Products for connecting and terminating current-carrying conductors. Termination and connection of cores of insulated wires and cables

Requirements for the quality of connection, branch and termination. According to the PUE, the following requirements are imposed on the quality of the connection, branch and termination:

1. Connection, branching and termination of conductors of wires and cables must be carried out by crimping, welding, soldering or clamping (screw, bolt, etc.).
2. At the points of connection, branching and connection of the cores of wires or cables, a supply of wire (cable) must be provided, which makes it possible to reconnect the branch or connection.
3. Connection points and branches of wires and cables must be accessible for inspection and repair.
4. At the junctions and branches, wires and cables should not experience mechanical tensile forces.
5. The places of connection and branching of the cores of wires and cables, as well as connecting and branch clamps, etc., must have insulation equivalent to the insulation of the cores of the entire places of these wires and cables.
6. Connection and branching of wires and cables, with the exception of wires laid on insulating supports, must be carried out in junction and junction boxes, in insulating cases of junction and junction clamps, in special niches building structures, inside the cases wiring accessories, devices and machines. When laying on insulating supports, the connection or branching of the wires should be carried out directly at the insulator, the clamp or on them, as well as on the roller.

Connection methods. Let's consider some ways of connecting conductors of wires and cables of electrical wiring.

• Terminal clamps. Available with a clamping plate, for connecting stranded wires, and without a clamping plate, for single-core. The device of the terminal blocks allows not to use additional insulation of the junction.
• Yoke clamp. It differs from conventional terminal clamps in that there are notches on the clamping plate that cut through the oxide layer on the wire core, increasing the contact area and the quality of the connection. In addition, the design of the body of this clamp prevents spontaneous unscrewing of the clamping screw.
• Piercing clamp. The peculiarity of the clamp is that when connecting the wires from the latter, it is not necessary to remove the insulation. The clamp consists of a plastic housing and an E-shaped contact plate, which, after mounting the clamp, pushes the wire insulation apart and ensures electrical contact between the wires to be connected.
• Spring clamp. It is the most in a simple way wire connections. It is only required to strip the core from insulation and insert it into the clamp, where it is securely fixed using a special spring mechanism. One of the advantages of these clamps is the ability to connect wires of different diameters, both copper and aluminum, they do not contact each other, which eliminates electrical corrosion. In addition, the gel that fills the internal volume destroys the oxide film on aluminum and protects it from corrosion.

Branch. To perform a branch, the same methods are used as for connecting the cores of wires and cables.

As clamps, in addition to the types described above, branch clamps of the “nut” type are often used, consisting of two steel plates with grooves for conductors, compressed by four screws, located in a plastic case. Between them there is another flat plate, which excludes direct contact between the cores, in the case when copper and aluminum wires are connected.

Picture. Branch clamp - "nut".

Very reliable contact is ensured by soldering, for the preparation for which pre-twisting is quite appropriate and even necessary for larger area contact (given that the electrical conductivity of the solder is lower than that of the soldered materials) and mechanical strength.

Quick connection options for aluminum and copper wires using Clem Vago

Soldering requires a soldering iron with a power of 60-100 watts. First, you need to remove the insulation from the wires (by 4–5 cm), and irradiate, i.e. cover with a thin layer of solder.

1. For copper wires, you can use ordinary rosin (solid or in the form of a solution) or special pasty or liquid fluxes. Rosin and neutral no-clean fluxes do not require subsequent removal, because do not cause corrosion.
2. It is undesirable to use soldering acid and other active fluxes - their residues can cause corrosion of wires and even short circuit.
3. There are soldering materials for aluminum, but their use is not recommended.

Tinned wires are twisted, then carefully soldered. The soldering should cool naturally, without forced cooling, which can lead to cracks in the joint. It is convenient to insulate the finished soldering with a heat shrink tube of a suitable size, which, when heated, tightly covers the junction. This is the most reliable way to connect wires and cables, both copper and aluminum.

Another option is ordinary electrical tape, preferably at least 3 layers.

Connecting insulating clips (PPE) it could be considered modern version old twisted wires. This is a plastic case with an anodized conical spring inside. The wires to be connected are stripped to a length of 10–15 mm, assembled into a bundle and PPE is wound on them - clockwise, until it stops. The total area of ​​the connection, depending on the size - from 2.5 to 20 mm 2. The quality of the connection is quite high, but somewhat less than that of screw terminals.

Connecting aluminum and copper wires with terminals

Screw terminals are the most common and are often used in junction boxes. Available for both small and very large currents. When using aluminum strands, care must be taken when tightening the screws because it is soft (and sometimes brittle) and easily damaged.

Connecting cables with screws and washers

This is a somewhat outdated option, suitable in the absence of screw terminals of a suitable size, provides a similar quality, can be used to connect aluminum wire to copper.

Branch clamp U-733

This is actually a variant of the screw terminal block, it allows you to make branches from the main line without cutting it.

