More rational transmission Line data

[ceraolo]

Consider Examples.Data.Lines.
It contains twin line data for RXline components and PIline components.
The latter have the same info of the former, plus additional info regarding transverse susceptances and conductances.
A few comments on them:

1. there is no need for this duplication: the more complete records can be used with RXline components without inconveniences. Thus I propose to leave in place only the more complete parameters, those having presently the underscore in the name
2. the data do not have any info showing which geometry they refer to. This can be improved.
3. duplication of data for the same line is risky. Consider for instance OHline_15kV1ph: is should contain the same data of OHline15kV1ph, plus additional susceptances and conductances. However, I read V_nom=132e3 which is apparently wrong. Consider Cable132 kV and Cable_132 kV: they should have the same x, which is not the case (0.8e-3 and 0.08e-3 respectively)

To contribute positively to this issue I attach here a OH line record with realistic data and info about the line geometry.

So I propose to:

1. to eliminate the records without susceptance and conductance info, since they are a somewhat duplication
2. progressively modify the supplied data using new data for which geometry is reported. One of them might be the one I propose here:

ItOHLine_132kV.txt

Note that I have a simple utility program which computes all the parameters for continuously transposed line from geometry and conductor data which I can share with anyone interested.