The end seal is carried out to seal the cable in the immediate vicinity of the connection point of its current-carrying cores to devices, switchgear busbars and other elements of the electrical installation.
Currently, the following types of termination of cables for voltages up to 10 kV are used: in a steel funnel, rubber glove, epoxy, and also from polyvinyl chloride tapes.
Termination of cables in steel funnels(type designation KVB) is still widely used for electrical installations with voltages up to 10 kV, located in dry heated and unheated rooms. This seal can be of three designs:
KVBm - with an oval small-sized funnel that does not have a lid and is mounted without porcelain bushings,
KVBk - with a round funnel, at the output of which the cable cores are located along the vertices of an equilateral triangle (at an angle of 120°),
KVBo - with an oval funnel, at the output of which the conductive cable cores are arranged in one row.
KVBo and KVBk terminations are used for terminating cables designed for voltages up to 10 kV, with conductive conductors of any cross-section; when terminating cables for voltages of 3, 6 and 10 kV, the funnel is mounted with a cover and porcelain bushings, and when terminating cables for voltages up to 1 kV - without cover and bushings.
Sealing the ends of cables in a steel funnel is most often used because the materials necessary for the manufacture and filling of funnels are always available in any electrical equipment. For termination of three-core cables for voltage up to 1 kV with a cross-section of up to 3 x 120 mm2 and four-core cables with a cross-section of up to 4 x 95 mm2, predominantly oval small-sized steel funnels KVBm are used. Sealing is carried out in the following order.
The steel funnel to be installed is cleaned of dirt, put on the cable (Fig. 1, a) and moved along it (after wrapping it with paper to protect the funnel from contamination). After cutting the end of the cable, heat the MP-1 mass to 120...130 °C and thoroughly scald the cut area.
The cores are insulated with adhesive polyvinyl chloride tape (Fig. 1, b), applying it with half-overlapping turns. Slide the funnel onto the cut end of the cable (Fig. 1, c), and separate the conductors in it. Then, having marked the location of the funnel neck on the cable, it is moved again.
Next, attaching the grounding wire to the sheath and armor of the cable with a wire bandage, solder it (Fig. 1, d...f). Having removed the remaining annular belt above the insulation, and then on the cable armor (in the place where the funnel neck should be located), several layers of resin tape are wound in a cone shape (Fig. 1, g) for a tighter fitting of the funnel neck.
A grounding wire is passed through the middle of the winding (after 3...4 layers). The funnel is pushed into place, forcefully pushed onto the winding, and secured to the structure vertically with clamps, to which the grounding wire is then attached (Fig. 1, h).
Tips are soldered or welded to the ends of the cable cores, the cable cores are bent so that they are spaced from each other and from the walls of the funnel at equal distances, and then, heating the funnel to 35...50 °C, they fill it with hot cable mass. As it cools and shrinks, the cable mass is added to the funnel so that its final level is no more than 10 mm below the edge of the funnel.
To protect against corrosion, the funnel, clamp and supporting structure are painted enamel paint. The funnel is marked, indicating on it the number and cross-section of the cable.
Rice. 1. Sequence of operations (a...h) of cable termination in a steel funnel
Terminating cables with rubber gloves(standard designation KVR) is allowed in rooms with a normal environment with a difference in the levels of the cable ends of no more than 10 m and is used for three-core cables rated for voltage up to 1 kV, with a core cross-section up to 240 mm2 and four-core cables with a core cross-section up to 185 mm2. Rubber gloves are made from nayrite rubber of the PL-118-11 brand.
After cutting the end of the cable, installation of the KVR seal (Fig. 2) is carried out in the following order. First, several layers of winding 2 made of adhesive polyvinyl chloride tape are applied staggered onto the stripped cable cores 4 to secure the paper insulation and round off its sharp edges to facilitate their passage through the tubes 3 and the extensions (fingers) 14 of the glove.
Using pliers, bend the body (body) 75 of the glove in several steps along the entire circumference in an area approximately equal to the width of the clamp 6 (25... 30 mm depending on the size of the glove).
The section of the cable sheath 9 between the two annular cuts is removed and a bandage 13 of harsh threads is applied to the bare section of the waist insulation 12, then a roughness is created on the bent section of the glove body 15, for which, after wiping it with a rag soaked in gasoline, it is treated with a bastard file or brush from card tape. The area of the shell to which the glove will be glued is cleaned until shiny, and then wiped with a rag soaked in gasoline.
Next, cover the bent part of the glove body and the section of the shell with a thin layer of glue No. 88N. If the diameter of the shell is smaller than the inner diameter of the glove, a tape of oil-resistant rubber is wound onto the shell, each layer of which is also coated with glue. After 5...7 minutes, required for the glue to dry, the glove body is folded over the tape. The depth of the glove attachment to the shell E should be 30...35 mm.
The glove body is secured to the shell with a special clamp or two bands made of four turns of copper or soft galvanized steel wire with a diameter of 1 mm (after having previously wound two layers of rubberized tape on the body at the places where they are installed).
Having temporarily tied the rubber tubes directly next to the glove with cotton or rubberized tape to protect the waist paper insulation from damage, separate and bend the cable cores.
The ends of the tubes insulating the cores are bent over an area equal to the length of the tube part of the tip 1 plus 8 mm, thus preparing the cable cores for termination. To make it easier to bend the tubes, the outer surfaces of these areas are coated with Vaseline or lubricating oil.
The tips are pressed, welded or soldered onto the ends of the conductive wires, and then their cylindrical (tubular) part is wiped with a rag moistened with gasoline.
Use a hog file or steel brush to roughen the bent part of the tube, after wiping it with a rag moistened with gasoline, and then apply it to it. thin layer glue No. 88N.
Place rollers, wound from an oil-resistant rubber tape and coated with glue No. 88N, into the wells of the tips formed during crimping using the local indentation method. If the diameter of the cylindrical part of the tip is smaller than the inner diameter of the tube, i.e. there is a gap between them, as many layers of oil-resistant rubber, previously wiped with gasoline and coated with glue No. 88N, are wound on the tip as necessary to completely eliminate it. To seal, unscrew the tube onto the cylindrical part of the tip.
The seal can also be made by gluing a piece of tube of such length that it completely covers the cylindrical part of the tip and extends onto the main tube at a distance equal to two of its diameters. In this case, the surfaces of the tubes to be glued together (main and section) are first roughened, wiped with rags soaked in gasoline, coated with glue No. 88N and allowed to dry. Then on inner surface Once a piece of tube is removed, a thick layer of glue No. 88N is re-applied and immediately placed on the tip.
Rice. 2. Design of the KVR seal (a) and type of rubber gloves for three-core and four-core cables (b): 1 - tip, 2, 11 - windings made of polyvinyl chloride tape, 3 - rubber tube made of nayrite, 4 - cable core, 5 - glove, 6 - clamp, 7 - ground wire, 8 - armor, 9 - cable sheath, 10 - seal with oil-resistant rubber tape, 12 - waist insulation, 13 - bandage, 14 - glove finger, 15 - glove body, 16 - extension for the fourth core four-core cable
When terminating the cores by welding using cast tips of the LA brand, a tape of oil-resistant rubber is wound onto the exposed section of the core with the transition of its turns to the tip and insulation of the cores. It is also possible to seal this winding with a continuous band of twisted twine with a diameter of 1.5... 2 mm, which is then coated with asphalt varnish.
The most common methods for sealing rubber tubes on tips are shown in Fig. 3. Rubber tubes 1 are secured to the tip body with a special bandage 3 or four turns of copper wire with a diameter of 1 mm.
Rice. 3. Methods for sealing rubber tubes on an aluminum tip: a - with preliminary unscrewing of the tube, b - using a piece of tube, c - twisted twine on a cast tip, 1 - rubber tube, 2 - winding with oil-resistant rubber tape, 3, 5 - bandages made of steel strip and twine, 4 - rubber tube couplings
Termination of cables with epoxy compound is characterized by simplicity of execution, reliability, high electrical and mechanical strength, safety and heat resistance ( working temperature such embedding from -50 to +90 °C).
