# Positive sequence impedance

These equations are based on the Cigré Guide 531 for symmetric systems without earth return path.

For subsea armoured three-core cables, the three screens are assumed to be solidly bonded to the armour at least at both ends.

Symbol
$Z_{pos}$
Unit
$\Omega$/m
Formulae
 $R_c+1j X_c$ single point or cross-bonding, and multi-core cables with common screen $R_c+1j X_c+\frac{{X_s}^2}{R_s+1j X_s}$ bonded at both sides $R_c \left(1+\lambda_2\right)+1j X_c+\frac{{X_s}^2}{R_s+1j X_s}$ armoured three-core cables bonded at both sides