The design and manufacturing technology of self-supporting insulated wires (SIP) was developed more than half a century ago by engineers of Finnish network companies with the assistance of manufacturers of power equipment as an alternative to bare aluminum wires and cable cable 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, the electric materials market offers various options for self-supporting wires: from SIP-1 - four-wire version with a zero-conductor carrier for 380 V networks - to complex systems including control conductors, and SIP-3, designed for a rated voltage of 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 mm 2 are made of aluminum alloy. Specialized CIP is produced: sealed (CIPg), not supporting combustion (CIPn) 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 attaching wires to supports, structural elements, building facades, distribution and input devices.
- Piercing clamps. They are used to create connections and branch lines, connecting SIP to wires and consumers.
- Grounding kits, safety devices, insulating materials.
- Tools and fixtures for installation.
For the manufacture of materials used high-quality steel with anti-corrosion coating and polymers that are resistant to weathering and UV radiation.
All according to the rules!
The requirements and norms for laying isolated overhead lines (VLI) are set forth in the regulatory document "PU VLI up to 1 kV", compiled on the basis of the PUE (Electrical Installation Rules) taking into account the standards of current SNiPs and GOSTs. In the control unit, the minimum permissible distances of the VLI wires to the surface of the earth, highways, shipping highways, walls and roofs of buildings, windows and balconies are registered. Clear instructions are given on how to install and mount the power line, the rules for connecting the self-supporting insulated wires, surge protection devices and grounding elements.
The minimum service life of self-supporting insulated wires, according to manufacturers, is 25 years, and the claimed one is about 40. The main advantage of such an overhead line is to minimize labor costs during installation, operation and maintenance.
Main highway
In preparation for the main work, they clean the area from large branches of trees, shrubs, freeing up space for installing supports, rolling out and pulling the self-supporting insulated wire. If possible, the brackets for wires are mounted on supports still on the ground. Laying overhead lines should be carried out at an ambient temperature above -10Λ. SIP are laid along the supports using a system of rollers and a tension rope. Next, the winch is a gradual stretching and fixing of wires on each span. The tension force is controlled by a dynamometer (the optimal tension values ββare indicated in the tables for each type and section of self-supporting insulated wires, in the accompanying technical documentation). At the same time conduct visual inspection of the amount of sag. If the length of the highway exceeds 100 meters, and the cross section of the cores is 50 mm 2 , the above work is carried out with the use of mechanization.
At the extreme supports, they are left behind the wire release clamps to connect the previous and subsequent sections of the power line.
Connections and Branches
Torsions traditional and familiar to many electricians in self-supporting systems have replaced special branching devices - hermetic piercing clamps. With their help, without stripping the insulation, it is possible to quickly, reliably and, very importantly, safely complete the SIP connections 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 stall head (most often turnkey 13 or 17 mm). In modern clamps, electrical contact between the plates and the head is excluded, therefore, work, if the contractor has the appropriate qualifications, can be performed without removing the voltage. On the case reinforced with fiberglass, sections of the main and branch lines for which the clip is intended are indicated.
Branch mounting
The branch to consumers can be performed by an air line or an underground cable. When electrifying private households, the first method is most often used. To connect, you can use SIP-4 (without a supporting zero core). An anchor mount with a wire clip is mounted on the trunk support closest to the structure. When connecting the self-supporting insulated wire to the trunk line (only after wiring the wires into the shield!), The above-described piercing devices are used. 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 structure). The height of the wire from the ground between the supports should be at least 6 meters. Regarding the rules for further laying the line from the attachment point to the introductory metering panel, unremitting lively disputes are being held on electrician forums. What is the essence of the problem?
SIP connection to the house
The options, when the electric switchboard is located on the outer wall of the building, almost do not cause disputes - SIP is recommended, running into the corrugation or cable channel, mounted on the facade, put into the shield and connect to the input machine. And if the switchboard is indoors? In this case, electricians, according to their beliefs, are divided into two irreconcilable camps.
The first ones say that SIP can be brought directly into the building through a hole in the wall with a pre-installed metal or plastic sleeve inside the building and then into the shield in the gate. Their opponents object that the self-supporting wires are intended only for laying overhead lines and constant contact with the surface of the walls and mechanical stresses will negatively affect the insulation of the self-supporting insulated wires, and it will not be able to ensure proper electrical and fire safety indoors. Therefore, close to the SIP mounting point, a sealed box with a terminal block or circuit breaker should be installed, and a cable (for example, VVGng) from it should go into the building.
Who is right?
Both options are quite common and do not cause objections from the controlling organizations during the acceptance of the building. Many manufacturers of cable products have developed their own specifications and mastered the production of SIP-5ng wire, according to their assurances, adapted for indoor installation. But if you follow the letter of regulatory documents (PUE and GOST R 52373-205), then the second option with the installation of a tight connection 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.
Service and Repair
The operating life of the self-supporting wires and clamping devices declared by the manufacturers that connect the SIP to the SIP is up to 40 years. In service, as such, such systems do not need. A periodic visual inspection is sufficient. If at the same time violations of the integrity of the insulation coating or the cores themselves are revealed, it will be necessary to carry out repair work.
A core with damaged insulation is separated from the general 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 mark. The joints are sealed with piercing clamps. With a longer length, it will be more advisable to completely replace the entire core (or harness).
Proper installation and timely repair is the key to uninterrupted power supply to the site.