During electrical work, cutting the ends of conductive lines to connect segments or connect to power equipment is a frequent phenomenon. To speed up the operation, end sleeves, cable sleeves, as well as transitional and connecting pieces are used. such devices on various grounds, the design of products of the first type is considered in more detail, as the most demanded. Heat-shrinkable CMs are in special demand.
Content
- Types of cable joints (KM)
- Design of modern end connectors
- Installation of heat shrinkable terminals
Types of cable joints (KM)
Electrical devices manufactured to speed up the process of installing branches and connecting umbilical cables to power devices and power transmission lines are called cable couplings.
Their purpose is to provide mechanical and electrical protection of adjacent conductors. There are classifications of CM according to the following features:
- Appointment. Couplings and end couplings. The first type is subdivided into classes: transitional CM, connecting conductors with different insulation; branching - they allow you to make a sectional branch from the main energy main. The second type is end couplings: external (outside the premises); mast ones used for connection to power lines (KNSt and KMA with steel and aluminum housings, respectively); internal - for connecting a cable to equipment in a room of any humidity category with an atmosphere from minus 50 to + 50 ° C.
- Manufacturing material. For highways up to 10 kV, lead (SS), epoxy (SEF, KNE, KVEl) and heat-shrinkable (STp, KNTp) couplings are used. Metal connectors made of Pb are bulky, have a body made of a piece of pipe Ø60―110 mm up to 65 cm long. KMs produced with the use of resin are protected with a steel casing and asbestos cloth if they work in a tunnel or other channel. Used for paper insulated conductors, therefore there are temperature and toxicity limits. The modern trend is heat-shrinkable connectors, they can be used in boxes, on hangers and laid directly in the ground.
- Insulation type. Rubber, oil-impregnated paper, plastic (XLPE and PVC).
- Number of phases: 1, 3, 4.
- Working voltage, kV: 1, 6, 10, 35, 64 and 100 kV.
By type of material consumers prefer to use CMthat fit the joint of the cores due to heating the product, such as connecting (SPTp, STP, PSTb) and end heat-shrinkable sleeves (KNTp, KVTp, PKNT). You can decipher the information hidden in the marking using the example of the code 4PKNTpb 1-70 / 120.
| Sign | Interpretation |
| NS | Plastic insulation |
| K, C | Coupling type - end, connecting |
| H, B | Execution - external, internal |
| T, n | Heat shrinkable - tubes, gloves |
| B, b | Set of bolts, armor on cable |
| 4 | Number of cores |
| 1−70/120 | Voltage, kV and cross-sectional area of covered conductors, mm2 |
The given marking means that the cable end sleeve for outdoor installation with plastic insulation and armor for four conductors under a voltage of 1 kilovolt and a cross-section of 70, 95, 120 mm². Suitable for electric cables ААШв, ВБбШв, АСБ, VVG and other similar brands.
Design of modern end connectors
Cable sleeves closing the electrical line are also used for telephone communication and separation of conductive conductors. The KM device is simple: a combination of handpieces as a basic structural element, with a collar as a body, winding, insulation and grounding parts.
The composition of the kit depends on the number of cores and the voltage in the network. At the request of the buyer, heat-shrinkable end sleeve maybesupplied complete with bolt lugs.
Heat-shrinkable models of end connectors are made of polymer materials using a special cross-linking technology using shape memory. When heated, the filler loses its structure and begins to flow, acquires the desired volumetric appearance. During the cooling phase, the polymer recovers its rigidity while remaining in the transformed model. Such technology gives end heat-shrinkable CM a number of advantages:
- high dielectric performance and tightness;
- resistance of the heat-shrinkable core coating to ultraviolet light, atmospheric and chemical attack;
- absence of toxic emissions, environmental safety, low weight and dimensions;
- flexibility of the coupling and ease of installation;
- the ability to turn the line into operation without preliminary time delay.
High strength and high-quality sealing contribute to the long-term operation of heat-shrinkable limit switches. A large selection of composite fillers and the latest technologies make it possible to manufacture couplings with specified characteristics.
Installation of heat shrinkable terminals
Fastening at the end of the cable line of the connector is carried out not only by heating, but also using the method of cold shrinkage: during manufacturing, a spring-loaded rubber band is installed inside the coupling. During installation, the part is easily removed, relieving stress, and the KM body shrinks, giving the product airtightness, and reliably insulates the conductors.
In any case, the termination process begins with exposing the cable cores. The work must be performed by a specialist with sufficient knowledge and skill. For installation you will need:
- heat shrinkable parts from the KM kit - they are in a stretched state and will fit well on prepared cores;
- glue melting from heating - a filler placed inside the sleeve: it will replace all voids after exposure to temperature;
- building hair dryer (150 ° C) or propane-butane burner.
Under a stream of hot air, the CM is compressed, tightly covering the cable, the sealant melts the free space around the cores and other voids. If necessary, the coupling is grounded with a flexible copper wire.