It has the general type designation KVE and is used for terminating power cables rated for voltages up to 10 kV and used indoors in any premises, as well as in outdoor electrical installations, subject to protection from direct exposure to precipitation and sunlight.
The epoxy termination body is formed after the epoxy compound has cured and is poured into a conical mold that is temporarily placed over the end of the cable.
The seal with epoxy casing (Fig. 4) can be of the following designs:
KVEN - with nayrite rubber tubes on cores for use in dry rooms,
KVED - with two-layer (lower layer of polyvinyl chloride, upper layer of polyethylene) tubes on cores for use in damp rooms and areas with tropical and subtropical climates,
KVEp - with the output of insulated wires from the housing, soldered inside to the stranded cable cores, rated for voltage up to 1 kV, for use in damp rooms and areas with tropical and subtropical climates,
KVEZ - with nairite rubber tubes on single-wire cable cores, rated for voltages up to 1 kV, and “locks” inside the housing for use in damp rooms and areas with tropical and subtropical climates.
Rice. 4. End epoxy termination of cables of various designs: a - KVEn, b - KVEd, c - KVEp, d - KVEz, 1 - tip, 2 - bandage or clamp, 3 - tube made of nayrite rubber, 4 - conductor in factory insulation, 5 - body made of epoxy compound, 6 - bandage made of gray threads on waist insulation, 7 - cable sheath, 8 - two-layer winding, 9 - wire bandage of the grounding wire, 10 - grounding wire, 11 - cotton winding paper tape coated with an epoxy compound, 12 - two-layer tube, 13 - insulated wire, 14 - soldered connection point for the cores, 15 - winding with adhesive polyvinyl chloride tape, 16 - bare section of the core
In addition to the above, KVEO terminations are also used without an epoxy cast body, and with a winding of cotton tapes glued with an epoxy compound, they are intended for termination of single-core cables rated for voltages up to 1 kV, under the same conditions as KVEn and KVED terminations.
The installation of terminations begins after cutting the cable, performed in accordance with the general instructions. The dimensions of the cable terminations for KVEp and KVEZ terminations are determined using Fig. 5 and table. 1.
Rice. 5. Cable cutting for installation of KVEp (a) and KVEZ (b) terminations: 1 - core in factory insulation, 2 - belt insulation, 3 - sheath, 4 - cable armor
The peculiarity of the KVEP termination is that it is not the current-carrying cable cores that come out of it, but the sections of insulated wire attached to them. It is performed as follows. Select a piece of insulated wire of the required length with a cross-section corresponding to the cross-section of the cable core, strip its ends, preparing to connect one of them to the cable core, and the other to the tip.
Table 1 Dimensions of cable terminations for installation of KVEp and KVEZ terminations
| Seal size | Dimensions of cutting sections, mm (see Fig. 5) | ||||
| A | ABOUT | P | G | B | |
| KVEp-1, KVEp-2 | 170 | 35 | 20 | 40 | - |
| KVEp-3, KVEp-4 | 210 | 50 | 20 | 45 | - |
| KVEp-5, KVEp-6 | 240 | 50 | 20 | 50 | - |
| KVEp-7 | 245 | 50 | 20 | 35 | - |
| KVEZ-1 | F+55 | 35 | 20 | - | 90 |
| KVEZ-2, KVEZ-3 | F+55 | 35 | 20 | 25 | 95 |
| KVEZ-4, KVEZ-5 | F+55 | 35 | 20 | 25 | 120 |
Notes:
1. The length of the cut cable cores (section L) is taken depending on the conditions of installation and connection, but not less than 150 mm.
2. Section G for terminating KVEZ is determined depending on the method of terminating the cores.
Stripped ends of the cable copper core and copper wire degrease, insert into the connecting copper sleeve and solder, pouring POS-30 or POS-40 grade solder into it. The aluminum core of the cable is connected to aluminum wire in an aluminum sleeve by soldering, pouring or crimping.
After connecting the cable core to the wire, a winding of adhesive polyvinyl chloride tape is applied to the exposed area, a grounding wire is soldered to the armor and tapes, and then the cores and the shell of the termination area are degreased with acetone to ensure better adhesion to the epoxy compound.
A removable conical shape is installed on the prepared end of the cable so that the cable cores are at a distance of at least 6...7 mm from any point on its edge, and the soldering area is inside. The mold is filled with epoxy compound and removed after curing.
The KVEZ epoxy seal (see Fig. 4, d) differs from the KBEp seal in that sections G 25 mm long, called locks, free from insulation, are left on the single-wire solid cores of the cable (see Fig. 5). A tube made of nayrite rubber is put on the cores with exposed areas of such a length that will allow one end to be pulled onto the cylindrical part of the tip, and the other to be immersed in the epoxy casing of the seal to a depth of at least 20 mm.
When installing and filling the mold with epoxy compound, KVEZ seals comply with the same requirements as when performing KVEP seals.
Rice. 6. KVV end seal: 1 - cable armor, 2 - ground wire, 3 - wire bands on the armor and sheath, 4 - cable sheath, 5 - factory-made insulation, 6 - bandage made of cotton yarn on belt insulation, 7 - core in factory insulation, 8 - belt glass-shaped winding, 9 - winding of cores, 10 - bandage made of cotton yarn on core insulation, 11 - bare section of the core, 12 - cable lug, 13, 15, 17 - bandages, 14 - filling composition, 16 - leveling winding
Cable termination with PVC tapes
End seals made of polyvinyl chloride tapes and varnishes (type designation KVV) are used for paper-insulated cables designed for voltages up to 10 kV and used indoors, as well as in outdoor installations at an ambient temperature not exceeding 40 ° C and subject to protection from direct exposure to precipitation and sunlight.
KVV termination is used when the difference between the levels of the highest and lowest points of the cable location on the route is no more than 10 m, otherwise a special KVV termination is used. Installation of KVV seals is carried out at an ambient temperature of at least 5 °C.
The sealing of KVV (Fig. 6) is carried out with sticky (first version) or non-sticky (second version) polyvinyl chloride tape using compositions No. 1 (covering) or No. 2 (filling), respectively. Polyvinyl chloride adhesive (with an adhesive layer) tape has a thickness of 0.2 ...0.3 mm and a width of 15...20 mm, and non-stick tape is 0.4 mm thick and 25 mm wide. The dimensions of the cable cut for terminating VVV are determined using table. 2 and fig. 5, a.
Cable lugs are welded, soldered or pressed onto the ends of the cable cores.
When terminating cable cores by crimping the tip using local pressing, only tubular lugs that are factory sealed are used. Before crimping on an aluminum cable core, clean the inner surface of the tip with a brush made of steel wires and lubricate it with quartz-vaseline paste.
Having removed the insulation along the length from the ends of the cores, equal to length the tubular part of the tip, and having cleaned them with a cardboard brush to a metallic shine, the cleaned area is also lubricated with quartz vaseline paste.
After such preparation, the tip is put on the core until it stops and, having inserted it into the crimping mechanism with a pre-selected punch and matrix, it is crimped. The holes formed on the tubular part of the tip after crimping are wiped with a rag moistened with gasoline, lubricated with composition No. 2, and then filled with rolls of polyvinyl chloride tape and polyvinyl chloride composition No. 2.
The volume and shape of the ribbon roll must correspond to the depth and shape of the hole. The skein is pressed into the hole and then coated with composition No. 2.
The ledges formed at the transition points from the outer surface of the cylindrical part of the cable lugs to the core insulation are leveled by winding a 7.5 mm wide polyvinyl chloride tape, for which a 15 mm wide tape roller is cut in half. In the same way, level the ledge at the point of transition from lead or aluminum shell to waist isolation.
