Though there are more and more every day wireless devices, the main transmission medium electric current there are still wires.
In the production of wires and cables are used different kinds isolation. Each type of wire insulation determines the scope of certain cable products.
During the installation of wires or cables, it becomes necessary to isolate the places of their connection or connection to electrical appliances. How can this be done?

Previously, paper was used to insulate cables, but now, with a huge number of modern materials it is used extremely rarely. The paper was wound in several layers, impregnated with oil and rosin. This helped to resist the influence of moisture.
Under production conditions, reliable insulation is made of fluoroplast. Fluoroplastic tapes are wound on wires and baked. A shell is formed that is not afraid of not only chemical or thermal, but also mechanical effects.

PVC (polyvinyl chloride) is also called vinyl insulation. Polyvinyl chloride is resistant to alkalis and acids, does not conduct current, does not dissolve in water, therefore it finds wide application in the manufacture of insulating materials. It is applied to production of isolation of wires and cables. PVC electrical tape is also made to insulate the wire connection.
One of the advantages of PVC insulation is its low cost. Polymer insulation is quite elastic and resistant to temperature extremes, does not burn in air. In the production of PVC materials, plasticizers can be added, they slightly worsen the insulating properties and resistance to chemicals, but increase elasticity and resistance to ultraviolet rays.

If the connecting cable uses vinyl insulation covering the wires, then . It can consist of 2-5 aluminum or copper conductors. The shell is either vinyl or rubber.
The service life of PVA cables exceeds 6 years. During all this time they do not require replacement. They are resistant to corrosion and mold, withstand frosts down to -40° and heat up to +40°. Their operating resistance is about 270 ohms per 1 km.
Cables with PVC sheath and aluminum conductors are used in urban electrical networks, for supplying electricity in production and in residential apartment buildings. PVA cables with copper conductors have become widespread when connecting almost all household appliances and other low-power equipment to the network; they are used for electrical wiring in private houses and apartments.

Application of rubber insulation

In industrial sectors, rubber sheaths are often used to insulate cables. Its positive qualities include:

• Moisture resistance.
• Elasticity.
• High resistance.
• Resistant to high temperatures.

Rubber insulation is produced on the basis of natural and synthetic materials. High quality synthetic braid best performance- ages longer, withstands exposure to aggressive chemicals and negative temperatures. Rubber is easy to bend, so the wires can be laid in any conditions. But over time, the rubber insulation ages, cracks and begins to pass current. In high temperature conditions, it is recommended to use vulcanized rubber for insulation. Rubber insulated cables are most often used where cable flexibility is required. These are the supply cables of cranes, descents to the control panels of crane beams. Connection of welding transformers, both from the supply side and from the low voltage side, to the electrode “holder” and the neutral wire.

Wire insulation methods

Insulation electrical wires designed primarily to ensure that there is no leakage of currents. For this reason, it is made of non-conductive (insulating) materials. Depending on the operating conditions and design features of cables or wires, the type of insulation is selected. For electrical work, the following types are used.

• Insulating tape.
• PVC tube.

Insulating tape

The insulation of electrical wires with electrical tape does not lose its relevance. Insulating tape is inexpensive and is sold in any hardware store in a wide range.

It must be wound at an angle, starting from the edge of the wire's native insulation. At parallel connection at the end of the twist, they make an empty winding-tube, bend it and continue to move in the opposite direction.

A common PVC insulating tape melts when heated strongly, but does not allow moisture to pass through. Cotton insulation tape, on the other hand, withstands high temperatures, but dries out over time, and can peel off when wet.

Cambric is also made of PVC - tubes for insulating wires and cables. In order for the tube to fit tightly, it is necessary to choose the correct diameter of the tube.

How to properly isolate the twisted wires is better to watch the video:

Heat shrink tubing

Heat shrink tubing is made from polymers (PVDF, PET, silicone, and others). They are used mainly on low-voltage equipment, when the voltage direct current does not exceed 1 kV.

If you want to use heat shrink for wires, then you need to follow a series of steps.

