. If possible, wire brackets are mounted on poles while still on the ground. Laying of overhead lines should be carried out at an ambient temperature above -10˚С. SIP is laid along the supports using a system of rollers and a tension rope. Further, the winch produces a gradual tension and fixation of the wires on each span. The tension force is controlled by a dynamometer (optimum tension values are indicated in the tables for each type and section of the self-supporting insulated wire, in the accompanying technical documentation). At the same time, visual control of the sag value is carried out. If the length of the line exceeds 100 meters, and the cross section of the wires is 50 mm2, the above works are carried out with the involvement of mechanization.
On the extreme supports, leave behind the wire release clamps to connect the previous and subsequent sections of the power line.
Connections and branches
Traditional and familiar to many electricians, twists in self-supporting systems have been replaced by specialbranch devices - sealed piercing clamps. With their help, without removing the insulation, it is possible to quickly, reliably and, most importantly, safely connect the SIP to the SIP trunk, to bare aluminum wires or to outgoing cables. The mechanism that provides good contact consists of plates with pyramidal teeth and a clamping screw with a shear head (most often a 13 or 17 mm wrench). In modern clamps, electrical contact between the plates and the head is excluded, therefore, if the performer has the appropriate qualifications, work can be performed without relieving stress. The fiberglass-reinforced body indicates the sections of the main and branch lines for which the clamp is intended.
Installation of branches
Branch to consumers can be done by overhead line or underground cable. When electrifying private households, the first method is most often used. For connection, you can use SIP-4 (without a carrier zero core). An anchor with a wire clamp is mounted on the main support closest to the building. When connecting SIP to the main line (only after inserting the wires into the shield!) Use the above-described piercing devices. The second clamp is screwed onto the wall of the building (at a height of at least 2.75 m) and the wire is pulled. If the distance is more than 25 meters, it is necessary to install an additional support with supporting clamps (no further than 10 m from the building). The height of the wire from the ground between the supports must be at least 6 meters. About the rulesfurther laying of the line from the attachment point to the introductory metering board on the forums of electricians there are unrelenting lively disputes. What is the problem?
Connecting the SIP to the house
Options when the electrical panel is located on the outer wall of the building almost do not cause controversy - it is recommended to run SIP into the corrugation or cable channel fixed on the facade, put it into the shield and connect it to the introductory machine. And if the electrical panel is located indoors? In this case, electrical specialists, according to their convictions, are divided into two irreconcilable camps.
The first argue that the SIP can be immediately led through a hole in the wall with a pre-installed metal or plastic sleeve inside the building and then in the pit - onto the shield. Their opponents object that self-supporting wires are intended only for laying overhead lines and the SIP insulation will be negatively affected by constant contact with the wall surface and mechanical loads, and it will not be able to provide proper electrical and fire safety indoors. Therefore, near the attachment point of the SIP, you should install a sealed box with a terminal block or a circuit breaker, and go into the building with a cable (for example, VVGng)
Who's right?
Both options are quite common and do not cause objections from the controlling organizations when accepting the building. Many manufacturers of cable products have developed their own specifications and have mastered the production of SIP-5ng wire, which, according to them, is adapted for laying insidepremises. But if you strictly follow the letter of the regulatory documents (PUE and GOST R 52373-205), then the second option with the installation of a connecting sealed box looks more preferable.
Now it remains only to connect the SIP to the SIP on the input support using a sealed piercing clamp. It remains to be noted that these devices are recommended to be used only once, although some modifications have dismantling bolts.
Maintenance and repair
The service life of self-supporting wires and clamping devices, which are used to connect SIP to SIP, declared by manufacturers, is up to 40 years. Maintenance, as such, such systems do not need. Periodic visual inspection is sufficient. If at the same time violations of the integrity of the insulating coating or the cores themselves are revealed, it will be necessary to carry out repair work.
The core with damaged insulation is separated from the common bundle using special wedges or improvised devices made of dielectric material and a double layer of electrical tape is applied to the defective area.
In case of damage to the conductive core (up to 2 m long), this section is replaced with a new wire, similar in cross section and brand. Connections are made with sealed piercing clamps. With a longer length, it would be more expedient to completely replace the entire core (or bundle).
Proper installation and timely repairs are the key to uninterrupted power supply to the site.