Table 2. Dimensions of cable cutting for installation of KVV termination
| Seal size | Core cross-section, mm2, for voltage cables, kV | Dimensions of cutting sections, mm (see Fig. 4, a) | ||||
| 1 | 6 | 10 | A | ABOUT | P | |
| KVV-1 | Up to 25 | - | - | F+65 | 30 | 15 |
| KVV-2 | 35...50 | 10...25 | - | F+70 | 50 | 20 |
| KVV-3 | 70...95 | 35...50 | 16...25 | F+105 | 80 | 25 |
| KVV-4 | 120... 150 | 70...95 | 35... 70 | F+105 | 80 | 25 |
| KVV-5 | 185 | 120...150 | 95...120 | F+125 | 100 | 25 |
| KVV-6 | 240 | 185 | 150 | F+125 | 100 | 25 |
| KVV-7 | - | 240 | 185 | F+125 | 100 | 25 |
| KVV-8 | - | - | 240 | F+125 | 100 | 25 |
Notes:
1. The length of the stripped cores (section L) is taken depending on the connection conditions, but not less than 150 mm for a cable with a voltage of 1 kV, 250 mm for a voltage of 6 kV and 400 mm for a voltage of 10 kV.
2. Section G is determined depending on the method of ending the cores.
Next, wipe the outer surfaces of the core insulation and belt insulation with a rag slightly moistened with gasoline, and each core from the belt insulation to the contact part of the tip is wrapped with polyvinyl chloride tape (in three layers for core cross-sections up to 95 mm2 and in four layers for cross-sections of 120 mm2 and above).
Layers of polyvinyl chloride tape are applied with a 50% overlap of the previous turn (full overlap) and with tension at which the tape is stretched with a decrease in the original width by no more than 1/4. Last layer winding of each core is carried out by entering the entire stage of the lead or aluminum sheath.
The winding of each core is coated with a brush with a thick layer of composition No. 2 in sections 70, 100 or 120 mm long (counting from the end of the belt insulation) with cable diameters along the sheath of up to 25, 40 and 55 mm, respectively. The composition is applied to that part of the surface of each core that faces inward.
Using a brush or wooden spatula, fill the internal space between the cores with composition No. 2. Then the veins are compressed by hand into a bundle and secured in this position with a bandage made of cotton tape at a distance of 10 mm from the area covered with composition No. 2.
The outer surface of the bundle of compressed wires is also coated with a thick layer of composition No. 2 (using the composition squeezed out when compressing them into a bundle). The amount of composition in the gutters formed by the veins must be such that it protrudes in the form of three rollers above the surface of the bundle, i.e., voids unfilled with the composition must not be left in which air and moisture can accumulate.
A belt cup-shaped winding made of eight layers of polyvinyl chloride tape with 50% overlap (regardless of the cable cross-section and voltage) is applied to the section of the cores compressed into a bundle and to the section of the cable sheath, and at a distance of 20 mm from the ends of this winding to the cylindrical part cable lug - bands made of twisted twine with a diameter of 1 mm (Table 3).
The bandages are coated with polyvinyl chloride composition No. 1 using a brush.
To increase moisture resistance outer surface the seals are covered with asphalt varnish or colored enamel paint.
A temporary bandage made of cotton tape, applied 10 mm above the glass-shaped winding, can be removed after bending the cores and attaching them to the contacts of the corresponding device or tires switchgear, and also after sufficient drying of composition No. 2.
In addition, before composition No. 2 dries, it is advisable to relieve the seal from the pressure of the impregnating composition, which arises due to the difference in the levels of the cable ends. Switching on a cable with a newly installed termination under load is allowed no earlier than 48 hours after completion of installation.
Sealing KVV using non-stick polyvinyl chloride tape and liquid composition No. 1 are installed in the same way as seals using adhesive tape. In this case, each layer of winding (to avoid weakening the density of its application before the next layer is completed) is temporarily secured with a bandage of 2-3 threads of gray thread.
Table 3. Dependence of the width of the bandage on the cross-section of the cable cores
| Core cross-section, mm2 | 16 | 25 | 35 | 50 | 70 | 95 | 120 | 150 | 185 | 240 |
| Bandage width, mm | 25 | 30 | 35 | 40 | 45 | 50 | 55 | 65 | 70 | 75 |
The surface of each layer of windings is first covered with one, and after it dries, with a second layer of composition No. 1. The next layer of tape is applied over the third layer of composition No. 1, which is not applied immediately over the entire length, but gradually in sections of 100 mm in length.
KVV terminations of special design are used for large differences in the levels of the cable ends. They differ from the terminations of the first and second versions in that the winding on the core insulation is made of five layers of polyvinyl chloride tape, and the sealing of the root of the termination is made with an epoxy compound instead of polyvinyl chloride composition No. 2.
In special-design KVV terminations, the leveling winding between the tip and the core insulation is made with cotton tape with a generous coating of each turn with epoxy compound.
The quality of installation of line-cable structures largely determines the performance of communication systems in which expensive active equipment is installed. How advisable is it to use a specialized tool and what can be obtained as a result?
Working with cables has always required special attention. The cost of a mistake when cutting a cable, stripping it and terminating it (installing connectors or cross-connecting) is quite high - the cable can be damaged so much that it will have to be laid again.
That is why, during the development of routes, it is necessary to provide places for placing reserve stock near the ends of the cable line. And during installation, it is necessary not only to provide such a reserve, but also to leave sections at the ends of the cable, which is necessary for termination. When determining the length of these sections, you should calculate the technological reserves for cutting the cable, as well as for installing a connector or installing a cross-connect (depending on their type and the manufacturer’s recommendations). Since switching devices are placed in certain structures, a reserve is also needed for cable placement inside the socket block, cross-connect cabinet, patch panel, etc., taking into account the appropriate mounting methods and internal organizers. Since the exact location of such a structure relative to the cable outlet is usually unknown in advance, a margin is required to take into account installation tolerances.
In addition, the necessary safety stock should be provided in case possible damage cable when terminated (usually it is a multiple of the amount of technological reserves). And what less experience installer - the larger the safety stock should be.
The likelihood of cable damage also depends on the tool used. We can say that the final quality of cable line termination largely depends not only on the accuracy and experience of the installer, but also on the degree of “professionalism” of the tool. The latter is determined by the level of specialization of the tool (accurate, high-quality and fast performance of individual operations requires the use of a special tool), as well as the durability of the working surfaces (if they wear out, the quality of the operations decreases).
Price factor
In tool catalogs you can always find several types of tools designed to perform the same operations. Products that are similar in their functions differ significantly in price.
In the lower price range there are tools with a short service life. This tool is usually used for minor repairs in the office or home. Ergonomics, ease of operation and productivity are sacrificed at the expense of low price. A tool of this class has a simplified design, and in its manufacture they use inexpensive materials(especially when implementing working bodies).
In the upper price range, a high-performance automated tool is presented, the purchase of which will undoubtedly pay off if the volume of work is large enough. At the same time, in a number of products with an average cost, you can find an ergonomic and reliable tool designed for a long service life.
Cable cutting
The first thing you have to deal with is cutting the cable. A cut is considered to be of high quality if it does not disrupt the structure of the cable, does not deform (flatten) its outer covering, or create burrs on the cores. This type of cut can only be done with a cable cutter. Specially profiled blades grip the cable and prevent it from being squeezed out when cutting. The blade profile and sharpening angle depend on the size and type of cable. There are special models for cutting twisted pair cables, coaxial, power, armored cables and cables with steel supporting elements. The latter require special attention in the selection of tools, since if you try to use a product that is not designed to work with steel, the cable cutter will be damaged.
For cutting copper and aluminum cable you can use a reinforced tool
Specialized compact tool designed to cut cables up to 2700 pairs
It should be noted that cutting optical cable, especially reinforced with steel cable, and cables in a metal sheath (for example, corrugated) require the use relevant tools. As a rule, such cable cutters have a separate, replaceable pad on the tip of one of the blades. When cutting self-supporting cables with a side-mounted cable, the latter should be bitten out with a special tool before work begins with the rest of the cable.
Depending on the outer diameter and design of the cable cores, the cable cutter can be simple (single-pass) or with a ratchet (multi-pass). Because cutting is accomplished in multiple strokes, a multi-pass tool may have a stop shoe on one of the handles. For telephone cables with a large number pairs (over 500) or electrical cables with large cross-section conductors, cable cutters with electric and manual hydraulic drives are used.
