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Thickness insulation—sheath, transient

For calculation of the cyclic and emergency current rating of cables acc. IEC 60853, the multi-core cable is replaced by an equivalent single-core construction dissipating the same total conductor losses. The space between the equivalent single-core conductor and the sheath is considered to be completely occuied by insulation. For oil-filled cables, this space is filled partly by the total volume of oil in the ducts and the remainder is oil-impregnated paper.

Symbol
$t_{1t}$
Unit
mm
Formulas
$t_1$single-core cables
$\frac{D_{it}-d_{ct}}{2}+t_{scb}+t_{scs}+\frac{\Delta d_{sh}}{2}$multi-core cables, type SS
$\frac{D_{it}-d_{ct}}{2}+t_{scb}+t_{scs}+t_f+\frac{\Delta d_{sh}}{2}$multi-core cables, type SC
$\frac{D_{it}-d_{ct}}{2}+t_f+t_{scb}+t_{scs}+\frac{\Delta d_{sh}}{2}$multi-core cables, type CC
$\frac{D_{it}-d_{ct}}{2}+t_{scb}$pipe-type cables
Related
$d_{ct}$
External diameter conductor, transient [mm]
$D_{it}$
Diameter over insulation, transient [mm]
$\Delta d_{sh}$
Depth of corrugation [mm]
$t_1$
Thickness insulation—sheath [mm]
$t_f$
Thickness of filler/belt insulation [mm]
$t_{scb}$
Thickness screen bedding [mm]
$t_{scs}$
Thickness screen serving [mm]