Technical characteristics and scope of NYM power cable

NYM cable is a category of copper electrical connectors designed for indoor wiring. It can be installed in buildings and structures of a wide range of categories, including fire hazardous ones, but not of the highest level. Initially, it was manufactured only in Europe, as evidenced by its name. Currently produced in many EU countries, including Turkey, as well as several factories in Russia according to their own specifications. The products of well-known and quality-responsible Russian brands, such as Sevkabel and Pskovkabel, do not differ in quality from the imported NYM cable.

Explanation of the name

The decoding of the name NYM cable goes back to the old German classification system, according to the German national standard VDE 250, part 204. Currently, the European Union has a different marking system on a pan-European scale, but NYM at one time gained such wide popularity that it was able to maintain the authentic the name by which most European and Russian consumers know it.

So, the marking means the following:

• N - the product complies with the German standard VDE 250;
• Y - insulation is made of polyvinyl chloride;
• M - there is an outer protective shell.

There are two main subtypes of this wire - NYM-J and NYM-O. The letter J indicates the presence of a yellow-green wire in the product, intended for connecting the “ground”. O - for the absence of it. In this case, O may not be indicated on the marking of the coil or on the outer sheath of the cable; J is always indicated. Thus, NYM-J is a cable with a “ground” conductor, just NYM is without it.

Also, each wire of the NUM type is marked with the type 3×2.5, 1×4, and so on. This is a typical marking of the number of cores and their cross-section. The first number is the number of conductors, the second is the cross-section in square millimeters.

Note: a wire of this type can have from 1 to 7 cores of a wide range of cross-sections, up to 2.5 mm square. Some manufacturers, in particular Sevkabel, provide the service of manufacturing wires of the NYM standard with conductors of a larger cross-section - according to the customer’s needs.

Review of manufacturers

Today, Russian wholesalers and retailers offer to buy NYM power cables produced by both foreign and local manufacturers. Let us recall that the production of this wire grade is regulated by the German standard - DIN VDE 0250 (part 204), which sets not rigid, but average parameters for the thickness of the insulating and outer layer, provided that they are not less than the nominal value. If NYM is produced in Russia, then the enterprise receives a special certificate-permission from the German side. Local requirements for the NYM cable are determined by the manufacturers' own specifications, as well as GOST 23286 and GOST IEC 60227-4-2011, which, unlike DIN VDE, determine the exact nominal values ​​for the diameter of the wire along the insulator and sheath with the smallest tolerances.

For more detailed information about manufacturing standards, read the article: “What is the difference between GOST, TU and VDE? Analysis of manufacturing standards"

Among the most famous foreign enterprises, we should mention manufacturers from the Republic of Turkey - Denizli Cable LTD, Germany - Lapp Kabel, TKD Kabel, Helukabel, Kabeltec, France - Nexans and Serbia - Novkabel AD. In the Russian Federation, licenses for the production of NYM power cables are held by Pskovkabel, Sevkabel, Kamkabel, Elektrokabel and others. All imported products must be marked with the abbreviation VDE.

When purchasing cable products, it is important to pay attention to the accuracy of the NYM brand. The fact is that there are a significant number of “clones” on the market that are manufactured according to specifications and are not licensed according to VDE standards, for example, NUM, HUM, NUM, NUM. Counterfeits most often have problems with the quality of the rubber compound filler, which is made from cheap materials or according to a non-original “recipe”. As a result, the filler plasticizer may be released onto the outside of the cable, forming oily stains. If the manufacturing technology of the insulating and outer layers is violated, these shells become fragile, which leads to premature failure of the product or force majeure in the form of melting, smoke or even fire.

Color coding

NYM cable produced in Russia or imported from Europe, if it is not a fake, always has color marking of conductor insulation that complies with the standards of Russian PUE (Electrical Installation Rules).

The colors of their internal insulation may vary depending on the number of cores.

1. Single-core - color is not regulated.
2. Twin-core type O - black and blue.
3. Three-core type O - black, brown and gray.
4. Four-wire type O - black, brown, gray, blue.
5. Three-core type J - black, blue, yellow -green.
6. Four-wire type J - black, brown, gray and yellow -green.
7. Five-core type J - black, brown, gray, blue and yellow -green.

By color marking you can easily determine the purpose of this particular cable. The conductor in the blue sheath is always zero in single-phase networks or neutral in three-phase networks. Yellow-green is a well-known designation for an “earth” conductor. All other colors indicate phases.

Please note: NYM cable, made in accordance with GOST 22483, which regulates the standards of such products, cannot have a conductor in white or white-blue insulation. If the wire you are embroidering contains a white core, this is a fake. You can use it only at your own peril and risk.