Cable cutting
The next operation - cutting the cable - involves removing all layers of insulation in in the right order and to the desired length. The more coatings, the more difficult it is to cut the cable. Metal or polymer armor, hydrophobic filling, load-bearing elements(cables or fiber). Therefore, in order to do the job correctly, you need to clearly understand the internal structure and sequence of cutting a particular cable.
Since the layers are cut from the outside to the inside, the top ones are removed at a greater length (“herringbone”). Failure to comply with this requirement may complicate the installation of the connector or reduce the quality of the cable embedded in it, which will cause problems during operation, since the cable will “hang” on some cores. It is best to use the template recommended by the manufacturer of the cable or connectors for which the cutting is being installed.
Specialized strippers for removing outer sheaths from optical and copper communication cables, power and other cables can perform longitudinal, transverse and spiral cutting of coatings
The plow knife carries out longitudinal and transverse cutting
When choosing a cutting tool, you must definitely consider how a particular product works with different cutting directions. If one option is possible in the transverse direction, then along the cable the cut can be straight longitudinal or spiral. The choice depends on the presence and location of metal armor, as well as the type of insulation. If hard and dense polymer insulation is easy to cut in any direction, then soft and loose (loose type) - only in a straight line along the cable. Otherwise, it turns and the knife damages the veins. Transverse cutting of such insulation is best done after the longitudinal cut has been made and it has been separated from the cable.
Since the upper layers of cable insulation fit tightly, damage to the cores most often occurs when cutting them. Guaranteed protection against such a nuisance is provided by the use of knives with adjustable cutting depth, as well as precise adjustment of the knives for this type of insulation. And the only thing possible way for ideal tuning - preliminary practice on the section of cable with which you will work. From the above, it is clear that for quick and high-quality cutting of a cable with several layers of insulation, several identical knives, but pre-configured differently, may be required.
In cases where it is necessary to remove insulation not at the end of the cable, but at an intermediate point, the cutting technology turns out to be different. Such situations require special attention, because if when processing the end of the cable the damaged part can be cut off and start all over again, then when cutting the middle part there is no such chance. Therefore, it is necessary to take into account that not every tool is suitable for such work.
Reinforced cable cutter for working with communication cables. Allows you to cut cables up to 57 mm thick in lead, plastic and rubber sheaths
The so-called "driving" tool places the conductor in the mortise contact
Universal crimping tool allows installation of modular RJ11, RJ22 and RJ45 connectors on the cable
Removal of external polymer insulation from thin (up to four pairs) cables of Category 3, 5 or higher is carried out using a combination tool. But for cables with larger diameters there is no combination tool. They are cut using special knives.
The simplest of them is a hand-held plow knife with a protective pad on the tip of the blade that prevents cutting of cable strands. This is the only knife that provides high-quality cutting of cables with soft, loose polymer insulation. However, this tool is quite versatile, as it can also be used for cutting cables with rigid polymer insulation. Its main advantage is the arbitrary direction of the cut.
Another type of knife (with a rotating blade) is intended only for this type of external insulation. Despite the apparent difference, they are built the same - a cable grip (sometimes spring-loaded) and a blade with a depth adjustment screw, with the ability to rotate 900 for longitudinal and transverse cuts, and also, for some knives, 450 for a spiral cut.
A particular problem is created by cutting cables (most often optical) in rigid polymer insulation with metal corrugation or wire armor. For the first type, there are special varieties of the knives mentioned above. Their main difference is a reinforced design and a blade made of high-quality steel.
Cutting Kevlar and other polymer fibers is carried out with special scissors
Strippers are available for stripping cables or conductors of different diameters
The plow knife has a ratchet drive and a stop for adjusting the immersion depth of the blade. The rotary blade knife has two powerful handles and a cable grip secured by a lever. This design allows you to cut the corrugation along with two layers of polymer insulation in one pass of the tool without the risk of damaging the cable cores. Cables with wire armor are cut in several passes. It is more convenient to remove the top polymer insulation with a knife with a rotating blade, setting the cutting depth so that the knife does not touch the armor wires. Then, using steel cutters, all the armor wires are bitten off one by one. The remaining polymer insulation is removed in any convenient way.
The topic of cutting cables in “heavy” armor would not be complete without mentioning several tools. The easiest way to cut the lead sheath of cables is with two types of special knives: heavy or light (the latter are used together with a hammer). The steel strip armor is removed using electrician's shears, which have serrated, hardened steel blades to prevent the material from being squeezed out when cutting. They are also used for cutting Kevlar fibers, but this work is more convenient and better done with scissors with ceramic blades.
Preparing the veins
The next operation is preparing the cable cores for termination, that is, for installing connectors or direct connection to cross-connect equipment. Modern methods, which are based on mortise contact technology, do not require stripping of the cores before installation. Despite this, in some cases it is impossible to do without stripping the insulation, for which a fairly wide selection of tools is still offered.
If the work is rarely performed, then to perform it you can choose a combination tool with wire cutters for cutting wires and several calibrated grooves for removing insulation from wires of various sections. Sometimes it is supplemented with pliers, a device for crimping contacts, or pliers for screws of several sizes. You have to pay for versatility - working with such a tool is not very convenient.
In cases where you have to deal with one type of wire, it is more convenient to use an adjustable tool. Its blades are adjusted to the required diameter using an adjusting screw or cam, which greatly simplifies the stripping process - you don’t need to think about which groove the wire will go into.
It is advisable to use a more expensive high-performance tool for processing a large number of cores of the same type. It is very easy to use, as it is operated by pressing a handle, but is designed to work only on the end of the conductor and is absolutely not suitable for stripping insulation at an intermediate point. The length of the core from which the insulation will be removed is adjustable. Simpler options are usually adjusted to the required core diameter and have a built-in knife for cutting wires. Professional models have a working body designed for two or three specific sections of the core.
One of the most common types of wiring used in the implementation of various systems inside buildings are four-pair cables of Category 5. Not only SCS, but also telephone and intercom systems, security and fire alarms, voice alarms, etc. are created on their basis. the design of these cables is quite unified; extremely convenient combined tools have been created to work with them, cutting the cable, removing (more precisely, ring trimming) the top insulation and stripping individual cores.
The reliability of the connections between the coaxial cable and the connectors directly depends on the quality of its cutting. An economical solution is the use of simple devices to ensure a given depth of cut of the shell for certain type cable, thanks to which cutting is carried out in several stages.
A professional tool allows you to prepare a coaxial cable in one operation. It is enough to place the cable in the cassette, make one full turn around it and remove the cut part of the insulation and screen. For getting the desired profile cable being stripped, the required number of replaceable blades is installed in the cassette, each of which is adjusted to the required cutting depth. It should be noted that large volumes of work on cutting coaxial cables can be performed with an automatic, electrically driven tool.
Using a mortise contact
After cutting the cable, they begin to terminate it. The most common operation is installing a cable on a cross-connect. As already noted, technologies such as soldering and screw connections are no longer found in cross equipment. To connect cores or install connectors on cables in low-current circuits, the mortise contact method is widely used. The meaning of this technology is simple - the contact has a knife-shaped shape, so that during installation it cuts through the insulation and cuts into the metal of the core conductor, as a result of which there is no need to remove the insulation. This not only significantly increases labor productivity, but also improves all characteristics of the connection, since the contact point is protected.
In all cross-connection systems, the core is pressed into the contact slot, but due to differences in the configurations of the contact and the plinth body, each type requires a special tool (punch down tool), with which the wire is pressed into the plinth contact slot and, if necessary, is cut off .
The economical and professional versions of this tool differ quite significantly. The most important point is the presence in the professional version of a spring impact mechanism, which ensures uniform force of pressing the wire into the contact of the plinth and the impact at the end. The blow ensures reliable cutting of the core into the contact of the plinth and in some types of plinths it is used to trim the remainder of the core. In more advanced cross systems, excess trimming is carried out with built-in scissors.