In this embodiment, sockets can actually be used as screw terminals, but for greater reliability, the wire connection should be soldered.

Self-clamping Wago terminal blocks

Self-clamping terminal blocks allow a cross section of up to 2.5 square millimeters, the permissible current can be up to 24 A. This is a very fast and technological way of connecting. Stripping is carried out to a length of only 10-12 mm, no twisting, no insulation, or even tightening of screws is required. Wires are simply inserted into the terminal block. It will not work in this way to connect only flexible stranded wires.

Another drawback is that due to the smaller contact area, this connection is still somewhat less reliable than a screw terminal or, moreover, soldering or welding.

Connection of two cable cores by welding

This is the most reliable way connections, it ensures perfect contact and is very long term trouble-free operation. Electric wires twisted to a length of at least 50 mm, welding of copper wires is carried out with a special carbon electrode with a copper coating. It is best to use an inverter welding machine, although other options are possible. When welding wires, as in any other welding work, strict adherence to safety precautions is necessary.

• Installation of modern electrical networks for various purposes often requires connecting cables. There are different ways to make these connections, but they must all meet the following requirements:
• transitional resistance should not be higher than the resistance on the solid part of the core;
• the dielectric strength of the insulation at the junction should not differ from the strength in other places;
• the connection point must be securely sealed and protected from mechanical damage.

High-quality cable connection ensures uninterrupted network operation, while up to 90% of all power supply problems that occur fall precisely on the contacts at the junction. Therefore, the choice of connection method should be taken with all responsibility.

Connection methods

Twisting- a fairly common type of connection in living conditions, until recently used in production. The method is used for single-core homogeneous conductors (copper or aluminum), carried out by twisting the conductors, followed by insulation of the contact point. The crimping of the twist is carried out by means of PPE (connecting insulating clamps). Such connections are quite convenient for installation work small volume. However, it should be borne in mind that at present, the twist connection is not provided for by the electrical installation rules (PES).

Soldering- an affordable and reliable one-piece connection, more often used to connect copper conductors, but aluminum connections of this kind are also allowed. Previously, the cores should be stripped, tinned and twisted. After soldering, the contact group is insulated, the best way is isolation by heat shrink tubing. The solder connection is quite reliable and has excellent conductivity, but it is not recommended for use in places with high level mechanical impact.

Crimping- reliable connection of conductive cores is carried out using special sleeves. Crimping is effective method connections for relatively high currents. The wire placed inside the sleeve is crimped with a special tool, forming a monolithic connection with the required resistance. Using this method, you can connect copper and aluminum conductors.

Welding– long-term connection with low resistance and heating level at the point of contact. By welding, it is possible to connect aluminum conductors of cables of any section or aluminum and copper conductors (with a section of not more than 10 mm2). Welding is performed in one of three ways: 1) contact heating; 2) thermite welding; 3) gas welding. To avoid corrosion, welding joints are varnished, followed by tape insulation (for greater efficiency, each layer of the tape is varnished).

The welding method is popular, despite its laboriousness, as it provides high mechanical stability and excellent electrical contact. However, this method is unacceptable for making connections inside mechanical structures due to the bulkiness of welding machines. In such cases, connections are best made using mechanical clamps of various kinds.

Mechanical connection methods by means of clamps

• Bolted connections are rather bulky connections for high current circuits. The contact resistance in such contacts is stabilized by tightening the bolt. Used to connect no more than 2 conductors;
• Screw terminal connections are an excellent option for switching conductors in junction boxes. Connection by this method of conductors from different materials is allowed. For connection, a special block is used with contacts placed inside, to which conductors are attached;
• Self-clamping terminal blocks are a fast and technological connection method, in which it is enough to insert the conductors into the terminal block. The method is not suitable for flexible stranded wires. This connection excludes short circuit and heating in contact points;
• Splice - a design for splicing a fiber optic cable. The fibers launched into the splice are brought into contact and fixed by means of special latches;
• Connection via is used for power cables. Metal or epoxy sleeves can be used, but currently the most effective is the use of heat-shrinkable sleeves made from thermoplastics according to the latest technologies.