1. Cut off a piece of heat shrink tubing that completely covers the exposed section of the wire (connection), with a margin of about 2 cm.
2. Then you need to put a tube on one of the ends of the wires to be connected.
3. Make a twist of conductors.
4. After that, the tube is moved to the twist and heated with a building hair dryer.

As a result of heat shrinking, the insulation is tightly pressed against the wires. If there is no hair dryer, then you can use a lighter, carefully holding it at a short distance.
This is done when insulating the twist of series-connected wires. If the connection of wires is parallel (the so-called bundle of wires), then first they twist, and then put on the tube.
In most cases, heat shrink tubing is more convenient to use than duct tape. The tube can be put on quickly, fits the wire connection more tightly and does not unwind. But removing it if necessary is already more difficult. You just have to clean it or cut it off.
On the tubes, manufacturers put a marking that shows what temperature it can withstand and what voltage it is suitable for. Tubes of different diameters and colors are produced, therefore, for various brands and cable cross-sections, it is always possible to choose the appropriate insulation and color marking.
How to properly insulate wires with heat shrink tubing, watch the video:

Terminal application

As insulation, it is used in a dielectric sheath. Terminals are sold in the form of caps or blocks that clamp the wires. If you want to insulate the wires in junction box, then the choice of terminals is one of the connection options.

But a lot depends on the load. At a high load, it is better to use soldering for the connection, and already put on an insulating tube on top.
Tightening the aluminum wire with screw terminals is not recommended, because under constant pressure, aluminum begins to flow. As a result, the connection weakens, the resistance increases and a short circuit occurs. If you decide to join aluminum wires terminals with screws, then at least once a year it is necessary to revise.
Connection of copper and aluminum wire twisting method is not allowed. When current passes between metals, an electric potential arises, the wires heat up, which can cause short circuit Or worse, a fire.
Nevertheless, in one case, twisting can be done - if copper wire cover with tin-lead solder (tin). But more often, terminal blocks or (screw, nut and washer) are used to connect both aluminum and copper.

Insulation resistance

Between cable cores and external environment current leakage may occur. One of the tasks of isolation is to prevent their occurrence. The value that indicates how well a wire is insulated is called the insulation resistance.
The higher the resistance, the more reliably protected the cores through which the current flows. Each brand of cables has its own value for this indicator. Insulation resistance is set by GOST or specifications(THAT).
The resistance is measured at a given temperature (about + 20 °) with a special device (megaohmmeter). If measurements are taken at negative temperatures, then its value will be underestimated, and in case of hot conditions it will be overestimated. After taking readings, they are entered into the protocol "Measurement of wire insulation", compared with the normative ones, and conclusions are drawn about whether the cables are suitable or not for further use. Wiring that fails the test must be repaired or replaced. The timing of the frequency of testing the insulation of wires is specified by the Rules. Also, checking the insulation of wires is carried out after the completion of electrical work, repair work, after wetting or overheating of the wiring.
How to correctly check the insulation resistance of conductors using a megohmmeter, see the video:

Details Updated on 04.11.2017 21:42

When installing or operating a submersible pump, it may be necessary to extend power cable. Actually, we are not talking about extension-connection, but about insulating the junction of the wires of the submersible pump. In this case, the connection must be completely sealed, since the operating conditions are simply extreme - under water.

Firstly, the connected ends of the cable must be soldered, or be in special clamping sleeves. For electrical waterproofing of wires submersible pumps can be used:

1. heat shrink tube
2. electrical tape
3. filling couplings.

When insulated with heat shrink tubing

Heat shrink must be adhesive. A layer of glue is applied on its inner surface, which, when crimped, melts and forms a continuous hermetic layer. Heat-shrinkable tubing is able to shrink when exposed to elevated temperatures and tightly cover insulated surfaces. This is usually performed using a torch, a special hair dryer or an open flame if the temperature range for the tube is not critical. In this case, a simple lighter will do. The heating temperature is indicated in the instructions for the tube.