Despite the fact that tools without an impact mechanism are suitable only for minor amounts of work (for example, for making changes to already installed systems), they are quite inexpensive and therefore continue to be popular. At the same time, a budget-level professional tool must have a striking mechanism. This is quite enough for high-quality and productive work. The limitation of the capabilities of such a tool is that it works with switching modules (for example, plinths) of only one type.
U universal tools due to replaceable working bodies, compatibility with various mortise contacts is ensured (66,110, KRONE, BIX, etc.). An additional replaceable working element is stored in the tool handle or a separate case. The handle is also equipped with devices for removing wires from the contacts of the plinths and removing the plinths from the mounting brackets. It should be noted that in the universal holder, in addition to replaceable parts for working with the cross, can also be installed whole line other tools: screwdriver, awl, punch, adapter for 1/4" hex replacement bits (screwdrivers and socket wrenches).
High productivity when sealing cable ends of SCS onto contacts of type 110 can be achieved using a group manual or electric tool, since it ensures simultaneous processing of all eight conductors.
When carrying out work on a cross-connection, you cannot do without a probe with a hook, the use of which allows you to simplify the search for the desired jumper. With this probe you can carefully move the wires apart, remove the necessary ones and check the quality of the seal.
Cable splicing
An equally common operation is cable splicing. There is no point in dwelling on the antediluvian technology (which, unfortunately, is still in use), when the connection of the cable cores of local telephone networks is carried out by twisting them. The method is, of course, cheap, but the connection quality is appropriate. Modern cable connection technology is based on the mortise contact technique. The group (10, 20, 25 pairs) or individual connectors used in this case provide splicing of two cables or a tap (connecting a cable to an existing one).
The latter type of connection, in particular, is very convenient when upgrading networks, when you need to switch from old equipment to new equipment in a short time (a section of cable that has become unnecessary can be removed after installation is completed).
Crimping of individual connectors is carried out with a very simple tool, reminiscent of ordinary pliers. The design of the tool for processing group connectors is much more complex, since they are designed for splicing cables in a limited volume of cable wells.
Such connectors are used not only for low-voltage circuits, but also for power circuits. Designed to organize a branch for connecting sockets to a distribution feeder (for example, in SKS cable ducts), they are most often crimped with ordinary pliers.
Article provided by the training center "A-COM Academy"
Cable cutting
To connect electrical wiring Cables and wires are terminated to assemblies of clamps, panels, consoles, junction boxes, to contacts of devices and devices. In dry rooms of all classes, dry terminations are made using polyvinyl chloride tubes, insulating tape and other materials.
For the electrical connection of cables to cables or for connecting electrical wiring to devices with connectors, end seals of cables and wires in plug connectors are used.
^ End seals must provide:
Sealing the ends of cables and wires to prevent moisture from penetrating under the cable sheaths and under the insulation of the cores, and for cables with impregnated paper insulation - also to prevent leakage of the impregnating oil-rosin composition;
High quality insulation of cable cores and wires between the end seal root and the contact of the device to which they are connected, and reliable connection of cable cores and wires to the device contacts;
Grounding of metal sheaths and armor of cables and marking of conductors.
When connecting a shielded cable to a plug connector, the terminations must additionally ensure an uninterrupted electrical circuit between the shielding shells of cables or wires with the metal housings of the connectors;
Securing cables or wires in the connector body, preserving the integrity of the connection of the cores with the connector contacts;
Insulation of current-carrying conductors of cables and wires among themselves and in relation to the connector body.
The installation of end seals begins after laying and fastening cables and wires along the route and installing inputs into panels and consoles.
D 
For cutting cables, various types of bandages are used: armored tape, wire, thread, etc.
Construction of bandages made of armored tape (a), wire (b) and threads (c):
1 - cable,
2 - armor,
3 - bandage,
4 - wooden block for applying a bandage,
5 - wire,
6 - polyvinyl chloride adhesive tape,
7- threads or twine Scissors NUSK-300 (a) and knife NKP-2 (b):
1, 2 - handles,
3 - fixed knife,
5-movable sector knife,
6 - ratchet device,
8 - clamp,
The procedure for cutting the cable:
1
)Cut the end of the cable to such a length that it can be connected to the most remote contact of the device or terminal assembly. Used for cutting cables hand saws or universal sector scissors NUSK-300 (Fig. a).
Cable end cutting for termination:
1 - first stage, b - second stage;
1.4 - bandages made of armored tape or galvanized steel wire,
2 - armor,
3 - outer jute cover,
5 - shell,
6 - longitudinal cuts,
7,8 - ring cuts,
9 - jute pillow,
10 - waist insulation,
11 - bandage,
12 - flanging,
13 cores in factory insulation
To cut a cable (or a bundle of wires), the handles of the scissors are compressed until full. If it is necessary to cut off a short piece, then the movable knife 5 is installed so that between it and the fixed knife 3 a hole of sufficient diameter is formed to enter the cable or wire to be cut. If you need to cut off the long end, but it is difficult to pass it into the gap between the knives, then use handle 1 to disengage the movable knife. A stationary knife is brought under the cable to be cut, and then a movable knife is placed on it, turning it around axis 4. To cut the cable, the movable knife is fed by a ratchet device 6.
2) On the outer jute cover 3 at the line defining the length of the cut end A, apply a bandage 4 10-12 mm wide made of galvanized steel wire with a diameter of 1 mm.
3) After removing the jute cover from the cut end, at a distance of 100 mm from the edge of the jute cover, a second similar bandage 1 is applied to the armor 2 cables.
4) at a distance of 3-5 mm above the bandage, 1 armor is cut along the annular line with a hacksaw and removed from the cut end.
5) Remove the jute cushion 9 and the paper tape from the shell 5.
6) The cable sheath is cleaned of bitumen, wiped with a rag soaked in gasoline, and wiped dry.
7) On the cable sheath at a distance B from the bandage 1 (for dry terminations B = 40 mm) make the first annular cut 8, at a distance of 10 mm from it - a second annular cut 7, and then two longitudinal cuts 6 at a distance of 8-10 mm one from the other.
8) The strip of the shell, followed by the shell itself, is removed with pliers
9) A single-row bandage 11 made of twisted threads is applied to the waist insulation 10. The following operations are performed depending on the type of seal.
^
Dry end seals.
Rubber and polyethylene insulation of wires and cables is protected with polyvinyl chloride tubes and tapes, since rubber insulation is susceptible to aging under the influence of environment(light, temperature, air oxygen), and polyethylene is a flammable material.
WITH 
hooting end cutting cables with rubber core insulation:
a - putting a polyvinyl chloride tube on the core, b - end cutting;
1- steel wire,
2 - polyvinyl chloride tube,
4 - winding made of rubberized fabric,
5 - winding made of polyvinyl chloride mite,
6, 8, 11 - bandages,
9 - outer cover,
10- shell
1) The ends of the tubes for the cores located outside the bundle are cut at an angle of 25-30°. Tubes 2 (Fig. a) are pulled onto the cores. In this case, the ends cut at an angle should be located on the winding of the cores.
2) The space between the cores with polyvinyl chloride tubes 2 in the cutting spine is filled with filler varnish No. 2.
3) Bandage 11 (Fig. b) made of twisted twine with a diameter of 1 mm is applied to the cores, starting from the end of the shell, to a width of 20 mm and coated with varnish No. 1.
4) The cable termination area is wrapped with 3-5 layers of adhesive polyvinyl chloride tape with a 50% overlap of each previous turn of tape. Such a winding 5 should have a width of about 50 mm and be located 30 mm above the shell and 20 mm down the shell.
Wire termination:
a - winding a bundle of wires with twine, b - sealing the PR and PV wires at the exit from the protective pipe; 1 - bundle of wires, 2 - bandage, 3 - protective pipe, 4 - bushing-terminator
The termination of single- or double-core wires consists of impregnating the bandages with bakelite varnish. Bunches of single-core installation wires of types PR, PV and PRTO are pre-assembled into an even bundle (bundle) and fastened with a twine winding along the entire length (Fig. a). At the exit from the protective pipe 3 (Fig. b), a bandage 2 20-25 mm wide made of twisted twine with a diameter of 1.5-2 mm is applied to the bundle of wires PR and PV and a plastic sleeve 4 is installed to protect the insulation of the wires at the exit from the pipe. A bandage of twisted coarse threads is first applied to a bundle of PRTO wires, then of twisted twine, and a winding of polyvinyl chloride tape is made on top of it.