For termination and connection of aluminum and copper cores of cables, welding, crimping or soldering are used.
Welding consists in fusion of core materials and filler material. Depending on the requirements and installation conditions, gas, thermite or electric welding is used.
Gas propane-air and propane-oxygen welding is used more often than other gas welding methods. It is based on the release of heat during the combustion of propane-butane combustible gas mixed with oxygen. With the help of gas welding in removable metal forms, aluminum conductors of all sections are connected and terminated. Protection of the metal from oxidation, carried out by a gas flame, ensures high quality connections. Detected welding defects, if necessary, can be easily eliminated.
Thermite welding is based on the release of heat during the combustion of thermite cartridges and is used to connect and terminate aluminum conductors and cables. This type of welding is highly productive and does not depend on the availability of other types of energy at the work site. The disadvantage of thermite welding is the difficulty in eliminating defects.
Electric welding is based on the release of heat at the point of contact of one carbon electrode with the end of the molten core or two carbon electrodes between themselves (directly or through a metal mold), as well as at the point of contact of the consumable electrode with the end of the molten core in a protective gas. This type of welding provides a stable contact joint, but is not widely used due to low productivity.
During crimping, the core is inserted into the tubular part of the tip (sleeve), pressure is created at the junction with a special tool, at which the metals become fluid, the wires of the core and the tubular part of the tip (sleeve) come closer and a monolithic connection is formed. Creation high pressure possible only for limited area contact surfaces, so the contact obtained by crimping takes the form of local indentation. The total area of ​​monolithic contact in this case is significantly less area contact surfaces. The high quality of pressed joints is ensured the right choice tips (sleeves) and tools. The advantages of crimping compared to other methods are sufficient performance and independence from external energy sources, as well as the absence of thermal effects on the insulation.
The method of connecting and terminating the cores by soldering is based on coating the soldered metal with solder and its subsequent crystallization. When soldering, the solder is heated to its melting temperature, the joint surfaces are cleaned and fused into a pre-prepared shape.
Methods for terminating, connecting and branching copper and aluminum conductors of cables up to 1 kV are given in Table. one.
The termination and connection of aluminum conductors by crimping is carried out with standard cable lugs TA (aluminum), TAM (copper-aluminum), pin SHP (copper-aluminum) and connecting aluminum sleeves GA, GAO and GM.

Table 1. Ways of termination, connection of cores, insulated wires and cables for voltage up to 1 kV

Depending on the section of the core, a tip (sleeve), a tool and a mechanism are selected. Marking of tips and sleeves corresponds to their inner diameters and coincides with the marking of punches and dies, facilitating their selection (Table 2). From the section of the core, equal to the length of the tubular part of the tip or half the length of the sleeve, the insulation is removed. The sector core is pre-rounded and then cleaned to a metallic sheen.
The tip or sleeve is put on the core. The core should enter the tip until it stops, and the ends of the core should be located in the middle of the sleeve and rest against each other.
The assembled end or connection is installed in the crimping mechanism, having previously removed the punch from the die to the extreme position, and then crimping is performed: tips - with a two-tooth tool in one step or a single-tooth tool - in two steps, connecting sleeves - with a two-tooth tool in two steps, a single-tooth tool - in four tricks.
The end of crimping is determined by the moment when the punch washer rests against the end of the die. In the process of pressure testing, the symmetrical arrangement of the holes along the axis of the end or connection is monitored.
After the mechanism is removed from the pressed end or joint, excess quartz-selpium paste is removed, sharp edges are blunted, degreased and insulated.
The termination and connection of copper conductors with a cross section of 16-240 mm 2 by crimping is carried out using the same technology as aluminum, but with the following features: quartz-vaseline paste is not used; the tip on the core is pressed with only one indentation, and the sleeve with two. The tip and sleeves, crimping mechanisms, dies and punches are selected in accordance with the data in Table. 3.
The termination of aluminum single-wire sector conductors with a cross section of 25-240 mm 2 is carried out by the method of volumetric stamping using powder presses PPO-95M and PPO-240. The dimensions of the tips, depending on the cross section of the core, are given in Table. 4.
The end of the core is installed on the matrix of the powder press, during the explosion of the powder charge, the press punch deforms the core and forms a tip with a polystyly shaped contact surface.
Termination, connection and branching of aluminum conductors by welding are carried out with tips made of aluminum alloy with a cross section of 16-2000 mm 2.
Lugs LA are used for terminating cores of cables with rubber, plastic and paper insulation by welding the end of the core with a protruding cylindrical part of the shank. LAS lugs with a solid shank are used to terminate cable cores by butt welding. The marking of the lugs corresponds to the cross-sections of the cable cores, which facilitates their selection.
Table 2. Mechanisms and tool for connection

Note. Designation of current-carrying conductors: C - sector shielded.

Depending on the design of the terminals of electrical equipment, lugs with different number holes on the contact.
Connection and branching of aluminum cores of cables by welding is carried out in steel forms and does not require the use of connecting and branching sleeves.
For gas propane-oxygen welding, a set of NSPU and NPG accessories is used. As a filler material, wire of the brand SvA5 or SvA5S is used in the form of rods, the diameter of which is at the cross section of the welded cores: 16-50 mm 2 - 2 mm, and 70-240 mm 2 - 4 mm, and ending by crimping the aluminum cores of the cables

stranded; CO - sector single-wire; CK- sector combined

In the absence of wires, conductor wires and flux AF-4a or VAMI are used as filler material. The flux compositions (% by mass) are as follows: AF-4a - sodium chloride (28), potassium chloride (50), lithium chloride (14), sodium fluoride (8); VAMI - potassium chloride (50), sodium chloride (30), cryolite K-1 (20).
The welding of the cores is preceded by operations to prepare the cores for termination, connection or branching. The length of the cleaned section of the core from insulation is given in table. five.
The connection of cable cores with a cross section of up to 240 mm 2 by propane-oxygen welding is performed according to the following technology.

