Capacitive load current

In the case of multi-core cables without conductive layers with a common metal sheath (design I) and with conductive layers over each core and a common metal sheath (design II), charging currents only flow in the conductors during undisturbed operation. In the jackets or shields, the charging currents, which are phase-shifted by $2\pi/3$ against each other, cancel each other out.

In the case of single- and multi-core cables with a metal sheath and, if necessary, a conductive layer over each core (design III), currents also flow in the sheaths or shields. They are equal to zero in the middle of the cable section, increase towards both ends and reach half of the charging current flowing in the conductor at the feeding end. The currents cancel each other out at the nodes (connection points of the sheaths or shields).

Note: refer to table 14.7 in $C_b$ for design I, II, III (called Bauform).

Symbol

$I_C$

Unit

A/m

Formulae

$U_e \omega C_b$

Related

$C_b$

Capacitance of insulation [F/m]

$\omega$

Angular frequency [rad/s]

$U_e$

Line-to-ground voltage [V]

Image

Kabel und Leitungen für Starkstrom, Kap. 25 Kapazität, L. Heinhold (Siemens/Pirelli 1999)