  Transformers and transmission lines are critical components of a grid
network. This paper analyzes the statistical properties of the electrical
parameters of transmission branches and especially examines their
interdependence on the voltage levels. Some interesting findings include: (a)
with appropriate conversion of MVA rating, a transformers per unit reactance
exhibits consistent statistical pattern independent of voltage levels and
capacity; (b) the distributed reactance (ohms/km) of transmission lines also
has some consistent patterns regardless of voltage levels; (c) other parameters
such as the branch resistance, the MVA ratings, the transmission line length,
etc, manifest strong interdependence on the voltage levels which can be
approximated by a power function with different power constants. The results
will be useful in both creation of synthetic power grid test cases and
validation of existing grid models.