Table 11 The length of the core section cleared of insulation for various welding methods

I install welding molds on the liberated sections of the cores and fix them with wedge locks. Forms are pre-coated with inside chalk diluted in water and dried. A thin layer of AF-4A flux is applied to the ends of the cores before the welding molds are installed. The cores are fixed in coolers, after which they heat the mold in the middle part with the flame of the burner, moving the flame to the sides, down and up. Approximately 20-30 seconds after heating the mold to red color, a filler rod is lowered into it, which is melted, while stirring the molten metal with a wire stirrer. Fusion of the additive is continued until the sprue hole is filled.
When connecting sector single-wire cores, their ends, freed from insulation, are rounded off, and when installing welding molds, they are additionally sealed with an asbestos cord.
Welding of three- and four-core cables begins with the cores located below. When fused into a monolith of stranded aluminum conductors with a cross section of up to 240 mm 2, removable metal molds are used, which are installed vertically. After heating the mold to a cherry color, the flame of one mouthpiece is transferred into the mold and at the same time the filler material is introduced into the mold.
Termination of aluminum cores of cables with LA lugs is carried out with burners with single-flame mouthpieces in a vertical position of the cores. A coal mold or a ring of steel strip 1 mm thick is put on the vertical part of the sleeve. The ends of the vein are covered with flux. The end part of the core and the edge of the tip sleeve are melted. In the final stage of welding, filler material is introduced into the mold until it is filled.
For electric welding of aluminum conductors by contact heating, complete sets USAP-2M are used, consisting of transformers for powering the welding station, electrode holders with carbon electrodes, coolers, and a set of welding molds. For arc welding in an argon environment with a non-consumable electrode, a set of welding transformer, oscillator, welding torch, argon cylinder, reducer, pressure gauge. For argon-arc welding with a consumable electrode at direct current, PSG-50 converters and PRM-5 mounting knapsack semiautomatic devices are used.

The technology of electric welding is not fundamentally different from the technology of gas welding. Butt jointing of cables with a cross section of 16-240 mm 2 is carried out with preliminary fusion of stranded conductors into monolithic rods. The cores are fused into a monolith in steel or carbon split molds in a vertical or slightly inclined position.
The wires of the cores and the filler rod, cleaned to a metallic sheen with a steel brush, are degreased with an organic solvent or gasoline. At the installation site of the cylindrical detachable forg, we make a winding with an asbestos cord so that the end: the cores protrude from the winding by 10-15 mm. After fixing the form, its upper end must be aligned with the end of the core. The cooler, which acts as a contact clamp, is installed on the core between the insulation and the form and is connected to the clamp of the secondary winding of the welding transformer.
Fusion of the end of the core into a monolith is performed by touching it with a carbon electrode connected to the second clamp of the welding transformer. With continuous contact, the electrode is moved along the ends of the wires. After the formation of the weld pool, a filler material is introduced, the liquid metal is mixed with a carbon electrode and a filler rod. The process is stopped simultaneously with the formation of a small bulge of liquid metal over the mold, the electrode is quickly withdrawn, preventing the occurrence of an arc, the molten metal is stirred a little more with a filler rod, after which the crystallization of the metal is monitored. After cooling, the cores are removed from the mold, the monolithic rod is cleaned with a steel brush and degreased.
Butt welding of aluminum cores of cables prepared in the form of monolithic rods is carried out in a horizontal position. Coolers fixed on the connecting film are installed on the bare areas. A winding of asbestos yarn is applied to the sections of the veins up to the monolithic part so that sealing is ensured when an open grooved form of steel is fixed.
The melting of the ends lived in. form is produced by touching the end of the electrode. The touch duration is no more than 10 s. When transferring the electrode, do not allow the occurrence of an arc. After the start of melting and the formation of a layer of molten metal at the bottom of the mold, filler material is introduced and melted until the mold is filled. The molten metal during the welding process must be mixed with an electrode and an additive rod.
After cooling, the joints are removed from the mold, the asbestos winding is removed, the slag and flux residues are removed with a steel brush. To give a connection cylindrical shape the outer surface is sawn off with a file.
The termination of aluminum conductors with L A tips is carried out using the technology of fusion of conductors into monolithic rods. In this case, the tip sleeve serves as a form for the formation of the weld pool. After melting the end of the core, the upper edges of the tip sleeve are melted to a depth not less than the thickness of its walls, and then a small amount of filler material is added.

