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Mutual heating coefficient

Mutual heating substitution coefficient for a group of equally loaded buried cables.

There are (q-1) terms considered in the product, with the term $d_{pp1}/d_{pp2}$ excluded. q is the number of non-touching cables within the same cable system.

For cables in a multi-layer backfill and for transient simulations, $F_{mh}$ = 1 with the mutual heating considered in the factor $\Delta\theta_p$ instead.

In case of cyclic loading $F_{mh}$ = 1.

Symbol
$F_{mh}$
Formulae
$\displaystyle \prod_{k=1}^{q} \frac{d_{pk1}}{d_{pk2}}$
Related
$d_{pk1}$
Distance to mirrored buried object [mm]
$d_{pk2}$
Distance between buried objects [mm]
Used in
$d_f$
Spacing from hottest object in group [m]
$\gamma_t$
Attainment factor for groups of cables
$T_{4iii}$
Thermal resistance to ambient [K.m/W]
$T_{4ss}$
Steady-state thermal resistance [K.m/W]
Image
IEC standard 60287-2-1 Ed. 2.0 (2015) Figure 1