^
End seals in plug connectors.
The cutting of the end of the shielded cable is shown in Fig. A. A continuous shield in cylindrical connectors of the PPH type is provided by contact between the connector body and washer 6 (Fig. b) made of sheet metal, soldered to the shielding braid.
R 
Termination of the end of the shielded cable:
a - removal of the screen, b - removal of the sheath, c - cut end of the cable;
1 - cable sheath,
3-time bandage,
4, 5 - annular and longitudinal cuts,
6 - washer,
8, 9 - insulated and bare cores
^ Sequence of shielded cable termination in the PPH connector:
A temporary bandage 3 made of copper wire is placed on the cut end of the cable and a nut 7 and then a washer 6 are put on to secure the braid to the connector body.
Having placed the washer at a distance of 15 mm from the cut of the braid, unravel the braid wires, bend them onto the washer and solder them to it with POS-61 solder with solder fat. The ends of the weeders are cut flush with the edges of the washers.
The ends of the cores 10-11 mm long are stripped of insulation and tinned.
To do this, they are coated with alcohol-rosin flux and immersed in a bath of molten solder, kept in it for 5-7 seconds, and then removed and allowed to cool.
The connector pipe is disassembled into two halves 1 (Fig. a), unscrewing two screws, and the wires are soldered to the contact shanks. Before soldering, the shanks of the contacts are filled with solder and allowed to harden, after which, heating the shank of each contact with a soldering iron until the solder melts in it, insert the end of the tinned core into its socket so that the cut of the insulation on the core does not reach the shank by 1-2 mm to avoid damage to the core insulation.
Slide the washer with the braid soldered to it along the cable by 25-30 mm. Having straightened the veins, divide them into two approximately equal parts and pass a pin 4 with a polyvinyl chloride tube on between them.
Having moved the pin as close as possible to the cut of the shell, press the conductors against the pin and, starting from the soldering side, wrap the bundle of conductors with one layer of adhesive polyvinyl chloride tape so that winding 3 touches the shell or rubberized tape by 10-15 mm.
The pin is secured with a bandage 5 made of raw threads, which is coated with varnish or BF glue, and the braided washer is pushed onto a winding made of polyvinyl chloride tape.
The completed seal is placed in one of the halves 1 of the connector pipe so that the ends of the pin fit into the sockets of the pipe.
Check the position of the cores in half of the pipe, apply the other half and fasten them with two screws.
Finally, screw the shielding nut 6 all the way in and remove the temporary bandage 3 from the braid.
The technological sequence of operations when cutting an unshielded cable (Fig. b) is the same as when terminating a shielded one (with the exception of terminating the screen).
TO 
Termination of shielded (a) and unshielded (b) cable into the PPH connector:
1 - half of the connector pipe,
2 - polyvinyl chloride tube,
3 - winding made of polyvinyl chloride tape,
4 - pin,
5 - bandage,
6 - shielding nut,
7 - nut with clamp,
8 - rubber sheet winding
^ Type A plug connectors used when it is necessary to seal the end seals of wires and cables.
P 
Wires and cables with an outer diameter of 10-12 mm are sealed during termination by wrapping the neck of the bushing 1 and the wire or cable for a length of 50 mm with adhesive polyvinyl chloride tape 2 (Fig. a). Then they make a bandage from threads and impregnate it with varnish or BF glue.
The end seals of wires and cables, regardless of their outer diameter, are sealed using a polyvinyl chloride or rubber tube 5 (Fig. b). In this case, the tube is put on the full length of the neck of the sleeve 1 and wrapped in two layers with adhesive polyvinyl chloride tape 4, capturing 15-20 mm of wire or cable. Then apply bandages from threads b and 7 and impregnate them with varnish or BF glue.
If it is necessary to seal a shielded wire or cable, then the screen 8 (Fig. c) is pushed onto the neck of the bushing 1, unscrewed by 15-20 mm and tightened with a clamp 9 or a bandage 6-10 mm wide made of copper wire with a diameter of 0.5-0 is applied, 8 mm. The screen wires protruding from under the clamp or bandage are trimmed.
The end seals of wires and cables in plug connectors A are sealed with a winding of adhesive polyvinyl chloride tape (a), a polyvinyl chloride or rubber tube (b), a shielded wire or cable (c) and a general view of the end seals of unshielded cables in plug connector A (d):
1 - sleeve, 2, 4 - polyvinyl chloride tape, 3, 6, 7 - thread bands, 5 - rubber tube, 8 - screen, 9 - clamp
10. Connection of cables and wires, dialing, connection to devices.
^
Connecting cables and wires
Connecting cables or wires is allowed only in cases where the length of the route exceeds the so-called construction length of the cable or wire (the length of the cable placed on the cable drum or in the wire coil), when replacing a damaged section or when connecting the ends of the wires after they have been pulled through protective pipes.
^ The connection of cables and wires must ensure the following :
Reliable electrical contact of the connected cores;
Electrical insulation of the veins among themselves and in relation to the ground, equivalent insulation of entire places of these veins;
Sealing the connected ends to prevent the penetration of moisture into them, and for cables with impregnated paper insulation - leakage of the impregnating oil-rosin composition;
Reliable electrical connection grounded metal shells and armor of cables with a grounding conductor.
TO 
Cables with rubber and polyvinyl chloride sheaths laid indoors are connected using junction boxes or polyvinyl chloride couplings (the latter are rarely used).
^
Steel junction boxes type KSK
(Fig. a) are intended for disconnecting cables with the number of cores from 2 to 37. Depending on the type, 8 rails are installed in the boxes; 16 and 32 ZKN type clamps for connecting cores with a screw.
^
Plastic boxes type KSP
They are produced in a round case (Fig. b) for 12 clamps and a rectangular one (Fig. c) for 30 and 50 clamps. The boxes are equipped with BZ type terminal blocks for 12, 30 and 50 terminals, respectively, with pin (without ring) termination of the ends of the connected wires or cable cores.
Junction boxes:
a - steel KSK.
b, c - plastic KSP-12 and KSP-30 (KSP-50)
KSI (a) and PK-2m (b) pliers:
1 - handle, 7 - rod,
2 - head, 8 - locking device
5 - matrix,
6 - punch,
^ Connecting wire cores by soldering.
1) Before soldering, remove the insulation from the ends of the cores and clean them from traces of insulation and oxides. To remove insulation from conductors with a cross-section of up to 2.5 mm 2, it is recommended to use KSI pliers (Fig. a), equipped with indicators that help regulate the length of the insulation to be removed.
2) Copper conductors with a cross-section of up to 2.5 mm2 are twisted before soldering (Fig. a), and with a cross-section from 4 to 10 mm2 they are connected in sleeve 2 (Fig. b).
3) For soldering copper conductors, POS-61 solder and acid-free fluxes (for example, rosin, LTI flux) are used.
Connecting wire cores before soldering:
a - twisting copper wires for connection and branching,
b - connection of copper cores in the sleeve,
c - twisting of aluminum conductors for connection and branching;
1 - groove,
2 - sleeve
4) The aluminum strands are overlapped and twisted so that a groove is formed at the point of their contact (Fig. c). A temporary winding of asbestos cord is applied to the insulation of aluminum conductors at the junction to avoid damage during soldering.
5) The twisted wires are heated blowtorch and tin the joint with solder rod A or B inserted into the flame, after which the grooves are filled with solder on both sides. 6) The cooled connection is insulated with insulating tape, applied with 50% overlap of turns.
^ Connecting wire cores by crimping.
1) It is recommended to connect only copper conductors by crimping, for which the stripped and stripped ends of the conductors are overlapped and wrapped with soft copper or brass tape 0.2-0.3 mm thick and 18-20 mm wide.
2) The joints are pressed with hand pliers PK-2m (Fig. b), intended for crimping wire and cable cores with a cross-section of up to 6 mm 2 in connecting sleeves or tubular lugs.