Thermal chucks are used for thermite-muffle welding of aluminum conductors of cables. various designs. Thermite cartridge PA is designed for butt-joining aluminum conductors with a cross section of 16-800 mm 2 and welding of the LAS tip on the conductors with a cross section of 300-800 mm 2. The cartridge consists of a cylindrical muffle, a steel mold (chill mold) and two aluminum caps or bushings. The muffle has a through hole along the longitudinal axis for introducing the cable cores to be welded and a sprue hole for monitoring welding and introducing filler material. The chill mold eliminates direct contact of the cable cores with the thermite mass of the muffle, which improves the quality of welding. When assembling the cartridge, the holes in the chill mold and the muffle are combined. Aluminum caps or bushings protect the side surfaces of the cores from melting. Caps put on stranded conductors also serve as bandages. For round conductors with a cross section of 300-800 mm 2, split cylindrical bushings are used, for welding sector single-wire conductors - bushings with holes in the shape of the conductor section. Thermite cartridges are selected according to macrosizes depending on the cross section of the cores. For thermite welding, a set of NSPU accessories is used,
Preparatory work for welding aluminum conductors with a cross section of 16-240 mm 2 consists in putting a thermite cartridge on the conductors and sealing them, fixing coolers on exposed sections of the insulation from the insulation and installing asbestos screens.
The ends of the cores connected end-to-end are freed from insulation, cleaned to a metallic sheen, covered with a flux paste and aluminum caps or bushings are put on them. The caps must go all the way, which is controlled through the holes in them.
The inner surface of the molds is degreased and covered with chalk, diluted with water to the state of a thick flipper, which prevents sticking to the walls of the mold; When installing a thermite cartridge, the core is slightly bent to the side, a thermite cartridge is put on it and it is shifted along the core to a distance equal to the length of the mold. Then the core is retracted to its previous position until it is aligned with the corresponding core of another cable. The cartridge is moved to reverse direction so that the vein enters the mold. At the same time, the ends of the cores with caps put on them are placed exactly against the sprue hole, and the gap between them is minimal.
At the places where the cores enter the chill mold, asbestos yarn is sealed, winding it between the mold and the core until it stops into the caps. Coolers are installed, choosing the distance between them depending on the length of the thermite cartridge, taking into account a gap of at least 5-8 mm; As a rule, this work is done by two people. The preparatory work is completed by the installation of screens made of asbestos cardboard 3-4 mm thick. The screen protrudes beyond the dimensions of the coolers by at least 10 mm and protects the cores that are not involved in welding from sparks.
The cartridge muffle is set on fire with a thermite match held by a special holder, rubbing it against the end in the place marked with a circle. As it burns, the match is moved over the surface of the muffle, as if rubbing it. Simultaneously with the ignition of the muffle, they begin to fuse the filler rod into the mold, slowly feeding it down as it melts. The light contact of the rod with the hot walls of the casting mold hole speeds up the process. After the formation of a liquid bath, a wire stirrer is introduced into the sprue hole, thoroughly mixing the molten metal for a more complete release of associated gases.
The moment of complete melting of the veins is determined by touching the bottom of the mold with a stirrer. As a rule, this happens 10-15 seconds after the end of the muffle burning. Fusion of the filler rod is continued until the sprue tube is filled.
After the crystallization of the metal, without waiting for it to cool completely, the muffle slag is chipped off, and the mold is removed.
Termination, connection and branching of aluminum and copper conductors of cables with a cross section of 16-240 mm 2 by soldering are made with stamped copper lugs P, copper connecting sleeves GP or copper branch sleeves GPO. When connecting conductors of different sections, sleeves with stepped inner diameters are used.
Soldering of aluminum conductors is carried out with their preliminary tinning and subsequent welding of solder directly into the mold or tip, and also without preliminary tinning with pouring molten solder into the mold. Soldering of copper conductors is carried out with. mandatory use of flux by pouring molten metal into the sleeve. Connection and branching of aluminum cores of cables with a cross section of 16-240 mm 2 by pouring pre-melted solder into the crucible is made in detachable forms. In this case, solders TsA-15 and TsO-12 are used. The amount of solder during its preliminary melting in the crucible does not exceed 7-8 kg. The crucible with solder is heated to about 700 ° C, which is determined by the immersion of the aluminum wire, which begins to melt.
When soldering by watering, the following technological operations are performed. The insulation is removed from the ends of the cable cores in such a way that a gap of 10 mm remains between the insulation and the form (sleeve). The connected cores are given round shape. In a special template, the ends of the cores are cut at an angle of 55 ° with a hacksaw.
The processed ends of the cores are placed in detachable forms with a gap between the ends of 2 mm. In order to avoid leakage of solder, the gaps between the core and the mold are sealed with a winding of asbestos yarn. Forms are placed in a horizontal position. A crucible with pre-melted solder is installed at the soldering point, and a metal tray is placed between the crucible and the soldering point. The heat released by the molten solder does not create additional heating of the conductor insulation, and the excess solder flows back into the crucible. Solder is poured through the sprue hole of the mold. The joints are additionally heated with hot solder, the oxide film is removed from the beveled surfaces of the cores under the solder layer with a mechanical scraper and the solder is simultaneously topped up as it shrinks. Solder smudges are removed from the sides of the molds. The duration of soldering in the form should not exceed 1-1.5 minutes. Before connecting the cable cores of each phase, the crucible with molten solder is heated.
The branches of the cores are performed similarly to the connections using detachable forms of the appropriate design. After mold removal, burrs are removed, sharp corners and irregularities from the place of soldering. The paper insulation of the cores and the solder joints are scalded with a hot composition of the MP brand.

