Resistive-inductive model that connects two AC three-phase unbalanced interfaces with neutral line. This model can be used to represent a cable in a three-phase unbalanced AC system. The voltage between the ports is

where Vi{p,n} is the voltage phasor
at the connector p or n of the
i-th phase, while Iip the
current phasor entering from the connector p of the
i-th phase.
The model is parameterized with an impedance matrix Z. The matrix is symmetric thus just the upper triangular part of it has to be defined.
The fourth line is the neutral one.
i1,
i2 and i3. Setting a zero start value led
Dymola 2017 on Linux to find a different solution for
AixLib.Electrical.AC.ThreePhasesUnbalanced.Validation.IEEETests.Test4NodesFeeder.BalancedStepDown.YD.
Also, the current is typically non-zero and zero is anyway the
default start value, hence there is no need to set it.