Color coding of wires and cables

Recommendation points

• Phase marking according to GOST and DIN
• Neutral and protective conductors
• Low-current and signal circuit marking
• If the colors are duplicated
• Other marking methods

On the one hand, it may seem that the choice of the color of the insulation of the conductors of cable and wire products is carried out at the whim of the manufacturer, although this is far from the truth. Today we will fully disclose the topic of vein marking both from the point of view of domestic and Western standardization, and from the point of view of practical use..

Phase marking according to GOST and DIN

Over the decades of the existence of three-phase AC networks, various conventions have been used. Confusion in the assignment of conductors can easily lead to an error that is too expensive for both the installer and the owner of the electrical installation. Therefore, in relation to electrical networks, the issue of standardization has always been especially acute.

Beginning in 2009, a serious dissonance began to be observed in the legend system. On the territory of the CIS, hundreds of thousands of electrical installations and millions of kilometers of wiring continue to operate, in which color designations are used, adopted even during the existence of the country of councils. The new standard introduced new industry rules, obliging electrical installers to adhere to the European labeling standard. Because of this, a modern electrician has to get acquainted with several color-coding systems for cable and wire products at once..

Color marking of wires in the USSR

In the well-established designation system, the phase conductors of conductors and busbars are marked in yellow, green and red. It is noteworthy that the colors correspond to the symbols of the phases A, B and C, and this marking previously corresponded to the real sequence of alternating voltage amplitudes in time. In other words, any qualified electrician could, on the first try, connect an induction motor so that it rotates in the right direction..

Preferred wire marking according to GOST R 50462-2009

State standard 50462, which came into force in 2009, regulates the designation of line conductors in brown, black and gray. At the same time, the color correspondence to the designation of the phases L1, L2 and L3 is only conditional: neither the aforementioned standard nor the current rules of the PUE oblige to observe the current phase sequence in the symbols.

As for single-phase networks, it is preferable to designate the phase conductor in brown. At the same time, the PUE mentions that the color of the phase conductor can be anything except blue and yellow-green, such marking is used for other purposes.

Neutral and protective conductors

In AC networks, the neutral conductor can perform various functions. In a single-phase power supply system, the neutral wire performs the function of connecting to the midpoint to form phase voltage, in three-phase it is used to ensure the symmetry of the loads. The most rare are zero conductors that perform the function of equipotential bonding, which can take place in the power supply circuits of bridge cranes and electrical equipment of livestock farms.

The neutral conductor should not be confused with a protective earth conductor called PE. It can also be combined and additionally perform the function of equipotential bonding, neutral wire, midpoint, and in especially rare networks – also a phase wire through which the operating current flows. The latter is found in residential buildings where a 127/220 three-phase power supply scheme is used with a delta connection, thus, individual 220 V consumers are connected according to a two-phase scheme and are supplied with line voltage..

As you can see, the protective and neutral conductors can have a different connection diagram and perform separate functions on each section of the network. And if the color designation of the phase power conductors allows certain liberties, then with the color of the neutral (zero) and protective grounded conductors, everything is categorically strict. The neutral is indicated exclusively in blue, regardless of the combined functions, the protective earth wire is yellow-green. Moreover, if the protective conductor flows into the zero conductor in the connection diagram, the marking must change accordingly. There is also a recommendation to mark the combined protective and neutral conductor (PEN) with yellow-green insulation and blue marks at the ends of the conductors..

Low-current and signal circuit marking

At first glance, the colors of the wires in the control and signaling circuits are arbitrary. However, if the purpose of the conductors in a three-phase power network can be established by a continuity or a phase indicator, then a number of problems appear in the “weak current”. Therefore, recommendations on the choice of wire marking are much more important here..

Typically, signal circuits are routed with a cable called a twisted pair cable. This definition includes the familiar to many cables of local computer networks, telephone cables, and cables of industrial signaling systems. The main difference lies in the number of pairs of conductors, which can be up to one hundred, and the cross-section of copper conductors. The cable is called twisted pair for the reason that all conductors in a common sheath are divided into pairs and twisted together. It seems that it is impossible to understand the purpose of each conductor in this “broom”.

However, everything is quite simple. The wires are actually numbered and follow in a clear color-coded sequence. When the number of pairs is more than five, they are divided into groups. In each group, the number of the pair from the first to the fifth is determined by the color of the solid-colored wire: blue, orange, green, brown and gray, respectively. The group number is determined by a wire with a double color, where an additional color other than the pair number indicator indicates the group number: white, red, black, yellow, purple for groups 1 through 5. If there are more than five groups of pairs in the cable, each five groups is wrapped with colored tape. Thus, it is enough for the installer to simply connect the wires in series to the terminal block or cross-block from the first pair of the first group to the fifth pair of the last group..

Also, when installing control circuits, several good form rules apply. For example, if a common GND contact needs to be connected to an alarm device, all green wires in the cable are used for this, that is, every third pair of five. If it is necessary to supply a constant voltage, for example, to the contacts of buttons, it is fed through a wire with a solid color, while the corresponding “return” signal follows a two-color core from the same pair.

If the colors are duplicated

The work of an electrician is subject to the requirements of GOST and PUE, while the production of cable products is not standardized with respect to color coding. For example, a cable from the remnants of a custom-made series, for example, with two brown and two blue cores, may enter the market. What to do if you need to connect a three-phase power supply system via such a cable?

In such cases, you can rely on the fact that all the cores inside the common shell follow strictly parallel. It is enough to establish the correspondence of at least one conductor at both ends of the cable, which can be done with a continuity against the ground or with a pole indicator. At the same time, if on the cut on one side, number the remaining veins L1, L2, L3 clockwise, then on the cut on the back side the conditional marks will be located counterclockwise, that is, mirrored.

By the way, GOST allows the absence of color coding for the so-called concentric veins, that is, located in a common shell around the circumference in one or more rows. In such cables, at least one core in each row has a color or other marking, with respect to it, the correspondence of all other cores is established as described above. An example of this is a self-supporting insulated wire without color marking, in which one of the veins has a raised strip along its entire length. This core is taken for a neutral wire, the rest are used as linear conductors. Please note that with this method of establishing the correspondence of the conductors, it is imperative to leave marks of different colors at their ends, for example, from segments of a heat-shrinkable tube.

Other marking methods

Of course, the whole variety of electrical installations is not limited only to AC networks. According to the current standard, the positive and negative conductors in DC circuits, designated L + and L- in the diagram, respectively, have brown and gray insulation. Previously, the positive conductor was usually designated in red, while the negative conductor could have any marking, although, as a rule, its insulation was black. The middle conductor according to current standards is marked in blue, as well as the grounded pole conductors.

Sometimes you may find that all the cores in the cable have the same color. However, if you take a closer look, it turns out that there is stamping on the insulation in the form of one or more strips, or letters and numbers. Also, in some imported cables, the cores differ in shape, they can be flattened on one or more sides..