The connection and branching of aluminum stranded conductors by direct solder fusion is carried out in compliance with the following technology. After removing the insulation at a length of 50, 60 or 70 mm, respectively, for wires with a cross section of 16-35, 50-95 and 120-150 mm 2, stepped cutting is performed. The ends of the wires are heated with a flame of a gas burner to the melting point of the solder, then, removing the oxide film, a layer of solder is applied to the entire surface of the end of the wire and thoroughly rubbed with a metal brush until it is completely tinned. Forms are established and the ends of the veins are inserted into them. The space between the living and the form is sealed with an asbestos cord.
To protect the insulation from flame, protective screens are put on both sides, and with large cross-section conductors, coolers.
The mold with the tinned ends of the cores inserted into it is heated by the flame of a gas burner, starting from the middle. At the same time, solder is introduced into the flame, which, when melted, fills the entire mold. The molten solder is mixed, the heating is stopped, after which it is compacted with a light tap on the form of the cooled joint, screens, coolers, molds are removed, and irregularities are removed.
Termination of aluminum cores of cables by soldering is carried out using copper tips P. In this case, solder grade TsO-12 is used. The ends of the strands are prepared using a template, cutting them at an angle of 55°. For the convenience of cleaning the surface of the core from the oxide film, the tips are installed with the beveled side to the contact part. The lower part of the tip is sealed with a putty of chalk and clay mixed with water, and wrapped with asbestos yarn. The soldering of the tip is carried out in the flame of a gas burner. One electrician removes the oxide film with a scraper and welds the solder, and the other continuously heats the termination point.
The connection of copper conductors with a cross section of 16-240 mm 2 is performed by soldering by pouring solder of the POSSu or POS brand in the connecting sleeves of the GP. When making the connection, the inner surface of the sleeves and the surface of the cores (after trimming the ends) are cleaned to a metallic sheen. The connected ends of the cores are covered with flux and inserted into the sleeve. To avoid leakage of solder between; asbestos yarn is wound up with the end of the sleeve and the edge of the insulation. The connection ready for soldering is placed strictly horizontally, while the ends of the cores touch in the middle of the sleeve, and the filling hole is on top. All subsequent operations are similar to the operations of attaching aluminum conductors by pouring with pre-melted solder.
The technology of soldering branch sleeves differs from the soldering of connecting sleeves by the location of the cable cores in a vertical plane.
The termination of the copper conductors of the cable by soldering is carried out with the help of copper lugs P. Conductive conductors having a sector shape are rounded off. After degreasing, a layer of flux is applied to the ends of the core, freed from insulation. When heated in the flame of a gas burner, the end of the core is tinned, on which the tip is then put on. Further operations are similar to operations for terminating aluminum conductors.
The connection of aluminum conductors with copper is performed in copper sleeves. The ends of the aluminum conductors are preliminarily tinned with solder A, and then with tin-lead solder, and the ends of the copper conductors with tin-lead solder. After tinning the copper sleeves, the soldering of the cores is performed with tin-lead solder according to the technology discussed earlier.

Quality control of contact connections during the installation of cable sleeves and terminations ensures the endowed operation of cable networks. It is carried out continuously while preparatory work, during the manufacture of the contact connection and after completion of work.
When making contact connections by crimping, their quality control is carried out by external inspection. The evaluation criteria are: coaxial and symmetrical arrangement of local indentations relative to the middle of the sleeve or tip shank; lack of curvature of the molded connector (more than 3% of its length); absence of cracks and other mechanical damages on the surface of the connector; compliance of the residual thickness after local indentation with the norms. The measurement of the residual thickness after local indentation is performed using calipers or line instruments.
.The dimensions of the contact pads obtained on single-wire conductors by powder presses are controlled with a caliper.
Quality control of welded joints is carried out by external inspection. Connections are considered unsuitable if they detect burnouts of the wires of the outer layer, external gas or slag shells with a depth of more than 2-3 mm, violations of the integrity of the weld metal.
On examination, pay attention to the degree of filling with solder of the gap between the tip (sleeve) and the conductive core. Cracks, traces of overheating, flux residues are not allowed in the joint.

Connection isolation.