Of electrical tapes, it is better to use LETSAR tape. Its main feature is the ability to monolithize, that is, to turn into a continuous tube. It is sold in large reels, wound with a layer of polyethylene (so as not to stick together). Layers of LETSAR tape should be wound with overlapping of the previous half. For high-quality insulation, 3-4 layers of tape are required.

The filling sleeve is essentially a box where the cable junction is laid and filled with a compound (resin cured in natural conditions). Unlike the first two more artisanal methods, the clutch is considered practical and has a longer service life.
Although in Soviet times, ordinary electrical tape was used for such work - and it served perfectly.

Traditionally, when branching a cable, either air insulation (soldering and branch boxes) or heat-shrink technology is used, which involves breaking the main cable, connecting the cores to the branch cable and installing a heat-shrinkable tube or cuff in place of the branch. In this case, certain difficulties may arise - if the heat-shrinkable sleeve is underheated or overheated, air remains at the cable junction, with a slight mechanical impact, loss of tightness is possible, moisture, air and foreign unwanted inclusions, such as dust and dirt, can get into the space between the insulation and the cable. Due to damage to the insulation, the metal oxidizes, a transient resistance occurs in the contacts, which leads to heating of the coupling and failure of the line. In cases where the cable is laid underground, in wet conditions or in areas with possible ground movement, where high mechanical strength and insulation retention are critical, alternative, more reliable and safer solutions can be used for a branch.

Method number 1 - jellied branch coupling

The pouring technology for splicing and repairing power cables appeared simultaneously with the emergence of the cable industry - bitumen preheated on a fire was poured into a cast-iron or lead mold at the junction of the cables, which, when solidified, created an insulating layer. Then bitumen was replaced by epoxy compounds, which were kneaded by hand from epoxy resin and hardener. However, unlike bitumen, epoxy compounds did not have an important property - elasticity, they cracked even with a small mechanical impact, therefore they did not receive wide distribution.

In the second half of the last century, the 3M company proposed using another material for cable insulation - a polyurethane compound, which had a combination of the desired properties - high mechanical strength, wear resistance and elasticity. But there was a difficulty with its use in couplings, since this material required an exact ratio of components to obtain the desired composition. With minimal deviations in the proportions of the components, the finished mixture did not have constant characteristics. Then 3M engineers patented a system for contactless mixing and pouring of the compound. The components of the compound - the base and the hardener - are placed in one bag with a removable partition. To obtain a composition with constant characteristics, it is enough to break the partition between the components, mix them inside the package and pour them into the coupling body through a special valve. At the same time, the exact proportions of the components are observed, there is no contact of chemicals with the hands of the installer, there is no harmful effect of the reaction products on the respiratory system. That is, mixing and pouring is fast, clean and safe.

Method number 2 - branch couplings with forced injection of the compound

This coupling has all the advantages of the poured technology, but does not have the limitation of the Scotchcast® 91-AB coupling described above: it can be mounted at any angle, incl. vertically, and allows you to make a U-shaped and T-shaped branch. In addition, the 3MTM GTS Coupling is compact in size and can save significant amounts of compound, which has a positive effect on cost.

Coupling 3M TM GTS can be branched in places where increased protection against chemical and mechanical influences is required, for example, in mountainous areas, in areas with ground movements, high level ground water, in laying conditions with partial or complete flooding. Voltage can be applied immediately after installation is completed.

Despite the fact that the installation of the 3M coupling TM The GTS is somewhat longer lasting than the Scotchcast® 91-AB coupler, which has a prefabricated plastic body, and is a reliable and cost effective solution.

Method number 3 - branch in a box with sealing compound

When mounting the coupling, a conventional junction box can be used as a housing. This method is suitable for cables, as a rule, of a small cross section and is used where, in addition to the standard sealing of the box itself, an additional one is needed, for example, when used in a room with a possibility of flooding or underground placement of a box for lighting networks.

Method number 4 - tape technology

Traditionally, branching with insulating tapes was used only for temporary power supply. During long-term operation, the temporary solution led to accelerated degradation of the cable insulation (primary cable insulation is not resistant to UV radiation), water ingress into the cable terminations and, as a result, to a breakdown.