The wire with the sleeve (or tip) attached to it is placed between the punch 6 and the matrix 5 installed in the pliers, and the handles 1 are smoothly squeezed until it stops. The end of crimping is determined by the contact of the shoulders of the punch and the matrix and the possibility of returning the handles to the initial (open) position. Until the crimping is completed, the locking device 8 does not allow the pliers to open and compresses the tip or sleeve. Pressure testing is carried out in two stages. After the first indentation, the pliers are rotated 180° from their original position, moved along the joint and a second indentation is made.
To connect or terminate cables, it is necessary to cut their ends. Cutting is the operation of stepwise removal of protective and insulating parts from a cable. The dimensions of the groove are determined by the design of the coupling or funnel, the cable voltage, the conditions for connecting the cable and the cross-section of its cores.
Finished cutting of the end of a three-core paper-insulated cable:
1 - outer jute cover,
2 — steel armor tapes,
3 - shell,
4 - waist insulation,
5 - core insulation,
6 - cable core.
A general view of the finished cutting of the end of a three-core cable with paper insulation for connection and termination is shown in the figure. Before cutting, the end of the cable is straightened and at a distance A from the end, a bandage of 2 - 3 turns of galvanized steel wire is placed over the jute cover. The jute cover is unwound from the end of the cable to the bandage, but is not cut off, but is left to protect the armor stage from corrosion after installation of the coupling - it is temporarily wound on the uncut part of the cable.
A second wire bandage is placed on the armor at a distance B from the first bandage. The length of the section between the first and second bands is 50 - 70 mm. In this section, the grounding wires are connected to the armor strips. In cast iron couplings, end funnels, as well as in special couplings used when laying cables in water, the specified section of armor is used to seal the neck of the coupling; its length in these cases is 100 - 150 mm.
Having placed bandages on the cable, they untwist its armor a little in order to somewhat distance it from the sheath. Use a hacksaw or armor cutter to cut the armor at the edge of the second bandage and remove the armor.
Unwind and remove the cable yarn and paper interlayer from the sheath, pre-heating the cut end of the cable with a quick fire of a blowtorch to 40 - 50 ° C. The cable sheath, freed from paper, is wiped with rags soaked in gasoline or transformer oil heated to 40 ° C to remove the bitumen composition from its surface.
Cutting paper insulated cable: 1-X - cutting operations.
Proceed with the operation of removing the cable sheath. To do this, two circular and two longitudinal cuts are made on the lead-sheathed cable. The distance between the ring cuts should be 20 mm for cables up to 1 kV, 25 mm for cables of 6 and 10 kV; the distance between longitudinal cuts is 10 mm.
The shell is cut to half its thickness using special cable cutters(type NKA, NKS) with a retractable blade. The strip of lead sheath formed between the two longitudinal cuts is removed by grabbing it with pliers, after which the entire sheath on the section of cable to be cut is manually removed.
To remove the aluminum cable sheath, use a knife with cutting discs. In this case, after the circular cuts, a spiral cut is made. To do this, set the knife at an angle of 45°, clamp the shell between the prism and the cutting disk and cut it in a spiral with rotational movements, and then remove it with pliers.
Cable cutting operations are completed by removing the belt paper insulation and semi-conducting (black) paper, which is unwound from the end of the cable and cut off (but not cut with a knife) at length I to the edge of the lead or aluminum sheath.
The fillers located between the cable cores are cut off with a knife, and the knife blade is directed along the cores towards the uncut part of the cable. The annular sheath belt above the belt insulation stage P is removed after connecting or terminating the current-carrying wires of the cable.
Having completed the cable cutting operations, they begin to prepare its ends for connection or termination.
"Electrical equipment repair industrial enterprises»,
V.B.Atabekov
Water the sections of cutting and connecting the cores with MP-1 scalding mass, heated to 120 - 130 ° C, in order to remove possible contamination and moisture from them, and also to introduce an additional amount of impregnating mass into the insulation. The connection area prepared in this way is insulated with paper rolls and rolls supplied by cable factories as a set in hermetically sealed metal cans filled with MP-1….
The application of additional paper insulation at the junctions of the conductors begins with the bare areas between the ends of the sleeve and the steps of the factory insulation of the conductors (when connecting cables with aluminum conductors by welding, the thickening formed at the junction of the conductors is considered as a sleeve). Using rollers 5 mm wide, the cores are wound to the diameter of the factory insulation or sleeve, depending on which...
After insulating the junctions of all three cores and washing the insulation with a scalding mixture, the cores are brought close together and a common bandage 2 mm thick is wound on them from impregnated paper tape 50 mm wide. The bandage is tied in two places with cotton yarn. Having completed the insulation, remove the annular bands of the lead aluminum sheath above the waist insulation. The waist insulation is tied with a cotton bandage...
Cable cutting and coupling installation are reduced to a series of strictly sequential operations. Performing operations in strict sequence is necessary to correct installation and trouble-free operation of the coupling and cable. Deviation from the sequence of operations may lead to premature failure of the end coupling due to electrical breakdown of its insulation.
Cable cutting for any type of termination is carried out by performing the same work, following in the same order. The general procedure for cutting the cable is as follows: removal of the outer cover, armor, cushion under the armor, compound-impregnated paper or PVC plastic compound, lead sheath and core insulation. Depending on the type of coupling used for installation, and on the method of removing the current-carrying core from it for connection to the current collector, on a certain length of cable, all elements of the cable structure are removed, one after another, by ledges, down to the cores, while they form a row along the entire length of the cutting steps.
Let's consider the procedure for cutting the end of an ASBE-1X50 cable and installing an end coupling with a KON-35 insulator. When starting to cut the end of the cable, you need to have a template, which is made from a round metal rod with a diameter of 10 mm and a length of about 1 m.
One end of the rod is clamped into the cable lug and secured together with it in the top plate cable sleeve; after this, the free end of the rod is passed through the upper hole of the cable coupling and the plate is secured to the coupling with two bolts. At the free end of the rod extending beyond the assembled cable coupling, the first mark is applied with a hacksaw or file, marking the lower boundary of the coupling. At the free end of the rod, two more marks are applied at intervals of 50 mm, after which the upper plate of the coupling with the metal rod is removed and markings are made on the rod, as shown in Fig. 36. Then ready-made template applied to the pre-straightened end of the cable and in accordance with the markings and Fig. 30 the cable is cut.
First, a first 3 mm wide bandage made of steel knitting wire with a diameter of 1-1.5 mm is applied to the cable over the outer cover to prevent unwinding of the cable covers during stepwise cutting of the latter. As a rule, the upper protective covers of the cable laid in production premises, are removed and the first bandage is applied to the armor. At a distance of 50 mm from the edge of the first bandage, a second wire bandage 3" mm wide is installed on the cable armor. Along the edge of the second bandage from the side of the free end of the cable, the upper and lower armor strips are cut and removed. The armor is cut with an armor cutter with a limiter or scissors after preliminary unwinding of the armor with end of the cable.
Remove the protective cover (cushion) from the lead sheath of the cable to the edge of the second bandage. The bitumen layer on lead is removed with a rag soaked in gasoline. Carefully, without damaging its sheath, put the gland nut 13, oil-resistant rubber gasket 14, coupling body 10 onto the end of the cable, lower it and temporarily secure them to the cable (see Fig. 34 and 36).
At a distance of 50 mm from the cut end of the cable, a circular cut is made in the lead sheath with a knife. Then remove the lead up to this cut and all the insulation along with the metallized patches up to the core, leaving only a 5 mm strip of metallized paper adjacent directly to the core, near the edge of the cut. Contact tip 1 is put on the core and secured with bolts. There should be a gap of 15 mm between the edge of the factory insulation and the tip,
A distance of 455 mm is measured from the lower end of the tip and a circular cut of the lead sheath is made to half its thickness using a knife with a depth limiter. From the annular cut to the end of the lead sheath, two longitudinal cuts are made at a distance of approximately 10 mm from each other. Then remove the cut strip with pliers and remove the lead sheath (Fig. 37); the remaining part of the lead shell is wiped with a rag soaked in gasoline. After this, remove the layer of outer metallized paper
leaving a strip of paper 5 mm wide near the edge of the lead sheath. According to the markings made using the template and Fig. 36, to increase the electrical strength of the cable cutting, bandages are applied to the factory insulation from rolls of cable paper and cotton yarn, impregnated with MP-1 mass, and the insulation is cut into a cone or ledges at a length of 40 mm, as indicated in Fig. 36. Before winding, the factory insulation is thoroughly degreased with acetone or aviation gasoline.
