ELECTRICAL WIRES AND STRANDS
Wiring is a basic and necessary element of any electrical installation. The selection of the suitable type and construction of the cables for the planned application is all the more important since in the vast majority of residential buildings and often also in large production halls, the electrical installation is installed at the stage of construction and is hidden under the plaster on the walls of the rooms. Incorrect selection of the cable can lead to detachment of the facade and, consequently, expensive replacement. Unfortunately, such a mistake can also have much more serious consequences, including the possibility of electrical shock or building fire. So what do you need to know when choosing an electrical cable?
RULES FOR SELECTING A CABLE FOR POWER
The basic criterion for selecting an electrical cable must be the safety of use. Due to protection against electric shocks and short circuits, electrical cables are protected with an outer insulating layer. Protects against direct contact of the user with the conductor and, at the same time, against short-circuiting of the adjacent phase conductors. Both mechanical destruction and overheating and consequently melting of the insulation therefore lead to immediate danger. In addition, the high temperature generated in the cables used for too high a current may cause a fire. Due to the possible consequences the electrical cable must meet a number of conditions. The requirements for the selection of cables for installation are described in detail in Polish and European standards, including the PN-IEC 60364-5-523:2001 standard, which presents the rules for selecting cables with respect to the load capacity of long term current.
Adequate mechanical resistance
An extremely important issue is the purpose of the cable as well as the place and method of installation. Depending on whether the cable is laid under the plaster or under the ground, or if it is routed as an overhead cable line, the risk of mechanical damage changes radically, which requires the selection of a suitable section and material of the conductors.
For example: cables that are permanently installed and protected from damage (such a solution can be found, for example, in a built-in electrical installation), must be made of copper conductors with a cross section of 1.5mm 2. However, if aluminum conductors are used, their cross section must be at least 2.5mm 2. For cables located outdoors on insulators, where the distance between the fixing points is greater than 20m, the cross section of the copper strand must be 6mm 2, and that of the aluminum strand must be min. 16mm2. Guidelines for selecting the appropriate conductor cross-section can be found in the German standard DIN VDE 0100:2002.
Resistance to voltage drops in the installation
For proper operation, electrical devices need a voltage equal to or with a slight deviation from the nominal value. These values are regulated by the PN-HD 60364-5-52:2011 standard. According to its guidelines, for low-voltage lighting installations powered from a low-voltage distribution network, the value of the nominal voltage must not be less than 3%, and for the rest of the receptors, less than 5%.