This method allows you not to break the main cable, create any geometry of the coupling body and conveniently use one set for all sections.

* A branch in a box is beneficial only for small cable cross-sections. From 16 mm2, large boxes are required, which require too much compound to fill.
** depends on the type of compound and box material.
*** depends on the qualification of the installer.

The connection of the cores of the wires to each other must be not only strong, but also safe. That is why twisted or soldered wires must be insulated with high quality. In addition to the usual electrical tape, core insulation can be done with heat shrink or with the use of special caps (PPE). Following the rules, the junction of the cores can be reliably isolated not only in the wall or in the ground, but also under water.

Basic safety rules

Those craftsmen who prefer to perform such a procedure exclusively on their own are recommended to follow the following requirements:

1. You can isolate only those wires that are disconnected from the power source (electric socket, transformer, etc.). The switch located in the switchboard must be turned off without fail;

2. Reliable insulation of the junction will be provided only by those materials that meet the standards of the PUE and are tested by tests in accordance with GOST. As a result of studies of the properties of such materials, their electrical strength, resistance to elevated temperatures and the degree of flammability are checked;

3. The use of adhesive tape as an insulating material is unacceptable. Its insulating ability is rather weak.

A brief overview of the most common insulating materials and wire insulation rules is given below.

Common insulating materials and their properties

The electrical safety rules provide for the use of:

1. PVC electrical tape. Its most important advantage is its high elasticity. The disadvantages include rapid deoxidation and peeling off in conditions of high humidity. Insulating tape is perfect for work in a dry room, as well as in the case when the wires need to be provided color marking. Multi-colored electrical tape can perfectly indicate the presence of a phase, zero or earth;

2. HB electrical tape. The specified material has a cotton base. It can be used not only for work at home, but also for manipulating wires under the hood of a car. HB electrical tape is more resistant to moisture, various kinds of pollution and low temperatures;

3. Heat shrink tubing (HUT). Modern heat shrink tubing is deservedly considered one of the most reliable insulating materials. It will equally well be able to isolate wires located in the house, in the ground, in a car and even under water. For domestic needs, this insulator is considered optimal;

4. PPE caps. This type of insulation is best suited for stranding. In terms of their insulating properties, the caps, of course, are inferior heat shrink tube, however, for insulation lived in a chandelier or under false ceiling fit quite well.

The insulation materials listed above are quite reliable and are in high demand. The rest of the article will give the basic rules for insulating bare cores.

Since at home the insulation of conductors has to be done quite often, it will not be superfluous to familiarize yourself with the main recommendations for its implementation:

Before using electrical tape, securely twist the bare cores. When working with stranded wires it is advisable to solder them carefully. To begin with, the twist should be bent to the side (as in the photo). The next step is to wind a double layer of electrical tape on it. Experienced electricians often do just that. Elastic electrical tape is perfect for insulating conductive cores in a junction box, any household appliance and when moving an outlet. The quality of the connection will not change even when a layer of plaster is applied to the resulting twist;

A fairly simple procedure is the insulation of cores and using heat shrink. It is important not to forget that the tube should be put on one of the conductors before they are connected. Upon completion of the connection, it will no longer be possible to put a tube (cambric) on the twist. After moving the piece of tube to the junction, it is heated with a building hair dryer;

If there is no hair dryer at hand, it can be effectively replaced with a regular lighter. Heat shrinkage when heated should “sit down” well on the twist. Tubes HERE are also recommended to be used in the case when the junction is immersed in water or laid in the soil. Insulation with heat shrink tubing will be the best option when the twisting point must be reliably protected from moisture.

The use of PPE caps will be a good option when manipulating wires in the house. Their main advantage is compactness and speed of use. Such a cap must be screwed all the way to the junction of the wires.

