The choice of electric cable has to begin with calculation of section of the carrying-out veins. Reliability of work of electrical wiring will depend on it. Correctly chosen cable will serve very long.
It is required to you
- the table for calculation of section of cable.
Instruction
1. Before beginning calculation electricof cable, first of all learn what electric devices will be switched on in electric power transmission line and also the nature of their inclusion and period of operation including the periods between inclusions and switching off. If it is going to turn on in network electric motors, then accept the section of cable cores with 20% stock.
2. When calculating cable take into account the nature of power line – single-phase network or three-phase. For transfer of identical power the cable section for single-phase network will be more. At possibility of asymmetrical loading, accept the section of zero conductor in three-phase network equal to section alone from feeding lived.
3. Consider also way of cable laying – internal or external and also the largest air temperature where the cable will be laid, at maximum load. At ambient temperature more than 40 degrees, it is necessary to increase the rated section of cable cores by 25% or a little more. When calculating you aspire to that during the work with maximum load temperature of cable did not exceed maximum permissible value. For the VVG cable this temperature is 70 degrees. Limit heating of cable accelerates isolation aging therefore choose maximum operating temperature below maximum value.
4. At material selection of cable cores take assignment of the projected wiring into account. Aluminum wires do not transfer vibration, repeated excesses hold long current capacities, than copper wires worse. Load characteristic of aluminum cable is improved by method of application of cable with a little big section of the carrying-out veins. Advantage of aluminum cable is its smaller cost. It is ideally better to use only copper cables.
5. For simplification of process of calculation use tables by calculation of cables.