After connecting the conductive cores or ringing, the joints are insulated. Insulation is performed with tapes of cable paper wound from rollers or rolls. Rollers and rolls are delivered from cable plant in sealed metal cans filled with oil rosin composition. The conductive core between the connecting sleeve and the paper factory insulation is wrapped with tape from a paper roller or yarn. Yarn is also delivered in cans, sealed and filled with oil rosin.
Before use, yarn, paper rollers or rolls are heated to 70-80 ° C in a special heater or in a bucket with transformer oil. It is not allowed to heat the kits in hermetically sealed factory jars due to the risk of explosion. It is also not allowed to heat the cans on a brazier, the flame of a gas burner or a blowtorch, as damage to the yarn and especially paper is possible. Rollers and yarn are removed from the cans with clean metal hooks.
With tapes wound from paper rollers, the insulation on the core is aligned to the factory size, i.e. paper tapes fill the space between the insulation steps on the cores, if the outer diameter of the connecting sleeve is less than the diameter of the core. If the diameter of the sleeve is larger than the diameter of the core, with the help of tapes from paper rollers in a section equal to the width of the paper roll, the insulation is wound so that it is cylindrical and smoothly passes to the core in the form of a cigar at the ends of the winding,
The paper tape of rollers and rolls is applied to the junction of the cores tightly and evenly, so that there are no air gaps under the layers, which can lead to a breakdown of the cable insulation.
The winding of the first layer of the tape is carried out, starting from the left end of the factory paper insulation. Then turn and wind the second layer of tape in the opposite direction. To prevent a wrinkle from forming on the tape when turning, a cut is made on it for half the length of the tape with a length of 100-200 mm. If the paper is loose during winding, it is removed and the winding is done with new paper. When winding with rollers, the surface of the insulated cores is periodically scalded with a heated MP-1 mass. After winding the cores with rolls, the cores are compressed and wrapped in several layers with tapes from a 50 mm wide roller, and then tied up with cotton yarn taken from a can.

Filling couplings with mass.

Before pouring into the coupling, the cable mass is released from the container in which it is delivered from the factory, placed in a special bucket and carefully heated on a brazier or in an electric heater. It is not allowed to heat up the mass in the original packaging without opening the lid, as an explosion may result. The cable mass is heated gradually. The temperature is controlled with a thermometer. During heating, the mass is thoroughly mixed with a clean metal stirrer (it is impossible to use a wooden one, since moisture can get into the mass from it). Insufficient or careless mixing, or when using a dirty mixer, the cable mass can burn and become contaminated. It is impossible to bring the mass to a boil - it deteriorates. Boiled, burnt or flared cable mass is unsuitable for pouring couplings. The flared mass is extinguished (the lids are closed and the buckets are covered with burlap soaked in water).
Before pouring the sleeve or before scalding, a small amount of cable mass should be drained to clean the bucket spout from possible contamination with debris or dust.

Pouring of cast-iron couplings and steel funnels.

Couplings are poured with bituminous cable mass in several steps to avoid the formation of voids inside the mass. At the same time, they must be warmed up before pouring, since the cable mass may not stick to cold couplings, and then voids are obtained between the coupling body and the cooled mass, into which moisture is sucked. The ingress of moisture into the sleeve leads to damage to the paper insulation and breakdown of the cable when it is turned on under voltage.
Cast-iron connecting, branch and end couplings are poured with bituminous mass in three stages; the first filling is not more than 50% of the sleeve volume, the second - up to 75% after the initially poured mass has solidified to a jelly-like state, and the third - up to the full volume after the first two portions have solidified. Between fillings, the inlet through which the mass is poured is covered with a clean rag.

Epoxy compounds are mixtures based on epoxy resins and are used in the installation of connectors and terminations for cables with paper and plastic insulation.
Epoxy resins used in conjunction with hardeners, with the introduction of which they pass from a liquid to a solid infusible state. In this form, resins do not dissolve in water. For the necessary change in properties, plasticizers are introduced into the epoxy compound (to improve plastic properties), fillers (to increase the mass of the compound and bring its linear expansion coefficient closer to the coefficients of linear expansion of metals), diluents and accelerators. After the introduction of additives, the epoxy compound is a liquid, the viscosity of which is determined by the temperature and the amount of filler (ground powdered quartz K.P-2 or K.P-3, calcined according to special technology to remove moisture, organic and mechanical impurities). If a hardener is added to the compound and the resulting mixture is mixed, an exothermic polymerization process will begin in it, as a result of which the epoxy compound will harden. The polymerization process, depending on the brand of epoxy compound, its mass and ambient temperature, lasts from several hours to several days. For cable sleeves and terminations, Russian-made cold-curing epoxy compounds K-176 and K-115, as well as E-2200 compound (made in the Czech Republic) are used. The most favorable temperature range for them is 10-25°C. At temperatures below 0°C, these compounds do not polymerize; at temperatures above 25°C, exothermic heating has a negative effect on the quality of couplings and seals, contributing to the appearance of pores and other unacceptable defects in them. Therefore, at temperatures below 10 or above 25 °C, the use of the epoxy compound of the above brands is accompanied, respectively, by artificial heating or cooling in the installation area.
At present, new brands of epoxy compounds (UP-5-199 and UP-5-199-1) and hardeners (UP-0636, UP-583 and UP-0633M) have been developed that do not require local heating in the temperature range from -40 to HO0°C. New compounds polymerize within 1-3 hours after pouring.
Epoxy compounds in the cured state have high dielectric and physical-mechanical properties, good adhesion to metals and other materials, and are resistant to changes in temperature conditions, exposure to aggressive media, humidity, and vibration loads. They resist most organic solvents, weak acids and alkalis, oils, gasoline, solar radiation.