When working with rather thin wires, for example, in headphones, the use of electrical tape will be ineffective. She won't be close to them. You can replace it with ordinary superglue - applying a few drops to the bare area. For networks with a voltage of 220V, this method is not suitable, since the glue or silicone sealant will quickly fall off from the twist. For the same reason, it is not recommended to use an adhesive gun to insulate wires. To ensure that the place of twisting is reliably protected from pets, it can be carefully wrapped with tin foil.

The above isolation methods can be easily repeated with your own hands. By using the right insulating material, you can insulate cores in walls, in the ground, and even underwater. If work is carried out in wet rooms or on the street, then it is recommended to additionally protect the electrical wiring with corrugation. It will create an additional barrier to the penetration of moisture to the place of twisting.

How to insulate the wires so that the contact connection lasts as long as possible, and the insulation resistance in this place is equivalent to the "native" insulation of the cable or wire?

This is especially important if we remember the fact that more than 90% of all damage to cable and wire products, and indeed electrical equipment in general, occur at the place of contact connections. That is why, the application of high-quality and properly executed insulation should be given the closest attention.

But before we analyze the types of insulating materials and how they are used, let's focus on. After all, the type of insulating material largely depends on this factor.

• Most often in everyday life, we are faced with the need to connect several wires. But the connection to the connection is different. Indeed, according to the norms of the PUE, wires can be connected by welding, soldering, pressing and bolting. Note that the method of twisting wires, which is so popular among the people, is not in this list. And this is no coincidence. After all, twisting the wires does not guarantee the quality of the connections and its reliability during operation.

Types of insulating materials and their scope

We decided on the contact connections - now let's figure it out, but how can we insulate the wires? For domestic use, there are usually two options - this is electrical tape or heat shrink. But each of these materials has a lot of varieties and applications. So let's look at them in more detail.

Insulating tape

Let's start with the most common and time-tested material - insulating tape. This material is applied to the conductor by winding on the conductive part. But the properties of this product depend on the material of manufacture. And there are not so few of them.

So:

• The most common option is PVC tape. It is made of polyvinyl chloride film, on the surface of which a special adhesive is applied. This solution should provide good adhesion of the tape to most types of materials.
• In our country, PVC electrical tape is produced with a thickness of 0.1 to 0.2 mm. The composition of the adhesive solution and the base of the sleeve also differ. In addition, the color range of such electrical tape has recently expanded, which in Soviet times was only blue.
• This material can be used to insulate any type of connection. The insulation resistance of such electrical tape, according to the norms, is tested for a voltage of 1000V.

Note! In practice, when insulating high-voltage installations, it is generally accepted that one layer of such electrical tape provides protection up to 660V. That is, to insulate a cable under a voltage of 6 kV, at least 6 layers should be applied.

• Another option is cotton tape. It is made on the basis of a fabric on which a special adhesive solution is applied. In our country, raw rubber production waste is often used for this. This gives the product additional tightness after drying.
• HB electrical tape is used as the main insulating material in electrical installations up to 1000V. In electrical installations above 1000V, it is often used to give the connection additional properties. For example, if we need frost-resistant insulation on the wire.

Note! It is necessary to apply PVC, HB and many other types of electrical tape at a temperature not lower than -10⁰С. But operation after the adhesive solution has dried, for some types of electrical tape, is also allowed at lower temperatures.

• There are also so-called epoxy tapes. They are elastic, wear-resistant, but their main advantage is high temperature stability. Such a tape is able to normally tolerate temperatures up to + 155⁰С.
• Mica tapes have even higher thermal stability. They are often used to isolate parts and assemblies. electrical machines. In addition to thermal resistance, such tapes are also fire resistant.
• Glass fabric tapes demonstrate maximum temperature resistance. They are able to withstand temperatures up to +200⁰С.
• In addition, there are other types of electrical tape. But in everyday life they are used extremely rarely, so we will not dwell on them in more detail.

Heat shrink

Now let's talk about heat shrink tubing. The main feature of this material is that it shrinks under the influence of temperature. This ensures reliable fixation and uniform fit of the material over the entire surface.

