One of the difficulties while performing subsea studies on
transmission is that the conventional parametric representations
of the transmission line model become inadequate to accom-
modate the physical factors that come into play during long
and under water at high pressure transmission. The physical
effects that come into the picture, while considering long
transmission lines for subsea are many. With long transmission
lines, the impedance should account for the shunt admittances
and the series impedances can no longer be lumped. The skin
effect and proximity effects also become prominent in long
transmission line studies. The insulation and design of power
umbilical need to be considered in complete analysis. The
multiple variable frequency drives (VFDs) operating together
for subsea operations cause harmonic power to be consumed
by the terminal network. It is critical to have appropriate
mathematical model of the transmission line which considers
the physical effects and equivalent impedance changes. Only
then, the analytical subsea power studies would be valid and
useful. Such models would contribute to accuracy of fault
identification in the long and medium transmission lines.