In any system, cables have to be bent. This must be done in accordance with the bending radius in order to guarantee the integrity of the cables and to limit the risk of short circuiting and/or fire.
Usually, the bending radius is expressed as a factor of the exterior diameter of the cable (e.g. 4xD or 12xD for which D is the exterior diameter of the cable).
How to Apply the Bending Radius Correctly
The cable must be bent around an imaginary circle of which the radius equals the bending radius of that specific cable.
Example: XVB Cca 1 kV 5G25
- Bending radius XVB Cca 1 kV = 12xD
- for which D = exterior diameter of the cable = 26 mm (nominal value, always check this by measuring on the cable).
- So: 12 x 26 mm = 312 mm.
- The XVB Cca 1 kV 5G25 must be bent according to a circle with a radius of 312 mm.
Note: angle and bending radius are not the same !
A typical situation is one in which a cable follows the lines of the wall and subsequently must be led along the ceiling. Naturally, the cable can be angled 90°, but only if it respects the bending radius. This means that 'cramming' the arc of the cable as far in the corner between the wall and the ceiling is out of the question. Should you do this, there will be a much smaller bending radius which can have dire consequences including fire.
The drawing clarifies the impact on the bending radius.
Wall and ceiling are at a 90° angle. In the drawing, the cable follows a wide bending radius in which the cable is already bent well before the angle from the wall to the ceiling.