• But if you think that heat shrink is no different from each other, then you are deeply mistaken. The most common heat shrink, shrinking in half. It is it that is mainly used for insulating wires.
• If it is necessary to ensure a more reliable fixation of the heat shrink with the surface, then materials with glue on the inner surface can be used. This adhesive is also hot-melt, and when heated fills the slightest voids between the tube and the surface.
• If you do not know how to insulate the wires in the car, then there are special oil and petrol resistant tubes. Ordinary PVC electrical tape, in this case, may be useless. It does not tolerate the effects of chemically active substances. But chemically resistant heat shrink, copes with this perfectly.

• For applications at elevated temperatures, special high-temperature tubes are used. Depending on the material of manufacture, they can withstand temperatures up to +260⁰С. For comparison, conventional heat shrink is designed for operation at temperatures from -50⁰С to +125⁰С.
• By the way, heat shrinks are successfully used not only for low-voltage networks. There are special high-voltage heat shrinks. They can be used in electrical installations up to 110kV.

In addition, there are also various ones: non-flammable, anti-tracking, semiconductor, self-extinguishing, fluorescent, with increased strength, with a corrugated surface - and many other heat shrinks. The list of such materials is constantly growing.

Rules for applying insulating materials

All these additional features are, of course, good. But first of all, we are interested in that the wire insulation at the junction is not inferior in resistance to the main insulation. To do this, the insulating material must be correctly applied.

Method of mounting the insulating tape

The method of applying electrical tape largely depends on the type of connection and, of course, the shape of the object - but there are general rules.

Let's look at all these aspects:

• Before applying electrical tape to the surface, it should be prepared. To do this, the wire should be wiped. The insulation and live parts must be free of moisture, oil, and dust. All this reduces the adhesion of the tape to the surface.
• Our further actions depend on the type of wire connection. If the wire is connected by soldering or pressing, and does not have twist-type branches, then we apply electrical tape as follows. We attach the edge of the electrical tape to that part of the conductor that has insulation. The instruction advises to do this at a distance equal to the width of the electrical tape. Then, wrapping the wire with electrical tape at a slight angle, we pass to the opposite edge of the wire with insulation from the junction.
• Here we securely fix the electrical tape with one or two turns around the wire, without an angle of rotation, and then we go in the opposite direction. With one or two wraps, we fix the electrical tape from the original side and cut off the excess. After that, we compress the place of application of insulation with our hand to level the surfaces and remove air.

• If we have a connection made by welding with a twist type branch. In this case, with one or two turns, we tightly fix the electrical tape on the surface of the wire that has insulation. Then, with rotational movements around the wires, at an angle, we isolate the connection to the edge and above. We need the electrical tape to protrude at least half of its width beyond the connection.
• After that, we bend the protruding edges, and fix it with the next turn along the edge of the connection. Rotational movements at an angle, we return to the edge of the application of electrical tape. We fix it with one or two turns, and cut off the edges.

Heat shrink mounting method

With heat shrink everything is much easier. It is used only for connections by pressing and soldering. In the case of welding, the junction must be pressed against the wire with the existing insulation. But let's talk about everything in order.

• So we have two wires. Before connecting them, you should cut off the heat shrink to the required length, and put it on one of the wires. The length of the tube should be such that after making the contact connection and moving it to this place, the tube protrudes at least 3-5 wire diameters beyond the insulated surface.
• After making the connection, we move the tube and securely fix it in the desired position, as in the video. After that, using a special hair dryer or just a lighter, heat the tube.

In the process of heating, the tube decreases in size and tightly fits the contact connection. We check that the tube after shrinkage with its edges lies on the surface of the wire insulation, and we do not have bare parts. This completes the installation of the heat shrink.

Conclusion

Now you know how to isolate the wires and how to do it correctly. And you probably have a natural question, so what type of insulating material is better?

There is no single answer to it. Heat shrinkage shows itself perfectly during operation, and its installation is much faster.

At the same time, not in all cases it is possible to perform isolation with its help, and the cost of such a connection is a bit more expensive. Based on this, you can independently choose how you isolate the wires.