Analogs of NUM wire

In Russia, the main analogue at a more reasonable cost is the domestic brand VVG or VVGng in a non-flammable design. Their main difference is in shape; for the NUM it is always round, while for the domestic analogue it is flat. This is an additional advantage, since this shape simplifies the process of laying into technological holes and promotes better tightness.

Design

This wire can only have copper conductors (for comparison, European standards imply the use of copper for cable products “by default”; aluminum wires are marked with the letter “A”). The cross-sectional shape is always round.

Thin, up to 10 mm square, conductors are single-core wire, starting from 16 mm - multi-core twisted. The insulation of the conductors is made, as follows from the designation, from polyvinyl chloride. Next comes a fairly dense and thick shell of a rubber mixture, which contains chalk, enveloping all the internal wires. The outer shell is durable PVC-based plastic.

The layer between two layers of insulation (usually white) serves to give the wire a regular round shape, as well as increase its flexibility and ease of cutting.

Benefits of use

Main advantages of power cables:

• High degree of elasticity. The rubber layer located between the sealing and insulating layers provides flexibility. This allows you to rationally use the product in hard-to-reach places and underground.
• The cable is made of non-flammable materials, so it is recommended for use in fire-hazardous building structures.
• High quality. Before hitting store shelves, each cable undergoes various tests.

The NUM wire has a large number of advantages, which are noted by experts in the field of electrical installation work. They are especially often used for power and lighting purposes.

Characteristics

The technical characteristics of the NYM cable are as follows:

• Maximum voltage: 660 VAC at 50 Hz;
• operating temperature range - from –50 to +50 degrees Celsius;
• the minimum styling temperature without heating is –5 degrees;
• minimum bending radius - four own diameters;
• maximum withstand air humidity - 98% at a temperature not exceeding 35 degrees;
• typical construction length - either 50 or 100 m (coils), or 500 m (winding on a drum);
• The service life under the warranty is 5 years, the maximum is within 30 years.

Briefly about the main thing

The technical characteristics of the NYM cable practically do not limit the scope of its application, subject to the correct selection of the cross-section and protective sheath, if used outdoors. Domestic products, "Kamkabel" and "Pskovkabel", are at least not inferior to foreign analogues in terms of conductive characteristics, but may be inferior in quality of protective coating - if this parameter is important, then it is better to choose a cable made in Germany, Turkey or France, despite the difference in price.

Application area

This type of wire is intended exclusively for internal electrical wiring. The fact is that PVC plastic is not resistant to radiation in the ultraviolet spectrum, which is present in sunlight. It decomposes under the influence of ultraviolet radiation, so if it is necessary to stretch the NYM cable in an open place, it must be enclosed in a steel or plastic corrugated pipe.

This cable is used for power and lighting wiring inside any structures, including the first class of electrical safety. They can connect single-phase and three-phase current consumers in rooms with explosion hazard classes B1 b, B1 g and Vpa. In areas with explosion hazard class B1a it can also be used, but exclusively for lighting.

NYM cable analogues

The main analogue the NYM power cable is considered to be the VVG brand, or rather its “non-flammable” modification VVGzng, where the “z” in the decoding means “with a filler” made of PVC. When choosing between NYM or VVG, you should remember that the technical parameters of both brands are approximately the same, but the price of the latter is approximately 1.5-2 times lower. Analogues of the NYM cable, which can be purchased on the domestic market, are also considered products of the KGVV group, which belong to the group of flexible conductors.

Design features

VVGng is a power cable with copper conductors. The core insulation is made of polyvinyl chloride plastic. The insulation material contains additives that make it flame retardant. This conductor is available with a number of cores from 2 to 5. For ease of installation, the core insulation is color-coded, which can be done by completely painting the core insulation, or with a colored stripe. The outside of the cable is covered with a sheath made of the same PVC plastic as the core insulation. The core can have a single-wire or multi-wire design. The cross-sectional shape of the core can be round or segmented.

NYM is the designation of an analogue of the Russian product brand VVGng, produced according to the German standard VDE 0250. The number of cores also varies from 2 to 5. The insulation material is the same polyvinyl chloride, which does not support combustion. The main design difference between this product and its Russian counterpart is the presence of an additional non-flammable seal between the core insulation and the outer sheath of the cable.

What is the difference between NYM and VVGng

The NYM cable will be useful only for single installations. If you are planning a group session, then it is better to make a choice in favor of VVG. Structurally, both products consist of several copper cores with polyvinyl chloride insulation and the same outer shell. However, only VVGng (the prefix “ng” indicates the non-flammability of the cable) is able to stop the flame and prevent its spread during group installation of several conductors.

We list the main technical and operational characteristics of NYM and VVGng and compare them in the table below: