Low frequency AC (LFAC) has been proposed as a means to
avoid some of the large converter station costs of high voltage
DC (HVDC) while delivering some of the benefits in terms of
better line or cable utilization and its technical feasibility has
been established. It is said to offer a lower costs than HVDC or
conventional high voltage AC (HVAC) for a range of
intermediate distances, with HVDC becoming cheaper over
long distances. However, the basis for identifying the distance
range and extent of cost saving has not been established. Here,
cost estimate methodologies are extended for LFAC. A
difficulty is the absence of commercial schemes that can
provide practical examples of costs. In this paper, costs are
broken down into constituent terms and estimates are made
from the most similar equipment from other schemes. The
capacity limits and power losses associated with subsea cables
are analyzed for low frequency cases. For a given power
transfer and for each distance, a choice of operating voltage,
cable size and number of parallel circuits is made in order to
find the lowest route cost. This yields cost as a function of
distance that is a non-linear and discontinuous function. The
cost curves for LFAC are compared with HVDC and HVAC
options. The results for current cost estimates show that LFAC
has a range of route length over which it is the lowest cost
option and but this range narrows and eventually ceases to exist
for higher power transfer ratings.