The general formula of an empirical equation for the non-adiabatic factor is as follows:
where:
F: is the factor which takes into account the imperfections of thermal contacts between the conductor or wire and adjacent non-metallic materials. It is common to take F = 0.7 for drivers and F = 0.5 for the screens.
A, B: are empirical constants based on the thermal properties of nonmetallic materials adjacent.
(mm2/s)1/2 where C1 = 2,464 mm/
(mm2/s) where C2 = 1,22 K.m.mm2/J
where:
: is the volumetric specific heat conductive component of current;
- For copper is common for the value of 3,45 x 106 J/K.m3
- For aluminium is common for the value of 2,5 x 106 J/K.m3
: is the volumetric specific heat of the adjacent non-metallic materials. You can take the value2,4 x 106 J/K.m3 for XLPE;
: is the thermal resistivity of the adjacent non-metallic materials. You can take the value 3,5 K.m/w for XLPE.