Having retreated 15 mm from the place where the lead sheath was cut, a winding of paper rolls 300 mm wide is applied to the cable phase. Paper rolls are made from KV-12 cable paper, tied with cotton yarn or glued with dextrin, dried under vacuum, impregnated with an oil-rosin composition and, together with bobbins of cotton yarn, packaged in tinplate cans with a thickness of 0.29-0.35 mm. Before sealing, the jars are filled with the same mass with which the rolls are impregnated so that it completely covers them. Sealed jars arrive from the factory, which before use are opened and heated to a temperature of ~80°C in an oil bath in a vessel with a double bottom. You can only remove heated rolls and yarn with clean, dry metal hooks. During winding, the vessel with rolls of cotton yarn is tightly closed with a lid, while the oil-nifol composition should cover the top roll in the jar. Rewinding paper can be used only after checking its strips (before heating the vessel) for the absence of moisture in them according to the method described above.
Immediately before starting to wind the paper, remove the top two or three layers of tape from the rolls. Rolls are wound with tension, tightly, without air gaps and folds, with tightening at each turn of the already wound layers of the roll and final tightening at the end of winding each roll by ironing it with your hand in the direction of winding. For this purpose, you can also use dry cable or glass paper. The lower winding cone is formed directly by winding the roll, and the upper one is carefully cut off with a knife. To avoid cutting the cable's own insulation, three or four layers of additional insulation are not cut, but torn off manually.
In order to avoid unwinding of additional insulation, after winding, each roll is tied with cotton yarn impregnated with MP-1 mass. The yarn is taken from the same cans as the rolls. After winding and tightening are completed, the top two layers of cable paper are opened, and all paper insulation is washed with hot MP-1 mass at a temperature of 120-130 ° C, which does not contain moisture.
To create a more uniform electric field, a screen made of tinned copper cord or lead wire with a diameter of 2 mm is placed on the cone of additional paper insulation adjacent to the lead sheath of the cable. To do this, four to five turns of the cord are placed on the edge of the lead sheath and soldered to the psi using a soldering iron. The last turns are wound tightly to each other on the surface of metallized paper, factory insulation and cone winding. The winding of the wire screen ends with a ring with an internal diameter of 50 mm. The ring is made from a lead tube with an outer diameter of 10 mm or specially cast from lead. The outer diameter of the ring is 70 mm. Four legs made of wire (tin) are soldered to the ring. Before installing the ring, its surface is carefully leveled with a file and sandpaper to eliminate the possibility of uneven electric field. The ring is put on the cable and installed at the end of the screen winding to its last thread so that the legs of the ring lie on its surface.
To attach the ring to the screen, a second layer of copper cord 15 mm wide is placed on its legs. The end of the rope is soldered with a soldering iron to the turns of the first layer. Then the first layer of the screen is soldered all the way from the lead sheath to the ring in an area about 10 mm wide and all unevenness in the solder is smoothed out with a file and sandpaper. To remove solder filings from the insulation and screen surface, they are washed with MP-1 mass, heated to a temperature of 120-130 ° C.
On the lead sheath, marks mark the place where the coupling body is secured, after which the coupling is installed on the supporting structure. Then a gasket made of oil-resistant rubber is inserted into the recess of the housing and the cut end of the cable is carefully inserted into the hole of the reinforced porcelain insulator. The bolts securing the bottom flange of the insulator to the coupling body must be tightened evenly. Then thoroughly wash the internal cavity of the coupling body and the entire cable cutting with the MP-1 steaming mass, having previously opened plug 11 to drain the mass. After washing the housing cavity, plug 11 and stuffing box nut 13 with pre-installed gaskets are screwed in completely.
Immediately before use, gaskets should be glued with epoxy glue. Glue composition: epoxy resin E-40 or epoxy putty E-4021, to which 8.5% of hardener No. 1 (50% solution of hexomethylenediamine in ethyl alcohol) is added. The hardener is thoroughly mixed with the resin or putty. After introducing the hardener into the putty, the resulting compound is suitable for use at ambient temperatures: from 8 to 15 ° C for 3 hours, from 20 to 25 ° C for 1.5 hours.
The porcelain insulator KON-35 is covered over the entire surface with asbestos cardboard or fiberglass and heated with a blowtorch to a temperature of 60-70 ° C. Only after heating the insulator can cable mass be poured into it, since otherwise hot cable mass may be ejected and even cracking may occur. porcelain insulator. The cable mass MK-45, poured into the coupling, is heated to a temperature of 140-145° C. Composition of the mass MK-45: autotractor oil AK-Yu according to GOST 1862-51 or cylinder oil 11 according to GOST 1841-51 and pine rosin of the highest and first grade varieties according to GOST 707-41.
MK-45 cable mass is easy to make yourself. Take 80% rosin and 20% oil. First, rosin is loaded into the boiler, and after it melts, mineral oil is loaded. Mix everything thoroughly with a wooden stirrer and cook at a temperature of 130° C until foaming stops (5-6 hours). The cooked mass is poured out of the boiler at: 140-150 ° C and must be filtered through thick metal mesh, since otherwise mechanical impurities, always present in rosin, can reduce the breakdown voltage of the mass.
The mass prepared in this way is tested for breakdown. To do this, the mass, like transformer oil, is poured into a clean, dry discharge vessel with electrodes, where it slowly cools to 18-20° over 12 hours. After this, a breakdown test is carried out. If the mass can withstand a voltage of 35 kV for 1 minute, then it is suitable for use.
To prevent rosin from falling out of the composition during cooling or operation of the cable coupling, it is necessary to ensure a strictly defined heating and cooling regime for the cable mass, established by the manufacturer.
Should the coupling filling mixture be heated up? in a special saucepan with a lid and spout, which is equipped with electric heating. In the absence of electric heating, the pan is heated on a brazier with coals. A mesh should be inserted into the spout of the pan to prevent foreign particles from entering the coupling. The lid should cover the pan tightly.
When heating on a charcoal brazier, you must ensure that there is a distance of 50-100 mm between the layer of coal in the brazier and the bottom of the vessel. Do not heat a vessel with mass directly on a fire or with a blowtorch. When performing the operation of heating the mass, installers must wear long gloves and safety glasses, since burns from hot mass are very painful and dangerous. Scalding and pouring operations are also carried out wearing long gloves and safety glasses.
The coupling is filled with mass in three to four steps, depending on the ambient temperature and the amount of mass shrinkage. After final filling, the level of the mass should be 10-15 mm below the level of the end of the insulator.
A gasket made of oil-resistant rubber is placed on the upper end of the cast iron flange 3 and in the groove of the plate 2, the coupling plate is put on and the bolts are tightened evenly. Screw two nuts onto contact tip 1, placing a washer under them.
Tinned copper lugs are pressed or welded onto a grounding conductor with a cross-section of 25 or 35 mm2 (MGG cable). One tip is secured under the contact grounding bolt on the prefabricated structure, and the other is secured under the grounding bolt of the coupling. After this, an electrical connection is made between the armor, the lead sheath of the cable and the supporting structure. To do this, the cable armor is stripped and tinned at the point where the grounding conductor is connected, the conductor is secured to the cable armor and the lead sheath with a copper wire bandage, and it is soldered to the lead sheath and cable armor.
When soldering the grounding conductor to the cable armor, bitumen may be released from the internal coating, which complicates soldering and makes it unreliable, and local overheating of the insulation at the soldering site under the lead may also occur. For this reason, the soldering operation is performed as quickly as possible.
