Thickness of insulation to sheath

Insulation thickness between conductors and sheath used to calculate $T_1$ with following considerations:

• For multi-core cables, $t_1$ is up to the sheath and $t_2$ is between sheath and armour.
• A tape screen is considered equivalent to a sheath, so for single-core cables with a tape screen and no sheath and for multi-core cables with a common screen and no sheath, the screen serving is added to $t_2$.
• A wired screen is not relevant for the calculation.
• For multi-core cables with separate sheaths, the filler is part of $t_2$.

Type of screen/sheath of multi-core cables

• SS: with separate screen and separate sheaths
• SC: with separate screen and common sheath
• CC: with common screen and common sheath

Symbol
$t_{1}$
Unit
mm
Formulae
 $\frac{\Delta d_{sh}}{2} + \frac{t}{2} + t_{scb} + t_{scs}$ single-core cables with sheath $\frac{t}{2} + t_{scb} + t_{scs}$ single-core cables without sheath, no screen $\frac{t}{2} + t_{scb}$ other single-core cables $\frac{\Delta d_{sh}}{2} + \frac{t}{2} + t_{scb} + t_{scs}$ multi-core cables type SS with sheath $\frac{t}{2} + t_{f} + t_{scb}$ multi-core cables type CC with screen and no sheath $\frac{\Delta d_{sh}}{2} + \frac{t}{2} + t_{f} + t_{scb} + t_{scs}$ other multi-core cables
Related
$\Delta d_{sh}$
$t_{f}$
$t_{scb}$
$t_{scs}$
$T_{1}$
$t_{1t}$