12. Components of epoxy compounds and hardeners

The electrical strength of a sample 1 mm thick at a frequency of 50 Hz is at least 20–25 kV/mm.
Epoxy compounds of various compositions are used with hardeners of certain brands in the required quantity. At the same time, the amount of hardener also depends on the ambient temperature in which cable work is performed (Table 12).
Symbols of cable networks on the plans are given in Table. 13.

Let's consider each of the types of connections separately.

Removable connections.

Simple twist

The easiest way to connect wires to each other is a simple twist. In order to implement it, it is necessary to free the ends of the wire at a length of 3-5 cm from insulation and clean them to a shine with a small file or sandpaper. It is necessary to twist the cores very tightly, coil to coil. The ends remaining after twisting are carefully cut off with a file, and the extreme turns are pressed with pliers.

bondage method

Wire twisting can also be done using the bandage method: the stripped ends are clamped in a hand vise and wrapped with soft stripped wire (for the bandage, it is best to take copper wire with a diameter of 0.6-1.5 mm; in this case, the diameter of the bandage wire should not be larger than the diameter of the twisted cores) . The middle part of the bandage should be made apart: if later it becomes necessary to solder this connection, the solder will better penetrate to the junction of the wires. After connecting, the ends of the wires are bent at a right angle, and another 8-10 turns of the bandage are applied on top. The ends of the veins remaining from the twisting are sawn off with a file.

The method of simple or bandage twisting is applicable only for connecting wires to each other; it is impossible to connect the wire to the contacts of electrical components by twisting.

The most convenient (and also quite reliable) way to connect wires to electrical components is to connect using contact clamps, which can be screw and spring.

Terminal connection

The technique for making connections with contact clamps is as follows. If single-wire aluminum and stranded copper conductors are involved in the connection, the screw terminals are equipped with a shaped washer or an asterisk washer, which prevents the core from being squeezed out from under the fastening;

Before connection, the wire is stripped in the usual manner in a section corresponding to three diameters of the screw terminal plus 2-3 mm. To ensure reliable contact, aluminum conductors can be cleaned with fine sandpaper lubricated with petroleum jelly. If the core is multi-wire, then at its end the individual wires are twisted into a tight flagellum.

Then the end of the core is bent into a ring with a diameter equal to the diameter of the clamp screw using round-nose pliers or pliers. It is best to bend the ring clockwise, this will prevent it from unwinding when the screw is tightened. The clamping screw or nut is tightened until the spring washer is fully compressed, after which it is tightened by about another half turn.

Currently, electrical components are equipped with clamp-type screw fasteners: when making such connections, the stripped and stripped end of the wire is not bent into a ring, and the straight end of the core is inserted into the clamp and pressed with a screw.

Spring-type clamp-type connections are mainly used in luminaires with fluorescent lamps for connecting wires to lamp sockets. Their design is a springy plate made of high-quality bronze, which firmly presses the wire core to the clamp body. This connection design completely eliminates spontaneous connector. To release the wire if necessary, it is enough to insert a steel knitting needle (sting of a thin screwdriver) into the clamp, bend the spring plate and release the wire.

All parts used for connection with aluminum wires must have an anti-corrosion galvanized coating. The same requirement applies to steel.

An aluminum wire with a cross section of 2.5 mm2 is connected to copper reinforcing wires (for example, with chandelier wires), single-core and stranded, using chandelier clamps. First, the wires to be connected are cleaned with sandpaper (copper in the usual way, and aluminum - under a layer of petroleum jelly) and lubricated with quartz-vaseline paste. After stripping, the wires are attached to the bar and pressed with screws with spring washers. The connection is inserted into the base of the chandelier clamp and closed with a lid.

When purchasing electrical components with screw clamps, it is necessary to pay attention to the type of clamps, because some electrical installation devices (a number of threaded cartridges for incandescent lamps, cartridges for fluorescent lamps and starters, walk-through and built-in small-sized switches) are equipped with clamps that provide connections only with copper wires.